Abbott, P.

• TRAFFIC CALMING IN GLOUCESTER, INFLUENCE ON NOISE AND GROUND-BORNE VIBRATION
  P. Abbott, G. Watts and G.J. Harris
[Abstract]

TRL have carried out noise and ground-borne vibration surveys alongside traffic calming schemes in the City of Gloucester in the UK as part of the 'Safer City' initiative financed by DETR to investigate the environmental impact of urban traffic management and safety schemes. Measurements of both traffic and vehicle noise taken at selected sites before and after traffic calming together with the results will be described. The traffic calming features studied were junction tables (raised areas at junctions), road humps (across the full road width) and speed cushions (humps of limited width which allow heavy vehicles, buses and some emergency vehicles to straddle the raised area). Measurements of ground-borne vibration were also taken at properties close to selected traffic calming features to determine levels of vibration generated by passing vehicles. The results showed substantial reductions in average noise from light vehicles of about 5 dB(A) compared with no significant change in the average noise from heavy vehicles although pass-by noise levels from some unladen trucks increased substantially as a result of body noise. Overall traffic noise levels were reduced by 4 to 6 dB(A) after normalising for differences in traffic flow and composition during the before and after surveys. Levels of ground-borne vibration were not found to have increased significantly following traffic calming. The paper will also discuss how these results compare with those obtained at other traffic calming schemes and indicate how, in general, traffic calming can impact both noise and vibration levels in community settings.

Abe, K.

• COMPARISON BETWEEN THE EFFECTS OF ADDITIONAL VERBAL AND VISUAL INFORMATION ON THE PERCEPTION OF ENVIRONMENTAL SOUNDS
  Y. Suzuki, K. Abe, K. Ozawa and T. Sone
[Abstract]

Three types of experiments (Experiments A, AL and AV) to examine actors in evaluating environmental sounds were conducted.In experiment A (Audio), the stimuli were composed of only sounds.In experiments AL (Audio & Linguistic) and AV (Audio & Visual), in addition to the sounds, verbal explanations and moving pictures, respectively, corresponding to the sounds were presented. The SD method was used in the experiments. Subjects were asked to evaluate 66 kinds of environmental sounds with 38 adjectives that express not only sound quality but also characteristics of sound fields, those of sound sources and emotional aspects evoked by the environmental sounds. As reported in internoise 1999 (pp. 1177-1182), it was shown that images of the sounds evoked by the additional visual information affected the evaluation of environmental sounds. In the present paper, the difference in the effects of verbal and visual information in environmental sound perception is examined. For most of the stimuli, the changes in factor scores by the addition of visual and verbal information seem almost similar. However, for some of the stimuli, the changes caused by additional visual and verbal information show different tendencies. Examination of such stimuli has shown that moving pictures greatly affect the evaluation. Moreover, the evaluation is also affected by the cross-modality consistency of stimuli such as whether sound sources can be recognized in pictures and whether movement of a sound source properly synchronizes its sound.

Abe, M.

• THE CONVERGENCE CHARACTERISTICS OF AN ADAPTIVE ALGORITHM FOR A MULTICHANNEL ACTIVE NOISE CONTROL SYSTEM
  G. Chen, M. Abe and T. Sone
[Abstract]

A lot of reports about active noise control (ANC) have been published, and its applications have been reported. However, most of them dealt with a single noise source and a single control point, and there are few works for multiple noise sources and multiple control points. Since a lot of multiple mixed noises frequently exist in actual cases, the previous studies are not enough for actual applications. In this paper, the convergence characteristics of an adaptive algorithm for multiple noise sources and multiple control points ANC system are discussed in detail, and it is shown that the matrices of the transfer functions are important for achieving a good performance of multiple active control system.

Åbom, M.

• PREDICTION OF LOW FREQUENCY SOUND GENERATION FROM AN AXIAL FAN
  M. Åbom and H. Bodén
[Abstract]

This paper treats the acoustical analysis of a 6 blade, subsonic axial fan which is mounted in a cylindrical duct. This type of fan is used for road tunnel ventilation and is known as a jet fan. The acoustic loading effect of the duct and the inflow conditions have been experimentally investigated and modelled. The work carried out is limited to the plane wave frequency domain. A model was developed for simulating the acoustic loading effect based on a two-port source description. Experiments have been carried out to validate the numerical results. The second step of the work was to analyse the primary fan sound generating mechanisms. A preliminary study showed that disturbed inflow conditions, i.e. turbulence ingestion and non-uniform inflow, were major sound generating mechanisms. It In order to understand these effects, it is necessary to be able to compare, experimental aeroacoustic, aerodynamic data and acoustic simulations. By the use of different turbulence grids, turbulence features of the flow have been changed, and measured, while fan sound power was determined in parallel. In this way it was possible to link turbulence characteristics and acoustic sound power changes. A code has been developed to predict the unsteady thrust of the fan using the work of Sevik and the radiated sound power.

• LOW FREQUENCY ACOUSTIC SOURCE CHARACTERISATION FOR IN-DUCT FANS
  H. Bodén and M. Åbom
[Abstract]

For low and intermediate frequencies a ducted fan can strongly interact with the system in which it is mounted. This interaction will cause variations in the acoustic power output of the fan and can in particular lead to higher power output than expected. This type of installation effect is not covered by the standard methods to characterise fans as acoustic sources, because in these methods the acoustic power output is simply measured for one specified acoustic load. In order to calculate the interaction between a fan and the duct system, in which it is mounted, a more detailed source characterisation is necessary. One possibility is to model fans as acoustic multi-port sources, an idea first suggested by Cremer. During the last decade measurement methods have been developed to determine the multi-port source data in practice. A series of works on the subject have been published by the authors of this paper and other researchers. It is the aim of this paper to present the main results of these studies and discuss their applicability.

Abraham, S.

• A LONG-TERM STUDY ON HIGH LEVEL MUSIC EXPOSITION AND HEARING EFFECTS IN ADOLESCENTS
  M.R. Serra, E.C. Biassoni, U. Richter, G. Minoldo, G. Franco, S. Abraham, S. Joekes, M.R. Yacci, A.R. Pollet and A.J. Carignani
[Abstract]

Sources of noise exposure outside the workplaces that are potentially damaging has been topic of many studies (Clark, 1991). Young people are exposed to high level music in discotheques or through personal listening devices. The literature reveals that there are different opinions about possible harmful hearing effects of music (Babish et al., 1988, West et al.,1990; Axelsson, 1990 & 1996; Royster et al., 1990; Ising et al., 1995). This paper deals with the early results of an interdisciplinary long-term study on hearing effects in adolescents by high level music exposition and its relation with physical and psychosocial variables, developed according international standards. Two groups of adolescents -males and females- are examined along four years of their high school level, from 14 to 17 years old. The study focus on changes both, in hearing threshold, applying conventional and extended high frequency audiometry, as well as, in recreational activities. Besides, sound inmission levels of the adolescents studied are measured: a) in discotheques using two methods: by personal dosimetry and by a system developed ad-hoc; b) using walkman and/or diskman: through manikin-technique. In the second year of the study the results show: a) hearing threshold shift in most of the extended high frequencies; b) increase in the music exposure through recreational activities; c) high sound inmission levels in discotheques and trough personal music devices. The whole study, during four years, let will us to know the real hearing effects by music exposition and their relation with psychosocial variables in the studied adolescents group.

Acharya, A.R.

• STUDY OF SOUND SCATTERING ON LAUNCH VEHICLES INTERSTAGES DURING HORIZONTAL FIRING OF ROCKET MOTORS
  P. Jeyajothiraj and A.R. Acharya
[Abstract]

The understanding of scattering of sound on launch vehicle structures is essential for the specification of environmental test levels. Though many experimental and theoretical studies have been carried out on different types of cylinders, there is very little information available on sound scattering on interstages of launch vehicles, which house a lot of sensitive electronic and control system packages. Interstages of launch vehicles are closely stiffened thin shell structure. In this paper, experimental investigation of sound scattering on a launch vehicle interstage is described. In this experimental were carried out on an interstage kept vertically by the side of a rocket exhaust during static horizontal firing. Free field sound levels were obtained by another acoustic sensor. The effect of sound scattering was studied in detail by the analysis of the measured data. Besides, the jet noise level prediction packages for launch vehicles, JAPDSA (Jet Acoustic Prediction by Discrete Source Allocation) and JAPSSDS (Jet Acoustic Prediction by Spectrum Source Distribution) are suitably modified to predict noise environment during static horizontal firing. The main modification is that the effects of ground reflections are included by mirror image technique. The predictions by the modified packages are compared with the measured values during the above tests. It is found that modified JAPSSD predicts the static test environment very well, when the core jet length obtained from more exact sources (like CFD or other methods which incorporate the effect of nozzle exit pressure ratio and gas properties) are included in the package.

Adams, K.

• HOW CAN WE BE SMARTER IN AIRCRAFT NOISE QUANTIFICATION AND MANAGEMENT?
  K. Adams
[Abstract]

In spite of many years of monitoring, modelling, and producing graphical and statistical reports of aircraft noise, its management seems as difficult as ever; in some cases it appears to have become more difficult. On some sites, although aircraft noise as commonly measured has decreased, complaints are more frequent and are coming from greater distances from the airports than before. In other cases where there is substantial noise, the complaints are not as frequent as might be expected. Indeed, changes in patterns of aircraft movements have sometimes produced unexpected results. With this experience we should question whether we are measuring or modelling the right quantities, or whether besides aircraft noise we should be managing something else. It is widely recognised that we are dealing with a multi-dimensional problem and that there is no known simple solution. In this paper we explore some of the issues which appear to be significant. In particular, we consider the accumulation in time of different short-term metrics and how they differ from common practice. We also show that using neural network methods, short-term recognition in real-time of sound sources can provide new insight into the proper quantification of noise from different source types. The training of neural networks presents some special problems in the context of aircraft noise, and improvement is needed in this area. We conclude with some newer approaches to training with a view to greater efficiency and accuracy. Results obtained from real data collected near airports will illustrate the discussion.

Agge, A.

• PLEASANT AND UNPLEASANT CHARACTERISTICS IN WIND TURBINE SOUNDS
  K. Persson Waye, A. Agge and M. Bjorkman
[Abstract]

In Sweden, wind turbines are often built in areas where the background noise level is low. Noise annoyance in such areas may be related to acoustical characteristics in the wind turbine sound that are easily perceived and considered unpleasant. Findings from a previous study showed that different annoyance ratings were given to wind turbine sounds of the same dBA level. A psycho-acoustic profile of noticeable and unpleasant characteristics was obtained for each sound. The psycho-acoustical descriptors: whistling, swisching and uneven was previously evaluated . In the study presented here one of the most noticeable and annoying psycho-acoustical descriptor ''lapping'' was evaluated. With the object to obtain a pleasant sound, a total of 24 test subjects were asked to vary four parameters related to the psycho-acoustical perception of ''lapping'' in the original sound. The variations of the parameters were carried out using an interactive sound processing system and done in such a way so the resulting sound always had a constant dBA level. The resulting values of three of the four parameters were significantly different compared to the original sound. A pleasant sound thus had low contents of the lapping characteristics. While no difference was found between the original sound and the resulting sound with regard to the equivalent frequency spectra, some differences could be detected using Zwickers loudness calculations. The LAeq values are not sufficient to predict subjects perception of noticeable and unpleasant characteristics in wind turbine sounds. Further analysis should be pursued of how to best describe an unpleasant or pleasant wind turbine sound.

• EXPERIMENTAL QUANTIFICATION OF ANNOYANCE TO UNPLEASANT AND PLEASANT WIND TURBINE SOUNDS
  K. Persson Waye and A. Agge
[Abstract]

Noise disturbance may be one critical factor for the public acceptance of wind turbines. Findings from a previous study indicated that the psycho-acoustical descriptors of lapping, swisching and whistling were considered unpleasant characteristics, while low frequent was considered a pleasant characteristic. These characteristics were evaluated in experimental studies where subjects interactively could adjust acoustical parameters with the object to obtain a pleasant sound. The aim of this study was to compare annoyance of pleasant sounds derived from the interactive studies to the original sound with a high content of unpleasant characteristics. A total of 27 subjects are currently being exposed to three wind turbine sounds at three sound levels, 40, 45 and 50 dBA. Subjective ratings of annoyance, pleasantness and time of awareness are rated after a 10 minute exposure for each noise. The dose response of annoyance and sound levels are analysed through analysis of regression which enables a comparisons between the sounds. Data from 12 subjects indicate a lower annoyance and higher pleasant rating for the pleasant sounds. The analysis and results of the total number of subjects will be presented and discussed at the conference.

Aghova, L.

• NOISE EXPOSURE RISKS IN TWO NOISE ANNOYANCE SURVEYS AFTER TEN YEARS
  J. Jurkovicova, L. Sobotova, L. Aghova and J. Volekova
[Abstract]

Road traffic noise represents a frequent, unavoidable and continuously increasing environmental factor in big cities throughout the world. In the European Union countries about 40% of the population are exposed to road traffic noise with the equivalent sound pressure level exceeding 55 dB/A daytime and 20% are exposed to levels exceeding 65 dB/A. The analysis of the noise environment should take into account not only the physical impact of noise and its physiological effects, but also psychosocial consequences, including annoyance. The global aim of our contribution was to compare two noise annoyance surveys conducted in ten year interval. This ten year period (1989-1999) includes political, socioeconomic and traffic management changes as well. Specific aims of these surveys were to quantify noise exposure affecting university students cohort, to evaluate their subjective response to road traffic noise in their residential areas in terms of sleep quality, annoyance, activity disturbances and psychosocial well-being and to calculate risks of urban noise on student`s health. Equivalent noise levels were assessed in the city Bratislava, capital of Slovak Republic, at the dormitory (exposed group) and in the residential areas (100 measuring stations average) where the other students lived (control group) by Brûel-Kjaer measuring technique. Mean dormitory equivalent noise levels increased from 64,7 dB/A to 67 dB/A after ten years. Subjective response of students was assessed by a validated noise annoyance questionnaire. Risks of different noise exposures were obtained by bivariate analysis (odds ratio, 95% CI). When comparing current and previous risks of different noise exposures, current risks are much higher concerning road traffic noise annoyance (OR=6,01; 95%CI=4,97-7,95 vs OR=2,56; 95%CI=1,93-3,42), entertainment facilities noise annoyance (OR=3,90; 95%CI=3,19-5,46 vs OR=1,51; 95%CI=0,90-2,52) and neighborhood noise annoyance (OR=2,43; 95%CI=1,99-3,03 vs OR=1,71; 95%CI=1,29-2,27) for exposed group. Current risks of road traffic noise interference with various activities were also higher than the previous ones. These preliminary results show that higher noise annoyance risks in dormitory students can be contributed to higher noise exposure. Comparison of two noise annoyance surveys confirms that community, especially road traffic noise load continuously increases in big cities as well as subjective response to it.

• ANALYSIS OF A NOISE LOAD IN DIFFERENT TYPES OF INFANTS' INCUBATORS
  J. Jurkovicova, L. Aghova and M. Huttova
[Abstract]

Advances in medical technology have led to major technological developments in the field of neonatal care. Over the past three decades there has been inreasing concern about noise levels in neonatal intensive care units, especially in incubators. Incubator noise is certainly an important cause of stress to infants and a source of serious and dangerous changes in their behavioral and physiologic states. Noise recorded inside the incubators has several components. The first one is background noise from the incubator motors, the second ones are: life supporting therapeutic and monitoring equipments, nursing staff (opening and closing incubator doors, contact with incubator wall etc.) and the infant itself. This study evaluated the noise levels inside the various types of incubators and identified its sources (SPL, A-weighted noise level, octave band and third-octave band analysis) and investigated the real noise load of infants during 24-hour periods (LAeq24h, LAmin, LAmax, 24-h level analysis). Average noise levels of incubator motors were 64,2-79,7 dB SPL; 51,6-62,9 dB(A) according to type with maximum energy in low frequency range (to 500 Hz). All other equipments not only increase the total noise levels (by about 6-18 dB/A) but also cause shift of energy maximum to higher frequency range (1-16 kHz). The highest noise levels were recorded during baby's crying, contacts with incubator walls and opening and closing the incubator doors with maximal levels up to 123 dB. Therefore the real noise load of premature infants is higher in average by 15 dB(A) during 24-hour period than the average noise level in empty incubators and than the average noise load of infants in open crib (p0,001). In 29% cases it was even higher than the WHO limit for the 8-hour work time in the workplace (75 dB/A). Recent standards require that the mean noise levels inside the incubator should not exceed 60 dB(A) which is safe for the adult human ear but real noise conditions in incubators are much more higher. When compared with the in utero environment the noise levels in incubators are high and potentially hazardous. A low-birth-weight and/or immature infant spend days, weeks or months in this damaging conditions. The following procedures could be taken to reduce the level of noise: reduction of alarm sounds to minimal level, better construction of incubator doors, instructions to nursing staff.

Agren, A.

• SOUND INSULATION IN LIGHT WEIGHT BUILDING STRUCTURES, A) DEVELOPMENT OF A FULL-SCALE TEST HOUSE AND A STEEL BEAM FLOOR, B) IMPROVED MODEL FOR IMPACT SOUND PREDICTIONS
  A. Agren, W. Shi and F. Ljunggren
[Abstract]

Light-weight building constructions for apartments are in Scandinavia traditionally built with timber joists. Heavy steel beams have mainly been used for industrial plants and offices and light-weight steel beams have not been so common, because of stiffness and damping problems. There has during the last decade been a growing interest from steel industry to take part of the growing light-weight building market. Therefore a couple of national projects have started in Sweden and a large European program is running since a couple of years. The paper will present the first results from one of the national projects. In the paper there will be shown a new prototype design for a light-weight steel beam floor that fulfils the sound insulation and production demands. A full-scale test building will also be presented, where all wall- and floor beams are made in light-weight steel and where direct sound transmission as well as flanking transmission have been considered. Two main problems with light-weight steel floors are damping and low frequency isolation. Several tests have been performed of various designs to increase the internal and boundary damping. One finding is that the boundary damping has a very significant influence. Experiments have also been performed on various floor versions. Results will be shown from measurements of damping, impact sound and airborne sound.

• PREDICTING INTERIOR FACTORY NOISE WITH RAY-TRACING MODELLING. AN EXAMPLE OF A HARDENING PLANT.
  R. Johnsson, B. Tingvall and A. Agren
[Abstract]

Prediction of the noise levels in a factory in an early stage when it still is on the drawing-table would improve the possibilities to evaluate different solutions to reduce the noise and to find the optimum solution. Doing these calculations by hand gives very approximate results, but the big improvement in computer speed has made it interesting to use computers to predict the sound level. This project has been done on a planned hardening plant. The company has set up high demands on noise levels in the plant and is therefore interested in taking actions at the construction stage to reduce the in-plant noise. As a part of this work the plant has been computer modelled and sound level maps have been predicted over the plant. The objectives of the project have been to optimise the use of absorption material, to find a model for a distributed source (machines and steel plates) and to predict the sound reduction that can be achieved. The noise radiation from the machines in the model is based on measurements of the machines in the existing steel hardening line. As the machines are large and the computer model uses monopoles the machines have been modelled as a number of monopoles. The sound level predictions are done in octave-band from 125 Hz to 4 kHz. Th

Aikawa, Y.

• DEVELOPMENT OF MULTI-FUNCTION TIME DOMAIN CONTRIBUTION ANALYZER AND ITS BASIC PERFORMANCE
  O. Sekiguchi, Y. Takano, H. Mae and Y. Aikawa
[Abstract]

This paper describes the development of multi-function time domain contribution analyzer and its basic performance. This analyzer has two functions. One is time domain contribution analysis and the other is spectrum analysis. The contribution analysis function is to identify the noise source using adaptive signal processing. The spectrum function is to monitor the signals from each channel and to calculate the power spectrum, coherence, transfer function and cross-correlation. The analyzer performance is verified by the speaker tests. Results show that the contribution level of each sound source can be estimated within 2dB.

Airo, E.

• AN EXACT METHOD TO DETERMINE THE INFLUENCE OF NOISE CONTROL MEASURES IN WORKPLACES
  J. Keränen, V. Hongisto, E. Airo and P. Olkinuora
[Abstract]

In a Finnish research project the effects of accomplished noise control measures were to be determined in 10 existing workplaces. One of the primary objects was to develop a simple and exact measurement method that could be used to verify the influence of typical noise control measures. The method should take into account fittings, screens and other obstacles that have influence on the sound propagation. In the new method sound pressure levels are measured at work stations using an omnidirectional loudspeaker in carefully selected locations. The workshop's inherent noise can not be utilized as the test sound because the noise level varies too much. Measurements are done before and after the noise control measures in the same measurement positions. The influence of the noise control measure is described in decibels as the in situ sound attenuation or insertion loss. The application of the method in one workplace will be presented as an example. The new method was compared to existing methods: the reverberation time method and the spatial sound distribution method according to ISO/CD 14257. The reverberation time method produced a rough underestimated approximation of the influence of noise control measures. ISO/CD 14257 produced DL2 and DLf parameters but not intuitive values of the influence in sound pressure levels. The new method produced the influence directly in decibels at work stations, which is the information that the customers are interested in. This method has also been used to test the reliability of the room acoustical computer model of a workplace. The test is especially recommended in large, flat and fitted halls.

Akdag, N.

• NOISE PROBLEMS CAUSED BY ROAD TRAFFIC IN CLASSROOMS
  N. Akdag, A. Erdem Aknesil and Z. Karabiber
[Abstract]

Human learning depends strongly on verbal learning. Research has shown that the quality of the acoustical environment is a significant element at the verbal learning. One of the most important factor that harms the excellency of the acoustics is noise. This fact motivated an impressing and growing body of research on the harmful effects of the noise throughout the educational process. In this context, the effects of road traffic noise has been investigated at the primary schools selected among schools situated at the various noise zones at ýstanbul. Outdoor and ýndoor measurements were carried out at the mostly effected classrooms of the schools. The architectural properties of these classrooms were also investigated from acoustical point of view. The results of the measurements were evaluated according to the National and International regulations, and high noise levels and long reverberation times have been determined. On the other hand, surveys have been realised on the users of these classrooms that's to say on the students and the teachers. The ratio of the students affected from noise was also determined to visualise the extent of the issue. Comparison of the subjective evaluations with the measurements shown good correlation. High noise levels caused annoyance, poor intelligibility and adverse effects both on students and teachers. As the ratio of the influenced users was also, it is determined that a widespreat research has to be realized in order to highlighten the problem in National dimention and a research project is designed in this frame.

• EFFECTS OF NOISE ON WORKERS IN PRODUCTION SPACES
  M. Serefhanoglu Sözen and N. Akdag
[Abstract]

The negative effects of noise pollution on our activity and health is known as a very important problems on these days. The existence of noise may effect almost all different kind of activities and cause many health problems. The noise problems has especially more important in the workshops and factories because of the existence of the noise sources like machines. The aim of this study is to examine the noise effects on workers in the ''ready to wear'' and leather workshops situated in Istanbul. On this aim, indoor noise levels have been determined in many workshops to select the workshops where the noise level exceed the acceptable levels in. At the selected workshops, the questionnarie survey has been done to determine the corelation between subjective evaluations and measurements. As a conclusion, it has been determined that, seveny percentage of workers have been effected by noise in negative way. A high ratio of workers are suffered disturbance due to the noise. On the other hand, this study has to be extended as a widespread research in order to visualize the importance of this problem in national dimension.

Akgül, A.

• SOUND QUALITY AND LOW NOISE DESIGN
  H.T. Belek, E. Altinsoy and A. Akgül
[Abstract]

The noise radiated from the household appliances is a serious problem in our daily life. Moreover sound quality of household appliances has become an important parameter in gaining the market advantage. Wet and dry type vacuum cleaners are among the noisiest household appliances and therefore their sound quality has high correlation with their sound power level. The reduction of the vacuum cleaner noise has become a main concern of manufacturers in order to comply with European Union Directives. Major parameters of vacuum cleaner design are sound power level, sound quality and efficiency. Vacuum cleaners should be designed with minimal disturbing sound without reducing their efficiency. The purpose of this study is to achieve acceptable noise reduction on a particular wet and dry type vacuum cleaner. For this purpose, the principal sound sources are evaluated, then systematic noise control techniques are applied on a prototype vacuum cleaner. Airborne noise and structural noise sources are effectively treated and the sound quality of the product is improved. The main purpose of this investigation is twofold; firstly, to describe a noise control study that resulted in 8 dB(A) reduction in sound power level at a moderately low cost with an efficiency reduction of only 2 %; secondly, to propose a set of design p

Akishita, S.

• 2DOF ACTIVE CONTROL OF SOUND TRANSMISSION IN INTELLIGENT COMPOUND STRUCTURE
  Y. Mitani, S. Akishita and S. Fang
[Abstract]

The paper describes 2DOF active control of sound transmission in an intelligent compound structure, size of which is 40(width)x150(length)x1.2(thickness)mm. The panel is made of piezoelectric element which contains three pole domains for actuators and sensors respectively. The element is sandwiched by stainless steel plates to reinforce the strength of structure. The filtered-epsilon and frequency weighted LQR algorithm are applied to cope effectively with random nature of incident sound wave. Sound power emitted from the panel with and without control is estimated to evaluate the effect of the control system.

Akita, T.

• INVESTIGATION OF SOUND INFORMATION THAT AFFECTS PERSON'S ATTENTION AND BEHAVIOR
  T. Akita
[Abstract]

Similarly to visual information, many kinds of sound that are intended to transmit some information to people exist in usual sound environment. People usually use such sound information to determine their action. However, it is not obvious what kind of sound information is available in usual sound environment. In the present research, a field study and a questionnaire survey are carried out to reveal what kind of sound information people take into account when they determine their behavior. Results show that people do not use sound information so much to determine which way to go under way-finding condition, but they use it to decide their immediate and short-term action, for example avoidance of risk, when sound information attracts their attention. Following the investigation, measurement to reveal the characteristics of typical sound information is carried out. Results show that nighttime signal-to-noise ratio is larger than daytime in almost all of the samples. They also show that multiple sound information that has similar intensity exists simultaneously in a small area. It is suggested that the physical character of sound information should be controlled according to the variation of the intensity of back ground noise for proper transmission of sound information, otherwise it may become noise source. It is also suggested that simultaneous existence of multiple sound information in a small domain makes the meanings of information difficult to recognize. It is necessary that each sound information is controlled spatially and timely in such a case.

Al-Saleh, O.

• NOISE INSIDE TRANSIT VEHICLES: MAGNITUDE AND RIDER PERCEPTION
  B.P. Chandrasekhar, P. Koushki, M.A. Ali and O. Al-Saleh
[Abstract]

Similar to worldwide trend, traffic congestion during the daily peak hours is gradually reaching serious proportions in Kuwait. The promotion of public transit systems and the consequential demand shift - from the private auto to public transit vehicles is a cost-effective method to relieve congestion. A competitive quality of service , however is a pre-requisite to shifting demand, away from the private auto to transit vehicles. The objectives of this research project were to: 1. Monitor traffic noise inside bus transit vehicles in Kuwait, and 2. Determine riders' perceptions of noise inside these vehicles. A sample of bus routes were randomly selected from among the Kuwait bus transit system routes. Traffic noise was measured continuously (2 samples per second) inside 60 randomly-selected buses operating on the study routes (mean route travel time was 22.6 minutes). Measurements were repeated six times during each peak and off-peak periods. During each noise monitoring period, the driver and a sample of passengers who were willing to participate in the study were questionnaire surveyed. In addition to their socio-economic traits, the sample respondents'perception of noise inside the bus transit vehicles were sought. The respondents also reported their perceived welfare and health impacts of noise. Surprisingly enough, the mean leq was 80.9 dBA ranging from a low of 70.6 to a high of 106.7. More than 71% were annoyed by noise inside the buses, 51% from the engine noise.53% believed that the traffic noise in general affected their physical and psychological health. Between 20-25% respondents indicated that noise caused headache, nervousness and potentially a hearing damage. More than 50% felt fatigued because of the noise inside the transit buses. 52% would shift to another mode of travel because of noise if they had a choice. Nearly 80% of the sample ridership however, reported satisfactions with bus travel time, service frequency and comfort. more than 35% indicated that both air and noise pollution inside buses were ''bad'' and ''very bad''. Different nationalities perceived annoyance differently (chi-square=20.7, df=10 p0.1). A number of recommendations conclude the paper.

Albertson, F.

• DIFFERENT METHODS TO COUPLE A NONLINEAR SOURCE DESCRIPTION IN TIME DOMAIN TO A LINEAR SYSTEM
  F. Albertson
[Abstract]

In duct acoustics the fundamental sound generating mechanisms must often be described by nonlinear time domain models, while a linear frequency domain model is sufficient for describing the sound propagation in the connected duct system. This applies both for fluid machines such as IC-engines and compressors and for brass wind instruments. Hybrid methods for coupling a nonlinear source description to a linear system description have been proposed by several authors. In this paper a number of those methods are compared concerning accuracy, calculation time and the possibility to perform parametric studies. The model problem is a simple piston - restriction system connected to a straight open pipe. In this model, the piston and restriction are considered as the source part, modelled nonlinearly, while the pipe is modelled linearly. The considered methods are the harmonic balance method, another iteration method, a convolution method and filter techniques like FIR and IIR. The harmonic balance method was for example found to be a powerful tool for prediction of the steady-state periodic regime. It is fast and it provides a possibility to perform parametric studies with a low computational cost.

Ali, M.A.

• NOISE INSIDE TRANSIT VEHICLES: MAGNITUDE AND RIDER PERCEPTION
  B.P. Chandrasekhar, P. Koushki, M.A. Ali and O. Al-Saleh
[Abstract]

Similar to worldwide trend, traffic congestion during the daily peak hours is gradually reaching serious proportions in Kuwait. The promotion of public transit systems and the consequential demand shift - from the private auto to public transit vehicles is a cost-effective method to relieve congestion. A competitive quality of service , however is a pre-requisite to shifting demand, away from the private auto to transit vehicles. The objectives of this research project were to: 1. Monitor traffic noise inside bus transit vehicles in Kuwait, and 2. Determine riders' perceptions of noise inside these vehicles. A sample of bus routes were randomly selected from among the Kuwait bus transit system routes. Traffic noise was measured continuously (2 samples per second) inside 60 randomly-selected buses operating on the study routes (mean route travel time was 22.6 minutes). Measurements were repeated six times during each peak and off-peak periods. During each noise monitoring period, the driver and a sample of passengers who were willing to participate in the study were questionnaire surveyed. In addition to their socio-economic traits, the sample respondents'perception of noise inside the bus transit vehicles were sought. The respondents also reported their perceived welfare and health impacts of noise. Surprisingly enough, the mean leq was 80.9 dBA ranging from a low of 70.6 to a high of 106.7. More than 71% were annoyed by noise inside the buses, 51% from the engine noise.53% believed that the traffic noise in general affected their physical and psychological health. Between 20-25% respondents indicated that noise caused headache, nervousness and potentially a hearing damage. More than 50% felt fatigued because of the noise inside the transit buses. 52% would shift to another mode of travel because of noise if they had a choice. Nearly 80% of the sample ridership however, reported satisfactions with bus travel time, service frequency and comfort. more than 35% indicated that both air and noise pollution inside buses were ''bad'' and ''very bad''. Different nationalities perceived annoyance differently (chi-square=20.7, df=10 p0.1). A number of recommendations conclude the paper.

Allard, J.F.

• OPTIMISATION OF A FREE FIELD TECHNIQUE FOR THE MEASUREMENT OF THE REFLECTION COEFFICIENT AT REAL ANGLES OF INCIDENCE
  G. Jansens, J.F. Allard, W. Lauriks and G. Vermeir
[Abstract]

One of the problems related to in-situ measurements are the finite dimensions of the sample and the presence of neighbouring walls, which cause disturbing reflections. One option is to apply a time window to the measured data and 'cutting' these reflections away. This can only be done when the delay of these reflections is sufficiently large. Therefore it is convenient to locate the source as near as possible to the surface. Often the reflected component of the sound field above a reflecting surface is considered coming from a 'mirror source' with corrected source strength. This 'mirror source' description of the sound field above an absorbing surface is not accurate enough if this source is located close to the surface. In this paper a more precise representation of the sound field above an absorbing plane will be presented, which results in a correction term in comparison with the mirror source model. This corrected mirror source model turns out to be valid for much smaller source-material distances then present models and makes no assumptions about the nature of the material local/extended reacting). It will be shown that the sound pressure at three positions above the material is sufficient to determine the reflection coefficient according to the corrected mirror source model. It appears however that this method is very sensitive to noise (source height, temperature and measurement noise), which makes it very difficult to obtain reliable results.

Allemang, R.

• NOISE SOURCE EVALUATION TESTING ON MTS SERIES 320 ROAD SIMULATOR
  E. Frenz, S. Dumbacher, R. Allemang and M. Mergeay
[Abstract]

The MTS Series 320 Road Simulator, well known for durability testing, are more and more used for general acoustic evaluations, e.g. squeak and rattle evaluations, ... during the development process of today's cars. This calls for specific noise characteristics of the testing devise. The purpose of this study was to perform a detailed noise source evaluation of the Road Simulator. A number of acoustic tests were conducted. First the baseline noise characteristics, followed by the location and quantification of the noise sources. In the next part of this paper the evaluation of use of enclosures in isolating the noise sources was studied. Finally, recommendations are formulated and implemented, resulting in strongly improved noise characteristics.

Almeida, A.M.

• A NOISE STUDY ON THE NEW LISBON AIRPORT
  M.J. Palma, J.L. Bento Coelho and A.M. Almeida
[Abstract]

The existing Lisbon airport is located practically within the city limits, since the city has developed towards the surrounding airport area. The planning of a new airport, outside the city boundaries, has called for a comparative noise study on two alternative locations: Ota and Rio Frio. A noise study was conducted which included a survey of the ambient noise and of their sources and the prediction of air traffic noise for two different scenarios of transport capacity: 12,000 and 25,000 passengers per year. The reduction of aircraft emissions owing to technological evolution was envisaged and accounted for. The impact of aircraft noise was assessed on the basis of the number of population exposed to noise levels, with 10 dB intervals above 55 dB(A). For values lower than this, annoyance was considered to be unimportant, during daytime. As expected, the population exposed to noise levels above 55 dB(A) rises with the increase of airport capacity for the two locations. Nevertheless, when a 5 dB(A) reduction in aircraft emissions is considered, as a benefit of technological development, the population exposed to LAeq values above 55 dB(A) is quite similar for the two scenarios and even decreases for levels above 65 dB(A). These results helped to show that the introduction of new noise control technologies would compensate for higher aircraft traffic. The investments of the airport authorities on noise measures and procedures for the new airport would then be valid and effective for a long period of time.

• NOISE MAPPING OF ROAD TRAFFIC NOISE IN PORTUGAL
  J.L. Bento Coelho, J.R. Mateus, M.J. Palma, A.M. Almeida and C. Patrício
[Abstract]

The Portuguese Road Authority has started a broad programme of mapping of road traffic noise for the major roads in the country. This work has been developed together with the Group of Acoustics and Noise Control of CAPS/IST, Lisbon Technological University. The maps will be available to the local authorities and the general public for planning purposes as well as for general information. The noise maps are drawn by calculation. Input data for the model include the traffic density and composition as well as the mean speed for each traffic lane, the type of pavement and the characteristics of the road and of the surrounding land. A set of measurements was made in order to verify and validate the model. These noise maps can be regularly updated by checking on the traffic and recalculating with new traffic data. The daytime values of LAeq are determined in points of a grid for an area established around the road line. This area was initially defined as 300 m wide, but it is now 500 m wide, since it was thought as more appropriate. Noise values are calculated in 5 dB(A) intervals and the colour code defined in ISO 1996 is used for presentation of the results. A sample of the first noise maps will be presented and discussed in terms of both the method and the results.

Alsina, R.

• URBAN PLANIFICATION AND GENERATION OF DIVERSE AREAS OF ACOUSTIC SENSIBILITY
  R. Alsina
[Abstract]

In urbanistic planning we have traditionally considered diverse parameters, such as transportation, parking places, different soil uses, edification conditions, leisure areas, services, etc. However, we have never considered noise as a determining factor, when it should be in the majority of cases,if we want to have urban zones with greater acoustic quality. The best preventative measure, referring to noise, for implanting in our cities and in most cases the only one, would be to consider preventing noise in the planning phase, attaining a good distribution of existing sources, protecting the reception areas and compatibilitating needs, suitibilities anb quality of life. The prevention of the sound impacts in the planification stage, be done fundamentally in the projects of new urbanistic areas. The biggest difficulty and the greatest challange will be improvement of the acoustic quality in historical centres and the other consolidates of our city areas. In these cases, the application of some correctative measures has great difficulties. In the future, a bigger effort will be necessary, as much in investments as in campaigns to introduce the population to new habits in their everyday life.

Altabella, J.

• ANALYSIS AND SYNTHESIS OF URBAN NOISE ENVIRONMENTS
  J. Altabella
[Abstract]

For the analysis of acoustic impact in the urban plans and the evaluation of improvement strategies in urban noise environments, it is of prime importance the use of a tool capable of simulating results both in numeric terms and sense perception. To introduce a methodology to evaluate noise in our towns, not only upon noise quantity criteria but also upon quality criteria of urban noise scenery, we have developed a system for analysis and synthesis of urban noise environments based on source analysis. Sources are separately identified, quantified and characterized in order to establish a set of rules and laws that allow synthesis from pure sources. In addition, we have designed two software tools for the analysis and synthesis. The first one is based on a GIS system to access data (urban,social, economics, energy, etc...) in Barcelona city. The second one consists of a GIS-connected software module, which makes calculations of noise level and indicators. Synthesis is realized by mixing up the corresponding sources according to the model chosen. Results are displayed, and synthesized noise is played by the system's multimedia tools. This analysis is being developed within the ''Life'' project, in Barcelona and other towns in Catalonia such as Mataró, Vilassar de Mar, Calella de la Costa, etc., by making simultaneous sound recordings and noise measurements that enable us to set up the model and gather the pure sources that constitute sound environment.

Altinsoy, E.

• SOUND QUALITY AND LOW NOISE DESIGN
  H.T. Belek, E. Altinsoy and A. Akgül
[Abstract]

The noise radiated from the household appliances is a serious problem in our daily life. Moreover sound quality of household appliances has become an important parameter in gaining the market advantage. Wet and dry type vacuum cleaners are among the noisiest household appliances and therefore their sound quality has high correlation with their sound power level. The reduction of the vacuum cleaner noise has become a main concern of manufacturers in order to comply with European Union Directives. Major parameters of vacuum cleaner design are sound power level, sound quality and efficiency. Vacuum cleaners should be designed with minimal disturbing sound without reducing their efficiency. The purpose of this study is to achieve acceptable noise reduction on a particular wet and dry type vacuum cleaner. For this purpose, the principal sound sources are evaluated, then systematic noise control techniques are applied on a prototype vacuum cleaner. Airborne noise and structural noise sources are effectively treated and the sound quality of the product is improved. The main purpose of this investigation is twofold; firstly, to describe a noise control study that resulted in 8 dB(A) reduction in sound power level at a moderately low cost with an efficiency reduction of only 2 %; secondly, to propose a set of design p

Ambrosini, A.

• A REFINED BE TECHNIQUE FOR MODELLING RADIATION AND SCATTERING FROM VIBRATING STRUCTURES: EXPERIMENTAL VALIDATION OF BEM RESULTS OBTAINED USING LASER DOPPLER VIBROMETRY
  R. Di Sante, R. Bernetti, G. Rossi and A. Ambrosini
[Abstract]

In this paper, a refined Boundary Element technique, developed to model radiation and scattering from vibrating structures in the frequency domain, is validated in the case of a small reverberating room by comparison with acoustic measurements. An experimental set-up was built consisting of a box-shaped structure, with a wall excited into vibration by an electro-dynamic shaker. A fairly good agreement was found between numerical and experimental results. In order to ease the definition of boundary conditions in the case of experimental vibration data, a special interface with a Scanning Laser Doppler Vibrometer was also developed.

Ameling, C.B.

• NOISE AND CARDIOVASCULAR DISEASES: FIRST RESULTS OF A META-ANALYSIS
  E. Van Kempen, H. Kruize, H.C. Boshuizen, C.B. Ameling and B.A.M. Staatsen
[Abstract]

To get more insight in the health effects of noise exposure, a meta-analysis of epidemiological studies on noise and cardiovascular effects was carried out. From reviews it appears that studies on the relationship between noise exposure and cardiovascular effects show contradictory results. Furthermore, some of the reviews had important drawbacks such as the lack of clear selection criteria for evaluating the literature and poor descriptions of the methods. Tables and/or figures, presenting individual study results, were hardly shown. At the moment, no reliable dose-response relationships on noise and cardiovascular diseases are available. Therefore a meta-analysis was carried out. This is a quantitative analysis of study results. Epidemiological studies investigating the relationship between noise exposure and blood pressure and/or ischeamic heart diseases (ICD-9: 410-414) and published between 1970-1999 in English, German or Dutch, were selected. Eventually, about 40 occupational and community-based studies were evaluated. Effects such as blood pressure changes, changes of hypertension rates, rates of angina pectoris and myocardial infarction, were investigated. Three noise exposure sources were distinghuished: noise from road traffic, air traffic and occupational noise. The studies showed contradictory results and appeared to be heterogeneous on several important study characteristics. Exposure characterisation was a problem: in community-based studies, stationary measurements are often used as an indicator for exposure. However, it remains the question if this is a good proxy for personal exposure to noise. Funnelplots showed publication bias: studies, finding negative results, are often not published. Further results, including quantitative risk estimates and sensitivity analysis, will be presented.

Andow, K.

• A MODIFIED CALCULATION METHOD AND ITS ACCURACY FOR FLOOR IMPACT SOUNDS ON LARGE-SPAN SLABS FROM SOFT AND HEAVY IMPACT SOURCES
  T. Koga, M. Tano and K. Andow
[Abstract]

The Impedance Method is a commonly used method to predict floor impact sounds by soft and heavy impact source. According to the development of structural design, condominiums constructed with large-span slabs have an area of approximately 80 square meters: nearly equal to the average for the typical one-family Japanese condominium. This structural method allows architectural designs without the restrictions of beams and columns. However, the Impedance Method overestimates these sounds in large-span slabs. Because this method originated from investigations on small slabs with an area of around 25 square meters, it should not be applied to large-span slabs. We modified the impedance method so it applies to these large-span slabs. Calculations using the modified method agreed with in situ measurements: within 1 dB on average with a standard deviation of 3 dB.

Andrade, S.M.

• URBAN NOISE CONTROL BY LEGISLATION IN RIO DE JANEIRO
  J. Slama, D. Da Silva De Sousa and S.M. Andrade
[Abstract]

The Humid Tropical Climate, as it is the case of Rio de Janeiro, imposes some restrictions in constructions. From bio-climatic architectural analysis, it is possible to verify that there is a necessity of natural ventilation and that the exterior walls should be of small thermal capacity. An observation of the facades of streets as ''Nossa Senhora de Copacabana'' shows that in general, in spite of a high external noise, the windows stay opened during almost all the day and then people are not well protected from the noise in its dwellings. A solution to control the urban noise would consist to close the windows and to install an air conditioning system. But this solution is usually very expensive for a great part of the local population whose income is relatively low. A different solution was tried in Rio de Janeiro. It consists in controlling the urban noise using legislation which limits the noise at the source. Usually, urban noise legislation try to limit the noise at the imission and not at the emission. This new legislation has to define maximum noise level at the emission and also the measurement method. It has to be compatible with an imission-based legislation. In this work a comparison is performed of the two strategies of emission and imission legislation showing the limitation of the first one.

Anfosso-Lédée , F.

• TIRE/ROAD NOISE : 3D MODEL FOR HORN EFFECT
  A. Fadavi, D. Duhamel, P. Klein and F. Anfosso-Lédée
[Abstract]

Within the problem of tire/road noise, this work deals with the horn effect. Between the curved tire tread fore and aft of the tire/road interface and the road surface there is a space which forms an acoustical horn which increases the radiation efficiency backwards and forwards up to 10 dB(A). This effect has to be considered in a general model for tire/road noise. A 3D tire model is used for this purpose. The tire is modeled by a cylinder. An excitation source is placed on the tread and sidewalls near the contact patch. The sound pressure and sound amplification are caculated in the space arround the 3D tire model using the Boundary Element Method (BEM). The influence of different parameters such as the position and size of the source are studied in terms of amplification and sound pressure spectrums. It is shown that the position of the source has a very important influence when its size has negligible influence. To validate the 3D model, a comparaison between numerical and analytical solutions is proposed for the case of a sphere on a flat surface. The 3D analytical model for the sphere is based on an existing model using modal decomposition of the sound pressure. Finaly, the 3D solution is compared to the 2D solution. An important difference between theses solutions is obsereved.

Anfosso-Lédée, F.

• TIRE/ROAD NOISE : COMPARISON OF 2D AND 3D MODELS FOR HORN EFFECT
  F. Anfosso-Lédée, P. Klein, A. Fadavi and D. Duhamel
[Abstract]

This paper deals with the amplification effect of tire/road contact noise, also called horn effect , that is due to the multiple reflections between the curved and hard surface of the tyre and the road pavement. This ''horn effect'' is expected to be reduced on porous pavements due to the properties of sound absorption. The approach described here is two dimensional : a rigid cylinder of infinite length is set on a rigid flat road surface. An acoustic line source is located on the tire near the contact. The amplification is calculated at a receiver point in the horn, first using an analytical model, based on the modal decomposition of the sound pressure. In order to introduce sound absorption properties on the road surface, a 2D-BEM model was used. Agreement for rigid case between analytical and BEM models was checked. Then, porous road pavement was introduced in the BEM, using a phenomenological model with 4 parameters (porosity, specific flow resistance, shape factor and thickness). A non local type of surface reaction was considered. The results are finally compared with experimental results in which a long tube of concrete is submitted to an acoustic point source. Amplification results are presented when the tube is set either on a dense or on a porous road surface. A separate additional paper by Fadavi & al. will present the three dimensional approach.

• IN SITU METHODS FOR THE CHARACTERISATION OF ROAD NOISE BARRIERS EFFICIENCY
  F. Anfosso-Lédée, V. Steimer and P. Demizieux
[Abstract]

Different acoustic properties of road noise barriers can be measured on site : global characteristics of insertion loss, or intrinsic characteristics of sound absorption and sound transmission. For insertion loss measurement, the standardised method ISO 10847 was tested on a basic case of real road barrier. The reliability of the method was checked, including location of receiver points and reference point, duration of measurements, meteorological considerations, comparison of direct and indirect approach on an equivalent site. The results of three independent laboratories were compared. Major practical difficulties arose showing a lack of applicability of the method. Moreover, rather poor comparison was obtained with this ISO method, showing that direct and indirect methods are not equivalent and meteorological conditions should be better defined, especially for long range characterisation of insertion loss (around 100 meters). Typical duration of measurements should be extended to 15 to 30 minutes, and a correcting factor of 4 dB instead of 6 dB should be considered for receiver points located on a reflecting surface. For intrinsic characteristics of sound absorption and transmission, an experimental comparison was made between two impulse methods : the French standardised method AFNOR 31089 using a gun shot, and Adrienne  method developed by a European research group and suggested as a future European Standard. This later method uses an MLS signal plus subtraction technique to get better results in low frequencies. A rather good agreement was found between both methods and differences are discussed.

Anthoine, J.

• NOZZLE DESIGN EFFECT ON VORTEX INDUCED INSTABILITIES IN AN AXIAL INJECTED COLD FLOW MODEL OF THE ARIANE-5 EAP
  J. Anthoine, D. Yildiz and J.-M. Buchlin
[Abstract]

The aeroacoustics of solid propellant boosters is currently being investigated at the von Karman Institute as a part of a CNES program related to the Ariane-5 solid propellant boosters. The geometry considered has a segmented combustion chamber consisting three cylindrical segments and a submerged nozzle. Two inhibitor rings ensuring thermal protection separate the three segments. The hot burnt gas flow in the combustion chamber originates radially from the solid fuel surface and then develops longitudinally before reaching the exhaust nozzle. During the combustion, the regression of the burning surface is faster than the one of the inhibitor rings. Then, the rings become obstacles into the flow-field and generate a significant risk of hydrodynamic instabilities. Flow oscillations are then resulting from periodic vortex shedding at the thermal protections and strong coupling between the vortices and the acoustics properties of the combustion chamber is expected. The research consists of cold flow experiments in order to investigate the nozzle design effect on sound production. Acoustic pressure measurements are taken in a 1/30-scale axisymmetric model of the Ariane-5 EAP with either pure axial or radial injected flows. The model segments are made of sintered-bronze sphere Poral cylinders to get the radial injected flow. Parametrical tests are performed to identify flow-acoustic coupling and to characterize the influence of the nozzle geometry on the pressure fluctuation levels. These measurements are obtained and discussed for different nozzle geometries, different values of inhibitor-nozzle distances, inhibitor internal diameters, booster length and Mach number. The flow-acoustic coupling has been found for some configurations and important conclusion has been addressed to the strong effect of geometry of the submerged nozzle on the amplification of the pressure fluctuations.

Antoni, J.

• INDIRECT RECONSTRUCTION OF IC ENGINE PRESSURE TRACE THROUGH STRUCTURAL VIBRATION INVERSE FILTERING
  J. Antoni, R.B. Randall and F. Guillet
[Abstract]

This paper addresses the feasibility of reconstructing the pressure trace in IC engine from non-intrusive structural vibration measurements, by means of an inverse periodically time-varying filter. Therefore, the deconvolution problem is first formulated in a signal extraction framework and demonstration is made of the optimality of the proposed filter. Then, a solution for its implementation is proposed, based on the assumption of cycloergodicity. Finally, applications are made to real vibration signals issued from a diesel engine. Successes and limitations of the method are discussed in light of these results.

Arana, M.A.

• NOISE CAUSED BY POWER ASSISTED BRAKE: CHARACTERISTICS AND CONTROL
  M.A. Arana, A. Vela and M.L. San Martín
[Abstract]

A power-assisted brake is an element of the braking mechanism which purpose is to supply aid power obtained by the vacuum generated into a chamber. The air intake generates noise inside of the vehicle. In general, this noise is clearly audible. In order to measure the levels and characteristics of that noise it had carried out an experimental device allowing the measurement of the mechanic variables of the actuation (stroke and force) hydraulic circuit (gauge pressure) and noise levels. It will show the dependencies between gauge pressure gradients and sound levels as well as with the actuation velocity. Likewise it will show the noise levels diminution caused by different silencers placed at the air intake. The more important conclusions are the following: a) the maximum noise levels happen simultaneously to the maximum pressure gradients. b) The maximum noise levels are lineal dependent with the actuation velocity, and c) spectral power is dominant around 6 kHz.

Arato-Borsi, E.

• PREDICTION OF THE AUDIBLE EFFECTS IN A BROADCASTING STUDIO, CAUSED BY A NEWLY PLANNED METRO LINE - PART I: ESTIMATION OF DESIGN VIBRATION SPECTRA ON THE STUDIO WALLS AND FLOORS
  P. Forián Szabó, E. Arato-Borsi and F. Augusztinovicz
[Abstract]

A new metro line is being planned in the vicinity of the main buildings of the Hungarian Radio in Budapest. The task, the proposed paper reports about was to predict, whether or not audible disturbances in consequence of the train pass-by in the tunnel are to be expected, and if this is the case, what kind of control measures are necessary and feasible (determination of minimum separation distance in the ground between the new tunnel and the broadcasting studios, vibration isolation in and construction of the tunnel etc.). A prediction method was elaborated and verified on existing metro lines and buildings under similar conditions. It consists of essentially three major steps: development of a vibration prediction model on the basis of measurements; adoption of calculation methods for sound level prediction from vibration data; and verification of the calculations and development of guidelines for the tunnel design. This lecture deals with the first step: How to estimate the design vibration spectra on several parts of the broadcasting studio structures, based on vibration measurements along the metro tunnel, transmission from similar tunnels and soil conditions as well as calculations on a similar building on an existing metro line.

• PREDICTION OF THE AUDIBLE EFFECTS IN A BROADCASTING STUDIO, CAUSED BY A NEWLY PLANNED METRO LINE - PART III: VERIFICATION OF THE PREDICTION METHOD, COMPARISON OF MEASUREMENTS AND CALCULATIONS
  E. Arato-Borsi, P. Forián Szabó, F. Kvojka and F. Augusztinovicz
[Abstract]

The third part of the paper series demonstrates the applicability and accuracy of those methods presented in Parts I and II. First, another building in the vicinity of an existing metro line was selected in the same area of Budapest with similar conditions (including building structures, soil conditions, tunnel depth and distance from the building etc.). Operational building vibrations were measured and eigenfrequencies determined. The finite element modal model was verified and updated on the basis of the measurements, and forced responses for realistic vibration conditions were run. The statistical calculations were based on measured wall vibrations and room acoustic parameters. The calculated sound pressure levels were compared to measured spectra and it was found that, in spite of many assumptions and approximations, relatively good agreement was found. Therefore, the method was applied to the studio building and it could be established, that without special vibration control measures, noise problems are to be anticipated.

Arcas, G.

• DESIGN OF A SOUND LEVEL METER WITH GSM INTERFACE
  J.M. López, M. Ruiz, M. Recuero and G. Arcas
[Abstract]

NOWADAYS ONE OF THE MOST COMMON TASKS FOR AN EXPERT IN ACOUSTICS IS TO EVALUATE THE ACOUSTIC IMPACT IN CERTAIN AREAS OF A CITY. THIS IMPLIES TO MOVE AROUND EXPENSIVE MATERIAL AND THE PEOPLE NEEDED TO HANDLE IT. FOR THIS PURPOSE THE DEVELOPMENT OF A DIGITAL SOUND LEVEL METER BASED ON A DIGITAL SIGNAL PROCESSOR (DSP) THAT COULD BE OPERATED REMOTELY USING THE PUBLIC COMMUNICATION NETWORKS IS PROPOSED. ONE OF THE POSSIBLE PUBLIC NETWORKS TO BE USED WOULD BE THAT OF G.S.M. USING THE SHORT MESSAGE SERVICE THAT PROVIDES THIS SYSTEM. THE DESIGN OF THIS SOUND LEVEL METER IS BASED ON A SINGLE DSP AND LOW POWER ELECTRONICS SO IT CAN BE OPERATED WITH BATTERIES.

Arditi, D.

• SOUND TRANSMISSION LOSS OF MULTILAYERED ELEMENTS: COMPARISON OF CALCULATED AND MEASURED RESULTS
  S. Kurra and D. Arditi
[Abstract]

The impedance model developed by Au and Bryne is one of the few models for prediction of sound transmission loss values of multilayered structures and validated by the measurements using the intensity technique. The model enables calculations for hard materials with or without damping layer and for air or porous material between the layers. This approach was developed as a computerized model for building elements consisting of various layer-structures to be able to facilitate further investigations on sound insulation as well as applications in practice and, the calculated results were in good agreement with the published data. Further comparisons were made with the experimental results by using ISO 140 method in the laboratory. In this paper, some of the findings from this study are presented and the discrepancies between the results are revealed.

Arlaud, B.

• THE GIS CHAOS (DESIGN AND PLANNING OF THE NOISE ENVIRONMENT)
  O. Balay and B. Arlaud
[Abstract]

Noise has been a subject of much concern for many years now to the ''city managers'' (elected representatives, town planners, architects.....). These latter have effective tools which can carry out the modelling of noise emissions and automatic calculations of noise levels in front of buildings exposed to road infrastructure. The map drawings which follow provide quantitative data (noise levels, areas of sound propagation...) which make it possible to diagnose the situation and decide on the implementation of protective and normative strategies (installing sound-proof walls, deviating traffic...). However, since the application of these strategies or norms the city dwellers do not necessarily feel better off. All studies over the last 15 years have shown the noise environment to be one of the main causes of dissatisfaction in French towns. It is for this reason that new directions of research have been opened up, notably by the CRESSON. They now lead the developer to take qualitative data into account to be able to apprehend better the relation between the town dwellers and their noise environment. The creation of GIS ChAOS has therefore been the occasion of designing an easy-access GIS tool, which would enable the noise situation of a particular site studied to be quickly apprehended. The data base has been created to orientate noise representation towards current operational attitudes and to foster the reflection and imagination of town developers and administrators. As sound qualifies time, ChAOS proposes to represent localised sound temporalities. Furthermore, on a pedagogical strain, this GIS links up the visualisation of qualitative information whilst distinguishing between the representation of the noise environment observed or estimated by an ''informed observer'' and the noise environment experienced by the town dwellers. Finally, it integrates sound tracks as referential aids to be able to devise concepts of noise planning or to propose and correct a given acoustic environment. In summary, the Paper will state the guiding lines which lead to the setting up of this GIS. It will reveal several possible applications for urban management. CRESSON : Research Centre on the urban noise environment UMR 1563 Architectural and urban surroundings, CNRS / Ministry of culture, Architectural Schools of Grenoble and Nantes, Address : Architectural School of Grenoble, 60 avenue de Constantine, BP 2636, F. 38036 Grenoble Cedex 2 GIS : Geographical Information System. Bibliography : The representation of the urban noise environment using a GIS, by Olivier Balay together with Blaise Arlaud, Sylvie Serbigne, Robert Laurini, Myoung-Ah Kang and Anne-Claire Chanlon. CRESSON (Research Centre on the urban noise environment UMR 1563 Architectural and urban surroundings, CNRS / Ministry of Culture, Architectural Schools of Grenoble and Nantes), LISI (Information systems engineering laboratory, Computer Department, Claude Bernard University, INSA Lyon), LISI, CRESSON, Lyon, Grenoble, October 1999.

Arlinger, S.

• THE DEVELOPMENT OF NOISE INDUCED HEARING LOSS DURING THE 1980'S AND THE 1990'S IN THE SWEDISH COUNTY OF ÖSTERGÖTLAND
  M. Johansson and S. Arlinger
[Abstract]

The objective of this study was to investigate the change over time in hearing threshold levels (HTL:s) among employees in different occupations. The question was; does the improvement of HTL:s during the 1970's and 1980's shown in previous studies continue into the 1990's? The subjects were selected from the existing HTL database in the county of Östergötland in Sweden and separated in age groups of 30-39, 40-49 and 50-59 years old. The time periods for audiometry were 1971-1976, 1981-1986 and 1991-1996. The subjects had been exposed to occupational noise more than two hours a day and the categories of occupation were mechanical work and wood processing. A total number of 15054 audiograms were included in the statistical analysis. The results show that the HTL:s of people employed in these occupations have decreased between the 1980's and the 1990's and the trend with decreasing noise-induced hearing loss in Sweden during the 1970's and 1980's continues into the 1990's. The difference between the right and the left ear was also investigated and in all groups with side difference the HTL was larger at the left ear. Possible explanations to the improvement might be a wider use of hearing protectors at work and during military service. The results show that the hearing conservation programs still are meaningful and that the awareness of noise induced occupational hearing loss has improved.

Arnau, J.

• NOISE STUDY OF RAILROAD TRAFFIC IN THE CITY OF GIRONA.
  J. Arnau
[Abstract]

During a six months period, readings of the noise produced by different types of trains were made (fast trains type ''TALGO'', conventional passenger trains and shipping trains) so were the speeds of all of them. This has been done on an elevated railway about 2 kms long, to check the distribution of ''isophones'' on the horizontal plan as on the vertical section. Different streets coming from the same railway were selected in order to realize these readings over different distances from the emission focus so this ''isophones'' could be appreciated and translated into graphs, and it's shape logically linked to the urban structure of the city. On the vertical section, noise controls were done over the same railway and in the adjacent buildings so the ''isophones'' could be obtained, and the incidence of noise in the different levels of the habitat be checked. Likewise surveys were done among the population straightly affected during the day and so at night, in order to check the degree of bothering caused by noise and related to the activity developed.

Arntzen, O.M.

• DESIGN AND FUNCTIONALITY OF A NEW MILITARY NOISE CALCULATION MODEL
  O.K.Ř. Pettersen, O.M. Arntzen, H. Olsen and N.I. Nilsen
[Abstract]

Noise from activity in military training fields is often regarded as a problem, and attracts attention from both local communities and national environment authorities. To cope with the different interests it is often necessary to optimize the military activity with respect to noise. Since topography and weather conditions have proven to influence sound propagation outdoors significantly, these effects has to be taken into account in the day to day planning and accomplishing of training activity. The Norwegian Defence Construction Service has initialized the development of a new military noise prediction model that is designed both for planning and follow up of military training activity. The model includes the acoustical effects of varying topography, meteorology and surface impedances. Most important however is the user interface of the program, which is designed for non-expert operation with easy visual point and click operations on a background of digital maps. The paper will present version 1.0 of this military calculation model, with focus on the underlying algorithms and functionality.

Arras, C.

• SIMPLIFIED CHARACTERISATION OF NOISE EXPOSURE TO TRAFFIC NOISE IN URBAN AREAS
  C. Arras
[Abstract]

The large number of exposure situations to traffic noise in cities make noise quality plans difficult. A methodology to classify noise exposure zones and to draw noise exposure maps is presented. Its purpose is to help local authorities make decisions on environmental design and assessment of performance of a plan in a simple way. The methodology is based on classifications of both sources and built environments. In cities, streets must be classified in terms of their function and their specific traffic parameters related to the governed flow patterns rather than in terms of averaged flow. A classification of built areas in terms of noise penetration effects linked with reflection, scattering and diffraction on building surfaces, with specific road cross sections is proposed. The strong interaction between the source and the receiving environment is discussed in terms of its influence on noise exposure. This approach has been applied to large urban areas in French cities. With this methodology and using a data base of in-situ studies, the characterisation of noise exposure in cities can be performed without large calculation and measurement programmes. It is an efficient tool to characterise an existing situation and to propose solutions to improve it.

Arruda, J.R.D.F.

• THEORETICAL COMPARISON OF ACTIVE NOISE CONTROL USING POTENTIAL ENERGY ERROR SENSING AND INTENSITY ERROR SENSING
  L.V. Donadon and J.R.D.F. Arruda
[Abstract]

This paper presents a theoretical comparison between pressure and intensity-based control strategies for active noise control in ducts. The control methods used for each strategy are the Frequency-Domain, Filtered-X LMS, which uses pressure as the cost function, and a method named ASIC (Active Sound Intensity Control), which uses mean active sound intensity as the cost function. A duct with two types of termination - open-ended, and rigidly terminated - was modeled using the Spectral Element Method. These models allowed the evaluation of the performance of the controllers in environments with propagation and reverberation. The criteria used to analyze the results were the potential energy density, the mean active intensity, and the total acoustic power radiated by the sources working together, compared with the primary source alone.

Arsenio, E.

• MEASURING HOUSEHOLDS' ANNOYANCE FROM ROAD TRAFFIC: AN INTERMEDIATE STEP WITHIN AN INNOVATIVE NOISE VALUATION MODEL
  E. Arsenio, J. Patrício, A. Bristow, A. Pinelo, F. Silva and M. Wardman
[Abstract]

In urban areas, road traffic noise is referred as the most important cause of community annoyance. Although road traffic can be associated to several impacts on human health and effects on psychological well-being, such as stress reactions, increase in risk of heart and circulatory diseases, interference with communications and activities, sleep disturbance, etc., these social costs are usually ignored in the transportation and land use planning process. As part of an on-going research study on the valuation of noise impacts from road traffic, this paper presents some of the results of an extensive survey that was administered to more than 400 households in a residential area in Lisbon. A computer program designated NOISE was developed, and several types of data (revealed, stated, attitudinal) were combined for valuing noise impacts, and the influence of differentiated 'noise environments' (indoors and outdoors) on households' location decisions was assessed. The case study covered respondents living in blocks with different conditions of exposure to noise from road traffic. Noise levels were also measured in each flat, and several noise parameters were reported (Leq, L50, L10, L90,L95, Lmax). The results presented herein show the link between households' perceptions of their noise environment indoors, degree of annoyance and type of disturbance effects, with those real physical noise measures taken in each location. In this phase, the most adequate parameter for representing this type of community annoyance can be presented.

Asdrubali, F.

• INFLUENCE OF FILTERING SYSTEM ON HIGH SOUND INSULATION VENTILATING WINDOWS
  F. Asdrubali and F. Cotana
[Abstract]

A new opportunity to protect buildings located near motorways or high traffic roads is constituted by High School Insulation Ventilating Windows (HSIVW). These windows show good insulation performances and, meanwhile, allow airflow through the window itself. In a previous work acoustic and airflow performances of the windows have been measured; in the present paper the research is carried on by putting a filter in the aerator of the windows; the filter is necessary to make the inlet airflow cleaner. Acoustic (single number sound reduction index Rw) and airflow (air flow through the aerator g) performances are again measured with regard to four different filters, including one with active carbon. Experimental investigation shows that the windows equipped with filters still present high sound insulation, with good airflow properties. The airflow reduction due to the filters, in fact, varies from 10 to 40%, but is still high enough for the ventilation and cooling of the building.

Ashihara, K.

• AUDIBILITY OF COMPLEX TONES ABOVE 20 KHZ
  K. Ashihara
[Abstract]

Psychoacoustic experiments were designed to investigate if ultrasonic components would have any influence upon sound impression. Human subjects were required to discriminate between complex sounds with and without ultrasonic components. The maximum level investigated was 80 DBSPL/component. All subjects could distinguish the harmonic complex with components above 20 kHz from one without any ultrasonic components when there were intermodulation distortions in the audible area. When there were no distortions, however, discrimination was not achieved. It was concluded that ultrasonic might not have any significant influence upon sound impression.

Asselineau, M.

• TRANSPORTATION NOISE IN CINEMA HALLS : SOME PRACTICAL WAYS OF REDUCING THE DIN
  M. Asselineau
[Abstract]

Most standards covering the acoustics of cinema halls specify some rather stringent background level limits, that range down to the 50 Hz mark and lower. However, for commercial purposes, cinemas are often located near such transportation corridors as motorways and rail lines. While the intrusion of such noise was considered unavoidable in older projects, the quest for quality is now prompting the operators to improve the sound insulation of their halls with regards to such sources. Following a brief reminder of the usual requirements in effect, a few case studies of recent projects (covering the noise and vibration control of cinemas located by such sources as a light rail terminal, a heavy rail line, and even a high speed rail line) are submitted, looking into the context of the situation as well as into the technical solutions that were eventually applied in the building or on the trackwork. One of the main conclusion is that while quite a few noise and vibration control solutions are now available, several of them are not really suitable to the fast pace of the cinema projects, especially when speed interferes with either technical prowess or coordination of various parties. More to the point, the acoustical education of building engineers and cinema operators often remains to be done, especially when acoustics have to be made compatible with the structural requirements or the safety regulations.

Atalla, N.

• NOVEL MIXED FINITE ELEMENT FORMULATION FOR THE ANALYSIS OF SOUND ABSORPTION BY POROUS MEDIA
  M.A. Hamdi, N. Atalla, L. Mebarek and A. Omrani
[Abstract]

This paper presents a novel mixed finite element formulation very well adapted for the analysis of the absorption of elastic and acoustic waves propagating in porous or fibrous media. The proposed formulation is based on modified Biot's equations written in terms of the skeleton displacement (U) and the acoustic pressure p in the pores of an inhomogeneous media. It generalizes the previous mixed (U,p) formulation proposed by Professor Atalla & co, and has the great advantage of automatically satisfying all boundary conditions without having to compute surface coupling integrals at porous sub-domain interfaces. When elastic forces in the skeleton are neglected, the formulation automatically degenerates to an equivalent fluid model taking into account inertial coupling with the skeleton.In addition the present formulation has the advantage over existing formulations of reducing the number of degrees of freedom per node (dof/node)to four (4) and only to one (1) when elastic forces are negligible in the skeleton. The implementation of this new generalized formulation and associated equivalent fluid finite element model in RAYON-PEM Solver developed and integrated by STRACO in the graphical environment of I-DEAS Vibro-Acoustics,solves several practical problems in transportation industry. It is shown in this paper that the results obtained with the new formulation agrees very well with the experimental results using impedance tube and vibro-acoustic measurements on treated multi-layered structures.


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• ACOUSTIC ABSORPTION OF HETEROGENEOUS POROUS MATERIALS
  F. Sgard, N. Atalla, X. Olny and R. Panneton
[Abstract]

The paper deals with the numerical investigation of the acoustic absorption performance of materials made up from a combination of thin porous patches, with different acoustic properties. The heterogeneous material is bonded onto a hard-walled termination of a semi-infinite rectangular wave-guide. The numerical model is based on an equivalent fluid finite element description for the porous material patches and a modal description of the acoustic field in the wave-guide. Experimental results are presented that validate the model in the special case of a double porosity porous material i.e macro-perforated porous material. The influence of several geometric and physical parameters is then predicted using the proposed model. It is shown that absorption may be increased in a large frequency band by using non-homogeneous patch-works.

• EXPERIMENTAL VALIDATION OF 3-D POROELASTIC FINITE ELEMENTS BASED ON BIOT THEORY
  N. Dauchez, S. Sahraoui and N. Atalla
[Abstract]

The paper deals with experimental validation of 3-D poroelastic finite elements based on Biot displacement theory in the context of vibroacoustic applications. The validation is based on the determination of the characteristics of the porous material as input parameters for simulations. Emphasis is made on the determination of the mechanical properties of the skeleton. The validation experiment concerns the impedance measurement of a porous sample in a duct. The porous sample has been chosen so that one resonance of the skeleton can be observed in the frequency range 50-500 Hz. In that case a real 3-D behavior of the material with skeleton motion and acoustic coupling is observed. Various lateral boundary conditions are carried out : sample bonded to the duct or separated by an air gap of thickness 1.8 mm or 5 mm. Isotropic and transverse isotropic elasticity laws for the skeleton are tested. Good tendencies are found in terms of resonance location and absorption efficiency. Isotropic law using adequate characteristics gives the best results, although the skeleton is not isotropic. This shows that the determination of the viscoelastic properties of the skeleton is a very sensitive matter in the modeling of poroelastic materials.

Atmoko, H.

• ACOUSTIC CHARACTERISTICS AND CANCELLATION PERFORMANCE OF A BASIC FREE-FIELD NOISE CANCELLOR
  S.E. Wright and H. Atmoko
[Abstract]

Before considering the acoustic characteristics and cancellation performance of multichannel freefield active noise control systems, it was considered important first to establish the detailed acoustic performance of a basic single channel system consisting of the successive axial alignment of the primary source (to be cancelled), the secondary cancelling source (loudspeaker) and the detection system (microphone). This paper addresses the radiation characteristics/sound cancellation performance of this fundamental canceller, both theoretically and by measurement. The computer modelling uses point sources. Here the propagating (radiation) terms are included, but the near field reactive terms are neglected. This is considered adequate for small but finite sources at low frequencies. The measurements were made in an anechoic facility at the University of Huddersfield. The chamber is 5mx5m by 4m high and treated with 10cm surface treated dense fiber glass, with a nominal cut of frequency of 200 Hz. It is confirmed that the basic radiation cancellation directivity depends on the primary-secondary source separation distance rps. It can be tripole, dipole or quadrupole like for rps equal to l/4, l/2 and l respectively, where l is the acoustic wavelength. The cancellation depth in the direction of the detector increasing with decreasing rps, increasing with increasing secondary source-microphone distance rsm and source-observer distance rpo and becoming sharper (narrower) with increasing frequency. The laboratory measurements compare well with the theoretical predictions given by the computer modelling. This gives confidence in predicting the radiation properties in the far field (at large distances from the source) and supports the notion that deep shadows generated by multi unit systems, implemented into hardware, will be realisable.

Attenborough, K.

• PREDICTIONS OF GROUND EFFECTS OVER UNEVEN AND DISCONTINUOUS TERRAIN IN THE PRESENCE OF REFRACTION AND TURBULENCE
  S. Taherzadeh, K. Attenborough and K.M. Li
[Abstract]

The De Jong semi-empirical formulation for sound propagation above a ground with an acoustic impedance discontinuity has been modified to incorporate effects of atmospheric refraction and turbulence. The revised model is described and used to predict the effect of an acoustically hard region of ground near the source on the sound level received by an observer. The predictions of the modified model for a non-turbulent atmosphere are compared with those of a hybrid Boundary Integral Equation/Fast Field Program (BIE/FFP) method developed previously. The predictions indicate that the extended model agrees reasonably well with the BIE/FFP at 1 kHz but not very well at 200 Hz.

• IMPROVED CALCULATION METHODS FOR ASSESSING ENGINE TEST NOISE
  O. Zaporozhets, V. Tokarev and K. Attenborough
[Abstract]

Engine testing can give rise to many complaints around airports. In the absence of barriers, the main influence on propagation from an engine test is ground effect - the influence of interference between direct and reflected sound waves. Three methods of predicting ground effect are compared with each other and with some data for aircraft engine noise at run-up. All techniques allow consideration of the different types of ground cover, including mixed covering, that are usually found inside and outside airports. Also it is possible to consider the influence of various types of source components including monopole, dipole or quadrupole.

• A CELL MODEL FOR THE ACOUSTICAL PROPERTIES OF FIBROUS ABSORBENTS
  O. Umnova, K. Attenborough and K.M. Li
[Abstract]

A new two-parameter cell model is developed to predict the acoustical properties of fibrous absorbents with fibres oriented normal to the sound propagation direction. The expressions for dynamic drag parameters are derived for monodisperse as well as for polydisperse arrays. A relationship between complex density and complex compressibility has been obtained. The model gives good agreement with acoustical data if measured values of permeability and porosity are used.

Audoly, C.

• FEASIBILITY OF EXPERIMENTAL DETERMINATION OF SEA DAMPING LOSS FACTORS OF SUBMARINE STRUCTURES
  C. Audoly and G. Borello
[Abstract]

Statistical Energy Analysis is a useful technique to predict at the design stage average noise and vibration levels on ships or submarines, in particular self noise levels on sonar arrays due to machinery on-board noise or flow noise. In order to achieve accurate predictions, it is necessary to introduce realistic damping loss factors in the models. For that purpose, an experiment was conducted on a specific facility whose structure is representative of a piece of submarine hull. Damping loss factors and other parameters of portions of the hull and of some connected structures have been obtained along frequency up to several kHz, using excitation either with a shaker or a hammer, the second method being quicker to operate. The results have shown consistency of the data and confirm the feasibility of the technique, even for thick structures as those used on ships or submarines.

Auger, J.-M.

• INSULATION OF ALUMINIUM FRAME-DOUBLE GLAZING WINDOWS BY MEAN OF BEA/FEA MODELING
  J.-M. Auger, H. Defosse, M.A. Hamdi, C. Barras, D. Benoualid, P. Mulocher, B. Mottelet, M. Rehfeld, P. Cotté, C. Midelet and M. Szezygiel
[Abstract]

This paper presents significant results of the research program on the insulation of aluminium framed windows glazed with sealed double glazing conducted by a consortium of partners. This consortium involves industrial partners which develop window components i.e.: SAINT GOBAIN for double glazings, HUTCHINSON for seals, TECHNAL and A.S. for aluminium window frames. The vibro-acoustic simulation of the window is conducted by STRACO by using I-DEAS Vibro-Acoustics and RAYON solver. The window insulation analysis is conducted both numerically and experimentally: - Experiments are performed by partners with their transmission facilities in order to compare results and validate models. - Simulation are conducted by using an original FEA/BEA modeling approach capable to represent the transmission problem by taking into account structural details related to seals, frame and glass as well as internal acoustic cavities and external radiation. Comparisons between experimental an numerical insulation results show a good agreement and a parametric analysis provides indications on the influence of parameters which characterize seals, frame and the double glazing.

• VIBRO-ACOUSTICS ANALYSIS OF A MEDICAL XRAY SOURCE : HYBRID APPROACH COMBINING EXPERIMENT AND FEA/BEA MODELING
  J.-M. Auger, F. Damagnez, M.A. Hamdi, S. Ayadhi and E. Chabin
[Abstract]

A vibro-acoustics analysis of a medical X-Ray source is presented . As the X-Ray source noise is generated by the interactions between the internal rotor and its bearing which are very complicated to describe, the analysis is carried out by using an hybrid approach combining experimental data measured on the system and an elasto-acoustics FEA/BEA model. This methodology , already applied for automotive and aerospace domains, uses RAYON solver integrated in the MCAE environment of I-DEASTM. Firstly, an inverse procedure is applied to determine an equivalent source model as a set of internal forces derived from vibration measurements in running condition and the elasto-acoustic model. Secondly, the BEA model and the source previously found are used to compute the radiated noise. Experimental and numerical results of both vibrations and radiated noise are finally compared. Such approach yields to a vibro-acoustics model capable to help for the path noise analysis and for the numerical modification analysis which have been applied to lead to several noise reduction improvements on the X-Ray source.

Augusztinovicz, F.

• INVERSE METHODS FOR SOURCE STRENGTH RECONSTRUCTION OF COMPLEX STRUCTURES
  F. Augusztinovicz and F. Márki
[Abstract]

Inverse methods for source strength reconstruction may be required when the source is not accessible for direct vibration measurement for any reason, e.g. when the source is rotating, too hot, too complex to access etc. A common feature of these methods is that the relationship between source vibration and the radiated field is expressed in terms of a transfer function matrix, generated in many different ways such as experimental, analytical or numerical methods. Provided that a detailed sound pressure field mapping around the source to be identified is feasible, the unknown vector of the vibration input of the system can be determined by matrix inversion. The paper gives a short overview of various inverse techniques. Special attention is paid to a newly emerging and promising numerical technique, the inverse boundary element method. Various mathematical procedures such as Singular Value Decomposition and Thikhonov regularization is outlined, and a physical interpretation of these highly abstract mathematical tools and the obtained data are discussed. The applicability and typical results of the procedure is demonstrated on real-life, mainly automotive structures.

• PREDICTION OF THE AUDIBLE EFFECTS IN A BROADCASTING STUDIO, CAUSED BY A NEWLY PLANNED METRO LINE - PART I: ESTIMATION OF DESIGN VIBRATION SPECTRA ON THE STUDIO WALLS AND FLOORS
  P. Forián Szabó, E. Arato-Borsi and F. Augusztinovicz
[Abstract]

A new metro line is being planned in the vicinity of the main buildings of the Hungarian Radio in Budapest. The task, the proposed paper reports about was to predict, whether or not audible disturbances in consequence of the train pass-by in the tunnel are to be expected, and if this is the case, what kind of control measures are necessary and feasible (determination of minimum separation distance in the ground between the new tunnel and the broadcasting studios, vibration isolation in and construction of the tunnel etc.). A prediction method was elaborated and verified on existing metro lines and buildings under similar conditions. It consists of essentially three major steps: development of a vibration prediction model on the basis of measurements; adoption of calculation methods for sound level prediction from vibration data; and verification of the calculations and development of guidelines for the tunnel design. This lecture deals with the first step: How to estimate the design vibration spectra on several parts of the broadcasting studio structures, based on vibration measurements along the metro tunnel, transmission from similar tunnels and soil conditions as well as calculations on a similar building on an existing metro line.

• PREDICTION OF THE AUDIBLE EFFECTS IN A BROADCASTING STUDIO, CAUSED BY A NEWLY PLANNED METRO LINE - PART III: VERIFICATION OF THE PREDICTION METHOD, COMPARISON OF MEASUREMENTS AND CALCULATIONS
  E. Arato-Borsi, P. Forián Szabó, F. Kvojka and F. Augusztinovicz
[Abstract]

The third part of the paper series demonstrates the applicability and accuracy of those methods presented in Parts I and II. First, another building in the vicinity of an existing metro line was selected in the same area of Budapest with similar conditions (including building structures, soil conditions, tunnel depth and distance from the building etc.). Operational building vibrations were measured and eigenfrequencies determined. The finite element modal model was verified and updated on the basis of the measurements, and forced responses for realistic vibration conditions were run. The statistical calculations were based on measured wall vibrations and room acoustic parameters. The calculated sound pressure levels were compared to measured spectra and it was found that, in spite of many assumptions and approximations, relatively good agreement was found. Therefore, the method was applied to the studio building and it could be established, that without special vibration control measures, noise problems are to be anticipated.

• COMPUTER AIDED ACOUSTIC DESIGN AT A THEATRE RECONSTRUCTION - REALITIES AND SIMULATION RESULTS
  A. Nagy, A. Kotschy, A. Fürjes and F. Augusztinovicz
[Abstract]

During the design of the reconstruction of a Hungarian theatre, several room acoustic measurements were carried out in the existing auditorium. The applied instrumentation was an MLS based digital signal processing system; reverberation times, impulse responses and more complex parameters derived from IR were determined. Parallel to the measurements, the acoustical analysis of the original condition and that of the new, designed interior was performed by means of computer models, based on the laws of geometrical acoustics. We have compared the results of the measurements carried out on the spot to those of the computer models, obtained from two different software systems. The results were applied to evaluate and update the room acoustic computer models of the currently existing state of the theatre, in order to enable to perform a meaningful simulation of the new interior design of the auditorium.

Aujard, C.

• DIAPASON: EFFICIENT HELP TOOL IN THE DECISION PROCESS FOR LOCAL AUTHORIT
  D. Vaucher De La Croix, C. Aujard and O. Laurent
[Abstract]

In the framework of LIFE Environment projects funded by the European Community, Greater LYON which gathers 55 local authorities composing the Lyon Urban Community, has successfully proposed the ''DIAPASON'' project, (Double InitiAtive Pour l'Amélioration de l'environnement SONore en milieu urbain) (Double Initiative for the Improvement of Noise Environment Quality in the City), in partnership with METRAVIB RDS and ACOUCITE association. The aim of DIAPASON is to put in place at Greater LYON a genuine follow-up and management tool of noise environment in the city and thus to contribute in an active manner to the improvement its citizens quality of life. Elaborated and developed by METRAVIB RDS (with a technical follow-up by a Committee of expert acousticians), who has been conducting for several years important projects relating to problems linked to city noise environment, this tool for help in the decision process is specifically designed for decision makers, the city services and technicians concerned by any problem of acoustic nuisance. Simple and userfriendly, DIAPASON is integrated in a Geographic Information System and thus offers a possibility of mapped data and relevant crossing (noise, population,...). The proposed paper/presentation will focus on the original content of the tool, with a special attention to both quantitative (physical noise) and qualitative (noise sensitivity, potential annoyance) approaches of noise in urban cities. The implemented methods on both aspects will be presented, as well as the range of present possibilities of DIAPASON in order to simulate dedicated urban projects (modifications in the city travels, new road infrastructures and/or implementation of new equipment, local developments,...) and to display their impact in terms of noise and potential annoyance at the city global scale. Finally, a brief outline will be given on the way the operation of DIAPASON software will assist local authorities to : help to define the priorities in terms of noise protection and their evolution in the long run, contribute to the implementation of a dynamic policy in the city noise control and promote a sustainable development of the city noise environment quality.

Auzilleau, S.

• SOUND PRESSURE LEVEL AND ENVIRONMENTAL NOISE: A NATIONAL REGULATION FOR NIGHTCLUBS AND CONCERT HALLS
  S. Auzilleau
[Abstract]

Since the end of 1999, a new regulation has come into effect in France. It concerns concert halls, nightclubs and any closed place where loud music is usually played. This new regulation aims to protect the hearing of the audience as well as the environment of these halls, while keeping in with the general pattern of the French government policy regarding noisy leisure and entertainment activities, such as motorcar races or shooting ranges. The sound pressure level inside nightclubs and concerts halls is limited to 105 dB LAEQ (measured on a period of 15 minutes) in every place where the audience can stand. In addition, the owners must make a complete noise impact study of their establishment, in order to ensure that the noise annoyance for the environment is reduced to the minimum.

Avikainen, T.

• THE PASSIVE FLOW AND NOISE CONTROL ELEMENT OF THE ELECTRONIC COOLING SYSTEM
  T. Avikainen
[Abstract]

Fans are commonly used for enhancing the cooling of electronics (improve heat transfer due to higher air velocities). Dynamic losses will increase flow vorticity and the turbulence level due to the complex flow fields of electronic devices. The flow turbulence is strenghtened further at the fans that increase the pressure drop. The air flow turbulence functions as a local noise source. Near to the fans there wuold be a great need for flow controlling elements. This presentation describes the principle that is beneficial in terms of a more effective airflow and a sufficient thickness of noise absorption material to damp even low frequency components of fan noise.

Ayadhi, S.

• VIBRO-ACOUSTICS ANALYSIS OF A MEDICAL XRAY SOURCE : HYBRID APPROACH COMBINING EXPERIMENT AND FEA/BEA MODELING
  J.-M. Auger, F. Damagnez, M.A. Hamdi, S. Ayadhi and E. Chabin
[Abstract]

A vibro-acoustics analysis of a medical X-Ray source is presented . As the X-Ray source noise is generated by the interactions between the internal rotor and its bearing which are very complicated to describe, the analysis is carried out by using an hybrid approach combining experimental data measured on the system and an elasto-acoustics FEA/BEA model. This methodology , already applied for automotive and aerospace domains, uses RAYON solver integrated in the MCAE environment of I-DEASTM. Firstly, an inverse procedure is applied to determine an equivalent source model as a set of internal forces derived from vibration measurements in running condition and the elasto-acoustic model. Secondly, the BEA model and the source previously found are used to compute the radiated noise. Experimental and numerical results of both vibrations and radiated noise are finally compared. Such approach yields to a vibro-acoustics model capable to help for the path noise analysis and for the numerical modification analysis which have been applied to lead to several noise reduction improvements on the X-Ray source.

Baaj, M.

• MANAGING NOISE EMISSION IMPACTS OF AIRPORT TRAFFIC
  M. El-Fadel, M. Chahine, M. Baaj and T. Mezher
[Abstract]

Airport traffic is a major source of community concerns due to aircraft noise emissions particularly in locations close to airports and aircraft flight tracts. The principal effects of aircraft noise on humans include hearing damage risk, and speech and sleep interference which can develop into stress. As such, it becomes essential to locate, design, and/or expand airports as well as optimize flight paths in a way to reduce noise exposure to nearby communities. For this purpose, it is essential to assess changes of noise impact resulting from new or extended runways or runway configurations, evaluate new traffic demand and fleet mix, evaluate revised routings and airspace structures, assess alternative flight profiles, and modifications to others operational procedures. This paper present the calibration and application of the US Federal Aviation Administration integrated noise model (INM) for the analysis and prediction of airport traffic emission noise impacts from aircraft operations on communities near the proposed expansion at the Beirut International Airport. For this purpose, field noise measurements were collected at sensitive noise receptors along selected locations around the airports and the corresponding airport traffic flow was characterized. Noise levels were then simulated as a function of the different airplane classes, flows, flight path and landing characteristics. The model was also used to predict future noise levels, optimize airplane flight path, and assess mitigation measures to minimize potential airport noise emission impacts. In addition, a local field survey was conducted to better understand the influence on the community response to aircraft noise and document the extent of annoyance and activity disturbance caused by noise.

Baba, H.

• STUDY OF EFFECTIVENESS OF AMBULANCE VEHICLE'S SIREN SOUND AS WARNING DEVICE FOR ITS DUTY RUN
  H. Baba
[Abstract]

The loud siren sound of an ambulance vehicle is intended to let the other drivers and pedestrians in the vicinity know of its approach, so that they can yield to its way. It is widely known to researchers that for the subject drivers, however, that warning sound is hardly audible because car windows are all closed air-tight. What is not known to most researchers is the degree of effectiveness that this warning device actually possesses for persuading drivers within the field of operations to yield. This research targeted 5,000 ambulance crews in 89 cities in Japan, and investigated their perceptions of siren sound as a feasible warning device during their duty operations in various field situations. This study data and analyses suggest the following conclusions: (1) The way other drivers yield to the ambulance is poorly mannered; (2) In the field, duty operations encounter various hindrances, especially at the cross road; (3) The siren sound is considerably effective for persuading for the yield actions; (4) Although the siren sound is appropriate in warning to some extent, alternative methods of warning should be devised for various reasons.

Babisch, W.

• ASSOCIATION BETWEEN NOISE ANNOYANCE AND INCIDENCE OF ISCHAEMIC HEART DISEASE IN THE CAERPHILLY AND SPEEDWELL STUDIES
  W. Babisch, H. Ising and J.E.J. Gallacher
[Abstract]

In a cohort study, the association between annoyance and disturbances due to road traffic noise and the incidence of ischaemic heart disease (IHD) was studied in 3930 middle aged men. During a 6y follow-up period 305 IHD cases were detected. Dependent on the item used, non-significant odds ratios between 0.9 and 1.4 were found in highly noise annoyed/disturbed subjects as compared to less annoyed/disturbed. However, this relationship was found to be strongly modified by pre-existent diseases. i. e. In subjects free of any chronic disease at the beginning of the follow-up, significant odds ratios between 1.7 and 2.9 were seen. In the subgroup with chronic diseases no noise effects were seen. This surprising result of non-effect in the potential risk group of sick people may be due to the dilution of the true effect due to recall bias. Regarding the objective noise level measurement the opposite was found. In this case noise and disease stress tended to act synergistic on the incidence of IHD. In conclusion, prevalence of disease is an important effect modifier on the articulation of subjective exposure indicators. Noise studies in which exposure is assessed on a subjective basis must be viewed with caution in this respect.

Badie-Cassagnet, A.

• CHARACTERISATION OF SMALL CIRCULATION PUMPS AS SOURCES OF VIBROACOUSTIC ENERGY
  K. Trdak, A. Badie-Cassagnet and G. Pavic
[Abstract]

Recently, a need for the characterisation of noise generated by small circulation pumps (P 200 Watts) arose given their application in heating systems for habitat. As their acoustic radiation is negligibly low, the vibration and the pressure pulsation are of primary concern for the vibroacoustic characterisation of circulation pumps. The characterisation method presented here is based on the energetic approach - the pump is characterised in terms of the structure- and the fluid- borne power that it injects in the pipe. The powers are determined on a specially designed test rig from vibration and pressure pulsation measured on the pipe by an arranged set of 4 accelerometers and 2 pressure transducers. The use of intensity measurement techniques allows to separate both the pipe's vibration and pressure pulsation into the out- and the in-coming waves. The injected power is calculated out of experimentally determined amplitude of the out-coming wave, geometric and material properties of the pipe and the internal water. The application of this method on the set of different pumps enabled to identify the vibration and pressure pulsation excitation frequencies for each pump as well as to classify selected pumps in terms of the structure- and the fluid-borne powers that they inject in the pipe. Finally, the comparative measurements realised with the same pump and different anechoic terminations show evidence of low sensibility of the injected power on the variation of the pipe's boundary conditions. This can be considered as a principal novelty concerning this work.

Bae, J.

• THE COUNTERMEASURE FOR THE NOISE AND VIBRATION OF COMBUSTION TURBINE EXHAUST GAS DUCT
  J. Bae, W. Kim and K. Chung
[Abstract]

An excessive noise and vibration was encountered in the combustion turbine exhaust gas duct connected to the heat recovery steam generator. This phenomenon was found only when water was added to the fuel injection to reduce NOx contents of the combustion turbine exhaust gas. To investigate the noise and vibration characteristics, measurement was performed around exhaust gas duct and gas turbine, and the acoustic analysis for the exhaust gas duct by SYSNOISE was carried out to check the cavity mode of the exhaust gas duct. From the measurement and analysis results, and the noneffective reinforement on the duct wall panel, it was concluded that the severe noise and vibration occurred due to the acoustic resonance between the duct cavity mode and the excitation frequency induced by turbulent gas flow during water injection. Therefore the installation of baffle plates inside the duct was proposed to change the cavity mode of the exhaust gas duct. To confirm the effect of the baffle plates and the change of the noise and vibration phenomenon, noise and vibration measurement was carried out. From the measurement results, the vibration response of the duct wall panel was considerably reduced to 20 - 30% of the original ones and more than 10 dB(A) of noise level was reduced in sound pressure level.

Bai, M.R.

• DSP IMPLEMENTATION OF ACTIVE NOISE CONTROLLER FOR CENTRIFUGAL FANS
  J.-D. Wu and M.R. Bai
[Abstract]

This paper describes an application of active noise control to reduce blade passing noise for centrifugal fans using an adaptive feedforward control structure. Most of studies for reducing fan noise are associated with aerodynamics and discuss the influence of different geometric parameters. In recent years, a variety of research have achieved the active cancellation (ANC) of noise in ducts. A proposed noise control system with a ontrol loudspeaker mounting at the cutoff region of the fan is designed. The controller based on the filtered-X LMS (least mean squares) with multi-sine reference input and frequency counting has accelerated the convergence of the algorithm by using a digital signal processor (DSP). Experiments are carried out to evaluate the proposed design for reducing the fundamental blade passing noise and harmonic frequency noise at various flow rates. The results of experiment indicate that the synthetic, periodic noise generated by loudspeaker can be reduced up to 25dB and blade passing noise from a pr

Bakir, F.

• STUDY OF AEROACOUSTIC BEHAVIOR OF AN AXIAL FAN: EXPERIMENTAL VALIDATION
  S. Kouidri, F. Bakir, K. Maaloum and R. Rey
[Abstract]

The research carried out in our research laboratory (LEMFI-Site Paris) has as aims the analysis and the design of turbomachinery: pumps, fans, and compressors. The developed computational tools, based on the flows between the blade, allow to define with an increasingly satisfactory precision, the fine kinematics of the internal flow. However, the complexity of the unsteady phenomena governing the aeroacoustic behavior of the fans requires at the same time a theoretical approach and, in the current state of the progress of the work, an experimental validation. The noise due to the blades is accessible today by calculation while the sound level broadband is still not easily foreseeable. It depends on the type of fan (axial, centrifugal, mixed-flow,...), of its immediate environment, the distance between the rotor and the stator, blade load, speed of rotation and functioning point: design flow rate or partial. The modelization proposed is based on the calculation of the unsteady load applying to the blade and finding their origin in the fluctuations of the modulus and the direction of the speed of upstream flow. A model was retained making it possible to take into account the statistical properties of the turbulence. The mode of the stacking up of the sections is also taken into account by considering the blade as three distinct radial sections. The validation of the measurement of noise constitutes the principal objective of this communication. For this we carried out an aeraulic test bench in conformity with the standard ISO 5801, equipped with the principal following apparatuses of measurement: - Tube Ø350 equipped with an anechoïc termination. - Micromanometers with analog link on chart of acquisition. - Tube of Pitot doubles Furness for the determination of the flow rate. - 3 microphonic 1/2 '' with turbulence screen in rotatable duct section. The whole of the installation allowed us to carry out tests in accordance with the standard ISO 5136 relating to the measurement of sound power generated by the fans in duct. The principal aeroacoustic results presented relate to an axial fan (Ø 300 mm) of which speed varies from 1200 to 3000 rpm: evolution of the global noise (balanced A) according to the speed of rotation and of the flow rate. In a second stage, the study carried on the variation of acoustic pressure level with the speed of rotation and its comparison with the dipolar models.

Balant, A.C.

• A COMPARISON OF TWO METHODS FOR THE EVALUATION OF PROMINENT DISCRETE TONES - PHASE 2
  R. Hellweg, M. Nobile and A.C. Balant
[Abstract]

The desire by manufacturers to evaluate the potential annoyance of prominent discrete tones in the noise emissions of their products has led to the development of two objective procedures: (1) the Tone-to-Noise Ratio (TNR) method, contained in ECMA-74-1997 and ANSI S1.13-1995, and (2) the Prominence Ratio (PR) method, also in ANSI S1.13. For many product noise emissions, the results of the two procedures are equivalent and correlate well with subjective ratings. However, for some noises, particularly those with harmonic series or multiple tones in the critical band, the procedures give conflicting results. A task group of the Inter-Committee Working Group on noise from information technology and telecommunications equipment (ITTE) has been conducting a study on both procedures in order to understand and resolve the conflicts, with an eventual goal of optimizing a single method and incorporating it into relevant international standards. This paper presents an update on the inter-company study of prominent discrete tones that was reported at INTER-NOISE 99. The task group has measured and recorded the sounds of many ITTE products that produce discrete tones and has evaluated these objectively and subjectively. A comparison of the objective ratings from different laboratories has been performed to estimate the inter-laboratory stability and reproducibility of the objective measures. The relative success of the two objective methods in predicting the engineers' subjective ratings also is discussed, as a

• PSYCHOACOUSTIC COMPARISON OF TWO METHODS FOR THE EVALUATION OF PROMINENT DISCRETE TONES
  A.C. Balant, K. Barringer, B.a. and M. Nobile
[Abstract]

This paper presents the results of two pilot studies comparing the efficacy of the Modified Tone-to-Noise Ratio method and the Prominence Ratio method in assessing the subjective prominence of discrete tones in noise. Ten normal-hearing subjects rated the prominence of synthetic stimuli and real machine noises containing spectral features that are problematic for the two methods. Both methods showed strong positive correlations with the subjective prominence ratings of the synthetic stimuli, and weaker positive correlations with the ratings of the machine noises. Results and implications for future research are discussed.

Balay, O.

• THE GIS CHAOS (DESIGN AND PLANNING OF THE NOISE ENVIRONMENT)
  O. Balay and B. Arlaud
[Abstract]

Noise has been a subject of much concern for many years now to the ''city managers'' (elected representatives, town planners, architects.....). These latter have effective tools which can carry out the modelling of noise emissions and automatic calculations of noise levels in front of buildings exposed to road infrastructure. The map drawings which follow provide quantitative data (noise levels, areas of sound propagation...) which make it possible to diagnose the situation and decide on the implementation of protective and normative strategies (installing sound-proof walls, deviating traffic...). However, since the application of these strategies or norms the city dwellers do not necessarily feel better off. All studies over the last 15 years have shown the noise environment to be one of the main causes of dissatisfaction in French towns. It is for this reason that new directions of research have been opened up, notably by the CRESSON. They now lead the developer to take qualitative data into account to be able to apprehend better the relation between the town dwellers and their noise environment. The creation of GIS ChAOS has therefore been the occasion of designing an easy-access GIS tool, which would enable the noise situation of a particular site studied to be quickly apprehended. The data base has been created to orientate noise representation towards current operational attitudes and to foster the reflection and imagination of town developers and administrators. As sound qualifies time, ChAOS proposes to represent localised sound temporalities. Furthermore, on a pedagogical strain, this GIS links up the visualisation of qualitative information whilst distinguishing between the representation of the noise environment observed or estimated by an ''informed observer'' and the noise environment experienced by the town dwellers. Finally, it integrates sound tracks as referential aids to be able to devise concepts of noise planning or to propose and correct a given acoustic environment. In summary, the Paper will state the guiding lines which lead to the setting up of this GIS. It will reveal several possible applications for urban management. CRESSON : Research Centre on the urban noise environment UMR 1563 Architectural and urban surroundings, CNRS / Ministry of culture, Architectural Schools of Grenoble and Nantes, Address : Architectural School of Grenoble, 60 avenue de Constantine, BP 2636, F. 38036 Grenoble Cedex 2 GIS : Geographical Information System. Bibliography : The representation of the urban noise environment using a GIS, by Olivier Balay together with Blaise Arlaud, Sylvie Serbigne, Robert Laurini, Myoung-Ah Kang and Anne-Claire Chanlon. CRESSON (Research Centre on the urban noise environment UMR 1563 Architectural and urban surroundings, CNRS / Ministry of Culture, Architectural Schools of Grenoble and Nantes), LISI (Information systems engineering laboratory, Computer Department, Claude Bernard University, INSA Lyon), LISI, CRESSON, Lyon, Grenoble, October 1999.

Baldanzini, N.

• MASS LOADING EFFECTS ON THE PARAMETERS OF A STATISTICAL ENERGY ANALYSIS EXPERIMENTAL MODEL
  N. Baldanzini, K. De Langhe and M. Pierini
[Abstract]

The effects of additional instrumentation mass on a structure in the high-frequency range were investigated in terms of the parameters of an experimental statistical energy analysis (SEA) model built using the power input method (PIM). In previous studies, such as those conduced by Ashory 1998 and Olbrechts et al., 1997, only low-frequency ranges were examined. A T-junction with three connected plates was used in modeling. First, a full set of measurements were carried out on instrumentation with no mass loading effects; on the basis of the results, the model parameters to be used as references in subsequent comparisons were determined. In the second phase, two full sets of measurements were carried out: one with the mass loading effect of the impedance head and one with the mass loading effect of the accelerometers. Comparison of the processed data and the reference values showed that the impedance head failed to affect the equivalent mass and the model's internal and coupling loss factors; the accelerometers, on the other hand, modified the equivalent mass. The impedance head and the accelerometers both affected the determination of the SEA subsystem's modal densities. This behavior may be qualitatively explained by the fact that although all the measurements were undoubtedly affected by the mass loading effect, a cancellation effect-also supported by the SEA formulas-occurred for some parameters. These results are especially important, since not all the errors introduced during measurements can be corrected before processing. Proper knowledge of the performance of the instrumentation and its effects on the model parameters is fundamental in obtaining a good SEA experimental model.

Baldauf, W.

• LOW NOISE PANTOGRAPH ASP - RECENT DEVELOPMENTS
  W. Behr, T. Lölgen, W. Baldauf, L. Willenbrink, R. Blaschko, K. Jäger and J. Kremlacek
[Abstract]

The aeroacoustic noise of a pantograph increases dramatically with the train speed. Especially at a very high speed of 300 km/h and above the aeroacoustic noise of the pantograph may exceed the rolling noise of the wheels. Since it is inappropriate and expensive to build high noise barriers to screen the pantograph, a new design of pantographs is necessary for future high speed trains. In cooperation with DaimlerChrysler Rail Systems an actively controlled single-arm pantograph (ASP) will be developed until next year in order to improve the quality of the contact force fluctuation and to reduce the aeroacoustic noise emission using computer simulation to estimate the aeroacoustic noise. These simulations are very helpful when developing an optimized design and avoiding unacceptable designs in an early state of development. First simulation results of the recent developments of the pantograph head will be presented.

Baligand, B.

• A SYSTEMATIC METHODOLOGY TO ASSESS SUBJECTIVE HUMAN PERCEPTION FROM OBJECTIVE PHYSICAL MEASUREMENTS WITH SEVERAL INDUSTRIAL APPLICATIONS IN TRANSPORT AND ENVIRONMENT
  B. Baligand, T. Mazoyer and D. Fernier
[Abstract]

This paper deals with the way to build a relationship between objective measurements (from physical sensors) and subjective assessments (expert evaluations). Metravib RDS has carried out several studies concerning the vibroacoustic annoyance, the quotation of car engine combustion noise, the gear box changes comfort and, more recently, the evaluation of car drivers ''workload'' for automotive safety. On these latter topics, the developments could be brought up to the stage of dedicated devices, including sensors and real-time onboard processing units, respectively the so-called Combustiometre and the Driver Situation Recognition Unit (DSRU). All these developments are based on a systematic and generic methodology to find a model of the links between measurements of various sensors and the come back of many experiences acquired by ''experts'' (acousticians, ergonoms, human sciences experts,...). The developed strategy is built on the following steps: 1. Over instrumentation of the studied phenomena: a significant number of sensors (chosen according rules of ''good sense'') are used and associated to various preprocessing (means, RMS, or more complex), providing a large set of signals; 2. First step: data reduction based on cross-correlation and signal to noise ratio; 3. Second step: data reduction (or data fusion) based on statistical correlation with the studied phenomena.; only the relevant inputs are kept in a reasonable number (compatible with real-time processing) for model identification; 4. Model identification: pattern recognition algorithms are exploited to assess the model able to link the physical measurements with the subjective data coming from human experts. In other words, a supervised learning phase is completed on adequate algorithms like multivariate mean square approach (Combustiometre*) up to Neural Networks (DSRU**), that guarantee flexibility and robustness. * This development has been run along a PSA/GIE MOTUS collaboration. ** DSRU is a methodology development lead within CEMVOCAS European Program

Ballagh, K.

• LIGHTWEIGHT TIMBER FLOOR DESIGN TO ACHIEVE HIGH SOUND INSULATION AND IMPACT ISOLATION WITHOUT CARPET
  K. Ballagh
[Abstract]

The design of a lightweight timber floor will be described. This floor design was used in a multi-storey apartment block and was required to meet a sound transmission loss of STC 55 and an impact sound insulation of IIC 55. The structural requirements were for a 65 mm thick timber deck, and for aesthetic reasons it was desired to leave the timber exposed. While it was relatively straight forward to add a ceiling to achieve the airborne sound insulation specification it was much more difficult to achieve the impact sound insulation specification with the bare timber surface. A series of experiments were carried out to provide design information and a floor/ceiling design was evolved to meet the specifications. Laboratory and field measurements show the floor design meets requirements.

• DESIGN OF A LIGHT TIMBER FRAMED WALL INCORPORATING STRUCTURAL BRACING
  K. Ballagh
[Abstract]

Light timber frame construction of houses is common practice in New Zealand however for structural reasons it is not commonly used for more then 3 or 4 storeys. In the situation to be described, an apartment building of 5-6 floors was to be built on top of an existing concrete carpark building. Because of the structural limitations of the existing building the weight of the apartment building had to be minimised. It was therefore desired to have a multistorey timber frame design. However this required much stronger structural design, incorporating plywood bracing on all walls. There were no existing designs of timber framed walls that would provide the required bracing. A new wall design was evolved, then tested in a laboratory to confirm its sound insulation performance.

Ballié , M.

• NOISE REDUCTION INDUCED BY USE OF VERY THIN WEARING COURSES AND CRUMB RUBBER PARTICLES
  M. Ballié and J. Gal
[Abstract]

For some years now, road innovations are mainly devoted to the comfort and safety for road users. The surface properties of wearing courses linked to these two parameters are of paramount importance for road companies and road authorities. Today it is a clearly established fact that the tire/pavement contact noise is the main source from wich savings can be made. The use of silent pavement allows for major reductions of the tire/pavement contact noise. Wearing courses that include crumb rubber particles are able to ensure drastic reductions in traffic noise when compared to results of conventional hot mixes. In this paper we present a survey of noise reduction studies using various measurement methods. Many sites : urban, periurban, main raods, highways in France or abroad were investigated. The methods are presend first. The noise reduction are then pointed out.

Bamnios, Y.

• RAILWAY NOISE IN GREECE: MEASUREMENT AND PREDICTION
  Y. Bamnios and A. Trochides
[Abstract]

This study describes a method of predicting railway noise in Greece. A series of measurements were conducted for the first time in Greece in order to investigate the specific characteristics of railway noise in the Greek network of railways. Based on the results of these measurements, a prediction model has been formulated and a measurement methodology has been proposed. Finally, a legislation with higher acceptable railway noise limits is proposed.

Bansal, A.S.

• VIBRATION ISOLATION CHARACTERISTICS OF TRACTOR SEATS OF INDIAN MAKE AND THE DESIGN IMPROVEMENT
  A.S. Bansal and S. Thapar
[Abstract]

Experimental studies of the vibration isolation characteristics of various tractor seats of Indian make have been conducted and compared by mounting the seats on a mechanical exciter capable of generating vertical oscillations over a frequency range up to 8 Hz. As a measure of vibration isolation, only the vertical transmmissibilities of various seats have been studied with a light-weight subject (55kg, 540 N) and sand dummy of equivalent weight in the seats. Most of the seats have been found to be fitted with springs and dampers of high rating and thus they provide poor isolation. The transmmissibilities with the sand dummy in the seat are some-what comparable with that of the subject; but it can not be used as a substitute for the subject. An isolation system with resilient springs and damper having adjustable rating has been designed and developed. Its performance has been found to be considerably better than that of the existing systems. Some studies have also been conducted under the actual field conditions. Keeping in view some discrepancy introduced due to non-linear response of the seat at different levels of vibration, the field results have been found to compare well with those obtained in the laboratory.

Baranov, S.

• STATISTICAL MODELING TECHNIQUE FOR ESTIMATING PROBABILITY CHARACTERISTICS OF ACOUSTIC FATIGUE WEAR
  S. Baranov and L. Kuravsky
[Abstract]

A statistical modeling technique intended for prediction of fatigue wear dynamics for oscillating structures suffered excitation in acoustic frequency range is presented. A parametric mathematical model in terms of the queuing theory is used to describe how the probabilities of being in given intervals of wear rate are varied in time domain. These intervals are determined via the percentage of either service life duration or critical crack length. It is assumed that interval-to-interval transitions meet the properties of Poisson's flows of events. Flow densities and, in some cases, characteristics of initial wear distribution are considered as free parameters of the model to be fitted to observed data collected during structure tests. Applied as goodness-of-fit measures are either maximum-likelihood-type function developed on the base of time history of experimental patterns or chi-square statistic that results from comparison of observed and expected service life histograms. Model parameters of interest are estimated with the aid of a numerical optimization procedure available via specially coded spreadsheets. The features of the approach in question are demonstrated using aircraft panels of different types. Obtained results make it possible to substantiate decisions concerning the time of structure examinations for detection of acoustically induced fatigue damages and to predict probabilities of given wear levels at different time points.

• EVALUATION OF VARIATIONS OF THE TURBULENT BOUNDARY LAYER NOISE INSIDE AIRPLANE CAUSED BY ITS MODIFICATION
  S. Baranov and B. Efimtsov
[Abstract]

In recent years the manufacturing firms have been modifying in increasing frequency the airplane being under production instead of developing the new ones. This is determined by their efforts to response timely to varying requests and requirements of air companies realizing transportations. In this connection the operative evaluation of the anticipated variation of sound pressure levels inside airplane after its modification becomes rather actual. For modern high-speed civil airplane first of all the sound pressure levels produced by the turbulent boundary layer which is the main source of internal airplane noise are to be evaluated. The present work analyzes possible variations of the wall pressure fluctuation field characteristics produced by the turbulent boundary layer on the external airplane surface, to which the airplane modification can lead and discusses possible variations of elasto-inertial properties of the fuselage skin as well as of vibro-acoustic characteristics of soundinsulating, soundabsorbing and vibro-absorbing structures. Asymptotical relations which describe the effect of these factors on the internal airplane noise produced by the turbulent boundary layer are presented. The experimental data supporting the validity of these relations are given. The predicted evaluation examples are illustrated. It is noted that the asymptotical relations can be used for evaluating the internal noise not only for modified airplane versions but also for new airplanes which have prototypes.

Barchi, A.

• ANNOYING NOISE LEVELS AT HOME: A COMPARISON AMONG DIFFERENT KIND OF SOURCES
  D. Bertoni and A. Barchi
[Abstract]

Noise emission from industry, mechanical devices and shops often annoy people in their dwellings. The document ''Community Noise'', edited by WHO in 1995, states that noise from ventilation systems in residential buildings may cause considerable concerns even at low and moderate sound pressure levels. The aim of this work is to find which noise levels are causing annoiance at home, according to different kind of sources. The statistical analysis of over 260 cases of complaints, addressed to the local authorities of the city of Modena since 10 years, make a comparison possible among noise levels taken in the dwellings by engeneers of the environmental Agency. Comparisons were carried out taking into account the period of the day and the condition of open or shut windows. Data were pooled according to the following kind of sources: a) rotating and reciprocating machines as fans, compressors, air conditioners; b) industrial noise; c) music live or reproduced; d) road traffic. Significant differences have been found among average noise levels from different kind of sources. During the daytime, with open windows, noise from rotating and reciprocating machines cause complaints at lower levels than industrial sources and these ones at lower levels than road traffic. The average traffic noise level in façade that cause complaints coincide with the average exposure level of very annoyed people as shown in the community noise surwey carried out in Modena in 1990. The average noise levels found may represent ''thresholds'' useful in fixing noise limits.

Barday, D.

• NOISE OPTIMISATION OF A REAR AXLE GEAR SET
  D. Barday
[Abstract]

Following the growing ecological consciousness, legislators have issued more and more severe regulations on the allowable noise levels for trucks and buses. Moreover, the customers do not accept to buy noisy vehicles, felt clearly as a lack of quality. In the power transmission line, rear axle contribute noticeably to the overall noise level, especially inside the vehicle. The hypoid gear set, acting as an exciter, generate some vibrations that can be characterised by the amplitude of the variation of the mesh stiffness, know as the transmission error. Due to recent advances in computer performances, it becomes now possible to evaluate the transmission error amplitude for a given gear set, and under given running conditions. In a first step, we describe the calculation method, based upon 3-dimensions Finite Element model, that leads to a load dependant transmission error level, for a given gear set, accurately described by mean of co-ordinates measuring machine (CMM) results (micor-geometry). Secondly, for different running conditions and different gear sets, we show the clear correlation between measured noise inside a vehicle and the calculated values of the transmission error. Finally, we describe how to optimise the booth surface (micro-geometry) to decrease the transmission error level under given running conditions. These calculations have been validated on vehicle, and showed an important noise reduction up to 6 dB. This package of software's, developed and validated at Renault VI, are now used at the first stage of development of new bevel and hypoid gear sets in order to optimise the noise behavior under working conditions.

Bardot, A.

• QUANTITATIVE DESCRIPTIVE ANALYSIS METHODOLOGY APPLIED TO THE DESCRIPTION OF VEHICLE SOUND QUALITY
  A. Bardot
[Abstract]

The development of vehicle sound quality is becoming increasingly important in the automotive industry. Acoustic specifications are traditionally developed to reduce the overall noise level of the vehicle, but this global attribute is not sufficient to describe sound quality. The acoustic field inside the vehicle is actually a combination of different sources which create a complex sound field of which the perception is complex. Concurrently, a lot of psychoacoustic parameters have been developed to describe dimensions of sound quality such as loudness, sharpness, tonality, fluctuation strength ...Based on a better knowledge of fundamental auditory perception and physiological scheme, these objective parameters are mainly validated on simple synthetised sound and become universally  applied to the complex sounds, although they would not be well appropriated. The complex acoustic field of vehicle is multi-source field result and attributes of perception can not be amounted to the classical parameters. For a better understanding of these components, different subjective assessments methodologies have been developed. Most of them depend on ingenuous judge who integrate sensory and psychological factors of perception. Subjects do not produce stable answers because of mixing descriptive and hedonic aspects of their perception. We proposed to apply a classical approach used to develop food product : the Quantitative Descriptive Analysis methodology (QDA) which allow to specify sensory profile of their product. In the first part, we will justify this strategy with regard to the classical psychoacoustic method. In the second part we will present the acoustic profile panel (12 assessors) developed for the evaluation of different vehicle for characteristic situations of vehicle noise. Finally, we will present and comment on results of panels with specific statistic tools (performance, repeatability and discrimination). This work will allow to illustrate the limit of the use of classical psychoacoustic parameters as reflectors of perception. The use of the method will be discussed in the paper, especially for sound design and sound quality control.

• VIBRO-ACOUSTIC SIMULATION USING GEOMETRICAL ACOUSTICS IN THE MEDIUM FREQUENCY RANGE INSIDE A CAR CAVITY
  C. Floc'h, A. Bardot, J.-D. Polack and X. Bohineust
[Abstract]

In the automotive industry, the need for listening the results of vibro-acoustic simulations is more and more expressed. This paper presents a vibro-acoustic model based on geometrical concepts, well suited to noise synthesis in the medium frequency range. Although geometrical acoustic models have been widely used in hall acoustics for ponctual sources, only Jean attempted to use them for structural radiation. He compared BEM and geometrical results in weak coupling conditions, for which he obtained a good agreement. The model presented here calculates the acoustic radiation of a vibrating structure inside a closed cavity using an integral formulation coupled to a geometrical approach for the acoustic propagation. It rests on a decoupling hypothesis between the acoustic pressure radiated and the vibration of the structure. The model is compared to experimental results. The experimental set-up consists in a rigidified car cavity with absorbing material on the walls, on which an elastic panel is mounted and excited through a shaker. The vibration of the structure, entry of the radiation model, is measured with an holographic interferometry system, which provides a very good accuracy in the frequency range measured, [0-1300 Hz]. Model validation is made both by comparing response curves in the time and frequency domains, and by conducting listening tests on a panel composed of 36 people. Comparison of modelisation and experimental results on perceptive criteria (triangular perceptive tests between measurements and simulations) shows that the model quality is correct, although some coloration differences are still perceived.

Bareille, O.

• MODAL AND PROPAGATIVE APPROACH IN STRUCTURAL-ACOUSTIC ANALYSIS BY MODAL DENSIFICATION METHOD
  O. Bareille, M. Ichchou and L. Jezequel
[Abstract]

The prediction of the behavior of complex structures in the medium and high frequency ranges is at stake here. Even if the last improvements of classical methods such as finite element methods, modal analysis methods and SEA are encouraging enough, a wide-range predictive tool is not yet available.The recent developments of the M.D.M. (Modal Densification Method) are exposed in this paper. Partitions of the spatial domain and of the frequency domain are the basis of this method. For each sub-domain, two models of coupling are defined : localy, the coupling between local and global degrees of freedom, globaly, the coupling between global degrees of freedom of neighbouring sub-domains. The application to the vibration analysis of structural-acoustic systems is straight, whether in 1D or 2D cases. Here are presented one-dimensional examples for better analytical understanding. Therefore, comparisons can be drawn, not only with the exact solutions but also with the solutions of existing methods.

Barras, C.

• INSULATION OF ALUMINIUM FRAME-DOUBLE GLAZING WINDOWS BY MEAN OF BEA/FEA MODELING
  J.-M. Auger, H. Defosse, M.A. Hamdi, C. Barras, D. Benoualid, P. Mulocher, B. Mottelet, M. Rehfeld, P. Cotté, C. Midelet and M. Szezygiel
[Abstract]

This paper presents significant results of the research program on the insulation of aluminium framed windows glazed with sealed double glazing conducted by a consortium of partners. This consortium involves industrial partners which develop window components i.e.: SAINT GOBAIN for double glazings, HUTCHINSON for seals, TECHNAL and A.S. for aluminium window frames. The vibro-acoustic simulation of the window is conducted by STRACO by using I-DEAS Vibro-Acoustics and RAYON solver. The window insulation analysis is conducted both numerically and experimentally: - Experiments are performed by partners with their transmission facilities in order to compare results and validate models. - Simulation are conducted by using an original FEA/BEA modeling approach capable to represent the transmission problem by taking into account structural details related to seals, frame and glass as well as internal acoustic cavities and external radiation. Comparisons between experimental an numerical insulation results show a good agreement and a parametric analysis provides indications on the influence of parameters which characterize seals, frame and the double glazing.

• THE VIBRO-ACOUSTIC SIMULATION OF MULTI-COMPONENT SYSTEMS
  D. Benoualid and C. Barras
[Abstract]

In order to assess the mechanical performances of his products, Hutchinson is increasing continuously the resources devoted to simulations and experiments. Vibro-acoustic performances of components and systems designed by Hutchinson (engine mounts, suspension parts ...) are the key issues in acoustic and vibration passenger comfort. Acoustic and structural codes have been tightly coupled thus enabling the simulations of full systems, and making it possible to model as precise as possible their realistic environment. Applications to three product families are presented : Car body sealing : vibroacoustic simulation of car door window including the adjacent components such as window run channel, lift-glass device etc. , acoustic transparency of sealing system for car door with double or triple sealing. Several discretization approaches, and in particular the boundary and the infinite element methods, used in acoustic modelling have been compared. Vibration isolation : dynamic simulations of individual components or complete systems such as engine suspension of full vehicle suspension have been performed. Results obtained by means of simulation are often compared with experimental results. Fluid transfer : shape optimisation of resonators and silencers for air intake systems and vibration analysis of air conditioning and engine cooling system hoses.

Barreiro, J.

• HOW MUCH PEOPLE ARE WILLING TO PAY FOR SILENCE? A ONE AND ONE-HALF-BOUND DC CV ESTIMATE
  J. Barreiro, M. Sanchez and M. Viladrich-Grau
[Abstract]

High levels of noise have negative implications not only for health but also for other types of human activities. Noise also affects the development of human activities, and has therefore economic consequences. Noise is, in economic terms, a negative externality and a public ''bad'', however, is one of the pollution problems which has attracted less attention by environmental economist. One of the goals of this paper is to advance in that direction estimating the economic value of a noise reduction through the contingent valuation method. The objective of this paper is to estimate the economic value of a reduction in the level of noise in the Spanish city of Pamplona. We estimate this value applying the Contingent Valuation Methodology and specifically the one and one-half-bounded (OOH) model. This method is more efficient that the double-bounded alternative (DB) and requires less information than the triple-bounded (TB) model. The preliminary results show that annually each household willingness to pay for a reduction in, both daytime and night-time, noise level is approximately of 6200 pts (38.75 euros).

Barrelet, S.

• ON THE SOUND RADIATION FROM TYRES
  F.-X. Bécot, S. Barrelet and W. Kropp
[Abstract]

A two-dimensional model for the sound radiation from tyres is presented here. Based on the multipole synthesis, it is shown to be robust and converge rapidly even with a low number of modes taken into account. Despite obvious deviations due to its two dimensional character, its prediction of the horn effect agree well with measurements and BE calculations. Due to its efficiency the model allows for studying the influence of parameters such as geometry or surface impedance on the sound radiation from tyres. Results of such a parameter study are presented in the following. However there is a need for an extension of the model to three dimensions.

Barriere, N.

• EXPERIMENTAL STUDY OF ROAD TRAFFIC NOISE CONTROL BY A PINE FOREST
  N. Barriere, Y. Gabillet, J. Blais, J. Defrance, P. Ducruet and F. Gaudaire
[Abstract]

In order to precisely bring to the fore the effect of meteorology on sound propagation through forests, an important measurements campaign has been carried out in the French Landes forest mainly composed of pine trees. The originality of the experiment is that road traffic noise and meteorological conditions have been measured simultaneously for both a forest situation and a plain situation, this for different positions of the receiver. All valid measured data have then been classified according to three propagation conditions: favourable to propagation, unfavourable to propagation and homogeneous conditions. As expected, the results depend on these conditions. In favourable conditions, the gain brought by the forest is between 3 and 5 dB(A) with the receiver at least 100 m away from the road. This meteorological situation occurs very often at night due to a temperature inversion phenomena. Moreover, it is of most interest since it corresponds to the periods when the annoyance due to the road in a plain situation is the highest. In unfavourable conditions, the forest may increase somewhat the received sound level. In homogeneous conditions, the sound propagation through the forest is not appreciably affected by meteorology anymore but only by the scattering by the trunks and foliage. Finally, these results have permitted to validate a new calculation method for the attenuation of road traffic noise by forests based on a fast implementation of the Parabolic Equation.

Barrigón, J.M.

• STUDY OF VITORIA-GASTEIZ BY CATEGORIZING CHARACTERISTICS ROADWAY
  J.M. Barrigón, V. Gomez Escobar, P.D. Gutierrez Marcos, J.A. Mendez Sierra and J. Ruiz De Azua
[Abstract]

In the city of Vitoria-Gasteiz (País Vasco, Spain) a preliminary urban noise survey was conducted. The city was categorised by its characteristics roadway. Thus, four different categories were studied with random selection of sampling points. Measure noise levels can be considered high (over 65 dB(A))in the city. Some comparisons were made with a previous (1991) noise map of the city. The study was developed in two different months, one on holiday period (August) and the second in a common month (September). Results showed differences between both months. Relationships between energy-averaged sound level (Leq) and statistical levels of exceedance (Lx) were established. Finally, a regression equation of Leq was developed as a function of logarithm of the number of vehicles per hour. Results showed a good agreement with other authors.

Barringer, B.a., K.

• PSYCHOACOUSTIC COMPARISON OF TWO METHODS FOR THE EVALUATION OF PROMINENT DISCRETE TONES
  A.C. Balant, K. Barringer, B.a. and M. Nobile
[Abstract]

This paper presents the results of two pilot studies comparing the efficacy of the Modified Tone-to-Noise Ratio method and the Prominence Ratio method in assessing the subjective prominence of discrete tones in noise. Ten normal-hearing subjects rated the prominence of synthetic stimuli and real machine noises containing spectral features that are problematic for the two methods. Both methods showed strong positive correlations with the subjective prominence ratings of the synthetic stimuli, and weaker positive correlations with the ratings of the machine noises. Results and implications for future research are discussed.

Barros Gonçalves, W.

• ACOUSTICAL CONDITIONING OF A LOCOMOTIVE LOAD TEST FACILITY
  E. Bauzer Medeiros, M. Machado Duarte and W. Barros Gonçalves
[Abstract]

Information on the acoustic impact of moving trains can be found in the literature. Moving trains produce acoustic impacts during well defined periods of time. Industrial facilities, on the other hand, can operate at any time, to carry for specific production needs. These facilities are normally speaking situated inside regions where the likelihood of acoustic related complaints is critical The installations under consideration comprise rail stock maintenance and manufacturing facilities, requiring a test area for locomotive operational clearance. The present work describes a series of acoustic studies carried out in one of these facilities, which even though is located inside an industrial area, has restricted acoustic limits, particularly during night hours. A set of typical results is presented and used as a basis for the presented acoustic design solution to control the existing wide spectrum. Operational and safety conditions are also considered, as well as atmospheric contaminants removal. Additional considerations about the presented solution shows the feasibility of the proposal.

Barsikow, B.

• NOISE SOURCES ON AMTRAK'S HIGH SPEED TRAIN
  C. Hanson and B. Barsikow
[Abstract]

Noise was identified as one of the key community concerns during the environmental assessment process conducted prior to the introduction of Amtrak's new high speed train, the Acela, in Northeast USA. Although the Canadian-French trainsets are similar to the TGV, there are significant differences for operation on American tracks. Noise sources were measured and identified during tests conducted at the Transportation Technology Center near Pueblo, Colorado. Measurements were made using a microphone array system. Line arrays and X-arrays were used to locate and quantify the noise sources. Roughness of the wheel treads and rail surfaces were measured to enable the array-measured rolling noise to be assigned to a particular level of roughness.

Barti, R.

• PERCEIVED TRAFFIC NOISE. LS INDEX. INTERNATIONAL RESULTS.
  R. Barti
[Abstract]

LS index was presented in the last Internoise'99 held in Florida. New measurements with new subjective criteria were do by some people of diferent social situation. Evaluation from different countries will be do. LS index is a psycho-acoustic based parameter. The energy distribution seems correlate well with the nuisance perceived by people. Only monoaural technique was used for recording signals. At the moment of writing this summary, some results of the evaluation by people, is not available yet.

Bartmanski, C.

• NEW-GENERATION EQUIPMENT TOGETHER WITH METROLOGICAL PROCEDURES FOR MEASUREMENT OF PARAMETERS OF MECHANICAL VIBRATION EMITTED TO THE ENVIRONMENT BY VEHICLES
  A. Lipowczan, J. Kompala, C. Bartmanski, A. Kobylecki and I. Kubik
[Abstract]

The paper presents general parameters of the system designed for measurement of vibration parameters generated by road traffic sources. Eight to sixteen channels system was developed for evaluation of influence of vibration on buildings. The system is developed in digital technology except the input blocks. It is dedicated for recording, evaluation and storing of vibration data. For these purposes the original software was developed. The system makes also possible the location of measurement points and areas by using the GIS and GPS methods. At present, the system is in the stage of technical verification.

Barwicz, W.

• DSP APPLICATION IN THE VEHICLE NOISE METER
  A. Podgórski, W. Barwicz and J. Mosakowski
[Abstract]

According to the Regulation 51 of the UNO agreement TRANS/SC1/WP26/276/Corr.1 (1990) for the common rules of vehicle acceptance, a vehicle should pass some special tests. One of those tests is the measurement of the noise generated by the non moving vehicle at the engine rotation equal to 75% of the maximum power. To fulfil the requirements of the test two channel instrument is needed: one channel - for noise measurement and one channel - for rotation measurement of the different engine types (''spark ignition'' and the Diesel type). There is no problem for noise measurement but there is for the measurement of the engine rotation equal to 75% of the maximum power. Many different algorithms were considered including time, spectrum and cepstrum analysis to measure properly the frequency. The results of the investigation will be presented. As a final solution a new DSP-based measurement instrument dedicated for this purpose is proposed. For the gasoline engines the instrument uses the inductive probe and for Diesel engines - the vibration probe. The results of the tests and data specification of the new handheld, battery charged instrument will be presented in the full text of the paper.

Baughan, C.J.

• RURAL RESIDENTS' RESPONSE TO REDUCTIONS IN TRAFFIC NOISE CAUSED BY RESURFACING A SECTION OF MOTORWAY WITH POROUS ASPHALT
  C.J. Baughan, L. Chinn, G.J. Harris and R. Stait
[Abstract]

Porous asphalt is known to produce lower traffic noise levels than conventional road surfaces, but relatively little information is available on the perceived benefits to people living some distance from the road. A section of the jointed concrete M40 motorway in rural Oxfordshire has been resurfaced with porous asphalt. This gave an opportunity to assess the resulting changes in noise and noise nuisance experienced by residents in villages within 1.5 km of the motorway. Residents were interviewed and noise measured at five villages just before the resurfacing work started and again one year and 3 years later. The paper reports the changes in noise levels resulting from the resurfacing and the associated changes in residents'ratings of dissatisfaction. The work was intended to inform the Highways Agency of the environmental benefits of porous asphalt as perceived by people living in the vicinity of a motorway, and help to quantify the circumstances in which the higher costs of porous asphalt can be justified. The first two surveys showed that reductions in vehicle noise (measured close to the motorway) of 4.5 to 7.6 dB(A) were achieved, depending on class of vehicle and measurement location. There were substantial reductions in traffic noise exposure at villages some distance from the motorway. Indices of community noise impact (such as dissatisfaction ratings) reduced considerably after the resurfacing, especially at the two villages with the biggest noise changes. A strong relation between dissatisfaction ratings and noise levels was observed. This paper will describe the study design and results obtained. It will also examine the relations between noise and dissatisfaction ratings, and indicate how noise changes can lead to changes in community response greater than would be predicted from 'steady state' relations between noise exposure and dissatisfaction.

Bauver, W.P.

• MEASUREMENT METHOD FOR THE LOW FREQUENCY ACOUSTICAL BEHAVIOR INSIDE THE EXHAUST SYSTEM OF A COMBUSTION TURBINE
  U. Scholz, and W.P. Bauver
[Abstract]

Exhaust systems are one of the most important noise sources at modern combustion turbine power plants. In some cases, acoustic resonance can occur, producing very high sound pressure levels, usually at low frequencies. Reducing such sound levels by secondary measures such as silencers is expensive and usually not the best solution to the problem. The best approach is have a good understanding of the parameters controlling resonance. This will permit designing systems to prevent resonance, or for existing units, develop effective inexpensive means of eliminating resonance. Modern CT exhaust systems can be very complex. The experience of the last years has shown that the classic standing waves models do not always predict actual measured frequencies. It is necessary to understand the internal acoustics of develop better models. This paper describes a methodology to measure sound pressure level distribution inside of an exhaust system. Some results are provided to show the potential and also the limits of th

Bauzer Medeiros, E.

• ACOUSTICAL CONDITIONING OF A LOCOMOTIVE LOAD TEST FACILITY
  E. Bauzer Medeiros, M. Machado Duarte and W. Barros Gonçalves
[Abstract]

Information on the acoustic impact of moving trains can be found in the literature. Moving trains produce acoustic impacts during well defined periods of time. Industrial facilities, on the other hand, can operate at any time, to carry for specific production needs. These facilities are normally speaking situated inside regions where the likelihood of acoustic related complaints is critical The installations under consideration comprise rail stock maintenance and manufacturing facilities, requiring a test area for locomotive operational clearance. The present work describes a series of acoustic studies carried out in one of these facilities, which even though is located inside an industrial area, has restricted acoustic limits, particularly during night hours. A set of typical results is presented and used as a basis for the presented acoustic design solution to control the existing wide spectrum. Operational and safety conditions are also considered, as well as atmospheric contaminants removal. Additional considerations about the presented solution shows the feasibility of the proposal.

• USING A GIS TOOL TO PLAN THE ACOUSTIC URBAN ENVIRONMENT
  M. Gomes De Oliveira, E. Bauzer Medeiros and C. Davies Jr.
[Abstract]

The economic development taking place in large urban centers can often provide an improvement in life quality as a consequence of the wider availability of services. However, severe environmental problems can also occur, if a coordinated strategy involving adequate monitoring of established businesses is not carried out. Adequate assessment of the environmental impact which may result from the economic development can only be carried out if suitable tools are available to the administrators, enabling proper supervision of land occupation. Noise is a major source of nuisance in urban environments, and in general 70% of the inhabitants of large cities usually describe noise related disturbances as a very important factor affecting life quality. This paper describes a set of GIS-based tools intended to provide the administrators with a methodology enabling a proper assessment of the acoustic impact within the urban environment. A model establishing the correlation between the spatial distribution of impacts and the relevant activities is developed. This model has been implemented as a prototype in a GIS environment, using Belo Horizonte's geographic database, which is intended to represent a typical large Brazilian city situation. Initial field measurements compare favorably with this prototype, indicating the feasibility of the proposed approach.

Beauvilain, T.

• USE OF RECIPROCITY PRINCIPLE IN A HYBRID MODELING TECHNIQUE (HMT) BASED ON INVERSE BOUNDARY ELEMENT METHOD (IBEM) FOR THE DETERMINATION OF THE OPTIMAL SPECTRAL CHARACTERISTICS OF A COMPLEX RADIATING NOISE SOURCE
  M.A. Hamdi, H. Defosse, F. Damagnez, T. Beauvilain and P. Varet
[Abstract]

The paper presents a robust hybrid modeling technique (HMT) based on near field acoustic measurements combined with numerical results derived from an Inverse Boundary Element Method (IBEM). The developed hybrid technique takes advantage from reciprocity principle to efficiently determine the optimal spectral characteristics of very complex noise sources, typically encountered in transportation industries. The first section of the paper reminds the direct link between reciprocity principle and integral representations of the acoustic field radiated by a noise source at finite number of discrete points located outside a closed surface enveloping the source. The second section describes the parameters chosen to describe the radiating source and the numerical optimization procedure used to determine the optimal spectral characteristics of source parameters. The third and last section of the paper illustrates successful practical applications of the method in automobile industry to characterize the noise radiated by a car engine.

Bécot, F.-X.

• ON THE SOUND RADIATION FROM TYRES
  F.-X. Bécot, S. Barrelet and W. Kropp
[Abstract]

A two-dimensional model for the sound radiation from tyres is presented here. Based on the multipole synthesis, it is shown to be robust and converge rapidly even with a low number of modes taken into account. Despite obvious deviations due to its two dimensional character, its prediction of the horn effect agree well with measurements and BE calculations. Due to its efficiency the model allows for studying the influence of parameters such as geometry or surface impedance on the sound radiation from tyres. Results of such a parameter study are presented in the following. However there is a need for an extension of the model to three dimensions.

Beguet, B.

• DEFINITION OF THE ENGINE SOUND QUALITY INSIDE VEHICLES
  L. Lamotte and B. Beguet
[Abstract]

Automotive constructors have reduced the noise level in the past and now want to guarantee a pleasant noise inside their vehicles. To reach such an objective, many works have been about subjective evaluation of the noise quality. This acoustic quality should also be determined from an objective study with objective results. This study is interested in quantifying the acoustic quality of the engine noise source inside the passenger compartment. (Noise sources due to aerodynamic or the wheels on pavement are not considered.) Some global metrics like loudness, sharpness, or pleasantness are usually used to quantify the acoustic quality as a global impression. In the case, some other metrics must be defined that are correlated to specifics problem of the engine. Moreover, to be sure of the right source of the measured noise at the level of the driver's ears, some sensors are placed in the engine compartment. The choice of the specific parameters and sensors are linked: - an accelerometer on cylinder head quantifies problems due to piston slap: the parameter ''shock balance'' quantifies repetitive pulses at the frequency of the main, half or second order. - accelerometers on engine mount arc well-adapted to quantify first order and also some ''shock balance'' - a microphone in the engine compartment is a good sensor to qualify airborne noise. The evolution of those parameters with the time is also an important aspect of the sound quality. Different circumstances of use of the car are studied: low idle, stationary, acceleration and cost down operating conditions. Such results give references in the design and development process of a vehicle.

• NOISE SOURCE LOCALIZATION - COMPARISON OF DIFFERENT MéTHODS
  B. Beguet
[Abstract]

The aim of this paper is to compare the capabilities of different methods developed in order to localize noise sources. Three methods are analyzed : -Intensity technique. Initially developed to quantify the acoustic power, this technique is often used to localize sources, -Acoustical holography. Based on a back propagation (by spatial Fourier transform), this technique increases the resolution by computation the acoustical field closer to the sources, -Focusing technique. This last one has been first used for application on moving sources (measurement in farfield). The capabilities of the methods are analyzed on several points of view: -The resolution (capability to distinguish two sources), -The precision of quantification of partial power, -The number of microphones required, -The distance between the array and the sources. Several experimental examples illustrate these comparisons. At last, a global strategy is presented to analysis noise emitted by a machine in run-up conditions. This strategy includes: -A focusing technique to do a first rough localization on a large range of speeds, -In a second step, an acoustical holography technique to do precise localization at different constant speeds.

Behr, W.

• LOW NOISE PANTOGRAPH ASP - RECENT DEVELOPMENTS
  W. Behr, T. Lölgen, W. Baldauf, L. Willenbrink, R. Blaschko, K. Jäger and J. Kremlacek
[Abstract]

The aeroacoustic noise of a pantograph increases dramatically with the train speed. Especially at a very high speed of 300 km/h and above the aeroacoustic noise of the pantograph may exceed the rolling noise of the wheels. Since it is inappropriate and expensive to build high noise barriers to screen the pantograph, a new design of pantographs is necessary for future high speed trains. In cooperation with DaimlerChrysler Rail Systems an actively controlled single-arm pantograph (ASP) will be developed until next year in order to improve the quality of the contact force fluctuation and to reduce the aeroacoustic noise emission using computer simulation to estimate the aeroacoustic noise. These simulations are very helpful when developing an optimized design and avoiding unacceptable designs in an early state of development. First simulation results of the recent developments of the pantograph head will be presented.

Beier, M.

• VEHICLE-MOUNTED SHIELDS AND LOW TRACKSIDE BARRIERS FOR RAILWAY NOISE CONTROL IN A EUROPEAN CONTEXT
  R. Jones, M. Beier, R.J. Diehl, C. Jones, M. Maderboeck, C. Middleton and J. Verheij
[Abstract]

The control of railway rolling noise by a combination of vehicle-mounted shields and very low, close, trackside barriers, has been explored extensively in the past, for example by British Rail Research, where an acoustically efficient experimental system was developed in the early 1990's. Within the EC 4th Framework projects Silent Freight and Silent Track, the concept has been further developed by formulating a system which was analytically optimised prior to manufacture and testing, and which would be acceptable, in gauging terms, for full interoperability across Europe. The paper presents the analytical and design process which was applied in specifying the parameters of the new interoperable system, as well as the results of subsequent full scale aco

• PREDICTION OF RAILWAY INDUCED GROUND VIBRATION
  R.J. Diehl, M. Beier, G. Hölzl and H. Waubke
[Abstract]

The wheel/rail-impedance modell RIM for the prediction of railway noise has been combined with soil modells to predict ground vibration induced by rail and wheel tread roughness as well as parametric excitation. The soil calculations are based on an analytical modell of a horizontally layered halfspace. The tool can be used to study the effects of the application of various mitigation measures suitable for track applications: resilient rail fastening systems, sleeper soffit pads, ballast mats and floating slabs. Furthermore the influence of the soil on the vibration levels can be investigated. The paper describes the modell, and its applications and shows results for two sites: an application of a floating slab in a tunnel and applications of soil improvement methods and ballast mats for surface lines. The results from the predictions are compared with those from measurements provided by DB AG also used for the ERRI project RENVIB.

Belek, H.T.

• SOUND QUALITY AND LOW NOISE DESIGN
  H.T. Belek, E. Altinsoy and A. Akgül
[Abstract]

The noise radiated from the household appliances is a serious problem in our daily life. Moreover sound quality of household appliances has become an important parameter in gaining the market advantage. Wet and dry type vacuum cleaners are among the noisiest household appliances and therefore their sound quality has high correlation with their sound power level. The reduction of the vacuum cleaner noise has become a main concern of manufacturers in order to comply with European Union Directives. Major parameters of vacuum cleaner design are sound power level, sound quality and efficiency. Vacuum cleaners should be designed with minimal disturbing sound without reducing their efficiency. The purpose of this study is to achieve acceptable noise reduction on a particular wet and dry type vacuum cleaner. For this purpose, the principal sound sources are evaluated, then systematic noise control techniques are applied on a prototype vacuum cleaner. Airborne noise and structural noise sources are effectively treated and the sound quality of the product is improved. The main purpose of this investigation is twofold; firstly, to describe a noise control study that resulted in 8 dB(A) reduction in sound power level at a moderately low cost with an efficiency reduction of only 2 %; secondly, to propose a set of design p

Bellina, L.

• DEFINITION OF A PROPAGATION MODEL OF TRAFFIC NOISE IN SATURATION CONDITIONS
  C. Varaldi, J. Fogola and L. Bellina
[Abstract]

This model of propagation here illustrated has been obtained through a regression model in traffic saturation conditions. In traffic saturation conditions the noise level does not follow a logarithmic curve but a quadratic curve in relation to the equivalent number of vehicles. In order to analyse this phenomenon a set of measurements has been carried out in the outskirts of Turin (Italy). The traffic flow has been analysed at different times of the day, paying special attention to moments of traffic congestion. Two different charts have been drawn up: a logarithmic chart for the first measure points (in situation of normal traffic flow) and a parabolic one for the traffic congestion points. A mathematical function joining the two curves has been found, in order to have a complete description of the phenomenon. The theoretic figures have proved to be basically in accordance with the experimental ones.

Bendtsen, Hans

• PERCEIVED ANNOYANCE FROM ROAD TRAFFIC NOISE
  H. Bendtsen, L. Ellebjerg Larsen and B. Mikkelsen
[Abstract]

When noise abatement planning is carried out, it is important to know the nuisance perceived by people along the roads at different noise levels. For the first time in Denmark doses response relations have been studied looking at nuisance in-doors with open and closed windows, in the garden and near the road, correlated with the actual noise levels expressed as Leq,24. The perception of annoyance form road traffic noise has been studied in the municipality of Århus, the second largest city in Denmark. A questionnaire send out by letters have been used. Out of 132.000 households in Århus around 6000 have been randomly selected. 55 % have returned the questionnaire. Nearly everybody who has answered, have filled in their address. The knowledge of these addresses have made it possibly to make a prediction of the noise in front of the windows, in the garden and at the street. People could express different degrees of annoyance. The following categories was used: extremely annoyed, very annoyed, annoyed, little annoyed and not annoyed. People were also asked how the noise affects their daily life. They were asked if they had done anything to reduce the noise, and if they had any ideas on what should be done and who should pay for these improvements. Doses response curves are generated. They draw a picture where 10 to 20 % are annoyed at low noise levels under 50 dB. The annoyence increases with noise levels over 55 dB. The highest level of annoyance is seen in the situation indoor with open windows. But there are also rather high levels of annoyance reported in the gardens.

• PERFORMANCE OF NEW TWIN-LAY DRAINAGE ASPHALT LAID IN DENMARK
  J. Kragh and H. Bendtsen
[Abstract]

The noise from individual vehicles in the normal traffic has been measured at three test sections of a city street with twin-lay drainage asphalt with maximum 5 or 8 mm grain size in the top layer, and maximum 16 or 22 mm grain size in the bottom layer. The total layer thickness was 55 mm, 70 mm, and 90 mm, respectively. The noise reduction (expressed as the difference in measured statistical pass-by noise index [SPBI], ISO 11819-1) at the thickest new twin-lay drainage asphalt, when compared to a reference section with dense asphalt concrete of the same age, was 6 or 7 dB two weeks after the test section had been opened for traffic. At the two other test sections the corresponding noise reduction was 5 or 6 dB. Compared with the noise level measured six months earlier at the old road surface, a 15-year-old asphaltic concrete, the noise level at the new reference surface was 3 dB lower. Thus, the change in traffic noise exposure of the adjacent buildings as a consequence of replacing the old asphalt concrete by new twin-lay drainage asphalt was up to 10 dB. Results from measurements carried out nine months after building the new twin-lay surfaces will be presented at the conference.

Bendtsen, Hans

• NOISE AND NUISANCE FROM ROAD HUMPS
  H. Bendtsen and L.E. Larsen
[Abstract]

Road humps are used on a big scale in Denmark and other countries as a tool to reduce speed and improve traffic safety. It is important to have knowledge about the consequences on noise and nuisance to those living along the road. For the first time noise, nuisance and driving pattern have been studied on the humps typically used in Denmark. Road humps are used on a big scale in Denmark as a tool to reduce speed and improve traffic safety. Through time neighbours have complained about increased noise near road humps. In this project these problems are studied for the type of road humps typically used in Denmark. Eight road sections with between 2 and 9 humps have been selected covering speeds from 30 to 60 km/h. For the project circle humps and modified circle humps have been selected, as they follow the latest Danish design standards. The speed and noise have been measured as LAE and LAmax for individual vehicles (divided into 4 categories) using the statistical pass-by method. For each road section the noise was measured by the middle of a hump, 10 meters from a hump and between 2 humps. The driving pattern was measured on selected vehicles using a special car following the vehicles. By the use of ques-tionnaires, the nuisance felt by the neighbours of the selected road sections was registered. The relationship between the noise and the nuisance felt by the neighbours was analysed. The speed is reduced on road sections with humps. The noise is measured by the humps and in the middle of a road section between two humps as LAE and as LAmax. The noise is reduced in both positions. The highest reduction is found near the road humps. But

Bengtsson , J.

• DOES LOW FREQUENCY NOISE DURING WORK INDUCE STRESS?
  K. Persson Waye, R. Rylander, J. Bengtsson , A. Clow, F. Hucklebridge and P. Evans
[Abstract]

Background and aim: The aim of the study was to evaluate the possible interference of low frequency noise on stress experienced during performance. Test persons classified as sensitive or non-sensitive to noise in general or to low frequency noise, worked with different performance tests in a noise environment with dominant low frequencies or dominant middle frequencies, both at a level of 40 dB LAeq. The effects were evaluated as changes in levels of Monoamine oxidase inhibator (MAO-I) and cortisol in saliva, taken at various times during the test. The total time for the sessions was 2.5 to 3 hours. Results: When the subjects worked in low frequency noise, the levels of cortisol were higher and there was a small non-significant increase in the levels of MAO-I. No clear difference in response could be related to sensitivity to noise in general or to low frequency noise, but a general observation was that the levels of the final samples of MAO I and cortisol were higher among subjects sensitive to noise or to low frequency. The low frequency noise was rated as more annoying than the reference noise and also considered to impair the working capacity more than the reference noise. The results suggest that working in low frequency noise conditions may induce stress indicators.

Bengtsson, J.

• LOW FREQUENCY NOISE "POLLUTION" INTERFERES WITH PERFORMANCE
  J. Bengtsson, K. Persson Waye, A. Kjellberg and S. Benton
[Abstract]

To study the possible interference of low frequency noise on performance and annoyance, 32 test persons classified as sensitive or non-sensitive to noise in general or to low frequency noise, worked for 2.5-3 hours with different performance tests in a noise environment with dominant low frequencies or dominant middle frequencies both at a level of 40 dB LAeq. The effects were evaluated as changes in performance and subjective reactions using questionnaires. The results indicated that low frequency noise interfered with a proof reading test by decreasing the number of markings made per line read. The results furthered showed that the response time in a verbal grammatical reasoning test was longer over time in the low frequency noise exposure. The subjects reported a higher degree of annoyance and work impairment when working in low frequency noise. The effects were more pronounced for subjects sensitive to low frequency noise, while partly different results were obtained for subjects sensitive to noise in general. The results suggest that work performance and perception of annoyance may be influenced by a continuous exposure to low frequency noise at commonly occurring noise levels and that subjects classified as sensitive to low frequency noise may be at highest risk.

Benoualid, D.

• INSULATION OF ALUMINIUM FRAME-DOUBLE GLAZING WINDOWS BY MEAN OF BEA/FEA MODELING
  J.-M. Auger, H. Defosse, M.A. Hamdi, C. Barras, D. Benoualid, P. Mulocher, B. Mottelet, M. Rehfeld, P. Cotté, C. Midelet and M. Szezygiel
[Abstract]

This paper presents significant results of the research program on the insulation of aluminium framed windows glazed with sealed double glazing conducted by a consortium of partners. This consortium involves industrial partners which develop window components i.e.: SAINT GOBAIN for double glazings, HUTCHINSON for seals, TECHNAL and A.S. for aluminium window frames. The vibro-acoustic simulation of the window is conducted by STRACO by using I-DEAS Vibro-Acoustics and RAYON solver. The window insulation analysis is conducted both numerically and experimentally: - Experiments are performed by partners with their transmission facilities in order to compare results and validate models. - Simulation are conducted by using an original FEA/BEA modeling approach capable to represent the transmission problem by taking into account structural details related to seals, frame and glass as well as internal acoustic cavities and external radiation. Comparisons between experimental an numerical insulation results show a good agreement and a parametric analysis provides indications on the influence of parameters which characterize seals, frame and the double glazing.

• THE VIBRO-ACOUSTIC SIMULATION OF MULTI-COMPONENT SYSTEMS
  D. Benoualid and C. Barras
[Abstract]

In order to assess the mechanical performances of his products, Hutchinson is increasing continuously the resources devoted to simulations and experiments. Vibro-acoustic performances of components and systems designed by Hutchinson (engine mounts, suspension parts ...) are the key issues in acoustic and vibration passenger comfort. Acoustic and structural codes have been tightly coupled thus enabling the simulations of full systems, and making it possible to model as precise as possible their realistic environment. Applications to three product families are presented : Car body sealing : vibroacoustic simulation of car door window including the adjacent components such as window run channel, lift-glass device etc. , acoustic transparency of sealing system for car door with double or triple sealing. Several discretization approaches, and in particular the boundary and the infinite element methods, used in acoustic modelling have been compared. Vibration isolation : dynamic simulations of individual components or complete systems such as engine suspension of full vehicle suspension have been performed. Results obtained by means of simulation are often compared with experimental results. Fluid transfer : shape optimisation of resonators and silencers for air intake systems and vibration analysis of air conditioning and engine cooling system hoses.

Bento Coelho, J.L.

• A NOISE STUDY ON THE NEW LISBON AIRPORT
  M.J. Palma, J.L. Bento Coelho and A.M. Almeida
[Abstract]

The existing Lisbon airport is located practically within the city limits, since the city has developed towards the surrounding airport area. The planning of a new airport, outside the city boundaries, has called for a comparative noise study on two alternative locations: Ota and Rio Frio. A noise study was conducted which included a survey of the ambient noise and of their sources and the prediction of air traffic noise for two different scenarios of transport capacity: 12,000 and 25,000 passengers per year. The reduction of aircraft emissions owing to technological evolution was envisaged and accounted for. The impact of aircraft noise was assessed on the basis of the number of population exposed to noise levels, with 10 dB intervals above 55 dB(A). For values lower than this, annoyance was considered to be unimportant, during daytime. As expected, the population exposed to noise levels above 55 dB(A) rises with the increase of airport capacity for the two locations. Nevertheless, when a 5 dB(A) reduction in aircraft emissions is considered, as a benefit of technological development, the population exposed to LAeq values above 55 dB(A) is quite similar for the two scenarios and even decreases for levels above 65 dB(A). These results helped to show that the introduction of new noise control technologies would compensate for higher aircraft traffic. The investments of the airport authorities on noise measures and procedures for the new airport would then be valid and effective for a long period of time.

• LISBON NOISE MAP
  J.L. Bento Coelho and M.J. Palma
[Abstract]

A noise map has been prepared for the city of Lisbon. Only the Municipality of Lisbon was considered. This is an area with about 700,000 inhabitants. Different sources contribute for the overall environmental noise: traffic (road, railway, tramway and aircraft), construction and leisure activities. The noise maps are drawn by calculation. Some measurements were made, however, in order both to verify and validate the model and to account for noise emissions where predictions were not so easy, such as tramway noise and leisure activities (especially at night). Input data for the model include the traffic characteristics (density and composition, mean speed, vehicle or aircraft type, air paths), the characteristics of the land and of the obstacles, especially the height of the buildings and the façades sound absorption. These noise maps can be regularly updated by checking on the input data and recalculating with the updated values. Although discussions on method and presentation are currently being held within the European Commission framework, namely within its Working Group 4, Noise Maps, the procedure for noise values determination followed the existing ISO standards. Daytime and nighttime values of LAeq were determined in points of a grid. The noise values were calculated in 5 dB(A) intervals and the colour code defined in ISO 1996 was used. Results will be presented and discussed.

• NOISE MAPPING OF ROAD TRAFFIC NOISE IN PORTUGAL
  J.L. Bento Coelho, J.R. Mateus, M.J. Palma, A.M. Almeida and C. Patrício
[Abstract]

The Portuguese Road Authority has started a broad programme of mapping of road traffic noise for the major roads in the country. This work has been developed together with the Group of Acoustics and Noise Control of CAPS/IST, Lisbon Technological University. The maps will be available to the local authorities and the general public for planning purposes as well as for general information. The noise maps are drawn by calculation. Input data for the model include the traffic density and composition as well as the mean speed for each traffic lane, the type of pavement and the characteristics of the road and of the surrounding land. A set of measurements was made in order to verify and validate the model. These noise maps can be regularly updated by checking on the traffic and recalculating with new traffic data. The daytime values of LAeq are determined in points of a grid for an area established around the road line. This area was initially defined as 300 m wide, but it is now 500 m wide, since it was thought as more appropriate. Noise values are calculated in 5 dB(A) intervals and the colour code defined in ISO 1996 is used for presentation of the results. A sample of the first noise maps will be presented and discussed in terms of both the method and the results.

Benton, S.

• LOW FREQUENCY NOISE "POLLUTION" INTERFERES WITH PERFORMANCE
  J. Bengtsson, K. Persson Waye, A. Kjellberg and S. Benton
[Abstract]

To study the possible interference of low frequency noise on performance and annoyance, 32 test persons classified as sensitive or non-sensitive to noise in general or to low frequency noise, worked for 2.5-3 hours with different performance tests in a noise environment with dominant low frequencies or dominant middle frequencies both at a level of 40 dB LAeq. The effects were evaluated as changes in performance and subjective reactions using questionnaires. The results indicated that low frequency noise interfered with a proof reading test by decreasing the number of markings made per line read. The results furthered showed that the response time in a verbal grammatical reasoning test was longer over time in the low frequency noise exposure. The subjects reported a higher degree of annoyance and work impairment when working in low frequency noise. The effects were more pronounced for subjects sensitive to low frequency noise, while partly different results were obtained for subjects sensitive to noise in general. The results suggest that work performance and perception of annoyance may be influenced by a continuous exposure to low frequency noise at commonly occurring noise levels and that subjects classified as sensitive to low frequency noise may be at highest risk.

Béra, J.-C.

• SEARCHING PHYSICAL CRITERIA OF SOUND QUALITY: PSYCHOACOUSTICAL STUDY ON THE SPECTRAL COMPOSITION OF DISCRETE-FREQUENCY NOISE
  J.-C. Béra and S. Khalfa
[Abstract]

For 20 years, technological improvements in noise reduction have provided powerful tools to control the noise pollution. However, their implementation shows that a reduction in noise acoustic level does not always correspond to an annoyance reduction. Therefore the noise annoyance has to be considered as a more global concept than the acoustic noise level. In that way, while numerous studies focus on improving the sound quality of a given product or phenomenon, we are interested in finding general physical criteria of sound quality, and more particularly of noise annoyance. The present study deals on discrete-frequency noise. Four signals were chosen corresponding to environment discrete-frequency noise of different spectral compositions. From each one, 8 signals were generated by spectral modifications. The acoustic signals were presented by pairs to 25 subjects, who compared them in term of noise annoyance. Statistics show significant preferences between the differently modified signals. It is principally noted that a deficit in mid frequencies increases the noise annoyance, while an high-frequency suppression improves the noise quality. Moreover, the addition of a broadband component in the noise is generally favourable, especially in the case of high-frequency discrete-frequency noise.

Berengier, M.

• CALCULATION OF METEOROLOGICAL CONDITIONS EFFECTS ON OUTDOOR SOUND PROPAGATION USING PARABOLIC EQUATION
  M. Berengier and B. Gauvreau
[Abstract]

The presence of high-trafficked roads around large cities produces substantial noise disturbances for neighbouring inhabitants. Due to the source traffic composition and the outdoor propagation conditions, the populations can be submitted to large sound pressure level variations. In order to predict these variations, an important research programme has been set up. Researches reported in this paper are dealing with a calculation method based on a numerical approach which allows to consider a large set of situations which can be met outdoors. The main phenomena taken into account are : ground effect, impedance discontinuity and screen diffraction and various atmospheric conditions. To solve these large and complex problems, the methods based on the parabolic approximation seem to be well adapted. Among these, the Split-Step Padé  method appeared to be the most reliable with respect to its obvious advantages in terms of angular aperture and CPU time, and to its capability to consider the most involved phenomena : homogeneous or mixed grounds, acoustic barriers, etc... The atmospheric turbulence is taken into account through the discrete random Fourier modes  technique. It is considered as isotropic, homogeneous and essentially due to temperature scalar fluctuations. The 2D spectral density is assumed to have a Gaussian distribution or a von Karman profile. The corresponding numerical code has been first validated through comparisons with literature data. Then, the propagation conditions have been progressively complexified in order to simulate more realistic propagation situations. Numerical and experimental data will be discussed in the paper.

• EFFECT OF LOW-NOISE PAVEMENTS ON TRAFFIC NOISE PROPAGATION OVER LARGE DISTANCES : INFLUENCE OF GROUNDS AND ATMOSPHERIC CONDITIONS
  M. Berengier, Y. Pichaud and J.-F. Le Fur
[Abstract]

In a large majority of industrialised countries, traffic noise abatement is considered as essential. Road pavements can contribute to this challenge. Researches carried out in the past fifteen years have made it possible to identify and to classify the acoustic performances of road surfaces for short range conditions, in terms of vehicle pass-by sound pressure levels LAmax. At the beginning of these researches, 0/20 mm to 0/10 mm single layer porous asphalts were the only low-noise pavements to be used in France and western Europe. Since the last five years, new pavements composed of small size chippings (0/6 mm), spread in thin layer, have been studied. After measurements carried out according to standardised methods, they can be considered as low-noise pavements too. First experiments show that they can be used as much in suburban as in urban situations. These preliminary results found for road near-field configurations have now to be confirmed for long range situations in terms of equivalent sound pressure levels LAeq, indicator more currently used for environmental nuisances. This is the purpose of this paper which will present firstly, some theoretical and experimental results at various distances, up to 200 m, for a few kinds of pavements and, afterwards a general study permitting to evaluate the effects of these recent low-noise surfaces, in terms of LAeq, on traffic noise propagation. For this, theoretical traffic and propagation conditions (ground and atmospheric parameters) have been considered. Preliminary results for reference day and night periods will be discussed in the paper.

Berge, T.

• EXPERIENCE WITH NOISE AND TRAFFIC CALMING IN NORWAY
  T. Berge
[Abstract]

In the period 1993-1995, the Public Road Administration in Norway carried out a test project on traffic calming in 5 small villages. In all these villages, the main street was originally not functioning well, neither aesthetically or from a safety point of view. The main goal for the project was to make the streets ''environmental friendly'' and increase the safety for pedestrians, cyclists and vehicle drivers. Besides these factors, a second goal was also to reduce the traffic noise levels. SINTEF was asked to do some measurement of noise and driving behaviour before and after rebuilding of the street at one of the 5 locations. At 2 other locations, the noise measurements were performed only after rebuilding of the street. In particular, the noise was measured at pedestrian crossing areas, where special stones were used to increase the attention to the drivers and from an aesthetic point. The paper will present the results from the noise measurements and the driving behaviour (speed profile measurements), and discuss important factors in traffic calming schemes regarding noise.

Bergen, T.

• NOISE REDUCTION EFFECTIVENESS OF WHEEL AND RAIL VIBRATION ABSORBERS
  J.T. Nelson and T. Bergen
[Abstract]

The rolling noise reduction effectiveness of wheel and rail vibration absorbers was evaluated at a section of tangent ballasted track with concrete sleepers in Portland, Oregon, USA, as part of Transit Cooperative Research Program Project C3A. Preliminary results of the rolling noise tests are reported here for various combinations of treated and untreated rails and wheels. The wheel and especially the rail vibration absorbers significantly reduced rail vibration at audio frequencies, but had little effect on wayside rolling noise. While the rail vibration absorbers did not reduce the maximum pass-by noise significantly, the ''singing rail'' noise was eliminated entirely. The ''singing rail'' vertical vibration transmission spectrum had a pass-band characteristic, as expected for periodic supports. The vibration data indicate that the wheel was the most significant source of noise above 250 Hz.

Berglund, B.

• THE POTENTIAL OF MASTER SCALING OF PERCEPTUAL ATTRIBUTES IN SOCIAL SURVEYS
  B. Berglund and M.E. Nilsson
[Abstract]

The goal of noise-annoyance social surveys is to examine in detail and ascertain the annoyance experienced by noise-exposed persons. In practice, a general quantitative relationship between annoyance and noise exposure is sought in order to be able to predict the annoyance experienced from noise assessments made in the future. The extensity of annoyance in a population, spread geographically, is typically utilized as an outcome measure (% HA) even though individual residents report their degree of annoyance on a category scale. The ecological fallacy has to be avoided. That is, dose-response relationships for differently exposed populations cannot be inferred to be valid for individual residents. This is a problem because we wish to change individual resident's annoyance by noise abatement, and prediction of the change cannot be inferred from population-based relationships. By using the principle of master scaling in quantifying annoyance in social surveys, it is possible to ''calibrate'' for interindividual differences. Comparability between populations can, thus, be obtained although different residents have reported annoyances uniquely linked to their own local noise exposure. So far, master scaling has been successfully applied in field studies and tested in psychoacoustical model experiments. The ''calibration'' of scales for perceptual attributes has also been validated experimentally. By master scaling annoyance and other perceptual attributes, it would be possible to predict changes in these variables and evaluate the efficiency of various noise abatement procedures.

• TOTAL ANNOYANCE AND PERCEPTUALLY DISCERNIBLE NOISE SOURCES
  B. Berglund and M.E. Nilsson
[Abstract]

Questionnaire-study respondents are obviously able to attribute their feelings of annoyance to specific sounds in their environment. A prerequisite is that these sounds can be discerned perceptually in the flow of sounds constituting the soundscape. If total annoyance of a noisy environment is to be assessed, the respondent will have to integrate the information derived from these discernible sounds. The key question is what type of information is integrated? According to present total annoyance models, the answer is simply annoyances, loudnesses, or sound pressure levels. None of these answers consider the fact that certain sounds are perceptually more discernible than others in the flow of sounds and some sounds play a more prominent role than others in the soundscape. Perceptually discernible sounds appear as ''foreground'' or ''background'' due to attributed characteristics such as ''familiarity'', ''predictability'', ''persistency'' or ''intrusiveness''. Consequently, total annoyance models based on energy summation processes for multiple noise sources are incompatible with total annoyance models based on perceptual-cognitive integration processes. The latter processes are necessarily and intuitively involved in respondents' reporting of total or specific noise-annoyances in questionnaire studies. Our research has shown that it is fruitful to develop total annoyance models as linked systems considering perceptual discernibility of sounds, cognitive attributions of annoyance to sources, and integration of acoustic properties of annoying noises in perceived soundscapes.

Bernetti, R.

• A REFINED BE TECHNIQUE FOR MODELLING RADIATION AND SCATTERING FROM VIBRATING STRUCTURES: EXPERIMENTAL VALIDATION OF BEM RESULTS OBTAINED USING LASER DOPPLER VIBROMETRY
  R. Di Sante, R. Bernetti, G. Rossi and A. Ambrosini
[Abstract]

In this paper, a refined Boundary Element technique, developed to model radiation and scattering from vibrating structures in the frequency domain, is validated in the case of a small reverberating room by comparison with acoustic measurements. An experimental set-up was built consisting of a box-shaped structure, with a wall excited into vibration by an electro-dynamic shaker. A fairly good agreement was found between numerical and experimental results. In order to ease the definition of boundary conditions in the case of experimental vibration data, a special interface with a Scanning Laser Doppler Vibrometer was also developed.

Bernhard, R.

• OBSERVATIONS OF THE STRUCTURAL ACOUSTICS OF AUTOMOBILES
  R. Bernhard
[Abstract]

Three structural acoustic databases are discussed. The first is an illustration of the variability of the structural acoustics of nominally identical automobiles due to naturally occurring environmental conditions and to normal manufacturing conditions. The second is a database that illustrates the range of tire/vehicle transfer characteristics that occur in various models of automobiles. The third is a twodimensional measurement of the vibration pattern of a tire that shows the wave behavior of the tire and suggests a relatively simple model of the tire for modeling purposes. The implications of these results to future design philosophy and better interior noise in automobiles is discussed.

• THE CHARACTERIZATION OF VIBRATION SOURCES AND MEASUREMENT OF FORCES USING MULTIPLE OPERATING CONDITIONS AND MATRIX DECOMPOSITION METHODS
  R. Bernhard
[Abstract]

The problem of understanding the sources in a machine is fundamental to building a model of the system including models of the forces that excite the system and models of the transfer paths between these forces and the responses of interest. Once the sources are understood, proper measurements can be made to experimentally determine the forces and the associated models can be developed to predict the response of the system to such forces. In this paper, strategies are described to formally characterize the sources to determine how many independent sources occur within the system. Additional strategies are developed to measure these forces indirectly using external measurements and to build a multiple-input, multiple-output model of the system. Both sets of strategies depend heavily on linear algebra to extract the independence of data gathered on the system. These data are interpreted to better understand the system and specify models.

• TIRE/PAVEMENT INTERACTION NOISE RESEARCH ACTIVITIES OF THE INSTITUTE FOR SAFE, QUIET, AND DURABLE HIGHWAYS
  R. Bernhard, N. Franchek and V. Drnevich
[Abstract]

Tire/road interaction noise is the major source of highway sideline noise at highway speeds. Increased traffic flows and population densities have caused a greater interest in this source of environmental noise. The Institute for Safe, Quiet, and Durable Highways (SQDH) was established at Purdue University in 1999 to investigate the development of quiet highway technology that is safe, durable, and economical. This Institute is a joint effort between the Schools of Civil and Mechanical Engineering. The goals of the SQDH Institute include education, research, and technology transfer activities. The research program of the SQDH Institute is intended to be complementary to world-wide research on tire/pavement interaction noise. Both tire and pavement issues will be studied. Initial emphasis will be given to fundamental investigations of the mechanisms of tire/pavement noise generation and control. Laboratory facilities will be constructed to facilitate acoustic and vibration measurements of tires rolling on realistic road surfaces. In addition, analysis methods will be developed to better understand wave transmission and sound radiation from tires. Future work will involve implementation of the understanding of tire/road noise generation mechanisms to the practical issues of quiet highway construction and maintenance, material design, and traffic management. This application of quiet highway technology will hopefully reduce the need for noise barriers. A review of ongoing SQDH Institute research programs and available results will be presented. Future plans and potential collaboration

Berry , B.

• AIRCRAFT NOISE AT SCHOOL AND CHILD PERFORMANCE AND HEALTH INITIAL RESULTS FROM THE WEST LONDON SCHOOLS STUDY
  S. Stansfeld, M. Haines, J. Head, B. Berry , M. Jiggins, S. Brentnall and R. Roberts
[Abstract]

Previous research suggests that children's cognitive performance and health are adversely effected by chronic noise exposure. However, uncertainty remains because cognitive performance is also influenced by school quality and social deprivation which may confound noise effects. By increasing the number of schools and children, the aim of this study is to test whether the noise effects previously found in children are attributable to noise and to test possible mechanisms. The cognitive performance (reading, memory, attention) and stress responses (annoyance, perceived stress, catecholamine secretion) of children attending 10 primary schools exposed to high levels of aircraft noise (63 dBA 16hr Leq) were compared cross-sectionally with 10 matched control schools exposed to lower levels of aircraft noise (57 dBA 16hr Leq) around Heathrow Airport in West London. Schools were matched across aircraft noise exposure by: age, sex, socio-economic status, ethnicity and non-aircraft environmental noise sources. The cognitive tests and questionnaires were group administered in the classroom while noise measurements were carried out to assess school noise exposure. Initial results will be presented using multi-level modeling and multivariate statistical techniques to adjust analytically for the potential confounding effects of school characteristics and socio-economic factors on associations between noise and performance at the individual level.

Bertellino, F.

• A COMPREHENSIVE STUDY OF HOT PRESSING NOISE IN AN ITALIAN SUBALPINE SCENERY: A NEW POLICY FOR DECISION MAKERS
  F. Bertellino, S. Roletti, D. Sartore and F. Mana
[Abstract]

Hot pressing plants have been since the first decades of the last century one of the main industrial resources of the Canavese region, a Piedmontese area well apart from the industrial concentration around Turin. In this subalpine area many pressing and forging plants grew up in close relationship with the urban context of the local small villages: the very consequence of this has been an increasing conflct due to noise and vibration problems, strictly linked with the peculiar activity of the hot pressing plants, that makes an intensive use of extremely noisy machines such as mallets and punch presses, all being featured by highly impulsive noise. The regional public authority decided to finance a comprehensive study of the problem, as more and more often the population seems to arise with violence against the industries, that often are still located too close to residential areas, thus seriously annopying people. In the papaer about 30 cases of annoyance have been taken into account, with the main purpose of havinga global look at the situation, but also in order to offer a real undertanding to decision makers and investigate noise abatement solutions, choosing among different choices: optimized noise abatement, re-location of the plant (with public financing, agreements between the parts. The study was positively considered ampong population and industries, and all of them cooperated to overtake this long lasting environmental problem.

Bertoni, D.

• ANNOYING NOISE LEVELS AT HOME: A COMPARISON AMONG DIFFERENT KIND OF SOURCES
  D. Bertoni and A. Barchi
[Abstract]

Noise emission from industry, mechanical devices and shops often annoy people in their dwellings. The document ''Community Noise'', edited by WHO in 1995, states that noise from ventilation systems in residential buildings may cause considerable concerns even at low and moderate sound pressure levels. The aim of this work is to find which noise levels are causing annoiance at home, according to different kind of sources. The statistical analysis of over 260 cases of complaints, addressed to the local authorities of the city of Modena since 10 years, make a comparison possible among noise levels taken in the dwellings by engeneers of the environmental Agency. Comparisons were carried out taking into account the period of the day and the condition of open or shut windows. Data were pooled according to the following kind of sources: a) rotating and reciprocating machines as fans, compressors, air conditioners; b) industrial noise; c) music live or reproduced; d) road traffic. Significant differences have been found among average noise levels from different kind of sources. During the daytime, with open windows, noise from rotating and reciprocating machines cause complaints at lower levels than industrial sources and these ones at lower levels than road traffic. The average traffic noise level in façade that cause complaints coincide with the average exposure level of very annoyed people as shown in the community noise surwey carried out in Modena in 1990. The average noise levels found may represent ''thresholds'' useful in fixing noise limits.

Bertrand, E.

• EXPERIMENTAL CHARACTERISATION OF AERO-ACOUSTIC SOURCES IN ENCLOSURES.
  Y. Knapp, L. Jourdan, E. Bertrand and J.P. Guibergia
[Abstract]

Experimental or numerical analysis of flows in a heater unit of an automobile air conditioning system is very important for fundamental design, improvement of efficiency, of aero-acoustic behaviour etc. The small size and complex geometry of such devices, makes the identification and localisation of aero-acoustic sources very difficult by classical acoustic methods. The present study aimed at using Powell's formulations of aerodynamic sound generation, expressing aero-acoustic source strength in terms of vorticity, to quantify aerodynamic sound generated in such enclosures. Therefore, a technique of whole field velocity measurements called Particle Image Velocimetry was used to map the instantaneous velocity distribution in the casing of a heater unit model. This instantaneous flow fields are differentiated twice to obtain the vorticity field, and the Powel's source term div(w x v) is directly computed from these measurements. The differentiation schemes are optimised to reduce cumulative errors. The possibility of estimating the 2D pressure field by numerical integration of the steady Navier-Stokes equation is also given. The main advantage of this technique is to perform aerodynamic measurements to approach acoustic problems, therefore giving the possibility to test modifications and judge their effects on both the flow and acoustic field.

Beslin, O.

• A HYBRID TOOL FOR QUICK CHARACTERIZATION OF COMPOSITE PANELS EQUIVALENT PROPERTIES.
  I. Sow, O. Beslin and J. Nicolas
[Abstract]

It is well established that to develop a quiet machine, the best way is to take into account its acoustic radiation properties at the early stage of the conception by optimizing its geometry and material properties using acoustic prediction tools. Usually, prediction is made using Finite Element Method (FEM) and in most cases, these FEM codes require input data that cannot be easily obtained. This is particularly true when the material is a ''home made'' composite material (glass fibers with polyester resin, etc.), in a procedure that cannot ensure a rigorous control on thickness, density, etc. Consequently, there is a need for a tool that allows to quickly and easily characterize the ''equivalent properties'' of unknown composite panels in order to get input data for FEM codes (or for itself). In this paper, a method is proposed which uses a simple experimental setup and a fast numerical code running on a personal computer. This allows to extract equivalent properties of composite panels in terms of ''young modulus'', ''density'' and ''damping factor'' versus frequency. The experimental setup allows to test small rectangular panels (225 mm by 285 mm) with a very easy installing procedure (clamped at the corners). A dedicated numerical code (based on hierarchical finite element method) is used to fit parameters in order to match measured and simulated data. It is shown that this method allows to quickly extract useful equivalent properties for composite materials.

Bessac, F.

• INFLUENCE OF THE MOUNTING CONDITIONS OF AIR DIFFUSION TERMINAL UNITS ON THEIR ACOUSTIC PERFORMANCES
  F. Bessac
[Abstract]

The in situ acoustic performances of air diffusion terminal units sometimes differ greatly from those measured in the laboratory in accordance with the ISO 5135 standard. This stems from the fact that the standard assumes that the grilles (or diffusers) will have a very large air supply plenum, while in practice they are connected to a small plenum, which radically alters their acoustic power level performances. CETIAT has tested a grille equipped with a plenum whose dimensions could be varied: length of the plenum, branch connection diameter and position of the branch connection (rear or side). Each parameter could have two states representative of the true situation found in the field. The purpose was firstly to determine the acoustic performances for each configuration and then to rank the importance of each parameter. These tests show that a grille's sound level can increase by approximately 15 dB(A) when a plenum is added, even though the latter is in its optimal configuration. The increase in sound level reaches 20 dB(A) between the plenum's two extreme configurations. These results confirm that the performances of grilles are radically modified by the type of plenum it is connected to. Regarding the dimensions used in the tests, the analysis also shows that the most influential parameter is the position of the branch connections, followed by the branch connection diameter and finally, the length of the plenum.

• CHARACTERISATION OF THE ACOUSTIC POWER LEVEL OF A RANGE OF RECTANGULAR DIFFUSERS USING A REDUCED NUMBER OF TESTS
  F. Bessac
[Abstract]

Since the sound level requirements are increasingly strict, the characterisation of the acoustic performances of complete product ranges has become essential for the manufacturers. This is particularly true for ranges of air diffusion terminal units composed of a large number of different types and sizes and for which it would be prohibitively expensive to carry out exhaustive laboratory tests. CETIAT has studied the possibility of carrying out a reduced number of test in order to characterise a complete range of rectangular diffusers. The acoustic power level was measured on a grille model available in 7 different sizes, from 200x200 mm to 600x300 mm (4 flow rates for each one). Then, the regression relation was determined between the global dB(A) level and the air flow and the area of the grill. This relation gave an average error of 1 dB(A) with 82% of the deviations lower than 1.5 dB(A). The next step was to determine how many initial tests were necessary to determine the acoustic performances of the rest of the range with an acceptable error. The regression coefficients were calculated for all the possible combinations of 3 grilles (respectively 4), then the error committed on the other 4 grilles (respectively 3) was calculated. These results show that 3 different sizes are sufficient to establish the regression coefficients for a given type of grille. In addition, if the 3 grilles used in the test are chosen intelligently so as to cover the different sizes and shapes (section and ratio of dimensions), the deviations observed over the rest of the range were among the smallest.

Biassoni, E.C.

• A LONG-TERM STUDY ON HIGH LEVEL MUSIC EXPOSITION AND HEARING EFFECTS IN ADOLESCENTS
  M.R. Serra, E.C. Biassoni, U. Richter, G. Minoldo, G. Franco, S. Abraham, S. Joekes, M.R. Yacci, A.R. Pollet and A.J. Carignani
[Abstract]

Sources of noise exposure outside the workplaces that are potentially damaging has been topic of many studies (Clark, 1991). Young people are exposed to high level music in discotheques or through personal listening devices. The literature reveals that there are different opinions about possible harmful hearing effects of music (Babish et al., 1988, West et al.,1990; Axelsson, 1990 & 1996; Royster et al., 1990; Ising et al., 1995). This paper deals with the early results of an interdisciplinary long-term study on hearing effects in adolescents by high level music exposition and its relation with physical and psychosocial variables, developed according international standards. Two groups of adolescents -males and females- are examined along four years of their high school level, from 14 to 17 years old. The study focus on changes both, in hearing threshold, applying conventional and extended high frequency audiometry, as well as, in recreational activities. Besides, sound inmission levels of the adolescents studied are measured: a) in discotheques using two methods: by personal dosimetry and by a system developed ad-hoc; b) using walkman and/or diskman: through manikin-technique. In the second year of the study the results show: a) hearing threshold shift in most of the extended high frequencies; b) increase in the music exposure through recreational activities; c) high sound inmission levels in discotheques and trough personal music devices. The whole study, during four years, let will us to know the real hearing effects by music exposition and their relation with psychosocial variables in the studied adolescents group.

Bidault, A.

• AUDITORY PERCEPTION OF ROAD TRAFFIC NOISE
  C. Lavandier, A. Bidault, N. Chouard and S. Viollon
[Abstract]

Our perceptual spatial representation of road traffic noises is revealed in this study by a dissimilarity factor analysis, on a corpus of fourteen stimuli, representative of urban and suburban environments. A cluster analysis is carried out too, to gather those same sound objects into homogeneous classes according to the aroused stress. To avoid the prominence of noise level which dominates our perception, the stimuli loudness is equalized. The multidimensional approach proposes three auditory factors. However, the correlation coefficients between factors and objective indices are not satisfying. Moreover, the first dimension reveals a perception in accordance with the categorization's results, the stimuli being separated into two groups: one is composed by typical urban sounds, the other consists mainly of suburban traffic noises. Listeners bring together sounds with regard to the meaning of sources. In each group only, they describe physical properties of the signal. So, the cluster analysis categories are used to correlate, class by class, the perceptual dimensions with physical parameters. The second dimension expresses the number of identified sources, which can be correlated with standard deviation of equivalent level for the suburban noises (95%). The third factor is a spectral one, which can be correlated with the sharpness of the typical urban noises (98%).

Biermayer, W.

• EFFECTIVE IMPLEMENTATION OF BRAND SOUNDS IN EXCLUSIVE PASSENGER CARS
  F. Brandl, S. Thomann and W. Biermayer
[Abstract]

A distinct brand sound is one important aspect in selling exclusive passenger cars. Such a brand sound has to be defined on the one hand via customer expectations which are different for different world markets. On the other hand, the implementation of a once desired brand sound into the vehicle requires extensive knowledge how this brand sound has to be composed and how this composition can be transferred into the relevant hardware modifications in the vehicle. In this paper examples of tailor made compositions of interior sounds and their implementation by the necessary changes to the powertrain will be discussed and presented.

Biondi, G.G.

• ITALIAN LEGISLATION ON NOISE ASSESSMENT AND CONTROL
  G.G. Biondi
[Abstract]

Till March 1991 the Italian legislation concerning the assessment and the control of the noise followed the adoption of the directives issued by the European Commission and Parliament. So that the regulations enforced until then were concerning the levels of noise from cars, trucks, outdoor machineries and so on. On the 1st March 1991 was issued the first Italian regulation on noise regarding ''Indoor and outdoor limits of exposure to the noise''. In this law, in addition to the noise limits expressed in dB(A) of Leq, were enounced also general criteria on the mapping and the zoning of the urban areas. After four years from the enforcement of the 1st March 1991 decree, it was clear the need of a general law in the assessing and controlling the noise, in order to assign specific competences to the municipalities, to the local authorities, to the regions and to the central administrations. The Italian general law on noise pollution has been issued by the parliament on 26th October 1995 and is in force since 1st January 1996. Since then the Italian Government has enacted regulations concerning: - the assessement and the control of the industrial noise in not industrial urban areas; - the noise levels allowed in different urban areas; - the assessement and the control of the airport noise; - the assessement and the control of the railway noise; - the noise into the discos, pubs and from entertainments; - the building requirements to reduce the indoor level of noise. A short presentation of these regulations is given.

Birch, R.

• FINITE ELEMENT METHOD (FEM) MODEL FOR THE HEARING PROTECTOR NOISE ATTENUATION FOR IMPULSIVE NOISE
  S. Gerges, F. Vergara and R. Birch
[Abstract]

This paper presents a numerical model by FEM of the human external earcanal, considering the acoustic impedance of the eardrum.The sound pressure level at the eardrum is calculated with and without the presence of the hearing protector ear plug. The effec

Birkedal Nielsen, J.

• NOISE MONITORING OF TRAIN WHEELS
  P. Ramussen, P. Buchwald and J. Birkedal Nielsen
[Abstract]

A system for automatic recording and processing of the noise emission from train wheels is described. The system is part of a procedure for systematic condition-based wheel maintenance, whereby the maintenance cost can be reduced and the lifetime of the wheels can be extended. The noise monitoring system has been established on one of the main tracks towards Copenhagen central station, Denmark, and automatically records the noise emission from all inbound trains. Based on the distance between the wheels and the noise profile known train types can be identified and the noise contribution from each individual wheel can be isolated and normalized with respect to the train speed. The data can be transferred via modem to the central maintenance facility for recalling of train units for service. The system has proved a potential cost reduction in maintenance and a reduction in noise emission.

Bisio, G.

• ACOUSTIC RESONATOR WITH NON-LINEAR STEADY STATE WAVES - ANALOGIES AND DIFFERENCES WITH OTHER SIMILAR DEVICES
  G. Bisio and G. Rubatto
[Abstract]

Recently, new acoustic resonators have been developed. They allow us to reach so high pressures that they can be utilized as usual compressors of air and other gases or for reversed cycle plants. Lucas has developed a technique by which standing sound waves resonating in specially shaped closed cavities can be loaded with thousands of time more power than it was previously possible. Lucas's wave-shaping technology is known as ''resonant macrosonic synthesis'' (RMS). Lucas states (and his statement seems acceptable) that the inherent simplicity of this technology could result in increased reliability and durability, and oilless operation. The first major application of RMS technology has been an acoustic compressor. The standing wave in the resona-tor causes the pressure to oscillate during one acoustic cycle of about 2 ms. When the pressure is low at the thinner end, the suction valve opens and low pressure gas flows in and enters the plenum. When the pressure is high at the thinner end, the discharge valve opens and high pressure gas flows from the resonator into the discharge plenum. High-pressure gas in the resonator holds the suction valve shut. In this paper a table with similarities and differences among several systems, including the new RMS, is reported. The following distinguishing criteria have been assumed: (i) the presence or absence of constructive irreversibilities, (ii) the presence or absence of a valuable mass transfer and then of a valuable power, (iii) the range of the employed fre-quencies. This table seems suitable to remark basic differences among devices that are usually considered similar.

Bite, M.

• EFFECTIVE NOISE REDUCTION BY A NEW-SHAPED NOISE BARRIER
  M. Bite
[Abstract]

During modernization of a railway line in Hungary, the claim for noise protection of the dwellings along the railway has arisen. The noise immission, originating from railway transport, was 71 LAeq dB at night, at the dwellings. The task was to reduce the noise immission by at least 16 dB. In this case the only possible solution for noise abatement was to build a noise barrier. However, based on the experience of recent years, a noise reduction of only 13-15 dB can be achieved by a noise barrier. To guarentee the required noise reduction a new construction was planned, which contained a noise barriere and an octahedron-shaped structure. The result of laboratory and field investigations

• ENVIRONMENTAL NOISE REDUCTION OF LARGE INDUSTRIAL PLANTS
  I. Dombi and M. Bite
[Abstract]

The evaluation of noise reduction in a large Hungarian power stations needs such methods which are capable to follow the expected results of planned technical solutions in noise reduction. Using our method we may have the expected results without establishing technical structure of the noise reductions. The method is based on the SOUNDPLAN computer program. The actual poster lecture presents a total acoustical planning procedure including ways of noise pollution's reduction.

Bjorkman, M.

• PLEASANT AND UNPLEASANT CHARACTERISTICS IN WIND TURBINE SOUNDS
  K. Persson Waye, A. Agge and M. Bjorkman
[Abstract]

In Sweden, wind turbines are often built in areas where the background noise level is low. Noise annoyance in such areas may be related to acoustical characteristics in the wind turbine sound that are easily perceived and considered unpleasant. Findings from a previous study showed that different annoyance ratings were given to wind turbine sounds of the same dBA level. A psycho-acoustic profile of noticeable and unpleasant characteristics was obtained for each sound. The psycho-acoustical descriptors: whistling, swisching and uneven was previously evaluated . In the study presented here one of the most noticeable and annoying psycho-acoustical descriptor ''lapping'' was evaluated. With the object to obtain a pleasant sound, a total of 24 test subjects were asked to vary four parameters related to the psycho-acoustical perception of ''lapping'' in the original sound. The variations of the parameters were carried out using an interactive sound processing system and done in such a way so the resulting sound always had a constant dBA level. The resulting values of three of the four parameters were significantly different compared to the original sound. A pleasant sound thus had low contents of the lapping characteristics. While no difference was found between the original sound and the resulting sound with regard to the equivalent frequency spectra, some differences could be detected using Zwickers loudness calculations. The LAeq values are not sufficient to predict subjects perception of noticeable and unpleasant characteristics in wind turbine sounds. Further analysis should be pursued of how to best describe an unpleasant or pleasant wind turbine sound.

• COMPARISON OF COMMUNITY RESPONSE TO ROAD TRAFFIC NOISE IN JAPAN AND SWEDEN, PART I: OUTLINE OF SURVEYS AND DOSE-RESPONSE RELATIONSHIPS
  T. Sato, T. Yano, M. Bjorkman and R. Rylander
[Abstract]

To investigate cross-cultural differences in the community response to road traffic noise, social surveys were conducted in Gothenburg, Sweden, and Kumamoto and Sapporo, Japan, using the same questionnaire and noise measurement method. Typical residential areas with both detached houses and apartments were selected as the target areas in each city. The questionnaire comprised 40 questions relating to environmental, housing and personal factors. The key questions concerned annoyance due to road traffic noise. The total numbers of respondents were 1,142 in Gothenburg, 837 in Kumamoto and 780 in Sapporo. The response rates were 68.8%, 69.3% and 57.5%. After the questionnaires were completed, noise measurements were made in each area. Community responses were compared on the basis of the dose-response relationships. The main results are summarized as follows: 1) There are no systematic differences in community responses between Sapporo and Kumamoto, which have the same culture; 2) People living in detached houses in Gothenburg were more annoyed by the same road traffic noise than those in Japanese cities; 3) Regarding the activity disturbances indoors, there are no systematic differences between the three cities, while activities and resting in gardens or on balconies are significantly disturbed in Gothenburg, due to the differences in life-style between two countries; 4) People living in detached houses are more annoyed by the house vibration caused by road traffic than people living in apartments; 5) People are annoyed by exhaust from road traffic to the same degree as noise.

• COMPARISON OF COMMUNITY RESPONSES TO ROAD TRAFFIC NOISE IN JAPAN AND SWEDEN, PART II: CAUSAL MODELING BY PATH ANALYSIS
  T. Yano, T. Sato, M. Bjorkman and R. Rylander
[Abstract]

Path analysis was applied to data obtained in social surveys in Kumamoto and Sapporo, Japan, and Gothenburg, Sweden, to compare the causal models that describe the multiple stratum relationships between road traffic noise annoyance, endogenous variables and exogenous variables. Path models can estimate not only the direct effect of a variable on annoyance but also the indirect effect of the variable via other variables. The exogenous variables were selected from housing, personal and environmental factors, and the endogenous variables were selected from various activity disturbances and related effects, based on the results of discrimination by factor analysis. At the beginning of the analysis, an a priori path model was constructed and the structure equations for the endogenous variables were formulated. The standardized partial regression coefficients are called path coefficients and show the strength of the linkage between variables. A revised path model was constructed by deleting insignificant paths. The characteristics of annoyance responses are as follows: 1) Noise annoyance is most strongly affected by exhaust; 2) Community responses regarding activity disturbances and the related effects are different between Japan and Sweden and between housing types, due to differences in life-style; 3) Noise level presented by LAeq(24) does not have a strong direct effect on noise annoyance.

Blais, J.

• EXPERIMENTAL STUDY OF ROAD TRAFFIC NOISE CONTROL BY A PINE FOREST
  N. Barriere, Y. Gabillet, J. Blais, J. Defrance, P. Ducruet and F. Gaudaire
[Abstract]

In order to precisely bring to the fore the effect of meteorology on sound propagation through forests, an important measurements campaign has been carried out in the French Landes forest mainly composed of pine trees. The originality of the experiment is that road traffic noise and meteorological conditions have been measured simultaneously for both a forest situation and a plain situation, this for different positions of the receiver. All valid measured data have then been classified according to three propagation conditions: favourable to propagation, unfavourable to propagation and homogeneous conditions. As expected, the results depend on these conditions. In favourable conditions, the gain brought by the forest is between 3 and 5 dB(A) with the receiver at least 100 m away from the road. This meteorological situation occurs very often at night due to a temperature inversion phenomena. Moreover, it is of most interest since it corresponds to the periods when the annoyance due to the road in a plain situation is the highest. In unfavourable conditions, the forest may increase somewhat the received sound level. In homogeneous conditions, the sound propagation through the forest is not appreciably affected by meteorology anymore but only by the scattering by the trunks and foliage. Finally, these results have permitted to validate a new calculation method for the attenuation of road traffic noise by forests based on a fast implementation of the Parabolic Equation.

Blanc-Benon, P.

• THE EFFECTS OF ATMOSPHERIC TURBULENCE ON THE INTERFERENCE OF THE DIRECT AND GROUND REFLECTED WAVES
  V. Ostashev, S. Clifford, R. Lataitis, P. Blanc-Benon and D. Juve
[Abstract]

For many geometries of sound propagation in the atmosphere, a sound field at a receiver is a sum of the direct wave from a source and that reflected from the ground. If there would no turbulence, the interference of these waves would result in maxima and very deep minima in sound pressure level. Atmospheric turbulence can partially or completely destroy the coherence between the direct and ground reflected waves, and therefore increase the mean sound pressure level at interference minima by several dozens dB. The most recent theory of this phenomenon was developed by Clifford and Lataitis (JASA, V.73, 1545-1550, 1983). The primary goal of the present paper is to generalize Clifford and Lataitis's theory by taking into account developments in atmospheric acoustics since 1983. In particular, we calculate the mean squared sound pressure by using a parabolic equation method. Furthermore, we take into account that the direct and reflected waves are scattered by both temperature and wind velocity fluctuations, and use Kolmogorov, Gaussian and von Karman spectra to model spectra of these fluctuations. Finally, we obtain a formula for the mean squared sound pressure and relate it to that of the coherence function of a spherical sound wave for line-of-sight propagation. Theoretical results obtained are also shown to be in good agreement with measurements of the mean squared sound pressure

• EXPERIMENTAL STUDIES OF SOUND PROPAGATION THROUGH THERMAL TURBULENCE NEAR A BOUNDARY
  P. Blanc-Benon, J. Wasier , D. Juve and V. Ostashev
[Abstract]

Outdoor experiments have established the influence of atmospheric turbulence on sound propagation. Especially, it was pointed out that turbulence affects the interference pattern due to the existence of direct and reflected waves, and changes the average sound pressure level. However, the uncertainties with regard to the meteorological parameters, namely the velocity and temperature gradients, the velocity and temperature fluctuations, make it critical to assess their influences on the sound pressure field. An experimental investigation of acoustic waves propagating through a thermal turbulence near a rigid boundary was achieved in well-controlled laboratory conditions. A heated grid in air was placed horizontally in a large anechoïc room. The mixing of free convection plumes above it generates an homogeneous isotropic random thermal field. A vertical rigid flat plate simulates the ground. Experimental data are obtained by varying both the frequency of the source and the distance of propagation along the plate. In this paper we present experimental results for the mean sound pressure and the interference pattern. Comparisons are made with theoretical results established by V.E. Ostashev et al.

Blanchet, A.

• COMFORT CLASS AND PASSENGER SHIPS
  A. Blanchet
[Abstract]

Since 96-97, the only official rules requiring noise and vibration limits, on board ships, were the IMO resolution A468-(XII)- 1981 and the ISO standard 6954-1985.These recommandations concerned essentially the crew accomodation, passenger spaces were excluded. This gap was filled, recently, by the classification societies which have included, in their own rules, comfort classes for passenger and crew accomodation. In this paper, the objectives and the application of these comfort classes to passenger ships are discribed, in particular how the highest comfort corresponding to the class 1 can be achieved.Some of the required targets are more an utopian view than realistic ones.In fact, the classification societies have not considered, in the application of these targets, the technical processing and the financial impact. Passenger comfort has become, these last years, a very important contractual point, subject to heavy penalties when the ship does not fulfill the required comfort class. These comfort classes will be able to evoluate,only if it exists exchanges with builders for leading to adapted solutions, for each objective, corresponding to the best compromise between cost and weight.

Blaschko, R.

• LOW NOISE PANTOGRAPH ASP - RECENT DEVELOPMENTS
  W. Behr, T. Lölgen, W. Baldauf, L. Willenbrink, R. Blaschko, K. Jäger and J. Kremlacek
[Abstract]

The aeroacoustic noise of a pantograph increases dramatically with the train speed. Especially at a very high speed of 300 km/h and above the aeroacoustic noise of the pantograph may exceed the rolling noise of the wheels. Since it is inappropriate and expensive to build high noise barriers to screen the pantograph, a new design of pantographs is necessary for future high speed trains. In cooperation with DaimlerChrysler Rail Systems an actively controlled single-arm pantograph (ASP) will be developed until next year in order to improve the quality of the contact force fluctuation and to reduce the aeroacoustic noise emission using computer simulation to estimate the aeroacoustic noise. These simulations are very helpful when developing an optimized design and avoiding unacceptable designs in an early state of development. First simulation results of the recent developments of the pantograph head will be presented.

Blau, M.

• INVERSE FORCE SYNTHESIS: STATE OF THE ART AND FUTURE RESEARCH
  M. Blau
[Abstract]

In analyzing structure-borne noise problems, it is often desired to characterize vibrational sources in conjunction with a given receiving structure. Since the dynamical behavior of the latter is most often described by transfer models relating to excitation forces, sources may be characterized by the forces they excert on the receiving structure under operating conditions. Over the last two decades or so, various techniques to experimentally determine these forces have been proposed. They all have in common that the forces are inferred from the resulting vibration responses on and the transfer characteristics of, the receiving structure. They mostly differ in the way how the transfer characteristics of the receiving structure is obtained: by nonparametric or various parametric models, both of which can be based on measured or synthetic data. Regardless of the transfer model employed, all these techniques suffer from a high sensitivity to uncertainties in the data (measured or calculated), which means that it may become very hard to reliably predict the forces one is interested in. This is true even when no formal inversion of the transfer model is required.Therefore, techniques to quantify errors and to ''regularize'' the problem have evolved. In the present paper, the advantages and drawbacks of the various methods are discussed. Special attention is paid to issues that are felt to be rather underrepresented in discussions found in the literature body, such as the choice of deterministic or stochastic force models. On the basis of this comparison, it is attempted to sketch the directions of possible further research.

Blauert, J.

• EFFECTS OF BINAURAL SOUND PRESENTATION ON LISTENERS' ASSESSMENTS IN A PRODUCT SOUND TASK AND PROBLEMS OF TODAY'S MEASUREMENT PROCEDURES
  T. Hempel and J. Blauert
[Abstract]

Today, binaural sound measurement and reproduction methods are already widely used for the assessment of product sounds in listening tests. But the respective instrumental measurement devices mostly still treat binaural recorded signals separately as two monaural ones rather than integrating them. Due to the fact that most instrumental evaluation methods do not take into account binaural differences, the assumption arises that errors occur between instrumental and human assessments. This assumption was investigated in a listening test on interior car sounds where listeners had to assess the sounds according to given verbal attributes. Significant differences in the results of the assessment for binaural and monaural presentation could be shown for some verbal attributes.

Blomqvist, J.

• DETECTION OF IMPACT SOURCES USING AN IMPULSE RESPONSE RECOGNITION TECHNIQUE. APPLICATIONS ON RATTLE SOURCES IN GEARBOXES
  J. Blomqvist
[Abstract]

A new approach is presented for the localisation of impulse sources in complex structures, e.g. engines, driving units or complete vehicles. The approach is based on a correlation technique similar to methods used in radar techniques. The method is developed for an engineering application aiming on the detection of gear rattle in gearboxes. Gear rattle occurs in gearboxes, is caused by relative motion between acting gearwheels and depends on the play between the gearwheels. The proposed analysis method is based on the idea to measure impulse response functions (so called characteristic signals) from possible source locations to a receiving point on the surface of the structure, e.g. the casing of a gearbox. These characteristic signals are compared with vibration measurements when the analysis object is running and impulse sources are active (e.g. rattle impacts between cogwheels). The comparison is done by calculating the correlation coefficient between the characteristic signals and the measured vibrations at the receiving point. Engineering solutions are suggested to handle the complex task to detect rattle source in gearbox under different driving conditions. The function of the method is demonstrated for both a modified gearbox under well-controlled conditions in a test rig and for a gearbox in a complete truck. It is shown that the method is a good tool for locating rattle sources in complex structures. It provides information concerning the location as well as the intensity of the impulse sources.

Bluhm, G.

• TRAFFIC NOISE AND ANNOYANCE.
  G. Bluhm and E. Nordling
[Abstract]

It is well known that traffic noise can cause annoyance and sleep disturbance. However, the association between different exposure levels of noise and the grade of noise complaints has to be studied further. The aim of this ongoing study is to investigate the degree of general annoyance and sleep disturbance related to noise among people living in the vicinity of main roads and railways including analysis of potential co-variables. The study is performed in a municipality outside of Stockholm with a lot of through traffic. A questionnaire used in a countywide study of health effects due to environmental factors, including several questions on noise exposure, was distributed to a random sample of 500 individuals, 19-80 years old, in the municipality. The sample was drawn from buffer zones around main highways and the main railway using geographic information system technique. To estimate the individual noise dose a well-evaluated Nordic prediction model for traffic noise is used. Frequent annoyance due to road traffic noise was reported by 15% in the road exposed group, while annoyance due to noise from railway traffic was found among 42% in the train exposed group. Regarding frequent sleep disturbance corresponding complaints were 4% and 5% respectively. The response rate was 75%. The association between different exposure levels and the degree of general annoyance will be analysed with a multivariate statistical model. Traffic noise is an important public health problem and the results from this study will be useful, when deciding on future noise abatement.

Bobrovnitskii, Y.I.

• LOWER ATTAINABLE BOUNDS FOR THE ERROR OF RECONSTRUCTING THE VIBRATION FIELD OF A STRUCTURE FROM LIMITED DATA
  Y.I. Bobrovnitskii
[Abstract]

Considered is the problem of expanding (reconstructing) the vibration field measured on a part of an elastic structure to its unmeasured parts. Solution to this problem is important, e.g., for the optimal placement of limited number of sensors to best control the global vibration field, as well as in model updating, in planning vibration tests and in similar problems of structural dynamics and acoustics. Most attention is paid to the principal reconstruction errors. The main result is derivation of the lower attainable bounds for the errors. General properties of the bounds are studied and illustrated by computer simulations and experiment.

Boccini, L.

• COMPARISON BETWEEN ITALIAN AND RECOMMENDED EUROPEAN NOISE INDICATORS.
  G. Licitra, M. Cerchiai, C. Chiari and L. Boccini
[Abstract]

The Commission of the European Communities is developing its own regulation for noise pollution, in order to harmonise the legislative current survey in different Member States and to obtain an unique description of noise pollution in all EU territory. The European Commission recommended in its ''Position Paper on EU Noise Indicators'' the use of two main indicators in order to describe noise from all outdoor sources for assessment, mapping and control purposes. The Italian Regulations differ from the EU recommendations on methodology to measure noise, especially for definition of the indicators to be used. In this paper we analyse the main differences between them and try to evaluate the corrections to be done to avoid losing of all data already collected. We use the data collected by ARPAT in two great noise mapping campaign held in Pisa and Livorno during last three years. We try to evaluate the correction due to reflections on close walls and the corrections due to different definition of indicators, especially for the European day overall value LDEN and the corresponding Italian LDAY. Finally we try to estimate the overall costs to save all works already done on noise mapping in Italy.

Bockhoff, M.

• CHARACTERISATION OF STRUCTURE-BORNE NOISE EMITTED BY SMALL COMBUSTION ENGINES POWERING LAWNMOWERS AND OTHER GARDEN EQUIPEMENTS
  M. Bockhoff, P. Thoquenne and J. Tourret
[Abstract]

Low noise design of machinery needs acoustic knowledge about the involved components and their behaviour as sources of airborne and structure-borne sounds. In addition, information about links between components and receiving structure must be available in terms of transfer functions. The airborne sound emission of a component is generally characterized by its sound power spectrum which can be determined according to ISO standards of series 3740 (based on pressure measurements) or 9614 (using intensity techniques). For structure-borne sound emission very little experience is available and standards are much less proved. Based on the so called 'reception plate method', already used for the characterisation of structure-borne noise of small components, such as pumps, fans, water appliances, a measurement procedure has been developed which fits to the particular conditions of combustion engines used in garden equipments. The structure-borne noise of the engine is characterised by the airborne sound power emitted from the reception structure to which the engines is connected. Systematic measurements have been carried out on several combustion engines (power = 5 kW) mounted on different kinds of lawnmower housing. For these measurements a test rig has been used which simulates real loading conditions at various speeds. The aim of this study is: - To analyse the influence of different parameters on the structure-borne sound emission: running conditions, reception structure (size, shape, material) - To compare the structure-borne and airborne sound emission. The experimences will be presented in the paper and discussed with respect to problems of systematic data collection for components and building of date bases needed by designers.

Boczkowski, A.

• NEW CONCEPTS OF USING VIBROACOUSTIC METHODS FOR THE NEEDS OF AUTOMOTIVE INDUSTRY
  J. Kazmierczak, A. Boczkowski, M. Komoniewki and A. Kuboszek
[Abstract]

Since many years the problems of acoustic noise and vibration generated by automobiles are considered in few ''classic'' group of tasks. The generation of acoustic noise by vehicles is considered as the basic problems affecting, first of all, on feelings of users of these vehicles and - on the other hand - on the environment of communication trails. The vibroacoustic effects emitted by vehicles are also considered as valuable signals that carry diagnostic information about the state of the vehicle and its parts during the exploitation. Authors of this paper are engaged since years in various research projects, carried out in the mentioned area. As part of results of these projects, some new concepts of using the vibroacoustic techniques problems, it was proposed to develop methods of testing gearboxes by means of acoustic signals in the stage of production testing and assembling of selected parts of vehicles (gears). Additionally, the idea of using ''individual vibroacoustical characteristics'' for the needs of advanced maintenance of automobiles was formulated. For the needs of designing vehicles and their infrastructure the new methods of computer simulation have been tested (for instance: mobile noise sources) as elements of advanced systems of CAD oriented on Noise Control tasks (Computer-Aided Noise Control - CANC). The first part of the paper shows very briefly ''the background'' of authors in research oriented on ''classic'' Noise Control. The second part introduced main ideas of the new conceptions, developed in the Technical University of Silesia, Poland.

Bodden, M.

• PERCEPTUAL SOUND QUALITY EVALUATION
  M. Bodden
[Abstract]

A prerequisite to improve the sound of a product is to evaluate Sound Quality. In contrast to other quality measures which can be defined by pure physical quantities, Sound Quality is based on human perception. As a consequence instrumental tools to predict Sound Quality can only be derived from perceptual tests with subjects. Since perception is moderated and influenced not only by the pure physical acoustic signal but also by other sensorial inputs and even cognitive aspects, Sound Quality evaluation becomes a complex, difficult and interdisciplinary task. In each experiment the corresponding moderating factors have to be identified and - if possible - controlled in such a manner that they do not significantly influence the measured responses. The methods to evaluate Sound Quality can thus not only restrict themselves to the pure acoustical signal, they also have to consider other modalities and the specific situation and background of the subject. Anyhow, for the application in the industrial environment the corresponding needs and restricitions have to be considered: methods have to be time-efficient, render results with a sufficient accuracy, and give direct clues on how to improve products. It is obvious that compromises between the theoretical pretension and the applicability have to be found, but it is of crucial importance that the user is aware of this. The process of Sound Quality Evaluation will be put into the above mentioned context in this paper. The suitability and riscs of methods will be discussed and explained on the basis of examples from automotive industries.

Bodén, H.

• PREDICTION OF LOW FREQUENCY SOUND GENERATION FROM AN AXIAL FAN
  M. Åbom and H. Bodén
[Abstract]

This paper treats the acoustical analysis of a 6 blade, subsonic axial fan which is mounted in a cylindrical duct. This type of fan is used for road tunnel ventilation and is known as a jet fan. The acoustic loading effect of the duct and the inflow conditions have been experimentally investigated and modelled. The work carried out is limited to the plane wave frequency domain. A model was developed for simulating the acoustic loading effect based on a two-port source description. Experiments have been carried out to validate the numerical results. The second step of the work was to analyse the primary fan sound generating mechanisms. A preliminary study showed that disturbed inflow conditions, i.e. turbulence ingestion and non-uniform inflow, were major sound generating mechanisms. It In order to understand these effects, it is necessary to be able to compare, experimental aeroacoustic, aerodynamic data and acoustic simulations. By the use of different turbulence grids, turbulence features of the flow have been changed, and measured, while fan sound power was determined in parallel. In this way it was possible to link turbulence characteristics and acoustic sound power changes. A code has been developed to predict the unsteady thrust of the fan using the work of Sevik and the radiated sound power.

• LOW FREQUENCY ACOUSTIC SOURCE CHARACTERISATION FOR IN-DUCT FANS
  H. Bodén and M. Åbom
[Abstract]

For low and intermediate frequencies a ducted fan can strongly interact with the system in which it is mounted. This interaction will cause variations in the acoustic power output of the fan and can in particular lead to higher power output than expected. This type of installation effect is not covered by the standard methods to characterise fans as acoustic sources, because in these methods the acoustic power output is simply measured for one specified acoustic load. In order to calculate the interaction between a fan and the duct system, in which it is mounted, a more detailed source characterisation is necessary. One possibility is to model fans as acoustic multi-port sources, an idea first suggested by Cremer. During the last decade measurement methods have been developed to determine the multi-port source data in practice. A series of works on the subject have been published by the authors of this paper and other researchers. It is the aim of this paper to present the main results of these studies and discuss their applicability.

Bohineust, X.

• VIBRO-ACOUSTIC SIMULATION USING GEOMETRICAL ACOUSTICS IN THE MEDIUM FREQUENCY RANGE INSIDE A CAR CAVITY
  C. Floc'h, A. Bardot, J.-D. Polack and X. Bohineust
[Abstract]

In the automotive industry, the need for listening the results of vibro-acoustic simulations is more and more expressed. This paper presents a vibro-acoustic model based on geometrical concepts, well suited to noise synthesis in the medium frequency range. Although geometrical acoustic models have been widely used in hall acoustics for ponctual sources, only Jean attempted to use them for structural radiation. He compared BEM and geometrical results in weak coupling conditions, for which he obtained a good agreement. The model presented here calculates the acoustic radiation of a vibrating structure inside a closed cavity using an integral formulation coupled to a geometrical approach for the acoustic propagation. It rests on a decoupling hypothesis between the acoustic pressure radiated and the vibration of the structure. The model is compared to experimental results. The experimental set-up consists in a rigidified car cavity with absorbing material on the walls, on which an elastic panel is mounted and excited through a shaker. The vibration of the structure, entry of the radiation model, is measured with an holographic interferometry system, which provides a very good accuracy in the frequency range measured, [0-1300 Hz]. Model validation is made both by comparing response curves in the time and frequency domains, and by conducting listening tests on a panel composed of 36 people. Comparison of modelisation and experimental results on perceptive criteria (triangular perceptive tests between measurements and simulations) shows that the model quality is correct, although some coloration differences are still perceived.

Boisson, C.

• USE OF A CONSTRUCTED VIBROACOUSTIC TRANSFER FUNCTION FOR PREDICTING SOUND RADIATION FROM A STRUCTURE IN SITU
  C. Marquis-Favre, N. Hamzaoui and C. Boisson
[Abstract]

Our work focuses on the construction of the Green's function for structures radiating in situ. This function has to behave as a transfer function between the structure vibratory behavior and the sound field. The different Green's functions, well-known in the literature, depend mainly on the geometric shape of the vibrating surface and the surrounding acoustic field; their knowledge enables the radiated sound field to be computed for any vibratory state. For an arbitrarily shaped structure in ordinary room, the difficulty of predicting noise lies in expressing the Green's function. We propose an approach based on the numerical construction of this transfer function from vibroacoustic data which are acoustic pressure and normal vibratory velocity measurements defining the structure in situ. This transfer function will allow the radiated sound field to be predicted for any new vibratory state undertaken on the structure located on its site. In this communication, we present some investigations concerning the ability of the built function to act as a transfer function when the vibratory behavior has been changed. Some confrontations between calculations and measurements in terms of sound pressure and sound power levels will illustrate these investigations, and will show the abilities and the limitations of the proposed approach.

Bolton, J.S.

• WAVE NUMBER DOMAIN REPRESENTATION OF TIRE VIBRATION
  J.S. Bolton and Y.-J. Kim
[Abstract]

In the work to be described here, wave number decomposition techniques have been used to study tire vibration. In the experimental component of this work a tire was driven radially at a point on its treadband. Measurements of the resulting radial treadband vibration were made at approximately two hundred points around the treadband circumference by using a laser Doppler velocimeter. From an inspection of the resulting space-frequency data, it was possible to identify the frequency ranges in which the tire responded either modally or non-modally. Further, by performing a circumferential wave number decomposition of the space-frequency data, the propagation characteristics of the wave types that contributed to the response of a tire could be determined. It was observed that a small number of circumferentially propagating waves combine to control the response of a tire in both low and high frequency ranges. The cut-on and propagation characteristics of these waves are closely related to propagating waveguide modes of flexural wave-bearing systems. Together these results are consistent with a curved waveguide model of a tire. It is therefore suggested that a membrane-like waveguide model combined with a propagating wave representation of the tire vibration may offer an efficient way of representing tire vibration.

• CULTURAL DIFFERENCES IN RESPONSES TO REFRIGERATOR NOISE
  P. Davies, P.G. May, J.S. Bolton and G.A. Long
[Abstract]

Korean-born and US-born subjects were asked to compare refrigerator sounds in terms of annoyance. The sounds were also evaluated using objective measures (metrics) to determine whether any of the objective measures correlated with the calculated average annoyance of the subjects, and thus to identify signal characteristics that may contribute to annoyance. Linear combinations of metrics were used to predict annoyance and the accuracy of these models was determined. It was found that Korean-born subjects were more sensitive than the US-born subjects, though the orderings of the signals in terms of annoyance by both groups were similar. Two-metric regression models containing stationary loudness (ISO532B) and Zwicker sharpness metrics were identified as having the strongest correlation to the subjective responses. There appeared to be slight differences in the individual contributions of sharpness and loudness to annoyance between the two groups, but further research is necessary to determine if these differences are significant.

Boman, E.

• AFTEREFFECTS OF NOISE PREDICTABILITY AND TASK LOAD ON MOTIVATION
  E. Boman and S. Hygge
[Abstract]

The main objective of this study was to examine aftereffects of noise predictability and task difficulty on motivation. In a 2 x 2 factorial design, two levels of noise predictability (predictable and unpredictable noise) were crossed with two levels of task difficulty. A total of sixty-four subjects were randomly assigned to one of these four conditions (n=8 males and 8 females in each group). The experiment was run as a group-experiment with two to six subjects in each session. The noise was the same as Glass and Singer's (1972) conglomerate of sounds superimposed upon one another, adjusted to 76 dBA at its maximum level. In the predictable conditions, the subjects were informed about the duration of the noise bursts and the silent interval between them. In the unpredictable conditions the noise bursts appeared randomly with duration ranging from 3 to 15 seconds. After noise termination, persistence on an unsolvable puzzle was taken as a measure of motivation. On the basis of a model of information overload, it was predicted that motivation after noise termination is dependent upon the predictability of the noise and how cognitively demanding the task during noise exposure was. The findings confirmed that less

Bonilha, M.W.

• EXPERIMENTAL CHARACTERIZATION OF MATERIALS FOR ACOUSTIC PERFORMANCE WITH APPLICATIONS
  H.-Y. Lai, C. Gentry-Grace, M.W. Bonilha and C.A.J. Yoerkie
[Abstract]

The acoustic performance of a porous material are determined by its bulk density, airflow resistivity, porosity, tortuosity, viscous and thermal characteristic lengths, elastic modulii and loss factor. A set of measuring techniques and equipment for characterizing such a material was implemented and is described in this paper. The procedure of conducting a material characterization is demonstrated by examples and the accuracy of these techniques is validated by comparing the prediction of the normal absorption coefficient of a material based its measured parameters to its measured absorption coefficient. Excellent agreement was observed over a broad frequency range and results of the test samples are presented.In addition, examples of applying these techniques in conjunction with analytical tools to design mulit-layered liners in noise control applications are also presented in this paper.

Bonnet, S.

• CAE METHODS IN AUTOMOTIVE INDUSTRY : OVERVIEW OF THE STAKES AND PROSPECTS
  J.-C. Kraemer and S. Bonnet
[Abstract]

The paper deals with these two questions : why acoustic performances are not fully predictive today for automotive vehicles and why CAE methodologies remain mainly in the research divisions of car manufacturers ? We'll see that the latter have recently set up projects in order to develop acoustic predictive computation in their design departments. To understand the objectives of such projects, we'll remind first the stakes and context of CAE methods in automotive industry. The second part will examine the state of art of today in computing booming noise, medium and high frequency engine noise, road noise, aerodynamic noise, HVAC noise and by pass noise. What can we modelise and compute and what not ? We'll make the distinction between sources, transfer paths and emitters. Hard points and perspectives will be point out. Then, we'll review the main methodologies for low and medium-high frequencies in vibro-acoustics and in aero-acoustics and point out the most promising ones for automotive industry, and for transportation industries in general. As a conclusion, the introduction of acoustic computational methodologies in the design process is not a purely computational or numerical problem but one has also to tackle with physics, modelisation , organization and trainings. All these topics are strongly linked together.

• STIFFENERS EFFECTS CONSIDERATION IN THE VIBROACOUSTIC BEHAVIOUR OF COMPLEX MECHANICAL STRUCTURES
  S. Le Moyne, J.-L. Tebec and S. Bonnet
[Abstract]

Predicting the vibroacoustic behaviour of an industrial product becomes a more and more important stake, especially for automotive manufactors. Many complex structures, like gearboxes or engine blocks, contain a lot of ribs on their radiating surface. Those ribs are generally designed for mechanical and vibrating reasons. Their effects on the acoustic radiation are rarely taken into account. However, these are not systematically negligible. The influence of stiffeners on the acoustic radiation can be divided in three physical effects : - the ''vibrating effect'' - the ''source effect'' - the ''obstacle effect'' In our paper we propose a study of these different effects, on the first hand with theoretical considerations, and on the second hand, with the help of some applications (stiffened plane plates, gearboxes, automotive engine blocks). Experimental and numerical results (boundary element method) are presented. The aim of our work is to understand the physical phenomenon, and to evaluate the different effects in order to take them into account in the design and modelling phases.

Boone, M.M.

• MICROPHONE ARRAY TECHNOLOGY FOR AIRCRAFT NOISE MEASUREMENTS
  M.M. Boone, T.C.V.D. Dool, P. Sijtsma and U. Stelwagen
[Abstract]

Presently available aircraft noise measurement systems are based on single channel omnidirectional microphone technology. An important disadvantage of this approach is that these systems are equally sensitive to other noise sources as to the airplanes to be measured. Furthermore they are sensitive to turbulence noise caused by wind. In this paper new approaches for the measurement of aircraft noise are presented that are based on microphone array technology. Using array technology extraneous noise sources and wind noise can effectively be suppressed. Results on optimization of array designs and signal processing for this application will be presented that are based on array processing theory as well as simulations and test measurements.

• MICROPHONE T-ARRAY TECHNOLOGY FOR MOVING NOISE SOURCE MEASUREMENTS
  T.C. Van Den Dool and M.M. Boone
[Abstract]

A disadvantage of single omnidirectional microphone measurements is that they do not discriminate between noise sources. Arrays of microphones can be used for that purpose. However, careful consideration of the array configuration and signal processing is necessary to avoid aberations. We will present a two-dimensional sparse array with swept focus processing that is both efficient and accurate. Measurements carried out on trains and other moving sources confirm the simulated performance.

Bordier, C.

• A 3D REAL-TIME ALGORITHM FOR ACTIVE SCATTERING CONTROL
  E. Friot, M. Winninger and C. Bordier
[Abstract]

Whereas active noise control usually deals with the total acoustic pressure, in some cases only one component of the noise has to be cancelled. This is the case for a submarine impinged by a primary field with unknown origin and frequency content; active control must cancel only the scattered field to make the submarine non-detectable. In the paper, an adaptive real-time algorithm is introduced to achieve reduction with additional sources of the noise scattered from a reflecting body. No prior information about the incident field is required. The algorithm consists of multichannel Internal Model Control with a well-known filtered-X Least Mean Square algorithm. Real-time measurements of the acoustic pressure around the reflecting body are used to build a minimization index accounting for the scattered field only. Furthermore, the control devices and algorithm can also be used to cancel the radiated noise due to sources inside the reflecting body. The algorithm for active scattering control was implemented in the LMA control hardware COMPARS. In the paper, experimental results of control in a duct of the field scattered from a reflecting termination are shown. Numerical simulations are given for the 2D case; they show how many noise sources and measurements are required in order to achieve a global reduction of the scattered field.

Borello, G.

• FEASIBILITY OF EXPERIMENTAL DETERMINATION OF SEA DAMPING LOSS FACTORS OF SUBMARINE STRUCTURES
  C. Audoly and G. Borello
[Abstract]

Statistical Energy Analysis is a useful technique to predict at the design stage average noise and vibration levels on ships or submarines, in particular self noise levels on sonar arrays due to machinery on-board noise or flow noise. In order to achieve accurate predictions, it is necessary to introduce realistic damping loss factors in the models. For that purpose, an experiment was conducted on a specific facility whose structure is representative of a piece of submarine hull. Damping loss factors and other parameters of portions of the hull and of some connected structures have been obtained along frequency up to several kHz, using excitation either with a shaker or a hammer, the second method being quicker to operate. The results have shown consistency of the data and confirm the feasibility of the technique, even for thick structures as those used on ships or submarines.

Borst, H.

• URBIS: INSTRUMENT FOR LOCAL ENVIRONMENTAL SURVEY
  H. Borst
[Abstract]

Mapping of noise and noise annoyance is an important aspect of the European Commission's future noise policy. Therefore, an instruments for the assessment of the noise situation in municipalities or regions, will be needed. A GIS based instrument, named Urbis, has been developed which makes it possible to assess the noise situation in a city or region as a whole with a high level of detail. The steps in the processing of data in Urbis correspond to the following steps in the cause-effect chain: Activities - Emissions - Exposure - Effects (annoyance). On the basis of activity or emission data (road traffic intensities, acoustical reports, etc.), noise loads are calculated for different source-types (road traffic, rail traffic, aviation, and industry). By using existing dose-response relations, the percentage highly annoyed can be calculated per neighbourhood for each type of source. Cumulated noise loads from different source types are calculated by first translating levels into the equal annoying road traffic noise levels and then combining them. The total percentage of highly annoyed can be determined on the basis of this combined noise load. Besides noise, air pollution, odour and safety hazards are integrated in the system. By using data that is available at the municipality or other information providers, and a high level of automation, the costs of the use of Urbis are kept relatively low. Urbis makes it also possible to assess and compare future situations on the basis of scenario's. Results of a survey in the town of Leiden, in the form of detailed noise maps and diagrams, will be presented.

Boscher, R.

• WIDE BAND ACOUSTIC IMAGING OF MOVING SOURCES USING SYNTHETIC APERTURE SONAR. APPLICATION TO TRANSPORTATION NOISE
  R. Boscher and J. Chatillon
[Abstract]

Road vehicle noise reduction is of major concern for environmental topics. This reduction can be achieved by the designers as far as they can identify the predominant radiating sources. Noise identification is usually done by beamforming with a long array which well-known results are limited especially for moving sources. This paper proposes a new method for locating and identifying moving sound sources using a short array associated to a signal processing technique that will explicitly integrate the vehicle movement in the array beamforming in order to improve the resolution: the synthetic aperture techniques. The method is based on the use of the movement of the acoustic source in order to synthesise a long virtual array called Synthetic Aperture. From the source point of view, the processing is equivalent to see a moving microphone in front of a fixed source. After spatial sampling of the sensor trajectory, we can define a set of virtual fixed sensors that will form the synthetic aperture. It is required that the speed of the vehicle is measured during the trajectory. With this information, we can compensate the Doppler effect of the received signals on each sensor. Thanks to the movement of the source, the problem can be solved by using conventional beamforming: a fixed stationary source in front of a long sensor array. The array length can be as long as the trajectory. This leads to an improved resolution that is independent of the frequency. The performance of the proposed method is evaluated with numerical simulations and in situ experiments on a lorry. The first results show that theoretical performance can be achieved in term of resolution and frequency identification.

Boshuizen, H.C.

• NOISE AND CARDIOVASCULAR DISEASES: FIRST RESULTS OF A META-ANALYSIS
  E. Van Kempen, H. Kruize, H.C. Boshuizen, C.B. Ameling and B.A.M. Staatsen
[Abstract]

To get more insight in the health effects of noise exposure, a meta-analysis of epidemiological studies on noise and cardiovascular effects was carried out. From reviews it appears that studies on the relationship between noise exposure and cardiovascular effects show contradictory results. Furthermore, some of the reviews had important drawbacks such as the lack of clear selection criteria for evaluating the literature and poor descriptions of the methods. Tables and/or figures, presenting individual study results, were hardly shown. At the moment, no reliable dose-response relationships on noise and cardiovascular diseases are available. Therefore a meta-analysis was carried out. This is a quantitative analysis of study results. Epidemiological studies investigating the relationship between noise exposure and blood pressure and/or ischeamic heart diseases (ICD-9: 410-414) and published between 1970-1999 in English, German or Dutch, were selected. Eventually, about 40 occupational and community-based studies were evaluated. Effects such as blood pressure changes, changes of hypertension rates, rates of angina pectoris and myocardial infarction, were investigated. Three noise exposure sources were distinghuished: noise from road traffic, air traffic and occupational noise. The studies showed contradictory results and appeared to be heterogeneous on several important study characteristics. Exposure characterisation was a problem: in community-based studies, stationary measurements are often used as an indicator for exposure. However, it remains the question if this is a good proxy for personal exposure to noise. Funnelplots showed publication bias: studies, finding negative results, are often not published. Further results, including quantitative risk estimates and sensitivity analysis, will be presented.

Bosmans, I.

• ESTIMATING JUNCTION ATTENUATION IN LIGHTWEIGHT CONSTRUCTIONS
  T. Nightingale and I. Bosmans
[Abstract]

Estimates of junction attenuation, are traditionally obtained using the concept of power balance between two coupled resonant systems and, require the measurement of the velocity level difference (VLD) between source and receive systems as well as the damping of the receive system. In building acoustics, the method has been successfully applied to heavy monolithic constructions, e.g. masonry and cast-in-place concrete. Sources of uncertainty and error have not been studied for lightweight constructions. This paper provides the results of a systematic study of VLD measurement in lightweight constructions, specifically the ability of the operators to repeat their own results, and to reproduce those of others when the specimen and measurement system is unchanged. It is shown that an operator can repeat his own results but repeatability between individuals is poor. The sensitivity of the VLD estimate to the choice of accelerometer positions is also examined and is found to greatly exceed that of operator reproducibility. This should not be the case, if the vibration field is diffuse. Draw-away curves and structural intensity plots are presented to show that the vibration field is not diffuse and that over a large fraction of the surface the direct field exceeds the reverberant. This is inconsistent with the use of power balance methods to both estimate junction attenuation and to predict flanking sound reduction. The suitability of these methods for lightweight constructions is then discussed.

Botteldooren, D.

• AN INDICATOR FOR ROAD TRAFFIC NOISE: MONITORING AND PREDICTION MODEL
  L. Dekoninck, D. Botteldooren, G. Vindevogel and R. Geens
[Abstract]

In this paper a pressure indicator for road traffic noise is discussed and a prediction model for the indicator is presented. The indicator is defined as the annual sound emission at a particular point near a major Flemish highway. When measuring this indicator one must be very careful to take into account weather effects and possible changes in road surface accurately. This is particularly important since the expected annual change in the indicator is very small. When modeling the indicator the evolution of car noise emission must be taken into account. This requires the type of cars and trucks and their age and relative density to be known. In this work the influence of product noise regulations is included in the model for the control period 1992-1998. Results are in good agreement with noise measurements. This increases the confidence in the model for predicting future evolution. Several future-scenario's (business as usual, sustainable) are presented in the paper.

• EXTRACTING LINGUISTIC RULES TO MODEL COMMUNITY TRAFFIC NOISE ANNOYANCE
  D. Botteldooren, A. Verkeyn and P. Lercher
[Abstract]

The vagueness and uncertainty involved in community noise annoyance modeling and prediction, inspires the use of fuzzy techniques. In this paper we will focus on predicting noise annoyance using a set of linguistic rules. The fuzzy membership functions for linguistic terms such as 'high' that are used in the rules are not extracted from the database but are obtained from external sources. Among these sources are the International Annoyance Modifier Study, dosage response relations found in literature, and various expert opinion. The annoyance prediction itself is based on a set of IF-THEN rules involving the linguistic terms, fuzzy AND, and fuzzy OR. The importance of each rule in the model is tuned by comparing the outcome to the results of a social survey. The quality of a proposed decision tree is measured by the uncertainty in the prediction. This results not only in a modeling tool, but also in knowledge on the construct of community noise annoyance. The technique is applied to a detailed Austrian survey involving people exposed to road and rail noise living in one valley [1]. Several variables are included. The sound exposure related rules dominate the prediction, but also variables describing the background soundscape and the so-called enviroscape and psychscape have some impact on the performance of the model.

• DEVELOPMENT OF ICT COURSE MATERIAL FOR ACOUSTICS EDUCATION
  V. Meerbergen, G. Vermeir, D. Botteldooren, R. Meuldermans and M. Van Overmeire
[Abstract]

Since 1997, an educational project on general acoustics is developed between three Flemish regional universities and one Flemish technical high school. The project has two major goals: to develop multimedia learning environments suitable for specialised studies and to develop a software agent for guidance and assistance by the course. These learning environments are websites and are linked to a central web ''the virtual science museum'' (see http://educinno.rug.ac.be/wetenschapsmuseum). This project uses a system of distributed development with several partners. The learning environments are building blocks that can be combined to specific courses on noise control, environmental acoustics, building and room acoustics,.... A ''guide'' is developed for this purpose. The presentation will focus on the introduction to room acoustics by use of a specially developed JAVA-applet. The applet is developed as a tool for virtual experiment. It calculates impulse responses for a rectangular box shape. The student can change dimensions, distribution of absorption, source characteristics, positioning of source and microphone, and read the effects on sound pressure levels, impulse responses, intelligibility,... This allows an inter-active introduction into the field of general room acoustics. As a conclusion the authors will also comment on the evaluation of the global approach by the students.

Bougdah, H.

• AN EXPERIMENTAL INVESTIGATION INTO THE ACOUSTIC PERFORMANCE OF EARTH MOUNDS COMBINED WITH SHORT NOISE BARRIERS
  H. Bougdah and I. Ekici
[Abstract]

Environmental noise is causing an increase in the number of complaint from the public. Despite this, action to reduce its impact has had a lower priority than that taken to address other environmental problems such as air and water pollution. According to the European Commission Green Paper on ''Future Noise Policy'', 1996, around 20% of the European Union's population or 80 million people suffer from noise levels more than 65 dB(A). These levels are considered by health experts to be unacceptable. An additional 170 million people throughout the E.U. live in 'grey areas' where the noise levels are likely to be between 55 and 65 dB(A) and can cause annoyance during the day. As well as environmental implications noise has economic costs to society. According to a study of ''The Social Costs of Transport'' (ECMT/ OECD, 1993 ), this is estimated around 0.2% and 2% of GDP. Even using the lower figures it still would come to around 170 billion ECU. Noise mitigation measures cover treatments of source, path and receiver. In the case of transport noise, environmental barriers can be used. A novel method of screening road traffic noise, consisting of earth mounds combined with short barriers, is discussed in this paper. Physical scale modelling was used to measure the insertion loss of eight different configurations. The results have shown that earth mounds could be used as environmentally friendly barriers. The addition of short barriers, can however in some cases reduce their efficiency.

Bourbon, C.

• TOOLBOX FOR THE INTEGRATED PLANNING AND MANAGEMENT OF ROAD TRAFFIC NOISE TO THE USE OF URBAN LOCAL AUTHORITIES
  C. Bourbon, E. Nicolas, R. Mummenthey and E. Wetzel
[Abstract]

Several cities facing similar problems and wishing to exchange experiences join forces in order to find common solutions related to road traffic noise. The project involves the design and the validation of a set of integrated, wide-ranging and progressive tools to be used by urban planners. Those tools would help them to understand and apprehend road traffic noise. These tools are designed to be primarily used by urban planners, both in town planning and local or regional development; and in traffic and noise control. However in the aim of a participative management of local authorities, they should be accessible to political decision-makers, investors, pressure groups and urban development project designers. The more important aspect of the work is to consider Noise mapping not as final tool but as one of the intermediary tool to apprehend the reality and the complexity of the noise management in a city. They consist of adapted guide books and guidelines, and of a mathematical tool to describe, predict and simulate noise. The tools and methodology are designed by the project's partner cities (Bruxelles, Birmingham, Hanover, Lyon). The toolbox should be usable in any urban authority, whatever its size and whatever level of its noise control. The present results show :  Definition of the actors involved and their needs  Proposal of tools (including mathematical tools)  The steps to succeed on noise mapping  The use of the tools with decision makers.

Boutin, C.

• THE INFLUENCE OF PRESSURE DIFFUSION EFFECTS ON ABSORBING PROPERTIES OF POROUS MEDIA WITH DOUBLE POROSITY
  X. Olny and C. Boutin
[Abstract]

Double porosity media are distinguished from classical  single porous media owing to the fact that two interconnected network of pores, of very different characteristic sizes, can be identified in the porous material. Recent works devoted to the study of dynamic behaviours of such materials showed that the macroscopic description highly depends on the contrast of permeability between the two networks of pores. First, the general description obtained in the case of strong permeability contrast by way of an homogenisation method considering periodic separated scales media is recalled. In this case of particular interest, a partial coupling between the networks of pores may occurred and the macroscopic description can be significantly modified by pressure diffusion effects. Models for macroscopic permeability and compressibility for infinite rigid frame materials are proposed for a simple geometry. In order to take finite size effects, some adjustments of the parameters involved in the models are also suggested. For the first time, we present experimental results that corroborate the existence of pressure diffusion effects. It appears that the confrontation between the model and measurements performed on artificial double porosity panels is very good. We also show that double porosity media can be of great interest with the aim of improving absorption performances of porous materials.

Bouvet, P.

• ROLLING NOISE FROM FREIGHT RAILWAY TRAFFIC: REDUCTION OF WHEEL RADIATION BY MEANS OF TUNED ABSORBERS
  P. Bouvet, N. Vincent, A. Coblenz and F. Demilly
[Abstract]

The rail, sleepers and wheel are the predominant acoustic sources for freight rolling noise. In the frame of the ''Silent Freight'' European project, optimised wheels have been developed to reduce the noise from rolling stock. This article deals with the optimisation of dynamic absorbers on a wheel.

The theoretical methods used for the design of tuned absorbers are presented. A finite element model is used to calculate the wheel modal parameters (natural frequency, mode shape, modal mass and damping). The wheel vibration response and wheel radiation are calculated with the TWINS software package (developed for the European Rail Research Institute). It is shown that in combination with a wheel shape optimisation, the use of tuned absorbers can lead to a wheel noise reduction of about 10 dB(A).

Dynamic absorbers have then been developed and set on prototype wheels. These wheels have been mounted on a test train in order to assess the actual noise reductions during field measurements. The measured wheel noise reduction is presented and compared to the theoretical result : a good agreement is found between measurements and calculations.

Keywords : railway wheels, damping, tuned absorbers, rolling noise, modelling.

Bragança, L.

• THE INFLUENCE OF SHUTTERS POSITION ON NOISE INSULATION OF FAçADES
  J. Patrício and L. Bragança
[Abstract]

It is assumed that the noise insulation of façades in situ integrates the contribution of all façade elements, such as the external walls and windows, and the way they are connected with each other and with all the adjoining elements. Generally, the contribution of shutters for the global noise insulation of façades against external noise is not taken into account because the tests are usually made with the shutters completely opened. Similarly, the effects of their different positions are not quantified. So, an experimental set of tests were carried out in a selected new housing building to study the influence of shutters position on noise insulation of façades. This tests were made in 3 different rooms with different window dimensions, on the first floor, and in a similar room and window, for the 3 subsquent floors, in accordance to what is established in the international standards EN ISO 20140-5 and 717-1, using a loudspeaker as a noise source. The selected shutters positions were respectively: completely closed, partially closed with all shutters inter-blades exposed, opened till half heigh and totally opened. The obtained results have shown that the calculated transmission loss curve for each shutter position differs with some significance whilst the noise insulation index of the façades remained almost constant for all positions exception made for the position where the shutters were completely closed. Additionally, some dependency on noise insulation along the building height for the same window system and shutters position was achieved. Finally, some conclusions are presented.

Brambilla, G.

• SOUND QUALITY AS A TOOL TO IMPROVE THE NOISE CLIMATE AT THE OPERATOR'S STATION IN EARTH-MOVING MACHINES
  G. Brambilla, E. Carletti and F. Pedrielli
[Abstract]

Nowadays the sound quality approach is a valuable tool in the engineering process aimed at improving the effectiveness of noise reduction treatments for industrial products. To investigate the potential and perspective of such approach also in the earth moving machines (EMMs) a research project has been undertaken and promising results have been obtained in its preliminary phase. The present paper describes a further laboratory experiment designed to investigate in more details how changes in the energy and shape of the noise spectrum influence the auditory perception. For this purpose the noise at the operator's station in a EMM has been binaurally recorded by a manikin with the machine in stationary and idle conditions. The spectrum of this noise recording has been modified by a digital equaliser in order to simulate the effect of some noise reduction treatments, i.e. those due either to an active noise control system tuned on a selected low frequency or to traditional passive systems less selective in frequency and operating at the mid-high frequencies. The sound stimuli obtained have been presented by headphones in laboratory to a listening jury. By the method of adjustment subjects modified the level of the comparison sound stimulus until it was judged as loud as the standard stimulus. In addition the paired comparison method has been used to obtain the subjective preference among the stimuli. The listening tests are still in progress and results will be available at the time of writing the manuscript.

Brandl, F.

• EFFECTIVE IMPLEMENTATION OF BRAND SOUNDS IN EXCLUSIVE PASSENGER CARS
  F. Brandl, S. Thomann and W. Biermayer
[Abstract]

A distinct brand sound is one important aspect in selling exclusive passenger cars. Such a brand sound has to be defined on the one hand via customer expectations which are different for different world markets. On the other hand, the implementation of a once desired brand sound into the vehicle requires extensive knowledge how this brand sound has to be composed and how this composition can be transferred into the relevant hardware modifications in the vehicle. In this paper examples of tailor made compositions of interior sounds and their implementation by the necessary changes to the powertrain will be discussed and presented.

Brauchle, G.

• THE ASSESSMENT OF NOISE ANNOYANCE IN SCHOOLCHILDREN AND THEIR MOTHERS
  P. Lercher, G. Brauchle, W. Kofler, U. Widmann and M. Meis
[Abstract]

Children and young persons differ substantially in their environmental needs and behavior (development, learning, playing). Nevertheless, the assessment of the effects on this population segment of a noisy environment is based on results from adult surveys. Currently, no dose-response curve is available for noise annoyance of children. Only recently (Bullinger 1995, Evans et al 1995, Evans et al 1998) a standardised methodology was developed to survey schoolchildren about their perception of the environment. In June 1998 we surveyed one thousand two hundred and eighty children in grades 3 - 4 (M=9.44 years) from 26 local schools in their classrooms. Furthermore, the mothers of these children completed a standardised questionnaire. The response rate was 79.5%. Noise exposure (dB,A,Ldn) was assessed by modeling and calibration through measurements from 31 sites. Data were linked via GIS. The extensive data base allowed the assessment of various dose-response curves for road and rail noise. Moreover a comparison is made with the mother's responses to the same noise sources. In addition the differences in the perception of the soundscape and the environmental, situational and personal modifying factors are reported.

Brekke, A.

• STRUCTURE BORNE NOISE FROM TRAINS IN ROCK TUNNELS
  A. Brekke
[Abstract]

In the new building regulations in Norway, the limit for structureborne noise from tunnels is L p,max,''fast'' = 32 dBA in dwellings. A measurement method for maximum structureborne noise is presented, in which the max value is defined as the 95 % confidence, and a microphone position in a corner is included. Results of measurement of structureborne noise in dwellings from trains in different rocktunnels in the Oslo area is presented, and a calculation method for structureborne noise transmission is given. Possibilities for noise reduction is discussed, and experiences from remedial actions in newly build tunnels are presented. The noise reduction is strongly dependant on the stiffness of the track. The limits for maximum rail deflection is discussed and measurement of rail deflections in tunnels with and without ballast mats is given. The variation in structureborne noise levels from tunnels, dependant on the tunnel building technique is discussed.

Bremner, P.

• TRANSMISSION LOSS OF DOUBLE WALLS: SEA MODELIZATION VERSUS EXPERIMENT
  S. Brühl, P. Bremner, A. Roeder and M. Grünewald
[Abstract]

Transmission loss experiments on different double wall configurations (thin aluminum panels of appr. 1m area) have been performed and recalculated with the new AutoSEA2 program. The interior cavity was studied under different conditions (empty and filled with two different absorbing foams). The SEA model takes into account possible flanking transmission paths through the mounting frame of the panels as well as the low frequency mass resonance behaviour. By choosing appropriate parameters for the panel/frame coupling an excellent coincidence between measurement and calculation results can be obtained for all studied cases.

Brentnall, S.

• AIRCRAFT NOISE AT SCHOOL AND CHILD PERFORMANCE AND HEALTH INITIAL RESULTS FROM THE WEST LONDON SCHOOLS STUDY
  S. Stansfeld, M. Haines, J. Head, B. Berry , M. Jiggins, S. Brentnall and R. Roberts
[Abstract]

Previous research suggests that children's cognitive performance and health are adversely effected by chronic noise exposure. However, uncertainty remains because cognitive performance is also influenced by school quality and social deprivation which may confound noise effects. By increasing the number of schools and children, the aim of this study is to test whether the noise effects previously found in children are attributable to noise and to test possible mechanisms. The cognitive performance (reading, memory, attention) and stress responses (annoyance, perceived stress, catecholamine secretion) of children attending 10 primary schools exposed to high levels of aircraft noise (63 dBA 16hr Leq) were compared cross-sectionally with 10 matched control schools exposed to lower levels of aircraft noise (57 dBA 16hr Leq) around Heathrow Airport in West London. Schools were matched across aircraft noise exposure by: age, sex, socio-economic status, ethnicity and non-aircraft environmental noise sources. The cognitive tests and questionnaires were group administered in the classroom while noise measurements were carried out to assess school noise exposure. Initial results will be presented using multi-level modeling and multivariate statistical techniques to adjust analytically for the potential confounding effects of school characteristics and socio-economic factors on associations between noise and performance at the individual level.

Bris, P.

• PREDICTION OF ACOUSTIC PARAMETERS OF LAYERED SYSTEMS
  P. Bris, S. Vasut, J. Pesl and L. Bujnoch
[Abstract]

Up to this time we meet in technical practice problems of vibrations, especially influence of vibrations upon human. A person is not ever protected in the effective way. It happens in some cases that the proclaimed protective element does not suppress effects of vibrations but increases them. The work describes possibilities of the mathematical modelling use at designs of antivibration systems (on the basis of layered systems). The frequency dependence of predicted transmission is compared with the frequency dependence of measured transmission or the transmission loss at the same layered system. The results showed that on the basis of this new proposed methodology it is possible to predict, with the great accuracy, antivibration effects of layered systems and in such way to optimize considerably the technical and economical preparation of manufacture.

Bristow, A.

• MEASURING HOUSEHOLDS' ANNOYANCE FROM ROAD TRAFFIC: AN INTERMEDIATE STEP WITHIN AN INNOVATIVE NOISE VALUATION MODEL
  E. Arsenio, J. Patrício, A. Bristow, A. Pinelo, F. Silva and M. Wardman
[Abstract]

In urban areas, road traffic noise is referred as the most important cause of community annoyance. Although road traffic can be associated to several impacts on human health and effects on psychological well-being, such as stress reactions, increase in risk of heart and circulatory diseases, interference with communications and activities, sleep disturbance, etc., these social costs are usually ignored in the transportation and land use planning process. As part of an on-going research study on the valuation of noise impacts from road traffic, this paper presents some of the results of an extensive survey that was administered to more than 400 households in a residential area in Lisbon. A computer program designated NOISE was developed, and several types of data (revealed, stated, attitudinal) were combined for valuing noise impacts, and the influence of differentiated 'noise environments' (indoors and outdoors) on households' location decisions was assessed. The case study covered respondents living in blocks with different conditions of exposure to noise from road traffic. Noise levels were also measured in each flat, and several noise parameters were reported (Leq, L50, L10, L90,L95, Lmax). The results presented herein show the link between households' perceptions of their noise environment indoors, degree of annoyance and type of disturbance effects, with those real physical noise measures taken in each location. In this phase, the most adequate parameter for representing this type of community annoyance can be presented.

Bronsdon, R.

• PREDICTING CONVERGENCE ZONE PROPAGATION IN ENVIRONMENTAL NOISE MEASUREMENTS
  R. Bronsdon and H. Forschner
[Abstract]

This paper deals with upwind propagation of sound in temperature inversion conditions. When the proper wind and temperature profiles exist it is possible to form either an elevated duct, where sound will propagate at 3dB/DD, or perhaps even a convergence zone where the propagating sound will not be attenuated any appreciable amount. We experience these types of propagation when we hear familiar sounds that seem to have moved closer. A good example would be the sound of a highway or train at a great distance, which suddenly seems to be running right through the back yard. A simplified calculation based on Gaussian Beams allows the investigation of conditions under which these types of phenomenon could possibly occur. More sophisticated analysis techniques also show how convergence zone propagation can impact noise measurements made out of doors.

Brooks, V.

• MULTILEVEL DISCRETE TIME HAZARDS MODELS OF SLEEP DISTURBANCE DUE TO AIRCRAFT NOISE AT NIGHT
  I. Diamond, L. Reyner, J. Horne and V. Brooks
[Abstract]

This paper provides a re-analysis of the data from a large 1991 UK Sleep Study. Data for 400 subjects were collected on each of 14 nights and include whether or not the individual was disturbed in any particular 30second epoch. The data set, comprising over 500,000 observations is analysed using multilevel discrete time hazards models to assess the xtent to which sleep disturbance at different times of the night is related to aircraft noise.

Brucker, M.

• NEW SOUND-ABSORBING FOAMS MADE FROM POLYOLEFIN RESINS
  C. Park, M. Brucker, L. Remy, S. Gilg and S. Subramonian
[Abstract]

Porous materials have been used for sound absorption and insulation. The materials include mineral fibers, open-cell thermoset foams and polymeric fibers. The conventional materials have one or more drawbacks. Being porous, all the materials absorb water during real-life uses, where they are often in contact with moist air, condensation or both. Fibrous materials lack mechanical integrity and mineral fibers pose a handling difficulty. Polyurethane foams and melamine resin foams tend to undergo hydrolysis during a prolonged exposure to moisture. In addition, these thermoset foams are not recyclable. A moisture-resistant sound-absorbing material that is recyclable has been in demand. We have successfully developed a group of novel materials that meet the demand. The materials are thermoplastic foams extruded from polyolefin resins. An optimum selection of the polymer resin and a proper control of the cell structure yield the desired foams that have been elusive. A large cell size and a controlled open-cell content characterize the novel products. Perforation and compression open the cells of the extruded foams. The polyolefin foams can be tailored to damp vibration as well as absorbing sound. Thus, the foam materials have been found to be useful not only for sound absorption but also for sound insulation and vibration damping. With advantages over the conventional materials, the polyolefin foams find numerous applications in automotive, appliance and industrial uses as well as in buildings. The primary attraction of the foam products is their low water pick-up in a humid environment.

Brühl, S.

• TRANSMISSION LOSS OF DOUBLE WALLS: SEA MODELIZATION VERSUS EXPERIMENT
  S. Brühl, P. Bremner, A. Roeder and M. Grünewald
[Abstract]

Transmission loss experiments on different double wall configurations (thin aluminum panels of appr. 1m area) have been performed and recalculated with the new AutoSEA2 program. The interior cavity was studied under different conditions (empty and filled with two different absorbing foams). The SEA model takes into account possible flanking transmission paths through the mounting frame of the panels as well as the low frequency mass resonance behaviour. By choosing appropriate parameters for the panel/frame coupling an excellent coincidence between measurement and calculation results can be obtained for all studied cases.

Brungart, T.

• MODIFICATIONS OF A VACUUM CLEANER FOR NOISE CONTROL
  G. Lauchle and T. Brungart
[Abstract]

Sound power measurements are described for a commercially manufactured, hand-held vacuum cleaner. An objective assessment of the measured results is performed to identify the aeroacoustic sources of noise, suggested routes to noise control are then implemented, and a reevaluating of the modified units is conducted and compared to the baseline results. The blade rate tone of the vacuum working fan is found to be the most annoying source, and it is reduced by up to 8 dB through a modification of the shroud that surrounds it. Unevenly spaced fan blades are also implemented as a noise control measure. This results in a comparable 8 dB reduction of the blade rate tone, but it introduces several new, side band tones to the sound power spectral data; the overall sound power increases slightly. Regardless, a subjective jury survey indicated that the modified unit having the unequally-spaced fan blades is preferred 3:1 to the unit with the modified shroud only.

Brunskog, J.

• A CLOSED FORMULATION OF SOUND FIELDS IN FRONT OF PERIODICAL ABSORBENTS
  D. Holmberg, J. Brunskog and E. Nilsson
[Abstract]

Periodic resonant absorbers are known to give excessive back scattering for frequencies above a limit which is governed by the proportions of the periodicity. One way to model this phenomenon is to express the pressure field as a series of pressure amplitude components in the wave number domain and solve the corresponding equation. A drawback with this approach is that the equation matrix consists of an infinite set of components and therefore has to be truncated in order to be solved. However, it is possible to make use of an approach that has been used in e. g. structural acoustics. This approach is based on a periodical assumption and yields a closed formulation that can be solved in the wave domain without truncation. It is possible to include an optional field at the backside of a periodic absorber. Furthermore, it is possible to transform this solution back to the spatial domain and obtain an exact formulation. This operation yields an infinite series consisting of components which can be designated a physical interpretation. The infinite series can then be expressed in closed form by utilising geometrical series.

• NEARLY PERIODICITY IN STIFFENED PLATES AND ITS INFLUENCE ON SOUND RADIATION
  J. Brunskog
[Abstract]

A structure designed to be spatially periodic in its configuration cannot be exactly periodic due to material, geometrical, and manufacturing variabilities. The presence of small irregularities in a nearly periodic structure may influence the propagation of vibration strongly and localise the vibration modes. A number of papers has been addressed to localisation phenomena in simplified structures. This paper will instead focus on the mean vibration field and its influence on sound radiation in a plate stiffened by beams.

Bruyère, J.C.

• NOISE EXPOSURE AROUND LYON SATOLAS AIRPORT
  J.C. Bruyère and M. Vallet
[Abstract]

The results of acoustic measurements presented constitute the point of reference in 1998 and 1999 of the levels of noise around Lyon-Satolas airport. This airport envisages an extension by the creation of two new runways towards 2015. The airport is not currently equiped with a permanent acoustic monitoring system. It wished to establish an assessment of the sound exposure in the bordering neighbourhoods. The noise can come from various sources: aircraft, railway, and road noise, and also other sources. The objective is to determine the noise levels in the surrounding neighbourhoods and the contribution of the various sources. The fleet of planes includes those of chapter II (old and noisy planes) and of Chapter III (recent and more silent planes). The planes were measured in the both directions, landing and taking off, with 3 microphones used during the measuring in the most representative direction (except for a neighbouring town). In the 13 measured neighbourhoods, the Leq 6 am - 11 pm goes from 48.1 to 61.3 dB (A) and the Leq 11 pm - 6 am goes from 40.8 to 58.3 dB (A). The level of sound exposure, during years to come, will not increase, according to a charter between the airport and the local authorities. A decree by the Minister for transport prohibited planes of chapter II from flying between 11.15 pm and 6.15 am, as of July first, 1999. From April 2002, chapter II planes will be prohibited. Such a data base will make it possible to establish a realistic cartography of noise levels for years to come.

Buchlin, J.-M.

• NOZZLE DESIGN EFFECT ON VORTEX INDUCED INSTABILITIES IN AN AXIAL INJECTED COLD FLOW MODEL OF THE ARIANE-5 EAP
  J. Anthoine, D. Yildiz and J.-M. Buchlin
[Abstract]

The aeroacoustics of solid propellant boosters is currently being investigated at the von Karman Institute as a part of a CNES program related to the Ariane-5 solid propellant boosters. The geometry considered has a segmented combustion chamber consisting three cylindrical segments and a submerged nozzle. Two inhibitor rings ensuring thermal protection separate the three segments. The hot burnt gas flow in the combustion chamber originates radially from the solid fuel surface and then develops longitudinally before reaching the exhaust nozzle. During the combustion, the regression of the burning surface is faster than the one of the inhibitor rings. Then, the rings become obstacles into the flow-field and generate a significant risk of hydrodynamic instabilities. Flow oscillations are then resulting from periodic vortex shedding at the thermal protections and strong coupling between the vortices and the acoustics properties of the combustion chamber is expected. The research consists of cold flow experiments in order to investigate the nozzle design effect on sound production. Acoustic pressure measurements are taken in a 1/30-scale axisymmetric model of the Ariane-5 EAP with either pure axial or radial injected flows. The model segments are made of sintered-bronze sphere Poral cylinders to get the radial injected flow. Parametrical tests are performed to identify flow-acoustic coupling and to characterize the influence of the nozzle geometry on the pressure fluctuation levels. These measurements are obtained and discussed for different nozzle geometries, different values of inhibitor-nozzle distances, inhibitor internal diameters, booster length and Mach number. The flow-acoustic coupling has been found for some configurations and important conclusion has been addressed to the strong effect of geometry of the submerged nozzle on the amplification of the pressure fluctuations.

Buchta, E.

• QUANTIFICATION OF CONTEXT EFFECTS IN THE DETERMINATION OF SOURCE-SPECIFIC ANNOYANCE RATINGS FOR SHOOTING AND ROAD-TRAFFIC SOUNDS
  J. Vos and E. Buchta
[Abstract]

Specific analyses of field survey data suggest that the context in which a sound is heard may substantially influence reaction to it. In the present paper, the relevance of the effect of context on the community response to single sources is estimated from the data obtained in two separate field surveys. In the first survey, the residents (n = 392) were exposed to the sounds from small firearms and road traffic. Multiple linear regression analyses showed that the predictability of the annoyance caused by road-traffic sounds from the A-weighted day-night level (ADNL) was not significantly enhanced by adding ADNL of the shooting sounds as a second predictor. The variance in the annoyance ratings for the shooting sounds that was explained by ADNL of these sounds, however, was slightly increased (less than one percent point) if ADNL of road traffic was added as a second predictor. In the second survey, the residents (n = 433) were exposed to the sounds from large firearms and road traffic. Here, the predictability of the annoyance caused by road-traffic sounds from ADNL tended to be enhanced by adding the adjusted ADN of the shooting sounds as a second predictor. Overall, an increase of 10 dB in the adjusted ADNL for the shooting sounds resulted in a decrease in the annoyance of the road-traffic sounds that was equivalent to a 2-dB shift in its ADNL. The predictability of the annoyance caused by the shooting sounds from the adjusted ADNL was not significantly enhanced by adding ADNL of road traffic as a second predictor. In all, the context effect was present only in part of the cases and hardly different from the mean effect obtained by Fields for more than 30 field surveys .

• LOW-FREQUENCY PROJECTILE NOISE FROM FLAT HOWITZER SHOTS
  E. Buchta and K.-W. Hirsch
[Abstract]

For noise prediction purposes it is important to know how great is difference between the muzzle blast and the projectile noise. Therefore, measurements were conducted to determine the source level and the propagation of both the muzzle blast and the projectile noise. Both types of noise are low-frequency high energy blasts. The paper reports on tests at the Bergen training area. The blasts were measured from direct howitzer shots at targets at distances of about 1000 m. The measuring positions were close to the line of fire and along the expected propagation path up to a distance of round about 2 km a height of 5 m above local ground.

• ANALYSIS OF LOW-FREQUENCY PROJECTILE NOISE SIGNALS MEASURED CLOSE TO THE GROUND
  K.-W. Hirsch and E. Buchta
[Abstract]

It is well-known that projectile noise from supersonic howitzer shells can significantly contribute to the noise load in the vicinity of military training facilities. As long as the shell follows a high parabolic trajectory, the calculation of the instantaneous local MACH-angle and the orientation of the shell is rather complex. However, if the source geometry is known, the sound propagation is rather simple because the blasts interact with obstacles and the ground only at the receiver site. Sound propagation models therefore are rather successful in those cases. For flat direct shots with tanks and howitzers the trajectory is much more simplier but the sound now propagates parallel to the ground. This case is comparable to projectile noise from rifle shots though - due to the larger diameter of the shells - the characteristic frequency is much lower. The angle of incidence is rather flat in such cases and the ground is playing an important role in understanding the measured signals and the derived levels.

Buchwald, P.

• NOISE MONITORING OF TRAIN WHEELS
  P. Ramussen, P. Buchwald and J. Birkedal Nielsen
[Abstract]

A system for automatic recording and processing of the noise emission from train wheels is described. The system is part of a procedure for systematic condition-based wheel maintenance, whereby the maintenance cost can be reduced and the lifetime of the wheels can be extended. The noise monitoring system has been established on one of the main tracks towards Copenhagen central station, Denmark, and automatically records the noise emission from all inbound trains. Based on the distance between the wheels and the noise profile known train types can be identified and the noise contribution from each individual wheel can be isolated and normalized with respect to the train speed. The data can be transferred via modem to the central maintenance facility for recalling of train units for service. The system has proved a potential cost reduction in maintenance and a reduction in noise emission.

Budijanto, H.

• SENSITIVITY OF AMPLITUDE AND PHASE DIFFERENCES OF NOISE CANCELATION SYSTEM IN A RECTANGULAR DUCT
  I.B.A. Putra and H. Budijanto
[Abstract]

Noise reduction in a rectangular duct using Active Noise Cancellation method has been widely conducted by many researchers. However, very limited successful results were reported in this field of investigation. A series of preliminary studies using a full scale model of straight rectangular duct have been conducted in laboratory. The results showed in-consistent cancellation results, such as, variation in time delay at fixed location of secondary source due to superposition of sound waves with different frequencies, inaccuracy in size of the secondary source and upstream sound propagation of the secondary source. These problems have disguised some important physical phenomena to be learned in an active noise cancellation. This paper discusses the study on an active noise cancellation using computer simulation based on finite element method with 3-dimensional isoparametric elements and twenty nodal points to illustrate physical phenomena of sound wave superposition between the primary and secondary sources. The working object was an air conditioning duct system with 2.0 x 0.12 x 0.12 m3 dimensions and assumed to have an anechoic end thus --000791-1.gif--. The secondary source was located at the middle of the duct and the duct wall was assumed to be acoustically hard, thus --000791-2.gif--. The results revealed that, (1) the finite element method of 3-dimensional isoparametric element with twenty nodal points was found to be sufficient for achieving the simulation requirements, (2) noise reduction of about 70 dB could only be achieved with amplitude difference between the noise and the anti noise waves not more than 0.025 dB, (3), the phase shift between the primary and secondary sound waves, was found to be very sensitive where accuracy of 0.25 deviation from 180 could reduce the cancellation capability of about 23 dB, (4) the monopole Chelsea model was found to be adequate for reducing the effect of secondary source on the microphone sensor.

Buell, J.C.

• COMBINED CFD/CAA METHOD FOR CENTRIFUGAL FAN SIMULATION
  F. Périé and J.C. Buell
[Abstract]

Computational fluid dynamics and computational aeroacoustics is a challenging task when dealing with complex phenomena involved in a centrifugal blower. A non restrictive list of modeling difficulties include : change of topology due to blade passing, turbulent phenomena at the blade tip, unsteadiness of the flow involving small to large scales, acoustic contribution of turbulence, acoustic wave propagation, impedance of inlet and outlet boundaries, noise transmission to shroud... A 140000 FE 2D model is used to simulate a 44 blades centrifugal fan. The purpose of this paper is to evaluate and compare two different numerical approaches. One is a classical CFD solution involving an implicit FE solver, a fixed topology with a rotating reference frame and a turbulent model. The other solution involves an explicit FE solver, which account for topology changes and takes advantage of LES to simulate unsteady turbulent structures as well as aeroacoustic noises. Interest and limitations of both methods are analyzed. Also compared is the predicted noise with experimental results in the far field.

Bugaru, M.

• NOISE RADIATED BY THIN RECTANGULAR PLATES SUBJECTED TO INPLANE LOADS
  M. Bugaru, I. Magheti, N. Enescu and M.V. Predoi
[Abstract]

The paper reveals recent developments of the noise radiated by thin rectangular plates parametrically excited. In the region of principal parametric resonance, starting from the temporal non-linear differential equation that describes the oscillatory movement and using the second order approximation of the asymptotic method was computed the amplitude as function of system parameters and geometric imperfections. In the anechoic chamber of Department of Mechanics were done the experiments concerning the non-linear dynamic response of such plates and the noise radiated in the region of principal parametric resonance. By recording and processing the two signals, were plotted three diagrams: spectral density of the two signals and their coherence. The three characteristic frequencies of the parametric vibration of the plate (L/2,L,3L/2), previously calculated, were put in evidence.

Bugge, J.J.

• THE NATO CCMS WORKING GROUP ON NOISE FROM WEAPONS - AN OVERVIEW
  G. Kerry and J.J. Bugge
[Abstract]

As part of a follow-up to a study on aircraft noise NATO CCMS (Committee on Challenges of Modern Society) has established a working group to consider ''Noise from Weapons and Sonic Booms and the Impact on Humans, Wildlife, Domestic Animals and Structures''. The study covers shooting noise, blast and sonic boom but excludes noise from vehicles, aircraft and helicopters. The terms of reference required the group to carry out a literature review into weapons noise measurement, metrics and emission characteristics, acoustic modelling of weapons noise propagation and the effects of weapons noise and sonic boom on animals, humans and structures, to determine the level of current knowledge and areas where further work might be required. In particular the study was to identify species of animals to be studied, to make recommendations on methodologies for further research and to establish data bases covering pertinent bibliography and weapons noise data. The final report is currently in preparation and this paper will review its content and likely conclusions and recommendations.

Bujnoch, L.

• PREDICTION OF ACOUSTIC PARAMETERS OF LAYERED SYSTEMS
  P. Bris, S. Vasut, J. Pesl and L. Bujnoch
[Abstract]

Up to this time we meet in technical practice problems of vibrations, especially influence of vibrations upon human. A person is not ever protected in the effective way. It happens in some cases that the proclaimed protective element does not suppress effects of vibrations but increases them. The work describes possibilities of the mathematical modelling use at designs of antivibration systems (on the basis of layered systems). The frequency dependence of predicted transmission is compared with the frequency dependence of measured transmission or the transmission loss at the same layered system. The results showed that on the basis of this new proposed methodology it is possible to predict, with the great accuracy, antivibration effects of layered systems and in such way to optimize considerably the technical and economical preparation of manufacture.

Bullinger, M.

• THE EFFECTS OF CHRONIC AND ACUTE TRANSPORTATION NOISE ON TASK PERFORMANCE OF SCHOOL CHILDREN
  M. Meis, S. Hygge, G.W. Evans, P. Lercher, M. Bullinger and A. Schick
[Abstract]

There are a number of reasons to expect that children are more susceptible than older persons to pathogenic and behavioural stress effects induced by noise (Cohen et al., 1986). Several researchers have examined the aftereffects of prolonged exposure to traffic noise on reading and school achievement. Many of these studies have shown that chronic noise exposure is associated with reading deficits and decrements in tasks with a high demand on attention capacity (Evans, 1990; Schick, 1990). In this paper findings of interactions between 'chronic traffic noise and acute laboratory noise' on cognitive performance and school achievement will be reported. Data were collected in the Munich Airport Noise Study (Evans et al., 1995) and the Tyrol School Study II (Meis et al., 1999). Most of the findings can be classified in terms of habituation: children from areas exposed to traffic noise were not or were less affected when they were confronted with laboratory traffic noise. Another prevailing habituation type of task performance under transportation noise can be described in terms of 'environmental stimulation congruence', indicating that children from noisy areas performed best under noisy laboratory conditions, whereas children from quiet areas performed best under quiet conditions. However, these short term 'benefits' are severely counteracted by impairment as a main effect due to chronic noise exposure in everyday life. We will discuss some of the possible advantages and disadvantages of the apparent ability of children to habituate to chronic noise.

• THE MUNICH AIRPORT NOISE STUDY - EFFECTS OF CHRONIC AIRCRAFT NOISE ON CHILDREN'S PERCEPTION AND COGNITION
  S. Hygge, G.W. Evans and M. Bullinger
[Abstract]

The shutdown of the former Munich International Airport in May 1992 and the inauguration of the new one have provided an unprecedented opportunity to investigate in a longitudinal, prospective design the psycho-physiological, perceptual cognitive, motivational, and quality of life effects of noise exposure on children. Before the change over of airports, children at both sites were recruited into experimental and control groups. The experimental groups consisted of children who were exposed to high levels of aircraft noise at the old airport, or would be so exposed at the new airport. The two control groups, one for each airport, were selected from silent areas and matched with their respective experimental group on sociodemographic characteristics. One wave of data collection occurred prior to the change over of airports, the second wave one year later, and the third wave two years later. The children were aged 9-12 years when the study started, and a total of 327 children took part in all three measurement waves. At each wave they were tested individually on a number of psychophysiological and psychological tests. In the present paper longitudinal results from the whole set of perceptual and cognitive measures will be presented and compared to each other. These perceptual and cognitive measures include: Audiometric screening, annoyance to different noise sources, annoyance to community noise (master-scaled), auditory discrimination against different noise backgrounds (signal-to-noise task), choice reaction time (in noise and quiet), running memory, embedded figures, long-term recall and a standardized German reading test and word test.

Buratti, C.

• NOISE OBSERVATORY INFORMATION SERVICE
  C. Buratti, F. Cotana, C. Simoncini, R. Caracciolo and S. Curcuruto
[Abstract]

The Italian Law about Noise Pollution (n. 447, 26.10.1995) provides for the drawing up of acoustic reclamation plans, the evaluation of noise impact and acoustic climate, the activities of planning, measurement and check aimed to control noise pollution. Some decisions about territory policies need that such data are elaborated and presented in synthetic form; instead, the drawing up of reclamation plans needs an analytical and detailed representation of existing situation. It includes the development of a data bank, organized both on local (Communes, Regions) and national (ANPA) basis. The main objectives of this work are: - definition of an original NOISE-CIRIAF system, to elaborate noise pollution data and based on cause relations between Drivers, Pressure, State, Impact, Responses, following the DPSIR model defined by the European Environmental Agency (EEA); - choosing indicators able to represent the general conditions pertaining to noise pollution for State, Pressure, Impact and Responses. In the system of Drivers, all information regarding anthropic activities causing acoustic emissions have been identified. The drivers create two kinds of Pressure on environment: acoustic emissions and vibrations. The NOISE model distinguishes between indoor and outdoor environmental States; they have a direct Impact on health and on the ecosystem and an indirect influence on the economy both for the sanctions dictated by legislation and for the production and installment of systems. The Responses, in terms of structural interventions to contain acoustic emissions, of prescriptive and technological interventions have been grouped as follows: Laws, Plans, Technological Innovations, Scientific Research.

• PORT AND MARITIME PLANT NOISE: CHARACTERIZATION AND NORMALIZATION
  F. Rossi and C. Buratti
[Abstract]

By means of a statistical processing of noise measurement carried out at Genova and Livorno ports and noise data collected from many other Italian ports, a typical port noise spectrum has been found. Such a spectrum has been converted into a distance insensitive one by normalization procedure (Normalised Port Noise Spectrum - NPNS). Noise measurement data show that each NPNS 1/3 octave band level differs less than 3dB from any port 1/3 octave band normalised noise spectrum level. NPNS has also been A-weighted. NPNS may be used for optimization of acoustical insulation systems against port noise. It may also be proposed to introduce an adaptation term (Cport) to evaluate sound insulation of buildings exposed to port noise.

Burgess, M.

• RESIDENTIAL INSULATION SCHEME AROUND SYDNEY AIRPORT
  M. Burgess, M. Cotton and K. Butler
[Abstract]

The Sydney Airport Noise Amelioration Program was implemented in 1994 and instigated by the construction of a new parallel runway. The Airport is surrounded by suburban areas on three sides with a bay on the fourth side. An insulation program for public buildings (schools, childcare centres, hospitals/health care centres and churches) within the ANEF 25 (approx LDN 60) was undertaken. Residences within ANEF 40 (approx LDN 75) were acquired and the land converted to a park. Eligibility for the residential sound insulation scheme is based on the ANEF 30 boundary (approx LDN 65) which includes around 3,800 houses. Various insulation techniques were trialed on a group of 18 houses. Then a package was developed which was based on a menu of options for treatment. The goal of the package was to provide a cost-effective solution to allowing maximum choice by the home owners without compromising the acoustic performance. A flexible approach to the whole program was essential to ensure effectiveness and user satisfaction. A mechanism for updating the menu options was needed as new products became available. Noise measurements in a sample of the dwellings treated allowed for monitoring of the noise level reductions achieved and for changes to the package as necessary. The menu was changed as appropriate. This paper will summarise the implementation of the residential insulation scheme including the procedures implemented to allow for user preference and the monitoring and improvement, the noise reductions achieved and the home owner satisfaction. The effects of the scheme on the community and the local building industry will also be discussed.

Burstein, J.

• UPDATED LATERAL ATTENUATION IN FAA'S INTEGRATED NOISE MODEL
  G.G. Fleming, J. Burstein, A.S. Rapoza, D.A. Senzig, J.M. Gulding and T.L. Connor
[Abstract]

The lateral attenuation algorithm in the Federal Aviation Administration's (FAA) Integrated Noise Model (INM) has historically been based on the two regression equations described in the Society of Automotive Engineers' (SAE) Aerospace Information Report (AIR) 1751. These equations, which together represent a single relationship developed from measured data for 1960s and 1970s aircraft with low-bypass ratio jet engines, are applied equally in INM to the entire aircraft fleet. Further, these equations cannot take into account the effects of propagation over acoustically hard terrain, such as water. Consequently, in 1997 the INM development team initiated the task of revising the lateral attenuation algorithm within the model. The primary component of the revised algorithm is an entirely new methodology for taking into account ground effects. The methodology, which is based upon a newly-compiled spectral data base, along with the physical acoustics model of Embleton, Piercy and Daigle, will exist in INM as a library of regression equations. As such, this approach will offer the accuracy and flexibility of a pure physical acoustics model, coupled with relatively modest computer runtimes. This paper documents the scientifically-founded and experimentally-validated approach to computing ground effects, which is slated for inclusion in the INM.

Busink, J.J.

• ENVIRONMENTAL BENEFITS OF CONTINUOUS DESCENT APPROACHES AT SCHIPHOL AIRPORT COMPARED WITH CONVENTIONAL APPROACH PROCEDURES
  F.J.M. Wubben and J.J. Busink
[Abstract]

Since a number of years, Continuous Descent Approaches (CDA) are used at Schiphol Airport, mainly at night on runway 06. An inquiry among residents of the area surrounding the airport showed that the noise nuisance during nightly hours has been substantially reduced since the introduction of the CDA. Until recently however, no operational data were available to demonstrate the reduction of the noise footprint and the fuel consumption. On behalf of the Dutch CAA, an investigation into the environmental benefits of CDA procedures compared to conventional approach procedures is carried out, using operational data of actual flights. The operational data mentioned are Flight Management System (FMS) data of actual approaches of both the 747-400 and the 737-300/400. The data were supplied for 3 types of approach: CDA and conventional radar vectored 2000ft and 3000ft procedures. For each type of approach, 10 sets of data were supplied, 60 sets in total. Using the operational data, Lamax footprints were calculated and for each footprint the area of the 55, 65 and 75 dB(A) contours was determined. Also, the total amount of fuel used during the last 45 km of the flight was calculated. The results so far support the inquiry among residents: the noise footprints of the CDA are substantially smaller than the footprints of both the 2000ft and 3000ft approach procedures. Also, fuel consumption is about 30% lower during the last 45 km of the flight.

Buss, S.

• COMBINING METHODS TO EVALUATE SOUND QUALITY
  S. Buss, B. Schulte-Fortkamp and P. Muckel
[Abstract]

Evaluating sounds concerning sound quality is a context-sensitive process based on different subjective factors. Within the EU-project OBELICS (Objective Evaluation of Interior Car Sound) the method AISP (Associated Imaginations on Sound Perceptions) was developed to explore people?s feelings while listening to interior car sounds. The method relies on spontaneous descriptions of sound perceptions and indicate how people judge on sounds. The AISP method was applied in tests with German subjects and assists to develop a suitable measurement set to judge on car sounds. A Semantic Differential has been developed to investigate intercultural differences in the perception of car sounds corresponding to AISP method. Consisting of fifteen adjective pairs this Semantic Differential concerning interior car sounds is available now in four different languages: German, English, French, and Italian. The Semantic Differential tests carried out in Germany, Italy and France show differences and similarities between the judgements in the three countries. These results are statistically tested in an analysis of variance. A factor-analysis on the adjective-pairs and on the sounds was carried out. The three factors Comfort, Power, and Sonority were detected. Results of the test series with the Semantic Differential compared with AISP data will be presented with a special attempt to context sensitivity.

Busturia, J.

• RAILWAY WHEEL RING DAMPERS
  I. Lopez, J. Vinolas, J. Busturia and A. Castanares
[Abstract]

Railway wheel manufacturers are challenged to get a silent wheel, which in combination with a silent track, would drastically reduce noise disturbance due to rail traffic. Many different possibilities are nowadays offered. The paper describes in detail a cost-effective solution to add damping to the wheel that has been investigated in the framework of the Brite-Euram project ''SILENT FREIGHT''. It consists basically of a ring fitted under the tread and fixed to the wheel by bolts, that was called CAF ring damper. A description of the system is included and the differences with conventional ring dampers -steel rings fitted inside grooves cut under the wheel rim- are outlined. The damping mechanism originated by ring dampers -energy dissipation by Coulomb friction at the wheel-ring interface-, which is caused by the ring-wheel dynamic interaction, has been analysed. Conventional ring dampers for railway wheels can be very effective in suppressing squeal noise and so is the new CAF ring damper. However the paper shows results in which the new solution proves to be also effective in reducing rolling noise. In this paper the authors explain how this ring damped railway wheel has been designed and tested. The importance of several parameters - such us ring mass, pre-load or geometry- on the efficiency of this ring damper is underlined. Results of the experimental work carried out in the laboratory and obtained in track tests are presented.

Butler, K.

• RESIDENTIAL INSULATION SCHEME AROUND SYDNEY AIRPORT
  M. Burgess, M. Cotton and K. Butler
[Abstract]

The Sydney Airport Noise Amelioration Program was implemented in 1994 and instigated by the construction of a new parallel runway. The Airport is surrounded by suburban areas on three sides with a bay on the fourth side. An insulation program for public buildings (schools, childcare centres, hospitals/health care centres and churches) within the ANEF 25 (approx LDN 60) was undertaken. Residences within ANEF 40 (approx LDN 75) were acquired and the land converted to a park. Eligibility for the residential sound insulation scheme is based on the ANEF 30 boundary (approx LDN 65) which includes around 3,800 houses. Various insulation techniques were trialed on a group of 18 houses. Then a package was developed which was based on a menu of options for treatment. The goal of the package was to provide a cost-effective solution to allowing maximum choice by the home owners without compromising the acoustic performance. A flexible approach to the whole program was essential to ensure effectiveness and user satisfaction. A mechanism for updating the menu options was needed as new products became available. Noise measurements in a sample of the dwellings treated allowed for monitoring of the noise level reductions achieved and for changes to the package as necessary. The menu was changed as appropriate. This paper will summarise the implementation of the residential insulation scheme including the procedures implemented to allow for user preference and the monitoring and improvement, the noise reductions achieved and the home owner satisfaction. The effects of the scheme on the community and the local building industry will also be discussed.

Cagno, E.

• A PROBABILISTIC MODEL FOR A BETTER EVALUATION OF WORKER NOISE EXPOSURE
  E. Cagno, A. Di Giulio and P. Trucco
[Abstract]

In the evaluation of the worker noise exposure the definition of a standard working-day is difficult due to the uncertainty related to exposure time, environmental distribution of sound levels (areas) and operative conditions. Such contributions of variability to the evaluation parameters make the overall index LEP,d little significative and representative of real exposure conditions. The paper presents a probabilistic model, within a wider investigative methodology, that allows to associate to the numerical value of personal noise exposure level its variability. This makes it a sound term of comparison with requested regulatory standards and allows to associate to the evaluation also medium-long period information, i.e. about periods (of the working-day) in which measurements are not made. The model has been applied to a case study of an automated plant (rotary press), where operators carry on maintenance and adjustment activities. Thus they don't stay always in the same position, but shift randomly from one position to another during the working-day according to machine needs. It is evident that in such a case the definition of a standard working-day for an operator is difficult not only due to different intervention conditions, but also because of a number of different factors allowing for parameters uncertainty (first of all the duration of intervention that is not possible to know in advance). Starting from the model, a software package has been developed and tested in the case study.

Cai, C.

• ACTIVE CONTROL OF SOUND RADIATION FROM ENGINE MOUNTED PLATES WITH PIEZOELECTRIC ACTUATORS
  X.M. Zhang, C. Cai, G.R. Liu and K.Y. Lam
[Abstract]

Active control of sound radiation from an engine mounted plate by a piezoelectric actuator is investigated. The optimal control voltage, which is applied on the piezoelectric actuator, is obtained by minimizing the sound radiation power. Case studies show that the highest reduction of the total power radiated from the plate could be 71 dB at resonant frequencies.

Cailhau, D.

• ANNOYANCE DUE TO COMBINED NOISE SOURCES
  S. Joncour, D. Cailhau, P.-E. Gautier, P. Champelovier and J. Lambert
[Abstract]

Former studies on transport noise annoyance most often considered single noise exposure situations, whereas double developments of infrastructures i.e. a motorway alongside a high speed railway line for example, lead to an increasing number of residents exposed simultaneously to several noise sources, each one having its own characteristics. However, nowadays, this kind of situation can't be qualified and assessed precisely. A national socio-acoustic survey was carried out in France on 63 different multi exposed locations (road and railway). The objective of this study was on the one hand to reassess annoyance in practical situations through a large combination of multisource situations including dominant sources and on the other hand to determine the effects of several noise sources on the overall annoyance perceived. For that purpose 700 people were interviewed on the following items: their own experience of noise, description and perception of the noise environment, annoyance assessment according to different periods or activities. Individual exposures to road, railway and total noise were assessed in front of the most exposed facades for daytime and night-time from 24 hour noise measurements and calculations with Mithra-fer software. Dose-response curves between noise exposure and annoyance levels have been established through logistic regression models. The results show that a dose response curve assessed for one single source (road or railway) depends on the noise exposure characteristics, particularly the difference between the noise exposure levels of the two sources considered.

Capdevila, R.

• ACTIVE IMPEDANCE CONTROL IN A SMALL WINDOW
  J. Romeu, S. Jiménez , X. Salueña and R. Capdevila
[Abstract]

This work is focussed on active control of an acoustic impedance in a transmission surface. The aim is to avoid noise propagation from the interior of an enclosure through an aperture in its wall. As it is known, acoustic impedance is reduced by the reduction of sound pressure, thus, the objective is to set the impedance value to zero by attenuating the sound pressure using active noise control techniques. With the reduction of impedance, the reflection coefficient tends to -1 and the sound waves of the interior of the enclosure are reflected, avoiding the noise transmission to the exterior of an enclosure. In order to achieve the sound pressure attenuation in the aperture, techniques of local noise control are used. To carry on the investigation, an experimental device was set up, composed by an enclosure with a small aperture. The primary source (soundspeaker or electric motor) is placed in the interior of the enclosure and a classic feedforward adaptive noise control system is used to control the sound pressure at the aperture. The results consists on the analysis of the relationship between the attenuation at the aperture and the attenuation outside the enclouse. The influence of the frequency and distance between the secondary source and the error microphone are also studied, and a good correlation between these results and the theory of local control strategies is found.

Capriotti, R.

• PREDICTION OF THE NOISE POLLUTION CAUSED BY MILITARY AIRCRAFT FLYOVERS
  L. Maffei, V. Filomena, R. Romano and R. Capriotti
[Abstract]

Military aircraft operation in the surroundings of airports may give rise to strong complaints by people living nearby. If possible, the operation should be scheduled and carried out in a way that minimizes the noise impact on inhabited areas. In this perspective, predictive noise models can help in attaining the above-mentioned goal. The authors are engaged in the experimental collection of data during military aircraft operations in order to obtain the information required by existing predictive models for aircraft noise (e.g. INM - Integrated Noise Model). First comparisons between predicted and measured values will be reported in this paper.

Caracciolo, R.

• NOISE OBSERVATORY INFORMATION SERVICE
  C. Buratti, F. Cotana, C. Simoncini, R. Caracciolo and S. Curcuruto
[Abstract]

The Italian Law about Noise Pollution (n. 447, 26.10.1995) provides for the drawing up of acoustic reclamation plans, the evaluation of noise impact and acoustic climate, the activities of planning, measurement and check aimed to control noise pollution. Some decisions about territory policies need that such data are elaborated and presented in synthetic form; instead, the drawing up of reclamation plans needs an analytical and detailed representation of existing situation. It includes the development of a data bank, organized both on local (Communes, Regions) and national (ANPA) basis. The main objectives of this work are: - definition of an original NOISE-CIRIAF system, to elaborate noise pollution data and based on cause relations between Drivers, Pressure, State, Impact, Responses, following the DPSIR model defined by the European Environmental Agency (EEA); - choosing indicators able to represent the general conditions pertaining to noise pollution for State, Pressure, Impact and Responses. In the system of Drivers, all information regarding anthropic activities causing acoustic emissions have been identified. The drivers create two kinds of Pressure on environment: acoustic emissions and vibrations. The NOISE model distinguishes between indoor and outdoor environmental States; they have a direct Impact on health and on the ecosystem and an indirect influence on the economy both for the sanctions dictated by legislation and for the production and installment of systems. The Responses, in terms of structural interventions to contain acoustic emissions, of prescriptive and technological interventions have been grouped as follows: Laws, Plans, Technological Innovations, Scientific Research.

Carignani, A.J.

• A LONG-TERM STUDY ON HIGH LEVEL MUSIC EXPOSITION AND HEARING EFFECTS IN ADOLESCENTS
  M.R. Serra, E.C. Biassoni, U. Richter, G. Minoldo, G. Franco, S. Abraham, S. Joekes, M.R. Yacci, A.R. Pollet and A.J. Carignani
[Abstract]

Sources of noise exposure outside the workplaces that are potentially damaging has been topic of many studies (Clark, 1991). Young people are exposed to high level music in discotheques or through personal listening devices. The literature reveals that there are different opinions about possible harmful hearing effects of music (Babish et al., 1988, West et al.,1990; Axelsson, 1990 & 1996; Royster et al., 1990; Ising et al., 1995). This paper deals with the early results of an interdisciplinary long-term study on hearing effects in adolescents by high level music exposition and its relation with physical and psychosocial variables, developed according international standards. Two groups of adolescents -males and females- are examined along four years of their high school level, from 14 to 17 years old. The study focus on changes both, in hearing threshold, applying conventional and extended high frequency audiometry, as well as, in recreational activities. Besides, sound inmission levels of the adolescents studied are measured: a) in discotheques using two methods: by personal dosimetry and by a system developed ad-hoc; b) using walkman and/or diskman: through manikin-technique. In the second year of the study the results show: a) hearing threshold shift in most of the extended high frequencies; b) increase in the music exposure through recreational activities; c) high sound inmission levels in discotheques and trough personal music devices. The whole study, during four years, let will us to know the real hearing effects by music exposition and their relation with psychosocial variables in the studied adolescents group.

Carles, J.L.

• SOUND QUALITY AND ENVIRONMENTAL QUALITY OBSERVED IN THE PUBLIC AREAS OF ALCALA DE HENARES
  J.L. Carles and I. López Barrio
[Abstract]

Public areas develop personal significance because there are connections between the area and the life of the people; when understood in this way, the sound landscape constitutes an important element in the structure, understanding and analysis of the territory. This study offers the results of an exploratory investigation carried out in a specific urban area, the city of Alcalá de Henares; the environmental quality of public squares and public areas was studied using a methodology which placed particular emphasis on the sound environment: how urban forms influence sound perception and how the interaction between sound and space is important for determining the identity of urban sound. To this end, a double approach has been developed, both quantitative and qualitative, with different types of methods for collecting data in situ: semi-directive interviews, questionnaires, acoustic measures and recordings of sound environments, as well as in situ observations. Firstly, this methodology has enabled us to determine which urban areas, in the citizens' opinion, are most relevant for the configuration of the city; the public areas are characterised according to a series of criteria related to the environmental quality observed and the subjective assessment of the different urban areas is determined as well as the importance of the criteria of the environmental quality perceived in this assessment. The significance of the sound environment has also been determined in the public areas studied and the effect this sound environment has on the utilisation of the public areas. It has been demonstrated how the urban area, as perceived by its inhabitants, is constructed as a multi-space system with connections between different places. Thus, whether the areas are central or peripheral has a determining influence on the citizens' assessment of them.

Carletti, E.

• SOUND QUALITY AS A TOOL TO IMPROVE THE NOISE CLIMATE AT THE OPERATOR'S STATION IN EARTH-MOVING MACHINES
  G. Brambilla, E. Carletti and F. Pedrielli
[Abstract]

Nowadays the sound quality approach is a valuable tool in the engineering process aimed at improving the effectiveness of noise reduction treatments for industrial products. To investigate the potential and perspective of such approach also in the earth moving machines (EMMs) a research project has been undertaken and promising results have been obtained in its preliminary phase. The present paper describes a further laboratory experiment designed to investigate in more details how changes in the energy and shape of the noise spectrum influence the auditory perception. For this purpose the noise at the operator's station in a EMM has been binaurally recorded by a manikin with the machine in stationary and idle conditions. The spectrum of this noise recording has been modified by a digital equaliser in order to simulate the effect of some noise reduction treatments, i.e. those due either to an active noise control system tuned on a selected low frequency or to traditional passive systems less selective in frequency and operating at the mid-high frequencies. The sound stimuli obtained have been presented by headphones in laboratory to a listening jury. By the method of adjustment subjects modified the level of the comparison sound stimulus until it was judged as loud as the standard stimulus. In addition the paired comparison method has been used to obtain the subjective preference among the stimuli. The listening tests are still in progress and results will be available at the time of writing the manuscript.

Carme, C.

• ACTIVE CONTROL IN ONE DIMENSIONAL FLOWS
  G. Leventhall and C. Carme
[Abstract]

Active control in flows has problems specific to the interaction of the flow with the transducers, including turbulence generation and the higher pressures normally associated with flow. The interaction causes problems in signal detection and generally leads to a diminution of effectiveness of the active system. Considering that the majority of applications are for installations in the presence of flow, the problem requires solution. In many cases of modest flow rates the solutions are standard, using turbulence screens etc on microphones, but there are limits to this, although high flow rates can be accommodated when the noise to be cancelled has prominent tonal components. The paper considers the effects of flow on the operation of active control and deals in detail with a flow modulation device (ExAct), which has been designed to make use of the flow by imposing fluctuations on the flow itself, which cancel the noise in the system. ExAct has been applied to a wide range of gas and liquid systems and is of particular application to controlling the noise of hot gas exhausts.

• FEED FORBACK™ CONTROL COMPARE TO CLASSICAL CONTROLS
  C. Carme
[Abstract]

The main idea of the Feed ForBack^TM control is not to simply add the Feedforward and the Feedback control, but rather to intimately combine the two effects in order to create a new form of hybrid control. Any experiences using Feedforward control show that this control needs a very good coherence between reference microphone and control microphone. A good point in favor of Feedback control, is ''independence'' with regards to the reference signal, which gives a useful alternative in comparison to Feedforward control. But by using the Feed ForBack^TM instead of Feedforward or Feedback control we can avoid several limitations given by these two classical technologies. The paper presents what are the improvements given by a Feed ForBack^TM in comparison to a Feedback control or a Feedforward control. Some applications using the Feed ForBack^TM control and already presented during the last Active 99 convention held in Florida will be checked in detail in order to really understand these improvement because this third way to manage active control is a new strategy control incorporating a combination and not an addition of the two classical principles systems. We will also give some specific results related to this new principle : an improvement of the negative effect of the Feedback control as pumping effect, or a fast convergence for the Feedforward, etc...

• ACTIVE NOISE CONTROL: APPLICATION TO THE COST REDUCTION OF THE UNDERGROUND VENTILATION BUILDINGS IN PARIS
  D. Gabay, C. Carme and V. Lagarrigue
[Abstract]

For several years RATP manages a wide program for the improvement of climatic comfort and fire safety of the underground. High flow ventilation buildings of 12 m2 cross section (60 to 120 m3/s) have been made and today, in order to decrease their cost to flow ratio, RATP wants to decrease their dimensions knowing that 80% of the cost is due to the concrete. Nowadays, these dimensions are related to the passive acoustical treatment and the objective of acoustic level. The use of an active noise control system would allow a cost reduction of 30 to 40 percent because of the possible dimensions reductions. To reach this objective, specific developments were needed in two particular ways: active noise control performances and treatment of flow induced noise sources. For active noise control, numerical simulations leaded to the definition of the association of both active and passive silencers: their number, their dimensions and the architecture of the whole. Tests on a special wind tunnel allowed to validate the silencer concept and to determine the limits of its efficiency especially in terms of maximum flow velocity. For flow induced noise sources, experiments were leading to study the main noise sources and to test particular solutions. These experiments were performed on a hydraulic loop with a 1/20 model on which visualisations, velocity profiles and pressure measurements were performed. The final tests on a full scale ventilation building will take place in 2000.

Carney, L.H.

• AUDITORY REPRESENTATIONS OF TRANSIENTS: THE IMPORTANCE OF PHASE IN THE ANALYSIS OF RATTLE EVENTS
  G.H. Wakefield, L.M. Heller, L.H. Carney and M. Mellody
[Abstract]

Engineering the sound quality of an automobile has drawn upon well known perceptual studies of loudness to set design targets for various noise sources, such as wind and power train. Attempts to apply these studies to design-target specification for squeak and rattle noises have met with limited success, primarily because the perceptual response to transient signals differs in several important dimensions from the response to wideband, steady-state noises, where the phase spectrum, for example, contributes little. We present psychophysical results that detail how the perception of a transient's magnitude spectrum can be affected by its phase spectrum. For certain phase spectra, observers appear to be unable to discriminate a magnitude spectrum that varies over a 20-dB range from one that is essentially flat. For other phase spectra, however, observers appear to be sensitive to as small as a 2-3 dB change in spectral shape. This phenomenon appears to depend on temporal isolation of the transients. For a train of transients, observers perform as well as they do in the case of single transients, regardless of the phase spectrum. Such phase effects are observed in a computational model of the auditory nerve. We show how this computational auditory model can be used to aid in visualizing rattle events and will discuss the impact of

Carniel, X.

• ON THE USE OF PROCESSING VIBRATING VELOCITY IN WAVENUMBER DOMAIN FOR COMPUTATION OF SOUND RADIATION OF A PLANAR PLATE
  J.-C. Pascal, J.-F. Li and X. Carniel
[Abstract]

Acoustical array techniques such as laser vibrometry, holographic interferometry and acoustical holography, enable the sound pressure or vibrating velocity in the source plane to be experimentally obtained. Sound radiation from the radiator can be computed by processing the vibrating velocity data in wavenumber domain (k-space). As Fourier transform is applied to a finite aperture, wavenumber processing is often accompanied with distortions, resulting errors in calculations. The objective of this paper is to show some techniques to solve the problems encountered in wavenumber processing. Green function in k-space is the first to be considered. Two modified expressions for Green function are given. Comparisons of the different expressions of Green function are made from the simulation results. Sound radiation fields respectively parallel and perpendicular to the plate plane are obtained by the use of the acoustical holography. Third the far-field directivity is calculated in wavenumber domain. An interpolation process is carried out to overcome the problem of lack points in the process especially at low frequencies. Investigations in the paper show that wavenumber processing technique is of efficiency in the calculation of sound radiation from vibrating velocity on a baffled and non-baffled plate. However techniques of wavenumber processing should be taken into account in order to obtain good results.

Carolus, D.-I.T.

• REVIEW OF NOISE PREDICTION METHODS FOR AXIAL FLOW FANS
  D.-I.T. Carolus and M. Schneider
[Abstract]

In the paper different noise prediction methods for low to medium speed axial flow fans are reviewed. The emphasis is put on broad band self noise caused by viscous sources. Lowson defined three classes of noise prediction methods: Class I: Estimation of overall level as a function of basic machine parameters Class II: Separate consideration of the various noise mechanisms using selected machine parameters Class III: Utilization of the detailed rotor geometry and flow field parameters for acoustic source modelling In order to illustrate a typical class I - noise prediction scheme the German Richtlinie VDI 3731, B2, which allows to estimate the sound power level and spectrum as a function of fan type, diameter, speed etc., is described shortly. Some of these methods are reviewed with respect to the noise mechanisms, taken into account, the required input parameters, their applicability to axial fans and the possible results. Eventually some theories which intend to estimate the affect of the popular blade skew on noise reduction are summarized.

Carter, N.

• COMPARISON OF REACTION (DISSATISFACTION, ANNOYANCE ETC.) TO AIRCRAFT NOISE AMONG SHIFT WORKERS AND NON-SHIFT WORKERS
  R.F.S. Job, J. Hatfield, N. Carter, P. Peploe, R. Taylor and S. Morrell
[Abstract]

Curfews at Sydney airport result in shift workers being exposed to more aircraft noise when they are trying to sleep than are non-shift workers. The present community survey of 1,015 residents of high and low noise areas in the vicinity of Sydney Airport assessed whether shift workers report greater noise-induced sleep disturbance than non-shift workers, and whether this translates into more negative reactions to noise (dissatisfaction, annoyance etc.). The role of noise sensitivity in the effects of shift work was also considered. Shift workers report more difficulty sleeping, more frequent use of sleeping pills, and more negative reaction to noise, than non-shift workers, although these differences did not reach statistical significance. Self-reported sleep disturbance correlated significantly and positively with reaction. The findings are consistent with the claim that sleep disturbance contributes to negative reactions to noise among shift workers.

• CROSS-SECTIONAL AND LONGITUDINAL RESULTS OF A FOLLOW-UP EXAMINATION OF CHILD BLOOD PRESSURE AND AIRCRAFT NOISE -- THE INNER SYDNEY CHILD BLOOD PRESSURE STUDY
  S. Morrell, R. Taylor, N. Carter, P. Peploe and S. Job
[Abstract]

Setting: The Inner Sydney Child Blood Pressure Study was undertaken to investigate the relationship, if any, between child blood pressure (BP) and exposure to aircraft noise in school children occasioned by the opening of an additional runway at Sydney (Kingsford-Smith) Airport. Methods: The Inner Sydney Child Blood Pressure Study comprised a baseline measurement phase in 1994-95 and a follow-up phase in 1997. BP measurements were taken on the same individuals to examine within-subject changes in BP in relation to corresponding changes in aircraft noise exposure. In both phases of the study, 3 BP measures were taken of each child (systolic & diastolic BP, heart rate), along with measures of body size and obesity. Parents were surveyed regarding family histories of high blood pressure, the child's eating habits and activity levels, and the type of residence they lived in. The children were also surveyed regarding their activity levels and eating habits. Noise exposures were measured by the National Acoustic Laboratories, recast in energy-averaged composit noise units (the Australian Noise Exposure Index, ANEI), and geocoded to each residential and school address by means of Geographic Information System software. Statistical analyses of systolic and diastolic BP, using the mean of the 2nd & 3rd BP measures as the outcome, were conducted in relation to Phase I and Phase II aircraft noise levels as continuous variables, and as categories of exposure (15, 20 or 25 ANEI versus 15, 20 or 25 ANEI). Results: 628 children participated in Phase II of the study, from 1,230 children who participated in Phase I of the study. Approximately 300 children were lost to follow-up due to change of school during the intervening period (1994/5-1997). Two schools refused to participate in the follow-up study. The remaining children did not participate due to parental refusal. Overall, little association was found between BP, or change in BP, and school exposure to aircraft noise, change in school exposure to aircraft noise, or the difference between school and home noise exposure. There appeared to be an association between systolic BP and exposure to aircraft noise 20 ANEI at school, but this was inconsistent with the negative relationship found when above or below 25 ANEI was used as a school noise exposure category (ie, lack of a dose-response relationship).

• THE INFLUENCE OF ACTIVITY DISTURBANCE ON REACTION THE SYDNEY AIPORT HEALTH STUDY
  R.F.S. Job, J. Hatfield, N. Carter, P. Peploe, R. Taylor and S. Morrell
[Abstract]

Noise-induced activity disturbances may promote negative reactions to noise. The relationship of noise-sensitivity to reaction may in turn reflect greater activity disturbance amongst noise-sensitive individuals, or a greater impact of activity disturbance on reaction amongst these individuals. The present community survey around Sydney Airport (N=1,015) assessed noise-induced disturbance of several activities (e.g. conversation, relaxing, entertaining), reaction to noise (annoyance and general reaction- dissatisfaction, affectedness), and noise-sensitivity. Activity disturbance correlated positively and significantly with reaction and noise-sensitivity in high and low noise areas. Reaction was significantly predicted by activity disturbance and noise-sensitivity in regression analyses. The difference between reaction and activity disturbance did not correlate significantly with sensitivity. These results are consistent with the view that activity disturbance, which is greater amongst noise-sensitive compared to non-noise-sensitive individuals, contributes to reaction. However, the contribution appears to be no greater amongst noise sensitive individuals.

Cartwright, J.

• RESEARCH METHODOLOGY - NOISE ANNOYANCE AND HEALTH
  J. Cartwright and I. Flindell
[Abstract]

The possibility that excessive residential exposure to general environmental noise might contribute to long term adverse health effects in addition to annoyance remains an issue of public concern. The underlying hypothesis that unwanted sound causes annoyance which contributes to stress and which in turn might contribute to long term adverse health effects appears plausible but it is difficult to define in scientific terms and our understanding of any possible aetiological mechanisms is incomplete. Where similar uncertainty exists in other areas of environmental research, regulatory authorities tend to err on the side of caution to minimise any residual risk. The field of environmental noise is perhaps more complicated because sound is intrinsically neutral and only becomes noise because of the way that people react to it. Unjustified or excessive sound level reduction could have equally significant social, economic, or unexpected health consequences. There are situations where the socio-economic costs of noise control could outweigh the benefits. The solution to many of these problems is to focus future research on mechanism rather than on prevalence. Instead of trying to find out the percentage of the population affected and then encountering what can be insurmountable difficulties because of confounding factors, we should be designing carefully controlled experiments to investigate mechanism. Only when we understand mechanism will we be able to make sensible predictions of future effects.

Carvalho De Assunção , S.

• ACOUSTICAL POST-OCCUPATION EVALUATION APPLIED TO POPULAR HABITATIONS IN HUMID TROPICAL CLIMATE
  M. Macedo, S. Carvalho De Assunção and J. Slama
[Abstract]

In areas with tropical-humid climate, the development of activities outdoor is usual; therefore, the problem of the exposition to the noise exceeds the limits of the building and extends at the urban scale level. Methods and constructive techniques that provide acoustic quality in the buildings can be incompatible with the local climate and with the social, economic and cultural condition of the population, in such areas. The Acoustical Post-Occupation Evaluation (Acoustical POE) can be an important tool to be used to analyse the architectural lay-out, the facade elements and the implantation of constructions and how they influence in its acoustic quality. Acoustical POE being an evaluation accomplished with the user's participation, it can supply data on the reaction of the population to noise exposure, which are not well-known in countries as Brazil. In this paper, results of researches performed in popular habitations in Rio de Janeiro, Brazil are presented, where Acoustical APO was used. It was possible to obtain data about the reaction of the community to the noise of such sources as the traffic of vehicles, recreational areas, neighbouring habitations and those internal to the residential units.

Carvalho, A.

• EXPEDITIOUS NOISE MAPPING AT A MUNICIPAL LEVEL
  A. Carvalho and R. Rodrigues
[Abstract]

The Portuguese Noise Code published in 1987 requires noise zoning using the LA50 parameter in two periods (day and night). The new Portuguese Noise Code (expected to be published soon) will use the parameter LAeq for the same periods and purposes but enforces the municipalities to determine their noise maps. This will be a huge task because none of the 307 Portuguese municipalities is known to have that duty done. Therefore there is a need to find a fast but valid method to perform that work with not many means in equipment or manpower. This paper describes our recent studies in order to find such expeditious model. For that purpose work was done to characterize and group a municipal soundscape in only two or three acoustics scenarios; to characterize the quantitative effect of the three day periods (day, evening and night); to analyze the effect of the day of the week in the measurements and to discuss the minimum measuring time to give reasonable and representative global results for those parameters. For this study the suburban municipality of Maia was used. It has 101,000 inhabitants and 84 km2 divided in 17 parishes (''freguesias''). The result of this study is an expeditious and low cost method for noise mapping in large areas using few resources. A conversion system between LA50 and LAeq was also studied to be applied to all the work already done using today's legal parameter (LA50). A possible future use of the GIS is also reported.

Casini, D.

• CONTRIBUTION OF DOUBLE LAYER ASPHALT IN REDUCTION OF URBAN TRAFFIC NOISE
  A. Poggi, D. Casini, C. Fagotti and S. Secchi
[Abstract]

Double layer asphalts have been used mainly to improve the security of the streets, by means of their drainage properties. Moreover, the benefit achievable with such product in terms of acoustic gain is well known, but until now tests and controls on their acoustical properties have been carried out for high velocity of the vehicles, such as highway or extra - urban roads. This paper concerns the use of two double layer asphalts employed in Florence to reduce traffic noise in two different urban streets. In this case, excitement of tire vibrations by the road roughness and aerodynamic noise, caused by air pumping, are negligible because of the low speed. For this reason it was expected that porous asphalts couldn't give a great contribution in the reduction of traffic noise. Nevertheless, the results show a quite significant reduction of sound pressure level. Measurements have been carried out during two years after the laying down of the new asphalts, taking sound pressure level at the border of the road, together with fluxes of vehicles per hour. A statistical analysis has been implemented on the base of a model that permits to evaluate the actual contribution of the asphalt in the reduction of traffic noise. Results point out that use of double layer asphalts may be efficient even in urban streets with low vehicle speed.

Castanares, A.

• RAILWAY WHEEL RING DAMPERS
  I. Lopez, J. Vinolas, J. Busturia and A. Castanares
[Abstract]

Railway wheel manufacturers are challenged to get a silent wheel, which in combination with a silent track, would drastically reduce noise disturbance due to rail traffic. Many different possibilities are nowadays offered. The paper describes in detail a cost-effective solution to add damping to the wheel that has been investigated in the framework of the Brite-Euram project ''SILENT FREIGHT''. It consists basically of a ring fitted under the tread and fixed to the wheel by bolts, that was called CAF ring damper. A description of the system is included and the differences with conventional ring dampers -steel rings fitted inside grooves cut under the wheel rim- are outlined. The damping mechanism originated by ring dampers -energy dissipation by Coulomb friction at the wheel-ring interface-, which is caused by the ring-wheel dynamic interaction, has been analysed. Conventional ring dampers for railway wheels can be very effective in suppressing squeal noise and so is the new CAF ring damper. However the paper shows results in which the new solution proves to be also effective in reducing rolling noise. In this paper the authors explain how this ring damped railway wheel has been designed and tested. The importance of several parameters - such us ring mass, pre-load or geometry- on the efficiency of this ring damper is underlined. Results of the experimental work carried out in the laboratory and obtained in track tests are presented.

Cavadini, L.

• ENHANCE: AN EVOLUTIONARY IMPROVEMENT TO AIRCRAFT NOISE MODELING
  T. Elliff, L. Cavadini and I. Fuller
[Abstract]

International guidance material is provided by ICAO (Circular 205), defining how to compute noise contours for aircraft around airports. However, it is acknowledged within the noise modeling community, that significant errors can exist between modelled noise levels, and those measured ''on the ground'' for similar scenarios. The aim of the project is to better understand the sources and magnitude of these errors, and attempt to mitigate for them in the modelling process. The project will deliver an ''Enhanced'' Noise study tool, enabling more accurate predictive studies to be conducted for European airports and fleets, and will directly support the evolving European Commission Common Noise Policy. The model is based on existing noise contour calculation software (for example, the Integrated Noise Model from FAA), but through a preprocessor function and ''European'' database, allows more accurate data input, eliminating, or at least reducing, known errors. The project is a combination of tool development and validation exercise, and is based around a significant data collection task, with the cooperation of operators and airport administrations. It is a programme of collaborative work in Europe, sponsored by EUROCONTROL, as a complement to the work being conducted in voluntary CAEP (ICAO Committee on Aviation Environmental Protection) working groups, which will ultimately propose revisions to the Circular 205 methodology.

Cepeda Riaño, J.

• INTELLIGIBILITY IN A SCHOOL IN LEÓN (SPAIN)
  J. Cepeda Riaño, E. García Ortiz, B. Melcón Otero and M.I. Vidal González
[Abstract]

One of the issues of obvious incidence in the performance of pupils in a school is that of the existent intelligibility in the classrooms. However, the planners of school buildings don not generally pay great attention to this, so that the situation is frequently highly deficient. The following information refers to a complete study of intelligibility carried out by the Acoustic Laboratory of the University of León in ''Juan del Enzina'' High School in León (Spain). All the 33 classrooms in the school were studied in two different phases of work. In the first study the RASTI Index was used, while in the second phase an analysis was made of the response of the pupils to a test carried out using lists of two-syllable words in which the emission levels were progressively changed in order to observe the variation in intelligibility. In addition, a sonometer study was realised, by which the situation in the school as to existing ''background noise'' could also be tested. The results show a very deficient situation with regard to intelligibility in the classrooms. 24 of the 33 studied can be considered ''poor'', while the situation in the remaining 9 can be described as ''weak''. Moreover, the study of the pupils'response leads us to certain conclusions about saturation in intelligibility. There is, at times, a decrease in this when the levels of emission are increased.

Cerchiai, M.

• COMPARISON BETWEEN ITALIAN AND RECOMMENDED EUROPEAN NOISE INDICATORS.
  G. Licitra, M. Cerchiai, C. Chiari and L. Boccini
[Abstract]

The Commission of the European Communities is developing its own regulation for noise pollution, in order to harmonise the legislative current survey in different Member States and to obtain an unique description of noise pollution in all EU territory. The European Commission recommended in its ''Position Paper on EU Noise Indicators'' the use of two main indicators in order to describe noise from all outdoor sources for assessment, mapping and control purposes. The Italian Regulations differ from the EU recommendations on methodology to measure noise, especially for definition of the indicators to be used. In this paper we analyse the main differences between them and try to evaluate the corrections to be done to avoid losing of all data already collected. We use the data collected by ARPAT in two great noise mapping campaign held in Pisa and Livorno during last three years. We try to evaluate the correction due to reflections on close walls and the corrections due to different definition of indicators, especially for the European day overall value LDEN and the corresponding Italian LDAY. Finally we try to estimate the overall costs to save all works already done on noise mapping in Italy.

Cervello, S.

• QUANTIFICATION OF THE PASS-BY NOISE EMISSION OF TRAIN WHEELS USING A MICROPHONE ARRAY TECHNIQUE
  J. Van Keymeulen and S. Cervello
[Abstract]

Reduction of pass-by noise caused by trains has become a major environmental issue. Many sources contribute to the pass-by noise of trains, like train wheels, tracks, train motors, auxiliary equipment and aerodynamic noise. As train wheels are a main contributor to the pass-by noise of trains, a huge interest lies in investigating the acoustical performance of specially designed low-noise train wheels in comparison with standard wheels when a train is passing-by, even at high speeds. Standard measurements are not capable to separate the noise generated by the different sources, especially when these are passing by at very high speeds. In that case, the microphone array technique needs to be applied. This technique allows the quantification of the noise emission of different sound sources and in particular of train wheels. This technique corrects for the Doppler-shifts, eliminates non-wheel noise and tracks the noise from each individual wheel. This paper presents the results of the application by LMS Engineering of the phased microphone array technique for quantification of the noise reduction of Lucchini prototype wheels mounted on a high-speed ETR470 Pendolino train and shows the significant reduction in OA-pass-by noise level obtained by the use of these prototype wheels.

Cha, K.S.

• IMPROVEMENT OF IMPACT NOISE ISOLATION OF FLOOR STRUCTURE BY RESILIENT MATERIAL IN APARTMENT BUILDINGS
  I.S. Shin, K.S. Cha, D.W. Lee, M.K. Cho and K.S. Chung
[Abstract]

The floor impact noise transmission has been a problem in the radiant heating floor system(so called On-dol) of the apartment housing buildings since housing developers have allowed the minimum floor thickness as well as floor height to make more floors to sell. Therefore in the text, the purpose of the study is to find the optimum resilient material that can reduce the floor impact noise transmission at a reasonable cost and satisfy the design criteria. To find an optimum material, 17 resilient materials were selected and adopted to the radiant heating floor system. Each floor model was tested in the acoustic laboratory(reverberation room) to measure the sound isolation level. To make an offer impact sound isolation of floor structure which can be satisfied with design criteria, first of all, by correlation analysis of impact sound isolation and material cost, the optimum resilient material is selected. As a result, among the 17 different materials, polystylene/and polyethylene are proved to be the most appropriate sound isolation material. Above materials satisfy the design criteria, and its material cost is most inexpensive among the materials that satisfy the design criteria.

Chabin, E.

• VIBRO-ACOUSTICS ANALYSIS OF A MEDICAL XRAY SOURCE : HYBRID APPROACH COMBINING EXPERIMENT AND FEA/BEA MODELING
  J.-M. Auger, F. Damagnez, M.A. Hamdi, S. Ayadhi and E. Chabin
[Abstract]

A vibro-acoustics analysis of a medical X-Ray source is presented . As the X-Ray source noise is generated by the interactions between the internal rotor and its bearing which are very complicated to describe, the analysis is carried out by using an hybrid approach combining experimental data measured on the system and an elasto-acoustics FEA/BEA model. This methodology , already applied for automotive and aerospace domains, uses RAYON solver integrated in the MCAE environment of I-DEASTM. Firstly, an inverse procedure is applied to determine an equivalent source model as a set of internal forces derived from vibration measurements in running condition and the elasto-acoustic model. Secondly, the BEA model and the source previously found are used to compute the radiated noise. Experimental and numerical results of both vibrations and radiated noise are finally compared. Such approach yields to a vibro-acoustics model capable to help for the path noise analysis and for the numerical modification analysis which have been applied to lead to several noise reduction improvements on the X-Ray source.

Chae, C.-K.

• CHARACTERIZATION OF DYNAMIC PROPERTIES OF POLYURETHANE FOAMS FOR AUTOMOTIVE SEATS BY VIBRATION TESTS
  C.-K. Chae, K.-J. Kim, H.-K. Jang and Y.-H. Cho
[Abstract]

Human occupants in a vehicle are in direct contact with seats, of which the primary function is to improve ride quality by isolating the passenger from vehicle body vibrations induced by road surface. Hence, tuning works for better ride quality are often done by changing the seat dynamics. Major portion of the seats is constructed with flexible polyurethane foams, which means that the seat dynamics is exclusively controlled by the shapes and material properties of the foams. For a given step compressive loading superimposed with harmonic excitations, dynamic stiffness increases and damping decreases as the time goes on due to the inherent creep characteristics of the polyurethane foams. Furthermore, variation of such properties with the time is heavily dependent on the static loading. Therefore, detailed investigation of such properties is essential to the seat design. In this paper, dynamic properties of several polyurethane foam materials are characterized by impedance tests focusing on the dependence on the static compression level applied on the foams. The impedance test method directly measures the foam dynamic properties as functions of frequency, loading time, static and dynamic loading condition. In addition, the intrinsic dependency of dynamic stiffness on static stiffness irrespective of foam types is commented by comparing the ratio of dynamic stiffness to static stiffness under same static stiffness conditions for various foam types. Transmissibility of the foam materials, which is crucial factor in dynamic comfort of automotive seats, is estimated by using the characterized dynamic properties. And then, the estimated transmissibility is compared with one measured directly under the more approximate operational conditions.

Chahine, M.

• MANAGING NOISE EMISSION IMPACTS OF AIRPORT TRAFFIC
  M. El-Fadel, M. Chahine, M. Baaj and T. Mezher
[Abstract]

Airport traffic is a major source of community concerns due to aircraft noise emissions particularly in locations close to airports and aircraft flight tracts. The principal effects of aircraft noise on humans include hearing damage risk, and speech and sleep interference which can develop into stress. As such, it becomes essential to locate, design, and/or expand airports as well as optimize flight paths in a way to reduce noise exposure to nearby communities. For this purpose, it is essential to assess changes of noise impact resulting from new or extended runways or runway configurations, evaluate new traffic demand and fleet mix, evaluate revised routings and airspace structures, assess alternative flight profiles, and modifications to others operational procedures. This paper present the calibration and application of the US Federal Aviation Administration integrated noise model (INM) for the analysis and prediction of airport traffic emission noise impacts from aircraft operations on communities near the proposed expansion at the Beirut International Airport. For this purpose, field noise measurements were collected at sensitive noise receptors along selected locations around the airports and the corresponding airport traffic flow was characterized. Noise levels were then simulated as a function of the different airplane classes, flows, flight path and landing characteristics. The model was also used to predict future noise levels, optimize airplane flight path, and assess mitigation measures to minimize potential airport noise emission impacts. In addition, a local field survey was conducted to better understand the influence on the community response to aircraft noise and document the extent of annoyance and activity disturbance caused by noise.

Chaikali, S.

• EXISTING NOISE ABATEMENT LEGISLATION IN GREECE AND PROPOSED LEGAL FRAMEWORK TOWARDS A REHABILITATION AND MANAGEMENT OF THE ACOUSTIC LANDSCAPE
  A. Hatzopoulou and S. Chaikali
[Abstract]

Noise is an important environmental factor affecting all problems related to the degradation of the urban environment and the quality of life. In Greece, the environmental protection regarding natural, cultural and urban environments, is already established by the Constitution (Article 24) and the quality of life is determined as a protected conception to be invistigated by judicial authorities. Quality of life is characterized by the sound environment, which contributes to the spaces' aesthetic determination. On the contrary noise contributes to space degradation. The making of a complete national and especially an international environmental policy, present increasing difficulties arising from the interaction between mitigation and legislation measures for different member states characterized by different levels of economic development. The existing greek legislation deals with noise in a basis of a quantitive approach i.e. max. permissible levels per source, and does not take into account a wider conception of the acoustic environment. Regulations regarding urban planning, do not implement noise as a design parameter, except certain cases (i.e. protection of special buildings). Therefore urban and architectural studies do not examine, within the spatial and urban structure organisation, the noise that can be created by the various project's requirements. Noise management in space and time is therefore ignored, and the determination of noise emissions per source is incomplete, for each activity and time period. Furthermore, Greek legislation implementation, even though in harmonization with the E.U.'s directives at an adequate level, is ineffective. This is mainly due to the fact, that some necessary administrative decrets and directives, for which the relevant legal authorization already exists, are still not implemented. Therefore, important administrative actions remain inactive and noise protection uneffective.

Champelovier, P.

• ANNOYANCE DUE TO COMBINED NOISE SOURCES
  S. Joncour, D. Cailhau, P.-E. Gautier, P. Champelovier and J. Lambert
[Abstract]

Former studies on transport noise annoyance most often considered single noise exposure situations, whereas double developments of infrastructures i.e. a motorway alongside a high speed railway line for example, lead to an increasing number of residents exposed simultaneously to several noise sources, each one having its own characteristics. However, nowadays, this kind of situation can't be qualified and assessed precisely. A national socio-acoustic survey was carried out in France on 63 different multi exposed locations (road and railway). The objective of this study was on the one hand to reassess annoyance in practical situations through a large combination of multisource situations including dominant sources and on the other hand to determine the effects of several noise sources on the overall annoyance perceived. For that purpose 700 people were interviewed on the following items: their own experience of noise, description and perception of the noise environment, annoyance assessment according to different periods or activities. Individual exposures to road, railway and total noise were assessed in front of the most exposed facades for daytime and night-time from 24 hour noise measurements and calculations with Mithra-fer software. Dose-response curves between noise exposure and annoyance levels have been established through logistic regression models. The results show that a dose response curve assessed for one single source (road or railway) depends on the noise exposure characteristics, particularly the difference between the noise exposure levels of the two sources considered.

Chan, K.S.

• LEGISLATION AND PLANNING ON THE NOISE ENVIRONMENT OF HONG KONG
  K.S. Chan, P.S. Ng and C.K. Lee
[Abstract]

Hong Kong is a metropolitan city with more than 6.8 million population sharing some 1000 sq.km of hilly terrain. During the rapid development of Hong Kong in the 60's and 70's, environmental issues have not been taken seriously leading to many problems including noise disturbing the community. With more focused attention since the mid 80's in the planning of land uses of new towns and infrastructures as well as the introduction of a comprehensive peice of legislation on the control of environmental noise in 1988, there are indications that deterioration of the acoustical environment has at least been stalled. This paper gives a comparison of ambient noise levels monitored in the late 90's to those obtained 10 years ago. The results indicate that despite the increase of 1 million inhabitants in the last 10 years, the noise exposure of inhabitants in new development areas have been maintained through better planning of land uses and infrastructures and commercial activities. At the same time, the reduction of industrial/residential interface in old urban areas also help to alleviate the noise problem.

• PLANNING OF NEW SUB-URBAN TOWNS IN HONG KONG
  E. Chui, K.S. Chan, M. Yeung and P.S. Ng
[Abstract]

Hong Kong is noted for its vibrancy and compactness with 6.8 million people living in 1,000 sq. km of hilly terrain. Tackling environmental noise problem is not an easy task. The population in Hong Kong is expected to rise to some 8.3 million by the year 2011. More areas for development are urgently needed to accommodate the fast growing population. Transportation demand, commercial and other activities coming with the population growth would inevitably further aggravate the noise situation if not handled properly. Proactive action at outset of planning of the development areas are required to avoid noise problem. Studies are being undertaken to formulate development plans for potential strategic growth areas. To make Hong Kong a liveable place with a good acoustic environment, innovative and proactive environmental planning principles are adopted in preparing the land use proposals for the strategic growth areas. This paper summarises the planning efforts spent in two development areas to arrive at development plans integrating transportation modes and environmentally friendly technologies. The efforts include optimisation of rail-based development; design of truck route, peripheral trunk roads and sunken roads. The provision of travelators and people-mover systems, and use of trolley bus and electric vehicles, etc. have been explored and adopted to enhance the noise environment.

Chandrasekhar, B.P.

• NOISE INSIDE TRANSIT VEHICLES: MAGNITUDE AND RIDER PERCEPTION
  B.P. Chandrasekhar, P. Koushki, M.A. Ali and O. Al-Saleh
[Abstract]

Similar to worldwide trend, traffic congestion during the daily peak hours is gradually reaching serious proportions in Kuwait. The promotion of public transit systems and the consequential demand shift - from the private auto to public transit vehicles is a cost-effective method to relieve congestion. A competitive quality of service , however is a pre-requisite to shifting demand, away from the private auto to transit vehicles. The objectives of this research project were to: 1. Monitor traffic noise inside bus transit vehicles in Kuwait, and 2. Determine riders' perceptions of noise inside these vehicles. A sample of bus routes were randomly selected from among the Kuwait bus transit system routes. Traffic noise was measured continuously (2 samples per second) inside 60 randomly-selected buses operating on the study routes (mean route travel time was 22.6 minutes). Measurements were repeated six times during each peak and off-peak periods. During each noise monitoring period, the driver and a sample of passengers who were willing to participate in the study were questionnaire surveyed. In addition to their socio-economic traits, the sample respondents'perception of noise inside the bus transit vehicles were sought. The respondents also reported their perceived welfare and health impacts of noise. Surprisingly enough, the mean leq was 80.9 dBA ranging from a low of 70.6 to a high of 106.7. More than 71% were annoyed by noise inside the buses, 51% from the engine noise.53% believed that the traffic noise in general affected their physical and psychological health. Between 20-25% respondents indicated that noise caused headache, nervousness and potentially a hearing damage. More than 50% felt fatigued because of the noise inside the transit buses. 52% would shift to another mode of travel because of noise if they had a choice. Nearly 80% of the sample ridership however, reported satisfactions with bus travel time, service frequency and comfort. more than 35% indicated that both air and noise pollution inside buses were ''bad'' and ''very bad''. Different nationalities perceived annoyance differently (chi-square=20.7, df=10 p0.1). A number of recommendations conclude the paper.

Chanut, J.

• BUILDING FOUNDATION LINING AGAINST GROUND BORNE VIBRATION FROM RAILWAYS
  M. Villot and J. Chanut
[Abstract]

The simple case of a concrete plate in contact with a half-space ground and excited by an incoming ground borne wave is studied using a wave approach on infinite structures. Ground borne incident in-plane compressional waves as well as in-plane and out-of-plane shear waves are considered. Using the now classical transfer matrix approach for multilayered infinite systems, the effect of inserting a resilient layer between plate and ground can be calculated in term of reduction of the net energy transmitted to the plate and reduction of the plate velocity amplitude. Results are given for single or random (diffuse field) incident plane waves. Typical soils as well as resilient layers of different Young modulus and different Poisson ratio are considered. It is found that inserting a relatively soft layer leads to an important reduction of the net energy transmitted to the plate in the usual frequency range of interest for ground borne vibration from railways. However the resilient layer frees the concrete plate and, consequently, the reduction obtained on the plate velocity amplitude is smaller than the reduction of the net energy transmitted, but still substantial (10 dB around 40 Hz for an efficient soft layer).

Chassaignon, C.

• NOISE AND VIBRATION ANALYSIS OF MACHINE TOOLS USING INVERSE METHODS.
  P. Wagstaff, J.-C. Henrio, R. Dib and C. Chassaignon
[Abstract]

The noise and vibration characteristics of machine tools create environmental problems and have an important influence on the quality of the finished surface as well as limiting the production rate due to increased tool wear and breakage. To solve these problems the exact identification of the sources of vibration is essential. For the turning process the dynamic forces acting at the tool-workpiece interface may be estimated with the aid of force dynanometers. At the higher frequencies associated with chatter and other vibratory phenomena the inertia andinternal resonances of this type of measurement system mask the true dynamic forces at the tool-workpiece interface. This information is required in order to correctly identify and model the vibrations generated by the cutting process. To solve this problem an inverse method of identification of the dynamic forces at the tool-workpiece interface was applied using previously measured frequency response functions measured on tool mount structure associated with accelerations mesured during the cutting process. The matrix of frequency response functions between the three input force directions and the output response data is processed by pseudo-inversion with the aid of the singular value decomposition to identify the dynamic force spectra at the tool-workpiece interface. Point impedance measurements may also be used to identify the acceleration response of the tool point. A simple model based on the work of Marui was developed to identify the cutting process parameters with different conditions. The methods have been successfully applied to several types machine tool to obtain a better understanding of the vibration generation mechanisms.

Chatel, G.

• USING AN EQUIVALENT SOURCE DESCRIPTOR TO CHARACTERIZE STRUCTURE-BORNE SOUND SOURCES
  G. Chatel and T. Loyau
[Abstract]

In a low noise design process, it is necessary to have acoustic information about the strength of the structure-borne sound sources. One of the main difficulties which arises in characterizing structure-borne sound sources is due to the fact that the dynamic properties are usually represented by a complex mobility matrix. A simplified method of characterizing the mobility matrix has been developed by Moorhouse and Gibbs, and Mondot and Peterson have introduced the source descriptor concept, focusing on a single point of contact in a source structure. The purpose of this paper is to present a further adapted method based on the 'equivalent source descriptor' concept, which provides a simplified overall characterization of a multi-point excited structure. The equivalent source descriptor takes into account the individual source descriptor corresponding to each contact point in the source substructure, as well as the coupling between the contact points. The equivalent source descriptor can be described as an index to the ability of the complete source substructure to deliver real power to the receiving substructure. The real power transmitted to the receiving substructure is expressed in terms of the equivalent source descriptor of the source substructure, along with the dynamic properties of the mounts and the mobility of the receiver. An example of an application is given, involving an air compressor mounted on a frame. On the test-rig, the vertical interaction forces between the source substructure and the receiving substructure can be measured directly using force transducers. Comparisons between the directly measured power transmitted to the receiving substructure (using force transducers) and the transmitted power determined using the simplified method (using the equivalent source descriptor concept) showed good agreement in the 50 - 2000 Hertz frequency range.

Chatillon, J.

• WIDE BAND ACOUSTIC IMAGING OF MOVING SOURCES USING SYNTHETIC APERTURE SONAR. APPLICATION TO TRANSPORTATION NOISE
  R. Boscher and J. Chatillon
[Abstract]

Road vehicle noise reduction is of major concern for environmental topics. This reduction can be achieved by the designers as far as they can identify the predominant radiating sources. Noise identification is usually done by beamforming with a long array which well-known results are limited especially for moving sources. This paper proposes a new method for locating and identifying moving sound sources using a short array associated to a signal processing technique that will explicitly integrate the vehicle movement in the array beamforming in order to improve the resolution: the synthetic aperture techniques. The method is based on the use of the movement of the acoustic source in order to synthesise a long virtual array called Synthetic Aperture. From the source point of view, the processing is equivalent to see a moving microphone in front of a fixed source. After spatial sampling of the sensor trajectory, we can define a set of virtual fixed sensors that will form the synthetic aperture. It is required that the speed of the vehicle is measured during the trajectory. With this information, we can compensate the Doppler effect of the received signals on each sensor. Thanks to the movement of the source, the problem can be solved by using conventional beamforming: a fixed stationary source in front of a long sensor array. The array length can be as long as the trajectory. This leads to an improved resolution that is independent of the frequency. The performance of the proposed method is evaluated with numerical simulations and in situ experiments on a lorry. The first results show that theoretical performance can be achieved in term of resolution and frequency identification.

Chen , S.

• DIFFERENCE OF NOISE EXPOSURE MEASURED BY DOSIMETER AND SOUND LEVEL METER FOR TEXTILE WORKERS
  Y. Zhao , X. Cheng and S. Chen
[Abstract]

Purpose: To compare noise exposure levels measured by dosimeter and sound level meter for textile workers. Subjects and Methods: Personal noise exposure data during a workday were collected by SH-126 dosimeter. The collected data were translated from dosimeter to IBM computer by cable and RS-232C interface. The data were stored and analyzed by SH126 software to calculate eight hours-weighted sound pressure level (LAeq.8h). Four workshops and six different kinds of equipment were included in the investigation with seven exposure groups. Three to six workers in each group were selected to collect the personal noise exposure data at each shift workday. Sound level meter was used to measure one minute-weighted sound pressure level (LAeq.1min) in working position of the seven groups of workplace. Results: The sound pressure level was stable during a workday for each sampling worker. The LAeq.8h of textile worker during workday was also stable, which collected by dosimeter. In each group, the variance of LAeq.8h among workers was bigger than that among shift workdays. It showed LAeq.1min and LAeq.8h were same or very near in lower 94 dB(A) groups. In over 94 dB(A) groups, the LAeq.8h was higher than LAeq.1min. The maximum difference arrives 4.6 dB(A). Noise exposure levels of two groups of weavers from two cities were very nearly either LAeq.8h or LAeq.1min by reason of using same equipment. Conclusion: Dosimeter can be used to measure the real active noise exposure for each textile worker. The noise exposure levels measured by dosimeter are equal or higher than those by sound level meter. It needs more data and experience before the new method is applied in noise exposure assessment. Key Words: dosimeter, industrial continuous noise, personal noise exposure, textile worker.

Chen, G.

• THE CONVERGENCE CHARACTERISTICS OF AN ADAPTIVE ALGORITHM FOR A MULTICHANNEL ACTIVE NOISE CONTROL SYSTEM
  G. Chen, M. Abe and T. Sone
[Abstract]

A lot of reports about active noise control (ANC) have been published, and its applications have been reported. However, most of them dealt with a single noise source and a single control point, and there are few works for multiple noise sources and multiple control points. Since a lot of multiple mixed noises frequently exist in actual cases, the previous studies are not enough for actual applications. In this paper, the convergence characteristics of an adaptive algorithm for multiple noise sources and multiple control points ANC system are discussed in detail, and it is shown that the matrices of the transfer functions are important for achieving a good performance of multiple active control system.

Cheng , X.

• DIFFERENCE OF NOISE EXPOSURE MEASURED BY DOSIMETER AND SOUND LEVEL METER FOR TEXTILE WORKERS
  Y. Zhao , X. Cheng and S. Chen
[Abstract]

Purpose: To compare noise exposure levels measured by dosimeter and sound level meter for textile workers. Subjects and Methods: Personal noise exposure data during a workday were collected by SH-126 dosimeter. The collected data were translated from dosimeter to IBM computer by cable and RS-232C interface. The data were stored and analyzed by SH126 software to calculate eight hours-weighted sound pressure level (LAeq.8h). Four workshops and six different kinds of equipment were included in the investigation with seven exposure groups. Three to six workers in each group were selected to collect the personal noise exposure data at each shift workday. Sound level meter was used to measure one minute-weighted sound pressure level (LAeq.1min) in working position of the seven groups of workplace. Results: The sound pressure level was stable during a workday for each sampling worker. The LAeq.8h of textile worker during workday was also stable, which collected by dosimeter. In each group, the variance of LAeq.8h among workers was bigger than that among shift workdays. It showed LAeq.1min and LAeq.8h were same or very near in lower 94 dB(A) groups. In over 94 dB(A) groups, the LAeq.8h was higher than LAeq.1min. The maximum difference arrives 4.6 dB(A). Noise exposure levels of two groups of weavers from two cities were very nearly either LAeq.8h or LAeq.1min by reason of using same equipment. Conclusion: Dosimeter can be used to measure the real active noise exposure for each textile worker. The noise exposure levels measured by dosimeter are equal or higher than those by sound level meter. It needs more data and experience before the new method is applied in noise exposure assessment. Key Words: dosimeter, industrial continuous noise, personal noise exposure, textile worker.

Cheng, M.C.

• EVALUATION OF COMMUNITY RESPONSE TO AIRCRAFT NOISE FOLLOWING COMPLETION OF A NEW RUNWAY AT VANCOUVER INTERNATIONAL AIPORT
  A.J. Grigg, E.F. Haboly and M.C. Cheng
[Abstract]

Vancouver International Airport opened a new 3,030 mtre parallel runnway in november of 1996. In order to scientifically assess community response, the Vancouver International Airport authority (Airport authority commissioned Dr Sanford Fidell and Laura Silvati of BBN technologies to complete a ''before'' and ''after'' social survey of nearby residential communities. It is not known which, if any, other airports have completed a noise social survey both prior to and following a similar runnway expansion project. In August 1995, the first round of telephone interviews were conducted to establish baseline information about the prevalence of aircraft noise annoyance in nearby residential areas. In 1998, almost two years after the initial survey was completed, the airport authority commissioned a follow-up survey of the same residential areas, as well as comparison of the results with the baseline conditions. In addition, airport authority staff prepared noise exposure data using computer based modelling so that annoyance could be correlated with estimated day-night average sound levels (DNL). Fidell and Silvati's findings assisted the airport authority in determining which neighbourhoods were annoyed by aircraft noise ; their level of tolerance to aircraft noise, and how results compared to the baseline study and communities located elsewhere. Results were roughly similar to those observed elsewhere, and with the dosage-response curve developed by the U.S. Federal Interagency committee on noise (Ficon, 1992). Results also showed that aircraft noise tolerance among residents in this study was lower than comparable communities elsewhere.

Cheung, W.-S.

• MEASUREMENT OF HEAD VIBRATION AND ITS ERROR ANALYSIS
  W.-S. Cheung, Y.-H. Park and H.-J. Eun
[Abstract]

This paper addresses issues encountered in measuring the general, 6-degree-of-freedom motion of a human head. This measurement requires the usage of multiple accelerometers, such as the well-known bite-bar which consists of three measurement blocks positioned differently and separated by a fixed gap. Six or nine linear accelerometers are normally chosen to measure the 6-degree-of-freedom motion at a position of the head. There are many ways of configuring them onto the three measurement blocks so as to measure it. For a chosen accelerometer configuration, its corresponding way of reconstructing the 6-degree-of-freedom motion from multiple acceleration measurements is uniquely determined. Resultantly, different accelerometer configurations yield different 6-degree-of-freedom motion-calculation methods such that they yield different measurement error characteristics. This point has not yet been well understood in the previous work on human vibration. This work proposes a systematic logic measure the head vibration and to make its error analysis. It includes theoretic formulations to evaluate effectively the 6-degree-of-freedom motion components of the head from six linear acceleration measurements. These formulations are shown to enable the analysis of measurement errors. Experimental results are illustrated to see what amount of measurement errors exists for chosen accelerometer configurations. Several interesting things observed so far are commented in this work.

Chevalier, Y.

• DESIGN OF AN OBJET ORIENTED FINITE ELEMENT SOFTWARE FOR VIBRO-ACOUSTIC PROBLEMS - APPLICATION TO POROELASTIC MULTILAYER INSULATING SYSTEMS OF AEROPLANES
  P. Lamary, I. Tawfiq and Y. Chevalier
[Abstract]

At the beginning of 80s, the first Finite Element programs dedicated to vibro-acoustic problems appeared. They were mostly issued from CAD softwares previously developed for structural mechanics. Industrial computations were shown. However it became difficult for researchers to investigate new methods in such a large and rigid environment. This was partially link to the languages used at that time, mainly FORTRAN 77. Thus around 90s, the advent of Object Oriented Languages opened new perspectives. The OO software we present is born in this context. In the first part of the paper, several CAD concepts are reviewed in an OO approach. These concepts are integrated in our program as an efficient visual aid to problem modelling, data checking and computations control. In the second part, we focus on a C++ implementation of the FEM. In contrast to many other works dealing with OO-FEM, which used class inheritance in order to specialise finite elements to acoustics and to structure, we present an implementation which solve Differential Equations in a formal manner. It is thus the user who creates the type of the finite element which best suited to the problem. If the first vibro-acoustic computations considered only problems of pure acoustics coupled to structural dynamics, it seems important today to take into account absorbing materials because a main goal is noise reduction. Thus, we illustrate our work with the study of poroelastic materials as glass wool, for which variationnal formulation is non obvious and was, in any way, out of reach of the first software generation.

Chiari, C.

• COMPARISON BETWEEN ITALIAN AND RECOMMENDED EUROPEAN NOISE INDICATORS.
  G. Licitra, M. Cerchiai, C. Chiari and L. Boccini
[Abstract]

The Commission of the European Communities is developing its own regulation for noise pollution, in order to harmonise the legislative current survey in different Member States and to obtain an unique description of noise pollution in all EU territory. The European Commission recommended in its ''Position Paper on EU Noise Indicators'' the use of two main indicators in order to describe noise from all outdoor sources for assessment, mapping and control purposes. The Italian Regulations differ from the EU recommendations on methodology to measure noise, especially for definition of the indicators to be used. In this paper we analyse the main differences between them and try to evaluate the corrections to be done to avoid losing of all data already collected. We use the data collected by ARPAT in two great noise mapping campaign held in Pisa and Livorno during last three years. We try to evaluate the correction due to reflections on close walls and the corrections due to different definition of indicators, especially for the European day overall value LDEN and the corresponding Italian LDAY. Finally we try to estimate the overall costs to save all works already done on noise mapping in Italy.

Chiba, T.

• PREDICTION AND EVALUATION METHODS FOR ROAD TRAFFIC NOISE IN BUILT-UP AREAS
  K. Uesaka, H. Ohnishi, T. Chiba and K. Takagi
[Abstract]

As the environmental quality standards for noise were revised in 1998, prediction and evaluation of road traffic noise in built-up areas becomes increasingly important in Japan. This paper presents the methods of calculating LAeq averaged in an evaluation section behind buildings facing a trunk road. In these methods, the built-up areas are classified into a row of buildings directly facing the road and the remaining buildings behind them. And the values of the section-averaged LAeq are simply calculated mainly according to the distance from the road by summing the contributions from the sound paths propagating among the buildings and over them. The validity of the methods presented herein is verified by model experiments and field surveys.

Chin, B.-J.

• AN INSERTION LOSS ANALYSIS OF PARTIALLY INCLINED BARRIER
  H.-S. Kim and B.-J. Chin
[Abstract]

To increase an insertion loss of the barrier, the top of the barrier is designed in various shapes such as ''Y'', ''T'', multiple edges, cylinder, etc., whereas one of the widely used way is to incline the upper part toward the noise source. So far, insertion loss of the barrier having complicated top shapes may have been predicted in an approximate way where the barrier is replaced by a simple screen type having increased height, as long as the dimension of the complicated top part is much smaller than the height. In this paper, more rigorous prediction method is developed for partially inclined noise barrier where the length of the inclined portion may be comparable to the total height. In addition to the diffraction at the top, the diffraction at the corner point in the middle portion is also considered, which is an extension of Kouyoumjian and Pathak's method. A 1/10 scaled-down model test is performed in anechoic room, where effect of the finite length of the barrier is also studied. The comparison of theoretical and experimental values in narrow band spectrum shows that the theoretical result generally represents the average value of experimental insertion loss, while there are many oscillations in experimental result.

Chinn, L.

• RURAL RESIDENTS' RESPONSE TO REDUCTIONS IN TRAFFIC NOISE CAUSED BY RESURFACING A SECTION OF MOTORWAY WITH POROUS ASPHALT
  C.J. Baughan, L. Chinn, G.J. Harris and R. Stait
[Abstract]

Porous asphalt is known to produce lower traffic noise levels than conventional road surfaces, but relatively little information is available on the perceived benefits to people living some distance from the road. A section of the jointed concrete M40 motorway in rural Oxfordshire has been resurfaced with porous asphalt. This gave an opportunity to assess the resulting changes in noise and noise nuisance experienced by residents in villages within 1.5 km of the motorway. Residents were interviewed and noise measured at five villages just before the resurfacing work started and again one year and 3 years later. The paper reports the changes in noise levels resulting from the resurfacing and the associated changes in residents'ratings of dissatisfaction. The work was intended to inform the Highways Agency of the environmental benefits of porous asphalt as perceived by people living in the vicinity of a motorway, and help to quantify the circumstances in which the higher costs of porous asphalt can be justified. The first two surveys showed that reductions in vehicle noise (measured close to the motorway) of 4.5 to 7.6 dB(A) were achieved, depending on class of vehicle and measurement location. There were substantial reductions in traffic noise exposure at villages some distance from the motorway. Indices of community noise impact (such as dissatisfaction ratings) reduced considerably after the resurfacing, especially at the two villages with the biggest noise changes. A strong relation between dissatisfaction ratings and noise levels was observed. This paper will describe the study design and results obtained. It will also examine the relations between noise and dissatisfaction ratings, and indicate how noise changes can lead to changes in community response greater than would be predicted from 'steady state' relations between noise exposure and dissatisfaction.

Chinoy, C.B.

• SOUND ATTENUATION OVER LONG RANGE GROUND-TO-GROUND PROPAGATION PATHS
  C.B. Chinoy
[Abstract]

The attenuation of sound as it propagates over a surface is strongly influenced by prevailing weather conditions. This complicates accurate prediction of sound attenuation considerably. This paper describes an effort aimed at obtaining a clarification and resolution of the problem. Rolls-Royce plc, Derby were commissioned by ESDU International plc to perform a series of tests to measure sound attenuation over distances up to 1.5 km. The tests were funded by government departments and industry in the UK. The site for the tests was the Rolls-Royce airfield in Hucknall, England. The sound source was a Rolls-Royce Avon single-stream jet engine. Two microphone arrays were set up, one over the runway and the other over grassland. Weather data were measured at three stations. A balloon traverse was also carried out to measure atmospheric data profiles. The first stage of the analysis has been completed. A method of predicting the attenuation of sound as it propagates through a homogeneous atmosphere has been issued as a Data Item. The second stage of the exercise was the development and validation of a method that would predict sound attenuation in the presence of wind and temperature gradients. This work was contracted out by ESDU to the Open University, and a Fast Field Program with turbulence effects has been developed by Prof. K Attenborough and Dr S Taherzadeh. The intention is to issue this work in the form of a Data Item and this paper will report on the progress made towards that aim.

Cho, C.G.

• EVALUATION OF IMPACT NOISE ISOLATION BY CEILING STRUCTURE IN APARTMENT BUILDINGS
  I.S. Shin, J.S. Park, C.G. Cho, S.K. Pang and S.H. Kong
[Abstract]

In the apartment buildings, the floor-impact sound has been regarded as the major source which induces complaints from residents. Due to the life style on the heating floor structure(so-called On-dol) in Korea, heavy-impact noise as well as light-weight impact noise has become an issue. The ceiling space of ceiling between concrete slab and ceiling panel is mainly used for space of electric wiring. In the floor impact noise aspect, it is possible to make good use of the ceiling space as an isolation layer that prevent radiating noise toward down-stairs through the floor. In the study, the propagation characteristics and the impact noise reduction effects of air thickness and plaster board in the existing ceiling structure were evaluated in the Mock-up laboratory. To improve the isolation performance, the two different ceiling structures were designed and put into the ceiling space. One was made of porous material and the other was made of foaming polyurethane. As a result, the proper air thickness was found to avoid resonance. The impact noise radiation characteristics of the newly designed ceiling structures as well as the existing ceiling structure were analyzed.

Cho, M.K.

• IMPROVEMENT OF IMPACT NOISE ISOLATION OF FLOOR STRUCTURE BY RESILIENT MATERIAL IN APARTMENT BUILDINGS
  I.S. Shin, K.S. Cha, D.W. Lee, M.K. Cho and K.S. Chung
[Abstract]

The floor impact noise transmission has been a problem in the radiant heating floor system(so called On-dol) of the apartment housing buildings since housing developers have allowed the minimum floor thickness as well as floor height to make more floors to sell. Therefore in the text, the purpose of the study is to find the optimum resilient material that can reduce the floor impact noise transmission at a reasonable cost and satisfy the design criteria. To find an optimum material, 17 resilient materials were selected and adopted to the radiant heating floor system. Each floor model was tested in the acoustic laboratory(reverberation room) to measure the sound isolation level. To make an offer impact sound isolation of floor structure which can be satisfied with design criteria, first of all, by correlation analysis of impact sound isolation and material cost, the optimum resilient material is selected. As a result, among the 17 different materials, polystylene/and polyethylene are proved to be the most appropriate sound isolation material. Above materials satisfy the design criteria, and its material cost is most inexpensive among the materials that satisfy the design criteria.

Cho, P.

• NOISE PREDICTION FOR ROTATING MACHINERY USING CAA
  S. Roy, F. Périé and P. Cho
[Abstract]

Due to stringent government regulations and competitive pressures, meeting noise goals are as important design criteria as meeting the flow rate and pressure head requirements. Although experimental sound measurement is quite straightforward, analyzing the origin of noise remains elusive. The challenge is to predict the flow induced noise for major noise contributors of agricultural and construction machinery such as cooling fans, exhaust muffler, and air handling system. There are several commercially available software in the market that address the noise generated due to fluid-structure interaction. However, the choice is very limited for predicting flow induced noise and subsequent fluid-structure interaction. In this paper, a comprehensive finite element methodology is developed to predict the compressible flow performance of a non-symmetric 7-blade axial flow fan, and to quantify the source strength and sound pressure levels at any location in the system. The computational aero-acoustics (CAA) technique utilized in this paper involves analysis of two computational components simultaneously. a.Computational fluid dynamics (CFD) is used for analyzing three dimensional flow structures in time domain and calculating the corresponding unsteady pressure fluctuations. The effect of turbulence is modeled with large scale eddy (LES) simulation. The computational method includes arbitrary Lagrangian Eulerian formulation (ALE), sliding non-conforming interfaces and silent radiation boundaries. b.Flow induced noise is determined in frequency domain using Fast Fourier Transform (FFT) for calculating the sound pressure level and the integrated sound power of the system based on the domain boundary unsteady pressure fluctuations. The acoustic and flow performances of the subject fan are predicted simultaneously using technique combining transient flow analysis and noise propagation. Corresponding flow induced noise solution is directly available at the boundary of the domain. The sound power level of the subject fan is then calculated by

Cho, S.-W.

• APPLICATION OF AN ARTICULATION INDEX FOR THE EVALUATION OF A TYRE NOISE
  G.-J. Kim, S.-W. Cho and N.-J. Kim
[Abstract]

A critical aspect of the performance of tires for passenger vehicles is the quality of vehicle interior noise as a results of tire-pavement interaction. Generally, vehicle manufacturers evalulate the noise performance of tires by subjevtive tests conducted by skilled test drivers. Drivers rate a tire on a 1 to 10 point scale with the higher being better. For the effective control of the tire noise, it is necessary to define the relationship of the subjective rating and the objective measurement. In this sutdy the articulation index method is applied to evalutate a tire noise from objective measurements. The measurement system is built to calculate an articulation index form vehicle interior noise due to a tire. An articulation index rating is newly introduced to set up the correlation of subjective feeling rating and the articulation index. The results show that AI rating and subjective rating have a good correlation. AI rating can be uses for the effective control and the evaluation of a tire noise.

• PREDICTION OF THE TREAD PATTERN NOISE OF THE QUASI-STATIC STATE ROLLING TYRE
  G.-J. Kim, S.-W. Cho and N.-J. Kim
[Abstract]

Noise generated by rolling automobile tyres greatly influences the ride comfort of vehicles. The characreristics of the tyre pattern noise are majorly determined by the tread pattern shape of a tyre. It is assumed that tyre pattern noise is genarated by the resultant force which is made up of a linear surperposition of the force produced by each tread element when it contacts with the road surface. For more realistic modeling of the resultant force due to the tread pattern, the uneven distributed contact pressure of a rolling tyre is considered. The contact pressure is measured using the flat-bed machine. The simulation results are compared with test results. The prediction accuracy was improved by considering the dynamic contact pressure.

Cho, Y.-H.

• CHARACTERIZATION OF DYNAMIC PROPERTIES OF POLYURETHANE FOAMS FOR AUTOMOTIVE SEATS BY VIBRATION TESTS
  C.-K. Chae, K.-J. Kim, H.-K. Jang and Y.-H. Cho
[Abstract]

Human occupants in a vehicle are in direct contact with seats, of which the primary function is to improve ride quality by isolating the passenger from vehicle body vibrations induced by road surface. Hence, tuning works for better ride quality are often done by changing the seat dynamics. Major portion of the seats is constructed with flexible polyurethane foams, which means that the seat dynamics is exclusively controlled by the shapes and material properties of the foams. For a given step compressive loading superimposed with harmonic excitations, dynamic stiffness increases and damping decreases as the time goes on due to the inherent creep characteristics of the polyurethane foams. Furthermore, variation of such properties with the time is heavily dependent on the static loading. Therefore, detailed investigation of such properties is essential to the seat design. In this paper, dynamic properties of several polyurethane foam materials are characterized by impedance tests focusing on the dependence on the static compression level applied on the foams. The impedance test method directly measures the foam dynamic properties as functions of frequency, loading time, static and dynamic loading condition. In addition, the intrinsic dependency of dynamic stiffness on static stiffness irrespective of foam types is commented by comparing the ratio of dynamic stiffness to static stiffness under same static stiffness conditions for various foam types. Transmissibility of the foam materials, which is crucial factor in dynamic comfort of automotive seats, is estimated by using the characterized dynamic properties. And then, the estimated transmissibility is compared with one measured directly under the more approximate operational conditions.

Choi, H.

• APPLICATION OF AUTOMATIC DYNAMIC BALANCING SYSTEM TO THE OPTICAL DISK DRIVE
  J. Sohn, D. Ro and H. Choi
[Abstract]

As the speeds of CD-ROM drives go up, the rotating speeds of spindle motors are rising up. Rotating speed of current model is above 10,000 RPM. So with small amount of unbalance, the CD-ROM drive can not read the disk, or severe vibration and noise problem occurs. Moreover, as optical disk players usually use removable disks, the position and amount of unbalance is unfixed, and it is not simple problem to compensate for it. As a counterplan to the problem, we applied an automatic dynamic balancing system called ''Auto Balancer'' to the high speed CD-ROM drive. In this paper, to find out the best conditions that the Auto Balancer realizes high compensation accuracy and repeatability, the sensitivity analysis and experiment about various parameters was accomplished. As the Auto Balancer is comprised of several balls and race, for the good performance, the balls should be moved easily by slight force. Accordingly, the characteristics of balls and race are very important. The balls and race of better quality make better Auto Balancer, but because better quality means higher price, we examined the optimum quality that satisfying the performance and economics simultaneously. Lubrication is also a very important element and the condition of lubrication decides not only the movability of balls but also stability and durability of the system. Here we found out the quantity, viscosity and kind of lubricant that maximize the performance.

Chouard, N.

• PERCEPTUAL FACTORS IN CAR SOUND ASSESSMENTS - COMPARATIVE ANALYSES OF SEMANTIC DIFFERENTIAL TESTS AND PAIRED COMPARISONS IN FRANCE, ITALY AND GERMANY.
  R. Weber and N. Chouard
[Abstract]

Indoor car sound quality has been evaluated using paired comparisons (for preference) and semantic differential tests. In three European countries the same set of indoor car sounds -artificial head recordings - from 9 different cars have been presented via headphones to the the subjects. Some of the sounds are loudness equalised in order to suppress the dominant role of loudness in the assessment process. Factor analyses have been carried out on the obtained polarity profiles (of about forty subjects in each country) and on the preference data (of about twenty subjects in each country). Comparisons of the factorial structures will be presented.

• AUDITORY PERCEPTION OF ROAD TRAFFIC NOISE
  C. Lavandier, A. Bidault, N. Chouard and S. Viollon
[Abstract]

Our perceptual spatial representation of road traffic noises is revealed in this study by a dissimilarity factor analysis, on a corpus of fourteen stimuli, representative of urban and suburban environments. A cluster analysis is carried out too, to gather those same sound objects into homogeneous classes according to the aroused stress. To avoid the prominence of noise level which dominates our perception, the stimuli loudness is equalized. The multidimensional approach proposes three auditory factors. However, the correlation coefficients between factors and objective indices are not satisfying. Moreover, the first dimension reveals a perception in accordance with the categorization's results, the stimuli being separated into two groups: one is composed by typical urban sounds, the other consists mainly of suburban traffic noises. Listeners bring together sounds with regard to the meaning of sources. In each group only, they describe physical properties of the signal. So, the cluster analysis categories are used to correlate, class by class, the perceptual dimensions with physical parameters. The second dimension expresses the number of identified sources, which can be correlated with standard deviation of equivalent level for the suburban noises (95%). The third factor is a spectral one, which can be correlated with the sharpness of the typical urban noises (98%).

• BINAURAL LOUDNESS EQUALISATION OF A SET OF REAL CAR SOUNDS
  N. Chouard
[Abstract]

When carrying out listening test, there is sometimes the need to get rid of the loudness dimension, because it is one one side already known as being the main dimension, and on the other side because it acts as a masking dimension on other second-order dimensions of the perceptual space. Some previously work carried out by the author showed that, at least for usual stationary car sounds, the interaural average of calculated loudnesses describes in a satisfactory way the overall perceived loudness. For car sounds presenting more peculiar characteristics (like e.g. slow intensity fluctuations, strong booming noise, ...) it is however unclear if this remains valid. Car sounds of different types and classes ranging from small to luxury were thus matched to the same loudness by subjects in a listening experiment featuring an adaptive forced choice procedure. These subjective results will be compared to predictions based on different model-proposals. This work was carried out within the frane of the BRITE EURAM Project BE-96-3727 OBELICS.

Christe, P.

• THE INTEGRATION OF THE NOISE CRITERIA INTO THE URBAN TRANSPORTATION PLANNING
  P. Christe
[Abstract]

1. Purpose of the lecture

Noise criteria should be considered as one of the basic constraints to take into account for any urban transportation planning elaboration, as well as quality of public space and multimodal accessibility to the city centre. This lecture will present the Transitec methodology as applied in many european cities.

2. Methodology: definition of a ''potential road network''

a) Available road network It is constituted by the current network, which is often inextensible in urban areas, and future/planned network.

b) Constraints and local objectives: - resident areas where traffic flows should be reduced - axes where mass transit should be improved - itineraries where pedestrians and bicycles should be securised - public spaces which need to be highlighted - axes where noise and air pollution should be reduced.

c) Potential use of the road network The superposition of the available road network and the constraints/objectives will defined: - the axes where there is an opportunity to increase traffic volumes - the axes where there is a possibility to maintain current traffic volumes - the axes where there is a necessity to reduce traffic volumes.

d) Transportation demand This demand depends on current traffic volumes, but mainly on the proposed voluntaristic functioning (for example: modal transfer from private vehicle to mass transit)

e) Future road network hierarchy The analysis gives a future road network hierarchy, which is conform to the objectives defined by the Authorities. The elaboration of this new transportation planning will contribute to noise reduction in urban areas.

3. Specific examples of Geneva and Grenoble will be presented.

Chui, E.

• PLANNING OF NEW SUB-URBAN TOWNS IN HONG KONG
  E. Chui, K.S. Chan, M. Yeung and P.S. Ng
[Abstract]

Hong Kong is noted for its vibrancy and compactness with 6.8 million people living in 1,000 sq. km of hilly terrain. Tackling environmental noise problem is not an easy task. The population in Hong Kong is expected to rise to some 8.3 million by the year 2011. More areas for development are urgently needed to accommodate the fast growing population. Transportation demand, commercial and other activities coming with the population growth would inevitably further aggravate the noise situation if not handled properly. Proactive action at outset of planning of the development areas are required to avoid noise problem. Studies are being undertaken to formulate development plans for potential strategic growth areas. To make Hong Kong a liveable place with a good acoustic environment, innovative and proactive environmental planning principles are adopted in preparing the land use proposals for the strategic growth areas. This paper summarises the planning efforts spent in two development areas to arrive at development plans integrating transportation modes and environmentally friendly technologies. The efforts include optimisation of rail-based development; design of truck route, peripheral trunk roads and sunken roads. The provision of travelators and people-mover systems, and use of trolley bus and electric vehicles, etc. have been explored and adopted to enhance the noise environment.

Chung, K.H.

• DEVELOPMENT OF FAN PERFORMANCE, FLOW AND NOISE ANALYSIS SOFTWARE
  D.J. Lee, W.H. Jeon and K.H. Chung
[Abstract]

Numerical predictions of fan noise have not been studied extensively. This is due to the scattering effect of the fan casing, duct, etc and to the difficulty to obtain aerodynamic acoustic source. So, we develop new method to predict the fan noise and performance numerically. A vortex method is used to model the fan and to calculate the flow field fast. In order to obtain acoustic signal from the unsteady force fluctuation of the blades, we use acoustic analogy. But acoustic analogy can be applied only in the free field. In order to consider the solid boundaries effect, the newly developed Helmholtz Kirchhoff BEM (Boundary Element Method) is introduced.With the above-mentioned method we make new analysis tool, FanNoise. In this program, we can calculates the flow field around the fan and predict the fan noise. Because of the many requirements to predict fan noise numerically, the software is developed to save the engineering time in designing and analysing the no noise fan. The user-friendly software can handle the typical geometry of the casing, the arbitrary shape of impeller, the performance of the fan and the acoustic field inside and outside the fan casing.

Chung, K.S.

• IMPROVEMENT OF IMPACT NOISE ISOLATION OF FLOOR STRUCTURE BY RESILIENT MATERIAL IN APARTMENT BUILDINGS
  I.S. Shin, K.S. Cha, D.W. Lee, M.K. Cho and K.S. Chung
[Abstract]

The floor impact noise transmission has been a problem in the radiant heating floor system(so called On-dol) of the apartment housing buildings since housing developers have allowed the minimum floor thickness as well as floor height to make more floors to sell. Therefore in the text, the purpose of the study is to find the optimum resilient material that can reduce the floor impact noise transmission at a reasonable cost and satisfy the design criteria. To find an optimum material, 17 resilient materials were selected and adopted to the radiant heating floor system. Each floor model was tested in the acoustic laboratory(reverberation room) to measure the sound isolation level. To make an offer impact sound isolation of floor structure which can be satisfied with design criteria, first of all, by correlation analysis of impact sound isolation and material cost, the optimum resilient material is selected. As a result, among the 17 different materials, polystylene/and polyethylene are proved to be the most appropriate sound isolation material. Above materials satisfy the design criteria, and its material cost is most inexpensive among the materials that satisfy the design criteria.

Chung, K.

• THE COUNTERMEASURE FOR THE NOISE AND VIBRATION OF COMBUSTION TURBINE EXHAUST GAS DUCT
  J. Bae, W. Kim and K. Chung
[Abstract]

An excessive noise and vibration was encountered in the combustion turbine exhaust gas duct connected to the heat recovery steam generator. This phenomenon was found only when water was added to the fuel injection to reduce NOx contents of the combustion turbine exhaust gas. To investigate the noise and vibration characteristics, measurement was performed around exhaust gas duct and gas turbine, and the acoustic analysis for the exhaust gas duct by SYSNOISE was carried out to check the cavity mode of the exhaust gas duct. From the measurement and analysis results, and the noneffective reinforement on the duct wall panel, it was concluded that the severe noise and vibration occurred due to the acoustic resonance between the duct cavity mode and the excitation frequency induced by turbulent gas flow during water injection. Therefore the installation of baffle plates inside the duct was proposed to change the cavity mode of the exhaust gas duct. To confirm the effect of the baffle plates and the change of the noise and vibration phenomenon, noise and vibration measurement was carried out. From the measurement results, the vibration response of the duct wall panel was considerably reduced to 20 - 30% of the original ones and more than 10 dB(A) of noise level was reduced in sound pressure level.

Cieplok, G.

• HIGH-EFFECTIVE VIBRATION INSULATION SYSTEM OF ROTOR MACHINES USED ON SHIPS AND TRANSPORT VEHICLES
  J. Michalczyk and G. Cieplok
[Abstract]

Technical solution for increasing the effectiveness of vibroinsulation system using synchronous elimination phenomenon is described in the paper. The system allows to preserve the high stiffness value of vibroinsulation system, required for ships and transport facilities due to their own non-stationery movement. The 3-D model of unbalanced rotor body was taken into consideration and the necessary and sufficient conditions where derived. Technical solution for synchronous elimination system was shown.

Cieslik, J.

• ANALYSIS IN MEDIUM FREQUENCY RANGE USING THE FINITE ELEMENT METHOD
  J. Cieslik and T. Uhl
[Abstract]

The paper presents the new approach to the modal analysis in medium frequency range. This method is specially dedicated for large mechanical systems where classical numerical modal analysis is not applicable due to number of elements. Presesnted method relay on subdivision of large model into several subsystems. On these subsystems are done the analysis using the FE method. For definition of parameters of interaction between subsystems the results derived from Transfer Path Analysis are used. The new approach leads to much faster and nence increased productivity in modelling and analysis of large complex mechnanical systems. Cocepts are illustrated using real-life examples of tram structure.

Claesson, I.

• A METHODOLOGY FOR PLANNING AND INSTALLING AN ACTIVE NOISE OR VIBRATION CONTROL SYSTEM
  P. Sjösten, S. Johansson and I. Claesson
[Abstract]

The application of active noise or vibration control to a real application is usually a great challenge. The step from computer simulations, or even lab studies, to the real implementation is often much larger than first expected. This is especially true for multiple-input, multiple-output control where questions like ''where shall I put my control microphones?'' and ''where shall I put my actuators?'' become relevant. In the present paper, a methodology for performing an active noise control installation is presented. This includes methods for evaluating the system performance. The importance of optimization is highly stressed as maybe the most important step in the installation process.

Clairbois, Jean-Pierre

• ANTI-NOISE DEVICES EFFECTIVENESS: PHYSICS, MODELS, VALIDATION, HOW ARE WE ABLE TO CONCLUDE ON THESE?
  J.-P. Clairbois and P. Houtave
[Abstract]

Experience about anti-noise devices for ground transport is now reaching 30 years of age. During this, numerous products have been developed in order to improve the effectiveness of these devices, including different shapes, different materials, or different added devices on existing ones. Sometimes, these devices are presented as the best ever found, claiming drastic improvements on existing ''common designs''. Some other times, the reverse is also demonstrated, i.e. that one demonstrates the uselessness of such or such product. Who is right, and who is wrong? What can be the method to objectively quantify the ''value'' of such products? The truth is in physics. If we understand physics correctly, we are the able to replace the effectiveness in its right context. Using models can be the best or the worst thing, as one can forget, or even ignore some essential parts of the physics, that can modify the interpretation of some trends. Testing devices, either in laboratory or in situ is also a difficult matter, as the conclusions are always, and only, related to the test conditions. Based on 20 year of expertise about anti-noise devices, a review of tools and test methods will be done, some advises will be drawn in order to conclude more objectively on the true effectiveness of these devices.

Clairbois, Jean-Pierre

• LIEGE-AIRPORT:NOISE MONITORING SYSTEM AS PART OF GLOBAL NOISE MANAGEMENT POLICY
  V. Trefois, J.-P. Clairbois and P. Houtave
[Abstract]

Liège-Airport is a regional airport of the southern region of Belgium and is now part of the ''Aéroports de Paris - A.D.P. - Consortium''. Its main problem was to implement at night, since March 1st, 1998, a mean number of 70 to 80 movements where no night traffic had ever been allowed. A global noise management policy had then been set up with the following main steps. A first evaluation of the short term and long term noise impacts and a first public enquiry in 1996. The consecutive build-up of a detailed Geographical Information System (G.I.S.) in 1997 and the optimization of the departure routes (SIDS), so as to minimize the long term global noise impact. A subsequent thorough public enquiry to refine the limits of the noise contours (noise quota) and the first mitigation measures in 1998, especially the acquisition on voluntary basis of about 900 houses. The implementation of a permanent noise monitoring system of the latest generation in 1999. This system aims first of all at stabilizing the limits of noise contours that are the geographical basis of all mitigation measures. SIDS must effectively be flown and noise quota are to be respected. Beside this automatic control the tool allows for detailed public information (inclusive noise event listening), for noise management and for the selection of new company through detailed and sensitive statistics.

Clarke, J.-P.

• NOISE ABATEMENT PROCEDURES ENABLED BY ADVANCED AIRCRAFT AND AIR TRAFFIC CONTROL TECHNOLOGIES
  J.-P. Clarke
[Abstract]

The impact of aircraft noise in residential communities is a major factor in the drive to limit the number of aircraft operation that may be performed at airports and prevent expansion of airport facilities to accommodate the increased demand for air transportation. Most airports in the United States and other developed countries have either noise curfews that restrict the hours during which all or certain types of aircraft may operate, or preferential runway assignments during certain times of the day to limit the noise impact in residential areas. Although significant reductions in source noise have been achieved through the use of advanced engine technology and improved engine design, we have now entered a period of diminishing returns with respect to source noise reductions. Noise abatement procedures provide an effective means of achieving further reductions in the impact of aircraft noise in communities surrounding airports. Use of noise abatement procedures, however, has been limited by guidance and navigation considerations. Existing guidance and navigation systems, such as the Instrument Landing System (ILS), utilize ground-based beacons, which, because they provide coverage over a limited area, limit the types of noise abatement procedures that may be employed. Advanced flight guidance technologies such as Area Navigation (RNAV) utilizing the Global Positioning System (GPS) offer the potential to reduce the impact of aircraft noise by enabling more flexible approach and departure procedures that reduce noise exposure to the most sensitive areas. The primary obstacle to the implementation of these procedures remains the inability of humans to manually maintain the precise sequencing and spacing required during high traffic situations to maximize takeoff and landing rates. Introduction of automation that predicts the performance and noise impact of aircraft, and uses this information to assist the controller in determining and maintaining the appropriate sequencing and spacing is critical to the successful utilization of noise abatement procedures. This paper will present the results of work done to develop new noise abatement procedures enabled by advanced aircraft and air traffic control technologies, quantify the benefits that these procedures offer, and develop the automation infrastructure required for implementation of these procedures in high density air traffic.

Clerfayt, G.

• A TWO-MONTH PUBLIC ENQUIRY ON URBAN NOISE IN BRUSSELS REGION FOR A GLOBAL PLANNING
  G. Clerfayt
[Abstract]

Facing to the noise multi-sources problem, the Brussels Regional authority decided to elaborate a fight against urban noise plan. Before his definitive adoption by the Regional Government, the plan project had been submit to a two moths public enquiry. This usual procedure in Brussels Region aim to collect the differents opinions about the plan noise abatement proposals. Theses opinions were asked to the population and also to the others actors involved with urban noise aspects: political and administrative of Regional and local level, private sector and associative middle. The pro-active communication means used lead to a massive participation. This success give legitimacy to this urban noise plan initiative. The examination of the results enlighten about the various priorities to consider in mater of noise. Theses options have been integrated to the definitive version of the plan adapted by the Regional Government. To day, this plan privileging partnership and dialogue between the actors involved by urban noise, have engaged several concrete actions. One of these consist in a negotiation of a convention between the national railway company and I.B.G.E. This agreement engage the former to integrate noise criterias in its management. On the other hand, the national airport authorities who don't accept the discussion, compel the Regional Government to adopt regulation text on planes noise.

Clifford, S.

• THE EFFECTS OF ATMOSPHERIC TURBULENCE ON THE INTERFERENCE OF THE DIRECT AND GROUND REFLECTED WAVES
  V. Ostashev, S. Clifford, R. Lataitis, P. Blanc-Benon and D. Juve
[Abstract]

For many geometries of sound propagation in the atmosphere, a sound field at a receiver is a sum of the direct wave from a source and that reflected from the ground. If there would no turbulence, the interference of these waves would result in maxima and very deep minima in sound pressure level. Atmospheric turbulence can partially or completely destroy the coherence between the direct and ground reflected waves, and therefore increase the mean sound pressure level at interference minima by several dozens dB. The most recent theory of this phenomenon was developed by Clifford and Lataitis (JASA, V.73, 1545-1550, 1983). The primary goal of the present paper is to generalize Clifford and Lataitis's theory by taking into account developments in atmospheric acoustics since 1983. In particular, we calculate the mean squared sound pressure by using a parabolic equation method. Furthermore, we take into account that the direct and reflected waves are scattered by both temperature and wind velocity fluctuations, and use Kolmogorov, Gaussian and von Karman spectra to model spectra of these fluctuations. Finally, we obtain a formula for the mean squared sound pressure and relate it to that of the coherence function of a spherical sound wave for line-of-sight propagation. Theoretical results obtained are also shown to be in good agreement with measurements of the mean squared sound pressure

Clow, A.

• DOES LOW FREQUENCY NOISE DURING WORK INDUCE STRESS?
  K. Persson Waye, R. Rylander, J. Bengtsson , A. Clow, F. Hucklebridge and P. Evans
[Abstract]

Background and aim: The aim of the study was to evaluate the possible interference of low frequency noise on stress experienced during performance. Test persons classified as sensitive or non-sensitive to noise in general or to low frequency noise, worked with different performance tests in a noise environment with dominant low frequencies or dominant middle frequencies, both at a level of 40 dB LAeq. The effects were evaluated as changes in levels of Monoamine oxidase inhibator (MAO-I) and cortisol in saliva, taken at various times during the test. The total time for the sessions was 2.5 to 3 hours. Results: When the subjects worked in low frequency noise, the levels of cortisol were higher and there was a small non-significant increase in the levels of MAO-I. No clear difference in response could be related to sensitivity to noise in general or to low frequency noise, but a general observation was that the levels of the final samples of MAO I and cortisol were higher among subjects sensitive to noise or to low frequency. The low frequency noise was rated as more annoying than the reference noise and also considered to impair the working capacity more than the reference noise. The results suggest that working in low frequency noise conditions may induce stress indicators.

Coblenz, A.

• ROLLING NOISE FROM FREIGHT RAILWAY TRAFFIC: REDUCTION OF WHEEL RADIATION BY MEANS OF TUNED ABSORBERS
  P. Bouvet, N. Vincent, A. Coblenz and F. Demilly
[Abstract]

The rail, sleepers and wheel are the predominant acoustic sources for freight rolling noise. In the frame of the ''Silent Freight'' European project, optimised wheels have been developed to reduce the noise from rolling stock. This article deals with the optimisation of dynamic absorbers on a wheel.

The theoretical methods used for the design of tuned absorbers are presented. A finite element model is used to calculate the wheel modal parameters (natural frequency, mode shape, modal mass and damping). The wheel vibration response and wheel radiation are calculated with the TWINS software package (developed for the European Rail Research Institute). It is shown that in combination with a wheel shape optimisation, the use of tuned absorbers can lead to a wheel noise reduction of about 10 dB(A).

Dynamic absorbers have then been developed and set on prototype wheels. These wheels have been mounted on a test train in order to assess the actual noise reductions during field measurements. The measured wheel noise reduction is presented and compared to the theoretical result : a good agreement is found between measurements and calculations.

Keywords : railway wheels, damping, tuned absorbers, rolling noise, modelling.

Cocchi, A.

• NOISE FROM AMUSEMENT ACTIVITIES: AN ENVIRONMENTAL IMPACT STUDY
  A. Cocchi and G. Semprini
[Abstract]

A passive noise control solution for a particular amusement attraction of the Gardaland Park (Italy) is presented following the previous study presented at the ICA Conference in 1998. The final solution approved by the Management of the Park consist in an acoustical barrier and in an electronic device devoted to the control of noise from the acoustic amplification system. As new attraction equipment will be built inside the Park, similar to an analogous plant working at the Efteling park in Nederland, an environmental noise impact study is required. In this paper a procedure for the acoustic characterisation of the amusement plant during normal operation in presence of visitors, is presented. The expected noise map is then showed.

Coiret, A.

• SELF-SUSTAINED FLOW NOISE REDUCTION USING A COANDA EFFECT
  S. Guerin, A. Coiret, A. Sakout and R. Henry
[Abstract]

Many industrial flow conditions lead to self-sustained flow noise which is the result of a feedback loop between a vortex shedding and acoustical waves. Howe and Powell have demonstrated the conditions to be fulfilled in order to allow the kinetic energy of the vortices to be converted into acoustical energy. Based upon this theory, a new way of noise reduction, neither active nor passive, is brought forward by reaching a noise reducing (20 to 30dB) stable branch of a turbulent bifurcation, which is maintained via a hysteresis-like effect. The initial noisy configuration, i.e. two standard baffles in tandem in a duct is modified with thin slots created on the upstream baffle. The key point is to be able to create a new velocity field which has to be drastically different in order to modify the Howe and Powell conditions. At the same time, the geometrical modification must be as small as possible in order not to affect the primary function of the industrial flow. Experimental results are reported on the ''noisy'' and ''silent'' paths of the bifurcation. A special emphasis is brought on new features of the dynamics of the small ''plane jets'' which are created by the thin slots. It allows a better comprehension of the silent situation. The question of identifying the parameters which govern the bifurcation arises but it is well known to be a difficult task. Nevertheless, such a method may open a door towards a costless self sustained-flow noise reduction.

Collier, S.

• SOURCE LOCALIZATION IN THE ATMOSPHERE BY MEANS OF BEAMFORMING AND TOMOGRAPHY
  K. Wilson, V. Ostashev, A. Voronovich and S. Collier
[Abstract]

This paper reviews progress made during the past decade for localizing audible-frequency-range sound sources in the atmosphere. The main techniques are array beamforming and tomography. Beamforming has been successfully demonstrated for both ground vehicles and subsonic aircraft. Special techniques have also been developed for determining the origin of shock waves. Typical beamforming arrays have microphone spacings of several meters or less. Compared to beamforming, application of tomographic methods is still in an exploratory stage. Recently J. L. Spiesberger localized calling birds using tomography. We propose a new tomographic scheme involving up to nine microphones on the ground that can track aircraft and other sources in the atmosphere. This scheme uses a model of a stratified moving atmosphere. From a signal processing standpoint, the tomographic methods are similar to beamforming in that they involve time delays between dispersed microphones. The microphone spacings in tomography are typically much larger, however: from tens of meters to hundreds of meters. Furthermore, the tomographic reconstructions allow one to simultaneously obtain information on the wind and temperature fields and source position in an inhomogeneous atmosphere. Beamforming and tomography have in common that good signal coherence is required between elements in the array. Atmospheric turbulence fundamentally limits coherence by dispersing sound waves. We will discuss recent efforts in modeling these effects, and their implications for the design of beamforming and tomographic arrays.

Collin, D.

• FUTURE PROSPECTS TO SATISFY NOISE LIMITS WITH FURTHER SOURCE REDUCTION - A EUROPEAN RESEARCH INITIATIVE
  D. Collin
[Abstract]

International standards governing the noise of newly manufactured aircraft are developed by ICAO (International Civil Aviation Organisation). The current standards, originated in 1977, are contained in Chapter 3 of the annex 16 to the convention on International Civil Aviation. Since 1991 a major review has been undertaken within the ICAO Committee for Aviation Environmental Protection (CAEP) which will eventually lead to the application of more stringent noise limits. In the process, recommendations were made in favour of a balanced approach, to address the airport noise problem, challenging the ICAO member states to ''study and prioritise research and development of economically justifiable technology'', besides complementary actions on airport land-use planning and noise abatement operational procedures. Taking the opportunity of the Aeronautics Task Force(ATF) set up in 1995 by the European Commission, the European industry has proposed,under the larger label of ''the Environmentally Friendly Aircraft'', an Aircraft Noise research action plan based on ICAO's ''balanced approach''. Following this initial work, the European industry has elaborated a coordinated approach, aimed at a 6 dB noise reduction objective over a 7-year period and regrouping into a ''clustered'' structure several Industrial and Scientific project proposals covering the needed technology base. Five individual 3-year research projects have been effectively started at the beginning of 1998. The coordinating ''cluster ''structure (X-NOISE) has been implemented and the European Commission Framework 5 programme will see follow up projects proposals that should allow a successfull shift to the technology validation phase, while covering all promising possibilities of aircraft noise reduction.

Connor, T.L.

• UPDATED LATERAL ATTENUATION IN FAA'S INTEGRATED NOISE MODEL
  G.G. Fleming, J. Burstein, A.S. Rapoza, D.A. Senzig, J.M. Gulding and T.L. Connor
[Abstract]

The lateral attenuation algorithm in the Federal Aviation Administration's (FAA) Integrated Noise Model (INM) has historically been based on the two regression equations described in the Society of Automotive Engineers' (SAE) Aerospace Information Report (AIR) 1751. These equations, which together represent a single relationship developed from measured data for 1960s and 1970s aircraft with low-bypass ratio jet engines, are applied equally in INM to the entire aircraft fleet. Further, these equations cannot take into account the effects of propagation over acoustically hard terrain, such as water. Consequently, in 1997 the INM development team initiated the task of revising the lateral attenuation algorithm within the model. The primary component of the revised algorithm is an entirely new methodology for taking into account ground effects. The methodology, which is based upon a newly-compiled spectral data base, along with the physical acoustics model of Embleton, Piercy and Daigle, will exist in INM as a library of regression equations. As such, this approach will offer the accuracy and flexibility of a pure physical acoustics model, coupled with relatively modest computer runtimes. This paper documents the scientifically-founded and experimentally-validated approach to computing ground effects, which is slated for inclusion in the INM.

Copley, D.

• AUDIBEL-DEVELOPMENT OF A WORLD CLASS PRODUCTION SOUND TEST PROCESS
  M. Sutherland, M. Gerold and D. Copley
[Abstract]

Caterpillar has complied with various construction equipment sound level requirements for many years. However, current production test methodologies are not capable of ensuring compliance to the new European Union (EU) Dynamic Sound Level Requirments. Failure to ensure compliance could result in loss of this key market. In order to provide Caterpillar Manufacturing Facilities around the world with the means to ensure compliance cost effectively, a new sound test process was developed and implemented. Of primary importance was to first identify and develop instrumentation capable of documenting compliance, process capability, and support failed machine diagnostics. Education and training was also vital to establishing an infrastructure that would promote the process control efforts of involved development, design, and manufacturing personnel. This paper will outline the new production sound test process implemented at all Caterpillar Facilities worldwide. The paper will further outline the functional specifications of Caterpillar's new patented dynamic sound test system, termed ''AudiBel'', and it's key role in the production sound test process. The ''AudiBel'' automated system has enabled Caterpillar to reduce lengthy test times, related costs, number of support personnel

Cotana, F.

• NOISE OBSERVATORY INFORMATION SERVICE
  C. Buratti, F. Cotana, C. Simoncini, R. Caracciolo and S. Curcuruto
[Abstract]

The Italian Law about Noise Pollution (n. 447, 26.10.1995) provides for the drawing up of acoustic reclamation plans, the evaluation of noise impact and acoustic climate, the activities of planning, measurement and check aimed to control noise pollution. Some decisions about territory policies need that such data are elaborated and presented in synthetic form; instead, the drawing up of reclamation plans needs an analytical and detailed representation of existing situation. It includes the development of a data bank, organized both on local (Communes, Regions) and national (ANPA) basis. The main objectives of this work are: - definition of an original NOISE-CIRIAF system, to elaborate noise pollution data and based on cause relations between Drivers, Pressure, State, Impact, Responses, following the DPSIR model defined by the European Environmental Agency (EEA); - choosing indicators able to represent the general conditions pertaining to noise pollution for State, Pressure, Impact and Responses. In the system of Drivers, all information regarding anthropic activities causing acoustic emissions have been identified. The drivers create two kinds of Pressure on environment: acoustic emissions and vibrations. The NOISE model distinguishes between indoor and outdoor environmental States; they have a direct Impact on health and on the ecosystem and an indirect influence on the economy both for the sanctions dictated by legislation and for the production and installment of systems. The Responses, in terms of structural interventions to contain acoustic emissions, of prescriptive and technological interventions have been grouped as follows: Laws, Plans, Technological Innovations, Scientific Research.

• INFLUENCE OF FILTERING SYSTEM ON HIGH SOUND INSULATION VENTILATING WINDOWS
  F. Asdrubali and F. Cotana
[Abstract]

A new opportunity to protect buildings located near motorways or high traffic roads is constituted by High School Insulation Ventilating Windows (HSIVW). These windows show good insulation performances and, meanwhile, allow airflow through the window itself. In a previous work acoustic and airflow performances of the windows have been measured; in the present paper the research is carried on by putting a filter in the aerator of the windows; the filter is necessary to make the inlet airflow cleaner. Acoustic (single number sound reduction index Rw) and airflow (air flow through the aerator g) performances are again measured with regard to four different filters, including one with active carbon. Experimental investigation shows that the windows equipped with filters still present high sound insulation, with good airflow properties. The airflow reduction due to the filters, in fact, varies from 10 to 40%, but is still high enough for the ventilation and cooling of the building.

• ACTIVE CONTROL SYSTEM FOR TYRE-GROUND CONTACT ROLLING NOISE: AN EXPERIMENTAL FACILITY
  F. Rossi and F. Cotana
[Abstract]

A new active system for reduction of rolling noise produced by tyre-ground contact is proposed (patent n.01297959). The system is constituted by acoustical emitters installed on the car mudguard close to tyre-ground point of contact. Acoustical emitters are fed by an electronic control unit which generates the control signal according to an error minimization technique. Acoustical emitter performances have been tested by means of an original experimental facility built at Acoustic Laboratory of the University of Perugia. Such a facility allows to optimize the acoustical performances of the active noise control system by simulating rolling noise on steady conditions. Active noise control emitter has been modeled by means of electrical equivalent circuit method; thus transfer function has been attained.

Cotoni, V.

• HIGH FREQUENCY PLATE RADIATION BY POWER FLOW ANALYSIS WITH EXPERIMENTAL VALIDATION
  V. Cotoni, A. Le Bot and L. Jezequel
[Abstract]

This paper deals with high frequency analysis of point excited fluid loaded plates. Acoustic and structural energy densities are calculated by a power flow approach. Coupling between subsystems is characterized by local power exchanges. Three radiation mechanisms are involved in these exchanges: radiation of supersonic waves, radiation from edges and direct radiation from the excitation point. These radiation processes induce local energy losses for the panel. They correspond to power sources for the acoustic. Using an integral power flow approach, energy fields are derived and compared to frequency averaged experimental results.

Cotté, P.

• INSULATION OF ALUMINIUM FRAME-DOUBLE GLAZING WINDOWS BY MEAN OF BEA/FEA MODELING
  J.-M. Auger, H. Defosse, M.A. Hamdi, C. Barras, D. Benoualid, P. Mulocher, B. Mottelet, M. Rehfeld, P. Cotté, C. Midelet and M. Szezygiel
[Abstract]

This paper presents significant results of the research program on the insulation of aluminium framed windows glazed with sealed double glazing conducted by a consortium of partners. This consortium involves industrial partners which develop window components i.e.: SAINT GOBAIN for double glazings, HUTCHINSON for seals, TECHNAL and A.S. for aluminium window frames. The vibro-acoustic simulation of the window is conducted by STRACO by using I-DEAS Vibro-Acoustics and RAYON solver. The window insulation analysis is conducted both numerically and experimentally: - Experiments are performed by partners with their transmission facilities in order to compare results and validate models. - Simulation are conducted by using an original FEA/BEA modeling approach capable to represent the transmission problem by taking into account structural details related to seals, frame and glass as well as internal acoustic cavities and external radiation. Comparisons between experimental an numerical insulation results show a good agreement and a parametric analysis provides indications on the influence of parameters which characterize seals, frame and the double glazing.

Cotton, M.

• RESIDENTIAL INSULATION SCHEME AROUND SYDNEY AIRPORT
  M. Burgess, M. Cotton and K. Butler
[Abstract]

The Sydney Airport Noise Amelioration Program was implemented in 1994 and instigated by the construction of a new parallel runway. The Airport is surrounded by suburban areas on three sides with a bay on the fourth side. An insulation program for public buildings (schools, childcare centres, hospitals/health care centres and churches) within the ANEF 25 (approx LDN 60) was undertaken. Residences within ANEF 40 (approx LDN 75) were acquired and the land converted to a park. Eligibility for the residential sound insulation scheme is based on the ANEF 30 boundary (approx LDN 65) which includes around 3,800 houses. Various insulation techniques were trialed on a group of 18 houses. Then a package was developed which was based on a menu of options for treatment. The goal of the package was to provide a cost-effective solution to allowing maximum choice by the home owners without compromising the acoustic performance. A flexible approach to the whole program was essential to ensure effectiveness and user satisfaction. A mechanism for updating the menu options was needed as new products became available. Noise measurements in a sample of the dwellings treated allowed for monitoring of the noise level reductions achieved and for changes to the package as necessary. The menu was changed as appropriate. This paper will summarise the implementation of the residential insulation scheme including the procedures implemented to allow for user preference and the monitoring and improvement, the noise reductions achieved and the home owner satisfaction. The effects of the scheme on the community and the local building industry will also be discussed.

Coutaz, L.

• SIMPLIFIED MODEL OF INTERNAL ACOUSTIC CAVITY IN RECIPROCATING REFRIGERATING COMPRESSORS
  L. Coutaz and L. Gavric
[Abstract]

When a noise abatement strategy of refrigerating and air conditioning machinery is considered, an investigation of noise generating components is necessary. One of the most important noise sources of such equipment is reciprocating compressor. The hermetic shell of the refrigerant compressor generates an important part of direct sound radiation. The hermetically sealed shell of compressor is excited by the compression mechanism/motor unit. These two sub-systems are mechanically connected by mounting springs and by discharge pipe. The structure borne sound is transmitted through these connecting elements to the compressor shell. When gas pulsation is considered, the hermetic shell is relied to the compression unit by the internal acoustic cavity filled of refrigerant gas. If the excitation frequency coincides with one of the acoustic cavity resonances, important shell vibrations can be generated by gas pulsation. The interior of the compressor shell is modelled as an annular cavity defined by two concentric cylinder representing the hermetic shell and the inner unit. Despite the geometric simplifications, the acoustic characterisation of the fluid /structure interaction involves complex modal calculation. Therefore, it was found necessary to model this annular cavity by a rectangular one. The geometric similarity of two cavities is preserved by unrolling the cylinder around his central axe. The co-ordinate change is carried out with respect of the cavity mid surface, similarly as in the thin shells theory. In the acoustic modal analysis, the modal forms corresponding to the annular cavity are imposed to the rectangular one. The shell vibration generated by the internal acoustic pressure distribution are calculated using modal synthesis. The gas pulsation excitation is superimposed to the mechanical one in order to compute the final shell vibration and noise radiation. The results obtained are in good agreement with experiments. The described analytical approach can be used as an efficient design tool for preliminary vibro-acoustic analysis of compressors.

Cox, S.

• EFFECTS OF RAIL FASTENING ON RAILWAY TRACK NOISE
  S. Cox and A. Wang
[Abstract]

This paper describes measurements of deflection, vibration and noise on three different track forms. Each track section was 50 m in length. The measurements were carried out as part of the Silent Track European project on railway noise on a test loop at the Velim test centre in the Czech Republic in May/June 1999. The three track forms consisted of conventional track with monoblock sleepers fitted with the relatively soft studded rubber railpad, a section of very similar track fitted with stiffer studded EVA railpads, and a third section of a new track type with twin block sleepers, a narrow foot rail, and a new fastening system. The construction of the track with this last system is also described in the paper. The tests showed the new fastening system to be performing satisfactorily from a mechanical and an acoustic point of view. The wayside noise level at 7.5 m from the track was about 4 dB(A) lower than for the reference soft railpad track. The noise level for the track with

• ADVANTAGE OF BASEPLATE WITH TWO RESILIENT LAYERS FOR RAILWAY SLAB
  A. Wang and S. Cox
[Abstract]

Vibration from trains may produce two distinct environmental nuisances. First, vibration may propagate to buildings, where it may be perceived either directly or as so called 'secondary' noise generated as a result of vibrations of the building. Secondly, vibrations of the vehicle, track, and supporting structure radiate airborne noise. This may affect the in-car noise level for the passengers, and for open track structures may lead to increased noise levels alongside the railway. Since there are few practical alternatives for reducing ground vibration levels near the track, resilient baseplates which reduce the track stiffness are a popular means of taking the first problem. However, an undesirable by-product of this low track stiffness may be that it can lead to high vibration levels of track components, and in particular the baseplate itself, which exacerbate the second problem. The paper describes measurements which demonstrate that a design of baseplate which include two layers of resilience can produce acceptable levels of ground borne vibration, while the baseplate itself is isolated from the rail vibrations so that airborne noise levels do not increased. Compared to a single layer baseplate system with a similar overall dynamic stiffness, the vibration level of this new baseplate was reduced by more than 8 dB.

Cox, T.J.

• HEARING LOSS IN THE BUILT ENVIRONMENT: THE EXPERIENCE OF ELDERLY PEOPLE
  W.J. Davies, T.J. Cox, A.T. Kearon, B.J. Longhurst and C.L. Webb
[Abstract]

A qualitative social survey has been conducted on a group of 207 elderly people with a hearing loss. The aim of the study was to determine the extent to which acoustic problems in the built environment affect this subject group. It was found that the speech communication of elderly people was significantly affected by the presence of background talkers in a reverberant environment. Considerable evidence of subjects adapting their behaviour to acoustic problems was found. For example, a large number of subjects experienced poor reception with hearing aids. This prompted them to use the aid selectively. Also, poor sound insulation in domestic dwellings gave a strong disincentive for some subjects to use their television sets at a sound level audible to them. Design consequences based on these results will be discussed.

• EXTENDING THE BANDWIDTH OF PROFILED SOUND ABSORBERS
  T. Wu, Y.W. Lam and T.J. Cox
[Abstract]

Schroeder diffusers were originally designed for enhanced scattering, but poorly structured samples can display significant sound absorption, including the frequency range below the design frequency. This has been used as inspiration towards designing new absorbers with extended bass response. This project investigated the mechanism of the high absorption coefficient below the lower limit of design frequency by employing perforated plates in some of the wells of the diffuser. A theory for the enhanced absorption is presented, and the usefulness of the perforations in the wells has been verified. The parameters of the perforated plate need to be chosen carefully to match the strong coupling of the wells in order to obtain optimum performance. A numerical optimization was performed to obtain the better absorption by adjusting the positions of the perforations in the wells and the depths of the wells in one period. The results clearly show that this type of profiled optimized absorber extends the absorption to lower frequencies as well as higher frequencies, and becomes a considerably better wideband sound absorber.

Craik, R.

• SOUND RADIATION INTO DISSIPATIVE MEDIA
  R. Wilson, R. Craik and D. Tomlinson
[Abstract]

Radiation of sound from a baffled rectangular plate into air is relatively well understood. Edge radiation is the dominant mechanism below critical frequency and surface radiation is important above critical frequency. This paper investigates the affect that replacing air with a dissipative medium (such as mineral quilt), has on the sound radiated by the plate. An existing formulation for the sound power radiated from a baffled rectangular plate coupled to a porous medium is studied. The porous medium is modelled as an equivalent fluid and the problem is evaluated using an asymptotic approach similar to that used by Leppington for a plate radiating into air. This yields analytic solutions for radiation efficiency in the regions above and below critical frequency. The results indicate that above critical frequency, the radiation efficiency tends to that of a plate radiating into air as frequency increases. Below critical frequency, the presence of a dissipative medium is shown to result in increased sound radiation. Experimental data are presented and show good agreement with the analytic solutions. The potential affect that positioning porous materials in the vicinity of structural components is discussed for different structure types.

• SOUND TRANSMISSION THROUGH MULTI-LAYER LIGHTWEIGHT PARTITIONS
  R. Craik
[Abstract]

Lightweight partitions are increasingly being used in situations, such as party walls, where good sound insulation is required. These walls are acoustically complex structures with many construction details having an effect on sound transmission. Often non acoustics requirements such as fire prevention requirements or the costs of specific components such as acoustic absorption will also have a significant influence on the design. This paper will examine the application of statistical energy analysis for predicting sound transmission through lightweight double and triple walls constructed from timber frames and plasterboard sheets. A comparison will be made between measured and experimental data on a range of test walls examining both the structural paths through the wall and the acoustic paths. It is found that even for complex walls sound transmission can be well predicted particularly for structural paths. Some of the limitations of the modelling methods will be examined.

Crouzet, F.

• A METHOD FOR PREDICTING THE TRAILING EDGE NOISE CONTRIBUTING TO THE SOUND EMISSION OF HEAT PUMPS FANS
  L. Dutrech, M. Guivarch and F. Crouzet
[Abstract]

The will to reduce the acoustic radiation of air conditioning outdoor units leads to study the contribution of their cooling fans to the noise emission. The broadband part of the noise emitted by the axial fans installed on such systems is generally the most important part of the total radiated noise. Related to the turbulence of the flows, it may have several origins. In this paper, we focus our attention on the self-noise  of an isolated blade profile, caused by the turbulence of the boundary layer, assuming no stall is occurring ( trailing edge noise ). We present a method to predict the noise emitted by a 2D isolated profile, knowing its geometric characteristics, the incidence and the speed of the incoming flow. Our process consist of performing 2D CFD calculations on a profile to obtain statistical information on the flow near the trailing edge. This information is then related to the spectral characteristics of the surface pressure fluctuations, using analytical models developped by Corcos and Benarrous. Finally these characteristics are used to deduce the spectrum of the noise emitted by the profile, thanks to Howe's acoustic model. An empirical correction is also provided to take into account the finite sharpness of the blade. Calculations have been performed on a NACA 012 profile, for several trailing edge sharpness, flow speeds and incidences. The results show good agreements with literature's measurement data. Such work must be continued to study and validate the more realistic case of a 3D rotating blade.

Curcuruto, S.

• NOISE OBSERVATORY INFORMATION SERVICE
  C. Buratti, F. Cotana, C. Simoncini, R. Caracciolo and S. Curcuruto
[Abstract]

The Italian Law about Noise Pollution (n. 447, 26.10.1995) provides for the drawing up of acoustic reclamation plans, the evaluation of noise impact and acoustic climate, the activities of planning, measurement and check aimed to control noise pollution. Some decisions about territory policies need that such data are elaborated and presented in synthetic form; instead, the drawing up of reclamation plans needs an analytical and detailed representation of existing situation. It includes the development of a data bank, organized both on local (Communes, Regions) and national (ANPA) basis. The main objectives of this work are: - definition of an original NOISE-CIRIAF system, to elaborate noise pollution data and based on cause relations between Drivers, Pressure, State, Impact, Responses, following the DPSIR model defined by the European Environmental Agency (EEA); - choosing indicators able to represent the general conditions pertaining to noise pollution for State, Pressure, Impact and Responses. In the system of Drivers, all information regarding anthropic activities causing acoustic emissions have been identified. The drivers create two kinds of Pressure on environment: acoustic emissions and vibrations. The NOISE model distinguishes between indoor and outdoor environmental States; they have a direct Impact on health and on the ecosystem and an indirect influence on the economy both for the sanctions dictated by legislation and for the production and installment of systems. The Responses, in terms of structural interventions to contain acoustic emissions, of prescriptive and technological interventions have been grouped as follows: Laws, Plans, Technological Innovations, Scientific Research.

• TRAFFIC NOISE IN THE CITIES AND COMPARISON WITH WITHOUT CAR DAY
  C. Fabozzi, S. Curcuruto, A. De Leo, F. Duretto, A. Iacoponi, G. Licitra, L. Menini, W. Piromalli, M. Poli and P. Simonetti
[Abstract]

In the 22nd September 1999 carried out in about 90 Italian towns the '' European Day: in city without my car'', promoted in Italy by the Italian Environmental Ministry, with the purpose of sensitising citizens and administrators about problems connected to environmental pollution linked to traffic. During the day, between the 7:00 and 21:00, different zones of the cities chosen by local administrations were closed to private traffic. At the same time a campaign of noise monitoring was carried out, organised and coordinated by Environmental Agency System (ANPA-ARPA). The campaign had the purpose to estimate the benefits that are possible to obtain limiting in the city the circulation of private tr.

• A COMPLEX LEGISLATION: THE AIR TRANSPORT NOISE
  S. Curcuruto and A. Franchi
[Abstract]

The italian framework law on environmental noise pollution of the 26 October 1995, n.447 establishes the general principles but defers to other following decrees the regulation for specific noise sources or noisy activities; in particular, for one of the most important noise sources as the aircraft noise it has been necessary to define five decrees to complete the specific legislative measures. The Italian legislative approach to obtain a reduction of noise produced by air transport is based on the following action lines: to characterise the areas around the airport fixing noise limits and limitations of the territory use for each area; to define a measure methodology of the air transport noise; to define for each airport antinoise procedures that must be respected by aircraft during landing and take-off; to impose monitoring in continuous systems around the airport to protect the population controlling the noise emitted by the aircraft and the relative antinoise procedures followed; to classify the airports on the basis of the noise pollution levels produced on the surrounding environment; to impose reclamation measures in case of non-respect of noise limits; to impose the limitation of air traffic during the night period. In our country, the characteristics of the land together with the strong urbanisation impose the duty of conciliating the necessity of development of the airport infrastructure and the needs of territorial planning of the municipality that can suffer a limitation for the fruition of its own territory.

Cuschieri, J.

• CHARACTERIZING THE SOURCES OF NOISE AND VIBRATION ON A SMALL AUTONOMOUS SUBMERSIBLE
  J. Cuschieri and F.-X. Debiesme
[Abstract]

Work is continuing in characterizing the source and acoustic signature of a small autonomous underwater vehicle (AUV). Following the finite element modeling and results presented at Internoise 99, measurements in open water and in a reverberant tank are being performed to corroborate with the FE results. The tank measurements are being performed on a model of the AUV using both direct measurements and reciprocity techniques. Additionally, alternative methods for mounting the propulsion and control motors units of the AUV and for treatment of the wet hull are being investigated in the tank experiments. This paper presents the results of these measurements and alternatives for mitigating the acoustic signature. (Work sponsored by ONR) This is an invited paper int he session organized by Andrew Moorhouse.

Cutanda, V.

• NOISE EFFECTS ON LOCAL SCHOOLS IN THE MADRID REGION
  M. Recuero López, C. Gil, V. Cutanda and J. Grundman Isla
[Abstract]

The results of a subjetive study performed on several municipalities are presented here. Opinions about noise effects in schools were asked, both to teachers and students. Questions include subjects like noise level in classrooms and their acoustic conditions, internal and external noise sources and their annoyance, as well as the causes that originate these sources. Results show that most teachers and student are concerned about noise (76.9% teachers and 58.3% students). When asked about their preferred schools location, they are inclined towards a quieter place, even being father away, than to a closer one but under the influence of urban noise (68.3% teachers and 52.2% students). Improvement in the classrooms acoustic conditions is also considered necessary by most of the teachers (70.1%) and students (60%). As for noise sources, while most important internal source is people (in the opinion of 88.4% teachers and 86.8% students), the external sources vary depending on the location, although people (41.2% teachers and 32.1% students) and vehicles (28.1% teachers and 32.1% students) can be considered the most important ones. Community Response to Noise.

Da Silva De Sousa, D.

• URBAN NOISE CONTROL BY LEGISLATION IN RIO DE JANEIRO
  J. Slama, D. Da Silva De Sousa and S.M. Andrade
[Abstract]

The Humid Tropical Climate, as it is the case of Rio de Janeiro, imposes some restrictions in constructions. From bio-climatic architectural analysis, it is possible to verify that there is a necessity of natural ventilation and that the exterior walls should be of small thermal capacity. An observation of the facades of streets as ''Nossa Senhora de Copacabana'' shows that in general, in spite of a high external noise, the windows stay opened during almost all the day and then people are not well protected from the noise in its dwellings. A solution to control the urban noise would consist to close the windows and to install an air conditioning system. But this solution is usually very expensive for a great part of the local population whose income is relatively low. A different solution was tried in Rio de Janeiro. It consists in controlling the urban noise using legislation which limits the noise at the source. Usually, urban noise legislation try to limit the noise at the imission and not at the emission. This new legislation has to define maximum noise level at the emission and also the measurement method. It has to be compatible with an imission-based legislation. In this work a comparison is performed of the two strategies of emission and imission legislation showing the limitation of the first one.

Damagnez, F.

• USE OF RECIPROCITY PRINCIPLE IN A HYBRID MODELING TECHNIQUE (HMT) BASED ON INVERSE BOUNDARY ELEMENT METHOD (IBEM) FOR THE DETERMINATION OF THE OPTIMAL SPECTRAL CHARACTERISTICS OF A COMPLEX RADIATING NOISE SOURCE
  M.A. Hamdi, H. Defosse, F. Damagnez, T. Beauvilain and P. Varet
[Abstract]

The paper presents a robust hybrid modeling technique (HMT) based on near field acoustic measurements combined with numerical results derived from an Inverse Boundary Element Method (IBEM). The developed hybrid technique takes advantage from reciprocity principle to efficiently determine the optimal spectral characteristics of very complex noise sources, typically encountered in transportation industries. The first section of the paper reminds the direct link between reciprocity principle and integral representations of the acoustic field radiated by a noise source at finite number of discrete points located outside a closed surface enveloping the source. The second section describes the parameters chosen to describe the radiating source and the numerical optimization procedure used to determine the optimal spectral characteristics of source parameters. The third and last section of the paper illustrates successful practical applications of the method in automobile industry to characterize the noise radiated by a car engine.

• VIBRO-ACOUSTICS ANALYSIS OF A MEDICAL XRAY SOURCE : HYBRID APPROACH COMBINING EXPERIMENT AND FEA/BEA MODELING
  J.-M. Auger, F. Damagnez, M.A. Hamdi, S. Ayadhi and E. Chabin
[Abstract]

A vibro-acoustics analysis of a medical X-Ray source is presented . As the X-Ray source noise is generated by the interactions between the internal rotor and its bearing which are very complicated to describe, the analysis is carried out by using an hybrid approach combining experimental data measured on the system and an elasto-acoustics FEA/BEA model. This methodology , already applied for automotive and aerospace domains, uses RAYON solver integrated in the MCAE environment of I-DEASTM. Firstly, an inverse procedure is applied to determine an equivalent source model as a set of internal forces derived from vibration measurements in running condition and the elasto-acoustic model. Secondly, the BEA model and the source previously found are used to compute the radiated noise. Experimental and numerical results of both vibrations and radiated noise are finally compared. Such approach yields to a vibro-acoustics model capable to help for the path noise analysis and for the numerical modification analysis which have been applied to lead to several noise reduction improvements on the X-Ray source.

Dance, S.

• SIMULTANEOUS PREDICTION OF INTERNAL AND EXTERNAL SOUND FIELDS.
  S. Dance and B. Shield
[Abstract]

The purpose of the project was too develop a mathematical model, which was both accurate and quick to execute, for the simultaneous prediction of steady state and temporal sound fields both in the interior of a room and out to the environment. The sound being modelled would propagate solely through apertures. Hence, it was necessary to model diffraction. A barrier diffraction theory based on the geometric theory of diffraction, as implemented in FAME, was extended to represent diffraction around the perimeter of a building. Measurements around a physical scale model of a building were found to be in good agreement with those of FAME. However, more traditional models based on the Maekawa formula, both single and double diffraction, were found to produce poor predictions in the same space. The speed advantage previously held by the FAME model was lost with the increased complexity of the problem.

Darpas, M.

• VIBROACOUSTIC CHARACTERIZATION OF REFRIGERATING COMPRESSORS AS A FUNCTION OF OPERATING CONDITIONS
  M. Darpas and L. Ricol
[Abstract]

In the growing air-conditioning market, one of the most important demand considers the low noise performances of the equipment. The individual house air-conditioning/heating systems are one of the most sensitive markets when acoustics is considered. To improve their noise and vibration performance, manufacturers need information about the main vibroacoustic source : the refrigerant compressor. In order to characterize noise directly radiated by the compressor and noise transmitted to the machinery in the form of structure-borne and fluid-borne energy, a specific test-rig is required. Since they affect vibroacoustic behaviour of compressor, the operating conditions have to be controlled when measurements are carried out. In this paper, the vibroacoustic characterisation of refrigerating compressors as the function of operating conditions is discussed. Three compressors available on the market have been selected. The compressors are based on two different compression mechanism technologies - piston and scroll. Their cooling capacities are about 10 kW for ARI operating conditions. Temperature and pressure parameters corresponding to heating and air-conditioning process are defined for three operating conditions. Several measurements are performed on several compressors running under steady state conditions in order to obtain their vibroacoustic characteristics. Different procedures are used to evaluate sound power levels, gas pulsation in suction and discharge lines and vibrations of pipes and feet of compressors. Post processing are defined to calculate integrated values of vibration and gas pulsations in order to compare noise and vibration sources. The results of measured vibration, gas pulsation and sound radiation are compared and discussed for different operating conditions. Results show the importance of the different frequency components of the noise radiated for several operating conditions and compressor technologies.

Dauchez, N.

• EXPERIMENTAL VALIDATION OF 3-D POROELASTIC FINITE ELEMENTS BASED ON BIOT THEORY
  N. Dauchez, S. Sahraoui and N. Atalla
[Abstract]

The paper deals with experimental validation of 3-D poroelastic finite elements based on Biot displacement theory in the context of vibroacoustic applications. The validation is based on the determination of the characteristics of the porous material as input parameters for simulations. Emphasis is made on the determination of the mechanical properties of the skeleton. The validation experiment concerns the impedance measurement of a porous sample in a duct. The porous sample has been chosen so that one resonance of the skeleton can be observed in the frequency range 50-500 Hz. In that case a real 3-D behavior of the material with skeleton motion and acoustic coupling is observed. Various lateral boundary conditions are carried out : sample bonded to the duct or separated by an air gap of thickness 1.8 mm or 5 mm. Isotropic and transverse isotropic elasticity laws for the skeleton are tested. Good tendencies are found in terms of resonance location and absorption efficiency. Isotropic law using adequate characteristics gives the best results, although the skeleton is not isotropic. This shows that the determination of the viscoelastic properties of the skeleton is a very sensitive matter in the modeling of poroelastic materials.

Daumal I Domènech, F.

• THE VOICES OF THE SUSTAINABLE CITY
  F. Daumal I Domènech
[Abstract]

The city has certain voices that we must preserve. Some of them are totally masked by the noises of some work activities or hobbies, as well as goods being transported or even the same citicens moving around the city. The existing manufacturing machinery and the public private transport are most annoying because of the noise and vibration they cause. But the situation is changing and the sustainable city wants to put and end to the noise problem. Once we succeed, what will we call ''noise''? What voices will be able to remain in our cities once the causers of the so known ''noises'' are eliminated? What will happen with the old and forgotten sounds of the church bells, clocks and factories? What will happen with the voices of guilds, schools and so many other activities of the human being? To sun up, what are the sustainable voices in the future our cities?

• ACOUSTIC STRATEGIES OF BARCELONA. SOUND CULTURE FOR THE 2004
  F. Daumal I Domènech
[Abstract]

The acoustic rehabilitation of any city bears with some secondary effects that might with alter it. In a touristic city, the anti-noise management should especially protect those places that are interesting from a touristic standpoint. The acoustic strategies for Barcelona that are being studied now are based on its urban and building morphology. The different authorities working on it must propose for the next 2004 a Sound Culture. This project should highlight the intrinsic qualities of the urban structure of the city, I'm refering to those qualities that have been adopted as a model of urban rehabilitation by other cities.

Davies Jr., C.

• USING A GIS TOOL TO PLAN THE ACOUSTIC URBAN ENVIRONMENT
  M. Gomes De Oliveira, E. Bauzer Medeiros and C. Davies Jr.
[Abstract]

The economic development taking place in large urban centers can often provide an improvement in life quality as a consequence of the wider availability of services. However, severe environmental problems can also occur, if a coordinated strategy involving adequate monitoring of established businesses is not carried out. Adequate assessment of the environmental impact which may result from the economic development can only be carried out if suitable tools are available to the administrators, enabling proper supervision of land occupation. Noise is a major source of nuisance in urban environments, and in general 70% of the inhabitants of large cities usually describe noise related disturbances as a very important factor affecting life quality. This paper describes a set of GIS-based tools intended to provide the administrators with a methodology enabling a proper assessment of the acoustic impact within the urban environment. A model establishing the correlation between the spatial distribution of impacts and the relevant activities is developed. This model has been implemented as a prototype in a GIS environment, using Belo Horizonte's geographic database, which is intended to represent a typical large Brazilian city situation. Initial field measurements compare favorably with this prototype, indicating the feasibility of the proposed approach.

Davies, P.

• CULTURAL DIFFERENCES IN RESPONSES TO REFRIGERATOR NOISE
  P. Davies, P.G. May, J.S. Bolton and G.A. Long
[Abstract]

Korean-born and US-born subjects were asked to compare refrigerator sounds in terms of annoyance. The sounds were also evaluated using objective measures (metrics) to determine whether any of the objective measures correlated with the calculated average annoyance of the subjects, and thus to identify signal characteristics that may contribute to annoyance. Linear combinations of metrics were used to predict annoyance and the accuracy of these models was determined. It was found that Korean-born subjects were more sensitive than the US-born subjects, though the orderings of the signals in terms of annoyance by both groups were similar. Two-metric regression models containing stationary loudness (ISO532B) and Zwicker sharpness metrics were identified as having the strongest correlation to the subjective responses. There appeared to be slight differences in the individual contributions of sharpness and loudness to annoyance between the two groups, but further research is necessary to determine if these differences are significant.

Davies, W.J.

• HEARING LOSS IN THE BUILT ENVIRONMENT: THE EXPERIENCE OF ELDERLY PEOPLE
  W.J. Davies, T.J. Cox, A.T. Kearon, B.J. Longhurst and C.L. Webb
[Abstract]

A qualitative social survey has been conducted on a group of 207 elderly people with a hearing loss. The aim of the study was to determine the extent to which acoustic problems in the built environment affect this subject group. It was found that the speech communication of elderly people was significantly affected by the presence of background talkers in a reverberant environment. Considerable evidence of subjects adapting their behaviour to acoustic problems was found. For example, a large number of subjects experienced poor reception with hearing aids. This prompted them to use the aid selectively. Also, poor sound insulation in domestic dwellings gave a strong disincentive for some subjects to use their television sets at a sound level audible to them. Design consequences based on these results will be discussed.

Day, C.

• MEASUREMENTS OF THE SOUND INSULATION OF HOUSES NEAR AUCKLAND INTERNATIONAL AIRPORT
  X. Oh and C. Day
[Abstract]

A series of aircraft sound insulation measurements has been conducted on nine houses in an area near Auckland International Airport with current noise levels of Ldn 61 to 63 dBA. Simultaneous indoor and outdoor measurements were analysed in terms of A-weighted and spectral SEL data. Data was collected with windows closed and slightly open (100 mm gap). Houses constructed with various claddings, roofs and windows were selected. The purpose of the study was to determine the level of sound insulation achieved in New Zealand dwellings and to assist in the design of acoustic insulation of existing and future homes. The paper presents some of the results of the measurements and conclusions that can be drawn.

De Beer, F.

• CURVE SQUEAL OF RAILBOUND VEHICLES (PART 1): FREQUENCY DOMAIN CALCULATION MODEL
  F. De Beer, M. Janssens, P.-P. Kooijman and W.-J. Van Vliet
[Abstract]

Curve squeal is the intense tonal noise that can occur when a railway vehicle traverses a curve or switch. During the curve passage, the wheels without flange contact perform lateral creepage relative to the rail. The unstable stick-slip phenomenon in this lateral creepage causes the wheel to oscillate and radiate noise. A frequency domain model is developed that combines existing sophisticated models for wheel, rail and contact dynamics with the creepage dependent friction coefficient. Wheel, rail and contact dynamics describe the vertical contact force and the creep velocity, given the lateral relative contact force between wheel and rail. In its turn, the friction coefficient gives the lateral force starting from the vertical force and the creep velocity. Combination of these relations gives a feedback system from lateral force via vertical force and creep velocity back to lateral force. The Nyquist stability criterion for feedback systems gives the frequencies at which instability may occur (180 degrees phase angle and an amplification factor greater 1). These frequencies align with the lateral wheel mode frequencies. Only one of these frequencies will appear in the squeal noise spectrum, depending on wheel load and wheel lateral contact position. For this frequency the force amplitude is calculated in the time domain. Part 1 of this paper describes the squeal noise model, part 2 and 3 describe the validation of the model.

• CURVE SQUEAL OF RAILBOUND VEHICLES (PART 2): SET-UP FOR MEASUREMENT OF CREEPAGE DEPENDENT FRICTION COEFFICIENT
  P.-P. Kooijman, W.-J. Van Vliet, M. Janssens and F. De Beer
[Abstract]

Curve squeal is the intense tonal noise that can occur when a railway vehicle traverses a curve or switch. During the curve passage, the wheels without flange contact perform lateral creepage relative to the rail. The unstable stick-slip phenomenon in this lateral creepage causes the wheel to oscillate and radiate noise. The stick-slip phenomenon depends on the friction coefficient: the ratio of lateral over vertical contact force. The friction coefficient of a rolling contact depends, among others, on the creepage. A measurement set-up was developed to evaluated squeal noise. The set-up consists of two wheels, representing the train wheel and the rail, with a rolling contact area in between them. Lateral creepage appears by adjusting the angle between the two wheel axes. Contact positions on wheel and rail, wheel load, wheel and rail profile and surface contamination can be altered and their influence on the creepage dependent friction coefficient was measured.

• CURVE SQUEAL OF RAILBOUND VEHICLES (PART 3): MEASUREMENT TECHNIQUES FOR WHEEL/RAIL CONTACT VELOCITIES AND FORCES AT SQUEAL NOISE FREQUENCIES
  M. Janssens, W.-J. Van Vliet, P.-P. Kooijman and F. De Beer
[Abstract]

Curve squeal is the intense tonal noise that can occur when a railway vehicle traverses a curve or switch. During the curve passage, the wheels without flange contact perform lateral creepage relative to the rail. The unstable stick-slip phenomenon in this lateral creepage causes the wheel to oscillate and radiate noise. The squeal noise spectrum consists of a single frequency with higher harmonics. A measurement set-up was developed to evaluated squeal noise. The set-up consists of two wheels, representing the train wheel and the rail, with a rolling contact area. Lateral creepage appears by adjusting the angle between the two wheel axes. Measurement techniques where developed to measure wheel and rail velocities nearby the rolling contact and contact forces at the squeal noise frequencies. The wheel vibrations were measured by pointing a contact free laser velocity sensor at the wheel and rail contact area. Transfer functions from force to velocity at the wheel tyre and railhead are used to determine the contact forces from the measured velocities. Measurement results are used to validate the squeal noise model and to evaluate measures against squeal noise. Measurement techniques and results will be presented in the paper.

De Certaines, J.D.

• MAGNETIC RESONANCE IMAGING OF ELASTIC WAVE FIELDS IN CONDENSED MATER
  C.J. Lewa, J.M. Franconi, M. Ruth and J.D. De Certaines
[Abstract]

At the beginning of the nineties, we have developed a method of motion sensitive gradient in-conjunction with a periodic mechanical compression for Magnetic Resonance Imaging (MRI) and Elasto-Magnetic Resonance Spectroscopy (EMRS) of visco-elastic properties. The first of elastic waves imaging method has been successfully applied, for transversal elastic waves, in 1995 by Muthupillai et al. under the name of Magnetic Resonance Elastography and by Plewes et al. in the range of low frequencies for tranverse waves, as well as for longitudinal waves at ultrasonic frequencies. These previous methods use a synchronization between the magnetic field gradient pulse and mechanical vibration and then require an a-priori knowledge of the frequency of the motion to bee detected. In addition to various ultrasonic methods, MRI can be a good challenger for such measurements as it provides imaging of 3D samples as higher quality than usually obtained by other imaging methods. Some recent MR elastography studies present interesting results on mammography and on ''brain palpation''. The goals of this study were to realize the unsynchronized EMRS method allowing the analysis of the intensity, direction and frequency of an unknown elastic wave field in a 3D sample. The experimental verification is performed on a routine low field MRI (0.2 T) device. An additional goal was to maintain the acquisition time enough short to make the method compatible with routine MRI examinations. The method raises hopes for possible applications in imaging of elastic wave fields (bio-acoustics, geo-acoustics, noise field analysis, material characteristics) as well as in fundamental research.

De Geetere, L.

• IN SITU MEASUREMENT OF THE ABSORPTION COEFFICIENT AT NORMAL INCIDENCE USING MLS-SEQUENCES AND 1 OR 2 MICROPHONE TECHNIQUES
  L. De Geetere, G. Vermeir and W. Lauriks
[Abstract]

For the in situ determination of acoustical properties (surface impedance, reflection- and absorption coefficient) of sound-absorbing materials, 1 or 2 microphone techniques are most widely used. An experimental system is developed for studying some techniques in a semi-anechoic room to examine the applicability of these techniques in real in-situ environments on (locally reacting) finite size test-materials. All these techniques are based on measured impulse-responses at 1 or 2 locations close to the test-surface. These responses are obtained using pseudo-random MLS-sequences. Low and high frequency limits are studied for the 'subtraction' technique and the 'impulse sharpening' technique (both 1 microphone) and for the 'spherical decoupling' technique (2 microphones). The techniques are compared and evaluated for their in-situ applicability. Some rules of thumb and guidelines are deduced.

De Jong, C.

• MULTI-POINT SOURCE CHARACTERISATION APPLIED TO A DIESEL ENGINE RIGIDLY MOUNTED ON A RAFT
  M. Termeer and C. De Jong
[Abstract]

This paper discusses the structure borne sound transmission from a source to a receiver via multiple connection points and directions. In such multi-point contacts coupling effects between degrees of freedom may be important for a correct source description. A ships Diesel engine mounted on a raft was taken as an example . Free velocities of the engine and mobility matrices of engine and raft have been measured. By using these measurements the power transmission from the engine to the raft via 4 translational degrees of freedom is studied in detail, accounting for coupling effects via 12 degrees of freedom. It can be concluded that multi-point effects play a role in the amount of power transmitted via each single degree of freedom. If the scope becomes more global, i.e. if one considers the total power transmission in a frequency-averaged sense, the coupling effects tend to become less important.

De Jong, R.G.

• ANNOYANCE AND HEALTH AROUND SCHIPHOL AIRPORT AND IN A CONTROL AREA
  E. Franssen, I. Van Kamp and R.G. De Jong
[Abstract]

In 1996 a questionnaire-based survey was carried out around Schiphol airport as part of the research programme ''Health Impact Assessment Schiphol Airport (GES)''. In the same period the Community Health Service in the Northwest part of the Netherlands conducted a survey, making use of the same questionnaire. This area is free from airport noise caused by Schiphol airport, and as such is suitable as a control area for the Schiphol study. Based on these two studies levels of annoyance and health indicators are compared in three exposure-categories: - A high exposed area around Schiphol airport with noise-exposure. - A low exposed area around Schiphol airport. - A control area with no Schiphol related aircraft noise. Previous analyses of the Schiphol data were restricted to effects of aircraft noise within a radius of 25 km around the airport. The results showed that even in areas with a low aircraft noise exposure, people are annoyed and report health effects. It is interesting to study whether also in a control area these effects occur. The hypothesis is that prevalance of annoyance and health aspects in the low exposed area around Schiphol are equal to those in the control area.

De Kluijver, H.

• NOISE MAPPING AND GIS: OPTIMISING QUALITY, ACCURACY AND EFFICIENCY OF NOISE STUDIES
  H. De Kluijver and J. Stoter
[Abstract]

Noise levels are calculated with special noise prediction computer models. Till now there is no widely used far-reaching integration of GIS and noise prediction models. GIS is only used as a pre- and post-processor (for example to gather and store data and to calculate the impact of noise on the environment). As a consequence GIS and the available digital data are not optimally used. This paper describes the results of a preliminary study on the possibilities and advantages of an integrated system of GIS and noise prediction models. The study shows the following benefits of an integrated system: With a central database unnecessary data conversion between both systems is prevented. This ensures the use of the same data. Input data for noise prediction models can automatically be generated, using available 3D-geographic information. With advanced interpolation techniques in GIS it is possible to obtain an accurate picture of the acoustic situation based on a limited number of sample points (calculated in a noise model). The accuracy and quality of the results depend on the scale and detail of the input data. The information density should be high enough but redundant information can be avoided. A GIS-module can tackle this problem. The points mentioned above improve the quality and efficiency of noise studies while reducing the data quantity, modelling effort and computation time. This paper also gives examples of a system to analyse the effects of noise caused by railways. For this purpose the Dutch railways developed a distinctive GIS-solution in 1995. Furthermore it shows future developments on noise mapping of highways and in towns in the Netherlands.

De Langhe, K.

• MASS LOADING EFFECTS ON THE PARAMETERS OF A STATISTICAL ENERGY ANALYSIS EXPERIMENTAL MODEL
  N. Baldanzini, K. De Langhe and M. Pierini
[Abstract]

The effects of additional instrumentation mass on a structure in the high-frequency range were investigated in terms of the parameters of an experimental statistical energy analysis (SEA) model built using the power input method (PIM). In previous studies, such as those conduced by Ashory 1998 and Olbrechts et al., 1997, only low-frequency ranges were examined. A T-junction with three connected plates was used in modeling. First, a full set of measurements were carried out on instrumentation with no mass loading effects; on the basis of the results, the model parameters to be used as references in subsequent comparisons were determined. In the second phase, two full sets of measurements were carried out: one with the mass loading effect of the impedance head and one with the mass loading effect of the accelerometers. Comparison of the processed data and the reference values showed that the impedance head failed to affect the equivalent mass and the model's internal and coupling loss factors; the accelerometers, on the other hand, modified the equivalent mass. The impedance head and the accelerometers both affected the determination of the SEA subsystem's modal densities. This behavior may be qualitatively explained by the fact that although all the measurements were undoubtedly affected by the mass loading effect, a cancellation effect-also supported by the SEA formulas-occurred for some parameters. These results are especially important, since not all the errors introduced during measurements can be corrected before processing. Proper knowledge of the performance of the instrumentation and its effects on the model parameters is fundamental in obtaining a good SEA experimental model.

De Leo, A.

• TRAFFIC NOISE IN THE CITIES AND COMPARISON WITH WITHOUT CAR DAY
  C. Fabozzi, S. Curcuruto, A. De Leo, F. Duretto, A. Iacoponi, G. Licitra, L. Menini, W. Piromalli, M. Poli and P. Simonetti
[Abstract]

In the 22nd September 1999 carried out in about 90 Italian towns the '' European Day: in city without my car'', promoted in Italy by the Italian Environmental Ministry, with the purpose of sensitising citizens and administrators about problems connected to environmental pollution linked to traffic. During the day, between the 7:00 and 21:00, different zones of the cities chosen by local administrations were closed to private traffic. At the same time a campaign of noise monitoring was carried out, organised and coordinated by Environmental Agency System (ANPA-ARPA). The campaign had the purpose to estimate the benefits that are possible to obtain limiting in the city the circulation of private tr.

De Man, P.

• A PHYSICALLY BASED STRATEGY FOR ROBUST FEEDBACK CONTROL OF NOISE RADIATION FROM A BAFFLED PLATE
  P. De Man, A. Francois and A. Preumont
[Abstract]

This study is based on the premise that the robustness of a control system often relies far more on the design of the open-loop system (i.e. the choice and location of sensors and actuators) than on the specific feedback compensator used. Accordingly, a careful vibroacoustic analysis is used to reduce the open-loop system to a single-input single-output control problem with a number of desirable features from the point of view of controllability and robustness. The strategy proceeds in three steps : (1) An array of piezoelectric patches located on a regular mesh is connected to a linear combiner to produce a volume velocity sensor; the coefficients of the linear combiner are determined from experiments to minimize the error between the reconstructed and the measured quantities. The volume velocity is known to be closely related to the sound power radiated by a baffled plate at low frequency. This step achieves a single-output sytem. (2) A small set of actuators (either point force or piezoceramic) is constrained to operate with the same voltage to achieve a single-input system; the location of the actuators is then optimized to provide the open-loop with the following desirable features: - Alternating poles and zeros are sought within the control bandwidth to enhance the immunity with respect to the parametric uncertainty. - The magnitude of the resonance peaks is maximized within the control bandwidth to increase the control authority. - The magnitude of the resonance peaks is minimized near and right after cross-over to improve the gain margin and reduce spillover. The optimization procedure uses a genetic algorithm. (3) Using this specially designed SISO open-loop system, the next step consists of designing the feedback compensator. This paper illustrates that low order, model independent, classical compensators such as a lead  produces a subtantial low frequency noise attenuation. The paper presents a hardware demonstration of step (1) and numerical simulations of step (2) and (3).

De Roo, F.

• TRIAS - TYRE ROAD INTERACTION ACOUSTIC SIMULATION MODEL
  F. De Roo and E. Gerretsen
[Abstract]

Since 1996 the development of the TRIAS simulation model for tyre-road noise emission has been in progress. At InterNoise '97, '98 and '99 papers have been presented about this simulation model, which may be considered as one of the most comprehensive attempts to predict tyre-road noise emission. Expectations are that this development will be completed in 2000 with a validation of all modules comprised in this model, dealing with: * tyre-road mechanical interaction; * tyre response to force excitations; * radiation of sound from mechanical vibrations; * generation of sound by air movements in the contact patch; * propagation of sound to the environment. The predictions may be based on measured values of the physical road surface characteristics. For design purposes also a module known as RODAS (ROad Design Acoustical Simulation) may be used, which predicts the surface characteristics as a function of material properties. This module is available as a stand-alone model and has already been validated. The paper will discuss the various validation results and will reveal the latest adjustments of the model based on these validations. Limitations to the use of the model will be addressed and a comparison will be made with the model described by Kropp, which was the starting point of the TRIAS development.

De Salis, M.

• LOW NOISE NATURAL VENTILATION SYSTEMS
  M. De Salis, D. Oldham and S. Sharples
[Abstract]

Natural ventilation systems in buildings need to have inherently low airflow resistances so that the relatively small pressure differentials utilized to drive them can achieve adequate ventilation rates. Low airflow resistance can be achieved by opening large areas of the building facade but this will have the associated problem of significantly decreasing the noise insulation. The treatment of inlet and outlet openings using conventional noise control treatments will cause significant increases in the airflow resistance at the inlet to the building and therefore will often prove untenable. Hence the option of natural ventilation will often be restricted to buildings in areas of low ambient noise. With an increasing trend to exploit natural ventilation it is pertinent to look at measures which will render it a viable option in a wider range of areas. This paper presents a quantitative analysis of the variation of airflow characteristics with sound insulation of a façade with ventilation openings incorporating a variety of noise control strategies. It is shown that reactive and active techniques can supplement conventional passive attenuation in the limiting low frequency region while adding minimal flow constraint to the ventilation path. Using such hybrid systems useful broad band sound reduction can be achieved for natural ventilation openings.

De Vos, P.

• NOISE-RELATED ROUGHNESS ON RAILWAY WHEELS GENERATED BY TREAD BRAKING
  P. De Vos and S. Van Lier
[Abstract]

The rolling noise created by passenger railway traffic in Europe has been significantly reduced over the last decade, thanks to the large scale introduction of disk brakes. For freight traffic, however, a similar development has not occurred, mainly because of its strongly international character. Cast iron is a suitable brake block material, but it causes roughness on the wheel tread, and consequently a high level of rolling noise. Therefore the Brite-Euram project Eurosabot was started to develop a brake material for tread braking of freight vehicles that should suppress the formation of wheel roughness, whilst still providing the required braking performance. The phenomena involved in the roughness generation were studied on the basis of dynamometer tests. Both thermo-elastic instabilities and material transfer between block and wheel, dynamic instabilities and periodic wear are felt to be responsible for the roughness generation. A series of models was developed that were able to reproduce qualitatively what had been observed in the tests. The results were used to select promising solutions from a large spread of ideas. These were then tested in practice. The results of the final tests are to some extent doubtful and disappointing. The project did not succeed in identifying a 'low roughness' brake block material suitable for a simple retrofit exchange of cast iron blocks. However, it did succeed in improving significantly the understanding of the processes that are important in wheel roughness generation. It is recommended to base the continued search for a retrofit brake block material on the improved understanding and modelling, rather than on trial-and-error.

• CLASSIFICATION AND REGULATION FOR RAIL TRANSPORT
  J. Van Den Brink and P. De Vos
[Abstract]

An active policy is required to regulate on a reasonable time scale the process of reducing railway noise ate source. The reduction is necessary because of the conflicting policies of growing demand of transport on the one hand and community noise control on the other. The two involved Dutch Ministries, i.e. of Environment and of Transport, have launched a new approach. International research of the last decade has led to the understanding that rolling noise is the predominant source in railway noise and should therefore be reduced. Studies of costs and benefits of different measures, carried out in The Netherlands, show that reduction of rolling noise is preferable to measures like sound barriers. For Europe the time is right for a new noise policy, since the Commission prepares a Noise Directive. The policy of the two Ministries in The Netherlands focuses on the stimulation of measures on rolling stock by using a mix of instruments for future legislation and corresponding temporary provisions. The main elements of the new policy are: technology available, noise generation standards for rolling stock, national limits for noise generation rather than for noise reception. A system of categorization of rolling stock is necessary as an instrument for track admission and capacity allocation. Other instruments may follow, which are aimed to optimize the balance between traffic intensity, track capacity and noise production. Such instruments are for example: variable track access charges, subsidies for quiet technology, accelerated depreciation of rolling stock etc. The lack of a European system of noise generation limits for rail vehicles made a system of classification of vehicles necessary. In the future Dutch legislation the will be a fixed limit value for the total noise output per railway line segment. The limits will be defined on the basis of the actual rail traffic intensity over the past years with a certain space for future growth. Once the system is implemented, there will be an automatic, economic

Debiesme, F.-X.

• CHARACTERIZING THE SOURCES OF NOISE AND VIBRATION ON A SMALL AUTONOMOUS SUBMERSIBLE
  J. Cuschieri and F.-X. Debiesme
[Abstract]

Work is continuing in characterizing the source and acoustic signature of a small autonomous underwater vehicle (AUV). Following the finite element modeling and results presented at Internoise 99, measurements in open water and in a reverberant tank are being performed to corroborate with the FE results. The tank measurements are being performed on a model of the AUV using both direct measurements and reciprocity techniques. Additionally, alternative methods for mounting the propulsion and control motors units of the AUV and for treatment of the wet hull are being investigated in the tank experiments. This paper presents the results of these measurements and alternatives for mitigating the acoustic signature. (Work sponsored by ONR) This is an invited paper int he session organized by Andrew Moorhouse.

Deboli, R.

• HAND-ARM VIBRATION MEASUREMENTS BY LASER VIBROMETRY AND CAPACITIVE SENSOR MATRICES
  G. Miccoli, R. Deboli, G. Di Giulio, J. Mariani, N. Paone and G. Rossi
[Abstract]

The use of accelerometer based measurement techniques in order to evaluate hand-arm transmitted vibrations has shown high levels of uncertainty in many applications. The aim of the present work consists on illustrating a new hand-arm vibration measure-ment technique. The technique has been applied in order to characterize hand held ma-chine vibrating parts/components usually coming into contact with the operator (hydrau-lic breaker handles, agricultural/earth moving machine steering-wheel and levers). The purpose consisting on identifying machine structural modifications aimed at reducing vibrations and, taking into account also ergonomic aspects, improving operator comfort/working conditions. The measurement technique proposes a parallel application of a) laser vibrometry b) capacitive sensing element matrices. The use of no contact laser vibrometer avoids many measurement problems due to the presence of transducers on the hand and/or the vibrating surface. Moreover, the laser beam scanning characteristics allow a fast and spatially detailed data acquisition. The contact pressure distribution at the operator's hand/machine handle interface has to be known in order to evaluate hand-arm vibration transmission. Moreover, the global grip force applied by the operator turns out to be an important parameter to be considered. On this purpose, capacitive sensors matrices have been developed and optimised to fit the different tested applications. The proposed measurement technique represents the topic of an European Community funded project in the Framework IV, SMT programme. The results shown in this work are those till now achieved in conclusion of the second year of activity of the project itself.

Dedene, L.

• IDENTIFICATION OF THE LINK BETWEEN DISTURBING ELEMENTS OF AUTOMOTIVE EXHAUST NOISE AND THE CONSTRUCTION OF THE EXHAUST SYSTEM
  L. Dedene, R. Valgaeren, M. Van Overmeire and P. Guillaume
[Abstract]

In this contribution a sound quality investigation concerning automotive exhaust noise will be presented. The investigation deals with the disturbing elements of exhaust noise (e.g. booming noise, hollow sound, whistle,...). The exhaust sounds are recorded behind the cars (exterior tailpipe noise) using an artificial head. The investigation consists of three parts. The first part consists in determining a definition for each disturbing element (establish a sound quality catalogue). The next step is to establish a metric for each defined element. With the use of signal analysis, signal manipulation and psycho-acoustic measures the physical aspects of the time signal, that make a disturbing element audible, can be determined and quantified. The final step is to find the link between the established metrics and the geometry of the exhaust system. This is a difficult step due to the large number of components (tubes, baffles, perforations,...). The exhaust noise is also strongly influenced by the flow-induced noise. The paper will be focused on determining the link between the metrics and the exhaust system's geometry. For 2 disturbing elements (hollow sound & whistle) the link between metric and geometry will be discussed in detail.

Defosse, H.

• USE OF RECIPROCITY PRINCIPLE IN A HYBRID MODELING TECHNIQUE (HMT) BASED ON INVERSE BOUNDARY ELEMENT METHOD (IBEM) FOR THE DETERMINATION OF THE OPTIMAL SPECTRAL CHARACTERISTICS OF A COMPLEX RADIATING NOISE SOURCE
  M.A. Hamdi, H. Defosse, F. Damagnez, T. Beauvilain and P. Varet
[Abstract]

The paper presents a robust hybrid modeling technique (HMT) based on near field acoustic measurements combined with numerical results derived from an Inverse Boundary Element Method (IBEM). The developed hybrid technique takes advantage from reciprocity principle to efficiently determine the optimal spectral characteristics of very complex noise sources, typically encountered in transportation industries. The first section of the paper reminds the direct link between reciprocity principle and integral representations of the acoustic field radiated by a noise source at finite number of discrete points located outside a closed surface enveloping the source. The second section describes the parameters chosen to describe the radiating source and the numerical optimization procedure used to determine the optimal spectral characteristics of source parameters. The third and last section of the paper illustrates successful practical applications of the method in automobile industry to characterize the noise radiated by a car engine.

• VIBRO-ACOUSTIC STUDY OF ARIANE V LAUNCHER DURING LIFT-OFF
  H. Defosse and M.A. Hamdi
[Abstract]

During lift-off of a launch vehicle, high acoustic sound pressure levels are generated which when transferred through the launcher fairing may lead to high acceleration levels at sensitive parts of the spacecrafts. Advanced vibroacoustic analysis tools are used to predict the response of these structures that are able to simulate the coupled vibro-acoustic system consisting of external sound field, fairing structure, cavity and payloads. These tools implemented inside the software RAYON developed by STRACO use a BEM approach for the infinite external domain and a FEM approach for the structures and cavities. This paper gives an overview on the theoretical background and presents the following aspects : - Reciprocity method application on a BEM model to determine the acoustic power of the horns of the ESTEC's reverberant chamber. - Sensitivity method application to update numerical model with respect to ground test. - Use of updated model to derive BEM axisymmetrical models of flight configurations (V501). Results of ARIANE V short fairing qualification test in reverberant chamber are presented together with comparisons of numerical and in-flight telemeasures. They show that predictive models determine acoustic pressures and structural vibrations with a good accuracy. Reciprocity method is quite promising for characterization of complex sources of noise and has a lot of potential applications in many industrial domains (car's engine noise, airplane's propeller noise,...).

• INSULATION OF ALUMINIUM FRAME-DOUBLE GLAZING WINDOWS BY MEAN OF BEA/FEA MODELING
  J.-M. Auger, H. Defosse, M.A. Hamdi, C. Barras, D. Benoualid, P. Mulocher, B. Mottelet, M. Rehfeld, P. Cotté, C. Midelet and M. Szezygiel
[Abstract]

This paper presents significant results of the research program on the insulation of aluminium framed windows glazed with sealed double glazing conducted by a consortium of partners. This consortium involves industrial partners which develop window components i.e.: SAINT GOBAIN for double glazings, HUTCHINSON for seals, TECHNAL and A.S. for aluminium window frames. The vibro-acoustic simulation of the window is conducted by STRACO by using I-DEAS Vibro-Acoustics and RAYON solver. The window insulation analysis is conducted both numerically and experimentally: - Experiments are performed by partners with their transmission facilities in order to compare results and validate models. - Simulation are conducted by using an original FEA/BEA modeling approach capable to represent the transmission problem by taking into account structural details related to seals, frame and glass as well as internal acoustic cavities and external radiation. Comparisons between experimental an numerical insulation results show a good agreement and a parametric analysis provides indications on the influence of parameters which characterize seals, frame and the double glazing.

Defrance, J.

• EXPERIMENTAL STUDY OF ROAD TRAFFIC NOISE CONTROL BY A PINE FOREST
  N. Barriere, Y. Gabillet, J. Blais, J. Defrance, P. Ducruet and F. Gaudaire
[Abstract]

In order to precisely bring to the fore the effect of meteorology on sound propagation through forests, an important measurements campaign has been carried out in the French Landes forest mainly composed of pine trees. The originality of the experiment is that road traffic noise and meteorological conditions have been measured simultaneously for both a forest situation and a plain situation, this for different positions of the receiver. All valid measured data have then been classified according to three propagation conditions: favourable to propagation, unfavourable to propagation and homogeneous conditions. As expected, the results depend on these conditions. In favourable conditions, the gain brought by the forest is between 3 and 5 dB(A) with the receiver at least 100 m away from the road. This meteorological situation occurs very often at night due to a temperature inversion phenomena. Moreover, it is of most interest since it corresponds to the periods when the annoyance due to the road in a plain situation is the highest. In unfavourable conditions, the forest may increase somewhat the received sound level. In homogeneous conditions, the sound propagation through the forest is not appreciably affected by meteorology anymore but only by the scattering by the trunks and foliage. Finally, these results have permitted to validate a new calculation method for the attenuation of road traffic noise by forests based on a fast implementation of the Parabolic Equation.

• METEO-BEM : A POWERFUL TOOL FOR COMPLEX OUTDOOR SOUND PROPAGATION
  E. Premat, Y. Gabillet and J. Defrance
[Abstract]

The new formulation Meteo-BEM based on the layer potential theory and recent propagation models , allows one to describe sound propagation in a complex outdoor environment. This new model accounts for meteorological effects as well as various absorbing properties and shapes of the boundaries. First, the theory of Meteo-BEM is briefly given, with a particular emphasis on the methodology used to include meteorological effects. The total sound pressure is expressed as the sum of the incident pressure and the pressure scattered by the obstacles in the propagation medium, involving simple and double layer potentials. The Green's function used in this formulation takes meteorological and ground effects into account and relies on recent models for propagation in inhomogeneous media. Then Meteo-BEM is applied to the case of sound propagation with refraction (downward and upward) around a sound barrier. The ground can be absorbing. The results are compared to experimental data obtained in controlled conditions with a scaled model (curved surface). The agreement is very good and shows that meteorological effects can be included in Boundary Element Methods. So Meteo-BEM is found to be a powerful tool for outdoor sound propagation prediction, which gives rise to many applications and developments.

• A NEW FRENCH METHOD FOR RAILWAY NOISE PREDICTION
  J. Defrance, Y. Gabillet, D. Van Maercke, C. Dine and P.-E. Gautier
[Abstract]

Regulations for railway noise are becoming more and more stringent and, along with a decrease of maximum acceptable sound levels, a more accurate environmental prediction is sought. This has brought about the need of sound level calculations at long ranges including meteorological effects. A new French prediction method for Railway Noise (NMPB-FER) has thus been developed on the basis of an already existing one for road traffic noise. This method specifies two calculation procedures: with meteorological conditions favourable to sound propagation and with atmospheric homogeneous conditions. The result is a long term equivalent A-weighted noise level obtained by the combination of the two calculations and taking into account the percentage of time when favourable conditions occur. The railway source is modelled as two independent sources, one being close to the rail/wheel contact plane (concerning highest frequencies) while the other is located at a height appropriate to a simple but correct representation taking into account aerodynamic sources (for lowest frequencies). This method implemented in the MITHRA ray tracing software offers some original specificities: barrier-carriage multi-reflections effects taken into account, calculation of the noise level vs time evolution, railway noise sources split up according to the total length of the convoy, composition of trains and determination of sound power level characteristics achieved by assembling the wanted rolling elements (locomotive and carriages, types and numbers). Input to the model can easily be obtained from multi-spectrum measurements close to the railway.

Dekoninck, L.

• AN INDICATOR FOR ROAD TRAFFIC NOISE: MONITORING AND PREDICTION MODEL
  L. Dekoninck, D. Botteldooren, G. Vindevogel and R. Geens
[Abstract]

In this paper a pressure indicator for road traffic noise is discussed and a prediction model for the indicator is presented. The indicator is defined as the annual sound emission at a particular point near a major Flemish highway. When measuring this indicator one must be very careful to take into account weather effects and possible changes in road surface accurately. This is particularly important since the expected annual change in the indicator is very small. When modeling the indicator the evolution of car noise emission must be taken into account. This requires the type of cars and trucks and their age and relative density to be known. In this work the influence of product noise regulations is included in the model for the control period 1992-1998. Results are in good agreement with noise measurements. This increases the confidence in the model for predicting future evolution. Several future-scenario's (business as usual, sustainable) are presented in the paper.

Delemotte, V.

• THE FIRST 1000 ACTIVE DUCT SILENCERS INSTALLED IN HVAC SYSTEMS - A SUMMARY OF APPLICATIONS, SUCCESSES, AND LESSONS LEARNED.
  S. Wise, J.-F. Nouvel and V. Delemotte
[Abstract]

The authors have been personally involved in the design and start-up of over 1000 active duct silencers installed in the USA and Europe to silence fans on a variety of HVAC applications. Sites include semiconductor manufacturing facilities, auditoria, sound test chambers, schools, cruise ships, hospitals, and office buildings Applications include both retrofit and new construction. Low-frequency noise attenuation of as high as 30 dB has been achieved. Multi-unit air distribution systems with air flow totaling over 3,000,000 m3/h have been treated. Controlled noise levels below the threshold of hearing have been obtained within sound test chambers. In some applications, poor duct design, flanking noise and vibration paths, and secondary sources limit the effectiveness of the active duct silencer. This paper reviews the rights and wrongs of active duct silencer applications, and answers these questions: How does one best measure the performance of the active duct silencer? What are the most common flanking paths? What types of fans are best silenced by active noise control? Where is the best location for active duct silencers? What is the realistic performance expectation for an active duct silencer?

Demilly, F.

• ROLLING NOISE FROM FREIGHT RAILWAY TRAFFIC: REDUCTION OF WHEEL RADIATION BY MEANS OF TUNED ABSORBERS
  P. Bouvet, N. Vincent, A. Coblenz and F. Demilly
[Abstract]

The rail, sleepers and wheel are the predominant acoustic sources for freight rolling noise. In the frame of the ''Silent Freight'' European project, optimised wheels have been developed to reduce the noise from rolling stock. This article deals with the optimisation of dynamic absorbers on a wheel.

The theoretical methods used for the design of tuned absorbers are presented. A finite element model is used to calculate the wheel modal parameters (natural frequency, mode shape, modal mass and damping). The wheel vibration response and wheel radiation are calculated with the TWINS software package (developed for the European Rail Research Institute). It is shown that in combination with a wheel shape optimisation, the use of tuned absorbers can lead to a wheel noise reduction of about 10 dB(A).

Dynamic absorbers have then been developed and set on prototype wheels. These wheels have been mounted on a test train in order to assess the actual noise reductions during field measurements. The measured wheel noise reduction is presented and compared to the theoretical result : a good agreement is found between measurements and calculations.

Keywords : railway wheels, damping, tuned absorbers, rolling noise, modelling.

Demizieux, P.

• IN SITU METHODS FOR THE CHARACTERISATION OF ROAD NOISE BARRIERS EFFICIENCY
  F. Anfosso-Lédée, V. Steimer and P. Demizieux
[Abstract]

Different acoustic properties of road noise barriers can be measured on site : global characteristics of insertion loss, or intrinsic characteristics of sound absorption and sound transmission. For insertion loss measurement, the standardised method ISO 10847 was tested on a basic case of real road barrier. The reliability of the method was checked, including location of receiver points and reference point, duration of measurements, meteorological considerations, comparison of direct and indirect approach on an equivalent site. The results of three independent laboratories were compared. Major practical difficulties arose showing a lack of applicability of the method. Moreover, rather poor comparison was obtained with this ISO method, showing that direct and indirect methods are not equivalent and meteorological conditions should be better defined, especially for long range characterisation of insertion loss (around 100 meters). Typical duration of measurements should be extended to 15 to 30 minutes, and a correcting factor of 4 dB instead of 6 dB should be considered for receiver points located on a reflecting surface. For intrinsic characteristics of sound absorption and transmission, an experimental comparison was made between two impulse methods : the French standardised method AFNOR 31089 using a gun shot, and Adrienne  method developed by a European research group and suggested as a future European Standard. This later method uses an MLS signal plus subtraction technique to get better results in low frequencies. A rather good agreement was found between both methods and differences are discussed.

Depuydt, M.

• EXPERIENCE LEARNED FROM ARIANE 5 WIND TUNNEL TESTS REGARDING AERODYNAMIC NOISE ON UPPER PART AND BUFFETING LOADS ON REAR PART
  B. Troclet and M. Depuydt
[Abstract]

Launch vehicles are subjected to steady and broadband unsteady pressure fields during transonic and maximum pressure dynamic phases. These pressure fields may be very severe in launch vehicle zones which have relatively rapid local variations of geometry. These geometrical variations lead to adverse pressure gradients and separated flow in significant part of the launch vehicle. These aerodynamic loads, which depend on vehicle geometry, Mach number and trajectory, may damage structures or subsystems and be dimensioning. Consequently, they have to be considered in the design of vehicles. This paper deals with the experimental analysis of : - aerodynamic loads on the ARIANE 5 upper part (5- 2000 Hz, full scale), - buffeting loads on the ARIANE 5 rear part (5- 80 Hz full scale). The experimental analysis have been performed in NLR and ONERA wind tunnels respectively. These test campaigns have been conducted on the responsibility of AEROSPATIALE within the framework of a CNES contract. After describing the tests and phenomena associated with these kinds of excitations, the following topics are discussed : - the test result analysis methods :The way of defining full scale loads from reduced scale tests regarding aerodynamic and buffeting, - the results in terms of levels, of correlation functions and comparison with results given by open literature, Lastly, the loads derived from reduced scale tests are compared with the ones measured in ARIANE 5 flight.

Dequand, S.

• SELF-SUSTAINED OSCILLATIONS OF GRAZING FLOW ALONG A HELMHOLTZ RESONATOR: A SIMPLIFIED THEORY.
  S. Dequand and A. Hirschberg
[Abstract]

Vortex induced self-sustained oscillations of the grazing flow along a Helmholtz(-like) resonator is considered at moderately high acoustical amplitudes. A modification of the single vortex model proposed earlier in the literature is discussed to take more accurately the effect of the geometry of the edges into account. The simplified model provides an analytical solution of the acoustical particle displacement in the neck of the resonator for a sharp-edged opening. We assume that the vorticity is concentrated into line vortices convected at a constant speed along a straight line from the upstream edge to the downstream edge. We propose a procedure in order to avoid the spurious singularity of the downstream sharp edge. The analytical results obtained by means of this simplified model are compared to original models and experimental results. The model predicts accurately the critical Strouhal numbers for oscillations and provides an estimation of the pulsation amplitude within a factor two. In particular the model removes spurious higher order hydrodynamic modes observed in the earlier models.

Descornet, G.

• LOW-NOISE ROAD SURFACE TECHNIQUES AND MATERIALS
  G. Descornet
[Abstract]

One reviews the state-of-the art in designing and building low-noise road surfaces. The following are considered: - Resin-bound surface dressing - Thin bituminous layers - Porous asphalt - Porous cement concrete - Exposed aggregate technique for cement concrete - Diamond grinding of cement concrete - Special structure: the ''euphonic'' pavement - Special material: expanded clay - Special material: rubber They are examined with respect to the following viewpoints: description, acoustic and non-acoustic performances and drawbacks. Research needs for further noise reductions are suggested. It is concluded that any significant progress requires widening the sound absorption spectrum of the pavement structure with respect to present achievements.

• VEHICLE NOISE EMISSION ON WET ROAD SURFACES
  G. Descornet
[Abstract]

A measurement campaign has been carried out with a view to determining the influence on vehicle noise emission of the presence of water on the road surface. The noise measurements were made according to the so-called CPB Controlled Pass-By  method using a car and a 16t, two-axle lorry. These measurements were performed both in dry and wet condition of the surface on fourteen road sections including a wide range of pavement materials and textures among which porous surfaces. The analysis of the recorded noise signals, also involving the examination of their spectra, has revealed the influence of a so far overlooked phenomenon by which the noise level on the wet surface is sometimes lower than on the dry surface. This effect is competing with the well-known noise level increase due to water droplet projections. The former attenuates the low and medium frequency components of the noise on the wet surface while the latter produces a typical noise level increase in the medium and high frequencies. Although the newly observed phenomenon occurs with the car as well as with the lorry, it is more frequent and important with the latter. As texture measurements were carried out by means of a laser profilometer, the overall influence of the wet surface on vehicle noise has been related in this study to surface texture.

Desmet, W.

• AN EFFICIENT PREDICTION TECHNIQUE FOR THE STEADY-STATE DYNAMIC ANALYSIS OF FLAT PLATES
  B. Van Hal, W. Desmet, D. Vandepitte and P. Sas
[Abstract]

The finite element (FE) method is the most commonly used prediction technique for solving time-harmonic plate problems. Since the dynamic variables within the plate domain are expanded in terms of simple, approximating shape functions, a large amount of elements is required to get a reasonable prediction accuracy and this amount increases with frequency. This may result in large, computationally expensive models, so that the use of FE models is practically restricted to low-frequency predictions. A newly developed technique, which is based on the indirect Trefftz method, uses wave functions, which are exact solutions of the governing partial differential equations, to expand the dynamic variables. The contributions of the wave functions to the field variable solutions are obtained from a weighted residual formulation of the boundary conditions. Since an approximation is only involved with the boundary conditions, the main asset of this method, compared with the FE method, is the small size of the resulting prediction model. The major drawbacks of the method is that the prediction model becomes fully populated and frequency-dependent. This paper compares the performance of the new prediction technique with conventional FE models for several convex plates with a mixture of various types of boundary conditions. These examples illustrates that the new technique provides a high (displacement and stress) prediction accuracy with smaller computational efforts. In this way, the Trefftz-based prediction technique can be applied up to much higher frequencies, allowing accurate deterministic predictions for the mid-frequency range.

Di Costanzo , F.

• ACOUSTIC COUPLING OF A CENTRIFUGAL COMPRESSOR
  F. Di Costanzo and E. Edon
[Abstract]

The paper deals with the acoustic coupling of a centrifugal compressor and its piping system. During the tests in similitude conditions at low pressure and low load, a centrifugal compressor exhibited, at low flow rate, unusual very low frequency vibrations. An acoustic study of the piping system of the lest loop was performed by TECHNICATOME with the LACTUS software (a computer-aided design tool for noise-free and reliable piping networks). It was found that the acoustic resonances were in accordance with the vibration frequencies measured on the compressor, and that the levels of the vibration peaks were proportional to the acoustic transfer function amplitudes. The absence of vibrations during the full load tests confirmed the assumption of the acoustic coupling between the compressor and the piping system of the test loop whose acoustic resonances amplified the pressure pulsations and forced the low frequency vibration of the rotor. The paper gives a brief description of the acceptance tests on specific loops (similitude and full load tests). Then, the experimental investigations of the phenomenon and the acoustic studies of the test loops by mean of the LACTUS software are presented for both similitude and full load tests. Finally, the main results are given (comparison between measurements and simulation), like the concluding remarks : - the hydro or aerodynamical excitation generated by a rotating machine such as a pump or a compressor may be amplified by the acoustic resonances of the piping network, - the modelling of pulsation and vibration phenomena is necessary for the success of the design of machines an piping networks, - a ''four-pole parameters'' method, such as the one used by the LACTUS software, has proven to be an efficient and effective method for the prediction and analysis of dynamic phenomena in piping networks.

Di Giulio, A.

• A PROBABILISTIC MODEL FOR A BETTER EVALUATION OF WORKER NOISE EXPOSURE
  E. Cagno, A. Di Giulio and P. Trucco
[Abstract]

In the evaluation of the worker noise exposure the definition of a standard working-day is difficult due to the uncertainty related to exposure time, environmental distribution of sound levels (areas) and operative conditions. Such contributions of variability to the evaluation parameters make the overall index LEP,d little significative and representative of real exposure conditions. The paper presents a probabilistic model, within a wider investigative methodology, that allows to associate to the numerical value of personal noise exposure level its variability. This makes it a sound term of comparison with requested regulatory standards and allows to associate to the evaluation also medium-long period information, i.e. about periods (of the working-day) in which measurements are not made. The model has been applied to a case study of an automated plant (rotary press), where operators carry on maintenance and adjustment activities. Thus they don't stay always in the same position, but shift randomly from one position to another during the working-day according to machine needs. It is evident that in such a case the definition of a standard working-day for an operator is difficult not only due to different intervention conditions, but also because of a number of different factors allowing for parameters uncertainty (first of all the duration of intervention that is not possible to know in advance). Starting from the model, a software package has been developed and tested in the case study.

Di Giulio, G.

• HAND-ARM VIBRATION MEASUREMENTS BY LASER VIBROMETRY AND CAPACITIVE SENSOR MATRICES
  G. Miccoli, R. Deboli, G. Di Giulio, J. Mariani, N. Paone and G. Rossi
[Abstract]

The use of accelerometer based measurement techniques in order to evaluate hand-arm transmitted vibrations has shown high levels of uncertainty in many applications. The aim of the present work consists on illustrating a new hand-arm vibration measure-ment technique. The technique has been applied in order to characterize hand held ma-chine vibrating parts/components usually coming into contact with the operator (hydrau-lic breaker handles, agricultural/earth moving machine steering-wheel and levers). The purpose consisting on identifying machine structural modifications aimed at reducing vibrations and, taking into account also ergonomic aspects, improving operator comfort/working conditions. The measurement technique proposes a parallel application of a) laser vibrometry b) capacitive sensing element matrices. The use of no contact laser vibrometer avoids many measurement problems due to the presence of transducers on the hand and/or the vibrating surface. Moreover, the laser beam scanning characteristics allow a fast and spatially detailed data acquisition. The contact pressure distribution at the operator's hand/machine handle interface has to be known in order to evaluate hand-arm vibration transmission. Moreover, the global grip force applied by the operator turns out to be an important parameter to be considered. On this purpose, capacitive sensors matrices have been developed and optimised to fit the different tested applications. The proposed measurement technique represents the topic of an European Community funded project in the Framework IV, SMT programme. The results shown in this work are those till now achieved in conclusion of the second year of activity of the project itself.

Di Sante, R.

• A REFINED BE TECHNIQUE FOR MODELLING RADIATION AND SCATTERING FROM VIBRATING STRUCTURES: EXPERIMENTAL VALIDATION OF BEM RESULTS OBTAINED USING LASER DOPPLER VIBROMETRY
  R. Di Sante, R. Bernetti, G. Rossi and A. Ambrosini
[Abstract]

In this paper, a refined Boundary Element technique, developed to model radiation and scattering from vibrating structures in the frequency domain, is validated in the case of a small reverberating room by comparison with acoustic measurements. An experimental set-up was built consisting of a box-shaped structure, with a wall excited into vibration by an electro-dynamic shaker. A fairly good agreement was found between numerical and experimental results. In order to ease the definition of boundary conditions in the case of experimental vibration data, a special interface with a Scanning Laser Doppler Vibrometer was also developed.

Diamond, I.

• MULTILEVEL DISCRETE TIME HAZARDS MODELS OF SLEEP DISTURBANCE DUE TO AIRCRAFT NOISE AT NIGHT
  I. Diamond, L. Reyner, J. Horne and V. Brooks
[Abstract]

This paper provides a re-analysis of the data from a large 1991 UK Sleep Study. Data for 400 subjects were collected on each of 14 nights and include whether or not the individual was disturbed in any particular 30second epoch. The data set, comprising over 500,000 observations is analysed using multilevel discrete time hazards models to assess the xtent to which sleep disturbance at different times of the night is related to aircraft noise.

• PERCEPTIONS OF HEALTH EFFECTS OF NIGHT AIRCRAFT NOISE
  I. Diamond, A. Smith, S. Hayward, S. Heatherley and Z. Sheppard
[Abstract]

Dib, R.

• ANALYSIS OF THE NOISE, VIBRATION AND TRANSMISSION CHARACTERISTICS OF INDUCTION MOTORS
  R. Dib, J.-C. Henrio, A. Hubert, G. Friedrich and P. Wagstaff
[Abstract]

The noise and vibration characteristics of induction motors constitute one of the principal problems facing their use in industrial applications. The high frequency components generated by the signal modulation of the electronic convertos are particularly disturbing and difficult to suppress. In order to reduce these effects the pulse width modulation frequency can be increased to above the range of the human ear, but this approach leads to reduced motor efficiency due to the higher electromagnetic losses and very high stress of the power electronics components. In order to successfully deal with these noise problems the internal vibration generation mechanisms, the transfer characteristics to the structure and the noise radiation by the motor body and the rest of the machine structure have to be thoroughly investigated. In this paper we deal briefly with the predicted results for the primary generation mechanisms in the motor, the effects of the coupling of the internal mechanisms with the vibration characteristics of the motor body and investigate the radiated sound levels of the motor under free running conditions. One of the specific problems is to quantify the vibrations transmitted to the machine structure when the motor is coupled to the machine. The transmitted vibrations are then transformed into noise levels which may be considerably greater than that generated directly by the motor. In order to investigate these effects, inverse force identification techniques were used to characterise the forces at the motor- structure interface. It is shown that the vibration response can be estimated using a relatively simple force distribution model at the motor flange and structure interface.

• NOISE AND VIBRATION ANALYSIS OF MACHINE TOOLS USING INVERSE METHODS.
  P. Wagstaff, J.-C. Henrio, R. Dib and C. Chassaignon
[Abstract]

The noise and vibration characteristics of machine tools create environmental problems and have an important influence on the quality of the finished surface as well as limiting the production rate due to increased tool wear and breakage. To solve these problems the exact identification of the sources of vibration is essential. For the turning process the dynamic forces acting at the tool-workpiece interface may be estimated with the aid of force dynanometers. At the higher frequencies associated with chatter and other vibratory phenomena the inertia andinternal resonances of this type of measurement system mask the true dynamic forces at the tool-workpiece interface. This information is required in order to correctly identify and model the vibrations generated by the cutting process. To solve this problem an inverse method of identification of the dynamic forces at the tool-workpiece interface was applied using previously measured frequency response functions measured on tool mount structure associated with accelerations mesured during the cutting process. The matrix of frequency response functions between the three input force directions and the output response data is processed by pseudo-inversion with the aid of the singular value decomposition to identify the dynamic force spectra at the tool-workpiece interface. Point impedance measurements may also be used to identify the acceleration response of the tool point. A simple model based on the work of Marui was developed to identify the cutting process parameters with different conditions. The methods have been successfully applied to several types machine tool to obtain a better understanding of the vibration generation mechanisms.

Dickens, J.

• SOLUTION OF A NOISE PROBLEM FOR AN ASYNCHRONOUS ELECTRICAL MOTOR
  J. Dickens
[Abstract]

This paper describes the effective elimination of tonal noise generated by a machine consisting of an asynchronous electrical motor driving a fan. Conventional methods aimed at reducing the air-borne and structure-borne noise by employing noise enclosures and vibration isolation elements were unsuccessful. The motor was a squirrel cage, three phase, two speed induction motor, and the noise source was identified as electromagnetic in nature. The solution was to electrically reduce the noise at its source, without compromising the operation of the machine. This represented an electrical solution to an acoustic problem. Experimental data are presented, and show a noise reduction of 20 dB.

• VIBRATION ISOLATOR PROPERTIES OF A PHASE MIXED POLYURETHANE
  J. Lee, J. Dickens, J. Fedderly, G. Lee and B. Hartmann
[Abstract]

As part of a program to relate the chemical composition of polymers to their vibration isolation properties, a polyurethane of known, controlled composition was synthesized and evaluated. Based on our earlier studies , the first polymer selected to be evaluated was phase-mixed to avoid the complication of hard segment crystallinity. The polymer was synthesized from poly(tetra methylene ether glycol) of molecular weight 1400 reacted with 4,4'-diphenylmethane diisocyanate and chain extended with dimethyl propanediol. Measurements were made in the new Vibration Isolation Test Facility . Four-pole parameters will be presented as a function of frequency from 5 Hz to 2 kHz at different temperatures and static loads. Results at low load will be compared with predictions based on dynamic mechanical measurements of the moduli of the material.

Didkovskiy, V.

• IDENTIFICATION TASK FOR ACOUSTIC MODEL OF AIRCRAFT AND ENGINE NOISE TESTING RESULTS
  O. Zaporozhets, V. Tokarev and V. Didkovskiy
[Abstract]

Strict requirements to the accuracy and reliability of aircraft noise computation results provide for use of more complicate acoustic model of aircrafts of various type. Previously it was proposed to solve the identification task for improvement of these models. Now it is shown how to use the results of engine noise testing (just before their implementation on aircraft) for improvement of models that don't need the flight measurements. The efficiency of the method is proofed by comparison between different approaches.

Diehl, R.J.

• VEHICLE-MOUNTED SHIELDS AND LOW TRACKSIDE BARRIERS FOR RAILWAY NOISE CONTROL IN A EUROPEAN CONTEXT
  R. Jones, M. Beier, R.J. Diehl, C. Jones, M. Maderboeck, C. Middleton and J. Verheij
[Abstract]

The control of railway rolling noise by a combination of vehicle-mounted shields and very low, close, trackside barriers, has been explored extensively in the past, for example by British Rail Research, where an acoustically efficient experimental system was developed in the early 1990's. Within the EC 4th Framework projects Silent Freight and Silent Track, the concept has been further developed by formulating a system which was analytically optimised prior to manufacture and testing, and which would be acceptable, in gauging terms, for full interoperability across Europe. The paper presents the analytical and design process which was applied in specifying the parameters of the new interoperable system, as well as the results of subsequent full scale aco

• PREDICTION OF RAILWAY INDUCED GROUND VIBRATION
  R.J. Diehl, M. Beier, G. Hölzl and H. Waubke
[Abstract]

The wheel/rail-impedance modell RIM for the prediction of railway noise has been combined with soil modells to predict ground vibration induced by rail and wheel tread roughness as well as parametric excitation. The soil calculations are based on an analytical modell of a horizontally layered halfspace. The tool can be used to study the effects of the application of various mitigation measures suitable for track applications: resilient rail fastening systems, sleeper soffit pads, ballast mats and floating slabs. Furthermore the influence of the soil on the vibration levels can be investigated. The paper describes the modell, and its applications and shows results for two sites: an application of a floating slab in a tunnel and applications of soil improvement methods and ballast mats for surface lines. The results from the predictions are compared with those from measurements provided by DB AG also used for the ERRI project RENVIB.

Dine, C.

• RAILWAY NOISE SOURCES. AN OVERVIEW OF RECENT APPROACHES IN IDENTIFICATION, MODELLING AND REDUCTION POTENTIALS
  P.-E. Gautier, C. Dine and B. Hemsworth
[Abstract]

As environmental requirements become tighter, understanding physics and relative importance of railway noise sources, became important, especially in view of global railway noise reduction. This paper aims at presenting an overview of recent developments in the knowledge of noise sources on trains, either by experimental identification or from modelling. It will be shown that different levels of accuracy or globalisation are required, depending on subsequent use of the knowledge : predicting railway traffic noise for designing a new line does not require the same modelling as assessing potential future reduction in railway noise emission. First, an overlook of global trends in identification of noise emission from railway system will be presented (for homologation purpose, for noise prediction in environment or even for specification design of ever quieter railway). Then, specific problems relevant to different sources (rolling noise, aerodynamic noise, fan noise...) will be emphasised. It will be shown that, in some cases, in order to get a full insight into reduction perspectives, refinements in modelling or understanding phenomena are needed. Finally, from the experience of several on-going research projects throughout Europe, global reduction potentials for various types of trains will be presented, in line with recent progress on operational systems. The needs for further progress in either source reduction or global modelling will be identified.

• A NEW FRENCH METHOD FOR RAILWAY NOISE PREDICTION
  J. Defrance, Y. Gabillet, D. Van Maercke, C. Dine and P.-E. Gautier
[Abstract]

Regulations for railway noise are becoming more and more stringent and, along with a decrease of maximum acceptable sound levels, a more accurate environmental prediction is sought. This has brought about the need of sound level calculations at long ranges including meteorological effects. A new French prediction method for Railway Noise (NMPB-FER) has thus been developed on the basis of an already existing one for road traffic noise. This method specifies two calculation procedures: with meteorological conditions favourable to sound propagation and with atmospheric homogeneous conditions. The result is a long term equivalent A-weighted noise level obtained by the combination of the two calculations and taking into account the percentage of time when favourable conditions occur. The railway source is modelled as two independent sources, one being close to the rail/wheel contact plane (concerning highest frequencies) while the other is located at a height appropriate to a simple but correct representation taking into account aerodynamic sources (for lowest frequencies). This method implemented in the MITHRA ray tracing software offers some original specificities: barrier-carriage multi-reflections effects taken into account, calculation of the noise level vs time evolution, railway noise sources split up according to the total length of the convoy, composition of trains and determination of sound power level characteristics achieved by assembling the wanted rolling elements (locomotive and carriages, types and numbers). Input to the model can easily be obtained from multi-spectrum measurements close to the railway.

Ding, H.

• TRAFFIC NOISE AND HUMAN LIVING ENVIRONMENT
  Z. Liu, H. Ding and L. Hao
[Abstract]

Road traffic noise has become more and more important in city ambient noise than ever. China is a developing country, recent years, accompany with the flying economic, the level of city road traffic noise increasing greatly. At the same time, people are dreaming for a better acoustics environment. So we represent a new method on the evaluation of city ambient noise,protect people's living environment form noise damage is the precondition of the evaluation. Now the method is certifyed can acquire well effect in the evaluation in some area in Beijing.

Dittrich, M.

• A FRAMEWORK FOR MEASUREMENT METHODS FOR RAILWAY NOISE
  M. Dittrich and M. Janssens
[Abstract]

Railway pass-by noise measurements are usually performed with a single microphone at 25m or 7.5m distance. The data thus obtained contains noise contributions from both the vehicle and the track. Although measured noise levels are well repeatable at the same site with the same train, additional techniques are required to be able to make such measurements reproducible between different sites. This is due to variation of rail roughness and track properties. In recent years a number of new techniques have been developed in the European project METARAIL which enable separation of contributions from track and vehicle and independent characterisation of vehicle and track. In this paper available methods are put into perspective and four levels of complexity are given. The type of method best used depends on the purpose of the measurement. For example, proper assessment of performance of bogie shrouds on rail vehicles requires that the noise reduction of vehicle noise should be quantified, as the total noise may show little change due to the contribution from the track.

With the increasing need for representative noise emission measurement of rolling stock and anticipated European regulations in this field, appropriate but practicable measurement methods are required. Some potential improvements to the existing standards are discussed.

Doi, T.

• COMPUTATIONAL AND EXPERIMENTAL APPROACH TO THE REDUCTION OF PRESSURE VARIATION CAUSED BY THE PASSAGE OF A HIGH-SPEED TRAIN
  T. Doi, K. Yokokawa and J. Kaku
[Abstract]

High-speed train moving causes a pressure distribution around the nose part of the train. The pressure field moves with the train, and a resultant pressure variation is observed at a position on the ground. It may bring environmental problems such as a rattle of windows and fittings. This paper shows the result of a computational and experimental study of the reduction of the pressure variation. The pressure field depends on train speed and nose configuration. A past study used an axisymmetric model of nose configuration. This study, however, uses a non-axisymmetric model to simulate the real nose configuration. The validity of the model is examined using the results of a numerical calculation and a scale-model experiment. In the calculation, we adopt a simple method to distribute flow sources on the surface of the three-dimensional train nose body. The result of calculation was in a qualitative agreement with that of the scale-model experiment. It suggests that the non-axisymmetric model together with the three-dimensional source distribution method is applicable to the analysis of pressure variation due to the passing of a high-speed train.

Dombi, I.

• ENVIRONMENTAL NOISE REDUCTION OF LARGE INDUSTRIAL PLANTS
  I. Dombi and M. Bite
[Abstract]

The evaluation of noise reduction in a large Hungarian power stations needs such methods which are capable to follow the expected results of planned technical solutions in noise reduction. Using our method we may have the expected results without establishing technical structure of the noise reductions. The method is based on the SOUNDPLAN computer program. The actual poster lecture presents a total acoustical planning procedure including ways of noise pollution's reduction.

Donadon, L.V.

• THEORETICAL COMPARISON OF ACTIVE NOISE CONTROL USING POTENTIAL ENERGY ERROR SENSING AND INTENSITY ERROR SENSING
  L.V. Donadon and J.R.D.F. Arruda
[Abstract]

This paper presents a theoretical comparison between pressure and intensity-based control strategies for active noise control in ducts. The control methods used for each strategy are the Frequency-Domain, Filtered-X LMS, which uses pressure as the cost function, and a method named ASIC (Active Sound Intensity Control), which uses mean active sound intensity as the cost function. A duct with two types of termination - open-ended, and rigidly terminated - was modeled using the Spectral Element Method. These models allowed the evaluation of the performance of the controllers in environments with propagation and reverberation. The criteria used to analyze the results were the potential energy density, the mean active intensity, and the total acoustic power radiated by the sources working together, compared with the primary source alone.

Dong, H.

• FINITE DIFFERENCE SOLUTION OF SOUND PROPAGATION OVER POROUS GROUND
  H. Dong, J.M. Hovem, L.R. Hole and C. Madshus
[Abstract]

This paper presents an axis-symmetric pressure-velocity finite-difference formulation (PV-FD) for sound propagation over ground based on Biot theory. Some typical results of simulation are presented and comparisons with the measurements during airblast tests performed in Haslemoen, Norway are presented in order to verify the proposed model. The model can also handle range-dependent and topographic ground. Representative results are presented for two cases of uniform ground with local alterations: one where a region of the ground is assigned a higher permeability, and the other where the same zone is replaced by stiffer zone. The case with a hill above homogeneous poro-elastic ground is also considered. The developed numerical code is shown to be a practical tool for simulating complicated ground features and a useful tool in calibrating empirical sound prediction models.

Dool, T.C.V.D.

• MICROPHONE ARRAY TECHNOLOGY FOR AIRCRAFT NOISE MEASUREMENTS
  M.M. Boone, T.C.V.D. Dool, P. Sijtsma and U. Stelwagen
[Abstract]

Presently available aircraft noise measurement systems are based on single channel omnidirectional microphone technology. An important disadvantage of this approach is that these systems are equally sensitive to other noise sources as to the airplanes to be measured. Furthermore they are sensitive to turbulence noise caused by wind. In this paper new approaches for the measurement of aircraft noise are presented that are based on microphone array technology. Using array technology extraneous noise sources and wind noise can effectively be suppressed. Results on optimization of array designs and signal processing for this application will be presented that are based on array processing theory as well as simulations and test measurements.

Driot, N.

• PREDICTION OF GEARBOX NOISE VARIABILITY FROM TOLERANCES ON PROFILE AND HELIX ANGLE
  N. Driot, E. Rigaud, J. Sabot and J. Perret-Liaudet
[Abstract]

Measurements on a population of a given kind of gearboxes reveal a high noise level variability due principally to tolerances on each gear design parameters. Gearbox noise results principally from vibrations of its housing induced by the static transmission error. Two main goals are addressed here: the first one is to rank the influences of each design parameter for given tolerances and their interaction on the total acoustic power with a full factorial experiments and variance analysis. The second issue consists of an estimation of mean value and standard deviation for noise level with modified Taguchi's method. We consider a gearbox fitted out with one helical gear inside a housing containing only one elastic radiating face, two gear design parameters (profile, helix angle) and one rotation frequency. Firstly, for each trial of the full factorial experiments (9 trials) we compute the static transmission error. Then we solve the system of second order differential equations with periodic coefficients with an iterative spectral method to obtain the housing vibratory response. Secondly, an integral direct baffled formulation coupled with boundary elements is implemented by SYSNOISE to compute the total acoustic radiated power. Variance analysis reveals a distinct predominance of helix angle and presence of interaction between both parameters. Variability appears for each ray of acoustic spectrum. The standard deviation is more sensitive to tolerances on helix angle. The statistical Tchebycheff's inequality provides the probability of a maximum noise level. This methodology works well. It is very easy to implement and is accurate for lightly non-linear responses.

Drnevich, V.

• TIRE/PAVEMENT INTERACTION NOISE RESEARCH ACTIVITIES OF THE INSTITUTE FOR SAFE, QUIET, AND DURABLE HIGHWAYS
  R. Bernhard, N. Franchek and V. Drnevich
[Abstract]

Tire/road interaction noise is the major source of highway sideline noise at highway speeds. Increased traffic flows and population densities have caused a greater interest in this source of environmental noise. The Institute for Safe, Quiet, and Durable Highways (SQDH) was established at Purdue University in 1999 to investigate the development of quiet highway technology that is safe, durable, and economical. This Institute is a joint effort between the Schools of Civil and Mechanical Engineering. The goals of the SQDH Institute include education, research, and technology transfer activities. The research program of the SQDH Institute is intended to be complementary to world-wide research on tire/pavement interaction noise. Both tire and pavement issues will be studied. Initial emphasis will be given to fundamental investigations of the mechanisms of tire/pavement noise generation and control. Laboratory facilities will be constructed to facilitate acoustic and vibration measurements of tires rolling on realistic road surfaces. In addition, analysis methods will be developed to better understand wave transmission and sound radiation from tires. Future work will involve implementation of the understanding of tire/road noise generation mechanisms to the practical issues of quiet highway construction and maintenance, material design, and traffic management. This application of quiet highway technology will hopefully reduce the need for noise barriers. A review of ongoing SQDH Institute research programs and available results will be presented. Future plans and potential collaboration

Dubail, P.

• THREE-DIMENSIONAL LOCALISATION AND CHARACTERISATION OF ACOUSTICAL SOURCES IN A TRUCK CABIN
  P. Dubail and M.E. Zakharia
[Abstract]

In a framework of acoustic comfort, an accurate localisation - in range and angles - of the sources transmitting noise to the driver has been investigated. The aim of such a localisation is to act on the predominant sources in priority, in a given frequency range. The sources are either vibrating ones corresponding to the excitation point, or fictive ones corresponding to complex propagation and multiple reflections on the cabin elements. An experiment has been conducted on a real cabin with a single point of excitation. The mechanical excitation is achieved via a shaker, and frequency-modulated signals have been used covering a very wide frequency range (0.03 to 15 kHz). Both active and digital corrections have been applied. We have employed two crossed line arrays of 112 microphones in reception, and all the signals have been digitized and processed later on. Standard wideband beamforming and beam steering have been used on both arrays, in the time domain. For every frequency (or frequency range), the 3D localisation (time, horizontal and vertical angles) of sources are achieved. The major sources have been isolated using the Radon transform. A fine major analysis has been performed in order to provide their spectral content, in addition to their 3D localisation.

Dubbink, D.

• HOW COMMUNITY GROUPS RESPOND TO ENVIRONMENTAL NOISE SIMULATIONS
  D. Dubbink
[Abstract]

The Interactive Sound Information System (ISIS), developed by the author, is a ''new media'' package designed to explain and de-mystify the complex metrics used to describe noise impacts. Central to the ISIS package is the idea that ''real'' noise examples, shaped to reflect local situations, are the very best way to build an understanding of noise management issues. Presentations can be customized to fit specific geographic settings. Presentation experiences in hundreds of community settings have produced interesting reactions from both audiences and sponsors. The technology works quite well at a community information level. Its accuracy is verifyable. Community groups and decision makers quickly appreciate the system's interactive capabilities and put it to use testing ideas. They trust in results. In contentious situations, the system is viewed as a ''neutral broker''. Political acceptablity of the system is more clouded. Program sponsors often have a project they wish to advance (or oppose)and want a noise demonstration system that supports their arguments. Broadened public access to authentically interactive noise demonstration technolgy may not fit this agenda. The popularization of noise planning

Dubois, D.

• AUDITORY COMFORT ON BOARD OF TRAINS : PASSENGERS POINT OF VIEW.
  M. Mzali, D. Dubois, J.-D. Polack, F. Letourneaux and F. Poisson
[Abstract]

The work presented in this paper deals with is a survey about comfort in trains. To understand the importance given to sound in comfort judgement inside trains, a survey was performed with travellers. We were looking for how the train trip taken as a whole is judged and which elements are taking part in comfort. Therefore, a questionnaire semi-directif  has been built, based on a psycholinguistic approach allowing not to direct the answer of the subject nor confine him into already defined categories. Among the whole of questionnaires, a sample was selected, the answers were classified and categories extracted to analyse data given by the questionnaires. This presentation aims to explain briefly the methodology involved and to display the following results. First, on the different comfort's elements, the results showed the importance of the aspects acoustic  and vibratory, kinaesthetic , which are coming out as first reasons of travellers' dissatisfaction. Subsequently, a list of sound sources and events perceived by travellers as their judgement, was established. We noticed differences in judgements induced by types of noises, which should be related to meaning given to the noise, and also by objective aspects as types of trains or types of class (1st and 2nd class). An other major result is that it is difficult to directly relate dissatisfaction to physical parameters in the way the comfort is depending on the activities in which the traveller is involved. This later remark opens to methodological issues : questionin

Ducruet, P.

• EXPERIMENTAL STUDY OF ROAD TRAFFIC NOISE CONTROL BY A PINE FOREST
  N. Barriere, Y. Gabillet, J. Blais, J. Defrance, P. Ducruet and F. Gaudaire
[Abstract]

In order to precisely bring to the fore the effect of meteorology on sound propagation through forests, an important measurements campaign has been carried out in the French Landes forest mainly composed of pine trees. The originality of the experiment is that road traffic noise and meteorological conditions have been measured simultaneously for both a forest situation and a plain situation, this for different positions of the receiver. All valid measured data have then been classified according to three propagation conditions: favourable to propagation, unfavourable to propagation and homogeneous conditions. As expected, the results depend on these conditions. In favourable conditions, the gain brought by the forest is between 3 and 5 dB(A) with the receiver at least 100 m away from the road. This meteorological situation occurs very often at night due to a temperature inversion phenomena. Moreover, it is of most interest since it corresponds to the periods when the annoyance due to the road in a plain situation is the highest. In unfavourable conditions, the forest may increase somewhat the received sound level. In homogeneous conditions, the sound propagation through the forest is not appreciably affected by meteorology anymore but only by the scattering by the trunks and foliage. Finally, these results have permitted to validate a new calculation method for the attenuation of road traffic noise by forests based on a fast implementation of the Parabolic Equation.

Dufournet, D.

• A LIGHT SOLUTION FOR ACOUSTIC SOURCE LOCALIZATION
  F. Magand and D. Dufournet
[Abstract]

The article presents a spatial localisation technique applied to MADRAS methodology. MADRAS is a software measurement assistant for automatic noise source recognition. It is based on a tree classifier using neural networks and spectral shape learning process. The presented module was developed and tested on a PC-based 4 channels analyser (Harmonie). Complementary to signal processing approach, the spatial localisation module is using a tetrahedral antenna. Array processing is applied to acquired signals. This paper presents the implementation of the localisation process on the Harmonie platform. The possible application areas of automatic localisation of acoustic sources is discussed. Two situations are described in more details : outdoor environment (vehicle displacement and moving noise source survey) and closed volume (squeaks and rattle problem in vehicle passenger cabin). Performances and limitations are presented, as tested in real situations.

• ADAPTIVE DETECTOR FOR NOISE SOURCES AUTOMATIC RECOGNITION
  D. Dufournet and P. Jouenne
[Abstract]

The paper presents an improvement of sources' detection applied to MADRAS methodology. MADRAS is an acoustic monitoring system that features the automatic recognition of noise sources in environment. The described improvement concerns the detection step, adapting it to better process complex situations and in particular multiple sources' environment. The previous detection criteria, based on an adaptive global acoustic level threshold, are discussed and their limitations emphasised. The new proposed solution is based on a spectral adaptive shape criteria. Its realisation applies the power of a PC-based dual channels analyser (Symphonie). The principle is to compare two signal estimations in consecutive temporal moving windows. A larger window is used to estimate a moving background noise model. This model is compared to innovation, e.g. shape of the current signal in a short-time window. A contrast function linked to an finite-state automation decides whether there is an acoustic event apparition. An audio signal recording is then triggered for a further processing in the automatic recognition procedure. Different estimators can be used for noise (background) and signal (source) models, such as third octave spectrum or specific loudness. The in situ tests show remarkable simultaneous robustness and sensitivity of the detector. The audio events are detected with high degree of confidence, up to 20% better than in the previous model. The current work consists of adapting different stages of the source class

Duhamel, D.

• TIRE/ROAD NOISE : COMPARISON OF 2D AND 3D MODELS FOR HORN EFFECT
  F. Anfosso-Lédée, P. Klein, A. Fadavi and D. Duhamel
[Abstract]

This paper deals with the amplification effect of tire/road contact noise, also called horn effect , that is due to the multiple reflections between the curved and hard surface of the tyre and the road pavement. This ''horn effect'' is expected to be reduced on porous pavements due to the properties of sound absorption. The approach described here is two dimensional : a rigid cylinder of infinite length is set on a rigid flat road surface. An acoustic line source is located on the tire near the contact. The amplification is calculated at a receiver point in the horn, first using an analytical model, based on the modal decomposition of the sound pressure. In order to introduce sound absorption properties on the road surface, a 2D-BEM model was used. Agreement for rigid case between analytical and BEM models was checked. Then, porous road pavement was introduced in the BEM, using a phenomenological model with 4 parameters (porosity, specific flow resistance, shape factor and thickness). A non local type of surface reaction was considered. The results are finally compared with experimental results in which a long tube of concrete is submitted to an acoustic point source. Amplification results are presented when the tube is set either on a dense or on a porous road surface. A separate additional paper by Fadavi & al. will present the three dimensional approach.

• TIRE/ROAD NOISE : 3D MODEL FOR HORN EFFECT
  A. Fadavi, D. Duhamel, P. Klein and F. Anfosso-Lédée
[Abstract]

Within the problem of tire/road noise, this work deals with the horn effect. Between the curved tire tread fore and aft of the tire/road interface and the road surface there is a space which forms an acoustical horn which increases the radiation efficiency backwards and forwards up to 10 dB(A). This effect has to be considered in a general model for tire/road noise. A 3D tire model is used for this purpose. The tire is modeled by a cylinder. An excitation source is placed on the tread and sidewalls near the contact patch. The sound pressure and sound amplification are caculated in the space arround the 3D tire model using the Boundary Element Method (BEM). The influence of different parameters such as the position and size of the source are studied in terms of amplification and sound pressure spectrums. It is shown that the position of the source has a very important influence when its size has negligible influence. To validate the 3D model, a comparaison between numerical and analytical solutions is proposed for the case of a sphere on a flat surface. The 3D analytical model for the sphere is based on an existing model using modal decomposition of the sound pressure. Finaly, the 3D solution is compared to the 2D solution. An important difference between theses solutions is obsereved.

Dumbacher, S.

• NOISE SOURCE EVALUATION TESTING ON MTS SERIES 320 ROAD SIMULATOR
  E. Frenz, S. Dumbacher, R. Allemang and M. Mergeay
[Abstract]

The MTS Series 320 Road Simulator, well known for durability testing, are more and more used for general acoustic evaluations, e.g. squeak and rattle evaluations, ... during the development process of today's cars. This calls for specific noise characteristics of the testing devise. The purpose of this study was to perform a detailed noise source evaluation of the Road Simulator. A number of acoustic tests were conducted. First the baseline noise characteristics, followed by the location and quantification of the noise sources. In the next part of this paper the evaluation of use of enclosures in isolating the noise sources was studied. Finally, recommendations are formulated and implemented, resulting in strongly improved noise characteristics.

Dunne, G.

• THE IDENTIFICATION OF POWERTRAIN SOUND QUALITY TARGET SOUNDS
  G. Dunne, A. Wheeler and P. Jennings
[Abstract]

Powertrain Sound Quality is increasingly becoming a factor by which customers judged the performance of their automobiles. This is particularly the case in the luxury car sector where sound levels between vehicles are comparable, but the difference in perception lies in the quality of the sound. To respond to these changing market requirements Jaguar Cars has developed a customer-focused Sound Quality Engineering (SQE) process. This process consists of setting detailed subjective and objective vehicle level Sound Quality targets, which are subsequently cascaded to system and component level specifications. This paper presents the results of a recent SQE cascade on one of Jaguar's new vehicle programmes. A Sound Quality profile is used to subjectively quantify a number of significant semantics that define the Targeted Sound Quality character of the product in relation to the existing competition. The primary semantics that quantify the degrees of Power and Refinement are then used to identify the key acoustic features within the sound signatures that determine the subjective preferences. Through the use of digital filtering and jury evaluation techniques the trade-off between the degrees of Power and Refinement are identified. A target sound that contains the optimum balance between the two semantics, and that also takes into account the subjective nature of the product, is then identified. The identification of this target sound is the focus of the proposed paper.

Duretto, F.

• A PURPOSE OF AN ACOUSTIC CRITICAL INDEX FOR THE ESTIMATE OF THE PRIORITIES OF INTERVENTION IN AN HIGHWAY GLOBAL REORGANISATION PLAN
  J. Fogola, F. Duretto, R. Giovinetto and R. Pisani
[Abstract]

The aim of our present study is to propose a method for an acoustical critical analysis of territories crossed by large road infrastructures (highways, freeways, etc..). Definition of the Critical Index of Priority. In a global highway acoustic reclamation plan, it is of fundamental importance to characterize in detail the different critical areas interested from the acoustic impact. The concept of the critical area must be unambiguously fixed in all the portions of territory in which the acoustic impact of the road exceeds the fixed limit values. It is possible to fix a critical index (C.I.) for each area in order to obtain in an objective way the priorities of a reorganization plan. The parameters that concur to the determination of this index should be, to judgement of writing, the following: Number of annoyed persons Noise levels Fixed maximum levels Corrective factors The determined index presupposes the knowledge of the noise level in front of all the buildings of a critical area, obtained through a limited number of measures in significant points and by means of forecast calculations in all the remaining points. Conclusions: the Critical Index gives an instrument for the definition of acoustic intervention priority to the competent institutions and a technical aid to the professional person in charge of the reorganisation plan to make the suitable choices for the projects.

• TRAFFIC NOISE IN THE CITIES AND COMPARISON WITH WITHOUT CAR DAY
  C. Fabozzi, S. Curcuruto, A. De Leo, F. Duretto, A. Iacoponi, G. Licitra, L. Menini, W. Piromalli, M. Poli and P. Simonetti
[Abstract]

In the 22nd September 1999 carried out in about 90 Italian towns the '' European Day: in city without my car'', promoted in Italy by the Italian Environmental Ministry, with the purpose of sensitising citizens and administrators about problems connected to environmental pollution linked to traffic. During the day, between the 7:00 and 21:00, different zones of the cities chosen by local administrations were closed to private traffic. At the same time a campaign of noise monitoring was carried out, organised and coordinated by Environmental Agency System (ANPA-ARPA). The campaign had the purpose to estimate the benefits that are possible to obtain limiting in the city the circulation of private tr.

Dürrer, B.

• STRUCTURE OF AUDITORY SIGNS: SEMIOTIC THEORY APPLIED TO SOUNDS
  B. Dürrer and U. Jekosch
[Abstract]

Most technical equipment or machinery produces sound as an inevitable side effect of its function; in addition, sounds are emitted as a conveyor of information. Both types of sounds are subject to research in the field of sound quality, for instance to enhance the overall product quality (e. g. product sound design) or to improve the efficiency of an auditory man-machine interface (e. g. warning sound design). In any case, as a prerequisite for sound design it is necessary to analyse the relation between the sound (the representamen), the listener (in whose mind forms the interpretant) and the sensation caused by the perception of the sound by the listener (the object to which the sign refers): This triadic relation is not a fixed relation but a process. The relation between these three entities and the process of interpretation forms a sign which can then be further analysed with the means of semiotic theory. In the case of auditory signs (i. e. the sign vehicle is a sound), a further subdivision between verbal and non-verbal auditory signs is advisable, though, of course, several properties of both types of signs can be captured in a similar way. Here, the view is restricted to non-verbal auditory signs. Compared to the task of designing verbal auditory signs, a non-verbal auditory sign might even be more complex to design because its content is not conventionally fixed: In most cases, the meaning attributed to a non-verbal sound is not formally learned but based on individual experience. Apart from conveying the desired information, the designer has to face the problem of distinctiveness of auditory signs. In order to investigate the process of interpretation of non-verbal auditory signs, listening experiments have been performed where properties of the presented sounds have been varied. The performance of the test subjects is discussed with respect to a model based on semiotic theory.

Dutrech, L.

• A METHOD FOR PREDICTING THE TRAILING EDGE NOISE CONTRIBUTING TO THE SOUND EMISSION OF HEAT PUMPS FANS
  L. Dutrech, M. Guivarch and F. Crouzet
[Abstract]

The will to reduce the acoustic radiation of air conditioning outdoor units leads to study the contribution of their cooling fans to the noise emission. The broadband part of the noise emitted by the axial fans installed on such systems is generally the most important part of the total radiated noise. Related to the turbulence of the flows, it may have several origins. In this paper, we focus our attention on the self-noise  of an isolated blade profile, caused by the turbulence of the boundary layer, assuming no stall is occurring ( trailing edge noise ). We present a method to predict the noise emitted by a 2D isolated profile, knowing its geometric characteristics, the incidence and the speed of the incoming flow. Our process consist of performing 2D CFD calculations on a profile to obtain statistical information on the flow near the trailing edge. This information is then related to the spectral characteristics of the surface pressure fluctuations, using analytical models developped by Corcos and Benarrous. Finally these characteristics are used to deduce the spectrum of the noise emitted by the profile, thanks to Howe's acoustic model. An empirical correction is also provided to take into account the finite sharpness of the blade. Calculations have been performed on a NACA 012 profile, for several trailing edge sharpness, flow speeds and incidences. The results show good agreements with literature's measurement data. Such work must be continued to study and validate the more realistic case of a 3D rotating blade.

Edon, E.

• ACOUSTIC COUPLING OF A CENTRIFUGAL COMPRESSOR
  F. Di Costanzo and E. Edon
[Abstract]

The paper deals with the acoustic coupling of a centrifugal compressor and its piping system. During the tests in similitude conditions at low pressure and low load, a centrifugal compressor exhibited, at low flow rate, unusual very low frequency vibrations. An acoustic study of the piping system of the lest loop was performed by TECHNICATOME with the LACTUS software (a computer-aided design tool for noise-free and reliable piping networks). It was found that the acoustic resonances were in accordance with the vibration frequencies measured on the compressor, and that the levels of the vibration peaks were proportional to the acoustic transfer function amplitudes. The absence of vibrations during the full load tests confirmed the assumption of the acoustic coupling between the compressor and the piping system of the test loop whose acoustic resonances amplified the pressure pulsations and forced the low frequency vibration of the rotor. The paper gives a brief description of the acceptance tests on specific loops (similitude and full load tests). Then, the experimental investigations of the phenomenon and the acoustic studies of the test loops by mean of the LACTUS software are presented for both similitude and full load tests. Finally, the main results are given (comparison between measurements and simulation), like the concluding remarks : - the hydro or aerodynamical excitation generated by a rotating machine such as a pump or a compressor may be amplified by the acoustic resonances of the piping network, - the modelling of pulsation and vibration phenomena is necessary for the success of the design of machines an piping networks, - a ''four-pole parameters'' method, such as the one used by the LACTUS software, has proven to be an efficient and effective method for the prediction and analysis of dynamic phenomena in piping networks.

Efimtsov, B.

• EVALUATION OF VARIATIONS OF THE TURBULENT BOUNDARY LAYER NOISE INSIDE AIRPLANE CAUSED BY ITS MODIFICATION
  S. Baranov and B. Efimtsov
[Abstract]

In recent years the manufacturing firms have been modifying in increasing frequency the airplane being under production instead of developing the new ones. This is determined by their efforts to response timely to varying requests and requirements of air companies realizing transportations. In this connection the operative evaluation of the anticipated variation of sound pressure levels inside airplane after its modification becomes rather actual. For modern high-speed civil airplane first of all the sound pressure levels produced by the turbulent boundary layer which is the main source of internal airplane noise are to be evaluated. The present work analyzes possible variations of the wall pressure fluctuation field characteristics produced by the turbulent boundary layer on the external airplane surface, to which the airplane modification can lead and discusses possible variations of elasto-inertial properties of the fuselage skin as well as of vibro-acoustic characteristics of soundinsulating, soundabsorbing and vibro-absorbing structures. Asymptotical relations which describe the effect of these factors on the internal airplane noise produced by the turbulent boundary layer are presented. The experimental data supporting the validity of these relations are given. The predicted evaluation examples are illustrated. It is noted that the asymptotical relations can be used for evaluating the internal noise not only for modified airplane versions but also for new airplanes which have prototypes.

Eide, A.B.

• COMBINING HEAVY AND LIGHT WEIGHT BUILDING CONSTRUCTIONS TO ACHIEVE HIGH SOUND INSULATION
  K. Selvaag and A.B. Eide
[Abstract]

The company of consulting engineers, Multiconsult has been involved in many projects with building constructions with high sound insulation requirements. We will like to introduce to you the experience achieved during design and verification of the Norwegian State Academy of Music. The most important construction methods to achieve satisfactory results will be highlighted. To achieve field measured apparent sound reduction indexes in the region of R'w = 64-75 dB, the control of flanking transmission is very important. The combination of lightweight ''box in box'' solution in heavy concrete structures has shown to provide sufficient reduction of flanking transmission. When high sound reduction indexes are required it is also often necessary to control sound transmission outside the common 100-3150 Hz range. When comparing the sound reduction in the common 100-3150 Hz range, with the sound reduction in the extended 50-3150 Hz range, the sound reduction for the extended range seems to vary more than for the normal range. This means that when designing constructions with sound reduction requirements below 100 Hz, the safety margin have to be increased to take account for larger deviations in the measurement results. The evaluation of the measurement results from the Norwegian State Academy of Music shows that the required sound reduction index R'w is fulfilled for the majority of the walls.

Ejsmont, J.

• TIRE/ROAD NOISE SIMULATION FOR OPTIMIZATION OF THE TREAD PATTERN
  J. Ejsmont
[Abstract]

There are many factors related to the tires which are important to the level and spectral characteristics of the tire/road noise. The tread pattern is one of the most important factors in this respect. The paper deals with one aspect of the tread influence - namely tread pattern randomization which is a measure used to decrease the tonality of the tire/road noise. An optimal tread randomization cannot be obtained by purely analytic means. Sometimes special optimization algorithms are used, but usually the proper randomization is accomplished by some kind of trial-and-error method. Two of the most important problems for optimization are, however, transformation of the data describing the tread pattern and to design and apply a certain tread randomization scheme to the ''time signal'' which may be analyzed in order to evaluate the quality of the solution in question. The first part of the paper gives a short overview and comments on methods of data transformation and optimization which were reported in the open literature. The next part deals with details in one of the possible approaches in this respect, which was developed and successfully used by the author in designing numerous tread patterns. Noise spectra for tires having the same tread pattern segments but being differently randomized are also presented together with corresponding computer simulated spectra.

• DETERMINATION OF THE CPX INDEX FOR A NUMBER OF SURFACES IN VARIOUS COUNTRIES
  J. Ejsmont, P. Mioduszewski, S. Taryma and W. Gardziejczyk
[Abstract]

Road surfaces may influence traffic noise in two ways. They directly influence the generation of the tyre/road noise that is one of the most important vehicle noise sources, and on top of it they affect the propagation of noise emitted from all sources in the vehicle. In order to investigate the influence of the road surface on tyre/road noise generation it is necessary to establish certain measuring procedures and indicators describing the results in a uniform and condensed form. One of the methods in use is the Close Proximity Method (CPX), which utilizes two microphones mounted close to the tyre/road interface. The so-called CPX Index, which is the final indicator of the road surface ''noisiness'', is evaluated on the basis of measurements performed with the CPX method using four reference tyres. Measurements with this method in a standardized way have been possible only recently since the method is currently subject of standardization efforts within the ISO. The first part of the paper outlines most important aspects of the CPX method. The main part of the paper presents results of CPX tests performed recently on many roads in Sweden, Poland, Germany and the Netherlands. Certain ''low noise'' road surfaces were included to the test program so it is possible to compare their performance with other, more traditional road surfaces. Also very noisy ''block pavements'' and paving stones were covered as they are again frequently used in certain ''low traffic'' and residential areas. The ranking of the surfaces according to their CPX Indexes is given as a final result of the investigation.

Ekici, I.

• AN EXPERIMENTAL INVESTIGATION INTO THE ACOUSTIC PERFORMANCE OF EARTH MOUNDS COMBINED WITH SHORT NOISE BARRIERS
  H. Bougdah and I. Ekici
[Abstract]

Environmental noise is causing an increase in the number of complaint from the public. Despite this, action to reduce its impact has had a lower priority than that taken to address other environmental problems such as air and water pollution. According to the European Commission Green Paper on ''Future Noise Policy'', 1996, around 20% of the European Union's population or 80 million people suffer from noise levels more than 65 dB(A). These levels are considered by health experts to be unacceptable. An additional 170 million people throughout the E.U. live in 'grey areas' where the noise levels are likely to be between 55 and 65 dB(A) and can cause annoyance during the day. As well as environmental implications noise has economic costs to society. According to a study of ''The Social Costs of Transport'' (ECMT/ OECD, 1993 ), this is estimated around 0.2% and 2% of GDP. Even using the lower figures it still would come to around 170 billion ECU. Noise mitigation measures cover treatments of source, path and receiver. In the case of transport noise, environmental barriers can be used. A novel method of screening road traffic noise, consisting of earth mounds combined with short barriers, is discussed in this paper. Physical scale modelling was used to measure the insertion loss of eight different configurations. The results have shown that earth mounds could be used as environmentally friendly barriers. The addition of short barriers, can however in some cases reduce their efficiency.

El-Fadel, M.

• MANAGING NOISE EMISSION IMPACTS OF AIRPORT TRAFFIC
  M. El-Fadel, M. Chahine, M. Baaj and T. Mezher
[Abstract]

Airport traffic is a major source of community concerns due to aircraft noise emissions particularly in locations close to airports and aircraft flight tracts. The principal effects of aircraft noise on humans include hearing damage risk, and speech and sleep interference which can develop into stress. As such, it becomes essential to locate, design, and/or expand airports as well as optimize flight paths in a way to reduce noise exposure to nearby communities. For this purpose, it is essential to assess changes of noise impact resulting from new or extended runways or runway configurations, evaluate new traffic demand and fleet mix, evaluate revised routings and airspace structures, assess alternative flight profiles, and modifications to others operational procedures. This paper present the calibration and application of the US Federal Aviation Administration integrated noise model (INM) for the analysis and prediction of airport traffic emission noise impacts from aircraft operations on communities near the proposed expansion at the Beirut International Airport. For this purpose, field noise measurements were collected at sensitive noise receptors along selected locations around the airports and the corresponding airport traffic flow was characterized. Noise levels were then simulated as a function of the different airplane classes, flows, flight path and landing characteristics. The model was also used to predict future noise levels, optimize airplane flight path, and assess mitigation measures to minimize potential airport noise emission impacts. In addition, a local field survey was conducted to better understand the influence on the community response to aircraft noise and document the extent of annoyance and activity disturbance caused by noise.

Elbers, F.

• EURANO99: POLICY TOOL FOR STRATEGY OF RAILWAY NOISE.
  F. Elbers and J. Oertli
[Abstract]

This paper presents the policy tool Eurano99 used for two major European studies. The first study is the UIC sponsored project ''Cost-Benefit Analysis for European Rail Noise Abatement'', supporting the decision making process of the UIC Action Program Noise Reduction Freight Traffic. The second study is the ERRI sponsored project ''Economic Study for Silent Track, Silent Freight and Eurosabot'' supporting the decision making process of introducing source measures on railway noise. The Eurano99 tool is a an upgraded version of the Dutch software program Gerano consisting of two elements. The first is a data collection tool called ''Eurano99 Data Manager'' currently being used by a network of railway noise research centres: in Germany by the DB-AG Forschungs Zentrum, in France by SNCF Direction de la Recherche, Switzerland by the SBB Rail Environmental Centre and in The Netherlands by the NS Technisch Onderzoek. The second element is a prediction and a analysis tool called ''Eurano99 Analysis'' which adds the national geographic and traffic data to a European dataset. Currently such a dataset is available for two major European freight railway lines namely Rotterdam-Köln-Basel-Milano and Bettembourg-Lyon. Eurano99 can give answers on the extent of the environmental impact of railway noise for given source reduction scenarios, noise legislation scenarios and/or traffic scenarios. Additionally Eurano99 automatically calculates the extent of required noise barriers for each scenario. Results of the two mentioned projects are described in the articles 'European Rail Noise Abatement: Cost-Benefit Analysis' and 'Economic study on railway noise: Environmental impact of different legislation scenarios'.

• ECONOMIC STUDY ON RAILWAY NOISE: ENVIRONMENTAL IMPACT OF DIFFERENT LEGISLATION SCENARIOS.
  F. Elbers and P. Van Der Stap
[Abstract]

In this paper we will present the results of the EU/ERRI sponsored project Economic study for Silent Track, Silent Freight and Eurosabot. These Brite Euram projects have resulted in several noise reducing measures. The impact is shown for three given noise legislation scenarios: no limits, a 65 dB(A) reception limit and a 55 dB(A) reception limit. Each scenario gives results of up to seven different combinations of source reducing variants. Within the Economic study the (cost) effectiveness of reduction by wagon-, track- and barrier measures is evaluated, by applying them to a single European Freight Freeway from Rotterdam to Milano. The evaluation will be based on the geographical noise policy tool Eurano99. The impact is expressed in length of noise barriers, number of insulation's of houses, number of wagons to improve and length of track to improve. The cost of the measures are calculated in Euro and are based on average prices.

Elias, G.

• ARIANE 5 AT LIFT OFF: LOCALIZATION AND RANKING OF ACOUSTIC SOURCES
  G. Elias
[Abstract]

For the Ariane 5 launcher, the stage of the flight when the maximum acoustic loads occur under the fairing is the liftoff. The origin of these loads is jet noise incident to the fairing and partially transmitted. Jet noise reduction devices are implemented on the ELA 3 launch pad such as water injection and jet flues roofing. Because the two boosters and the main engine are operating at liftoff, it is not evident to predict, in each frequency band, which is the main noise source (to plan or optimize if needed reduction devices) in this rather complex situation. This is why an array of twelve flush-mounted microphones has been implemented on the fairing to localize the jet noise sources. Moreover, vibroacoustic codes intended to predict the acoustic noise levels under the fairing from outer data need a description of the incident field in terms of a minimum number of uncorrelated plane waves. The localization process has therefore to be continued for providing in a first step the amplitudes of the sources after localization, and in a second step an equivalent model consisting of a minimum number of sources. For all these tasks, one main difficulty is to take into account the non stationary character of the signals, the situation from deviated jets interacting with the launch pad in the earlier stage of liftoff to free jets evolving very fast. After presenting the signal processing adapted to the objective of localization and ranking, results are shown for the flights 503 and 504 of the Ariane 5 launcher.

Elias-Juarez, A.

• MAXIMUM BACKGROUND NOISE LEVELS ON AUDIOMETRIC ROOMS: A CASE OF STUDY
  N. Razo-Razo and A. Elias-Juarez
[Abstract]

Ambient noise level requirements for audiometric rooms clearly depend on the field of application. This gives rise to proper characterization of audiometric rooms and their conformance to national or international standards. A comparison between values stated in standards ISO8253-1.1989 and ANSI-S3.1-1991 (Maximum permissible ambient noise levels for audiometric test rooms) is performed from 31,5 Hz to 8 kHz. Experimental studies are though focused on the frequency interval of 125 Hz to 8000 Hz using maximum, minimum and equivalent sound pressure levels. Each data set consisted of 20 hours of continuous measurements, analized on one-third octave and octave bands, for different ambient conditions (e.g., air-conditioning On and Off). Measurement uncertainties may lead to non-conformances on frecuency bands from 100 Hz to 1600 Hz, specially in places whose barometric pressures vary from reference conditions. Sound pressure levels due to ambient noise for audiometry tests with cover and uncover ears require a more thorough uncertainty estimation at 125 Hz.

Ellebjerg Larsen, L.

• PERCEIVED ANNOYANCE FROM ROAD TRAFFIC NOISE
  H. Bendtsen, L. Ellebjerg Larsen and B. Mikkelsen
[Abstract]

When noise abatement planning is carried out, it is important to know the nuisance perceived by people along the roads at different noise levels. For the first time in Denmark doses response relations have been studied looking at nuisance in-doors with open and closed windows, in the garden and near the road, correlated with the actual noise levels expressed as Leq,24. The perception of annoyance form road traffic noise has been studied in the municipality of Århus, the second largest city in Denmark. A questionnaire send out by letters have been used. Out of 132.000 households in Århus around 6000 have been randomly selected. 55 % have returned the questionnaire. Nearly everybody who has answered, have filled in their address. The knowledge of these addresses have made it possibly to make a prediction of the noise in front of the windows, in the garden and at the street. People could express different degrees of annoyance. The following categories was used: extremely annoyed, very annoyed, annoyed, little annoyed and not annoyed. People were also asked how the noise affects their daily life. They were asked if they had done anything to reduce the noise, and if they had any ideas on what should be done and who should pay for these improvements. Doses response curves are generated. They draw a picture where 10 to 20 % are annoyed at low noise levels under 50 dB. The annoyence increases with noise levels over 55 dB. The highest level of annoyance is seen in the situation indoor with open windows. But there are also rather high levels of annoyance reported in the gardens.

Elliff, T.

• ENHANCE: AN EVOLUTIONARY IMPROVEMENT TO AIRCRAFT NOISE MODELING
  T. Elliff, L. Cavadini and I. Fuller
[Abstract]

International guidance material is provided by ICAO (Circular 205), defining how to compute noise contours for aircraft around airports. However, it is acknowledged within the noise modeling community, that significant errors can exist between modelled noise levels, and those measured ''on the ground'' for similar scenarios. The aim of the project is to better understand the sources and magnitude of these errors, and attempt to mitigate for them in the modelling process. The project will deliver an ''Enhanced'' Noise study tool, enabling more accurate predictive studies to be conducted for European airports and fleets, and will directly support the evolving European Commission Common Noise Policy. The model is based on existing noise contour calculation software (for example, the Integrated Noise Model from FAA), but through a preprocessor function and ''European'' database, allows more accurate data input, eliminating, or at least reducing, known errors. The project is a combination of tool development and validation exercise, and is based around a significant data collection task, with the cooperation of operators and airport administrations. It is a programme of collaborative work in Europe, sponsored by EUROCONTROL, as a complement to the work being conducted in voluntary CAEP (ICAO Committee on Aviation Environmental Protection) working groups, which will ultimately propose revisions to the Circular 205 methodology.

Emond, J.-P.

• HOW DOES EUROPEAN NOISE LEGISLATION INFLUENCE THE GLOBAL MARKET?
  V.K.P. Irmer and J.-P. Emond
[Abstract]

European noise legislation since the 1970ies consisted of directives on the approximation of the laws of the Member States in order to ensure the smooth functioning of the internal European market. In the late 90ies, the protection of human health and well-being started to play a more important role; consistently the Amsterdam Treaty reaffirms: ''the Commission, the European Parliament and the Council, within their respective powers, will take as a base for legislation a high level of protection, taking account in particular any new development based on scientific facts.'' The new EU directive on noise emission from equipment for use outdoors lays down provisions concerning noise limits and noise marking for about 55 types of equipment, for some types noise limits are reduced compared to earlier legislation. Noise limits are demanding but the current state of the art of noise reduction allows to meet them without excessive additional costs. The impact on internal combustion engine emissions has been taken into consideration for setting these noise limits. The directive being in force only equipment complying with these provisions may be placed on the European market, as demanded by its 375 Million citizens. Most of the European manufacturers are prepared to comply with the new directive. However, only few manufacturers of other continents are aware of this new legislation and for them it could be a big challenge to meet the legal provisions. In the future, a better cooperation between European and non-European manufacturers is urgently needed to minimise problems arising due to further European legislation.

Enescu, N.

• NOISE RADIATED BY THIN RECTANGULAR PLATES SUBJECTED TO INPLANE LOADS
  M. Bugaru, I. Magheti, N. Enescu and M.V. Predoi
[Abstract]

The paper reveals recent developments of the noise radiated by thin rectangular plates parametrically excited. In the region of principal parametric resonance, starting from the temporal non-linear differential equation that describes the oscillatory movement and using the second order approximation of the asymptotic method was computed the amplitude as function of system parameters and geometric imperfections. In the anechoic chamber of Department of Mechanics were done the experiments concerning the non-linear dynamic response of such plates and the noise radiated in the region of principal parametric resonance. By recording and processing the two signals, were plotted three diagrams: spectral density of the two signals and their coherence. The three characteristic frequencies of the parametric vibration of the plate (L/2,L,3L/2), previously calculated, were put in evidence.

Engdahl, B.

• AIRCRAFT NOISE IN RECREATIONAL AREAS ; RESULTS FROM TELEPHONE SURVEYS BEFORE AND AFTER THE 1998 TRANSITION OF NORWAY’S MAIN AIRPORT
  N.H. Krog and B. Engdahl
[Abstract]

The 1998 transition of Norway's main airport from Fornebu to Gardermoen provided a unique opportunity to study the impact of changes in aircraft noise on the enjoyment and use of nearby recreational areas. In this study, visitors' experience of aircraft noise is also compared to their experience of other environmental factors. One recreational area is studied at each airport; Bygdøy close to Fornebu, and Romeriksåsen near Gardermoen. Samples of visitors and potentially visitors of the recreational areas were drawn from postal addresses adjacent to the recreational areas and telephone interviewed both before and after the transition (n = 1418 - Bygdøy, 1264 - Romeriksåsen). Visitors were interviewed about their activities in, and experiences with the area the last three months. A sample of non-visitors was interviewed about why they had not visited the area. The change in mean score on aircraft noise annoyance is highly significant at both sites. Before the transition, 23 percent were highly annoyed by aircraft noise at Bygdøy and 4 percent at Romeriksåsen. At both sites, aircraft noise was rated as the most annoying factor before the transition. After the transition, almost no one was annoyed by aircraft noise at Bygdøy, and 17 percent were highly annoyed at Romeriksåsen. An interesting change in experience of the whole area was demonstrated at Bygdøy. Five out of seven other potentially annoying factors were rated as significantly less annoying after Fornebu was closed down. The opposite effect was not found at Romeriksåsen. Implications for use of the areas will be discussed.

Engel, Z.

• ASYMPTOTIC FORMULAS FOR ACTIVE AND REACTIVE MUTUAL POWER OF FREE VIBRATIONS OF A CLAMPED ANNULAR PLATE
  W.J. Rdzanek, Z. Engel and W.P. Rdzanek, Junior
[Abstract]

Normalized mutual power of radiation, active and reactive, has been analyzed in this paper. The sound source is an annular plate, clamped to a planar, rigid and infinite baffle. The plate vibrates sinusoidally with respect to time. Vibrations are axisymmetric. A Kirchhoff-Love's model of a perfectly elastic plate has been used. First, the integral formulas for the mutual power of radiation have been presented and then asymptotic formulas for fast numerical computations of the mutual power of radiation have been calculated. The asymptotic formulas consist of elementary expressions and functions with no integration. They can be used for acoustically fast waves, i.e. when the acoustic wavenumber is greater than the structural wavenumber. The contour integral computation method has been used to obtain the mutual active power. The stationary phase method has been used for the mutual reactive power of radiation. Approximation errors for those formulas have also been presented. Some frequency characteristics have been presented for both integral and asymptotic formulas. This allows us to confirm the high accuracy of the asymptotic formulas. All the theoretical analysis presented deal with free vibrations of a plate. The friction forces have been ignored. The analysis presented can be used as a basis for analysis of the total power of excited and damped vibrations. The interactions of the air column above the plate and the baffle have also been taken into account.

• THE TOTAL POWER OF FORCED AND DAMPED VIBRATIONS OF A CLAMPED ANNULAR PLATE
  W.P. Rdzanek, Junior, Z. Engel and W.J. Rdzanek
[Abstract]

The sound radiation of a clamped annular plate has been analyzed in this paper. The plate is clamped to a planar, rigid baffle and is excited to vibrations under external pressure. The vibrations vary sinusoidally with respect to time. The processes of steady state vibrations, also harmonic with respect to time, have been investigated. The analysis is basis on the complex mutual power of radiation of free vibrations of a plate discussed elsewhere. Such factors as forcing, internal damping of plate material and interactions of the air column above the plate have been coupled into the equation of the plate's motion. As a result an inhomogeneous equation of the plate's motion in the form of algebraic equation system has been obtained. Its solution provides the normalized, total power of radiation. Some frequency characteristics have been obtained for the power of radiation related to the power of a model plate. For that reason those characteristics are independent from the plate's material and geometric parameters. On the basis of them some analogous characteristics for any plates can be obtained, provided that their vibrations are elastic and reversible. Some frequency characteristics for the mutual power of different vibration modes have also been obtained by their isolation from the algebraic equation system. Some directional characteristics of the total pressure have been determined. To obtain all the frequency characteristics the results of the modal analysis have been used. They are the normalized, complex power of the successive modes of the plate's free vibrations for the acoustically fast waves.

Enmarker, I.

• THE EFFECTS OF AIRCRAFT NOISE ON MEMORY, STRESS AND AROUSAL IN OLDER PERSONS
  I. Enmarker and S. Hygge
[Abstract]

The aim of the present study was to examine memory, stress and arousal in older persons during aircraft noise (66 dBA Leq) exposure. The study replicated the design of Hygge's (1997) classroom experiments. The subjects, 105 senior citizens 66-74 years of age (62 females and 43 males), took part in three experimental morning sessions. The first session was a pre-test in silence for learning ability, and the second and third sessions were counterbalanced as the silent and the aircraft noise conditions. It was predicted that aircraft noise would impair long-term recall but not recognition of a written text studied exactly one week earlier. Improvements on serial position recall on items late in the list and impaired performance on earlier items were expected when exposed to noise. It was also predicted that subjects would report themselves more stressful and aroused in the aircraft noise session compared to silence. The results showed that aircraft noise impaired long-term recall but also recognition. In ser

Erdem Aknesil, A.

• NOISE PROBLEMS CAUSED BY ROAD TRAFFIC IN CLASSROOMS
  N. Akdag, A. Erdem Aknesil and Z. Karabiber
[Abstract]

Human learning depends strongly on verbal learning. Research has shown that the quality of the acoustical environment is a significant element at the verbal learning. One of the most important factor that harms the excellency of the acoustics is noise. This fact motivated an impressing and growing body of research on the harmful effects of the noise throughout the educational process. In this context, the effects of road traffic noise has been investigated at the primary schools selected among schools situated at the various noise zones at ýstanbul. Outdoor and ýndoor measurements were carried out at the mostly effected classrooms of the schools. The architectural properties of these classrooms were also investigated from acoustical point of view. The results of the measurements were evaluated according to the National and International regulations, and high noise levels and long reverberation times have been determined. On the other hand, surveys have been realised on the users of these classrooms that's to say on the students and the teachers. The ratio of the students affected from noise was also determined to visualise the extent of the issue. Comparison of the subjective evaluations with the measurements shown good correlation. High noise levels caused annoyance, poor intelligibility and adverse effects both on students and teachers. As the ratio of the influenced users was also, it is determined that a widespreat research has to be realized in order to highlighten the problem in National dimention and a research project is designed in this frame.

Eun, H.-J.

• MEASUREMENT OF HEAD VIBRATION AND ITS ERROR ANALYSIS
  W.-S. Cheung, Y.-H. Park and H.-J. Eun
[Abstract]

This paper addresses issues encountered in measuring the general, 6-degree-of-freedom motion of a human head. This measurement requires the usage of multiple accelerometers, such as the well-known bite-bar which consists of three measurement blocks positioned differently and separated by a fixed gap. Six or nine linear accelerometers are normally chosen to measure the 6-degree-of-freedom motion at a position of the head. There are many ways of configuring them onto the three measurement blocks so as to measure it. For a chosen accelerometer configuration, its corresponding way of reconstructing the 6-degree-of-freedom motion from multiple acceleration measurements is uniquely determined. Resultantly, different accelerometer configurations yield different 6-degree-of-freedom motion-calculation methods such that they yield different measurement error characteristics. This point has not yet been well understood in the previous work on human vibration. This work proposes a systematic logic measure the head vibration and to make its error analysis. It includes theoretic formulations to evaluate effectively the 6-degree-of-freedom motion components of the head from six linear acceleration measurements. These formulations are shown to enable the analysis of measurement errors. Experimental results are illustrated to see what amount of measurement errors exists for chosen accelerometer configurations. Several interesting things observed so far are commented in this work.

Evans, G.W.

• THE EFFECTS OF CHRONIC AND ACUTE TRANSPORTATION NOISE ON TASK PERFORMANCE OF SCHOOL CHILDREN
  M. Meis, S. Hygge, G.W. Evans, P. Lercher, M. Bullinger and A. Schick
[Abstract]

There are a number of reasons to expect that children are more susceptible than older persons to pathogenic and behavioural stress effects induced by noise (Cohen et al., 1986). Several researchers have examined the aftereffects of prolonged exposure to traffic noise on reading and school achievement. Many of these studies have shown that chronic noise exposure is associated with reading deficits and decrements in tasks with a high demand on attention capacity (Evans, 1990; Schick, 1990). In this paper findings of interactions between 'chronic traffic noise and acute laboratory noise' on cognitive performance and school achievement will be reported. Data were collected in the Munich Airport Noise Study (Evans et al., 1995) and the Tyrol School Study II (Meis et al., 1999). Most of the findings can be classified in terms of habituation: children from areas exposed to traffic noise were not or were less affected when they were confronted with laboratory traffic noise. Another prevailing habituation type of task performance under transportation noise can be described in terms of 'environmental stimulation congruence', indicating that children from noisy areas performed best under noisy laboratory conditions, whereas children from quiet areas performed best under quiet conditions. However, these short term 'benefits' are severely counteracted by impairment as a main effect due to chronic noise exposure in everyday life. We will discuss some of the possible advantages and disadvantages of the apparent ability of children to habituate to chronic noise.

• THE MUNICH AIRPORT NOISE STUDY - EFFECTS OF CHRONIC AIRCRAFT NOISE ON CHILDREN'S PERCEPTION AND COGNITION
  S. Hygge, G.W. Evans and M. Bullinger
[Abstract]

The shutdown of the former Munich International Airport in May 1992 and the inauguration of the new one have provided an unprecedented opportunity to investigate in a longitudinal, prospective design the psycho-physiological, perceptual cognitive, motivational, and quality of life effects of noise exposure on children. Before the change over of airports, children at both sites were recruited into experimental and control groups. The experimental groups consisted of children who were exposed to high levels of aircraft noise at the old airport, or would be so exposed at the new airport. The two control groups, one for each airport, were selected from silent areas and matched with their respective experimental group on sociodemographic characteristics. One wave of data collection occurred prior to the change over of airports, the second wave one year later, and the third wave two years later. The children were aged 9-12 years when the study started, and a total of 327 children took part in all three measurement waves. At each wave they were tested individually on a number of psychophysiological and psychological tests. In the present paper longitudinal results from the whole set of perceptual and cognitive measures will be presented and compared to each other. These perceptual and cognitive measures include: Audiometric screening, annoyance to different noise sources, annoyance to community noise (master-scaled), auditory discrimination against different noise backgrounds (signal-to-noise task), choice reaction time (in noise and quiet), running memory, embedded figures, long-term recall and a standardized German reading test and word test.

Evans, P.

• DOES LOW FREQUENCY NOISE DURING WORK INDUCE STRESS?
  K. Persson Waye, R. Rylander, J. Bengtsson , A. Clow, F. Hucklebridge and P. Evans
[Abstract]

Background and aim: The aim of the study was to evaluate the possible interference of low frequency noise on stress experienced during performance. Test persons classified as sensitive or non-sensitive to noise in general or to low frequency noise, worked with different performance tests in a noise environment with dominant low frequencies or dominant middle frequencies, both at a level of 40 dB LAeq. The effects were evaluated as changes in levels of Monoamine oxidase inhibator (MAO-I) and cortisol in saliva, taken at various times during the test. The total time for the sessions was 2.5 to 3 hours. Results: When the subjects worked in low frequency noise, the levels of cortisol were higher and there was a small non-significant increase in the levels of MAO-I. No clear difference in response could be related to sensitivity to noise in general or to low frequency noise, but a general observation was that the levels of the final samples of MAO I and cortisol were higher among subjects sensitive to noise or to low frequency. The low frequency noise was rated as more annoying than the reference noise and also considered to impair the working capacity more than the reference noise. The results suggest that working in low frequency noise conditions may induce stress indicators.

Fabozzi, C.

• TRAFFIC NOISE IN THE CITIES AND COMPARISON WITH WITHOUT CAR DAY
  C. Fabozzi, S. Curcuruto, A. De Leo, F. Duretto, A. Iacoponi, G. Licitra, L. Menini, W. Piromalli, M. Poli and P. Simonetti
[Abstract]

In the 22nd September 1999 carried out in about 90 Italian towns the '' European Day: in city without my car'', promoted in Italy by the Italian Environmental Ministry, with the purpose of sensitising citizens and administrators about problems connected to environmental pollution linked to traffic. During the day, between the 7:00 and 21:00, different zones of the cities chosen by local administrations were closed to private traffic. At the same time a campaign of noise monitoring was carried out, organised and coordinated by Environmental Agency System (ANPA-ARPA). The campaign had the purpose to estimate the benefits that are possible to obtain limiting in the city the circulation of private tr.

Faburel, G.

• THE SOCIAL COST OF AIRCRAFT NOISE: THE CONTINGENT VALUATION METHOD APPLIED TO PARIS-ORLY AIRPORT
  G. Faburel and S. Luchini
[Abstract]

Although social demand for a better protection against noise annoyance in living areas proves to be important, public décision makers are still missing accurate information on transport noise social costs. In order to estimate a such cost due to air trafic in Orly airport aera, the CVM was elected as an interesting methodologie, provided a cross discipline approach is used. Most implementations of CVM to noise have neglected many scientific opportunities offered by psycho-sociology among which the analysis of the relation between a person and his environment seems very promising. Commited knowledge has led to study the influence of individual aircraft noise sensibility on the WTP, used a measure of social cost. The data processing of the survey conducted between October 1998 and April 1999 near Orly airport gives the following results : (i) more than 50% of the sample declare to be annoyed by aircraft noise, (ii) opinions and practises towards accommodation have an impact on the declared annoyance, (iii) the acoustic exposure's and stated annoyance's parameters have a significant influence on WTP, (iv) as a final result, the social cost of aircraft noise approximate, under validity constraints, twelve millions of French francs (2 millions US$) per year.

Fadavi, A.

• TIRE/ROAD NOISE : COMPARISON OF 2D AND 3D MODELS FOR HORN EFFECT
  F. Anfosso-Lédée, P. Klein, A. Fadavi and D. Duhamel
[Abstract]

This paper deals with the amplification effect of tire/road contact noise, also called horn effect , that is due to the multiple reflections between the curved and hard surface of the tyre and the road pavement. This ''horn effect'' is expected to be reduced on porous pavements due to the properties of sound absorption. The approach described here is two dimensional : a rigid cylinder of infinite length is set on a rigid flat road surface. An acoustic line source is located on the tire near the contact. The amplification is calculated at a receiver point in the horn, first using an analytical model, based on the modal decomposition of the sound pressure. In order to introduce sound absorption properties on the road surface, a 2D-BEM model was used. Agreement for rigid case between analytical and BEM models was checked. Then, porous road pavement was introduced in the BEM, using a phenomenological model with 4 parameters (porosity, specific flow resistance, shape factor and thickness). A non local type of surface reaction was considered. The results are finally compared with experimental results in which a long tube of concrete is submitted to an acoustic point source. Amplification results are presented when the tube is set either on a dense or on a porous road surface. A separate additional paper by Fadavi & al. will present the three dimensional approach.

• TIRE/ROAD NOISE : 3D MODEL FOR HORN EFFECT
  A. Fadavi, D. Duhamel, P. Klein and F. Anfosso-Lédée
[Abstract]

Within the problem of tire/road noise, this work deals with the horn effect. Between the curved tire tread fore and aft of the tire/road interface and the road surface there is a space which forms an acoustical horn which increases the radiation efficiency backwards and forwards up to 10 dB(A). This effect has to be considered in a general model for tire/road noise. A 3D tire model is used for this purpose. The tire is modeled by a cylinder. An excitation source is placed on the tread and sidewalls near the contact patch. The sound pressure and sound amplification are caculated in the space arround the 3D tire model using the Boundary Element Method (BEM). The influence of different parameters such as the position and size of the source are studied in terms of amplification and sound pressure spectrums. It is shown that the position of the source has a very important influence when its size has negligible influence. To validate the 3D model, a comparaison between numerical and analytical solutions is proposed for the case of a sphere on a flat surface. The 3D analytical model for the sphere is based on an existing model using modal decomposition of the sound pressure. Finaly, the 3D solution is compared to the 2D solution. An important difference between theses solutions is obsereved.

Fagotti, C.

• CONTRIBUTION OF DOUBLE LAYER ASPHALT IN REDUCTION OF URBAN TRAFFIC NOISE
  A. Poggi, D. Casini, C. Fagotti and S. Secchi
[Abstract]

Double layer asphalts have been used mainly to improve the security of the streets, by means of their drainage properties. Moreover, the benefit achievable with such product in terms of acoustic gain is well known, but until now tests and controls on their acoustical properties have been carried out for high velocity of the vehicles, such as highway or extra - urban roads. This paper concerns the use of two double layer asphalts employed in Florence to reduce traffic noise in two different urban streets. In this case, excitement of tire vibrations by the road roughness and aerodynamic noise, caused by air pumping, are negligible because of the low speed. For this reason it was expected that porous asphalts couldn't give a great contribution in the reduction of traffic noise. Nevertheless, the results show a quite significant reduction of sound pressure level. Measurements have been carried out during two years after the laying down of the new asphalts, taking sound pressure level at the border of the road, together with fluxes of vehicles per hour. A statistical analysis has been implemented on the base of a model that permits to evaluate the actual contribution of the asphalt in the reduction of traffic noise. Results point out that use of double layer asphalts may be efficient even in urban streets with low vehicle speed.

Fang, S.

• 2DOF ACTIVE CONTROL OF SOUND TRANSMISSION IN INTELLIGENT COMPOUND STRUCTURE
  Y. Mitani, S. Akishita and S. Fang
[Abstract]

The paper describes 2DOF active control of sound transmission in an intelligent compound structure, size of which is 40(width)x150(length)x1.2(thickness)mm. The panel is made of piezoelectric element which contains three pole domains for actuators and sensors respectively. The element is sandwiched by stainless steel plates to reinforce the strength of structure. The filtered-epsilon and frequency weighted LQR algorithm are applied to cope effectively with random nature of incident sound wave. Sound power emitted from the panel with and without control is estimated to evaluate the effect of the control system.

Farrington, D.

• THE DEVELOPMENT OF A RAIL DAMPING DEVICE FOR REDUCING NOISE FROM RAILWAY TRACK
  D. Thompson, C. Jones and D. Farrington
[Abstract]

The component of railway rolling noise radiated by the track is dominant in the frequency range up to about 1.5 kHz and often can be more important than the wheel component for the overall noise level. A promising means to reduce this track component of noise is to increase the damping experienced by the rail. This reduces the length over which vibrations are transmitted along the rail and thereby the noise radiated. Reduction of noise is quite difficult because the level of damping of the rail in situ is already quite large. Decay rates of vibration in the rail are in the region of 1 to 10 dB/m and are equivalent to loss factors of the rail of typically 0.1. In order to increase the damping of the rail significantly, particularly at frequencies below 1 kHz, a tuned mass-spring absorber system has been designed. To cover a wide range of frequencies, multiple tuning frequencies are used along with a visco-elastic material with a high loss factor. Suitable materials have been found from tests on samples and prototypes of the damper have been built and tested both in the laboratory and in the field. Results are very promising with reductions of the track component of noise of about 6 dB being found.

Fastl, H.

• PRIVACY VERSUS SOUND QUALITY IN HIGH SPEED TRAINS
  C. Patsouras, H. Fastl, U. Widmann and G. Hoelzl
[Abstract]

The disturbance of privacy in high speed trains has become more evident in the recent years. In psychoacoustic investigations, the contradictory requirements of speech intelligibility and privacy on the one hand, and the desired sound quality on the other hand, were assessed. Speech intelligibility was measured with different typical indoor noises of high speed trains as background noise. In separate hearing tests sound quality of those background noises was investigated. The results will be opposed. Furthermore two different absorbing barriers attenuating speech were simulated. The thereby obtained deterioration in speech intelligibility at equal sound quality will be compared to the results without absorbing measures.

• AN ACTIVE ABSORBER TO IMPROVE THE SOUND QUALITY IN THE PASSENGER COMPARTMENT OF VEHICLES
  H. Spannheimer, R. Freymann and H. Fastl
[Abstract]

It is true that luxurious (chauffeur driven) sedan vehicles offer a high acoustic comfort. Due to the implementation of an effective passive sound attenuation treatment package, the major part of the overall acoustic annoyance can be reduced to an acceptable level. This especially applies to the higher frequency range where the acoustic treatment, e.g. with regard to its absorption capabilities, can significantly contribute to improve the acoustic performance of the vehicle. On the other hand, passive treatments do not allow to noticeably influence the low frequency comfort in the passenger compartment. This must be considered as a great disadvantage since it is a well known fact that especially a further improvement of the low frequency noise characteristics could significantly improve the noise quality perceived by the passengers. The benefits of active absorbers to reduce the low frequency acoustic level in the passenger compartment of a vehicle are shown. A highly compact active system, consisting out of microphones as sensors, loudspeakers as actuators and of a control system circuit, will be presented. Special focus will be placed on the system's operation characterized by its broad-band frequency behaviour comparable to the acoustic properties of a system realized by a series of narrow-banded Helmholtz resonators. Thus, the system presented can be regarded as an active absorber formed by an active device featuring the characteristics of a broad-band Helmholtz resonator. In addition to the description of the optimum construction and tuning parameters of the active absorber, detailed results as to its acoustic overall performance and with regard to its many possibilities offered to influence the sound quality in the passenger compartment of vehicles will be presented.

• SOUND QUALITY OF ELECTRIC RAZORS - EFFECTS OF LOUDNESS
  H. Fastl
[Abstract]

In a pilot study, the sound quality of nine different electric razors was assessed in psychoacoustic experiments by a ranking procedure. In particular with respect to the highest and lowest ranking of sound quality, data of the subjects were in excellent agreement. The sound qualtiy of the different products was highly correlated to their percentile loudness N5, i.e. the softest product was ranked best and the loudest product worst. This result stresses again that loudness is a dominant factor in sound quality evaluation. In several labs, original sounds of different products are manipulated to produce the same loudness in order to stress other aspects like sharpness or roughness. Therefore, all nine razor sounds were edited to produce the same percentile loudness N5. Since larger level variations often lead to quite ''unnatural'' sounds, these manipulations had dramatic effects on the ranking: the product ranked best at its original level was ranked worst after a level increase by 11 dB, the product first ranked worst improved by two ranks with a level decrease of 5 dB. The variations in ranking are stongly related to the magnitude of the level shift. Therefore, it is recommended to use in psychoacoustic experiments on sound quality as much as possible original sound levels.

• THE TIMBRE AND ANNOYANCE OF AUDITORY WARNING SIGNALS IN DIFFERENT COUNTRIES
  S. Kuwano, S. Namba, A. Schick, H. Hoege, H. Fastl, T. Filippou, M. Florentine and H. Muesch
[Abstract]

It is desirable to have internationally standardized warning signals which are used for informing people of dangerous happenings. The results of our former studies suggest that there is a cross-cultural difference in the impression of some signals and that generally speaking frequency-modulated sounds are perceived as being dangerous. On the basis of these results, the present study was designed to investigate the effects of frequency components and temporal factors. Systematically controlled simulated sounds were used as stimuli. The stimuli consist of a sound of 500 msec which is repeated 10 times with off-time. Six kinds of frequency components and four kinds of off-time were used. These 24 kinds of sound were prepared with and without low frequency components. In total 48 kinds of sound were used and their timbre was judged by subjects using semantic differential. The experiment was conducted in Osaka, Oldenburg, Munich and Boston. The differences and similarities among these experiments and the properties of sounds which are appropriate for danger signals will be discussed.

Fedderly, J.

• VIBRATION ISOLATOR PROPERTIES OF A PHASE MIXED POLYURETHANE
  J. Lee, J. Dickens, J. Fedderly, G. Lee and B. Hartmann
[Abstract]

As part of a program to relate the chemical composition of polymers to their vibration isolation properties, a polyurethane of known, controlled composition was synthesized and evaluated. Based on our earlier studies , the first polymer selected to be evaluated was phase-mixed to avoid the complication of hard segment crystallinity. The polymer was synthesized from poly(tetra methylene ether glycol) of molecular weight 1400 reacted with 4,4'-diphenylmethane diisocyanate and chain extended with dimethyl propanediol. Measurements were made in the new Vibration Isolation Test Facility . Four-pole parameters will be presented as a function of frequency from 5 Hz to 2 kHz at different temperatures and static loads. Results at low load will be compared with predictions based on dynamic mechanical measurements of the moduli of the material.

Feng, L.

• A NEW DESIGN OF LIGHTWEIGHT PANEL TO IMPROVE STATIC STRENGTH AND SOUND ISOLATION
  L. Feng and A. Nilsson
[Abstract]

The requirements of strength and of sound reduction of a lightweight panel are sometimes contradictory. In order to increase the static strength of a panel, people often use sandwich panel or make the panel in corrugated shapes. One result of that is a dramatic decrease of sound reduction index, since the high bending stiffness results in low coincidence frequency. One question may arise from that: is it possible to make a material with a high static stiffness to fulfill stability requirement, and with a low dynamic stiffness to make the coincidence frequency higher? A single-sided honeycomb panel, which consists of a honeycomb core bonded to an aluminum face at one side, may fulfill the requirements. The design is tested for three types of configurations with a flat steel panel with similar surface density as a reference: single-sided honeycomb panel alone; the panel plus a woolen absorbent; and the combination of the panel, woolen absorbent and an extra plastic panel (with air gap). Results show that the sound reduction of the complete panel is 4 - 7 dB better than that of the reference one in 1/3 octave band from 250 to 1 kHz. The weighted sound reduction index is also 2 dB better. At the same time, the static stiffness is much higher than that of a flat steel panel.

Feng, Y.

• THREE-PEAK PHENOMENON IN THE SOUND FIELD OF TRANSONIC AXIAL COMPRESSOR
  Y. Lu, Z. Hu, Y. Feng and C. Tsui
[Abstract]

In the cases of different rotating velocity and different duct wall conditions (hard wall and single-segmented or two-segmented liners with perforated plate honeycomb structure), the in-duct noise measurements have been made in a transonic axial compressor facility mounted with an isolated rotor compressor or a single stage compressor. The in-duct noise spectra in subsonic and transonic operating conditions are obtained. By means of studying the noise spectra of the isolated rotor compressor or single stage compressor, a middle peak noise which exists in the BPF bandwidth between shaft passage frequency SPF and blade passing frequency BPF or between two adjacent harmonics of BPF is found. Hence, adding two adjacent harmonic peaks, so called three-peak phenomenon occurs within the BPF bandwidth. When rotors operate at supersonic tip relative speed, the three-peak phenomenon becomes much more obviously. The frequencies corresponding to the middle peak noise are named for BVKF and its harmonics. The interval of two neighboring BVKF harmonics is BPF bandwidth. At the BVKF and its harmonics, not only the discrete pure tone occurs, but also the broadband noise is increased. In addition, the middle peak noise still has a significant influence on the outfield noise. The corresponding predicting formulas of BVKF and its harmonics are presented. The generation of the middle peak noise probably deals with the transmission and multi-interaction of unsteady airflow wakes between support struts or inlet guiding vanes and rotor-stator blades. The mechanism of the middle peak noise will require to be studied further.

Ferng, J.C.

• A REAL-TIME AURALIZATION SYSTEM FOR PC
  J.-H. Wang and J.C. Ferng
[Abstract]

Virtual acoustic simulation is a very important technology in the field of multimedia or virtual reality. Auralization is a process of acoustic simulation by considering the characteristics of the listening space and the binaural effect of humans. Theoretically, the sound pressure heard by a person in an existing space can be recreated by the convolution of the binaural room impulse response (BRIR) with the original signal. However, due to the high sampling frequency of the original signal (for instance, 44.1KHz for CD) and also due to the long duration of the BRIR (for instance, 2s for a typical concert hall), it is impossible to calculate the convolution in real time by the PC nowadays. In this work, the development of a real-time auralization system for PC was described. The binaural room impulse response is the key component of an auralization system. In this work, an efficient method to calculate the BRIR was developed. The method uses the room frequency response function and the head related transfer function (HRTF) to calculate the binaural room transfer function (BRTF). The BRIR is then obtained by the inversed Fourier transform of the BRTF. The BRIR calculated by the proposed method was verified by comparison with the BRIR measured with a dummy head. In order to realize the convolution of BRIR with the original signal in real time, the data points of the BRIR should be properly reduced. It is well known that the BRIR in principle can be considered as the combination of the direct sound, the early reflections and the later reverberation. However, so far no criteria exists to define the so called early reflections quantitatively. In this work, a factor based on the statistical mean free path of the reflections was proposed to define the end point (time) of the early reflections. The data points of the BRIR which belong to the early reflections were then carefully selected according to its importance of contribution to spatial impression and the data points which belong to the later reverberation were modeled by an IIR filter. In other words, only some early reflections which are very important to spatial impression were kept and an IIR filter was added to the early reflections to simulate the later reverberation. The quality of the reduced BRIR is verified by listening test with headphones. According to the proposed method, the computational load can be reduced to 1/360 so that the convolution can be handled by PC in real time. The final auralization system developed in this work can get the signal from HD or CD-ROM and then convolute in real time with the selected BRIR which is stored in PC in advance. The convolution result is output via normal sound card in real time and one can then hear the virtual 3-D sound by headphones.

Fernier, D.

• A SYSTEMATIC METHODOLOGY TO ASSESS SUBJECTIVE HUMAN PERCEPTION FROM OBJECTIVE PHYSICAL MEASUREMENTS WITH SEVERAL INDUSTRIAL APPLICATIONS IN TRANSPORT AND ENVIRONMENT
  B. Baligand, T. Mazoyer and D. Fernier
[Abstract]

This paper deals with the way to build a relationship between objective measurements (from physical sensors) and subjective assessments (expert evaluations). Metravib RDS has carried out several studies concerning the vibroacoustic annoyance, the quotation of car engine combustion noise, the gear box changes comfort and, more recently, the evaluation of car drivers ''workload'' for automotive safety. On these latter topics, the developments could be brought up to the stage of dedicated devices, including sensors and real-time onboard processing units, respectively the so-called Combustiometre and the Driver Situation Recognition Unit (DSRU). All these developments are based on a systematic and generic methodology to find a model of the links between measurements of various sensors and the come back of many experiences acquired by ''experts'' (acousticians, ergonoms, human sciences experts,...). The developed strategy is built on the following steps: 1. Over instrumentation of the studied phenomena: a significant number of sensors (chosen according rules of ''good sense'') are used and associated to various preprocessing (means, RMS, or more complex), providing a large set of signals; 2. First step: data reduction based on cross-correlation and signal to noise ratio; 3. Second step: data reduction (or data fusion) based on statistical correlation with the studied phenomena.; only the relevant inputs are kept in a reasonable number (compatible with real-time processing) for model identification; 4. Model identification: pattern recognition algorithms are exploited to assess the model able to link the physical measurements with the subjective data coming from human experts. In other words, a supervised learning phase is completed on adequate algorithms like multivariate mean square approach (Combustiometre*) up to Neural Networks (DSRU**), that guarantee flexibility and robustness. * This development has been run along a PSA/GIE MOTUS collaboration. ** DSRU is a methodology development lead within CEMVOCAS European Program

Fidell, S.

• DEVELOPING A CRITERION FOR THE ANNOYANCE OF LOW FREQUENCY AIRCRAFT NOISE
  S. Fidell
[Abstract]

Low frequency aircraft noise, such as that caused by thrust reverser application, start of takeoff roll, and (to a lesser extent) overflight noise, can create secondary emissions of windows, doors, and household paraphernalia. These rattling noises can annoy residents of airport neighborhoods independently from the noise of aircraft per se. One interpretation of the findings of recent studies of annoyance due to aircraft noise-induced vibration and rattling suggests a means for developing a criterion for the acceptability of such noise, in terms comparable to the familiar land use compatibility guidance of the U.S. Federal Interagency Committee on Noise.

• STUDIES OF THE ANNOYANCE OF LOW FREQUENCY AIRCRAFT NOISE AT TWO CIVIL AIRPORTS
  L. Silvati, S. Fidell, K. Pearsons, R. Howe and M. Sneddon
[Abstract]

Two field studies of the annoyance of aircraft-induced rattle and vibration in the homes of airport neighborhood residents have yielded information about relationships between noise levels in the one-third octave bands from 25 to 80 Hz and the prevalence of a consequential degree of annoyance among respondents. The findings of the two studies are quite similar with respect to the prevalence of annoyance due to vibration and rattle, as well as the frequency of notice of rattle and the household objects identified as rattling.

• LABORATORY STUDY OF THE ANNOYANCE OF AIRCRAFT-INDUCED SECONDARY EMISSIONS
  K. Pearsons, S. Fidell, L. Silvati and M. Sneddon
[Abstract]

An adaptive paired comparison study was conducted to determine the relative annoyance of runway sideline and aircraft overflight noise, and of the annoyance of rattle associated with low-frequency runway sideline noise. All annoyance judgments were collected in a specialized test facility in which it was possible to produce high sound levels at very low frequencies. It was found that runway sideline noise is more annoying than that of aircraft overflights of similar A-weighted sound levels, and that addition of even minor amounts of rattling noise notably increases the annoyance of runway sideline noise.

• SUMMARY OF FINDINGS OF RECENT FIELD STUDIES OF NOISE-INDUCED SLEEP DISTURBANCE IN THE UNITED STATES
  K. Pearsons, B. Tabachnick and S. Fidell
[Abstract]

Field studies of similar design of the ability of aircraft noise to disturb sleep been completed within the last several years near five airfields in the United States. These have included large military and civil airfields, as well as a general aviation airport. The results of these studies indicate that relatively few nighttime noise intrusions disturb sleep, and that residential populations near airports are either self-selected or adapted to such nighttime noise. Non-acoustic factors (such as the meaning of nocturnal noise intrusions) may well account for much of the ability of sounds to awaken people sleeping in familiar quarters.

• INTERPRETING THE FINDINGS OF SOCIAL SURVEYS OF NOISE-INDUCED ANNOYANCE
  S. Fidell
[Abstract]

Much of the rationale for policy positions taken by regulatory agencies concerning habitability of residential areas and compatibility of land uses with transportation noise is supplied by analyses of social survey findings. These findings admit of more than one interpretation, are easily over-interpreted, and are widely mis-understood. Under such conditions, dosage-response relationships derived from the corpus of social survey findings can be little more than de facto policy statements. Because their work may have a direct bearing on the public interest, those who conduct primary and secondary analyses of findings in this area should be knowledgeable and cautious about the uses to which their work may be put.

Fields, J.M.

• A TEST OF THE EFFECT OF QUESTION WORDING ON MEASURED NOISE REACTIONS: A COMPARISON OF JAPANESE AND ENGLISH QUESTIONS
  J.M. Fields, T. Yano, K. Masden, J. Hatfield and R.F.S. Job
[Abstract]

An internationally comparable noise reaction measure has been proposed that consists of a pair of standard social survey questions with answer scales developed from empirical studies. It was previously reported that when English-speaking and Japanese-speaking subjects used these scales to report their feelings about the same sounds, Japanese subjects gave more negative scores. This paper provides the results from a further study that seeks to explain those negative scores by contrasting the annoyance reactions measured with three social survey questions that use identical answer scales but differ in the severity of the reaction presented in the base (stem) of the question. The three forms of the questions differed in asking subjects for either: (Form#1) a rating of the noise, or (for the other forms) the extent to which subjects were personally either (Form#2) annoyed or (Form#3) worried, irritated or concerned. Sets of Japanese subjects and English-speaking countries' subjects used one of the three questions to rate 16 sounds and 10 environmental noise situations in their respective languages. The analysis does not support the hypothesis that a more severe response question reduces reports of annoyance reactions.

Filippou, T.

• THE TIMBRE AND ANNOYANCE OF AUDITORY WARNING SIGNALS IN DIFFERENT COUNTRIES
  S. Kuwano, S. Namba, A. Schick, H. Hoege, H. Fastl, T. Filippou, M. Florentine and H. Muesch
[Abstract]

It is desirable to have internationally standardized warning signals which are used for informing people of dangerous happenings. The results of our former studies suggest that there is a cross-cultural difference in the impression of some signals and that generally speaking frequency-modulated sounds are perceived as being dangerous. On the basis of these results, the present study was designed to investigate the effects of frequency components and temporal factors. Systematically controlled simulated sounds were used as stimuli. The stimuli consist of a sound of 500 msec which is repeated 10 times with off-time. Six kinds of frequency components and four kinds of off-time were used. These 24 kinds of sound were prepared with and without low frequency components. In total 48 kinds of sound were used and their timbre was judged by subjects using semantic differential. The experiment was conducted in Osaka, Oldenburg, Munich and Boston. The differences and similarities among these experiments and the properties of sounds which are appropriate for danger signals will be discussed.

Filomena, V.

• PREDICTION OF THE NOISE POLLUTION CAUSED BY MILITARY AIRCRAFT FLYOVERS
  L. Maffei, V. Filomena, R. Romano and R. Capriotti
[Abstract]

Military aircraft operation in the surroundings of airports may give rise to strong complaints by people living nearby. If possible, the operation should be scheduled and carried out in a way that minimizes the noise impact on inhabited areas. In this perspective, predictive noise models can help in attaining the above-mentioned goal. The authors are engaged in the experimental collection of data during military aircraft operations in order to obtain the information required by existing predictive models for aircraft noise (e.g. INM - Integrated Noise Model). First comparisons between predicted and measured values will be reported in this paper.

Fleming, G.G.

• UPDATED LATERAL ATTENUATION IN FAA'S INTEGRATED NOISE MODEL
  G.G. Fleming, J. Burstein, A.S. Rapoza, D.A. Senzig, J.M. Gulding and T.L. Connor
[Abstract]

The lateral attenuation algorithm in the Federal Aviation Administration's (FAA) Integrated Noise Model (INM) has historically been based on the two regression equations described in the Society of Automotive Engineers' (SAE) Aerospace Information Report (AIR) 1751. These equations, which together represent a single relationship developed from measured data for 1960s and 1970s aircraft with low-bypass ratio jet engines, are applied equally in INM to the entire aircraft fleet. Further, these equations cannot take into account the effects of propagation over acoustically hard terrain, such as water. Consequently, in 1997 the INM development team initiated the task of revising the lateral attenuation algorithm within the model. The primary component of the revised algorithm is an entirely new methodology for taking into account ground effects. The methodology, which is based upon a newly-compiled spectral data base, along with the physical acoustics model of Embleton, Piercy and Daigle, will exist in INM as a library of regression equations. As such, this approach will offer the accuracy and flexibility of a pure physical acoustics model, coupled with relatively modest computer runtimes. This paper documents the scientifically-founded and experimentally-validated approach to computing ground effects, which is slated for inclusion in the INM.

Flindell, I.

• NIGHT-TIME AIRCRAFT NOISE AND SLEEP - THE 1999 UK TRIAL METHODOLOGY STUDY USING BOTH FIELD AND LABORATORY METHODS
  K. Robertson, I. Flindell, M. Jiggins, N. Wright and C. Turner
[Abstract]

The 1992 UK Field Study of night-time aircraft noise and sleep found a low incidence of objectively measurable sleep disturbance (awakenings once asleep) attributable to individual aircraft events. On the other hand, aircraft noise at night remains an issue of public concern and laboratory studies generally find higher sensitivity to noise at night than is typically observed in field studies. The 1999 UK Trial Methodology Study was commissioned by the Government to assist it in arriving at an informed decision on whether or not to proceed with a full-scale sleep study. It is investigating the feasibility of 'extending' the 1992 UK Field Study to the shoulder hours; whether sleep patterns in 'high' and 'low' night-time aircraft noise areas exhibit systematic differences; and the feasibility of studying sleep disturbance among noise-sensitive people. An additional objective was to compare field and laboratory data under test conditions that were as closely matched as possible. The trial study utilised a full set of in-situ EEG and other phsyiological measurements including actigraphs as used in the 1992 UK Field Study, together with comprehensive acoustical (simultaneous indoor and outdoor) measurements and next day performance and sleep latency measurements. The shoulder hours issue was addressed by controlling the distribution of noise events in the laboratory, something which cannot easily be done in the field. Subjects for the field study were selected from representative areas with differing amounts of aircraft noise. Only self-reported noise sensitive people were invited to take part. The preliminary results show some statistically significant effects even with relatively small numbers of subjects, and indicate the potential of the combined laboratory and field study experimental paradigm.

• RESEARCH METHODOLOGY - NOISE ANNOYANCE AND HEALTH
  J. Cartwright and I. Flindell
[Abstract]

The possibility that excessive residential exposure to general environmental noise might contribute to long term adverse health effects in addition to annoyance remains an issue of public concern. The underlying hypothesis that unwanted sound causes annoyance which contributes to stress and which in turn might contribute to long term adverse health effects appears plausible but it is difficult to define in scientific terms and our understanding of any possible aetiological mechanisms is incomplete. Where similar uncertainty exists in other areas of environmental research, regulatory authorities tend to err on the side of caution to minimise any residual risk. The field of environmental noise is perhaps more complicated because sound is intrinsically neutral and only becomes noise because of the way that people react to it. Unjustified or excessive sound level reduction could have equally significant social, economic, or unexpected health consequences. There are situations where the socio-economic costs of noise control could outweigh the benefits. The solution to many of these problems is to focus future research on mechanism rather than on prevalence. Instead of trying to find out the percentage of the population affected and then encountering what can be insurmountable difficulties because of confounding factors, we should be designing carefully controlled experiments to investigate mechanism. Only when we understand mechanism will we be able to make sensible predictions of future effects.

• THE IMPLICATIONS OF CONTEXT-BASED ASSESSMENT FOR NOISE MANAGEMENT
  I. Flindell and N. Porter
[Abstract]

Practical noise management is about balancing noise assessment against the many other consequences of proposed noise control actions. Most human activities generate sound, which only becomes noise when it has some unwanted effect on people. The social or economic consequences of changing or regulating noise generating activities can outweigh the benefits of lower noise levels achieved, but it can be difficult to make such comparisons because of the different scales and weightings which necessarily apply. For noise assessment the key outcome variable is reported or implied annoyance. This is essentially a psychological construct and can be highly dependent on individual differences in interpretation. Other outcome variables such as speech interference, sleep disturbance or alleged non-auditory health effects can also involve considerable uncertainty. While generalised dose-effect curves provide simple solutions for strategic assessment, they cannot reflect the true complexity of individual cases where differences in (for example)context, soundscape, or public perceptions of institutional motives can be as or more important than noise levels per se. The implications for effective management are these: first, any presenting noise problem should be defined in terms of the available alternative courses of action; second, assessment should be addressed to all the main variables affected by the available alternatives. Many of these variables will need to be reported separately in some kind of framework which may need to be adapted to suit a particular case; third, noise assessment must be balanced against all other consequences of the available alternatives and only then should practical decisions be taken.

Floc'h, C.

• VIBRO-ACOUSTIC SIMULATION USING GEOMETRICAL ACOUSTICS IN THE MEDIUM FREQUENCY RANGE INSIDE A CAR CAVITY
  C. Floc'h, A. Bardot, J.-D. Polack and X. Bohineust
[Abstract]

In the automotive industry, the need for listening the results of vibro-acoustic simulations is more and more expressed. This paper presents a vibro-acoustic model based on geometrical concepts, well suited to noise synthesis in the medium frequency range. Although geometrical acoustic models have been widely used in hall acoustics for ponctual sources, only Jean attempted to use them for structural radiation. He compared BEM and geometrical results in weak coupling conditions, for which he obtained a good agreement. The model presented here calculates the acoustic radiation of a vibrating structure inside a closed cavity using an integral formulation coupled to a geometrical approach for the acoustic propagation. It rests on a decoupling hypothesis between the acoustic pressure radiated and the vibration of the structure. The model is compared to experimental results. The experimental set-up consists in a rigidified car cavity with absorbing material on the walls, on which an elastic panel is mounted and excited through a shaker. The vibration of the structure, entry of the radiation model, is measured with an holographic interferometry system, which provides a very good accuracy in the frequency range measured, [0-1300 Hz]. Model validation is made both by comparing response curves in the time and frequency domains, and by conducting listening tests on a panel composed of 36 people. Comparison of modelisation and experimental results on perceptive criteria (triangular perceptive tests between measurements and simulations) shows that the model quality is correct, although some coloration differences are still perceived.

Florentine, M.

• THE TIMBRE AND ANNOYANCE OF AUDITORY WARNING SIGNALS IN DIFFERENT COUNTRIES
  S. Kuwano, S. Namba, A. Schick, H. Hoege, H. Fastl, T. Filippou, M. Florentine and H. Muesch
[Abstract]

It is desirable to have internationally standardized warning signals which are used for informing people of dangerous happenings. The results of our former studies suggest that there is a cross-cultural difference in the impression of some signals and that generally speaking frequency-modulated sounds are perceived as being dangerous. On the basis of these results, the present study was designed to investigate the effects of frequency components and temporal factors. Systematically controlled simulated sounds were used as stimuli. The stimuli consist of a sound of 500 msec which is repeated 10 times with off-time. Six kinds of frequency components and four kinds of off-time were used. These 24 kinds of sound were prepared with and without low frequency components. In total 48 kinds of sound were used and their timbre was judged by subjects using semantic differential. The experiment was conducted in Osaka, Oldenburg, Munich and Boston. The differences and similarities among these experiments and the properties of sounds which are appropriate for danger signals will be discussed.

Fog, C.L.

• HOW CAN PSYCHOMETRIC METHODS BE USED IN THE DESIGN OF AN ADEQUATE PRODUCT SOUND?
  C.L. Fog
[Abstract]

Sounds from products are a very essential part of the perceived quality. Although the Product Sound should not be treated as an isolated phenomenon, it makes sense in many cases to optimise this characteristic to improve the overall perceived quality and thereby the user satisfaction with the product. Product Sound can be considered as information, which is relevant in relation to sounds in for example the user interfaces of the products/systems, but Product Sound can also be considered a part of the total experience using a product/system, which is a more marketing-oriented approach. For the development or redesign of the sound from a product a model for the working process called the ''Product Sound Wheel'' has been created. The use of test panels plays here an important role, and some viewpoints concerning methods and techniques will be given. A practical application of the model for optimising a typical consumer product from the ''white goods family'' will be discussed. Finally, some outline for future research work within a new project on Human Perception of Sound will be presented.

Fogola, J.

• A PURPOSE OF AN ACOUSTIC CRITICAL INDEX FOR THE ESTIMATE OF THE PRIORITIES OF INTERVENTION IN AN HIGHWAY GLOBAL REORGANISATION PLAN
  J. Fogola, F. Duretto, R. Giovinetto and R. Pisani
[Abstract]

The aim of our present study is to propose a method for an acoustical critical analysis of territories crossed by large road infrastructures (highways, freeways, etc..). Definition of the Critical Index of Priority. In a global highway acoustic reclamation plan, it is of fundamental importance to characterize in detail the different critical areas interested from the acoustic impact. The concept of the critical area must be unambiguously fixed in all the portions of territory in which the acoustic impact of the road exceeds the fixed limit values. It is possible to fix a critical index (C.I.) for each area in order to obtain in an objective way the priorities of a reorganization plan. The parameters that concur to the determination of this index should be, to judgement of writing, the following: Number of annoyed persons Noise levels Fixed maximum levels Corrective factors The determined index presupposes the knowledge of the noise level in front of all the buildings of a critical area, obtained through a limited number of measures in significant points and by means of forecast calculations in all the remaining points. Conclusions: the Critical Index gives an instrument for the definition of acoustic intervention priority to the competent institutions and a technical aid to the professional person in charge of the reorganisation plan to make the suitable choices for the projects.

• DEFINITION OF A PROPAGATION MODEL OF TRAFFIC NOISE IN SATURATION CONDITIONS
  C. Varaldi, J. Fogola and L. Bellina
[Abstract]

This model of propagation here illustrated has been obtained through a regression model in traffic saturation conditions. In traffic saturation conditions the noise level does not follow a logarithmic curve but a quadratic curve in relation to the equivalent number of vehicles. In order to analyse this phenomenon a set of measurements has been carried out in the outskirts of Turin (Italy). The traffic flow has been analysed at different times of the day, paying special attention to moments of traffic congestion. Two different charts have been drawn up: a logarithmic chart for the first measure points (in situation of normal traffic flow) and a parabolic one for the traffic congestion points. A mathematical function joining the two curves has been found, in order to have a complete description of the phenomenon. The theoretic figures have proved to be basically in accordance with the experimental ones.

Forián Szabó, P.

• PREDICTION OF THE AUDIBLE EFFECTS IN A BROADCASTING STUDIO, CAUSED BY A NEWLY PLANNED METRO LINE - PART I: ESTIMATION OF DESIGN VIBRATION SPECTRA ON THE STUDIO WALLS AND FLOORS
  P. Forián Szabó, E. Arato-Borsi and F. Augusztinovicz
[Abstract]

A new metro line is being planned in the vicinity of the main buildings of the Hungarian Radio in Budapest. The task, the proposed paper reports about was to predict, whether or not audible disturbances in consequence of the train pass-by in the tunnel are to be expected, and if this is the case, what kind of control measures are necessary and feasible (determination of minimum separation distance in the ground between the new tunnel and the broadcasting studios, vibration isolation in and construction of the tunnel etc.). A prediction method was elaborated and verified on existing metro lines and buildings under similar conditions. It consists of essentially three major steps: development of a vibration prediction model on the basis of measurements; adoption of calculation methods for sound level prediction from vibration data; and verification of the calculations and development of guidelines for the tunnel design. This lecture deals with the first step: How to estimate the design vibration spectra on several parts of the broadcasting studio structures, based on vibration measurements along the metro tunnel, transmission from similar tunnels and soil conditions as well as calculations on a similar building on an existing metro line.

• PREDICTION OF THE AUDIBLE EFFECTS IN A BROADCASTING STUDIO, CAUSED BY A NEWLY PLANNED METRO LINE - PART III: VERIFICATION OF THE PREDICTION METHOD, COMPARISON OF MEASUREMENTS AND CALCULATIONS
  E. Arato-Borsi, P. Forián Szabó, F. Kvojka and F. Augusztinovicz
[Abstract]

The third part of the paper series demonstrates the applicability and accuracy of those methods presented in Parts I and II. First, another building in the vicinity of an existing metro line was selected in the same area of Budapest with similar conditions (including building structures, soil conditions, tunnel depth and distance from the building etc.). Operational building vibrations were measured and eigenfrequencies determined. The finite element modal model was verified and updated on the basis of the measurements, and forced responses for realistic vibration conditions were run. The statistical calculations were based on measured wall vibrations and room acoustic parameters. The calculated sound pressure levels were compared to measured spectra and it was found that, in spite of many assumptions and approximations, relatively good agreement was found. Therefore, the method was applied to the studio building and it could be established, that without special vibration control measures, noise problems are to be anticipated.

Forschner , H.

• PREDICTING CONVERGENCE ZONE PROPAGATION IN ENVIRONMENTAL NOISE MEASUREMENTS
  R. Bronsdon and H. Forschner
[Abstract]

This paper deals with upwind propagation of sound in temperature inversion conditions. When the proper wind and temperature profiles exist it is possible to form either an elevated duct, where sound will propagate at 3dB/DD, or perhaps even a convergence zone where the propagating sound will not be attenuated any appreciable amount. We experience these types of propagation when we hear familiar sounds that seem to have moved closer. A good example would be the sound of a highway or train at a great distance, which suddenly seems to be running right through the back yard. A simplified calculation based on Gaussian Beams allows the investigation of conditions under which these types of phenomenon could possibly occur. More sophisticated analysis techniques also show how convergence zone propagation can impact noise measurements made out of doors.

Forssén, J.

• CALCULATION OF NOISE BARRIER PERFORMANCE IN A TURBULENT ATMOSPHERE BY USING SUBSTITUTE SOURCES ABOVE THE BARRIER
  J. Forssén
[Abstract]

A model is presented that can be used for calculating the sound reduction by a noise barrier in a turbulent atmosphere. The field due to the acoustic source is substituted by a distribution of sources above the barrier (here called substitute sources). The mean power at the receiver is calculated as line-of-sight propagation through a turbulent atmosphere from all substitute sources using a mutual coherence function. In this study the strengths of the substitute sources are calculated using the Kirchhoff approximation and a two-dimensional geometry. The calculated results show good overall agreement with those from using a parabolic equation method.

Frances, A.K.

• A STUDY OF VIBRATION TRANSMISSION AT JOINTS IN TIMBER FRAMED BUILDINGS USING STATISTICAL ENERGY ANALYSIS
  J.A. Steel and A.K. Frances
[Abstract]

Vibration transmission at joints between walls and floors in timber framed buildings is studied in this work. To calculate sound insulation in this type of lightweight construction modelling airborne and structure borne noise is needed. Much work has been carried out modelling the airborne noise transmission using statistical energy analysis (SEA) but it is very difficult to verify models of structural vibration between walls and floors where beams, plate elements and stiffeners are present. In this work a series of simplified laboratory models of these joints are studied so that the best ways of modelling vibration transmission can be identified. Measured level difference data for transmission between plates representing the floors and walls is presented. The measured data is compared with predictions calculated using SEA models of the joints and good agreement is found. Coupling is calculated using wave methods and wave dynamic stiffness techniques to model the plate elements and beams in the joints. The results show that vibration transmission at this type of joint can be predicted using SEA techniques.

Franchek, N.

• TIRE/PAVEMENT INTERACTION NOISE RESEARCH ACTIVITIES OF THE INSTITUTE FOR SAFE, QUIET, AND DURABLE HIGHWAYS
  R. Bernhard, N. Franchek and V. Drnevich
[Abstract]

Tire/road interaction noise is the major source of highway sideline noise at highway speeds. Increased traffic flows and population densities have caused a greater interest in this source of environmental noise. The Institute for Safe, Quiet, and Durable Highways (SQDH) was established at Purdue University in 1999 to investigate the development of quiet highway technology that is safe, durable, and economical. This Institute is a joint effort between the Schools of Civil and Mechanical Engineering. The goals of the SQDH Institute include education, research, and technology transfer activities. The research program of the SQDH Institute is intended to be complementary to world-wide research on tire/pavement interaction noise. Both tire and pavement issues will be studied. Initial emphasis will be given to fundamental investigations of the mechanisms of tire/pavement noise generation and control. Laboratory facilities will be constructed to facilitate acoustic and vibration measurements of tires rolling on realistic road surfaces. In addition, analysis methods will be developed to better understand wave transmission and sound radiation from tires. Future work will involve implementation of the understanding of tire/road noise generation mechanisms to the practical issues of quiet highway construction and maintenance, material design, and traffic management. This application of quiet highway technology will hopefully reduce the need for noise barriers. A review of ongoing SQDH Institute research programs and available results will be presented. Future plans and potential collaboration

Franchi, A.

• A COMPLEX LEGISLATION: THE AIR TRANSPORT NOISE
  S. Curcuruto and A. Franchi
[Abstract]

The italian framework law on environmental noise pollution of the 26 October 1995, n.447 establishes the general principles but defers to other following decrees the regulation for specific noise sources or noisy activities; in particular, for one of the most important noise sources as the aircraft noise it has been necessary to define five decrees to complete the specific legislative measures. The Italian legislative approach to obtain a reduction of noise produced by air transport is based on the following action lines: to characterise the areas around the airport fixing noise limits and limitations of the territory use for each area; to define a measure methodology of the air transport noise; to define for each airport antinoise procedures that must be respected by aircraft during landing and take-off; to impose monitoring in continuous systems around the airport to protect the population controlling the noise emitted by the aircraft and the relative antinoise procedures followed; to classify the airports on the basis of the noise pollution levels produced on the surrounding environment; to impose reclamation measures in case of non-respect of noise limits; to impose the limitation of air traffic during the night period. In our country, the characteristics of the land together with the strong urbanisation impose the duty of conciliating the necessity of development of the airport infrastructure and the needs of territorial planning of the municipality that can suffer a limitation for the fruition of its own territory.

Franco, G.

• A LONG-TERM STUDY ON HIGH LEVEL MUSIC EXPOSITION AND HEARING EFFECTS IN ADOLESCENTS
  M.R. Serra, E.C. Biassoni, U. Richter, G. Minoldo, G. Franco, S. Abraham, S. Joekes, M.R. Yacci, A.R. Pollet and A.J. Carignani
[Abstract]

Sources of noise exposure outside the workplaces that are potentially damaging has been topic of many studies (Clark, 1991). Young people are exposed to high level music in discotheques or through personal listening devices. The literature reveals that there are different opinions about possible harmful hearing effects of music (Babish et al., 1988, West et al.,1990; Axelsson, 1990 & 1996; Royster et al., 1990; Ising et al., 1995). This paper deals with the early results of an interdisciplinary long-term study on hearing effects in adolescents by high level music exposition and its relation with physical and psychosocial variables, developed according international standards. Two groups of adolescents -males and females- are examined along four years of their high school level, from 14 to 17 years old. The study focus on changes both, in hearing threshold, applying conventional and extended high frequency audiometry, as well as, in recreational activities. Besides, sound inmission levels of the adolescents studied are measured: a) in discotheques using two methods: by personal dosimetry and by a system developed ad-hoc; b) using walkman and/or diskman: through manikin-technique. In the second year of the study the results show: a) hearing threshold shift in most of the extended high frequencies; b) increase in the music exposure through recreational activities; c) high sound inmission levels in discotheques and trough personal music devices. The whole study, during four years, let will us to know the real hearing effects by music exposition and their relation with psychosocial variables in the studied adolescents group.

Francois, A.

• A PHYSICALLY BASED STRATEGY FOR ROBUST FEEDBACK CONTROL OF NOISE RADIATION FROM A BAFFLED PLATE
  P. De Man, A. Francois and A. Preumont
[Abstract]

This study is based on the premise that the robustness of a control system often relies far more on the design of the open-loop system (i.e. the choice and location of sensors and actuators) than on the specific feedback compensator used. Accordingly, a careful vibroacoustic analysis is used to reduce the open-loop system to a single-input single-output control problem with a number of desirable features from the point of view of controllability and robustness. The strategy proceeds in three steps : (1) An array of piezoelectric patches located on a regular mesh is connected to a linear combiner to produce a volume velocity sensor; the coefficients of the linear combiner are determined from experiments to minimize the error between the reconstructed and the measured quantities. The volume velocity is known to be closely related to the sound power radiated by a baffled plate at low frequency. This step achieves a single-output sytem. (2) A small set of actuators (either point force or piezoceramic) is constrained to operate with the same voltage to achieve a single-input system; the location of the actuators is then optimized to provide the open-loop with the following desirable features: - Alternating poles and zeros are sought within the control bandwidth to enhance the immunity with respect to the parametric uncertainty. - The magnitude of the resonance peaks is maximized within the control bandwidth to increase the control authority. - The magnitude of the resonance peaks is minimized near and right after cross-over to improve the gain margin and reduce spillover. The optimization procedure uses a genetic algorithm. (3) Using this specially designed SISO open-loop system, the next step consists of designing the feedback compensator. This paper illustrates that low order, model independent, classical compensators such as a lead  produces a subtantial low frequency noise attenuation. The paper presents a hardware demonstration of step (1) and numerical simulations of step (2) and (3).

Franconi, J.M.

• MAGNETIC RESONANCE IMAGING OF ELASTIC WAVE FIELDS IN CONDENSED MATER
  C.J. Lewa, J.M. Franconi, M. Ruth and J.D. De Certaines
[Abstract]

At the beginning of the nineties, we have developed a method of motion sensitive gradient in-conjunction with a periodic mechanical compression for Magnetic Resonance Imaging (MRI) and Elasto-Magnetic Resonance Spectroscopy (EMRS) of visco-elastic properties. The first of elastic waves imaging method has been successfully applied, for transversal elastic waves, in 1995 by Muthupillai et al. under the name of Magnetic Resonance Elastography and by Plewes et al. in the range of low frequencies for tranverse waves, as well as for longitudinal waves at ultrasonic frequencies. These previous methods use a synchronization between the magnetic field gradient pulse and mechanical vibration and then require an a-priori knowledge of the frequency of the motion to bee detected. In addition to various ultrasonic methods, MRI can be a good challenger for such measurements as it provides imaging of 3D samples as higher quality than usually obtained by other imaging methods. Some recent MR elastography studies present interesting results on mammography and on ''brain palpation''. The goals of this study were to realize the unsynchronized EMRS method allowing the analysis of the intensity, direction and frequency of an unknown elastic wave field in a 3D sample. The experimental verification is performed on a routine low field MRI (0.2 T) device. An additional goal was to maintain the acquisition time enough short to make the method compatible with routine MRI examinations. The method raises hopes for possible applications in imaging of elastic wave fields (bio-acoustics, geo-acoustics, noise field analysis, material characteristics) as well as in fundamental research.

Franssen, E.

• ANNOYANCE AND HEALTH AROUND SCHIPHOL AIRPORT AND IN A CONTROL AREA
  E. Franssen, I. Van Kamp and R.G. De Jong
[Abstract]

In 1996 a questionnaire-based survey was carried out around Schiphol airport as part of the research programme ''Health Impact Assessment Schiphol Airport (GES)''. In the same period the Community Health Service in the Northwest part of the Netherlands conducted a survey, making use of the same questionnaire. This area is free from airport noise caused by Schiphol airport, and as such is suitable as a control area for the Schiphol study. Based on these two studies levels of annoyance and health indicators are compared in three exposure-categories: - A high exposed area around Schiphol airport with noise-exposure. - A low exposed area around Schiphol airport. - A control area with no Schiphol related aircraft noise. Previous analyses of the Schiphol data were restricted to effects of aircraft noise within a radius of 25 km around the airport. The results showed that even in areas with a low aircraft noise exposure, people are annoyed and report health effects. It is interesting to study whether also in a control area these effects occur. The hypothesis is that prevalance of annoyance and health aspects in the low exposed area around Schiphol are equal to those in the control area.

Frantzeskakis, J.

• REHABILITATION OF THE ACOUSTIC ENVIRONMENT OF THE CITY OF RHODES
  J. Frantzeskakis, J. Simandonis and C. Vogiatzis
[Abstract]

The Ministry of Planning, Environment and Public Works assigned in 1997 to the Department of Transportation Planning and Engineering of the National Technical University of Athens, the research project ''Programme for Noise Abutment in Tourist areas''. The project, completed in 1999, investigated the causes of noise in tourist areas, developed guidelines and general specifications for planning and implementing a programme of short and long-term antinoise measures and projects and carried out a pilot application in a Greek tourist city. The paper presents this pilot application in the selected city of Rhodos. Detailed acoustic measurements, compled with traffic counts and opinion surveys were carried out in the summer of 1998 with 1999 in Rhodos and were compared with the results of similar earlier works. Based on the evaluation of the above, noise sources were identified and a quantitative and qualitative differentiation of the effects by category of source and time was carried out. Short and long-term interventions were proposed concerning: a. Legal changes b. Administrative changes c. Town Planning d. Transportation Planning and Traffic Management e. Technical Applications f. Information of Public and Competent Authorities Such interventions included measures extending from the relocation of night activities away from noise-sensitive areas, to the proper noise-control of the large and increasing number of motorcycles which, in some cases, constitute the 50% of the traffic flows.

Frenne, N.

• CALCULATION OF TIME HISTORIES FROM A SUBDIVIDED SOUND SOURCE
  N. Frenne and Ö. Johansson
[Abstract]

A sound source, for example an IC Engine, might be seen as a combination of different partial sources. Usually the receiver of the sound, from e.g. a vehicle, is exposed by the sound of the engine through several different transfer paths, where each influences the perception of the sound. Here, analyses of transfer functions give a possibility to describe effects of emitted sound from partial sources of a complex source in various acoustical environments. Sound quality should therefore be easier to improve with knowledge of how transfer paths effect the sound emitted from these sources. The objective of this study is to use a method of partial source characterisation and reciprocally measured transfer functions in combination with inversion methods to receive the time history of the source strength of the partial sources. Also, a comparison of different receiving positions is made to see their influence on the calculated time histories. The result is presented as a comparison of frequency spectra from the partial sources of the sound source and frequency spectra of the calculated time histories of these partial sources. Conclusions and suggestions of proceeding work are stated from the result.

• RELATIONSHIP BETWEEN HRTF'S AND ANTHROPOMETRIC DATA
  D. Trapenskas, N. Frenne and Ö. Johansson
[Abstract]

The objective of the experiment is to investigate the feasibility of the technique to relate HRTF's to physical dimensions of the human subjects. For this purpose HRTF's and five physical dimensions of the pinna were measured on 7 subjects. HRTF's were measured at 12 positions in horizontal plane at the level of the subject ears in anechoic chamber. Physical dimensions were estimated from scanned images of the subject ears. Frequencies of the first predominant dip in HRTF's were estimated and correlated with measured physical dimensions. Correlation coefficients between concha breath and first predominant dip at the sound source position in front, and ear breadth and first predominant dip at the sound source position in back were found to be statistically significant.

Frenz, E.

• NOISE SOURCE EVALUATION TESTING ON MTS SERIES 320 ROAD SIMULATOR
  E. Frenz, S. Dumbacher, R. Allemang and M. Mergeay
[Abstract]

The MTS Series 320 Road Simulator, well known for durability testing, are more and more used for general acoustic evaluations, e.g. squeak and rattle evaluations, ... during the development process of today's cars. This calls for specific noise characteristics of the testing devise. The purpose of this study was to perform a detailed noise source evaluation of the Road Simulator. A number of acoustic tests were conducted. First the baseline noise characteristics, followed by the location and quantification of the noise sources. In the next part of this paper the evaluation of use of enclosures in isolating the noise sources was studied. Finally, recommendations are formulated and implemented, resulting in strongly improved noise characteristics.

Freymann, R.

• AN ACTIVE ABSORBER TO IMPROVE THE SOUND QUALITY IN THE PASSENGER COMPARTMENT OF VEHICLES
  H. Spannheimer, R. Freymann and H. Fastl
[Abstract]

It is true that luxurious (chauffeur driven) sedan vehicles offer a high acoustic comfort. Due to the implementation of an effective passive sound attenuation treatment package, the major part of the overall acoustic annoyance can be reduced to an acceptable level. This especially applies to the higher frequency range where the acoustic treatment, e.g. with regard to its absorption capabilities, can significantly contribute to improve the acoustic performance of the vehicle. On the other hand, passive treatments do not allow to noticeably influence the low frequency comfort in the passenger compartment. This must be considered as a great disadvantage since it is a well known fact that especially a further improvement of the low frequency noise characteristics could significantly improve the noise quality perceived by the passengers. The benefits of active absorbers to reduce the low frequency acoustic level in the passenger compartment of a vehicle are shown. A highly compact active system, consisting out of microphones as sensors, loudspeakers as actuators and of a control system circuit, will be presented. Special focus will be placed on the system's operation characterized by its broad-band frequency behaviour comparable to the acoustic properties of a system realized by a series of narrow-banded Helmholtz resonators. Thus, the system presented can be regarded as an active absorber formed by an active device featuring the characteristics of a broad-band Helmholtz resonator. In addition to the description of the optimum construction and tuning parameters of the active absorber, detailed results as to its acoustic overall performance and with regard to its many possibilities offered to influence the sound quality in the passenger compartment of vehicles will be presented.

Frid, A.

• BOGIE SKIRTS FOR RAILWAY VEHICLES: EFFECTS ON INTERNAL NOISE
  U. Orrenius and A. Frid
[Abstract]

To meet the external noise requirements from trains, bogie skirts are often suggested as a noise control measure. However, such measures also affect the internal noise as acoustic energy is redistributed from outside the car-body walls to the bogie area. Accordingly, requirements on noise insulation of floors and walls should be redefined to reach the same internal noise levels as for a standard vehicle, keeping an optimum weight distribution of walls and floor. For certain rail vehicles, e.g. when requirements on interior space and vehicle weight are restricting the potential sound insulation on the walls, bogie skirts may be beneficial to reach a design optimum with respect to weight and interior noise. Furthermore, if the sound pressure levels outside car-body walls can be reduced, simpler window solutions can be chosen, saving costs and weight. In the present work, insertion loss functions from measurements on a bogie model with various skirt lay-outs are compared to results from a simple analytical model. It is shown that the level in the bogie room is generally increasing whereas those outside the car-body wall are decreasing as an effect of bogie skirts. These effects are rather strongly depending on the rail/wheel source configuration and frequency. The results are discussed with respect to noise insulation requirements on walls and floors as well as potential weight savings on the vehicle.

• DESIGN OF A RAILWAY WHEEL WITH ACOUSTICALLY IMPROVED CROSS-SECTION AND CONSTRAINED LAYER DAMPING.
  C. Jones, D. Thompson, A. Frid and M. Wallentin
[Abstract]

The rolling-noise generating characteristics of a railway wheel design have been studied theoretically. Two aspects of design for reducing noise have been investigated, optimisation of the cross-sectional shape of the wheel and addition of a constrained layer damping treatment. Both strategies are followed allowing for the thermo-mechanical constraints for tread-braked wheels. A finite element model is used to produce the modal responses of the wheel. For the wheel without damping treatment, approximate damping ratios are known from previous measurement experience. The exact modal damping ratios are not important since energy loss from the wheel is dominated by the effect of its contact with the rail during rolling. In order to produce significant noise reduction the damping achieved by the constrained layer treatment must exceed the effective 'rolling damping'. To predict the modal damping of a wheel with visco-elastic layers a method of complex eigenvalue analysis has been used. The analysis indicates that the wheel component of rolling noise from the UIC standard tread-braked freight wheel can be reduced by more than 6 dB (A) by a combination of the two measures.

Friedrich, G.

• ANALYSIS OF THE NOISE, VIBRATION AND TRANSMISSION CHARACTERISTICS OF INDUCTION MOTORS
  R. Dib, J.-C. Henrio, A. Hubert, G. Friedrich and P. Wagstaff
[Abstract]

The noise and vibration characteristics of induction motors constitute one of the principal problems facing their use in industrial applications. The high frequency components generated by the signal modulation of the electronic convertos are particularly disturbing and difficult to suppress. In order to reduce these effects the pulse width modulation frequency can be increased to above the range of the human ear, but this approach leads to reduced motor efficiency due to the higher electromagnetic losses and very high stress of the power electronics components. In order to successfully deal with these noise problems the internal vibration generation mechanisms, the transfer characteristics to the structure and the noise radiation by the motor body and the rest of the machine structure have to be thoroughly investigated. In this paper we deal briefly with the predicted results for the primary generation mechanisms in the motor, the effects of the coupling of the internal mechanisms with the vibration characteristics of the motor body and investigate the radiated sound levels of the motor under free running conditions. One of the specific problems is to quantify the vibrations transmitted to the machine structure when the motor is coupled to the machine. The transmitted vibrations are then transformed into noise levels which may be considerably greater than that generated directly by the motor. In order to investigate these effects, inverse force identification techniques were used to characterise the forces at the motor- structure interface. It is shown that the vibration response can be estimated using a relatively simple force distribution model at the motor flange and structure interface.

Friot, E.

• A 3D REAL-TIME ALGORITHM FOR ACTIVE SCATTERING CONTROL
  E. Friot, M. Winninger and C. Bordier
[Abstract]

Whereas active noise control usually deals with the total acoustic pressure, in some cases only one component of the noise has to be cancelled. This is the case for a submarine impinged by a primary field with unknown origin and frequency content; active control must cancel only the scattered field to make the submarine non-detectable. In the paper, an adaptive real-time algorithm is introduced to achieve reduction with additional sources of the noise scattered from a reflecting body. No prior information about the incident field is required. The algorithm consists of multichannel Internal Model Control with a well-known filtered-X Least Mean Square algorithm. Real-time measurements of the acoustic pressure around the reflecting body are used to build a minimization index accounting for the scattered field only. Furthermore, the control devices and algorithm can also be used to cancel the radiated noise due to sources inside the reflecting body. The algorithm for active scattering control was implemented in the LMA control hardware COMPARS. In the paper, experimental results of control in a duct of the field scattered from a reflecting termination are shown. Numerical simulations are given for the 2D case; they show how many noise sources and measurements are required in order to achieve a global reduction of the scattered field.

Fry, J.

• NEURAL NETWORKS FOR NOISE PREDICTION : AN AUTOMOTIVE CASE STUDY
  P. Jennings and J. Fry
[Abstract]

Conventional analytical techniques for noise prediction are unable to produce sufficiently accurate results in the most complex cases. One such case is the prediction of pass-by noise, early in the development of a new vehicle. A solution to this problem would be very beneficial to automotive manufacturers since all new vehicles currently have to comply with the European Union's pass-by noise legislation which sets a test limit at 74 dB(A). The current approach, which relies upon waiting for a prototype vehicle to be ready, can result in significant time and cost penalties if any re-designs prove to be necessary. However, the existence of a large amount of historical pass-by noise test data suggests that a neural network approach could prove to be a successful alternative to conventional analytical techniques, given the use of appropriate input parameters available early in the design process. The paper describes how this noise prediction problem can be posed in a manner suitable for prediction by a neural network. This has been achieved by dividing it into two simpler problems, first the prediction of vehicle performance, then the prediction of pass-by noise using performance as one of the inputs. It explains the procedures and experiments that have been carried out to determine the optimum parameters that should be used as neural network inputs, as well as which type of neural network to use and how much test data is required to train it. Preliminary results for both neural networks are presented and the achievable accuracy is discussed.

Fujii, K.

• NEW COEFFICIENT UPDATE METHOD FOR FEEDBACK CONTROL FILTERS IN ACTIVE NOISE CONTROL SYSTEM
  J. Ohga, K. Fujii and M. Muneyasu
[Abstract]

Active noise control systems require the process of identifying the secondary and the feedback paths previous to updating the coefficients of the noise control filter. These paths, however, are continuously changed in practical systems after the identification. This change inevitably degrades the performance of the system. The authors have already presented a method to update the coefficients of the secondary path filter modeling the former path under active noise control. This paper proposes another new useful coefficient refresh method for the feedback control filter modeling the latter path. For this refreshment, two independent equations are formed by using the estimation error involved in the coefficients of the noise control filter. This paper also introduces a system identification technique to solve the equations.

Fujita, Hachiteru

• THE PRESENT SITUATION AND THE TREND OF STANDARDS AND REGULATIONS FOR SOUND ENVIRONMENT PROTECTION IN JAPAN
  Y. Okumura, H. Tachibana, H. Fujita, Y. Suzuki and E. Toda
[Abstract]

Japanese government established environmental quality standards for the sound environment protection such as Environment Quality Standards for Noise, Environmental Quality Standards for Aircraft Noise and Environmental Quality Standards for SHINKANSEN Superexpress Railway Noise. These standards are defined in Article 16, Basic Environment Law as standards desirable for the protection of human health and the conservation of the living environment. This article also prescribes that the Government shall make efforts to attain the standards by comprehensively and effectively implementing policies concerning environmental pollution control. The government also established regulatory standards such as Maximum Permissible Levels of Motor Vehicle, Regulatory Standards for Noise Emitted Specified Factories, Standards for Noise Emitted from Specified Construction Works, and Request Limits for Motor Vehicle Noise based on Noise Regulation Law which prescribes regulation on noise level at noise sources according to Article 21, Basic Environment Law. This paper will describe the present situation and the trend of these standards and regulations.Japanese government established environmental quality standards for the sound environment protection such as Environment Quality Standards for Noise, Environmental Quality Standards for Aircraft Noise and Environmental Quality Standards for SHINKANSEN Superexpress Railway Noise. These standards are defined in Article 16, Basic Environment Law as standards desirable for the protection of human health and the conservation of the living environment. This article also prescribes that the Government shall make efforts to attain the standards by comprehensively and effectively implementing policies concerning environmental pollution control. The government also established regulatory standards such as Maximum Permissible Levels of Motor Vehicle, Regulatory Standards for Noise Emitted Specified Factories, Standards for Noise Emitted from Specified Construction Works, and Request Limits for Motor Vehicle Noise based on Noise Regulation Law which prescribes regulation on noise level at noise sources according to Article 21, Basic Environment Law. This paper will describe the present situation and the trend of these standards and regulations.

Fujita, Hajime

• EXPERIMENTAL STUDY OF THE SOUND SOURCE OF THE EDGE TONE
  H. Fujita, M. Iwasaki and M. Ishii
[Abstract]

A laminar two-dimensional jet impinging on a wedge produces self-sustained oscillation which results in a pure tone flow noise, so called edge-tone. The oscillation is sustained essentially by the feedback, or upstream propagation of the disturbance produced at the wedge to the sensitive area of the shear layer. Although this phenomenon has been studied widely and was reviewed by Rockwell and Naudascher in depth, the precise details of its generation mechanism still remains as an open question. In this study, the characteristics of the edge-tone produced by a laminar jet are studied experimentally for the velocity range of 38 m/s to 62 m/s, using 10 mm x 100 mm jet and wedges with various nose angles with pressure transducers embedded in the wedge surface. The coherence functions between the surface pressure fluctuations and the edge-tone are measured in order to identify the sound sources. Two coexisting sound sources corresponding to two peak frequencies in the edge tone spectrum are found on the wedge surface. The spanwise distributions of both sources show strong two-dimensionality while the chordwise distributions show distinguished difference. The coherence function for the source with lower frequency has one rather flat peak while it shows two separate peaks for the higher frequency source. It is concluded that a double vortex structure seems to exist in the flow near the wedge surface resulting in two distinctive pure tones.

Fukano, T.

• PREDICTION OF SPECTRAL DISTRIBUTION OF BROADBAND NOISE GENERATED FROM AN AXIAL FLOW FAN
  T. Fukano, H. Saruwatari and H. Hamakawa
[Abstract]

The mechanism of turbulent noise generation from an axial flow fan is still unknown. In the present paper we treat theoretical and experimental studies on the relation between the generated broad band noise and the periodic velocity fluctuation in the near wake of a rotating axial fan blade.Firstly we discuss the experimental results of periodic velocity fluctuation which was measured by a hot wire sensor from a rotating frame of reference fixed to the rotating blade. This periodic velocity fluctuation was caused by Karman vortex shedding.This phenomenon in the rotating flow field is similar to the one in the uniform flow field. The frequency of the Karman vortex shedding was constant at a fixed radius of the blade, and noise generated there was discrete. The frequency of the velocity fluctuation, however, increases with increasing radius of the blade in the rotating flow field, then the spectral distribution of noise generated from whole span of the blade becomes broadband.A theoretical flow model was introduced to predict the spectral distribution of generated noise from a rotating blade. In the model the blade span is divided into several element. The spanwise scale of the element is assumed to be as large as the coherent scale of the Karman vortex. The sum of the sound pressure generated from each blade element, i. e., from the whole span of the blade make broad band spectrum. The estimated spectral distributions agree well with the measured.

Fukushima, K.

• NEW WIND SCREEN DEVELOPED FOR UNATTENDED LOW FREQUENCY NOISE MEASUREMENT
  K. Fukushima, H. Ochiai, K. Makino, A. Yokota, I. Yamada and H. Tsukioka
[Abstract]

This paper talks about a new windscreen that effectively rejects wind-induced low frequency noise. In field measurements wind noise inevitably occurs and disturbs (or deteriorates the quality of) the measurement. Especially, in long-term unattended monitoring of low frequency noise using C or Flat frequency weighting, wind noise sometimes makes the measurement impossible. Conventional windscreens are however not effective when the wind speed exceeds several meters per second. The basic idea of the newly developed windscreen is to use double layered nylon nets (mesh interval; 1 2 mm). The nets are installed several centimeters distant each other around a microphone. Field experiments show that a prototype of the new windscreen is effective in decreasing wind noise up to a wind speed of 20 m/s.

Fuller, I.

• ENHANCE: AN EVOLUTIONARY IMPROVEMENT TO AIRCRAFT NOISE MODELING
  T. Elliff, L. Cavadini and I. Fuller
[Abstract]

International guidance material is provided by ICAO (Circular 205), defining how to compute noise contours for aircraft around airports. However, it is acknowledged within the noise modeling community, that significant errors can exist between modelled noise levels, and those measured ''on the ground'' for similar scenarios. The aim of the project is to better understand the sources and magnitude of these errors, and attempt to mitigate for them in the modelling process. The project will deliver an ''Enhanced'' Noise study tool, enabling more accurate predictive studies to be conducted for European airports and fleets, and will directly support the evolving European Commission Common Noise Policy. The model is based on existing noise contour calculation software (for example, the Integrated Noise Model from FAA), but through a preprocessor function and ''European'' database, allows more accurate data input, eliminating, or at least reducing, known errors. The project is a combination of tool development and validation exercise, and is based around a significant data collection task, with the cooperation of operators and airport administrations. It is a programme of collaborative work in Europe, sponsored by EUROCONTROL, as a complement to the work being conducted in voluntary CAEP (ICAO Committee on Aviation Environmental Protection) working groups, which will ultimately propose revisions to the Circular 205 methodology.

Furihata, K.

• APPLICATION OF NEW BONE CONDUCTION PICKUPS AND EARPHONES OF EARPLUG TYPE FOR SPEECH COMMUNICATION UNDER HIGH AMBIENT NOISE
  E. Matsuyama, K. Furihata and T. Yanagisawa
[Abstract]

An acceleration-type vibration pickup made of piezo-electric element is now widely used for the speech transmission under high ambient noise. But, the spectra and acceleration levels of speech obtained with the vibration pickup change by the position of attachment on the head and face. The speech intelligibility of the vibration pickup decreases gradually under high ambient noise of 110dB or more. In order to improve these problems, we developed the following two kinds of vibration pickups: (a) A noise-canceling-type vibration pickup, which is inserted in the external auditory canal, is composed of two monomorph elements. If the surrounding noise responses of two elements are equal, this pickup can cancel the surrounding noise (45dB at 2.5kHz). (b) The vibration pickup attached to lip part can pick up the speech with a high signal-to-noise ratio because the position of attachment is close to the speech organs. Therefore, intelligibly speech can be obtained under the high ambient white noise (95% at 115dB). There is another problem to improve: the ordinary headphones and earphones are unsuitable for listening under high ambient noise because of air leakage. We proposed the new type earphones made of magnetic diaphragm adhered to earplug (ACTIVE 99) can be used under high ambient noise. It can be concluded that the pickups and the earphones proposed here are very useful for speech communication under high ambient noise. Furthermore, it can be clarified that the articulation scores of those speech transmission systems can be predicted from the AI value.

• PSYCHOLOGICAL EVALUATION ON TRANSMISSION LOSS OF BUILDING MATERIALS BY ROAD VEHICLE NOISE SIMULATOR
  K. Furihata and T. Yanagisawa
[Abstract]

Road traffic is the most widespread source of noise in all countries and the primary reason for annoyance and interference with human activities. In Japan, it is difficult to reduce noise in area where houses are directly exposed to high-level traffic noise. For such limited areas adjacent to trunk roads, exceptional standard values (70dB / 65dB) should be considered in order to promote measures to reduce noise. Compliance of these values means that guidelines of indoor noise for roadside area (45dB / 40dB) of these values means that roadside houses have average sound insulation (closed-window: 25dB) and their windows are closed all day. From the aspect, we simulated with the vehicle noise simulator proposed in the previous paper (inter-noise 99) on the model of a house facing a national road in an anechoic room. The psychological evaluation on the effects of various kinds physical conditions (vehicle noise sources, traffic conditions, barrier, building materials) was adopted with the following terms: annoyance, the subjective effect on transmission loss and the subjective impression of considering all the factors, which each scale has seven -point scales. From the results of the psychological experiment, if roadside houses have average sound insulation (30dB or above), the subjects evaluated as follows: about 40dB of LAeq(5min) corresponds to ''kininaranai (not annoyed)'', the transmission loss is ''effective'' and the subjective impression of considering all the factors is ''good''.

• PSYCHOLOGICAL EVALUATION BY VEHICLE NOISE SIMULATOR USING NEW EARPHONE OF EARPLUG TYPE FOR VIRTUAL REALITY
  T. Nagano, K. Furihata and T. Yanagisawa
[Abstract]

Road traffic is the most widespread source of noise in all countries and the primary reason for annoyance and interference with human activities. Experiments designed to evaluate the psychological effects (loudness, perceived noisiness and annoyance) of road vehicle noise have basically to be carried out in an anechoic room or a soundproof room. If, however, a simulator based on a virtual reality system capable of audio-visual experiencing for various kinds of noise control elements at a residential site is available; one can select the most suitable noise control technique. The simulator described here uses (a) a glasstron personal display and some earplug type electroacoustic transducers proposed in the previous paper. They are as follows: (b) the microphones for sound pressure measuring in the external auditory canal, (c) the magnetic earphones adhered to earplugs and (d) the microphones for sound pressure measuring in the small cavity, which is enclosed by the earplug and the eardrum. In this paper, the simulator was discussed experimentally whether it obtains the presence as if there are lots of cars on the road by the virtual binaural recording and reproducing. From the results, it can be found that the virtual reality system proposed here may be obtained one's feelings of direction, distance and movement with the interaction between audible and visible. As a conclusion, it can be said that this system can be applied with confidence to the subjective impression of noise control elements for road vehicle noise.

• RELATION BETWEEN CLOSE CARVED SURFACE AND MEASURING POINTS OF SOUND POWER LEVELS FOR ELECTRIC CLEANERS USING SOUND INTENSITY METHOD
  S. Nagata, K. Furihata and T. Yanagisawa
[Abstract]

The sound power measurement by the sound intensity method has the following merit: the sound intensity method is not easily influenced by the stationary noise sources from the outside of a close curved surface of measurement. However, the sound power level contains a measuring error because the sound intensity level measures at the dividing discrete points of a close curved surface. The error changes by the properties of a noise source, a sound field and a shape of close curved surface. First, we selected three kinds of electric cleaners. Second, those sound power levels were measured with a reverberation room (68.7m3) method (JIS Z 8734). Third, the sound intensity method was used with the intensity probe microphone (B&K 3545), the microphone traverse & controller (NITTOBO MT-3000) and the frequency analyzer (B&K 2133A) in an anechoic room (215.6 m3). The shape of a close curved surface was a parallelepiped and the number of measuring points was 96. Fourth, the sound intensity measurement in an ordinary room was adopted the shape of a hemisphere and a cylinder surfaces with a microphone stand made by us. From the comparison among them, it can be said as follows: The number of dividing discrete points needs to measure about 24. Then, the power levels based on the sound intensity method can measure within the standard deviation 1.5dB, which satisfies the measurement accuracy of JIS and ISO, regardless of the properties of the noise sources above, the sound fields and the shapes of close curved surface.

• PSYCHOLOGICAL EFFECTS OF LIGHTING AND TEMPERATURE ON NOISE ANNOYANCE WITH NOISE SOURCE SIMULATOR
  K. Furihata and T. Yanagisawa
[Abstract]

Light and temperature have a psychophysical influence on people. They can soothe or excite, stimulate or depress. For example, audio-visual interaction between sound and light-color has an important role in show business, in cinematography, in TV and in school psychology, where light-color and sound complement one another. From the aspect, this paper discusses how degree the annoyance on various kinds of noise (steady noise, train noise, intermittent noise, vehicle noise) is influenced by the following factors: illumination (0lx, 30lx, 200lx, 2000lx), hues (red, purple, yellow, green, blue), flickering (welding simulated) and temperature (about 30(C in summer, about 18(C in winter). As the results, it can be said as follows: (a) The relation between ''urusasa (annoyance)'' under normal lighting (30lx) and LAeq(5min) corresponds to the standard noise-rating scale based on judgement of residents in and around Nagano city. (b) The relation between ''urusasa'' under night simulated (0lx) and LAeq(5min) is parallel (-7dB) to the standard noise-rating scale. When it is -5dB under 2000lx. (c) The effects of audio-visual interaction between noise and light-hues can bring about annoyance in the following order: blue, green, yellow, purple and red. (d) The subjective effect of flickering on noise prevails the effect of visible. From the rating scale obtained, ''a little annoying'' corresponds to 32.5dB of LAeq(5min), ''annoying'' to 52.5dB and ''very annoying'' to 70dB. (e) The effect of audio-cutaneous interaction between ''urusasa'' on noise and seasons is little.

Fürjes, A.

• COMPUTER AIDED ACOUSTIC DESIGN AT A THEATRE RECONSTRUCTION - REALITIES AND SIMULATION RESULTS
  A. Nagy, A. Kotschy, A. Fürjes and F. Augusztinovicz
[Abstract]

During the design of the reconstruction of a Hungarian theatre, several room acoustic measurements were carried out in the existing auditorium. The applied instrumentation was an MLS based digital signal processing system; reverberation times, impulse responses and more complex parameters derived from IR were determined. Parallel to the measurements, the acoustical analysis of the original condition and that of the new, designed interior was performed by means of computer models, based on the laws of geometrical acoustics. We have compared the results of the measurements carried out on the spot to those of the computer models, obtained from two different software systems. The results were applied to evaluate and update the room acoustic computer models of the currently existing state of the theatre, in order to enable to perform a meaningful simulation of the new interior design of the auditorium.

Gabay, D.

• ACTIVE NOISE CONTROL: APPLICATION TO THE COST REDUCTION OF THE UNDERGROUND VENTILATION BUILDINGS IN PARIS
  D. Gabay, C. Carme and V. Lagarrigue
[Abstract]

For several years RATP manages a wide program for the improvement of climatic comfort and fire safety of the underground. High flow ventilation buildings of 12 m2 cross section (60 to 120 m3/s) have been made and today, in order to decrease their cost to flow ratio, RATP wants to decrease their dimensions knowing that 80% of the cost is due to the concrete. Nowadays, these dimensions are related to the passive acoustical treatment and the objective of acoustic level. The use of an active noise control system would allow a cost reduction of 30 to 40 percent because of the possible dimensions reductions. To reach this objective, specific developments were needed in two particular ways: active noise control performances and treatment of flow induced noise sources. For active noise control, numerical simulations leaded to the definition of the association of both active and passive silencers: their number, their dimensions and the architecture of the whole. Tests on a special wind tunnel allowed to validate the silencer concept and to determine the limits of its efficiency especially in terms of maximum flow velocity. For flow induced noise sources, experiments were leading to study the main noise sources and to test particular solutions. These experiments were performed on a hydraulic loop with a 1/20 model on which visualisations, velocity profiles and pressure measurements were performed. The final tests on a full scale ventilation building will take place in 2000.

Gabillet, Y.

• EXPERIMENTAL STUDY OF ROAD TRAFFIC NOISE CONTROL BY A PINE FOREST
  N. Barriere, Y. Gabillet, J. Blais, J. Defrance, P. Ducruet and F. Gaudaire
[Abstract]

In order to precisely bring to the fore the effect of meteorology on sound propagation through forests, an important measurements campaign has been carried out in the French Landes forest mainly composed of pine trees. The originality of the experiment is that road traffic noise and meteorological conditions have been measured simultaneously for both a forest situation and a plain situation, this for different positions of the receiver. All valid measured data have then been classified according to three propagation conditions: favourable to propagation, unfavourable to propagation and homogeneous conditions. As expected, the results depend on these conditions. In favourable conditions, the gain brought by the forest is between 3 and 5 dB(A) with the receiver at least 100 m away from the road. This meteorological situation occurs very often at night due to a temperature inversion phenomena. Moreover, it is of most interest since it corresponds to the periods when the annoyance due to the road in a plain situation is the highest. In unfavourable conditions, the forest may increase somewhat the received sound level. In homogeneous conditions, the sound propagation through the forest is not appreciably affected by meteorology anymore but only by the scattering by the trunks and foliage. Finally, these results have permitted to validate a new calculation method for the attenuation of road traffic noise by forests based on a fast implementation of the Parabolic Equation.

• METEO-BEM : A POWERFUL TOOL FOR COMPLEX OUTDOOR SOUND PROPAGATION
  E. Premat, Y. Gabillet and J. Defrance
[Abstract]

The new formulation Meteo-BEM based on the layer potential theory and recent propagation models , allows one to describe sound propagation in a complex outdoor environment. This new model accounts for meteorological effects as well as various absorbing properties and shapes of the boundaries. First, the theory of Meteo-BEM is briefly given, with a particular emphasis on the methodology used to include meteorological effects. The total sound pressure is expressed as the sum of the incident pressure and the pressure scattered by the obstacles in the propagation medium, involving simple and double layer potentials. The Green's function used in this formulation takes meteorological and ground effects into account and relies on recent models for propagation in inhomogeneous media. Then Meteo-BEM is applied to the case of sound propagation with refraction (downward and upward) around a sound barrier. The ground can be absorbing. The results are compared to experimental data obtained in controlled conditions with a scaled model (curved surface). The agreement is very good and shows that meteorological effects can be included in Boundary Element Methods. So Meteo-BEM is found to be a powerful tool for outdoor sound propagation prediction, which gives rise to many applications and developments.

• A NEW FRENCH METHOD FOR RAILWAY NOISE PREDICTION
  J. Defrance, Y. Gabillet, D. Van Maercke, C. Dine and P.-E. Gautier
[Abstract]

Regulations for railway noise are becoming more and more stringent and, along with a decrease of maximum acceptable sound levels, a more accurate environmental prediction is sought. This has brought about the need of sound level calculations at long ranges including meteorological effects. A new French prediction method for Railway Noise (NMPB-FER) has thus been developed on the basis of an already existing one for road traffic noise. This method specifies two calculation procedures: with meteorological conditions favourable to sound propagation and with atmospheric homogeneous conditions. The result is a long term equivalent A-weighted noise level obtained by the combination of the two calculations and taking into account the percentage of time when favourable conditions occur. The railway source is modelled as two independent sources, one being close to the rail/wheel contact plane (concerning highest frequencies) while the other is located at a height appropriate to a simple but correct representation taking into account aerodynamic sources (for lowest frequencies). This method implemented in the MITHRA ray tracing software offers some original specificities: barrier-carriage multi-reflections effects taken into account, calculation of the noise level vs time evolution, railway noise sources split up according to the total length of the convoy, composition of trains and determination of sound power level characteristics achieved by assembling the wanted rolling elements (locomotive and carriages, types and numbers). Input to the model can easily be obtained from multi-spectrum measurements close to the railway.

Gade, S.

• FFT VS. VOLD-KALMAN BASED ORDER ANALYSIS OF A GEARSHIFT EVENT
  S. Gade, H. Herlufsen, H. Konstantin-Hansen and H. Vold
[Abstract]

In this paper a comparison between two order analysis techniques is made, namely a real-time FFT based order analysis using fixed sampling frequency and Vold-Kalman based post-processing order tracking. The measurement was done on a light truck with a V-8 engine and an overdrive automatic transmission, which was run on a dynamometer in a semi anechoic room. A full-throttle run-up was performed under light load condition from 1st to 4th gear through 2nd and 3rd gear. Especially around the gearshift events the results have been compared. The advantages and disadvantages of the two methods are also summarized.

Gaja, E.

• URBAN TRAFFIC NOISE MEASUREMENT OPTIMIZATION
  A. Reig, E. Gaja, J.-L. Manglano and S. Sancho
[Abstract]

The laboratory of Acoustic Engineering in the Universidad Politecnica de Valencia has a wide experience in acoustic pollution. As an example of this work, the laboratory has developed a traffic noise map of the city. Due to this large experience, a new measurement system was required in order to avoid spending too much time measuring with sonometers. In this research work, a new measurement methodology is presented; the measurement techniques for urban traffic noise are based on the calculus of the minimum exposure time for the equivalent level, that represents a longer period of time. This method was developed from actual continuous one-minute measurements. It is very interesting to observe how the equivalent noise level becomes stable after a certain period of time, which is very useful to know the length of urban traffic noise measurement. Time stabilization is also correlated with other parameters as well.

Gal , J.

• NOISE REDUCTION INDUCED BY USE OF VERY THIN WEARING COURSES AND CRUMB RUBBER PARTICLES
  M. Ballié and J. Gal
[Abstract]

For some years now, road innovations are mainly devoted to the comfort and safety for road users. The surface properties of wearing courses linked to these two parameters are of paramount importance for road companies and road authorities. Today it is a clearly established fact that the tire/pavement contact noise is the main source from wich savings can be made. The use of silent pavement allows for major reductions of the tire/pavement contact noise. Wearing courses that include crumb rubber particles are able to ensure drastic reductions in traffic noise when compared to results of conventional hot mixes. In this paper we present a survey of noise reduction studies using various measurement methods. Many sites : urban, periurban, main raods, highways in France or abroad were investigated. The methods are presend first. The noise reduction are then pointed out.

Galanenko, V.

• SIMULATION OF A LOW FREQUENCY NOISE INSIDE A CAR CABIN BASED ON ANALYTICAL-NUMERICAL SOLUTION OF THE WAVE EQUATION.
  A. Kovtonyuk, V. Galanenko and A. Kalyuzhny
[Abstract]

The problem of noise simulation within a cabin of a moving car (or another vehicle) is discussed. As for many typical cases the main part of noise energy belongs to a low frequency range the ray acoustics methods are not convenient. Analytical solution of wave equation is not available due to complicated cabin geometry. Numerical solution for 3D region is difficult as well. The combined analytical-numerical approach is proposed. According to the method proposed a cabin is approximated by a rectangular prism. The height of the prism is equal to the cabin width and its polygonal base approximates the cabin profile. Sound absorption of the cabin boundaries is specified for each frequency. Distributed noise sources are approximated by the sets of cross-correlated point sources. For each frequency of the range point source sound field is presented by the series of eigenfunctions of some boundary problem. . The expansion coefficients (as the functions of two coordinates belonging to the prism base) are found out numerically by use of finite elements method. Computations result in Creen's matrix which is applied later for noise simulation. Respective software package is developed. This soft allows to simulate noise at arbitrary point within a cabin using experimental data on vibration characteristics of the cabin surfaces. Vibration and sound noise characteristics have been measured for examination of proposed algorithm. The spectrums of natural and simulated sound noise are presented and discussed.

Gallacher, J.E.J.

• ASSOCIATION BETWEEN NOISE ANNOYANCE AND INCIDENCE OF ISCHAEMIC HEART DISEASE IN THE CAERPHILLY AND SPEEDWELL STUDIES
  W. Babisch, H. Ising and J.E.J. Gallacher
[Abstract]

In a cohort study, the association between annoyance and disturbances due to road traffic noise and the incidence of ischaemic heart disease (IHD) was studied in 3930 middle aged men. During a 6y follow-up period 305 IHD cases were detected. Dependent on the item used, non-significant odds ratios between 0.9 and 1.4 were found in highly noise annoyed/disturbed subjects as compared to less annoyed/disturbed. However, this relationship was found to be strongly modified by pre-existent diseases. i. e. In subjects free of any chronic disease at the beginning of the follow-up, significant odds ratios between 1.7 and 2.9 were seen. In the subgroup with chronic diseases no noise effects were seen. This surprising result of non-effect in the potential risk group of sick people may be due to the dilution of the true effect due to recall bias. Regarding the objective noise level measurement the opposite was found. In this case noise and disease stress tended to act synergistic on the incidence of IHD. In conclusion, prevalence of disease is an important effect modifier on the articulation of subjective exposure indicators. Noise studies in which exposure is assessed on a subjective basis must be viewed with caution in this respect.

Garai, M.

• EXPERIMENTAL VERIFICATION OF THE EUROPEAN METHODOLOGY FOR TESTING NOISE BARRIERS IN SITU: SOUND REFLECTION
  M. Garai and P. Guidorzi
[Abstract]

(Invited paper #2 for the special session 7.2 ''Anti-noise devices: new techniques, new materials, public acceptance'')

In the frame of the 1994-97 SMT (standard, measurement and testing) program, the European Commission funded a research project, named Adrienne, to define new test methods for measuring the intrinsic characteristics of road traffic noise reducing devices in situ. The research team produced innovative methods for testing the sound reflection/absorption and the airborne sound insulation characteristics of noise barriers. These methods are now under consideration at CEN/TC 226/WG 6 to become European standards. The present work reports a detailed verification of the test method for sound reflection over a selection of seventeen noise barriers, representative of the Italian and European production. The samples were tested both outdoors, using the new Adrienne method, and in laboratory, following the EN 1793 standards. In both cases the EN single number rating for sound absorption was calculated. The new method proved to be easy to use and reliable for all the kinds of barrier. It has been found sensitive to the shape and the acoustic impedance of the tested barrier. The comparison between field and laboratory results shows a quite good correlation, while existing differences can be explained with the different sound fields and measurement techniques used for the tests. It is concluded that the Adrienne method is the most promising one for its intended use.

• EXPERIMENTAL VERIFICATION OF THE EUROPEAN METHODOLOGY FOR TESTING NOISE BARRIERS IN SITU: AIRBORNE SOUND INSULATION
  M. Garai and P. Guidorzi
[Abstract]

(Invited paper #1 for the special session 7.2 ''Anti-noise devices: new techniques, new materials, public acceptance'') In the frame of the 1994-97 SMT (standard, measurement and testing) program, the European Commission funded a research project, named Adrienne, to define new test methods for measuring the intrinsic characteristics of road traffic noise reducing devices in situ. The research team produced innovative methods for testing the sound reflection/absorption and the airborne sound insulation characteristics of noise barriers.These methods are now under consideration at CEN/TC 226/WG 6 to become European standards. The present work reports a detailed verification of the test method for airborne sound insulation over a selection of seventeen noise barriers, representative of the Italian and European production. The samples were tested both outdoors, using the new Adrienne method, and in laboratory, following the EN 1793 standards. In both cases the EN single number rating for airborne sound insulation was calculated. The new method proved to be easy to use and reliable for all the kinds of barrier. It has been found sensitive to quality of mounting, presence of seals and other details typical of outdoor installations. The comparison between field and laboratory results shows an excellent correlation, while systematic differences can be explained with the different sound fields used for the tests. It is concluded that the Adrienne method is adequate for its intended use.

García Ortiz, E.

• INTELLIGIBILITY IN A SCHOOL IN LEÓN (SPAIN)
  J. Cepeda Riaño, E. García Ortiz, B. Melcón Otero and M.I. Vidal González
[Abstract]

One of the issues of obvious incidence in the performance of pupils in a school is that of the existent intelligibility in the classrooms. However, the planners of school buildings don not generally pay great attention to this, so that the situation is frequently highly deficient. The following information refers to a complete study of intelligibility carried out by the Acoustic Laboratory of the University of León in ''Juan del Enzina'' High School in León (Spain). All the 33 classrooms in the school were studied in two different phases of work. In the first study the RASTI Index was used, while in the second phase an analysis was made of the response of the pupils to a test carried out using lists of two-syllable words in which the emission levels were progressively changed in order to observe the variation in intelligibility. In addition, a sonometer study was realised, by which the situation in the school as to existing ''background noise'' could also be tested. The results show a very deficient situation with regard to intelligibility in the classrooms. 24 of the 33 studied can be considered ''poor'', while the situation in the remaining 9 can be described as ''weak''. Moreover, the study of the pupils'response leads us to certain conclusions about saturation in intelligibility. There is, at times, a decrease in this when the levels of emission are increased.

Garcia, A.

• LOCALISATION OF SOURCE. APPLICATION ON A CELLO.
  C. Langrenne and A. Garcia
[Abstract]

An isoparametric element formulation is used for implementing the Helmholtz integral formulation associated with arbitrary shaped three dimensional bodies. The inverse problem is solved, i.e., the normal velocity distribution is determined on the surface of the instrument. Because of difficulties to solve the inverse problem (ill-posed problem, i.e., solution very sensitive to the errors of measurements), a regularisation method is used to find the most nearest solution of the real one. The cello is a good exemple of sound source : one way, his shape is complex, but it's possible to use accelerometers on his surface and, other way, the holes provide a good test to valid our algorithm. Several experimental vibroacoustic characterisations are done from holography measurements, without any contact with the stucture of the instrument by the help of a robot. The first one describes a planar surface in the near field of the instrument and the second, a cylindrical surface in the far field. So, the effect of the regularisation process can be tested. The direct problem can also be solved : the acoustic field is calculed anywhere (near field, far field). The reactive intensity can be used to localise the sources on the structure, while the active intensity show the zones which are responsible for the far field radiation.

Gardziejczyk, W.

• DETERMINATION OF THE CPX INDEX FOR A NUMBER OF SURFACES IN VARIOUS COUNTRIES
  J. Ejsmont, P. Mioduszewski, S. Taryma and W. Gardziejczyk
[Abstract]

Road surfaces may influence traffic noise in two ways. They directly influence the generation of the tyre/road noise that is one of the most important vehicle noise sources, and on top of it they affect the propagation of noise emitted from all sources in the vehicle. In order to investigate the influence of the road surface on tyre/road noise generation it is necessary to establish certain measuring procedures and indicators describing the results in a uniform and condensed form. One of the methods in use is the Close Proximity Method (CPX), which utilizes two microphones mounted close to the tyre/road interface. The so-called CPX Index, which is the final indicator of the road surface ''noisiness'', is evaluated on the basis of measurements performed with the CPX method using four reference tyres. Measurements with this method in a standardized way have been possible only recently since the method is currently subject of standardization efforts within the ISO. The first part of the paper outlines most important aspects of the CPX method. The main part of the paper presents results of CPX tests performed recently on many roads in Sweden, Poland, Germany and the Netherlands. Certain ''low noise'' road surfaces were included to the test program so it is possible to compare their performance with other, more traditional road surfaces. Also very noisy ''block pavements'' and paving stones were covered as they are again frequently used in certain ''low traffic'' and residential areas. The ranking of the surfaces according to their CPX Indexes is given as a final result of the investigation.

Gaudaire, F.

• EXPERIMENTAL STUDY OF ROAD TRAFFIC NOISE CONTROL BY A PINE FOREST
  N. Barriere, Y. Gabillet, J. Blais, J. Defrance, P. Ducruet and F. Gaudaire
[Abstract]

In order to precisely bring to the fore the effect of meteorology on sound propagation through forests, an important measurements campaign has been carried out in the French Landes forest mainly composed of pine trees. The originality of the experiment is that road traffic noise and meteorological conditions have been measured simultaneously for both a forest situation and a plain situation, this for different positions of the receiver. All valid measured data have then been classified according to three propagation conditions: favourable to propagation, unfavourable to propagation and homogeneous conditions. As expected, the results depend on these conditions. In favourable conditions, the gain brought by the forest is between 3 and 5 dB(A) with the receiver at least 100 m away from the road. This meteorological situation occurs very often at night due to a temperature inversion phenomena. Moreover, it is of most interest since it corresponds to the periods when the annoyance due to the road in a plain situation is the highest. In unfavourable conditions, the forest may increase somewhat the received sound level. In homogeneous conditions, the sound propagation through the forest is not appreciably affected by meteorology anymore but only by the scattering by the trunks and foliage. Finally, these results have permitted to validate a new calculation method for the attenuation of road traffic noise by forests based on a fast implementation of the Parabolic Equation.

Gaumain, C.

• SIMULATIONS OF THE NOISE RADIATION OF HIGH SPEED TRAINS
  C. Talotte, S. Guerrand and C. Gaumain
[Abstract]

Experimental and numerical studies had been carried out at SNCF to characterise the noise of TGV which has two origins : rolling and aerodynamics which becomes predominant above 300 km/h. The knowledge of the physical phenomena linked to each kind of source, obtained through different research projects (including a specific co-operation with DBAG) allowed to define source models including mainly spectrum aspects and evolution with speed. The following step was the development of a numerical tool, for the simulation of the noise radiation of trains built from these source models. The software, called MAT2S, developed at SNCF in C++ is presented in this paper. The software use involves modelling a train with its different sources and all the parameters that might influence its noise radiation, performing a calculation and looking at the results. The features of the software are : the capability to modify easily sources and to define a new train configuration the parameters included in the algorithm (directivity correction, spherical attenuation, ground effect, atmospheric absorption and Doppler effect) the capability to obtain the results as levels but also as spectra or signatures. The software, which is user friendly, allows to carry out parametrical studies to assess potential of reduction of the different sources and how they balance. First computation of a TGV configuration had been compared with experimental results on line. The very satisfactory comparison is presented in this paper. Future developments will be focused on source models improvement and simulations of other trains configurations.

Gaunt, D.

• LOW FREQUENCY NOISE EMITTED BY COMPUTER DISK DRIVES-EFFECT OF MULTIPLE DISK DRIVE INSTALLATIONS
  D. Gaunt
[Abstract]

The intent of this paper is to explain why low frequency noise from computer disk drives has become a relavant noise control issue in the computer industry and to explain the effect of multiple drive installations on noise emission . Results will be presented demomstrating the effect of the low frequency tone on the A weighted sound power level This shows an inherent measurement difficulty since the dominant low frequency tone in the 125 1/3 rd octave band is non -stationary ,when emitted by multiple drive installations ,due to the interference effects between drives .A measurement solution will be proposed and supporting results presented.

Gautier, P.-E.

• SILENT FREIGHT AND SILENT TRACK PROJECTS
  B. Hemsworth, P.-E. Gautier and R. Jones
[Abstract]

Silent Freight and Silent Track are two EU sponsored 4th Framework Brite Euram projects. Commencing in 1996 and 1997 respectively they have the combined objective of reducing the rolling noise from freight vehicles on ballasted track by at least 10 dB(A) using control at source as opposed to suppression by noise barriers. An integral part of the project was the use of the rolling noise simulation software model TWINS to initially identify likely low noise components for vehicles and tracks. This software would be updated through the life of the project with more comprehensive modules. Additional modules would also be provided to enhance its capability. Following a process of numerical simulation, development of pre prototypes and laboratory testing, full scale testing of prototype low noise vehicle and track components was carried out at the Czech Republic test track in Velim in 1999. These tests indicated that the measured benefits were similar to those predicted and that to achieve a 10 dB(A) reduction in overall noise it is necessary to include added damping or web screening to wheels, added damping to rails, bogie shrouds and low trackside barriers. Implementation studies are current on those mitigation options.

• RAILWAY NOISE SOURCES. AN OVERVIEW OF RECENT APPROACHES IN IDENTIFICATION, MODELLING AND REDUCTION POTENTIALS
  P.-E. Gautier, C. Dine and B. Hemsworth
[Abstract]

As environmental requirements become tighter, understanding physics and relative importance of railway noise sources, became important, especially in view of global railway noise reduction. This paper aims at presenting an overview of recent developments in the knowledge of noise sources on trains, either by experimental identification or from modelling. It will be shown that different levels of accuracy or globalisation are required, depending on subsequent use of the knowledge : predicting railway traffic noise for designing a new line does not require the same modelling as assessing potential future reduction in railway noise emission. First, an overlook of global trends in identification of noise emission from railway system will be presented (for homologation purpose, for noise prediction in environment or even for specification design of ever quieter railway). Then, specific problems relevant to different sources (rolling noise, aerodynamic noise, fan noise...) will be emphasised. It will be shown that, in some cases, in order to get a full insight into reduction perspectives, refinements in modelling or understanding phenomena are needed. Finally, from the experience of several on-going research projects throughout Europe, global reduction potentials for various types of trains will be presented, in line with recent progress on operational systems. The needs for further progress in either source reduction or global modelling will be identified.

• ANNOYANCE DUE TO COMBINED NOISE SOURCES
  S. Joncour, D. Cailhau, P.-E. Gautier, P. Champelovier and J. Lambert
[Abstract]

Former studies on transport noise annoyance most often considered single noise exposure situations, whereas double developments of infrastructures i.e. a motorway alongside a high speed railway line for example, lead to an increasing number of residents exposed simultaneously to several noise sources, each one having its own characteristics. However, nowadays, this kind of situation can't be qualified and assessed precisely. A national socio-acoustic survey was carried out in France on 63 different multi exposed locations (road and railway). The objective of this study was on the one hand to reassess annoyance in practical situations through a large combination of multisource situations including dominant sources and on the other hand to determine the effects of several noise sources on the overall annoyance perceived. For that purpose 700 people were interviewed on the following items: their own experience of noise, description and perception of the noise environment, annoyance assessment according to different periods or activities. Individual exposures to road, railway and total noise were assessed in front of the most exposed facades for daytime and night-time from 24 hour noise measurements and calculations with Mithra-fer software. Dose-response curves between noise exposure and annoyance levels have been established through logistic regression models. The results show that a dose response curve assessed for one single source (road or railway) depends on the noise exposure characteristics, particularly the difference between the noise exposure levels of the two sources considered.

• A NEW FRENCH METHOD FOR RAILWAY NOISE PREDICTION
  J. Defrance, Y. Gabillet, D. Van Maercke, C. Dine and P.-E. Gautier
[Abstract]

Regulations for railway noise are becoming more and more stringent and, along with a decrease of maximum acceptable sound levels, a more accurate environmental prediction is sought. This has brought about the need of sound level calculations at long ranges including meteorological effects. A new French prediction method for Railway Noise (NMPB-FER) has thus been developed on the basis of an already existing one for road traffic noise. This method specifies two calculation procedures: with meteorological conditions favourable to sound propagation and with atmospheric homogeneous conditions. The result is a long term equivalent A-weighted noise level obtained by the combination of the two calculations and taking into account the percentage of time when favourable conditions occur. The railway source is modelled as two independent sources, one being close to the rail/wheel contact plane (concerning highest frequencies) while the other is located at a height appropriate to a simple but correct representation taking into account aerodynamic sources (for lowest frequencies). This method implemented in the MITHRA ray tracing software offers some original specificities: barrier-carriage multi-reflections effects taken into account, calculation of the noise level vs time evolution, railway noise sources split up according to the total length of the convoy, composition of trains and determination of sound power level characteristics achieved by assembling the wanted rolling elements (locomotive and carriages, types and numbers). Input to the model can easily be obtained from multi-spectrum measurements close to the railway.

Gauvreau, B.

• CALCULATION OF METEOROLOGICAL CONDITIONS EFFECTS ON OUTDOOR SOUND PROPAGATION USING PARABOLIC EQUATION
  M. Berengier and B. Gauvreau
[Abstract]

The presence of high-trafficked roads around large cities produces substantial noise disturbances for neighbouring inhabitants. Due to the source traffic composition and the outdoor propagation conditions, the populations can be submitted to large sound pressure level variations. In order to predict these variations, an important research programme has been set up. Researches reported in this paper are dealing with a calculation method based on a numerical approach which allows to consider a large set of situations which can be met outdoors. The main phenomena taken into account are : ground effect, impedance discontinuity and screen diffraction and various atmospheric conditions. To solve these large and complex problems, the methods based on the parabolic approximation seem to be well adapted. Among these, the Split-Step Padé  method appeared to be the most reliable with respect to its obvious advantages in terms of angular aperture and CPU time, and to its capability to consider the most involved phenomena : homogeneous or mixed grounds, acoustic barriers, etc... The atmospheric turbulence is taken into account through the discrete random Fourier modes  technique. It is considered as isotropic, homogeneous and essentially due to temperature scalar fluctuations. The 2D spectral density is assumed to have a Gaussian distribution or a von Karman profile. The corresponding numerical code has been first validated through comparisons with literature data. Then, the propagation conditions have been progressively complexified in order to simulate more realistic propagation situations. Numerical and experimental data will be discussed in the paper.

Gavric, L.

• SIMPLIFIED MODEL OF INTERNAL ACOUSTIC CAVITY IN RECIPROCATING REFRIGERATING COMPRESSORS
  L. Coutaz and L. Gavric
[Abstract]

When a noise abatement strategy of refrigerating and air conditioning machinery is considered, an investigation of noise generating components is necessary. One of the most important noise sources of such equipment is reciprocating compressor. The hermetic shell of the refrigerant compressor generates an important part of direct sound radiation. The hermetically sealed shell of compressor is excited by the compression mechanism/motor unit. These two sub-systems are mechanically connected by mounting springs and by discharge pipe. The structure borne sound is transmitted through these connecting elements to the compressor shell. When gas pulsation is considered, the hermetic shell is relied to the compression unit by the internal acoustic cavity filled of refrigerant gas. If the excitation frequency coincides with one of the acoustic cavity resonances, important shell vibrations can be generated by gas pulsation. The interior of the compressor shell is modelled as an annular cavity defined by two concentric cylinder representing the hermetic shell and the inner unit. Despite the geometric simplifications, the acoustic characterisation of the fluid /structure interaction involves complex modal calculation. Therefore, it was found necessary to model this annular cavity by a rectangular one. The geometric similarity of two cavities is preserved by unrolling the cylinder around his central axe. The co-ordinate change is carried out with respect of the cavity mid surface, similarly as in the thin shells theory. In the acoustic modal analysis, the modal forms corresponding to the annular cavity are imposed to the rectangular one. The shell vibration generated by the internal acoustic pressure distribution are calculated using modal synthesis. The gas pulsation excitation is superimposed to the mechanical one in order to compute the final shell vibration and noise radiation. The results obtained are in good agreement with experiments. The described analytical approach can be used as an efficient design tool for preliminary vibro-acoustic analysis of compressors.

• CHARACTERIZING OF ACOUSTIC RADIATION OF HERMETIC RECIPROCATING COMPRESSOR USING VIBRATION MEASUREMENTS
  L. Gavric
[Abstract]

Noise and vibration performance of refrigerating and air-conditioning machinery and systems becomes an important selling argument. The main vibroacoustic source of such machinery is refrigerant compressor. Two principal components of the noise generation by the compressor can be distinguished: the noise directly radiated by the compressor and the noise transmitted to the machinery in the form of structure-borne and fluide-borne vibroacoustic energy. The relative contribution of the different noise components depends on the type of machine considered. This paper deals with the direct sound radiation of the hermetic shell of the reciprocating refrigeration compressor. The sound power level of compressor can be evaluated by applying well known conventional methods: using sound pressure levels measured in reverberant or in anechoic chamber or by integrating the sound intensity readings over a closed surface containing the source. In this paper an alternative method using 6 accelerometer measurements for evaluating the sound power level radiated by the hermetic compressor is presented. The method is based on modelling the acoustic radiation of compressor shell by 4 simple acoustic sources - 1 monopole and 3 dipoles. The monopole accounts for the change of the volume of the compressor shell, known as shell ''breathing'', while each of 3 dipole stands for the ''rigid body'' vibration movements in the direction of one of 3 principle axe - X, Y and Z. The amplitudes of vibration corresponding to the 4 simple acoustic sources are computed from the measurement results. The sound power level is then evaluated by the superposition of the sound power levels of the 4 simple acoustic sources. The method is applied on a small refrigerator compressor 1.2 kW. The sound power level of the compressor is evaluated using the intensity measurement technique according the standard ISO - 9614-1. The same quantity is computed using the 6 accelerometers measurement. The obtained results are discussed. The accuracy as function of frequency range and dimensions of source are examined.

Ge, P.

• THE STUDY OF SOUND ABSORPTION CHARACTERISTIC OF MICRO-PERFORATED PANEL WITH DIFFERENT DIAMETER HOLES
  B. Zhang, S. Lang, P. Ge and W. Zhuang
[Abstract]

Generally, we are having used micro-perforated panels composed by single diameter holes to reduce noise. In this case, the panel's sound absorbption can be predicted precisely. However, in another case, we may use several piece of panel with different diameter holes to compose a piece of panel for getting higher sound absorption. Its sound absorbing performance is different from single aperture panel. Therefore this paper tries to explain the difference between the two cases. According to the sound absorbing theory of Micro-perforated panel, some testing samples have been developed and tested. It shows from test results that sound absorption in some frequency is different in the two cases. This paper presents sound absorbing performance of the composite construction of some micro-perforated panel with different diameter holes, and discuses the sound absorbing difference between the two cases. With the composite method, wider sound absorbing band can be obtained easyly.

Geens, R.

• AN INDICATOR FOR ROAD TRAFFIC NOISE: MONITORING AND PREDICTION MODEL
  L. Dekoninck, D. Botteldooren, G. Vindevogel and R. Geens
[Abstract]

In this paper a pressure indicator for road traffic noise is discussed and a prediction model for the indicator is presented. The indicator is defined as the annual sound emission at a particular point near a major Flemish highway. When measuring this indicator one must be very careful to take into account weather effects and possible changes in road surface accurately. This is particularly important since the expected annual change in the indicator is very small. When modeling the indicator the evolution of car noise emission must be taken into account. This requires the type of cars and trucks and their age and relative density to be known. In this work the influence of product noise regulations is included in the model for the control period 1992-1998. Results are in good agreement with noise measurements. This increases the confidence in the model for predicting future evolution. Several future-scenario's (business as usual, sustainable) are presented in the paper.

Geerlings, A.C.

• A HYBRID CALCULATION TOOL FOR THE EVALUATION OF COMPLEX NOISE BARRIER GEOMETRIES INCLUDING METEOROLOGICAL EFFECTS
  A.C. Geerlings and J. Mank
[Abstract]

The Dutch statutory calculation model is obligatory for the acoustical evaluation of road- and trackside noise barriers in Holland. It is however, limited by barrier complexity and propagation distance. Sometimes the statutory model is stretched beyond these specifications, for instance to evaluate barrier effects on environmentally sensitive areas. The Dutch authorities consider this an undesirable situation and have asked TNO to design correction terms as an add-on instrument. A two-stage hybrid approach was chosen in which two advanced calculation models are blended into one. Operated alone, both models are restricted as well. Together, they maximise their combined capabilities. The two tools are: 1) a raytracing tool (TOMAS), suitable to evaluate complex barrier geometries through the analysis of multiple diffractions and reflections in a homogeneous atmosphere, 2) a one-way wave-field extrapolation tool (PE) well adapted to include the influence of the meteorology over long propagation distances. TOMAS is used to generate complex pressure values just behind the barrier, which are subsequently fed into PE. The effect on the propagation of the disturbed sound velocity field, due to the presence of the barrier, is taken into account. The hybrid tool has been applied to tilted as well as absorbing double barrier configurations, depressed roads and elevated roads including different types of road surfaces. The new tool generates correction terms to relate the effects of complex barrier geometries to a reference geometry. These are combined with noise impact predictions for the reference geometry, calculated with the statutory calculation tool.

Gentry-Grace, C.

• EXPERIMENTAL CHARACTERIZATION OF MATERIALS FOR ACOUSTIC PERFORMANCE WITH APPLICATIONS
  H.-Y. Lai, C. Gentry-Grace, M.W. Bonilha and C.A.J. Yoerkie
[Abstract]

The acoustic performance of a porous material are determined by its bulk density, airflow resistivity, porosity, tortuosity, viscous and thermal characteristic lengths, elastic modulii and loss factor. A set of measuring techniques and equipment for characterizing such a material was implemented and is described in this paper. The procedure of conducting a material characterization is demonstrated by examples and the accuracy of these techniques is validated by comparing the prediction of the normal absorption coefficient of a material based its measured parameters to its measured absorption coefficient. Excellent agreement was observed over a broad frequency range and results of the test samples are presented.In addition, examples of applying these techniques in conjunction with analytical tools to design mulit-layered liners in noise control applications are also presented in this paper.

Genuit, K.

• THE FUTURE OF SOUND QUALITY OF THE INTERIOR NOISE OF VEHICLES
  K. Genuit
[Abstract]

For several years the sound quality inside vehicles can be measured by means of binaural recordings and analyses based on psychoacoustic parameters. The subjective classification of the sound quality inside vehicles depends not only on psychoacoustic parameters, but on the personal expectation of the driver, too. That means, two cars with identical psychoacoustic parameters could be classified differently, depending on the listener's personal attitude. For the further development of tools to predict sound quality we have to investigate whether the existing psychoacoustic parameters are suitable to describe the complete signal processing of human hearing. Especially for cars with low loudness levels not only absolute parameters like loudness, roughness and so on are important, but more the dynamic behavior of these parameters depending on rotation, speed and load. A further important question is the design of listening tests to get the right answers with respect to the question for the best sound quality. Furthermore, we have to find solutions for the complete new sound quality inside electric motor driven cars. This will be a great task for the acoustical engineers in the future.

Gerges, S.

• FINITE ELEMENT METHOD (FEM) MODEL FOR THE HEARING PROTECTOR NOISE ATTENUATION FOR IMPULSIVE NOISE
  S. Gerges, F. Vergara and R. Birch
[Abstract]

This paper presents a numerical model by FEM of the human external earcanal, considering the acoustic impedance of the eardrum.The sound pressure level at the eardrum is calculated with and without the presence of the hearing protector ear plug. The effec

Germain, P.

• USING AN ACTIVE CONTROL SYSTEM TO INCREASE THE INSERTION LOSS OF A BLAST FENCE FOR RUN-UP NOISE AT VANCOUVER AIRPORT
  J. Guo, M. Hodgson and P. Germain
[Abstract]

Night-time aircraft run-up noise has been a problem that causes annoyance to adjacent communities at the Vancouver International Airport. It was found that the main contribution to the noise is the propeller aircraft that generate blade-passing low-frequency noise, which makes it feasible to apply the active noise control (ANC) to mitigate this noise. An existing blast fence at the run-up site was found to have a noise insertion loss of 4-15 dB over the frequency range 20-2000 Hz. In the work reported here, a multi-channel ANC system was applied to the blast fence, in the hope of increasing the insertion loss of the fence. Numerical simulations indicated that the sys

Gerold, M.

• AUDIBEL-DEVELOPMENT OF A WORLD CLASS PRODUCTION SOUND TEST PROCESS
  M. Sutherland, M. Gerold and D. Copley
[Abstract]

Caterpillar has complied with various construction equipment sound level requirements for many years. However, current production test methodologies are not capable of ensuring compliance to the new European Union (EU) Dynamic Sound Level Requirments. Failure to ensure compliance could result in loss of this key market. In order to provide Caterpillar Manufacturing Facilities around the world with the means to ensure compliance cost effectively, a new sound test process was developed and implemented. Of primary importance was to first identify and develop instrumentation capable of documenting compliance, process capability, and support failed machine diagnostics. Education and training was also vital to establishing an infrastructure that would promote the process control efforts of involved development, design, and manufacturing personnel. This paper will outline the new production sound test process implemented at all Caterpillar Facilities worldwide. The paper will further outline the functional specifications of Caterpillar's new patented dynamic sound test system, termed ''AudiBel'', and it's key role in the production sound test process. The ''AudiBel'' automated system has enabled Caterpillar to reduce lengthy test times, related costs, number of support personnel

Gerretsen, E.

• TRIAS - TYRE ROAD INTERACTION ACOUSTIC SIMULATION MODEL
  F. De Roo and E. Gerretsen
[Abstract]

Since 1996 the development of the TRIAS simulation model for tyre-road noise emission has been in progress. At InterNoise '97, '98 and '99 papers have been presented about this simulation model, which may be considered as one of the most comprehensive attempts to predict tyre-road noise emission. Expectations are that this development will be completed in 2000 with a validation of all modules comprised in this model, dealing with: * tyre-road mechanical interaction; * tyre response to force excitations; * radiation of sound from mechanical vibrations; * generation of sound by air movements in the contact patch; * propagation of sound to the environment. The predictions may be based on measured values of the physical road surface characteristics. For design purposes also a module known as RODAS (ROad Design Acoustical Simulation) may be used, which predicts the surface characteristics as a function of material properties. This module is available as a stand-alone model and has already been validated. The paper will discuss the various validation results and will reveal the latest adjustments of the model based on these validations. Limitations to the use of the model will be addressed and a comparison will be made with the model described by Kropp, which was the starting point of the TRIAS development.

• MULTI-FAMILY HOUSES WITH CAVITY BRICK WALLS: SOUND INSULATION AND VIBRATION TRANSMISSION INDICES
  H. Martin, M. Van Gaal, E. Gerretsen and J. Niggebrugge
[Abstract]

Cavity brick walls (120-50-120 mm) provide a good way to achieve a high sound insulation between single-family houses in a row. Because of flanking sound transmission in vertical direction along the relatively lightweight leafs these walls have not been applied in multi-family houses unless -according to Dutch rules of practice- the surface mass of each leaf exceeds 350 kg/m2. To obtain a better understanding of the behaviour of this type of buildings, measurements have been carried out in multi-family houses with two types of cavity brick walls: 150-50-150 mm (total surface mass 525 kg/m2) and 214-52-214 mm 750 kg/m2)calcium silicate blocks. In order to check up on building regulation demands both the airborne and impact sound insulation have been determined in horizontal as well as in vertical direction. The vibration transmission indices Kij across different junctions have been determined to gain data and to evaluate the differences. The sound insulation has also been calculated according to prEN 12354-1 and -2. This was done twice: once using the measured vibration transmission indices as input data and once completely on the basis of the calculation model.For junctions that consist of homogeneous building components good agreement was found between (a) the measured and calculated vibration transmission indices and (b) the measured and calculated airborne and impact sound insulation in vertical direction. With respect to the latter, negligible differences seemed to occur between the junctions with 150 mm and 214 mm leafs. For junctions that (partly) consist of inhomogeneous building components like cavity walls the calculated vibration transmission indices were found to considerably exceed the measured ones. Consequently the calculated airborne and impact sound insulation in horizontal direction sketched a rather positive picture compared to the measured sound insulation when based on the calculated values of Kij. Therefore for these situations a closer examination of the calculated values of Kij across cavity walls is necessary.

• PREDICTION MODEL FOR SOUND TRANSMISSION FROM MACHINERY IN BUILDINGS: FEASIBLE APPROACHES AND PROBLEMS TO BE SOLVED
  E. Gerretsen
[Abstract]

Prediction models for the airborne and impact sound transmission in buildings have recently been established (EN 12354-1&2:1999). However, these models do not cover technical installations and machinery as a source of sound in buildings. Yet these can cause unacceptable sound levels and it is therefore desirable to have design tools available to predict sound levels caused by machinery in advance or to design measures to reduce the sound level in existing situations. Future parts of the EN 12354-serie should treat that subject. The transmission of airborne and structure borne sound from a machine or installation will in principle be comparable to that already treated, but the situation is much more complicated than in case of a loudspeaker (EN 12354-1) or a tapping machine (EN 12354-2) as sound source. The sources to be considered consist in general of several partial sources, will be connected to the building structure at various points and in various ways, can be much more complicated as source than just a force source, could be a predominant low frequency source etc. etc. And even if the description as structure borne source could be rather simple, there are hardly any source data available nor measurement methods established to collect such data. This paper will therefor focuses on the possible practical approach to deduce a prediction model and discuss the various, yet unsolved, problems, which will have to be dealt with.

Gesret, V.

• PROPELLER NOISE
  V. Gesret
[Abstract]

Propeller cavitation is one of the most important noise source on board ships. Therefore, an accurate calculation of this noise would be very useful. Cavitation noise is very difficult to predict, and various approaches may be considered : - Empirical calculation based on model or full-scale measurements ; - Theoretical prediction. The determination of our empirical calculation is carried out into 2 steps : 1 : Use of full-scale measurements to calculate propeller noise ; 2 : Determination of an empirical model based on full-scale measurements (Available at an early design stage) At full-scale, pressure fluctuation measurements are performed on the hull above the propeller during sea trials. A monopole is then used to modelize propeller source in order to calculate noise. A statistical model is already available[1], using fixed regression coefficients. Our model, presented in this paper, is based on the same calculation, but new regression coefficients are determined for each propeller : 1 -Propeller characteristics (geometry and hydrodynamic), pressure fluctuations measurements and associated noise calculations are placed in a database ; 2- To calculate the noise of a given propeller, different measurements are extracted from the database. Depending on the similarity of the new propeller with chosen propellers, weights are given to each measurement selected . A calculation of new regression coefficients is then performed by the program. To obtain an accurate model, the database has to be as exhaustive as possible and enlarged each time measurements are carried out. A comparison between the calculation of noise from measurements and the statistical approach will be produced.

Bibliography : [1] : Prediction method far the acoustic source strength of propeller cavitation A.de Bruijn, W.H.Moelker, and F.G J.Absil Shipboard acoustics - Proceedings ISSA '86 - J.Buiten (editor) [2] : SECAV : Propeller noise calculation program SPACE HELICE [3] : Noise Sources in ships - 1 : Propellers - Nordforsk - 1981 [4] : Marine propeller cavitation : A noise prediction method for practical applications Ottavio Pinto, Cesare Tarditi - Inter Noise 99 [5] : Tip Vortex Index - An Engineering Approach to noise prediction Arnt Egil Raestad, DNV Noise and Vibration Group Published in 'The Naval Architect' Issue : July/August 1996

Gibbs, B.M.

• INCLUSION OF DAMPING IN A FEM MODEL OF LOW FREQUENCY SOUND IN ROOMS
  S. Maluski and B.M. Gibbs
[Abstract]

A Finite Element (FE) model was developed to investigate the sound insulation between dwellings at low frequencies. It has been found that for small empty rooms (smaller than 50m3), the airborne sound insulation properties of the party wall depend on the structural modal characteristic of the party wall and on the acoustic modal characteristics of the two rooms. They therefore are influenced by the edge conditions of the party wall and by room configuration and size. As dwellings usually are furnished, it also is necessary to examine the effects of localised absorption on the acoustic modal characteristic. Preliminary comparisons between measurements and prediction of the frequency response and sound level difference were promising despite the fact that damping was not included in the FE model. At higher frequencies, the agreement is less good for the empty room and damping must be included in an appropriate form, before investigating the effects of furniture and fittings. Different ways of including 'room' damping are considered and comparisons between measured and predicted frequency response were carried out to validate the FE model.

Gil, C.

• NOISE EFFECTS ON LOCAL SCHOOLS IN THE MADRID REGION
  M. Recuero López, C. Gil, V. Cutanda and J. Grundman Isla
[Abstract]

The results of a subjetive study performed on several municipalities are presented here. Opinions about noise effects in schools were asked, both to teachers and students. Questions include subjects like noise level in classrooms and their acoustic conditions, internal and external noise sources and their annoyance, as well as the causes that originate these sources. Results show that most teachers and student are concerned about noise (76.9% teachers and 58.3% students). When asked about their preferred schools location, they are inclined towards a quieter place, even being father away, than to a closer one but under the influence of urban noise (68.3% teachers and 52.2% students). Improvement in the classrooms acoustic conditions is also considered necessary by most of the teachers (70.1%) and students (60%). As for noise sources, while most important internal source is people (in the opinion of 88.4% teachers and 86.8% students), the external sources vary depending on the location, although people (41.2% teachers and 32.1% students) and vehicles (28.1% teachers and 32.1% students) can be considered the most important ones. Community Response to Noise.

Gilg, S.

• NEW SOUND-ABSORBING FOAMS MADE FROM POLYOLEFIN RESINS
  C. Park, M. Brucker, L. Remy, S. Gilg and S. Subramonian
[Abstract]

Porous materials have been used for sound absorption and insulation. The materials include mineral fibers, open-cell thermoset foams and polymeric fibers. The conventional materials have one or more drawbacks. Being porous, all the materials absorb water during real-life uses, where they are often in contact with moist air, condensation or both. Fibrous materials lack mechanical integrity and mineral fibers pose a handling difficulty. Polyurethane foams and melamine resin foams tend to undergo hydrolysis during a prolonged exposure to moisture. In addition, these thermoset foams are not recyclable. A moisture-resistant sound-absorbing material that is recyclable has been in demand. We have successfully developed a group of novel materials that meet the demand. The materials are thermoplastic foams extruded from polyolefin resins. An optimum selection of the polymer resin and a proper control of the cell structure yield the desired foams that have been elusive. A large cell size and a controlled open-cell content characterize the novel products. Perforation and compression open the cells of the extruded foams. The polyolefin foams can be tailored to damp vibration as well as absorbing sound. Thus, the foam materials have been found to be useful not only for sound absorption but also for sound insulation and vibration damping. With advantages over the conventional materials, the polyolefin foams find numerous applications in automotive, appliance and industrial uses as well as in buildings. The primary attraction of the foam products is their low water pick-up in a humid environment.

Gimenez, A.

• ANNOYANCE PRODUCED BY THE NOISE OF THE AIRPORT OF ALTET-ALICANTE, ON THE CITIES OF ALTET, TORREMOLINOS AND ELCHE
  M. Mallebrera , J. Romero, A. Gimenez, A. Marin and A. Sanchis
[Abstract]

During the last years, the airport of Altet - Alicante has grown much in number of flights, especially due to the charter ones. Currently it is the forth all over Spain in traffic air, behind of Madrid, Barcelona and Torremolinos, but upon working with an only one runway, the noise that produces is much more concentrated in a zone. The present work shows the results of a inquiry accomplished to the resident of three cities located in this zone, that it has permitted us to know the indices of annoyance of the noise and its relationship to the other environmental factors, as well as its correlation with the acoustics measures obtained. The inquiry also included a question about the possible solutions that they would propose. In the work, the results of the study of the impact of the flights, carried out by means of the program IMN (Integrate Model Noise) of the Federal Aviation Administration (USA), is also shown.

Giovinetto, R.

• A PURPOSE OF AN ACOUSTIC CRITICAL INDEX FOR THE ESTIMATE OF THE PRIORITIES OF INTERVENTION IN AN HIGHWAY GLOBAL REORGANISATION PLAN
  J. Fogola, F. Duretto, R. Giovinetto and R. Pisani
[Abstract]

The aim of our present study is to propose a method for an acoustical critical analysis of territories crossed by large road infrastructures (highways, freeways, etc..). Definition of the Critical Index of Priority. In a global highway acoustic reclamation plan, it is of fundamental importance to characterize in detail the different critical areas interested from the acoustic impact. The concept of the critical area must be unambiguously fixed in all the portions of territory in which the acoustic impact of the road exceeds the fixed limit values. It is possible to fix a critical index (C.I.) for each area in order to obtain in an objective way the priorities of a reorganization plan. The parameters that concur to the determination of this index should be, to judgement of writing, the following: Number of annoyed persons Noise levels Fixed maximum levels Corrective factors The determined index presupposes the knowledge of the noise level in front of all the buildings of a critical area, obtained through a limited number of measures in significant points and by means of forecast calculations in all the remaining points. Conclusions: the Critical Index gives an instrument for the definition of acoustic intervention priority to the competent institutions and a technical aid to the professional person in charge of the reorganisation plan to make the suitable choices for the projects.

Gjestland, T.

• A NOISE METRIC FOR MULTI-SOURCE NOISE ENVIRONMENTS
  H.M. Miedema and T. Gjestland
[Abstract]

Many people are exposed not to one but to multiple noise sources. There is, however, no widely accepted noise metric that predicts the noise annoyance for such situations. Here the so-called representational approach to finding such a metric is described. In this approach a model is constructed for a multi-source noise environment, and a metric for the total noise is derived from that model. The model consists of five statements which reflect what we know (or take) to be true about the relationship between exposures caused by the individual noise sources that affect the same person, and the noise annoyance caused by the total, multiple exposure. The metric derived from the model has a consistent relation with the ordering of multiple noise exposures with respect to the annoyance they cause, provided that the five statement are valid. Each of the five statements can be discussed and tested. In this way the decision on a metric for a multi-source noise environment is broken down in the evaluation of five clear and explicit statements. Four of the five properties will be accepted in general either as empirically plausible, or as a reasonable simplification. The fifth property is independence. A violation of independence may occur if the annoyance caused by a very irritating sound (tonal, impulsive, low frequency) is reduced by masking with e.g. road traffic noise. However, situations where these specific sounds are masked, occur relatively seldom. In general the metric presented here can be used for the description of combined environmental noises.

Glav, R.

• A SEMI-ANALYTICAL APPROACH TO DESIGN A LOW-FREQUENCY ABSORBER
  R. Glav and O. Jönsson
[Abstract]

This paper describes a straightforward and accurate technique to design a resonant low-frequency absorber using any kind of penetrable facing. The technique is based on in-duct measurements of the acoustical 2-port matrix of the facing using the 2-microphone technique. The 2-port of the facing is then combined with a lumped model of the partitionated backing volume to enable simulation and optimisation of the wall impedance of the complete absorber. As a practical example the technique has been applied to a micro-slotted aluminium plate well suited for use in a dusty and harsh environment such as for instance the engine compartment of a vehicle. Measurement of the plane wave wall impedance has also been performed to verify the proposed technique. The knowledge of the impedance of the absorber enables accurate location of the absorber in the actual enclosure to ensure that the desired attenuation is reached.

Gogu, G.

• CALCULATION OF THE ACOUSTIC RADIATION OF STRUCTURES WITH OPENINGS
  F. Polonio, T. Loyau, J.-M. Parot and G. Gogu
[Abstract]

The acoustic radiation of structures with openings can be calculated by several methods. One can use the Boudary Element Method (BEM) in the inside and outside surface. The problem can also be resolved by coupling the interior and the exterior acoustic fields. These two fields can be coupled by the pressure at the openings. The inside and outside acoustic pressure are calculated using BEM. In our method the interior acoustic field is calculated by a Finite Element Method (FEM). This approach is very convenient to introduce acoustic materials inside the cavity and is less sensitive to numerical problems. We have compared the results obtained by two methods in the case of a vibrating parallelelipedic structure with an opening. The first method is based on the calculation of the interior and exterior field by BEM. The second one calculates separately the interior acoustic field by FEM, the exterior field by BEM. The coupling between the two fields is modelised by continuity of both the acoustic pressure and the velocity at the opening. Results are compared through directivity diagrams of the acoustic pressure. Limits of each method are given. A close agreement is observed between results obtained with these two methods, making us confident in our model. Further, validations (calculation/experiment) will be done on more complex structure, containing for instance absorbent materials inside the cavity.

Goldberg, J.L.

• THE LEGAL IMPEDIMENT TO ENVIRONMENTAL JUSTICE IN AUSTRALIA - A CASE STUDY INVOLVING TRAFFIC NOISE
  J.L. Goldberg
[Abstract]

In 1996 a community group in the state of New South Wales (NSW) Australia, was affected by a proposal by the NSW Roads and Traffic Authority (RTA) to widen a two-lane road to five lanes. The widened road was likely to result in increased usage by heavy vehicles at night but the RTA ignored the potential for sleep disturbance. It did not specify allowable maximum noise levels nor evaluate the costs of noise. The community group challenged the proposal in the NSW Land and Environment Court, the state jurisdiction responsible for justice in environmental matters. A method of assessing the costs of noise is to value time lost by disruptions such as sleep disturbance is a similar way to time saved by the road user. This method, which reflects the costs of noise more equitably than housing market models, was presented to the Court on behalf of the applicant. The judgement placed the legality of the action in widening the road above the merits of the case based on environmental and economic grounds, and considered that it was ''not unreasonable'' for the costs of noise to have been omitted by the RTA. The judgment had highly adverse consequences for the community when the widened road carried large numbers of heavy vehicles at night. The case illustrates the need for reform of the NSW jurisdiction.

Golebiewski, R.

• NOISE ANNOYANCE WITH RESPECT TO THE DISTANCE OF THE NOISE SOURCE
  A. Preis and R. Golebiewski
[Abstract]

Noise produced by source located farther from a listener is estimated as less annoying than noise produced by source of the same type that is located closer. This is explained by pointing to the fact that increase in distance of the source of noise causes decrease in loudness and at the same time decrease in annoyance. The aim of the present paper is to answer another question: what is the annoyance of noise produced by sources at different distances but having the same loudness at the point of listener's location. To answer this one has to consider that the ground effect and air absorption phenomenon change not only the sound level of the stimulus but also its spectral content. In this work railway noise was used as the source of noise annoyance. The original railway noises recorded at two distances were artificially modified to make them equal in sound level and in loudness. In psychoacoustical experiments subjects were asked to assess noise annoyance of original and modified sounds. In the independent experiment they were asked to judge the distance of the source by considering the original and modified stimuli. The results of the experiments are discussed in the reference to the existing noise annoyance models.

Gomes De Oliveira, M.

• USING A GIS TOOL TO PLAN THE ACOUSTIC URBAN ENVIRONMENT
  M. Gomes De Oliveira, E. Bauzer Medeiros and C. Davies Jr.
[Abstract]

The economic development taking place in large urban centers can often provide an improvement in life quality as a consequence of the wider availability of services. However, severe environmental problems can also occur, if a coordinated strategy involving adequate monitoring of established businesses is not carried out. Adequate assessment of the environmental impact which may result from the economic development can only be carried out if suitable tools are available to the administrators, enabling proper supervision of land occupation. Noise is a major source of nuisance in urban environments, and in general 70% of the inhabitants of large cities usually describe noise related disturbances as a very important factor affecting life quality. This paper describes a set of GIS-based tools intended to provide the administrators with a methodology enabling a proper assessment of the acoustic impact within the urban environment. A model establishing the correlation between the spatial distribution of impacts and the relevant activities is developed. This model has been implemented as a prototype in a GIS environment, using Belo Horizonte's geographic database, which is intended to represent a typical large Brazilian city situation. Initial field measurements compare favorably with this prototype, indicating the feasibility of the proposed approach.

Gomez Escobar, V.

• STUDY OF VITORIA-GASTEIZ BY CATEGORIZING CHARACTERISTICS ROADWAY
  J.M. Barrigón, V. Gomez Escobar, P.D. Gutierrez Marcos, J.A. Mendez Sierra and J. Ruiz De Azua
[Abstract]

In the city of Vitoria-Gasteiz (País Vasco, Spain) a preliminary urban noise survey was conducted. The city was categorised by its characteristics roadway. Thus, four different categories were studied with random selection of sampling points. Measure noise levels can be considered high (over 65 dB(A))in the city. Some comparisons were made with a previous (1991) noise map of the city. The study was developed in two different months, one on holiday period (August) and the second in a common month (September). Results showed differences between both months. Relationships between energy-averaged sound level (Leq) and statistical levels of exceedance (Lx) were established. Finally, a regression equation of Leq was developed as a function of logarithm of the number of vehicles per hour. Results showed a good agreement with other authors.

Gonneau, E.

• DESIGN AND IMPLEMENTATION OF ALGORITHMS FOR ACTIVE CONTROL OF MULTI-MODAL NOISE IN DUCTS
  L. Tardy, E. Gonneau and J.-P. Guilhot
[Abstract]

Many studies have already been realised in active noise control to reduce the sound radiated by fans in ducts. Most of these works act on the plane wave propagation, due to the lowpass behaviour of the primary source. This paper presents a modal controller implemented in order to reduce the tonal noise which emerges from the broadband noise and is due to higher order modes. This allows simultaneous and independent reduction of the acoustic pressure of each mode at each frequency. Notch filters have been implemented and compared to the classical FXLMS algorithm using FIR filters. Simulations have shown their performance concerning the computational time. Results are equally presented with the use of a variable stepsize algorithm. This latter method, where the stepsize is a variable dependent of the error signals energy, optimises the convergence time. It equally reduces instability problems when local minima are not well detected by the control system. These different algorithms have been then experimentally tested to reduce the sound emitted by an axial fan used as ventilation and pressurisation system in aircraft cabins. Simulation results have been confirmed, with the use of a floating point DSP controller driving a multiple error microphones/loudspeakers system.

González, J.

• DESCRIPTIVE ANALYSIS OF THE TEMPORARY EVOLUTION OF THE URBAN NOISE.
  J.I. Sánchez , J. González, M. Machimbarrena and M.C. Valsero
[Abstract]

The following paper develops an analysis of the daily evolution of noise in a specific street in Valladolid, (SPAIN), a medium size city with about 350.000 people. The data have been taken every thirty minutes continuously, beginning on a Friday at 14:00 and finishing seventeen days later, Monday, at the same hour. This yields a total amount of 818 sets of data. Each of these sets includes five acoustical magnitudes (Leq, L10, L50, L90, ) and the standard deviation of (s). Three different time periods will be analysed: day time (8:00 to 20:00), evening time (20:00 to 23:00) and night time (23:00 to 8:00). The descriptive analysis shows that the behaviour of the acoustical magnitudes is similar between them and different to the behaviour of s. When the urban noise is small, then s is high, and when the urban noise is high then s is small. This behaviour is found in every subset of data analysed. It can also be seen, that the acoustical variables (Leq, L10, L50, L90, ) present the same patterns on Monday-Friday weekdays, but Saturday and Sunday patterns are different from regular weekdays and from one another. Concerning the statistical variable s, Monday through Thursday (M-Th) weekdays have a similar behaviour, but Friday, Saturday and Sunday have a specific and different behaviour, both between them and compared to M-Th behavior. If the three different periods of the day are compared, it can be seen that they are all different from one another. Once the descriptive analysis has been made, we have used the Kolmogorov-Smirnov statistic to contrast if the days of the week are similar and if the periods are similar. It has been obtained that they are not and that the behaviour of all magnitudes responds to what was obtained with the descriptive analysis.

Gonzalez-Rojo, S.

• A FUZZY LOGIC APPROACH FOR URBAN TRAFFIC MONITORING USING NOISE MEASUREMENTS
  S. Gonzalez-Rojo, A. Lopes-Pereira, J. Slama and F. Mora-Camino
[Abstract]

The Artificial Intelligence (AI) techniques, which have been developed in the last decades within an engineering perspective (Fuzzy Logic, Neural Networks, Genetic Algorithms and others), are now used in many practical applications in many fields. In the case of management and control of urban traffic, many promising applications have been already detected. In general AI techniques, particularly fuzzy and neuro-fuzzy approaches, are well suited to tackle different problems related with the management and control of urban traffic, leading to simplified data collection procedures and to more efficient processing techniques to get accurate evaluations of present situations as well as predictions. Then, new tools become available for the integration of environmental goals into decision processes and to get efficient solutions free from intricate mathematical applicability conditions. In this paper an approach to monitor current traffic conditions is proposed : traffic noise, which has been regarded for many decades only as a nuisance while its structure and intensity are directly related to the current traffic conditions, is considered to be a rich source of information about traffic. In this communication we present the extraction of traffic patterns from traffic noise measurements, using Fuzzy Logic and Neuro-Fuzzy Logic techniques. Then, we propose an approach for on-line area traffic control, which makes use of Advanced Automatic Control and Operations Research tools at the control level, while, at the management level, AI and Acoustic techniques are introduced to monitor the current traffic conditions.

Goto, K.

• ANNOYANCE AND MENTAL HEALTH STATUS OF PEOPLE AROUND AN AIRPORT IN JAPAN.
  K. Goto, T. Kaneko and Y. Tokita
[Abstract]

Aircraft noise is one of the frequent causes of annoyance in a community. Stress related health disorders are the concerns of the people living near airports. By their requests the mobile service of health examination has been conducted by our foundation. To investigate the association between annoyance and other factors, along with the service reservation annoyance in a community was surveyed with the questionnaire comprising questions to assess the mental health status and social support. Here we used an anxiety and depression score derived from clinical field. Subjective value of environmental conditions including ambient noise and level of social supports from family, relates or neighbors were also measured with the questionnaire. Data from 390 respondents of women (average age 54.7+/-12.4) were divided into three groups with varying aircraft noise levels and analyzed statistically. The proportions of highly annoyed persons in the three areas were dependent on the noise levels. Evaluation for ambient noise by residents showed also significant association with aircraft noise level. The average of depression score in the noisiest area was highest of the three but the difference was not significant. Anxiety scores in three areas were almost the same on average. No significant association was seen between noise level and anxiety or depression levels. Dissatisfaction to environmental noise showed significant correlation with mental health levels based on anxiety and depression score. The dissatisfaction also showed correlation with social support levels. The multi-regression analysis for mental health levels revealed that the contributors with statistical significance are not the air craft noise levels but the dissatisfaction to ambient noise and social support levels of residents.

Gottlob, D.P.A.

• OVERVIEW OVER THE PRESENT NOISE REGULATIONS IN THE EU MEMBER STATES
  D.P.A. Gottlob
[Abstract]

In the last twenty years the noise policy of the European Communities has been mainly related to the reduction of trade barrieres. In the framework of this policy, regulations concerning the limitation of noise emissions from various vehicles, machines, and products have been set up. In 1996 the European Commission started a new policy which includes the set up of regulations concerning the noise exposure of the population. This new policy is based on shared responsibility of European, national, regional, and local authorities for the improvement of the noise situation with the member states. For the preparation of such regulations it is useful to evaluate the legislation related to noise exposure in the member states and to compare the approaches for the

• THE NEED FOR A HARMONISATION OF PREDICTION MODELS FOR RAILWAY NOISE
  D.P.A. Gottlob
[Abstract]

The European Commission is preparing a directive relating to the assessment and reduction of environmental noise exposure. The directive aims among others at the determination of the environmental noise exposure in the member states based on common methods. The commission set up a working group which shall elaborate proposals for harmonised measurement and prediction methods especially for railway noise. An evaluation of the methods currently used in the member states has shown that the prediction procedures are very similar in principle but there are large differences in detail e. g. concerning the classification of engines, vehicle, tracks and the corresponding emission values. Therefore, there is a need for a harmonisation of procedures. In course of this harmonisation the representation of the different sources (engine, ventilators, rail/wheel, aerodynamic sources) shall be improved, and emission data shall be separated strictly from transmission data. In the paper a comparison of current methods wil

Granneman, J.H.

• ACOUSTICAL OPTIMAL DESIGN OF (UN)LOADING FACILITIES OF SHOPPING CENTRES NEAR RESIDENCES
  J.H. Granneman and J.P.J. Oostdijk
[Abstract]

Increasing traffic jam problems in the day period in combination with change of opening times of shops has enlarged the demand of supplying stores in the evening and night period. When provisioning activities take place near adjacent dwellings, it can be very disturbing to neighbours. A guideline has been made concerning the acoustical optimal adaptation and/or design of such (un)loading facilities near small and large, existing and projected shopping centers. Based on the relevant acoustical parameters, such as different noise sources with specific sound power levels, distances to dwellings, specific handling devices and geographical configurations, a step by step approach is described by which the owner, designer and local government can assess the (un)loading facility regarding the noise aspect (especially maximum noise levels). Based on this assessment, adequate noise reducing provisions can be selected, related to the exceeding of noise limits. The different kinds of provisions are described. The methodical structure and basic contents of the guideline will be presen-ted in this paper.

Granøien, I.

• SINGLE EVENT AIRCRAFT NOISE PREDICTION BY NORTIM
  H. Olsen, I. Granøien and K. Liasjø
[Abstract]

Models to predict aircraft noise around airports, traditionally computes long term averaged sound immission for land use planning purposes. The objective of this paper is to present how the Norwegian aircraft noise prediction model NORTIM is extended to predict short term noise levels. The model is capable of predicting time histories with up to 1 second resolution, and includes the effects of local topography. This kind of model is an effective tool to understand and explain the different aspects og noise in the surrounding community, as well as to provide direct comparison with short term noise measurements. The algorithms and features of the program will be illustrated by calculation examples at Oslo airport Gardermoen, and by results from a comprehensive NATO CCMS validation project.

Gratt, W.

• PRESENTATION OF ENVIRONMENTAL NOISE
  E. Marth, W. Gratt and D. Kath
[Abstract]

Establishment of new roads causes a changed load of noise for the population. A shift of traffic is able to induce as well an increase, as well a decrease of noise-burden. In order to present this dynamic process and to give the official a help for the assessment, a new graphic-statistical presentation of data of noise was chosen. Sound levels was subdivided into individual categories 5 dB(A) too, and frequencies of categories were presented in a histogram. The project was structured in 4 levels. The first level supported the total project from point A (village) to point D (altogether 16,5 km). Sound levels were compared with and without building of the new road in the prognosis-year 2015 and the load was assessed by comparison of histograms. In the second level, noise of the individual four villages (A-D) were discussed in above stated procedure. In the third level, the respective noise of individual important immission-areas (each village consists of several areas) were represented in form of Box-Plot. This form of presentation has on the one hand the advantage that different statistical sizes, like median, quartile, skew, gives information of the distribution of data and can be assessed graphically, on the other hand, on basis of skew of the distribution of data, trends are observable. Finally, the fourth level contains the medical assessment of each single result.

Griffin, S.

• INNOVATIVE VIBROACOUSTIC CONTROL APPROACHES IN SPACE LAUNCH VEHICLES
  S. Griffin, S. Lane and D. Leo
[Abstract]

Vibroacoustics during space vehicle launch has been blamed for as many as 60% of first day satellite failures. At the Air Force Research Laboratory in Albuquerque NM USA, modeling and analysis was performed to determine the feasibility of various control approaches to reduce noise levels of the shroud interior. These studies were performed in cooperative research efforts with several universities and engineering contractors including VPI, Duke, MIT, Boeing and CSA Engineering. Candidate active actuation technologies included PMA's, piezoceramics and volume velocity acoustic sources. Preliminary active control experiments were conducted in a joint research effort with the Center for Applied Control at Duke University on a full-scale fiberglass shroud testbed, contributed by the Air Force Research Laboratory. An innovative idea for a passive vibroacoustic attenuator for the fairing resulted from on-going research and analysis of the structural/acoustic problem and results from this device will also be presented.

Grigg, A.J.

• EVALUATION OF COMMUNITY RESPONSE TO AIRCRAFT NOISE FOLLOWING COMPLETION OF A NEW RUNWAY AT VANCOUVER INTERNATIONAL AIPORT
  A.J. Grigg, E.F. Haboly and M.C. Cheng
[Abstract]

Vancouver International Airport opened a new 3,030 mtre parallel runnway in november of 1996. In order to scientifically assess community response, the Vancouver International Airport authority (Airport authority commissioned Dr Sanford Fidell and Laura Silvati of BBN technologies to complete a ''before'' and ''after'' social survey of nearby residential communities. It is not known which, if any, other airports have completed a noise social survey both prior to and following a similar runnway expansion project. In August 1995, the first round of telephone interviews were conducted to establish baseline information about the prevalence of aircraft noise annoyance in nearby residential areas. In 1998, almost two years after the initial survey was completed, the airport authority commissioned a follow-up survey of the same residential areas, as well as comparison of the results with the baseline conditions. In addition, airport authority staff prepared noise exposure data using computer based modelling so that annoyance could be correlated with estimated day-night average sound levels (DNL). Fidell and Silvati's findings assisted the airport authority in determining which neighbourhoods were annoyed by aircraft noise ; their level of tolerance to aircraft noise, and how results compared to the baseline study and communities located elsewhere. Results were roughly similar to those observed elsewhere, and with the dosage-response curve developed by the U.S. Federal Interagency committee on noise (Ficon, 1992). Results also showed that aircraft noise tolerance among residents in this study was lower than comparable communities elsewhere.

Grimwood, C.

• THE 1999/2000 NOISE SURVEYS OF ENGLAND AND WALES - A PROGRESS REPORT
  M. Ling, P. Wright and C. Grimwood
[Abstract]

BRE Acoustics Centre is currently involved in two major noise research projects. The first to investigate the attitude of people in England and Wales to environmental noise, and the second to measure the incidence of environmental noise across England and Wales. Both surveys are being conducted for the Department of Environment Transport and Regions (DETR) and are amongst the largest environmental noise surveys conducted worldwide. For the noise attitude survey, over 5000 respondents were asked to identify the noise sources that they heard whilst at home, and to quantify their response to these noises. One half of the sample used a structured questionnaire identical to that used in the last study in 1991, and the second half utilising a revised modular structure. The noise incidence survey is measuring 24 hour noise levels outside 1000 dwellings. At the same time, occupants fill in a self-completion questionnaire about their attitude to the environmental noise. This paper describes the survey methodologies, and discusses some of the initial findings.

Grundman Isla , J.

• NOISE EFFECTS ON LOCAL SCHOOLS IN THE MADRID REGION
  M. Recuero López, C. Gil, V. Cutanda and J. Grundman Isla
[Abstract]

The results of a subjetive study performed on several municipalities are presented here. Opinions about noise effects in schools were asked, both to teachers and students. Questions include subjects like noise level in classrooms and their acoustic conditions, internal and external noise sources and their annoyance, as well as the causes that originate these sources. Results show that most teachers and student are concerned about noise (76.9% teachers and 58.3% students). When asked about their preferred schools location, they are inclined towards a quieter place, even being father away, than to a closer one but under the influence of urban noise (68.3% teachers and 52.2% students). Improvement in the classrooms acoustic conditions is also considered necessary by most of the teachers (70.1%) and students (60%). As for noise sources, while most important internal source is people (in the opinion of 88.4% teachers and 86.8% students), the external sources vary depending on the location, although people (41.2% teachers and 32.1% students) and vehicles (28.1% teachers and 32.1% students) can be considered the most important ones. Community Response to Noise.

Grünewald, M.

• TRANSMISSION LOSS OF DOUBLE WALLS: SEA MODELIZATION VERSUS EXPERIMENT
  S. Brühl, P. Bremner, A. Roeder and M. Grünewald
[Abstract]

Transmission loss experiments on different double wall configurations (thin aluminum panels of appr. 1m area) have been performed and recalculated with the new AutoSEA2 program. The interior cavity was studied under different conditions (empty and filled with two different absorbing foams). The SEA model takes into account possible flanking transmission paths through the mounting frame of the panels as well as the low frequency mass resonance behaviour. By choosing appropriate parameters for the panel/frame coupling an excellent coincidence between measurement and calculation results can be obtained for all studied cases.

Guazzotti , M.

• SOUND INSULATION BUILDING IN URBAN AREAS NEAR AIRPORTS
  L. Mazzarella and M. Guazzotti
[Abstract]

The present work is dealing with two different aspects of noise building protection in airports area. The first investigated aspect is the assesment of the tipical sound spectrum produced by aeronautical traffic on the external wall of the building during the take off fase. For this purposes measurement have been taken on the outside of a school building and the average spectrum is derivbed; the spectracompound of every single whole take off phase, typical for every kind of aeroplane. In the second step the acoustic impedances of the facade walls, as well as the transmission losses of the facade elements, have been calculated according to the usual procedures. Thus such impedances have been composed with the average spectrum to identify noise protection failures for each wall elements for every third octave band. This procedure is able to provide those information which may lead to possible improvements for the acoustic bonify of the building.

Guazzotti, M.

• VERTICAL EFFICIENCY OF SPEEDWAY ACOUSTIC FRAMES
  L. Mazzarella, M. Guazzotti and E. Rendina
[Abstract]

In this work tridimensional acoustic fields near highway frames are examined, both through experimental measurements and as well as by a numerical simulation of the phenomena using an appropriate software. In the first part the measurements taken in front of and behind the highway frames are presented. The highway is located in a periferic urban area of Milan near an elementary school having woodden acoustic frames. Acoustic measurements have been taken at different levels from the ground and in the whole range of the octave band spectrum between 63 Hz and 4000 Hz for every height and also in different position respect to the frame. This work had been carried out for both validating the softaware has been used later to extend the analysis and eventually deriving calibration coefficents based on such experimental results. Then the simulation has produced 3D isophonic rappresentations for each frequency, identified through this work as isophonic shells wich give a clear view of the spectral interaction between the frame and the buildings or among the frame, field, building and other walls.

Guedel, A.

• NOISE OF PROPELLER FANS USED IN AIR-CONDITIONING UNITS
  A. Guedel
[Abstract]

Fans and compressors are the two main noise sources of air-conditioning equipment. This paper deals with the noise radiated by propeller fans of external units of split systems. These fans usually have 3 to 5 large chord blades and are mounted within the unit in front of a heat exchanger. The objective of this work is to improve the knowledge on the acoustic mechanisms of this kind of fans in order to predict and reduce the noise level, especially the broadband noise level which provides the major contribution to the A-weighted OASPL since the BPF tones occur at frequencies usually much lower than 100 Hz. After a short presentation of the main aerodynamic and acoustic characteristics of these fans the paper shows results of tests performed on two 400-mm propeller fans of quite different geometry. These fans have nearly the same performance but their sound power spectra, which depend on the operating point, show some differences which are analysed. Tests also include the determination of mean flow velocity profiles in a plane closely downstream to the blade trailing edge in order to assess the repartition of the mean load and mean flow along the fan span and try to correlate this information with acoustic performance. Furthermore the measured profiles are compared with those predicted by Fluent code. This comparison appears quite good and confirms that CFD codes are well adapted today for fan performance and mean flow prediction. Flow velocity measurement with a fixed hot film downstream the trailing edge allows to determine the blade wake width at several radiuses along the fan span. These data are used to check the validity of the sound power level prediction from the analytical model of Fukano. This prediction on both fans proves not too bad provided that the tip chord length is accounted for in the model.

• DESIGN OF TERMINATING DUCTS FOR FAN NOISE TESTING
  A. Guedel
[Abstract]

A new ISO Standard (ISO 13347) is being prepared by Technical Committee ISO/TC117/WG2 Industrial Fans - Acoustics, which describes different methods for the determination of fan sound power levels under standardised laboratory conditions. The measurement procedures cover the following fan installations: free inlet/free outlet, free inlet/ducted outlet, ducted inlet/free outlet, ducted inlet/ducted outlet. The sound levels are measured either in the duct, according to a procedure described in ISO 5136, or outside the duct. A duct in which the sound pressure is to be measured for determination of the in-duct sound power is called a ''test duct''. Such a duct has to be terminated with a good anechoic termination to minimise duct end reflections which contaminate the pressure signals measured in the duct. On the other end, a duct in which no sound measurements are to be made is called a ''terminating duct''. This duct still needs to be fitted with an anechoic termination in order to specify a standardised acoustic load impedance, as it is now well known that the sound power level radiated by a fan depends on the acoustic impedance of the ducts connected to the fan. The performance of the anechoic termination of a terminating duct does not need to be as high as that of a test duct. Standard specifies that below 160 Hz the maximum permissible pressure reflection coefficients for a terminating duct is twice higher than those of a test duct. This paper presents results of tests carried out for defining ''simplified'' anechoic terminations for terminating ducts, which are less expensive and bulky than true anechoic terminations. This simplified termination is a set of simple cylindrical silencers in series with stepped outer diameters. It is shown that only two silencers suffice to conform to the reflection coefficients of the standard for duct diameters between 400 and 800 mm and a single silencer is suitable above 800 mm. The influence of the termination configuration on the fan sound power level measured on the side opposite to the terminating duct is also shown. This paper could be cited as a reference in the new standard.

Guerin, J.-M.

• THE STRUGGLE AGAINST NOISE IN NICE
  M. Lafaurie, R. Tiquet, J.-M. Guerin and G. Maurel
[Abstract]

Three plans for noise control are already into effect: - Noise maps concerning the highways and railways - Noise plan for others roads (carried out by Environment planning department) - Aircraft noise map near the airport The Mayor of Nice, aware of the problem of noise in the city, has decided to study the plan of the first line (8,5 km) of the public transport system tramway. Likewise, a survey was carried out in 1997 among 1000 municipal employees concerning noise in the city environment. An overhelming majority (80%) found the traffic was the major source of noise pollution. The enquiry led to targets being defined and a number of measures being taken to reduce noise exposure levels: - The installation of appliances on two buildings belonging to the city to measure aircraft noise levels. - NOISE REDUCTION PROGRAMME FOR 2000 - 5 500 000 Euros A study entitled ''Noise and environment'' will be made to define the noise landscape of some different districts of the town. This study will help the deciders in town planning. Noise and traffic reduction: reducing the width of streets in the city centre. Anti noise devices: ''quiet'' road surfacing on three main thoroughfares and on the cross-city urban highway as well as the installation of screen shieldings. Sound insulating materials in schools. New equipment such as glass collection containers. Subsidies for householders to install double-glazing in houses located near roads with heavy traffic. - NOISE REDUCTION PROGRAMME FOR 2001 - 2003 Not completed at present - to be included in the manuscript.

Guerin, S.

• SELF-SUSTAINED FLOW NOISE REDUCTION USING A COANDA EFFECT
  S. Guerin, A. Coiret, A. Sakout and R. Henry
[Abstract]

Many industrial flow conditions lead to self-sustained flow noise which is the result of a feedback loop between a vortex shedding and acoustical waves. Howe and Powell have demonstrated the conditions to be fulfilled in order to allow the kinetic energy of the vortices to be converted into acoustical energy. Based upon this theory, a new way of noise reduction, neither active nor passive, is brought forward by reaching a noise reducing (20 to 30dB) stable branch of a turbulent bifurcation, which is maintained via a hysteresis-like effect. The initial noisy configuration, i.e. two standard baffles in tandem in a duct is modified with thin slots created on the upstream baffle. The key point is to be able to create a new velocity field which has to be drastically different in order to modify the Howe and Powell conditions. At the same time, the geometrical modification must be as small as possible in order not to affect the primary function of the industrial flow. Experimental results are reported on the ''noisy'' and ''silent'' paths of the bifurcation. A special emphasis is brought on new features of the dynamics of the small ''plane jets'' which are created by the thin slots. It allows a better comprehension of the silent situation. The question of identifying the parameters which govern the bifurcation arises but it is well known to be a difficult task. Nevertheless, such a method may open a door towards a costless self sustained-flow noise reduction.

Guerrand, S.

• SIMULATIONS OF THE NOISE RADIATION OF HIGH SPEED TRAINS
  C. Talotte, S. Guerrand and C. Gaumain
[Abstract]

Experimental and numerical studies had been carried out at SNCF to characterise the noise of TGV which has two origins : rolling and aerodynamics which becomes predominant above 300 km/h. The knowledge of the physical phenomena linked to each kind of source, obtained through different research projects (including a specific co-operation with DBAG) allowed to define source models including mainly spectrum aspects and evolution with speed. The following step was the development of a numerical tool, for the simulation of the noise radiation of trains built from these source models. The software, called MAT2S, developed at SNCF in C++ is presented in this paper. The software use involves modelling a train with its different sources and all the parameters that might influence its noise radiation, performing a calculation and looking at the results. The features of the software are : the capability to modify easily sources and to define a new train configuration the parameters included in the algorithm (directivity correction, spherical attenuation, ground effect, atmospheric absorption and Doppler effect) the capability to obtain the results as levels but also as spectra or signatures. The software, which is user friendly, allows to carry out parametrical studies to assess potential of reduction of the different sources and how they balance. First computation of a TGV configuration had been compared with experimental results on line. The very satisfactory comparison is presented in this paper. Future developments will be focused on source models improvement and simulations of other trains configurations.

Guibergia, J.P.

• EXPERIMENTAL CHARACTERISATION OF AERO-ACOUSTIC SOURCES IN ENCLOSURES.
  Y. Knapp, L. Jourdan, E. Bertrand and J.P. Guibergia
[Abstract]

Experimental or numerical analysis of flows in a heater unit of an automobile air conditioning system is very important for fundamental design, improvement of efficiency, of aero-acoustic behaviour etc. The small size and complex geometry of such devices, makes the identification and localisation of aero-acoustic sources very difficult by classical acoustic methods. The present study aimed at using Powell's formulations of aerodynamic sound generation, expressing aero-acoustic source strength in terms of vorticity, to quantify aerodynamic sound generated in such enclosures. Therefore, a technique of whole field velocity measurements called Particle Image Velocimetry was used to map the instantaneous velocity distribution in the casing of a heater unit model. This instantaneous flow fields are differentiated twice to obtain the vorticity field, and the Powel's source term div(w x v) is directly computed from these measurements. The differentiation schemes are optimised to reduce cumulative errors. The possibility of estimating the 2D pressure field by numerical integration of the steady Navier-Stokes equation is also given. The main advantage of this technique is to perform aerodynamic measurements to approach acoustic problems, therefore giving the possibility to test modifications and judge their effects on both the flow and acoustic field.

Guidorzi, P.

• EXPERIMENTAL VERIFICATION OF THE EUROPEAN METHODOLOGY FOR TESTING NOISE BARRIERS IN SITU: SOUND REFLECTION
  M. Garai and P. Guidorzi
[Abstract]

(Invited paper #2 for the special session 7.2 ''Anti-noise devices: new techniques, new materials, public acceptance'')

In the frame of the 1994-97 SMT (standard, measurement and testing) program, the European Commission funded a research project, named Adrienne, to define new test methods for measuring the intrinsic characteristics of road traffic noise reducing devices in situ. The research team produced innovative methods for testing the sound reflection/absorption and the airborne sound insulation characteristics of noise barriers. These methods are now under consideration at CEN/TC 226/WG 6 to become European standards. The present work reports a detailed verification of the test method for sound reflection over a selection of seventeen noise barriers, representative of the Italian and European production. The samples were tested both outdoors, using the new Adrienne method, and in laboratory, following the EN 1793 standards. In both cases the EN single number rating for sound absorption was calculated. The new method proved to be easy to use and reliable for all the kinds of barrier. It has been found sensitive to the shape and the acoustic impedance of the tested barrier. The comparison between field and laboratory results shows a quite good correlation, while existing differences can be explained with the different sound fields and measurement techniques used for the tests. It is concluded that the Adrienne method is the most promising one for its intended use.

• EXPERIMENTAL VERIFICATION OF THE EUROPEAN METHODOLOGY FOR TESTING NOISE BARRIERS IN SITU: AIRBORNE SOUND INSULATION
  M. Garai and P. Guidorzi
[Abstract]

(Invited paper #1 for the special session 7.2 ''Anti-noise devices: new techniques, new materials, public acceptance'') In the frame of the 1994-97 SMT (standard, measurement and testing) program, the European Commission funded a research project, named Adrienne, to define new test methods for measuring the intrinsic characteristics of road traffic noise reducing devices in situ. The research team produced innovative methods for testing the sound reflection/absorption and the airborne sound insulation characteristics of noise barriers.These methods are now under consideration at CEN/TC 226/WG 6 to become European standards. The present work reports a detailed verification of the test method for airborne sound insulation over a selection of seventeen noise barriers, representative of the Italian and European production. The samples were tested both outdoors, using the new Adrienne method, and in laboratory, following the EN 1793 standards. In both cases the EN single number rating for airborne sound insulation was calculated. The new method proved to be easy to use and reliable for all the kinds of barrier. It has been found sensitive to quality of mounting, presence of seals and other details typical of outdoor installations. The comparison between field and laboratory results shows an excellent correlation, while systematic differences can be explained with the different sound fields used for the tests. It is concluded that the Adrienne method is adequate for its intended use.

Guigou-Carter, C.

• STUDY OF PASSIVE/ACTIVE CONTROL ON OPENINGS FOR NATURAL VENTILATION IN BUILDINGS
  J. Maillard and C. Guigou-Carter
[Abstract]

Due to the increase of exterior noise in urban environments, natural ventilation systems cannot any longer be a solution to improve thermal comfort in buildings. In this paper, the potential of using passive/active control to increase the sound insulation performance of natural ventilation openings is discussed. An opening is represented by a rectangular duct located in a rigid wall. Sound transmission through the opening can be improved in the mid-high frequency range using a passive control approach, i.e. by covering the opening walls with porous material. At low frequencies where sound transmission is dominated by the plane wave (first acoustic mode), an active control technique becomes more appropriate. A single-channel (SISO) active control system including an error sensor (microphone) and a control source (loudspeaker) is therefore considered. A 3-dimensional theoretical model based on the combination of a wave and a modal approach was developed to evaluate the sound transmission through the opening. The porous layer on the opening walls is modelled using a surface complex acoustic impedance. The effect of the duct dimensions, the type of porous material, the position of the error sensor and control source are investigated in terms of sound transmission. A prototype of such a passive/active system was then mounted in a concrete wall representative of a building exterior wall to verify the analytical predictions and validate the approach. Analytical and experimental results both demonstrate the advantage of the active/passive control combination. An increase in sound insulation of 10 dB(A) (compared to a duct with rigid wall) is obtained with respect to traffic noise.

Guilhot, J.-P.

• DESIGN AND IMPLEMENTATION OF ALGORITHMS FOR ACTIVE CONTROL OF MULTI-MODAL NOISE IN DUCTS
  L. Tardy, E. Gonneau and J.-P. Guilhot
[Abstract]

Many studies have already been realised in active noise control to reduce the sound radiated by fans in ducts. Most of these works act on the plane wave propagation, due to the lowpass behaviour of the primary source. This paper presents a modal controller implemented in order to reduce the tonal noise which emerges from the broadband noise and is due to higher order modes. This allows simultaneous and independent reduction of the acoustic pressure of each mode at each frequency. Notch filters have been implemented and compared to the classical FXLMS algorithm using FIR filters. Simulations have shown their performance concerning the computational time. Results are equally presented with the use of a variable stepsize algorithm. This latter method, where the stepsize is a variable dependent of the error signals energy, optimises the convergence time. It equally reduces instability problems when local minima are not well detected by the control system. These different algorithms have been then experimentally tested to reduce the sound emitted by an axial fan used as ventilation and pressurisation system in aircraft cabins. Simulation results have been confirmed, with the use of a floating point DSP controller driving a multiple error microphones/loudspeakers system.

Guillaume, P.

• IDENTIFICATION OF THE LINK BETWEEN DISTURBING ELEMENTS OF AUTOMOTIVE EXHAUST NOISE AND THE CONSTRUCTION OF THE EXHAUST SYSTEM
  L. Dedene, R. Valgaeren, M. Van Overmeire and P. Guillaume
[Abstract]

In this contribution a sound quality investigation concerning automotive exhaust noise will be presented. The investigation deals with the disturbing elements of exhaust noise (e.g. booming noise, hollow sound, whistle,...). The exhaust sounds are recorded behind the cars (exterior tailpipe noise) using an artificial head. The investigation consists of three parts. The first part consists in determining a definition for each disturbing element (establish a sound quality catalogue). The next step is to establish a metric for each defined element. With the use of signal analysis, signal manipulation and psycho-acoustic measures the physical aspects of the time signal, that make a disturbing element audible, can be determined and quantified. The final step is to find the link between the established metrics and the geometry of the exhaust system. This is a difficult step due to the large number of components (tubes, baffles, perforations,...). The exhaust noise is also strongly influenced by the flow-induced noise. The paper will be focused on determining the link between the metrics and the exhaust system's geometry. For 2 disturbing elements (hollow sound & whistle) the link between metric and geometry will be discussed in detail.

Guillet, F.

• INDIRECT RECONSTRUCTION OF IC ENGINE PRESSURE TRACE THROUGH STRUCTURAL VIBRATION INVERSE FILTERING
  J. Antoni, R.B. Randall and F. Guillet
[Abstract]

This paper addresses the feasibility of reconstructing the pressure trace in IC engine from non-intrusive structural vibration measurements, by means of an inverse periodically time-varying filter. Therefore, the deconvolution problem is first formulated in a signal extraction framework and demonstration is made of the optimality of the proposed filter. Then, a solution for its implementation is proposed, based on the assumption of cycloergodicity. Finally, applications are made to real vibration signals issued from a diesel engine. Successes and limitations of the method are discussed in light of these results.

Guivarch , M.

• A METHOD FOR PREDICTING THE TRAILING EDGE NOISE CONTRIBUTING TO THE SOUND EMISSION OF HEAT PUMPS FANS
  L. Dutrech, M. Guivarch and F. Crouzet
[Abstract]

The will to reduce the acoustic radiation of air conditioning outdoor units leads to study the contribution of their cooling fans to the noise emission. The broadband part of the noise emitted by the axial fans installed on such systems is generally the most important part of the total radiated noise. Related to the turbulence of the flows, it may have several origins. In this paper, we focus our attention on the self-noise  of an isolated blade profile, caused by the turbulence of the boundary layer, assuming no stall is occurring ( trailing edge noise ). We present a method to predict the noise emitted by a 2D isolated profile, knowing its geometric characteristics, the incidence and the speed of the incoming flow. Our process consist of performing 2D CFD calculations on a profile to obtain statistical information on the flow near the trailing edge. This information is then related to the spectral characteristics of the surface pressure fluctuations, using analytical models developped by Corcos and Benarrous. Finally these characteristics are used to deduce the spectrum of the noise emitted by the profile, thanks to Howe's acoustic model. An empirical correction is also provided to take into account the finite sharpness of the blade. Calculations have been performed on a NACA 012 profile, for several trailing edge sharpness, flow speeds and incidences. The results show good agreements with literature's measurement data. Such work must be continued to study and validate the more realistic case of a 3D rotating blade.

Gulding, J.M.

• UPDATED LATERAL ATTENUATION IN FAA'S INTEGRATED NOISE MODEL
  G.G. Fleming, J. Burstein, A.S. Rapoza, D.A. Senzig, J.M. Gulding and T.L. Connor
[Abstract]

The lateral attenuation algorithm in the Federal Aviation Administration's (FAA) Integrated Noise Model (INM) has historically been based on the two regression equations described in the Society of Automotive Engineers' (SAE) Aerospace Information Report (AIR) 1751. These equations, which together represent a single relationship developed from measured data for 1960s and 1970s aircraft with low-bypass ratio jet engines, are applied equally in INM to the entire aircraft fleet. Further, these equations cannot take into account the effects of propagation over acoustically hard terrain, such as water. Consequently, in 1997 the INM development team initiated the task of revising the lateral attenuation algorithm within the model. The primary component of the revised algorithm is an entirely new methodology for taking into account ground effects. The methodology, which is based upon a newly-compiled spectral data base, along with the physical acoustics model of Embleton, Piercy and Daigle, will exist in INM as a library of regression equations. As such, this approach will offer the accuracy and flexibility of a pure physical acoustics model, coupled with relatively modest computer runtimes. This paper documents the scientifically-founded and experimentally-validated approach to computing ground effects, which is slated for inclusion in the INM.

Gunn, P.

• BRIDGING THE GAP - PRACTICAL WORKPLACE NOISE CONTROLS
  P. Gunn and R. Macmillan
[Abstract]

There is a wide gap between the knowledge presented at international conferences and action taken by people in workplaces to control occupational noise problems. To assist workplaces in Western Australia prepare for new, more stringent occupational noise legislation, WorkSafe Western Australia, the State Government department for occupational safety and health, worked with eight companies in the construction and metal manufacturing sectors to document successful practical noise control measures. These were categorised according to the 'hierarchy of control : New Equipment, New Workplace Layout, Elimination, Substitution, Isolation, Engineering Control at Source, Engineering Control on Transmission Path, Quieter Work Practices and Administrative Control.

Guo, J.

• USING AN ACTIVE CONTROL SYSTEM TO INCREASE THE INSERTION LOSS OF A BLAST FENCE FOR RUN-UP NOISE AT VANCOUVER AIRPORT
  J. Guo, M. Hodgson and P. Germain
[Abstract]

Night-time aircraft run-up noise has been a problem that causes annoyance to adjacent communities at the Vancouver International Airport. It was found that the main contribution to the noise is the propeller aircraft that generate blade-passing low-frequency noise, which makes it feasible to apply the active noise control (ANC) to mitigate this noise. An existing blast fence at the run-up site was found to have a noise insertion loss of 4-15 dB over the frequency range 20-2000 Hz. In the work reported here, a multi-channel ANC system was applied to the blast fence, in the hope of increasing the insertion loss of the fence. Numerical simulations indicated that the sys

Guski, R.

• ASPECTS CONTRIBUTING TO GLOBAL ANNOYANCE JUDGMENTS IN FIELD INTERVIEWS
  R. Guski
[Abstract]

Global annoyance judgments of respondents in field interviews often are considered to be the most important psychological reactions to environmental noise. They usually show the highest covariation with global variables describing the acoustical situation of the living area of the respondents. Although there is a certain agreement among noise researchers about the definition of annoyance, it is not certain which variables contribute to which extent to the global annoyance judgment during the interview. For instance, the respective roles of the noise source, of single loud events, quiet periods, background noise, noise history, noise expectations, day and night interferences with intended activities, outside, and inside disturbances are not at all understood. A better understanding of the aspects contributing to global annoyance judgments seems necessary in order to predict noise annoyance judgments in future situations, especially in situations involving a change in noise. This paper considers some of the aspects believed to work during the decision process of respondents leading to the global annoyance judgment, and it proposes a model which will be tested in a planned field study.

Gutierrez Marcos, P.D.

• STUDY OF VITORIA-GASTEIZ BY CATEGORIZING CHARACTERISTICS ROADWAY
  J.M. Barrigón, V. Gomez Escobar, P.D. Gutierrez Marcos, J.A. Mendez Sierra and J. Ruiz De Azua
[Abstract]

In the city of Vitoria-Gasteiz (País Vasco, Spain) a preliminary urban noise survey was conducted. The city was categorised by its characteristics roadway. Thus, four different categories were studied with random selection of sampling points. Measure noise levels can be considered high (over 65 dB(A))in the city. Some comparisons were made with a previous (1991) noise map of the city. The study was developed in two different months, one on holiday period (August) and the second in a common month (September). Results showed differences between both months. Relationships between energy-averaged sound level (Leq) and statistical levels of exceedance (Lx) were established. Finally, a regression equation of Leq was developed as a function of logarithm of the number of vehicles per hour. Results showed a good agreement with other authors.

Guyader, J.L.

• THE INTENSITY POTENTIAL APPROACH TO PREDICT SOUND PROPAGATION THROUGH PARTIAL ENCLOSURES
  M. Thivant and J.L. Guyader
[Abstract]

The prediction of sound propagation from acoustic sources through partial enclosures is of great interest in machinery and vehicle noise control. The use of classical integral equation is possible for low frequencies but quite unrealistic in mid and high frequencies. Energy methods seem to be interesting alternatives. However difficulties arise, due to the diffusion constant to be used. To overcome this problem, we propose here the Intensity Potential Approach, that describes propagation phenomena , and ignores local reactive effects. One can predict the irrotational part of active intensity, propagating in an acoustic medium with obstacles. Then it can be difficult, in perturbed fields, to establish a relation between intensity and pressure. However this can be done easily in the free field. From a practical point of view, this method allows us to use heat transfer analysis in usual Finite Element software. An application to trucks engine noise is under development.

Habermehl, K.

• USE OF GEOGRAPHIC INFORMATION SYSTEMS IN NOISE ABATEMENT STRATEGIES
  K. Habermehl and L. Ohse
[Abstract]

In the last decades the noise-load at housing areas increased. Therefore the urgency of a comprehensive noise abatement strategy became obvious. In Germany in the Federal Act for Immission Protection (Bundes-Immissionsschutz-Gesetz, BImSchG) was established §47a ''Noise Abatement Strategy''. The responsible authorities, usually the communities, have to draw up noise-immission-plans with the value of noise pollution and conflict-plans with exceeding of threshold values. For calculating these plans a computing model with emittents, topography and buildings is necessary. The efforts for this work can be reduced by using the data of the national surveying authority. The following files were used: - Official Topographic - Cartographic Information System (ATKIS) with the emittents road, railway, parking, light and heavy industry, sports, leisure, ... - Automatically map of estate (ALK) with buildings etc. - Digital Height Model with the topography. - Special files with levels of emission, heights of buildings and other relevant objects. The result of the calculation is the noise-immission-plan. By deducting the threshold values the conflict-plan will be received. The procedure will be illustrated by a realised planning in Hesse. Beside the technical dimension of the planning appeared problems in the co-operation of administration, politicans and inhabitants. From this actual situation result recommendations for futurew development of noise abatement planning and also in the planning procedure.

Haboly, E.F.

• EVALUATION OF COMMUNITY RESPONSE TO AIRCRAFT NOISE FOLLOWING COMPLETION OF A NEW RUNWAY AT VANCOUVER INTERNATIONAL AIPORT
  A.J. Grigg, E.F. Haboly and M.C. Cheng
[Abstract]

Vancouver International Airport opened a new 3,030 mtre parallel runnway in november of 1996. In order to scientifically assess community response, the Vancouver International Airport authority (Airport authority commissioned Dr Sanford Fidell and Laura Silvati of BBN technologies to complete a ''before'' and ''after'' social survey of nearby residential communities. It is not known which, if any, other airports have completed a noise social survey both prior to and following a similar runnway expansion project. In August 1995, the first round of telephone interviews were conducted to establish baseline information about the prevalence of aircraft noise annoyance in nearby residential areas. In 1998, almost two years after the initial survey was completed, the airport authority commissioned a follow-up survey of the same residential areas, as well as comparison of the results with the baseline conditions. In addition, airport authority staff prepared noise exposure data using computer based modelling so that annoyance could be correlated with estimated day-night average sound levels (DNL). Fidell and Silvati's findings assisted the airport authority in determining which neighbourhoods were annoyed by aircraft noise ; their level of tolerance to aircraft noise, and how results compared to the baseline study and communities located elsewhere. Results were roughly similar to those observed elsewhere, and with the dosage-response curve developed by the U.S. Federal Interagency committee on noise (Ficon, 1992). Results also showed that aircraft noise tolerance among residents in this study was lower than comparable communities elsewhere.

Hagberg, K.

• NEW MUSICAL CLASSROOM WITH HIGH SOUND INSULATION IN AN EXISTING BUILDING AND HIGH SOUND INSULATION IN SYUDENT ROOMS
  K. Hagberg
[Abstract]

In a typical School building near Malmö in Sweden, erected 1970, a new musical classroom was planned 1996. Primarily the aim was to create a musical classroom with high sound insulation, designed to make it possible to carry on teaching without being disturbed during musical lessons, both in a new adjoining classroom (student room) as well as in the current auditorium next-door, and vice versa. In cooperation between the client and the acoustic consultant it was stated that if the sound reduction index exceeds R'w 60 dB in the completed construction it might be acceptable conditions in current rooms. Therefore, R'w 60 dB, was settled as a minimum requirement in this particulary case. Hence, it was initially necessary to judge whether it was possible to fulfil this requirement without too large and cost consuming modifications in the existing building construction . If this was judged not possible the musical classroom would not have been designed and built. After some initial investigations it was estimated that the requirement will be fulfiled both for the existing wall adjoining the auditorium and for the new wall to be mounted, adjoining the classroom. The main problem was to prevent flanking transmission of the existing floor construction and the interior part of the facade wall. Therefore some minor modifications where made in these parts. Besides this, the existing walls and the ceiling was supplied with additional sound insulation.

Haines, M.

• THE SATS STUDY: THE EFFECTS OF AIRCRAFT NOISE EXPOSURE ON STANDARDISED PERFORMANCE TESTS AROUND HEATHROW AIRPORT
  M. Haines, S. Stansfeld, J. Head and R.F.S. Job
[Abstract]

Previous studies examining the association between chronic noise exposure at school and at home with standardised reading and other intellectual achievement tests have found preliminary evidence of a relationship between environmental noise exposure and school performance. These results raise further questions, three of which were addressed in this study. First, were previously found associations confounded by social class and school quality ? Second, does aircraft noise affect school performance uniformly or are impairments more likely to be found in language-based tasks? Third, are cognitive noise effects dose-response or threshold effects? This study was a multi-level modeling study in which the National Standardised Scores (SATS) for Key Stage 2 in Mathematics, Science and English were analysed in relation to aircraft noise exposure around Heathrow Airport for 11,000 scores of children aged 11 from 128 schools. The analyses were at both the school and individual level, with adjustment made for socio-economic and school quality factors. The results of this study suggest that chronic exposure to aircraft noise is associated with school performance in reading and mathematics in a dose-response function after adjustment for school effects, but that this association is influenced by socio-economic factors. These results suggest that it is still open as to whether chronic aircraft noise exposure effects language based tasks exclusively because aircraft noise had the strongest effect on mathematical performance.

• MEASURING ANNOYANCE AND HEALTH IN CHILD SOCIAL SURVEYS
  M. Haines and S. Stansfeld
[Abstract]

Children are annoyed by chronic aircraft noise exposure; found in studies around Munich Airport and Heathrow Airport in London. In Munich, it was found that children living in noisier areas were significantly more annoyed by noise in their community as indexed by a calibrated community measure that adjusts for individual differences in rating for annoyance judgements. In London, noise annoyance was measured with child adapted standard self-report questions. Measuring annoyance and health in child social surveys requires careful questionnaire design and administration to ensure that reliable data is collected from children. This requires different techniques from those used with adults. Psychometric analyses are also important to assess the precision of survey measurement. The aim of this paper is to: 1) outline methodological techniques to increase the likelihood of obtaining reliable results in child surveys and 2) report psychometric results from the Heathrow survey. Methodological techniques outlined will include: strategies for question order and wording, contractual consent to research, stressing scientific importance, verbal administration and task oriented administration style. Psychometric analyses indicate that the self-reported annoyance question has good psychometric properties which suggests that the questions are able to provide reliable results in child samples.

• AIRCRAFT NOISE AT SCHOOL AND CHILD PERFORMANCE AND HEALTH INITIAL RESULTS FROM THE WEST LONDON SCHOOLS STUDY
  S. Stansfeld, M. Haines, J. Head, B. Berry , M. Jiggins, S. Brentnall and R. Roberts
[Abstract]

Previous research suggests that children's cognitive performance and health are adversely effected by chronic noise exposure. However, uncertainty remains because cognitive performance is also influenced by school quality and social deprivation which may confound noise effects. By increasing the number of schools and children, the aim of this study is to test whether the noise effects previously found in children are attributable to noise and to test possible mechanisms. The cognitive performance (reading, memory, attention) and stress responses (annoyance, perceived stress, catecholamine secretion) of children attending 10 primary schools exposed to high levels of aircraft noise (63 dBA 16hr Leq) were compared cross-sectionally with 10 matched control schools exposed to lower levels of aircraft noise (57 dBA 16hr Leq) around Heathrow Airport in West London. Schools were matched across aircraft noise exposure by: age, sex, socio-economic status, ethnicity and non-aircraft environmental noise sources. The cognitive tests and questionnaires were group administered in the classroom while noise measurements were carried out to assess school noise exposure. Initial results will be presented using multi-level modeling and multivariate statistical techniques to adjust analytically for the potential confounding effects of school characteristics and socio-economic factors on associations between noise and performance at the individual level.

Hald, J.

• OPTIMAL INTERPOLATION OF BAD OR NON-EXISTING MEASUREMENT POINTS IN PLANAR ACOUSTICAL HOLOGRAPHY
  J. Hald
[Abstract]

The present paper deals with the following problems in planar Near-field Acoustical Holography. In some cases it is very difficult or even impossible to measure the required complete regular rectangular measurement grid. This may be due to obstacles or hazardous measurement conditions, such as high temperatures or moving parts. Another type of problem is a bad signal discovered only after a measurement has been completed. It may be then impossible or at least very expensive to re-take the measurement. A general solution to the problem is to use an interpolation procedure capable of interpolating the complex sound pressure between an arbitrary set of measurement positions in a plane. The paper describes a new such interpolation procedure, which is optimised to the characteristics of the sound pressure distribution over a plane at some distance from the sound sources. Some computer simulations are presented, showing that over the major part of the frequency range, the new method performs much better than standard general purpose interpolation procedures. The paper also presents results from actual measurements.

Hamakawa, H.

• PREDICTION OF SPECTRAL DISTRIBUTION OF BROADBAND NOISE GENERATED FROM AN AXIAL FLOW FAN
  T. Fukano, H. Saruwatari and H. Hamakawa
[Abstract]

The mechanism of turbulent noise generation from an axial flow fan is still unknown. In the present paper we treat theoretical and experimental studies on the relation between the generated broad band noise and the periodic velocity fluctuation in the near wake of a rotating axial fan blade.Firstly we discuss the experimental results of periodic velocity fluctuation which was measured by a hot wire sensor from a rotating frame of reference fixed to the rotating blade. This periodic velocity fluctuation was caused by Karman vortex shedding.This phenomenon in the rotating flow field is similar to the one in the uniform flow field. The frequency of the Karman vortex shedding was constant at a fixed radius of the blade, and noise generated there was discrete. The frequency of the velocity fluctuation, however, increases with increasing radius of the blade in the rotating flow field, then the spectral distribution of noise generated from whole span of the blade becomes broadband.A theoretical flow model was introduced to predict the spectral distribution of generated noise from a rotating blade. In the model the blade span is divided into several element. The spanwise scale of the element is assumed to be as large as the coherent scale of the Karman vortex. The sum of the sound pressure generated from each blade element, i. e., from the whole span of the blade make broad band spectrum. The estimated spectral distributions agree well with the measured.

Hambric, S.

• VIBRATIONS OF FLAT PLATES EXCITED BY LOW MACH NUMBER TURBULENT BOUNDARY LAYERS
  S. Hambric and Y.F. Hwang
[Abstract]

Turbulent boundary layer (TBL) excited vibrations in a clamped plate are predicted using random vibration analysis of a finite element model. The predicted vibrations are compared to measurements made at the Ray Herrick Labs at Purdue University using a laser-doppler vibrometer. The plate was flush-mounted into a wind tunnel wall and air was driven past the plate at a Mach number of 0.1. The measured boundary layer displacement thickness and flow velocity were used to estimate the wall pressure fluctuation auto-spectrum using a model developed by Smolyakov and Tkachenko. Two models for estimating the wall pressure cross-spectra were investigated: the Corcos and so-called Modified-Corcos models. Since the ratio of the plate bending wave and convective wavenumbers is well below the convective ridge (where the wavenumber ratio is equal to one), using the original Corcos model leads to finite element vibration predictions that are 10-20 dB higher than those measured. The high predictions are directly due to the original Corcos model significantly overestimating the low-wavenumber excitation of the plate. Using the modified Corcos model however, which better estimates low-wavenumber excitation, leads to excellent agreement between predicted and measured vibrations on the plate.

Hamdi, M.A.

• USE OF RECIPROCITY PRINCIPLE IN A HYBRID MODELING TECHNIQUE (HMT) BASED ON INVERSE BOUNDARY ELEMENT METHOD (IBEM) FOR THE DETERMINATION OF THE OPTIMAL SPECTRAL CHARACTERISTICS OF A COMPLEX RADIATING NOISE SOURCE
  M.A. Hamdi, H. Defosse, F. Damagnez, T. Beauvilain and P. Varet
[Abstract]

The paper presents a robust hybrid modeling technique (HMT) based on near field acoustic measurements combined with numerical results derived from an Inverse Boundary Element Method (IBEM). The developed hybrid technique takes advantage from reciprocity principle to efficiently determine the optimal spectral characteristics of very complex noise sources, typically encountered in transportation industries. The first section of the paper reminds the direct link between reciprocity principle and integral representations of the acoustic field radiated by a noise source at finite number of discrete points located outside a closed surface enveloping the source. The second section describes the parameters chosen to describe the radiating source and the numerical optimization procedure used to determine the optimal spectral characteristics of source parameters. The third and last section of the paper illustrates successful practical applications of the method in automobile industry to characterize the noise radiated by a car engine.

• VIBRO-ACOUSTIC STUDY OF ARIANE V LAUNCHER DURING LIFT-OFF
  H. Defosse and M.A. Hamdi
[Abstract]

During lift-off of a launch vehicle, high acoustic sound pressure levels are generated which when transferred through the launcher fairing may lead to high acceleration levels at sensitive parts of the spacecrafts. Advanced vibroacoustic analysis tools are used to predict the response of these structures that are able to simulate the coupled vibro-acoustic system consisting of external sound field, fairing structure, cavity and payloads. These tools implemented inside the software RAYON developed by STRACO use a BEM approach for the infinite external domain and a FEM approach for the structures and cavities. This paper gives an overview on the theoretical background and presents the following aspects : - Reciprocity method application on a BEM model to determine the acoustic power of the horns of the ESTEC's reverberant chamber. - Sensitivity method application to update numerical model with respect to ground test. - Use of updated model to derive BEM axisymmetrical models of flight configurations (V501). Results of ARIANE V short fairing qualification test in reverberant chamber are presented together with comparisons of numerical and in-flight telemeasures. They show that predictive models determine acoustic pressures and structural vibrations with a good accuracy. Reciprocity method is quite promising for characterization of complex sources of noise and has a lot of potential applications in many industrial domains (car's engine noise, airplane's propeller noise,...).

• INSULATION OF ALUMINIUM FRAME-DOUBLE GLAZING WINDOWS BY MEAN OF BEA/FEA MODELING
  J.-M. Auger, H. Defosse, M.A. Hamdi, C. Barras, D. Benoualid, P. Mulocher, B. Mottelet, M. Rehfeld, P. Cotté, C. Midelet and M. Szezygiel
[Abstract]

This paper presents significant results of the research program on the insulation of aluminium framed windows glazed with sealed double glazing conducted by a consortium of partners. This consortium involves industrial partners which develop window components i.e.: SAINT GOBAIN for double glazings, HUTCHINSON for seals, TECHNAL and A.S. for aluminium window frames. The vibro-acoustic simulation of the window is conducted by STRACO by using I-DEAS Vibro-Acoustics and RAYON solver. The window insulation analysis is conducted both numerically and experimentally: - Experiments are performed by partners with their transmission facilities in order to compare results and validate models. - Simulation are conducted by using an original FEA/BEA modeling approach capable to represent the transmission problem by taking into account structural details related to seals, frame and glass as well as internal acoustic cavities and external radiation. Comparisons between experimental an numerical insulation results show a good agreement and a parametric analysis provides indications on the influence of parameters which characterize seals, frame and the double glazing.

• VIBRO-ACOUSTICS ANALYSIS OF A MEDICAL XRAY SOURCE : HYBRID APPROACH COMBINING EXPERIMENT AND FEA/BEA MODELING
  J.-M. Auger, F. Damagnez, M.A. Hamdi, S. Ayadhi and E. Chabin
[Abstract]

A vibro-acoustics analysis of a medical X-Ray source is presented . As the X-Ray source noise is generated by the interactions between the internal rotor and its bearing which are very complicated to describe, the analysis is carried out by using an hybrid approach combining experimental data measured on the system and an elasto-acoustics FEA/BEA model. This methodology , already applied for automotive and aerospace domains, uses RAYON solver integrated in the MCAE environment of I-DEASTM. Firstly, an inverse procedure is applied to determine an equivalent source model as a set of internal forces derived from vibration measurements in running condition and the elasto-acoustic model. Secondly, the BEA model and the source previously found are used to compute the radiated noise. Experimental and numerical results of both vibrations and radiated noise are finally compared. Such approach yields to a vibro-acoustics model capable to help for the path noise analysis and for the numerical modification analysis which have been applied to lead to several noise reduction improvements on the X-Ray source.

• NOVEL MIXED FINITE ELEMENT FORMULATION FOR THE ANALYSIS OF SOUND ABSORPTION BY POROUS MEDIA
  M.A. Hamdi, N. Atalla, L. Mebarek and A. Omrani
[Abstract]

This paper presents a novel mixed finite element formulation very well adapted for the analysis of the absorption of elastic and acoustic waves propagating in porous or fibrous media. The proposed formulation is based on modified Biot's equations written in terms of the skeleton displacement (U) and the acoustic pressure p in the pores of an inhomogeneous media. It generalizes the previous mixed (U,p) formulation proposed by Professor Atalla & co, and has the great advantage of automatically satisfying all boundary conditions without having to compute surface coupling integrals at porous sub-domain interfaces. When elastic forces in the skeleton are neglected, the formulation automatically degenerates to an equivalent fluid model taking into account inertial coupling with the skeleton.In addition the present formulation has the advantage over existing formulations of reducing the number of degrees of freedom per node (dof/node)to four (4) and only to one (1) when elastic forces are negligible in the skeleton. The implementation of this new generalized formulation and associated equivalent fluid finite element model in RAYON-PEM Solver developed and integrated by STRACO in the graphical environment of I-DEAS Vibro-Acoustics,solves several practical problems in transportation industry. It is shown in this paper that the results obtained with the new formulation agrees very well with the experimental results using impedance tube and vibro-acoustic measurements on treated multi-layered structures.


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Hamet, J.-F.

• ROAD TEXTURE AND TIRE NOISE
  J.-F. Hamet and P. Klein
[Abstract]

Although the road texture influence on tire noise was shown some 20 years ago, the understanding of the phenomena at stake and the principles for designing low noise surfaces remain today rather qualitative. Correlation between texture and noise spectra continue to be studied and new relations to be proposed. In the low and medium frequency range where the noise is associated to the vibrations of the tire it is suggested to consider, for the road profile, the enveloped profile. The road surface stiffness may also play a role. Its importance remains however a matter of debate. The rather recently developed rolling tire models offer possibilities for a better understanding of the processes. The research project presented here concerns the road texture influence on the noise associated to the vibrations of the tire. The envelopment of the road surface by the tire is performed by considering a static contact process between the road profile and a semi-infinite elastic medium. It is compared to a rolling tire approach. Experimental investigations are planed in laboratory and in situ.

• A COMPARISON OF THE 2D RING AND 3D ORTHOTROPIC PLATE FOR MODELLING OF RADIAL TIRE VIBRATIONS
  J. Perisse and J.-F. Hamet
[Abstract]

Among all acoustical sources of tire-road noise, the radiated sound from radial tire vibrations is of major importance in low and medium frequency ranges. Different mathematical models for tire vibrations modelling have been developed over thirty years: ring on an elastic foundation (2D), orthotropic plate under tension on an elastic foundation (3D), thin shell (3D)coupled with finite element method - FEM - or purely FEM model (3D). Whereas FEM is a powerful means to model the complexity of tire dynamic behaviour or road-contact interactions, analytical approaches like ring and plate models are still of interest to understand physical phenomena and structure-borne sound . The paper focuses on comparing ring and plate models for evaluating the radial dynamic response of a tire excited by a point force. The tire is considered at rest and unloaded. Theoretical and experimental comparisons are presented for each model. General physical insights are finally discussed for each approach.

Hamzaoui, N.

• USE OF A CONSTRUCTED VIBROACOUSTIC TRANSFER FUNCTION FOR PREDICTING SOUND RADIATION FROM A STRUCTURE IN SITU
  C. Marquis-Favre, N. Hamzaoui and C. Boisson
[Abstract]

Our work focuses on the construction of the Green's function for structures radiating in situ. This function has to behave as a transfer function between the structure vibratory behavior and the sound field. The different Green's functions, well-known in the literature, depend mainly on the geometric shape of the vibrating surface and the surrounding acoustic field; their knowledge enables the radiated sound field to be computed for any vibratory state. For an arbitrarily shaped structure in ordinary room, the difficulty of predicting noise lies in expressing the Green's function. We propose an approach based on the numerical construction of this transfer function from vibroacoustic data which are acoustic pressure and normal vibratory velocity measurements defining the structure in situ. This transfer function will allow the radiated sound field to be predicted for any new vibratory state undertaken on the structure located on its site. In this communication, we present some investigations concerning the ability of the built function to act as a transfer function when the vibratory behavior has been changed. Some confrontations between calculations and measurements in terms of sound pressure and sound power levels will illustrate these investigations, and will show the abilities and the limitations of the proposed approach.

Han, M.-H.

• THE MEANING OF SOUND QUALITY TO CREATE A COMFORTABLE SOUND ENVIRONMENT
  S.-W. Kim, G.-S. Jang, K.-Y. Jung and M.-H. Han
[Abstract]

It is very important to understand the psychological attributes and meaning of sound in order to create a comfortable sound environment for indoor and outdoor spaces. According to the sound meaning, it can be decided whether to control, add, change, or preserve the sound in these spaces. Therefore, this study was designed to inquire minutely into the adjectives for expressing korean impressions or sensations, and to investigate the psychological attributes of sound and the relation between sounds and their attributes. For this purpose, first of all, the classification among adjectives and sounds were analyzed by using the method of selected description in order to classify the sensation of pleasantness and unpleasantness. Then, the evaluation factors of pleasing sounds and unpleasing sounds were analyzed respectively by using the method of rating scales against sound stimuli. On the basis of the results, it was found that there are three important factors for expressing the image of pleasing sounds, these being activity, stability and powerfulness, and there are four primary factors for evaluating the quality of unpleasing sound, these being unpleasantness, intensity, irregularity, and sharpness. Also, the relationship between these factors and sound stimuli was ascertained using MDPREF technique of multi-dimensional scaling. These results will provide important clues to analyze the physical evaluation method of sound and to create a comfortable sound environment.

Hankanen, M.

• AIRCRAFT NOISE - A SURVEY METHOD FOR MEASUREMENTS OF FAÇADE INSULATION IN DWELLINGS AROUND ARLANDA AIRPORT, STOCKHOLM
  C. Pagoldh and M. Hankanen
[Abstract]

The Swedish Civil Aviation Administration has the commission to insulate all dwellings around Arlanda Airport which are exposed to 60 dB(A) or higher equivalent aircraft noise (in Sweden called FBN). To control an outside inventory carried out earlier, façade insulation measurements were carried out in 17 houses. In three of the houses the measurements were carried out both with aeroplanes and loud-speaker as a noise source. The goal was to be able to use a loudspeaker sending out continuous noise with a typical aircraft noise spectrum, and to measure A-weighted sound level indoors and outdoors simultanously. Advantages with such a ''Survey Method'' are * Independency of flying routes, wind-situation and aircraft types. * No influence from background noise * Time efficiency The loudspeaker and the microphone outdoors were mounted according to the standard ISO 140/5 (loudspeaker on the ground exposing the window with noise at 45 degrees angle incidence and flush mounted microphone on the façade). When measuring façade-insulation with aeroplanes as a noise source, the microphone outdoors was mounted on the façade and on the roof. The loudspeaker method and the method with aeroplanes as a noise source show quite good agreement when the microphone outdoors is mounted on the façade. The loud-speaker method gives up to 5 dB(A) lower façade insulation (with microphone on the façade) than the method with aeroplanes as a noise source (with microphone on the roof) when the façade is located perpendicular to the direction of the aeroplanes.

Hanna, D.

• A HYBRID ACTIVE-PASSIVE SYSTEM FOR CONTROLLING LOCOMOTIVE EXHAUST NOISE
  P. Remington, S. Knight, D. Hanna and C. Rowley
[Abstract]

Diesel electric locomotives represent the primary source of motive power in the US railroad industry, and are a significant source of environmental noise. There are a variety of noise sources on a locomotive; however, two sources will have to be controlled before significant reductions in locomotive noise can be achieved: diesel engine exhaust noise and cooling fan noise. Here we describe a system that uses both active and passive components to control broad band exhaust noise below 4 kHz. The active system utilizes ten actuators and eight residual microphones in an adaptive feedforward configuration to control tonal noise below 200 Hz. The passive system is a compact exhaust silencer designed to control exhaust noise above that frequency while still fitting within the limited space available beneath the locomotive hood. Both active and passive systems will be described in detail, and practical problems encountered in the design and installation of the system will be discussed. The system has been installed on an F40PH locomotive on the Chicago Metra and tested under stationary conditions. The system performed well providing 6dBA of noise reduction depending on operating condition and measurement location while maintaining the temperature of critical components within allowable limits. This work was supported under contract to the US Federal

Hanson, C.

• NOISE SOURCES ON AMTRAK'S HIGH SPEED TRAIN
  C. Hanson and B. Barsikow
[Abstract]

Noise was identified as one of the key community concerns during the environmental assessment process conducted prior to the introduction of Amtrak's new high speed train, the Acela, in Northeast USA. Although the Canadian-French trainsets are similar to the TGV, there are significant differences for operation on American tracks. Noise sources were measured and identified during tests conducted at the Transportation Technology Center near Pueblo, Colorado. Measurements were made using a microphone array system. Line arrays and X-arrays were used to locate and quantify the noise sources. Roughness of the wheel treads and rail surfaces were measured to enable the array-measured rolling noise to be assigned to a particular level of roughness.

Hao, L.

• TRAFFIC NOISE AND HUMAN LIVING ENVIRONMENT
  Z. Liu, H. Ding and L. Hao
[Abstract]

Road traffic noise has become more and more important in city ambient noise than ever. China is a developing country, recent years, accompany with the flying economic, the level of city road traffic noise increasing greatly. At the same time, people are dreaming for a better acoustics environment. So we represent a new method on the evaluation of city ambient noise,protect people's living environment form noise damage is the precondition of the evaluation. Now the method is certifyed can acquire well effect in the evaluation in some area in Beijing.

Hargreaves, J.

• A VALIDATED CAE METHOD FOR PREDICTING RAILWAY VIADUCT STRUCTURE-BORNE NOISE
  J. Hargreaves, R. Sturt and M. Willford
[Abstract]

In common with many industries today the rail industry has to meet many noise and vibration requirements. The impact of train pass-by noise on the surrounding environment is of particular importance where high-speed lines operate and where new railways are being designed. Rail structures such as viaducts pose a particular problem in that resonance in the structure itself can often be major source of radiated noise. While many ameliorative measures exist for treating structure-borne noise, such as soft rail pads, sleeper soffit mats and ballast mats, they all carry a significant cost penalty. In addition a choice has to be made between the alternative solutions and an inevitable compromise between reduced noise levels and cost is necessary. The work presented demonstrates how predictive methods can be used to quantify the structure-borne noise levels radiated from a railway viaduct during a train pass-by event and demonstrates the accuracy of the solution by making comparisons with noise measurements made around an existing operating viaduct. Measured wheel and rail roughness spectra have been transformed into roughness profile height as a function of distance along the track or wheel circumference. These profile functions then form the basis of a line contact between the rail and a set of wheels. The dynamic loading is generated by projecting a dynamic model of the train vehicles at a prescribed forward velocity along the rails, the train model wheels sliding over the rails with a Hertzian contact spring at each wheel-rail interface. This approach used a time domain simulation of the main processes that cause the vibration in practice and involves the coupling of the train to the track and deck system. Predicted and measured structure-borne noise, in the frequency range below 300Hz, for a particular viaduct during the passage of a high-speed passenger train is then presented. A-weighted sound exposure levels in the 1/3rd octave band along with total noise levels are compared and shown to be in good agreement. The paper concludes with a quantitative discussion of the effects of variance in the model input parameters on the accuracy of the noise prediction.

Hariyama, T.

• DEVELOPMENT AND PROSPECT FOR LOW NOISE PANTOGRAPHS
  T. Okamura, Y. Kusumi and T. Hariyama
[Abstract]

The Shinkansen train runs mainly on an elevated railway and the noise caused by its running consists of trolley-pantograph noise, body aerodynamic noise, wheel/rail noise, and structure-borne noise. Among these, wheel/rail noise has the biggest energy, but it has been cut off effectively by soundproof walls all along the line. Therefore, for the Shinkansen, reduction of trolley-pantograph noise has been the main problem. Trolley-pantograph noise, especially the aerodynamic noise of the pantograph, is proportional to the sixth power of the train speed, and requires a special abatement technique for the speed-up of Shinkansen trains. So far we restrained the aerodynamic noise by installing pantograph covers on the train roof. However, when smaller cars were used to reduce the aerodynamic noise, pantograph covers got larger and the aerodynamic noise from the covers increased. At present, the most noiseless pantograph of our company (JR EAST) is the single-armed type PS206. This type was installed on series E3 cars with small pantograph covers, and contributed to 275 km/h commercial operation speed. To reduce the trolley-pantograph noise further, it is necessary to do without pantograph covers. Therefore, we studied the noise reduction of support insulators of pantographs, and developed the low-noise insulator. Also, we started the development of the new low noise pantograph to reduce the noise of the pantograph itself. The new low noise pantograph is based on PS206, but we aimed at improvement of the collector shoe, shoe support and base frame which have been covered with pantograph covers. At first, we carried out wind tunnel tests with 1/10 model, and found a good shape of the noise profile about the base frame. Next, we carried out wind tunnel tests with 1/5 model, and designed the low noise shape considering devices mounted in the base frame. For the collector shoe, we designed a shape that could reduce the noise without deteriorating effects on the lift force of the PS206. Next, full scaled wind tunnel tests were done, and confirmed the aerodynamics and noise characteristics. The noise characteristic achieved a reduction of more than 3dB compared with the pantograph cover system (1/10 model). And, we could almost keep the same PS206 lift force in the aerodynamics. We introduce the development of the low noise pantograph and insulator focusing on results of wind tunnel test and main specifications.

Harris, G.J.

• TRAFFIC CALMING IN GLOUCESTER, INFLUENCE ON NOISE AND GROUND-BORNE VIBRATION
  P. Abbott, G. Watts and G.J. Harris
[Abstract]

TRL have carried out noise and ground-borne vibration surveys alongside traffic calming schemes in the City of Gloucester in the UK as part of the 'Safer City' initiative financed by DETR to investigate the environmental impact of urban traffic management and safety schemes. Measurements of both traffic and vehicle noise taken at selected sites before and after traffic calming together with the results will be described. The traffic calming features studied were junction tables (raised areas at junctions), road humps (across the full road width) and speed cushions (humps of limited width which allow heavy vehicles, buses and some emergency vehicles to straddle the raised area). Measurements of ground-borne vibration were also taken at properties close to selected traffic calming features to determine levels of vibration generated by passing vehicles. The results showed substantial reductions in average noise from light vehicles of about 5 dB(A) compared with no significant change in the average noise from heavy vehicles although pass-by noise levels from some unladen trucks increased substantially as a result of body noise. Overall traffic noise levels were reduced by 4 to 6 dB(A) after normalising for differences in traffic flow and composition during the before and after surveys. Levels of ground-borne vibration were not found to have increased significantly following traffic calming. The paper will also discuss how these results compare with those obtained at other traffic calming schemes and indicate how, in general, traffic calming can impact both noise and vibration levels in community settings.

• RURAL RESIDENTS' RESPONSE TO REDUCTIONS IN TRAFFIC NOISE CAUSED BY RESURFACING A SECTION OF MOTORWAY WITH POROUS ASPHALT
  C.J. Baughan, L. Chinn, G.J. Harris and R. Stait
[Abstract]

Porous asphalt is known to produce lower traffic noise levels than conventional road surfaces, but relatively little information is available on the perceived benefits to people living some distance from the road. A section of the jointed concrete M40 motorway in rural Oxfordshire has been resurfaced with porous asphalt. This gave an opportunity to assess the resulting changes in noise and noise nuisance experienced by residents in villages within 1.5 km of the motorway. Residents were interviewed and noise measured at five villages just before the resurfacing work started and again one year and 3 years later. The paper reports the changes in noise levels resulting from the resurfacing and the associated changes in residents'ratings of dissatisfaction. The work was intended to inform the Highways Agency of the environmental benefits of porous asphalt as perceived by people living in the vicinity of a motorway, and help to quantify the circumstances in which the higher costs of porous asphalt can be justified. The first two surveys showed that reductions in vehicle noise (measured close to the motorway) of 4.5 to 7.6 dB(A) were achieved, depending on class of vehicle and measurement location. There were substantial reductions in traffic noise exposure at villages some distance from the motorway. Indices of community noise impact (such as dissatisfaction ratings) reduced considerably after the resurfacing, especially at the two villages with the biggest noise changes. A strong relation between dissatisfaction ratings and noise levels was observed. This paper will describe the study design and results obtained. It will also examine the relations between noise and dissatisfaction ratings, and indicate how noise changes can lead to changes in community response greater than would be predicted from 'steady state' relations between noise exposure and dissatisfaction.

Hartmann, B.

• VIBRATION ISOLATOR PROPERTIES OF A PHASE MIXED POLYURETHANE
  J. Lee, J. Dickens, J. Fedderly, G. Lee and B. Hartmann
[Abstract]

As part of a program to relate the chemical composition of polymers to their vibration isolation properties, a polyurethane of known, controlled composition was synthesized and evaluated. Based on our earlier studies , the first polymer selected to be evaluated was phase-mixed to avoid the complication of hard segment crystallinity. The polymer was synthesized from poly(tetra methylene ether glycol) of molecular weight 1400 reacted with 4,4'-diphenylmethane diisocyanate and chain extended with dimethyl propanediol. Measurements were made in the new Vibration Isolation Test Facility . Four-pole parameters will be presented as a function of frequency from 5 Hz to 2 kHz at different temperatures and static loads. Results at low load will be compared with predictions based on dynamic mechanical measurements of the moduli of the material.

Hartog Van Banda, E.

• THE POTENTIALS OF NEW TECHNOLOGIES IN INTEGRATED URBAN NOISE MANAGEMENT SYSTEMS
  D. Manvell, P. Larsen, E. Hartog Van Banda, P.J. Henning and L. Winberg
[Abstract]

The tasks involved in managing urban noise are many and varied - for example, solving noise complaints, noise mapping, noise monitoring, noise abatement and zoning. In addition, there is a wide variety of noises from different sources such as industry, road traffic, rail traffic, aircraft and many different recreational activities. An integrated approach to the overall task of urban noise mangement has the potential to increase efficiency through the sharing and reuse of data, optimisation of noise abatement activities and prevention of new problems arising. Modern technology can ease this process. At Internoise in 1999, a paper on ''Managing Urban Noise In Cities - an Integrated Approach to Mapping, Monitoring, Evaluation And Improvement'' was presented highlighting what advances in technology can be used in new, modular systems based on an integrated approach covering the techniques of noise mapping, monitoring and evaluation. This paper will present an investigation into the implementation of these technologies such as GPS/DGPS to identify measurement date, time and position, mobile phones to allow low-cost remote access to all monitoring units, CIC to ensure data integrity, WAV and MP3 files for later analysis and use in court, GIS for multi-parameter analysis and presentation, ActiveX to link measurement results to case notes, AutoCAD for intelligent interface for optimising accuracy and calculation time, LAN/WAN for data sharing, security and for faster transfer, and internet for citizen information service and dialogue. The potentials of the various technologies, their status and limitations will be highlighted.

Hashimoto, T.

• BOOMING INDEX AS A MEASURE FOR EVALUATING BOOMING SENSATION
  S. Hatano and T. Hashimoto
[Abstract]

We have proposed the measure called booming level for evaluating booming sensation caused by car interior noise. In this measure, the scale was constructed by the arithmetic average of the weighted sound pressure level within specific frequency bands that contributed booming sensation. The weighing function was obtained by the subjective test using magnitude estimation. But this method had some difficulty to find out suitable frequency bands contributing booming sensation for calculation. In order to solve this problem, new method was introduced which based on the power summation of the weighted 1/3 octave band signals that was free from extracting specific frequency bands for calculation. This measure was name as booming index. As a result, good correlation was obtained between the subjective evaluation on booming sensation and booming index.

• EVALUATION OF SOUND QUALITY OF CAR INTERIOR NOISE UNDER REAL DRIVING - THE DIFFERENCE OF SUBJECTIVE IMPRESSION BETWEEN DRIVER AND GUEST
  T. Hashimoto and S. Hatano
[Abstract]

The evaluation of sound quality of car interior noise will be different between a driver and a guest because the main task of the driver is to drive a car safely instead of judging the sound. On the other hand, the guest of a car has more free time to enjoy car interior noise. In order to investigate this difference under real car driving conditions, the real time response acquisition system was constructed utilizing a hand held personal computer for collecting time varying subjective evaluation on pleasantness, powerfulness, roughness and booming sensation. Each impression was judged by categories with five steps as like the usual SD method. The results obtained revealed that the impression of sound quality by driver was more moderate compared with that obtained by the guest seated at the rear seat.

• A CONTRIBUTION OF SOUND QUALITY ON ANNOYANCE CAUSED BY ROAD TRAFFIC NOISE
  T. Ishiyama and T. Hashimoto
[Abstract]

This paper describes a laboratory study of an influence of sound quality on the annoyance caused by road traffic noise. To measure the annoyance caused by road traffic noise, two kinds of subjective evaluation test were carried out ; one using 48 road traffic noise recorded simultaneously at the location where direct sound propagation from the main traffic was confirmed and at the location behind the building without direct sound propagation, the other using 24 artificially modified road traffic noise in its frequency contents originally recorded in urban area. As a result, we found that: (1) Contribution of high frequency contents of road traffic noise on annoyance was significant. (2) When noise exposure level was 70dB(A) in LAeq, the contribution of the variations of high frequency noise to the listening interference was equivalent to 3dB(A) under the exposure of various modified road traffic noise in their high frequency contents. (3) Multiple regression models of annoyance were constructed by roughness and sharpness as well as LAeq as their explanatory variables. The trade off of one standard deviation in roughness (asper) and sharpness (acum) in the multiple regression model for annoyance was equivalent to 4.3dB(A) and 0.9dB(A) respectively provided

Hatano, S.

• BOOMING INDEX AS A MEASURE FOR EVALUATING BOOMING SENSATION
  S. Hatano and T. Hashimoto
[Abstract]

We have proposed the measure called booming level for evaluating booming sensation caused by car interior noise. In this measure, the scale was constructed by the arithmetic average of the weighted sound pressure level within specific frequency bands that contributed booming sensation. The weighing function was obtained by the subjective test using magnitude estimation. But this method had some difficulty to find out suitable frequency bands contributing booming sensation for calculation. In order to solve this problem, new method was introduced which based on the power summation of the weighted 1/3 octave band signals that was free from extracting specific frequency bands for calculation. This measure was name as booming index. As a result, good correlation was obtained between the subjective evaluation on booming sensation and booming index.

• EVALUATION OF SOUND QUALITY OF CAR INTERIOR NOISE UNDER REAL DRIVING - THE DIFFERENCE OF SUBJECTIVE IMPRESSION BETWEEN DRIVER AND GUEST
  T. Hashimoto and S. Hatano
[Abstract]

The evaluation of sound quality of car interior noise will be different between a driver and a guest because the main task of the driver is to drive a car safely instead of judging the sound. On the other hand, the guest of a car has more free time to enjoy car interior noise. In order to investigate this difference under real car driving conditions, the real time response acquisition system was constructed utilizing a hand held personal computer for collecting time varying subjective evaluation on pleasantness, powerfulness, roughness and booming sensation. Each impression was judged by categories with five steps as like the usual SD method. The results obtained revealed that the impression of sound quality by driver was more moderate compared with that obtained by the guest seated at the rear seat.

Hatfield, J.

• COMPARISON OF REACTION (DISSATISFACTION, ANNOYANCE ETC.) TO AIRCRAFT NOISE AMONG SHIFT WORKERS AND NON-SHIFT WORKERS
  R.F.S. Job, J. Hatfield, N. Carter, P. Peploe, R. Taylor and S. Morrell
[Abstract]

Curfews at Sydney airport result in shift workers being exposed to more aircraft noise when they are trying to sleep than are non-shift workers. The present community survey of 1,015 residents of high and low noise areas in the vicinity of Sydney Airport assessed whether shift workers report greater noise-induced sleep disturbance than non-shift workers, and whether this translates into more negative reactions to noise (dissatisfaction, annoyance etc.). The role of noise sensitivity in the effects of shift work was also considered. Shift workers report more difficulty sleeping, more frequent use of sleeping pills, and more negative reaction to noise, than non-shift workers, although these differences did not reach statistical significance. Self-reported sleep disturbance correlated significantly and positively with reaction. The findings are consistent with the claim that sleep disturbance contributes to negative reactions to noise among shift workers.

• THE INFLUENCE OF ACTIVITY DISTURBANCE ON REACTION THE SYDNEY AIPORT HEALTH STUDY
  R.F.S. Job, J. Hatfield, N. Carter, P. Peploe, R. Taylor and S. Morrell
[Abstract]

Noise-induced activity disturbances may promote negative reactions to noise. The relationship of noise-sensitivity to reaction may in turn reflect greater activity disturbance amongst noise-sensitive individuals, or a greater impact of activity disturbance on reaction amongst these individuals. The present community survey around Sydney Airport (N=1,015) assessed noise-induced disturbance of several activities (e.g. conversation, relaxing, entertaining), reaction to noise (annoyance and general reaction- dissatisfaction, affectedness), and noise-sensitivity. Activity disturbance correlated positively and significantly with reaction and noise-sensitivity in high and low noise areas. Reaction was significantly predicted by activity disturbance and noise-sensitivity in regression analyses. The difference between reaction and activity disturbance did not correlate significantly with sensitivity. These results are consistent with the view that activity disturbance, which is greater amongst noise-sensitive compared to non-noise-sensitive individuals, contributes to reaction. However, the contribution appears to be no greater amongst noise sensitive individuals.

• A TEST OF THE EFFECT OF QUESTION WORDING ON MEASURED NOISE REACTIONS: A COMPARISON OF JAPANESE AND ENGLISH QUESTIONS
  J.M. Fields, T. Yano, K. Masden, J. Hatfield and R.F.S. Job
[Abstract]

An internationally comparable noise reaction measure has been proposed that consists of a pair of standard social survey questions with answer scales developed from empirical studies. It was previously reported that when English-speaking and Japanese-speaking subjects used these scales to report their feelings about the same sounds, Japanese subjects gave more negative scores. This paper provides the results from a further study that seeks to explain those negative scores by contrasting the annoyance reactions measured with three social survey questions that use identical answer scales but differ in the severity of the reaction presented in the base (stem) of the question. The three forms of the questions differed in asking subjects for either: (Form#1) a rating of the noise, or (for the other forms) the extent to which subjects were personally either (Form#2) annoyed or (Form#3) worried, irritated or concerned. Sets of Japanese subjects and English-speaking countries' subjects used one of the three questions to rate 16 sounds and 10 environmental noise situations in their respective languages. The analysis does not support the hypothesis that a more severe response question reduces reports of annoyance reactions.

• FACTORS CONTRIBUTING TO REPORTED REACTION TO COMBINED NOISE SOURCES
  R.F.S. Job and J. Hatfield
[Abstract]

People report less reaction to a combined noise source than to the sum of reaction to its component noises separately. This paradox may represent a methodological artefact. The present study assessed the role of question phrasing and response scale in producing the paradox. Undergraduate psychology students identified three outside noises which they hear regularly where they live. They then rated their annoyance with each of these noises separately, their annoyance with the noises in pairs ''whether or not they occur at the same time'', and their annoyance with the noises in pairs ''when they occur at the same time''. Responses were made either on a 10-point ''opinion thermometer'' or on an open-ended response scale. For each of these conditions, it was assessed whether the ''combined noise sources'' paradox occurred. Results are discussed in terms of the future measurement and consideration of reaction to combined noise sources.

Hatoh, T.

• SOUND QUALITY OF ROAD TRAFFIC NOISE TRANSMITTED THROUGH DIFFERENT TYPES OF SIMULATED WALL
  S. Namba, S. Kuwano and T. Hatoh
[Abstract]

Quality of sounds transmitted through walls is affected by the structures and the materials of walls. Sounds from four kinds of wall, i.e. concrete block, a single glass, double glasses and plaster board, were simulated using a digital filter and the sound quality of road traffic noise was tested using semantic differential. Under the same LAeq condition, it was found that the impression of the sound quality, especially sharpness and roughness, was different among the stimuli. Physical measures were examined to predict the sound quality of road traffic noise transmitted through walls on the basis of these results.

Hatzopoulou, A.