On site acoustic characterization of optimized very thin asphalt concretes
Invited paper
IFSTTAR, AME, LAE, LUNAM Université
Tuesday 2 june, 2015, 14:20 - 14:40
0.2 Berlin (90)
Abstract:
This paper deals with in situ characterization of Very Thin Asphalt Concretes (VTAC) optimized for tyre/road noise abatement. Two sites have recently been tested in France, the first one paved with a five years old VTAC 0/4 and the second one paved with a one year old VTAC 0/6. The measurement campaign included tyre/road noise testing as well as assessment of road surface properties like 3D texture and sound absorption. Close-ProXimity (CPX) and Coast-By (CB) tyre/road noise measurements were performed simultaneously over a distance of 20 meters long. The test vehicle was a passenger car fitted with patterned tyres. Several runs were performed at steady speed from 40 km/h up to 110 km/h, leading to the estimation of CPX and CB noise levels and spectra at different reference speeds. The 3D texture of the road surfaces was evaluated with a newly developed device involving a 2D laser sensor. The texture sample size was about 0.35 m by 1.5 m with a sampling interval of 0.1 mm. A specific protocol was used to record four aligned texture samples with overlapping zones, leading to a final complete surface of about 6 m by 0.35 m. Texture data were processed to get the height probability densities, the mean texture depth as well as the raw and the enveloped longitudinal texture spectra. Sound absorption was also measured following ISO 13472-1 leading to absorption peaks around 1000 Hz for the VTAC 0/4 and around 800 Hz for the VTAC 0/6. The CPX and CB noise results of the tested road surfaces are compared to results for reference road surfaces, i.e. a VTAC 0/6 and a DAC 0/10 located on a reference test track. Noise performances of the optimized VTAC are finally discussed with regards to texture and sound absorption properties.