Modeling the interaction between the hearing protector attenuation function and the hearing loss profile on sound detection in noise
University of Ottawa
Wednesday 3 june, 2015, 10:40 - 11:00
0.4 Brussels (189)
Hearing protectors with a flat or nearly uniform attenuation across frequency maintain the spectral balance of workplace sounds and are often recommend when, in additional to protection, good signal audibility, speech communication and auditory situational awareness are essential. Such protectors have been especially indicated for wearers with high-frequency hearing loss to maintain audibility at all frequencies. However, few studies are available on the specific merits of flat/uniform protectors and relatively little is known on the exact conditions when such devices can be beneficial. Furthermore, while such devices are described in some acoustical standards, the definition of flatness is generally unspecified, and even when cited, the requirements have wide tolerances. This study reports on the effects of the noise spectrum, hearing loss profile and shape of the attenuation-frequency function on detection thresholds computed using a psychoacoustic model of sound detection in noise. For normal-hearing users, detection thresholds are found to be hardly affected by use of hearing protectors, even in quite extreme conditions of low-frequency noise and steeply increasing attenuation-frequency functions. With aging and noise- induced hearing loss, sound detection in noise above 2500 Hz becomes progressively more sensitive to the slope of the attenuation function as well as to the overall protected level achieved. Shallower slopes are warranted for individuals with moderate-severe hearing loss to limit the upward spread of masking in low-frequency noise, while controlling the amount of attenuation at high frequencies prevents excessive elevation of absolute thresholds. Further work is needed to quantify the benefits of flat/uniform hearing protectors in more complex tasks and other auditory dimensions such as speech communication, sound quality and the interpretation and recognition of important sounds in one’s environment.
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