Mathematical Simulation of the Cochlear Mechanism Applied to Damage-Risk Criteria for Impulse Noise

Summary

A mathematical simulation of the human hearing mechanism, involving the non-linear effect of the middle ear, has been used to compute the risk of impairment for hearing produced by impulse noise. This model provides, therefore, a reference method which can be used for evaluating the loudness of any kind of acoustical noise. The results of impulse noise analysis obtained from different damage-risk criteria can then be compared with the results of the theoretical model, allowing for evaluation of the respective merits of these criteria.

The main conclusion of this study is that the A-weighted sound exposure level L_AE appears to be the best damage-risk criterion for impulse noise. The spectral sensitivity of the human hearing mechanism might then be approximated by the A-weighting filter. These elements emphasize the possibility of using a unique damage-risk criterion applicable for any kind of noise, including continuous and fluctuating noises as well as industrial and gunfire impulse noises. This criterion would be applicable for the high peak pressure levels up to 170 dB, which can be experimentally encountered for gunfire. The damage level for a daily exposure of eight hours would be around 130 dB, corresponding to a steady state pressure level equal to 85 dB. This conclusion is in full agreement with the most recent results on impulse noise obtained by psychoacoustical experiments in the U.S., Germany, the Netherlands, and Japan.