Assessment of Impulse Noise regarding Harmfulness to Hearing

Regular paper

Beat Hohmann

Suva, Bereich Physik

Tuesday 2 june, 2015, 18:00 - 18:20

0.4 Brussels (189)

For prevention or for compensation cases, a simple assessment of intensive impulse noise is needed. But which is the most appropriate frequency weighting, and which time constant should be chosen? The oft-heard argument based on equal loudness contours that C-weighting should be used for high sound levels, represents a fundamental misunderstanding, because it is the transfer function from the free sound field (where we measure) to the inner ear (where damage occurs) that must be simulated. A-weighting is much closer than C-weighting. Moreover, many results indicate that it is not the peak level (rise time 50 microseconds), but rather the short-term sound energy that is correlated with permanent hearing damage. Therefore the criterion of 135 dB(C, peak) in EU Directive 2003/10/EC is not appropriate at all for damage risk assessment. In Switzerland since many years a sound exposure level of 120/125 dB(A) is used as a criterion for damage risk. Comparisons with other criteria and with the Auditory Hazard Assessment Algorithm for Humans (AHAAH) will be shown. For very high sound levels (e.g. heavy weapons), AHAAH should be used which simulates the nonlinear behaviour of the hearing system. Sometimes, low frequencies may even have a protective effect.

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