Relative hazard of weapons impulses

Abstract

Arguments in favor of a theoretically based damage-risk criterion (DRC) for intense noise were developed to make a crucial prediction. Based on measured spectral differences, it was predicted that rifle impulses would cause permanent threshold shifts at .apprx. 9 dB lower peak pressures than cannon impulses. DRC in use in the world predicted that the cannon would be more hazardous than the rifle by 7-10 dB. Electrophysiological measures of sensitivity were used in 38 cats (76 ears) which were exposed to 60 impulses, .apprx. 3 s apart, at various peak pressures, from a rifle or a 105 mm Howitzer. Hearing changes were followed until recovery was complete (2 mo.). Permanent threshold shifts began at .apprx. 140 dB for rifle impulses and 150-155 dB for cannon impulses, confirming the prediction and supporting the contention that there was a spectrally dependent critical level for the ear at high intensities. Implications for present DRC and future risk assessment schemes were discussed.