Validation of the Single-Impulse Correction Factor of the CHABA Impulse-Noise DRC

Abstract

The 1968 CHABA criterion specifies peak pressure level and duration tradeoffs designed to prevent excessive TTS in all but 5% of exposed ears. The basic criterion assumes exposure to 100 impulses/day; a tentative trading relation (based on little empirical evidence) was proposed for exposures ranging from 1 to 1000 impulses/day. In this study, subjects were exposed to single impulses produced by two small rockets. Exposure conditions were chosen to approximate the CHABA limits for grazing-incidence exposure, viz., (1) peak level 161 dB, B-duration 12.6 msec, and (2) peak level 159 dB, B-duration 33 msec. At 6000 Hz (the worst frequency), exposure under these conditions produced TTS exceeding the CHABA limits in 7% and 4% of ears, respectively. Thus the CHABA correction for single impulses appears to afford an appropriate degree of prediction of TTS.