Audiologic profile of noise-induced hearing loss

Audiologic results for 450 ears presumed to have uncomplicated noise induced hearing loss were analyzed to describe their typical profile and to quantify the characteristic audiometric notch. Data consisted of tonal and speech thresholds, speech discrimination scores, Bekesy tracings, and short increment sensitivity index scores, and tone decay at 4,000 hertz. In each case, the pattern of results indicated a cochlear site of lesion, although the only uniformly cochlear sign was the absence of a pattern of abnormal adaptation in Bekesy tracings. In each case, the audiogram could be approximated by a quartic equation. The mean difference between actual thresholds and those predicted by the best-fit quartic did not exceed 7.72 dB and was less than 5 dB for eight of the 11 frequencies for which comparisons were made. We propose the application of this characteristic to clinical practice and to automated hearing conservation programs.