Effects of nosocusis, and industrial and gun noise on hearing of U.S. adults.

Hearing losses estimated for exposure to industrial and gun noise and for "typical" nosocusis are applied to the distributions of the hearing levels of adult males and females of the general population of an industrialized society unscreened for exposure to noise or ear disease. Noise exposure and demographic data applicable to the United States, and procedures for predicting noise-induced permanent threshold shift (NIPTS) and nosocusis, were used to account for some 8.7 dB of the 13.4 dB average difference between the hearing levels at high frequencies for otologically and noise screened versus unscreened male ears; (this average difference is for the average of the hearing levels at 3000, 4000, and 6000 Hz, average for the 10th, 50th, and 90th percentiles, and ages 20-65 years). According to the present calculations, this difference is due, in order of importance, to (1) nosocusis, (2) exposure to gun noise, and (3) exposure of workers to industrial noise. For these same frequencies and overall average, adjustments for nosocusis accounts for 2 dB of the 5.9-dB difference between the hearing levels of screened and unscreened female ears. For the average at 500, 1000, and 2000 Hz, the overall differences between the screened and unscreened populations is but 3.4 dB for males and 2.9 dB for females. The adjustment procedures reduced these differences to -0.5 and 0.9 dB, respectively.