Tinnitus and impulse noise-induced hearing loss in drop-forge operators.

Tinnitus is frequently accompanied by noise-induced hearing losses, and perhaps as it is assumed--particularly with those arising from exposure to impulsive types of noise. In order to explain it and to estimate a prevalence of tinnitus in the industrial, impulse noise workers the group of 261 drop-forge operators exposed to impulses with peak levels of 135 dB versus 169 age-matched controls was subjected to otological and audiometric examination, and then the complaints for tinnitus in both groups have been analysed. The prevalence of tinnitus, highest in operators with longer exposure duration (> 10 years) was found in 184 individuals (70.4%) versus 6 (3.5%) in controls. The findings closely corresponded with the degree of impulse noise-induced hearing loss. As the maximum audiometric notch was mostly localised at 6 kHz and rarely at 4 kHz, consequently the approximate pitch of the tinnitus was related to the frequencies where hearing was most affected. It is concluded that impulse noise-induced tinnitus may be sometimes more severe in its effects than is hearing loss, thus it creates an additional reason for strict hearing conservation programmes.