Auditory evoked potentials and audiological follow-up of subjects developing noise-induced permanent threshold shift.

Three examinations, including cochlear microphonics (CM) to 99/s 1-kHz tones and auditory brainstem evoked potentials (ABEP) to 10/s and 55/s clicks, as well as psychoacoustical tests, were performed on 31 normally hearing subjects, exposed to occupational noise for over a year. The results showed prolongation of the absolute latency of peaks I, III and V, without significant changes in interpeak latency differences (IPLD) or CM latency. The site affected by increasing stimulus rate, giving rise to increased IPLD, appears to be central rather than cochlear. The efficacy of increased stimulus rate in detecting noise-induced auditory changes was higher than achieved applying the 10/s click rate.