The Cumulative Effect of Auditory Fatigue Following Repeated High Level Pure Tone Stimulation

Abstract

Fatigue has been one of the most extensively studied phenomena of the auditory system. Many of the parameters of fatigue have been defined and limited. There are several comprehensive monographs which deal specifically with this problem and provide an excellent review of the literature (Hood, 1950; Kyiin, 1960; Ward, 1963). Auditory fatigue, also called temporary threshold shift, is identified as a shift toward poorer threshold (less sensitivity) following exposure to a supra-threshold auditory stimulus. Immediately upon cessation of the exposure stimulus the shifted threshold begins to return to normal, swiftly at first and then more slowly. Ewing and Littler (1953) were among the first to definitely establish the existence of fatigue and to relate its extent to the intensity, frequency, and duration of the exposure stimulus. Harris (1955) attempted to show that an ear is not physiologically the same following exposure even though the threshold has recovered. Jerger (1958) reported that the time required for a threshold to return to within 10 or 20 dB of its pre-exposure value increases with repeated exposures. In today’s clinical procedures audiologists use high intensity masking noises without control or concern of how the fatigue caused by this masking might affect later measures. Many experimenters have assumed that once the threshold has returned to its pre-exposure level, the exposed ear is normal. There have been few rigorous attempts to examine the cumulative affects that repeated high level stimulation might have upon the auditory system.