FAA Office of Aerospace Medicine
Civil Aerospace Medical Institute

Report No: DOT/FAA/AM-63/19

Title and Subtitle: A central factor in pure tome auditory fatigue

Report Date: September 1963

Authors: Wernick JS, Tobias JV

Abstract: A long accumulation of psychophysical and physiological evidence indicates that auditory fatigue has its locus of effect in the cochlea; transfer studies with negative or questionable results, and studies of cochlear chemistry and potentials with positive results all lead to the same conclusion. However, Galambo's reports of inhibition through efferent stimulation taken together with his finding of changes in cochlear potentials corresponding to differences in attentiveness provide a basis for testing the existence of a central factor operative in auditory fatigue.

The present study was design to evaluate the possibility that a listener's level of mental activity constitutes and adequate central factor. Subjects were presented with a 4000 cps, 40 dB SL or 90 dB SL tone for 3 minutes under conditions of a) a mental or b) reverie. Pre- and post-fatigue thresholds were measured with a switched (0.2 sec on, 0.2 sec off) tone. For low level (40 dB) fatigue the frequency of the test tone was 4000 cps and for high level (90 dB) fatigue, 5656 cps.

Subjects consistently showed grater temporary threshold shift and longer recovery time when the fatiguing tone was presented in the mental task condition. Results indicate a central factor in pure tone auditory fatigue. It is suggested that the degree of effect of a fatiguing tone is a function of the listener's degree of mental activity during stimulation.

Key Words: ear, hearing, physiological acoustics, senses and sensation, fatigue

No. of Pages: 12