Absence of Central Factors in Auditory Fatigue

Abstract

At the last Society Meeting, Wernick and Tobias reported that listeners consistently showed greater temporary threshold shift (TTS) when a fatiguing tone was presented during a “mental task” than when they simply sat quietly (“reverie”). We cannot confirm this report. Twelve listeners were exposed to a 4000-cps tone at 100 dB SPL for 3 min under two conditions: (1) sitting quietly and (2) adding columns of figures. Pre- and post-exposure thresholds at 5600 cps were determined with Békésy audiometer, interrupted tones. Order was balanced, initial postexposure setting was at preexposure threshold, and instructions to the subjects were neutral in regard to expected outcome. Indeed, the person actually running the subjects was unaware of the outcome of Wernick and Tobias' study. No significant differences in TTS were found at any time after exposure; in fact, the greatest mean difference at any time was in the opposite direction: the TTS at 2 min 15 sec was 14 dB for the “reverie” condition, 12 dB for the “mental task.” It is concluded that the efferent system need not be invoked to account for any aspects of auditory fatigue. [Supported by grants from the Public Health Service, U. S. Department of Health, Education, and Welfare.]