Frequency Discrimination following Auditory Fatigue

Abstract

Threshold measures and frequency jnd's at 1000, 2000, and 4000 cps were obtained before and after fatigue by wide-band noise. Two test-stimulus SPL's were used during the postfatigue discrimination measures such that stimuli were presented at 10 or 40 dB SL re TTS3. The SPL remained constant throughout recovery during each experimental session. When test stimuli were equated in terms of SL, no differences between pre- and post-fatigue jnd's were noted at 40 dB SL or greater at any frequency. At low-stimulus SL's (10–20 dB), however, a differential effect on the jnd occurred owing to fatiguing stimulation that was not explainable in terms of TTS. At 4000 cps (maximum TTS), there was little discrepancy betwen pre- and post-fatigue jnd's. At 2000 cps, about 10% impairment in the jnd due to fatigue existed in the latter stages of recovery. At 1000 cps (no TTS), the postfatigue jnd's were about 40% greater than prefatigue jnd's and independent of recovery time. A paradox thus exists at low SL's between amount of threshold shift and frequency discrimination. [These data are based on a portion of a Ph.D. thesis completed at the University of Iowa under the direction of Prof. Arnold M. Small, Jr.]