Frequency discrimination following exposure to noise.

Abstract

Measures of threshold and frequency discrimination were obtained at 1000, 2000, and 4000 Hz before and after exposure to wide-band noise. Two test-stimulus SPL's (sound-pressure levels) were used during the postexposure discrimination measures such that stimuli were presented at 10 or 40 dB SL (sensation level) re TTS3 (temporary threshold shift). 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-exposure jnd's (just-noticeable differences) 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 noise exposure that was not explainable in terms of TTS. At 4000 Hz (where maximum TTS occurred), there was little difference between pre- and postexposure jnd's. At 2000 Hz, a 10% impairment in the jnd existed in the latter stages of recovery. At 1000 Hz (no TTS), the postexposure jnd's were about 40% greater than pre-exposure jnd's and independent of recovery time. A paradox thus exists at low SL's between amount of threshold shift and frequency discrimination.