Effect of Two Interaural Phase Conditions for Binaural Exposures on Threshold Shift

Monaural temporary threshold shift (TTS) was measured following 2 min of exposure under three conditions of presentation, monaural, binaurally in phase, and binaurally out of phase by 180°. When listeners were exposed to 500 and 750 Hz at 120 and 110 dB, respectively, TTS at test signals of 750 and 1000 Hz was greater for monaural than for binaural exposure conditions, and no phase effect was noted. For an exposure-test signal combination of 4000 and 6000 Hz, the binaural-monaural difference was eliminated but there was a significant phase effect for the two binaural exposure conditions. More TTS occurred when the exposure signal was 180° out of phase. No difference was observed among the exposure conditions for TTS at 750 Hz following exposure to a 400–600-Hz band of noise at 120 dB. The “frying-noise” tinnitus that follows high-level tonal exposure was reported to disappear at 70–80 sec postexposure for both binaural and monaural exposure.