Monaural Temporary Threshold Shift following Monaural and Binaural Exposures

The monaural temporary threshold shift (TTS) was measured under several experimental conditions to ascertain whether or not it depended upon whether one ear or both ears were exposed to sound. The TTS for 1000 cps is the same whether the tested ear alone or both ears simultaneously are exposed to a 1000-cps tone at 20, 80, or 100 db sensation level. There is also no difference in the initial part of the recovery curve for 1400 cps after exposure to 1000 cps at 100 db SL, but the diphasic recovery curve or “bounce” is clear only after monaural exposure, not after binaural. The TTS for 4000 cps after a 3-min exposure to white noise at 110 db SPL also shows little or no difference between monaural and binaural exposure. Somewhat different conclusions are reached if one separates the TTS for the less susceptible ear of all listeners from the more susceptible ear. The less susceptible ear shows more TTS after binaural exposure than after monaural, while the more susceptible ear shows less TTS after the binaural exposure.