Effects of intense pure tones on auditory temporal acuity

Gap detection thresholds (GDTs) were obtained from human listeners before and after exposure to a brief 0.4- or 1.7-kHz tone. The temporary threshold shift (TTS) produced 2 min after an exposure was approximately 10 dB. GDT stimuli were octave-band noises centered at one of three frequencies: the exposure frequency, one-half octave above the exposure frequency or one octave above the exposure frequency. GDTs were obtained at 35, 55, and 75 dB SPL at each center frequency. GDT and TTS recovery were monitored at logarithmically-spaced time intervals after the exposures. Following the 1.7-kHz exposure, shifts in post-exposure GDT were only obtained with the low-level stimulus conditions--the magnitude of GDT shift was correlated with the size of the TTS, and the shifts in GDT and absolute threshold required similar amounts of time to recover. Significant post-exposure shifts in GDT were also observed following the 0.4-kHz exposure. However, shifts were found at frequencies where there was no measurable TTS, and they required longer periods of time to recover than did absolute threshold.