Permanent changes in psychophysical tuning curves following exposure to weak, steep-sided noise

Abstract

Two of three listeners participating in an experiment involving the use of a high-pass noise with a very steep skirt (about −400 dB/octave below about 3000 Hz) now yield forward-masking tuning curves that are considerably less steep on the high-frequency side than was true prior to exposure to the steep-sided noise. The exposures were monaural and intermittent both within daily sessions and across an eight-week period, the “multiplied” noise was weak (spectral level 35 dB SPL, overall level 65 dB SPL), and there is no evidence of threshold shift (PTS). The greatest detuning occurs in the ipsilateral ear at a signal frequency of 2400 Hz, and there is little or no effect at 1700 Hz. There are also contralateral effects, but the patterns are different—the primary change is an elevation in the master level necessary when the masker and signal are the same frequency. There was some initial recovery, but deficits persist three months after the last exposure. These preliminary results indicate that noises with steep skirts should be treated with caution until their damage potential is better understood. [Work supported by NINCDS.]