Masking of Tones before, during, and after Brief Silent Periods in Noise

Abstract

Thresholds were measured for a 5-msec tone which occurred at a number of different times before, during, and after a silent period of 25, 50, 200, or 500 msec duration in an otherwise continuous 70-dB-SPL (sound-pressure level) masking noise. When a 1900-Hz tone was masked by wide-band noise or by a narrow band of higher frequencies, threshold levels for signals occurring soon after the end of the silent period were elevated by as much as 15 dB compared with thresholds 250 msec after the noise began. This threshold elevation (previously termed “overshoot” when the noise burst followed an “infinite” silence) increased with the duration of the silent period. Smaller threshold elevations preceded the silent period. For a 2600-Hz tone centered in the narrow band of noise (a situation previously yielding no “overshoot” even for single bursts of noise), negligible threshold change occurred except during the silent period. Results are interpreted in terms of neural on effects and temporal development of auditory-frequency contours. [Supported by a program project grant of the National Institutes of Health, United States Department of Health, Education, and Welfare.]