Tracking a temporal gap in band-limited noise: frequency and level effects.

Abstract

Temporal gap resolution in band-limited noise signals was examined with a B6k6sy procedure in which listeners tracked the minimum signal intensity needed to resolve a periodic temporal gap of fixed duration. Gaps from 25 msec to the smallest detectable value were tested to derive performance functions that described intensity threshold as a function of gap duration. Each of four octaveband signals, centered at .5, 1.0, 2.0, and 4.0 kHz, was presented with a complementary filtered noise masker to restrict the listening band and avoid extraneous spectral cues. Performance functions were also derived in different levels of a white-noise background that was added to shift the subject’s audibility thresholds to greater sound-pressure levels. Results show that gap resolution improves to a basic limit as signal level is increased from audibility threshold; the rate of improvement, however, increases progressively as audibility threshold is elevated. This observation suggests that shifts in audibility criteria for gap resolution are correhted with loudness changes. The smallest detectable gap for each signal was largely independent of sound-pressure level in a 35-40-dB range, but decreased systematically as a function of signal frequency. The frequency dependency is consistent with the hypothesis that temporal resolution is limited in part by spectral filtering in the auditory periphery.