Effect of ripple repetition rate on discrimination of ripple glide direction and the detection of brief tones in spectro-temporal ripple noise.

Abstract

The effect of temporal repetition rate R on the discrimination and internal representation of stimuli with spectro-temporal ripples was examined. Experiment 1 measured the highest ripple density D at which upward- and downward-gliding ripples could be discriminated. Thresholds varied only slightly for R from 2 to 8 Hz, with a median threshold just above 5 ripples/oct. The threshold decreased (worsened) when R was increased to 16 and 32 Hz, suggesting that the limited temporal resolution of the auditory system plays a role for these higher values of R. Experiment 2 explored the internal representation of stimuli with static and downward-gliding spectral ripples by measuring the detection threshold for a brief tone presented at a peak or a valley in the stimulus spectrum. Thresholds were generally higher when the signal was at a peak than when it was at a valley. The peak-valley difference tended to decrease with increasing D, and the variation of thresholds with D was greater for low R than for high R. The results suggest that the discrimination of spectro-temporal ripples is limited mainly by frequency resolution for lower ripple rates (up to 4-8 Hz) but temporal resolution plays a major role for higher rates.