Discrimination of redundant spectral-temporal cues. II. Level and duration effects.

Abstract

The effectiveness of stimulus level and duration on listeners’ ability to attend to and discriminate redundant increments in frequency and duration of pure tones is studied. The stimuli comprised pairs (T1, T2) of 1500-Hz tone bursts separated by a 60-ms silent interval. Sensation level was either 66 dB SL for both tones, or one of the tones was attenuated 25 or 40 dB relative to the other 66-dB SL tone. Tone duration was either 80 ms for both bursts, or T2 was two or three times longer than the 80-ms T1 burst. In the same three-interval, 2AFC task described in the above paper, listeners discriminated a ‘‘standard’’ pair of tone bursts from a ‘‘comparison’’ pair containing increments in the duration of T1 and/or in the frequency of T2. Data were obtained for eight highly trained listeners with normal hearing sensitivity. In three listeners, better discrimination performance was obtained for the increment occurring in the louder or longer burst. In four other listeners, tone level and duration had little or no effect on discrimination of either kind of increment. One listener failed to discriminate both increments in practically all conditions. Another source of interindividual variability is the listener’s ability to shift attention from one kind of increment to the other. [Work supported by OCAST Grant HSO-005 and Presbyterian Health Foundation.]