An examination of temporal signal uncertainty for sequences of noise or random-frequency maskers

Abstract

The effect of temporal uncertainty was examined on detection of a 1000-Hz tone presented simultaneously with one of a sequence of five masker bursts, using a 2-AFC, adaptive procedure. The signal and each masker burst were 100-ms (10-ms rise/fall), with no temporal overlap between masker bursts. Each masker burst was 60 dB SPL. Across conditions, maskers were broadband-noise (300–3000 Hz) or random-frequency multi-tonal maskers with 1, 2, or 10 components. Components for the random-frequency maskers were drawn from 300 to 3000 Hz, excluding a 160-Hz band around the signal. Thresholds for conditions with no temporal uncertainty (signal presented with the first, third, or fifth masker burst on all trials) were compared to performance with maximal temporal uncertainty (signal position varied on every trial). There was no effect of temporal uncertainty for the noise masker. For random-frequency maskers, performance was uniformly poor for both fixed- and random-position signals, except for some release from masking for signals presented with the last masker burst. For three of four listeners, even 1-component maskers showed large amounts of masking in all conditions. These results suggest that the effects of temporal uncertainty are minimal for these stimuli. [Work supported by NIDCD.]