ASA 124th Meeting New Orleans 1992 October

3aPP8. Detection of an interaural delay of a reproducible target noise band in the presence of reproducible diotic noise bands.

M. A. Stellmack

Parmly Hear. Inst., Loyola Univ., 6525 N. Sheridan Rd., Chicago, IL 60626

The purpose of this study was to examine the ability of listeners to detect an interaural delay of a target noise band in the presence of diotic noise bands when the target and distractors have identical or different temporal envelopes. The target noise band was centered at 750 Hz, while two flanking distractor bands were equally spaced in frequency around the target. In each block of trials, the target and distractors were of equal bandwidth. For 20-Hz-wide stimuli, spacings between target and distractor center frequencies of 50, 100, and 200 Hz were examined. For 10-Hz-wide stimuli, a 100-Hz spacing between the target and distractors was examined. On each trial, one of three envelopes was randomly chosen for the target and distractors. The two distractor bands always had identical envelopes, while there was a 1/3 probability of the target and distractors having the same envelopes. The target band was presented either diotically or with a fixed ongoing interaural delay. The target and distractors were synchronously gated. For the 20-Hz bandwidth conditions, detectability of the interaural delay of the target was poorest when the target and distractors had identical envelopes. For the 10-Hz bandwidth conditions, interaural delays of targets with certain envelopes proved more detectable than others, independent of the relationship between target and distractor envelopes. [Work supported by NIH.]