ASA 124th Meeting New Orleans 1992 October

3aPP11. The effect of nonsimultaneous off-frequency cues on the detection of a tonal signal masked by narrow-band noise.

Leslie R. Bernstein

Constantine Trahiotis

Ctr. for Neurol. Sci. and Surgical Res. Ctr., Dept. of Surgery, Univ. of Connecticut Health Ctr., Farmington, CT 06030

Listeners' detection thresholds were measured for a 125-ms, 1-kHz tonal signal masked by a similarly gated 50-Hz-wideband of noise. A two-cue, two-interval adaptive, forced-choice procedure was employed and the presence and nature of the cues were varied across conditions. In the baseline conditions, no cues were provided and the maskers were either chosen randomly or were identical within but not across trials. In the conditions of interest, the envelopes and phase-modulations of the maskers were ``frozen'' across all four intervals of a trial, but were randomly chosen across trials. The center frequency of the bands of noise that served as cues (first and fourth intervals) was either 1 kHz (on-frequency) or 900 or 700 Hz (off-frequency). Detection with 1-kHz cues was greatly improved over baseline conditions and this improvement declined rapidly when the center frequency of the cue was changed to 900 or 700 Hz. Roving-level conditions were also employed to assess the nature of the information used by the listeners. [Work supported by AFOSR and NIH.]