ASA 124th Meeting New Orleans 1992 October

4pPPa17. Testing an auditory streaming hypothesis of the comodulation masking release effect.

Patrick W. Rappold

Dept. of Speech Pathol. and Audiol., Univ. of South Alabama, Mobile, AL 36688

Lee Mendoza

John K. Cullen, Jr.

Louisiana State Univ., Baton Rouge, LA 70803

An auditory streaming hypothesis has been proposed to explain the comodulation masking release (CMR) effect. This hypothesis suggests that threshold for a masked pure-tone is lower when the temporal envelope of a masker-band fluctuates in synchrony with a flanker-band (s) because of auditory cross-spectrum fusion of the noise-bands. Thus the pure-tone may be ``removed'' from the stream comprising the noise bands and become perceptually isolated in a stream of its own and ``easier'' to detect. Two stimulus conditions were created using only synchronously fluctuating noise bands: strongly fused and weakly fused. To investigate a possible relationship between auditory fusion of noise bands and the CMR effect, thresholds were determined for a pure tone while attempting to impair fusion of the noise bands in the weakly fused condition. Fusion was impaired by capturing the single flanker band into a sequential stream with a captor band. In the strongly fused condition, no attempt was made to manipulate fusion of the noise bands. Thresholds did not differ significantly across the two conditions.