ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

2pPP27. The effects of incremental change in temporal envelope correlation on auditory fusion.

John R. Carter

Patrick W. Rappold

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

Madhuri S. Muelkar

Univ. of South Alabama, Mobile, AL 36688

The effects of incremental change in degree of temporal envelope correlation on the auditory fusion of narrow-band noise (NBN) pairs was examined by placing fusion in competition with sequential streaming for one component of a NBN pair. Seven levels of envelope correlation were represented (r=1.0, 0.75, 0.50, 0.25, 0.00, -0.25, -0.35) by three sets of NBN pairs, for a total of 21 NBN pairs. A NBN pair consisted of a target-band spectrally centered at 2000 Hz, and a flanker-band centered at 1500 Hz. A NBN pair was played alternately with the target-band alone (captor-band) at an initial interstimulus-interval (ISI) of 500 ms. The ISI decreased automatically in 5- or 2-ms increments until a subject exited the program when judging the perceptual prominence of sequential streaming as greater than that of fusion. The ISI at exit was used to infer strength of fusion for the NBN pair. Shorter ISIs suggested stronger fusion; longer ISIs suggested weaker fusion. Results showed a trend for ISI to increase with a decrease in the degree of envelope correlation, which suggested a gradual decline in fusion strength as envelope correlation was incremented downward from perfect correlation.