ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06
2pPP14. Stimulus-driven, time-varying weights for comodulation masking
release.
Soren Buus
Commun. and Digital Signal Processing Center, Dept. of Elec. and Comput.
Eng., 409 DA, Northeastern Univ., 360 Huntington Ave., Boston, MA 02115-5096
Lei Ji Zhang
Mary Florentine
Northeastern Univ., Boston, MA 02115
This study tests the hypothesis that CMR is mediated by ``listening in the
valleys'' [S. Buus, 1958--1965 (1985)]. Detectability was measured for
signals consisting of 6 consecutive 25-ms, 1-kHz tone bursts presented in a
50-Hz wide masker or in maskers consisting of seven 50-Hz wide noises, one
critical band apart, with either correlated or uncorrelated envelopes. Each
burst varied randomly around masked threshold according to Gaussian
distributions with 3- or 6-dB standard deviations. For each listener and
condition, the responses from 5000 trials were sorted to construct conditional
psychometric functions for d' as a function of burst energy for 10 ranges of
short-term level of the on-frequency masker band during the burst. The slopes
of these functions for three normal listeners decrease markedly with increasing
short-term masker level for the correlated multiband masker, but are largely
constant for the other maskers. This indicates that the weight applied to the
signal channel is high when the masker level is low and vice versa for the
correlated masker, but is approximately constant for single-band and
uncorrelated mutliband maskers. This finding provides direct evidence that CMR
is mediated by ``listening in the valleys.'' [Work supported by NIH-NIDCD
R01DC00187.]