ASA 124th Meeting New Orleans 1992 October

3aPP2. Effect of noise envelope coherence, modulation rate, and duration on the detection of a sinusoid in narrow-band noise.

Pierre L. Divenyi

Alain Algazi

Speech and Hear. Res., V. A. Med. Ctr., Martinez, CA 94553

Signal-to-noise ratios (E[sub s]/N[sub 0]) necessary to detect a 1-kHz tone presented in 100-Hz quasirandom noise were measured in trained young, normal-hearing subjects. The noise was generated by digital addition of random-phase sinusoids separated by 1 Hz. In one set of conditions, 20-Hz-wide spectral slices of the 100-Hz noise band were provided with envelopes either identical to or uncorrelated with the envelope of the 20-Hz wideband centered at 1 kHz, thus generating degrees of envelope coherence (r) between 0 and 1. The duration of the sinusoidal signal was 400 ms. In another set of conditions, the noise was divided into two to five equal-width slices, each having an identical envelope; signal duration was constant at 400 ms. In the final set of conditions, the duration of the signal varied between 25 and 400 ms, with the envelope being either random or maximally coherent in the five 20-Hz spectral slices. By regarding a fixed E[sub s]/N[sub 0] as an indicator of a fixed degree of envelope correlation detection [V. M. Richards, J. Acoust. Soc. Am. 82, 1621--1630 (1987)], a comparison of the results in the three sets of conditions allows one to specify some of the temporal constraints that limit the envelope following process. [Work supported by the National Institute on Aging and the Department of Veterans Affairs.]