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

3aPP3. Trade-off between depth and phase of modulation in the perception of pitch of complex amplitude-modulated tones.

Pierre L. Divenyi

Speech and Hear. Res., V.A. Medical Center, Martinez, CA 94553

Steven Greenberg

Univ. of California, Berkeley, CA 94720

Alain P. Algazi

V.A. Medical Ctr., Martinez, CA 94553

Complex amplitude-modulated (CAM) tones were generated through amplitude modulating a high-frequency carrier f[sub carH] (3--10 kHz) by an AM tone having a modulating frequency and a carrier f[sub carL] about 10% of f[sub carH] modulated at a rate f[sub 0] in the 100-Hz range. CAM sounds have been shown to have a low pitch corresponding to f[sub 0], whose discriminability decreases as the modulation of f[sub carL] is shifted from AM to QFM phase [S. Greenberg and P. L. Divenyi, Proc. 18th Midwinter Mtg. ARO, p. 55 (1995)]. In the present experiments, pitch discrimination was measured for pairs of CAM tones having fixed f[sub 0] differences but either variable depth (1%--200%) or variable phase (1--1.5(pi)) of modulation in the f[sub carL] complex. Results of the experiments show a pattern of modulation depth-phase trade-off over a range is constant above, and much reduced below f[sub carH]=4 kHz. These findings portray time-based pitch extraction as being a process in which phase spectrum plays a role consistent with the one proposed by W. H. Huggins [ 582--589 (1952)] in his theory. [Work supported by NIH and the VA Medical Research.]