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
[