Abstract
The stimuli were complex tones consisting of the first 12 harmonics of 100 Hz, with duration of 1.5 s. The even-numbered harmonics of the complex had a linearly falling or linearly rising spectral envelope and were frequency modulated by either a sinusoid with 90° or 270° phase or by a linear ramp. Frequency and depth of modulation were 0.66 Hz (1.0 cycle/1.5 s) and 6%,respectively. The odd-numbered harmonics had a flat spectral envelope and were frequency modulated by a 0° phase sinusoid with frequencies of 0.3, 0.66, or 2.0 Hz, and depths of 3, 6, or 10%. In agreement with McAdams [J. Acoust. Soc. Am. Suppl. 1 68, S109 (1980)], we observed that when a different modulation function is impressed upon each subset of harmonics, the 12-component complex is perceived as having two pitch values, which seem to correspond to those of the individual subsets of harmonics when presented in isolation. An absolute identification experiment was conducted in which listeners were asked to identify the spectral envelope (timbre) and pattern of frequency modulation of the even-numbered harmonics of the 12-component complex. Accuracy of identification ranged from 40%–75% over the various stimulus conditions. In a second experiment, listeners were asked to judge the strength of the periodicity pitch of two-tone complexes (2500 and 3000 Hz, or 500 and 600 Hz) in which only the higher partial was frequency modulated by a linear ramp with frequency of 1.0 cycle per signal duration. Preliminary results suggest that the periodicity pitch of the two-tone complex becomes weaker as modulation depth increases. The relation between the perceptual data and the time and frequency domain characteristics of the signals will be discussed.
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