Effects of instantaneous phase shifts and gap duration on pitch of unresolved complex tones

Abstract

Introducing a phase change between two short bursts of a sinusoid can produce a pitch shift which corresponds to a shift in the peak of the long-term spectrum [I. V. Nabalek, Acustica 82, 531–539 (1996)]. The present experiment examined this effect with a complex tone consisting of unresolved harmonics where the phase change was applied to the envelope of the complex. The hypothesis that a long-term pitch mechanism sensitive to envelope phase is reset in response to a discontinuity in the stimulus was tested: The stimulus was an unresolved complex tone consisting of the harmonics of a 250-Hz F0 filtered between 5500 and 7500 Hz. Two 20-ms bursts separated by short gaps were presented; the starting phase of the first burst, the phase between the bursts, and the duration of the gap were varied. A pitch-matching paradigm was used. If the gap between the bursts causes the mechanism to reset, the resetting hypothesis predicts that a phase manipulation of the second burst will not alter the pitch of the complex. Pitch shifts were obtained which do not support a resetting hypothesis, but rather a mechanism in which the mean pulse rate is used to determine pitch.