Pitch shifts for complex tones with unresolved harmonics and the implications for models of pitch perception

Complex tone bursts were bandpass filtered, 22nd-30th harmonic, to produce waveforms with five regularly occurring envelope peaks ("pitch pulses") that evoked pitches associated with their repetition period. Two such tone bursts were presented sequentially and separated by an interpulse interval (IPI). When the IPI was varied, the pitch of the whole sequence was shifted by between +2% and -5%. When the IPI was greater than one period, little effect was seen. This is consistent with a pitch mechanism employing a long integration time for continuous stimuli that resets in response to temporal discontinuities of greater than about one period of the waveform. Similar pitch shifts were observed for fundamental frequencies from 100 to 250 Hz. The pitch shifts depended on the IPI duration relative to the period of the complex, not on the absolute IPI duration. The pitch shifts are inconsistent with the autocorrelation model of Meddis and O'Mard [J. Acoust. Soc. Am. 102, 1811-1820 (1997)], although a modified version of the weighted mean-interval model of Carlyon et al. [J. Acoust. Soc. Am. 112, 621-633 (2002)] was successful. The pitch shifts suggest that, when two pulses occur close together, one of the pulses is ignored on a probabilistic basis.