Pitch matches between unresolved complex tones differing by a single interpulse interval

The experiment compared the pitches of complex tones consisting of unresolv ed harmonics. The fundamental frequency (F0) of the tones was 250 Hz and th e harmonics were bandpass filtered between 5500 and 7500 Hz. Two 20-ms comp lex-tone bursts were presented, separated by a brief gap. The gap was an in teger number of periods of the waveform: 0, 4, or 8 ms. The envelope phase of the second tone burst was shifted, such that the interpulse interval (IP I) across the gap was reduced or increased by 0.25 or 0.75 periods (1 or 3 ms). A " no shift" control was also included, where the IPI was held at an integer number of periods. Pitch matches were obtained by varying the F0 of a comparison tone with the same temporal parameters as the standard but wi thout the shift. Relative to the no-shift control, the variations in IPI pr oduced substantial pitch shifts when there was no gap between the bursts, b ut little effect was seen for gaps of 3 or 8 ms. However, for some conditio ns with the same IPI in the shifted interval, an increase in the IPI of the comparison interval from 3 to 8 ms (gap increased from 0 to 4 ms) changed the pitch match. The presence of a pitch shift suggests that the pitch mech anism is integrating information across the two tone bursts. It is argued t hat the results are consistent with a pitch mechanism employing a long inte gration time for continuous stimuli that is reset in response to temporal d iscontinuities. For a 250-Hz F0, an 8-ms IPI may be sufficient for resettin g. Pitch models based on a spectral analysis of the simulated neural spike train, on an autocorrelation of the spike train, and on the mean rate of pi tch pulses, all failed to account for the observed pitch matches. (C) 2000 Acoustical Society of America. [S0001-4966(00)01408-9].