Pitch mechanisms for unresolved harmonics I: Duration effects

Abstract

The experiment measured the effects of duration, fundamental frequency (F0), spectral region, and relative phase of harmonics on F0 discrimination for complex tones consisting of unresolved harmonics. The F0 discrimination was measured for complexes with durations between 20 and 160 ms, and with F0s of 62.5, 125 and 250 Hz. The complexes were bandpass filtered between either 2750 and 3750 Hz or between 5500 and 7500 Hz. Finally, either all the harmonics were in sine phase (SINE) or alternating harmonics had a cosine phase shift (ALT). The pitch of an unresolved ALT complex is one octave higher than that for an unresolved SINE complex with the same F0 [T. M. Shackleton and R. P. Carlyon, J. Acoust. Soc. Am. 95, 3529–3540 (1994)]. For the SINE stimuli the improvement in F0 discrimination with duration was dependent on F0, with a larger effect of duration for the lower F0s. However, for the ALT stimuli the improvement with duration was the same as that for a SINE complex with twice the F0. Overall the results suggest that pitch, rather than F0 per se or spectral region, is the main determinate of the duration effect and also possibly of the integration time of the pitch mechanism.