Abstract:
There is a large effect of duration on fundamental frequency (F0) discrimination for complex tones consisting of harmonics unresolved by the peripheral auditory system [C. J. Plack and R. P. Carlyon, J. Acoust. Soc. Am. 98, 1355--1364 (1995)]. The present experiment investigated the mechanisms underlying this effect by measuring F0 discrimination for complexes of unresolved harmonics with continuous durations between 20 and 160 ms and for pairs of 20-ms unresolved complexes separated by a silent interval of between 5 and 80 ms. For the continuous signals, d[sup '] increased by a factor of 2.4 between the 20-ms signal and the 40-ms signal. For the paired signals d' increased relative to the 20-ms signal by a factor between 1.2 and 1.6, independent of the silent interval duration. This increase is similar to that predicted by signal detection theory. These data support the hypothesis that the pitch mechanism for unresolved harmonics can use a long integration window for continuous signals but reverts to a ``multiple looks'' mechanism, involving the efficient combination of discrete short-duration samples, when there is some discontinuity in the signal. [Work supported by MRC (UK).]