Detecting time and amplitude jitter in a click train

Abstract

A series of 2IFC experiments was performed with click trains to determine (a) the temporal jitter and (b) the amplitude jitter necessary to discriminate a regular click train from a jittered click train. The period of the regular click train was varied from 10 ms, where the sound is heard as a 100-Hz buzzy tone, up to 120 ms, where it is heard as a stream of discreet clicks. A fixed percentage jitter was applied to the period (or the amplitude) of each click in the train with positive jitter, negative jitter, and no jitter being given equal probability. The results show that the auditory system is much more sensitive to time jitter (around 12%) than to amplitude jitter (around 50%), and there is a ‘‘hump’’ in the Weber fraction around periods of 40–50 ms between the ‘‘buzzy tone’’ and ‘‘distinct clicks’’ regions. The results are interpreted in terms of the auditory image model of auditory perception [Pattersonet al., J. Acoust. Soc. Am. 98, 1890–1894 (1995)] which preserves phase-locking information in a buffer which is limited to time intervals less than about 40 ms.