Interaural time and amplitude differences together

Abstract

Interaural time jnds were measured for a 500-Hz and 1000-Hz tone-burst signal using a 2IFC adaptive procedure. The time delay was presented to one ear in one interval. In addition, an interaural amplitude difference was presented simultaneously. Thus, perceptual movement was created by both an interaural time difference and an interaural amplitude difference, which either reinforced or opposed each other (i.e., time delay accompanied by amplitude increase or decrease). With the interaural amplitude difference remaining constant for each jnd measurement, the interaural time jnd was determined for alpha ranging from +2 dB to −2 dB in 12 dB steps. Results indicate that combining the interaural amplitude difference and interaural time difference so that they reinforce each other decreases the interaural time jnds. That is, when each is below threshold, they combine to be detectable. Similarly, when they oppose each other the interaural time jnd increases. The trading ratio (μsec/dB) is substantially larger when time and amplitude are in opposition than when they reinforce each other.