An Ideal-observer standard for evaluating relative cue reliance on multi-talker speech segregation

Abstract

Modern hearing research identifies the ability of listeners to segregate simultaneous speech streams with a reliance on three major voice cues, fundamental frequency, level, and location. Few of these studies, however, present cues simultaneously as in natural listening, and fewer still consider the relative reliance listeners placed on these cues owing to the cues’ different units of measure. In the present study, trial-by-trial analyses were used to isolate listener reliance on the three voice cues presented simultaneously, with the behavior of an ideal observer (Green and Swets, 1966, pp. 151–178) serving as standard for determining their relative reliance. Listeners heard on each trial a pair of randomly selected, simultaneously recordings of naturally spoken sentences. One of the recordings was always from the same talker, a distracter, the other, with equal probability, was from one of two target talkers differing in the three voice cues. The listener’s task was to identify the target talker. Among 33 clinically normal-hearing adults only one relied predominantly on voice level, the remaining were split between voice fundamental frequency and location. The results are discussed regarding their implications for the common practice of using target-distracter level as a dependent measure of multi-talker speech segregation.