Sequential Stream Segregation Affects Localisation of Diotic Tones among Tones with Time-Varying Interaural Time Difference

In this study, I examined how sequential stream segregation contributes to the detection of diotic tones among tones with time-varying interaural time differences (ITDs). Target (T) and distractor (D) tones, and a silent duration (–) formed a sequence (DTD–) and this sequence was presented repeatedly. A frequency difference was introduced between target and distractor tones. The distractor tones were also given time-varying ITDs to produce a percept of smooth auditory motion along the interaural axis. In half of the trials, the target tones were not given time-varying ITDs, and thus were diotically presented. The task of the listeners was to determine whether the repeated sequences of DTD–had target tones without motion. The sensitivity d′ for the detection of diotic target tones was higher with larger frequency differences. On the other hand, the criterion c was lower with larger frequency differences. In another session, I confirmed that proportions of reports “two streams” was positively and negatively correlated with d′ and c, respectively. The results indicate that the localisation of a sound image could be influenced by sequential stream segregation in complex sound environments.