Effects of time intervals and tone durations on auditory stream segregation

Adult listeners rated the difficulty of hearing a single coherent stream in a sequence of high (H) and low (L) tones that alternated in a repetitive g alloping pattern (HLH-HLH-HLH...). They could hear the gallop when the sequ ence was perceived as a single stream, but when it segregated into two sub- streams, they heard H-H-... in one stream and L-L-... in the other. The ons et-to-onset time of the tones. their duration, the interstimulus interval ( ISI) between tones of the same frequency, and the frequency separation betw een H and L tones were varied. Subjects' ratings on a 7-point scale showed that the well-known effect of speed's increasing stream segregation is prim arily due to its effect on the ISI between tones in the same frequency regi on. This has implications for several theories of streaming.