The dynamics of auditory stream segregation: Effects of sudden changes in frequency, level, or modulation

Three experiments explored the effects of abrupt changes in stimulus properties on streaming dynamics. Listeners monitored 20-s-long low- and high-frequency (LHL–) tone sequences reported number streams heard throughout. Experiments 1 2 used pure tones examined changing triplet base frequency level, respectively. Abrupt (±3–12 semitones) caused significant magnitude-related falls segregation (resetting), regardless transition direction, but an asymmetry occurred for level (±12 dB). Rising-level transitions usually decreased significantly, whereas falling-level had little or no effect. Experiment 3 (unmodulated) narrowly spaced (±25 Hz) pairs (dyads); two evoke similar excitation patterns, dyads are strongly modulated with a distinctive timbre. Dyad-only induced segregated percept, limiting scope further build-up. Alternation between groups produced large, asymmetric streaming. Dyad-to-pure substantial resetting, pure-to-dyad sometimes elicited even greater than corresponding interval dyad-only (overshoot). The results indicate that timbre can affect likelihood stream without introducing peripheral-channeling cues. These direction reminiscent subtractive adaptation vision.