Primitive stream segregation of tone sequences without differences in fundamental frequency or passband

Abstract

Peripheral-channeling theorists argue that differences in excitation pattern between successive sounds are necessary for stream segregation to occur. The component phases of complex tones comprising unresolved harmonics (F0=100 Hz) were manipulated to change pitch and timbre without changing the power spectrum. In experiment 1, listeners compared two alternating sequences of tones, A and B. One sequence was isochronous (tone duration=60 ms, intertone interval=40 ms). The other began isochronously, but the progressive delay of tone B made the rhythm irregular. Subjects had to identify the sequence with irregular rhythm. Stream segregation makes this task more difficult. A and B could differ in passband (1250-2500 Hz, 1768-3536 Hz, 2500-5000 Hz), component phase (cosine, alternating, random), or both. Stimuli were presented at 70 dB SPL in pink noise. Dissimilarity in either passband or phase increased discrimination thresholds. Moreover, phase differences raised threshold even when there was no passband difference. In experiment 2, listeners judged moment-by-moment the grouping of long ABA-ABA-... sequences. The measure was the proportion of time a sequence was heard as segregated. The factors that increased segregation were very similar to those that increased threshold in experiment 1. Overall, the findings indicate that substantial stream segregation can occur without differences in power spectrum. It is concluded that differences in peripheral channeling are not a requirement for stream segregation.

Properties of auditory stream formation

“…In one experiment, Roberts et al [51] used subjective judgements of streaming to examine the perception of sequences of the form CAC-CAC or CRC-CRC. The tones C and A were either filtered into the same frequency region (high-high or low-low) or into different frequency regions.…”

“…In a second experiment, Roberts et al [51] used a rhythm-discrimination task requiring judgement of the relative timing of successive sounds. When the tones were filtered into the same frequency region, performance was much poorer when successive sounds differed in phase spectrum (CACAC.…”

“…(b) Segregation based on difference in phase spectrum Roberts et al [51] studied the effect of phase spectrum on streaming. The stimuli were harmonic complex tones with F0 ¼ 100 Hz, filtered so as to contain only high harmonics, which are not resolved, i.e.…”

Human Cortical Activity during Streaming without Spectral Cues Suggests a General Neural Substrate for Auditory Stream Segregation

“…Psychophysical studies have demonstrated that sounds designed to evoke very similar tonotopic patterns of excitation in the auditory periphery can nonetheless form separate streams if they differ along other perceptual dimensions, such as pitch or perceived fluctuation rate Grimault et al, 2000Grimault et al, , 2002Roberts et al, 2002). The neurophysiological substrates for streaming under such conditions are unknown.…”

Objective and Subjective Psychophysical Measures of Auditory Stream Integration and Segregation

“…In general, faster presentation rates, or shorter tone intervals, and longer sequence lengths promote segregation (van Noorden 1975;Bregman 1978;Bregman et al 2000). Auditory streaming has been demonstrated using a variety of sounds, including pure tones, harmonic complex tones (Cusack and Roberts 1999;Grimault et al 2000Grimault et al , 2001Roberts et al 2002Roberts et al , 2008, synthetic vowels (Gaudrain et al 2007(Gaudrain et al , 2008, and noises (Bregman et al 2001;Grimault et al 2002), with streaming depending on differences in fundamental frequency (F0), spectral content, or temporal envelope modulation rate.…”