The cross-spectral grouping of complex sounds was investigated with the rhythmic masking release (RMR) paradigm. RMR involves the discrimination of one of two possible rhythms, despite perceptual masking of the rhythm by an irregular sequence of sounds identical to the rhythmic sounds that are interleaved among them. The rhythm can be released from masking by inducing the perceptual fusion of the irregular interfering sounds with concurrent "flanking" sounds situated in different frequency regions. The accuracy of the identified rhythm and its rated clarity in a two-alternative forced-choice procedure measured the degree of cross-spectral fusion of the interfering sounds with the flanking sounds. / The results obtained in six experiments suggest that temporal synchrony is sufficient for the fusion of (i) brief noise bursts that are widely apart in frequency (large DeltaF), that have uncorrelated high-rate intensity changes (HRIC), and that are spatially separated; and (ii) brief tones that are not harmonics of a common fundamental frequency (F0) and that are spatially-separated. An asynchrony of 20--40 ms is sufficient for the segregation of: (i) brief temporally-overlapping noise bursts with correlated HRIC and without spatial separations; and (ii) brief overlapping tones sharing a common F0 and without spatial separations. Intermediate asynchronies of 10--20 ms produce ambiguous cases of grouping and the presence of other segregation or fusion cues is critical to disambiguate them. / Thus, whereas uncorrelated ERIC, large DeltaF's, different F0's, and dichotic presentation all significantly affect the fusion of simultaneous or nearly simultaneous sounds, they are not sufficient by themselves to fully segregate these sounds; however, when a group of them act together, their synergetic action reinforces the effect of a small asynchrony in promoting segregation. When two sources are simultaneously active and emit short-duration sounds, separation of the sound sources in space has a negligible effect on their segregation. This research demonstrates the dominance of spectro-temporal cues (e.g., temporal synchrony) over spatial cues (e.g., common sound-source location) for the grouping of brief concurrent sounds. It also demonstrates that the auditory system is highly sensitive to any deviation from temporal synchrony. Further research is needed to establish whether the present conclusions apply to sounds of a longer duration.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.36724 |
| Date | January 1999 |
| Creators | Turgeon, Martine. |
| Contributors | Bregman, Albert S. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Psychology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001744964, proquestno: NQ64685, Theses scanned by UMI/ProQuest. |
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