Formant-frequency variation and its effects on across-formant grouping in speech perception

Brian Roberts*, Robert J. Summers, Peter J. Bailey

*Corresponding author for this work

Research output: Chapter in Book/Published conference outputConference publication


How speech is separated perceptually from other speech remains poorly understood. In a series of experiments, perceptual organisation was probed by presenting three-formant (F1+F2+F3) analogues of target sentences dichotically, together with a competitor for F2 (F2C), or for F2+F3, which listeners must reject to optimise recognition. To control for energetic masking, the competitor was always presented in the opposite ear to the corresponding target formant(s). Sine-wave speech was used initially, and different versions of F2C were derived from F2 using separate manipulations of its amplitude and frequency contours. F2Cs with time-varying frequency contours were highly effective competitors, whatever their amplitude characteristics, whereas constant-frequency F2Cs were ineffective. Subsequent studies used synthetic-formant speech to explore the effects of manipulating the rate and depth of formant-frequency change in the competitor. Competitor efficacy was not tuned to the rate of formant-frequency variation in the target sentences; rather, the reduction in intelligibility increased with competitor rate relative to the rate for the target sentences. Therefore, differences in speech rate may not be a useful cue for separating the speech of concurrent talkers. Effects of competitors whose depth of formant-frequency variation was scaled by a range of factors were explored using competitors derived either by inverting the frequency contour of F2 about its geometric mean (plausibly speech-like pattern) or by using a regular and arbitrary frequency contour (triangle wave, not plausibly speech-like) matched to the average rate and depth of variation for the inverted F2C. Competitor efficacy depended on the overall depth of frequency variation, not depth relative to that for the other formants. Furthermore, the triangle-wave competitors were as effective as their more speech-like counterparts. Overall, the results suggest that formant-frequency variation is critical for the across-frequency grouping of formants but that this grouping does not depend on speech-specific constraints.

Original languageEnglish
Title of host publicationBasic aspects of hearing
Subtitle of host publicationphysiology and perception
EditorsBrian C.J. Moore, Roy D. Patterson, Ian M. Winter, Robert P. Carlyon, Hedwig E. Gockel
Place of PublicationNew York (US)
Number of pages9
ISBN (Electronic)978-1-4614-1590-9
ISBN (Print)978-1-4614-1589-3
Publication statusPublished - 2013
Event16th International Symposium on Hearing (ISH) - Cambridge, St. John’s College, United Kingdom
Duration: 23 Jul 201227 Jul 2012

Publication series

NameAdvances in experimental medicine and biology
ISSN (Print)0065-2598


Conference16th International Symposium on Hearing (ISH)
Country/TerritoryUnited Kingdom
CitySt. John’s College

Bibliographical note

Proceedings of the 16th International Symposium on Hearing (ISH), held from 23 to 27 July 2012 in St. John’s College, Cambridge, UK.

This research was supported by Research Grant EP/F016484/1 from the Engineering and Physical Sciences Research Council (UK).


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