Formant-frequency variation and informational masking of speech by extraneous formants: evidence against dynamic and speech-specific acoustical constraints

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

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


How speech is separated perceptually from other speech remains poorly understood. Recent research indicates that the ability of an extraneous formant to impair intelligibility depends on the variation of its frequency contour. This study explored the effects of manipulating the depth and pattern of that variation. Three formants (F1+F2+F3) constituting synthetic analogues of natural sentences were distributed across the 2 ears, together with a competitor for F2 (F2C) that listeners must reject to optimize recognition (left = F1+F2C; right = F2+F3). The frequency contours of F1 - F3 were each scaled to 50% of their natural depth, with little effect on intelligibility. Competitors were created either by inverting the frequency contour of F2 about its geometric mean (a plausibly speech-like pattern) or 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. Adding a competitor typically reduced intelligibility; this reduction depended on the depth of F2C variation, being greatest for 100%-depth, intermediate for 50%-depth, and least for 0%-depth (constant) F2Cs. This suggests that competitor impact depends on overall depth of frequency variation, not depth relative to that for the target formants. The absence of tuning (i.e., no minimum in intelligibility for the 50% case) suggests that the ability to reject an extraneous formant does not depend on similarity in the depth of formant-frequency variation. Furthermore, triangle-wave competitors were as effective as their more speech-like counterparts, suggesting that the selection of formants from the ensemble also does not depend on speech-specific constraints.

Original languageEnglish
Pages (from-to)1507-1525
Number of pages19
JournalJournal of Experimental Psychology : Human Perception and Performance Psychology
Issue number4
Early online date19 May 2014
Publication statusE-pub ahead of print - 19 May 2014

Bibliographical note

This article has been published under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Copyright for this article is retained by the author(s). Author(s) grant(s) the American Psychological Association the exclusive right to publish the article and identify itself as the original publisher.

Funding: UK EPSRC (Grant EP/F016484/1) .

Supplemental material:


  • auditory grouping
  • cocktail party effect
  • formant frequency
  • informational masking
  • speech perception


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