Detection and direction-discrimination of diotic and dichotic ramp modulations in amplitude and phase

Caroline Witton*, Michael I.G. Simpson, G. Bruce Henning, Adrian Rees, G.G.R. Green

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


When the source of a tone moves with respect to a listener's ears, dichotic (or interaural) phase and amplitude modulations (PM and AM) are produced. Two experiments investigated the psychophysical characteristics of dichotic linear ramp modulations in phase and amplitude, and compared them with the psychophysics of diotic PM and AM. In experiment 1, subjects were substantially more sensitive to dichotic PM than diotic PM, but AM sensitivity was equivalent in the dichotic and diotic conditions. Thresholds for discriminating modulation direction were smaller than detection thresholds for dichotic AM, and both diotic AM and PM. Dichotic PM discrimination thresholds were similar to detection thresholds. In experiment 2, the effects of ramp duration were examined. Sensitivity to dichotic AM and PM, and diotic AM increased as duration was increased from 20 ms to 200 ms. The functions relating sensitivity to ramp duration differed across the stimuli; sensitivity to dichotic PM increased more rapidly than sensitivity to dichotic or diotic AM. This was also reflected in shorter time-constants and minimum integration times for dichotic PM detection. These findings support the hypothesis that the analysis of dichotic PM and AM rely on separate mechanisms. © 2003 Acoustical Society of America.

Original languageEnglish
Pages (from-to)468-477
Number of pages10
JournalJournal of the Acoustical Society of America
Issue number1
Publication statusPublished - Jan 2003

Bibliographical note

© 2003 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in The Journal of the Acoustical Society of America 113, 468 (2003) and may be found at


  • psychophysics
  • acoustic analysis
  • binaural hearing
  • thermodynamic properties


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