Cochlear delays measured with amplitude-modulated tone-burst-evoked OAEs

Shawn S. Goodman, Robert H. Withnell, Egbert De Boer, David J. Lilly, Alfred L. Nuttall

Research output: Contribution to journalArticle

16 Scopus citations

Abstract

Delay times in the mammalian cochlea, whether from measurement of basilar membrane (BM) vibration or otoacoustic emissions (OAEs) have, to date, been largely based on phase-gradient estimates from steady-state responses. Here we report cochlear delays measured directly in the time domain from OAEs evoked by amplitude-modulated tone-burst (AMTB) stimuli. Measurement using OAEs provides a non-invasive estimate of cochlear delay but is confounded by the complexity of generation of such OAEs. At low to moderate stimulus levels, and provided that the stimulus frequency range does not include a region of the cochlea where there is a large change in effective reflectance, AMTB stimuli evoke an OAE with an envelope shape that is similar to the stimulus and allow a direct calculation of cochlear group delay. Such delays are commensurate with BM estimates of delay, estimates of cochlear delay inferred from neural recordings, and previous OAE measures of delay in the guinea pig. However, a nonlinear distortion mechanism, variation in effective reflectance, and intermodulation distortion products generated by the nonlinear interaction in the cochlea of the carrier and sidebands of the AMTB stimulus, may all contribute to OAEs arising with envelope shapes that are not a scaled representation of the stimulus, confounding the estimation of cochlear group delay.

Original languageEnglish (US)
Pages (from-to)57-69
Number of pages13
JournalHearing Research
Volume188
Issue number1-2
DOIs
StatePublished - Feb 2004

Keywords

  • Amplitude
  • Cochlea
  • Group delay
  • Otoacoustic emission

ASJC Scopus subject areas

  • Sensory Systems

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