Two-tone suppression of stimulus frequency otoacoustic emissions

Douglas H. Keefe, John C. Ellison, Denis F. Fitzpatrick, Michael P. Gorga

Research output: Contribution to journalArticle

46 Scopus citations

Abstract

Stimulus frequency otoacoustic emissions (SFOAEs) measured using a suppressor tone in human ears are analogous to two-tone suppression responses measured mechanically and neurally in mammalian cochleae. SFOAE suppression was measured in 24 normal-hearing adults at octave frequencies (fp =0.5-8.0 kHz) over a 40 dB range of probe levels (Lp). Suppressor frequencies (fs) ranged from -2.0 to 0.7 octaves re: fp, and suppressor levels ranged from just detectable suppression to full suppression. The lowest suppression thresholds occurred for "best" fs slightly higher than fp. SFOAE growth of suppression (GOS) had slopes close to one at frequencies much lower than best fs, and shallow slopes near best fs, which indicated compressive growth close to 0.3 dBdB. Suppression tuning curves constructed from GOS functions were well defined at 1, 2, and 4 kHz, but less so at 0.5 and 8.0 kHz. Tuning was sharper at lower Lp with an equivalent rectangular bandwidth similar to that reported behaviorally for simultaneous masking. The tip-to-tail difference assessed cochlear gain, increasing with decreasing Lp and increasing fp at the lowest Lp from 32 to 45 dB for fp from 1 to 4 kHz. SFOAE suppression provides a noninvasive measure of the saturating nonlinearities associated with cochlear amplification on the basilar membrane.

Original languageEnglish (US)
Pages (from-to)1479-1494
Number of pages16
JournalJournal of the Acoustical Society of America
Volume123
Issue number3
DOIs
StatePublished - 2008

ASJC Scopus subject areas

  • Arts and Humanities (miscellaneous)
  • Acoustics and Ultrasonics

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