Breaking away: Violation of distortion emission phase-frequency invariance at low frequencies

Sumitrajit Dhar, Abigail Rogers, Carolina Abdala*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

32 Citations (Scopus)

Abstract

The phase versus frequency function of the distortion product otoacoustic emission (DPOAE) at 2f1 - f2 is approximately invariant at frequencies above 1.5 kHz in human subjects when recorded with a constant f2/f1. However, a secular break from this invariance has been observed at lower frequencies where the phase-gradient becomes markedly steeper. Apical DPOAEs, such as 2f1 - f2, are known to contain contributions from multiple sources. This experiment asked whether the phase behavior of the ear canal DPOAE at low frequencies is driven by the phase of the component from the distortion product (DP) region at 2f1 - f2, which exhibits rapid phase accumulation. Placing a suppressor tone close in the frequency to 2f1 - f2 reduced the contribution of this component to the ear canal DPOAE in normal-hearing adult human ears. When the contribution of this component was reduced, the phase behavior of the ear canal DPOAE was not altered, suggesting that the breaking from DPOAE phase invariance at low frequencies is an outcome of apical-basal differences in cochlear mechanics. The deviation from DPOAE phase invariance appears to be a manifestation of the breaking from approximate scaling symmetry in the human cochlear apex.

Original languageEnglish
Pages (from-to)3115-3122
Number of pages8
JournalJournal of the Acoustical Society of America
Volume129
Issue number5
DOIs
Publication statusPublished - May 2011
Externally publishedYes

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