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Title: Suppression of otoacoustic emissions evoked by simultaneously presented tone bursts
Author: Killan, Edward Charles
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2013
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Tone burst-evoked otoacoustic emissions (TBOAEs) may be reduced in amplitude (suppressed) by the simultaneous presentation of additional tone bursts. This simultaneous suppression of TBOAEs has not previously been studied in detail and the mechanisms responsible for it are not well understood. The literature suggests a number of possible underpinning mechanisms, including mechanisms involving TBOAE components generated at basal basilar membrane (BM)sites (i.e. basalsource components). However, the weight of evidence indicates that a mechanism wherein suppression caused by local nonlinear interactions (LNI) between BM vibration patterns, governed by the compressive nonlinearity of TBOAE generator channels, is primarily responsible. The aim of the work described in this thesis is to determine the extent to which this LNI-based mechanism can account for simultaneous suppression of TBOAEs. This was achieved by . testing four hypotheses of suppression behaviour derived from a simple mathematical model of the LNI-based mechanism. Each of these hypotheses was tested via a specific experiment, where suppression was measured from normal human ears. It was reasoned that a close agreement between the hypothesised behaviours and the suppression data measured from human ears could be held as support for the LNI-based mechanism being responsible for suppression. In contrast, any substantial differences might argue against the LNI-based mechanism. The results of the four experiments demonstrated some agreement between suppression data and the model-derived hypotheses, though some discrepancies were also observed. It was therefore reasoned that the LNI-based mechanism (as represented in the simple model) cannot account for all the behaviours exhibited by the suppression data. It was argued that some of the discrepancies could be understood in terms of limitations of the model of the LNI-based mechanism.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available