Horn, Jennifer
(2015)
2f2-f1 DPOAE Sources in Contradiction to the Two-Source/Two-Mechanism Model?
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Distortion product otoacoustic emissions (DPOAEs) can be separated into distortion (active/hair-cell-generator based) and reflection sources (passive/hydro-mechanically based). These sources are linked to specific physiological-acoustic events along the cochlear partition. Researchers have shown that the 2f1-f2 component (using parameters of f2/f1=1.22, 65/55 dB SPL) is dominated by the distortion source. However, the 2f2-f1 is far less well understood and rarely tested. Measured with presumed optimal parameters, f2/f1=1.08, 65/65 dB SPL it is likely dominated by the reflection source. Researchers rarely have described ripple characteristics of the 2f2-f1 fine structure (the function of magnitude versus frequency assessed using high-resolution analysis) well known for 2f1-f2. Differences are expected between components due to their putative differences of kind and place of production.
The purpose of this study was to determine how ripple characteristics differ between 2f1-f2 and 2f2-f1 using fine-structure DPOAE analyses elicited by parameters promoting robust responses for components using two sets of parameters: (1) f2/f1=1.22, 65/55 dB SPL and (2) f2/f1=1.08, 65/65 dB SPL. Inverse Fast Fourier Transform conversion of frequency into time–domain measures separated the sources.
The first prediction was 2f1-f2 would be dominated by the distortion source, given f2/f1=1.22, 65/55 dB SPL, and dominated by the reflection source with f2/f1=1.08, 65/65 dB SPL. The 2f2-f1 component, posited on theoretical grounds, would be dominated by the reflection source for both parameter sets. The second prediction was the two components would differ in ripple spacing, depth, and prevalence, presumably in deference to the diversity in their respective origins.
The following conclusions could be made: First, the distortion source was affirmed to be dominant for the 2f1-f2 DPOAE when measured using the f2/f1=1.22, 65/55 dB SPL parameter set for all participants (24/24). Furthermore, the reflection source was confirmed to be dominant for the other three conditions, with 100% occurrence for the 2f2-f1 DPOAE measured using the f2/f1=1.08, 65/65 dB SPL. There also were significant differences among the ripple characteristics measured under the four conditions. These results, while not contradicting two-source/two-mechanism model overall, nevertheless suggest need for some revision, as proposed. They also may help to promote greater interests in 2f2-f1, including applications.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
28 September 2015 |
| Date Type: |
Publication |
| Defense Date: |
21 July 2015 |
| Approval Date: |
28 September 2015 |
| Submission Date: |
14 June 2015 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
174 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
School of Health and Rehabilitation Sciences > Communication Science and Disorders |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
DPOAEs, 2f1-f2, 2f2-f1, sources, mechanisms, ripple characteristics |
| Date Deposited: |
28 Sep 2015 19:54 |
| Last Modified: |
19 Dec 2016 14:42 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/25389 |
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