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PERCEPTUAL ADAPTATION TO SPECTRALLY SHIFTED VOWELS: EXPERIMENT STUDIES AND AN ACOUSTIC ANALYSIS FRAMEWORK
by
Tianhao Li
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
BIOMEDICAL ENGINEERING
December 2008
Copyright 2008 Tianhao Li
Object Description
| Title | Perceptual adaptation to spectrally shifted vowels: experiment studies and an acoustic analysis framework |
| Author | Li, Tianhao |
| Author email | tianhaol@usc.edu; tianhaol@gmail.com |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Biomedical Engineering |
| School | Viterbi School of Engineering |
| Date defended/completed | 2008-07-28 |
| Date submitted | 2008 |
| Restricted until | Unrestricted |
| Date published | 2008-09-09 |
| Advisor (committee chair) |
Fu, Qian-Jie Mel, Bartlett |
| Advisor (committee member) |
Biederman, Irving Shannon, Robert |
| Abstract | Most currently available cochlear implant devices are designed to reflect the tonotopic representation of acoustic frequencies within the cochlea. Unfortunately, the electrode array cannot cover the entire cochlea due to physical limitations or patient-related factors. Therefore, CI patients generally listen to spectrally up-shifted and/or distorted speech. Acute studies suggest that speech performance is best when the acoustic input is spectrally matched to the cochlear place of stimulation; performance deteriorates as the spectral mismatch is increased. However, many CI users are able to somewhat adapt to spectrally shifted and distorted speech as they gain experience with their device. Motivated by both the theoretical and clinical implications of CI users’ perceptual adaptation, the present study explores perceptual adaptation to spectrally shifted vowels using behavioral studies and an acoustic analysis framework. Normal-hearing subjects are tested while listening to acoustic simulations of CI processing. These experiments are designed to address several issues related to perceptual adaptation to spectrally shifted speech. The first issue addressed by an experiment in this project is whether and where along the cochlea the lexically meaningful feedback is necessary for improving recognition performance of spectrally shifted vowels. Secondly, the effects of spectral shift extent on perceptual adaptation to spectrally shifted vowels are systematically investigated using an unsupervised learning protocol, including the effect of linearly spectral shift, the effect of different spectral envelope distortions, and the effect of spectral resolution on perceptual adaptation to severely-shifted vowels with and without concurrent exposures to moderately-shifted vowels. Finally, an acoustic analysis framework is developed to interpret experimental findings.; This framework is used to explore mechanisms that may underlie perceptual adaptation to spectrally shifted speech, as well as to functionally model speech recognition performance for spectrally shifted and/or degraded vowels in CI users. In terms of clinical relevance, the present study provides important guidelines for the development and refinement of fitting procedures and training protocols for post-lingually deafened CI users. In terms of theoretical relevance, the present study introduces some new perspectives regarding speech perception and adaptation. The result of the present study may also benefit currently available engineering techniques for automatic speech recognition. |
| Keyword | cochlear implant; perceptual learning; speech perception; acoustic analysis |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m1590 |
| Rights | Li, Tianhao |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | http://www.usc.edu/isd/libraries/services/ask_a_librarian/email/ |
| Filename | etd-Li-2354 |
| Archival file | uscthesesreloadpub_Volume44/etd-Li-2354.pdf |
Description
| Title | Page 1 |
| Full text | PERCEPTUAL ADAPTATION TO SPECTRALLY SHIFTED VOWELS: EXPERIMENT STUDIES AND AN ACOUSTIC ANALYSIS FRAMEWORK by Tianhao Li A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY BIOMEDICAL ENGINEERING December 2008 Copyright 2008 Tianhao Li |
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