Date of Award

Spring 2012

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical and Computer Engineering

Supervisor

Ian Bruce

Language

English

Abstract

In this thesis, the importance of temporal fine structure (TFS) in speech perception is investigated. It is well accepted that TFS is important for sound localization and pitch perception, while envelope (ENV) is primarily responsible for speech perception. Recently, a significant contribution of TFS in speech perception has been suggested. This was linked to the improved ability of normal-hearing subjects to understand speech in fluctuating-power background noise as compared to hearing-impaired people. However, the accuracy of this claim is questionable since TFS and ENV are correlated and one can recover ENV to some extent if provided with TFS-only speech. In this work, we quantify the relative advantages of TFS and the possible influence of recovered ENV on speech recognition scores. We used a computational model for the cat auditory periphery, which was modified to match the available data for human cochlear tuning. The output of the model was analyzed by the spectro-temporal modulation index (STMI) metric to predict speech intelligibility. A speech recognition experiment was conducted on five normal-hearing subjects and the STMI predictions were mapped to intelligibility using a specially constructed mapping function. The TFS role was quantified by examining the TFS intelligibility scores and the corresponding intelligibility predictions from ENV recovery. Our results show that although ENV recovery has some influence on the intelligibility results, it cannot account for the total reported intelligibility.

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