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Neurophysiological Mechanisms of Speech Intelligibility under Masking and Distortion

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posted on 29.07.2021, 16:19 by Vibha ViswanathanVibha Viswanathan

Difficulty understanding speech in background noise is the most common hearing complaint. Elucidating the neurophysiological mechanisms underlying speech intelligibility in everyday environments with multiple sound sources and distortions is hence important for any technology that aims to improve real-world listening. Using a combination of behavioral, electroencephalography (EEG), and computational modeling experiments, this dissertation provides insight into how the brain analyzes such complex scenes, and what roles different acoustic cues play in facilitating this process and in conveying phonetic content. Experiment #1 showed that brain oscillations selectively track the temporal envelopes (i.e., modulations) of attended speech in a mixture of competing talkers, and that the strength and pattern of this attention effect differs between individuals. Experiment #2 showed that the fidelity of neural tracking of attended-speech envelopes is strongly shaped by the modulations in interfering sounds as well as the temporal fine structure (TFS) conveyed by the cochlea, and predicts speech intelligibility in diverse listening environments. Results from Experiments #1 and #2 support the theory that temporal coherence of sound elements across envelopes and/or TFS shapes scene analysis and speech intelligibility. Experiment #3 tested this theory further by measuring and computationally modeling consonant categorization behavior in a range of background noises and distortions. We found that a physiologically plausible model that incorporated temporal-coherence effects predicted consonant confusions better than conventional speech-intelligibility models, providing independent evidence that temporal coherence influences scene analysis. Finally, results from Experiment #3 also showed that TFS is used to extract speech content (voicing) for consonant categorization even when intact envelope cues are available. Together, the novel insights provided by our results can guide future models of speech intelligibility and scene analysis, clinical diagnostics, improved assistive listening devices, and other audio technologies.

Funding

Neurophysiological Mechanisms of Speech Intelligibility in Noise - A Quantitative Framework

National Institute on Deafness and Other Communication Disorders

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Effects of Sensorineural Hearing Loss on Robust Speech Coding

National Institute on Deafness and Other Communication Disorders

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Individual differences in supra-threshold sound encoding

National Institute on Deafness and Other Communication Disorders

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Physiological Signatures and Behavioral Correlates of Hidden Hearing Loss

National Institute on Deafness and Other Communication Disorders

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Individualized assays of supra-threshold hearing deficits

National Institute on Deafness and Other Communication Disorders

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Physiological evaluation of the signal-to-noise envelope power ratio with sensorineural hearing loss: Implications for speech intelligibility

Action on Hearing Loss

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ONR N00014-20-12709

History

Degree Type

Doctor of Philosophy

Department

Biomedical Engineering

Campus location

West Lafayette

Advisor/Supervisor/Committee Chair

Michael G. Heinz

Advisor/Supervisor/Committee co-chair

Barbara G. Shinn-Cunningham

Additional Committee Member 2

Edward L. Bartlett

Additional Committee Member 3

Joshua M. Alexander