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Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Date of Graduation

Spring 2018

Document Type

Dissertation

Degree Name

Doctor of Audiology (AuD)

Department

Department of Communication Sciences and Disorders

Advisor(s)

Yingjiu Nie

Lincoln C. Gray

Christopher G. Clinard

Abstract

This project will use an objective approach to evaluate the effect of inter-subsequence frequency difference and amplitude-modulation rate on build-up stream segregation in CI users. Six post-lingually deafened CI users, between 18 and 75 years old, have been studied and compared to four normal-hearing listeners, between 18 and 75 years old. Repeated pairs of A and B noise bursts were adopted from a previous work (Nie et al., 2014) with modifications and additional conditions, where A and B bursts are narrow-band noise carrying sinusoidal amplitude modulation (AM). The A and B bursts in a stimulus sequence differed either in the center frequency of the noise band, or in the AM-rate, or both. Subjects identified a deviant in a rhythmic stream and performance (d’) reflects the strength of stream segregation. The build-up effect was assessed by comparing performances during long and short sequence durations. Results of this study reveal both CI users and NH listeners showed evidence of build-up effect; however, NH listeners showed stronger stream segregation abilities. Duration has the strongest effect for the 16-10 condition and the weakest effect for the 10-10 condition when both groups were analyzed together. This could indicate that frequency separation is a cue for build-up effect. Frequency separation elicited stream segregation in both CI users and NH listeners. Any amount of frequency separation (within the given conditions) provided cues for stream segregation in NH listeners. Only the largest frequency separation (16-10) provided cues for stream segregation in CI listeners. This could indicate spectral interference still occurs even with 3 channels of separation. Finally, AM-rate separation did not elicit stream segregation in either CI users or NH listeners. These findings are contradictory to previous findings and indicate temporal pitch perception may be used by CI users to separate target auditory streams from background noise.

Available for download on Tuesday, April 14, 2020

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