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The impact of spectrally asynchronous delay on the intelligibility of conversational speech

Ortmann, Amanda (2012) The impact of spectrally asynchronous delay on the intelligibility of conversational speech. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Conversationally spoken speech is rampant with rapidly changing and complex acoustic cues that individuals are able to hear, process, and encode to meaning. For many hearing-impaired listeners, a hearing aid is necessary to hear these spectral and temporal acoustic cues of speech. For listeners with mild-moderate high frequency sensorineural hearing loss, open-fit digital signal processing (DSP) hearing aids are the most common amplification option. Open-fit DSP hearing aids introduce a spectrally asynchronous delay to the acoustic signal by allowing audible low frequency information to pass to the eardrum unimpeded while the aid delivers amplified high frequency sounds to the eardrum that has a delayed onset relative to the natural pathway of sound. These spectrally asynchronous delays may disrupt the natural acoustic pattern of speech. The primary goal of this study is to measure the effect of spectrally asynchronous delay on the intelligibility of conversational speech by normal-hearing and hearing-impaired listeners.
A group of normal-hearing listeners (n = 25) and listeners with mild-moderate high frequency sensorineural hearing loss (n = 25) participated in this study. The acoustic stimuli included 200 conversationally-spoken recordings of the low predictability sentences from the revised speech perception in noise test (r-SPIN). These 200 sentences were modified to control for audibility for the hearing-impaired group and so that the acoustic energy above 2 kHz was delayed by either 0 ms (control), 4ms, 8ms, or 32 ms relative to the low frequency energy. The data were analyzed in order to find the effect of each of the four delay conditions on the intelligibility of the final key word of each sentence.
Normal-hearing listeners were minimally affected by the asynchronous delay. However, the hearing-impaired listeners were deleteriously affected by increasing amounts of spectrally asynchronous delay. Although the hearing-impaired listeners performed well overall in their perception of conversationally spoken speech in quiet, the intelligibility of conversationally spoken sentences significantly decreased when the delay values were equal to or greater than 4 ms. Therefore, hearing aid manufacturers need to restrict the amount of delay introduced by DSP so that it does not distort the acoustic patterns of conversational speech.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairPalmer, Catherinepalmercv@upmc.eduCVP
Committee MemberDurrant, Johndurrant@pitt.eduDURRANT
Committee MemberPratt, Sheilaspratt@pitt.eduSPRATT
Committee MemberUchanski,
Date: 11 June 2012
Date Type: Publication
Defense Date: 13 April 2012
Approval Date: 11 June 2012
Submission Date: 20 April 2012
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 140
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: speech perception, hearing aids
Date Deposited: 11 Jun 2012 16:21
Last Modified: 19 Dec 2016 14:38


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