Vowel Identification by Listeners With Hearing Impairment in Response to Variation in Formant Frequencies PurposeThis study examined the influence of presentation level and mild-to-moderate hearing loss on the identification of a set of vowel tokens systematically varying in the frequency locations of their second and third formants.MethodFive listeners with normal hearing (NH listeners) and five listeners with hearing impairment (HI listeners) identified synthesized vowels ... Article
Article  |   August 01, 2011
Vowel Identification by Listeners With Hearing Impairment in Response to Variation in Formant Frequencies
 
Author Affiliations & Notes
  • Michelle R. Molis
    National Center for Rehabilitative Auditory Research, Portland VA Medical Center, Portland, OR
    National Center for Rehabilitative Auditory Research, Portland VA Medical Center, Portland, OR
  • Marjorie R. Leek
    National Center for Rehabilitative Auditory Research, Portland VA Medical Center, Portland, OR
    National Center for Rehabilitative Auditory Research, Portland VA Medical Center, Portland, OR
  • Correspondence to Michelle R. Molis: michelle.molis@va.gov
  • Editor: Robert Schlauch
    Editor: Robert Schlauch×
  • Associate Editor: Kathryn Arehart
    Associate Editor: Kathryn Arehart×
Article Information
Hearing Disorders / Speech, Voice & Prosody / Hearing
Article   |   August 01, 2011
Vowel Identification by Listeners With Hearing Impairment in Response to Variation in Formant Frequencies
Journal of Speech, Language, and Hearing Research, August 2011, Vol. 54, 1211-1223. doi:10.1044/1092-4388(2010/09-0218)
History: Received October 1, 2009 , Revised May 1, 2010 , Accepted December 14, 2010
 
Journal of Speech, Language, and Hearing Research, August 2011, Vol. 54, 1211-1223. doi:10.1044/1092-4388(2010/09-0218)
History: Received October 1, 2009; Revised May 1, 2010; Accepted December 14, 2010
Web of Science® Times Cited: 4

PurposeThis study examined the influence of presentation level and mild-to-moderate hearing loss on the identification of a set of vowel tokens systematically varying in the frequency locations of their second and third formants.

MethodFive listeners with normal hearing (NH listeners) and five listeners with hearing impairment (HI listeners) identified synthesized vowels that represented both highly identifiable and ambiguous examples of /i/, /ʊ/, and /ɝ/.

ResultsResponse patterns of NH listeners showed significant changes, with an increase in presentation level from 75 dB SPL to 95 dB SPL, including increased category overlap. HI listeners, listening only at the higher level, showed greater category overlap than normal and overall identification patterns that differed significantly from those of NH listeners. Excitation patterns based on estimates of auditory filters suggested smoothing of the internal representations, resulting in impaired formant resolution.

ConclusionsBoth increased presentation level for NH listeners and the presence of hearing loss produced a significant change in vowel identification for this stimulus set. Major differences were observed between NH listeners and HI listeners in vowel category overlap and in the sharpness of boundaries between vowel tokens. It is likely that these findings reflect imprecise internal spectral representations due to reduced frequency selectivity.

Acknowledgments
This research was supported by National Institute on Deafness and Other Communication Disorders Grant R01 DC 00626. Some support for preparation of this article was provided by the Department of Veterans Affairs. Portions of this work were carried out while we were affiliated with the Army Audiology and Speech Center, Walter Reed Army Medical Center, Washington, DC. The opinions or assertions contained herein are our private views and are not to be construed as official or as reflecting the views of the Department of Veterans Affairs, the Department of the Army, or the Department of Defense.
Portions of this research were presented at the 146th meeting of the Acoustical Society of America, held in Austin, Texas, in November 2003 (and published in The Journal of the Acoustical Society of America, Volume 114, p. 2359), and at the March 2006 meeting of the American Auditory Society, held in Scottsdale, AZ.
We would like to thank Van Summers and Frederick Gallun for their helpful suggestions and discussions as well as Garnett McMillan for statistical assistance.
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