Intelligibility of Clear Speech: Effect of Instruction PurposeThe authors investigated how clear speech instructions influence sentence intelligibility.MethodTwelve speakers produced sentences in habitual, clear, hearing impaired, and overenunciate conditions. Stimuli were amplitude normalized and mixed with multitalker babble for orthographic transcription by 40 listeners. The main analysis investigated percentage-correct intelligibility scores as a function of the 4 conditions ... Article
Article  |   October 01, 2013
Intelligibility of Clear Speech: Effect of Instruction
 
Author Affiliations & Notes
  • Jennifer Lam
    University at Buffalo, State University of New York
  • Kris Tjaden
    University at Buffalo, State University of New York
  • Correspondence to Jennifer Lam: jkyun@buffalo.edu
  • Editor: Jody Kreiman
    Editor: Jody Kreiman×
  • Associate Editor: Kate Bunton
    Associate Editor: Kate Bunton×
Article Information
Hearing Disorders / Speech, Voice & Prosody / Speech
Article   |   October 01, 2013
Intelligibility of Clear Speech: Effect of Instruction
Journal of Speech, Language, and Hearing Research, October 2013, Vol. 56, 1429-1440. doi:10.1044/1092-4388(2013/12-0335)
History: Received October 23, 2012 , Revised December 20, 2012 , Accepted January 8, 2013
 
Journal of Speech, Language, and Hearing Research, October 2013, Vol. 56, 1429-1440. doi:10.1044/1092-4388(2013/12-0335)
History: Received October 23, 2012; Revised December 20, 2012; Accepted January 8, 2013
Web of Science® Times Cited: 7

PurposeThe authors investigated how clear speech instructions influence sentence intelligibility.

MethodTwelve speakers produced sentences in habitual, clear, hearing impaired, and overenunciate conditions. Stimuli were amplitude normalized and mixed with multitalker babble for orthographic transcription by 40 listeners. The main analysis investigated percentage-correct intelligibility scores as a function of the 4 conditions and speaker sex. Additional analyses included listener response variability, individual speaker trends, and an alternate intelligibility measure: proportion of content words correct.

ResultsRelative to the habitual condition, the overenunciate condition was associated with the greatest intelligibility benefit, followed by the hearing impaired and clear conditions. Ten speakers followed this trend. The results indicated different patterns of clear speech benefit for male and female speakers. Greater listener variability was observed for speakers with inherently low habitual intelligibility compared to speakers with inherently high habitual intelligibility. Stable proportions of content words were observed across conditions.

ConclusionsClear speech instructions affected the magnitude of the intelligibility benefit. The instruction to overenunciate may be most effective in clear speech training programs. The findings may help explain the range of clear speech intelligibility benefit previously reported. Listener variability analyses suggested the importance of obtaining multiple listener judgments of intelligibility, especially for speakers with inherently low habitual intelligibility.

Acknowledgments
This research was supported by National Institute on Deafness and Other Communication Disorders Grant R01DC004689. Portions of this study were presented at the June 2011 Conference on Speech Motor Control, Groningen, the Netherlands. We thank Joan Sussman and Elaine Stathopoulos for their valuable comments on a previous version of this article.
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