Assessing Vowel Centralization in Dysarthria: A Comparison of Methods Purpose The strength of the relationship between vowel centralization measures and perceptual ratings of dysarthria severity has varied considerably across reports. This article evaluates methods of acoustic-perceptual analysis to determine whether procedural changes can strengthen the association between these measures. Method Sixty-one speakers (17 healthy individuals and 44 ... Research Article
Research Article  |   February 01, 2017
Assessing Vowel Centralization in Dysarthria: A Comparison of Methods
 
Author Affiliations & Notes
  • Annalise R. Fletcher
    Department of Communication Disorders and New Zealand Institute of Language, Brain & Behaviour, University of Canterbury, Christchurch
  • Megan J. McAuliffe
    Department of Communication Disorders and New Zealand Institute of Language, Brain & Behaviour, University of Canterbury, Christchurch
  • Kaitlin L. Lansford
    School of Communication Science & Disorders, Florida State University, Tallahassee
  • Julie M. Liss
    Department of Speech and Hearing Science, Arizona State University, Tempe
  • Disclosure: The authors have declared that no competing interests existed at the time of publication.
    Disclosure: The authors have declared that no competing interests existed at the time of publication. ×
  • Correspondence to Annalise R. Fletcher: annalise.fletcher@canterbury.ac.nz
  • Editor: Joan Sussman
    Editor: Joan Sussman×
  • Associate Editor: Joan Sussman
    Associate Editor: Joan Sussman×
Article Information
Speech, Voice & Prosodic Disorders / Dysarthria / Hearing & Speech Perception / Acoustics / Speech, Voice & Prosody / Speech / Research Articles
Research Article   |   February 01, 2017
Assessing Vowel Centralization in Dysarthria: A Comparison of Methods
Journal of Speech, Language, and Hearing Research, February 2017, Vol. 60, 341-354. doi:10.1044/2016_JSLHR-S-15-0355
History: Received October 9, 2015 , Revised April 11, 2016 , Accepted July 15, 2016
 
Journal of Speech, Language, and Hearing Research, February 2017, Vol. 60, 341-354. doi:10.1044/2016_JSLHR-S-15-0355
History: Received October 9, 2015; Revised April 11, 2016; Accepted July 15, 2016

Purpose The strength of the relationship between vowel centralization measures and perceptual ratings of dysarthria severity has varied considerably across reports. This article evaluates methods of acoustic-perceptual analysis to determine whether procedural changes can strengthen the association between these measures.

Method Sixty-one speakers (17 healthy individuals and 44 speakers with dysarthria) read a standard passage. To obtain acoustic data, 2 points of formant extraction (midpoint and articulatory point) and 2 frequency measures (Hz and Bark) were trialed. Both vowel space area and an adapted formant centralization ratio were calculated using first and second formants of speakers' corner vowels. Twenty-eight listeners rated speech samples using different prompts: one with a focus on intelligibility, the other on speech precision.

Results Perceptually, listener ratings of speech precision provided the best index of acoustic change. Acoustically, the combined use of an articulatory-based formant extraction point, Bark frequency units, and the formant centralization ratio was most effective in explaining perceptual ratings. This combination of procedures resulted in an increase of 17% to 27% explained variance between measures.

Conclusions The procedures researchers use to assess articulatory impairment can significantly alter the strength of relationship between acoustic and perceptual measures. Procedures that maximize this relationship are recommended.

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