Research Note  |   February 2010
Formant Centralization Ratio: A Proposal for a New Acoustic Measure of Dysarthric Speech
 
Author Affiliations & Notes
  • Shimon Sapir
    University of Haifa, Haifa, Israel
  • Lorraine O. Ramig
    University of Colorado at Boulder and National Center for Voice and Speech, Denver, CO
  • Jennifer L. Spielman
    University of Colorado at Boulder and National Center for Voice and Speech, Denver, CO
  • Cynthia Fox
    National Center for Voice and Speech, Denver, CO
  • Disclaimer
    Disclaimer×
    Lorraine O. Ramig and Cynthia Fox have ownership interest in LSVT Global LLC (a for-profit organization that runs training courses and sells products related to LSVT treatment). All members of this research team have fully disclosed any conflict of interest, and their conflict-of-interest management plan was approved by the Office of Conflict of Interest and Commitment at the University of Colorado at Boulder.
    Lorraine O. Ramig and Cynthia Fox have ownership interest in LSVT Global LLC (a for-profit organization that runs training courses and sells products related to LSVT treatment). All members of this research team have fully disclosed any conflict of interest, and their conflict-of-interest management plan was approved by the Office of Conflict of Interest and Commitment at the University of Colorado at Boulder.×
  • Contact author: Shimon Sapir, Department of Communication Sciences and Disorders, Faculty of Social Welfare and Health Sciences, University of Haifa, Haifa, Mount Carmel, 39105 Israel. E-mail: sapir@research.haifa.ac.il.
Article Information
Speech, Voice & Prosodic Disorders / Dysarthria / Hearing & Speech Perception / Acoustics / Speech, Voice & Prosody / Speech
Research Note   |   February 2010
Formant Centralization Ratio: A Proposal for a New Acoustic Measure of Dysarthric Speech
Journal of Speech, Language, and Hearing Research, February 2010, Vol. 53, 114-125. doi:10.1044/1092-4388(2009/08-0184)
History: Received August 31, 2008 , Revised January 25, 2009 , Accepted July 4, 2009
 
Journal of Speech, Language, and Hearing Research, February 2010, Vol. 53, 114-125. doi:10.1044/1092-4388(2009/08-0184)
History: Received August 31, 2008; Revised January 25, 2009; Accepted July 4, 2009
Web of Science® Times Cited: 21

Purpose: The vowel space area (VSA) has been used as an acoustic metric of dysarthric speech, but with varying degrees of success. In this study, the authors aimed to test an alternative metric to the VSA—the formant centralization ratio (FCR), which is hypothesized to more effectively differentiate dysarthric from healthy speech and register treatment effects.

Method: Speech recordings of 38 individuals with idiopathic Parkinson’s disease and dysarthria (19 of whom received 1 month of intensive speech therapy [Lee Silverman Voice Treatment; LSVT LOUD]) and 14 healthy control participants were acoustically analyzed. Vowels were extracted from short phrases. The same vowel-formant elements were used to construct the FCR, expressed as (F2 + F2ɑ + F1 + F1 ) / (F2 + F1ɑ), the VSA, expressed as ABS([F1 × (F2ɑ – F2 ) + F1ɑ × (F2 – F2 ) + F1 × (F2 – F2ɑ)] / 2), a logarithmically scaled version of the VSA (LnVSA), and the F2 /F2 ratio.

Results: Unlike the VSA and the LnVSA, the FCR and F2 /F2 ratio robustly differentiated dysarthric from healthy speech and were not gender sensitive. All metrics effectively registered treatment effects and were strongly correlated with each other.

Conclusion: Albeit preliminary, the present findings indicate that the FCR is a sensitive, valid, and reliable acoustic metric for distinguishing dysarthric from unimpaired speech and for monitoring treatment effects, probably because of reduced sensitivity to interspeaker variability and enhanced sensitivity to vowel centralization.

Acknowledgment
This research was funded by National Institute on Deafness and Other Communication Disorders Grant R01 DC1150.
Order a Subscription
Pay Per View
Entire Journal of Speech, Language, and Hearing Research content & archive
24-hour access
This Article
24-hour access