Effects of Loud and Amplified Speech on Sentence and Word Intelligibility in Parkinson Disease PurposeIn the two experiments in this study, the author examined the effects of increased vocal effort (loud speech) and amplification on sentence and word intelligibility in speakers with Parkinson disease (PD).MethodsFive talkers with PD produced sentences and words at habitual levels of effort and using loud speech techniques. Amplified sets ... Article/Report
Article/Report  |   August 01, 2009
Effects of Loud and Amplified Speech on Sentence and Word Intelligibility in Parkinson Disease
 
Author Notes
  • Contact author: Amy T. Neel, Department of Speech and Hearing Sciences, University of New Mexico, MSC01 1195, Albuquerque, NM 87131-0001. E-mail: atneel@unm.edu.
Article Information
Special Populations / Older Adults & Aging / Speech, Voice & Prosody / Speech
Article/Report   |   August 01, 2009
Effects of Loud and Amplified Speech on Sentence and Word Intelligibility in Parkinson Disease
Journal of Speech, Language, and Hearing Research, August 2009, Vol. 52, 1021-1033. doi:10.1044/1092-4388(2008/08-0119)
History: Received June 6, 2008 , Accepted October 12, 2008
 
Journal of Speech, Language, and Hearing Research, August 2009, Vol. 52, 1021-1033. doi:10.1044/1092-4388(2008/08-0119)
History: Received June 6, 2008; Accepted October 12, 2008
Web of Science® Times Cited: 28

PurposeIn the two experiments in this study, the author examined the effects of increased vocal effort (loud speech) and amplification on sentence and word intelligibility in speakers with Parkinson disease (PD).

MethodsFive talkers with PD produced sentences and words at habitual levels of effort and using loud speech techniques. Amplified sets of sentences and words were created by increasing the intensity of habitual stimuli to the level of loud stimuli. Listeners rated the intelligibility of the 3 sets of sentences on a 1–7 scale and transcribed the 3 sets of words.

ResultsBoth loud speech and amplification significantly improved intelligibility for sentences and words. Loud speech resulted in greater intelligibility improvement than amplification.

ConclusionsBy comparing loud and amplified scores, about one third to one half of intelligibility improvement with loud speech could be attributed to increases in audibility or signal-to-noise ratio. Thus, factors other than increased intensity must be partly responsible for the loud speech benefit. Changes in articulation appear to play a relatively small role: Initial /h/ was the only consonant to consistently show improvement with loud speech. Phonatory changes such as improvements in F0 and spectral tilt may account for improved speech intelligibility using loud speech techniques.

Acknowledgments
This study was supported by a Research Allocations Committee Small Grant from the University of New Mexico. Thanks to Amy Wohlert for providing the participants for this study and to Amy Beveridge for her assistance in the listening experiments.
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