Vocal Dose Measures Quantifying Accumulated Vibration Exposure in Vocal Fold Tissues Research Article
Research Article  |   August 01, 2003
Vocal Dose Measures
 
Author Affiliations & Notes
  • Ingo R. Titze
    University of Iowa, Iowa City and National Center for Voice and Speech, The Denver Center for the Performing Arts Denver, CO
  • Jan G. Švec
    National Center for Voice and Speech, The Denver Center for the Performing Arts Denver, CO
  • Peter S. Popolo
    National Center for Voice and Speech, The Denver Center for the Performing Arts Denver, CO
  • Contact author: Ingo R. Titze, PhD, National Center for Voice and Speech, Denver Center for the Performing Arts, 1245 Champa Street, Denver, CO 80204. E-mail: ingo-titze@uiowa.edu
Article Information
Speech, Voice & Prosody / Speech / Research Articles
Research Article   |   August 01, 2003
Vocal Dose Measures
Journal of Speech, Language, and Hearing Research, August 2003, Vol. 46, 919-932. doi:10.1044/1092-4388(2003/072)
History: Received September 4, 2002 , Accepted January 2, 2003
 
Journal of Speech, Language, and Hearing Research, August 2003, Vol. 46, 919-932. doi:10.1044/1092-4388(2003/072)
History: Received September 4, 2002; Accepted January 2, 2003
Web of Science® Times Cited: 84

To measure the exposure to self-induced tissue vibration in speech, three vocal doses were defined and described: distance dose, which accumulates the distance that tissue particles of the vocal folds travel in an oscillatory trajectory; energy dissipation dose, which accumulates the total amount of heat dissipated over a unit volume of vocal fold tissues; and time dose, which accumulates the total phonation time. These doses were compared to a previously used vocal dose measure, the vocal loading index, which accumulates the number of vibration cycles of the vocal folds. Empirical rules for viscosity and vocal fold deformation were used to calculate all the doses from the fundamental frequency (F0) and sound pressure level (SPL) values of speech. Six participants were asked to read in normal, monotone, and exaggerated speech and the doses associated with these vocalizations were calculated. The results showed that large F0 and SPL variations in speech affected the dose measures, suggesting that accumulation of phonation time alone is insufficient. The vibration exposure of the vocal folds in normal speech was related to the industrial limits for hand-transmitted vibration, in which the safe distance dose was derived to be about 500 m. This limit was found rather low for vocalization; it was related to a comparable time dose of about 17 min of continuous vocalization, or about 35 min of continuous reading with normal breathing and unvoiced segments. The voicing pauses in normal speech and dialogue effectively prolong the safe time dose. The derived safety limits for vocalization will likely require refinement based on a more detailed knowledge of the differences in hand and vocal fold tissue morphology and their response to vibrational stress, and on the effect of recovery of the vocal fold tissue during voicing pauses.

Acknowledgment
The work was supported by National Institutes of Health Grant DC RO1 04224–01.
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