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Vocal dose measures: quantifying accumulated vibration exposure in vocal fold tissues
Ingo R Titze1, Jan G Svec, Peter S Popolo
1University of Iowa, Iowa City, USA. ingo-titze@uiowa.edu
Journal of Speech, Language, and Hearing Research : JSLHR
|September 10, 2003
Summary
New vocal doses measure tissue vibration exposure during speech. Phonation time alone is insufficient; safe vocalization limits are lower than industrial vibration limits.
Area of Science:
- Biomechanics
- Speech Science
- Occupational Health
Background:
- Assessing vocal fold vibration exposure is crucial for understanding vocal health.
- Existing measures like the vocal loading index may not fully capture tissue stress.
Purpose of the Study:
- To define and compare novel vocal dose measures for self-induced tissue vibration in speech.
- To establish preliminary safety limits for vocal fold vibration exposure.
Main Methods:
- Defined distance dose, energy dissipation dose, and time dose based on vocal fold tissue particle oscillation.
- Calculated doses using fundamental frequency (F0) and sound pressure level (SPL) from speech recordings.
- Compared vocal doses across normal, monotone, and exaggerated speech patterns.
Main Results:
- Vocal dose measures are significantly affected by variations in F0 and SPL.
- Derived safe distance dose limit for vocalization is approximately 500 m, translating to ~17 minutes of continuous phonation.
- Voicing pauses in natural speech extend safe phonation time, highlighting the importance of non-phonatory segments.
Conclusions:
- Phonation time alone is an inadequate measure of vocal fold vibration exposure.
- Preliminary safety limits for vocalization suggest lower tolerance compared to hand-transmitted vibration.
- Further research is needed on tissue morphology and recovery during pauses to refine safety limits.