A computational study of the effects of vocal fold stiffness parameters on voice production.
Xiaojian Wang, Weili Jiang, Xudong Zheng and 1 others
PMID 31628047WHAT IT FOUND
Lengthwise stiffness in the ligament layer had the largest effect on pitch and airflow in a computer model of vocal fold vibration.
Cover stiffness was small overall, but changing sideways stiffness in the cover layer could markedly alter open phase and closing speed.
Key findings
01Ligament longitudinal stiffness had the largest effect on vocal fold natural frequencies, and cover transverse stiffness almost had no effect.
02Among all stiffness parameters, ligament longitudinal stiffness had the most dominant effect on fundamental frequency and was most effective in controlling flow rates.
03Although cover layer stiffness overall had a very small effect, varying cover transverse stiffness could cause significant changes in open quotient and closing speed.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
This is a computer model, not a study of patients, so it does not show what stiffness changes do to a real person's voice. The model used one vocal fold shape, one set of layer thicknesses and one subglottal pressure, so other anatomy or voice tasks may behave differently. The vocal tract shape was fixed, so the results are limited to one speech sound or phonation condition. Vocal fold tissue was modeled as linear elastic, while real vocal fold tissue is nonlinear. An artificial gap was enforced between the vocal folds, and leakage was about 28% of the maximum flow rate, which may affect closure-related outputs. Cases with chaotic vibration were excluded from analysis.
The easy way to misread this
Do not read these stiffness effects as tested clinical findings. The work used one computer model of a single vocal fold shape and one subglottal pressure, and it did not treat patients or measure voice outcomes.