The effect of sound intensity on velopharyngeal function in normal individuals

Velopharyngeal closure is an important physiological process contributing to the normal function of speech and swallowing. The aim of this study was to analyze the influence of sound intensity on velopharyngeal function in normal individuals.

Lateral cephalograms of 38 volunteers obtained at rest and during phonation of vowel /i:/ at both high and low sound intensity were carefully analyzed. The digital sound level meter was used to evaluate and record the sound intensity of the phonation process. The angular and linear parameters on the lateral cephalograms were then measured to reveal the correlation between sound intensity and velopharyngeal closure.

All the angular parameter values measured in the study were significantly greater in high sound intensity condition. As for linear parameters, all values were found to be significantly larger at high sound intensity, except for the effective velopharyngeal length and the vertical velopharyngeal length. A multiple linear regression model was set up to describe the correlation between the sound intensity, the effective velopharyngeal length, and velopharyngeal closure. With the increase of sound intensity and the decrease of the effective velopharyngeal length, the width of velopharyngeal closure is enlarged.

As one of the characteristic features of sound wave, the sound intensity was found to affect the objectively measured parameters of velopharyngeal closure on lateral cephalograms.