THE EFFECTS OF FREQUENCY AND INTENSITY LEVEL ON GLOTTAL CLOSURE IN NORMAL SUBJECTS

The degree of glottal closure during phonation has an influence on voi ce quality and it is related to the robustness of the voice source. To quantify glottal closure a frame of reference was created by investig ating 47 healthy men and 92 healthy women with no vocal complaints usi ng videolaryngostroboscopy. Observing recorded images the degree of gl ottal closure was rated with a percentage. Results indicate that men h ave better glottal closure than women (P < 0.001). An increase in voca l intensity is related to improved glottal closure (P < 0.001), and in women a negative relationship was established between pitch and glott al closure (P < 0.001). Normal glottal closure in men is a complete cl osure, whereas in women a closure of at least 90% should be attained. If these percentages cannot be established during loud phonation, it s uggests the presence of a less robust larynx. To evaluate and quantify the function of the voice source, in clinical practice the larynx sho uld not be observed at only one intensity level, but at a variety of i ntensity and frequency levels.