Physiological aspects of the glottal sound generator
M. Hirano · The Journal of the Acoustical Society of America · 1978
This paper describes the function of laryngeal muscles in regulating the glottal sound generator. The glottal sound generator, i.e., the vocal fold, has a layered structure. From the anatomical point of view, one can differentiate five layers, all having different mechanical properties [M. Hirano et al., J. Acoust. Soc. Am. 58, S13 (1975)]. From the physiological point of view, the layers may be divided into two major categories: the outer layer, i.e., the mucous membrane, which receives only passive regulation of the mechanical property, and the inner layer, i.e., the vocalis muscle, which has both active and passive regulations for the mechanical property. The ratio of the stiffness of each layer during normal phonation is estimated based on the measurement of the degree of elongation of each layer of an excised fresh human vocal fold. Then, the effect of laryngeal adjustment on the change in stiffness of the entire vocal fold is investigated by simulating the contraction of each of the cricothyroid and the vocalis muscles in dogs' larynx. The results are examined in reference to behavior of each layer during normal vibration of vocal fold observed with ultra-high-speed photography.