I have used planigraphy in the study of the physiology of the larynx during phonation. Phonation starts with breathing. Most of the laryngeal sounds for the purpose of speaking or singing are produced during expiration. Breathing during speaking differs in many ways from breathing during rest. When at rest one inhales and exhales a small amount of air, about 500 to 600 cc., but for the purpose of speaking one must inhale about 1,500 to 2,400 cc. of air or more. During rest the periods of inhalation and exhalation are equal. During speech the period of exhalation is much longer than that of inhalation. Inhalation should be rapid and noiseless. Exhalation is audible as an aspirated sound. As the inspiration becomes deeper and inaudible, the vocal cords come to lie almost flush against the lateral wall of the larynx. The chink of the glottis becomes almost the same size as
GRIESMAN BL. MECHANISM OF PHONATION DEMONSTRATED BY PLANIGRAPHY OF THE LARYNX. Arch Otolaryngol. 1943;38(1):17–26. doi:10.1001/archotol.1943.00670040026003
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