Mechanism of Phonation Demonstrated by Planigraphy of the Larynx

Abstract

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 the lumen of the trachea. During expiration, however, there are narrowing of the chink and adduction of the vocal cords, ventricles and ventricular folds toward the midline. This approximation of the false and true cords produces resistance to the expiratory current of air, and therefore a friction noise.During expiration without tone production there is a wide glottic chink, through which air escapes easily. In order that a tone may be produced the vocal cords are drawn close together in the position of phonation. There remains always a very small phonatory gap between the approximated vocal cords. This gap is necessary because there must be some room for the vibrations of the vocal cords.The approximated vocal cords are set in vibration by the air pressure from below. The obstructed air current escapes in puffs during the opening phase of the vibration and is interrupted by the closing phase.The vibrating vocal cords interrupt the constant flow of the air current and generate condensation and rarefaction of air, i. e., a sound wave. The pitch of this sound wave is determined by the frequency of the interruptions a second.The sound originating at the vocal cords consists of a fundamental tone and numerous harmonically related overtones. The changing shapes and dimensions of the resonating cavities, particularly the air column spaces above the vocal cords, such as the supraglottic space, the pharynx, the mouth and lips, the nasal cavities and the nasopharynx, diminish or amplify certain overtones and give the voice its characteristic qualities and human peculiarity. Figure 1 demonstrates four phases of sound production. All planigraphs were made at the same depth of 2 cm. behind the Adam's apple. A shows the larynx sounding the vowel a at a frequency of 435 cycles ; B, the vowel u at the same frequency ; C, the vowel u one octave lower, at a frequency of about 218 cycles, and D, the vowel it one octave higher, at a frequency of 870 cycles.Read at the meeting

Four Laminagraphic Studies of Vocal Fold Thickness

“…Griesman [1] also reported th a t the folds appeared thinner in the falsetto register. In order to clarify this relationship, two related studies were conducted: in the first, vocal fold thickness -as a function of frequency -is compared for both the modal and the falsetto regis ters; in the second, data were obtained concerning the nature of vocal fold thickness as a function of f0 in the falsetto register only.…”

“…Since Griesman's publication in 1943 of his use of lam inagraphy in the study of vocal folds [1], a num ber of authors have utilized this technique of laryngeal investigation. Van den Berg [11] and Moolenaar-B ijl [8], for example, have used lam inagraphy to explain and illustrate observations of basic laryngeal physiology, while others [9,12] have used this m ethod to investigate voice disorders.…”

Correlating Degree of Thyroid Tilt Independent of fo Control as a Mechanism for Phonatory Density with EGG and Acoustic Measures across Loudness Conditions

“…Seen as indicating similar concepts, modal, M1 [43], or chest registration has often been suggested linked to vocal fold shortening and increased intensity through thyroarytenoid engagement [21]. However, previous studies of vocal registers related to vocal fold vibratory patterns and vocal intensity measured in dB have produced disparate findings related to vocal fold lengthening and tilting [6‒8, 11, 12, 14, 16, 21, 44]. These disparities may be related to what Hollien et al [11], Hollien and Curtis [12] highlighted as as-of-yet unstudied variations within modal registers, calling for further studies of types and classes of vocal fold activity related to vocal fold length changes.…”