Subglottic Pressure Lab Report

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Subglottic pressure:23

The force of the expiratory blast of air, as well as determining the volume of sound, also influences slightly the pitch. Increase in air pressure in associated with increase in pitch, when it is increased in volume. It has been suggested that in the production of very high notes the false cords come into contact with the upper surface of vocal cords and this raise the frequency of their vibrations.

Theories of mechanism of vocal fold vibration The vocal fold vibration is essential to voice production was demonstrated in the first canine vocal fold experiment performed by Ferrein in 1974. Subsequently, there have been a number of hypothesis about how vocal fold vibration is controlled.24

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The vibrations are brought about by a rapid series of separate active contractions of the thyroarytenoid muscle. The vibrations of the cords are not dependent on the air stream through larynx. It is claimed that the thyroarytenoid muscles contains special transverse fibers. The contraction of these transverse fibers separates the approximated cords, while their relaxations allows the cord to recoil by virtue of their inherent elasticity and to close the glottis. Thus the cord vibrations are maintained by rhythmical cycles of active contraction and relaxation of thyroarytenoid muscles. These rhythmic contractions are the result of excitation by rhythmic discharge of impulse of motor neurons, which in their form are stimulated during phonation by rhythmic bursts of impulse generated in cerebral cortex. All these are at the same specific frequency (thus clonic contraction produces vibrations of the cords at this particular frequency). The end result of this is that the series of puffs of air emerging from the larynx are also at this self same frequency resulting therefore in the production of a tone or intended specific frequency or pitch. The laryngeal air pressure has no modifying effect on the frequency of the movements of vocal cords but it may have a supplementary action in varying the amplitude of these cord…show more content…
(1). The Bernoulli’s effects of airflow through the glottis generate negative force that pulls the vocal fold medially.
(2). The elasticity (mainly passive recoiling) of the vocal fold, and
(3). Drop in subglottal pressure. These factors together cause the vocal folds to close toward their approximated position. When the closure of the aperture obstructs airflow, a new rise of subglottal pressure builds up until it is again sufficient to deform the vocal fold tissues, and another cycle of the opening phase starts. This cycle of vibration is called the glottal cycle.

Classification of voice disorders
Currently there is no standardized nomenclature regarding voice disorder and pathological conditions do the vocal folds. A number of classification proposal have been advanced, but these have been limited to specific types of voice disorders such as muscle tension dysphasia. Traditional texts have also tried to classify voice disorders as functional or organic, or as disorders resulting from vocal fold closure or lack of vocal fold closure. These descriptive categories lack reference to pathologic conditions or the presence or absence of a lesion. No such

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