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CSDL8 - Physiology of Phonation Non-speech Laryngeal...

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Unformatted text preview: Physiology of Phonation Non-speech Laryngeal Functions Coughing Irritation of the respiratory passages Deep inhalation Wide abducted vocal folds Tensing & tight adduction of vocal folds Elevation of the larynx Throat clearing Abdominal fixation Swallowing The Bernoulli Effect Given a constant volume flow of air or fluid..... At a point of constriction there will be a decrease in air pressure perpendicular to the flow AND an increase in velocity of the flow 1 The Bernoulli Effect & Phonation The vocal folds are what forms the constriction that changes pressure and flow Air pressure builds up and forces the vocal folds open Because the vocal folds are elastic they want to return to a state of rest (closed) but the pressure is too great The pressure drops because of the Bernoulli effect and the vocal folds close The cycle begins again The Bernoulli Effect & Phonation Stages of Phonation Adduct the vocal folds & move them into the airstream Vocal attack Hold the vocal folds in a fixed position in the airstream Sustained phonation Abduct the vocal folds Termination of phonation 2 Types of Vocal Attack Simultaneous vocal attack Adduction of the vocal folds & the onset of respiration occur simultaneously Breathy vocal attack Significant airflow begins before adduction of the vocal folds Glottal attack Adduction of vocal folds occurs prior to airflow Termination of Phonation Abduct the vocal folds & move them out of the airstream far enough to reduce the turbulence When turbulence is reduced sufficiently, the vocal folds stop vibrating Muscles controlling both abduction and adduction can completed contraction in about 9 msec Sustained Phonation Requires maintaining laryngeal posture through tonic (sustained) contraction of the musculature The vocal folds are "held in place" Vibration of the vocal folds is NOT the product of repeated adduction and abduction of the vocal folds 3 Vocal Registers Mode of vibration Pattern of activity that the vocal folds go through during one cycle of vibration Cycle of vibration From one point in the vibration pattern until that point is reached again Vocal registers Several different modes of vibration (registers) that affect the perception of phonation Vocal Registers Modal Register Modal phonation Pattern of phonation used in daily conversation Glottal Fry Pulse register Usually low in pitch and sounds rough Complex glottal configuration at a low frequency Requires low subglottal pressure to sustain it Vocal Registers Falsetto Highest register of phonation Vocal folds lengthen and become very thin High-pitched vocal Highproduction Whistle Register Register above falsetto Not really a mode of vibration Due to turbulence on the edge of the vocal folds Frequency can be as high as 2,500 Hz Seen mostly in female speakers 4 Variations on Modal Phonation Pressed phonation Medial compression is greatly increased This results in stronger, louder phonation Forceful adduction can damage the vocal folds Breathy phonation Vocal folds are inadequately approximated so that air flows between them Results in "wasted" air but is not damaging Whispering Not a phonatory mode because no voicing occurs Laryngeal adjustments still occur Vocal folds do not vibrate Vocal folds are partially adducted and tensed This produces turbulence in the airstream and this is the "noise" you use to form speech Intensity Relative power or pressure of the acoustic signal Measured in decibels (dB) Vocal intensity 5 Pitch Closely related to frequency As frequency increases, pitch increases As frequency decreases, pitch decreases Vocal folds are made up of masses and elastic elements Therefore, the vocal folds tend to vibrate at the same frequency when the mass and elastic elements remain constant Fundamental frequency Optimal Pitch Pitch (actually the frequency) of vocal fold vibration that is optimal for a given individual Varies as a function of gender and age Estimated based on the individual's range of phonation 1/4 octave above the lowest frequency of vibration an individual can phonate Estimated based on biological function Vibration during throat-clearing or coughing throat- Habitual Pitch The frequency of vibration of the vocal folds that is habitually used during speech Ideally, this is the same as optimal pitch For some individuals there are compelling reasons to speak using an abnormally higher or lower fundamental frequency Can result in vocal & physical fatigue 6 Average Fundamental Frequency Frequency of vocal fold vibration during sustained phonation or conversational speech This reflects habitual pitch over a longer average period Pitch Range Range of fundamental frequency for an individual The difference between the highest and lowest frequencies an individual can produce Flexibility of the vocal mechanism Typically capable of two octaves of change in fundamental frequency Pitch Alterations Intrinsic Laryngeal Muscles Cricothyroid muscle (higher pitch) Tilting forward of the thyroid lengthens the vocal fold and increase fundamental frequency Thyrovocalis muscle (higher pitch) Tenses vocal folds by bring cricoid and thyroid closer together Must be opposed by contraction of posterior cricoarytenoid muscle Thyromuscularis (lower pitch) Lowers pitch by moving cricoid and thyroid closer together 7 Pitch Alterations Extrinsic Laryngeal Muscles To reach tones on the extreme ends of pitch range, the extrinsic laryngeal muscles are engaged Heightened activity of the sternothyroid muscle when the larynx is depressed and thyrohyoid muscle when it is elevated Intensity Alterations To increase intensity of the vibrating vocal folds, you must increase the vigor with which the vocal folds open and close Increase subglottal pressure Increase medial compression 8 ...
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