Physiology of Phonation

Physiology of Phonation Ch. 5

Nonspeech Laryngeal function • Protection is the most important role • Prohibits entry of foreign objects into the lungs • Cough- • response by the tissues of the respiratory passageway to an irritant or foreign object • Mediated by the visceral afferent (sensory) portion of the Vagus nerve that innervates the bronchial mucosa • Deep inhalation-widely abducted vocal folds, followed by tensing and tight adduction of the vocal folds and elevation of the larynx • Arytenoids are rocked for adduction and directed downward, providing more force

Nonspeech Laryngeal Function • Throat Clearing • Not as violent as a full cough • Build pressure in the subglottal region and clamp the vocal folds shut to restrain the pressure • Places vocal folds under a great deal of strain • Involve the muscles of adduction; lateral cricoarytenoid, arytenoids and thyrovocalis.

Nonspeech Laryngeal Function • Abdominal fixation • Capturing air within the thorax to provide the muscles with a structure to push/pull • Similar to a cough • Take in a large breath, tight adduction of the vocal folds • Thorax becomes a rigid frame • Some air may escape through the adducted vocal folds and you may “grunt” when lifting something heavy

Nonspeech Laryngeal Function • Breathing • Normal breathing requires the vocal folds to be abducted • During forced exhalation (like when exercising)- the need for air causes you to increase the abduction of the vocal folds

Laryngeal Function for Speech • Bernoulli Effect • This explains how we maintain phonation • Need a constant volume flow of air • Vocal folds become a source of turbulence in the vocal tract • Effects of constricting a tube during air flow • As it flows through the constriction- the rate (velocity) of flow increases, however, the pressure decreases • Vibration of the vocal folds is the product of airflow interacting with the tissue in the absence of repetitive muscular constriction

Laryngeal Function for Speech • Attack • Process of bringing vocal folds together to begin phonation, requires muscular action • Simultaneous vocal attack-coordinate adduction and onset of respiration so that they occur simultaneously (i.e. say the word “zany”- you start the flow of air before voicing)

Laryngeal Function for Speech • Breathy vocal attack-starting significant airflow before adducting the vocal folds (i.e. running speech “Harry is my friend.” you can feel the air flow past your lips • Glottal attack- adduction of the vocal folds occurs prior to the airflow, much like a cough (i.e. bring vocal folds together like you are going to cough- and then say /a/, or say “okay, I want the car.” • Hard Glottal attack- an attack is misused- too much force- causes damage to vocal folds

Laryngeal Function for Speech • Termination • When phonation stops the vocal folds abduct • We pull vocal folds out of the airstream far enough to reduce the turbulence, using muscular action- the vocal folds stop vibrating • It occurs many times during running speech

Adduction • Is constant in all types of phonation and attack • The arytenoid cartilages move in three dimensions: rotating, rocking, and gliding • Primary movement for adduction is inward rocking • Combined forces of the cricothyroid and posterior cricoarytenoid cause the entire glottis to lengthen

Vocal Fold Nodules • Aggregates of tissue arising from abuse- Unilateral or Bilateral • Continued abuse results in the formation of a protective layer of epithelium that is callous-like • Usually on the juncture of the anterior and middle thirds of the vocal folds- greatest impact during phonation • Yelling, screaming, cheerleading, singing • Laryngitis-inflammation of the larynx, hoarseness ad possible loss of voice (aphonia). • Swelling of the vocal fold tissue with a breathy voice • Can be caused by vocal hyperfunction (over adduction of the vocal folds) • After a thrilling football game

Sustained Phonation • Vocal attack and termination requires muscular action • Sustained phonation requires maintenance of a laryngeal posture through sustained contraction of musculature. • Vocal folds are held in place- it is not the product of repeated adduction and abduction- muscle spindles embedded within the thyrovocalis and thyromuscularis serve the function in holding sustained posture

Vocal Register • Mode of vibration- pattern of activity that the vocal folds undergo during a cycle of vibration • Three registers-differences in the mode of vibration of vocal folds • Modal register • Glottal fry or pulse register • Falsetto

Modal Register • Pattern of phonation used in daily conversation • Vertical mode of phonation is when the vocal folds open from bottom to top and close from bottom to top- like a wave • Primary frequency of vibration- vocal fundamental frequency • Anterior-Posterior dimension of phonation- vocal folds open from posterior to anterior but closure is made by contact at the medial edge

Glottal Fry • Also called “fry, pulse, and straw bass” voice • Crackly, popcorn quality of voice • Low in pitch, sounds rough • Frequencies as low as 30 Hz to 80-90 Hz • Low subglottal pressure and tension of the vocalis is reduced • Vibrating margin is flaccid and thick • Lateral portion of the vocal folds is tensed – strong medial compression with short, thick, vocal folds and low subglottal pressure • Syncopated mode of vibration- a secondary beat for every cycle- the vocal folds don’t just vibrate slower, but differently

Falsetto • Vibratory pattern that varies from modal production • Vocal folds lengthen and become thin and “reed like” • Vibrate along the tensed, bowed margins • Make contact only briefly and the degree of movement is reduced • Thin, high- pitched voice • Whistle register- above falsetto- product of turbulence on the edge of the vocal fold- frequencies as high as 2500 Hz

Pressed and Breathy Phonation • Pressed phonation • Medial compression is greatly increased • Increase in stridency or harsh quality • Increase in abuse to the voice • Stronger, louder phonation • Forceful adduction often results in damage to vocal fold tissue

Pressed and Breathy Phonation • Breathy voice • Vocal folds are inadequately approximated • Vibrating margins permit excessive airflow between then • Inefficient and causes air wastage • May signal the presence of vocal nodules, polyps or laryngeal cancer

Whispering • Not a phonatory mode • No vibration of the vocal folds • Vocal folds are partially adducted and tensed to develop turbulence in the airstream • The turbulence is the noise you use to make speech • Arytenoid cartilages are rotated slightly in but are separated posteriorly • No voicing, however, it is strenuous and can cause vocal fatigue

Intensity • Relative power or pressure of an acoustic signal, measured in decibels (dB) • Amount of pressure exerted by the sound wave

Ventricular Phonation • False or ventricular vocal folds are technically unable to vibrate for voice • In some instances- clients may use ventricular phonation as an adaptive response to severe ocal fold dysfunction • Forces the lateral superior walls close together • Phonation is deep, raspy

Sustained and Maximum Phonation • P. 237 • Sustain /ah/ • Sustain /s/ • Sustain /z/

Pitch • Psychological correlate of frequency • As frequency increases, pitch increases • Vocal folds tend to vibrate at the same frequency when mass and elastic elements remain constant • Frequency of vibration changes when mass and elastic elements change

Optimal Pitch • Vocal fold vibration that is most appropriate for an individual • Most efficient for a pair of vocal folds • Considered 1/4th octave above the lowest frequency • Can be estimated from a throat clearing • Varies from gender and age • Females average 212 Hz, Males 132 Hz

Habitual Pitch • Frequency of vibration of vocal folds that is habitually used during speech • Ideally this would be the same as optimal pitch • The choice to use an abnormally higher or lower fundamental frequency is often not a conscious decision • When forcing vocal folds to extremes of their range of ability- greater effort and physical fatigue

Average Fundamental Frequency • Frequency of vibration of sustained phonation or conversational speech • Reflects habitual pitch over a longer averaging period • Use conversational speech or reading tasks to accurately reflect • Pitch range- difference between the highest and lowest frequencies- capable of approximately two octaves

Pitch Changing • Stretching and tensing the vocal folds • Use the cricothyroid and thyrovocalis muscles • Changeable elements are tension, length and mass through elongation • Cricothyroid- thyroid tilts down, lengthening the vocal folds and increasing fundamental frequency • Thyrovocalis- pulls cricoid and thyroid closer

Pitch changing • Posterior cricoarytenoid- has muscle spindles that moitor and maintain tonic muscle length • Cricothyroid makes the gross adjustment, Thyrovocalis fine tunes the adjustment • Increased subglottal pressure is a response to the increased tension • Mass is rearranged by lengthening or shortening • Relaxing the vocal folds- contraction of the thyromuscularis- folds are relaxed and shortened becoming more massive and less tense

Intensity • Loudness is the pscyhological correlate of intensity • Physical measure of power or pressure • Increase the vigor with which the vocal folds open and close • Subglottal pressure and flow provide the energy • Increase subglottal pressure to increase vocal intensity

Changing Intensity • Increased medial compression of vocal folds • Vocal folds are tightly compressed • Takes more force to blow them open • They close more rapidly • Stay closed because they are tightly compressed Intensity and Frequency are controlled independently, however, it is difficult to increase intensity without increasing pitch unless you are trained. Intensity and frequency increasing together is a natural process

Clinical Considerations • Perturbation (jitter) • Measures cycle-by-cycle variability in phonation- measures perception of “hoarseness” • Increased mass (vocal nodules) will increase perturbation • Neuromotor dysfunction will increase perturbation • Provides another measure of how the phonatory system is functioning

Clinical Considerations • Prosody • System of stress used to vary the meaning in speech • Elements include pitch, intonation, loudness, stress, duration and rhythmn • Provides information concerning emotion and intent and can provide clearer meaning • Diadochokinesis • Alternation of articulators (puhtuhkuh) • Assesses the coordination between the phonatory and articulatory systems

Physiology of Phonation