anatomy 6 phonation physiology

PhonationPhysiology : 

PhonationPhysiology

Methods for investigating laryngeal physiology : 

Methods for investigating laryngeal physiology 1. Indirect Laryngoscopy examination of interior larynx with laryngeal mirror Problems: -dark so need outside light source -during vf vibration, movements are too fast to see

Methods for investigating laryngeal physiology : 

2. Stroboscopy rapid flashing light can make viewed object look like slow motion in laryngeal stroboscopy, light source flashes, making vfs appear in slow motion varying speed of flashing light over time can see whole cycle of vf movement Modern technique: videostroboscopy - Use strobe attached to video camera to record movements below Methods for investigating laryngeal physiology

Methods for investigating laryngeal physiology : 

3-Endoscopy (fiberoptic endoscope) direct visualization of internal structures i.e. larynx, esophagus, bronchi – tube with light source at end to illuminate structure, tube attached to a scope Peroral endoscopy - means visualized by looking through mouth - Bronchoscopy, esophagoscopy Nasendoscopy – enter thru nasal passage - tube inserted through nose winds down to view structures below; if tube attached to videorecorder, can tape movements below -again may need strobe light to make movements appear slowed -needed to view laryngeal structures during speech Methods for investigating laryngeal physiology

Methods for investigating laryngeal physiology : 

4-high-speech cinematography 4000 frames per second (as opposed to 24 frames per second) Requires light source shined into mouth Dr. G. Paul Moore was pioneer in laryngeal high-speed cinema, learning much about laryngeal function Methods for investigating laryngeal physiology

Methods for investigating laryngeal physiology : 

5-EMG - electromyography difficult because of surrounding superficial muscles use hooked wire electrodes - implanted with a hypodermic needle “not much pain” tells that a muscle is active or not Methods for investigating laryngeal physiology

Phonation Cycle : 

Phonation Cycle How do the vocal folds vibrate and produce sound? The Short Story Vfs generate a rapid series of pulses which allow air to exit and excite the supralaryngeal air column in order to produce a complex tone

Phonation Cycle : 

Phonation Cycle The longer story: Myoelastic-aerodynamic theory of phonation 1-Initial Closing Phase: -closed 2-opening phase -open 3-Closing phase Closed Back to 2-3 again and again and again

Phonation Cycle : 

1-Initial Closing Phase: -vocal folds adduct for tight medial compression – adductor muscle action VFs remain adducted for duration of phonation restricts air flow from lungs which muscles? simultaneous contraction of lateral cricoarytenoids and arytenoids posterior cricoaryts also contract – to anchor aryts from behind and provide tight medial compression (arytenoids alone: pull wrong way; lat. cricoaryts alone: whisper) Phonation Cycle

Phonation Cycle : 

Closed Once VFs closed, exhalation proceeds results in increased subglottal air pressure (vertical pressure) Phonation Cycle

Phonation Cycle : 

2-Opening Phase: increase subglottal pressure as air pressure reaches sufficient level, blows apart vocal folds, releasing puff of air approx +3 cm H2O greater medial compression, greater subglottal pressure needed to open VFs Open – for a few milliseconds Phonation Cycle

Phonation Cycle : 

3-Closing Phase: a-decreased vertical pressure - release of air results in immediate decrease in subglottal pressure b-tissue is elastic and moves toward closed position c- decreased horizonal pressure – the Bernoulli Effect – sucks VFs together Phonation Cycle

Phonation Cycle : 

Bernoulli Effect: d x ½ (v2p) = c d=density; v=velocity; p=pressure; c=constant velocity – air flow as flowing fluid (air) encounters a constriction (VFs), velocity must increase to get all air molecules thru narrowing If v increases, pressure must decrease i.e. pressure along walls of narrowing (VF walls) Phonation Cycle

Phonation Cycle : 

Closed again return to step 2 - beginning process once again one cycle = 1 Hertz this happens hundreds of times per second! * Vibration is an aerodynamic process, and not the act of repetitive muscle contractions Phonation Cycle

Phonation Cycle : 

1-Initial Closing Phase: contraction continues closed 2-opening phase open 3-Closing phase Closed Back to 2-3 again and again and again Phonation Cycle

Fundamental frequency = average rate of VF vibration : 

Fundamental frequency = average rate of VF vibration Men - 125 cycles per second/125 Hz Women - 210 cycles per second/210 Hz Factors determining Fundamental Frequency: 1) length of vocal folds: Increase length, decrease rate 2) mass of vocal folds: Greater mass, decrease rate 3) elasticity of vocal folds - passive tension More tense passive state, increase rate 4) tension on vocal folds - active tension Greater tension, increase rate

Slide 21: 

Glottal Tone Fundamental Frequency = Fo Harmonic Frequencies = Multiples of Fo

Attack phase of phonation : 

Attack phase of phonation initial closing phase relative to release of airstream = vocal attack 1) simultaneous attack balance between respiratory & laryngeal mechanisms so air released just as vfs come to midline and start vibrating 2) breathy attack air released before vocal fold adduction complete, so much air is released before vibration starts 3) glottal attack air released in context of great medial compression, so voice sounds like sudden onset and explosive ***clinical relevance Breathy attack - less efficient and weak voice Glottal attack - may sound rough/harsh; abusive over time

Slide 23: 

Male 125 Hz Fo Closing phase 3 msec Closed phase 1 msec Opening phase 4 msec Characteristics of vibratory cycle:

Characteristics of vibratory cycle: : 

Vertically – VFs open from bottom to top VFs close from bottom to top Horizontally – VFs open from back to front VFs close from front to back Characteristics of vibratory cycle:

Registers : 

Registers series of tones produced in same mechanical way and differ from other series of tones produced in substantially different mechanical way Modal Register Falsetto Register Glottal Fry/Pulse Register

Registers : 

1) Modal Voice Register -used in daily conversation Horizontal plane -open from posterior to anterior - close from anterior to posterior Vertical plane -most vibration in horizontal plane, but also some vertical displacement with increasing speaking intensities -open from lower margin to upper margins -closes from lower margin to upper margins Registers

Slide 28: 

Modal Pattern of Vocal Fold vibration Vertically – VFs open from bottom to top VFs close from bottom to top Horizontally – VFs open from back to front VFs close from front to back

Registers : 

2) falsetto highest register peculiar high-pitched tone because of the manner of vocal fold vibration vfs vibrate only at the free margins, other parts of the vocal fold do not vibrate; vfs appear stiff and long and bow-shaped vocal fold muscles and cricothyroid muscles are all tensed a pitch with a very high fundamental frequency has fewer harmonic components (and sound ‘thin’) than lower fundamental frequencies (which then sound “richer”) when vfs are under such extreme tension, they never completely approximate at midline during phonation, allowing air to escape; that’s why falsetto has a breathy quality to the tone Registers

Registers : 

3) glottal fry/pulse register low end of pitch range vocal folds approximated tightly; but flaccid along fold; subglottal air just bubbles up between flaccid folds minimal amount of air pressure necessary (2 cm H20) frequency of vibration 30-80 per second closed phase - 90% of the vibratory cycle; opening and closing 10% normal part of speaking pattern at the end of sentences if overlies other places in speaking, then is inappropriate Registers

Voice quality : 

Voice quality has to do with the clarity/purity of tone vocal fold vibration should be symmetrical in tension, mass, medial compression, subglottal pressure, and physical symmetry However, conditions can occur to change the symmetry, changing the quality of voice tone

Pitch-changing mechanism : 

Pitch-changing mechanism Pitch level - Men - 125 hz range 50-250 hz Women - 225 hz range 125-500 hz -considerable overlap Natural pitch level - Optimum pitch level frequency of VF vibration that is most appropriate and efficient about 1/4 way up pitch range depends upon size and characteristics of each person (age, gender, size) Habitual pitch pitch level used most commonly during speaking Sometimes habitual pitch is not = optimum pitch Pitch range - varies over two octaves during normal conversation

Raising Pitch : 

Raising Pitch 1)vocal fold changes mass changes/per unit of length - cross-sectional mass of vf measured in thickness of vf need to decrease mass to increase pitch increased tension may be the primary phenomenon toward increasing pitch Mass changes may just be a result of tension changes on this elastic mass

Raising Pitch : 

2) muscle action A- cricothyroid muscle Moves thyroid and cricoid together, increasing distance from thyroid to arytenoids within stretches vocal folds extending from thyroid to arytenoids this action simply elongates vfs, not contributing to their tension B- thyroarytenoid muscle - vocalis/thryomuscularis vf tensor; act with cricothyroid to tense elongated vocal folds to increase pitch C-posterior cricoarytenoid muscles: muscles of abduction, important for anchoring movement of arytenoids during adduction & pitch changing, so helps keep the vfs elongated from behind Raising Pitch

Raising Pitch : 

3) other findings about vfs during pitch increases at higher pitch levels, only edges of vfs seem to vibrate, not whole vf at high pitches, vfs never completely close in region of vocal processes of arytenoids; therefore air can escape and we have a breathy quality at high pitches Raising Pitch

Raising Pitch : 

4) subglottal pressure and pitch as long as vocal fold tension is constant, increases in subglottal pressure do not result in pitch increases as pitch increases, may be some need for increased subglottal pressure to overcome resistance as vocal fold tension is increased, subglottal pressure increases to overcome tension, but only at some pitch levels as a function of glottal resistance glottal resistance - measure of amount of resistance vfs cause for airflow Pg (glottal resistance) = subglottal pressure flow rate (volume velocity) Raising Pitch

Raising Pitch : 

1) as fundamental frequency increases, subglottal pressure increases 2) glottal resistance high at lower range of frequency glottal resistance high at higher end of frequency range 3) habitual pitch: resistance drops off substantially at about 30% of frequency range, i.e. there is a most efficient point where to talk - optimum pitch Raising Pitch

Pitch-lowering mechanism : 

Pitch-lowering mechanism Pitch ranges: habitual pitch 125 hz; ranges 70-500 hz; i.e. habitual pitch is at lower end of pitch continuum Lowering pitch: Decrease tension and increase mass - these two interplay Main way is to reduce tension on VF tissue elastic property of tissue causes them to relax once tensor force removed; this would return to habitual pitch other active forces necessary to lower pitch further

Pitch-lowering mechanism : 

Muscle action: 1-Contraction of thyromuscularis muscle by itself shortens and relaxes vocal folds; 2-must have help from lateral cricoarytenoids to maintain medial compression when thyroarytenoid is contracting alone Pitch-lowering mechanism

Extrinsic muscles and pitch-changing : 

Extrinsic muscles and pitch-changing larynx rises and falls as pitch changes Laryngeal elevators and depressors: - sternothyroid muscle active when larynx is depressed - thyrohyoid muscle active when the larynx is elevated

Intensity changing mechanism : 

Intensity changing mechanism Intensity = loudness measured in decibels db the human range of speaking intensity can range from Very low to as high as 70 db “crescendo” = gradual increase intensity

Intensity changing mechanism : 

1) subglottal pressure and vocal intensity increased subglottal pressure leads to increased intensity double subglottal pressure results in 8-12 db increase in intensity regular intensity speech - 2-3 cm H20 pressure loud speech - 15-20 cm H20 pressure may be observed Intensity changing mechanism

Intensity changing mechanism : 

2) vocal fold movement and intensity changes displacement of the vocal folds to midline is increased closed phase lasts longer as intensity increases (instead of 50/37/13 – 33/37/30) displacement of vocal folds laterally increased Intensity changing mechanism

Intensity changing mechanism : 

3) relationship between pitch and intensity Pitch and Intensity are Independent Factors in Vocal Fold Movement But…“intensity ranges are frequency dependent” (Coleman et al 1977) -at low frequencies - intensity range is lower/restricted max 10-20 db -at 50-70% of our frequency range - intensity range is max i.e. 40-50 db -at highest frequencies - intensity range again restricts - max 30 db Intensity changing mechanism

Intensity changing mechanism : 

4) glottal resistance, air flow, and vocal intensity medial compression increases with increasing intensity increased medial compression results in increased glottal resistance therefore…glottal resistance increases as a function of increasing intensity this increased glottal resistance must be compensated for by an increase in subglottal pressure Intensity changing mechanism

Intensity changing mechanism : 

5) muscles responsible for changes in vocal intensity i.e. need to increase subglottal pressure muscles of expiration are critical here Forceful adduction - medial compression - lateral cricoarytenoids, arytenoids, Increased glottal tension - thyroarytenoids and cricothryoid increased pitch often noted at increased intensities is related to muscles of tension that are assisting in process of maintain resistance at midline Intensity changing mechanism

Review : 

Review Incr subglottal > no change pitch incr intensity Incr pitch > incr subgl pressure incr glot resistance Incr intensity > incr glot resistance no pitch change

Parameters of voice production : 

Parameters of voice production 1) Maximum Phonation Time we use 100-200 cc air per second during phonation we should be able to sustain phonation 15-25 seconds MPT often used as best clinical indicator of vocal efficiency Vocal pathology - often prevents complete medial compression of vocal folds and allows excess air escapage; therefore MPT may be reduced

Parameters of voice production : 

2) Jitter measure of phonation quality how consistent/variable are length of phases of vocal fold vibration across cycles 3) Shimmer Cycle-to-cycle variability in amplitude of vocal fold vibration Both require specialized computer equipment to measure good quality tone has consistent phases Parameters of voice production

Parameters of voice production : 

4) Habitual pitch - average rate of vocal fold vibration use equipment to quantify in Hz -optimum pitch - usually considered to be at about 25% of our pitch range -um-hum technique for determining optimum pitch Parameters of voice production

Parameters of voice production : 

5) maximum frequency (pitch) range - Pitch variability is the norm - Monotone - refers to flat pitch or no variability Normal pitch range = 2 octaves i.e. 14 - 16 notes Voice problems: often result in restricted frequency range 6) minimum-maximum intensity at various pitches need sound level meter to determine at mid frequency, min-max intensity range is 50 db Parameters of voice production

Age and sex differences in larynx : 

Age and sex differences in larynx Infant larynx sits higher in neck than in adult epiglottis relatively higher and may actually touch soft palate, allowing child to breathe during feeding hyoid and thyroid cartilage in direct contact arytenoid cartilages proportionately larger vocal folds, at birth, 2.5-3 mm vocal fold mucosa is very thick and vocal ligament is not well developed thyroid lamina creates a rounded semicircle

Age and sex differences in larynx : 

Child larynx growth of vertebral column causes larynx to descend in larynx vocal folds slowly grow and vocal ligament develops no sex differences in infants and children i.e. same voice quality all children have decrease in Fo in elementary years thyroid lamina become more angled Age and sex differences in larynx

Age and sex differences in larynx : 

Puberty - Male mutation - cartilaginous structures grow rapidly vocal folds increase in length and thicken, the layered structure of the vocal folds develops lower range of voice increases by an octave Female also experience growth, but at slower pace lower range increases by 2-3 notes Age and sex differences in larynx

Age and sex differences in larynx : 

Postpubertal vocal folds Male - 17-20 mm long Female - 12 - 17 mm long thyroid lamina angle Male - 84 degree and more angled Female - 86 degrees and more rounded Age and sex differences in larynx

Age and sex differences in larynx : 

Aging larynx especially in male changes in layered structure of vocal folds Become less elastic, loss of muscle tissue changes in pitch increases somewhat and pitch range decreases ossification and calcification of thyroid and cricoid cartilages less so for arytenoids Age and sex differences in larynx