Phonation Physiology

Functions of the larynx

Respiration

Airway protection

Thoracic fixation

Sound generation

Main laryngeal functions during speech

Voicing

Voiceless

Intonation

Vocal folds

masses that can be set into vibration; have mass and elasticity

Vocal folds abduction during quiet and forced respiration

During normal, quiet respiration, the vocal folds are abducted to provide a width of about 8 mm in the adult.

During forced respiration, the need for air causes you to dilate, or open, the respiratory tract as widely as possible, doubling that width

The effect of vocal fold mass on vibration rate?

As the mass increases, the frequency of vocal fold vibration decreases (inverse relationship)

The effect of vocal fold length on vibration rate?

Provided the same mass, shorter vocal folds have higher frequency and therefore higher pitch (inverse relationship)

Glottal configuration during production of plosives (/p/, /t/, /k/)

1- Pressurization phase

2- Release phase

Glottal configuration during production of glottal fricatives (/h/) and whispering

1- Glottal configuration adjustment

2- Turbulent airflow

Sustained voice generation

Sustained airflow (VF opening/closing)

Elasticity

It is that property of a material that causes it to return to its original shape after being displaced.

Stiffness

tterm-4he strength of elastic forces

Myoelastic Aerodynamic Theory

the vocal folds vibrate partly because of the forces and pressure of air and the elasticity of the vocal folds

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

inferior-superior mode of phonation

vocal folds tend to open from inferior to superior

Anterior-posterior mode of phonation

vocal folds (in addition to opening from inferior to superior) tend to open from posterior to anterior

Minimum driving pressure in modal phonation

3 to 5 cm H2O subglottal pressure

*if the pressure is lower than this, the vocal folds will not be blown apart

*a patient who cannot maintain this pressure for 5 seconds will not be able to use the vocal folds for speech

Pitch

the perceptual correlate of frequency

As frequency increases, cycles per second increase and pitch increases

Optimal pitch

the pitch (frequency) of vocal fold vibration that is optimal for an individual

varies depending on age and gender

Average optimal pitches

adult female: 230Hz

adult male: 120Hz (greater muscle mass and longer vocal folds=lower frequency)

Children: 250Hz

Infants: 800Hz

Habitual pitch

the frequency of vibration of vocal folds that is habitually used during speech

**ideally this is the same as optimal pitch

Average fundamental frequency

the average frequency of vibration of the vocal folds during some sustained phonation (eg. conversation)

Pitch range

the range of fundamental frequency for an individual

*calculated as the difference between the highest and lowest frequencies

Changeable elements of the vocal folds

1. mass - we can change the mass per unit length by spreading the muscle out over more distance

2. tension - we can stretch them tighter or relax them

3. length - elongation is what really affects the tension and mass

Cricothyroid role in fundamental frequency adjustment

it stretches the vocal folds

thyrovocalis role in fundamental frequency adjustment

contraction pulls the cricoid and the thyroid closer together

Muscles involved in changing Fo

cricothyroid: larger adjustments

Thyromuscularis: fine adjustments

Vocalis

medial portion of the thyroarytenoid

main mass of the vocal folds

tenses the vocal folds and works with the cricothyroid to stiffen the vocal folds

Thyromuscularis

origin is the thyroid and insertion is the arytenoids.

Pulls the arytenoids anteriorly to shorten the vocal folds

The effect of VF tension on pitch?

Increases pitch

The effect of VF mass on pitch?

Decreases pitch

The effect of VF length on pitch?

Decreases pitch

vocal registers

Glottal fry: lowest pitch

Modal: normal intermediate pitch

Falsetto: highest pitch

Glottal fry

Lowest F0

VF's close quickly, long closed phase of the cycle

Folds held tight together

Free edges bubble sound out

Popcorn sound

Modal register

the mode of vibration used for daily speaking

Falsetto register

Produced with elongated, tight vocal folds

The relation of subglottal pressure with intensity

There is a direct relation

Objective voice analysis

Acoustic parameters

Open quotient

Speed quotient

Subjective parameters

-hoarse

-rough

-strained

-strangled

-breathy

-male versus female

laryngoscopy

visual examination of the larynx

Two types of laryngoscopy

Direct

Indirect

Direct laryngoscopy

direct viewing of the larynx and adjacent structures by use of a laryngoscope under full anesthesia

indirect laryngoscopy

Dental mirror

Rigid laryngoscopy

Flexible laryngoscopy

Videostroboscopy

- Allows the human eye to see the vibratory motion of the VF in slow motion.

tracheostomy

surgical creation of an opening into the trachea through the neck

What is the effect of tracheostomy on subglottal airpressure?

Because it redirects the airflow to the stoma, it decreases the subglottal air pressure.

What is the effect of vocal fold masses or paralysis on subglottal air pressure?

Because vocal cords can not be adducted completely, the subglottal air pressure will be decreased.

laryngectomy

surgical removal of the larynx