HIS 120 Function of the Larynx and Speech Production

Function of the Larynx & Speech Function of the Larynx & Speech productionproduction

The two primary functions of the The two primary functions of the larynx are:larynx are:

1.1. Biologic functionsBiologic functions

2.2. Non-biologic functionsNon-biologic functions


The The biologic functionsbiologic functions of the larynx: of the larynx:

1.1. Prevent air from escaping the lungsPrevent air from escaping the lungs

2.2. Prevent foreign substances from Prevent foreign substances from entering the larynx.entering the larynx.

3.3. Forcefully expel foreign substances Forcefully expel foreign substances which threaten the larynx or which threaten the larynx or tracheatrachea


The The non-biologicnon-biologic function function is sound production.is sound production.


The The vocal foldsvocal folds lay within the larynx lay within the larynx and their movement creates and their movement creates contributes to sound production. contributes to sound production.

They are muscle tissue which may be They are muscle tissue which may be lengthened or shortened, tensed or lengthened or shortened, tensed or relaxed, abducted or adducted. relaxed, abducted or adducted.


The cycle of a vocal fold in glottal sound The cycle of a vocal fold in glottal sound production has three phases.production has three phases.

(ref. Zemlin pg 151) (ref. Zemlin pg 151) They are: They are:

1.1. The opening phase (50% of the cycle).The opening phase (50% of the cycle).

2.2. The closing phase (37% of the cycle).The closing phase (37% of the cycle).

3.3. The closed phase (13% of the cycle).The closed phase (13% of the cycle).


During normal vowel production, During normal vowel production, such vibration occurs at a rate of such vibration occurs at a rate of about 125 vibrations per second for about 125 vibrations per second for men; and about 210 vibrations per men; and about 210 vibrations per second for women.second for women.


Adductor musclesAdductor muscles can forcibly stop can forcibly stop the vocal folds from moving. This is the vocal folds from moving. This is referred to as a referred to as a glottal stopglottal stop. The . The abrupt release by the adductor abrupt release by the adductor muscles is known as a muscles is known as a glottal attack. glottal attack.


The vocal fold contains five layers. The vocal fold contains five layers.

They are:They are:1.1. The epithelium (maintains the shape of the vocal The epithelium (maintains the shape of the vocal

fold).fold).

2.2. The superficial layer (similar to a mass of soft The superficial layer (similar to a mass of soft gelatin).gelatin).

3.3. The intermediate layer (similar to a bundle of soft The intermediate layer (similar to a bundle of soft rubber bands).rubber bands).

4.4. The deep layer (somewhat like a bundle of cotton The deep layer (somewhat like a bundle of cotton thread).thread).

5.5. The vocalis muscle (it’s the main body of the vocal The vocalis muscle (it’s the main body of the vocal fold and is like a bundle of rather stiff rubber bands.fold and is like a bundle of rather stiff rubber bands.


The Glottis is the variable opening The Glottis is the variable opening between the vocal folds.between the vocal folds.

Its dimensions are highly variable Its dimensions are highly variable depending upon the laryngeal depending upon the laryngeal activity and the adjustments of the activity and the adjustments of the cartilages.cartilages.

Note: Review Zemlin pages 120 and 121Note: Review Zemlin pages 120 and 121


The onset of Phonation may be The onset of Phonation may be divided into two phases. They are:divided into two phases. They are:

1.1. The prephonation phase.The prephonation phase.

2.2. The attack phase.The attack phase.


The Prephonation PhaseThe Prephonation Phase

The vocal fold begins to obstruct air flow The vocal fold begins to obstruct air flow from the lower respiratory tract.from the lower respiratory tract.

The pressure beneath the folds begins to The pressure beneath the folds begins to build.build.

The velocity of air flowing through the The velocity of air flowing through the glottal restriction is raised sharply.glottal restriction is raised sharply.


The Attack PhaseThe Attack Phase There are three types of vocal There are three types of vocal

attack. They are:attack. They are:1.1. Simultaneous attack Simultaneous attack (healthy balance (healthy balance

between laryngeal and respiratory mechanism)between laryngeal and respiratory mechanism)

2.2. Breathy attack Breathy attack (air stream is released (air stream is released before vocal fold adduction is completed)before vocal fold adduction is completed)

3.3. Glottal attack Glottal attack (the initiation of phonation (the initiation of phonation with an explosive nature)with an explosive nature)


The average rate of vocal fold The average rate of vocal fold vibration is known as its vibration is known as its fundamental fundamental frequencyfrequency. It . It determines determines to a large to a large extent the extent the pitchpitch of the voice of the voice


The average The average fundamental pitchfundamental pitch for a for a male voice is 130Hz.male voice is 130Hz.

Almost an octave higher, you will Almost an octave higher, you will find the find the fundamental pitchfundamental pitch for a for a female voice at 220Hz.female voice at 220Hz.

Ref. Zemlin page 163 Ref. Zemlin page 163


Not only does the vibration of the Not only does the vibration of the vocal cords determine pitch but, also vocal cords determine pitch but, also the subglottal air supply to the larynx the subglottal air supply to the larynx has been recognized to also be a has been recognized to also be a factor in the influence of pitch.factor in the influence of pitch.


When subglottal pressure increases, When subglottal pressure increases, so does the intensity of one’s voice.so does the intensity of one’s voice.

A general rule is when the subglottal A general rule is when the subglottal pressure is doubled, the voice pressure is doubled, the voice intensity increases by about 8 to 10 intensity increases by about 8 to 10 decibels.decibels.


Intensities of low and high pitches Intensities of low and high pitches

Low pitched phonation is accomplished Low pitched phonation is accomplished when voice intensity was raised by an when voice intensity was raised by an increase in glottal resistance.increase in glottal resistance.

High pitched intensity is accomplished High pitched intensity is accomplished by the rate of air flow through the by the rate of air flow through the glottis—not its resistance. glottis—not its resistance.


In the mid-frequency range, an In the mid-frequency range, an expected normal intensity level for expected normal intensity level for speech production will be about speech production will be about 50dbSPL.50dbSPL.


There are age related pitch changes There are age related pitch changes due to vocal fold development.due to vocal fold development.

At birth the infant larynx does not At birth the infant larynx does not resemble an adult larynx. It differs in resemble an adult larynx. It differs in shape, size, and the position in the shape, size, and the position in the neck.neck.


Prior to the onset of puberty, there is Prior to the onset of puberty, there is little difference in the pitch range little difference in the pitch range between males and females. The between males and females. The fundamental pitch frequency fundamental pitch frequency decreases upon the onset of puberty. decreases upon the onset of puberty.


The aging larynx usually finds a The aging larynx usually finds a decrease in pitch range due to the decrease in pitch range due to the deterioration of the muscle tissue deterioration of the muscle tissue and an increase in connective tissue and an increase in connective tissue within the vocal folds. within the vocal folds.


There are two theories formed There are two theories formed regarding voice production. regarding voice production.

They are:They are:

1.1. Myoelastic—aerodynamic theoryMyoelastic—aerodynamic theory

2.2. Neurochronaxic theoryNeurochronaxic theory


Myoelastic—aerodynamic theoryMyoelastic—aerodynamic theory

It states that the vocal folds are subject to It states that the vocal folds are subject to well established aerodynamic and physical well established aerodynamic and physical properties. The compressible and elastic properties. The compressible and elastic vocal folds are set into vibration by the air vocal folds are set into vibration by the air stream from the lungs and trachea.stream from the lungs and trachea.


The Neurochronaxic TheoryThe Neurochronaxic Theory

It states that each vibratory cycle of the It states that each vibratory cycle of the vocal fold muscle is initiated by a nerve vocal fold muscle is initiated by a nerve impulse from the brain.impulse from the brain.


Various models have been developed Various models have been developed for the study of the larynx and for the study of the larynx and speech production.speech production.

(Ref. Zemlin pages 183 thru 185)(Ref. Zemlin pages 183 thru 185)

HIS 120 Function of the Larynx and Speech Production

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Transcript of HIS 120 Function of the Larynx and Speech Production