PHONATIONPHONATION

DR NITIN THOMASDR NITIN THOMAS

Process

by which vocal folds produce certain sounds through periodic vibration..

OSCILLATION OSCILLATION Repeated back & forth movement

VOCAL CORD OSCILLATIONVOCAL CORD OSCILLATIONFlow induced oscillationFlow induced oscillation

Steady flow of air Pass by a wall / surface Surface vibrates Steady flow of air Pass by a wall / surface Surface vibrates

VOCAL FOLDS• Housed with protective cartilage of larynx• Vocal folds very small {18mm - women ; 23mm -men}• Part of fold responsible for sound production is further

smaller• During phonation – only anterior part of fold is free to

vibrate• Appearance : Pearly white bands• looks like “ V ” on rest• During phonation they close together at Posterior part

• Bottom of this V points to front of neck and Adams

apple• Space b/w vocal folds GLOTTIS which opens for

respiration & closes for phonation• above the folds pink-coloured ventricular folds , also k/a

false vocal folds

A curved structure k/a epiglottis

arise from the closed point of the vocal folds

cover airway during swallowing and direct food into the

esophagus toward the stomach

VOCAL FOLD STRUCTURE

Vocal folds – body & cover

Cover - lined by Stratified Squamous Epith

Aka Mucosa of the vocal folds

Below vocal folds – lined by Ciliated Columnar Epith.

Body : Has thyroaretynoid muscle

(Origin : Thyroid cartilage & Insetion : Arytenoid

cartilage)

A transitional layer b/w muscle & epithelial cover

LAMINIA PROPRIA

Has 3 layers

Superficial Intermediate Deep

Outer most layer Middle layer Inner layer

Superficial Layer

Joins epith. Via basement memb

Thinnest layer

Lowest viscosity

Intermediate Layer

More wider

More viscous

Vocal ligament passess through this layer

Deep Layer

Densest & most viscous

Transition from vocal fold cover to body is completed

Lamina propria compared :

To a 3-layered gelatin dessert in which

Superficial layer - incompletely set

Intermediate layer - normal gelatin

deep layer more - resembles a gummi

This pattern helps the cover to slide gently in position relative to body

oscillation facilitated In healthy vocal folds

.

using high-speed or stroboscopic cameras ,surface of fold appears to ripple in a wave like motion k/a MUCOSAL WAVE

Voice disorders impair phonation:

By impeding mucosal wave formation ( Eg: the hoarseness or loss of voice) from

laryngitis (laryngeal inflammation) – d/t vocal fold swelling - makes the cover adhere tightly to body. The folds lose their suppleness and become too rigid to oscillate

THEORIES OF VOCAL FOLD OSCILLATIONTHEORIES OF VOCAL FOLD OSCILLATION

Muscular activities alone are not able to open and close the glottis rapidly enough for sound

Production

To sing vocal folds must open and close at a much

faster rate up to 1400 times / sec

No muscles can do this

Vibration of this velocity – AIRFLOW ASSISTANCE

MYOELASTIC AERO DYNAMIC THEORYMYOELASTIC AERO DYNAMIC THEORY

Vocal cord oscillation Muscular + Aerodynamic process

Aerodynamic ProcessDemonstrated by Daniel Bernoulli (18 century)

Fluid Dynamic

If Vol. of fluid / Gas Pass confined area Constant energy

inversely propotional to Expressed as pressure & flow

each other

Eg : Water passing through a pipe

VOCAL FOLD OSCILLN. & ROLE OF BERNOULLI EFFECT

Laryngeal mus. Close vocal folds Air pr. ses` beneath

Air flows thru glottis opens glottis from bottom to top

with velocity & press. until air escapes

Glottis closes d/t air flow pr. Process repeats

The time of Open : close ratio of vocal folds

Measuring the images by

High speed or Stroboscopic motion picture

Also measured by a painless , non invasive

Electroglottograph (EGG)

{ Elecrodes placed on either side of neck - radio freq waves passed via larynx - Glottic opening & closing induce changes in electrical resistance - measured & plotted by EGG }

RATE OF GLOTTIC OPENING & CLOSING

OPEN : CLOSED RATIO

NORMAL PHONATION

BREATHY PHONATION

{ Vocal Cords are not fully closed on Stroboscopy & EGG }

THE ONE MASS MODEL THEORYTHE ONE MASS MODEL THEORYMyoelastic-Aerodynamic theory was improved by adding the

contribution of the vocal tract & its impact on airflow

In the physical world

objects experience inertia

which is

resistance to starting & stopping movement

vocal folds and the air moving through the vocal tract also

are subject to this natural law

In A-M theory

glottis initially closed by muscles in larynx

`

Subglottal air pr.

Till it overcomes muscular & tissue resistance & opens glottis

Air pr. through glottis (Bernoulli)

& elasticity / Inertia of vocal folds

Brings glottis back together

flow of air

Becoz of inertia, air above glottis cont. its 4ward motion through

the glottis

Producing area of low air pr. immediately above glottis

Combined forces of

elastic recoil of the folds + pressure drop through the glottis + low pressure region above the glottis

completes cycle ,closing the glottis

Asymmetry of air pr. below & above glottis

allows

Vocal fold oscillation

to continue for as many times per second depending on the pitch that is spoken or sung

THREE MASS MODELTHREE MASS MODELVocal folds consider as 3 interconnected masses

First & largest mass - body of the vocal fold ( thyroarytenoid muscle)

Two smaller masses - upper and lower portions of the cover (lamina propria and epithelium)

Glottis opens and closes asymmetrically with vertical phase difference from bottom to top.

Air pressure also is asymmetrical

When glottis is

convergent Divergent

(Bottoms of 2 folds r farther apart) (tops of 2 folds r farther apart)

Increasing decreasing

Asymmetry of air pressure + impact of pr. changes above glottis caused by

Inertia sufficient to sustain vocal fold oscillation

NEUROCHRONAXIC THEORYNEUROCHRONAXIC THEORY Raoul Husson (1901-67)

French scientist &voice enthusiast

believed that nerve impulses from brain

sole cause of vocal fold vibration &

that airflow only is needed to carry the sound

outside the body

DEGREE OF PHONATIONDEGREE OF PHONATION

VOICELESSNESSVOICELESSNESS - NO VIBRATION - NO VIBRATION

BREATHY VOICEBREATHY VOICE

VOCAL CORDS VIBRATE WHILE THEY ARE FURTHER APART

o MODAL VOICEMODAL VOICE

Max. VibrationMax. Vibration

o STIFF VOICESTIFF VOICE

Glottal opening is narrowerGlottal opening is narrower

Faucalized voice Faucalized voice (hollow or yawny (hollow or yawny voice)voice)

Laryngeal cavity is expandedLaryngeal cavity is expanded

WHISPERWHISPER

Greater adduction Greater adduction

than in breathy voicethan in breathy voice

HARSH VOICEHARSH VOICE

Ventricular or pressed voice `Ventricular or pressed voice `

PHONATION DISORDERSPHONATION DISORDERS

• MYAESTHENIA GRAVISMYAESTHENIA GRAVIS auto-immune disease affect the nerve-muscle interface

causing general muscle weakness.

HOARSENESS

VOICE FATIGUE

DIFFICULTY IN CONTROLLING PITCH OF VOICE

T/T:

Anti cholinesterase –

restore muscle strength & tendency towards fatigue

• PARKINSONS DISEASEPARKINSONS DISEASE Degenerative disorder of the CNS

Motor symptoms of Parkinson's disease result from death of dopamine-generating cells a region of the midbrain

low volume voice with a "monotone“

(expressionless) quality

T/t :

Levadopa and dopamine agonists

• VOCAL HYPER FUNCTIONVOCAL HYPER FUNCTION

It’s the functional abuse of the vocal mechanism.

e.g : excessively loud speech.

- Can cause nodule

MCC :MCC :

T/T :T/T :

Speech TherapySpeech Therapy

VOCAL FOLD PARALYSISVOCAL FOLD PARALYSIS

Inability of 1 or both vocal folds (vocal cords) to move

d/t damage to nerves going to vocal cords

d/t damage to the brain itself

How does it affect voice?

Abductor: phonation in inspiration and exhalation

Adductor: no phonation

T/t :

Voice therapy:

To make the working vocal cord "compensate" for the vocal cord paralysis..

Surgical:

Almost IMMEDIATE improvement of all symptoms seen, especially vocal quality and strength.

VOCAL CORD POLYPVOCAL CORD POLYP

Non cancerous growths on the vocal cords that affect

voice.

Sometimes caused by vocal abuse

T/t :

Small polyps can be treated with

Voice therapy, but typically they are

surgically removed

VOCAL FOLD CANCERVOCAL FOLD CANCER

T/t depends on the site and

extent of involvement

+

consideration of other

health issues the person

may have

• Treatment optionso Surgeryo Laser surgeryo Radiation therapyo Chemotherapyo Combination therapy

Eg of a very early cancer of the vocal folds.If these lesions are detected early, they can be treated with either radiation or surgery, with a cure rate approaching 96%.