PHONATION AND ITS MECHANISM HOW PHONATION WORKS HOW SOUND IS PRODUCED PHONATION DIORDERS DIFFERENT CONDITIONS AFFECTING PHONATION VOCAL FOLDS AND ITS ANATOMY AND FUNCTIONING

1. PHONATIO
N

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

4. OSCILLATION
Repeated back & forth movement
VOCAL CORD OSCILLATION
Flow induced oscillation
Steady flow of air
Pass by a wall / surface
Surface vibrates

6. VOCAL FOLDS
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•
•
•
•
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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

7. 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

11. 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

12. Superficial
Outer most layer
Intermediate
Middle 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
Inner layer

13. 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

14. 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

15. THEORIES OF VOCAL
OSCILLATION
FOLD
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

16. MYOELASTIC AERO DYNAMIC
THEORY
Vocal cord oscillation
Muscular + Aerodynamic process
Aerodynamic Process
Demonstrated by Daniel Bernoulli (18 century)
Fluid Dynamic
If Vol. of fluid / Gas
Pass confined area
inversely propotional to
Constant energy
Expressed as pressure & flow

17. 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

19. 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

20. NORMAL PHONATION
BREATHY PHONATION
{ Vocal Cords are not fully closed on Stroboscopy & EGG }

23. THE ONE MASS MODEL THEORY
Myoelastic-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

24. 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

25. 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

26. THREE MASS MODEL
Vocal 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
(Bottoms of 2 folds r farther apart)
Divergent
(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

27. NEUROCHRONAXIC 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

28. DEGREE OF PHONATION
VOICELESSNESS - NO VIBRATION

29. 
BREATHY VOICE
VOCAL CORDS VIBRATE
WHILE THEY ARE
FURTHER
APART

30. MODAL VOICE
Max. Vibration
o
STIFF VOICE
Glottal opening is narrower
o

31. 
Faucalized voice (hollow or yawny
voice)
Laryngeal cavity is
expanded

32. WHISPER
Greater adduction
than in breathy voice

HARSH VOICE
Ventricular or pressed voice
`

33. PHONATION DISORDERS
•
MYAESTHENIA 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

34. •
PARKINSONS 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

35. •
VOCAL HYPER FUNCTION
It’s the functional abuse of the vocal mechanism.
e.g : excessively loud speech.
-
Can cause nodule

36. MCC :
T/T :
Speech Therapy

37. VOCAL 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

38. 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.

39. VOCAL 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

40. VOCAL FOLD CANCER
T/t depends on the site and
extent of involvement
+
consideration of other
health issues the person
may have
• Treatment options
o Surgery
o Laser surgery
o Radiation therapy
o Chemotherapy
o Combination therapy

41. 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%.