the ppt includes the anatomy of larynx, the physiology of sound production and pathology of vocal cords explaining the myoelastic aerodynamic theory and bernoulli effect in phonation

1. PHYSIOLOGY OF
PHONATION
Presented by: Dr. Farhat Khan
M.S (ENT)

2. • Introduction
• Definition
• Relevent anatomy
• Theories of phonation
• Mechanism of voice production
• Properties of phonation
• Changes in voice

3. • Portrays our thoughts, emotions , joys and fears
• Signatures of the individuals
• Ancient Greeks thought that the voice actually
originated in the heart.
Human speech requires coordinated interaction of the
mouth, pharynx, larynx, lungs, diaphragm, and abdominal
and neck muscles.
HUMAN VOICE

4. • Phonation can be defined as laryngeal motor behaviour
used for speech production ,which involves a highly
specialised coordination of laryngeal and respiratory
neuromuscular control.
• It is the process of sound production by means of the
release of air puffs through glottal opening and closing as
a result of the interaction among tissue characteristics
and muscular and aerodynamic forces.
Definition

5. • Phonation, or the production of voice, involves a power
source (generator), oscillator(phonator), and resonance
chamber and articulator each with different anatomical
parts and specialized roles.
• Together, these three subsystems produce sound
perceived as voice.

6. Articulator
Resonator
Phonator
Generator

7. Laryngeal Anatomy and Structure
• Location: C3 to C6
• Connects pharynx to trachea
• Cartilages
• Membranes and ligaments
• Muscles
• Nerve supply

8. Cartilages :9 [3 paired, 3 unpaired]
HYLANINE
Thyroid
cartilage
Cricoid
cartilage
Aretenoid
cartilage
ELASTIC
Epiglottis
Corniculate
Cuneiform

10. Muscles: 7
1. Cricothyroid
2. Thyro arytenoid
3. Inter arytenoid
4. Lateral cricoarytenoid
5. Posterior cricoarytenoid
6. Oblique arytenoid
7. Vocalis

11. Intrinsic muscles : act on vocal cord or laryngeal inlet
Vocal cord:
1. Abductors-PCA
2. Adductors-LCA,IA,TA
3. Tensors –CT,Vocalis
Laryngeal inlet:
1.Elevators
Primary Secondary
Stylopharyngeous Mylohoid
Salphingopharyngeous Stylohyoid
Palatopharyngeous Geniohyoid
Thyrohyoid Digastric
2.Depressors
Stenohyoid
Omohyoid
sternothyroid

14. Musculature of the Vocal Fold
• The intrinsic laryngeal muscles- control the position and
shape of the folds along with the elasticity and viscosity of
each layer.
• The fibers of the thyroarytenoid muscle run parallel to the
vocal ligament.
• The part of the muscle that borders the vocal ligament is
called the vocalis muscle.
• Contraction of the thyroarytenoid muscle lowers,
shortens, adducts, and thickens the vocal fold, bringing
the arytenoid and thyroid cartilages closer.

15. • When the thyroarytenoid muscle is activated, the
length and tension of the vocal ligament are
decreased, lowering the pitch of the voice.
• The vocalis muscle can provide fine control of the
tension in the vocal ligaments enabling rapid
variation in the pitch.
• The posterior cricoarytenoid muscle abducts,
elevates, elongates, and thins the vocal fold by
rocking the arytenoid cartilage posterolaterally.
• The lateral cricoarytenoid muscle adducts, lowers,
elongates, and thins the vocal fold, making the edge
of the vocal fold sharp while passively stiffening all
layers.

16. • The interarytenoid muscle serves to adduct the
cartilaginous portion of the vocal folds.
• The extrinsic muscles of the larynx, mainly the strap
muscles, serve an important function of preserving the
position of the larynx in the neck.

17. Structure of the Vocal Fold Edge
• The vocal folds are two infoldings of mucous membrane
stretched horizontally across the larynx.
• The most important aspect of voice production is vibration
of the vocal folds that converts aerodynamic energy into
acoustic energy.
• The cross-section of the vocal fold reveals a five-layered
structure, with each layer having a different mechanical
property.
• The outer four layers are controlled passively and the
innermost layer is controlled both actively and passively.

18. Functionally, the vocal fold acts as three separate layers - The cover
(epithelium and Reinke space),
-The transition (intermediate and deep layers of the lamina propria) and
-The body (vocal is muscle ).

19. Nerve supply:
• All muscles > adductors; except PCA > abductor
• All muscles are supplied by recurrent laryngeal nerve ; except
cricothyroid (strongest adductor) > superior laryngeal nerve
Xth nerve
Superior
laryngeal nerve
External (motor)
Internal(sensory)
Recurrent
laryngeal nerve
mixed

20. Position of vocal cord
DISTANCE(mm) NORMAL DISEASE
MEDIAN 0 phonation RLNP
PARAMEDIAN 1 whisper RLNP
INTERMEDIATE
(cadaveric
position)
3 xxxxx BOTH N PALSY
GENTLE
ABDUCTION
7 Quite respiration SLNP
FULL
ADDUCTION
9 Deep respiration SLNP

21. Management
U/L RLNP
P
Hoarseness wait and watch
B/L RLNP
P P
Severe dyspnoea tracheostomy
U/L SLNP
abd
Hoarseness
No aspiration
No dyspnoea
Wait and watch
B/L SLNP
abd abd
Aspiration
Aphoneoa
No dyspnoea
Epiglotoplasty
tracheostomy

22. HISTORICAL ASPECT OF PHONATION
• In 1950, Husson presented the neurochronaxic
hypothesis, which held that glottic vibrations were
caused by rhythmic impulses in the nerves to the
larynx, synchronous with the frequency of the sound
produced, so that each vibratory cycle was caused
by a separate neural impulse—a physiologically
impossible hypothesis.

23. HISTORICAL ASPECT OF PHONATION
• In the 1950s, van den Berg used high-speed motion
pictures to document the motion of the vocal folds during
vibration and subsequently reported his theory of the
mechanism of phonation; now widely accepted, the
myoelastic-aerodynamic theory holds that the interaction
of aerodynamic forces and the mechanical properties of
the laryngeal tissues are responsible for inducing vocal
fold vibration and generating vocal sound.

24. • Normal phonation requires that five conditions be
satisfied;
• 1. Adequate breath support
• 2. Approximation of vocal folds
• 3. Favorable vibratory properties
• 4. Favorable vocal fold shape
• 5. Control of length and tension

25. • The process of phonation begins with the inhalation of air, and
then glottic closure positions of the vocal folds near the midline.
• Explanation of phonation is that exhalation causes subglottic
pressure to increase until the vocal folds are displaced laterally,
which produces a sudden decrease in subglottic pressure.
• The forces that contribute to the return of the vocal folds to the
midline include this pressure decrease, elastic forces in the
vocal fold, and the Bernoulli effect on airflow.
• When the vocal folds return to the midline, pressure in the
trachea builds again, and the cycle is repeated. Vocal fold
structure determines whether the resulting vibration is periodic
or chaotic.

26. • The “body-cover” concept of phonation is that the
vibration of the mucosa does not correspond directly to
that of the rest of the vocal fold.
• Instead, the “body” of the vocal fold is relatively static,
whereas the wave is propagated in the mucosal “cover.”
This mucosal wave begins on the inferomedial aspect of
the vocal fold and moves rostrally.

29. • Helmholtz (1863) showed us that phonation was the
product of puffs of air released through the glottis.
• Voice is produced by a steady flow of air from the lungs,
segmented at the laryngeal level into a series of air puffs
at a fundamental frequency that generates higher
harmonics in the cavities of the upper airway.
• Which frequencies will be produced with a minimum
attenuation will be determined by the configuration of the
supra-laryngeal cavities.
• Acoustic energy concentrations due to cavity resonation
are called formant frequencies.

30. Myoelastic-Aerodynamic Theory (Van
Den Berg, 1958)
1. Muscular activity rotates and rocks the arytenoid cartilages so
that their vocal processes come together in the midline, thus
positioning the vocal folds close together or in actual contact.
2. Air pressure increases below the glottis until folds forced
apart
3. Air travels faster through the glottis when it is narrow. This
causes a local drop in air pressure (Bernoulli effect) which
causes the folds to be sucked towards each other.
4. The Bernoulli effect, together with the elastic recoil force
exerted by the displaced vocal folds, causes complete glottal
closure again.
5. The process begins again at step 2.

32. • Physics of the Myoelastic-aerodynamic theory of
phonation is given by Lieberman (1968)
• Two forces act on the vocal folds:
(1) Aerodynamic-aerostatic forces displacing the vocal folds
from their adducted position in preparation for phonation and
(2) Tissue forces that act to restore the vocal folds to their
adducted position.

33. Bernoulli Effect :Daniel bernoulli, Swiss mathematician and
physicist(1700-1782)
 Inverse relationship
 Increase in air flow results
in air pressure decrease

34. • Timcke et al. (1958, 1959) pioneered the frame-by-
frame analysis of ultraspeed photographs of the
vocal folds during phonation showing the opening
and closing of the glottis during each vibratory cycle.
• In a normal vibratory cycle, glottal width is displayed
on the vertical axis, and duration of the cycle is
shown on the horizontal axis. Each cycle is divided
into an opening, a closing, and an approximation
phase. In a normal voice, the vocal folds abduct at a
higher rate of speed than they adduct. An equation
expressing the ratio of abductor to adductor duration
is called the speed quotient (S.Q.):

36. • In normal voices, the S.Q. is always less than 1.0,
but as vocal intensity increases, the S.Q. increases
(i.e., duration of the opening phase is increased).
• A second measure of vocal fold behavior during the
glottic cycle is the ratio of the duration of the open
period of the vocal folds to the total period of the
cycle, called the open quotient (O.Q.):
• In normal voice, the O.Q. ranges from 0.6 to 0.8 and
increases with vocal intensity.

37. • Importance of these measures and the profile of the
glottal wave shape is they change with changes in
pitch and loudness and when the voice becomes
dysphonic. By knowing the configuration of the
normal shape and its variants related to pitch,
loudness, and various voice qualities, we can use
the wave shape to tell us something about how
voice is being produced.
• For example, when the closed phase is long, we
assume hyperfunction, and when there is no closed
phase, we assume inadequate closure as seen in
closed head injuries and breathy asthenic
phonation.

38. Vibratory Function of Vocal Fold Mucosa
• The body-cover theory of vocal fold vibration was introduced by
Hirano in 1974.
• He was one of the first to recognize that the morphologic
structure of the vocal folds was central to normal vibration
patterns.
• The theory assumes that the differences in histologic structure
and contractile properties result in a five-layered histologic
structure that vibrates as a two-layered biomechanical
structure.
• The body, thyroarytenoid, is active, whereas the cover,
epithelium, and lamina propria is passive.

39. • The cover - pliable, elastic, and noncontractile
• The body - stiff and has active contractile properties.
• The body is able to adjust concentration and
stiffness of mass. The overall tension is dependent
upon the coupling of the cover to the contractile
muscular body.
• The cover is important in its wave-like movement
during phonation. Loss of cover movement or
mucosal wave is detrimental to vocal quality.
• During phonation produced at normal pitch and
loudness, the body is stiff and the cover loose.

40. • The difference in stiffness between the two layers
facilitates the mucosal wave.
• If any of the tissue cover is stiff because of changes
in the epithelium, collagen, or elastin, the mucosal
wave becomes reduced or eliminated.
• Conversely, in cases of paralysis when the muscle
no longer contracts, the cover movement is aberrant
because there is not the underlying stiffness so that
the body and cover vibrate as one passive unit.
• During normal changes in pitch and loudness, the
laryngeal muscles act on the passive tissue
covering to produce differences in shape and
tension.

41. • As example, during high pitch the elongated vocal folds
stretch the cover leaving only a small margin of tissue free
to oscillate, whereas the converse is true for low pitch.
• These differences in vibratory pattern were primarily
determined from high-speed photography done by von
Leden and Moore in the 1940s and later by Hirano.

43. Properties of Phonation
• Sound can be described in terms of the physical
properties of its pressure waveform
• Amplitude
• Frequency
• Pitch

44. Amplitude
• Amplitude of the pressure wave is perceived as loudness or
sound intensity
• The amplitude is largely determined by the force of the
transglottal airflow.
• “Shimmer” or amplitude perturbation

45. Frequency
• The frequency of the glottal signal is a result of
the number of vibratory cycles / sec ( measured
in Hz)
• Function of
• Vocal fold length
• Elasticity
• Tension
• Mass

46. Pitch
• Frequency, intensity and spectral properties of
sound interact in very complex ways to lead to a
given pitch perception.
• “Jitter” or pitch perturbation
• It is generally accepted that there are three pitch
registers
– Loft (or falsetto) register
– Modal (or middle) register
– Pulse (or chest) register

47. Modal or Middle Register
• Pattern of phonation used in daily conversation
• Complete glottal closure occurs
• Results in the majority of the mid frequency range voice
• Vocal fold mucosa vibrates independently of the vocalis

48. Loft or Falsetto Register
• A singing technique that produces sounds that are pitched
higher than the singer's normal range
• Vocal folds are lengthened and become extremely thin
• Only the edges of the vocal cord vibrate, not the entire vocal
cord
• It is a very common technique in soul music, and has also been
made popular in heavy metal
• Thin, high- pitched voice
• Voice of mickey mouse is another example of falsetto

49. Pulse or Chest register
• Also known as strohbass (straw bass)
• Crackly, popcorn quality of voice
• Low in pitch, sounds rough
• Vocal folds vibrate between 30 and 90 hz
• Frying pan sound of eggs frying (also called glottal fry)
• Low subglottal pressure
• Tension of the vocalis is significantly reduced relative to modal
vibration, so that the vibrating margin is flaccid and thick
• The lateral portion of folds is tensed creating thick folds

50. Whistle Register
• Register above falsetto
• (flageolet register) is the highest register of the human
voice
• Up to 2500 Hz in females
• Product of turbulence on the edge of the vocal fold
• Not considered a mode of vibration as product of
turbulence

51. Attacks
• Process of bringing vocal folds together to begin phonation,
requires muscular action
• There are three kinds of attacks (or beginning of the each
voiced sound)
• Simultaneous - attack-coordinate adduction and onset of
respiration so that they occur simultaneously (i.e. say the word
“zany”- you start the flow of air before voicing)
• Glottal- adduction of the vocal folds occurs prior to the airflow,
much like a cough (i.e. bring vocal folds together like you are
going to cough- and then say /a/, or say “okay, I want the car.”
• Breathy- starting significant airflow before adducting the vocal
folds (i.e. running speech “Harry is my friend.” the air flow past
your lips

52. Termination
• Process of fold retraction (abduction)

53. Changes in voice

54. Changes in voice
•Pathological
• Processes involved in voice disorders
• Generation of air pressure
• Glottic closure
• Vocal fold vibration
• Voice loudness
• Voice pitch

55. GeneratingAir Pressure
• Pulmonary disease
• Asthma
• Subglottic stenosis
• Paresis of muscles
• Symptoms
• Shortness of breath
• Weak voice

56. Glottic Closure
• Nerve Paresis
• Unilateral Recurrent Laryngeal Nerve
• Bilateral Recurrent Laryngeal Nerve
• Unilateral Superior Laryngeal Nerve
• Bilateral Superior Laryngeal Nerve
• Combined Recurrent & Superior laryngeal Nerve
• Symptoms
• Hoarseness
• Effortful phonation
• Vocal fatigue

57. Vocal Fold Vibration
• Vocal fold scar or vocal fold lesions
• Cysts, nodules, polyps ,papilloma ,vocal fold granuloma
• Swelling and inflammation (reflux laryngitis, viral laryngitis)
• Reinke’s edema
• Paresis, haemorrhage, vascular ectasis
• Symptoms
• Hoarseness
• Effortful phonation
• Weak voice
• Speaking voice lower than usual “glottal fry”

58. Voice Loudness
• Vocal fold scar
• Paresis
• Vocal fold lesions: cysts, nodules, polyps, papilloma
• Vocal fold granuloma
• Swelling and inflammation (reflux laryngitis, viral laryngitis)
• Symptoms
• Unable to project voice
• Weak voice
• Voice breaks

59. Voice Pitch
• SLN paresis
• Vocal fold scar
• Reinke’s edema
• Vocal fold lesions
• Symptoms
• Unable to hit high notes
• Voice breaks

60. Dysphonia Plica Ventricularis
• Voice is produced by ventricular folds (false cords)
• Seen in Mimicry
• Voice is rough, low pitch and unpleasant
• May be secondary to impaired function of the true vocal
cord such as paralysis, fixation, surgical excision or
tumors
• Ventricular bands in these situations try to compensate or
assume phonatory function of true vocal cords

61. Androphonia
• Male like voice in female
• Low pitch
• Treatment:type IV thyroplasty

62. Mogiphonia
• Abnormal voice in front of public
• Traetment : speech therapy

63. Puberphonia
• High pitch voice at puberty
• This condition is only seen in emotionally dependent
boys.
• Non organic cause (functional cause)
• Clinical diagnosis: GUTZMANN TEST – push thyroid
backward and downward

64. Functional aphonia
• Seen in young females
• No voice with normal cough sound
• Larynx – normal
• Treatment : psychotherapy

65. Non Vocalized Sounds
• Whisper
• Whistle

66. REFERENCES
• Scott brown
• Thieme book of laryngology
• Ballenger
• Kenhub
• Dhingra

67. THANK YOU