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Phonation Laryngeal Physiology

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Phonation + Laryngeal Physiology January 14, 2010 The Aerodynamics of Speech Lung Compression Lung Expansion Riding the Wave Back to Aerodynamics Trills Any volunteers? – PowerPoint PPT presentation

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Title: Phonation Laryngeal Physiology


1
Phonation Laryngeal Physiology
January 14, 2010
2
The Aerodynamics of Speech
  • Note all sounds are created by the flow of air
  • Most (but not all) speech sounds are produced by
    a pulmonic egressive airstream mechanism.
  • air flows out of the lungs
  • Note air flows naturally out of the lungs when
    they are compressed
  • ? air always flows from areas of high pressure
    to low

3
Lung Compression
  • In speech, lung compression is typically a
    passive process.
  • The linkage between the lungs and the thoracic
    (rib) cage tends toward an equilibrium--
  • at which the lungs are larger than they would be
    alone
  • and the rib cage is smaller than it would be
    alone.
  • When the linked pair is expanded beyond the
    equilibrium point, it will naturally contract
    back to it.
  • (and vice versa)

4
Lung Expansion
  • The expansion of the lungs is primarily driven
    by the contraction of the muscles in the
    diaphragm.
  • This increases volume in the vertical dimension.
  • Contraction of the external intercostal muscles
    also pulls out the rib cage in the front-back and
    side-to-side dimensions.
  • intercostal between the ribs

5
Riding the Wave
  • Speech is normally produced on the passive
    expiration that follows an expansion of the
    lungs.
  • Airflow may be fine-tuned by contraction of the
    internal intercostal muscles.
  • Active contraction results in
  • higher airflow
  • higher intensity
  • ? greater perceived stress

6
Back to Aerodynamics
  • Remember sounds are created by the flow of air
  • but speech often becomes interesting when that
    flow of air is interrupted.
  • E.g., aerodynamic method 1 Stops
  • start air flow
  • stop air flow
  • release air flow
  • Heres an example of aerodynamic method 2.
  • What kind of sound was that?

7
Trills
  • A a Trill. A Bilabial Trill
  • Examples from Kele and Titan (spoken on the
    island of Manus, north of New Guinea)

8
Any volunteers?
  • Does anyone else know how to produce a bilabial
    trill?
  • And would anyone like to demonstrate?
  • How fast do your lips open and close when you
    make a bilabial trill?
  • Lets take a look at the waveform in Praat
  • Waveform representation of the change in air
    pressure over time.

9
Some Terminology
  • Frequency is the rate at which the lips are
    opening and closing
  • measured in Hertz (cycles per second)
  • Period is the length of time between cycles
  • Frequency 1 / Period
  • Some questions
  • In a bilabial trill, do we close and relax our
    lips on each cycle?
  • When air blows the lips apart, why dont they
    stay apart?

10
Bernoulli Effect
  • In a flowing stream of particles
  • the pressure exerted by the particles is
    inversely proportional to their velocity
  • Pressure constant
  • velocity
  • P k / v
  • ? the higher the velocity, the lower the
    pressure
  • ? the lower the velocity, the higher the pressure

Daniel Bernoulli (1700-1782)
11
Bernoulli Examples
  • Airplane wing
  • Shower curtain
  • Pieces of paper
  • Bilabial trills!

12
A Trilling Schematic
  • Lips are closed
  • adducted brought together
  • Fad adductive force

upper lip
Fad
inside of mouth
outside of mouth
lower lip
Fad
13
Trilling Stage 1
  • Pressure builds up inside mouth from compression
    of lungs
  • Pin Air Pressure inside mouth
  • Outside pressure remains constant
  • Pout Air Pressure outside mouth

Fad
Pout k
Pin
Fad
14
Trilling Stage 1
  • Pressure differential between inside and outside
    builds up
  • This exerts force against the lips

?P (Pin - Pout )
Fad
Pout k
Pin
Fad
15
Trilling Stage 2
  • Pressure differential blows open lips
  • Air rushes from high to low pressure

Fad
Pout k
Pin
air
Fad
16
Trilling Stage 2
  • The opening of the lips means
  • ?P decreases slightly
  • High velocity of air flowing between lips
  • Air pressure decreases between lips (Bernoulli
    Effect)

Fad
Pout k
Pin
Pbl
Fad
17
Trilling Stage 3
  • Lips get sucked back together

Fad
Pout k
Pin
Fad
18
Trilling Back to Stage 1
  • If air is still flowing out of lungs, pressure
    will rise again within mouth
  • Process will repeat itself as long as air is
    pushed up from lungs and lips are held lightly
    against each other

Fad
Pout k
Pin
Fad
19
Trilling Back to Stage 1
  • Air rushes through the lips in a series of short,
    regular bursts

Fad
Pin
Fad
20
Trill Places
21
Phonation
  • Glottal trilling is known as phonation.
  • It distinguishes between voiced and voiceless
    sounds.
  • z vs. s v vs. f, etc.
  • Glottal trilling is made possible by the
    presence of two vocal folds within a
    complicated structure known as the larynx.
  • When the vocal folds are
  • 1. open air passes cleanly through ( voiceless
    sound)
  • 2. closed air does not pass through ( no sound)
  • 3. lightly brought together vocal folds vibrate
    in passing air
  • ( voiced sound)

22
Voicing, Schematized
Voiceless (folds open) Voiced (folds together)
( abducted)
( adducted)
23
Laryngoscopy
Source http//homepage.mac.com/changcy/endo.htm
24
Voicing, in Reality
25
Creaky Voicing
  • The flow of air from the lungs forces the vocal
    folds to open and close.
  • The slowest type of voicing is called creaky
    voice.

26
Modal Voice
  • In normal, or modal voicing, the rate of
    glottal trilling is considerably faster.
  • How fast do you think the vocal folds open and
    close in normal voicing?

27
Vocal Fold Specs
  • In bilabial trills, lips open and close 20-25
    times a second
  • In modal voicing, the glottal trill cycle
    recurs, on average
  • 120 times a second for men
  • 220 times a second for women
  • 300 times a second for children
  • For voiced speech sounds, this rate is known as
    the fundamental frequency (F0) of the sound.
  • Lets check it out

28
Vocal Fold Specs
  • Air rushes through vocal folds at 20 to 50
    meters per second
  • between 72 and 180 kph (45 120 mph)
  • Due to Bernoulli Effect, pressure between vocal
    folds when this occurs is very small
  • Speed of glottal trill cycle depends on
  • thickness of vocal folds
  • tenseness of vocal folds
  • length of vocal folds

29
Vocal Fold Specs
  • In men, vocal folds are 17-23 millimeters long
  • In women, vocal folds are 12-17 millimeters long
  • Adult male vocal folds are 2-5 millimeters thick
  • Adult female vocal folds are slightly thinner
  • Thicker, longer folds vibrate more slowly
  • Think violin strings vs. bass strings
  • Tenseness of vocal folds can be changed to alter
    the speed of glottal opening and closing.
  • Like tuning a violin or a guitar

30
The Larynx
  • The larynx is a complex structure consisting of
    muscles, ligaments and three primary cartilages.

31
1. The Cricoid Cartilage
  • The cricoid cartilage sits on top of the trachea
  • from Greek krikos ring

cricoid cartilage
  • It has facets which connect it to the thyroid
    and arytenoid cartilages.

32
2. The Thyroid Cartilage
  • The thyroid cartilage sits on top of the cricoid
    cartilage.
  • from the Greek thyreos shield
  • The thyroid cartilage has horns!
  • Both lower (inferior) and upper (superior) horns
  • The lower horns connect with the cricoid
    cartilage at the cricoids lower facet.
  • The upper horns connect to the hyoid bone.

33
Thyroid Graphic
thyroid cartilage
cricoid cartilage
34
Thyroid Angles
  • The two broad, flat front plates of the
    thyroid--the laminae--meet at the thyroid angle.
  • The actual angle of the thyroid angle is more
    obtuse in women.
  • ...so the Adams Apple juts out more in men.

35
3. The Arytenoid Cartilages
  • There are two arytenoid cartilages.
  • from Greek arytaina, ladle
  • They are small and pointy, and sit on top of the
    back side, or lamina, of the cricoid cartilage.

arytenoid cartilages
cricoid cartilage
36
The Vocal Folds
  • These three cartilages are connected by a
    variety of muscles and ligaments.
  • The most important of these are the vocal folds.
  • They live at the very top of the trachea, in
    between the cricoid and thyroid cartilages.
  • The vocal folds are a combination of
  • The vocalis muscle
  • The vocal ligament
  • The vocal folds are enclosed in a membrane
    called the conus elasticus.

37
Vocal Fold View 1
  • Just above the true vocal folds are the false
    (!) vocal folds, or ventricular folds.
  • The space between the vocal folds is the glottis.

38
Vocal Fold View 2
  • The vocal ligaments attach in the front to the
    thyroid cartilage.
  • ...and in the back to the arytenoid cartilages.
  • The glottis consists of
  • the ligamental glottis
  • the cartilaginous glottis

39
Things Start to Happen
  • Note that the arytenoid cartilages can be moved
    with respect to the cricoid cartilage in two ways.

1 rocking
2 sliding
40
The Upshot
  • The arytenoids can thus be brought together
    towards the midline of the body.
  • Or brought forwards, towards the front of the
    thyroid.
  • The rocking motion thus abducts or adducts the
    glottis.
  • The sliding motion shortens or lengthens the
    vocal folds.
  • Check out the arytenoids in action.

41
  • When the vocal folds are abducted
  • air passes through the glottis unimpeded and
    voicelessness results.
  • The posterior cricoarytenoid muscles are
    primarily responsible for separating the
    arytenoid cartilages.

42
  • Voicing may occur when the vocal folds are
    adducted and air is flowing up through the
    trachea from the lungs.
  • Two muscles are primarily responsible for
    adducting the vocal folds.
  • The first is the lateral crico-arytenoid muscle.

43
  • Note that the lateral cricoarytenoid muscles
    only adduct the ligamental glottis.
  • The transverse arytenoid muscles pull together
    the arytenoid cartilages themselves.
  • Thereby closing the cartilaginous glottis.

44
The Consequences
  • The combined forces drawing the vocal folds
    towards each other produce adductive tension in
    the glottis.
  • Adductive tension is increased by
  • lateral cricoarytenoid muscles
  • transverse arytenoid muscles
  • Adductive tension is decreased by
  • posterior cricoarytenoid muscles
  • Adduction vs. abduction determines whether or
    not voicing will occur.
  • But we can do more than just adduce or abduce
    the vocal folds...

45
Factor Two
  • We can also change the longitudinal tension of
    the vocal folds.
  • I.e., tension along their length, between the
    thyroid and arytenoid cartilages.
  • Higher tension higher F0
  • Lower tension lower F0
  • Q How is this possible?

46
  • A We can rotate the thyroid cartilage up and
    down on its connection with the cricoid
    cartilage.
  • ...like the visor of a knights helmet.
  • This either stretches or relaxes the vocal folds.
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