Transcript Anatomy and physiology of human respiration and phonation

Anatomy and physiology of human
respiration and phonation
Paper 9
Foundations of Speech Communication
Sarah Hawkins
2: 17 October 2008
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Aims
1. To outline principles of muscle behaviour
and some anatomy and physiology for
breath control and phonation
2. To explore some consequences of these
principles for aspects of linguistic form
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Control of muscles in the body
• Muscles are made up of lots
of fibres, each one of which
has its own nerve endings
• A muscle fibre contracts
when the neuron (single nerve
fibre) that innervates it fires;
and relaxes when the neuron
stops firing
• Muscle fibres in a single
muscle are organised into
groups (motor units). Each
motor unit is innervated by a
single motor neuron
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Nerve fires once  motor unit twitches once, due to a chemical
reaction. Faster firing  more continuous contraction (recruits more
motor units). Too much firing for too long  cramp-like state (tetanus)
Using muscles to move parts of the body
• For most voluntary movement, muscles move
one part of the body relative to another because
each muscle is attached to two different solid
structures, e.g. two bones, across a joint.
– origin of muscle is on one bone
(which usually stays fixed during contraction)
– insertion is on the other
relaxed
(which usually moves)
contracted
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3 types of skilled movement
1.
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Movements of fixation
– opposing groups of muscles
(agonistic and antagonistic)
hold a body part in position
muscles fix a joint
that is next to the
joint to be moved
antagonist muscle
contraction counteracts
agonist contraction
2.
Controlled movements
–  2 opposing muscle groups work in synergy
3.
Ballistic movements Plan trajectory to reach a target
– the movement consists of a single contraction of the
agonist muscle group, with the antagonist group(s)
relaxed. It is impossible to change the course of the
movement once it is started. The antagonist group(s)
normally contracts to terminate it.
Summary: Principles of skilled movement
Control: high-level coordinates
• identify target
• plan trajectory
• calculate the contribution of each of several body
parts to the actual trajectory: “functional synergies”
easy example: to make /bu/ (“boo”):
lips, jaw, and tongue can contribute to different degrees;
how much each contributes in a given instance depends on
individual habit, preceding and following context (planning for
smooth transitions etc)
Later lectures will apply the same types of principle to
perception:
• the big picture matters (the normal goal being to understand meaning)
• physically identical sensory detail is used in different ways depending on
circumstances
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The respiratory pump
• The spongy lungs can be
likened to two balloons that are
inflated and deflated as if by a
bicycle pump
• The basis for the action of the
respiratory pump is the way the
lungs are linked to the ribcage
(thorax) and abdomen by two
pleurae (membranes). A layer
of fluid between the pleurae
allows them to move freely and
provides suction to maintain the
linkage
• The consequence of the linkage
is that the lungs expand and
contract as the ribcage and
abdomen expand and contract
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EI
R abdominal
muscles led by
rectus
abdominus
II
D
D diaphragm
R
EI external
intercostal
muscles
II internal
intercostal
muscles
The respiratory pump
1.
Because volume and pressure
are related, altering the lung
volume changes the air
pressure in the lungs (Pa, Ps)
– Increasing lung volume
(e.g. by pushing the ribcage
or abdomen outwards)
lowers air pressure
– Decreasing lung volume
raises air pressure
instantaneous
air pressure
equilibrium
lung volume
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EI
R abdominal
muscles led by
rectus
abdominus
II
D
D diaphragm
R
EI external
intercostal
muscles
II internal
intercostal
muscles
Life breathing and speech breathing
• Life breathing: relatively effortless in healthy person
• Neuropathology can affect breathing for speech: e.g.
trying to impose metabolic breathing on speech;
sufferers from anarthria sometimes take a breath
between each word
• Lung diseases: e.g. asthma (inflamation and clogging of
airways) makes exhalation difficult
• Young children’s lungs are smaller than adults’: their
airways are more resistant to airflow. But they need to
generate approximately the same airflows as adults do.
Therefore, they need more muscular effort (esp.
expiratory) to achieve the right pressure. Consequences
e.g. shorter breath groups.
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The larynx
Biological function
a valve to keep bad stuff out, and to
expel any bad stuff that is already in!
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Laryngeal anatomy basic checklist
1. 4 main cartilages (cricoid, thyroid, pair of arytenoids, epiglottis)
•
joined to each other and slung from one bone (the hyoid) by membranes
•
joined to bones by extrinsic muscles – these fix it or move it in the neck
•
joined to each other by (mainly paired) intrinsic muscles which
–
move the cartilages relative to one another (4 main pairs)
–
comprise the bulk of the vocal folds (2 pairs)
2. The vocal folds are inside (and thus part of) the larynx
•
bundles of muscle, ligament and mucous membrane
•
extend horizontally from the front (thyroid notch) to the back (arytenoids)
•
space between them is the glottis
3. Laryngeal musculature enables vocal fold closure and opening (affecting
size and shape of the glottis) , and all adjustments for phonation
Innervation: part of the vagus, a cranial nerve that also controls breathing, heart, digestion etc.
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Phonation (voicing) basic checklist
1. To phonate, the vocal folds must vibrate
2. To vibrate, they must be held close enough
together to impede the airflow through the
glottis
3. Muscles bring them together & hold them there
4. The transglottal airflow itself sets them into
vibration, and maintains the vibration
– myoelastic aerodynamic theory of phonation
(elastic recoil and Bernoulli forces)
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Structure of the larynx
• 3 +1 main cartilages:
– large thyroid (Adam’s apple) comprising 2 plates and 4 horns.
connected upwards to hyoid bone by thyrohyoid muscle/ligament)
– smaller, circular cricoid with ‘signet ring’ shape: higher at back
than front
– 2 small, pyramid-shaped arytenoids sitting on top of posterior
surface of cricoid
– (+ epiglottis: up from thryoid angle, rests against back of tongue)
• Vocal folds connect vocal process of arytenoids to inner front of
thyroid cartilage
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Front view
Rear view
Side view
View from top
Inside the larynx
mid-sagittal (vertical, middle) view
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Inside the larynx: the vocal folds
mid-sagittal view
Vocal folds can be in an open (abducted)
or closed (adducted) configuration
Glottis = space between folds
View from above:
Folds open (abducted)
View from above:
Folds closed (adducted)
fiberscope_insertion.mov
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Vibration of the vocal folds
results in phonation (voicing)
Myoelastic aerodynamic theory of vocal fold vibration (van den Berg, 1950s)
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. (The
subglottal pressure increase leads to a transglottal pressure drop.)
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.
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Vertical views of the vocal folds during
one vibratory cycle
The folds are threedimensional, and they vibrate
in three dimensions.
1
4
The pattern of vibration is like
a ‘wave’ travelling up them.
The lower sections part first,
and come together first.
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2
5
‘Cover’ (outer layer) and ‘body’
(inner layers) of folds are often
distinguished, because they
vibrate fairly independently
3
6
After Stevens (1998) Acoustic Phonetics
(Baer, 1975)
Vertical views of the vocal folds during
one vibratory cycle
Two-mass model:
1
4
The pattern of vibration
can be quite well modelled
using 2 quasi-independent
masses for each vocal fold.
one large, one small,
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2
5
3
6
the two connected by a
spring
After Stevens (1998) Acoustic Phonetics
(Baer, 1975)
Vocal folds
during a vibratory cycle
http://sail.usc.edu/~lgoldste/General_Phonetics/Larynx_film_festival/Demo_320_RLS_1A.mpg
Open for
breathing
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http://cspeech.ucd.ie/~fred/teaching/oldcourses/phonetics/pics/vfold1.gif
Controlling phonation:
Intrinsic laryngeal muscles
This lecture does not address external
laryngeal muscles, nor detailed vocal fold
anatomy (read e.g. Hardcastle)
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No phonation, or stopping phonation
Front view
Rear view
Side view
from above
• Abduction: Vocal processes of arytenoids (front
part) rotated backwards and outwards
(posterior cricoarytenoid muscle)
• This moves the vocal folds apart and so widens
the glottis
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Starting and maintaining phonation
Front view
Rear view
Side view
from above
• Adduction: vocal processes of arytenoids moved
together (lateral cricoarytenoid, interarytenoid
muscles)
• This brings the vocal folds together, thus closing
the glottis
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Pitch control
Front view
Rear view
Side view
from above
• Increasing pitch: contracting cricothyroid muscle:
pulls front of cricoid up towards thyroid, so back of
cricoid moves down and back, taking arytenoids
with it and stretching/tensing vfs  vibrate faster
• vocalis – shortens/thickens & tenses vocal folds
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Pitch control
Front view
Rear view
Side view
from above
• Increasing pitch: contracting cricothyroid muscle:
pulls front of cricoid up towards thyroid, so back of
cricoid moves down and back, taking arytenoids
with it and stretching/tensing vfs  vibrate faster
• vocalis – shortens/thickens and tenses vocal folds
(complex adjustments to length, tension, thickness & medial compression)
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Voice qualities
• Primarily laryngeal and respiratory
• Classification systems vary from very simple e.g.
creak
- modal
- breathy, to very complex
(e.g. Laver)
Ladefoged (2001)
Vowels and consonants
• Reasons for variation:
– physiological: laryngeal physiology is poorly
understood, partly because there are so many degrees
of freedom (different combinations of controlling factors)
– perceptual and functional: multiple factors, often with
multiple functions
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Communicative uses of voice quality
Cultural: some cultures have distinctive voice
qualities (start noticing if you haven’t already)
Indexical: part of an individual’s characteristic
speech patterns
Communicative function:
– controlling conversation cf. ‘so’, ‘I think’, ‘and’
– conveying affect (emotion)
Phonetic roles: ‘segmental’ and ‘prosodic’
– underpin all the above
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Pathological disorders
of vocal fold vibration or breathing
e.g.
• neural: e.g. paralysis, spastic dysphonia → incomplete closure
→ breathy → quiet; usually high pitch; or harsh if tense. Parkinson’s →
immobile + tremor, quiet, restricted pitch range (often high), hoarse
• viral laryngitis → oedema, dryness → hoarse, or silent
• habitual abuse (shouting, smoking) → hoarse, harsh
• physical damage to the folds (nodules, polyps, scars....):
incomplete closure + irregular vibration → breathy, hoarse, low volume
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Vocal fold nodules
Sulcus vocalis (vocal fold scar)
Coordinating glottal and oral constrictions
oral closure
oral release
oral constriction area
stop
VOT
[aba]
voiced
negative
[apa]
voiceless unasp.
zero
[apha]
voiceless
aspirated
positive
[ahpa]
preaspirated
[aʔpa]
glottalised
[abʱa]
breathy
glottal constriction and vibration
time
key
Air pressures and
flows also affect the
acoustic outcome
top row: complete oral closure; all other rows: vocal folds adducted but not vibrating
top row: oral articulators open; all other rows: vocal folds abducted and not vibrating
modal phonation: vocal folds adducted and vibrating
breathy phonation: vocal folds partially adducted and vibrating
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“zero”
Coordinating glottal and oral constrictions
oral closure
oral release
oral constriction area
stop
VOT
[aba]
voiced
negative
[apa]
voiceless unasp.
zero
[apha]
voiceless
aspirated
positive
[ahpa]
preaspirated
[aʔpa]
glottalised
[abʱa]
breathy
glottal constriction and vibration
time
key
“zero”
Air pressures and
flows also affect the
acoustic outcome
top row: complete oral closure; all other rows: vocal folds adducted but not vibrating
top row: oral articulators open; all other rows: vocal folds abducted and not vibrating
modal phonation: vocal folds adducted and vibrating
movie: Gujarati: Retroflex
breathy phonation: vocal folds partially adducted and vibrating
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Unasp vs Aspirated [ ʈ ]
How does the breath shape the
prosody of speech?
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Prosody in speech
• Commonly used to refer to a range of
phonetic features, such as pitch, loudness,
tempo, and rhythm.
• To describe the prosody of speech, we need
to think about levels of organisation larger
than the phonetic segment, e.g.
– syllable
– foot
– prosodic phrase
– breath group
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Stress and focus
• Different kinds of prominence borne by syllables
– Lexical stress
e.g. below [] vs. billow []
– Sentence stress and focus
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a) (Does Deb love Bob?)
No, BEV loves Bob
b) (Does Bev love Rob?)
No, Bev loves BOB
What is the respiratory contribution to
speech prosody?
A separate muscular contraction for every syllable?
Classic work by Stetson (1951) proposed that:
1. The syllable is constituted by a ballistic movement of
the intercostal muscles.
2. This movement is terminated either by a consonant
constriction (which checks airflow) or by contracting
the inspiratory muscles
3. Longer-term prosodic units (foot, breath group) are
defined by contractions of the abdominal muscles.
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What is the respiratory contribution to
speech prosody?
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•
Pressure, flow and movement data seemed to support
Stetson’s view.
•
But work in the 1950s using electromyography and
other techniques (e.g. Draper, Ladefoged and
Whitteridge 1959, Ladefoged 1967) discredited it.
•
They argued that the respiratory system contributes to
stress, but does not define syllables.
•
Others proposed a role for the laryngeal muscles in
regulating intensity (loudness – an important part of
stress).
•
See Kelso and Munhall (1988) edition of Stetson
What is the respiratory contribution to
defining speech prosody?
•
But DLW’s results are also in question now.
•
Finnegan et al. (1999, 2000) measured tracheal
pressure, laryngeal muscle activity, and airflow.
•
They showed that the respiratory system contributes
much more than laryngeal muscle activity to both
short-term and long-term changes in intensity.
Finnegan, Luschei, Hoffmann (1999, 2000)
See advanced reading list for complete reference
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What is the respiratory contribution to
defining speech prosody?
•
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Messum (2003) returns to an account like Stetson’s,
but based around the foot rather than the syllable (for
stress-timed languages like English and German). On
his account, each foot is produced by a single,
invariant pulse of effort from the muscles of the chest.
Speculative but interesting, especially in that it tries to
integrate both developmental and adult physiology with
speech behaviour…
Summary
Respiration and laryngeal activity for speech
• are at least as complex as upper articulator activity
• interact with upper articulators in complex ways
• have an important role in explaining
– many phonetic phenomena (segments & prosody)
– many related linguistic phenomena
(grammar, meaning)
– a vast range of other communicative
phenomena (broadly, pragmatic, interactional, and indexical)
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