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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

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)

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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 (which usually moves)

relaxed

contracted

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3 types of skilled movement

1. Movements of fixation – opposing groups of muscles

(agonistic and antagonistic)hold a body part in position

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.

antagonist muscle contraction counteracts agonist contraction

muscles fix a joint that is next to the joint to be moved

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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

R abdominal muscles led by rectus abdominus

D diaphragm

EI external intercostal muscles

II internal intercostal muscles

D

R

EI

II

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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

R abdominal muscles led by rectus abdominus

D diaphragm

EI external intercostal muscles

II internal intercostal muscles

D

R

EI

II

instantaneousair pressure

lung volume

equilibrium

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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 checklist1. 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

Front view Rear view Side view View from top

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Inside the larynxmid-sagittal (vertical, middle) view

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Inside the larynx: the vocal folds

Vocal folds can be in an open (abducted) or closed (adducted) configuration

View from above: Folds open (abducted)

View from above:Folds closed (adducted)

Glottis = space between folds

mid-sagittal view

fiberscope_insertion.mov

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Vibration of the vocal foldsresults 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 bythe 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 three-dimensional, and they vibrate in three dimensions.

The pattern of vibration is like a ‘wave’ travelling up them.

The lower sections part first, and come together first.

‘Cover’ (outer layer) and ‘body’ (inner layers) of folds are often distinguished, because they vibrate fairly independently

After Stevens (1998) Acoustic Phonetics(Baer, 1975)

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Vertical views of the vocal folds during one vibratory cycle

Two-mass model:

The pattern of vibration can be quite well modelled using 2 quasi-independent masses for each vocal fold.

one large, one small,

the two connected by a spring

After Stevens (1998) Acoustic Phonetics(Baer, 1975)

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2

3

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5

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Vocal foldsduring a vibratory cycle

Open for breathing

http://cspeech.ucd.ie/~fred/teaching/oldcourses/phonetics/pics/vfold1.gif

http://sail.usc.edu/~lgoldste/General_Phonetics/Larynx_film_festival/Demo_320_RLS_1A.mpg

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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

• 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

Front view Rear view Side view from above

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Starting and maintaining phonation

• Adduction: vocal processes of arytenoids moved together (lateral cricoarytenoid, interarytenoid muscles)

• This brings the vocal folds together, thus closing the glottis

Front view Rear view Side view from above

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Pitch control

• 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

Front view Rear view Side view from above

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Pitch control

• 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)

Front view Rear view Side view from above

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Voice qualities• Primarily laryngeal and respiratory

• Classification systems vary from very simple e.g. creak - modal - breathy, to very complex

• 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

(e.g. Laver)

Ladefoged (2001)Vowels and consonants

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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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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

Sulcus vocalis (vocal fold scar)Vocal fold nodules

Pathological disordersof vocal fold vibration or breathing

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Coordinating glottal and oral constrictionsoral closure oral release

oral constriction area

stop VOTglottal constriction and vibration

[aba] voicednegative

[apa] voiceless unasp. zero

[apha] voicelesspositive

aspirated

[ahpa] preaspirated

[aʔpa] glottalised “zero”

[abʱa] breathy

timekey

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

Air pressures and flows also affect the acoustic outcome

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Coordinating glottal and oral constrictionsoral closure oral release

oral constriction area

stop VOTglottal constriction and vibration

[aba] voicednegative

[apa] voiceless unasp. zero

[apha] voicelesspositive

aspirated

[ahpa] preaspirated

[aʔpa] glottalised “zero”

[abʱa] breathy

timekey

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

Air pressures and flows also affect the acoustic outcome

movie: Gujarati: Retroflex Unasp vs Aspirated [ ʈ ]

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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 stresse.g. below [] vs. billow []

– Sentence stress and focusa) (Does Deb love Bob?) No, BEV loves Bob

b) (Does Bev love Rob?) No, Bev loves BOB

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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?

• 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

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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?

• 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…

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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)