Anatomy and physiology of human respiration and phonation Paper 9 Foundations of Speech Communication Sarah Hawkins 2: 17 October 2008
Aims • To outline principles of muscle behaviour and some anatomy and physiology for breath control and phonation • To explore some consequences of these principles for aspects of linguistic form
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 contractswhen 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)
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. • originof muscle is on one bone (which usually stays fixed during contraction) • insertionison the other (which usually moves) relaxed contracted
antagonist muscle contraction counteracts agonist contraction 3 types of skilled movement muscles fix a joint that is next to the joint to be moved • Movementsof fixation • opposing groups of muscles(agonistic and antagonistic)hold a body part in position • Controlled movements • 2 opposing muscle groupswork in synergy • Ballistic movements Plantrajectory 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
EI II D R 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 EIexternal intercostal muscles II internal intercostal muscles
EI II D R instantaneousair pressure equilibrium lung volume The respiratory pump • 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 EIexternal 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.
The larynx Biological function a valve to keep bad stuff out, and to expel any bad stuff that is already in!
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.
Phonation (voicing) basic checklist • To phonate, the vocal folds must vibrate • To vibrate, they must be held close enough together to impede the airflow through the glottis • Muscles bring them together & hold them there • The transglottal airflow itself sets them into vibration, and maintains the vibration • myoelastic aerodynamic theory of phonation (elastic recoil and Bernoulli forces)
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 cricoidwith ‘signet ring’ shape: higher at back than front • 2 small, pyramid-shaped arytenoidssitting 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 View from top Side view Rear view
Inside the larynx: the vocal folds mid-sagittal view Vocal folds can be in an open (abducted) or closed (adducted) configuration View from above:Folds closed (adducted) View from above: Folds open (abducted) Glottis = space between folds fiberscope_insertion.mov
Vibration of the vocal foldsresults in phonation (voicing) Myoelastic aerodynamic theory of vocal fold vibration (van den Berg, 1950s) • 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. • Air pressure increases below the glottis until folds forced apart. (The subglottal pressure increase leads to a transglottal pressure drop.) • Air travels faster through the glottis when it is narrow. This causes a local drop in air pressure (Bernoulli effect)whichcauses the folds to be sucked towards each other. • The Bernoulli effect, together with the elastic recoil force exerted bythe displaced vocal folds, causes complete glottal closure again. • The process begins again at step 2.
1 4 2 5 3 6 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)
1 4 2 5 3 6 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)
Open for breathing Vocal foldsduring a vibratory cycle http://sail.usc.edu/~lgoldste/General_Phonetics/Larynx_film_festival/Demo_320_RLS_1A.mpg 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)
Side view from above Front view Rear view No phonation, or stopping phonation • Abduction: Vocal processes of arytenoids (front part) rotated backwards and outwards (posterior cricoarytenoidmuscle) • This moves the vocal folds apart and so widens the glottis
Side view from above Front view Rear view 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
Side view from above Front view Rear view 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
Side view from above Front view Rear view 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)
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
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
Vocal fold nodules Sulcus vocalis (vocal fold scar) Pathological disordersof 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
Coordinating glottal and oral constrictions oral closure oral release oral constriction area stop VOT glottal constriction and vibration [aba] voiced negative [apa] voiceless unasp. zero [apha] voiceless positive aspirated [ahpa] preaspirated [aʔpa] glottalised “zero” [abʱa] breathy time key 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
Coordinating glottal and oral constrictions oral closure oral release oral constriction area stop VOT glottal constriction and vibration [aba] voiced negative [apa] voiceless unasp. zero [apha] voiceless positive aspirated [ahpa] preaspirated [aʔpa] glottalised “zero” [abʱa] breathy time key 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 ]
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
Stress and focus • Different kinds of prominence borne by syllables • Lexical stress e.g. below  vs. billow  • Sentence stress and focus 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: • The syllable is constituted by a ballistic movement of the intercostal muscles. • This movement is terminated either by a consonant constriction (which checks airflow) or by contracting the inspiratory muscles • Longer-term prosodic units (foot, breath group) are defined by contractions of the abdominal muscles.
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
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
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…
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)