The Anatomy and Physiology of Speech Production(Phonetics)

Sources :John Clark -2007 and J.C.Catford -1989 sundarabalu

• The nervous System• The respiratory system• The larynx• Phonation• The Pharynx• The velum and the nasal cavity• The tongue• The lips

The nervous system

• The nervous system is usually considered to have two parts CNS consisting of brain and the spinal medulla, and PNS consisting of the nerves distributed through the body.

• From birth , human development shows increasing evidence that one of the two cerebral hemispheres is dominant in the functioning of spoken languages.

• The PNS consists of three components: the central nerves which arise from the brain stem and the head and neck area (much of which is involved in speech

production), the spinal nerves, which innervate the trunk and lungs, and the autonomic nervous system which is responsible for involuntary activities such as blood flow and breathing

• The cranial nerves innervating the vocal tract consist of mixed nerves- that is , they contain both efferent (motor) fibers sending muscle control signals from the CNS , and afferent (sensory) fibres sending information to the CNS from receptors in the skin, mucosa and muscles

• The functional unit of the CNS is the NEURON , which consists of a nerves cell and its nerve fibre extensions extensions (or process)

Motor neuron

• Above figure shows a motor neuron , consisting of a

cell body , the axon (nerve fibre which conducts impulses to

muscles, as shown here, or to other nerves) and dendrites (which

are similar to axons but are shorter and may conduct impulses to neuron). On

the cell body and dendrites are connecting points or

SYNAPSES , which allow connections with other

neurons.

• Hence the neuron system consists of a complex

interconnecting network of neural pathways which can

conduct nerve impulses. Muscle commands initiated in

the CNS do not travel to their destination via single

nerve cells . Rather , they may pass across many

synaptic junctions with nearby cells interacting with

and modifying the original command impulse before it

reaches the muscle

Nerve_impulse_Animation.mp4

• Neural signals travelling along nerves fibres take the form of

short impulses of electrochemical energy caused by the firing

of the associated nerve cell. The magnitude of nerve activity

is determined not by the strength of amplitude of the pulse

but by the number of pulses per unit of time travelling down

the axon.

• A nerve cell can fire only if the impulse energy arriving at one

or more of its synapses is above a threshold level. Beyond

that level any increase will have no further effect. This ‘ all-or

– none ’ principal is reflected in the behaviour of muscle

fibre.

• The respiratory system

• The respiratory system(aside from the upper airways in the supraglottal vocal tract ) is contained within the chest, or Thorax. It consists of the barrel- shaped rip structure which forms the side of the thoracic cage itself, the associated rib structure which forms the side of the thoracic cage itself, the associated muscles, and the lung structure contained within it.

• In the process of inspiration and expiration in the normal respiratory cycle, they perform the vital function of replenishing oxygen and removing unwanted carbon dioxide from the blood

• The lungs are connected to the wind pipe , or TRACHEA by two bronchial tubes which join at the base of the trachea. Within each lung the bronchial tubes divide into smaller and smaller tubes, or bronchioles, which distribute the air supply throughout the lung. the two lungs actually form a single mechanical unit.

The larynx• The basic function of the larynx is as

a valve in the respiratory system. Thus in the process of swallowing , the larynx is automatically shut to ensure that food or drink pass through the pharyngeal cavity into the esophagus (a muscular tube for the passage

of food from the pharynx to the stomach) and not into the windpipe. The value action of the larynx is also important in short- term physical exertion as a means of stiffening the thorax when we inhale deeply and hold our breath. In speech, the larynx is important as a source of sound and as an articulator.

Coronal slice through the larynx; rear portion removed, leaving front portion. (Viewed from behind.)

Anatomy of Vocal Organs

• Phonation

• THE FUNCTIONAL COMPONENTS OF SPEECH • From the organic-aerodynamic point of view the

production of speech-sounds involves two essential functional components:

• (1) some method of initiating a flow of air in and through the vocal tract-that is, some form of initiation, as we call it; and

• (2) some method of shaping or articulating the air-stream so as to generate a specific type of sound-that is, some form of articulation.

• There is a third functional component of speech-production, present in most, but not all, sounds, and consisting of certain types of modulation of the air-stream as it passes through the larynx-that is phonation.

• In order to understand the mechanism of speech it is essential to have a clear conception of these three functional components-of the forms that they can take, and of how they interact to produce speech-sounds.

• Initiation : a bellow –like ,or position –liken, movement of an organ , that generates positive or negative air pressure adjacent to it in the vocal tract and thus initiates an egressive (outgoing ) or ingressive (ingoing ) flow of air

• Articulation: an organic posture or movement – most commonly in the mouth – that modulates the initiatory airflow in such a way as to generate a sound of some specific types.

• As we have pointed out , these two components are essential – without them no specific sound can be produced . In addition to theses essential components , however , every many sounds have a third basic component that modulates their quality in certain ways. This component of speech production is called phonation , and as usual we shall approach it experimentally

Phonation : Basic Component

• Principal phonation Types• Two types of phonation 1. Voiceless (glottis wide open so that air passes

through with minimal obstruction) 2. Voiced (Vocal folds brought together and

thrown into vibration by the passage of air through the glottis).

But these are only two of several different states of the glottis that are responsible for phonation

• In exploring states of the glottis we start with the vocal folds as widely separated as possible.

• This is the position of deep breathing .Even when the folds are as wide separately as possible the larynx still represent an orifice (An opening, especially to a cavity) only about half as wide as the windpipe, or trachea, that extends below it to the lungs.

• Consequently , even the open glottis offers some resistance to air passing through , and in breathing in and out one can normally hear some sound generated by turbulent flow through the open glottis.

• Only if we slow down our breathing to a considerable extent is the sound of exhalation and inhalation abolished.

• From this wide –open position ( the state of the glottis for breathing or for voiceless sound )

• We can narrow the glottis , so that the orifice present a much greater obstacle to the passage of air through it , and the flow thus becomes quite strongly turbulent , generating the “ hushing” sound that we call whisper.

• There is one more type of phonation to be

considered. This is creak . It is very low frequency

‘creaking’ or crackling sound which – perhaps

because it reminds some people of the sputtering

noise of frying eggs or bacon – is sometimes called

‘glottal fry’. Creak is produced with the glottis

completely ( but not very tightly) closed, except for

a small segment near the front end of the vocal folds

which is vibrating rather slowly.

• Four different types of phonation:1. Voiceless (breath): with the glottis wide open, as in

breathing or the production of voiceless sounds, such as [f ,s, p, t, k,]

2. Whisper: with a considerably narrowed glottis , so that the highly turbulent air – flow through glottis generates a strong ‘hushing ’ noise : this is the phonation types of whispered speech, in which whisper is substituted for voiced sounds (while voiceless sounds remain voiceless ).

3. Voice: the tone produced by the vibrating vocal folds: the phonation type of all voiced sounds , such as [ v, z, m, l, I, a, u,]

4. Creak: the crackling sound produced by keeping the vocal folds closed along most of their length , but allowing the air to escape in a low frequency series of bursts through a small vibrating segment near the front end of glottis

• Four phonation types and for complete closure.• In c, and d, is intended to suggest a difference in the

frequency of vocal fold vibration – medium to high frequency for voice (c),and very low frequency for creak (d). Note that complete glottal closure is not a type of phonation.

• Phonation always involves a flow of air through the glottis

• There are various possible combinations of these types of phonation, the chief ones being breathy voice, whispery voice (also known as murmur), and creaky voice.

• Breathy voice : the glottis is rather widely open , but the rate of airflow is so high that the vocal folds are set ‘flapping in the breeze ’ as the air rushes by. Exhale very strongly, contriving to produce some voice at the same time . Imagine that you are trying to blurt out a message when extremely out of breath , or speaking while sighing deeply

• Whispery voice or murmur: the vocal folds are vibrating to produce voice but at the time there is a continuous escape of air generating the sound of whisper. Produce an energetic and prolonged strong whisper, and while it is going on add voice, to produce the mixture called ‘whispery voice’. Producing voice with very relaxed vocal folds may help.

• Creak voice: proceed start with low – pitched voice, then go still lower still some creak is heard mixed with voice- but in this case make no attempt to produce the pure creak that was the end result.

The Pharynx: The pharynx or pharyngal

cavity is the voice box. This acts as a

vibrating cavity for the sounds produced by

the vibration of the vocal cords. The partial

or complete stoppage of the air-stream can

be achieved by modifying the shape of this

cavity that makes the soft-palate or the

tongue act.

(The cavity between the root of the tongue

and the walls of the upper throat.)

The Pharynx• The pharynx is a tube of muscle shaped rather like

an inverted cone. Typically around 12 cm long, it is lies between the glottis and the base of the skull. It acts as an air passage for respiration ,aids in the ingestion of food, and provides drainage for the nasal passage. It makes a passive contribution to speech production by forming part of the length of suraglottal vocal tract, but its geometry and volume can also be adjusted to vary this contribution or for other articulatory effects. there are three functional areas

Lungs

Trachea

Vocal Cords (within the Larynx)

Pharynx

Nasal Cavity

The velum and the nasal cavity

• The soft palate or VELUM is a continuation of the roof of the mouth , posterior to the bony structure of the hard palate. It is consists of a flexible sheet of muscular tissue covered in mucous membrane ending at the UVULA , a small tip o f muscle and flexible tissue.

The oral cavity

In the head we have the organs of articulation and two cavities. : (i) the oral cavity, and (ii) the nasal cavity. The oral cavity is the mouth and the

nasal cavity is the nose.  The shape of the mouth cavity depends on the positions of the tongue

and the lips. The roof of the mouth can be divided into the following three parts;

the alveolar ridge or teeth ridge having hard convex surface just behind the upper teeth; ALVEOLAR RIDGE

A short distance behind the upper teeth is a change in the angle of the roof of the mouth. This is the alveolar ridge. Sounds which involve the area between the upper teeth and this ridge are called alveolars.

the hard palate, (the hard concave surface); (HARD) PALATE The hard portion of the roof of the mouth. The term "palate" by itself usually refers to the hard palate.

the soft-palate or the velum at the back, with the uvula at its end SOFT PALATE/VELUM The soft portion of the roof of the mouth, lying behind the hard palate. The tongue hits the velum in the sounds [k], [g], and [N]. The velum can also move: if it lowers, it creates an opening that allows air to flow out through the nose; if it stays raised, the opening is blocked, and no air can flow through the nose.

UVULAThe small, dangly thing at the back of the soft palate. The uvula vibrates during the r sound in many French dialects.

VOCAL FOLDS/VOCAL CORDS Folds of tissue stretched across the airway to the lungs.

They can vibrate against each other, providing much of the sound during speech. GLOTTIS

The opening between the vocal cords. During a glottal stop, the vocal cords are held together and there is no opening between them.EPIGLOTTISThe fold of tissue below the root of the tongue. The epiglottis helps cover the larynx during swallowing, making sure (usually!) that food goes into the stomach and not the lungs. A few languages use the epiglottis in making sounds. English is fortunately not one of them.

VOCAL FOLDS PRODUCING A SOUND AT TWO DIFFERENT PITCHES

The tongue• With in the oral cavity is the tongue , which makes

the greatest contribution to changes in the volume and geometry of the cavity. The tongue consists largely of muscle , with an covering of mucous membrane and a fibrous septum dividing it longitudinally

The Tongue; The tongue is a very important organ of speech. It can take up a very large number of different positions for the articulation of different vowel and consonant sounds. The tongue has five parts which are as follows:

  A. the tip B, the blade C. the front D. the back E. the root.

 The extreme edge of the tongue is called the tip. Immediately after the tip is the blade and it is the part of the tongue that lies opposite the teeth-ridge when the speech organs are at rest. Beyond the blade is the front of the tongue which lies opposite the hard palate when the speech-organs are at rest.

TONGUE BLADE The flat surface of the tongue just behind the tip.

TONGUE BODY/DORSUM The main part of the tongue, lying below the hard and soft palate. The body,

specifically the back part of the body, moves to make vowels and many consonants. TONGUE ROOT

The lowest part of the tongue in the throat.

• The Lips: The lips play their part in the articulation of certain consonants.

For example, the initial sound in the English words, pill, bil1 and mill are produced with the lips tightly close. Also, the lips play an important part during the articulation of vowel sounds.

The lips assume different positions-spread, neutral, or rounded-for different vowel sounds. For example, the vowel in the English word see is produced with spread lips, that in the word sat is produced with neutral lips and that in the word shop is produced with rounded lips.

The lips

Speech mechanism

1. The Respiratory System consists of the following organs: A. The lungs B. The muscles of chest. C. The wind-pipe ('trachea').

 2. The phonatory system: is formed by the larynx. It is generally called 'voice-box' It is box like space at the top of the wind-pipe, containing the vocal cords which produce the voice.

 3. The Articulatory System: Its consists of the following organs:

  A. The nose B. The mouth.

The mouth includes the following: A. The tongue B. The teeth C. The roof of the mouth D. the lips.

 

The Air-stream Mechanism

a)Pulmonic

b) Glottic

c) Velaric

We breathe in and breathe out air. When we breathe in air, no sound is produced but it is not so in the case of breathe outing air form the lungs. Sound is produced when air is puff out form the lungs.

 Technically speaking, for the production of speech we

need air stream mechanism. There are three types of air-stream mechanism. They are as follows :

 A. Pulmonic B. Glottalic C. Veleric  

A. Pulmonic air-stream mechanism is one which consists of the lungs and the respiratory muscles, which set the sir-stream in motion.

•  Pulmonic Sounds• Air flow is directed outwards towards

the oral cavity• Pressure built by compression of lungs• English [p], [n], [s], [l], [e]

•Glottic Egressive Sounds•Air flow is directed outwards towards the oral Cavity• Pressure built by pushing up closed glottis [p’], [t’], [k’]

B. Glottalic air-stream mechanism is one in which the larynx, with the glottis firmly closed, is moved up or down to initiate the air-stream.

Velaric Sounds•Air flow is directed inwards from the oral cavity•Pressure reduced by forming velaric and alveolar closure and pulling down tongue

C. Veleric air-stream mechanism is one in which the back of the tongue in firm contract with the soft palate also called the velum, is pushed forward or pulled back to initiate the air-stream.  

The Types of Air-stream

We have just seen that the air-stream mechanism is of three types. Let us note that the air-stream is of the following two types :

 Air-streams

Egressive Ingressive

1. The Egressive air-stream is one in which the air is pushed out (It must be remembered that for the sounds of English and most of the Indian languages, we generally make use of an egressive pulmonic air-stream, that is, the air is pushed out of the lungs).

 2. The ingressive an-streams is one in which

the air is pulled out (It is interesting to note that Sindhi language has some sounds produced with an ingressive glottalic air-stream.)