sph302 articulation 02.ppt - Macquarie...

Speech Physiology

Articulation and ResonanceLecture 2Lecture 2

Dr Robert H. MannellDepartment of Linguistics

Macquarie University1

Articulators and ArticulationArticulators and Articulation

• In this course, which focuses on the production of speech, we talk constantly p p , yabout “articulators.

• Speech “articulation” is a secondary• Speech articulation is a secondary characteristic of these organs whose

fprimary function relates to breathing and/or eating and drinking. g g

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Articulation and Resonance (1)Articulation and Resonance (1)

Wh h th iti d h• When we change the position and shape of the tongue, lips, velum, jaw and pharynx for the purposes of speech we are said to be articulating.

• We change the position of the articulators in order to change the shape of the vocal o de to c a ge t e s ape o t e ocatract.

• Changing the shape of the vocal tract• Changing the shape of the vocal tract changes its acoustic properties.

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Th l t t b id d t b• The vocal tract can be considered to be a tube of non-uniform cross sectional shape and area.

• Tubes have acoustic properties known as p presonance. Different shapes result in different resonant characteristics.d e e t eso a t c a acte st cs

• These resonant characteristics affect the sound of the speech by changing thesound of the speech by changing the position of important spectral peaks.

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• When we learn to speak we learn to move our articulators in ways that produce y pspeech patterns appropriate to the language that we are learninglanguage that we are learning.

• We simultaneously learn to perceive (spectral peaks (amongst other acoustic

features) as corresponding to different ) p gpatterns of articulation.

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A ti l t tt d t i th l• Articulatory patterns do not, in themselves, create audible spectral peaks. We must also have a sound source.

• For many speech sounds (vowels, and y p ( ,many consonants) the source of sound is the glottis, or the gap between the vocal t e g ott s, o t e gap bet ee t e ocafolds in the larynx.

• In voiced sounds this results from vibrating• In voiced sounds this results from vibrating vocal folds.

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In this image we can see a very i lifi d i f h lsimplified view of the vocal

tract.

For most speech sounds the psource of energy is air from the lungs.

For many speech sounds theFor many speech sounds the source of sound is the vibrating vocal folds.

The resonators that shape that sound are the pharynx, tongue, oral cavity, lips, velum and

l inasal cavity.

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In this slide we can see a schematic diagram of the spectrum of a voiced sound a the larynx, the resonant characteristics of the vocal tract, and the resultant acoustic (or “radiated”) spectrum for a vowel (similar to the

l i “h d”)vowel in “heard”).

The peaks in the vowel spectrum are known asspectrum are known as “formants”.

We have differentWe have different formant patterns for different vowels.

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• Vowel articulation (whether the vowel is voiced or whispered) is achieved by p ) ymoving and shaping the tongue and lips (and the velum for nasalised vowels)(and the velum, for nasalised vowels).

• In the next slide we can see a schematic ( )(and only very approximately accurate) view of tongue position for the cardinal g pvowels.

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I th t t lid• In the next two slides we can see some typical articulatory patterns for two vowels.

• An articulatory pattern for a vowel involves the position and shape of the tongue, the p p g ,position of the lips and the position of the velum (particularly important for languages e u (pa t cu a y po ta t o a guageswith oral/nasal vowel distinctions).

• You will note that these are oral vowels as• You will note that these are oral vowels as the velum is closed.

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• In the next two slides we can see the articulatory position of the tongue at the y p g“target” of two different vowels.

• We can see that two different tongue• We can see that two different tongue positions result in two different vowel acoustic spectra.

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Simplified models of the vocal ptract consisting of a number of tubes greatly simplifies the mathematical modelling of the acoustics of the vocal tract.

Such models typically consist of between 1 and 4 tubesof between 1 and 4 tubes connected in series, but some more complex models have even more tubes.

Here is a very simple one tube model for the “neutral” vowel (the vowel in “heard”)(the vowel in heard ).

Details of these tubes models and the “acoustic theory of speech production” are covered in SPH301 speech Acoustics.

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Different sized vocal tracts l i diff l fresult in different values for

the vowel formants.

We can see the different formant patterns for a typical adult male, adult female and small child.

What’s important to note here is that whilst the frequencies are different the actual patternare different the actual pattern of formant frequencies are very similar.

S k f l dSpeakers of a language tend to produce the same articulatory patterns and we

d t i i thare used to ignoring those aspects of these patterns that only relate to vocal tract size.

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• Consonant articulation works in a similar fashion and particularly affects the place p y pdimension of consonants.

• Changes to consonant articulation affect• Changes to consonant articulation affect the place, manner, nasality, lateral/central,

faspects of consonant production.

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• Consonant articulation can also result in the creation of supra-laryngeal sound p y gsources, particularly in fricative and oral stop consonantsstop consonants.

• That is, the consonant manner-of-articulation dimension is also controlled by adjusting the position and shape of the j g p particulators.

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Its convenient to divide upIts convenient to divide up the tongue into several regions. These parts of the tongue can be used in o gue ca be useddescribing vowel articulation, but they are particularly useful in the description of pconsonant articulation.

These parts of the tongue are moved into proximity of aare moved into proximity of a “passive articulator” to generate the place dimension of consonants anddimension of consonants and the degree of “stricture” (or closure) can also define a supra-glottal sound source sup a g o a sou d sou cefor fricative or stop stricture.

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S f h t t d h ti l ti• So far we have treated speech articulation as if it were a sequence of discrete places of articulation.

• Nothing could be further from the truth.g• Speech is best described as a coordinated

pattern of articulationpattern of articulation.• Speech “targets” are a useful abstraction

b t gi e an o er simplified ie of speechbut give an over-simplified view of speech production.

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• Articulatory patterns are a complex pattern of overlapping gestures.pp g g

• The articulation of one speech sound overlaps with and affects that of adjacentoverlaps with and affects that of adjacent speech sounds.

• The overlapping of speech gestures during speech is know as coarticulation.speech is know as coarticulation.

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Coarticulation (1)Coarticulation (1)

“A ti l t l i ” ( t l i ) i• “Articulatory planning” (or motor planning) is a process that is assumed to occur in certain centres of the human brain (primarily the left frontal lobe) during speech production.

• The cortical centres that plan articulatory e co t ca ce t es t at p a a t cu ato ymovements during speech production are typically described as producing a series oftypically described as producing a series of increasingly more concrete specifications for articulator muscle movement.for articulator muscle movement.

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• At the most abstract level of motor planning each articulator might be thought of as g ghaving a target position that it must attempt to achieve for each phonemeto achieve for each phoneme.

• This relatively simplistic model might posit “ ” fan “ideal” target for each phoneme. This

ideal target would depend upon an g p pindividual's physiology and linguistic experience.experience.

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• This overly simple model of articulatory planning assumes a fixed ideal articulatory p g ytarget for each contrastive articulator.

Two ideal articulatory targets for a single articulator and twoa single articulator and two adjacent phonemes. PB1, PB2 and PB3 are the idealised phoneme boundaries forphoneme boundaries for Phoneme 1 and Phoneme 2.

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• There is increasing evidence that suggests that the most basic unit of articulatory yplanning in speech is the syllable, rather than the phonemethe phoneme.

• In English there is a large number of syllable ftypes and the majority consist of a vowel and

from 1 to 6 consonants (0-3 initial consonants (and 0-3 final consonants).http://clas.mq.edu.au/speech/phonetics/phonology/syllable/index.htmlp q p p p gy y

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Th dil d fi bl ti l t• There are no readily definable articulatory or acoustic boundaries between phonemes, except at intonational phrase boundaries which are often characterised by pauses.

• Phonemes are best described in terms of o e es a e best desc bed te s otarget positions with articulatory (and resulting acoustic) transitions between theresulting acoustic) transitions between the two targets which share the characteristics of the two targets.of the two targets.

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• A "transition" in speech production is caused by the movement of articulators ybetween phoneme targets.

• The transition between two phonemes• The transition between two phonemes shares the articulatory and acoustic

fcharacteristics of both phonemes but gradually changes from being more like the g y g gfirst phoneme target to being more like the second phoneme target.second phoneme target.

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An idealised articulatory transition from the target of one phoneme (T1) to the target ofphoneme (T1) to the target of another phoneme (T2).

PB represents the approximatePB represents the approximate position of the phoneme "boundary". At this point the articulator is about half wayarticulator is about half way between the two targets.

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Coarticulation (8)Coarticulation (8)Contrasti e Artic latorsContrastive Articulators• A contrastive articulator is an articulator

whose configuration (ie. shape) or position is important to the accurate transmission ofis important to the accurate transmission of the intended phoneme to a listener (who ideally shares the same language or dialectideally shares the same language or dialect and therefore the same expectations for the articulatory, acoustic and auditory characteristics of each phoneme).p )

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Th iti f th t b d i th• The position of the tongue body in the front-back and the high-low dimensions are contrastive for vowels and so the tongue body is a contrastive articulator for vowels.

• Nasality is not contrastive in English asa ty s ot co t ast e g svowels and so the velum (ie. whether open or closed) is not a contrastive articulatoror closed) is not a contrastive articulator for English vowels (but it is for some French vowels).French vowels).

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V l i i t ti f l t• Velum opening is contrastive for oral stops and fricatives (must be closed) and for nasal stops (must be open) but it is not contrastive(in English) for vowels. English Vowels are identified as the same phoneme whether the velum is open or closed.

• A vowel between two oral stops has a closed velum whilst a vowel between twoclosed velum whilst a vowel between two nasal stops has an open velum and the vowel is said to be nasalised.vowel is said to be nasalised.

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Articulator Inertia• Inertia is the tendency of a stationary bodyInertia is the tendency of a stationary body

to resist movement or for a moving body to resist changes in its rate or direction ofresist changes in its rate or direction of movement. In general, the more massive ( )(ie. bigger and heavier) an articulator is the greater its inertia or resistance to gmovement.

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• For example, the tongue body is more massive than the tongue tip and so it g pmoves more slowly than the tongue tip.

• The jaw is even more massive (more• The jaw is even more massive (more inertia) and so it moves even more slowly.

• The velum and the lower lip have greater inertia than the tongue tip and less inertiainertia than the tongue tip and less inertia than the tongue body.

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Two articulators with different degrees of inertia will take a gdifferent times to move the same distance. Articulator 1 (A1) has less inertia than articulator 2 (A2). Therefore, articulator 1 (A1) can move from its first target (T1) to its

( )second target (T2,1) in much less time than articulator 2 (A2) can move the same di t t it d t tdistance to its second target (T2,2).

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Two articulators with different degrees of inertia can move gdifferent maximum distances in the same time. Articulator 1 (A1) has less inertia than articulator 2 (A2).

Therefore, articulator 1 (A1) can move a greater distancecan move a greater distance from its first target (T1) to its second target (T2) than can articulator 2 (A2).( )

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Target Undershoot• Target undershoot occurs when there isTarget undershoot occurs when there is

insufficient time for an articulator to reach its target position Target undershoot canits target position. Target undershoot can occur in both vowels and consonants. Undershoot is the "compromise" between idealised articulatory curves.y

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This figure illustrates target g gundershoot. In this example the ideal target of phoneme 2 (T2) is represented by the articulator position value IT whilst UT represents the undershot target value. This would be typical of an unaccented short low vowel between two alveolar or velar stops, for example.

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Overlapping Gestures• A "gesture" is the movement of oneA gesture is the movement of one

articulator from an articulatory position characteristic of one speech sound to ancharacteristic of one speech sound to an articulatory position characteristic of the next speech sound.

• Articulatory gestures overlap. This meansArticulatory gestures overlap. This means that different articulators may be moving at the same timethe same time.

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Coarticulation (18)Coarticulation (18)The gestures of three articulators (A1, A2, A3) overlap in time as they pass through three idealised phoneme targets (T1, T2, T3).

Overlapping gestures are not necessarily synchronisednecessarily synchronised. Relative timing depends upon articulator contrastiveness and inertia.inertia.

Non-contrastive articulators have no need to move rapidly.

Heavy (high inertia) articulators can’t move rapidly.

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Coarticulation and Syllables• Coarticulation tends to be stronger withinCoarticulation tends to be stronger within

syllables rather than across syllable boundaries This greater degree ofboundaries. This greater degree of coarticulation within syllables is evidence

f fthat the syllable is a fundamental unit of articulatory organisation. y g

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• Some sounds are more resistant to coarticulation than other sounds.

• This may be due to differences in phoneme duration differences in thephoneme duration, differences in the inertia of contrastive articulators, and/or

ffdifferences in the distance that articulators need to move or it may be due to the yphoneme inventory effect (see below).

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• Coarticulation is greatest when there is the greatest articulator movement between gphonemes.

• Most lingual consonants have a high• Most lingual consonants have a high tongue position. Because of this, high

ffvowels are least affected by these high consonants, and low vowels are most affected by these high consonants

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L l i t t t t t• Long vowels are more resistant to target undershoot than are short vowels as there is more time for the articulator to reach its target. Accented and stressed vowels are more resistant to undershoot than are unstressed vowels as they are longer.

• Schwa is not realised by a defined target as it is usually very short and is thereforeit is usually very short and is therefore greatly affected by coarticulation with adjacent consonants.adjacent consonants.

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Phoneme Inventory Effects• Coarticulation is resisted when it will resultCoarticulation is resisted when it will result

in perceptual confusion. Th h f t l f i• The chances of perceptual confusion occurring is greatest in languages that have a large number of phonemes of a particular class.particular class.

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• Vowels coarticulate most in languages with a small number of vowels.

• Consonants coarticulate most in languages with a small number of placeslanguages with a small number of places of articulation (eg. strong coarticulation for

/ /English velar stops /k,g/ as there is only one stop place of articulation that uses the p ptongue body as the active articulator).

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Coarticulation (25)Coarticulation (25)L ThLocus Theory• Strong Version: All consonants have a fixed

ti l t t t hi h i li d t i larticulatory target which is realised at a single precise place of articulation. The articulatory target for a particular consonant is known as itstarget for a particular consonant is known as its articulatory locus.

• Weak Version: Consonants don't have a fixed• Weak Version: Consonants don t have a fixed target as their targets are affected by coarticulation but they do tend to have a locuscoarticulation, but they do tend to have a locus space defined by a range of articulatory possibilities. p

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Th t j it f t• The vast majority of contemporary research favours the weak version of the locus theory over the strong version.

• We adjust the “target” of each phoneme j g pdepending especially upon its within-syllable context, to a lesser extent its sy ab e co te t, to a esse e te t tsacross-syllable-boundary context, and also the effects of prosody and non-linguisticthe effects of prosody and non linguistic effects such as vocal affect (emotion).

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Further ReadingFurther Reading• Clark, J., Yallop, C. & Fletcher, J. (2007), An introduction

to phonetics and phonology, 3rd. edition, Blackwell, Oxford (pages 84 90 and Section 7 17)Oxford (pages 84-90 and Section 7.17)

• J.A. Seikel, D.W. King and D.G. Drumright, (1997), Anatomy and Physiology for Speech Language andAnatomy and Physiology for Speech, Language, and Hearing, Singular, San Diego (or a more recent edition of the same text)

• The following web pages:

http://clas.mq.edu.au/speech/phonetics/phonetics/coarticulation/index.html

http://person.sol.lu.se/SidneyWood/coartdem/

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ReferencesReferences

The following books were used as sources for materials used in this lecture:-

• Perkins, W. H. and Kent, R, D. (1986) Textbook of Functional Anatomy of Speech, Language, and Hearing. Taylor and Francis, LondonLondon

• J.A. Seikel, D.W. King and D.G. Drumright, 1997, Anatomy and Physiology for Speech, Language, and Hearing, Singular, San Diego

• Zemlin, W. R. (1998) Speech and Hearing Science. 4th edn. Allyn and Bacon Bostonand Bacon, Boston.

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