speech seminar - copy

8/6/2019 Speech Seminar - Copy

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SPEECH

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ORAL AND MAXILLOFA C IAL P AT H OLOGY


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C ONT E NT S

DefinitionHistoryPhysiology of speechSpeech centers of brainReparatory systemLarynxPhonation

Articulation

ResonatorsVowel soundsConsonantsInfluence of malocclusion and dental procedures on speech sounds

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D E FINITION

In humans sounds of a carefully controlled kindare produced as a means of communication ,such sounds are called speech.

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T he word speech is derived from old Englishspeche related to specan which means to speak

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H I S TORY

F rench physician F errein (1741),who was the first to performlaryngeal experiments.

F rench neurologist Paul Broca,

controlling muscles of the lips, jaws, soft palate and vocal cords.

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w(1824-1880)


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PH Y S IOLOGY OF SPEECH

T he speech process involves thei) speech center of the brainii) the respiratory center in the brain stemiii) the respiratory systemiv) the larynxv) the nose and nasal cavitiesvi) the structures of the mouth and related facial

muscles.

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SPEECH CE NT E R OF BRAIN

Control of vocalization is from the cerebralcortex, called Brocas area.It controls word formation and the necessaryadjustment to respiration by activatingappropriator muscle signals in the motor cortex.

It is in turn control of Wernicks area

Linked to Brocas area by arcute fasciculus.

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Lesion of wernicks area / fasciculus results ina condition termed fluent aphasia

Lesion of Brocas results in errors of articulation

Speech production is controlled from categorical

hemisphere; lesions on the representational sidehave no effect on speech.

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R ESP IRATORY S Y S T E M

M outh can control and modify air flow through itself and this provides the means of alteringexpiration of air produce a variety of soundswhich can then be used for communication .

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During phonic respiration, i.e. our breathingduring speech, the inhalation time is reduced (sometimes to as little as half a second), whereasthe exhalation time is increased to about 5-10 seconds, though in rapid, excited speech whenwe wish to convey more speech it can go upconsiderably.

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(a) there is a gradual automatic change fromresting to speech respiration

(b) the degree of internal verbalization (activation of motor speech areas) defines the degree of

activation of the speech respiratory pattern( conord , schole P, 1979)

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LARYNX

T he larynx is comprised of a number of cartilages.

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Larynx midsagittal view

Thyroid

cartilage

Arytenoidcartilage

Cricoidcartilage

Epiglottis

Trachea


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Larynx lateral view


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Larynx posterior view


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T he production of intelligible speech sounds is amodification of expiration by forcing by the outflowing air through a narrow gap bounded by

structures of variable and controlled elasticity.

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MYO E LA S TI C T HE ORY

T hey are caused to vibrate, and hence to impartvibration to the air passing through them , bytheir own elastic resistance to the airflow.

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T he vocal folds are made up of fibro elasticconnective tissue and contains two muscles, thelateral crico-arytenoid and thyro- arytenoid

T hyro arytenoid controls the tension of the cord- vocalis muscle

In normal respiration the vocal folds give verylittle restriction to air flow.

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T he triangular space between them the rima glottis is sufficiently wide to allow air to passeasily.

In swallowing or vomiting , the lateral crico aryretynoid muscles and thyro-arytenoid muscles cause the cricoid cartilages to rotate and their arms to move together; simultaneously the transverse and oblique arytenoid arms to movetogether.

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Simultaneously the transverse and obliquearytenoid muscles move the picot points of thecartilages together.

T his combination of activities closes the glottis

and stops air flow, protecting the respiratory tract.

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In order to generate sounds the glottis must be closed but only to such a degree that it can be forced openby the airflow.

A tightly closed glottis is associated with louder sounds because a greater air pressure is needed toopen it ; when the cords are only lightly approximate

d because a greater air pressure is needed to openit.

when the cords are only lightly approximated the expirator ressure can be small and the sound uite.

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T he compressed air will force apart the vocal folds so that a little air escapes for a brief moment. T his phase is the release.

As the air flows past, the vocal folds are brought back together as a result of two forces: the

elasticity of the folds, and the so-called Bernouilli effect.

The air rushes through the narrow opening in the vocalfolds at great speed (faster than the usual outflow speedfrom the lungs).

As a result, the pressure between the vocal folds drops (i

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wThe cycle of glottal vibration (from Daniloff, p. 171)w

w1. folds at rest w2. musclew contraction

w3. increase inw pressure

w4. forcing foldsw apart

w5. explosionw open w6. acousticw shockwave

w8. folds close,w goto step (3)

w7. rebound towardw closure


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wThe cycle of glottal vibration (from Pickett, p. 5 0)

wclosure to opening, 0 to 2.1 msec

wopening to closure, 2.4 to 4.5 msec

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It is the force of this negative pressure whichsucks the vocal folds back together.

T his phenomenon has been named after theSwiss physicist Daniel Bernouilli (1700-1782),who discovered a similar process during hisexperiments with fluids and gases.

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In whispering only the anterior part of the rimeglottis is closed and the cords are separatedposteriorly.

T he initial max frequencies is given by the lengthand tension of the vocal folds or cords.



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wTypes of phonation (from Daniloff, p. 194)w

wquietw breathing

wforcedwinhalation

wnormalw phonation wwhisper


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T he neural control of the sound frequenciesgenerated at the cords is the vagus nerve, principally through the recurrent laryngeal nerve.

Cricothyroid muscle is innervated by externallaryngeal nerve.



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T he sound generated is modification of mixtureby stoppage or airflow and amplification of certain frequencies that turns sound into speech.

T he sound frequency is related to the length and tension of the cords and a number of harmonics of these.



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Loudness of the sound depends primarily on theforce of expiration,

M easurement of the loudness achieved by shouting gives figures up to 110dB.



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T here is simultaneous comparison of the soundintended with that produced and then heard bythe ears to give the final tuning.

A complication is that sound produced is produced by bony conduction , whereas in the matching with an externally generated sound the latter isheard by airborn conduction.



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Speech is composed of two mechanicalfunctions:

(1) phonation, which is achieved by thelarynx, and

(2) articulation, which is achieved by thestructures of the mouth.

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PH ONATION

During normal breathing, the cords are wide open to allow easy passage of air.

During phonation, the cords move together sothat passage of air between them will causevibration

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T he muscles within the vocal cords can changethe shapes and masses of the vocal cord edges,sharpening them to emit high-pitched sounds an

d blunting them for the more bass sounds.

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ARTI C ULATION

T he three major organs of articulation are the lips, tongue, and soft palate.

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R ES ONAT E R S

T he resonators include the mouth, the nose and associated nasal sinuses, the pharynx, and eventhe chest cavity.

Frequencies are selected by the use of Helmholt z resonators.

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T here are no of pipe resonators :Larynx , pharynx and the nose

T he upper respiratory tract infections like thecommon cold , and abnormalities of the pipe

such as a cleft palate giving communicationbetween the oral and nasal cavities, will producepredictable changes in the sound of the voice.

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O ral resonators is readily divided into tworesonators: the anterior and the posterior whichis separated by the tongue.

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T he position of the tongue in relation to thepalate can be varied and thus the relative sizesof the these two resonating chambers can also b

e varied.

T he two frequencies selected in this way areknown as format and they give the characteristicsound of vowel.

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V owel sounds

Anterior chamber is the labial resonatorsPosterior resonators are the laryngealresonatorsT he two main formant frequencies for vowel are:

Lower frequency amplified by posterior chamber Higher frequencies are amplified by the anterior

chamber.T he third format frequency has been described f or vowel sounds but is relatively constant for allEnglish language

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C ON S ONANT S

Consonants are produced by stopping airflow, the site and manner of stoppage give the sound.

It can be classified either according to the structure involved in the airflow stoppage or according to the completeness of the stoppage.

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Anatomical classification:Labiodental, linguodental and linguopalatal

Linguopalatal is subdivided defining the specificareas of palate involved and so termed alveolar,

prepalatal, (medio)platal, velar and glottal

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INFLU E NCE OF MALOCCLUSION AND


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INFLU E N CE OF MALO CC LU S ION AND D E NTAL P RO CE DUR ES ON SPEECH

S OUND

S T he position or size of structures involved in impending airflow during articulation, will effect the quality of speech.

High and low palatal vault with tongue large or small in relation to the size of the oral cavity

Cleft palate

Hypertrophy of the lymphoid tissues

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Deficiency of the palatal musculature

F unctionally abnormal as in neurotransmissioneffect in myasthenia gravis

Short upper lip, missing/ malposition upper/lower

incisors,when tongue to palatal contact is difficult- consonantal sounds will change

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Lips may arise from almost any condition upper incisors are displaced or absent and where the tongue-palate contact is difficult to achieve.

Angles class II relationship predisposition to alisp.

F itting odf a denture/orthodontic appliance results in change in s and the th sounds.

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AGING

As the person ages the speech is not affected but the lower frequencies may be lost as tissue elasticity decreases.

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