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SPEECH oral cavity

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									SPEECH

    Oral Physiology
       Dent 207
Speech

   Oral cavity only assists in breathing when
    nasal breathing is insufficient
   Mouth controls & modifies expiratory air flow
    –   Producing a variety of sounds
Generation of sound frequency

   The production of intelligible speech sounds
    is a modification of expiration by
    –   Forcing outflowing air through a narrow gap –
    –   Bounded by structures of variable & controllable
        elasticity (vocal cords)
   Position, length & tension of vocal cords are
    controlled by the laryngeal muscles
Neural control of speech

   Vagus nerve
    –   Recurrent laryngeal nerve
    –   External laryngeal nerve
   Ultimate control from cerebral cortex
    –   Broca’s area, controlled by
    –   Wernicke’s area
   Speech production is controlled from the categorical
    hemisphere (left)
    –   Lesions on the representational side (right) have no effect
        on speech
Broca’s area

   Just above the Sylvian fissure
   Controls actual word formation & necessary
    adjustment of respiration
   By activating appropriate muscle signaling in
    the motor cortex
Wernicke’s area

   In the superior temporal gyrus
   Linked to the Broca’s area by arcuate
    fasciculus
   Concerned with
    –   Understanding of language (spoken or written)
    –   Generation of intelligible speech
Lesions affecting speech areas

   Fluent aphasia
    –   Wernicke’s area or arcuate fasciculus
    –   Patient can generate a mixture of recognizable &
        nonsense words that do not link together into
        intelligible speech
   Errors of articulation
    –   Broca’s area
Sound vs. speech

   Sound
    –   Control of expiration
    –   Vocal cords
    –   A mixture of frequencies
   Speech - sound modified by
    –   Stoppage of airflow
    –   Amplification of certain frequencies
    –   By muscular activity of oral & perioral regions

   Loudness depends on force of expiration
   Bony conduction vs. airborne conduction
   Bony sinuses
Vocal sounds become intelligible
speech

   Two process
    –   Selective amplification of particular frequencies
            By variation of size of resonating chambers
    –   Controlled release of expired air
   Two terms
    –   Phonation
            Production & selection of frequencies (vowels)
    –   Articulation
            Patterning of air release (consonants)
Males vs. females
   Later puberty of males
   More time for growth of laryngeal cartilages
   Longer vocal cords
   Changes in puberty
     –   Frequency in males drops by an octave
     –   Frequency in females drops by 2-3 tones
   Voice frequency
     –   Human ear: greatest sensitivity 1000 – 4000 Hz
     –   Males: 100 – 150 Hz
     –   Females: 200 – 300 Hz
     –   Singers
             Trained for 50 Hz or 1000 Hz
             The lowest is 27 Hz
             Highest 4000 Hz
Resonators

   Vestibular, laryngeal, pharyngeal resonators
    –   Fixed in form
   Nasal, paranasal sinus resonator
    –   Fixed in form
    –   Variation of sound depends on whether used or not
    –   Not used when air is directed through the mouth
   Labial, vestibular resonator
    –   Unimportant
   Oral resonator – separated by the tongue into
    –   Anterior, posterior
    –   Size affected by tongue position
Resonators
Vowel sound

   Two formant frequency for a vowel
    –   A lower frequency amplified by posterior oral chamber
    –   A higher frequency amplified by anterior oral chamber
   Position of the tongue
    –   Changes the relative size of anterior & posterior resonators
    –   Tongue posterior – a
    –   Tongue further forward – i
    –   Space between tongue & palate gives different qualities of the
        vowel
   Soft palate seals off the nasal cavity in English vowels
   Nasal cavity remains continuous with oropharynx in
    some French vowels
    Clicks & consonants

   Controlling the release of the vibrating air
   Bringing oral structure together & then
    separating them
Clicks

   Sound produced when air flows through a
    low pressure zone created when articulating
    structures are held together then separated
    over a small area
Consonants

   Sound produced when airflow is stopped in initiation,
    ending & separation of vowel sounds
   Classified according
    –   Anatomical location at which airflow is impeded
    –   Degree of impedance – partial / complete
   Bilabial, labiodental, linguodental
   Lingupalatal
    –   Alveolar
    –   Prepalatal
    –   Velar
    –   Glottal
Bilabial consonants

   Nasal sound - M
   Plosive sound – B, P
   At mandibular rest position
    –   Used to determine rest position in dental
        prosthetics
Incomplete stoppage of airflow

   Rolled sound - R
   Lateral sound – L
   Fricative sound
    –   Leaving a slit or rounded opening
    –   Th, Z, V, Y, F, S, W, Y
   Affricative sound (with sudden release)
    –   J, CH
Other factors

   Volume of airflow
    –   D vs. T
   Voiced consonants – strong
    –   that
   Unvoiced consonant – weak
    –   Thin
Influence of malocclusion & dental
procedures on sounds

   Alteration in the volume of oral & nasal
    resonators
   Position & size of structures impeding airflow
    during articulation
Malocclusive & dental factors

   Palatal vault height
   Tongue size
   Clefts
   Tonsilitis
   Functional abnormality of palatal muscles
     –   Myasthenia gravis
   Short upper lip
   Lack of lip seal
   Missing, malposed incisors
   Tied tongue
   Prosthetic / orthodontic appliance

								
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