Phonation
Functions of the larynx
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3 valves which:
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Permit airflow in and out
Prevent inflow of unwanted substances
Expel through cough
Create subglottic pressure to brace thorax
Produce vocalisation
Reflexes control all above except
phonation
Valving for Speech
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Phonation occurs through the use of the
intrinsic laryngeal muscles and the laws
of physics.
Glottis opened by posterior cricoarytenoid during unvoiced sounds
Glottis closed by lateral cricoarytenoid
and inter-arytenoids
Valving for Speech
Glottic Cycle
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Vocal cords together
Build up subglottic pressure
Vocal cords forced apart
Air rushes through gap
Reduced subglottic pressure
Vocal cords slap back together
Glottic Cycle
Glottic Cycle
Aerodynamic Myoelastic
Theory
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Aerodynamic- air pressure and flow
Myoelastic- Elasticity of vocalis- the
muscle in the vocal cord and the vocal
ligament.
Bernoulli principleAerodynamics
Myoelastics -stiffness
Another muscular force is stiffness. If the
vocal cords are stiff then they will give more
resistance to the air. The effect is like the
difference between punching a bag of water
and a bag of molasses. There will be less
movement in the molasses. Vocal cords may
become stiffer through contraction, infection
or swelling. Consider splat balls and normal
rubber ball or Newton’s cradle
Periodicity
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A period is a complete and closing
cycle.
Cycles/second = Frequency = Pitch
Regularity/Irregularity may occur in:
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Pitch = Jitter
Amplitude = Shimmer (not singing
shimmer
Vibrato may be called a fluctuation as it
is regular
Brainstorm
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How is pitch controlled in instruments?
Pitch Control
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Theory is changing
Three main variables
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Mass- cross sectional bulk
Stiffness- longitudinal tension
Length
Other factors
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Nervous tension
Lack auditory feedback
Pitch Control
Cover, Transition Body Model
Hirano
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Cover is epithelium
Transition is the middle and deep layers
of the lamina propria making the vocal
ligament
Body of vocal cord is vocalis muscle
Body and Cover Model
New models
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Epithelium
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Metabolically active
Microvilli
Catching mucous
Basement membrane
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Boundary between epithelium and lamina
propria
Anchoring fibres (allow some gliding) and
proteins such as hyaluronic acid
Properties of the vocal cords
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Stiffness mainly regulated by length
Stretch and contracted muscle is also
stiffer
Vocal cords quite stretchy
Wet slap due to compliance
Optimum Pitch
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The pitch created by the larynx in its
neutral position
Debate
Larynx not move vertically to create this
pitch
Methods to achieve –
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Mmhmm
Neutral counting
Control of Vocal Intensity
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Increase in volume occurs with:
Increased subglottic pressure
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Medial compression of the vocal cords
Resistance to increased pressure by:
Medial compression
 Tightness of abduction
NB Trained singers may use less lung
pressure to produce high volume
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Control of Vocal Intensity
Phonation onsets
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Glottal- closure before sound
Breathy- air before sound
Simultaneous.
Phonation types
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Thick vocal folds,
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Thin vocal folds
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Quiet voice, Head register
Stiff vocal folds
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Speaking voice, Chest register
Falsetto
Floppy vocal cords
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Creak - irregular vibration