What is Needed to Support the Production of Speech at
~Constant Vocal Intensity, ~Constant f0?
 Steady lung pressure
 Steady (DC) flow thru trachea (prior to voicing)
 Gradual drop in lung volume over time
Lung volume
Air flow thru trachea
Hillenbrand: Respiration
Lung (alveolar)
pressure
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Broad Principles Needed to Understand Respiration
1. Air flows from regions of high pressure to regions of low
pressure.
2. Volume and pressure are inversely proportional (Boyle’s
Law).
 V  P (think of squeezing a basketball)
 V  P (think of pulling out on the arms of a
bellows)
3. Speech places special demands on the respiratory system:
 Short inhalation phase
 Long exhalation phase
 ~Steady lung pressure, steady flow (except when changes in
loudness are required)
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Vertical axis = lung volume
Speech
Quiet breathing
Note the short inhalation phase, long
exhalation phase while speaking.
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Respiration can’t be understood
without appreciating the role of
lung recoil forces.
Elasticity of lung tissue exerts a
force that drives toward smaller
lung volumes.
Thorax exerts a force that drives
toward larger lung volumes.
The combined effect of lungs-thorax is shown to right. Net
effect can be viewed as a single spring – the balance point of
lung and thorax springs.
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Lungs are often viewed as two elastic bags – two
balloons. Not accurate physiologically since lungs have
a complex internal structure, but functionally, the
elastic-bag view will work just fine for us.
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Viewing the lungs as a
bellows also works –
again, from the point
of view of function,
not anatomy.
Inhalation: Pull outward – (a) volume increases,
pressure decreases (re: atm. pres.), air flows inward.
Exhalation: Pull inward – (a) volume decreases,
pressure increases (re: atm. pres.), air flows outward.
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Inspiration: Volume increased by: (1) contracting
diaphragm, (2) lifting the rib cage, (3) outward rotation of
the rib cage.
Expiration: Volume decreased by: (1) relaxing the
diaphragm, (2) dropping the rib cage, (3) contracting the
abdominal muscles, forcing abdominal viscera (guts) into the
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thorax.
Contraction of the abdominal muscles produces a drop in
the volume of the thoracic cavity (and an increase in
pressure) by forcing the abdominal viscera into the
thoracic cavity.
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• There are 12 ribs.
• They attach to thoracic
vertebrae in back, and to
the sternum in front.
• Ribs attach to the costal
cartilage, which attaches
to the sternum.
• Arch-shaped bones slope
downward at rest.
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Major Muscles of Inspiration
Diaphragm
External
Intercostals
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More Inspiratory Muscles
Note the direction of these
muscle forces – they
spread the ribs, increasing
lung volume.
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Still more
inspiratory
muscles
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Major Muscles of Expiration
These muscles: (a) pull
down on the ribs, (b)
squeeze in on the
abdomen, or (c) both.
Results: Decrease in
lung volume, increase
in lung pressure,
outward airflow
(exhalation).
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More Expiratory
Muscles
Note the downward
pull of these muscle
forces.
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Why Recoil Forces Matter
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Muscle Activity During Expiration
Note that inspiratory muscles are active during the initial phase
of the expiration. When the elastic recoil forces of the lungthorax unit reach their resting state, expiratory muscles take
over to effect further decreases in lung volume. The inspiratory
force that is applied decreases over time. The expiratory force
that is applied increases over time.
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Push on chest
Moral: Respiratory force affects vocal
intensity, but it also affects voice pitch.
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Push on chest
Why does f0 increase with higher respiratory force?
The effect is entirely aerodynamic: the increase in
respiratory force increases particle velocity. Since it is the
particle velocity increase that is responsible for the
Bernoulli force, there is an increase in the size of the
Bernoulli force. The increase in the magnitude of the
Bernoulli force causes the vocal folds to return to midline
more quickly, which shortens the fundamental period,
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increasing f0.
Push on chest
Is This a Fact That’s Worth Knowing?
Suppose you have a voice client who would
benefit from increasing voice pitch (especially
due to glottal fry). What are the options for
increasing f0?
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