Download vocal folds - Bases Produced

Respiration +
Pulmonic Airflow
February 7, 2012
These notes are largely adapted from Thomas J. Hixon (1973), “Respiratory Function in Speech”,
in Normal Aspects of Speech, Hearing and Language.
Taking Care of Business
• Course Project Report #2 to hand in.
• Course Project Report #3 guidelines to hand out
• Suprasegmentals + prosody
• due after the break! (February 28th)
• Also: last TOBI exercise due on Friday
• And then:
• Respiration
• Phonation
• Okay. Everybody take a deep breath!
From the Bottom Up
•
All speech sounds require airflow.
•
The vast majority of sounds in the world’s languages
use a pulmonic egressive airflow.
•
•
= out of the lungs
Questions to answer/consider:
1. How do we make air flow out of the lungs?
2. How does pulmonic airflow differ in breathing and in
speech?
3. How does pulmonic airflow relate to language?
•
primarily: suprasegmentals (stress, F0)
The Machinery
•
The human torso (from
the neck to the legs) has
two major divisions:
1. The thorax
•
consisting of the heart
and lungs
•
the “chest”
2. The abdomen
•
includes the digestive
system and other
interesting glands
•
the “belly”
The Thorax
• The heart and the
pulmonary system are
enclosed by the thoracic
cage.
• the “rib cage”
• Ribs are connected by
cartilage to the sternum.
• The intercostal muscles fill
in the gaps between ribs...
• and also cover the
surfaces of the thoracic
cage.
Connections
•
The thorax is split from the
abdomen by a domeshaped structure known
as the diaphragm.
•
The lungs sit on top of the
diaphragm.
•
Two membranes link the
lungs to the ribs:
1. The visceral pleura
covers the lungs.
2. The parietal pleura lines
the inside of the thoracic
cage.
Equilibrium
• The linkage
between the lungs
and the rib cage
makes:
• The lungs are
bigger than they
would be on their
own.
• The rib cage is
smaller than it
would be on its own.
• The linkage tends
towards a natural
equilibrium point.
v
o
l
u
m
e
Taking A Step Back
• Air flows naturally from areas of high pressure to areas of
low pressure.
• Q: How do we make air pressure differences?
• A: We take advantage of Boyle’s Law.
• Boyle’s Law states that:
• the pressure of the gas in a chamber is inversely
proportional to the volume of gas in the chamber
•  The pressure of the gas can be increased or decreased
by changing the volume of the chamber.
• decreasing volume  increases pressure
• increasing volume  decreases pressure
Inspiration
• A normal breathing cycle begins with inspiration
• “breathing in”
• Air will flow into the lungs if...
• the air pressure inside the lungs is lower than it is
outside the lungs
• Air pressure can be decreased inside the lungs by...
• expanding the volume of the lungs.
• Lung volume can be expanded:
• In all three dimensions
• With two primary muscle mechanisms
Expansion #1
• The vertical expansion of the thorax is primarily driven by
the contraction of the muscles in the diaphragm.
• This bows out the
front wall of the
abdomen.
• Also: diaphragm
contraction
elevates the lower
ribs.
•  expands the
circumference of
the thorax.
Expansion #2
• The thorax can also be expanded through the
contraction of the external intercostal muscles.
• Contraction of each
intercostal muscle lifts
up the rib beneath it.
• Also pulls each rib
forward with the
sternum.
• = expansion in the
front-back dimension.
sternum
Expansion #3
• The thorax can also be expanded through the
contraction of the external intercostal muscles.
• Contraction of the
intercostals elevates
the lower ribs more
than the upper ribs
• Lower ribs lift like a
“bucket handle”
• Expansion in the
side-to-side
dimension.
Expiration
• Air flows out of the lungs whenever air pressure in the
lungs is greater than external air pressure.
• Note: technical term
• alveolar pressure = air pressure inside the lungs
• Alveolar pressure may be increased by decreasing lung
volume.
• Lung volume is decreased through both passive and
active forces.
• Normally, lungs contract after inspiration due to passive
forces alone.
• No muscular effort is necessary!
Passive Expiration
• Thorax + lungs combo
contracts back to its
equilibrium point
without any external
impetus.
• Relaxation pressure
is inherent pressure on
the lungs to revert back
to the equilibrium point.
• Note: relaxation
pressure works both
ways.
Active Expiration
•
Lung volume can be actively decreased by contracting
a variety of muscles which:
1. Lower the ribs and/or sternum
•
thereby compressing the thorax in the front-to-back
and side-to-side dimensions
2. Increase abdominal pressure
•
thereby driving the diaphragm upwards
Expiration #1
• The thoracic cage can
be compressed by
contracting the internal
intercostals and the
transversus thoracis.
• These pull the ribs
downward...
• effectively the
opposite action of
contracting the external
intercostals.
Expiration #2
• The most important
muscles for active expiration
increase pressure in the
abdomen.
• These include the rectus
abdominis, the external
and internal obliques, and
the transversus abdominis.
• Contracting these muscles
drives in the abdomen...
• and pulls down the sternum
and lower ribs.
Expiration Dynamics
• Technical term: the equilibrium point of thorax + lung
volume is called the resting expiratory level.
• At volumes above the resting expiratory level, the lungs
will contract due to relaxation pressure alone.
• ...although active expiration forces may contribute.
• Below the resting expiratory level, the lungs will tend to
expand due to relaxation pressure.
•  To continue expiration at this level, active expiration
is necessary.
More Verbiage
1. Total lung capacity: volume of air in the lungs after a
maximum inspiration.
2. Residual volume: amount of air that remains in the
lungs after a maximum expiration.
3. Vital capacity: greatest amount of air that can be
expelled from the lungs after a maximum inspiration.
•
= total lung capacity - residual volume
4. Functional residual capacity: volume of air contained
in the lungs at the resting expiratory level.
5. Inspiratory capacity: maximum volume of air that can
be inspired from the resting expiratory level.
•
= total lung capacity - functional residual capacity
Verbiage Diagram #1
residual
volume
total
lung
capacity
vital
capacity
Verbiage Diagram #2
functional
residual
capacity
total
lung
capacity
inspiratory
capacity
Note: FRC - RV  only 35% of vital capacity
Keeping it Steady
• The production of speech generally requires a
continuous flow of air from the lungs.
• A continuous flow of air requires constant alveolar
pressure in the lungs.
• Accomplishing this is tricky...
• Because there is more relaxation pressure at the
extremes (both high and low) of lung capacity.
•  Active inspiratory and expiratory forces have to
dynamically compensate.
external air pressure
expiratory pressure
inspiratory pressure
• Relaxation
pressure
changes from
expiratory to
inspiratory...
• in going
from
maximum to
minimum vital
capacity
constant pressure needed for utterance
Effort required to maintain constant alveolar pressure:
active
inspiratory
pressure
active
expiratory
pressure
effort initially
requires
inspiratory
forces!
effort
eventually
requires
expiratory
forces
Electromyography (EMG)
• The activity of inspiratory and expiratory muscles during
continuous exhalation has been documented with
electromyography (EMG) studies.
• In EMG, an electrode is inserted into a particular muscle.
• When that muscle
contracts, it discharges
an electrical signal (an
action potential).
• The voltage and
timing of this discharge
may be recorded
through the electrode.
EMG Recordings
Diaphragm
inspiratory
External Intercostals
Internal Intercostals
Rectus Abdominis
External Oblique
Latissimus Dorsi
expiratory
Loudness
• The intensity of an
utterance is primarily
determined by alveolar
pressure.
• Doubling alveolar
pressure increases
intensity by 9 -12 dB.
•  Louder utterances require a greater difference between
alveolar and external air pressures
•  Louder utterances require more active expiratory force.
Differences
• Conversational speech makes different demands on the
respiratory system than either normal breathing or the
production of a continuous vowel.
• For instance, a normal breath cycle lasts about five
seconds:
• 40% of the cycle is devoted to inspiration
• 60% of the cycle is devoted to expiration
• In speech:
• 10% of the cycle is devoted to inspiration
• 90% of the cycle is devoted to expiration (i.e., talking)
Volume Differences
• Normal breathing encompasses 35% - 45% of vital
capacity.
• Note: normally ends above the resting expiratory level.
• Normal conversational speech encompasses 35% - 60%
of vital capacity.
• Loud speech usually starts at 60% - 80% of vital capacity.
• and may end considerably above resting expiratory
level.
• Note: extremes of the vital capacity are not normally used,
in either breathing or speech.
• (requires too much muscular effort)
Modulating Airflow
• During conversational speech, there are frequent
demands for rapid changes in muscular pressure.
• These changes are primarily required for differentiating
between stressed and unstressed syllables.
• Rapid
modulations to
airflow are
primarily made
by the internal
intercostal
muscles.
Lastly
• Higher airflow from lungs = increase in F0
• The have-your-friend-punch-you-in-the-stomach
experiment.
• Increased F0 also contributes to stress.
• However, F0 level is primarily determined by laryngeal
activity...
• which we’ll talk about next...
Phonation +
Vocal Fold Physiology
Feburary 7, 2012
Where Were We?
• Air squeezed out of
the lungs travels up
the bronchi...
• Through the trachea
(windpipe)
• To a complicated
structure called the
larynx.
• ...where phonation
happens.
The Larynx
• The larynx is a complex structure consisting of
muscles, ligaments and three primary cartilages.
1. The Cricoid Cartilage
• The cricoid cartilage sits on top of the trachea
• from Greek krikos “ring”
• It has
“facets” which
connect it to
the thyroid
and arytenoid
cartilages.
cricoid
cartilage
2. The Thyroid Cartilage
• The thyroid cartilage sits on top of the cricoid cartilage.
• from the Greek thyreos “shield”
• The thyroid cartilage has horns!
• Both lower (inferior) and upper (superior) horns
• The lower horns connect with the cricoid cartilage at the
cricoid’s lower facet.
• The upper horns connect to the hyoid bone.
Thyroid Graphic
thyroid
cartilage
cricoid
cartilage
Thyroid Angles
• The two broad, flat front plates of the thyroid--the
laminae--meet at the thyroid angle.
• The actual angle of the thyroid angle is more obtuse in
women.
• ...so the “Adam’s Apple” juts out more in men.
3. The Arytenoid Cartilages
• There are two arytenoid cartilages.
• from Greek arytaina, “ladle”
• They are small and pointy, and sit on top of the back
side, or lamina, of the cricoid cartilage.
arytenoid
cartilages
cricoid
cartilage
The Vocal Folds
• These three cartilages are connected by a variety of
muscles and ligaments.
• The most important of these are the vocal folds.
• They live at the very top of the trachea, in between
the cricoid and thyroid cartilages.
• The vocal folds are a combination of:
• The vocalis muscle
• The vocal ligament
• The vocal folds are enclosed in a membrane called the
conus elasticus.
Vocal Fold View #1
• Just above
the true vocal
folds are the
“false” (!)
vocal folds,
or ventricular
folds.
• The space
between the
vocal folds is
the glottis.
Vocal Fold View #2
• The vocal ligaments
attach in the front to
the thyroid cartilage.
• ...and in the back to
the arytenoid
cartilages.
• The glottis consists
of:
• the ligamental
glottis
• the cartilaginous
glottis
Things Start to Happen
• Note that the arytenoid cartilages can be moved with
respect to the cricoid cartilage in two ways.
#1: rocking
#2: sliding
The Upshot
• The arytenoids can thus be brought together towards
the midline of the body.
• Or brought forwards, towards the front of the thyroid.
• The rocking motion thus abducts or adducts the glottis.
• The sliding motion shortens or lengthens the vocal folds.
• Check out the arytenoids in action.
• When the vocal folds are abducted:
• air passes through the glottis unimpeded and
voicelessness results.
• The posterior cricoarytenoid muscles are primarily
responsible for separating the arytenoid cartilages.
• Voicing may occur when the vocal folds are adducted
and air is flowing up through the trachea from the lungs.
• Two muscles are primarily responsible for adducting the
vocal folds.
• The first is the lateral crico-arytenoid muscle.
• Note that the lateral cricoarytenoid muscles only
adduct the ligamental glottis.
• The transverse arytenoid muscles pull together the
arytenoid cartilages themselves.
• Thereby closing the cartilaginous glottis.
The Consequences
• The combined forces drawing the vocal folds towards
each other produce adductive tension in the glottis.
• Adductive tension is increased by:
• lateral cricoarytenoid muscles
• transverse arytenoid muscles
• Adductive tension is decreased by:
• posterior cricoarytenoid muscles
• Adduction vs. abduction determines whether or not
voicing will occur.
• But we can do more than just adduce or abduce the
vocal folds...