Download vocal folds

Version WS 2007/8
Speech Science
Speech production II – Phonation
Topics
• Kinetic energy to acoustic energy
• The phonatory process
• Structures of the larynx
Homework: a) Kent, Chap. 4, pp. 100-134
b) Borden, Harris & Raphael, Chap. 4/5, pp. 72-88/65-193
Deutsch:
c) Pompino-Marschall, Teil II, 31-42
d) Reetz, Kap. 3, Teil 3.2, S. 110-128
Übung 3 (22 Nov): Looking at the glottal signal: Laryngography
Homework: Exercise sheet.
Kinetic to acoustic energy
• The kinetic energy of the airstream must be transformed
into acoustic energy; otherwise we can‘t hear anything!
• This is achieved by introducing some “disturbance“ into
the uniformity of the (laminar) airflow.
• The “disturbance“ can either be regular or irregular.
(periodic or aperiodic)
• The first point at which the transformation of the airstream can occur on the way from the lungs to the outside
is at the larynx, when it passes between the vocal folds
(through the glottis, as the gap is called)
• If the vocal folds vibrate, the result is a periodic fluctuation
of the air-pressure; if they are stiff, the result is aperiodic.
P + 1/2 p U2 = constant
The folds
vibrate …
• because the
vocal folds are
close together
• because of
the airflow
• and because the
muscle tissue
has elasticity
• = aerodynamic
myo-elastic
theory
Pressure + 1/2 density x Volume velocity2 = constant
i.e., when the airflow increases in the narrowed glottis,
the pressure decreases.
The folds
vibrate …
• because the
vocal folds are
close together
• because of
the airflow
• and because the
muscle tissue
has elasticity
• = aerodynamic
myo-elastic
theory
A mechanical
model
• shows the
elasticity of
the folds
• allows the twopart movement;
top and bottom
• with a flexible
link between
top and bottom
Quelle
The vocal
folds…
• have two
muscular parts:
• the external (here)
the internal (next)
thyroarytenoid
(muscle names
are given after
the places where
the muscles are
attached)
The vocalis
muscle…
• is the internal
thyroarytenoid
Activating or relaxing the
vocalis together with, or
independent of the external
thyro-arytenoid muscle ….
… means that the vocal
folds can have many
different properties which
affect the way they vibrate.
The vocal folds together and apart
• They have to be together (adducted) to vibrate for voiced
sounds…. (and even more firmly together to stop things
going down!)
• …and they have to be apart (abducted) to:
- let us breathe freely and
- produce voiceless sounds
• This mobility has nothing to do with the vocal folds themselves;
it is done with the arytenoid cartilages (the posterior attachment
point of the vocal folds – cf. the name of the muscles)
The arytenoid cartilage movements
The arytenoid cartilage movements
transverse and oblique
arytenoid muscles
Degrees of adduction
a) normal adduction
(“modal voice“)
b) extreme adduction
(“hard/pressed voice“)
c) weak adduction
(“breathy voice“)
The rest of the larynx
• The arytenoid cartilages
(with the thyro-arytenoid
muscles attached)
rest on the cricoid c.
• The thyroid cartilage
(also with the thyro-aryt.
muscles attached) rests
on the cricoid cartilage
too, standing on two legs
• This arrangement means
that the thyroid c. can tip
forwards and back …..
The thyroid
cartilage
Movement of thyroid c.
relative to the cricoid c.
Difference in angle of
male and female thyroid c.
Stretching the vocal folds
The whole
picture
• Muscle connections
between the larynx
and other structures
(head and thorax)