COMD 320 Physiology of phonation

3 theories of phonation

-neurochronaxic theory
-myloelastic-aerodynamic theory
-cover-body theory

Neurochronaxic theory

problem with lengths of recurrent laryngeal nerve

Myloelastic-aerodynamic theory

3 components:
-sub-glottal pressure
-Bernoulli effect
-tissue force (recoil)

rate of flow

rate of airflow through a tube will increase at the point of constriction

Bernoulli effect

as velocity of flow increases, pressure must decrease; so long as total energy remains a constant
-pressure is perpendicular to the direction of the flow
- d x 1/2(v^2p) = c

Cover-body theory

two mass model of vocal folds --
-upper mass = cover
-lower mass = body
-masses act separately but appear to be connected by a spring

Glottal cycle

2 phases:
-open phase: opening & closing phases
-closed phase

jitter

timing variability between glottal cycles

shimmer

amplitude variability between glottal cycles

rocking laryngeal muscles

-transverse arytenoid
-oblique arytenoid
-LCA

rotating laryngeal muscles

LCA (adducts)
PCA (abducts)

gliding laryngeal muscle

thyromuscularis

attack

process of adducting the folds

simultaneous attack

adduction and onset of respiration occur simultaneously
-ex. "zip"

breathy attack

respiration starts before folds are adducted
-ex. "harry"

glottal attack

adduct folds before respiration starts
-ex. "okay"

termination

abducting the vocal folds

perceptual

what is heard

acoustic

what is measured with an instrument

pitch

measured as a fundamental frequency
- Hertz; Hz

loudness

measured as intensity
- deciBels; dB

length

measured as duration

- milliseconds; ms

(interspeaker pitch changing element)
as length increases...

frequency of vibration decreases
-if mass and tension are constant

(intraspeaker pitch changing element)
as tension increases...

frequency of vibration increases

(intraspeaker pitch changing element)
as mass increases...

frequency of vibration decreases

(intraspeaker pitch changing element)
as sub-glottal pressure increases...

there is a slight increase in frequency of vibration

1st pitch raising mechanism

-cricothyroid - tilts thyroid cartilage forward

2nd pitch raising mechanism

thyroarytenoid (thyrovocalis) - tenses the vocal fold

3rd pitch raising mechanism

PCA - prevents anterior sliding of arytenoids

4th pitch raising mechanism

increase in sub-glottal pressure

1st pitch lowering mechanism

passive lowering - tissue elasticity

2nd pitch lowering mechanism

active lowering - thyroarytenoid (thyromuscularis)

3rd pitch lowering mechanism

decrease in sub-glottal pressure

optimal pitch

vocal fold vibration that is optimal or most efficient and appropriate for an individual
-varies by age, gender, size

male, female and child optimal pitch averages

male - 125 Hz
female - 210 Hz
child - 300-400 Hz

habitual pitch

fundamental frequency habitually used during speech - ideally the same as optimal pitch

pitch range

difference between the lowest and highest fundamental frequencies
-about 2 octaves normally

modal

normal voicing

breathy (murmur)

vocal folds are held loosely & somewhat abducted, but still vibrate; air escapes even during the closed phase

whispering

vocal folds are very tense and somewhat abducted, but do not vibrate; sound comes from turbulence in the air stream

creaky

arytenoid cartilages held so tightly the vocal folds only vibrate on a small anterior portion