Speech Science-Lecture 8/9

vocal-fold cycle

1) air pressure from the lungs blows the vocal folds apart

2) glottis opens during each vibration

3) the folds come together during each vibration (adduction during phonation, elasticity)

4) subglottal air pressure drops, and vocal folds are forced together (Bernoulli effect)

transglottal pressure

relative difference between the pressure above and below the vocal folds

“driving pressure”

phonation requires

the pressure difference of a minimum of 2cm h20

conversational speech

7cm h20

what must be greater than supraglottal pressure?

lung pressure or equivalently subglottal pressure

2 mass theory "(ishizaka + flanagan 1972)

• lower part of vf are forced open by pressure from lungs (subglottal pressure)

• upper parts of vf remain closed

• later the upper parts are opened as well (partly as a result of subglottal pressure, partly bcs they are pulled apart by tissue of lower part)

• both the upper and lower part execute the opening and closing movement,

• the lag between the movement of the upper and the lower parts of the vocal folds enables them to complete closure

arytenoid cartilages

rock inward to adduct the vocal folds (partially or completely)

The pulmonic pressure

pushes the lower parts of the vocal folds apart

1st step: Subglottal pressure

Increases and pushes against elastic vocal folds

2nd step: When the pressure is great enough (subglottal)

To overcome vocal fold resistance, the glottis is pushed to open laterally

• Convergent-shaped glottis

What part of the vocal folds separates first?

Inferior part of the vocal folds separates before superior

3rd step: upper margins of vocal folds

Are separated and airflow commences

• subglottal pressure: is greater than supraglottal pressure

• Pressure across the vocal folds drop

4th step: the lower border

Is reaching maximal excursion; the upper body continues to open due to the inertia of the mass of the folds

Step 5: the lower portion of the vocal folds

Is returning to the middle due to Bernoulli effect and the elastic recoil forces

Step 6: upper parts

Are still moving apart

Divergent-shaped glottis

Step 7: lower parts

are fully closed (Bernoulli effect is strong)

Step 8: upper border

Returning to the midline due to elastic recoil forces (not Bernoulli effect); airflow stopped

Step 9: full contact of the vocal cords

Full contact of the vocal cords

vertical phase difference: mucosal wave

1) open

2) closed

3) opening

4) closing

out-of-phase movement

upper & lower margins in early part of closing phase are moving in opposite directions

• due to mucosal wave traveling wave of mucosa from inferior to superior margin

coronal section of vocal fold

intraoral pressure

higher pressures are produced during

• voiceless compared to voiced

• prevocalic compared to postvocalic consonants

• stressed compared to unstressed syllables

• stops compared to fricatives

what do children produce?

higher intraoral pressure compared to adults because they tend to speak at higher SPL

phonation threshold pressure

the lung pressure required to initiate phonation is greater than the lung pressure required to sustain phonation (due to inertia and momentum); minimum lung pressure required to initiate vibration

what is the minimal lung pressure required to initate vibration?

0.3-0.5 kPa (3-5cm H20)

what is the lung pressure required to maintain vibration?

0.1-0.2kPa

4 factors affecting phonation threshold pressure

• lowered by decreased vocal fold viscosity

• lowered by decreased mucosal wave velocity

• lowered by increased approximation of vocal folds (in pre-phonatory stage (phonation onset)

• raised by increased frequency of vibration

what do the vocal folds need to be in order to permit oscillation?

within the phonatory adductory range (not too far apart and not too overly compressed) and the transglottal pressure must be at or greater than phonation threshold pressure

phonation onset

pre-phonatory or phonation-ready phase can vary; initiation of phonation

• simultaneous

• breathy

• glottal attack/hard onset

simultaneous onset (gentle/easy/soft onset)

complete adduction and exhalation are simultaneous

breathy onset (aspirate onset)

exhalation precedes complete adduction

glottal attack (hard onset)

complete & forceful adduction precedes exhalation; initial movement of vocal folds is lateral

phonation onset-vocal rise time

helpful for assessing phonation onset

equals duration from the onset of sound to the moment at which the amplitude of the acoustic wave reaches a steady-state

Fundamental frequency controlled by? (LOOK NOTES NOT FINISHED)

• criciothyroid muscle contraction

• thyroarytenoid muscle contraction

• subglottal pressure

• extrinsic muscle activity for articulatory functions

Fo is

rate of vib of VFs

pitch is the perceptual correlate (Fo is physical correlate of pitch)

male Fo

125 Hz

women Fo

> 200 Hz

children Fo

300+ Hz

Fo varies within speakers

longer more massive VFs yeild lower Fos; lengthening the VFs increases tension and decreases mass, leading to highr Fos