1. Topic 3b: Phonation

2. Learning Objectives
Possess a knowledge of laryngeal anatomy sufficient to understand the biomechanics and acoustics of phonation

3. Behrman Chapter 5, 6 Place less emphasis on…
Minor anatomical landmarks and features
Extrinsic muscles of the larynx
Blood supply to the larynx
Central motor control of larynx
Peripheral Sensory control of larynx
Stress-Strain Properties of Vocal Folds

4. What is the basic role of the larynx in speech and song
Sound source to excite the vocal tract
Voice
Whisper
Prosody
Fundamental frequency (F0) variation
Amplitude variation
Realization of phonetic goals
Voicing
Devoicing
Glottal frication (//, //)
Glottal stop (//)
Aspiration
Para-linguistic and extra-linguistic roles
Transmit affect
Speaker identity

5. The vocal fold through life…
Newborns
No layered structure of LP
LP loose and pliable
Children
Vocal ligament appears 1-4 yrs
3-layered LP is not clear until 15 yrs
Old age
Superficial layer becomes edematous & thicker
Thinning of intermediate layer and thickening of deep layer
Changes in LP more pronounced in men
Muscle atrophy

6. Learning Objectives Describe a single cycle of vocal fold oscillation
Describe why phonation is considered “quasi-periodic”
Describe the relationship between vocal fold motion (kinematics), laryngeal aerodynamics and sound pressure wave formation
Describe and draw idealized representations of the glottal sound source

7. Complexity of vocal fold vibration
Vertical phase difference
Longitudinal phase difference

8. The Glottal Cycle

9. Phonation is actually quasi-periodic
Complex Periodic
vocal fold oscillation
Aperiodic
Broad frequency noise embedded in signal
Non-periodic vocal fold oscillation
Asymmetry of vocal fold oscillation
Air turbulence
Voicing vs. whispering

10. Flow Glottogram

11. Synchronous plots Sound pressure waveform (microphone at mouth)
Glottal Airflow
(inverse filtered mask signal)
Glottal Area
(photoglottogram)
Vocal Fold Contact
(electroglottogram)

12. Sound pressure wave
sound pressure
Instantaneous
Time

13. Learning Objectives
Briefly describe range of instruments used to capture phonatory behavior
Explain vocal fold motion using the 2-mass model version of the myoelastic-aerodynamic theory of phonation

14. Measuring Glottal Behavior
Videolaryngoscopy
Stroboscopy
High speed video

15. Photoglottography (PGG)
illumination
Time

16. Electroglottography (EGG)
Human tissue =  conductor
Air:  conductor
Electrodes placed on each side of thyroid lamina
high frequency, low current signal is passed between them
VF contact  =  impedance
VF contact  =  impedance

17. Electroglottogram

18. Glottal Airflow (volume velocity)
Instantaneous airflow is measured as it leaves the mouth
Looks similar to a pressure waveform
Can be inverse filtered to remove effects of vocal tract
Resultant is an estimate of the airflow at the glottis

19. Glottal Aerodynamics Volume Velocity Driving Pressure
Phonation Threshold Pressure
Initiate phonation
Sustain phonation
Laryngeal Airway Resistance

20. Myoelastic Aerodynamic Theory of Phonation
Necessary and Sufficient Conditions
Vocal Folds are adducted (Adduction)
Vocal Folds are tensed (Longitudinal Tension)
Presence of Aerodynamic pressures (driving pressure)

21. 2-mass model Upper part of vocal fold Mechanical coupling stiffness
Lower part of vocal fold
Coupling between
mucosa & muscle
TA muscle

22. VF adducted & tensed → myoelastic pressure (Pme )
Glottis is closed
subglottal air pressure (Psg) ↑
Psg ~ 8-10 cm H20, Psg > Pme
L and R M1 separate
Transglottal airflow (Utg) = 0
As M1 separates, M2 follows due to
mechanical coupling stiffness
Psg > Pme
glottis begins to open
Psg > Patm therefore Utg > 0

23. Utg ↑ ↑ since glottal aperature << tracheal circumference
Utg ↑ Ptg ↓ due to
Bernoulli effect
Pressure drop across the glottis
Bernoulli’s Law
P + ½ U2 = K
where
P = air pressure
 = air density
U = air velocity

24. Utg ↑ Ptg ↓ due to Bernoulli effect
Plus “other” aerodynamic effects
Ptg < Pme
M1 returns to midline
M2 follows M1 due to
mechanical coupling stiffness
Utg = 0
Pattern repeats times a second

26. Limitations of this simple model