1. Physiology of the Laryngeal System

2. Non-Speech laryngeal Functions
Preventing the entry of foreign bodies
Coughing:
Violent response by the tissues in the respiratory tract
Mediated by the sensory part of the X nerve
Involves abduction of the VF followed by adduction and elevation of the larynx
The high Psub expels the irritant out
Could lead to vocal abuse
Psub- subglotal pressure

3. Non-Speech laryngeal Functions
Throat Clearing
Not as violent as the cough
involves the same processes as that for the cough
Could lead to vocal abuse
Can also be used as a treatment technique for patients with weak vocal fold muscles
Abdominal fixation
capturing air within the thorax in order to facilitate pushing or pulling
Similar initiatory processes as that used during coughing

4. Non-Speech laryngeal Functions
Dilation
process of abducting the vocal folds
important during exertion as the oxygen requirement is increased
the width during dilation is twice as that maintained during tidal breathing (8mm)
Swallowing
The larynx is elevated
Epiglottis sits over the opening
The VF are adducted
Aryepiglottic fold is tense

5. Laryngeal Functions for Speech
Two major functions for voice production:
Medial compression: the force with which the vocal folds are brought closer
Longitudinal tension: extent of the stretching force
These two functions interact with dynamic air supply, resulting in an increase in sub-glottal pressure
This increased pressure results in setting the vocal folds into vibration
Thus, the vibrations modify the air stream passing through the glottis into glottal pulses/voice
More firm adduction the more power you will have…more subglotal airpressure. Length of vocal folds will be important to the ouput.

6. Direct Visualization

7. How are vocal fold vibrations produced?
Neurochronaxic Theory (Husson, 1950)
Every new vibratory cycle is initiated by a nerve impulse transmitted via the X nerve
Frequency of the VF vibration is dependent on the rate at which the impulses are transmitted
Problems
The course of the RT and the LT X nerve are different in length (about 10cm)
VF don’t vibrate without the air stream
Theories of vocal fold vibrations.
Burnulli affect happens when the vocal folds are phonating. There is a small area of low pressure that occurs in th glotal area that causes the vocal folds to open and close. FO the rate at which they open and close.j

8. How is voice produced? Myoelastic-Aerodynamic Theory (Muller, 1843)
Based on aerodynamic and physical principles
The air stream sets the elastic VF in to vibration
Frequency of vibration is dependent on the length in relation to the tension and mass
Properties of the vocal tract also contribute to the mode and frequency of the VF
Regulated by the intrinsic muscles
Hence myo = muscle/vf and other soft tissue in conjunction with airflow and pressure through constricted area
Elasticity is what helps brings the vf back together along with Bernoulli effect, promoting return by dropping the pressure at the constriction - this is seen with continuous artificial air supply even in cadavers.

9. Convergent to Divergent
Convergent – process of coming together
Divergent – process of going apart

10. Onset of Phonation/Vibration
Pre-phonation Phase
period during which the VF are brought from an abducted position to an adducted or partially adducted position
The extent of force applied to maintain adduction is medial compression and this is brought by the adductor muscles (LCA & IA)
The PCA prevents the arytenoids from sliding forward
LCA – lateral
PCA – posterior
innerarytenoid

11. Attack Phase
begins with the vocal folds in the adducted position and extends through the initial phase of the vibratory cycle
Complete adduction is not required for initiating phonation, however sufficient Psub is required (3-5 cm H2O)
Three types of attacks: breathy, simultaneous and glottal
Breathy – resp. occurs before vf adduction
Simultaneous – vf and resp. occur at the same time
Glottal – resp. after vf adduction

12. Maintaining Phonation/Vibration
The Bernoulli effect
After the attack phase, the air stream pushes itself in an upward direction
The air stream starts to pass through a narrow constriction i.e., the glottis
As a result the velocity of the air column passing through the glottis will increase/higher when compared to the velocity of air in the trachea as the cross-sectional area is smaller at the glottis
As a results, a negative pressure develops perpendicular to the flow of air between the medial edges of the vocal folds
Finger over end of water hose – increased velocity

13. Bernoulli Effect Summarized
Why is negative pressure generated, how is it related to velocity and why is velocity increased in the first place?
The rate at which a given quantity of mass (in this case air) flows through a tube is a product of the density of the mass, the velocity of the mass and the cross-sectional area of the tube and this relationship is constant
Therefore, at the glottis the cross-sectional area is smaller when compared to the trachea; This results in an increase in the velocity to compensate for the decrease in area in order to keep the product constant
Now, velocity of the air column and Pressure in the tube are directly proportional as well and their product is always a constant
Therefore, if the velocity of the air column at the glottis will increase as it moves through the glottis, the pressure has to decrease at the level of the glottis in order to keep the product constant

14. Bernoulli Effect
Thus, the negative pressure sucks the medial edges of the vocal folds towards each other, resulting in the completion of one cycle
The cycle (opening and closing of the vocal fold vibration….not adduction and abduction) continues as long as there is adequate Psub in order to push the air stream in an upward direction

15. Glottal Cycle Arrows represent driving air pressure changes
closed phase
opening phase
closing phase
Opening phase and closing phase. The force of air going through creates the region of low presure inbetween the folds which will cause them to get sucked back together causeing them to close then the subglotal pressure builds up again causing them to be blown open again.
open phase
Arrows represent driving air pressure changes
Notice that the vocal folds are always in transition from open to closed (it is a vibration)

16. Summary of the different phases of VF vibration
Closed phase
Opening phase (longer than closing)
Closing phase
Changes in these phases are based on the differences in the mode and frequency of vibration
Thus producing the voice characteristics
Frequency of the vocal fold vibration
pattern or mode of VF vibration
configuration of the vocal tract

17. Mode of VF Vibration
The Anterior 2/3rd is primarily vibrating as it is membranous; the posterior 1/3rd of the folds are cartilaginous
The horizontal plane has the maximum displacement, with the posterior sections opening first and its moves anterior; the direction is the opposite during closing
There is some displacement in the vertical plane as well wherein the lower edges of the VF open first and is followed by the upper edges. The same occurs during closing

18. VF Vibration Mucosal Wave
As there is a simultaneous horizontal and vertical movement, the cover is able to slide over the rest of the layers to generate a wave that moves along the superior surface of the VF and travels about 2/3rd of the way to the lateral edge.
Will generally dissipate.
Abnormalities usually disrupt this movement and is the first sign associated with a change of voice quality.

19. Movement of vocal folds
Spread of glottal opening
Vertical Phase difference
Note how the vocal folds open from bottom to top & back to front and close from bottom to top & front to back

20. Frequency of Vibration
F= T/ML
Increase in Tension will increase frequency
Increase in vibrating Length will reduce fundamental frequency
Increase in Mass will reduce fundamental frequency
Study through slide 20 is fair game for the test!!!!!!!!!!!!!!!!!!!!!!!!!!!STOP DON’T STUDY MORE!!!!!!!!!!!

21. Changes in Vocal Parameters
Please note that
Pitch is the psychophysical correlate of frequency
Loudness is the psychophysical correlate of intensity
Optimal frequency: frequency of the VF vibration that is most optimal for the individuals system (mass and stiffness)
Habitual frequency: frequency of the VF vibration that is habitually used by the speaker in speech
Most easily elicited with a cough ……………..START HERE FOR FINAL EXAM!!!!!!!!!!!!
Restoring force and resonats frequency are porportional to each other.

22. Changes in Vocal Parameters
Pitch changing mechanism
Intensity changing mechanism
Changes in vocal Quality
Limits on vocal vibrations

23. Pitch Changing mechanism
The Frequency is dictated by:
Tension of the VF
Length of the VF and this is with reference to the length of VF set into vibration. The length is maximum in the abducted position.
Mass of the VF and this is not so much to do with the actual mass; rather it is the mass set into vibration.

24. Vocal Pitch F0: Average rate of vocal fold vibration.
Harmonics (integer multiples of the F0) will contribute to the perception of vocal quality, and will provide the power for vocal tract filtering
Males: 130 Hz; Females: 220 Hz; overlap observed between subjects and within each subject depending on the content of the utterance.

25. Pitch Increase
Changes in the length of the VF results in a change of cross-sectional mass
Note that the length is already at its maximum during abducted position.
Tension can be varied by the CT and the TA with help from the PCA. The CT is for increase in tension in a gross manner while the TA is for fine adjustments.
Thyrohyoid (extrinsic muscle) might be used during high pitches in order to raise the thyroid cartilage and thereby increase the tension of the VF

26. Pitch Manipulation
As the length of the VF is increased, there is an increase in frequency of the glottal pulse as well; the VF resemble narrow elastic bands that are stiff and rigid.
VF approximation (or closure) at the center of the glottis is reduced at high pitches.
Increase in frequency is associated with increase in Psub (as a means of compensation) but an increase in Psub is not always associated with increase in frequency.

27. Pitch Decrease
Our habitual pitch is at the lower end of the frequency range of hearing (70 to 525 Hz).
Produced by reducing tension and increasing mass per unit length that can be set into vibration.
Relaxation is due to the recoil forces that will work towards reducing the tension as soon as the muscle contraction inducing the tension ceases.

28. Pitch Decrease
A further decrease in tension below the habitual pitch requires active forces whereby the thyroarytenoid (less stiff) lowers the pitch and the LCA helps in medial compression.
Some extrinsic muscles may be active (e.g., sternothyroid).
The false cords may also aid in reducing the pitch (inc. mass to the system)

29. Intensity Changes
Involves muscular effort and its effect on aerodynamic parameters.
SPL is the sound pressure level that is used to designate the intensity of the voice generated.
SPL is proportional to the square of Psub
voice changes by 8 to 12 dB as the Psub is doubled.
At 3-6 cm H2O pressure, the intensity is about dB SPL
Psub about 20 cm H2O or higher for shouting.
And increase of 10 db corresponds with a preseived doubling of loudness….

30. Vocal level modification
The intensity controlling mechanism is not due solely to Psub changes
The degree and duration of vocal fold closure dictates the Psub and is therefore responsible for intensity changes.
The duration of closed phase is higher as intensity is increased; this increases Psub
Further, increase in medial compression will offer more resistance
Distortion- when energy is added into the spectrum that is not normally there…happens when you shout for long periods of time. Horsness comes from incomplete closure of vocal cords…abuse of vocal fold tissues.

31. Summary
In summary, intensity changes are associated with increased Psub
There are several factors inherent to this process that produces the increase in Psub and thus increase in intensity
Degree and Time of vocal fold closure
Glottal resistance
Rate of air flow through the glottis
Increased adduction of VF would be porportional to glottal resistance and rate of air flow through the glottis.

32. Quality Changing Mechanism
Usually the influence of pitch has not been found to dramatically alter quality judgments.
A combination of the vibratory characteristics, vocal tract shape and configuration dictate voice quality (e.g., length, ratio of oral to pharyngeal cavity size, diameters of the cavities).

33. Valving for Speech Laryngeal mechanics for different speech sounds:
Voiceless consonants (first sounds of: pad, tad, cad)
Laryngeal valve open/not set in vibration
Airflows unobstructed
Restricted partially by tongue or lips
Voiced Consonants
Laryngeal valve is set in vibration
Air flow is obstructed
There is obstruction in the superior regions as well
Sibilent- a constriction right at the teeth.
Obstruction or acclusion is closed off.

34. Limits of the VF vibration
Falsetto:
vibration of the VF free borders and the rest are firm and non-vibratory
appear stiff, long, very thin and bow shaped
indicates the heightened activity of the CT

35. Limits Laryngeal Whistle Glottal Fry (Pulse register)
may not be produced by VF vibrations. rather may be produced by the air passage through the vocal tract
very high Psub (about 30cm H2O)
Glottal Fry (Pulse register)
Lowest pitch possible
Long, inefficient closed phase
very low due to incomplete, or poor closure Psub

36. Voice Disorders Location and Size of the pathology
Glottal Incompetence
(A)symmetry of VF movement
Uniformity within each fold
Structural differences with the layers
Mass and Stiffness of each layer.
Interference of vibration.

37. Age and Sex Differences in the Larynx: Maturation

38. Infant Larynx
Differences in the shape, relative size, and position when compared to an adult
Lower border of the cricoid between the 2nd and the 3rd cervical vertebrae (rostral to its eventual location)
Epiglottis is in contact with the soft palate permitting the infant to breathe and nurse simultaneously
Thyroid and hyoid in direct contact, thus no anterior space

39. Young Larynx
Immediately after birth, the changes in the vertebral column and in the relationship between the base of the skull and column lowers the larynx position.
At age 5, the lower border of the cricoid cartilage is at C6 and by years, it is at C7.
After this, there is a slow descent with age.

40. Four voicing signals in the neonate
Birth Signal
short duration (1 sec.)- vowel pattern
Pain Signal-
long in duration, high-pitched
strained harsh quality
Hunger signal
rising & falling of pitch; glottal signal
Pleasure Signal
more nasal, pitch variability, glottal quality

41. Young Larynx
No discernable changes in the infants and the larynx of a small child (toddler) with respect to the sex of the child; thus similarity in voices.
No significant differences in the pitch or the pitch range.
General shape remains essentially unchanged until puberty.
During puberty, the cartilaginous structures grow rapidly.

42. Changes in Vocal Folds
At birth, the VF are about 2.5 to 3 mm in length.
By one year, the length is about 5.5 mm.
Little sex differences in the vocal fold length until the age of 10.
In males, the post-pubertal VF length reaches about 17 to 20 mm while it is about 12.5 to 17 mm in females.

43. Changes in Vocal Folds with age
The mucosa in the newborn is very thick.
Vocal ligament is not developed until the age of 4.
By age 16 the inner structures are the same as that of adults.
The layer structures mature during adolescence. Until then, the inter and deep layers are not differentiated till 6.
Thus voice is associated with both change in the VF length and the inner structures of the VF mucosa.

44. Changes in the Vocal Folds with age
Elastic fibers become fragmented with age, especially in males.
Density of the vocal ligament decreases.
Loss of muscle tissue.
Increase in connective tissue stiffness within the body of the VF
Folds more prone to inefficient closure, producing a variety of voicing problems

45. Aging Larynx
Vocal pitch lowers at a rate that is approximately parallel to the laryngeal growth.
By middle age, the pitch level begins to rise.
This may be due to the deterioration of the muscle tissue and an increase in connective tissue stiffness in the VF.
Also, ossification of the thyroid and cricoid cartilage (in the early 20’s).

46. Aging Larynx
By 65 years, the entire framework, except for the elastic cartilage is more bony.
The valving effectiveness is poor in men over 75.
No major changes in the airway resistance in women (its generally higher in females anyways).

47. Thyroid Angle
In infants the laryngeal cross section approximates a semicircle
The angle (relative to the axis of the vetebral column) is essentially the same for both males and females till puberty.
By adulthood, the angle is about 84 degrees in males while it is about 92.5 degrees in females.

48. Summary of Gender and Age
Prepubescent
minimal, similar pitch
Puberty
male v.f.’s enlarge 8-10mm & females 4mm
thyroid angle is 90 ° in males and 120 °in females.
v.f.’s enlarge in both female & male
epiglottis flattens
v.f. mucosa becomes less transparent
tonsils & adenoids atrophy

49. Fundamental Frequency changes