Physiology of the Phonatory system Flashcards
Layered Structure of the Vocal Folds: Five Layers
- (superficial)
- Epithelium
- Superficial L.P.
- Intermediate L.P.
- Deep L.P.
- Vocalis Muscle
- (deep)
Vocal Cords
Phonation (+ KEY POINTS)
•A self sustaining, quasi-periodic oscillation of the vocal folds that results from the interaction of muscular and aerodynamic forces in the vocal tract
Key points:
- Self sustaining
- Quasi-periodic oscillation
- Interaction of muscular & aerodynamic forces
Voice is…
- A series of puffs of air separated by closure of the vocal folds between each “puff”
- The “puffs of air” reflect local changes in air pressure (compression, rarefaction)
Vocal Fold as a Valve
- Vocal folds are major source of periodic vibration for the production of sound for speech
- Vocal folds act as regulating valve because of their close mid-line approximation. They let small puffs of air pass through the glottis, one at a time.
- Act as an interruption of the airflow source
medial compression
- Forces that act to approximate vocal folds at midline
- Combination of LCA and IA to rotate arytenoids
Longitudinal Tension
- Stretching forces applied to vocal fold tissue
- Use of CT, TA
Vocal fold positions for various functions
Laryngeal Vibration – Sound Source for Speech
- A single cycle of opening and closing takes approximately 1/100th second: therefore, the cycle repeats at rates in the region of 100 times per second (adult male speaker).
- This rate is too rapid for human ear to be able to discriminate each individual opening/closing of the vocal cords.
- However, we perceive variations in the overall rate of vibration as changes in the pitch of the voice.
Laryngeal Engagement: process of adjusting the vocal mechanism so vibration can begin (and continue)
1) Medial Compression
2) Longitudinal Tension
Bernoulli’s Principle
- Formulated in 1738 by Swiss mathematician & physicist Daniel Bernoulli
- As the speed (velocity) of a moving fluid (liquid or gas) increases, the pressure within that fluid decreases
- Total energy in a steadily flowing fluid system is a constant along the flow path. An increase in the fluid’s speed must therefore be matched by a decrease in its pressure.
Vibration of vocal folds is primarily a passive mechanism! This includes two forces:
Aerodynamic Forces and Elastic Forces
aerodymanic forces
- Vocal folds are “blown apart” due to Ptrach (tracheal or subglottal pressure)
- Bernoulli Effect:
- Relation between airflow velocity and changes in pressure
- Vocal folds are “sucked” toward each other
Elastic Forces:
•Margins of vocal folds rebound due to tissue elasticity (elastic forces = restoring force in opposition to displacement)
Vocal nodules
- Additional tissue that arises from misuse and abuse of the vocal folds
- Large portion of vocal disorders in children and adults that we will treat with voice disorders
- Can be unilateral or bilateral but are usually bilateral
•THREE BASIC LARYGNEAL ADJUSTMENTS (phonation)
- Vocal attack (adduction of vocal folds)
- Sustained phonation (hold vocal folds in a fixed position
- Terminate phonation (abduction)
Types of Vocal Attack
- Simultaneous vocal attack
- Breathy vocal attack
- Glottal attack
Simultaneous vocal attack
- This is when expiration and vocal fold adduction occur simultaneously
- Used to initiate phonation
- Zany -no airflow before the word if you had airflow first would have the word -sany
Breathy Attack
- Start of significant airflow before adducting the vocal folds
- Occurs frequently during running speech because airflow continues throughout the production of long strings of words
- Some of the adductions involved have to be produced with air already flowing
- Harry is my friend
Glottal attack
- Adduction of the vocal folds occurs prior to the airflow much like a cough
- Used when words begin with a stressed vowel
- “Okay I want the car”
- Should have a buildup of tension and pressure for these words
Ventricular phonation
- False or ventricular folds are used for voicing
- Usually an adaptive response to severe vocal fold dysfunction (growths)
- Phonation is usually heard as deep or raspy because of the thickness of the vocal folds
- False cords may hypertrophy (increase in size) which causes ventricular phonation
Dynamic Adjustments of Laryngeal Mechanism for Changing Pitch
- Average rate of vocal fold vibration is referred to as one’s Modal fundamental frequency. F0 determines relative pitch of one’s voice. (Pitch is a perceptual concept – we perceive frequency of the voice as pitch).
- Modal F0
- Male ~ 120 Hz
- Female ~ 200 Hz
- Children ~ 300-400 Hz
- Normal adult: capable of producing pitch variations that range over two octaves
- Octave is a doubling of frequency. 100-200Hz is an octave difference, 500-1000Hz is also an octave difference
Vocal register
•Refers to differences in modes of vibration of the vocal folds during sustained phonation:
- Modal register
- Glottal fry or pulse register
- falsetto
Modal Register
- Modal phonation
- Pattern of phonation used in daily conversation
- Most important for speech language pathologists
- Also the most efficient
- Vocal folds open from inferior to superior (bottom to top) and close from inferior to superior (top to bottom)
glottal fry
- Second register
- Also called pulse register or Strohbass (straw bass)
- Crackly popcorn quality of the voice
- Low in pitch and sounds rough
- Secondary beat for every cycle of fundamental frequency
Puberphonia
•Maintenance of the childhood pitch despite having passed the developmental stage of puberty
