3.2: Phonatory Physiology Flashcards
Phonation
- Any laryngeal sound production resulting from vibration of VFs (speech, laughter, cough, cry)
- Conditions for sound production:
a. approximation of VFs
b. Airflow from lungs - Alternating adduction and abduction of VFs
Myoelatic-Aerodynamic Theory of Voice Production
- Myo=Muscle contraction -LCA> Approximate VFs
- Elastic=Stretched, compressed -> Return to original state
- Aerodynamic=Air pressure & Airflow = Resistance (Pressure/Airflow)
Myoelastic-Aerodynamic Theory:
Opening Phase of Vibratory Cycle
- Contraction of LCA
a. Approximation of VFs - Build-up of subglottal pressure
- Opening force develops
a. Force exceeds resistance offered by adducted VFs
b. VFs are forced apart - Complete abduction of VFs
a. Flow of air dissipates
Myoelastic-Aerodynamic Theory:
Closing Phase of Vibratory Cycle
- Elastic recoil of VFs
a. Returns VFs to position of equilibrium - Aerodynamic forces & biomechanical properties
a. Inertia
i. Keeps VFs moving closer together
Inertia
Definition: tendency for an object (matter) to stay in its current state
-At rest or preserving its current state of motion
Pressure Differentials (Aerodynamic forces and biomechanical properties)
- Lower glottal pressures and driving forces as VFs close, compared to opening phase
- Slightly convergent VF configuration for glottal opening
a. Allows more pressure to build open before opening, helps overcome resistance of tissue
b. Achieved with vertical phase difference of VFs during vibration (mucosal wave)
Bernoulli Effect (Aerodynamic forces and biomechanical properties)
Air flowing through a constriction creates suction force perpendicular to movement of air
-As air molecules speed up, pressure drops to keep total energy constant
-Greater flow rate, greater suction force (negative pressure)
Additional Biomechanical Properties
- To maintain oscillation, energy needs to be constantly added to the system
- Energy damping factor:
a. Energy gets lost in the system:
i. Viscous Friction: opposition to flow or motion
ii. Loss of air stream energy to surrounding tissue - Need continual injection of more energy into system
-> airstream
Pitch
- Perception measure of fundamental Frequency (F0)
a. Number of cycles of VF vibration per second (Hz)
b. Average rate of VF vibration/second
Male~100 Hz
Female ~ 200 Hz - Mechanisms for changing pitch
a. Vocal length <-> tension <-> mass
*↑ length — ↑ tension — ↓ mass = ↑ pitch
*↓length — ↓ tension — ↑ mass = ↓ pitch
Relationship between VF length and vibration frequency
- Increases in VF length are associated with increased VF vibration frequency
- Increased VF length will decrease effective vibrating mass and increase tension
- Increased VF length associated with decreased VF thickness
Cover-Body Theory
- Cover (Epithelium and Superficial & Deep LP)
- Body (Deep LP and muscle)
- F0 mainly determined by cover
- SLN (CT muscle) and RLN (TA muscle) helps differential control of muscles in regulating F0
Cover Body Theory: Muscle Control
- CT muscle contraction alone
a. stretch both cover and body -> increase F0 - TA muscle contraction alone
a. Tightens muscle but releases cover -> decrease F0
❖CT muscle and TA muscle contraction
*Low pitch: some CT muscle and more TA muscle
*High pitch: some TA muscle and more CT muscle
Mechanisms for changing pitch
*↑ Subglottal pressure
*Medial compression
*Squeezing force directed towards midline during voicing
* ↑ medial compression may elevate F0
*Shortens effective vibrating mass of VFs
*Laryngeal height
*Larynx moves upward in neck for higher pitch sounds
*Extrinsic muscles may stretch quadrangular membrane and conus elasticus → increase tension on vocal ligament
Voice Register
*Difference modes or patterns of VF vibration
*Range of pitch sounds
Modal
*normal speaking and singing voice
*TA and some CT activity → body and cover vibrates
Vocal fry
lowest register
*Creaky, popping sound
*TA and CT activity is low → tension on cover is low = cover is slack
Falsetto
*CT and some TA activity → tension on body and cover = cover taut
*Vibration mostly affects cover
Loudness
-Perceptual measure of sound intensity
-Measured in dB
-Conversational speech: 60 dB
-Whisper: 30 dB
Mechanisms for changing loudness
-Adjustments below VFs
-Adjustments within VFs
-Adjustments above VFs
Below VF Loudness Adjustments
*Subglottal adjustments (below VFs)
*↑ subglottal pressure = ↑ intensity
*↑ lateral excursion (amplitude) of VFs
*↑ force of air puff release
*Glottal source power increases 8-12dB with every doubling of subglottal pressure
Within VF Loudness Adjustments
*↑ medial compression = ↑ intensity
*↑ resistance offered to air stream from lungs
*↑ subglottal pressure
*↑ force of air puffs release
Above VF Loudness Adjustments (Supraglottal)
*Resonance and vocal tract adjustments
*Adjust formants to coincide with harmonics of the source
*Harmonics: other frequencies present in the sound source (integer multiples of F0)
*Formants: peaks in harmonics due to vocal tract configurations
*Adjust vocal tract configuration to coincide formants with harmonics
*Mouth acts like megaphone
*Can increase intensity by 6dB
Intensity and Frequency Relationship
*Intensity ranges are frequency dependent
*Intensity ranges at minimum for low F0
*Increases in intermediate F0 range
*Decreases again at high F0
Quality
Perceptually rated <-> acoustic correlated
Factors that Affect Quality
*VF vibratory periodicity during voicing
*VF tissue status
*Muscular tension levels
*Degree of VF approximation
*Vocal tract resonance
Source-Filter Theory
*Source (input)
*VF vibration to produce sound
*Filter
*Vocal tract
*Resonators function as acoustic filters
*Spectrum (output)
CN X orign
Medulla
CN X Control
Sensory, motor, and autonomic functions
CN X Voice production
Motor: Intrinsic Laryngeal Muscles
Sensory: Laryngeal Cavities
CN X Pharyngeal Nerve
Motor: Most pharyngeal and soft palate muscles
CN X Recurrent Laryngeal Nerve (RLN)
Motor: all intrinsic laryngeal muscles, except CT muscle
Sensory: VFs and subglottal region
CN X: Superior Laryngeal Nerve
-Internal Branch: Sensory: Supraglottal region
-External Branch: Motor: CT muscle
Central Neural Control of Voice: Involuntary
*Involuntary vocalizations
*Brainstem control
*Midbrain and medulla
Central Neural Control of Voice: Voluntary
*Complex, voluntary control of voice during speech and language
*Bilateral sensorimotor cortex
*Supplemental motor area
*Auditory cortex
*Subcortical regions
*Cerebellum
*Brainstem
Cortical Control
*Primary motor cortex: movement of laryngeal and respiratory muscles
*Premotor and supplemental motor areas: planning and coordination of voice production
*Broca’s area: speech motor planning and expressive language
*Auditory cortex: auditory feedback during voice modulation
*Cingulate cortex: vocalization in emotional speech
Subcortical Control
-Basal ganglia: voice initiation and smoothness of voice control
-Thalamus: integrates sensory and motor signals
Cerebellar Control
-Cerebellum: adjust vocal timing, frequency, intensity
-Ensure smooth and precise voice production
Brainstem Control
-Midbrain
-Periaqueductal gray (PAG): emotional vocalizations and involuntary vocal control
-Medulla
-Nucleus ambiguous (NA): motor nucleus of CN X
-Respiratory CPG: coordinate breath support for voice production
