Voice Flashcards
What is the Myoelastic Aerodynamic theory
Myoelastic Aerodynamic Theory: Pressure builds up, forces VFs apart
Recoil: VFs move back toward the midline because of tissue elasticity and the Bernoulli effect
What are the limitations of the Myoelastic theory
Need asymmetry of forces during open/closed phases
Otherwise equilibrium position- fixed glottal gap and no vibration so we need a nonlinear driving/ restoring force (asymmetry)
Describe Titze’s Self Oscillation Theory
Asymmetric forces for vocal fold vibration
External: Vocal tract inertance- demonstrated by one mass model
Internal: Asymmetric tissue movement, Multimass model
Asymmetric Forces: Two ways of providing asymmetric force- External ( driven oscillation)
Internal (self oscillation) and in both cases: forces differ b/w positive and negative phases
What does Titze’s theory account for that the Myoelastic does not
Internal Asymmetric force: Due to non uniform tissue movement
Different glottic configurations in different parts of cycle ( convergent and divergent)
Convergent glottis- Higher mean intraglottal pressure and therefore greater force
Divergent glottis- Lower mean intraglottal pressure and therefore lesser force. Asymmetry of intraglottal pressure over vibratory cycle permits transfer of energy from airstream of VF
Describe the asymmetry of air flow between the open and closed phases
External driving force: Asymmetry of air pressure between opening vs closing phases of VF vibration
During opening phase- Rate of airflow is increasing thus intraglottal pressure is high
During closed phase: Air mass continuous up vocal tract( due to vocal tract interia- inertance)
Leaves relative vacuum just above Vfs( low pressure) Unlike Bernoulli, this external force is phase-dependent
Describe the glottal source signal
Volume velocity waveform not acoustic
Frequency components- All even and odd harmonics similar to sawtooth wave
Roll off of freq. Components- 12 dB per octave similar to triangular wave
Real voices also have non harmonic partials
