larynx is a
sphincter
sphincters are
biological valves
-open and closing allows certain basic and higher biological functions
unique aspects of laryngeal sphincter
inhalation/exhalation
coughing
forceful closing of vocal folds and downwards rocking of arytenoids
glottal stop
tiny communicative cough
swallowing
VFs closed
-epiglottis descends and larynx pulled up to shut laryngeal inlet
each of these functions are
reflexive
-can be modified to some extent during different activities
phonation
self sustained oscillation of the VFs for speech or song
VF vibrations occur for
speech
song
emotional vocalizations
-VF oscillation that occurs during emotional vocalizations are not volitional
-each of these has distinctive neural correlates
vocalization is
general term that can encompass VF oscillation
vocal fold characteristics ____ and ____ determine ____ ____ and ____ of speech and sound
muscle tension and Psub
frequency, loudness, and quality
-vowels, semi-vowels, liquids and voiced consonants
-transmit tiny puffs of air to vocal tract that excites air column
determines pitch of voice
fundamental frequency F0
BUT VF vibration is a biomechanical event while pitch is a percept
vocal fold characteristics
vibrations of VFs is a ____ process
passive
active processes
adducting, changing length/tension, abducting
conditions for initiating phonation
-VF adduction or vocal attack
-LCA causes artyenoids to rock together bringing folds towards midline
(voluntary for speech involuntary for laughing crying etc)
-Psub>Psupra (transglottal pressure difference)
-Psub > Laryngeal resistance
phonation pressure threshold
minimun pressure (lung pressure) required to initiate phonation
3-5 cm H20
-higher pressures necessary to maintain typical and loud speech
-if pressure is equalized above and below glottis phonation will stop
VF cycle
one phenomena
sustaining phonation requires
-VFs be actively approximated at midline
-power source maintained (Psub)
-asymmetrics in vocal fold oscillation
-differences in how energy is transferred to the tissue during opening vs closing of the VF
adduction force allows pressure below glottis to build up - Psub
-once Psub > Psupra VF are blown apart passively
-breif period of opening dissipates pressure difference
-VFs come back together
what causes VFs to come back together
elastic restoring forces
-elasticity in the tissues
non-linear interactions
divergent pattern in closing reduces ____ _____
intraglottal pressure
-bernoulli effect reduces intraglottal pressure during closing
bernoulli effect
as air passes through VFS the velocity increase while pressure decrease, this allows VFS to come back together
**pressure difference
velocity increases between glottis because pressure drops can increase in VFS coming back together
return to midline during phonation