MYOELASTIC AERODYNAMIC THEORY • First introduced in 1843 by Johannes Muller • AERO - air pressure and fow • DYNAMIC - movement and change • MYO - muscular involvement • ELASTIC - ability to return to original state • Consider how these are involved in voice production. .. Steps in MYOELASTIC AERODYNAMIC Theory • STEP ONE • Diaphragm lowered • Chest cage expanded • Air drawn in lungs • Vocal ±olds are open Steps in MYOELASTIC AERODYNAMIC Theory • STEP TWO • Vocal ±olds are closed • Vocal ±olds set to involuntarily proper length and tension ±or desired pitch by contraction o± ²ve laryngeal adductor muscles Steps in MYOELASTIC AERODYNAMIC Theory • STEP THREE • Muscular ±orces collapse lungs • Air is ±orced out o± the lungs ◦ Through the bronchi ◦ Up the trachea Steps in MYOELASTIC AERODYNAMIC Theory • STEP FOUR • Air slows at underside o± vocal ±olds • Air pressure increases
• Air fow increases Steps in MYOELASTIC AERODYNAMIC Theory • STEP FIVE • Air pressure overcomes strength with which the vocal ±olds are held together • Vocal ±olds are blown apart • Pu±± o± air is emitted • Airfow rate increases again • Complete obstruction not necessary to initiate phonation ◦ Steps in MYOELASTIC AERODYNAMIC Theory • STEP SIX • Subglottal pressure reduced when the ²rst pu±± o± air is emitted • Elasticity and muscular conditions o± vocal ±olds and Bernoulli E±±ect cause adduction to occur again Steps in MYOELASTIC AERODYNAMIC Theory • BERNOULLI EFFECT • Occurs when velocity o± subglottal pressure increases while approaching and passing through constricted glottis • Increased velocity creates negative pressure between and just below the medial edge o± the vocal ±olds • Vocal ±olds are drawn together because o± the negative pressure Steps in MYOELASTIC AERODYNAMIC Theory • STEP SEVEN • Vocal ±olds are symmetrical and consistent in weight and mass • Because o± symmetry and consistency, the process can be repeated in a periodic manner as long as air is exhaled Vocal Production • Entire vocal ±old vibrates in normal phonation
• Greatest excursion occurs at juncture of anterior 1/3 and posterior 2/3 of vocal folds • Greatest amount of displacement from midline • Posterior portion (cartilaginous portion) vibrates less because of weight of vocal process in the folds
This is the end of the preview. Sign up to
access the rest of the document.