According to the Myoelastic-Aerodynamic Theory, what happens to the vocal folds during phonation?

In the context of the Myoelastic-Aerodynamic Theory, the concept that the vocal folds open and close automatically during phonation is central to understanding how sound is produced in the larynx. According to this theory, phonation results from the combination of muscular activity and the physical principles of airflow and pressure.

When air is pushed from the lungs through the trachea, this airflow creates a negative pressure at the level of the vocal folds, which are initially closed. As the pressure builds up below the closed vocal folds, they are eventually forced apart to allow air to escape. This opening occurs passively due to the aerodynamic forces in play rather than solely through muscular contraction. Once the airflow causes the folds to open, they are then drawn back together by their elastic properties and the Bernoulli effect, which states that as airflow increases through a constricted space, the pressure decreases, pulling the folds back together.

Thus, the opening and closing of the vocal folds during phonation is a dynamic process that relies on both the elastic recoil of the vocal fold tissues and the aerodynamic forces acting upon them, making it an automatic response to changing airflow. This natural cycle continues rapidly, creating the vibration necessary for sound production.