Aerodynamic back pressure

One More Small Step in Solving the Mystery of the Benefits of Semioccluded Vocal Tract Exercises (Article)
In addition to aerodynamic considerations, Titze observes, a vocal tract air column that vibrates (up and down) above the vocal folds can create a reactive push and pull on the tissue surfaces so that vocal fold vibration is reinforced a vocal tract that is narrow (semioccluded) in some region along its length (e.g., at the lips or the epiglottis) helps to produce this favorable push-pull. (posted 2:34 PM, August 27, 2014)