Mechanisms of speaker adaptation to semi-occluded vocal tract exercises: Insights from computational phonation modeling

Semi-occluded vocal tract exercises (SOVTE) are vocal exercises involving partial occlusion in the front part of the vocal tract, often through phonation into a narrow tube. Although SOVTE are widely used in voice therapy and pedagogy, the physiological mechanisms underlying their therapeutic benefits remain unclear. In this computational study, voice production at different vocal fold configurations with and without semi-occlusion was investigated in a three-dimensional model. Semi-occlusion significantly increased phonation threshold pressure under conditions of weak vocal fold adduction. Under conditions of strong vocal fold adduction, semi-occlusion reduced mean glottal area and increased the duration of glottal closure. These findings suggest two possible adaptation mechanisms through which SOVTE may guide speakers toward an efficient phonatory configuration. For speakers with hypofunctional voice, increased respiratory effort associated with elevated phonation threshold pressure may encourage increased vocal fold adduction. For speakers with habitually tight vocal fold adduction, increased duration of vocal fold contact may alter mechanosensory feedback and promote compensatory reductions in vocal fold adduction. Together, these adaptations may facilitate adoption of an intermediate vocal fold adduction configuration, which is associated with high vocal efficiency and reduced risk of vocal fold injury. Such adaptation effects may persist briefly after SOVTE but gradually diminish over time.