Immediate Effects of the Vocal Function Exercises Semi-Occluded Mouth Posture on Glottal Airflow Parameters: A Preliminary Study

Summary Objectives The study aimed to quantify immediate alterations in the airflow glottogram between the Vocal Function Exercises semi-occluded mouth posture (/ol/ with lip buzz) and the sustained vowel /o/ in individuals with normal voices, and to determine if noted changes were in agreement with established semi-occluded vocal tract aerodynamic theory. Based on semi-occluded vocal tract aerodynamic theory, we hypothesized the following immediate changes in the flow glottogram during the /ol-buzz/ condition: a greater open quotient, a greater skewing quotient, a greater maximum flow declination rate, increased average airflow, decreased peak airflow, and increased minimum airflow. Methods A cohort of eight men with normal voices produced the sustained vowel /o/ and the Vocal Function Exercises semi-occluded mouth posture (/ol-buzz/). Flow glottograms for both conditions were obtained from the inverse-filtered oral airflow signal via a circumferentially vented pneumotachograph mask. Results Data revealed that open quotient and minimum airflow rates increased significantly between conditions. All other measures trended in the directions predicted by aerodynamic theory, but were not statistically significant. Conclusions The Vocal Function Exercises semi-occluded mouth posture appeared to provide an effective vocal tract semi-occlusion that immediately altered the flow glottogram in accordance with predictions made by computer-modeled aerodynamic theory.