Relationship between intraglottal geometry, vocal tract constriction, and glottal flow during phonation of a canine larynx

Hypothesis: The rapid reduction of the glottal volume flow rate, which usually occurs in normal phonation during the closing of the vocal folds, is measured by a quantity known as the maximum flow declination rate (MFDR). Our preliminary work highly suggests that intraglottal flow separation vortices (FSV), which form near the superior aspect of the divergent folds during closing, can directly affect MFDR. In this project, we hypothesize that the strength of the vortices is highly correlated with higher MFDR, larger divergence angles and stronger FSV. Methodology: We use particle image velocimetry to measure the strength of the FSV as well as the intraglottal pressures during phonation in four excised canine larynges with an attached mechanical vocal tract. Two vocal tract models are used, one with a false fold gap of 7 mm, one with a gap of 3 mm. Results: Stronger FSV (measured by vorticity) are correlated with glottic efficiency, larger glottal divergence angles and/or with decreased distance between the false folds. Conclusion: We show correlation of the strength of the FSV with different variables. These data are currently being used to validate computational flow structure models. These computational models then can be used to determine causation.