Phase-averaged analysis of jet dynamics in a scaled up vocal fold model with asymmetric motions*

This study focuses on the effects of glottal jet dynamics on phonation when one of the vocal folds does not move as much as the other. This can be a pathological condition in which a vocal fold is completely or partially paralyzed. Experiments were conducted using a 10x scaled-up model in a free surface water tunnel. 2-D vocal fold models with semi-circular ends were computer driven inside a square duct with constant opening and closing speeds. Four cases were studied in which one vocal fold moved 0%, 50%, 75%, and 100% of the other; the last case being, of course, the nominally 'healthy', symmetric case. Time resolved DPIV and pressure measurements along the duct centerline were made at Re = 7200 at a reduced frequency of 0.0261, corresponding to an equivalent life frequency of 97.5 Hz. Phase-averaged analysis of key contributors to sound production was conducted using terms in the streamwise integral momentum equation. The goal was to try to decouple effects associated with varying maximum gap opening, asymmetry due to partial motion of one vocal fold, and pseudo-frequency effects arising when the two vocal folds move at different speeds. Implications on energetics and sound quality are explored.