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Experimental Investigation Of The Flow-Acoustic Interaction In Human Phonation

Christoph Näger (1), Stefan Kniesburges (2), Stefan Schoder (3), Stefan Becker (1)

1. Institute of Fluid Mechanics, FAU Erlangen-Nürnberg, Erlangen, Germany
2. University Hospital Erlangen, FAU Erlangen-Nürnberg, Erlangen, Germany
3. Institute of Fundamentals and Theory in Electrical Engineering, TU Graz, Erlangen, Germany


In the human phonation process, acoustic standing waves in the vocal tract can influence the fluid flow through the glottis. To investigate the amount of two-way coupling between the flow field and the acoustics, the supraglottal flow field has been recorded via high-speed particle image velocimetry (PIV) in a synthetic larynx model for several configurations with different vocal tract lengths. Based on the obtained velocity fields, aeroacoustic source terms were computed. Furthermore, the hydrodynamic pressure in the vocal tract was recorded via wall pressure measurements. The recordings revealed that near a vocal tract resonance frequency, the focal fold oscillation frequency jumps onto the resonance. This is accompanied by a substantial relative increase in aeroacoustic sound generation efficiency. At the same time, the glottal volume flow needed for stable vocal fold oscillation decreases strongly. The pressure measurements showed that acoustic anti-resonances of the vocal tract directly dampen the harmonic content of the hydrodynamic pressure field when matching frequencies. This result shows that back-coupling of the acoustics onto the flow field does not only occur in the case where the vocal fold oscillation frequency and a resonance frequency of the vocal tract match, but also under more other conditions.

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