Summary
Within the fully coupled multiphysics phonation process, the fluid flow plays an important
role for sound production. This study addresses phenomena in the flow downstream of
synthetic self-oscillating vocal folds. An experimental setup consisting of devices
for producing and conditioning the flow including the main test channel was applied.
The supraglottal channel was designed to prevent an acoustic coupling to the vocal
folds. Hence, the oscillations were aerodynamically driven. The cross-section of the
supraglottal channel was systematically varied by increasing the distance between
the lateral channel walls. The vocal folds consisted of silicone rubber of homogenous
material distribution generating self-sustained oscillations. The airflow was visualized
in the immediate supraglottal region using a laser-sheet technique and a digital high-speed
camera. Furthermore, the flow was studied by measuring the static pressure distributions
on both lateral supraglottal channel walls. The results clearly showed different flow
characteristics depending on the supraglottal configuration. In all cases with supraglottal
channel, the jet was located asymmetrical and bent in medial-lateral direction. Furthermore,
the side to which the jet was deflected changed in between the consecutive cycles
showing a bifurcational behavior. Previously, this phenomenon was explained by the
Coanda effect. However, the present data suggest that the deflection of the jet was
mainly caused by large air vortices in the supraglottal channel produced by the flow
field of previous oscillations. In contrast, for the case without supraglottal channel,
the air jet was found totally symmetrical stabilized by the constant pressure in the
ambient region. The emitted sound signal showed additional subharmonic tonal peaks
for the asymmetric flow cases, which are characteristics for diplophonia.
Key Words
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Article info
Publication history
Published online: August 01, 2013
Accepted:
April 15,
2013
Footnotes
The work was funded by the German research foundation (DFG, Deutsch Forschungsgesellschaft) in the framework of the researcher group FOR894/2 with the title “Strömungsphysikalische Grundlagen der menschlichen Stimmgebung.” As members of the graduate school of Advanced Optical Technologies (SAOT) funded by the DFG the authors also acknowledge its support to this work.
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Copyright
© 2013 The Voice Foundation. Published by Elsevier Inc. All rights reserved.
