Influence of lips on the production of vowels based on finite element simulations and experiments
Résumé
Three-dimensional (3-D) numerical approaches for voice production are currently being investigated
and developed. Radiation losses produced when sound waves emanate from the mouth aperture
are one of the key aspects to be modeled. When doing so, the lips are usually removed from
the vocal tract geometry in order to impose a radiation impedance on a closed cross-section, which
speeds up the numerical simulations compared to free-field radiation solutions. However, lips may
play a significant role. In this work, the lips’ effects on vowel sounds are investigated by using 3-D
vocal tract geometries generated from magnetic resonance imaging. To this aim, two configurations
for the vocal tract exit are considered: with lips and without lips. The acoustic behavior of each is
analyzed and compared by means of time-domain finite element simulations that allow free-field
wave propagation and experiments performed using 3-D-printed mechanical replicas. The results
show that the lips should be included in order to correctly model vocal tract acoustics not only at
high frequencies, as commonly accepted, but also in the low frequency range below 4 kHz, where
plane wave propagation occurs.