(36) FEM analysis of acoustic characteristics of the vocal tract with the
nasal cavity¡¡during phonation of Japanese /a/
¡¡¡¡¡¡4th Joint Meeting of ASA/ASJ,Vol.120,No.5,pp.3371-3372,2006-12
¡¡For this study, the transfer functions and active sound intensities of a
vocal tract model with and without a nasal cavity were computed using three-dimensional
finite element method (FEM). The models were based on vowel data obtained
by magnetic resonance imaging(MRI) of the vocal tract with a nasal cavity
during phonation of the Japanese /a/. The oral cavity was also coupled with
the nasal cavity in a three-dimensional volume of radiation. Effects of wall
impedance were also examined. Coupling of the nasal cavity to the oral cavity
indicated the following aspects. Additional peaks appeared below 3 kHz for
the lossless condition. However, they disappeared in the simulation for the
soft wall condition. The sound energy circulation did not occur in the simulation
for the soft wall condition. Regarding effects of the wall boundary condition
on the spectral envelope, three-dimensional simulations confirmed the upward
shift of lower formant frequencies. However, disagreement of the formant
frequencies between simulated and real speech should be investigated further
by adjusting the wall boundary condition to a more realistic one.