  This thesis investigates acoustic properties of the vocal tract. Starting
from a historical background (to name a few: Galen, Ibn Sina/Avicenna,
Mersenne, Hooke, Euler, Kempelen, Abbe Mical, Kratzenstein, Wheatstone,
Helmholtz, Riesz, Dudley, Dunn, Kelly, Lochbaum, Chiba, Kajiyama, Saito,
Itakura, Burg, Gray...) finaly an improvement in respect to the tube model of
the vocal tract is developed: The acoustics of vocal tract is numerical
simulated in 3 dimensions with Finite-difference in time-domain (FDTD) applied
on an oral-cavity spatially constructed by parameter estimation of speech
signals and laterally by MRI (Magnet Resonance Imaging). Further, the FDTD is
applied on the acoustics of the nasal tract, including paranasal cavities. The
spatial properties of the nasal tract are drawn for CT (Computer Tomographies).
It is shown, that the (absolute) cross section area influences the resonance
charateritic of the vocal tract significant, further the actual shape of the
cross section introduces zeros in the transfer functions. The shape can be
approximated by an elliptical contour, and a 2 dimensional FDTD approach is
discussed. Important absorption machanism are modeled, and a method to
translate the hounsfield-value of a voxel to an acoustic impedance, is shown,
which leads to a more accurate simulation. The thesis further elucidates some
aspects of a numerical efficient FDTD-implementation.
