Higher order modes propagation in the human vocal tract

Rafael Laboissière (1) , Hani Yehia , Xavier Pelorson

1 CRNL - Centre de recherche en neurosciences de Lyon - Lyon Neuroscience Research Center

The representation of the vocal tract in terms of its cross sectional area function is useful to obtain an approximation of the acoustics of the vocal tract based on plane waves, which takes into account only for longitudinal resonance modes. However, for frequencies above 4 or 5 kHz (depending on the vocal tract geometry), transverse resonance modes can have a significant effect and must be taken into account. In this paper, we describe a method to calculate the vocal tract acoustics for the case of cross-sectional shapes measured by MRI. Since these shapes are arbitrary, a method to numerically derive the eigenfunctions and eigenmodes has been implemented. Validation of this method has been performed by comparison with analytical solutions for rectangular and elliptical geometry. First a comparison between the results obtained with this new method and the classical approximation using a concatenation of uniform ducts of rectangular or elliptical cross-sections is presented. The effect of higher acoustical modes is illustrated on the basis of not only the transfer function but also on the radiated sound pressure field. Then, the results obtained by numerical simulation are compared with acoustical measurements performed on mechanical replicas of the vocal tract with various shapes.

Mots clés: speech; higher order modes; simulation; anatomical data

Domaines: Acoustique [physics.class-ph]

Rafael Laboissière, Hani Yehia, Xavier Pelorson. Higher order modes propagation in the human vocal tract. Acoustics 2012, Apr 2012, Nantes, France. ⟨hal-00811334⟩