Individual Differences of Airflow and Sound Generation in the Vocal Tract of Sibilant /s/

To clarify the individual differences of flow and sound characteristics of sibilant /s/, the large eddy simulation of compressible flow was applied to vocal tract geometries of five subjects pronouncing /s/. The vocal tract geometry was extracted by separately collecting images of digital dental casts and the vocal tract of /s/. The computational grids were constructed for each geometry, and flow and acoustic fields were predicted by the simulation. Results of the simulation showed that jet flow in the vocal tract was disturbed and fluctuated, and the sound source of /s/ was generated in different place for each subject. With an increment of the jet velocity, not only the overall sound amplitude but also the spectral mean was increased, indicating that the increment of the jet velocity contributes to the increase of amplitudes in a higher frequency range among different vocal tract geometries.