Numerical production of /s/-like sound as Helmholtz resonance in the turbulence-induced pressure field inside a two-dimensional oral front cavity

Abstract

A numerical production of /s/-like sound is dealt with by means of computational fluid dynamics in a two-dimensional model of oral front cavity. The basic hypothesis is that the target sound is the outcome of the lowest or first-mode resonance to the pressure field inside the front cavity, whose resonance frequency is in the range 5∼8 kHz. The model domain is composed of a small semi-closed area representing the front cavity, the upstream half-space, the downstream half-space and two channels that connect the upstream/downstream half-spaces to the cavity. Computation was carried out with the method of direct numerical simulation on the two-dimensional Navier-Stokes equations. The pressure wave emitted into the downstream half-space has a continuous spectrum with a single spectral peak around the assumed resonance frequency. The spatial/temporal characteristics of the turbulence and pressure fields are studied in relation to the so-called quadrupole field.