Modélisation de la propagation ultrasonore dans les milieux complexes

Abstract

This thesis work aims at modeling the propagation of sound waves in complex medium, or porous materials, and the study of sound absorption of these materials to reduce the noise generated by manufactures. Poroelastic materials are porous materials in the case where the structure is set in motion, that are to say the structure is deformable or movable. The theory of Biot-Johnson-Chompoux-Allard (or model of generalized Biot-Allard) is used to describe the behavior of these poro-viscoelastic materials modeled as two-phase systems consisting of a solid phase and a fluid phase, air, coupled with time and space. An analytical approach is proposed in the context of the generalized Biot-Allard theory. This approach is a method of the transfer matrix. Acoustic indicators were calculated from this method. A numerical approach based on the finite elements is used to calculate the real and imaginary part of the surface impedance and the absorption coefficient, using a calculated code called COMSOL Multiphysics. A comparison between the simulations used by the two approaches was made to calculate the acoustic indicators. But also the effects of mechanical parameters of sound absorption were studied. A notable effect was observed in the case the Young’s modulus parameter, but nothing has been observed for other parameters.