Nonlinear sound beam propagation in the porous viscoelastic medium

The high intensity acoustic wave and wave beam propagation in structurally inhomogeneous vis-coelastic medium containing highly compressible inclusions - gas pores - are investigated. The system of equations describing the self-consistent acoustic field in such medium is suggested. Nonlinear effects associated with the response of strongly compressible inclusions are taken into account. It is shown that a strong contrast of inclusions and medium compressibilities leads to a significant increase of the effective nonlinear parameter. The simplified equation for high intensity bounded acoustic beams in such media is derived. A method of constructing the analytical solution for the field of nonlinear beams is suggested. The method is suitable in the focal region and adequately takes into account diffraction effects. Analytical solutions for the field along the beam axis and the transverse structure of the field are obtained.