Acoustic wave in a medium with point defects

Within the framework of Hamiltonian formalism, we derive the equations for acoustic wave interacting with the point defects. The change of the defects number due to the various interactions is described by kinetic equations. The linear absorption coefficient and the dispersion are derived from the obtained closed system of equations. The nonlinear three-dimensional Schrödinger equation is derived, the stability of nonlinear acoustic wave is investigated and a condition of the wave focusing is found.