The theory of the propagation of sound in an inhomogeneous moving medium (Review)

A linearized system of hydrodynamics equations is presented, which is used as a basis in studies of sound propagation, and the eikonal equation, as well as formulas for phase and group velocities of a sound wave, are considered. One of the results of recent investigations reviewed is a Hamiltonian solution to the eikonal equation, which enables the trajectory of a sound beam to be calculated for a medium with three-dimensional temperature and wind velocity inhomogeneities. Other results under consideration include: the law of refraction of the normal to the wavefront and the law of refraction of the sound beam in a stratified moving medium; the method of computing the sound pressure in a stratified moving medium; and the field of a point source in a stratified moving medium.