Integration of equations of acoustics of inhomogeneous media

We propose two approaches to integrating linear acoustic equations in inhomogeneous media. The first is based on the Laplace cascade method. For one-dimensional nonstationary equations, new solutions are obtained that depend on two arbitrary functions. These solutions are generalizations of relatively undistorted waves. In the two-dimensional case, conformal maps are used that allow reducing some equations with variable coefficients to equations with constant coefficients. Special three-dimensional equations can also be transformed to a wave equation.