Abstract: Starting from the fundamental wave equation for acoustics of moving media, a systematic study concerning the reflection and refraction of plane sound waves on the interface between two moving homogeneous media has been made under the assumption that the Mach numbers M of moving media are low, such that M₂<<1. The representations for reflection and refraction coefficients as well as the equation decribing the total reflection zone are obtained. The processes have been extended to a "slowly varying" vertical stratified medium, and the W. K. B. solution and the successive modifications have been worked out. Furthermore, the field in the region for which geometrical acoustics can no longer be appropriate is studied by the approach after Gans, and a suitable solution which ought to be connected with the geometrical solutions on the boundaries of this region is found.