A model of acoustic propagation in solid media has been derived. It is a one‐way wave equation based on a high‐order approximation, called a Padé approximation, to the square‐root function. The physical properties of the environment are modeled as stratified, thin, homogenous layers. The model can be applied to obtain an approximate solution in range‐dependent environments by allowing the properties of the layers to vary in range. Furthermore, the effects of rough or sloping reflecting interfaces can be approximated using an equivalent reflector, consisting of two thin layers whose properties vary in range.