The attenuation of a sound wave in a steady flow, with the flow gradient normal to the flow lines, is approximated by three different methods. The first method approximates the steady flow by layers of constant velocity and applies the boundary conditions of Ribner at each interface. The second method uses the analytic solution for the continuous flow. The last method is similar to the first but uses the boundary conditions of earlier authors. It is found that the first and second methods give the same answer, and this answer disagrees with that obtained by the third method.