The problem of two concentric spherical regions containing different fluid media suspended in a third fluid and excited by an incident plane wave is analyzied using Coustyx Multidomain model. Analytical solutions are also derived by expanding the plane wave as a series of spherical Bessel functions and enforcing continuity of sound pressure and normal velcoity at each interface boundaries. Coustyx solution is in excellent agreement with the analytical solution for both the surface solution as well as the field point solution.