GTD analysis of scattering by two elastic spheres

Sound scattering by a system of two immersed identical elastic spheres insonified by an incident plane wave is studied. The pressure in the backscattered wave is obtained against the direction of the incident wave by using Geometrical Theory of Diffraction (GTD). Three surface waves play a significant role in the scattering: the Stoneley wave, the Rayleigh wave and one particular Brekhovskikh wave. The study is done for various distances d between the two spheres and for various values of the reduced frequency ka of the incident wave. Moreover, all the interactions between the two spheres are considered and compared: it is shown that, depending on the region considered, either the geometrical interaction or the Stoneley wave interaction provides the main contribution.