This thesis deals with the acoustic scattering by a cylindrical object in the vicinity of an elastic plane interface. In modal theory context, we have tried to develop the most general model. Actually, we have defined a new theoretical method called Generalised Images Method. In the first part of this document, we describe the mathematical expression of this new method. Then, we analyse the theoretical and numerical limits. In order to verify the coherence of the new model, we compare it with others standard theories (integral method, geometrical theory). We prove the Generalised Images Method can be used in concrete experimental situation: a underwater cylinder lain nearby a plane sedimentary interface (sea-beds). More, we show that scattering by a cylindrical object buried in an underwater sedimentary media can be described using Generalised Images Method. Eventually, we consider the scattering by a cylinder with not-circular section, and we develop a new approach in modal theory.

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