Analysis of acoustic wave scattering by scatterers in layered media using the hybrid ray-mode (boundary integral equation) method

Acoustic wave scattering by scatterers in layered media is studied using a new method that combines the hybrid ray-mode and boundary integral equation methods. The latter is used to formulate the scattering process and the former is used to provide the Green's function of the layered environment. Following standard procedures of the boundary integral equation method, integral equations are formulated first for field distributions along the boundaries of the obstacles. By expressing these unknown distributions in terms of appropriate basis functions, the integral equations are then reduced to algebraic equations that are solved numerically. In the integral equations, it is necessary to compute the Green's function of the layered environment for various arrangements of locations of source and receiver. None of these conventional approaches (rays, modes, and spectral integration) to evaluate the Green's function are satisfactory for all possible arrangements. Only the newly developed hybrid ray-mode method is best suited for this purpose because it combines rays and modes self-consistently within a single framework and optimizes the advantages of each. Numerical implementation illustrates these aspects.