A FAST INTEGRAL-EQUATION APPROACH TO ACOUSTIC SCATTERING FROM 3-DIMENSIONAL OBJECTS USING A NATURAL BASIS-SET

Boundary value integral equations and the moment method solution techn ique provide a succinct and elegant strategy for the solution of acous tic surface scattering problems. This paper explores the application o f a subdomain basis set, based on the phase of the incident radiation, which is used to solve for the unknown normal pressure gradient on th e surface of the scatterer using the moment method. The advantage of t his basis set lies in the fact that it can accurately represent the fa st phase character of the pressure gradient on the surface of the scat terer. This allows for far fewer discretizations/basis elements in the moment method formulation and therefore significantly reduces the den sity of unknowns that must be numerically computed. The main contribut ion of this paper is to show how to efficiently employ this natural ba sis and to explore the physical justification for using this approach. The method is compared with other techniques including the Kirchhoff solution technique, high frequency single scattering techniques, the N ussenzveig-Fock technique, and the parabolic equation approximation. U nlike these methods no approximation to the physical system need be in troduced. (C) 1998 Acoustical Society of America.