Explicit Analytical Representations in the Multiple High-Frequency Reflection of Acoustic Waves from Curved Surfaces: The Leading Asymptotic Term

In the context of wave propagation through a three-dimensional acoustic medium, we develop an analytical approach to study high-frequency diffraction by multiple reflections from curved surfaces of arbitrary shape. Following a previous paper (of one of us) devoted to two-dimensional problems, we combine some ideas of Kirchhoff's physical diffraction theory with the use of (multidimensional) asymptotic estimates for the arising diffraction integrals. Some concrete examples of single and double reflection are treated. The explicit formulas obtained by our approach are compared with known results from classical geometrical diffraction (or Ray-) theory, where this is applicable, and their precision is tested by a direct numerical solution of the corresponding diffraction integrals.