This work is related to modeling of synthetic sonar images of naval mines or other objects. Considered here is the computation of high frequency scattering from the surface of a rigid 3D-object numerically represented by plane triangular facets. The far field scattered pressure from each facet is found by application of the Kirchhoff approximation.
Fawcett [J. Acoust. Soc. Am. 109, 1319–1320 (2001)
] derived a time domain expression for the backscattered pressure from a triangular facet, but the expression encountered numerical problems at certain angles, and therefore, the effective ensonified area was applied instead. The effective ensonified area solution is exact at normal incidence, but at other angles, where singularities also exist, the scattered pressure will be incorrect. This paper presents a frequency domain expression generalized to bistatic scattering written in terms of sinc functions; it is shown that the expression improves the computational accuracy without loss of robustness.