Source localization in an uncertain acoustic scattering environment

Abstract

The sensitivity of conventional matched-field processing algorithms to uncertainty in ocean acoustic environmental parameters has prompted the design of more robust methods for source localization. In a recent study, Richardson and Nolte [J. Acoust. Soc. Am. 89, 2280–2284 (1991)] reported on the development of a new algorithm which incorporates prior knowledge of the environmental uncertainty into the design of the matched-field processing algorithm. The result was the optimum uncertain field processor (OUFP). The present study addresses the problem of source localization in an imperfectly known acoustic scattering environment. The propagation scenario of interest, the surface duct, is characterized by the property that the received pressure field consists primarily of rays which are scattered from the sea surface. The surface roughness statistics are presumed to be axisymmetric, parametrized by rms height and correlation length. Two approaches to modeling the scattered field will be considered (1) the Eckart reflection coefficient and (2) numerical evaluation of the Helmholtz–Kirchhoff integral for the quadrature components in the specular direction. In each case, simulation results demonstrate that the OUFP outperforms a conventional matched-field processor when surface statistics are imperfectly known. It is also noted that, in the context of source localization, the Eckart method is only suitable for modeling scatter from slightly rough surfaces. For rougher surfaces, it is seen that combining the Kirchhoff model with the OUFP algorithm results in robust localization performance for a propagation channel that is dominated by acoustic interaction with a nondeterministic boundary.