Matched-field processing enhancement in a shallow-water environment by incoherent broadband averaging

Abstract

Incoherent broadband averaging is a method that uses the broadband nature of an acoustic source to acquire additional gain against ambient noise and to decrease background variance common to matched-field ambiguity surfaces. In this paper, the relationship between the performance of incoherent broadband averaging and averaging parameters (i.e., bandwidth and the number of ambiguity surfaces averaged) is explored, and general guidelines for choosing these parameters are described. Expressions relating environmental parameters to the width and spacing of the sidelobes are obtained. These expressions predict the minimum bandwidth needed for incoherent broadband averaging for the case where one sidelobe dominates. Computer simulations in a Pekeris waveguide using a simulated but realistic noise field are used to verify the theoretical results. The simulations confirm the existence of the minimum bandwidth below which no effective averaging occurs. If the bandwidth equals or exceeds the minimum bandwidth, measures of peak-to-background resolution expressed in units of the variance improve by 5 log(L), where L is the number of surfaces included in the average.