Three applications of David Weston’s work to studies of scattering from fish

Abstract

The Naval Research Laboratory has for many years conducted a program, comprising both experimental and theoretical components, to determine the low- to mid-frequency acoustic scattering characteristics of individual fish and fish schools. This paper discusses three procedures, developed during the course of our work, whose intellectual genesis can be traced directly from David Weston. First, we discuss the ‘‘Weston correction’’ to the monopole resonance frequency of a prolate spheroidal air bubble. This is used to model variations in the resonance frequency of a fish swimbladder as its aspect ratio changes under compression, and to facilitate fish species identification and abundance estimation through the water column. Second, we discuss a scattering model, inspired by Weston’s work on arrays of air bubbles, which incorporates coherence and multiple scattering effects between swimbladders of comparable size to investigate the levels and fluctuations of scattering from fish schools. Third, we discuss an acoustic reference target, constructed from sheets of ‘‘Bubble-Wrap®’’ packaging material and successfully deployed and tested, which is a practical implementation of Weston’s theory for the scattering response of planar arrays of identical bubbles. [Work supported by ONR.]