Computing the Far-Field Scattered by a Spherical Target Near the Seabed

Abstract

This study proposes a numerically efficient technique for computing the far-field scattered by a spherical target placed near the seabed. The bottom is supposed to be a homogeneous liquid attenuating half-space. The transmitter and receiver are situated at different points of a homogeneous water half-space. The distances between the transmitter, receiver, and object of interest are assumed to be much larger than the acoustic wavelength in water. The scattered far-field is ascertained using Hackman and Sammelmann’s general approach. The arising scattering coefficients of a sphere are assessed using the steepest descent approach. The branch cut contribution is also considered. The obtained formulas for the form-function can be used for acoustically rigid or soft scatterers, as well as elastic targets or spherical elastic shells. Numerical simulations are conducted for an acoustically rigid sphere. Asymptotic expressions for the scattering coefficients allow a decrease in the number of summands in the formula for the target strength and a significant reduction in computational time.