Statistical Characteristics of Acoustic Fields Scattered at the Sea Surface: A Helmholtz-Gulin Model

摘要

Statistical properties of acoustic fields scattered from wind-driven surfaces are studied using a numerical simulation technique. The technique consists of the numerical integration of the Helmholtz equation, as further developed by Gulin (Gulin, 1962), over simulated numerical model surfaces. The statistical quantities are calculated as averages over an ensemble of 30 random surfaces. The surfaces are numerical realizations of the sea surface having a Neumann-Pierson directional spectrum for 5-m/sec (10-knot) wind speed. The surface is assumed to be insonified by a directional source, and the forward-scattered field is sampled at a rectangular receiver array set perpendicular to the wind direction and consisting of 63 omnidirectional hydrophones centered at the specular direction and extending into nonspecular directions. The field is evaluated for frequencies between and including 0.75 and 3.0 kHz. The statistical quantities studied are total intensity, coherent intensity, degree of coherence, phase and amplitude fluctuations, scattering coefficient, and spatial correlation.