The theoretical responses of vertical and horizontal line arrays to wind-induced noise in shallow water

Abstract

A wave theory model for the propagation of noise from a surface source layer has been used to investigate the directional response of vertical and horizontal arrays to wind noise in shallow water. The model assumes an infinite layer of sources radiating sound with pressure directionality of the form cosm α, where m >1 and α is an angle measured from the downward vertical. The field incident on the array is inhomogeneous in the vertical plane, and directional responses have been calculated from the appropriate spatial correlation matrix for various bottom types, sound-speed profiles, and values of m up to 3. Results show that both components of the noise field, the discrete normal modes and the continuous spectrum, can contribute significantly to the total noise level and to the array responses. The mode arrivals give rise to high vertical array responses near broadside and high horizontal array responses towards endfire. Thus considerably different forms of directional response pattern can be produced compared to those predicted by a simple model for ideal conditions. The extent of these differences is strongly dependent on bottom type and on the source directionality parameter m, and slightly dependent on sound-speed profile.