Analysis of sound propagation in the direct-arrival zone in deep water with a vector sensor and its application

Abstract

The receiver at larger depth can receive the direct-arrival signal from a shallow source in a certain range in deep water. During a deep-water experiment conducted in 2014, a vector sensor located at a depth of 3146 m received the direct-arrival signals from the transducer towed at about 140 m depth by the source ship. In this paper, the propagation properties of the sound field in the direct-arrival zone in deep water are studied based on the ray theory and subsequently a source-range-estimation method is proposed. In the direct-arrival zone, the arrival angle is one of the most important properties of sound field, and the sound field is mainly composed of the contributions of a direct ray and a surface-reflected ray. The theoretical analysis and simulation results show that the amplitudes of horizontal particle velocity and vertical particle velocity are related to the mean arrival angle of the direct ray and the surface-reflected ray, and the larger the arrival angle, the greater the vertical particle velocity is, but the weaker the horizontal particle velocity is. Furthermore, the energy difference between horizontal particle velocity and vertical particle velocity can be approximately expressed by a monotonic function of the arrival angle, which varies fast with the horizontal distance between source and receiver. This property is applied to the estimation of source range. The analysis of the experimental data shows that the estimated source ranges are consistent with the GPS ranges within the range of 8 km, and the mean relative error of source range estimation is within 10%.