Horizontal Correlation of Long-Range Bottom Reverberation in Shallow Sloping Seabed

Abstract

The performance of active sonar detection systems is seriously affected by the reverberation at the bottom of the waveguide in shallow water. In order to improve the performance of active sonar detection, it is necessary to understand the horizontal correlation of shallow-water bottom reverberation in active towed-array processing technology. However, the current research on the spatial correlation of reverberation is mainly based on vertical correlation, little work has been done on the horizontal correlation characteristics of long-distance seabed reverberation, and there is no support from sea test data. In this paper, the coupled mode reverberation model is applied to the horizontal correlation, and is studied according to the receiving position, time, and frequency. The simulation results show that, for the long-range bottom reverberation, the lateral correlation is greater than the longitudinal correlation in the horizontal space. By introducing the adiabatic mode solution, the mathematical model of horizontal correlation in the range-dependent waveguide with depth is derived. The numerical results show that the influence of the seabed dip angle on the horizontal correlation should be considered and that the horizontal correlation is affected obviously by the propagation effects of the sloped sea floor. Finally, the experimental data processing and analysis are given and verify the correctness of the algorithm.

[Retracted] Analysis of VLF Wave Field Components and Characteristics Based on Finite Element Time‐Domain Method

“…Numerical calculation of sound propagation mechanism in the shallow sea has always been an important research topic in ocean acoustics [1,2]. After 50 to 60 years of research, several acoustic field numerical calculation methods have been developed, such as the normal mode method, ray method, parabolic equation method, fast field method, and their derivative methods [3][4][5][6][7]. However, these methods mainly calculate sound propagation characteristics in the frequency domain, for example, the transmission loss and frequency response of underwater acoustic energy in seawater.…”

“…However, these methods mainly calculate sound propagation characteristics in the frequency domain, for example, the transmission loss and frequency response of underwater acoustic energy in seawater. At the same time, the sea bottom is treated as a liquid medium with horizontal stratification during calculations [6][7][8]. In reality, the shallow sea is generally a complex ocean environment with an elastic sea bottom that is not horizontally stratified.…”

Sound Propagation with Undulating Bottom in Shallow Water

“…Figures 10 and 11 show the comparisons of experimental and numerical TLs of T1O and T3O with different receiver depths (11,37, and 71 m), respectively. Figure 10a shows the comparisons of experimental (black line) and numerical TLs (red line and blue line) of T1O with different bottoms for the source depth 7 m and the receiver depth 11 m. The blue line is the numerical result for a flat bottom with a depth of 98 m from 40-80 km.…”

“…In the actual marine environment, the sea bottom is generally rough and uneven. Sound propagation from an uneven sea bottom has long been recognized in underwater acoustics, and there are many essential works [2][3][4][5][6][7][8][9][10][11].…”

“…In addition, the incidence and reflection angles of the sound rays on the sea bottom are also changed due to the undulating sea bottom. The work presented in [11] showed that the influence of the seafloor dip angle on the horizontal correlation should be considered, and that the horizontal correlation is affected significantly by the propagation effects of the sloping seafloor.…”