Improving the horizontal-longitudinal correlation of acoustic field in the shadow zone in deep water using range-frequency interference structures

The horizontal-longitudinal correlation of the sound field decreases rapidly in the shadow zone of the deep sea, which severely limits the detection performance of the horizontal array in this area. This paper employs a range-frequency interference structure to frequency-shift compensate the acoustic field at different longitudinal intervals to improve the horizontal-longitudinal correlation of the acoustic field in the shadow zone. Firstly, the range-frequency interference structure and the horizontal-longitudinal correlation are analyzed by simulation based on a deep-sea experimental environment, and the simulated horizontal-longitudinal correlation of the acoustic field is improved through frequency-shift compensation by using an equivalent waveguide invariant. Then the experimental acoustic data from the deep-sea experiment is analyzed. The horizontal-longitudinal correlation of the received acoustic field in the first shadow zone at three depths and two ranges is processed. The data processing results show that the horizontal-longitudinal correlation length after frequency-shift compensation is increased by approximately 4 to 11 times compared to before the frequency-shift compensation. The simulated and experimental results demonstrate that the use of a range-frequency interference structure for frequency-shift compensation of the received acoustic field can effectively improve the horizontal-longitudinal correlation of the sound field in the shadow zone of the deep sea.