Analysis of the influence of the continental shelf slope in the South China Sea on sound propagation

Continental shelf slopes are widely found in transitional sea areas, which are the connecting part between shallow and deep seas. The sound propagation in this part has special effects. This paper takes the continental shelf slope sea area of the South China Sea (SCS) as the research object to analyze the influence of the shelf slope on sound propagation at different seasons. The seasonal difference in the three-dimensional sound ray trajectory and its corresponding transmission loss (TL) are mainly reflected in the case of a shallow sound source, which is caused by the difference in the sound speed field environment. Due to the presence of a strong surface sound channel in winter, the sound source at shallow depths can achieve long-distance propagation. As the strength of the surface sound channel becomes weaker, sound rays with large grazing angles can deflect across the surface sound channel towards the seabed, and sound energy leaks out of the surface sound channel. This part of the sound energy complements the area that the original sound energy can not reach, so the TL in this area is less than 90 dB. As for the slope enhancement effect, we verify it from the perspective of sound ray propagation, calculate the maximum distance between the sound ray and the shelf slope, and the mean absolute percentage error (MAPE) between the theoretical value and the actual value is 7.6%. The above results will have important implications for target detection and hydroacoustic communication in the sea area of continental shelf slopes.