Title: The convergence of sound field in a South China Sea canyon

Author(s): ZHANG Qingqing; LI Zhenglin; QIN Jixing; LI Wen; WU Shuanglin;

Affiliation(s): State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences; University of Chinese Academy of Sciences

Abstract: The sound propagation characteristics in a canyon environment are analyzed using the data from the northern South China Sea. The experimental results show that the energy begins to bend to a deeper place with the depth change of the canyon and the sound transmission losses (TLs) reach the maximum near the center of the canyon due to the combined effect of the negative gradient sound speed profile and the seabed topography. As the sea become shallow gradually, the energy is concentrated due to the seabed reflection, thus the TLs reduce by over 20 d B compared with the TLs results got from the simple slope to the deep water environment. Moreover, when the convergence effects are less than the loss caused by diffusion, seabed reflection, etc. the TLs are minimized and then increase with an increase in distance. In the last segment, the gradual convergence of the energy is highlighted again, and the TLs decrease 10 d B when the water depth suddenly decreases from 850 m to 311 m within 8 km. Finally, the convergence of sound field, which is caused by the topographic change in the canyon environment, is explained by the ray theory and the parabolic equation method.