Acoustic propagation from the transitional area to deep water

Abstract

Sound propagation over the continental shelf and slope is complicated and is also an important problem. Motivated by a phenomenon in an experiment conducted in the Northwestern Pacific indicating that the energy of the received signal around the sound channel axis is much greater than that at other depths, we study sound propagation from the transitional area to deep water. Numerical simulations with different source depths are first performed, from which we reach the following conclusions. When the source is located near the sea surface, sound wave will be strongly attenuated by bottom losses in a range-independent environment, whereas it can propagate to a very long range because of the continental slope. When the source is mounted on the slope bottom in shallow water, acoustic energy will be trapped near the sound channel axis, and it converges more evidently than the case where the source is located near the surface. Then, simulations with different source ranges are performed. By comparing the relative energy level in the vertical direction between the numerical results and the experimental data, the range of the unknown air-gun source is approximated. The phenomenon can be confirmed by the experiment with a deterministic source located in the transitional area. [Work supported by the National Natural Science Foundation of China under Grant Nos. 11434012 and 41561144006.]