Transmission characteristics of convergence zone in deep-sea slope

We analyzed the experimental data from two survey lines in an experiment conducted in the South China Sea. The bottom of one survey line is flat, and that of the other line has a large slope. Comparison indicated significant difference in the convergence zones between the two survey lines. We simulated the experimental phenomenon by using the Bellhop model. Simulation results are consistent with the experimental findings and explained the mechanism underlying the occurrence of the phenomenon. The following conclusions were derived. (1) A strong signal reflection zone, similar to the convergence zone, exists in the near field. (2) The convergence zones in the slope appear earlier and are higher in number. (3) The complexity of the slope (i.e., large fluctuation) easily affects the transmission of the converging sound lines, resulting in significant attenuation of the acoustic signal. (4) When the sound source is deep, the convergence zone widens and the first convergence zone disappears in the signal reflection zone in the case of a flat seabed; Convergence zone in the slope directly disappears.