Convergence zone formed by bottom reflection in deep water with an incomplete channel

In an incomplete deep-sea channel, when a low-frequency sound source is located shallower than the conjugate depth, a region with higher sound intensity compared to the surrounding areas can form near the sea surface within the seabed reflection zone. This region, where reflected sound rays converge, is referred to as the "seabed reflection convergence zone". Horizontally, the seabed reflection convergence zone is situated before the reversal point zone of a complete deep-sea channel, and its convergence effect on reflected sound rays can exceed 10 dB. This provides a potential means for detecting weak targets within the seabed reflection zone. This paper utilizes Gaussian ray acoustics simulation software to analyze the formation conditions of the seabed reflection convergence zone, the structure of sound ray arrivals within the zone, and the frequency/distance interference patterns. The study finds that the convergence gain and spatial distribution of the seabed reflection convergence zone are related to the depth of the sound source and the emission angle of the sound rays. The results have important implications for the long-distance detection of weak targets under incomplete deep-sea channel conditions.