Air–water interfaces can enable distinct target scattering mechanisms different from the mechanism under free field conditions. In this study, backscattering experiments are performed by lowering an acrylic or polymethylmethacrylate sphere through the air–water interface into the water and insonifying the sphere from below at grazing incidence. Pronounced backscattering enhancements associated with the subsonic Rayleigh wave propagation mechanism are observed before the specular reflection point of the sphere reaches the water. The results indicate that, for a partially exposed sphere, subsonic Rayleigh waves can pass through the air–water interface and circumnavigate the sphere multiple times. The phase velocities of Rayleigh waves are different when propagating above and below the air–water interface. Moreover, subsonic Rayleigh waves are partially reflected when passing through the air–water interface, generating wavefronts that propagate in the reverse direction.

中文翻译：

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由于空气-水界面反射的亚音速瑞利波，部分暴露球体的反向散射增强

空气-水界面可以实现不同于自由场条件下机制的不同目标散射机制。在这项研究中，反向散射实验是通过将丙烯酸或聚甲基丙烯酸甲酯球体通过空气-水界面降低到水中并在掠入射时从下方对球体进行声化来进行的。在球体的镜面反射点到达水之前观察到与亚音速瑞利波传播机制相关的明显的反向散射增强。结果表明，对于部分暴露的球体，亚音速瑞利波可以穿过空气-水界面并多次环绕球体。瑞利波在空气-水界面上方和下方传播时的相速度不同。而且，