Acoustic Scattering From Rough Bubbly Ocean Surface Based on SSA and EMM

Abstract

In this article, the small slope approximation in conjunction with the equivalent medium method is applied to analyze the acoustic scattering from a rough bubbly ocean surface, in which seawater with bubbles is regarded as a special medium, and the effect of subsurface bubbles is considered to have three main aspects: First, the attenuation effect, which is manifested as sound energy absorption, effective wave number correction, and sound speed reduction. Second, the modulation of incident and scattering angles of sound waves. Third, the volume scattering by bubbles. Also, it should be pointed out that different from previous papers, the rough sea surface is established, the acoustic scattering from each rough sea surface is simulated and an ensemble average is performed. By comparing with critical sea test results, it is found that the algorithm in this article can effectively predict the acoustic scattering from the sea surface with bubbles. The bistatic and monostatic acoustic scattering strength of the rough bubbly ocean surface under different conditions are calculated and discussed in detail. The results show that the peak of scattering strength appears in the direction of the specular scattering angle, and the farther away from the specular direction, the smaller the scattering strength. As the wind speed increases, the scattering strength first decreases and then stabilizes in the specular scattering direction, first increases and then stabilizes in the forward scattering direction, and continuously increases in the back-scattering direction.