The influence of wind direction on acoustic backscattering from sea surface

The acoustic backscattering from the sea surface has an important impact on the performance of active sonar. Accurate knowledge of backscattering characteristics would improve sonar performance. In conventional two-dimensional sea surface scattering models, the sea surface is assumed to be isotropic, making it impossible to evaluate the influence of wind direction or wave direction on sea surface backscattering. Due to equipment limitations, few studies have investigated three-dimensional acoustic scattering from anisotropic sea surfaces in the 1–20 kHz frequency band. In this paper, a parametric acoustic array with a narrow beam was used to measure backscattering intensity at different incident azimuths and frequencies, thereby revealing the three-dimensional acoustic backscattering characteristics of the sea surface. Experimental results show that, when wind speed is below the threshold required to saturate subsurface bubble scattering, the backscattering intensity of mid-frequency signals (4 kHz and 8 kHz) is significantly affected by wind direction for wind speeds of 8.5–10.0 m/s. Furthermore, the influence of wind direction on backscattering intensity decreases with increasing frequency.