远离航道海域低频海洋环境噪声垂直指向性

海洋环境噪声垂直指向性是声呐背景场的典型空间特性之一，既可体现噪声源的空间特性及其传播特性，还可用来反演海洋环境的特征参数。分析了南海某岛礁海域实测海洋环境噪声的垂直指向性，发现当接收阵远离航道时，低频海洋环境噪声垂直指向性的主瓣集中在-30°～30°范围内(0°对应水平方向)，且水平方向不存在凹槽。基于舰船自动识别系统(Automatic Identification System, AIS)航船分布数据得到简化航道区域航船噪声源模型，利用3D射线声传播算法，结合实际岛礁海域地形数据，计算的低频海洋环境噪声垂直指向性与实测数据处理结果相符。研究结果表明，当接收阵距航道较远时，由航道航船引起的低频海洋环境噪声以接近水平方向入射垂直接收阵，研究结果可为声呐在远离航道海域的性能提高提供技术支持。

Vertical directionality of low frequency ocean ambient noise in areas far away from the shipping lane

The vertical directionality of ocean ambient noise is one of the typical spatial characteristics of sonar background. It can not only reflect the spatial characteristics and propagation characteristics of the noise source, but also can be used to invert the characteristic parameters of the ocean environment. The vertical directionality of ocean ambient noise in the South China Sea waters with island and reefs is analyzed according to the measured noise data in field, and the results show that the main lobe of the vertical directionality pattern of low-frequency ocean ambient noise is concentrated in the angle range from -30° to 30° when the receiving array is far away from the shipping lane, and there is no notch in the horizontal direction. A simplified ship noise source model in shipping lane areas is obtained from the AIS ship distribution data, and the 3D ray algorithm of sound propagation combined with the topographic data in the island and reef area is used to calculate the vertical directionality of low-frequency ocean ambient noise. The calculation results are consistent with the analytical results of the measured data, which indicates that when the receiving array is far away from the shipping lane, the low-frequency ocean ambient noise is incident to the vertical receiving array in a nearly horizontal direction. The research results can provide support for improving sonar performance in the areas far away from shipping lanes.