During an experiment conducted in the deep South China Sea, a bottom-mounted horizontal linear array (HLA) collected the radiated noise from a moving cooperative ship at a distance less than 13 km. Bearing-time records of the HLA through plane-wave beamforming showed significant bearing estimation errors and two or three split bearing tracks of the ship that leads to misjudgment of target numbers. To reveal the physics underlying the experimental phenomena, the directional response of the HLA to an acoustic source at close range was developed by normal mode theory. Numerical simulations were conducted to analyze the acoustic intensity distribution characteristics and the arrival structures of the acoustic field. Comparative results of beamforming obtained with normal mode and ray theory show that the ray model provides an easy way to predict the split bearings for HLA beamforming. When sources are near the endfire of the array, significant bearing estimation errors and the beam splitting effect for a large aperture array were the main issues. For sources near the broadside of the array, the beam broadening effect was the most significant concern. The effect of the array length on the beamforming anomalies and the array gain loss was also investigated. With the present theories, the HLA beamforming anomalies during the experiment were well explained.

在南海深处进行的一项实验中，底部安装的水平线阵 (HLA) 收集了距离小于 13 公里的移动合作船的辐射噪声。通过平面波波束形成的 HLA 的轴承时间记录显示了显着的轴承估计误差和船舶的两个或三个分裂轴承轨道，导致对目标数量的误判。为了揭示实验现象背后的物理原理，HLA 对近距离声源的定向响应是通过正常模式理论开发的。通过数值模拟分析了声强分布特征和声场的到达结构。用法向模式和射线理论获得的波束成形的比较结果表明，射线模型提供了一种简单的方法来预测 HLA 波束成形的剖分轴承。当源靠近阵列端火时，大孔径阵列的显着方位估计误差和分束效应是主要问题。对于靠近阵列宽边的源，光束展宽效应是最重要的问题。还研究了阵列长度对波束形成异常和阵列增益损失的影响。根据目前的理论，实验过程中的 HLA 波束形成异常得到了很好的解释。对于靠近阵列宽边的源，光束展宽效应是最重要的问题。还研究了阵列长度对波束形成异常和阵列增益损失的影响。根据目前的理论，实验过程中的 HLA 波束形成异常得到了很好的解释。对于靠近阵列宽边的源，光束展宽效应是最重要的问题。还研究了阵列长度对波束形成异常和阵列增益损失的影响。根据目前的理论，实验过程中的 HLA 波束形成异常得到了很好的解释。