Fig. 1. Spatial structure of receiving ocean ambient noise using vertical line array in shallow water浅海中利用垂直阵接收噪声空间结构

Fig. 2. (a) True BL; (b) computed by vertical directionality of ocean ambient noise using OASN; (c) two methods compare under 1800 Hz, the full line is BL, the imaginary line is (a) 真实反射损失BL; (b) 根据噪声垂直空间指向性利用OASN模块仿真得到的 ; (c) 1800 Hz下两种方法的比较, 实线为BL, 虚线为

Fig. 3. The of different structure of sub-bottom under 1800 Hz: (a) Infinite acoustic half space; (b) 1 layer of sediment. The full line corresponds to the condition that the elements set across the sea. The imaginary line corresponds to the condition that 42 elements set at the depth of 30 m 1800 Hz下不同海底分层结构下的 (实线为阵元遍布全海深, 点划线为42阵元, 间隔均为0.2 m)　(a) 海底为无限大液体声学半空间; (b) 海底为单层沉积层

Fig. 4. Model of sub-bottom stratification: (a) Infinite acoustic half space; (b) 1 layer of sediment海底分层模型　(a)液体无限大声学半空间海底; (b) 存在一层沉积层海底

Fig. 5. Pekeris branch cut mapPekeris分支割线、极点和积分的复波数平面

Fig. 6. Vertical directivity and of ocean ambient noise in different spectral domain: (a), (b) Near field continuous spectrum; (c), (d) far field discrete spectrum; (e), (f) full spectrum domain 不同谱域内噪声场的指向性和 　(a), (b)连续谱部分噪声场; (c), (d) 离散谱部分噪声场; (e), (f)全谱域噪声场

Fig. 7. The BL under different parameters of sub-bottom: (a) Attenuation coefficient ; (b) sound speed c; (c) density 不同海底参数下的BL 　(a)衰减系数 ; (b)声速c; (c)密度

Fig. 8. Reflection model of sub-bottom with 1 layer of sediment单层沉积层海底反射模型

Fig. 9. (a) True BL computed by equation (8); (b) BL after simplified computed by equation (10); (c) the curves of BL of two methods under 1800 Hz (a) (8)式计算的真实BL; (b) (10)式计算化简后的BL; (c) 1800 Hz下两条BL曲线

Fig. 10. Curve of BL after simplified computed by equation (10) with the horizontal axis converted to by equation (7) (10)式计算化简后的BL(横轴利用(7)式转为 )

Fig. 11. (a) with 42 elements at the depth of 30 m; (b) the curve of under 1800 Hz. (a) 42阵元设置在水下30 m处 ; (b) 1800 Hz下 曲线

Fig. 12. Sound speed profile of the experiment实验实测海水声速剖面

Fig. 13. Results of the 9th set of data: (a) ; (b) curve of under 1600 Hz 第9组数据处理结果　(a) ; (b) 1600 Hz下的 曲线

Fig. 14. Results of the 11th set of data: (a) ; (b) curve of under 1600 Hz 第11组数据处理结果　(a) ; (b) 1600 Hz下 曲线

Fig. 15. Statistical distribution histogram of 20 sets of data: (a) Sound speed of the sediment; (b) sound speed of the basement; (c) thickness of the sediment数据计算结果统计分布直方图　(a)沉积层声速; (b)基底声速; (c)沉积层厚度

Fig. 16. Sub-bottom structure of the experimental area detected by sub-bottom profiler. The interface is marked by black spot in panel (b)浅地层剖面仪探测试验海区海底结构(图(b)中用黑点标明海底分界面)

Table 1. Parameters of ocean and sub-bottom