摘要
海底地形变化对声传播具有重要影响.针对在南海深海区域海底斜坡环境下进行的一次声传播实验中观测到的一些不同于平坦海底的声传播现象,利用射线声学方法分析并解释了海底地形变化引起声传播差异的原因.结果表明,当声源深度位于131 m处时,在第一影区内,海底斜坡前较小幅度的海底山丘(凸起高度小于1/10海深),对第一次与海底作用而入射到该小海底山丘处的小掠射角(绝对值在10°–20°范围内)声波有反射遮挡作用,导致在其反射区特定传播距离上出现影响深度可达海面以下1300 m的倒三角声影区,比平坦海底环境下相同影区位置处的传播损失增大约8 dB.在第一会聚区内,海底斜坡对声波的反射阻挡作用使得从海面反射及水体向下折射的小掠射角(绝对值小于10°)声波所形成的会聚区结构消失,只保留从水体向上折射的会聚结构.因此,准确的海底地形对深海声传播预报及目标探测等应用非常重要.
Variation ofbathymetry has large effects on sound propagation. An acoustic propagation experiment was conducted in the South China Sea. Some different propagation phenomena are observed for two different tracks with the flat bottom and the sloping bottom environments when the source depth is 131 m. Numerical analysis based on the ray methods is carried out to explain the causes of the differences. The experimental and numerical results show that when a sea hill with height of 320 m, which is less than 1/10 of water depth, exists at the range of sound beams with the grazing angles from 10° to 20° incident on bottom first time, an inverted-triangle shadow zone appears at the reflection-blockage area of the sea hill. Compared with the TLs results in the flat bottom environment, TLs increase up to about 8 dB in the corresponding area of the first shadow zone, and the abnormal TLs effects can reach to maximal depth of 1300 m. The first convergence zone caused by refractions of sound beams with small grazing angles within 10° from the water above the axis of sound channel is lost. There are only the sound beams refracted back from water below the axis of sound channel. It＇s quite different from the convergence-zone structure in deep water with flat bottom. Thus, the accuracy of bathymetry is meaningful for sound propagation and target detection in deep water.
出处
《中国科学：物理学、力学、天文学》
CSCD
北大核心
2016年第9期18-27,共10页
Scientia Sinica Physica,Mechanica & Astronomica
基金
国家自然科学基金资助项目(编号:11434012
41561144006
11174312
11404366)
关键词
深海
海底斜坡
声传播
本征声线
deep water, sloping bottom, sound propagation, eigenrays
