北极水下声信号跨冰层变化分析

北极海冰阻碍了海水和空气两个空间的信息传输。为获得冰层对水下声信号跨冰层传输的影响,采用三维检波器在北冰洋中心区开展了水下声信号的跨冰层实验。利用水冰界面反射模型和自由冰层Lamb波模型,对水下声信号小角度(小于10°)入射冰层时测量数据进行分析,结果表明:(1)20 Hz~1 kHz声信号入射到光滑冰层时,某些频率声波的反射率会明显降低,其中93%的反射率低点超过-10 dB,有的甚至会达到-20 dB以上。(2)冰层反射率低点对应的频段声波,能被冰层上方检波器接收到,并显示出较强的合振速谱,且与该站位自由冰层模型中同时产生的A2和S2模态Lamb波在频段上相符。这些结果可为跨冰层水声信号拾取和水声传播研究提供参考。 

Analysis of the variation on underwater acoustic signal across ice layer in the Arctic

Information transmission between the sea water and the air was blocked by the sea ice in the Arctic.In order to obtain the effect of ice on underwater acoustic signal transmission across ice layer,an underwater acoustic signal detected experiment was carried by using a three-dimensional geophone in the Arctic Ocean centre area.The incident angle to the ice layer is small(<10°).A physical model of ice reflection and "free" Lamb modes were used to analyze the test data,the result are presented:(1) When 20 Hz~1 kHz acoustic signal was incident into the smooth ice layer from water,the reflectivity of some frequencies would be significantly reduced,93% of the value of dips in reflectivity map would be lower than-10 dB,and some would even be lower than-20 dB.(2) The acoustic wave corresponding to the dips of ice reflectivity can be received by the geophone above the ice layer,and shows stronger vibration velocity spectrum.It is consistent with the A2 and S2 Lamb mode waves generated simultaneously in the free ice model of the station in the frequency band.These results can provide a reference for the study of underwater acoustic signal pick-up and propagation.