北极典型冰下声信道建模及特性

将Burke-Twersky (BT)散射模型与射线理论相结合研究北极典型冰下的水声信道特性。BT模型将极地冰水界面的冰脊视为随机分布在自由表面的半椭圆柱。首先根据BT模型分别对高频和低频情况下的冰面反射系数取近似,计算不同频率的冰面反射系数。然后结合射线理论计算冰下声场并分析冰下信道特性,并与相同条件下绝对软界面的水声信道进行对比研究。结果显示,由于冰界面的存在,冰水界面与绝对软界面相比,冰面反射系数较小,使得部分声线不会传播很远,且随频率的增加衰减越发严重,因此不利于声信号远距离传播;此外在信道结构上,由于冰层反射系数较小,冰下信道多径相较于无冰的水-空气界面其多途现象不明显。研究结果对认知极地冰下水声信道特性以及开展极地水声系统性能预报具有一定意义。

Modeling and characterizing the typical under-ice acoustic channel for the Arctic

In this paper,properties of arctic underwater acoustic channel using Burke-Twersky(BT) model and ray theory was reserached.In the BT model sea ice ridge is assumed as a set of elliptical semi-cylinder randomly distributed on a stress-free surface based on BT model which is usually used to describe ice-sea surface in polar region.By approximation of low frequency and high frequency of BT model,the reflection coefficients were calculated at different frequencies.On the basis of ray theory,we calculate the acoustic field and analyze the properties of underwater acoustic channel.Compared to underwater acoustic channel properties when the boundary is air,the result shows that under the ice surface some sound rays disappear during transmission,because the ice surface reflection coefficients are smaller than absolutely soft surface.Especially under-ice transmission loss is higher when the frequency is higher.As a result,underice condition is not beneficial for acoustic signals to travel far.Under the ice surface,the multi-path structure of the channel is not significant compared to air surface.The research results are valuable for predicting performance of sonar system working in the polar region.