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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。
The Burke-Twersky (BT) scattering model is combined with the ray theory to study underwater acoustic channel characteristics under the typical Arctic ice. The BT model treats the ridges of polar ice-water interfaces as semi-elliptical columns randomly distributed on free surfaces. First of all, according to the BT model, the ice reflectivity at high frequency and low frequency are approximated respectively, and the ice reflection coefficients at different frequencies are calculated. Then, the sound field under ice is calculated by combining the ray theory and the ice channel characteristics are analyzed, and compared with the underwater acoustic channel of the absolute soft interface under the same conditions. The results show that due to the existence of the ice interface, the ice-water interface has a smaller ice reflection coefficient compared with the absolute soft interface, so that part of the sound rays do not propagate far and the attenuation becomes more and more serious as the frequency increases, which is not conducive to sound signals In addition, on the channel structure, due to the small reflection coefficient of ice layer, the multi-path phenomenon of multipath under ice is not obvious compared with the ice-free water-air interface. The results of this study are of great significance for understanding the characteristics of underwater acoustic channels under polar ice and for predicting the performance of polar acoustic systems.