深海海底反射区声场的相干结构及其有源声呐估距

有源声呐在探测深海海底反射区的目标时,由于声线大掠射角弯曲且声速沿声线传播路径不断变化,造成了常规估距方法产生较大的误差。有效声速法是减小常规估距方法误差的有效途径,但由于需要预先计算空间每一位置点的"声线时延有效声速"对,复杂度高,实时性差。针对有效声速法的实时性问题,本文基于深海海底反射区声场的相干结构,提出一种改进的有效声速估距方法.首先指出深海声场能量沿声源出射角强弱相间变化及其引起的海底反射区离散声呐可探测区现象,并利用深海近水面声源的声线干涉效应解释了该现象的物理机理,建立了声呐可探测区与高能量声线的量化关系。在此基础上,计算声呐可探测区边界位置的"声线时延-有效声速"对,并线性拟合出可探测区所有位置点对应的值。经仿真验证,该方法与传统的有效声速法均可实现对常规估距方法估距误差的有效校正。虽然该方法估距精度较传统的有效声速法略有增大,但计算复杂度和计算时间显著减小,实时性好,具有良好的工程应用前景。 

Interference structure of sound field in bottom bounce area and range estimation of active sonar

In deep ocean,to detect the underwater target located in the first shadow zone,the bottom bounce mode is often used by the low frequency active sonar.However,the range estimation error occurs due to the variable sound speed which produces a bending acoustic ray path from the sonar to the target.To reduce the active ranging error,the method using the effective sound speed can be used.However,this method faces a heavy computation burden which comes from the calculation of the time delay-effective sound speed pairs at each position in the bottom bouncing area.To solve the problem above,an improved effective sound speed estimation method based on the interference structure of the sound field is proposed.We show that the sound field fluctuation in the bottom bouncing area is due to the energy fluctuation of the sound rays having different grazing angles.And a quantitative relationship between the detectable areas and the sound rays with high energies is calculated based on the sound ray interference theory.The time delay-effective sound speed pairs in the boundary location of the detectable areas can be calculated according to this relationship.And hence,time delay-effective sound speed pairs of all the positions can be obtained by the linear fitting.The simulation results show that the improved method can obtain a similar range estimation error to the conventional effective sound speed estimation method,while the former has a much low computation burden which is useful for the real-time calculation.