浅海宽带简正模相干/非相干能量比值特征匹配的源深估计

无源声源深度估计一直是水声领域的一个难题。针对浅海波导中低频宽带脉冲声源深度估计问题,提出了利用单水听器接收信号中多阶简正模相干项能量与非相干项能量比值的特征匹配处理方法,不仅消除了声源未知激发谱的影响,而且由于在预先估计声源距离基础上实现对声源深度的独立估计,运算量小。同时,由于利用了实测数据与拷贝声场中具有相同简正模贡献的相干能量特征进行匹配,参数估计具有较高的稳健性。首先通过向量线性相关数学理论,在理想波导条件下讨论了简正模数目与源深估计单值性的关系,证明了仅利用两阶简正模时源深估计具有多值性,而声场含有三阶以上简正模时源深估计存在唯一解。进一步的仿真分析表明,当信噪比高于0 dB时源深估计结果的平均误差整体上在5 m之内。分析了水文参数、沉积层声学参数及声源距离失配时方法的鲁棒性。最后,利用浅海垂直阵采集的低频宽带脉冲实验数据对方法进行验证,声源深度估计结果绝对误差小于5 m的概率在79.1%以上。方法可推广应用于浅海水平或垂直基阵对低频宽带声源的深度估计。 

Source depth estimation by matching broadband coherent and incoherent energy ratios of normal modes in shallow water

Passive source depth estimation is always one of the difficult problems in underwater acoustic field.Aiming at the estimation of low-frequency broadband pulse source depth in the shallow water waveguide,a model-based approach employing the ratio of energy between coherent terms and incoherent terms of normal modes in the signal autocorrelation function by a single hydrophone is proposed.It eliminates the influence of the source radiating spectrum and reduces greatly the computation amount of the source depth estimation as an independent variable with the prior estimated source range.Moreover,it also enhances the stability of parameter estimation because of employing same normal modes for the coherent energy feature match between the measured data and the replica field.At first,the relationship of the uniqueness for source depth estimation with normal mode orders is discussed through the mathematical theory on vector’s linear correlation.When at least three-order normal modes are employed,it is proved that there exists unique solution for source depth estimation in the ideal waveguide environment.Furthermore,the simulations show that the mean error of source depth estimation is less than 5 meters when the signal-to-noise ratio is greater than 0 dB.The robustness of the approach is analyzed when the hydrological parameters,the acoustic parameters of sediments and source range are mismatched.Finally,the approach is verified by using the low-frequency broadband pulse data received by the vertical array in shallow water and the probability of source depth estimation within the error of 5 meters is greater than 79.1%.The approach could be generalized to estimate the low-frequency broadband source depth by a horizontal or vertical array.