水声学中地声反演的新进展

Progress of geoacoustic inversion in underwater acoustics

地声反演自20世纪70年代以来一直是水声学中的热点问题,至今热度未减。然而,几乎所有的海底反演工作都建立在假设的地声模型之上,因此反演得到的海底地声参数只是“等效”意义上的结果,而不是介质本身的固有参数,尤其是海底衰减系数的频率特性会发生严重的畸变。该文通过重新回顾海底声学反射特性的概念,给出所谓“等效”海底参数的物理意义;为了克服地声模型失配的困难,建议采用海底反射特性参数(P;Q)来描述海底(海底分层时用P(f)、Q(f));最后介绍两种能够提取海底介质真实衰减系数的新方法:“WKB+P(f)”方法和“N×HHS”方法。

Research on geoacoustic (GA) properties inversion has been a very active area in underwater acoustics, since 1970s until today. Most of those approaches are “model-based”, thus only so-called “effective” parameters can be obtained and critical distortion in α(f) exists due to “model-mismatching”. In this paper, we recall the concept of bottom reflective coefficient and provide an explanation on the physical meaning of “effective parameters”. In order to overcome the model-mismatching problem, we propose to use model-free reflective parameters P and Q (P(f) and Q(f) for layered bottom). Two new approaches:“WKB+P(f)” and “N×HHS” are introduced in order to invert the intrinsic (f).