INFERENCE OF SEA-BOTTOM IMPEDANCE PROFILE FROM THE REFLECTION OF NORMALLY INCIDENT PLANE SOUND WAVES

The inverse method to infer the profiles of acoustical parameters under the sea-bottom from exactsolutions of the wave equation is generally not applicable to situations where discontinuity exists in theacoustical impedance profile.However,the ray approximation is still effective,and satisfactory results havebeen obtained under some practical circumstances. In this paper a scattering-inverse method is presented based on the equithickness(measured in thepropagation time)division of the subbottom medium.The program is capable of judging the existence ofmultiple reflectio is and elimnating their influence.The problem of the occurence of pseudo boundaries arising from multiple reflections and the computation errors caused by them have been preliminarily solved.     

由平面波垂直反射反演海底的声阻抗分布

以严格求解波动方程反演海底声学参数分布的方法一般不适用于声阻抗变化不连续的情况。而射线近似方法不受此限制。在某些实际场合中射线方法已得到令人满意的反演结果。 本文介绍一种以传播时间为尺度的等层厚细密分层海底的散射求逆方法。反演程序具有判断是否存在多次散射并消除其影响的能力。初步解决由于多次散射而产生的虚假界面和在虚界面之后带来的计算误差问题。     

提高分层海底反演方法抗干扰性初探

本文采用等时间层厚概念得到声场反演的冲激响应选代法。这种方法的抗干扰能力极差。为提高其抗干扰能力,有意避开谱分析不可少的FFT步骤,提出信号取样迭代法。其抗干扰能力显著提高。数值模拟计算表明,取样迭代法有误差累积效应,为进一步提高其抗干扰性引入统计平均方法,得到取样平均迭代法。在信噪比为6.3情况下,取样平均迭代法的相对误差比取样迭代法约小三倍。     

求三维本征声线的一种新方法

本文采用“自动搜寻”法求海洋中均匀声速背景上有三维声速扰动时的本征声线。与传统方法比较,这种方法计算声线的次数减小约二个数量级。