用垂直阵确定浅海波导特性

本文介绍利用声场复简正波近似确定浅海波导特性的方法。该方法的优点在于:(1)对环境参数的依赖程度大大降低。(2)在对海底介质结构(诸如层的数量、层的厚度、纵波和横波的速度和衰减等)知之不多或根本不了解的情况下,可同时获得波导特性参数(k_m,β_m)。(3)确定波导海底界面平面波的反射系数V(k)。数值结果显示:对海底是单层或两层软固态的波导,用90M长、18阵元组成的垂直接收阵,接收频率分别为250Hz、150Hz的声信号,(1)获得的简正波水平波数k_m的精度均在10^-5以上;简正波衰减系数β_m的相对误差绝大部分在20%以内,其中前几号都在10%范围内,且简正波号数越低,误差越小。(2)基本反映海底在小掠角的反射相移和反射损失。本文在数值仿真的基础上,重点分析声场复简正波近似对93年冬季海上实验数据的处理结果。

Waveguide characterization estimation in shallow water using a vertical array

Waveguide characterization estimation in shallow water using the complex mode approxi metion of acoustic field is presented. The advantages of the method are that (l) the dependence on the environment parameters will obviously decrease. (2) the waveguide characterization parameters(k_m, β_m)can be obtained the same time, when the fine structure in the bottom medium, such as the number and thickness of layers, the velocity of compressive and shear wave, and attenuation is less known or unknown. (3) it can extract the bottom reflection coefficient V(k). Numerical examples illustrate that (1) the accuracy of k_m is at least 10^-5, the related error of β_m is mostly less than 20%, and the smaller the mode number, the smaller the related error is; (2) the reflection coefficient in the the bottom at low grazing angle can be obtained using by a vertical array which the total number of samples is N=18 and length L=90 m. The experimental data of 500 Hz is emphatically discussed here. The results for f=500 Hz wide impulse acoustic signal source which locates at z_s=11 m, r_s=21 km show that the extracted accuracy of k_m is between 10^-4 and 10^-5, the related error of β_m is between 9% and 26%.