浅海信道中舰船辐射噪声包络线谱传播特性

包络线谱是舰船辐射噪声的一个重要特征,反映了辐射噪声中低频线谱成分以及其他一些周期性对宽带连续谱噪声的调制效应,对包络谱线谱特征的提取分析,有利于目标信号的检测和识别.本文将舰船辐射噪声建模成为周期性局部平稳过程,在包络谱估计和包络线谱特性分析基础上,得到包络线谱高度等特征参数的具体表示,然后从传播过程中接收信噪比变化的角度,分析了包络线谱传播特性及其特征参数的变化.数值计算表明:从能量角度看,舰船辐射噪声中周期性局部平稳谱与平稳谱服从一样的传播规律,与通常的声场传播律一致;包络线谱高度的传播衰减取决于信噪比,信噪比较高时(正信噪比)它几乎保持不变,信噪比较低时(负信噪比)它按信噪比衰减规律下降;在浅海信道传播条件下,由于传播衰减较自由场情况要小,同样的包络线谱高度可以传播到更远的距离上.

Propagation characteristic of envelope line spectrum of ship radiating noise in shallow water channel

Envelope line spectrum （ELS） is a critical feature of ship radiated noise, which reflects the modulation of those low frequency line spectra and periodic movement. It is very helpful for target detection and identification to analyze the ELS＇s features. Herein the ship radiated noise has been modeled as a periodic local-stationary random process. By use of envelope spectrum estimation and line spectrum analysis, parameters of ELS such as the height relative to the background were given. The propagation characteristics of ELS and the variation were given as a function of the receiving SNR. The numerical results show that the periodic local-stationary spectrum and the stationary spectrum of ship radiated noise obey the same law as ordinary acoustic fields from the point of view of energy propagation. The height of ELS relative to the background varies with the receiving SNR. For high positive SNR, it almost remains as a constant. For low negative SNR, it decreases proportionally with the receiving SNR. In shallow water channels, the same height of ELS can be propagated to some further ranges in contrast to the free space case.