激光相干探测水下声信号的特征提取与分析

发布时间：2018-05-28 17:23

本文选题：激光 + 水下声源　；参考：《烟台大学》2017年硕士论文

【摘要】：本文采用激光干涉法设计光路和搭建实验平台,对水下声信号提取进行了实验探索,验证了激光相干探测水下声源的可行性。实验对自然水面波动情况进行了提取,并对三组不同位置、不同频率以及不同振幅的数据进行了对比分析。同时,针对信号特征微弱的问题,本课题在传统频谱分析的基础上,分别采用了滤波、短时傅里叶变换、小波分析、Wigner-Ville分布以及时频分布的重排等时频分析手段,以实现信号降噪和特征信号增强。实验结果表明:(1)水面自然波动频率主要集中在500 Hz以下的低频区,水面波动频率范围的确定为进一步的滤波降噪和时频分析等提供了参考,也便于将水面自然波动频率同特征信号频率区分。(2)三组设定条件的数据采集和分析结果表明:距离探测位置越远,信号衰减越严重。相同频率的水下扬声器设备,随着输入幅值的增大,可探测到的信号强度明显增强。输入幅值一定时,频率越高,信号强度越微弱。(3)在特征信号微弱的情况下,对采集的数据直接做傅里叶变换,特征信号不明显,容易淹没在背景中。采用滤波和小波分析等频谱分析方法处理后,噪声信号可以得到有效的滤除,特征信号增强明显。(4)频谱分析结果只能得到某一时刻各个频率分量的相对强度分布,为了实现观察一段时间内频率随时间的变化情况的目的,本课题采用了短时傅里叶变换、谱图以及Wigner-Ville分布等时频分析方法。针对二次型时频分布方法存在的交叉项等问题,本文采用增加窗口函数的方法来抑制交叉项。为了增加时频聚集性,本文对数据做了时频分布的重排。结果表明:交叉项干扰得到了相当程度的抑制,时频聚集性显著改善。该系统采用光纤型的实验装置,避免了光路暴露在空气中,大大减少了外界环境的影响。
[Abstract]:In this paper, the laser interference method is used to design the optical path and build the experimental platform. The experimental exploration of underwater acoustic signal extraction is carried out, and the feasibility of laser coherent detection of underwater acoustic source is verified. Three groups of data of different positions, frequencies and amplitudes were compared and analyzed. At the same time, aiming at the problem of weak signal characteristics, based on the traditional spectrum analysis, the paper adopts filtering, short-time Fourier transform, wavelet analysis and Wigner-Ville distribution to rearrange the time-frequency distribution. In order to achieve signal noise reduction and feature signal enhancement. The experimental results show that the natural wave frequency of water surface is mainly concentrated in the low frequency region below 500 Hz. The determination of the frequency range of water surface fluctuation provides a reference for further filtering noise reduction and time-frequency analysis. It is also convenient to distinguish the natural wave frequency of water surface from the frequency of characteristic signal. The results of data acquisition and analysis of three set conditions show that the farther away from the detecting position, the more serious the attenuation of the signal is. With the increase of input amplitude, the detectable signal intensity of the same frequency underwater loudspeaker equipment is obviously enhanced. When the input amplitude is constant, the higher the frequency is, the weaker the signal intensity is.) when the characteristic signal is weak, the collected data is directly transformed by Fourier transform, and the characteristic signal is not obvious and easily submerged in the background. The noise signal can be effectively filtered by using the methods of filtering and wavelet analysis, and the characteristic signal can be enhanced obviously. The spectrum analysis results can only obtain the relative intensity distribution of each frequency component at a certain time. In order to observe the change of frequency with time in a certain period of time, the methods of time-frequency analysis, such as short time Fourier transform, spectrum diagram and Wigner-Ville distribution, are adopted in this paper. Aiming at the problems of crossover terms in quadratic time-frequency distribution method, this paper uses the method of adding window function to suppress the crossover term. In order to increase the time-frequency aggregation, the time-frequency distribution of the data is rearranged. The results show that the cross term interference is suppressed to a certain extent and the time-frequency aggregation is improved significantly. The optical fiber type experimental device is used in the system, which avoids the exposure of the light path to the air and greatly reduces the influence of the external environment.
【学位授予单位】：烟台大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB56

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