本文選題：激光 + 水下聲源��； 參考：《煙臺(tái)大學(xué)》2017年碩士論文

【摘要】：本文采用激光干涉法設(shè)計(jì)光路和搭建實(shí)驗(yàn)平臺(tái),對(duì)水下聲信號(hào)提取進(jìn)行了實(shí)驗(yàn)探索,驗(yàn)證了激光相干探測(cè)水下聲源的可行性。實(shí)驗(yàn)對(duì)自然水面波動(dòng)情況進(jìn)行了提取,并對(duì)三組不同位置、不同頻率以及不同振幅的數(shù)據(jù)進(jìn)行了對(duì)比分析。同時(shí),針對(duì)信號(hào)特征微弱的問(wèn)題,本課題在傳統(tǒng)頻譜分析的基礎(chǔ)上,分別采用了濾波、短時(shí)傅里葉變換、小波分析、Wigner-Ville分布以及時(shí)頻分布的重排等時(shí)頻分析手段,以實(shí)現(xiàn)信號(hào)降噪和特征信號(hào)增強(qiáng)。實(shí)驗(yàn)結(jié)果表明:(1)水面自然波動(dòng)頻率主要集中在500 Hz以下的低頻區(qū),水面波動(dòng)頻率范圍的確定為進(jìn)一步的濾波降噪和時(shí)頻分析等提供了參考,也便于將水面自然波動(dòng)頻率同特征信號(hào)頻率區(qū)分。(2)三組設(shè)定條件的數(shù)據(jù)采集和分析結(jié)果表明:距離探測(cè)位置越遠(yuǎn),信號(hào)衰減越嚴(yán)重。相同頻率的水下?lián)P聲器設(shè)備,隨著輸入幅值的增大,可探測(cè)到的信號(hào)強(qiáng)度明顯增強(qiáng)。輸入幅值一定時(shí),頻率越高,信號(hào)強(qiáng)度越微弱。(3)在特征信號(hào)微弱的情況下,對(duì)采集的數(shù)據(jù)直接做傅里葉變換,特征信號(hào)不明顯,容易淹沒(méi)在背景中。采用濾波和小波分析等頻譜分析方法處理后,噪聲信號(hào)可以得到有效的濾除,特征信號(hào)增強(qiáng)明顯。(4)頻譜分析結(jié)果只能得到某一時(shí)刻各個(gè)頻率分量的相對(duì)強(qiáng)度分布,為了實(shí)現(xiàn)觀察一段時(shí)間內(nèi)頻率隨時(shí)間的變化情況的目的,本課題采用了短時(shí)傅里葉變換、譜圖以及Wigner-Ville分布等時(shí)頻分析方法。針對(duì)二次型時(shí)頻分布方法存在的交叉項(xiàng)等問(wèn)題,本文采用增加窗口函數(shù)的方法來(lái)抑制交叉項(xiàng)。為了增加時(shí)頻聚集性,本文對(duì)數(shù)據(jù)做了時(shí)頻分布的重排。結(jié)果表明:交叉項(xiàng)干擾得到了相當(dāng)程度的抑制,時(shí)頻聚集性顯著改善。該系統(tǒng)采用光纖型的實(shí)驗(yàn)裝置,避免了光路暴露在空氣中,大大減少了外界環(huán)境的影響。
[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.
【學(xué)位授予單位】：煙臺(tái)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TB56

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本文編號(hào)：1947554