通信工程專業(yè)本科畢業(yè)論文_語音信號去噪_——數(shù)字濾波器的設(shè)計(1)

1、in 26 cases, long-term measures to implement the rate is 77% deployed 40 couples free pre-pregnancy health checks. -Balanced development of education. I attach great importance to control fits and starts work, to ensure that school-age children to school on time, hope dream poor students go to schoo

2、l to help poor students, help students complete nine years of compulsory education. Township school-age children enrollment rate up to 100%. -Home to poverty alleviation work in order. Complete the rural minimum living standard security system and the effective connection between pro-poor developmen

3、t policies, establish the Township poor electronic records and paper file documentation work, and cooperate with the superior unit holders, such as the statistical work of the poor masses. As of now, I enjoy the low 94 families, a total of 305, 44310 rural minimum living standard security issued org

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7、sfully 6; State criminal case 3, case 7, has been investigating the 7. -Stabilisation work of letters and calls for further strengthening. Received mass petitions from 10 successful mediation, 8, investigation 1, collective skipping appeal event does not occur. Meanwhile, further strengthen publicit

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10、sure time, organizations in the elderly in the rural culture of Hui Xiang Hui fitness dance square, greatly enriched the lives of the masses. Use of Arbor Day, 51 labor day, May Fourth youth day festivals, organize the education campaign for the festive, educational guide people to foster patriotism

11、, socialism, collectivism and strengthen love and loyalty to the party, firmly follow the party go . Implementation of the one gang double responsibility established number one responsibility, team member management works. Five are team building. Open-minded, innovative ways to meet the actual needs

12、 of target, combining education and political education in party lecture, unified planning, unified plan, take active measures to enhance cadres quality and ability. (B) a solid foundation steadily promoting the construction of皖西學(xué)院本科畢業(yè)論文(設(shè)計)語音信號去噪 數(shù)字濾波器的設(shè)計作 者指導(dǎo)教師摘要：在現(xiàn)代各種通信系統(tǒng)中，由于自然界中的各種各樣的復(fù)雜噪聲不免會摻雜在其

13、中，數(shù)字信號處理這門經(jīng)典學(xué)科恰好能夠解決這個問題，其中最通用的方法就是利用濾波器來濾除這些雜波噪聲，F(xiàn)IR數(shù)字濾波器就是濾波器設(shè)計的基本部分。本論文研究的主要內(nèi)容就是基于Matlab軟件仿真設(shè)計一個數(shù)字濾波器，將摻雜在語音信號中的高頻噪音消除，在此將分析消除高頻噪音前后語音信號的時域及頻域特性，對比分析即可驗證濾波前后特性差別。在本課題中，將利用簡單的窗函數(shù)法來設(shè)計FIR數(shù)字濾波器，通過Matlab仿真說明所設(shè)計濾波器的正確性。通過這次畢業(yè)設(shè)計，將會進(jìn)一步理解語音信號原理分析及濾波處理，為更好的設(shè)計濾波器打好基礎(chǔ)。關(guān)鍵詞：Matlab；窗函數(shù)法；FIR數(shù)字濾波器Remove noise in

14、the speech signalthe design of digital filterAbstract：In modern communication systems, a variety of complex noise may mix in the nature of sounds. The classic disciplines of the digital signal processing can solve this problem, one of the most common method is to use a filter to filter those clutter

15、 noise. FIR digital filter is the basic part of filter design. The main research content of this paper is based on Matlab software simulation to design a digital filter, in which to cancel the high frequency noise of the speech signal, then it will eliminate the high frequency noise and the speech s

16、ignals from time domain and frequency domain characteristics in this analysis before and after, and analysis the differences test the filtering characteristics. In this issue, using a simple window function method to design a FIR digital filter, Matlab simulation shows the correct of the designed fi

17、lter. Through the design of this graduation design, we will understand the principle of speech signal analysis and filtering, and lay the foundation for the filter design.Key words: Matlab; window function method; FIR digital filter grass-roots party organizations is focus of new party members. Furt

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20、is on construction of village-level activities, comprehensive corrosion activities of grass-roots party organization construction in various fields, with village-level party organization function setting, achieving more efficient use of venues, activities for grass-roots party organizations and part

21、y members, and create good conditions for serving the masses, by using village-level activities. Third is to conscientiously implement the village group living subsidy distribution work. In strict accordance with the parent document, fully according to the actual situation, further improve the villa

22、ge cadres of the group registration through the one card uniform forms, living subsidies timely payment on time each month to the hands of village cadres of the group, to ensure, without delay, not in arrears, and to ensure that earmarks. Four village election preparations are made. Organization sur

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25、ay solid based. (C) to speed up the pace of the adjustment of industrial structure and increase farmers income through various channels. One is to strengthen its efforts to readjust the industrial structure. At the same time accelerate the process of industrialization in rural areas, and actively pr

26、omote the development of industries with local industry and quality, reasonable and effective solution to my single issues of the industrial structure, for example: turtle and introduced sheep farming project, strengthening the educational plant support. Second, broaden the channels of sales of agri

27、cultural products. Actively carry out famous brand construction of agricultural products, to create brand agriculture, expand marketing channels, enhance brand awareness and market competitiveness of farm products. Third, strengthening agro-technical training. Through training, to improve the scient

28、ific quality of peasants, farmers quality of life, promote the surplus labor force transfer output, really be my shortcut to rural farmers for agricultural development. Four is the comprehensive strengthening of the construction of ecological environmental protection, further establishing ecological

29、 compensation mechanism construction of ecological construction and industry, development of local characteristic, strongly supports the ecological transition Industrial construction, focus on the development of第 19 頁目 錄1 引 言31.1 課題研究現(xiàn)狀31.2 課題研究目的31.3 課題研究內(nèi)容31.4 MATLAB軟件設(shè)計平臺簡介42 原始語音信號采集與處理52.1 課題設(shè)計

30、步驟及流程圖52.2 語音信號處理52.2.1 語音信號的采集52.2.2 語音信號的時域頻譜分析62.2.3 語音信號加噪與頻譜分析83 FIR數(shù)字濾波器的設(shè)計103.1 數(shù)字濾波器基本概念103.2 常用窗函數(shù)介紹103.3 FIR數(shù)字濾波器概述103.4 FIR濾波器的窗函數(shù)設(shè)計113.5 濾波器的編程實現(xiàn)133.6 用濾波器對加噪語音信號進(jìn)行濾波143.7 回放語音信號164 結(jié) 論18致 謝19參考文獻(xiàn)201 引 言1.1 課題研究現(xiàn)狀20世紀(jì)60年代中期數(shù)字信號處理領(lǐng)域形成的諸多富有實踐性的的理論和算法，如快速傅立葉變換（FFT）以及各種數(shù)字濾波器等是語音信號數(shù)字處理的各項理論和技

31、術(shù)基礎(chǔ)。在70年中后期之后，線性預(yù)測技術(shù)（LPC）已經(jīng)用于語音信號的信息壓縮和特征提取，并已成為語音信號處理中非常重要的一個工具。80年代語音信號處理技術(shù)的重大發(fā)展是隱馬爾可夫模型（HMM）描述語音信號過程的產(chǎn)生過程。進(jìn)入上世紀(jì)90年代以來，語音信號采集與分析技術(shù)在實際應(yīng)用方面取得了許多突破性的研究進(jìn)展。近年來，隨著科學(xué)技術(shù)的不斷進(jìn)步，人工神經(jīng)網(wǎng)絡(luò)(ANN)的研究取得了迅速發(fā)展，語音信號處理的各項科學(xué)研究課題是促進(jìn)其發(fā)展的催生力，同時，它的許多成果也體現(xiàn)在有關(guān)語音信號處理的各項技術(shù)之中。1.2 課題研究目的語音是人類獲取知識和各種各樣信息的重要手段和最初來源，人類離不開自然界中各種不同的語音，

32、但在獲取語音的過程中，將不可避免的會受到外界環(huán)境的干擾和影響，如各種機(jī)器的轟鳴聲或者自然界太多的電磁噪聲干擾等這些不可避免的有害噪聲信號都會附加摻雜在語音信號中，這樣獲取的語音信號將不再是單純的語音，摻雜的噪聲不但降低了語音質(zhì)量和語音的可懂度，嚴(yán)重時將導(dǎo)致不可預(yù)知的不良效果。語音信號處理的好壞將影響并導(dǎo)致語音信號的好壞，只有通過將這些語音信號進(jìn)行一系列的的數(shù)字處理，才能將那些非必要的噪聲雜波妥善濾除，得到純凈的單純的語音信號。現(xiàn)在社會衍生了很多現(xiàn)代的語音通信方式，手機(jī)通話、QQ或MSN等這些語音聊天軟件以及語音小說等，涉及語音的方方面面已經(jīng)存在于我們生活中的大部分，因此語音信號去噪處理是具有現(xiàn)

33、實意義的研究課程。1.3 課題研究內(nèi)容1.用MATLAB程序?qū)υ颊Z音信號進(jìn)行采樣，并繪制出采樣后語言信號時域波形和頻譜圖，并針對此圖分析語音信號特點。2.將干擾噪聲加入到已經(jīng)獲取的語音信號中，然后進(jìn)行頻譜分析，并對比未加入噪聲的信號，分析差異。3.設(shè)計FIR數(shù)字濾波器，并對被噪聲污染的語音信號進(jìn)行濾波，畫出濾波前后信號的時域和頻譜，對濾波前后有噪音與無噪音的語音信號進(jìn)行比較，分析信號的變化，從而驗證所設(shè)計濾波器的濾波效果。4.回放語音信號。1.4 MATLAB軟件設(shè)計平臺簡介Matlab是MATrix和LABoratory的縮寫，是由Mathworks公司開發(fā)的一套用于科學(xué)工程計算的可視化高

34、性能軟件，是一種交互式的以矩陣為基本數(shù)據(jù)結(jié)構(gòu)的系統(tǒng)，應(yīng)用廣泛。MATLAB的主要特點如下：(1) 程序的可移植性良好應(yīng)用于其他程序。(2) 程序限制寬泛，程序設(shè)計自由。有大量已經(jīng)系統(tǒng)定義的函數(shù)可直接應(yīng)用，并且能夠用戶自定義函數(shù)。(3) 語言簡潔，使用靈活方便，庫函數(shù)相當(dāng)豐富。(4) 源程序向大眾開放。用戶可靈活的對源文件進(jìn)行修改以及加入自己的設(shè)計語音構(gòu)成新的工具箱。(5) 最后MATLAB的一個重要特點是功能強(qiáng)大的工具箱。MATLAB包含兩個重要的部分：核心部分和各種可選的工具箱。2 原始語音信號采集與處理2.1 課題設(shè)計步驟及流程圖本課題設(shè)計主要是針對一段原始語音信號，加入設(shè)計噪聲后，用窗函

35、數(shù)法設(shè)計出的FIR濾波器對加入噪聲后的語音信號進(jìn)行濾波去噪處理，并且分析對比前后時域和頻域波形。課題的設(shè)計流程圖如下圖2.1所示。在Windows下錄制一段格式為.wav的語音加入高頻噪聲信號對語音信號進(jìn)行頻譜分析，繪制出時域和頻域圖 用漢寧窗設(shè)計FIR濾波器畫出頻率響應(yīng)函數(shù)用FIR濾波器對語音信號進(jìn)行濾波畫出語音信號濾波前后頻譜波形并進(jìn)行分析開始結(jié)束圖2.1 課題設(shè)計流程圖2.2 語音信號處理2.2.1 語音信號的采集將話筒輸入計算機(jī)的語音輸入插口上,啟動錄音機(jī)，要求為8000HZ，8位單聲道的音頻格式，如下圖2.2所示，按下錄音按鈕,接著對話筒一段話,說完后停止錄音,屏幕左側(cè)將顯示所錄聲音

36、的長度。點擊放音按鈕,可以實現(xiàn)所錄音的重現(xiàn)。以文件名“1”保存入C: MATLAB work 中。 圖2.2 語音信號的采集2.2.2 語音信號的時域頻譜分析Matlab軟件平臺下，利用wavread函數(shù)對語音信號進(jìn)行采樣，采集出原始信號波形與頻譜，y,fs,bits=wavread(Blip,N1 N2)，用于讀取語音，采樣值放在向量y中，fs表示采樣頻率(Hz)，bits表示采樣位數(shù)。N1 N2表示讀取從N1點到N2點的值（若只有一個N的點則表示讀取前N點的采樣值）。其程序如下：y,Fs,bits=wavread(1.wav); y=y(:,1); sigLength=length(y);

37、 Y = fft(y,sigLength); Pyy = Y.* conj(Y) / sigLength; halflength=floor(sigLength/2); f=Fs*(0:halflength)/sigLength; figure;plot(f,Pyy(1:halflength+1);xlabel(Frequency(Hz); t=(0:sigLength-1)/Fs; figure;plot(t,y);xlabel(Time(s);得到原始語音信號時域波形如下圖2.3所示，頻域幅度譜如下圖2.4所示。從圖中可以看出語音信號有兩個特點：在時域內(nèi)語音信號隨著時間的延續(xù)而緩慢變化，但

38、在一較短時間內(nèi)，語音信號基本保持穩(wěn)定；在頻域內(nèi)語音信號的頻譜量主要集中在3003400Hz的范圍內(nèi)，利用這個特點，可以利用一個帶通濾波器將此范圍內(nèi)的語音信號頻率分量取出，然后按8000Hz的采樣頻率對語音信號進(jìn)行采樣，就可以取得離散的語音信號。圖2.3 原始信號時域波形圖2.4 原始信號頻譜2.2.3 語音信號加噪與頻譜分析利用MATLAB程序產(chǎn)生3.8kHz的余弦信號噪聲加入到語音信號中，模仿語音信號被污染，并對其頻譜分析。其主要程序如下：fs=8000; x1=wavread(1.wav);t=(0:length(x1)-1)/8000;f=fs*(0:1023)/2048;Au=0.05

39、;d=Au*cos(2*pi*3800*t); %噪聲為3.8kHz的余弦信號x2=x1+d;y1=fft(x1,2048); y2=fft(x2,2048);figure(1)運行程序后得到加噪后的語言信號波形如下圖2.5所示。圖2.5 加噪后的語音信號從上圖可以看出，加入3.8KHz的噪聲信號后，在時域圖上與原有信號的時域圖有明顯差異，在幅度“0”位置處附近多出了高頻成分，使加噪后的語音信號顯得更加緊湊。plot(t,x2)xlabel(time(s);ylabel(幅度);figure(2)subplot(2,1,1);plot(f,abs(y1(1:1024);xlabel(Hz);y

40、label(幅度);subplot(2,1,2);plot(f,abs(y2(1:1024);xlabel(Hz);ylabel(幅度);sound(x2,fs,bits); 運行程序后得到原始語音信號和加噪后的語言信號的頻譜如下圖2.6所示。圖2.6 原始語音信號頻譜與加噪后的語音信號頻譜比較從上圖對比可以看出，加噪后的語音信號表現(xiàn)在頻譜圖上在3.8KHz的位置多出一個高頻脈沖成分，表現(xiàn)在回放語音上能聽到很刺耳很不舒適的噪音，原有信號聽著比較模糊。3 FIR數(shù)字濾波器的設(shè)計3.1 數(shù)字濾波器基本概念所謂數(shù)字濾波器，是指輸入、輸出均為數(shù)字信號，通過一定運算關(guān)系改變輸入信號所含頻率成分的相對比例

41、或者濾除某些頻率成分的一種數(shù)字濾波形式。因此，數(shù)字濾波的概念個模擬濾波的相同，只是信號的形式和實現(xiàn)濾波方法不同。由于數(shù)字濾波通過數(shù)值運算實現(xiàn)濾波，所以其處理精度高、穩(wěn)定、體積小，重量輕、靈活、不存在阻抗匹配問題，可以實現(xiàn)模擬濾波器無法實現(xiàn)的特殊濾波功能。3.2 常用窗函數(shù)介紹常用的窗函數(shù)有矩形窗（Rectangle Window）、三角窗（Bartlett Windows）、漢寧窗（Hanning），又稱為升余弦窗、海明窗（Hamming），又稱為改進(jìn)的升余弦窗，除了以上幾種常用窗函數(shù)以外，尚有布拉克曼（Blackman）窗、凱塞（kaiser）窗等。對于選擇何種窗函數(shù)，應(yīng)充分考慮被處理信號的

42、性質(zhì)與處理要求等。如果僅要求準(zhǔn)確分辨出主瓣頻率，而不考慮這種幅值精度，則可選用主瓣寬度較窄從而便于分辨的矩形窗，例如探測物體的自然震動頻率等；如果分析的信號是窄帶信號，而且具有較強(qiáng)的干擾噪聲信號出現(xiàn)的話，則應(yīng)當(dāng)選用旁瓣幅度較小的窗函數(shù)，如漢寧窗、三角窗等。3.3 FIR數(shù)字濾波器概述FIR(Finite Impulse Response)濾波器又叫有限長單位沖激響應(yīng)濾波器，是數(shù)字信號處理系統(tǒng)中最基本的元件，它可以在保證任意幅頻特性的同時具有嚴(yán)格的線性相頻特性，同時其單位抽樣響應(yīng)是有限長的，因而濾波器是穩(wěn)定的系統(tǒng)。因此，F(xiàn)IR濾波器在通信、圖像處理、模式識別等領(lǐng)域都有著廣泛的應(yīng)用。這類濾波器對于

43、脈沖輸入信號的響應(yīng)最終趨向于0，因此而得名。有限脈沖響應(yīng)濾波器的優(yōu)點：（1）脈沖響應(yīng)為有限長：造成當(dāng)輸入數(shù)位信號為有限長的時候，輸出數(shù)位信號亦為有限序列長度。（2）比無限脈沖響應(yīng)濾波器較容易實現(xiàn)到最佳狀態(tài)。（3）線性相位造成h(n)是偶對稱或奇對稱且有限長。（4）肯定是穩(wěn)定的：因為Z轉(zhuǎn)換后所有的極點都在單位圓內(nèi)3.4 FIR濾波器的窗函數(shù)設(shè)計FIR濾波器設(shè)計問題在于尋求一系統(tǒng)函數(shù)，使其頻率響應(yīng)逼近濾波器要求的理想頻率響應(yīng)，其對應(yīng)的單位脈沖響應(yīng)為。用窗函數(shù)設(shè)計FIR濾波器的的設(shè)計思想：從時域出發(fā)，設(shè)計逼近理想。設(shè)理想濾波器的單位脈沖響應(yīng)為。例如低通線性相位FIR濾波器的理想頻率響應(yīng)與單位脈沖響應(yīng)

44、分別如下：一般是無限長的，且是非因果的，不能直接作為FIR濾波器的單位脈沖響應(yīng)。要想得到一個因果的有限長的濾波器，最直接的方法是截斷，即截取為有限長的因果序列，并用合適的窗函數(shù)進(jìn)行加權(quán)作為FIR濾波器的單位脈沖響應(yīng)。按照線性相位濾波器的要求，必須的偶對稱的。對稱中心應(yīng)該等于濾波器的時延常數(shù)，即下面著重介紹用窗函數(shù)法設(shè)計FIR濾波器的步驟如下：(1) 根據(jù)對阻帶衰減及過渡帶的指標(biāo)要求，選擇串窗數(shù)類型（矩形窗、三角窗、漢寧窗、哈明窗、凱塞窗等），并估計窗口長度N。先按照阻帶衰減選擇窗函數(shù)類型。原則是在保證阻帶衰減滿足要求的情況下，盡量選擇主瓣的窗函數(shù)。然后根據(jù)過渡帶寬度估計窗口長度N，待求濾波器的

45、過渡帶寬度Bt近似等于窗函數(shù)主瓣寬度，且近似于窗口長度N成反比，N=A/Bt，A取決于窗口類型。(2) 構(gòu)造希望逼近的頻率響應(yīng)函數(shù)Hd(ejw) 。所謂的“標(biāo)準(zhǔn)窗函數(shù)法”，就是選擇Hd(ejw)為線性相位理想濾波器，如本論文的低通濾波器，該Hdg(w)應(yīng)滿足：(3) 計算hd(n)。如果給出待求濾波器的截止頻率響應(yīng)函數(shù)為Hd(ejw)，那么單位脈沖響應(yīng)用下式求出：(4) 加窗得到設(shè)計結(jié)果：，驗證技術(shù)指標(biāo)是否滿足設(shè)計要求。針對該課題用窗函數(shù)法設(shè)計線性相位FIR數(shù)字濾波器的參數(shù)如下：通帶截止頻率=0.2過渡帶寬度40 dB具體計算如下：(1) 由給定的指標(biāo)確定窗函數(shù)和長度N由于阻帶衰減As40dB

46、，漢明窗和漢寧窗都滿足要求，若再考慮從濾波器節(jié)數(shù)最小的原則出發(fā)，這里選用漢寧窗。也可取N=21。(2) 確定時延值 。(3) 求理想的單位脈沖響應(yīng)。 (4) 求濾波器的單位取樣響應(yīng)h(n)。 3.5 濾波器的編程實現(xiàn)按此要求設(shè)計的FIR數(shù)字低通濾波器，用MATLAB的程序?qū)崿F(xiàn)如下：deltw = 0.4 * pi; Wc = 0.2 * pi; As = 40;N=ceil( 8 * pi/deltw)+1;win=hanning(N);h=fir1(N-1,Wc/pi,win);omega=linspace(0,pi,512);mag=freqz(h,1,omega);magdb=20*lo

47、g10(abs(mag);plot(omega/pi,magdb);axis(0 1-100 0);grid;xlabel(歸一化頻率);ylabel(幅度/dB);此低通濾波器圖像如下圖3.1所示。圖3.1 低通濾波器的歸一化頻率3.6 用濾波器對加噪語音信號進(jìn)行濾波上一節(jié)利用窗函數(shù)法按照論文要求設(shè)計了FIR低通濾波器并繪圖，觀察所設(shè)計的濾波器是否能夠?qū)Σ杉囊徊糠终Z音信號進(jìn)行相關(guān)處理，并將濾波前后的時域波形進(jìn)行相比較，且對其快速傅里葉變換，即X=fft(signal)，其目的是對比前后的頻域頻譜波形，分析所設(shè)計的濾波器能否達(dá)到設(shè)計要求。在Matlab程序設(shè)計中，F(xiàn)IR濾波器則是利用函數(shù)ff

48、tfilt對語音信號進(jìn)行濾波。程序如下：y,fs,nbits=wavread(1.wav); N=length(y) Y=fft(y,N); sound(y); figure(4); plot(y); figure(5);plot(abs(Y); Fp=1200; Fs=1100; Ft=8000; As=20; Ap=1; wp=2*pi*Fp/Ft;ws=2*pi*Fs/Ft;fp=2*Ft*tan(wp/2);fs=2*Ft*tan(ws/2);n,wn=buttord(wp,ws,Ap,As, s); b,a=butter(n,wn, s); num,den=bilinear(b,a,

49、1); h,w=freqz(num,den); figure(2)d=Au*cos(2*pi*3800*t);x2=x1+d;y1=fft(x1,2048); y2=fft(x2,2048);figure(3)plot(w*8000*0.5/pi,abs(h);z=filter(num,den,y);sound(z);m=z; figure(1)subplot(2,2,3);plot(abs(m), r);grid;subplot(2,2,4);plot(z, b);grid;subplot(2,2,2);plot(y,b);grid;subplot(2,2,1);plot(abs(Y),r);grid;圖3.2 頻率特性曲線圖3.3 濾波前后語音信號頻譜的比較圖3.4 濾波前后的信號波形比較由圖3.2頻率特性曲線可得知，該低通濾波器濾除1200Hz