基于MATLAB的滤波器课程设计

课程设计课程名称数字信号处理题目名称应用Matlab对语音信号进行频谱分析及滤波学生学院信息工程学院专业班级学号学生姓名指导教师2011 年 1 月 4 日一、设计题目应用Matlab对语音信号进行频谱分析及滤波二、设计目的1、进一步巩固数字信号处理的基本概念、理论、分析方法和实现方法；2、增强应用Matlab语言编写数字信号处理的应用程序及分析、解决实际问题的能力；3、掌握用MATLAB对采样信号进行频谱分析基本原理；4、学会用MATLAB设计FIR和IIR滤波器的基本方法；5、学会用MATLAB的GUI功能设计用户界面。

三、设计内容1、语音信号的采集；2、语音信号的频谱分析；3、设计数字滤波器和画出其频率响应；4、用滤波器对信号进行滤波；5、比较滤波前后语音信号的波形及频谱；6、设计系统界面；7、回放语音信号。

四、设计结果分析1、主界面截图其中上面两个大图是输入信号的频谱分析；下面的则是输出信号的频谱分析；右边两个小图是滤波器函数的图像。

右边界面可以选择滤波器的参数。

本程序具有录音、载入音频、设计各种滤波器、滤波、回放滤波后的声音等功能。

2、用窗函数法和双线性变换法设计下面要求的3种滤波器。

(1)低通滤波器性能指标fb＝1 000 Hz，fc＝1 200 Hz，As＝100 dB，Ap＝1 dB。

(2)高通滤波器性能指标fc＝4 800 Hz，fb＝5 000 Hz As＝100 dB，Ap＝1 dB。

(3)带通滤波器性能指标fb1＝1 200 Hz，fb2＝3 000 Hz，fc1＝1 000 Hz，fc2＝3 200 Hz，As＝100 dB，Ap＝1 dB。

本次设计利用函数fir1设计FIR滤波器，利用函数ellip设计IIR滤波器。

①IIR低通②FIR低通分析：对于不同滤波器而言，每个频率的信号的减弱程度不同。

当低通滤波器使用在音频应用时，它有时被称为高频剪切滤波器, 或高音消除滤波器。

从上面的IIR与FIR低通滤波器频谱分析图中可以看出，音频的高频部分被滤掉了，输出的声音低沉，且声音信号有失真。

③IIR高通④FIR高通分析：高通滤波器的作用是滤去音频信号中的低音成分，增强中音和高音成分以驱动扬声器的中音和高音单元。

有时被称为低频剪切滤波器, 或低音消除滤波器。

从上面的频谱分析图中可以看出，声音信号的低频部分被滤除了，输出的声音高昂刺耳。

同时还可以看出声音信号有失真。

⑤IIR带通⑥FIR带通分析：带通滤波器的作用是将频带外的频段滤除，即可滤除低频和高频成分，保留声音信号的中间频段，除去了高音与低音，增强了中音成分，声音清晰。

五、设计心得体会（1）从电脑上录取一段音频后，将信号载入设计的滤波器中进行滤波。

通过观察图像、回放滤波后的音频来作分析。

原始音频信号经过滤波器后输出的信号受到滤波器的滤波作用，把高频或低频分量滤掉，出来的信号一个是带限信号，频带在一定范围内。

滤波后的波形还伴随着一定的失真，使得声音信号有些音质上的变化。

为了减少这种失真，我们可以选择不同的滤波器，设置不同的参数来测试各种性能，最终是信号的滤波作用达到最佳。

（2）在设计用户界面时，由于是第一次接触GUI，我下了很大的功夫查阅资料和查看帮助文件。

在弄清楚双线性变换法设计IIR滤波器和窗函数法设计FIR滤波器的基本概念之后，我用了2天时间在做滤波器的，忽略了用户界面的设计。

等真正在做用户界面时才发现原来GUI设计界面、布局、写入逻辑语句等才是设计的重点。

为了构建一个实用好看的界面，我又通过网络和帮助文件深入的了解了GUI。

搞定一切之后，敲入所构思的程序，一个具有录音、滤波、频谱分析的用户界面诞生了。

通过此次设计，我认识到MATLAB的帮助文件真是学习MATLAB的好工具，它在整个设计过程中帮了我很多，而且让我的英语水平也有了提高。

六、参考文献［1］程佩青清华大学出版社，2009.附录：function varargout = NEWS(varargin)gui_Singleton = 1;gui_State = struct('gui_Name', mfilename, ...'gui_Singleton', gui_Singleton, ...'gui_OpeningFcn', @NEWS_OpeningFcn, ...'gui_OutputFcn', @NEWS_OutputFcn, ...'gui_LayoutFcn', [] , ...'gui_Callback', []);if nargin && ischar(varargin{1})gui_State.gui_Callback = str2func(varargin{1});endif nargout[varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});elsegui_mainfcn(gui_State, varargin{:});endfunction NEWS_OpeningFcn(hObject, eventdata, handles, varargin)handles.output = hObject;guidata(hObject, handles);function varargout = NEWS_OutputFcn(hObject, eventdata, handles)varargout{1} = handles.output;function pm1_Callback(hObject, eventdata, handles)val = get(hObject,'Value');str = get(hObject, 'String');switch str{val};case'IIR Filter'% User selects Filter Typehandles.yhx1 = 1;set(handles.p6,'enable','off');set(handles.pm2,'enable','on');case'FIR Filter'% User selects Filter Typehandles.yhx1 = 2;set(handles.p6,'enable','on');set(handles.pm2,'enable','off');case'Filter Type'% Error Warningerrordlg('You Must Choose The Filter Type ',' Error');endguidata(hObject,handles)function pm1_CreateFcn(hObject, eventdata, handles)if ispc && isequal(get(hObject,'BackgroundColor'),get(0,'defaultUicontrolBackgroundColor'))set(hObject,'BackgroundColor','white');endfunction pm2_Callback(hObject, eventdata, handles)val1 = get(hObject,'Value');str1 = get(hObject, 'String');switch str1{val1};case'Buttord'% User selects Filter Functionhandles.yhx2 = 1;case'Cheb1ord'% User selects Filter Functionhandles.yhx2 = 2;case'Cheb2ord'% User selects Filter Functionhandles.yhx2 = 3;case'Ellipord'% User selects Filter Functionhandles.yhx2 = 4;case'Filter Function'% Error Warningerrordlg('You Must Choose The Filter Function ',' Error'); endguidata(hObject,handles)function pm2_CreateFcn(hObject, eventdata, handles)if ispc && isequal(get(hObject,'BackgroundColor'),get(0,'defaultUicontrolBackgroundColor'))set(hObject,'BackgroundColor','white');endfunction p6_Callback(hObject, eventdata, handles)val2 = get(hObject,'Value');str2 = get(hObject,'String');switch str2{val2};case'Rectwin'handles.yhx3 = 0; % User selects Window Function case'Bartlett'handles.yhx3 = 1; % User selects Window Function case'Hann'handles.yhx3 = 2; % User selects Window Function case'Hamming'handles.yhx3 = 3; % User selects Window Function case'Blackman'handles.yhx3 = 4; % User selects Window Function case'Kaiserord'handles.yhx3 = 5; % User selects Window Function case'Window Function'errordlg('You Must Choose The Window Function','ERROR'); endguidata(hObject,handles);function p6_CreateFcn(hObject, eventdata, handles)if ispc && isequal(get(hObject,'BackgroundColor'),get(0,'defaultUicontrolBackgroundColor'))set(hObject,'BackgroundColor','white');endfunction pm4_Callback(hObject, eventdata, handles)val3 = get(hObject,'Value');str3 = get(hObject, 'String');switch str3{val3};case'Lowpass'% User selects Passband Typehandles.yhx4 = 1;set(handles.edit4,'enable','off');set(handles.edit4,'backgroundcolor',[0.90,0.90,0.90]);set(handles.edit5,'enable','off');set(handles.edit5,'backgroundcolor',[0.90,0.90,0.90]);case'Highpass'% User selects Passband Typehandles.yhx4 = 2;set(handles.edit4,'enable','off');set(handles.edit5,'enable','off');set(handles.edit4,'backgroundcolor',[0.90,0.90,0.90]);set(handles.edit5,'backgroundcolor',[0.90,0.90,0.90]);case'Bandpass'% User selects Passband Typehandles.yhx4 = 3;set(handles.edit4,'enable','on');set(handles.edit5,'enable','on');set(handles.edit4,'backgroundcolor','white');set(handles.edit5,'backgroundcolor','white');case'Passband Type'% Error Warningerrordlg('You Must Choose The Passband Type',' Error');endguidata(hObject,handles)function pm4_CreateFcn(hObject, eventdata, handles)if ispc && isequal(get(hObject,'BackgroundColor'),get(0,'defaultUicontrolBackgroundColor'))set(hObject,'BackgroundColor','white');endfunction pushbutton3_Callback(hObject, eventdata, handles)handles.Fs=str2double(get(handles.edit1,'String')); %Sampling frequency guidata(hObject,handles);Fc1=str2double(get(handles.edit2,'string')); %Passband cut-off frequency Fst1=str2double(get(handles.edit3,'string')); %Stopband cut-off frequencyFc2=str2double(get(handles.edit4,'string'));Fst2=str2double(get(handles.edit5,'string'));Rp=str2double(get(handles.edit6,'string')); %The maximum passband rippleRs=str2double(get(handles.edit7,'string')); %The minimum stopband attenuationWp1=Fc1/(handles.Fs/2);Ws1=Fst1/(handles.Fs/2);Wp2=Fc2/(handles.Fs/2);Ws2=Fst2/(handles.Fs/2);switch handles.yhx1 %User selects the Filter Typecase(1)switch handles.yhx2 %User selects the Filter Functioncase(1)switch handles.yhx4 % User selects Passband Typecase(1)ftype='low';case(2)ftype='high';case(3)Wp1=[Wp1 Wp2];Ws1=[Ws1 Ws2];ftype='bandpass';end[n,Wn]=buttord(Wp1,Ws1,Rp,Rs,'s');[handles.b,handles.a] =butter(n,Wn,ftype);case(2)switch handles.yhx4 % User selects Passband Typecase(1)ftype='low';case(2)ftype='high';case(3)Wp1=[Wp1 Wp2];Ws1=[Ws1 Ws2];ftype='bandpass';end[n,Wn]=cheb1ord(Wp1,Ws1,Rp,Rs,'s');[handles.b,handles.a] =cheby1(n,Rp,Wn,ftype);case(3)switch handles.yhx4 % User selects Passband Typecase(1)ftype='low';case(2)ftype='high';case(3)Wp1=[Wp1 Wp2];Ws1=[Ws1 Ws2];ftype='bandpass';end[n,Wn]=cheb2ord(Wp1,Ws1,Rp,Rs,'s');[handles.b,handles.a] =cheby2(n,Rp,Wn,ftype);case(4)switch handles.yhx4 % User selects Passband Typecase(1)ftype='low';case(2)ftype='high';case(3)Wp1=[Wp1 Wp2];Ws1=[Ws1 Ws2];ftype='bandpass';end[n,Wn]=ellipord(Wp1,Ws1,Rp,Rs,'s');[handles.b,handles.a] =ellip(n,Rp,Rs,Wn,ftype);end[h,f]=freqz(handles.b,handles.a,128,handles.Fs);plot(handles.axes3,f,20*log10(abs(h))); %Amplitude-frequency responseplot(handles.axes7,f,angle(h)); %Phase-frequencyresponseecase(2)Wn1=(Wp1+Ws1)/2;Wn2=(Wp2+Ws2)/2;switch handles.yhx3 % User selects Window Functioncase(0)switch handles.yhx4 % User selects Passband Type case(1)dw=Ws1-Wp1;wtype='low';case(2)dw=Wp1-Ws1;wtype='high';case(3)dw=min((Wp1-Ws1),(Ws2-Wp2));Wn1=[Wn1 Wn2];wtype='bandpass';endN = 2*ceil(1.8/dw)+1;window=rectwin(N);case(1)switch handles.yhx4 % User selects Passband Typecase(1)dw=Ws1-Wp1;wtype='low';case(2)dw=Wp1-Ws1;wtype='high';case(3)dw=min((Wp1-Ws1),(Ws2-Wp2));Wn1=[Wn1 Wn2];wtype='bandpass';endN = 2*ceil(4.2/dw)+1;window=bartlett(N);case(2)switch handles.yhx4 % User selects Passband Typecase(1)dw=Ws1-Wp1;case(2)dw=Wp1-Ws1;wtype='high';case(3)dw=min((Wp1-Ws1),(Ws2-Wp2));Wn1=[Wn1 Wn2];wtype='bandpass';endN = 2*ceil(6.2/dw)+1;window=hann(N);case(3)switch handles.yhx4 % User selects Passband Typecase(1)dw=Ws1-Wp1;wtype='low';case(2)dw=Wp1-Ws1;wtype='high';case(3)dw=min((Wp1-Ws1),(Ws2-Wp2));Wn1=[Wn1 Wn2];wtype='bandpass';endN = ceil(6.6/dw)+1;window=hamming(N);case(4)switch handles.yhx4 % User selects Passband Typecase(1)dw=Ws1-Wp1;wtype='low';case(2)dw=Wp1-Ws1;wtype='high';case(3)dw=min((Wp1-Ws1),(Ws2-Wp2));Wn1=[Wn1 Wn2];wtype='bandpass';endN = 2*ceil(11/dw)+1;window=blackman(N);case(5)if(Rs>=50)beta=0.1102*(Rs-8.7);beta=0;else beta=0.5842*(Rs-21)^0.4+0.07886*(Rs-21); %The Kaiser Window figure ¦Âendswitch handles.yhx4 % User selects Passband Typecase(1)dw=Ws1-Wp1;wtype='low';case(2)dw=Wp1-Ws1;wtype='high';case(3)dw=min((Wp1-Ws1),(Ws2-Wp2));Wn1=[Wn1 Wn2];wtype='bandpass';endN = ceil((Rs-7.95)/(2.286*dw));window=kaiser(N,beta);endhandles.c=fir1(N-1,Wn1,wtype,window);[h,f]=freqz(handles.c,1,128,handles.Fs);plot(handles.axes3,f,20*log10(abs(h))); %Amplitude-frequency responseplot(handles.axes7,f,angle(h)); %Phase-frequencyresponseeendxlabel(handles.axes3,'Frequency (Hz)')title(handles.axes3,'Amplitude-frequency response')axis(handles.axes3,'tight');xlabel(handles.axes7,'Frequency (Hz)')title(handles.axes7,'Phase-frequencyresponsee')axis(handles.axes7,'tight');guidata(hObject,handles);function edit1_Callback(hObject, eventdata, handles)function edit1_CreateFcn(hObject, eventdata, handles)if ispc && isequal(get(hObject,'BackgroundColor'),get(0,'defaultUicontrolBackgroundColor'))set(hObject,'BackgroundColor','white');endfunction edit2_Callback(hObject, eventdata, handles)function edit2_CreateFcn(hObject, eventdata, handles)if ispc && isequal(get(hObject,'BackgroundColor'),get(0,'defaultUicontrolBackgroundColor'))set(hObject,'BackgroundColor','white');endfunction edit3_Callback(hObject, eventdata, handles)function edit3_CreateFcn(hObject, eventdata, handles)if ispc && isequal(get(hObject,'BackgroundColor'),get(0,'defaultUicontrolBackgroundColor'))set(hObject,'BackgroundColor','white');endfunction edit4_Callback(hObject, eventdata, handles)function edit4_CreateFcn(hObject, eventdata, handles)if ispc && isequal(get(hObject,'BackgroundColor'),get(0,'defaultUicontrolBackgroundColor'))set(hObject,'BackgroundColor','white');endfunction edit5_CreateFcn(hObject, eventdata, handles)if ispc && isequal(get(hObject,'BackgroundColor'),get(0,'defaultUicontrolBackgroundColor'))set(hObject,'BackgroundColor','white');endfunction edit6_Callback(hObject, eventdata, handles)function edit6_CreateFcn(hObject, eventdata, handles)if ispc && isequal(get(hObject,'BackgroundColor'),get(0,'defaultUicontrolBackgroundColor'))set(hObject,'BackgroundColor','white');endfunction edit7_Callback(hObject, eventdata, handles)function edit7_CreateFcn(hObject, eventdata, handles)if ispc && isequal(get(hObject,'BackgroundColor'),get(0,'defaultUicontrolBackgroundColor'))set(hObject,'BackgroundColor','white');endfunction pushbutton1_Callback(hObject, eventdata, handles)button2 = questdlg('Do You Want To Record A New Sound?',...'Record Or Load','Yes','No,Choose From Computer','Yes'); switch button2case'Yes',handles.rate =8000;handles.data= wavrecord(5*handles.rate,handles.rate,'double');case'No,Choose From Computer',[FileName,PathName] = uigetfile('*.wav','Select the wav file'); %To slect the wav filehandles.string = [PathName FileName];[handles.data, handles.rate] = wavread([PathName FileName]);set(handles.edit8,'String',PathName); %Display the path name at edit8endset(handles.edit1,'String',handles.rate);guidata(hObject,handles);function pushbutton2_Callback(hObject, eventdata, handles)handles.L=length(handles.data);plot(handles.axes1,handles.data);axis(handles.axes1,'tight');title(handles.axes1,'Time domain representation of input signal')xlabel(handles.axes1,'time (milliseconds)')temp=fft(handles.data); %Fast Fourier transformationtemp=abs(temp);plot(handles.axes2,temp)axis(handles.axes2,'tight');xlabel(handles.axes2,'Frequency (Hz)')xlim(handles.axes2,[0 handles.L/2])title(handles.axes2,'Frequency representation of input signal')guidata(hObject,handles);function pushbutton4_Callback(hObject, eventdata, handles)switch handles.yhx1case(1)handles.y=filter(handles.b,handles.a,handles.data);%Through the IIR FilterY=fft(handles.y);case(2)handles.y=fftfilt(handles.c,handles.data);%Through the FIR FilterY=fft(handles.y);endplot(handles.axes4,handles.y);axis(handles.axes4,'tight');plot(handles.axes5,abs(Y));axis(handles.axes5,'tight');xlim(handles.axes5,[0 handles.L/2]);title(handles.axes4,'Time domain representation of ouput signal')xlabel(handles.axes4,'time (milliseconds)')xlabel(handles.axes5,'Frequency (Hz)')title(handles.axes5,'Frequency representation of ouput signal') guidata(hObject,handles);function pushbutton5_Callback(hObject, eventdata, handles) sound(handles.y,handles.rate); %Replay soundguidata(hObject,handles);function pushbutton6_Callback(hObject, eventdata, handles) sound(handles.data, handles.rate); %Play soundfunction edit8_Callback(hObject, eventdata, handles)function edit8_CreateFcn(hObject, eventdata, handles)if ispc && isequal(get(hObject,'BackgroundColor'),get(0,'defaultUicontrolBackgroundColor'))set(hObject,'BackgroundColor','white');endfunction pushbutton7_Callback(hObject, eventdata, handles) button = questdlg('Ready to quit?', ...'Exit Dialog','Yes','No','No');switch buttoncase'Yes',disp('Exiting Object');%Save variables to matlab.matsavedelete(NEWS)case'No',quit cancel;end。