数字信号处理课程设计报告

数字信号处理课程设计报告题目：数字调音台学院：信息工程学院专业：通信工程指导教师：指导时间:目录1背景与内容 (1)2设计目的 (1)3设计原理 (1)3.1研究语音信号的特点； (1)3.2IIR数字滤波器 (2)3.3滤波器设计所涉及的matlab函数 (2)3.4总体方案 (3)4设计过程 (4)4.1系统流程图 (4)4.2具体设计 (4)5实验代码及结果 (7)5.1MATLAB源程序 (7)5.2系统运行与测试 (19)6实验体会及总结 (24)7参考文献 (24)1.背景与内容根据数字信号处理课程设计教学大纲的要求，利用Matlab（工程设计软件）设计数字调音台，并且给出了具体的软件实施方案。

Matlab功能强大、简单易学、编程效率高,深受广大科技工作者的欢迎。

特别是Matlab还具有信号分析工具箱,不需具备很强的编程能力,就可以很方便地进行信号分析、处理和设计。

此次设计利用Matlab对音频信号进行采样后；并画出音频信号的时域波形、频谱图；然后利用IIR设计高通、低通、带通以及帯阻滤波器对现有的音频信号进行滤波，实现音频音色的改变实现调音台的功能，并画出滤波后信号的时域波形和频谱，对滤波前后的信号进行对比，分析信号的变化；最后利用GUI设计一个数字信号系统界面。

1、选一首歌曲，采用已经学过的信号处理知识，设计高通、带通、低通、带阻几种滤波器，对其进行数字信号滤波，观察信号的变化；2、实时显示处理前的信号频谱和处理后的信号频谱；3、设计系统界面：为了使编制的程序操作方便，设计处理系统的用户界面，在所设计的系统界面上可以选择滤波器的类型，输入滤波器的参数、显示滤波器的频率响应等。

2.设计目的1、通过对常用数字滤波器的设计和实现，掌握数字信号处理的工作原理及设计方法；熟悉用IIR 数字滤波器和FIR滤波器的原理与方法，掌握利用数字滤波器对信号进行滤波的方法2、掌握数字滤波器的计算机仿真方法，并能够对设计结果加以分析。

3、通过对Matlab的使用，掌握Matlab的程序设计方法，掌握Matlab设计IIR数字滤波器和FIR滤波器的方法，并学会用Matlab对信号分析和处理。

4、学习使用MATLAB GUI设计工具应用平面。

3.设计原理3.1研究语音信号的特点；语音信号的带宽约为5KHz，主要能量集中在低频段。

语音信号是典型的随机信号，人的每次发音过程都是一个随机过程。

很难得到两次完全相同的发音样本。

语音时域信号特征1）清音段：能量低，过零率高，波形特点有点像随机的噪声。

这部分信号常与语音的辅音段对应。

2）浊音段：能量高，过零率低，波形具有周期性特点。

所谓的短时平稳性质就是处于这个语音浊音（元音）段中。

3）过渡段：一般是指从辅音段向元音段信号变化之间的部分。

信号变化快，是语音信号处理中最复杂、困难的部分。

3.2 IIR数字滤波器设计IIR数字滤波器一般采用间接法（脉冲响应不变法和双线性变换法），应用最广泛的是双线性变换法。

基本设计过程是：①先将给定的数字滤波器的指标转换成过渡模拟滤波器的指标；②设计过渡模拟滤波器；③将过渡模拟滤波器系统函数转换成数字滤波器的系统函数。

3.3滤波器设计所涉及的matlab函数[y,fs]= wavread(wavFile1)，此函数能读取.wav格式的音频文件。

其中y为语音信号，fs为采样频率，wavFile1为WA V音频文件存放路径。

[N,wc]=buttord(wp,ws,Rp,As)，用于计算巴特沃斯数字滤波器的阶数N和3dB 截止频率wc。

调用参数wp，ws分别为数字滤波器的通带、阻带截止频率的归一化值，要求：0 ≤wp≤1，0≤ws≤1。

1表示数字频率pi。

rp，rs分别为通带最大衰减和组带最小衰减（dB）。

当ws≤wp时，为高通滤波器；当ws≥wp时，为低通通滤波器；当wp 和ws为二元矢量时，当wsl<wpl<wpu<wsu为带通滤波器；当wpl<wsl<wss<wps 为带阻滤波器。

N，wc作为butter函数的调用参数。

[B,A]=butter:[b,a]=butter(N,wc,'high'):设计N阶高通滤波器。

[b,a]=butter(N,wc,'low'):设计N阶低通滤波器。

[b,a]=butter(N,wc):当wc为具有两个元素的矢量wc=[w1,w2]时，它设计2N 阶带通滤波器[b,a]=butter(N,wc,'stop'):若wc=[w1,w2]，则它设计2N阶带阻滤波器。

利用冲激响应不变法，把系统函数为（式1）模拟滤波器变换成等价的数字滤波器，采样间隔T=1S。

先经过计算得到：（式2）则有如下式子(式3) Matlab实验参考程序如下:B=[1,1];A=[1,5,6];T=1;Fs=1/T;[Bz,Az]=impinvar(B,A,Fs); %用冲激响应不变法将模拟滤波器变换成数字滤波器运行结果：Bz =1.0000 -0.2209Az = 1.0000 -0.1851 0.0067得到的数据和先前计算得到的数据相同，故利用冲激响应不变化法把模拟滤波器设计成数字滤波器正确。

z=filter(B,A,x) (式4) 输入X为滤波前序列，Y为滤波结果序列，B/A 提供滤波器系数，B为分子，A为分母。

整个滤波过程是通过下面差分方程实现的：a(1)*y(n) = b(1)*x(n) + b(2)*x(n-1) + ... + b(nb+1)*x(n-nb) - a(2)*y(n-1) - ... - a(na+1)*y(n-na)3.4总体方案系统的总体设计界面主要分为三个区域：播放区域、滤波器参数设置区域、滤波器类型选择区域。

3.4.1播放区域包括播放和停止音乐的功能按键。

3.4.2滤波器参数设置区域能够设置数字滤波器的各参数3.4.3滤波器类型选择区域在设置数字滤波器的参数之后，点击各类型滤波器按钮后弹出相应的波形图。

4设计过程4.1系统流程图图1：系统流程图4.2具体设计（1）首先建立GUI界面，具体界面如下：图2 GUI界面建立（2）系统的总体设计界面主要分为四个区域：播放区域、滤波器参数设置区域、滤波器类型选择区域。

具体界面如下图图3 GUI界面建立（3）播放区域设计包括播放、停止两个按钮，界面如下：图4 播放按钮（4）滤波器参数设置区域包括，包括六个参数：wp(fp1) ws(fs1) rp rs fsu fpu区域界面如图所示:图5 参数设置按钮（5）滤波器类型选择区域包括高通、低通、带通、帯阻四个按钮，区域界面如下图所示。

图6 选择按钮5.实验代码及结果5.1 MATLAB源程序（1）HIGH PASS FILTER 按钮所对应代码：function pushbutton1_Callback(hObject, eventdata, handles)global name1;global name2;global p;name1='D:\WWW\m2.wav';name2='D:\WWW\tu1.jpg';[x,Fs]=wavread(name1);h=axes('units','normalized','position',[0,0,1,1]);uistack(h,'up');i=imread(name2);image(i);set(h,'handlevisibility','off','visible','off');x1=x(:,1);N=length(x);f=Fs*(0:N/2-1)/N;figure(2);subplot(4,1,1);plot(x1);title('滤波前信号时域波形'));X2k=abs(fft(x1,N));subplot(4,1,2);plot(f,X2k(1:N/2));title('滤波前信号频谱图');wp=2*str2num(get(handles.edit1,'String'))/Fs;ws=2*str2num(get(handles.edit2,'String'))/Fs;Rp=str2num(get(handles.edit3,'String'));As=str2num(get(handles.edit4,'String'));[N,wc]=buttord(wp,ws,Rp,As);%巴特沃斯滤波法[B,A]=butter(N,wc,'high');%求模拟滤波器的两个参数[Bz,Az]=impinvar(B,A,Fs);%将模拟滤波器转换成数字滤波器w=pi/2:pi;Hk=freqz(Bz,Az,w); %求H（z）的频响wf=w*Fs/(2*pi); % 转化为Hzz=filter(B,A,x);subplot(4,1,3);plot(z);title('滤波后信号时域波形');Y1=abs(fft(z,Fs));subplot(4,1,4);plot(Y1(1:length(Y1)/2));title('滤波后信号的频谱');p=audioplayer(z,Fs);play(p);% hObject handle to pushbutton1 (see GCBO)% eventdata reserved - to be defined in a future version of MATLAB % handles structure with handles and user data (see GUIDATA) （2）LOW PASS FILTER 按钮所对应代码：function pushbutton2_Callback(hObject, eventdata, handles)global name1;global name2;global p;name1='D:\WWW\m2.wav';name2='D:\WWW\tu1.jpg';[x,Fs]=wavread(name1);h=axes('units','normalized','position',[0,0,1,1]);uistack(h,'up');i=imread(name2);image(i);set(h,'handlevisibility','off','visible','off');x1=x(:,1);N=length(x);f=Fs*(0:N/2-1)/N;figure(2);subplot(4,1,1);plot(x1);title('滤波前信号时域波形');X2k=abs(fft(x1,N));subplot(4,1,2);plot(f,X2k(1:N/2));title('滤波前信号频谱图'); wp=2*str2num(get(handles.edit1,'String'))/Fs;ws=2*str2num(get(handles.edit2,'String'))/Fs;Rp=str2num(get(handles.edit3,'String'));As=str2num(get(handles.edit4,'String'));[N,wc]=buttord(wp,ws,Rp,As);[B,A]=butter(N,wc,'low');[Bz,Az]=impinvar(B,A,Fs);w=pi/2:pi;Hk=freqz(Bz,Az,w); %求H（z）的频响wf=w*Fs/(2*pi); % 转化为Hzz=filter(B,A,x);subplot(4,1,3);plot(z);title('滤波后信号时域波形');Y1=abs(fft(z,Fs));subplot(4,1,4);plot(Y1(1:length(Y1)/2));title('滤波后信号的频谱');p=audioplayer(z,Fs);play(p);(3) BAND PASS TILTER 按钮所对应代码function pushbutton3_Callback(hObject, eventdata, handles) global name1;global name2;global p;name1='D:\WWW\m2.wav';name2='D:\WWW\tu1.jpg';[x,Fs]=wavread(name1);h=axes('units','normalized','position',[0,0,1,1]);uistack(h,'up');i=imread(name2);image(i);set(h,'handlevisibility','off','visible','off');x1=x(:,1);N=length(x);f=Fs*(0:N/2-1)/N;figure(2);subplot(4,1,1);plot(x1);title('滤波前信号时域波形');X2k=abs(fft(x1,N));subplot(4,1,2);plot(f,X2k(1:N/2));title('滤波前信号频谱图');fsl=str2num(get(handles.edit2,'String'));fsu=str2num(get(handles.edit5,'String')); fpl=str2num(get(handles.edit1,'String'));fpu=str2num(get(handles.edit6,'String')); wp=[2*fpl/Fs,2*fpu/Fs];ws=[2*fsl/Fs,2*fsu/Fs];Rp=str2num(get(handles.edit3,'String'));As=str2num(get(handles.edit4,'String'));[N,wc]=buttord(wp,ws,Rp,As);[B,A]=butter(N,wc);[Bz,Az]=impinvar(B,A,Fs);w=pi/2:pi;Hk=freqz(Bz,Az,w); %求H（z）的频响wf=w*Fs/(2*pi); % 转化为Hzz=filter(B,A,x);subplot(4,1,3);plot(z);title('滤波后信号时域波开形');Y1=abs(fft(z,Fs));subplot(4,1,4);plot(Y1(1:length(Y1)/2));title('滤波后信号的频谱');p=audioplayer(z,Fs);play(p);（4）BAND STOP TILTER 按钮所对应代码function pushbutton4_Callback(hObject, eventdata, handles)global name1;global name2;global p;name1='D:\WWW\m2.wav';name2='D:\WWW\tu1.jpg';[x,Fs]=wavread(name1);h=axes('units','normalized','position',[0,0,1,1]);uistack(h,'up');i=imread(name2);image(i);set(h,'handlevisibility','off','visible','off');x1=x(:,1);N=length(x);f=Fs*(0:N/2-1)/N;figure(2);subplot(4,1,1);plot(x1);title('滤波前信号时域波形');X2k=abs(fft(x1,N));subplot(4,1,2);plot(f,X2k(1:N/2));title('滤波前信号频谱图');fsl=str2num(get(handles.edit2,'String'));fsu=str2num(get(handles.edit5,'String')); fpl=str2num(get(handles.edit1,'String'));fpu=str2num(get(handles.edit6,'String')); wp=[2*fpl/Fs,2*fpu/Fs];ws=[2*fsl/Fs,2*fsu/Fs];Rp=str2num(get(handles.edit3,'String'));As=str2num(get(handles.edit4,'String'));[N,wc]=buttord(wp,ws,Rp,As);[B,A]=butter(N,wc,'stop');[Bz,Az]=impinvar(B,A,Fs);w=pi/2:pi;Hk=freqz(Bz,Az,w); %求H（z）的频响wf=w*Fs/(2*pi); % 转化为Hzz=filter(B,A,x);subplot(4,1,3);plot(z);title('滤波后信号时域波开形');Y1=abs(fft(z,Fs));subplot(4,1,4);plot(Y1(1:length(Y1)/2));title('滤波后信号的频谱');p=audioplayer(z,s);play(p);(5) PLAY按钮所对应代码function pushbutton5_Callback(hObject, eventdata, handles) global name1;global name2;global p;[x,Fs]=wavread(name1);h=axes('units','normalized','position',[0,0,1,1]);uistack(h,'up');i=imread(name2);image(i);set(h,'handlevisibility','off','visible','off');%全屏背景p=audioplayer(x,Fs);play(p);% hObject handle to pushbutton5 (see GCBO)% eventdata reserved - to be defined in a future version of MATLAB% handles structure with handles and user data (see GUIDATA)(6) STOP 按钮所对应代码function pushbutton6_Callback(hObject, eventdata, handles)global p;stop(p);% hObject handle to pushbutton6 (see GCBO)% eventdata reserved - to be defined in a future version of MATLAB% handles structure with handles and user data (see GUIDATA)其他相关代码function varargout = projecttry(varargin)% PROJECTTRY M-file for projecttry.fig% PROJECTTRY, by itself, creates a new PROJECTTRY or raises the existing% singleton*.% H = PROJECTTRY returns the handle to a new PROJECTTRY or the handle to% the existing singleton*.%% PROJECTTRY('CALLBACK',hObject,eventData,handles,...) calls the local% function named CALLBACK in PROJECTTRY.M with the given input arguments.%% PROJECTTRY('Property','Value',...) creates a new PROJECTTRY or raises the% existing singleton*. Starting from the left, property value pairs are% applied to the GUI before projecttry_OpeningFcn gets called. An% unrecognized property name or invalid value makes propertyapplication% stop. All inputs are passed to projecttry_OpeningFcn via varargin.%% *See GUI Options on GUIDE's Tools menu. Choose "GUI allows only one% instance to run (singleton)".%% See also: GUIDE, GUIDATA, GUIHANDLES% Edit the above text to modify the response to help projecttry% Last Modified by GUIDE v2.5 21-May-2014 22:53:44% Begin initialization code - DO NOT EDITgui_Singleton = 1;gui_State = struct('gui_Name', mfilename, ...'gui_Singleton', gui_Singleton, ...'gui_OpeningFcn', @projecttry_OpeningFcn, ...'gui_OutputFcn', @projecttry_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{:});end% End initialization code - DO NOT EDIT% --- Executes just before projecttry is made visible.function projecttry_OpeningFcn(hObject, eventdata, handles, varargin)% This function has no output args, see OutputFcn.% hObject handle to figure% eventdata reserved - to be defined in a future version of MATLAB% handles structure with handles and user data (see GUIDATA)% varargin command line arguments to projecttry (see V ARARGIN)% Choose default command line output for projecttryhandles.output = hObject;% Update handles structureguidata(hObject, handles);% UIWAIT makes projecttry wait for user response (see UIRESUME)% uiwait(handles.figure1);% --- Outputs from this function are returned to the command line.function varargout = projecttry_OutputFcn(hObject, eventdata, handles)% varargout cell array for returning output args (see V ARARGOUT);% hObject handle to figure% eventdata reserved - to be defined in a future version of MATLAB% handles structure with handles and user data (see GUIDATA)% Get default command line output from handles structurevarargout{1} = handles.output;function edit1_Callback(hObject, eventdata, handles)% hObject handle to edit1 (see GCBO)% eventdata reserved - to be defined in a future version of MATLAB% handles structure with handles and user data (see GUIDATA)% Hints: get(hObject,'String') returns contents of edit1 as text% str2double(get(hObject,'String')) returns contents of edit1 as a double% --- Executes during object creation, after setting all properties.function edit1_CreateFcn(hObject, eventdata, handles)% eventdata reserved - to be defined in a future version of MATLAB% handles empty - handles not created until after all CreateFcns called% Hint: edit controls usually have a white background on Windows.% See ISPC and COMPUTER.if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))set(hObject,'BackgroundColor','white');endfunction edit2_Callback(hObject, eventdata, handles)% hObject handle to edit2 (see GCBO)% eventdata reserved - to be defined in a future version of MATLAB% handles structure with handles and user data (see GUIDATA)% Hints: get(hObject,'String') returns contents of edit2 as text% str2double(get(hObject,'String')) returns contents of edit2 as a double% --- Executes during object creation, after setting all properties.function edit2_CreateFcn(hObject, eventdata, handles)% hObject handle to edit2 (see GCBO)% eventdata reserved - to be defined in a future version of MATLAB% handles empty - handles not created until after all CreateFcns called% Hint: edit controls usually have a white background on Windows.% See ISPC and COMPUTER.if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))set(hObject,'BackgroundColor','white');endfunction edit3_Callback(hObject, eventdata, handles)% eventdata reserved - to be defined in a future version of MATLAB% handles structure with handles and user data (see GUIDATA)% Hints: get(hObject,'String') returns contents of edit3 as text% str2double(get(hObject,'String')) returns contents of edit3 as a double% --- Executes during object creation, after setting all properties.function edit3_CreateFcn(hObject, eventdata, handles)% hObject handle to edit3 (see GCBO)% eventdata reserved - to be defined in a future version of MATLAB% handles empty - handles not created until after all CreateFcns called% Hint: edit controls usually have a white background on Windows.% See ISPC and COMPUTER.if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))set(hObject,'BackgroundColor','white');endfunction edit4_Callback(hObject, eventdata, handles)% hObject handle to edit4 (see GCBO)% eventdata reserved - to be defined in a future version of MATLAB% handles structure with handles and user data (see GUIDATA)% Hints: get(hObject,'String') returns contents of edit4 as text% str2double(get(hObject,'String')) returns contents of edit4 as a double% --- Executes during object creation, after setting all properties.function edit4_CreateFcn(hObject, eventdata, handles)% hObject handle to edit4 (see GCBO)% eventdata reserved - to be defined in a future version of MATLAB% handles empty - handles not created until after all CreateFcns called% Hint: edit controls usually have a white background on Windows.% See ISPC and COMPUTER.if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))set(hObject,'BackgroundColor','white');endfunction edit5_Callback(hObject, eventdata, handles)% hObject handle to edit5 (see GCBO)% eventdata reserved - to be defined in a future version of MATLAB% handles structure with handles and user data (see GUIDATA)% Hints: get(hObject,'String') returns contents of edit5 as text% str2double(get(hObject,'String')) returns contents of edit5 as a double % --- Executes during object creation, after setting all properties.function edit5_CreateFcn(hObject, eventdata, handles)% hObject handle to edit5 (see GCBO)% eventdata reserved - to be defined in a future version of MATLAB% handles empty - handles not created until after all CreateFcns called% Hint: edit controls usually have a white background on Windows.% See ISPC and COMPUTER.if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))set(hObject,'BackgroundColor','white');endfunction edit6_Callback(hObject, eventdata, handles)% hObject handle to edit6 (see GCBO)% eventdata reserved - to be defined in a future version of MATLAB% handles structure with handles and user data (see GUIDATA)% Hints: get(hObject,'String') returns contents of edit6 as text% str2double(get(hObject,'String')) returns contents of edit6 as a double% --- Executes during object creation, after setting all properties.function edit6_CreateFcn(hObject, eventdata, handles)% hObject handle to edit6 (see GCBO)% eventdata reserved - to be defined in a future version of MATLAB% handles empty - handles not created until after all CreateFcns called% Hint: edit controls usually have a white background on Windows.% See ISPC and COMPUTER.if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))set(hObject,'BackgroundColor','white');end5.2 系统运行与测试（1）播放曲目单击GUI右侧“PLAY”按钮播放音乐，GUI会出现歌曲相应背景图图7：系统界面（2）停止曲目单击GUI右侧“STOP”按钮停止播放音乐。