1、语音信号采集与处理初步题目：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回放和存储语音信号 一、 语音信号的读入：y fs nbit = wavread(天后.wav);语音信号的播放：wavplay(y,fs);语音信号的存储：wavwrite(soutl,fs, 天后 低通 );二、 滤波器的设计与分析：1.用 fir1 设计的低通滤波器代码如下：% 设计FIR 低通滤波器fp=1000HZ,fc1200HZ,Ap=1db ,fs=2*fc-fp=1400HZ(阻带截频)，% wp=fp/Fs(抽样频
2、率)=0.023*pi,ws=fs/Fs=0.032*pi,%由于As=100, 这里选择Kaiser窗作为窗函数 %计算可得A=-20lg(min ws = 0.032*pi;tr_width = ws - wpM = ceil(100-7.95)/tr_width/2.285) + 1;beta=10.06;n=0:1:M-1;wc = (ws+wp)/2;win = (kaiser(M,beta);h=fir1(M-1),wc/pi,kaiser(M,beta);H,w=freqz(h,1);mag = abs(H);db = 20*log10(mag+eps)/max(mag);sub
3、plot(3,1,1); stem(n,win);title(kaiser Window)axis(0 M-1 0 1.1); xlabel(n); ylabel(w(n)subplot(3,1,2); stem(n,h);title(Actual Impulse Response)axis(0 M-1 -0.1 0.3); xlabel(n); ylabel(h(n)subplot(3,1,3); plot(w/pi,db);title(Magnitude Response in dB);grid;axis(0 1 -150 10);xlabel(frequency (pi); ylabel
4、(Decibels)set(gca,XTickMode,manual,XTick,0,0.023,0.032,1)set(gca,YTickMode,manual,YTick,-100,0)低通滤波器的设计效果：2.高通滤波器的设计与选择：1）直接法设计的 butterworth 高通滤波器%设计IIR 高通滤波器fp=5000HZ,fc=4800HZ;As=100db,Ap=1db%fs=2*fc-fp=4600HZ(阻带截频), wp=fp/Fs(抽样频率)=0.113*pi,%ws=fs/Fs=0.104*piwp=0.113*pi; ws=0.104*pi; rp=1; rs=100;
5、N,Wn=buttord(wp/pi,ws/pi,rp,rs);b,a=butter(N,Wn,high);h1,w=freqz(b,a,256,2);plot(w,20*log10(abs(h1);grid;title( High-pass DF );2)双线性变换法设计的 butterworth 高通滤波器wp=0.113*pi; ws=0.104*pi; rp=1; rs=35; Fs=44100;wap=2*tan(wp/2); was=2*tan(ws/2);n,wn=buttord(wap,was,rp,rs,s); z,p,k=buttap(n);b,a=zp2tf(z,p,k)
6、;bt,at=lp2hp(b,a,wap););bz,az=bilinear(bt,at,Fs);h,w=freqz(bz,az,256,2);plot(w,20*log10(abs(h);grid; title( High-pass DF );3)用 FIR1 设计的高通滤波器：wp = 0.113*pi; ws = 0.104*pi;tr_width = wp - ws;M = ceil(100-7.95)/tr_width/2.285) + 1;beta=10.06;n=0:1:M-1;wc = (ws+wp)/2;win = (kaiser(M,beta);h=fir1(M-1),wc
7、/pi,high,kaiser(M,beta);H,w=freqz(h,1);mag = abs(H);db = 20*log10(mag+eps)/max(mag);subplot(3,1,1); stem(n,win);title(kaiser Window);axis(0 M-1 0 1.1); xlabel(n); ylabel(w(n)subplot(3,1,2); stem(n,h);title(Actual Impulse Response)axis(0 M-1 -0.1 0.3); xlabel(n); ylabel(h(n)subplot(3,1,3); plot(w/pi,
8、db);title(Magnitude Response in dB);grid;axis(0 1 -150 10);xlabel(frequency (pi); ylabel(Decibels)set(gca,XTickMode,manual,XTick,0,0.023,0.032,1)set(gca,YTickMode,manual,YTick,-100,0)经过调试发现 As=100db 的 Butterworth 高通滤波器很难实现，最终选择了用 Kaiser 窗设计的 FIR 高通滤波器。三、主程序的实现与效果y fs nbit = wavread(天后.wav);wavplay(y
9、,fs);n=length(y);k=1:n;f=fs/n*k;Y=fft(y,n);figure(1);subplot(311);plot(k,y);xlabel(n);ylabel(y);grid;title(原始信号);subplot(312);plot(f,Y); xlabel(Frequence(Hz);ylabel(Magnitude);grid;title(原始信号幅频响应 );ang=angle(Y);subplot(313)plot(f,ang);xlabel(Frequence(Hz);ylabel(Phase);grid;title(原始信号相频响应 );figure(2
10、)wp = 0.023*pi; ws = 0.032*pi;tr_width = ws - wpM = ceil(100-7.95)/tr_width/2.285) + 1;beta=10.06;wc = (ws+wp)/2;h=fir1(M-1),wc/pi,kaiser(M,beta);soutl=fftfilt(h,y);Soutl=fft(soutl,n);wavplay(soutl,fs);wavwrite(soutl,fs,天后低通);subplot(221);plot(k,y);xlabel(n);ylabel(y);grid;title(原始信号);subplot(222);
11、plot(f,Y);xlabel(Frequence(Hz);ylabel(Magnitude);grid;title(原始信号幅频响应 );subplot(223)plot(k,soutl);xlabel(n);ylabel(y);grid;title(低通滤波后的幅频响应 );subplot(224);plot(f,Soutl);xlabel(Frequence(Hz);ylabel(Magnitude);grid;title(低通滤波后的相频响应 );figure(3)wp = 0.113*pi; ws = 0.104*pi;tr_width = wp - wsM = ceil(100-
12、7.95)/tr_width/2.285) + 1;beta=10.06;n=0:1:M-1;wc = (ws+wp)/2;hd = ideal_hp(wc,M);w_ham = (kaiser(M);h1 = hd .* w_ham;south=fftfilt(h1,y);South=fft(south,n);wavplay(south,fs);wavwrite(south,fs,天后高通);subplot(221);plot(k,y);xlabel(n);ylabel(y);grid;title(原始信号);subplot(222);plot(f,Y);xlabel(Frequence(Hz);ylabel(Magnitude);grid;title(原始信号幅频响应 );subplot(223)plot(k,south);xlabel(n);ylabel(y);grid;title(高通滤波后的幅频响应 ); subplot(224);plot(f,South);xlabel(Frequence(Hz);ylabel(Magnitude);grid;title(高通滤波后的相频响应 );
