iirlowpass.m

matlab的滤波器

fb=1000;fc=1200;fs=4100;
rp=1;rs=100;
wp=2*pi*fb/fs;
ws=2*pi*fc/fs;
fs=fs/fs;
wap=tan(wp/2);
was=tan(ws/2);
[n,wn]=buttord(wap,was,rp,rs,'s');
[z,p,k]=buttap(n);
[Bap,Aap]=zp2tf(z,p,k)
[b,a]=lp2lp(Bap,Aap,wn)
[bz,az]=bilinear(b,a,fs/2)
[x1,fs]=wavread('music');
x2=filter(bz,az,x1);
sound(x2,44100);f=fft(x2,length(x1));
printf(x2,abs(f),abs(length(x1)),bz,az);
[H,W]=freqz(bz,az);
figure(2);
plot(W*fs/(2*pi),abs(H))
grid
xlabel('频率／Hz')
ylabel('频率响应幅度')
title('IIR低通滤波器')