音乐信号的处理 matlab

figure;plot(w,abs(fh1));

2、音乐信号的抽取（减抽样）

[y,fs,bit]=wavread('2');

sound(y,fs); figure; subplot(1,2,1); plot(y);

title('原音乐信号波形');

y1=y(:,1); M=512; fh1=fft(y1,M); w=2/M*[0:M-1]; subplot(1,2,2); plot(w,fh1);

title('原音乐信号频谱');

grid on; j=0;

d=10; %减抽样间隔 取3和10 代表混叠与非混叠

y3=y1(1:100000); for i=1:d:length(y3);

j=j+1; yd(j)=y1(i); end

sound(yd,fs/d);

figure;

subplot(1,2,1); plot(yd);

title('减抽样时域'); fh2=fft(yd); l1=length(fh2); w2=2/l1*(0:l1-1); subplot(1,2,2); plot(w2,abs(fh2)); title('减抽样频域');

3、音乐信号的AM调制和巴特沃斯IIR滤波器滤波

[w,fs,bit]=wavread('2');

w1=w(:,1); l=length(w1); ww=2/l*(0:l-1); n=0:length(w1)-1;

t1=w1.*cos(0.6*pi*n)'; T1=fft(t1); plot(t1);

title('AM低/高频调制后波形'); figure;

plot(ww,abs(T1));

title('AM低/高频调制后频谱');

sound(t1,fs);

t2=t1.*cos(0.6*pi*n)';

T2=fft(t2);

figure;

plot(t2);

title('AM低/高频解调后波形');

figure;

plot(ww,abs(T2));

title('AM低/高频解调后频谱'); sound(t2,fs);

[N,wc]=buttord(0.2,0.3,2,15);

[b1,a]=butter(N,wc); [h,wi]=freqz(b1,a);

figure;

plot(wi/pi,abs(h)); title('iir滤波器频谱'); %用iir对信号滤波 y=filter(b1,a,t2);

Y=fft(y); figure;

plot(y);

title('低/高频解调滤波后时域');

figure;

plot(ww,abs(Y));

title('低/高频解调滤波后的频域');

sound(y,fs);

用窗函数法设计FIR滤波器（矩形窗和布莱克曼窗）

[w,fs,bit]=wavread('2');

w1=w(:,1); n=0:length(w1)-1;

t1=w1.*cos(0.6*pi*n)'; j1=t1.*cos(0.6*pi*n)'; %用FIR对信号同步解调 N=55;wc=pi/4;% boxcar N取9 hd=ideal(N,wc);

w=blackman(N);%blackman和boxcar

h=hd.*w'; M=512; fh=fft(h,M); ww=2/M*(0:M-1);

plot(ww,abs(fh));

title('矩形窗fir滤波器频率响应');

y=conv(j1,h); Y=fft(y,M);

figure plot(y);

title('矩形窗fir滤波后时域'); figure

plot(ww,abs(Y));

title('矩形窗fir滤波后频域');

sound(y,fs);

三余弦和白噪声的实验 [y,fs,bit]=wavread('2');

y1=y(:,1); f=fft(y1);

l=length(f);

ww=2/l*(0:l-1); n=0:length(y1)-1;

x=0.05*(cos(2*pi*3000*n/fs)+cos(2*pi*5000*n/fs)+cos(2*pi*8000*n/fs));

fx1=fft(x);

plot(ww,abs(fx1)); title('三余弦噪声频谱'); r=rand(size(y1),1)-0.5;

fx2=fft(r);

figure

plot(ww,abs(fx2)); title('随机白噪声频谱');

x1=y1'+x; figure

plot(x1);

title('加三余弦噪声的信号音谱'); fx3=fft(x1); figure

plot(ww,abs(fx3));

title('加三余弦噪声的信号频谱');

x2=y1+r;

figure plot(x2);

title('加白噪声的信号音谱');

fx4=fft(x2);

figure

plot(ww,abs(fx4));

title('加白噪声的信号频谱');

sound(x1,fs); sound(x2,fs);

三余弦噪声滤波 [y,fs,bit]=wavread('2');

y1=y(:,1); f=fft(y1);

l=length(f);

ww=2/l*(0:l-1); n=0:length(y1)-1;

x=0.05*(cos(2*pi*3000*n/fs)+cos(2*pi*5000*n/fs)+cos(2*pi*8000*n/fs));

fx1=fft(x);

plot(ww,abs(fx1)); title('三余弦噪声频谱');

x1=y1'+x; figure

plot(x1);

title('加三余弦噪声的信号音谱');

fx3=fft(x1);

figure

plot(ww,abs(fx3));

title('加三余弦噪声的信号频谱');

sound(x1,fs);

[N,wc]=buttord(0.1,0.14,5,20);

[b1,a]=butter(N,wc); R=filter(b1,a,x1);

fr=fft(R); figure

plot(R);

title('滤波去噪后信号的音谱'); figure

plot(ww,abs(fr));

title('滤波去噪后信号频谱');

sound(R,fs);

随机白噪声滤波 [y,fs,bit]=wavread('2');

y1=y(:,1); f=fft(y1); l=length(f); ww=2/l*(0:l-1); n=0:length(y1)-1; r=rand(size(y1),1)-0.5;

fx2=fft(r); figure plot(ww,abs(fx2)); title('随机白噪声频谱');

x2=y1+r; figure

plot(x2);

title('加白噪声的信号音谱');

fx4=fft(x2);

figure

plot(ww,abs(fx4));

title('加白噪声的信号频谱'); [N,wc]=buttord(0.06,0.1,2,20);

[b1,a]=butter(N,wc); G=filter(b1,a,x2); fg1=fft(G);

figure

plot(G);

title('滤波去噪后信号的音谱'); figure

plot(ww,abs(fg1));

title('滤波去噪后信号频谱');

sound(x2,fs); sound(G,fs);

设计低通滤波器 [y,fs,bit]=wavread('2');

y1=y(:,1); fx1=fft(y1);

l=length(fx1); ww=2/l*(0:l-1);

figure;

plot(ww,abs(fx1)); title('原信号频谱'); [N,wc]=buttord(0.1,0.15,1,20);

[b1,a]=butter(N,wc); [h,wi]=freqz(b1,a);

figure; plot(wi/pi,abs(h)); title('滤波器特性曲线'); y=filter(b1,a,y1); fx2=fft(y); figure; plot(ww,abs(fx2)); title('滤波后频谱'); sound(y1,fs); sound(y,fs);

设计高通滤波器 [y,fs,bit]=wavread('1');

y1=y(:,1); fx1=fft(y1);

l=length(fx1); ww=2/l*(0:l-1);

figure;

plot(ww,abs(fx1)); title('原信号频谱'); [N,wc]=buttord(0.15,0.2,1,20); [b1,a]=butter(N,wc,'high'); [h,wi]=freqz(b1,a,'whole');

figure; plot(wi/pi,abs(h)); title('滤波器特性曲线'); y2=filter(b1,a,y1); fx2=fft(y2); figure; plot(ww,abs(fx2)); title('滤波后频谱'); sound(y1,fs); sound(y2,fs);

幅度谱和相位谱交叉组合 [x,fs,bit]=wavread('1');

x1=x(:,1);

[y,fs,bit]=wavread('2');

y1=y(:,1); N=10240; fx1=fft(x1,N); fy1=fft(y1,N); Ffx1=abs(fx1); Afx2=angle(fy1); F3=Ffx1.*exp(j*Afx2);

x3=ifft(F3); sound(real(x3));