音乐信号的滤波去噪

音乐信号的滤波去噪

clear all;close all;clc;

[y,fs]=wavread('c:\My

Music\wozhizaihuni.wav');

y=y(:,1);

n=length(y)

w=2/n*[0:n-1];

Y=fft(y,n);

figure

subplot(211),plot(y)

title('原信号时域图')

subplot(212),plot(w,abs(Y))

title('原信号频域图'）%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

n1=0:n-1;

c=(cos(6000*pi*n1/fs)+cos(10000*pi*n1 /fs)+cos(16000*pi*n1/fs))*0.05;

C=fft(c,n);

length(c)

figure

plot(w,abs(C))

title('余弦噪声频谱图') %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

y1=y+c';

Y1=fft(y1,n);

figure

subplot(211), plot(y1)

title('带余弦噪时域')

subplot(212), plot(w,abs(Y1))

title('加余弦噪后的音乐信号频谱')

%sound(y1,fs) %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

r=rand(1,n)-0.5;

y2=r'+y;

Y2=fft(y2,n);

figure subplot(211),plot(y2)

title('加白噪声后音乐时域图')

subplot(212),plot(w,abs(Y2))

title('加白噪声后的音乐信号频谱')

%sound(y2,fs) %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Wp=0.02;Ws=0.04;

Rp=1;Rs=15;

[N,Wc]=buttord(Wp,Ws,Rp,Rs);

[B,A]=butter(N,Wc)

[H,W]=freqz(B,A,'whole');

figure

plot(W/pi,abs(H))

title('数字巴特沃斯滤波器') %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

y11=filter(B,A,y1);

%sound(y11,fs)

Y11=fft(y11,n);

figure

subplot(211),plot(y11)

title('叠加余弦噪声的音乐信号滤波后的时域图')

subplot(212),plot(w,abs(Y11))

title('频域图') %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

y21=filter(B,A,y2);

sound(y21,fs)

Y11=fft(y21,n);

figure

subplot(211),plot(y11)

title('叠加白噪声的音乐信号滤波后时域图')

subplot(212),plot(w,abs(Y11))

title('频域图')

一原音乐信号

二余弦信号

三音乐信号叠加噪声

加余弦噪声后，音乐信号中明显有一部分高频分量，噪声尖锐，响度较高。

加白噪声后，音乐信号一直处于混杂状态，噪声响度略小，如电视选择空频道时的声音。四用巴特沃斯滤波

为了将白噪声尽量减少，故而选择了较低的禁止频率。

滤波效果还可以，但是声音不够丰满，高频被滤波器所滤掉的原因所致。

噪声得到了减少，但无法滤除。这是因为，白噪声与原音乐存在相同的频率（在低频阶段），若将白噪声滤除，则音乐信号不复存在。