给图片添加了正弦噪声，利用MATLAB源代码消除噪声.rar

%m源代码 function demo=fftdemo(); %FFT Discrete Fourier transform Demo. % Luoyao 2-26-2006 % Revised N % http://hi.baidu.com/geophysics % geophysics_21@163.com % Copyright 2006-2008 Luo Yao. % % FFT(X) is the discrete Fourier transform (DFT) of vector X. For % matrices, the FFT operation is applied to each column. For N-D % arrays, the FFT operation operates on the first non-singleton % dimension. % % Type fftdemo with no input parameters for demo application % % If this code works, it was written only by Luo Yao. % If not, I don't know who changed it. % % See also FFT, FT2, FFTN, FFTSHIFT, FFTW, IFFT, IFFT2, IFFTN. % Copyright 2006-2008 Luo Yao. % $Revision: 1.0 $ $Date: 2008-3-18 $ % Built-in function. clear clc fs=5000 t=0:1/fs:0.6; f1=100; f2=300; x=sin(2*pi*f1*t)+sin(2*pi*f2*t); subplot(411) plot(x); xlim([0 200]) title('f1(100Hz)/f2(300Hz)的正弦信号，初相0') xlabel('序列（n）') grid on number=1024*1 y=fft(x,number); n=0:length(y)-1; f=fs*n/length(y); subplot(412) plot(f(1:number/2),abs(y(1:number/2))/number); xlim([0 1000]) title('f1/f2的正弦信号的FFT（1024点）') xlabel('频率Hz') grid on demo=['fft demo by 骆遥']; xr=x+randn(1,length(x)); subplot(413) plot(x,'r') hold on plot(xr); xlim([0 200]) title('原f1/f2的正弦信号（含随机噪声）') xlabel('序列（n）') grid on yr=fft(xr,number); n=0:length(y)-1; f=fs*n/length(yr); subplot(414) plot(f(1:number/2),abs(yr(1:number/2))/number); xlim([0 1000]) title('原f1/f2的正弦信号（含随机噪声）的FFT（1024点）') xlabel('频率Hz') grid on end