fft_noise.m

matlab从入门到精通第6章书后源码对初学者很有帮助

% fft_noise.m
% 傅立叶变化示例
% 产生带有噪声的声源信号，并提取离散信号
t=0:0.001:0.6;
% 噪声信号的主频为60Hz和150Hz
x=sin(2*pi*60*t)+sin(2*pi*150*t);
y=x+2*randn(size(t));
plot(1000*t(1:50),y(1:50))
title('Signal Corrupted with Zero-Mean Random Noise')
xlabel('time (ms)')
grid on;

% 进行512点的快速傅立叶变换
Y=fft(y,512);
% 功率谱测量计算
Pyy=Y.* conj(Y)/512;
f=1000*(0:256)/512;
% 绘制频谱图形
figure;
plot(f,Pyy(1:257))
title('Frequency content of y')
xlabel('frequency (Hz)')
grid on;