www.pudn.com > voiceprocessingtoolbox.rar > fftSynthesis.m

N=21; 
fs=8000; 
time=(1:N)'/fs; 
x=rand(N,1); 
plot(time, x, 'o-'); 
 
X=fft(x)/N; 
 
plotNum=fix(N/2)+2; 
subplot(plotNum, 1, 1) 
plot(time, x, 'o-'); 
%axis([-inf inf -1 1]); 
subplot(plotNum, 1, 2); 
N2=(N-1)*5+1; 
fineTime=linspace(min(time), max(time), N2); 
plot(fineTime, X(1)*ones(N2,1), '.-', time, X(1)*ones(N,1), 'or'); 
%axis([-inf inf -1 1]); 
 
x2=X(1)*ones(N,1); 
 
for i=1:N/2 
	y1=real(X(i+1))*cos(2*pi*(i*fs/N)*fineTime)-imag(X(i+1))*sin(2*pi*(i*fs/N)*fineTime); 
	y2=real(X(i+1))*cos(2*pi*(i*fs/N)*time)    -imag(X(i+1))*sin(2*pi*(i*fs/N)*time); 
	subplot(plotNum, 1, i+2); 
	plot(fineTime, y1, '.-', time, y2, 'or'); 
%	axis([-inf inf -1 1]); 
	x2=x2+y2; 
end 
sum(abs(x-x2))