|
Dear Members, I acquired one-dimensional data by sound card of my PC with sample frequency 22050 Hz and period of observation (duration) 30 s. I want to apply fft on the data and to plot the spectrum. I would like F to be with real values, not normalized values. I tried this: Ys(fft(data)); F=0:0.03:11025; plot(F,Y) but I get vectors Y and F with different length. Where is my mistake and if the vector F is given in right way from me? Best Regards, Tio
|
fft
Started by ●December 18, 2003
Reply by ●December 18, 20032003-12-18
|
You have truncated the bin size, 1/30, to 0.03. Since this is the step size used for creating F, F will have the wrong number of elements. Try instead: fs = 22050; %Sample rate, Hz Ys(fft(data)); Y=Y(1:length(data)/2+1); %For real data, only need the first (N/2)+1 points, assuming N is even F=[0:length(Y)-1]/(length(Y)-1)*fs/2; %Frequency points Sincerely, Glen Ragan -----Original Message----- From: tio tio [mailto:] Sent: Thursday, December 18, 2003 2:32 AM To: Subject: [matlab] fft Dear Members, I acquired one-dimensional data by sound card of my PC with sample frequency 22050 Hz and period of observation (duration) 30 s. I want to apply fft on the data and to plot the spectrum. I would like F to be with real values, not normalized values. I tried this: Ys(fft(data)); F=0:0.03:11025; plot(F,Y) but I get vectors Y and F with different length. Where is my mistake and if the vector F is given in right way from me? Best Regards, Tio _____ _____________________________________ Note: If you do a simple "reply" with your email client, only the author of this message will receive your answer. You need to do a "reply all" if you want your answer to be distributed to the entire group. _____________________________________ About this discussion group: To Join: To Post: To Leave: Archives: http://www.yahoogroups.com/group/matlab More DSP-Related Groups: http://www.dsprelated.com/groups.php3 _____ > . |
