[PD] frequency

marius schebella marius.schebella at gmail.com
Fri Aug 28 09:07:32 CEST 2009

if you do a fft and look at the array with the results, you will have 
the DC at arrayposition 0 and a frequency of SR/WS (samplingrate divided 
by window size) at position 1.
with your settings this would be around 86Hz. the other elements of the 
array hold multiples of 86Hz.
on pos2 2*86, on pos3 3*86...
on pos128 you should get the Nyquist frequency (sample rate/2=11025) 
which is the highest frequency you can analyze. the rest of the array 
are mirror frequencies, that you don't need for analysis.
if you want to get the array position for 5000Hz
you do 5000/86... so you should feed the number 58 into your tabread.

bear in mind that the fft will use the first 129(!) pins of the 256 
array (position 0-128) to put frequency values. that is, because the DC 
and the nyquist frequency don't have(/need) a phase information. at 
least that's the theory...


brandt at subnet.at wrote:
> hi all
> can anybody telle me how to get the right frequencys out of a frequency
> analysis at 22050 samplingrate in an array with 256 adresses
> thank you in advance
> der.brandt
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