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...

marius.

brandt@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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