# Convert Real and Imaginary part from FFT to bands

how can I convert real and imaginary part from FFT to octave bands? I know how to do it for Absolute value, but dont know for Re, Im parts. Thanks

• Pick any functions $h_m : 0\ldots N-1 \to [0,1]$ such that $\sum_{m=1}^M H_m(k) = 1$ then $x= \sum_{m=1}^M y_m$ where $y_m = FFT^{-1}[Y_m], Y_m(k) =H_m(k) X(k), X = FFT[x]$. The octaves bands are obtained when $H_{m+1}(k) \approx 1_{[2^m,2^{m+1}]}+1_{N-[2^m,2^{m+1}]}$ – reuns Mar 17 at 18:40
• what exactly means 1[2m,2m+1]+1N−[2m,2m+1]? – user148733 Mar 22 at 13:04
• And do you mena hm=Hm? – user148733 Mar 22 at 13:10