title: fast fourier transform apply window and overlap
body: <p>This may be a naive question, but I didn't find exact details in searching.</p>
  
  <p>In FFT with window overlapping, after we've applied window functions to sequences of data set with overlapping and got the FFT results, how do we combine those FFT results for overlapping sequence? </p>
  
  <p>Do we just add them together, treating those frequency domain results as non-overlapping parts?</p>
  
  <p>Are magnitudes of these results in complex numbers frequency magnitudes?</p>
  
  <p>Thank you. </p>