On Mon, Nov 18, 2013 at 08:22:08AM -0500, Robert James wrote: > Wow, switching to a rectangular window of fft_size solved it! I'm > baffled: I know windows are a way of pretransforming the wave prior to > FFT, to eliminate artifacts. I just used the default window. Why did > I need a rectangular window here? In what other cases do I need it?
If you want to keep all the properties of the signal, you need a rect window. What you did was: apply a window, then do an FFT, apply the window again, do an IFFT. Obviously, you're distorting the signal every time you do the (I)FFT. A boxcar window won't change the signal. For spectral analysis or filter design, you typically use other windows. MB -- Karlsruhe Institute of Technology (KIT) Communications Engineering Lab (CEL) Dipl.-Ing. Martin Braun Research Associate Kaiserstraße 12 Building 05.01 76131 Karlsruhe Phone: +49 721 608-43790 Fax: +49 721 608-46071 www.cel.kit.edu KIT -- University of the State of Baden-Württemberg and National Laboratory of the Helmholtz Association
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