[pd] FFT sine to saw oscilator (was:[pd] hanning window + fft)

Charles Henry czhenry at gmail.com
Thu Sep 7 01:49:59 CEST 2006


> By the way, when I read this discussion, I tried to compute the fft of
> the hanning window, on paper.  I've had a little trouble.
> It's that usual law when you multiply in the time domain, you convolve
> in the frequency domain.
> I don't get why to use a Hanning window rather than a triangular window, for instance.

duh....figured that one out.  I had the wrong formula for the hanning
window....it's pretty obvious

hanning window, y(n)=.5-cos(2*pi*n/N)

so the fourier transform is Y(0)=.5 , Y(1) = -.5 , Y(2)=0 , Y(3)=0,
etc...., Y(N-1)=-.5

unlike the triangular window, the hanning window has just three
non-zero fourier coefficients.  Don't know if that's important...

Chuck




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