[chuck-users] spectrum magnitudes
eduard aylon
eduard.aylon at gmail.com
Wed Nov 14 20:43:37 EST 2007
I've been examining a bit more the output of the fft and I am not
sure about the spectrum magnitudes obtained after analysis. For
instance, analysing the peaks of a SinOsc with unity gain in a
similar manner as in examples/analysis/tracking/pitch-track.ck will
print out values of max (maximum peak) around 0.26 instead of values
near 1 (depending on the window used and the frequency. I've used a
hamming window and a freq proportional to sample_rate/fft_size). Why
is this? I've forgotten some of the implications of performing an FFT
but I believe the values of the magnitudes obtained after an FFT are
half the original value, but then, in the example above, one should
obtain peak values near 0.5. What is the cause for this? Could it be
that windowing is not normalised? I'd like to be sure of the values I
should expect in order to set thresholds above which spectral peaks
will be taken into account.
thanks in advance,
eduard
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