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/usr/share/puredata/doc/3.audio.examples/F03.pulse.spectrum.pd is in puredata-doc 0.46.7-3.

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#X text 184 23 bandwidth;
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#X text 63 1 PULSE SPECTRUM MEASUREMENT;
#X text 14 357 Here is a measured amplitude spectrum for the pulse
train. Nutice that \, other than a smallish spillover \, the energy
sits in one "lobe" whose changing width justifies our calling the squeeze
factor the "bandwidth.";
#X text 16 428 The spectrum is in units of amplitude. THe sidelobes
\, although they look small \, are actually only about 34 dB down.
You can design more complicated pulse trains \, little Blackman window
functions \, which control the sidelobes much better.;
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#X text 93 93 Fourier series;
#X text 98 146 magnitude;
#X text 96 131 calculate;
#X text 21 3 This subpatch computes the spectrum of the incoming signal
with a (rectangular windowed) FFT. FFTs aren't properly introduced
until much later.;
#X text 83 61 signal to analyze;
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#X text 191 182 for better graphing;
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#X text 605 488 updated for Pd version 0.37;
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