Elenco Projects PC1-PC73 - Manual (Page 33)

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Build the circuit shown. If continuing from the previous experiment
then close the Winscope program and run it again, to reset the
settings. Click on the On-Line button to activate, turn on the switch
(snap part S1), and press the press switch (part S2). Try the
settings shown here.
The waveform at left shows the signal just after pressing the press
switch, the waveform below uses the same settings and shows the
waveform just before the sound stops. You see the pulses slowly
spread out as the tone of the sound changes.
Settings
Now change to FFT mode to look at the frequency spectrum as the
sound fades away. Try the
settings shown here.
Settings
The spectrum at left is for just after pressing the press switch. The
spectrum below uses the same settings and shows the spectrum
just before the sound stops. The frequencies and amplitude slowly
get lower as the sound fades away.