Elenco PK101 w/ Computer Interface - Manual (Page 13)

Project PC2
OBJECTIVE: To see what your voice looks like in electrical form.
Speaker Microphone
A speaker uses electrical energy to create mechanical vibrations. These vibrations create variations in
air pressure, called sound waves, which travel across the room. You “hear” sound when your ears feel
these air pressure variations. But if air pressure variations reach the speaker from another source, they
will cause it to vibrate too. This, in turn, causes the speaker to create a small electrical signal just like
a microphone does (though not very efficiently, since speakers were not designed to be microphones).
Connect the PC-interface cable directly the speaker as shown; no other parts are needed here. If con-
tinuing 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.
Hold the speaker next to your mouth and talk into it to see what your voice looks like after the speak-
er converts it to electrical energy. Adjust the Y1 gain control to get the best view of it, since the ampli-
tude is greater if you talk louder or
are closer to the microphone. You
may also want to increase the gain
of your microphone input for this
project only (see page 6 for
details). Notice how the waveform
is different depending on which
words or tones you say.
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