Elenco Snap Circuits SOUND &reg - Manual (Page 49)

Build the circuit, and turn on the slide switch (S1).
The resistance of the 5.1k
W resistor (R3) and
microphone (X1) determine the pitch (frequency)
of the tone.
Push the press switch (S2) to bypass the
microphone, and the tone changes.
Build the circuit, and turn on the slide switch (S1).
The color LED (D8) is dimly lit, because the
resistance of the microphone (X1) keeps the
current low.
Push the press switch (S2) to bypass the
microphone, and the LED gets bright.
You can also try replacing the microphone with
the 5.1k
W resistor (R3), to see how their
resistances compare.
Project 69 Microphone
Resistance - Audio
Project 68 Microphone
Resistance - LED
The microphone changes resistance when
exposed to changes in air pressure, such as
from sound waves or blowing on it. Talking
into the microphone or blowing on it will
change the LED brightness, but probably not
enough for you to notice the difference.
-48-