Manual

-69-
D
o you know of someone who is a big mouth? (Or,
have you ever been accused of being one?) This
experiment lets you and your friends see who’s got
t
he most ear-splitting voice.
How does this work? When you yell, you create
sound waves, which are actually variations in air
pressure. These air pressure variations create
pressure on the crystalline structure in the
earphone. In a crystal structure, pressure creates
voltage through a process called piezoelectricity.
The voltage produced by the earphone is applied to
a two-transistor circuit, which amplifies it. You can
use the control to adjust the amount of the signal
from the earphone that is amplified. Two NAND
gates in series control the lighting of LED 1.
Set the switch position A and set the control to
position 5. Watch LED 1 as you yell into the
earphone; it probably lights. To make it more difficult
to light LED 1, try turning the control counter-
clockwise. (Try adjusting it just a tiny bit each time.)
See how far you can lower the control to reduce the
strength of the amplifier and still light the LED.
N
otes:
EXPERIMENT #52: MONSTER MOUTH
Wiring Sequence:
o 27-79
o 28-110
o 124-131-31-49
o 33-55
o 41-43-100-81
o 42-72
o 44-109-99-83
o 45-88-78
o 46-80
o 47-115-51-50
o 52-53-54
o 77-71-123
o 119-132
o 40-87-13-EARPHONE
o 121-26-48-116-62-60-59-57-56-84-82-14-EARPHONE
Schematic
EP-130_62315RevC.qxp_EP-130_062812 6/23/15 11:17 AM Page 69