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Project #236
OBJECTIVE: To show how sound waves travel on a
Sound Wave Magic
Project #237
OBJECTIVE: To amplify sounds from the
Build the circuit, turn on the switch, and press the press
switch (S2) several times. You will hear loud space war
sounds, since the sound from the space war integrated
circuit is amplified by the power amplifier integrated
circuit. Nearly all toys that make sound use a power
amplifier of some sort.
Space War
Amplifier
Build the circuit shown on the left and connect the speaker using the two (2)
jumper wires. Then, lay the speaker on a flat hard surface.
Setup: Use some paper and scissors to cut out a rectangular pattern. Use
the one shown below as a guide. Use colored paper if available. Fold at the
points shown. Scotch tape the corners so the tray has no cracks at the
corners. Place the tray over the speaker and sprinkle a small amount of white
table salt in the tray. There should be enough salt to cover the bottom with a
little space between each salt grain.
Sound Magic: Turn on the circuit by closing slide switch (S1). Adjust the
adjustable resistor (RV) for different pitches and watch the salt particles.
Particles that bounce high are directly over the vibrating paper and ones that
do not move are in the nodes where the paper is not vibrating. Eventually, all
the salt will move to the areas that have no vibration, and stay there.
Change the position of the tray and the material used to create different
patterns due to the sound. Try sugar and coffee creamer, for example, to see
if they move differently due to the sound waves.
Paper Tray
Salt
Sample Cut-out Pattern
(fold)
(fold)
(fold)
(fold)
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