Physics, Fun and Beyond: Electrifying Projects and Inventions from Recycled and Low-Cost Materials

Playing with Sounds: Acoustics

1 Telephone With A Wire

Lend a new ear to the old can-and-string telephone.

Supplies

• 2 empty tin cans (like soup cans)

• 11 to 16 yd (10–15 m) of twine

• small piece of cotton or a candle

Step By Step

Make two holes in the bottom of the cans, right in the center. Pull the ends of the twine through the holes and tie knots so the twine can’t slip through when it is pulled tight (see the picture). Ask someone to place the can over his or her ear, and stretch the twine while you speak with your mouth very close to the other can. Try also placing the can on your forehead. Can you still hear sounds? Ask someone to ...