- a paper cup
- a paper clip
- a two foot piece of string (they say kite string, but we used regular sewing string)
- and a needle
Tie one end of the string to the paper clip, and thread the other through the needle. Then, poke a hole through the top of the cup, and pull the string through...
...until the paper clip is tight against the top of the cup, and the string is hanging down, through the open end of the cup.
Wet the string.
Then hold the cup with one hand, and grasp the string lightly with your forefinger and thumb, just under the cup, pull down, and repeat.
As you run your fingers down the string, it vibrates. The vibrations move the air inside the cup, and the shape of the cup amplifies the sound. If you use your imagination a little, it sound like the cup is laughing.