The Keening Factory

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Materials

• Plastic Cup
• Yarn and Paperclip
• Wet Paper Towel
• Plastic Straw

What to Do: Plastic Cup Chicken Squawk

1. Tie one end of yarn to the middle of the paper clip
2. Push the other end of the yarn through the hole in the plastic cup and pull it through.
3. Get a piece of paper towel about the size of a dollar bill, then fold it once and get it damp in the water.
4. Hold the cup firmly in one hand, and wrap the damp paper towel around the string near the cup.  While you squeeze the string, pull down in short jerks so that the paper towel tightly slides along the string.  You should hear a chicken sound.

How Does it Work?

This is an example of how a sounding board works.  The vibrations from the string would be almost silent without the cup, but when you add the cup, it spreads the vibrations and amplifies them.

What to do: Plastic Straw Horn

1. Flatten one end of a plastic straw.
2. Cut the flattened end to a point.
3. Blow hard through the pointed end to get sound.
4. Add straws to make different sounds.

Discussion

What are the properties of sound that make these experiments work?

Why do different lengths of straws make different sounds?

Does the string make a sound without the cup? Why or why not?