How to do it

1. All you need is a drinking straw and a plastic cup filled with water.
2. Put one end of the straw in the water and blow across the other end with your mouth.
3. When you move the straw deeper into the water, the tone changes.
4. When you blow across the top of the straw trombone, the air inside vibrates and you can hear a sound. Sound is made of vibrations.
5. The straws make different sounds when you put them in different depths of water because the air is vibrating differently.