Sound travels in waves.

The waves are caused by vibrations - motion back and forth.

If you bang on something, you cause it to vibrate - and to make sound. Depending on how slow or fast the vibrations are, that's how high or low the sound will be.

The more water, the slower the vibrations, and the lower the tone. The higher sounds come from the glasses with the least amount of water in them.

The Glass Band

For this experiment, find eight glasses. They don't have to all be the same size, but it's a little easier if they are. The glasses must be made of actual glass - plastic will not work.

Fill the first glass with the most water.

Fill the next glass with less water, and so on.

Take a spoon and listen to the sounds that the glasses make.