Visible Effects of the Invisible

It’s easy to make a model of the eardrum (also called the “tympanic membrane”) and see how sound travels through the air.

Materials:

Stretch a piece of plastic wrap over a large bowl or pot (any container with a wide opening will work). Make sure the plastic wrap is stretched tightly over the container. The plastic represents the eardrum. Place about 20-30 grains of uncooked rice on the top of the plastic wrap. Now you need a noise maker. A tin cookie sheet or baking tray works well. Hold the cookie sheet close to the plastic wrap. Hit the cookie sheet to create a “big bang” noise and watch the rice grains jump.

The “big bang” produces sound waves (changes in air pressure) that cause the plastic sheet to vibrate, which causes the rice grains to move. Sound waves vibrate the eardrum in much the same way.