This experiment is one that I have noticed while doing my electricity shows. I use a balloon in the show to demonstrate positive and negative static charges. While holding this balloon, I noticed that I could feel a variety of sounds, especially when I was using a microphone and loud speaker.
For this experiment, you will need:
- a balloon (Small, cheap balloons seem to work best.)
- A variety of sound sources
Inflate the balloon and tie it off, so that it stays inflated. Hold the balloon loosely in one hand, about 1-2 feet in front of your face. Now talk. Sing. Laugh. Notice the way the balloon vibrates as you make sounds.
Try holding the balloon near a television or radio. Do you notice that you can feel some sound more than others? Try feeling very high pitched sounds and very low pitched sounds. Is there a difference?
How can you feel sound? To understand this, you need to know a little bit about how sound works. Hold your fingers lightly against your throat and hum. You will feel your throat vibrating, just as the balloon did. When something vibrates, it causes the air around it to vibrate. The vibrations spread through the air, just as ripples spread across a bathtub of water when you wiggle your fingers on the surface of the water. As these vibrations spread out through the air, they can cause other things to vibrate. When the vibrating air hits the balloon, the balloon vibrates too.
This is what lets you hear. When the vibrating air hits your eardrum, it causes your eardrum to vibrate, just as the balloon did. These vibrations are transferred through the tiny bones in your ear to the inner ear. These vibrations are detected by nerves, which send impulses that your brain "hears" as sound.