Vibration of Objects> Sound, beautiful sound! Loud sounds, soft sounds, high sounds, low sounds - I love them all! But just what IS sound? Sound is what we hear, that’s clear. But what? And how? And why?
To a scientist, sound is a special kind of energy, carried through the air as invisible vibrations that our ears can pick up. But most of those invisible vibrations in the air start out as very visible vibrations of something you CAN see: a string, a gong, a drum head, etc.
And even if you can’t see the vibration that makes a sound, you can still sometimes feel it. Touch the front of your <#5676,11><!throat> when you hum or talk. Feel the vibrations? When something vibrates, it moves quickly back and forth. It’s this back and forth vibration that makes sound.
When you strike the gong, it vibrates rapidly back and forth. As the gong moves back and forth, it pushes or squeezes on the air next to it, and then lets it spring back. Back and forth, back and forth. Squeeze, relax, squeeze, relax. The vibrating gong starts the air vibrating on its own, and these air vibrations travel outward in all directions. We call these squeeze-and-relax vibrations of the air sound <#5675,6><!waves>.
Here’s a simple experiment: Take a rubber band and stretch it between two fingers of one of your hands. Pluck the rubber band with your other hand. Twaannngg! Hear the sound? Feel the vibration? See the moving rubber band? As the rubber band moves quickly back and forth, it pushes and squeezes air as it moves out, then lets it return as it moves back. The vibration of the rubber band makes the air vibrate in turn. When the rubber band stops moving, there’s no more vibration, and the sound stops. To make a sound, make something vibrate!
