Pluck a guitar string — it wobbles back and forth. As it wobbles, it pushes the air. The air bumps the air next to it. And on, and on, until that wave of pushed air bumps your eardrum. Your eardrum wobbles too — and your brain calls that sound.
Put your hand on your throat and hum 🎶 — you'll feel the vibration. Your voice box is the wobbling thing.
If something wobbles slowly, you hear a deep, low note (like a big drum). If it wobbles fast, you hear a high, squeaky note (like a whistle). Move the slider — listen, then look at the wave drawn on screen.
The size of the wobble decides how loud something is. We measure it in decibels (dB). Whisper = small wobble. A rocket launch = enormous wobble.
In space there's no air. So nothing to wobble, no waves, no sound. If you screamed in space, the astronaut next to you wouldn't hear a thing. They'd have to use a radio (radio waves are different — they don't need air).
Sound travels fastest through solids (try clinking spoons through a table), slower through liquids, and slowest through air. Light is way, way faster — that's why you see lightning before you hear thunder.
Every musical instrument, every voice, every door slam — all the same recipe. Something wobbles → it shakes the air → the air shakes your eardrum → your brain says "sound!"
Fast wobbles make high notes. Big wobbles make loud sounds. Take away the air, take away the sound.