What sound is
Sound is made of vibrations, tiny back-and-forth wiggles. When you clap, pluck a guitar string or talk, the air shakes in waves. Those waves travel to your ears.
Try it: stretch a rubber band and pluck it. You can see it wiggle and hear it hum at the same time.
Fast wiggles make high sounds, like a bird's tweet. Slow wiggles make low sounds, like a big drum.
The outer ear and the eardrum
The part you can see is your outer ear. Its curvy shape catches sound like a funnel and sends it down the ear canal, a short tunnel into your head.
At the end of the tunnel is your eardrum. It's a thin, tight skin, like the top of a drum. When sound waves hit it, it vibrates.
Your ear canal makes earwax. It may look yucky, but it's helpful! It traps dust and germs, and it slowly moves out of your ear on its own.
Three tiny bones and a snail
Behind the eardrum are the three smallest bones in your body. They are nicknamed the hammer, the anvil and the stirrup. The stirrup is about as big as a grain of rice.
When your eardrum vibrates, these little bones pass the wiggles along and make them stronger.
Next comes the cochlea (KOK-lee-uh). It's curled up like a snail shell and filled with liquid. Inside are thousands of tiny hair cells. When the liquid ripples, the hairs bend and send messages to your brain along a nerve.
Different hair cells answer to different sounds, high or low. Your brain puts it all together, so you can tell a giggle from a dog's bark.
Your balance sensors
Your ears have a second job: balance. Next to the cochlea are three small loops called semicircular canals. They are filled with liquid too.
When you tilt or turn your head, the liquid sloshes, and tiny hairs feel it move. They tell your brain which way you are going.
When you spin around and then stop, the liquid keeps swirling for a moment. Your brain thinks you're still turning, even though you've stopped. That's why you feel dizzy!
Your eyes and the feelings in your feet and muscles help you balance too. Try standing on one foot with your eyes closed. It's harder, isn't it?
Keeping your hearing safe
The tiny hair cells in your cochlea do not grow back once they are hurt. So it's important to protect them.
Very loud sounds, or loud sounds that go on for a long time, can harm them. Think of fireworks, very loud music in headphones, or power tools.
Here's a simple test: if you have to shout for a friend an arm's length away to hear you, it's too loud. Turn it down, move away or cover your ears.
Earplugs or earmuffs help at loud places like car races, concerts and fireworks shows.