Why do we hear the sea in a seashell? -Steve, Minnewaska School, Minnesota 

Dear Steve,

Whenever us cats go to the beach, we tend to keep a safe distance from the water and like to explore the shore. I once stumbled upon a big, beautiful pink and white seashell.

When I put my ear up to it, I heard the familiar sound of whooshing waves. While there wasn’t actually an ocean inside, I figured the sound had to be coming from somewhere. So, I decided to investigate. You can try it out, too.

First, close your eyes and listen without a shell. Well, I suppose you are interested in reading this so you may not want to close your eyes, but definitely take a listen.seashell.dru

Perhaps you hear people talking, music playing, or a cat meowing. These sounds travel as waves from their sources at 761 miles per hour. When the waves reach your ears, they make your eardrums vibrate, and you can hear the sounds.

Just like a ball, these sound waves can bounce. A shell has a hard and curved surface. It is pretty good at reflecting, or bouncing the sounds around.

That’s what I found out from my friend Allison Coffin, a scientist at Washington State University. Her research helps people who experience hearing loss.

“When we hold a seashell up to our ear, we don’t actually hear the sea,” she said. “What we hear is normal sound from the environment we are in at the time—whether that’s your bedroom or the beach.”

As the sound waves bounce around inside the shell, they get a bit distorted, Coffin adds. A shell is a good kind of resonating device as air vibrates through it’s hollow inside.

It’s similar to the phenomenon of blowing across an empty glass bottle to make a whirring sound. Scientists can use their knowledge of how sounds move through different spaces as they engineer car engines, create musical instruments, and even reduce noise in planes.

You can find out more about how this distorted sound works by playing with some sound waves. Grab a shell, a cup, a mug, or even a toilet paper tube. You can also just place your hand around your ear and cup the end with your other hand.

Put one of these listening devices up to your ear and walk into rooms with different sounds. Listen to how the sounds in the shell change as you move from room to room. You might even try it out in a quiet room to hear what happens.

If you already happen to be standing on the beach, then you might just pick up on the sounds of the actual sea. After all, when you hear the sound of the sea in a shell, you are really hearing a combination of all the sounds around you at that very moment.

Sincerely,
Dr. Universe