Echotube

How does the exhibit work?

Shout into the tube. You can hear your echo. Press a button. A valve in the tube seals the tube. Depending on which valve you close, you will hear your echo faster or slower.

What is the science behind it?

Do you hear the echo of your voice faster in the short tube (25 m) or the long tube (50 m)? That’s right, you hear it faster in the short tube. Twice as fast, in fact!

When you shout, you make a sound. That sound travels as waves through the tube, right to the end. There it bounces back and reaches your ear again. Then you hear your voice, but with a delay. We call this the “echo”. In the short tube, you will hear this echo sooner, because the sound does not have so far to travel. It only has to cover half the distance.

You only hear an echo if the distance is long enough. If the sound bounces back too quickly, you hear it (virtually) at the same time as the sound that you made. That’s why you don’t hear an echo in shallow wells, for example, but you do in very deep wells.

Echoes with animals

Some animals, like dolphins and bats, use echoes to find out where prey or obstacles are. They make a sound and then listen for the echo to estimate the distance and the direction. This is called “echolocation”

Echoes to look inside a body

How can you look at a baby that is still in its mother’s belly? It’s possible with echoes.

The doctor sends sound waves - that you can’t hear - through the body of the mother (and the baby). These waves come up against various tissues in the body. These bounce the sound waves back. A computer then converts these echoes into video images.

We call this technique “echography” or ultrasound. As well as babies, you can use it to look at your heart, bladder, kidneys, blood vessels and more.