Hearing yourself again

The idea

An echo is a sound heard again after it reflects off the hard surface of a distant object and comes back to the listener.

Shouting at a cliff

Rohan stands in front of a tall cliff and shouts "Hello!". A moment later he hears "Hello!" again.

Where do you think the second "Hello!" comes from?

• The sound bounced off the cliff and came back
• Someone else on the cliff repeated it
• The first sound never left his ears

Follow the sound

Press Next step.

A returning sound

An echo is your own sound coming back. It needs a hard surface of a distant object, like a cliff, to reflect the sound.

An echo is a sound heard again after it reflects off the hard surface of a distant object and comes back to the listener.

Notes

An echo is a sound heard again after it reflects off the hard surface of a distant object and returns to the listener.

Check yourself

What is an echo?

What happens to the sound when it hits the hard surface of a cliff?

Where might you hear an echo?

Rohan hears an echo of his shout from a cliff. What did the sound do?

• A sound that does not reach the listener. An echo is heard because the reflected sound does come back to the listener.
• A sound made by a vibrating tuning fork. An echo is a reflected sound that is heard again.
• A sound heard again after it reflects off a distant hard surface — correct. Yes!
• It is reflected back towards the listener — correct. Yes!
• It stops completely. In an echo the sound reflects off the hard surface and comes back to the listener.
• It turns into light. The sound is reflected as sound and comes back to the listener.
• Inside a vacuum. Sound cannot propagate in a vacuum, so there is nothing to reflect or hear.
• Near a mountain, near a cliff or in a long corridor — correct. Yes!
• On a soft cloth. Soft surfaces absorb sound. Echoes come from hard surfaces of distant objects like a mountain, cliff or long corridor.
• Travelled to the cliff and stayed there. He hears an echo because the reflected sound comes back to him.
• Stayed near Rohan the whole time. The echo is the sound that travelled to the cliff, reflected off it and came back to him.
• Travelled to the cliff, reflected and came back — correct. Yes!