Elizabeth (9) asked “If you picked up a shell from the beach and put it close to your ear why does it have the sound of waves?”

 

Elizabeth, I think we need to do some experiments, firstly did you know that sound can be reflected? Sound can be reflected like light, and like light the surface it bounces off can affect the bounce. Try reflecting sound using a mirror (preferably plastic). You could use a loud ticking clock as a sound source. You then use your ears to detect the reflection. Now cover the mirror with some paper see how it affects the reflection. You might have some difficulty in making the experiment ‘fair’ but never mind (a sound detector would help make it fairer).

Now instead of a shell, place (carefully) a cup over your ear and listen. Replace the cup with a closed cardboard tube and listen. Do you hear anything? You might hear a low quiet whistling sound. Try making the tube shorter/longer and see how it affects the sound.

How was what you heard different from what you heard when you used the shell? What is the difference between the surface of the cup and cardboard tube and the shell surface?

My thoughts are that we are living in a ‘sound’ environment. Putting the cup over our ear cuts out most of the sound but not all of it. We call that an ambient sound. This sound manages to enter our cup and it is bounced around in the cup, but inside a shell the bouncing is slightly different.

Let me know what you think by filling in the Reply box below and post your comment or ask another Question . Anybody can do this.

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