Great question. Sound takes place when a
vibration (in the form of a wave) passes through a
substance like air, or water, or something hard
like a rock, and is understood by our brain.
How does that happen though? It all
starts with the outside of your ear.
Your ear (the part you can see on the side of
your face) is set up to focus sound waves
traveling through the air into your ear canal
(like a funnel with water). When the sound
waves are moving in your ear, they vibrate your
ear drum, which then vibrates little bones
connected to the ear drum. These bones,
shake and move a part of your ear that is full of
fluid, and based on how this fluid in your ear
shakes, can be understood by your brain that
something is making a noise.
This is how we understand sound. However, the
sound was caused by something. This source of
sound, like a rock falling, or me shouting, caused
the air (or water) around it to move.
Next time you take a bath, or go swimming, try
to snap your fingers or make a noise and see if
someone can hear it really far away. Water,
because it is a fluid, is really good at moving
sound - and things that sound pretty quiet in
air are louder underwater.
A fun question to think about is whether
something makes a sound if no one is around to
hear it. The famous one is "if a tree falls
in the woods, and no one is around to hear it,
does it make a sound?"
Is sound caused my something making a noise?
Is something a noise if no one hears it?
All the best!