What to do with this activity?

Sound is vibration that travels through the air or through another medium (like water or a metal sheet as below) before it reaches our ears and is re-interpreted as sound by our brain. 

If you throw a rock into a pool of water it creates water waves that travel out from the rock in a circular pattern. Sound travelling through air is similar to this - the molecules of air pulse outward from where the sound was created. If your child would like to read more about sound and vibration have a look at this link from Kids Discover.  

Over two hundred years ago a German scientist and musician, Ernst Chladni, showed what amazing and beautiful patterns sound vibrations can make (see the picture above). He used a thin metal plate that vibrated when stroked with a violin bow. Look at this video to see Chladni's experiment demonstrated by some musicians. The sounds make different parts of the metal plate vibrate in different directions. The sand settles on the parts of the plate that don't move (called nodal lines).

All you need to know is that vibrations cause different and beautiful patterns to form.