Have you seen sound ?
First of all , watch the video below and see for yourself what we are talking about.
Practically sound travels through a medium and cannot travel through an empty space ( vacuum ).
You can make sound visible by some tricks like the video shown above.
Sound is just the waves like the waves you see at beaches but, without sand and organic stuff 😛
The thing you saw is Chladni Plate invented by Ernst Florens Friedrich Chladni and is used to demonstrate frequencies. Sound is a wave of varying frequencies.
Change the frequencies and you will get different patterns. Voilà !!!
To know more about sound , click here