Sci Fri: Sound Vibrations

The Secret Gong!
Such a simple experiment that produces such surprised smiles.
http://www.fizzicseducation.com.au/Free+experiments/light+and+sound/coathanger+gong.html
(wire clothes hanger version)

http://www.kcedventures.com/blog/the-science-of-sound-waves-an-awesome-experiment-for-kids  (spoon version)

EXPAND ON SOUND VIBRATION
Seeing Sound. http://coolscienceexperimentshq.com/how-to-see-sound/