The effect of resonance on rice [WARNING: see "Description"]

youtube.com — WARNING! This video contains ultra-sound frequencies that may be harmful for your pets or young family members! This is a display of membrane resonances: powerful speaker is connected to a tone generator and covered by plywood. Lose rice, when poured on top, forms unique geometrical shapes. This effect might explain some famous crop circles. Mar 31, 2008 View in Crawl 4