apparently different pitches of sound affect different bits of the body. thus, a high-pitched noise makes you cover yer ears, bass sounds at a gig / club you can feel in the pit of your stomach, and deeper bass sounds can make you cack yourself. as demonstrated by wanky subversives Psyckick TV (sic?) in a wee club in germany in the 80's, when they managed to make the entire audience, um, 'follow through'.

:)
"You know, for a long period of time we thought oceans could protect us from danger"
(George Bush, 25th Sept 2003)