Strange sounds when you hit a metal rod

Visit my blog here: http://stevemould.com Follow me on twitter here: http://twitter.com/moulds Buy nerdy maths things here: http://mathsgear.co.uk When you hit an aluminium rod it vibrates in at least two distinct ways and you can hear that as two different sounds. Here's colcol83ful's image from the comments: http://imgur.com/Y4hGdP9 Great analysis, thanks colcol! - Music written by Tom Cusack