Contact Mic

I made my first contact mic today.

I damaged it slightly when I was playing with it, but hasn't affected the sound at all.  I still need to find something to house it in, and I need an easy way to attach it to vertical surfaces with out it sliding off.  I read some where about someone using magnets to do it, which I may do.  But what about non metallic surfaces?

Got any tips?

I've got a lot of piezo discs lying around, so I'm going to be making more of these and experimenting with them.  In fact, next time I'll be building one with a FET buffer preamp, following the schematic and advice on this page (thanks to Durk Kooistra for sharing this with me).  I'll also be attempting to make a hydrophone. ^.^

Here's a little recording I made with it by pressing it against a USB fan:

Download: MP3/WAV