are microphones you put in contact with a vibrating surface to pick up the sounds. Some examples are
a contact microphone is a piezo transducer. They can be plugged straight into guitar pedals and amplifiers, mixers and such, so they are really easy to use.
cost, where from and what type
They are very cheap, around 70p.
Electronic stores like maplin (link to product page), farnell, rs etc sell them.
They come in different sizes with different resonant frequencies, so get a few and try them all out for your application.
getting them ready to go!
- remove the original wires
- lightly sand the gold part so it holds the glue better
- resolder some new wires (about 2m long) in such a way so I can glue them down firmly
- use an epoxy resin to hold the wires (strain relief)
- solder a 1/4″ mono jack plug on the other end.
attaching them to a surface
there are lots of ways, but a really good one is to use magnets. These can then hold the mic tightly to a surface, but allow easy repositioning. They make very different sounds depending on where they are placed.