how to make a pick up / microphone

You will need to make a device that transfers vibration into an electronic signal.
If your machine is using a "ferros" metal (eg something with steel in the vibrating / atenuating part you can use an electromagnetic pick up (like on a guitar). The principle is simple:
http://www.bbc.co.uk/dna/h2g2/A3176165
http://www.diyhappy.com/how-to-make-a-guitarbass-pickup/
If your machine is acoustic (ie: the sound it makes in real life is the sound you want to broadcast and it contains no ferros metal then you need a microphone. Again the principle is very simple - in fact you could use a speaker or a set of old headphones and just reverse the cycle - force sound into them and not out of - some links:
http://art.simon.tripod.com/stealth.html
http://www.oldbird.org/mike_home.htm
http://www.mp3forkidz.com/mic/

the net is full of info on this type of stuff - so go searching.