Tapping into the noise - building a contact microphone

There is a constant humming in the wires above.

We are told that at either end sits a small terminal box that listens carefully and modulates the cosmic pulses to find what is useful.

But in recent years, the wires have stretched out. The terminal has receded to some unattainable point in the distance. We find ourselves in the open: Alone and listening, but unable to separate the signal from the noise.

Parts needed

• Piezo disk
• scraps of wire
• audio jack socket
• something to amplify and listen with
• soldering iron and solder (optional)
• something to secure the mic in place (optional)

Instructions

Sound doesn’t only travel through the air. A contact microphone picks up the sounds from inside of solid objects. You can shout as loud as you want, the contact mic can’t hear you. But if you stick it to a wooden board and scrape a nail across it you can hear the sound of the wood grain resonating, crushing the piezo crystals and generating a small electric field.

Doesn’t work? Make sure your contact mic is connected to an amplifier of some sort; PC speakers will work if they’re turned all the way up. Disconnect the wires and try them the other way around, then try the first way again.