I’m always looking for new ways to grow my sound design repertoire. To that end, Loring and I here at 90 have started building a tool that many sound designers have in their toolbox for extracting something a little more obscure from the natural world we hear: a contact microphone.
When people think of a microphone, they probably imagine the common air microphone: an instrument which converts sound traveling through the air – air-borne noise – into the electrical realm. And that’s how we hear most sound, right? Through the air. But sound waves also travel and resonate through solid material objects – structure-borne noise. There are many sounds that can be picked up through structural transmission that can’t necessarily be picked up through the air. A contact microphone is a very cool device that does just that – picks up vibrational frequencies in solid materials.
I remember watching a National Geographic doc on insects and was amazed by how remarkably clear the sounds were of the tiny creatures they had filmed. The crunches of a spider chewing on its prey, the pitter patter of the tiny legs of a millipede as it crawls across earth, the crackle and pops of a butterfly breaking out of a cocoon. Capturing these practically inaudible sounds with such clarity is made possible by utilizing the contact mic. Check out how they captured the sound of a centipede walking (skip down to 3:40).
A contact microphone consists of simply a small ceramic disc (about 1.5 inches in diameter) glued to a brass disc, connected to audio wire that leads to… well, the electrical realm. The ceramic material has the inherent quality of being piezoelectric: meaning that any pressure applied to it will produce a small electrical current. Thus, any vibrational fluctuations the ceramic disc picks up can be transduced into electrical current, amplified and then recorded. This can lead to some very unique sounds, as recording audio through different materials can produce varied, sometimes surprising effects. Master Sound Designer Ben Burtt created his famous Star Wars laser gun sound (among many other sounds) utilizing a contact microphone, attaching it to an old radio tower guy-wire and striking the wire with a hammer. Here’s a quick demonstration:
Digging a little deeper into the use of this tool, I’ve discovered the contact mic can inspire all sorts of sonic creativity. Some of my favorite sound design artists employ this instrument quite frequently. So, of course, I decided to build one for myself! Loring and I ordered the parts and soon enough we’ll have a brand new contact mic to start making all sorts of unique sounds – like this!