Sound Cameras

~~~~ NEW 6/21/08: Listen to the archive of sound camera recordings here. ~~~~

Although human eyes are marvelous sensors, they don’t tell us the whole story. The effect called persistence of vision limits our ability to percieve rapidly changing light sources. Thus if a light source is blinking or modulating faster than about 20 times a second, it appears continuous. However, there are many types of light around us that oscillate and modulate much faster than that, coming from both nature and technological sources. I’ve been curious to hear these modulations for quite a while.

Recently I’ve begun designing electronics to convert film cameras into audio transducers, or optical microphones. Obsolete 8mm film cameras are exciting to work with, partially because their design aesthetics are so different than what you get with new products today. Besides that, the 8mm format interfaces nicely with the size of semiconductor light sensors - not too big, not too small.

In the process of converting a camera, the film transport and shutter are removed, so I prefer to work with “dead” specimens rather than destroy a marvelous working machine.

My standard modifications include a battery-powered preamp with audio line-out (1/4″ mono jack) + a viewfinder-mounted LED that indicates sensor overload, and a headphone amplifier (1/8″ jack).  I’ve prototyped an accessory mount that holds the sound camera steady along side a video camera, focused on the same point for audiovisual recording.  Experimental field recording using this technique will appear in an upcoming documentary by John Moore.

Trilux Lumicon 8-III camera w/ sound camera modification

Looking through the viewfinder, you see a normal image. The light sensor’s active region corresponds to a tiny spot in the center of the viewfinder; sweeping the camera across a scene can reveal different sounds, and their source can be pinpointed easily.

Using the Lumicon, I experimented with sonification of vibration in drops of water from a faucet. I focused the sound camera on the point where the drops hit the sink basin, and illuminated the area with an LED flashlight. First you hear a stream of water, then I adjust it to drip slowly; we hear strange modulations after every few drops, presumably from vibrations in a small pool of water:

sonification of dripping water

In another experiment, I recorded the sound of the sun as it rose at dawn. The sun sounds awesome, it is a roaring blast of pink noise! (in the middle of this recording, I put my hand over the lens, as a control experiment to separate the sun’s noise from the amplifier’s intrinsic hiss)

Sound of Dawn

I showed this to my stepfather Dr. Christopher Gurgiolo, a geophysicist involved with NASA and ESA (European Space Agency) satellite research. Here is some of his insight:

“I think that when you listen to the sun you are really listening to
the atmosphere. There are so many scattering centers there (density
bubbles) that there should be significant light modulation - not that
you can see it but you should hear it.

… Too bad you’re not in Alaska. Point that thing at an aurora and you
probably would hear a full concert. There the light intensity varies
both in reponse to the atmosphere and the electromagnetic instabilities
generated by the incoming accelerated electrons.”

Hell yeah! Someday I’m going to be in Alaska to listen to the aurora borealis! It would be incredible to pair the sound camera with a natural radio receiver.

So, that’s some of the stuff I’ve heard in nature with my sound camera. But what about art and music? What can we do with it for creative purposes?

Several 20th century experimental musicians have already opened up the field of lightwave modulated music: Daphne Oram, Jacques Dudon, … (this list will be expanded). Indeed, in 1880, Alexander Graham Bell was already experimenting with voice communications on a modulated beam of sunlight with a device he called the Photophone…

Since this page is a work in progress, I will stop here for now… but finally, here’s a recording of a musical performance technique I’m developing involving a feedback loop between the sound camera and an oscilloscope.  It is played by moving the hand in the space between the camera and scope… ’nuff said about that for now though : )

oscilloscope feedback technique