LITE2SOUND

This is a sensitive lightwave reciever that lets you explore the hidden sounds of modulated light.  Its not a synthesizer; its more like a microphone.   LITE2SOUND is a simple kit with 24 parts that solder to the board.  It has a ¼” line output jack and runs on a coin cell battery.  A detailed step-by-step assembly tutorial has been thoughtfully prepared by sound artist Rudi Giot; it can be viewed here.

lite2sound may be mis-spelled light2sound, lighttosound, litetosound 

 lite2sound kit contents lite2sound assembled pcb

lite2sound case fit lite2sound case long pickup

10/15/09: Lite2Sound is OUT OF STOCK.  A redesigned version is being planned.

The pickup is a photodiode on 8″ flexible cable.  It connects to LITE2SOUND with an RCA plug.  Its detachable so you can experiment with making your own pickups - just cut an RCA cable, strip the cut end, and solder a photodiode to the leads.

To hear LITE2SOUND, plug it in to a guitar amp, effect pedal, mixer, or the mic input of a recording device.

LITE2SOUND reveals unusual sounds.  For instance, pointing it at a computer CRT yields a strange humming tone that varies depending on what the screen is displaying.  The LED in an optical computer mouse plays strange chirping whistles.  Infrared remote controls make wild bursts of noisy data.  You’re hearing frequencies from lines of code executing in a microprocessor… stuff that was never intended to be heard.  When you combine LITE2SOUND with a laser pointer, things get really interesting.  There is bizarre audio from a vinyl record as it spins on the turntable, using a laser instead of the needle.  Listening to reflected laser light as you move it over the surface texture of objects is often a surprise; it plays the texture like a phonograph needle.  You can even pick up unusual sounds from a guitar string as the laser reflects off of it.  There are still many things to try…

Of course, not every light source is modulated.   For example, LEDs running on pure DC are inaudible.

Here are some samples recorded with LITE2SOUND.
Click on multiple icons below to mix your own optical sound collage!

Light bulbs
incandescent
Fluorescent
Neon

LEDs
optical mouse
LED message sign
7-segment LED number display
computer hard drive activity light
infrared remote control

screens
CRT monitor
CRT monitor + mouse
cellphone screen 1
cellphone screen 2

vacuum fluorescent displays
sony receiver
flashing digit on cd player

Laser pointer reflections
vinyl record sample 1
vinyl record sample 2
surface texture of fabric
vibrations from music instruments
Eavesdropping (?)

 

The signal level can vary from mic level to line level depending on what you’re observing, and how strongly the light source is modulated.  You can’t usually judge this with your eyes; some light sources appear bright but aren’t modulated deeply.  Other sources can appear dim or dark but are strongly modulated, such as infrared remotes and LED message signs.  Other lights are bright but not modulated at all, like status LEDs on some electronic devices, and any LED running on DC power.

If LITE2SOUND receives too much light, its output goes silent temporarily.  You can compensate for this by switching it to low gain, moving the pickup further from the source of the light, or by changing the angle of the pickup.  For example, direct sunlight or shining a laser directly into the pickup will overload it.

So what’s really going on here?

We are surrounded by light. Our eyes detect it and provide details about color, brightness, and motion. They are limited though by the physiological effect of persistence of vision, which limits our perception of rapidly changing light intensity to a low bandwidth; for instance, theatrical film runs at 24 frames per second but gives the impression of smooth motion. Compare this to the bandwidth our ears can receive; 20 - 20,000Hz (Hz = hertz, cycles per second) being the quoted figure for normal human hearing. So in a way, our ears pick up where our eyes leave off; visual events faster than about 20Hz are perceived as continuous, and sound waves below 20Hz are inaudible.

Many modern technologies create modulated light at high frequencies; CRT monitors, infrared remote controls, fiber optic communications, laser barcode scanners, etc. are deliberately engineered sources of modulated light. Light bulbs are the most common source of modulated light in our living environment.  Lighting that runs off of the AC grid is modulated at 60Hz and its harmonics. If our eyes were to communicate this to our brains as sound, we would hear a very strange electronic hum and buzz around us almost all the time.  Its interesting to hear the different tones from various types of bulbs.  Neon, fluorescent, and incandescent all sound different.  Neon has a distinct buzzing sound like an electric arc;  incandescent has a characteristic warm low frequency sound.

Modulated light has been used for music and audio in various ways. At one time, analog audio was encoded onto celluloid movie film as a stripe of varying density beside the image frames. A light shining through this stripe is modulated as the film passes, and the modulated light was picked up by a photosensitive device. From that point, the sound waves return to the electronic realm and are amplified and heard through speakers.

There is also an interesting keyboard instrument called the optigan (optical organ) that produced melodic and percussive sounds via a similar technique, although the optigan was based on a spinning disc rather than a strip of film. The optigan played discs containing many concentric tracks of audio waveforms encoded as dark/light patterning using a photocell-based light pickup system. It can be considered along side the mellotron as a pioneering step towards sample-based music.

Sound artist Derek Holzer has prepared an excellent historical timeline of optical musical instruments as part of his research, called A Brief History of Optical Synthesis, covering creative and advanced ways that people have used light to generate music.