Friday, July 22, 2011

The Light Listener


As with anything new, listening to light might sound like just a bunch of noise, but over time a trained ear could distinguish the difference between hundreds if not thousands of sources. Eventually, you could detect the subtle differences between a TV and fluorescent room lights, or between a flashlight and car headlights.

Some light sources are completely invisible to the human eye (infrared and ultraviolet) and can be converted easily to sound. Infrared remote controls give off coded light signals that make easily discernable tones for each different function of the remote. Everything from LEDs to fireflies make a sound with the light that they emit.By building this simple circuit you can listen to the light that you encounter on a day to day basis.

Listening to Natural Lights

Lightning flashes produce sharp clicks and pops. These sounds are picked up from the flashes of light and have no direct relationship with the sound of thunder that is heard much later after the lightning strike. Nighttime is the best time to listen to sounds produced by the light from lightening. It’s also possible that you will be able to hear sounds from lightning flashes that can not be seen by the human eye. Obviously, being outside in a lightning storm isn’t the safest course of action. If you intend to “listen” the lightning flashes, do it from inside a house or car.

Flames produce many different sounds. When the air is still, a soft rushing sound is heard. When the flame is disturbed by moving air, crackles and pops are heard. These sounds are seperate from the sounds emitted by a the fuel such as wood or wick that is reacting as it is burned.

Sounds can also be detected from winged insects that are flying in sunlight. When their wings reflect light to the detector, a buzz or hum will be heard. At dusk, a nearby firefly will produce a soft click for each flash. These sounds are independent from other physical sounds created by insects such as the hum of their wings moving air.

Sunlight can also produce sounds that can be detected by the listener as the sunlight is filtered through leaves, reflected off of windows, and passed through the gaps in a picket fence; resulting in a pop, pop, pop sound.

Listening to Artificial Lights

Flashlight beams, when swept across the light listener at different speeds, will create different sounds ranging from a soft swoosh to sharp pops. Tap the flashlight with a pencil and a ringing sound will be heard as the filament vibrates.

The headlights of cars, trucks, and motorcycles will produce a distinctive ringing sound when the vehicle is moving on a rough or bumpy road. The various rings can sometimes create what some describe as singing.

Electronic Displays are usually powered by rapid pulses of current. The flashes are merged into continuous light by the slow response of the eye. They can, however, be heard clearly as a buzz or a hum with the listener.

The displays of older televisions and computer monitors are formed by sweeping an electron beam across a phosphor coated screen. The light listener will transform that pulsating phosphor into a recognizable pulsating buzzing sound.

With a light listener circuit and a little time on your hands, you can listen to the sounds of the visible, and sometimes invisible, world around you as broadcast by light.

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