Thursday, October 29, 2009

Laser/Smoke Microphone

American digital audio pioneer David Schwartz, who invented the MP3 sound format, has come up with a novel new type of microphone. Sound reproduction can be used for many applications including military, security, recording industry, entertainment and smoking (checking to see if you are still awake). Traditional microphones have used diaphragms. The diaphragm reacts to sound and the measured results of deflection is what we know as sound reproduction. The problem with this method is that the accuracy of the reproduction is reliant on the diaphragms ability to react. Since diaphragms are made of various substrates the reaction will be different for each substrate. Each substrate will have it's own inertia, resistance, and mass. These variations ultimately color the sound reproduction with their unique attributes. Enter the Laser/smoke microphone. The lack of mechanical interference virtually eliminates the microphones effect on reproduction of sound.

The laser/smoke microphone is the lucky combination of technology that is now commonplace. We use lasers daily in our lives at the grocery store checking out, during workplace presentations, in our CD players and even in surgery. How does this new technology work? A laser beam is passed through a column of smoke to detect the deflections that sound waves cause in the smoke particles. As each smoke particle is virtually weightless, the theory is that they will deflect in ways that much more closely follow the contours of the original sound wave. The microphone is currently in a very early prototype stage, but Schwartz is already able to take a low-quality signal from it. See below:

The use of light in sound transduction isn't new - in fact, it can be traced at least as far back as Leon Theremin's

infrared remote eavesdropping system in 1947, which used an infrared beam to detect the sonic vibrations in glass windows. More modern surveillance laser mics work by measuring the vibrations in any surface that is free to vibrate with the sound waves.
Audio engineering is an arena which leaves a vast crevice for exploration. In my former life I used light and chemical synthesis for nanometer size etch patterns. Sound might be the solution for light in this circumstance as light uses chemicals in a fiduciary manner while sound can physically move particles. I digress....

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