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Behold the World's First Laser Microphone


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Smoke and Lasers Could Disrupt Microphone Market
David Schwartz, who laid the foundation for MP3 with his undergraduate and Ph.D. work in the 80s, has another big idea: a microphone that uses lasers and smoke to detect the minute variations in air pressure the rest of us call sound.

His invention appears to be the worlds first laser microphone, and it works by streaming smoke across a laser beam aimed at a very, very fast and sensitive photocell designed for fiber-optic networks. The photocell converts variations in the beam into electrical signal that carries the audio signal.

Wired.coms exclusive video of Schwartzs second prototype, below, shows his design in action. Its sound quality leaves a lot to be desired, and Schwartz knows it. Its really crappy audio, he explained, but at this point, were at what I call the talking dog phase of the project. We dont care if the dog is delivering a Shakespeare sonnet its just the fact that the dogs talking.

Schwartz plans to demonstrate a prototype at the 127th annual Audio Engineering Society convention next month in the hope that a manufacturer will license the patented technology and take it to market. He said that could happen as early as next year, with the resulting microphones for professional onstage applications costing $1,200 and up (assuming the standard retail markup of four times the cost of parts). Less-expensive lavaliere and portable microphones are not out of the question, he said, because the smoke chamber, laser and photocell can each be made smaller and far more cheaply $5 or so if produced on a mass scale.

As far as I know, and Ive been an AES member for 25 years, nobody has ever made a laser-based microphone work. Were the first, said Schwartz. And were the first change in audio-transducer technology since day 1. Theres been a mechanical element in every microphone since [douard-Lon] Scotts very own first phonautograph in 1859.

The idea to pick up sound optically rather than with a mechanical diaphragm came to Schwartz in classic inventor fashion as he spaced out during a conversation with his wife:

In 2004, I was having a fancy holiday dinner with my wife at a nice white-tablecloth restaurant, a really dark and romantic place, recalled Schwartz. They had one of those little oil-lamp-candletype things on the table, you know, for atmosphere, and that oil-based, floating-type candle, it was sending up a solid little white stream of smoke. And I noticed, every time my wife said something which was all the time the smoke column would wiggle. When she wasnt talking, the smoke column looked like a string hanging in the air. And it dawned on me that the air coming out of her mouth [and the resulting] changes in air pressure were passing through that smoke [and interfering with it].

Two days later, I was replaying that scene in the restaurant, it kept coming back to me like, why am I replaying these inane conversations in my head? And I realized it wasnt the content of the conversations; it was because of what I was seeing. It was obvious to me that we could pass a laser through the smoke to detect those changes.

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