56:(for example, a picture on a wall) in response to the pressure waves created by noises present in the room. The object preferably should have a smooth surface for the beam to be reflected accurately. The laser beam is directed into the room through a window, reflects off the object, and returns to a receiver that converts the beam to an audio signal. The beam may also be bounced off the window itself. The minute differences in the distance traveled by the light as it reflects from the vibrating object are detected
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in free air ("Particulate Flow
Detection Microphone based on a laser-photocell pair with a moving stream of smoke or vapor in the laser beam's path"). Sound pressure waves cause disturbances in the smoke that in turn cause variations in the amount of laser light reaching the photo detector. A
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eavesdropping system. This worked by using a low power infrared beam (not a laser) from a distance to detect the sound vibrations in the glass windows.
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prototype of the device was demonstrated at the 127th Audio
Engineering Society convention in New York City from 9 through 12 October 2009.
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The object is typically inside a room where a conversation is taking place and can be anything that can
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The technique of using a light beam to remotely record sound probably originated with
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in a distant object. It can be used to eavesdrop with minimal chance of exposure.
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was issued for a device that uses a laser beam and smoke or vapor to detect
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in the Soviet Union at or before 1947, when he developed and used the
189:"Schwartz Engineering & Design Laser-Optic Microphone Prototype"
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224:"Special Section: Leon Theremin, Pioneer of Electronic Art"
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259:. Urbana, Illinois: University of Illinois Press.
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300:Smoke and Laser Mic Prototype Two Demo
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255:Theremin: Ether Music and Espionage
234:. Translated by Vladimir Chudnovsky
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195:. 20 Oct 2009. Archived from
329:. You can help Knowledge by
283:Smoke & Laser Microphone
141:Optical heterodyne detection
126:The Thing (listening device)
27:Acoustic surveillance device
396:Inventions by Léon Theremin
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222:Galeyev, Bulat M. (1996).
18:Buran eavesdropping device
391:Covert listening devices
294:New Mic Proof of Concept
251:Glinsky, Albert (2000).
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121:Laser Doppler vibrometer
325:-related article is a
228:Leonardo Music Journal
131:List of laser articles
90:U.S. patent 7,580,533
302:, David M. Schwartz
296:, David M. Schwartz
87:On 25 August 2009,
58:interferometrically
38:device that uses a
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386:Surveillance
331:expanding it
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236:. Retrieved
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201:. Retrieved
197:the original
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36:surveillance
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381:Microphones
290:), Gearwire
177:Glinsky 261
370:Categories
238:2007-11-22
216:References
111:Photophone
98:vibrations
47:vibrations
323:espionage
193:Gearwire
105:See also
163:Galeyev
64:History
54:vibrate
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203:21 Oct
321:This
147:Notes
95:sound
74:Buran
44:sound
40:laser
34:is a
327:stub
288:here
261:ISBN
245:LMJ6
205:2009
82:KGB
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