The acquired signal was post-processed to remove noise with analog technology available at the time.
#Laser listening device code#
The device code named "Buran" was reliable up to distances of 500 m, but it was ineffective in case of rain or fog. Early versions of this approach utilizing infrared beams instead of lasers in interferometer configuration were used as early as 1947 by the Soviet government. This article focuses mainly on one particular surveillance method: intelligence gathering through optical devices-informally known as laser microphones-aimed at windowpanes to pick up minute vibrations resulting from human speech in the room (see Fig. The financial loss due to the theft of proprietary information is estimated at several tens of millions of dollars each year in the United States alone. Owing to the influence of popular culture, covert surveillance is mainly associated with government activity, but private companies can also engage in industrial and economic espionage.
Products of the science of surveillance left classified research laboratories and have been turned into commercialized goods, allowing any person or organization with a sufficient budget to conduct long distance monitoring. The documented history of espionage goes back to several centuries and with the advent of different electronic devices added to the arsenal of governments and corporations, the importance of developing effective technical countermeasures has been escalating throughout the last century. Results are applicable only to reflected light-intensity systems, as the efficacy of the method cannot be confirmed without classified surveillance equipment with broader dynamic range. However, the analysis presented here also suggests that the use of a sinusoidal signal with a frequency equal to the first resonant frequency of the windowpane disrupts surveillance signals – depending on the properties of the target – without generating significant acoustic by-products. It has been found that, while the use of a high amplitude random signal does block surveillance attempts effectively, the resulting acoustic noise can be bothersome to the occupants of the protected room. The article evaluates the simulated surveillance data gathered experimentally on a simplified laboratory model when supplying the proposed blocking system with different types of disturbance signals. The technical countersurveillance method is based on driving a piezoceramic transducer mounted on the window pane with a sinusoidal input coincident with the first resonant mode of the surface. This paper proposes a semi-active mechanical blocking method against reflected light-intensity instrument based surreptitious signal gathering via vibrating window surfaces.
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