The Mosquito sonic devices have been used in the United Kingdom to deter teenagers from lingering around shops in target areas. A similar system is called a "magnetic acoustic device". More commonly this device and others of similar design have been used to disperse protesters and rioters in crowd control efforts. An LRAD was used by the crew of the cruise ship Seabourn Spirit in 2005 to deter pirates who chased and attacked the ship. The Long Range Acoustic Device (LRAD) produces a 30 degree cone of audible sound in frequencies within the human hearing spectrum (20 Hz – 20kHz). Some detective work implicated a newly installed extractor fan that, Tandy found, was generating infrasound of 18.9 Hz, 0.3 Hz, and 9 Hz. This "spook" was characterised by a feeling of unease and vague glimpses of a grey apparition. The possibility of a device that produces frequency that causes vibration of the eyeballs-and therefore distortion of vision-was suggested by paranormal researcher Vic Tandy in the 1990s while attempting to demystify a "haunting" in his laboratory in Coventry.
The use of these frequencies to incapacitate persons has occurred both in anti-citizen special operation and crowd control settings. Less powerful sound waves can cause humans to experience nausea or discomfort. This is usually sufficient to incapacitate a person.
An NYPD officer stands ready with the LRAD 500X at an Occupy Wall Street protest on Novemnear the city hallĮxtremely high-power sound waves can disrupt or destroy the eardrums of a target and cause severe pain or disorientation.
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