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Long-range acoustic device

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The LRAD is the round black device on top of the New York City police Hummer.

The Long Range Acoustic Device (LRAD) is a crowd-control and hailing device developed by LRAD Corporation.

According to the manufacturer's specifications, the equipment weighs 45 pounds (20 kg) and can emit sound in a 30° beam (only at high frequency, 2.5 kHz) from a device 83 centimetres (33 in) in diameter. At maximum level, it can emit a warning tone that is 146 dBSPL (1,000 W/m2) at 1 metre. The maximum usable design range extends to 300 metres. At 300 metres, the warning tone (measured) is less than 90 dB.

Function

The parameter "ka", which is the wave number multiplied by the speaker radius, is often used to characterize sound source directivity. For this source, ka=19 at 2.5 kHz, and according to the LRAD data sheet, the beam angle of about 30 degrees total is precisely what is predicted for a regular loudspeaker.[1] The device does not use ultrasound, nor is it a phased array; it uses an array of conventional acoustic tweeters, the same as those used in professional audio applications, all driven together in parallel.[citation needed]

Carl Gruenler, former vice president of military and government operations for American Technology Corporation (and who now runs a company making a competing device), says that being within 90 metres (98 yd) of the device is extremely painful, but its use should be limited to 270 metres (300 yd) to be effectively used. He concedes that the device is powerful enough to cause permanent auditory damage, but that it is only meant to be used for a few seconds at a time.

Small spherical "point-source" acoustic devices follow the known inverse square law, which predicts the loss of 6 dB per doubling of distance from the source. Large speakers (or large arrays), such as these mentioned above or those commonly used in concert halls, etc., produce less loss with distance in the nearfield, typically 3–4 dB per doubling of distance from the source. The larger the speaker, and the higher the frequency, the longer the effective nearfield is. Devices like this generally have nearfields of only a few meters.

Usage

The LRAD in use on a U.S. Navy patrol ship.
LRAD on RMS Queen Mary 2

The device was originally intended to be used by American warships to warn incoming vessels approaching without permission, and some reports claim that this is now a "non-lethal weapon". Its output up to 155 db, focused at a distance, is sufficient to produce permanent ear damage and temporarily disrupt vision.[2] It may also be used simply as a very effective megaphone prior to any use as a weapon.

LRAD is used by the US Navy, most notably on USS Typhoon (PC-5).

Against insurgents

These devices are currently used at Camp Bucca Iraq and are being tested in regions of Baghdad, Fallujah, along with other regions of Iraq.

Against protesters

The LRAD device was on hand at protests of the 2004 Republican National Convention in New York City[3] but not used; it was extensively used against opposition protesters in Tbilisi, Georgia, in November 2007.[4][5][dead link][6]

The magazine Foreign Policy has revealed that LRADs have been sold to the government of the People's Republic of China. American companies have been banned from selling arms to China since the 1989 Tiananmen Square Massacre, but the LRAD is described by ATC as a “directed-sounds communications system".[7]

Local residents of Dusit in Bangkok witnessed it in use during protests of Triumph factory employees against dismissals on August 28, 2009.[8] The LRAD was used for the first time in the United States in Pittsburgh during the time of G20 summit on September 24–25th, 2009.[9][10] Similar devices have also been purchased by Toronto Police for the 2010 G20 summit. In a judgement rendered prior to the G20, an Ontario court granted an injunction filed by the Canadian Civil Liberties Association preventing use of the LRAD against protestors.

That same week, the government of Honduras used it on at least two occasions, on September 22 and 25, against people inside the Brazilian embassy. In addition to embassy staff, these included the deposed president of Honduras, Manuel Zelaya, his family, and some supporters and journalists.

Against pirates

On 5 November 2005, the luxury cruise ship Seabourn Spirit employed an LRAD while repelling pirates who attacked the vessel with rocket-propelled grenades (RPGs) about 160 km off the coast of Somalia in early November 2005.[11][12] The effectiveness of this device during the attack is not completely clear, but the pirates did not succeed in boarding the vessel and eventually fled.

The Liberian vessel MV Biscaglia was attacked on November 28, 2008. The security detachment aboard Biscaglia used an LRAD device in an effort to repel attackers armed with assault rifles and rocket-propelled grenades. Following a one-sided shootout, the ship was seized and the unarmed security contractors forced to abandon ship or be killed.[13] The incident caused the usefulness of LRADs to be called into question by Lloyd's List.[14]

Against / by whalers

In February 2009, the Japanese whaling fleet operating in Antarctic waters near Australia installed LRADs on their vessels. The devices were then used to deter activists of the Sea Shepherd Conservation Society after they harassed the factory ship.[15] The Japanese fleet later escalated the use of LRAD, deploying it against a Sea Shepherd helicopter carrying a camera crew.[16][17] Sea Shepherd noted that they had their own LRAD, but as of early 2010, had not been put into use.[18] On August 21st, the it was revealed that the LRAD was being use to scare away pods of whales. [19]

See also

References

  1. ^ Beranek, Leo L. 1986. Acoustics, p.132, American Institute of Physics.
  2. ^ Sonic Cannon Gives Pirates an Earful
  3. ^ ABC News. Technology & Science. August 25, 2004. Amanda Onion. RNC to Feature Unusual Forms of Sound: Unusual Forms of Sound to Emanate From RNC
  4. ^ RussiaToday : News : Georgian police accused of brutality
  5. ^ Georgia Police Turns Sonic Blaster on Demonstrators | Danger Room from Wired.com
  6. ^ Acoustic Weapon Hits Georgian Protesters (Updated) | Danger Room | Wired.com
  7. ^ [1][dead link]
  8. ^ www.cleanclothes.org
  9. ^ Protesters Are Met by Tear Gas at G-20 Conference - NYTimes.com
  10. ^ LRAD used in residential neighborhood in Pittsburgh, Pa during the G20 summit
  11. ^ Ship Blasted Pirates With Sonic Weapon
  12. ^ "I beat pirates with a hose and sonic cannon". BBC News. May 17, 2007. Retrieved May 11, 2010.
  13. ^ Sonic Device used to repel pirates
  14. ^ David Osler, Sonic solution may not be a sound investment[dead link], Lloyd's List, December 2, 2008.
  15. ^ Darby, Andrew (February 6, 2009). "Whalers attack activists at sea". The Age. Melbourne.
  16. ^ Video - Sea Shepherd
  17. ^ Sea Shepherd Battles Japanese Whalers in the Ross Sea - Sundance Channel, 7 February 2009
  18. ^ "Street Fight on the High Seas". The New Yorker. 2010-01-12. Retrieved 2010-01-16.
  19. ^ http://www.seashepherd.org/news-and-media/news-100820-1.html

External links

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