Police in Pittsburgh are using sound blasters and other non-lethal weaponry to ward off protesters at the G-20 summit. The sonic weapon is the LRAD or Long Range Acoustic Device, a super loud-hailer deployed by U.S. forces and famously used to fight off pirates.

According to the Guardian, LRAD is being used in two ways: as a megaphone to order protesters to disperse, and, when they disobey, as an "ear-splitting siren" to drive them away. This has happened repeatedly, with the crowd assembling again a few streets away. It's one of a number of controversial tactics being employed in the city; check out this video of a seeming "snatch-and-grab" arrest in the middle of a demonstration.

The sonic weaponry appears to be having a much greater effect thousands of miles from Pittsburgh, in Honduras.

A siege situation has developed in the capital Tegucigalpa, where ousted President Manuel Zelaya is holed up in the Brazilian Embassy. The security forces can't launch an assault, but they are stepping up the pressure with sound blasters and psychological warfare tactics.

Forced into exile in a coup three months ago, Zelaya sneaked back into the country on Monday. He gave speeches to crowds of supporters from an embassy balcony, calling for a peaceful solution to the current crisis. Recognizing the risk of a popular response, the coup leaders sent in security forces to clear the area using tear gas and water cannon. According to the Guardian, twenty people were injured and at least 170 detained following the disturbance; the BBC say that at least one person died.

The embassy is now surrounded. Water, electricity and telephone lines have been cut off. Embassy staff were permitted to leave, but access is now restricted. According to the BBC the embassy occupants have no soap, towels or fresh clothes and are surviving on biscuits. These are fairly routine methods of making the subjects of a siege feel isolated and uncomfortable, but an added dimension has been added by the use of noise.

According to Reuters, a truck-mounted speaker was used "to blast the embassy with harsh sounds." The Guardian describes the speakers as being used to generate "high-pitched noise." The Miami Herald cites witness reports that "soldiers used a device that looked like a large satellite dish to emit a loud shrill noise."

The device seems to have spooked Zelaya; in the Herald report, he claims that he is under attack by some sort of radiation weapon. This reminds me of someone I talked to who once told some protesters that the LRAD sonic blaster emitted radiation that would shrivel their testicles. He was impressed at how fast they got out of the way.

The Herald quotes a police spokesman as saying that no such device is in use: "The only elements surrounding that embassy are police and military, and they have no such apparatus.''

The use of speakers in siege situation harks back to the situation in Panama in 1989 when President Noriega took refuge in the Vatican Embassy. U.S. forces blasted him with heavy rock music (which was eventually turned off after a complaint by the Pope). The idea is to cause sleep deprivation and increase the target's stress levels.

The FBI used the same tactic at the Waco siege in 1993, but with a wider variety of sounds including the squeal of rabbits being killed. It was even proposed that they should use a Russian technique known as "acoustic psycho-correction," a form of subliminal messaging in which commands are hidden in white noise or other sound to influence the target's unconscious. However. The FBI was skeptical , and was concerned that the device might have unpredictable effects.

Speakers are also used to subject detainees to constant music in Iraq, Afghanistan and Guantanamo Bay. The endless loop of Barney the Dinosaur received a lot of publicity, but interrogators also use Eminem, AC/DC and Bruce Springsteen. One theory has it that the music used contains hidden messages as a form of acoustic psycho-correction. Another is that the music itself is a form of "no touch torture."

The political situation in Honduras remains in limbo. The interim government that forced Zelaya out has not won international recognition. The World Bank has suspended financial aid and EU countries have withdrawn their ambassadors. But equally there is little international pressure for the interim government to stand down. Zelaya has called in president Obama to apply sanctions, as Honduras relies on the U.S. for 75% of its trade, but there is no sign of this happening.

Meanwhile, Zelaya is talking to the interim government , but they insist that this is not about returning him to power. They're probably hoping that if the siege continues long enough, and they keep the psychological pressure up on Zelaya, he will eventually cave in.

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