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Focused Sound 'Laser' for Crowd Control

Crowd control is a constant challenge to law enforcement -- how to stop potential troublemakers without endangering those who are simply in the wrong place at the wrong time. Rubber bullets can kill, tear gas drifts with the wind.

Several police departments across America are planning to try a new device that uses focused sound, turned way up. These so-called non-lethal acoustic devices are already in use by U.S. forces in Iraq -- and some are already in place in areas hit by Hurricane Katrina.

These devices are more than just fancy speakers. California-based HPV Technologies recently demonstrated a "magnetic acoustic device" or MAD that can broadcast a targeted beam of sound for a more than mile. At close range, the sound from these devices can be terrifying and painful.

The same devices can also be used as public address systems, projecting instructions or warnings at lower settings -- and at higher settings, forcing crowds to disperse. The sonic devices could prove less deadly than so-called "non-lethal" weapons such as Tazers and pepper spray guns that have actually caused some fatalities.

That's not to say that sonic weapons can't do harm. Earlier this year in Jerusalem, the Israeli Army used a device nicknamed "The Scream" to scatter protest groups. The Scream sends out noise at frequencies that affect the inner ear, creating dizziness and nausea. The device can also cause hearing damage.

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Xeni Jardin
Xeni Jardin can be heard on NPR’s Day to Day, offering technology insights for listeners nationwide. Jardin is also a contributing writer for Wired Magazine, as well as a tech culture journalist and co-editor of the collaborative weblog BoingBoing.net, the award-winning "Directory of Wonderful Things."