NOISE MAY HELP FIGHT CRIME MILITARY-USE LOUDSPEAKERS DEMONSTRATED AT PLANT 42.

Byline: Charles F. Bostwick Staff Writer

PALMDALE - Police facing rock-throwing rioters or drug dealers refusing to exit a crack house may soon have a new recourse: ultrapowerful loudspeakers designed for the U.S. military.

Created to let soldiers and sailors hail approaching vehicles or boats while still safely hundreds of yards away, the high-tech loudspeakers can also emit powerful, nerve-jarring tones that can turn back a mob or chase a gunman from his hide-out.

``We know the human brain is sensitive to certain frequencies. It's like squeaking chalk on a blackboard, or scraping your fingers across a blackboard, and everybody winces,'' Los Angeles County sheriff's Cmdr. Sid Heal said. ``You can use it similarly to an electric broom to move the rioters out of the way.''

American law-enforcement agencies for decades have used ``nonlethal'' or ``less-than-lethal'' devices on crowds and individuals: tear gas, pepper spray, rubber bullets.

But even those can kill: tear gas can endanger an infant held hostage by a gunman, or the patients in the hospital overlooking a riot. Rubber and wooden projectiles fired at a crowd can kill a person hit in the wrong place.

In Boston last October, a 21-year-old college student died after she was hit in the eye by a police pepper-spray ball as revelers celebrating the Red Sox's pennant victory began smashing store windows and setting fires.

On Thursday, sheriff's officials along with officials from the Army's Picatinny Arsenal, the 1st Marine Expeditionary Force and even the United Kingdom gathered at Air Force Plant 42 to watch demonstrations of high-tech loudspeakers.

San Diego-based American Technology Corp. showed off its Long Range Acoustic Device - a circular loudspeaker about three feet in diameter and eight inches thick - that it designed after the October 2000 suicide boat attack on the U.S. Navy destroyer Cole.

Hundreds of LRADs are in service with the American military. They're part of the equipment at checkpoints on Iraqi roads, and on Navy ships in the Persian Gulf are used to warn fishing boats and freighters away from oil platforms.

Even Princess Cruise ships carry them.

A laser projector can be mounted on the loudspeakers to flash in the eyes of a driver or a boatman who doesn't stop when hailed. The loudspeaker also is built to accommodate another company's digital decoder that can translate commands like ``Put down your weapons'' into 50 languages.

American Technology has come out with a smaller version, the Medium Range Acoustic Device, designed to be carried on Humvees.

The devices were on Broward County, Fla., patrol boats in June when President George W. Bush spoke to a meeting of the Organization of American States in Fort Lauderdale. New York police used them to control crowds during the 2004 Republican National Convention protests and at Times Square on New Year's Eve.

In Santa Ana, police used a unit on loan in June to order people out of a house for which they had a search warrant. When the occupants didn't come out, officers turned on the LRAD's alert tone - an excruciating, high-pitched warble, like a giant car alarm from hell - and panned the narrow sound beam back and forth across the house.

``It drove 10 suspects out of the location,'' said Ryk Williams, American Technology's project manager. ``People want to get out of the sound beam.''

The law-enforcement and military officials at Plant 42 also heard even-more powerful devices created by Costa Mesa-based HPV Technologies. The experimental devices linked dozens of transducers into three black squares, the largest about six feet across, the smallest about 3 1/2 feet.

The officials walked down a patrol road bordering the installation's fence to listen to HPV's Magnetic Audio Devices play recordings of a siren, a bugler blowing reveille, submachine gun fire, a young Mohammed Ali taunting Sonny Liston and Frank Sinatra singing ``Mack the Knife.''

From three-quarters of a mile away, the sound from the largest was at 60 decibels - about the level of a normal conversation.

From a mile away, a command to stay away from a Navy ship was still plain.

``The key is not how loud it is if you're standing 50 feet away. It's how intelligible it is a quarter-mile away or a half-mile or a mile away,'' said Vahan Simidian II, one of HPV Technologies' owners.

Four of the American Technology's loudspeakers were donated Thursday to equip a Marine Corps military police unit headed to the Gulf Coast in the aftermath of Hurricane Katrina. HPV has also offered its midsize experimental loudspeaker for use in Louisiana.

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2 photos

Photo:

(1 -- color in AV edition only) Dragoslav Colich with Costa Mesa-based HPV Technologies performs a demonstration Thursday at Air Force Plant 42 of his firm's ultraloud speaker system for law-enforcement officials for possible use in nonlethal riot control.

(2 -- color in AV edition only) Members of the media and law enforcement officials get a loudspeaker demonstration from more than a quarter-mile away.

Gene Blevins/Special to the Daily News