Gallery Place business owners met with District officials a few weeks ago to voice their concern that loitering teenagers who sometimes get into fights in one of the city's busiest retail and entertainment strips were costing them customers. The result of that session premiered this week: a device that emits a high-pitched, headache-inducing sound that only young ears can hear.

The Mosquito, as the $1,000 device is called, hung outside the Chinatown entrance to the Gallery Place Metro station Tuesday, annoying its intended targets and then some. The young and a few not-so-young could hear the piercing, constant beeeeep, beeeeep, beeeeep.

"I can definitely hear it very loudly," 19-year-old Brooke Sawinski said. "It's pretty blasting."

Beeeeep, beeeeep, beeeeep.

"I'm about to leave because it's annoying," said her friend, Cassie Boiselair, 20. The two Connecticut natives were in town looking at colleges and said they understand the problem. Boiselair used to work in the neighborhood and said she won't take her iPod out until she's on her Metro train for fear of having it stolen, but she questioned the solution. "Couldn't they think of something different?"

Gallery Place has become a popular hangout spot for teenagers in recent years and was the site of a brawl last month that spilled into the Metro system and left several passengers injured, ending with the arrests of three teenagers.

It was around that time that business owners arranged to meet with a staff member of D.C. Council member Jack Evans (D-Ward 2). About a dozen people gathered, including representatives of the city's police department, transportation department and Metro.

"There was a general concern of lawlessness on the streets," said Evans, who represents the East End business area. "I am concerned anytime residents and businesses complain to us about feeling unsafe."

Evans did not attend the meeting and knew nothing about the device until Tuesday. He said it was purchased by Herbert Miller, founder of Western Development, which built Gallery Place. Miller did not return calls for comment.

"Our role -- I want to stress this -- was convening a meeting," Evans said. "We had absolutely nothing to do with this Mosquito."

Mike Gibson, president of Moving Sound Technologies, which distributes the Mosquito, said the device emits a tone set at 17.5 kilohertz, the high end of the hearing range for 13- to 25-year-olds. "The bottom line is that the Mosquito is installed where 13- to 25-year-olds aren't supposed to be," Gibson said. "Adults just walk through the sound."

The device, he said, is sold mainly to schools, which activate the sound at night to ward off vandals, and to skateboard parks, tennis courts and playgrounds. In Fairfield, Calif., the device was installed at a low-income housing project at the request of residents who wanted to chase off prostitutes and drug dealers who congregated outdoors.