By Steve Tawa

PHILADELPHIA (CBS) – When city-run playgrounds and recreation centers want to put up the ‘keep out’ sign during the off-hours, they are turning to an electronic device known as ‘The Mosquito’ to shoo potential young vandals away.

The president of Moving Sound Technologies, Michael Gibson says each small speaker emits a high-frequency tone, said to be harmless, but highly irritating to teenagers and young adults. “They find it extremely annoying and will leave an area within a couple of minutes.”

Councilman Brian O’Neill says, “That happens to be the age group that we want to keep out of our playgrounds when they’re closed at night, when a lot of vandalism happens and destructive behavior goes on.”

Gibson says as we age, hair cells in our ears die off and fall out, and generally speaking, folks over 25 are unaffected by the sonic waves.

O’Neill, whose district covers Northeast Philadelphia, is among the first to install those Mosquito devices along with cameras at playgrounds and recreation centers.

“They work in tandem. If, for some reason, something’s going on and it doesn’t chase them away, we have their photos. And that’s worked.”

Councilman O’Neill recalls listening to the demonstration about how it sends out sonic waves when turned on, to ward off potential trouble-makers when the lights go off.

“This Mosquito device chased two interns — I believe from Temple — out of the office, and nobody else could hear anything among the dozen people in the presentation. And, I said, ‘I want it.'”

Now, the city is mounting The Mosquito systems at several locations, as it installs cameras as city facilities over the next three years.