Philadelphia teens who want to hang out in area parks and rec centers after hours may be subject to an Orwellian deterrent.

According to a report from Billy Penn, Philadelphia has been implementing a device called the Mosquito at its parks since 2014. Banned in many parts of the world, the Mosquito emits a constant noise at such a high frequency that only young people can hear it. 

Mosquitos are currently installed at 30 city-run locations around Philadelphia, according to the Parks and Recreation Department. At night they send out a high-pitched ringing sound to which anyone over the age of 25 is supposed to be immune.

The devices aim to keep kids from loitering in parks and outside rec centers after the spaces are closed.

Some say the devices unfairly target young people.

“It very clearly discriminates against young people,” Brian Conner, 20, president of the National Youth Rights Association, told Billy Penn. “It punishes non-criminal behavior, and the idea that youth are more prone to commit crimes than adults is just wrong.”

Michael Gibson, president of Moving Sound Technologies, refutes those claims, saying that parks and rec centers become private property after they’re closed.

“We do install in the parks in Philadelphia, but…they’re not actually activated until the park or rec center becomes private property,” Gibson told Billy Penn. “People have the right to protect their property.”

Andy Berg is Executive Editor of Athletic Business.