STEVE INSKEEP, HOST:
In this country, Philadelphia is trying to keep certain unwanted people out of parks. The city has been playing a constant, high-pitched noise at night - a noise that only teenagers and young adults can hear. Here's Michaela Winberg of our member station WHYY.
MICHAELA WINBERG, BYLINE: If you look at the rec center building at Philadelphia's East Poplar Playground, you'll see a small beige speaker screwed into the wall. Every night at 10 p.m., that tiny speaker activates. And for eight hours, it plays nonstop. Here's what it sounds like.
(SOUNDBITE OF STATIC)
WINBERG: Didn't hear anything? If so, it's likely you are not between the ages of 13 and 25. That's the age group this sound is targeted toward. As we age, some of the cells in our ears start to die off. So when we get older, we have trouble hearing higher-frequency noises like the one that this device plays.
Philadelphia resident Lamar Reed is 17, and he hears the noise loud and clear.
LAMAR REED: It's so loud. Like, it can - like, what if it damages our ears or anything like - something like that?
WINBERG: It's called the Mosquito, and it's an acoustic deterrent device, technology used to keep humans or animals away from a designated area. It's usually used by law enforcement or the military. The Mosquito was manufactured by Vancouver-based Moving Sound Technologies. Michael Gibson is the company's president and says he has worked with about 20 parks departments in cities around the country to install his devices.
MICHAEL GIBSON: The intention was just to move, non-confrontationally, youth from an area where they should not be. And that will prevent vandalism. It'll prevent graffiti, loitering.
WINBERG: But Mary Kate Riecks is 27 years old, and she also hears the annoying sounds. She says the Mosquito installed at her local rec center gives her headaches when she walks around her neighborhood.
MARY KATE RIECKS: It almost is more like a feeling than a sound. It, like, kind of is in the back of your head. And it - at least for me, I get a headache if I'm near it for too long, so I usually skip around this block or, like, walk very quickly down it.
WINBERG: The city has been installing these devices for five years, but they're just now causing an uproar. Philadelphia Councilwoman Helen Gym calls them sonic weapons.
HELEN GYM: In a city that is trying to address gun violence and safe spaces for young people, how dare we come up with ideas that are funded by taxpayer dollars that turn young people away from the very places that were created for them?
WINBERG: Gym didn't know the devices were in use until recently. And she argues they discriminate against young people and worries they might have permanent consequences for children's hearing or local wildlife.
GYM: I don't think that this project is going to go any further until it meets with the full scrutiny of the public and that we have some serious attention paid to whether this is the best use of our money.
WINBERG: Each of Philadelphia's 30 devices cost around $5,000 to buy and install. And there's precedent for banning them. Localities all over the world have already rejected them. In the U.S., Washington, D.C., removed its Mosquito in 2010 after receiving complaints. It had been operating in the Gallery Place Metro station.
But Philadelphia park officials defend the device, saying it's only on at night, and it's just one part of an overall anti-vandalism strategy, which includes fences and gates, security cameras and night watch staff. For now, Philadelphia is moving forward with installation. Despite the backlash, two new Mosquito devices are currently being installed at other city playgrounds as part of major renovation projects.
For NPR News, I'm Michaela Winberg. Transcript provided by NPR, Copyright NPR.