An anti-vandalism device aimed at teens has started a heated debate in Philadelphia. Thirty-one of the city’s public spaces are equipped with a speaker called the Mosquito, which emits a high-pitched noise that theoretically only those under 25 can hear.* (Some older people, however, say they still hear it.) Officials point out that the devices are just on at night to prevent loitering—but critics say it’s age-based discrimination. In response to public outrage, the city has halted new installations of the device, pending a comprehensive review. This isn’t the first time the Mosquito has sparked a dispute; transit officials in Washington, D.C., removed the devices from a Metro station several years ago after complaints. Some lawmakers in Philadelphia are calling for an end to the program. “We create parks and recreation centers . . . to be welcoming of all people, especially young people,” says City Council member Helen Gym. “And if we start to employ sonic weaponry and devices that are meant to dissuade young people from these places, what does it say about us as a city?”