Subject: Listen up, serfs: Sonic Devices Play High-Pitched Noises To Repel Teens Wed Jul 10, 2019 10:07 pm
In Philadelphia, 30 parks and recreation centers are outfitted with a small speaker called the Mosquito. It blares a constant, high-pitched ringing noise all night long — but one that only teenagers and young adults can hear. Anyone over age 25 is supposed to be immune because, basically, their ear cells have started to die off.