Philadelphia parks officials have implemented a device called the Mosquito, which only people under age 25 can hear, in an effort to decrease loitering and vandalism late at night.
Source: Sonic Devices in Philadelphia Parks Target Teens : NPR
Philadelphia parks officials have implemented a device called the Mosquito, which only people under age 25 can hear, in an effort to decrease loitering and vandalism late at night.
Source: Sonic Devices in Philadelphia Parks Target Teens : NPR
Ericson Report 