A Sonic device called "Mosquito" has been installed in a Park in Tokyo's Adachi ward where it is supposed to drive away young folks who have nothing better to do than loitering and disturbing the neighborhood. By making use of high frequency audio waves  that are supposed to be audible only to people in their early twenties and below, the Mosquito device aims at  preventing young people from gathering in the area during 11 p.m. and 5 a.m.

 

Being a Tokyo resident myself I have noticed these devices a lot especially in front of banks and big shops in the Shibuya area. It is obvious that the age restriction works only in theory as many people in their 30ies and 40ies still appear to be still hearing the sound, rendering the devices somewhat unreliable. Recently even they seem to be installed increasingly in residential areas, possibly causing more disturbance than "for the main part" theoretical loiterers. 

 

When mentioning the device to other locals I realized that most people are not aware of their frequent use and it appears that after the news coverage there even is some sort of a tourism boom to said park. Possibly only to check if their ability to hear sounds over 17kh is fading yet.

 

 

 

Via Mainichi