A few weeks ago I was visiting the Bedford Public Library and a friend who lives in the area alerted me to the fact that once school let out, the maze area would fill up with teenagers with less than pleasant conversation and manners. She did add; however, that it was not as bad as it used to be since they started piping Classical Music out there. Apparently, today's teens can't stand it!
Well, here is a new invention in England that also uses sound and it is called the Mosquito! The trail run has met with great success! Check it out! It uses high pitched sounds that only younger people can hear to drive away the teens!
On an interesting note, in the last 10 years I was at my mom's house and she had a device on their chimney to repel birds, the high pitched sound drove me batty! She has moved and I don't hear it when I visit now, but I don't know if that is because they no longer have one or my hearing has gotten to where those really high frequencies no longer bother me.