Seems there's a new product called Mosquito which is being used by people to keep kids off their property. It's put in doorways and other places where the owners don't want the kids loitering. Apparently it works and can be targeted to certain age groups. I found a link to a youtube site which has sounds scaled to age. I'm over forty and in fact I can't hear the sounds listed for those below 40. Let's see if it works for you. It's a simple video with sounds that last for 25 seconds so it loads quickly. Check it out. What sounds can you hear and do they relate to your age.
Mosquito ringtone
On a strange note, ever since I listed to the sounds I am hearing similar high frequency sounds as I sit here in silence. Maybe hearing the sounds triggered something. But then again I am sitting in a very quite room right now with very little noise outside as well.