I can link to the stories or just give the short version, which I think I’m going to do.  

Store owners in England came up with a new speaker / audio device that emits a high pitched noise in order to thrawt away young kids that keep loitering around their stores.  The high pitched noise is around the 17.4khz range and can only be heard by people under the age of approximately 24. 

That’s an interesting and good thought.  I certainly wouldn’t like it if I was younger and my favorite store or shop had one going but then again I don’t think I’d be shopping at places that would be using such an annoying device.  

Even more interesting to me is that the kids out smarted the adults.  There’s now websites that offer the frequency for ring tones.   Now the teacher, parent, or anyone else over 25 isn’t going to hear that the young’n keeps getting txt’s from his girlfriend.  

Check out this site that offeres different ring frequences so you can tell which ones you can and can’t hear.

Ouch! According to this and my ears I can’t hear the ones under 30 years old.