This is a new ringtone that's being marketed to kids so they can exchange text messages in class without their teacher noticing. It's based on the idea that as you age, you become less able to hear high-frequency sounds. They call it "The Mosquito Ringtone". I played it on my computer. I could hear it, alright... and I'm kinda sorry that I did. It kind of hurt my ears, and to me, it sounded a lot like that horrible ringing I used to get in my ears after I'd spent a night clubbing.
Here is the link; see if you can hear it.
http://www.freemosquitoringtone.com/...FQqXHgodGBm_wQ