This sounds really interesting. Heck, mind making a teen only ringtone? Now that would be useful.
Just did the tests. I could hear all frequencies up until 18 khz, which is strange because it says 24 years and younger. I'm 15. At 18khz I couldn't hear a thing. 17khz I could barely hear it. I hope this data helps.
Ok I just went online to do another test from a different source and I could hear 18khz (I couldn't hear 19 however) from a different website, but still can't hear it from your app.
Ok I turned up my volume on my Pre, and I could then hear 18khz, and almost 19khz if I put my ear up to the speakers. Sorry for the confusion.