This is a ZIP file containing ALL the frequencies of the ‘mosquito ringtone’ that came out a while back so teens could get calls or text message and adults wouldn’t hear the ring.  Some of the higher frequencies are not audible by adults because as you get older you lose frequency range in your hearing and can only hear lower kHz sounds.  Here is the ZIP file and a chart showing hearing average ages for each frequency…

http://www.corusa.com/blog/wp-content/uploads/2008/11/mosquito_ringtones.zip