*Updated! 02/05/08 New version of the program has come out! Use step 4 and ignore 2! Ill try to move them later but I get A Java error when I try to now*
The Concept is simple, as you get older, the less higher frequencies you can hear. But when you were younger you could here much higher frequencies then you can hear as you get older. So using a freeware program NCH Tone/Waveform Generator, http://www.world-voices.com/software/nchtone.html
you can create higher frequencies that only younger people can hear.