I hope you all keep in mind that your audio devices may not be able to transmit the highest frequency, and some might have harmonic distortion thus causing the pitch to not be correct enough to accurately demonstrate your highest audible frequency range.
Also, 21.1
My soundcard doesn't appear to be able to output 22.4+, because when I check my mixer it doesn't display any volume changes.
Edit: Also, Dag, you're wrong, at least, sort of. It does drop. Anything you hear drops your hearing range, but not by anything significant enough to really 'count.' The frequency doesn't really make a difference, it's really the dB that affects you. If it's high pitched or low pitched, it'll still damage your hearing, but how much it does damage your hearing depends on the actual volume, not the frequency. (at least, to a significant enough amount to count)
Edit: The last one has no sound, nevermind, my soundcard's fine. <3
Edit: Wow, that's a lot of edits. The 19.9 one said I take good care of my ears, and I'm not even a teenager yet. My birthday (15th) is in 6 days, and I destroy my ears with unnecessarily loud headphones. I don't know what's up.