I had my hearing tested recently and can still hear up to 21k-22k or so before it rolls off, and I'm 30. I wear hearing protection when using power tools, and I wear ear plugs at concerts (I have a set with nice flat "response".. they don't color the sound much, just make it quieter). When I was 14 I was tested up to 25k. You can't even really hear that, but you can "feel" it.. actually, I perceived it mostly as a sort of altering of the noise floor that let me know sound was occurring rather than as a tone or note. It's (was) almost painful. I never thought it was all that great to hear up there, all that makes noise up that high is rodent repelling devices, automatic door sensors, some fluorescent lights, bug zappers, and the oscillators in analog televisions. Even in music, a lot of it is just squeeks from fingers on strings or feedback. No one has ever wanted to listen to a song centered at 20kHz so I don't think anyone should be too bummed if they are in the 18Khz range or so. Also remember a lot of sound cards have low pass filters taking off everything above 20kHz, to keep them from amplifying the noise of the computer itself.