That info is completely wrong. You do not have to be 18 or younger to hear 22kHz. As long as your hearing has not been damaged then it should be fine. Now, 22kHz at 50 years old and on would be interesting, but not completely unheard of.
Wanna fuck with your ears? Listen to a Shepard Scale at a moderate volume. It is known to make some people nauseous (not all though). Here is a decent one if you ignore the goofy spiral in the video. Just listen to it.