The limit is for pure tones, and is approximate. I can hear at least to 21.5kHz (next time I need a hearing test, I'll see if I can have them test higher). Since we do not hear in pure tones most of the time (white noise from electronics and and motors are an exception), but in the change of various tones, and cominations of them (one reason the same note sound different from different instruments). There are cases where things in higher frequencies can be heard. I can't recall the term now, though (what we hear is the lower-frequencies, but the high frequency's effect on the waveform does some stuff--I need to read up more ).
Where and how you grow up makes a significant difference. Many people from cities lack anything above 15k or so by their mid-twenties, simply due to excessive damage. However, much like the low-pass comment, aside from pure tones, it is often not noticed, as the brain knows what certain things should sound like.