I've just tried it using the tone generator in audacity listening on Yamaha HS50s. Not exactly scientific, but assuming the frequency is what it says it is I can hear to 18.5K, but not much above that, 18.7 was a bit painful though. 18K easy, that would be a very annoying noise to have in the background for me.
It's possible there's some aliasing happening in audacity, but I don't think it sounds like that.
Chris
It's possible there's some aliasing happening in audacity, but I don't think it sounds like that.
Chris