I'm 22 and my upper limit is 19kHz. I think you might have an advantage with the gear you are using
I'm using the Sony MH1, which is a bit too forgiving when it comes to voices. I will try the test again with different gear when I have the time.
I found the reverb questions to be straight forward, though.
Maybe IEMs would pick it up easier. Hmm. Is there any audible music up at 19kHz?