The highest I could hear was 16kHz (Macbook Pro into Grado SR60 headphones). I'm only 37 .
To be honest, the difference between 16kHz and 20kHz is probably only about 2 or 3 notes, and this sonic territory is the stomping ground of harmonics as opposed to fundamentals, so I'm not too worried.
Also it's off the internet - everything on the internet is a lie anyway.