The older you get, the less frequency your ears can detect. That doesn't mean that those frequencies aren't out there; or that others can't perceive them.
Here is an example. (Hat tip: N.D.) It produces a sound that most people over 25 years old shouldn't be able to hear. I have no clue if this particular test is reliable. (FYI, I'm 31, and I heard the sound with head phones on.)
Still, it's a scientific fact that teens can literally hear things that old people cannot. Old people will way, "It doesn't exist!" Well, quite clearly, it does.
There is no objective reality.