most people can hear frequencies as high and possibly higher that are
recorded ontp cd. you have to realize that a recording frequency of 44kH
only reproduces frequencies up to 22kH because you have to sample a
waveform at twice it's actual frequency. like if you had a sine wave of
5 kH and sampled it at 5kH you wouldn't hear it because every sample of
it would be identical. you'd have to sample it at 10kH, then it would
get sampled at both peaks.
B R E N D E N
PS also consider that even though a person may not realize explicitly
that they are hearing a sound, it still may be affecting their brain and
body.