Humans hearing 50Khz?? I think that when you are young you could hear up to 20 or 22 Khz, when you’re getting older it wil probably drop to around 16 or 18 Khz depending on how much volume voilence you had to bear your whole life.
What I heard from many People is that the frequencies above 20 Khz can influence the sound perception, more like I’m not hearing it but feel it.