Ok so can yall listen to these sounds and tell me where do you stop listening?

It goes from 3k hertz to 20k hertz. I stopped at 12k, I can't hear/distinguish 13k? At all? (and subsequent sounds)

I stopped at 12k

12k

Mess so apparently you need to raise the volume a lot to hear some of these

I actually can hear up to my age (18k, under 24). But very vaguely, though.

I could actually hear all of them. Had to turn the volume up to hear it though.

Stopped at 14k

19k (second video)

Okay this is weird, I couldn't hear 15k-17k but then I could hear 18k-20k

Same! Someone explain!