It's good to know the last one was empty, otherwise I heard them all. The 'weakest' were 15.8 & 16.7 kHz. If your hearing is the first thing to go I'm doing ok for an old guy.
Jim

A local business once piped that high tone onto the sidewalk in front of their business. It didn't bother the adults who couldn't hear it, but it was obnoxious enough to stop the hoodlums from loitering there.

At "normal" volume, I could only hear up to 18.8kHz.
I turned the speakers up to 11 and can hear the next two, but they don't sound right. I suspect that my sound card or speakers cannot reproduce those tones (as suggested by Gogar).

Even at 11, the 22.4kHz tone wouldn't even make my speakers "click".