I can hear 16khz sine waves when played on their own. ¯\_(ツ)_/¯
Handy resource:
https://www.szynalski.com/tone-generator/
Note that higher frequencies are very directional and you may have to move your head around a bit to catch the tone, this works best by finding something you just can't hear and then to move your head around to see if you really can't hear it or if you only can't hear it from that particular direction.