>>106574957
>ramble on about "you can't hear anything past (Whatever) khz!1"
Testing which frequencies you can hear is super easy.
And I don't know about other countries but we had standard hearing tests at school so millions got tested and out of those millions, essentially the entire population, not a single child could hear above 20kHz.

You also don't hear anyone complaining about dog whistles at the park, which would be a massive annoyance if you could hear them.