As someone who grew up with iPhones coming out around the time I was in middle school and apps producing noises like this were used as pranks in class I have to ask that people don't do this. The sound is painful.

Yeah I'm pretty sure there are plenty of adults that can hear those frequencies though. It's not like everyone reaches 18 and suddenly loses hearing.

Stupid devices IMO. When they first came out I downloaded a sample audio file from the manufacturers website to see if I could hear it. I couldn't.... because they encoded it as MP3 and it was completely filtered out by the encoding! Literally an empty file.

These are everywhere in Japan as anti loitering devices

I can hear whatever my PC can output, but I can't hear anything in our Zoom meeting rooms. Maybe it's low volume, though.