Usually they’re tolerable, just annoying.
The screenshot is from one I found installed outside Lidl (supermarket) now, above the entrance. Probably loud enough to “cover” the entire parking lot. Loud enough to get painful after a few seconds. Sweeping between 15.5kHz to 18.7kHz. For comparison, a CRT TV is around 15.7kHz.
I wonder if not caring about loudness of these higher frequencies contributes to hearing damage among people.
Lower frequency, but also awfully loud buzzers can be found in trains near doors, working as a warning when the doors are closing. Thankfully, this probably annoyed some of the staff enough for them to start taping these over.
But those are loud enough to sound distorted.
Anyway, I just hid behind a corner where I couldn’t hear it that much while waiting for the manager to call us in.
They did install something like this one time at one of my local supermarkets to deter loitering teenagers, I have sensitive ears and am not even close being a teenager anymore but could hear this shit and it was loud as fuck. Went shopping elsewhere…
And then there are some cars which give off really annoying high pitched sounds to fend of rodents or something, at least that is what I guess. Really awesome when you have to work near a patking lot…
None of my coworkers can hear any of it, but they never wear hearing protection and some of them are nearly deaf.
Those anti-teenager ones are only put up by sociopaths, or people who should not be allowed to make executive decisions regarding own life.
Because kids younger than teens also hear them, and they can often damage the hearing of babies and toddlers.