“It’s probably just a misconfiguration that was never fixed because the people working on it couldn’t experientially confirm any issue with it.”
PA systems in malls and metro stations blast a constant tone near 20 kHz so the system can confirm each speaker still works. Set it a little low, like 19.595 kHz, and people with good ears get a permanent screech. It stays broken because the people working on it can’t hear it. The same tone bounces off arriving trains and skateboarders, so every shopping centre runs an accidental sonar.