If anyone is wondering, here's what 50 Hz and 60 Hz ground hums sound like.
As a European, yes, that 50 Hz hum does sound viscerally far more familiar! But I would not notice if lights in a film sound "wrong". If anything, they'd just sound like "film lights", I suppose.
farside.link/invidious/watch?v…
youtube.com/watch?v=pMtn-loUrg…
It also has a 400 Hz A/C "hum" and a comment seems to be suggesting that happens in electrical systems on airplanes?