maybe i got lucky to somehow hear them over my tinnitus. and no, if you live around them long enough, its not just a fan spinning (which will get noisy over time when they get manky and imbalanced, which in turn causes secondary vibrations). personally, i prefer air to air heatpumps i had when i lived in nz. not the noisy bastards i put up with in sweden.
that said, despite my hearing loss and tinnitus, i can pick up on annoying sounds nobody notices until i point them out.