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Secondly, AC units do not create a vacuum. Even if they did, houses are not air tight spaces, there are gaps underneath your door and cracks in your window, almost certainly there are cracks in the cover for the window. AC units work by circulating air through a condenser that sucks the heat out and moves it outdoors, that's why the back is constantly dripping water: its accumulating moisture from the outside air, since the back of the unit is just a giant heat sink.
As for the noise, nothing you can do about that. Most Americans are used to it and find it comforting since summer nights in the US can get very hot and these units are often run through the night to help people keep cool while they sleep, often from the youngest age. If you didn't grow up with them then you're probably going to hate it either way.
> AC units do not create a vacuum
I have to insist of this, please watch the video I linked, single-hose portable AC units absolutely create a vacuum, and single-hose designs are the only ones you can get in Europe. The air for cooling the evaporator coils comes from the room and is expelled through the hose outside. This is of course different than any sort of real AC unit.
> houses are not air tight spaces
Indeed, this is how single-hose portable AC units can work, and the more air tight your house is, the more dangerous it gets with gas heating. Installing a single-hose portable AC unit in an old building with gas heating is not only very dangerous, it is also illegal (but people do it anyway). The only way to do it properly is to install an intake valve in your apartment (nobody does this). Please educate yourself about this, it is a very serious problem.
As for AC noise in general, no, a split-unit AC system makes only a trivial amount of noise. Even a crappy window unit makes far less noise than a portable AC unit because the compressor and fan is outside for a window unit, as opposed to inside.
Have you considered that they might just have a point?
Or in a slightly more friendly way - Vienna has the highest standard of living, but your personal preferences do not mash with it and if the Viennese lived like you would like to, it would no longer be as livable?