A horde of Poxwalkers dropping from a vent in the ceiling make no noticeable noise.
Same goes for a dozen armored guys coming through a door.
Basically when you have your back turned to it (because you’re fighting) losing health will be the first noticeable indication of new enemies appearing behind you.
There should be some audio cues, like naked feet and hands impacting on concrete for the dropping poxwalkers, and a noticeable grinding for the shi… formerly sacred and blessed imperial doors.
Especially the doors. Moreover they should take some time to open and close, at the moment they remind me more of StarTrek doors in the way they open, let a dozen guys through and close without making any noise.