My little Badger compressor is about 65DB. It's not what I'd call "super quiet", but as long as it's well isolated from the floorboards it's at least non-disruptive. Loud enough to likely annoy others if they had to share a room with it, but quiet enough that the sound doesn't carry to other rooms. I could paint with someone trying to sleep or work or watch TV in the next room, and they wouldn't notice a bit, but I wouldn't want to do it in the same room.
Isolating it from the floor turned out to be really important. The physical vibration it puts out transmits EXTREMELY well through the structural members of the house, so if I put it on the floor or on a regular wood table, then you can hear it clearly everywhere. I put it on some heavy books atop an upturned plastic crate, and now the noise is confined to the room it's in.
IMO 40DB is true "super quiet" for casual living space use. 60DB is "quiet enough" if you've got a room or closet to separate it from other folk. 70-80DB is only "super quiet" for wood shop, construction site, our auto shop standards.
if noise is an issue.
