Ambient noise was already 40dB and sound from 3M was 41dB while gaming. DF says that it was barely noticeable from that distance.
http://www.eurogamer.net/articles/digitalfoundry-hardware-test-playstation-4
I'll be getting mine on Tuesday and I'll compare it to my PS3 slim. Most reports I've heard have the PS4 between the PS3 slim and super slim, which seems to be more than fine for me. But again, everyone's sensitivity to sound differs.
I think you will be able to hear it too, especially when the game is silent. But it comes and goes, and is a little unpredictable when I launched KZSF for the first few times.