Just replied to a similar comment below with: "I have this system sitting next to me in my home office which I share with my wife. Both of us work from home full time and the server is quiet enough that she doesn't complain about it."

One thing to consider is that I'm in the northeast US (philly) where the ambient temperature is generally lower than other places. I've also only had this server running through the colder months (built it in fall), so it may get noisy as the house gets warmer in summer. I would definitely not want this server in my bedroom or living room, but so far, it's been okay in my office.

edit: I should also point out that, regarding the server passing the "wife test", she tends to get hyper focused on whatever task she's working on, so background noise doesn't bother her as much as it does other people. YMMV!