I completely agree about hating the noise... but these are 24/7 loaded devices, they need cooling at least for the hdd's if you want them to last.. typically making it more quiet means lowering the fan's speed and that decreases cooling ability. I hate noise so much I went to great effort to sound proof my server room and all my rack mount servers are giant ones I make with water cooling.. not thin 1U units that blast 110db of fans..
Your NVR should be secured physically, and luckily FAN's are a high frequency noise and it is very easy to block.. its the low frequency that is hard/expensive to sound-proof.. I would think installing it in a closet with a solid wood door would be more than enough.. but it wouldn't be my bedroom closet thats forsure
Trying to build/find a perfectly silent system can be alot more difficult than getting a quiet one and putting it in a hardwood cabinet or something.
My mini NFS Server is totally fanless and silent, the cameras just save directly to ftp so it can be a tiny fanless server if I use a decent external HDD enclosure that has adequate radiant cooling and a WD purple drive that sips power well, PogoPlug has no fans and you can get multi-port PoE injectors with no fans.. just need a fanless switch.. but your sacrificing a bunch of nice NVR features like video output/split display w/synced playback, etc. To get a completely silent system your going to have to be willing to sacrifice something (like longevity and cash), at least thats my experience