I have the same gripe about mine (CS210). I was shocked at how loud it is, but I've gotten over it for how easy it is to manage. Temperature of the room doesn't seem to matter. Either the hardware doesn't support throttling the fans down, or the programming isn't addressing it.
It's especially irritating for me because my "server room" (essentially a closet) is right behind my office with drop ceilings and it's all I hear all day long. The fans lull me to sleep on long afternoons...
I'm new to the Nimble world, just starting the config of a CS235. My background is in EMC and I have been very surprised as to the noise that the Nimble makes. The kind of noise that a VNX array would only make in hardware failure mode. Is it normal for the fans to seem to go flat out all of the time? (room temp below 22 degrees) There are no alarms in the GUI regarding temp or fans.