you dont say if it does if when stationary or when driving. If its when you are driving then could be wheel bearings, if when stationary thats a different matter!
I'm having a similar problem with my 325 - everything left of center will produce different levels of noise. The noise only occurs when I am moving - I can turn lock to lock without any noises on the spot. There is plenty of power steering fluid in the reservoir, although it is quite dirty.
If it's the bearings, what should I check to confirm this?