McGeeM,
There is another lenghty posting on this stuff and opinions vary, but I dont think its loud at all. As silent as pure wool, no. But, then again I used to buy Gore windstopper material and wear a layer of it under my Johnson Wool and Columbia Gallatain to cut the wind prior to finding the wooltimate. Compared to that, it is infinitely quieter.
Also after wearing them for over a season, what little noise there was dissappered. Another vote for this stuff. I think it rocks, especially for the price! With it on the outside, and enough wool under, there hasnt been a single day that I was worried about getting cold on.