You need a .scr to set ambient noise.
My basic values for fog are:
Farplane
2200
Farplane_bias
600
Farplane_color
.433 .433 .433
There's a really nifty guide to putting in a loading screen here:
http://users.1st.net/kimberly/Tutorial/ ... screen.htm
As well as a sticky topic in Scripting here:
/forum/viewtopic.php?t=1545
(Yeah, I just copied them from the other guy's thread about loading screens)