Possible explenation to your sound problems
 

I've noticed that alot of post are going up about gettin errors in there sounds. A possible explanation is that there is a conflict between Omaha2 and SH. Simply open up the Omaha 2 pk3 file, and any other of the add-ons, and look for a file named "ubersound.scr" Delete that and your sound probs MIGHT be solved. If not then I'm not really sure.