This is something you guys would really benefit from having in RO, or your future projects. A guy made a sound mod for BF2, inspired by my "Best of Tactical Gaming" article, that introduces pretty realistic supersonic bullet cracks for passing rounds. It's far above and beyond the pathetic "whoosh" noise you get in most games.
You can find a page about it here, with videos.
You can find a page about it here, with videos.