Sorry about bringing the thread up again, but I noticed same issue in my LFS...
While in multiplayer (never while HotLapping, or Practice Sessions) with more than 20 cars on track, the sound becames choppy, more likely to happen while steering, not while dragging/going straight or braking
Already tried to lower volume inside LFS and gaining in OS but nothing, still there with that crazy sounds, its painfull to race like that.
I guess its related to the many sounds the sound card tries to reproduce, and while steering, the tyres and skids just makes the sound go freak

(just my idea, don't know how to confirm it). Also, its hard to reproduce and try to fix it while its happening, because its only in MP with +20 cars online...
By the way, i didnt notice this while in patch W.