No in game sound. Please help.

So I’ve heard I’m not the only one experiencing this but I have no in game sound on my Halo 4? But I do have sound when it comes to cutscenes. There is a scratch on my Halo 4 which I thought may have been weirdly causing this but now that I’ve heard other people have had this happening I don’t know for sure now. Sometimes when I have tried a ton of times I got ingame sound but that was after a whole lot of times and that only worked once so far I think. If you know how to fix this please tell me. And if I have to buy a new copy of H4 tell me so I can.
-Thank You

Do you have a headset that allows sound to be played via the headset? And have you by any chance muted your xbox game volume? Btw, the scratch MAY actually be the problem.