I am playing through the prologue for Halo 4’s campaign playlist for legendary and when the voices for Halsey and the interrogator came up, the voices were really quiet. I started out with the volume at 20% when it first happened so as a response, I jacked the volume to 100% and the voices were still just as quiet. I then quit out of the game to see if verifing the cache on steam would solve the problem with no avail. I also tried to see if it was because I was playing on a playlist and had the competative score on and had no luck fixing the problem.
Having the same problem on the Windows Store version,
too
As this appears to be an issue with your game, we recommend heading over to https://aka.ms/HaloSupport for further assistance. Please review the latest known issues and submit a ticket if your issue is not listed.
Thanks!