Library mod problems
I have no idea why this works, but whenever I don't hear any sound, I just play a music file in Real One Player, and sound starts again. As to replacing your sounds.map file. Assuming your CD drive is the D:, there is a folder on the Halo CD, D:\FilesCab. Extract the Cab5 to your halo maps folder. The Cab5 is your sounds.map, so you will want to replace it. Give it a try then. And use ppf-o-matic in the future.