With this guide, you now possess the technical knowledge to manipulate the very voice of Rook Island. Mod safely, and remember: "Did I ever tell you the definition of a corrupted .fat file?"
Repacking requires matching checksums. If your custom .wav is 0.1 seconds longer, the lip-sync in cutscenes will break.
If you try to open soundenglish.dat with Notepad or VLC, you will see digital garbage (hex code). You need specific tools. Here are the community-vetted solutions.