This fix was found by user WaterHag on here. Follow in this order.

1. Have For Honor closed and end task forhonor.exe if it is running in the background.
2. Open Uplay.
3. Locate For Honor install directory.
4. Move For Honor install directory to a different disc! so if it is on c: move it to d: or some other drive.
5. Goto Uplay and tell it to uninstall For Honor.
6. Tell Uplay to locate For Honor files at the new disc.
7. Boom you have sound back.

If you have no room on another disc you can instead use this guide.

1. Have For Honor closed and end task forhonor.exe if it is running in the background.
2. Open Uplay.
3. Locate For Honor install directory.
4. Rename For Honor install directory.
5. Goto Uplay and tell it to uninstall For Honor.
6. Goto another disc even one that has no room or insert a usb stick that has ntfs file system on it.
7. Create a directory on it called mount.
8. Goto disc management on windows and mount the drive that has for honor to the otherdrive mount directory.
9. Tell uplay to located the file on the newdrive\mount\....forhonor
10. Boom you have sound back.