Quick follow-up of last post: the sounds are there!
Thanks to the help of some more experienced developers (including, but not limited to, clone2727, fuzzie and SylvainTV), I managed to implement the right amount of code so that the ambient SFX and the misc sounds are played, but not the speech. \o/
The console is still spitting warning messages about missing or unexpected things, so there's still some work on that topic, but it's already satisfying :)
Criezy started to polish the English translation. If you have some time, please don't hesitate to join the effort :)