Hence, if the original file is in the BSA as "sound\ambient\mine\beep.mp3", then create a folder tree called "sound\ambient\mine\" in your data folder and drop your silent file in as "beep.mp3".
The names will be different, of course, I just made that up as an example so I didn't have to spend 10 minutes unpacking the BSA.
You can explore the BSA's structure without unpacking it using FOMM's unpacker (I think).
@Freakydoo that's very doable. How much slower do you think time should move? Reply in a PM, so as to avoid cluttering this thread.