There's no way to do this "standing" in the SA - it'd involve inserting a new row into the streamfiles table that referenced the same file name but had a seperate language code - this wasn't something designed for in the UI so currently there are no tools to do this.
It might be possible to do by expanding Audio Text Manager perhaps - I'd have to test if duplicate file references are even allowed (there may be a foreign key constraint to avoid duplicated references which may cause headaches on delete sequences). But right off hand there's no easy way to pull this off without doing it manually (download wav, copy up to new language which inserts a seperate copy of the file with a different ID which avoids any FK conflicts).
