question about sound files

i noticed that in the sound folder there is a speech folder containing 9 folders of the exact same files.

i dont remember the ID letters but each folder has 3 sets of the same sounds but at 3 different excited levels of volume. now all this is in just one of these folders, so why then are there 9 sets of these folders if only one has all the voice sounds that the game needs?

i tried them and they are all in english so its not about other languages. some files are missing from some folders at random, many of these files have 1 or 2 or a dozen sound files missing from them so i am really confused by that. would it help to go through them and replace all those missing files in all the folders?