weather you use mods or mod yourself you should keep a full backup copy of the entire data folder on thumb drive or burn it to a dvd just for this and other sorts of problems
anyway, a simple solution is to download the
" Ultimate Sound Mod " that replaces all stock sounds with high def sounds. (it replaces and improves them)
the post and link is here:
http://www.subsim.com/radioroom/showthread.php?t=108512