There is no uncouple sound supplied by Ring Engineering. I pulled mine from recordings that were made for train simulator games. There are a number of mods out there for those games that replace the sound. If you download some of those files you can find a few things in there of use. New couple and uncouple sounds are the ones I used. I believe that if it's for personal use there is no issue, but you cannot share them. Someone may know more than me on this though.
-Kevin