At this point you are just giving out bad information.
You can hold a copyright on ANYTHING if you actually copywrote it.
The chances of anyone copyrighting the sound rain makes are pretty much the same as the mayor of Chicago not inciting gun confiscation. NONE. zilch. zero.
You will literally never be issued a copyright for anything the like by the copyright office even if you go and die of a hunger strike to try and motivate them to issue you the license
As such, in 99% of cases, you - the one who recorded that sound - will have no claim against anyone what so ever.
Further, poorman copyright has no importance what so ever on digital files.
In practice.
You could mail yourself the recording of a fake suppressed gun you made yourself, and then try and sue every movie maker for using the sound of a suppressed gun in their movie because it is very similar to yours.
GOOD LUCK.