I think that if you edited the sound yourself (in whatever way), then technically you're the author of that specific file since it was created on your computer and no one has an identical file like it.
For example:
Some of the FF7 Music used in my maps, I downloaded the MIDI formats. I then took out sections of that and edited it so it would loop nicely or if I just needed a disired piece. Then I would converted it to Starcraft format for optimal compression.
So I would say that the Author slot should stay and that the person who edited the file and made it ready to use in Starcraft is the Author.
p.s. Where ya been Rev?
Edit: However, lets say "Joe" took a sound out of "Bob's" map, that Bob made, and Joe uploaded it to SEN and called it his own... Then that would be considered stealing the wav.
But lets say I wanted to take a sound from a random b.net map that was really cool, but I had no idea who created the file... Then I would simply submit "Unknown" or something to that nature for the Author... You don't wanna put the name of the map creator linked with the wav file because he might've gotten it from another source as well.