Okay, so I have Portal 2 on my PC. I would like to use one of its sound effects for a little project, so I started searching the installed files. Well, eventually I found a bunch of "sound" files. I tried to run them, but apparently I can't.
When I go to properties, the file type says: Sound on format AU (.snd)
I don't get it (is the file .au or .snd?), how can I use such file? How could I convert it to, say, .mp3?