Sounds -- .au, .wav, or both?

What should be done about sounds? It's been rumored that MS Windows doesn't grok .au -- XEmacs/Linux (and I presume BSD) sound support handles both .wav and .au so I don't particularly care either way. They probably should be put in a package, regardless. Is there any platform that absolutely requires .au and cannot handle .wav? If we need both, it will definitely have to be a package and we'll have to upgrade the sound playing code to have lists of valid extensions so that `play-sound-file' can Do The Right Thing and either play "im_so_happy.au" or "im_so_happy.wav" as the situation warrants. I like sound (a lot); I consider this an issue that needs to be resolved prior to release.