As far as when Fairy started to gain traction as an "official leak", it's what other people said. I actually predicted it a while before that, mere hours after the first leak of "Ninfia" (even before any other translations of its name was announced), but it never really caught on. Once people really started talking about it, all I could do was shout "first" and post links to this topic (which, as time went on, turned out to be right about pretty much everything I mentioned): http://www.gamefaqs.com/boards/696959-pokemon-x/65440756
As for Sound, it's something that people have been talking about for a looooong time. There are enough sound-based moves that they actually make up their own subcategory, like punches, so people started insisting that it was only a matter of time before it got its own type. It definitely predates the announcement of X and Y. --- Socran's Razor: "Never attribute to massive stupidity by someone else, what could be explained by a tiny bit of stupidity on your own part."
The rumors of two new types existed before the game was even announced. There was that rumor around the late half of 2012 from someone who supposedly leaked some lineups or something. It stated that the game would be released late 2014 (I'm not sure on this.) with not that many new Pokemon. It also stated that there would be two new types.
It seems that Gamefaqs did not keep an archive of all posts made before the games were announced, when the X board was simply known as Pokemon, or something like that.
Sylveon and Noivern were 2 of the first pokemon revealed. There are people who deduced fairy type from Sylveon before it was revealed to be one. Noivern seems like a likely candidate for sound. --- Rotom Fan With an Air Balloon YO DOG i heard you like yo Rotom's High. So i gave it a balloon so it can be fly while he high while he way up in the sky! Dog!