You spelled it wrong explaining why you could not find anything.
> Cacophony (Japanese: そうおん Noise) is an Ability introduced in Generation III (unused and thus dropped in Generation IV), that avoids sound moves. This Ability is identical to Soundproof, but only usable in Generation III games.
Cacophony is an Ability coded in the Generation III games, but no Pokémon have it. It cannot be acquired by normal means, hence it was removed in Generation IV.
Due to its use on the Exploud released in Great Encounters, it is possible that this Ability was initially intended to be that of the Whismur family. The reason for the change is unknown; however, several other Abilities are equivalent in effect to another (such as Air Lock and Cloud Nine). -Bulbapedia
So basically it is the equivalent to soundproof but was dropped in gen 4