Well, if we explain why you are hearing that deck 6 cabins can be noisy- This came about because on the Conquest class ships, the Promeade deck is deck 5. This is the deck that has the bars, the casino, the piano bar, the disco etc..
The deck 6 cabins above these areas (and maybe even the deck 4 cabins below) can has noise issues, but not ALL deck 6 cabins have issues. It really depends on how the ship is designed. Its possible that there are now cabins above some of the noise generating areas. You have to check the deck plans for your ship
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007, Celebrity Silhouette 2013