If you can be midships you will be fine. The bow you can get wave "thumping" sounds and in the aft you can get vibration sounds when entering/leaving port. If you are schedule to be in port early you will most likely be rattled out of bed in the morning. ANY other time you have no issues with noise. Actually the Riviera deck can be quieter than decks closer to the Lido and Promenade deck due to noise sources there that happen all evening long.
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