I don't know about the noise in the balcony cabins on deck 7 but we were on the victory and assigned to the aft dining room on deck 4. Occationally when the ship would change speeds, enter, or leave ports the cavidation from the engines caused so much noise and vibrations you could talk to each other for several minutes.
I didn't notice the sound and vibrations any where else on the ship so it could have just been the location of the dining room in relation to the engines.
If you try out the rear balconies, let us know what you find. I've always thought the views from them would be great.