Dolebludger, my beer friend , and Adrenn (now at sea) your remarks are perfectly well on point. We were on the same VTC cruise together and remember a cocktail party we had on the aft (blunt end) cabin where the vibrations were felt at about 25 knots. We were mid-ships and felt nothing.
We left Voyager last Saturday . La Verandah outside vibrated a little, but not inside. We dined with the ship's chief engineer and he stated that it could not be eliminated completely.
It is a large ship with engines so one can expect some noise. My neighbour in the cabin next door complained about some creaking in the ceiling. No comment. This is a ship that moves over ocean waves, not a Hilton hotel !!!