Very Noisy!
Ask Viking personnel, including booking agents, or query the Web about Viking ocean ship cabin sound-proofing and you will get assurance that the cabins are very sound-proofed. However, that is not true.
You can hear doors slam on each side, as well as the rooms above and below, which makes for door wars -- bad design. Some hotels have fixed it, but not Viking. You can hear the TV as well as voices from both sides. If you get heavy people above your cabin, as I did, you will hear them as they move around. The patio door is especially loud and annoying whenever any of the cabin’s adjacent doors are opened or closed.