I just came back on a round trip with the LH B748 FRA-HKG-FRA. Generally a great plane. The interior is up to date. On the first trip I sat right behind the wing. Absolutely quiet flight even during takeoff (the only noisy part was the air conditioning). On my return trip I sat in the last row. I was surprised by the amount of vibration in the fuselage. It started right after lift off. First I thought there were small turbulences, but after 11 hours same vibrations, sometimes quite remarkable, I am sure that it is some normal phenomena due to the long fuselage. I wonder how the crew can rest back there. Has this always been a B747 issue even without any turbulence?