The story, as told by McDouglas: Boeing, Daco and Lockheed were all faced with this buzz saw noise in the cabin at takeoff for the first time with their new widebodies. Lockheed L-1011 engineers were super smart, so they drilled, trimmed, etc., to quiet the noise at the source.
Boeing and McDouglas weren't so smart; they just added a ton of sheet lead noise dampening to the sidewalls of the fuselages of the 747s and DC-10s.
Result: They were all comfortable noise-wise on takeoff. When they got to cruise, the 747 and DC-10 were quiet inside, while the L-1011 was noisy.
GB