Originally Posted by
ClueByFour
The barking dog noise and what I think you are referring to are probably the PTU.
I was referencing the "clunking" noise another poster mentioned. The "clunk" that I hear is the brakes, but the problem may be in how I describe "clunk" versus how any of the other posters here parse "clunk."
You are correct, the clunking noise is the application/release of the breaks. Other noises include: the "barking" caused by the PTU on engine start-up and shut-down, the buzz-saw sound on take-off (only heard by those ahead of the engines) due to the fan blades exceeding the speed of sound, the pig-like or donkey-like noise of the flaps extending and retracting, and the high-pitched squeal and thunk of the cargo doors operating on the ground.