Normal 10 speed operation. The noise comes from the transmission pump and is considered normal per Ford (Personally I think it sounds like hell). There is a TSB on the noise considering it normal, even though not all of them do it or are not as loud as others. The 10 speed in my 6.7l does not do it at all, however my wife's Lincoln Aviator with the 10 speed does it and is loud. It my only complaint with her car. I did tell the dealer that the noise was unacceptable and we test drove 2 other Aviators and 1 Explorer ST with the 10 speed and they all had some type of noise. The GM version of the transmission has the same sound/issue.
Personally I think the installation of the pump which is gear driven is installed out of specs, which causes the noise to become louder. I would love to meed the engineer that designed this and thought this was an acceptable noise to come from a vehicle. Hopefully they come up for some type of fix for this.