Dynamic Range Control. Basically compression. TrueHD, every time I've looked, auto-flags this wherever the unpacking of the codec is taking place. If you are using PS3, then its in the player obviously.
The worst, by far, that I've heard was with Iron Man. TBH, I didn't know of this issue until this title. A lot of folks here didn't know until they watched this as well, and saw me complaining about this crap. I think mike c said he was going to come out of retirement as a hit man, or something. I think he's offering deals to AHers as a promotional thing. Wanna kill anyone?