Folks,
I have used a David Clark 10-13.4 with gel ear seals for many years. Don't use ANR headsets (even though some airlines supply them), that may well blank out things you want to hear.
All DC headsets meet all relevant TSO's, so that is not a problem, and they have the best guarantee of any manufacturer I have come across. Beware of el-cheapo's made for the GA market, there has to be a reason why such a large proportion of the military use D-C in transport/patrol and similar aircraft.
Noise levels in the 747 (all models) is a serious issue, there have been quite a few payouts for industrial deafness, across a range of carriers.
Tootle pip!!