I fly on the 747-400 and initially used the Sennheiser HMEC 25-KA ANR headset, but as there is no voice activated intercom on that airplane I ended up uncovering one ear in order of beeing able to undertsand the other guy. I felt uncomfortable becaues one ear was getting the full noise and the other one was more or less completely sealed. I stopped using it. Some colleagues use it though and are happy with it.
Hope that helped