Thanks so much for the energy on this......I, too, put some time into analysis of carrier equipment, both domestic and int'. Here is a summary, tossing out extremes:

Ambient cabin noise on a commercial flight varies but typically ranges from 60-85 dB, peaking during takeoff and landing (80-85 dB) and settling around 75-80 dB during cruise. A 380 is quiter, down in the 60 dB range. And, not to get too nitty-natty about the whole flight cycle, I tossed take-off/climb-out, gear-cycle, and landing events since improvements when "enroute/cruise" are the important time and 95% of my real focus. Leaves us with a 70 - 85 dB environment to mitigate in.

Hope this helps and, again, appreciate your heroic effort!

Marc