ANR headsets
From some comments it is obvious that there is a huge misunderstanding about Active Noise Reduction (ANR) Some are frightened they can't hear if a problem in the engine were to happen. The truth is ANR targets the lower spectrum noise whichis mostly generated by the propellors and exhaust. If a problem were to develope in the engine or some other mechanical component you would actually be able to hear it better. There are documented cases where this has in fact been the case.