I was looking at a device last week that may be ideal for this application. It is a lightweight headset originally designed for rapid intervention military and police teams,and the sound comes from a pair of slim flat transducers that fit against the bones in front of your ears. It is designed to be worn under a helmet, and it is fully waterproof and ruggedised. You hear the sound through bone conduction - the audio quality is excellent. Normally the user wants to hear what is going on around them, but for a high noise application such as a helicopter,you can just wear simple earplugs of whatever attenuation factor you desire to keep the background noise out The end result is far lighter and more comfortable than a full noise cancelling headset. The mic is a normal type on a goose neck in front of your mouth.
This device is not available for the aviation market yet, but it would not be too difficult to make one if the demand was there. It is also considerably cheaper than the top end ANR units made for the aviation market.
Would anybody be interested in being a guinea pig if I was to develop this product for helicopter use?