Bose A 20, WITH BATTERY PACK, and Bluetooth.
Its the best headset I think. Its light, comfortable, can connect to cellphone, listen to music, etc...
It gets quit, but you can still hear some from engines and gearbox.
The headset itself, adjusts according to the noise environment.
I use them in the S-61N, it performs very well, and all the pilots in the company seem to be very happy with it. A fresh set of batteries runs for about 45 hours.
I also use it when flying as passenger, and it just gets very quit.
My ears was very tired of noise after a long day in the S-61N, but not anymore.
god luck with your choice.
best reg.