Thanks for your answer...
I already checked the clarity aloft (has been recommended by a friend), but i am not sure about itīs proctectionin helicopter operations...
The noise level-especially when flying "doors off" is different from a normal "airplane cockpit..."...
I am checking the website of "Protec" right now-they offer a lightweight "Crew Helmet" that should work well with a headset (in their military line)...