I can't read Norwegian but looking at the graphs it seems to have be 120 db at 16 Hz. (I could be wrong on that) That is quite loud.
Have any of the 92 pilots tried an ANC headset (like Bose, DC or Zulu)? They take out a lot of the low end frequencies to make the ride quieter. I know Bose has a 30 day free trial. It might be worth it. I put one in my MSA helmet and am really enjoying it.