I've never rode with a N90, however I do have a Paralbellum.
I do have a Nolan 102 flip up helmet, and an Arai Quantam. For me, the Nolan is significantly more noisy in every scenario.
Recently I was doing some back to back testing of the Parabellum and the Givi Airflow. I did the testing without earplugs. I've got the Touratech adjustable bracket, and in addition to comparing the screens, I was optimizing the position both. Once I got them dialed in and decided the Parabellum was the keeper for me, I tried both helmets back to back. I really like a flip up, the Nolan is the only one that I can find that fits though. However, it has a lot more noise that the Arai. What I did notice was that if I left the face shield up on the Nolan it was significantly better. If you wear sunglasses you might consider trying it with the shield up.
I'm a big fan of earplugs, after getting a set molded at a bike show, I road them for a couple of years and lost one. My ENT had suggested that I consider Westone Sleep Plugs for maximum comfort and good protection too. I had him take impressions and order me a set. The best $150 I've spent on gear, ever. Super comfortable, and nice and quiet. I can't emphasize enough how comfortable they are. Had 'em in for eighteen hours straight last week, didn't even know they were in.
http://www.westone.com/defendear/index.php?option=com_k2&view=item&layout=item&id=13&Itemid=118