Yep, it's a combination between screen effectiveness, and helmet. If you sit on your bike at a reasonable speed, say 60mph and listen to the noise on a faired bike, then it'll be quite noisy. Lift your bum off the seat into 'clean air', and the vast majority of the noise will go. If it doesn't get quieter, then your helmet is noisy!
I've done this on all my bikes ranging from nakeds, to tourers, and then adapted things until it goes quiet such as either replace the screen, or trim it down a bit at a time until it's right. Generally, the bigger screens for me have been too noisy. My Tiger 1050 was unbearable, and my current FZ1s has a touring screen which at motorway speeds was deep bass boomy. Trimmed 1 1/2" off it, and now it's pretty quiet. Got a cheapo screen on order which I'm cutting right down for the summer.
I also fitted a neck screen and chin piece to my Shoei lid which made a bit of a difference in reducing noise. As for earplugs, well you take your chances, and doctors opinions vary massively! I don't wear them, and my hearing has suffered. My old 250 mile commute from Blackpool to Sailsbury used to leave me with subdued hearing for a good few hours, and now it's permanently damaged, luckily not to the point of job threatening.