F3, does your helmet fit you correctly, not too loose, snug, but not too tight? Yes, typically, helmets with less ventilation will provide superior noise protection. Also, it sounds like you may be inserting the plugs too far into your ears, putting too much pressure on the sensitive membranes of your inner ear. I dunno, though, it's just a guess. Maybe try a different brand of plugs. And if your helmet is 4 years old, and you aren't sure of how it was taken care of (i.e., do you know for certain it was never dropped or whatever), it may be a wise move to go helmet shopping. Not that that has anything to do with your noise problem, but for the peace of mind and ensuring a proper fit with the features you want, it's well worth the expense.