Use ear plugs, and get helmet speakers. I just did 4500 miles, and without earplugs, I would be deaf. Most people don't realize it, or are too macho to believe it, but even moderate highway speeds (70mph) will induce permanent hearing damage. There is absolutely no benefit to not using earplugs if you are doing highway riding. Use them every time you do such riding. I keep a pair or two in each of my jackets just in case. It makes the ride a heck of a lot more enjoyable not to be distracted by the near-pain of wind noise. And a good helmet-mounted speaker system will be able to project through earplugs (provided you don't get overly-strong plugs. 20dB or so is recommended for helmet-mounted speakers.)