I wear earplugs every time I ride my motorcycle. I do this because wind noise at freeway speeds is plenty loud enough to damage hearing. A helmet by itself does not block enough of this noise so earplugs are a must.
A few years ago I bought a sampler pack of earplugs in order to find out which brand worked best for me. I ended up going with the Howard Leight MAX brand myself. Twenty-one dollars for 200 pairs of earplugs is cheap hearing protection.
Yes, it is technically against the law to wear earplugs. On the few (*cough*) occasions that I have been pulled over on my motorcycle the fact that I was wearing earplugs never came up. I just don't see ticketing motorcyclists for wearing earplugs as an enforcement priority of the police department at this time.
At first I was worried about not being able to hear horns or sirens while riding. That turned out to not be a problem at all. Earplugs block much of the wind noise but you can still hear horns and sirens just fine.
A pleasant side effect of wearing earplugs is that I end a long ride feeling much more rested. I think this is because my brain isn't trying to process all that loud background noise for hours at a time.
If you do decide to try wearing earplugs give it at least a week or two before giving up. It took that long for my ears to get used to the feeling of wearing earplugs. Now I can't imagine riding without them.
Spikus Maximus 