working as a metal framer and acoustical subcontractor I always protect my hearingwhile using powder actuated tools and also when shooting firearms . I always wear a helmet ... no ear plugs but now I'm going to try them
What?................ Just kidding. YES. Very important if you do not want to live with ringing in your ears for the rest of your life. Helmets are getting better but there is still alot of wind noise which is very high decibel level. Kinda like running a 6hp Genie Shop Vac next to your ear.
My kind of "road noise" is AC/DC cranked to the max on my earphones. Talk about ruining your hearing. Plugs are probably a good idea for long trips, loud pipes, etc. I'm gonna try it next time I ride. The rock is a kinda distracting in traffic anyway. These holiday cage drivers will kill you.
I have read papers suggesting riding at highway speeds (120km/h say) is akin to standing next to a demo-hammer in terms of sound level. If you ride at high speed every day, and you do not use ear plugs, you will suffer hearing loss. I do not believe that helmets reduce sound levels significantly. I remember with some disappointment buying a Shoei X8 (very streamlined in appearance) and finding it to be as loud as a motocross lid!
Oh yeah, I always use plugs.