I wear ear plugs every time I ride, otherwise my ears well scream at me for a month. I do have a history of some hearing damage from guitar amps (tinnitus), but the wind on your helmet at 70 mph is enough to do damage to your ears no doubt.
I wear these every time I ride,
[ame=http://www.amazon.com/EAR-Ultra-Plugs-Pair-Corded/dp/B0001AGMU6]Amazon.com: EAR Ultra Fit Ear Plugs 1 Pair Corded: Health & Personal Care[/ame]
ear ultrafit corded plugs
These are great because of the cord, they just hang around your neck when you hop off your bike, and the cord keeps them from getting separated, I always managed to loose one plug when I didn't use the corded kind.
As for options, I have tried a bunch. I have custom plugs made by the VA, I have used Etymotic Research's ER20 ETY-Plugs
[ame="http://www.amazon.com/dp/B0044DEESS/?tag=hyprod-20&hvadid=15473413779&hvpos=1o3&hvexid=&hvnetw=g&hvrand=696653397882059634&hvpone=&hvptwo=&hvqmt=&ref=asc_df_B0044DEESS"]Amazon.com: Etymotic Research ER20 ETY-Plugs Hearing Protection Earplugs, Standard Fit, Clear Stem with Blue Tip (Blue): Electronics[/ame]
and the foam kind you find at any hardware store. The Etymotic's are nice for lower volumes, they cut about 20 db of sound, I use these for music in a small club. I don't think they would be good under a helmet however, the stem is very hard plastic and over all the plugs are big in the ear, a bit uncomfortable.
The custom plugs are nice but I like the corded ones better because of the cord, they both block around 30 db of noise, so there is no loss in performance with the ultra fit corded plugs and they cost a fraction of the price of customs.
Something I did that changed dramatically the wind nosie at my helmet was to get a new wind screen. I bought a Madstad windscreen but they are pricey (about the same cost as a nice helmet). There are handful of good options out there though, and for me this just about eliminated the wind noise on my helmet, even still I wear plugs. (Just as a side note, the new screen eliminated all buffeting at highway speeds.)
I hear my engine well with plugs. I think it is an adjustment in listening with plugs, you listen vs being exposed if that makes sense. Maybe one relies more on feeling the bike too, the revs are there, it's just that the volume has been turned down a good bit. I figure this is something one would get used to pretty quick.
Anyway, this is what works for me.
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