I use RaceQuiet earphones-
http://earplugstore.stores.yahoo.net/raiseawihepr.html
I find they reduce background sound and wind noise just fine, and because the sound is directed into your ear canal you get to hear everything. For reference I did a 330mile trip with them in under my Davida open face and for the 6 hours they were in (we were staying off motorways) they were fine. Even at speeds up to 120mph *ahem private roads.
I know they are a lot chepaer than proper moulded plugs/phones, but they come with two different sizes of plug and you can buy replacement plugs.
