I have 3 including 2 HJC's and none of them are quiet enough to ride w/o earplugs unless you stay as conservative street speeds. even then it's annoying to a degree. When i was young and riding in the 70's b4 helmet laws i rode w/o a helmet. (yea, i know) I never had any issues as far as noise. I believe helmets generally increase noise over no helmet because they trap the wind and it ripples all thru the helmet, and the helmet acts as an acoustic amplifier.
that said, i hate them but i always weea earplugs. Wish i didn't have to, but it can become almost tortue at freeway sppeds w/o them. This place has a good selection and great prices in quantity that'll allow you to use a new pair each time you ride w/o breaking the bank. I got 200 pairs of really good plugs for $20. I use each pair for a few rides so my box is still mostly full after 6 months. they are a hassle, but at least try a few pairs for a couple weeks and if you're anything like me you won't wanna ride w/o them once you get used to it.
http://store.yahoo.com/earplugstore/difoearpl.html
