Very true THIS is why the modular ones are soooo quiet because it is so tight around the neck area you could never get them on if it didn't open up.The reduction in road noise comes more from proper fit than anything else. I've always worn large helmets until I bought my AGV and it is a medium small and fits proper. Night and day difference.
Easy. The new Shoei Neotec II is the quietest around. You may not want to go modular, but this helmet is the best thing on a motorcycle. It has a flip down sun shade so you only need one shield. Clear visor comes with a pin bar system. Quality is class leading. It actually looks great too. Very aggressive, not your dad's modular. Only negative is most tracks won't allow a modular.
If you want ultimate quiet but still want music or Nav/cell, go with an In Ear Monitor (IEM). These are generally molded custom to your ear and start in the $250's. But the isolation is remarkable. You can also go off the shelf with something like Bose quiet Comfort 20's for $100 and get decent isolation. Put something like this with the Neotec and it's very quiet.
If you just want quiet, there are custom molded shooting ear protection that will make things very quiet. Cycle Gear also sells ear plugs called pinbars. You get to sets in the box, one is high isolation and the other a little less. Those are $20 and I keep a pair on the bike.
If you see some riding at 60+ mph with no hearing protection they are damaging their hearing. I currently have hearing aids for this very reason. Remember that riding with the sound isolation is a bit different than riding naked. It takes some getting used to but you use your eyes more than just your ears.
Protecting your ears is smart, just like protecting your brain and skin. Be safe!
We can go on about THE quietest out there like Willie's Neotec above or Schuberth for it's small shell modular, I like both but use a Shoei RF 1200 as it is near as quiet but a one piece light full face (I think best all around) but it doesn't matter cause without ear protection none will prevent hearing loss over time.
Then with ear plugs it doesn't matter again because the plugs reduce to noise by up to 33 DBs so if one is 73 DB and the other is 74 the important thing goes back to fit, comfort, style and what is best protection.
I always use foam 33 rated plugs but I just bought the bose QC20 (like Willie mentioned) to test out but am waiting for the Cardo Freedom bluetooth to tie it to my device to see how much it cuts out. (may be a whole new world...or not) We will see ;<)
I've worn many helmets, many for over 52 years. The best helmet I ever had and still wear is the Aria. The comfort is unbelievable. It hugs your face so comfortable even at high speeds. The material is so soft and supple and it's the quietest one I ever had over Shoei, Bell,Agv and Hjc. The Schuberth is probably quiet and probably hot, as air is the noise maker. But for overall, all around handmade carefully in Japan, Aria!