<<wind noise at 15 MPH is good for 85 decibels>>
Had not thought about this, but seems plausible.
I recommend cat ears:
www.cat-ears.com They are little fuzzy things that wrap around your helmet straps where the fuzz breaks up the wind noise ahead of your ears. Their argument is that this is the reason that owls have feathery legs and pigeons don't, and your cat has hairy ears and you don't.
I can attest that they really work, and in the nebulous, subjective world of sound assessment, I would say they knock the wind noise down by half. I bought a new helmet once and forgot to move them over. The first downhill I hit, the wind noise had me wondering 'what is Wrong with this helmet?'
Also recommend bone conduction headphones. They don't obstruct your ears and are pretty comfortable. There's a headphone law in Georgia, which they probably put you on the wrong side of, but you can easily hear traffic sounds.