Fixed. Or really, really close to fixed.
Been lurking this thread, and now I'm ready to chime-in with my observations, and an idea of how to minimize (or even fix) this issue.
The problem as I see it, is that the road/tire noise is being funneled straight up to the rider, and IMO, the solution isn't to change the tires, rather it's to re-direct or block the sound. Stay with me.
My previous bike was a 2015 F800GSA; and after a few months of ownership, I shipped my forks to have them upgraded. When I re-installed them a few weeks later, I neglected to re-install a plate-sized plastic part that sits between the forks. Immediately upon riding, I experienced a very loud road noise that wasn't previously there. Once I realized my mistake, I reinstalled that part, and voila, that loud noise was back to it's normal low level.
That plate-sized plastic part, present on the F800GSA, is called a fork bridge cover (photo attached.) Now, before you run out and buy one, it doesn't fit the 1200--so save yourself the $33.12 + shipping. (btw, I have one for sale... brand new)
I've been experimenting with a few pieces of thick cardboard, which I laminated, and zip-tied between the forks. The laminated cardboard layers do a good job of dampening/blocking the noise, so I'm going to construct a more durable test model, from a few sheets of kydex.
I don't have photos of the cardboard mock-up, but you can see what it's mimicking, and how it could work on your bike.
Pic 1: the part itself
Pic 2: the part installed on the f800gsa, looking up, from the right underside front
Pic 3: looking down the tunnel to the road.
What do ya'll think? Any other ideas?
(OBVIOUSLY: make sure you test out the fit BEFORE you go riding; to make sure it doesn't interfere with turning, etc.)