My 2015 650LT had a significant and very annoying buzz starting at 4k rpm. Just discovered that it was the handguards. The buzz is gone after removing the handguards. Removed the whole unit but left the inside mounting brackets on the handlebars.
What a relief not to hear that buzz!
Sorry, no solution offered up by me at this point. I know it shouldn't take much experimenting, but since I have no urgent need to get them back on, I'm leaving them off for now.
Note that this buzz is different from the buzz that is coming from the dash or fairing somewhere. My bike had that buzz beginning around the 600 mile mark. Last year I tried the solution that was suggested by another member, putting the weather stripping on the fairing around the headlight. It did not eliminate that buzz, which on my bike, starts around 3200 rpm. Still would like to eliminate that buzz some time, however currently it's insignificant in volume compared to how loud the handguard buzz was.
Anyway, if anyone with a 2015+ 650LT has a similar significant buzz, try removing that handguards. And maybe you'll determine the solution before I get around to it