John,
glider's suggestions may very well help you do away with the buzz.
However, your problem may mirror my recent experiences.
I noticed a buzzing a couple of months ago; it was very faint. Over time, the buzzing grew louder, and more annoying, especially while sitting at stop lights at idle. Eventually, it got to the point that while riding at night, I could see the my headlight beam jumping around on highway signs and other items ahead of me.
It was now to the point that I could grab the headlight, and feel it rock up/down as I moved it around. The headlight housing on my Wide Glide is attached to the mounting bracket utilizing four rivets. The rivets have started to lose their "pinch". So now my headlight buzzes like an electric shaver.
I went to the dealer, who was aware of this issue as he stated he had about 5 other Wide Glides with new headlights on order for the same thing.
The first new headlight the dealer received for my bike already had loose rivets. Dealer told me he was sending it back for a new one. The second headlight received by the dealer did not fit my trim ring and dealer assumed Harley sent him the wrong part number.
I'm now waiting on my third headlight... and my bike still sounds like an electric shaver.
Check to see if this may be your problem. Hopefully you won't have the same issues with your dealer getting the right part...