Do you have a GoPro Buzz?
Ours started small, almost unnoticeable, but gradually got worse till it was very annoying.
Now we can identify the GoPro buzz in many videos folks post on the net.
We chased our small buzz in our video for days. The buzz continued to get worse as we kept attempting to isolate the annoying sound. If we shook the Go Pro a certain way, we could hear a very faint little rattle. This was the little rattle that was amplified in the GoPro case. We found for us the little plastic lens on the front of the Go Pro was the culprit. The lens is held in place by a two small little round protrusions built into the front half of the case. When the lens's are installed, it appears the little protrusions are melted to hold the lens in place.
Well, ours worked its way loose. The solution for us was to put two very small dabs of epoxy next to where the little protrusions are, holding the lens tight to the case. In the picture, GoPro Buzz you can see the two small little dabs of shiny clear epoxy.
Hope this helps and saves some time for someone :)