Hi Andy
That was me with the feedback from the ANR control box near the PTT switch. Just for fun I wrapped the box in aluminum foil (NO difference). Now I just hang my controllers on each side,under the panel. Keeps them out of the way,easy to adjust and NO noise!! It sure was a "bear" trying to figure out what was happening though.
Good luck.
Don
PS The old non ANR D/C`s did not have this issue. They do attract a lot of engine/charging system/cabin noise however. I bring along a spare set just in case the ANR`s act up again.