converter buzzing...a little guidance appreciated

I've got a PD4560 in my unit and it does the same thing. I agree it's annoying. In our last trailer you could never hear the converter unless the fan turned on, this one has the loud buzzing which goes away if some lights are turned on. If there is a way to fix it I would happily try it out. I mentioned it to the dealer and, not surprisingly, was told that this is normal.