I don't know where either of those are in the car yet, but the noise at first I thought was in the side-mirror (heard it clearly inside the cabin), and when I was inspecting from the engine bay it was clear to be coming from that pocket that houses the brake master.

The thing is the noise came once while the engine was stopped and I was out of the car, so it's definitely an electric device that is independent from actual engine running and independent from driver input. Would the abs pump do that?

Fuel pump I kind of rule out though because it is working perfectly and I am not having any weakness in pull while the noise kicks in.

Thanks for the tips. I guess dust is not an indication of a problem other than thinking of upgrading pads and rotors. Check.

Any more thoughts about any of the three points still appreciated.