It is described as AC Power Line Conditioners. This is what the manufacture said: The first in a new line of Audio Products -- Mulder Audio Snuffers are passive line filters that you plug into unused receptacles in a "circle" around your listening space, as close as possible to your system. A second set of three can be placed outside your listening space near computers and kitchen appliances for even further noise reduction. Sonically, You will notice a more refined, cleaner presentation with a blacker background and additional space between instruments.
I had a dealer loan me one, and did not find in my system that it made a difference, especially as you describe. But it is best to get a loaner and try in your own system as each system's power sourcing is different.