Speaking very broadly, conducted emissions from an offending source (say a computer) don't get very far in premises AC wiring. I like to think of that wiring as a haphazard network of mis-terminated transmission lines, teeming with reflections and standing waves at frequencies over a few MHz (think about their electrical wavelengths). The folks who use the power-line for home automation know this first-hand! Some offending sources, such as the notorious cheap light dimmer, create a very wide spectrum of interference at at repetition rate twice the mains frequency. This means that the audible "buzz" isn't much of a clue as to whether the victim device is responding to an in-band audio frequency or the RF harmonics of the interference. A power-line "interference filter" wouldn't have much effect on the former but might cure the latter. Trying to pinpoint the route taken by the interference in these cases can be a real challenge!Hi, Bill.....thanks for your comments.
I was thinking more along the lines (no pun intended) about "hash" from computers, and who knows what else, being radiated from the wiring versus a electromagnetic field. Do your comments also apply for this situation?
Bri