Seek and Ye Shall Find.........
RFI = Radio Frequency Interference.
Electrical resistance is anything that impedes the flow of electricity, either by design or by accident. A corroded terminal, or a "resistor" which is part of almost every piece of electronic equipment made, for the express purpose of limiting the flow of electricity. Different materials have different resistance characteristics. Water, pretty good, salt water, way better, a dry block of wood, not at all, it's an "insulator", the same as the covering on wires.
Any search for noise in a system requires a process of elimination approach.
From your description you're suggesting that this noise began in 2 different systems simultaneously. This would lead one to believe that the environment has somehow changed. The alternative is that both systems suffered a failure that exhibits the same symptoms. Or that two systems have encountered different types of failures simultaneously that exhibit exactly the same symptoms. It's certainly not impossible, but it seems unlikely.
So, the most likely (at least from your description), is that somehow an environmental change has occurred. The problem is that many things generate broadband noise. A sparking armature on an electric motor, a bad electrical connection, an improperly filtered power line. a dirty ham or CB radio and so forth.
In my neighborhood you can't watch analog OTA TV below channel 9, since there is so much crap in the airways, you can barely see the picture.
So, you do have to investigate, and possibly purchase filtered surge protectors, or RFI filters if you honestly believe that it isn't in the equipment isn't at fault..
I honestly don't have enough information to make even an informed guess. If you say you have noise in both systems, are you using the same source materials, (CDs) or whatnot 'cause it could be there
