This is so off-topic, but no one ever believes me when I'm complaining about a wall adapter across the room driving me mad. Glad to know I'm really not imagining things hah!
It can be an issue even if you think you understand it at the design stage. I've sold services to identify sources so boards or assemblies can be redesigned. In one case two different clocks for two ICs on different boards interfered with each other causing problematic noise. Filtering the power supplies helped, but changing how one IC was used made the single biggest contribution to reducing the noise levels.
