Just some thoughts....

Is this interference coming down the mains wire, through the air, or is it the 2k itself?

SO

Try feeding the power apapter through a main filter or (even better) a PC UPS system. Can you get your hands on a portable generator - try it in the garden!

Is the behaviour the same at a neighbours house? Different block / town / state?

Do you have light dimmers in the house? Dodgy flourescents? Does the noise go away if you turn off the Lights / TV / Freezer / Fridge / Aquarium?