If you can operate your receiver off battery power, I suggest shutting
off all the power at your circuit breaker. Then turn your receiver on
and see how much 'quieter' things are. That should show you how much of
the noise you hear is atmospheric and how much of it is from sources
inside the house.

If you want to minimize the noise coming from various appliances in
your home, pick up some ferrite beads and attach them to all the power
cords. I did this and it helps. I also keep my receivers as far away
from other appliances, especially computers, printers, etc., as
possible. Yes, this might mean that you won't be able to control the
receiver with your computer, but--at least in my case--the trade off
was well worth it.