I have an icom 751, a butternut vertical and a dipole for 20 meters.  I recently moved all of my things into my new ham shack.  I have 2 computers, a refrigerator, an window unit air conditioner and my radio.  When I turn on my rig I hear static similar to the noise you hear when you hear engine noise through a radio.  Only difference is that the pitch of the noise doesn't change.  It seems to be more noticeable when you are on the lower bands say 80 or 160 meters but it is present on all bands.  I tried moving the rig and turning various things off, also tried both antennas and still the same thing.  Any thoughts or ideas?