If I'm not mistaken a AT&T cell tower went up. Not sure how long ago. We added a new phone and voice mail controller, but that was at least 4 to 6 months before the noise started. I have our IT person looking into dates and equipment that was installed around that time. Equipment that we have and has been running before this:
Computer Servers ( Wire less )
Video Surveillance ( I believe some is wire less )
Heating and cooling Zone controller ( Damper motors )
1 Bathroom vent fan, runs constant.
