I have been hearing the hum since the early 1990's. At first I only heard it outside and it sounded like a train in the distance.
In the fall of 2004 BPL or Broadband over the Powerlines came to our area. The BPL is in a short concept electric lines being used as antennas. Here they put super conducting magnets in the center of the road under the surface. I stood here and watched them. Shortly afterward we had a large blackout in the NE U.S. and up here into Ontario, Canada. Shortly after the sound started inside my home.
I have one other experience that has pointed me into this direction. I was visiting the open house for a TELESAT Base Station and heard the signals. The speaker gave acknowledgement to my hearing of the sound.
If you look into the OET Bulletin #56 of The F.C.C. they mention and comment on the Microwave Auditory Effect. It is mentioned in N.A.T.O,and it can be tracked in the I.E.E.E.
Paper entiled: Health Aspects of Wireless Communication: Auditory Perception of Microwaves - Hearing Microwaves James C. Lin, University of Illinois at Chicago
Human Auditory Perception of Pulsed Radiofrequency Energy
J.A. Elder and C.K. Chou Motorola Florida Research Labs
So far it is not considered a HAZARD in the telecommunications world. I know this summation to be not true.