I thought my neighbor was nuts for complaining about a humming noise, but now I hear it too.
For a year, he kept saying there was a constant low hum at night from somewhere on our block. I wrote it off until my power went out for an hour last Tuesday and the hum stopped completely. Anyone else have a mystery noise that turned out to be a real problem?
Read an article about that exact thing. It's called The Hum. People all over report a low drone with no clear source. Some blame power lines, others say it's industrial equipment. Quinn_wood is right, a bad transformer can make that sound. My cousin had one buzzing outside his apartment for months. The power company finally replaced it and the noise stopped.