I had heard people mention this phenomena but didn't know much about it or the other named hums. I looked into it and them earlier this week because for the past number of months I have been experiencing the same thing but did not know it.

Is there anyone on here who hears what sounds like a diesel idling outside? Maybe the sound of a generator running??
It is weird and annoying and wakes me up and is usually louder at night but not always. It goes on for hours at a time. You can hear this insde and outside.

I do not ever hear this anyplace but where I live.