In article , Jonny R wrote:
Story about 60 Hz buzzing in the floor

Although I agree with the doorbell transformer hypothesis, I can think
of other things to check - especially since there appears to be more than
source (Jonny says shutting down a particular circuit reduces the noise by
75%).

Look for starterless fluorescent fixtures that have missing or burnt out
bulbs but are receiving power. Also, are there any fluorescent night
lights?

How about any wall transformers left plugged in - such as for a battery
charger or a charger for a cordless power tool?

Could there be more than one doorbell transformer?

Do the telephones have features powered by a transformer? (Most home
phones do not but some do and many office phones do.)

Are any appliances with transformers sitting on the floor or on
rigid furniture on the floor anywhere?
Floor vibrations can travel far and the floor may even vibrate the most
a few or possibly several feet from the source of the vibration. In
addition, acoustic standing waves may make the sound louder near a wall
or in a corner across a room from the source than at locations closer to
the source (or the part of the floor that is vibrating the most).

- Don Klipstein )