I'm not sure if its always been present and I've never noticed it
before, but for the past year I always hear a buzzing sound coming
from underneath the floor in my kitchen. It is on at all times. If I
go in the basement below the kitchen, I can hear this same buzzing
sound coming from overhead in the ceiling. It sounds like the
standard 60 Hz buzz that you get from old transformers. Its
especially obvious at night, when everything is quiet (if actually
sounds louder although I'm not sure if this is my imagination or not).
I have tried to isolate where this sound is coming from but it is
proving to be quite difficult (I have read posts on the Internet that
says that the human ear has a difficult time pinpointing the source of
a 60 Hz tone, and its true. I'll be in the basement with my head in
the ceiling, and it'll sound like the sound is right in front of me.
I'll turn my head 45 degrees and it'll sound like its right behind
me).

I have tried turning off the power to the entire house at the fuse
box, and the sound disappears. So I know that it's not coming from
the pipes (certain people have said that a toilet slowly leaking can
create this type of buzzing sound). I have also tried removing the
fuses one at a time (that is, removing one, listening for the noise,
then putting the fuse back in and removing the next fuse), and oddly
enough I have noticed that removing a particular fuse reduces the
sound by about 75% but doesn't get rid of it completely. Only
shutting down the whole power eliminates the buzzing 100%.

Is it possible for old electrical wires to make this buzzing sound?
Or would it come from something else (ex: a light fixture that has a
bad ground). I'm not sure how to go about fixing this problem. But
like I said I can isolate it to something within the kitchen floor (or
within the basement ceiling) itself.