I own a raise ranche home that is split into a 2 family house, 1st and
2nd floor.

I recently put hard wood flooring in my living room. The gaps where
the wall and floor meet I used caulk to seal off that bit of space,
thinking it will block some noise. The wall plugs I used electric foam
covers that go inside the plate.

I managed to cut down the noise level I hear from the 1st floor a
little. One of the problems is noise coming from the 1st floor where
the 1st floor door is. There is an almost 1 inch gap under the door.
Is there something I could do to muffle the noise a little without
replacing the door.

I was wondering if anyone also has any other advice on muffling the
noise coming from downstairs.