Unexplained Sound

So I am writing for the first time what I experienced. I had completed my exams and had been living with my aunt (father's sister), her daughter (S) and S's son (J).

Where they live is an empty apartment building. There are two buildings and they are on the opposite side of each other. My aunt lives in building A and the opposite one is B. In building A, only my aunt's family (consisting of 3 people) live on the first floor and an old lady lives on the 4th floor. In the opposite building one couple and 4 boys live on 2nd floor and 4th floor respectively.

As there are not many people living there it's kind of a peaceful place. So it was Friday afternoon and me and J were talking about ghosts and were watching videos related to the same. (There is very little age difference between me and my nephew because I am the youngest sister.)

The next morning we were going to have picnic so that night we slept early, but the excitement kept both J and me awake. Now around 1:30 I heard a sound like someone was dragging a chain along the road and not just once but through the whole night until almost 5:00. I couldn't sleep the whole night, and woke up around 5:15. Everyone else was asleep.

Then I see J also waking up in his bedroom. So we both after having refreshed, started talking as there was still time before everyone else woke up. The first thing he asked me was "Did you heard the sound of chain dragging?" and I was like you heard it too? We both explained each other what we heard. It was same but he said that whenever he heard the sound the door of his room would be shaking violently without making a single noise.

Now as I mentioned earlier it is a very old apartment and the doors were replaced 10 years ago. So it is bound to make noise even if you just open it. After that I described it to my another sister (my aunt has 4 daughters) and she said that she also heard the same sounds most of the night when she took care of our grandma.

We used to be a joint family before the family separated. The whole family lived in various apartments in the same building for 17 years and once I casually asked my mother about anything paranormal there and she said no. No one has even committed suicide there. So I don't know what caused the noise but it was there.

P.S. J heard that same noise twice after the above incident.