actually I will go with your husband, air flow and air infiltration.
Your house is old and is not sealed tight. Lots of out side air comes in through the cracks. Outside conditions can change the conditions inside. At
night the air starts to condense and with this your house is more likely to have more pressure problems.
a good test would be put a door stop on your door but leave the door open a crack like an inch open, hang a piece of tissue paper from the crack, and
watch the tissue paper. When pressure differences are greatest you will see the tissue paper move. It seems to me that your room is pressurized more
causing the door to close.
A small opening will cause greater air flow, like a wind tunnel. Also you can hang a piece of tissue/toilet paper all the way from the top middle of
the door frame down to about an inch away from the floor and leave the door open as normal.
I've seen in my own home a big picture on my wall vibrate, I went to the picture with out touching it I felt the air from the a/c run down the top of
wall and get behind the picture causing it to vibrate. I re adjusted the picture and after that the damn thing hasn't vibrated since! urr. kind of
like the vibrating picture.
The door bell
sometimes water, humidity can create a slight bridge for electrical current to flow causing it to ring. Since it was muffled this sounds like
something that could have caused it. The muffled sound to me sounds like some sort of resistance like water only letting part of the current to flow
to the doorbell. If it was a sharp normal ring that may be a different banana.
Were you thinking of someone deceased before the doorbell rang? I've personally had the doorbell ring when I was under stress of a loss. I have no
you will just have to go and check next time, check immediately if your husbands is in his room, if so get him and you both go and check it out.
you lived there for 18 years, recently you have been watching a lot of ghost stuff on tv so your mind travels away from reality.
Remove that fear and hit it head on and more than not, it won't be a spirit. if you find it to be a spirit, Use it to get proof and get rich!