Thud Thud
I used to live in a house with two roommates... let's called them Anna and Erica. I lived on the second floor and Anna and Erica lived downstairs. Every night I would hear this "thud, thud" coming from downstairs. I would investigate and it always came from Anna's room. I thought it was her doing burpees or working out at night (which seems dumb looking back). I never talked to Erica about it because I thought it was in my head and since I was on the second floor it never really bothered me.
Fast forward two years and we all move into a new house with another roommate. Anna, Erica, and I live on the same floor upstairs. I start hearing the "thud, thud" louder now. I go up to Anna's door and it sounds like she's hitting herself against a wall and whispering and crying or laughing. I also noticed when she left the room she had her sheets all scattered on the floor. I ask my other roommate Erica about it and she says she hears it too. Anna starts staying at her parents house more often, but every time she comes home we hear the same "thud, thud" noise. We started asking Anna about it and she makes up excuses like "I was moving furniture" or "my porch door was swinging open."
After we started questioning her more, she only came to our house maybe one a month to pick up some clothes. It was so strange. I never think we'll get an explanation.