Our previous upstairs neighbors were a very nice professor and her sweet, cheerful daughter. They would get up early in the morning, quietly prepare for their day, and head out to the university and the elementary school, leaving our ceiling in blissful silent peace. In the afternoons and early evenings, there would be occasional sounds of youthful exuberance or violin practice, both quite pleasant to overhear.
Then they moved out, and these people moved in. We thought "Oh, they're grad students, they'll be nice and quiet!" but they are not. They are home all day, with the TV or the stereo on the whole time. They run the vacuum cleaner at 8:30 in the morning. They have an annoying little dog, which they yell at a lot. Their bedsprings squeak really loudly. They do laundry almost every day (since the washer and the dryer are in the basement, this makes a lot more noise in our place than in theirs).
And this evening, while they were having a very loud Christmas party and we were in the living room packing books, we heard the sound level from upstairs suddenly increase, as though someone were stomping on the floor as hard as they could. Then we heard an enormous crash from our kitchen, as the stomping dislodged the glass cover over the overhead light, sending it smashing to the floor.
I'm just glad neither of us was in the kitchen at the time, or we could have been seriously hurt.