I have seen many comments where people seem to not really believe that the roommates could sleep through possible noises. I want to throw my side in as someone on the other spectrum.
In college, 6 of us rented a 5 bedroom house. It was ALWAYS a hive of activity, roommates in and out, friends, classmates, etc We all had different schedules plus part time jobs. Our doors were never locked. Neighborhoods full of student housing are never quiet, you get used to the background noise.
A few of us, on a normal day, could sleep through most anything. After a night of partying, sleeping in until 3pm was not uncommon. And even more unlikely that we would wake. I can say with certainty that I have slept through 5 people practicing drunk cartwheels on the hardwood floor directly under my poorly insulated bedroom. This was all in the mid 90's, prior to earbuds and TV's in every room.
MOO college kids sleep in often and that is not suspicious to the heavy sleepers out there.