Ghost in the hall

We may or may not have a ghost in our hall. This morning several of us were woken up by the repeated slamming of a door, like someone was going in and out of the kitchen. But, those of us who were woken up were sleeping, so we couldn't slam, and the ones who were not woken up were also sleeping, so they couldn't slam. So we may have a ghost in our hall. Or it may be a door from any of the several houses nearby: the walls in our dorm are so thin, the sound travels an incredible amount.