Soundproofing an apartment bedroom?

Here's the situation guys:

I'm living in an apartment with 3 people and my room is directly parallel to another bedroom. Us two guys have separate doors to our rooms but theres bars coming about 1 feet down from the ceiling before the actual wall starts. We share a wall in other words but theres about 1-2 feet of open space up there. There is nothing in between the bars so I can hear what's going on in the other room and vice versa.

Can you give me some serious suggestions for soundproofing the room? Like what could I stick up there between the bars(which are about 6 inches apart and there are about 10 of them) to keep at least some of the sound out? Thanks.