What is this thing?

[MattismodderX]

So i was doing the whole *listen to what rattles* and i peeled back the "carpet" in the trunk on the passenger side and saw the thing in the picture below. it has rubber flaps that seem to be going to the outside. the rubber makes quite a bit of noise when the subs play. so my question is..

1. what is it
2. what does it do/do i need it


edit: not the wire thing, but the rectangle shaped thing