Like before, I believe that the sounds were just that (mostly). This time, taking the cue from the title, and the SciFi series mentioned about the humans being the horror story for the aliens, as well as the contained box-like apartment set, I believe the author was shading the story with another explanation. That we could consider the family of humans as we'd look at the behavior of family of animals in a box. [and the sounds were from the "world outside"] Not that this was necessarily actually happening, but that it was possible to consider it from the other perspective.
The first time, I was convinced that Eric had hit such a dead-end in his situation that he was about to commit suicide by compactor. (Perhaps the difference in actors may have contributed to this).
This time, I think that it's mostly a convenient coup de theatre to block things and end the play with a bang ...and a question to talk about. (an interbang?)