it´s all fake!
well, not all, I just wrote that to get your attention. But I do believe that in almost every clip, the sound effects are dubbed over. You know, all those cameras in stores and stuff don´t have audio I think, so all the sound effects have been added afterwards to make it more suspenseful less boring. And obviously the music as well, but I guess that´s more acceptable.
This trick is super-well done, but it can be detected if you´re aware of it. Notice how they re-use the same punch-sound for punches, and sometimes the same screams for men and females(all of which can be found in the hollywood sfx archive).
Think about imagine. Imagine the clip youre watching silent, and then try to count up all the added effects. They even have angry-crowd noises for some of the riot-clips! It probably makes the clips more fun, but it distorts reality in a way that I think is highly questionable, especially when considering the subject matter.
This has started to ruin the show for me, since it makes me wonder how much more of it is fake.