General noises inside of the car while driving not on smooth road

I'm wondering if is normal and someone else has it, or I need to do something about it? I hear a lot of general noises from the back of my car - sometimes this thing on the left from me - plastic speaker cup type of looking thing - I think is like plastics in the car are not connected/insulated well? I'm getting use to it when I play music but I'm wondering if is normal compare to other cars or maybe my expectations are too high?