DIY Soundproofing with MDF and 12" thick rubber

Hi, I have a home studio and I'm trying to eliminate a mild amount of traffic noise. I am on the 8th floor of an 8 floor building. Three of the walls face into the house and are very quiet. One wall faces the street and low levels of traffic "shwooshing" and engine noise come through. The wall is 6 feet by 10 feet. It is made from standard drywall. It has 3 foot high window set 3 feet from the floor and running the length of the wall. I don't mind completely blocking out the windows. The apartment structure is unique in outside the above wall, 2 feet away, there is another wall that stretches to the roof. This outer wall is made from Concrete, windows, and aluminum siding. Between the two walls is accessible and was built for storage. I had thought of covering the dimensions of the offending wall completely with 9 or 18 inch MDF. I also have access to rolls of 10-16 inch thick industrial rubber that I could hang down the walls. I would like to keep the construction 'non-permanent' as I'll need to take it down when I leave. Would either of these solutions help? Which would be best? Should I place these items in the room or in between the outer and inner wall? Thanks, Nick