Wanted to ask the group what everyone uses for mufflers for your dyno setups.  I live in a residential area and have neighbors all around me very close and need to keep things as quiet as possible.  Want to see good experiences of things that work and how I could do this so I don't get complaints.  

Currently I have two 55 gallon drums filled with tires and some baffle plates sitting outside the garage and they work okay but the neighbor across the street (a friend of mine luckily) can still hear an engine running wide open.  

So any good systems that are easy to implement would be great.  Thanks