Sound Deadener
more than you would think, I used 2 boxes of this
Noico 80 mil 36 sqft car Sound deadening mat, Butyl Automotive Sound Deadener, Audio Noise Insulation and dampening,
Got it from Amazon, then about halve a box of the eastwood stuff,(pretty much same stuff) that did my floors inside doors and trunk area, then I used this on the roof from Summit did my entire ceiling with a little left over.
RetroSound MAT-50-HD 14.6sqft