Our Winnebago is a gas coach, powered by a Ford V10 engine. It is a great powertrain, but the doghouse, or engine cover, is right between the front seats. Whenever you accelerate, especially when climbing a hill, the engine noise can be pretty annoyingly loud.
Being a hot rodder for most of my adult life I was familiar with a product called Dynamat. It is renowned for mitigating heat and noise. If it works for custom cars, it must work for RV’s, right?
I bought a Dynamat Extreme kit from Amazon. It consisted of four 32″ x 18″ sheets. The sheets have a foil cover on one side and very sticky adhesive on the other side.
The first step is to remove the thin layer of foil on the engine cover. This little bit isn’t doing much sound deadening! 
Here you can see just how thin the foil is. 
These installation tools are a must-have to do this job properly. Also, be sure to wear gloves! 
Lay out the sheets in the sun to make them a little more flexible. 
This is the finished product. Take your time, lay out the strips, smoothing as you go. The roller tool makes all the difference when you start smoothing out the seams.