Thick felt is what I use (see picture), but it has always been used on top of a rug or ½” EPS foam. What I don’t know is would the felt alone be a good enough sound deadener over plywood. I also know what I’m not doing again and that is ½” EPS foam as a base because I have to spend too much time crawling around on it.
I’m starting to consider Homasote (440?) as a base that would be covered by the felt. And maybe I should just bit the bullet and do the grades with the Homasote as well. But at $30+ a board, for a one month layout. Probably my biggest problem is dismantling and storing the layout and all its components… I’m not getting younger.
Tom Stoltz