I'm laying plywood over combo of plywood & particle board. Painting the new plywood for finished floor. Can I use this b/w the layers to reduce noise?

It would provide some reduction of noise as it has an IIC rating of 58. Please ensure that your construction and sub-floor is such that it does not allow moisture to be trapped e.g. over a crawl space etc.

Well, that's an "off label" use for sure. It's made to cushion and even out floors under laminate floors, but mostly to keep moisture from coming through the floor. It does have a cushioning and sound deadening effect. If you have noise conducted through the building frame into the subfloor, it will help to decouple the layers of plywood. It won't reduce sound generated in the room. I did a similar thing in my cellar, where I supported the edges of OSB with pressure treated 1X2 sleepers, and filled in between the sleepers with closed cell foam sheets, 3/4 inch. Been there 25 years so far. the sleepers are necessary because otherwise the edges of the OSB would dig into the foam. It might not be a problem with stiff plywood and very thin foam.