Roadbed choice and noise dampening

Everyone should be aware by now that laying track directly on top of Extruded (XPS) Foam creates a “drum effect”. Over at the Model Railroad Hobbyist forum there had been some great threads (Foam Drum, Foam Drum II) about this issue, some good science behind it, and possible solutions to minimizing the effect.

I am one of those people who really can’t stand that noise having experience it on my mock layouts in the past. So, I have been looking for a way to find a suitable roadbed that would dampen noise. After a lot of reading and research, turns out a final solution for the roadbed would be either concrete, brick, or iron/steel.
Since I’m not building a skyscraper, I have to be realistic about available materials. My current choice is closed-cell foam, which I’ll use on my Staging level as a trial run.

There is a number of available options off the shelf from Woodland Scenics Track-bed System, DCC Concepts Trackbed, and others, all of which utilize one or another kind of closed-cell foam (PE, EVA, Neoprene Rubber, etc).

Seeing how I’ll need lots of sheets and commercial solutions aren’t really cheap on the long run, I decided to find a generic kind. Enter the Volara foam. I opted for the locally available Type A, 2 lbs/ft³ density, closed-cell roll which ended up costing me CAD 75.00 including tax, for a ⅛” x 30″ x 25 ft. roll.

Just for comparison, that roll would yield 240 strips, 30″ long and 1¼” wide. To purchase 240 strips of WS Track-bed would cost over CAD 200.00, and since they are 24″ long, they would be 120 ft. shorter.

I’m thinking for the 1st and 2nd Deck I might try the Neoprene Rubber Foam strips or sheets, or even Camper Tape, the latter being a blend of closed-cell foam kinds. There’s a local supplier here that sells strips and sheets of Neoprene Rubber Foam with or without adhesive backing.

Important to note is that all of this goes out the window if any kind of solid drying glue is used (Elmer’s White, or Wood glue) because once ballasted, it will be a direct conduit for the noise to transfer from track to the sub-roadbed. Some water soluble latex based glue should be used in a 50/50 or ratio.

Also, to glue XPS foam to plywood you have to have a hard back surface for the foam or the noise will just go through the frame of the benchwork), it has been suggested to use Latex based glue that does not dry solid but more rubbery (due to Latex content). Choices could be:  No More Nails, Carpet Glue, DAP Alex/Dynaflex 230 caulk, Green Glue Noiseproofing Sealant, Auralex TubeTak, Butyl caulk, or a ghetto solution using PL Acousti-Seal (used for vapour barriers, doesn’t dry quickly and remains sticky for years).

I’m considering giving the Green Glue a shot because many in the audio industry seem to be using it in their studio construction to acoustically insulate panels from the rest of the wall framework. It is not cheap by any means, so we’ll see…

Green Glue also has a joist tape, about 1.5″ wide, and 100 ft. costs CAD 55.00 plus tax. This could be another alternative to other closed-cell tape for roadbed in the scenic areas.