sound insulation

Hello all. I originally posted this question under the HO Forum, but thought maybe this was the better forum for it.
First of all a quick thank you to those of you who have answered some of my other questions. There is some great knowledge here and thanks for sharing it. it makes it fun for us newbies.

As back ground, I have completed my baseboard as seen in the attached pictures. I have covered the plywood with 3/4" and 1" foam for sound deadening. I have a riser that is approximately 25' long also made of plywood. Now finally to my question. Is cork roadbed sufficient sound insulation right on the plywood riser or should I put foam on it as well? Also do you you think the 3/4" foam is adequate sound insulation on the rest of the board?

Thanks

 

I am not using any foam, the cork is glued to the plywood.

There are discussion threads regarding the sound deadening qualities of foam and opinions vary tremendously.

 

I hate to disappoint you, especially if having a quiet running model railroad is important to you. Extruded Styrofoam does not "deaden" sound. It acts as a resonator, or a drumhead and actually amplifies the sound of your trains. Plywood does the same thing, but not to as great a degree as Styrofoam sheets.

Now, I'm not drawing a conclusion from anything but my personal experience of building layouts for myself and others over the past 35 or so years.

Here's what I've learned as far as sound deadening is concerned for N-scale and HO scale layouts and modules.

Gluing cork roadbed to your subroadbed will do little to deaden sound no matter what your subroadbed is made of.

The worst thing to make your subroadbed from is extruded Styrofoam...unless you want to build a layout directly on a big bass drum.

The second worst thing to lay both cork roadbed and track on (from a sound-deadening aspect) is a hollow-core door.

The third worst thing to use as a subroadbed is 1/4" plywood.

The 4th best thing to use as a sound-deadening subroadbed is 3/4" plywood (1/2" is somewhere between 1/4" and 3/4" plywood...about 2/3rds of the way towards 3/4").

The 3rd best material to use is splined wood subroadbed made from a soft wood such as pine, spruce or redwood.

The 2nd best material to use is splined Masonite subroadbed for sound deadening.

The VERY BEST semi practical material to use for sound deadening is...(Ta Da!!)...cast plaster subroadbed.

I'm sure if you could fashion subroadbed out of sheet lead, it would be the best...or maybe Tungsten Carbide or depleted Uranium...because DENSE is best.

Since I use both 3/4" plywood and splined Masonite as materials for subroadbed, and then use various thicknesses of extruded Styrofoam for a scenery base, here's is my experience with them.

I use 3/4" plywood for yards and large industrial areas, and when my trains come in off the splined Masonite right of ways at the yard limits, they get very noticeably louder as they come on to the scenery that's built on the 3/4" plywood whether the track is ballasted or not. I use cork roadbed everywhere but I have run trains on sections without cork, and the track noise volume is the same according to my ears, but less "deep". Cork seems to absorb high frequencies, and the track noise of my trains with it is "duller" (not counting actual digital sound coming out of my sound decoders).

Ballasting helps. Trains get quieter with well ballasted track, and I use only "real rock" N-scale ballast. I don't know how the track noise would be affected using walnut shells or cat litter since I've never used either of them. Incidently, using matte medium is better than using white glue, because matte medium is slightly flexible and will absorb some vibrations, whereas white glue is hard and readily transmits vibrations.

Okay...now it's time for me to put my extruded Styrofoam scenery base on..and what do you know????...my trains' track noise gets LOUDER when I have just an extruded Styrofoam scenery base with no actual scenery on it, the scenery base edges being hot-glued to my subroadbed and layout fascia (also Masonite).

If I use a layer of plaster impregnated cheescloth over the top of my Styrofoam scenery base, that quiets it down some...and as I add dirt, felt, trees, paint, structures, etc., each addition makes it progressively quieter. By the way, I rarely put a layer of plaster impregnated cheesecloth over my extruded Styrofoam any more. It was an experiment, which proved to be superfluous.

I have sections of scenery where I used cheesecloth and plaster (without any Styrofoam underneath) as a hardshell scenery base, and it is quieter than my extruded Styrofoam scenery base, that is until I get the scenery finished, then it's about equal.

Soooo...there are some solutions to the noisy sheet Styrofoam "table top" that is popular today as both a scenery base and subroadbed, and that is to apply a sound-deadening material on the underside, such as sound-deadening materials you can get at stereo installations shops. I haven't done it, but when thinking about it, I think that strips of it would work just as well as covering the entire underside with it, which will lessen the expense.

For your plywood subroadbed, you could spray or brush automotive undercoat on it, which will work quite well as a vibration absorber. I'd do it before I started wiring anything...the same for the sound deadening material from the car stereo installation shop.

AND, as a bonus, the more scenery you put on top of your Styrofoam sheets, the less drumhead-like it will become, so your layout will get quieter just by completing it.

That's my experience with track vibration transmission and amplification, and what to do to lessen it.

Hope this assists you.

Cheerio!!
Bob Gilmore

 

Excellent explanation Bob. In referring to audio installations a number one material used is MDF board for its density and inability to transmit vibrations. As noted thicker is better when it comes to plywood.

As a foot note do not use metal wheels and convert any rolling stock with metal wheels to dilrin (plastic / nylon). Unfortunately locos with metal wheels and motors / gears transmit vibrations and there is not much that can be done about it.

Other improvements within the layout area that can reduce a room's sound acoustics is the use of a curtain below the layout, carpeting on the floor, curtains over windows if present that are not in conflict with the layout and an acoustic ceiling.

Jerry

 

If you think making the road bed out of dense material will dampen the sound, please explain the hard maple sound board in a piano.

 

My response is derived from my experience, not from conjecture. I haven't laid any track on a maple, piano sound board yet. But, I'll venture a guess. Maple is a hardwood, and is probably not "dense", but it is hard and stiff. There's a big difference between "dense" and "hard/stiff".

Dense and thick absorbs vibration, whereas hard/stiff and thin amplifies vibration...especially when it's a large surface in relation to the vibration causing instrument, such as a slap bass, or a drum head being whacked by the tip of a drumstick or just about any musical instrument that depends on a string or stick to provide the vibratory impulses.

I'm guessing that a piano's soundboard wouldn't be much good if it was just a strip wide enough to perform its mechanical function, or, if it was a couple of inches thick. I haven't looked inside my piano in a long time, so I'm gonna guess that the sound board is a big piece with good surface area, and only thick enough to support any mechanical stresses, so it will amplify the vibrations of the struck piano wires.

Good enough for pure conjecture.

The suggestion to provide a cloth valence on the underside of the layout, and perhaps build the layout on a carpeted floor is a very good suggestion to help deaden reflected sound vibrations. Interestingly, my layout is built with these features, and I haven't really thought of them as providing sound deadening. I'll have to include those features in my next sound-deadening description whenever that may be!

On the other hand, if you took some maple, cut it into strips (splines) and made laminated roadbed out of it, gluing each strip together with yellow wood glue, just so it would be barely wider than the cork roadbed on top...it would probably be somewhat sound-deadening also, although not as much as the denser/heavier laminated Masonite subroadbed. Strips of MDF might work good too as splines, since MDF is used quite universally in speaker enclosure construction.

But, it's all a guess (albeit based on experience) and you really don't know what you're gonna get from a sound deadening aspect until you build it, run trains on it and compare it to other construction techniques.

One thing that I didn't mention in my previous post is that Styrofoam subroadbed made up like traditional plywood subroadbed with risers supporting it rather than just laying track on a big sheet would also be much more quiet than the big sheet because there is less surface area to radiate vibrations.

One model railroader is making laminated Styrofoam subroadbed from thin Styrofoam splines which he precisely cuts with a tool he's made. He finds this sufficient for his needs, although I haven't read a comment as to how quiet/noisy it is.

With sound decoders becoming more prevalent, it is important for our trains to run quietly, and the proper benchwork will go a long way to help.

Cheerio!
Bob Gilmore

 

You mention using Styrofoam. Is that what you really mean? The stuff used for coffee cups? Or do you mean the pink or blue insulation board used by many so they can carve out landscape features. Styrofoam is nasty stuff to work with and the pink/blue board is a lot denser.

Have you tried acoustical ceiling tiles?

 

No I am using extruded foam not Styrofoam.

 

Extruded polystyrene foam that is made by Dow Chemical Company is called "Styrofoam". The process was discovered by Dow in 1941, so it's been around a while. I have a lot of it in various thicknesses and right on the top 4X8x2" sheet of my stack it says "Styrofoam" in big black letters, with a Dow logo above it. It's a product name which is why I capitalize it. Other manufacturers call theirs whatever they want, except they are not allowed by law to call theirs "Styrofoam" which belongs to Dow. For instance, BASF calls theirs "Thermacol", Owens Corning calls theirs "Foamular".

Extruded polystyrene foam insulation is all basically the same, no matter what it's called, but Dow was the inventor, so I use the product name "extruded Styrofoam", or just plain old "Styrofoam" when talking about it. My experience says that it comes in white, green, pink, blue and a light purple, and it's not always the same density. I have several 3" thick sheets that are very heavy and stiff and were salvaged from some concrete forms at a commercial construction site....and they are also "Styrofoam"

The material "styrofoam" (not-capitalized) is what cups, plates, packing beads and craft sheets are made out of and is a different process and material than "Styrofoam" (capitalized) and is usually called "expanded polystyrene foam"...not "extruded polystyrene foam".

It can be a bit confusing.

I prefer structurally rigid and stable methods of building my subroadbed. Acoustical ceiling tiles and Homasote, although used a lot by model railroaders, have several problems that I don't wish to contend with since I lay my own turnouts and some trackage which is all code 55 and code 40...and these products have a tendency to expand, contract and warp much more due to temperature and humidity than plywood or splined Masonite subroadbed. I need my subroadbed to be stable and durable...as well as deaden sound, so I use splined Masonite...cheap, easy, readily available, stable, strong and very sound-deadening.

There's always a trade-off between good carpentry/mechanical durability and sound-deadening. You'll find that track that is just laying there, not glued, not nailed, is a LOT quieter than track that's been glued down to the cork roadbed. For myself, I gotta glue it down securely...and that makes it "louder" than if it's just floating there. Part of the enjoyment I get from the hobby is reliable operation, and non-secured track just won't allow me either the reliability or durability I demand from my benchwork so I can transport my portable layout in a trailer to various train shows in my area. Plus, unsecured track also is subject to expansion/contraction a whole lot more than glued down and ballasted track. That's why at shows in hot weather, you'll see a lot of Atlas track that's just been secured with nails (not glued), then ballasted "popping" due to heat expansion. With my glued-down Micro Engineering track, and thorough ballasting...the only spots I get "popping" are on areas on unfinished parts such as where bridges will eventually be built and the subroadbed cut away...so I haven't glued the track down at those points.

Cheerio!
Bob Gilmore

 

I just bought a hobby sized sheet of that. It is expanded polystyrene not extruded. And kudos to Bob, misuse of Styrofoam is a pet peeve of mine. The Blue extruded polystyrene made by Dow is Styrofoam. The coffee cup is not.

 

Extruded poly us also sometimes called headboard. And there is another insulation material that's silvered but is tan. That I believe is a form of fiberglass.

 

Yep xps beadboard. My dad insulated the basement with it. The beads are a staticy mess.

 

Quality pianos use 3/16 to 3/8 of an inch spruce soundboards, cheap pianos use plywood soundboards. Maple is frequently used for other parts of a piano.

Jerry

 

Robert, thank you for clearing that up. Around here if I asked for Styrofoam board what it would be is much like the cups. Little beads pressed into a sheet and heated to make them stick together. Very, very messy to cut or form. And thanks for the warning about the acoustic tiles.

 

styrofoam is used in the US and Canada the way Kleenex is. As a generic. It is not.

If you buy Dow Blue, it will say Styrofoam right on it. Most lumber shops that carry Dow know.

Home Depot can barely spell Lumber much less Styrofoam. They'd probably look at you funny if you said Foamular even though it's right there on the sheet.