Sound deadening

[2021]

As my railroad continues to grow, I noticed that quite a bit of sound is heard as the train goes thru the mountain tunnels (ideally it would be fairly quiet inside the mountain). Do any of you try to sound insulate the tunnel walls and if so how do you do it and with what material? This is, of course, most noticable when I'm alone as the ambient noise is very low (please, don't suggest turning up the radio). I am in the process of building a coal mining section with my main line running underneath and would appreciate anys suggestions.
Thanks, Ron K.

[rolleiman]

What are the tunnels made of?? Plaster and screen or foam?? If plaster and screen, and I don't know how you would do this after the fact, you might try building an interior tunnel out of foam.. Also, what is the base of your RR?? Plywood, foam, cork on plywood, homasote ? Foam and Homasote are the only of these that won't transmit sound.. Cork on plywood is quieter until you ballast (with glue) the track and recreate a sound path from the rails to the plywood but it's still quieter than bare plywood.

Jeff

[2021]

I know it's probably too late for my existing tunnel (foam walls, cardboard and plaster roof, drywall back wall, cork roadbed, ballasted). How about a new tunnel?
Ron K.

[rolleiman]

Sounds like you might have an echo chamber with the drywall backwall.. Truthfully, before you asked I never gave it much thought.. Few of my layouts have ever made it to tunnel stage.. You Might try, on the newer ones, a lining of sort, both sides and a roof made out of foam.. But of course, you run the risk of not being able to fish a train out of the tunnel.. Setting up a temporary structure lining though will tell you if it's going to work..

Good luck,
Jeff

[selector]

I anticipated this problem and purposefully placed oddly oriented and odd-shaped pieces of extruded foam inside my hollow foam mountain to absorb sound. Since the closure to the open access at the back of the mountain is a sheet of 1" foam, it caps that problem, too.

How well does it all work? I'd give it a B-. Unfortunately, it would have undoubtedly been nearer to an A if I had not designed in a substantial mine shaft facing the operator.
D'oh!

[dwiemer]

Before trying to demoli***he mountain and rebuild, you may want to try using the expanding foam "Great Stuff" found at home improvement stores. Find a hole or make one in any place on the mountain that will give access to the open areas inside the mountain. Then spray the foam inside being very careful to not over fill as this has a very high expansion rate. Then cover the hole. If you over fill, you will either have to repair or replace the mountain.
Hope this helps,
Dennis

[davidh48]

I might sound like a right-wing gun-crazed nut, but have you considered that what you really want is a "silencer?"

If you can access the length of your tunnel then a series of soft baffles (think multiple portals) along with soft lining should take almost all sound out of the "ballistic" train passing through.

I'd use the tunnel profile at any baffle point along with a NMRA gauge to create the baffles out of foam, in this case the sponge type is the best (the more porous the surface, the lesser the reverbs.)

There are many ways to do this, so just search the net for silencers for ideas.

-D

[ham99]

My tunnels are Sculptamold over a 1" foam base. The whole mountain lifts off. I glued 1/4" dowels in the base that drop into 5/16" holes in the benchwork. You can see the joint if you look carefully, but most of it is hidden behind scenery. I hardly hear the train in the tunnel, but it is running on unballasted cork once it gets a few inches inside.

[davidh48]

Agree,

I use foam board as "first contact" before any dense material (wood for framing) gets near the rails. I glue ties to the foam, and don't "spike" rails.

P.S. I also used to think the "rumble" of a Lionel loco in a tunnel on a 4'x8' plywood sheet was "keen." I'd lay my head on the track and watch the headlight come sweeping out towards me from a "tunnel/mountain"; which only covered about two cars in my train.

-D

[davidh48]

Oops,

Forgot to ask: "Are you concerned about steam or diesel/electric?"
The latter are really quiet in tunnels, steam is not.

I'd also "assumed" that you had managed to create some sort of echo chamber.

I've hiked the tunnels on the Grangeville extension out of Lewiston, ID and you've got to be aware thatt a diesel loco coming downgrade is going to be very quiet. You won't even sense the pressure wave, it's moving slowly.

A steam loco, upward bound is going to be MUCH louder.

I'd never considered this from a modeling standpoint, but it "sounds" like another great use of DCC.

[Anonymous]

IF your tunnel is completely enclosed for it entire length, try some fiberglass insulation. (Insert all safety warnings about inhalation and splinters in skin,Etc.) This is used to deaden the sound on Dishwashers and in the construction of rooms in homes and offices that require noise abatement or sound privacy. Just loosely apply the insulation around the tunnel structure. Dishwashers use just about 1/2" and it deadens quite a roar of activity. It should silence a model train completely.

Another idea that just occured to me is ceiling tiles as used in drop ceilings are sound deadening as well. This could be used with a tunnel that is not completely enclosed.

[nbrodar]

Is your track base pink or blue foam? These act like sounding boards. And the enclosed tunnel only serves to amplify that resonance. Try leaving the back of the tunnel open. It works for me.

Nick

[donbpage]

I think the fiberglass idea would work best. I would use insulation with a vapor barrier on one side and remove glass until you got a thickness of about 1/2". The glass side could then be covered with aluminum screening to prevent fraying. I'm not sure you could get this into your existing tunnel, but it should work for new construction.

I don't think Great stuff would be very effective as it is closed cell and forms a smooth, hard surface. You need something that is open cell that will allow the sound to penetrate and expend its energy vibrating the material which would dissipate it by creating small amounts of heat through internal friction.

[selector]

QUOTE: Originally posted by nbrodar

Is your track base pink or blue foam? These act like sounding boards. And the enclosed tunnel only serves to amplify that resonance. Try leaving the back of the tunnel open. It works for me.

Nick

Not for me. If the tunnel back is near or against a wall, the sound will merely reflect off that surface. I have found that a foam slab shaped and taped to fit the orifice of the mountain does a great job of silencing the noise.

I like the idea of fiberglass insulation. It could even be fixed to the inside of the foam "door" to improve its silencing characteristics.

[Anonymous]

If you go with the fiberglass batt method, lay the fiberglass in loose, do not compress it or wad it up tight.....and don't expose it to bare wiring, it will burn or melt. It should offer the most sound attenuation.

[2021]

Thanks for the suggestions. I will try the fiberglas insulation on my next tunnel as it sounds easy and logical. I do run steam and diesel and your right that the steam is much louder. I also like the idea of not ballasting the track inside the tunnel as you can hear a significant difference before and after ballasting. One other lesson learned - ALWAYS make sure you have full access to all track (I can reach in to retrieve any derailments should they occur).
Thanks again, Ron K.

[Anonymous]

You might try rubberized shelf liner (the kind with the little holes in it).
I'm using Bachmann's EZ Track on a foam base and it was really noisy. I put the shelf liner under the track and it worked wonders.
You could try lining the walls of the tunnel with the shelf liner.
An added benefit is that the shelf liner comes in different colors.

[Anonymous]

QUOTE: Originally posted by fourfouro

You might try rubberized shelf liner (the kind with the little holes in it).
I'm using Bachmann's EZ Track on a foam base and it was really noisy. I put the shelf liner under the track and it worked wonders.
You could try lining the walls of the tunnel with the shelf liner.
An added benefit is that the shelf liner comes in different colors.

Hey I like that idea! may try it myself.

[Anonymous]

Check out your local carpet store dumpster for some foam-backed scraps. Staple strips to plywood tunnel sides or for curved tunnels, use contact cement to masonite. Glue-onor screw a mounting block about every six inches or so. Make a plywood cap with carpet (facing down). Also, glue narrow strips along the sides of the track to en wheel noise. If your dumpster dive yields only light lolor carpeting, take it outside and shade it with flat black spray paint. Free stuff is good.