Egg cartons for soundproofing? - Model Railroader Magazine

Egg crates, egg crate foam, Sonex, etc. are upper mid to high frequency absorbers. They are used to prevent unwanted reflections from hard surfaces. If you think of the train as being the magnet in a speaker, the table can become diaphragm or paper cone if energy is transmitted through rigid materials from the track to large sheets of plywood.

Normal scenery on top of the layout will absorb varying amounts of sound energy coming off plywood, layers of foam and plaster will soak up close to all of it. But the bottom of the layout is usually untreated. It will radiate the vibrations into the cavity under the benchwork without attenuation of any kind. You could treat the floor with carpet, but you'd still get some leakage around the edges of the table. Carpet, in fact any surfacer treatment will not absorb mid and lower frequency sound energy.

In order then, your options, from best to worst, for quiet operations, are:

1. Quiet trains and track. Stop the problems before they start.

2. Foam, cork, rubber or other deadening material for roadbed.

3. Surface treating the underside of the layout.

4. Surface treating the layout room's walls, ceiling, and/or floor.

A final note on surface treatments like eggcrate foam...since it only absorbs part of the sound spectrum, and since anechoic (zero reverberation) chambers are uncomfortable for most people, total coverage with this type treatment usually yields unlivable results. Most studios and production facilities use surface treatment judiciously, along with proper dimensioning and construction of walls, diffusion, low frequency absorption and other techniques to achieve a reduction in reverberation, not its absence, and the main goal is to leave the room acoustically transparent across the spectrum, not solely at selected frequencies.

An excellent reference on low-cost sound manipulation techniques can be found here: