Here from "Handy Physics Answer Book":
"Different materials will absorb certain frequencies of sound better than other frequencies, but some of the best absorbers of sound are soft objects. Materials such as felt, carpeting, drapes, foam, and cork are good at matching the impedance of a sound wave and reflecting back very little sound. Materials such as concrete, brick, ceramic tile, and metals, on the other hand, are effective reflecting materials of sound. That is why gymnasiums (with hardwood floors, concrete walls, and metal ceilings) have relatively long reverberation times, while concert halls furnished with upholstered seats, carpeted floors, and long drapes have relatively short reverberation times. People are also effective sound absorbers, so a full concert hall has different acoustic properties than an empty one."
Foam absorbs sound and plywood reflects it. Plywood does a good job of preventing sound from passing through it because it is dense. Homasote, it seems to me, is the best of both worlds: it is dense, which reduces sound transmission and it also absorbs sound. The real question remains: How much do these materials reduce the sounds we hear and is it worth it? Clearly everything in our train rooms matter regarding sound. Skirting under our tables might play a larger role than just covering up the boxes we store (which probably help reduce sound, too!). I never realized the felt I use for skirting might be better than curtains because it absorbs more sound. And the rugs over my tile, help, too.
Stuff to keep in mind, Jay, as you move forward.
