This is fundamentaly a question about soundproofing and sound absorbtion. When working this project I've realised I don't understand the concepts as much as I though I did.
I basically set up a shelf train set. The shelving is made out of fiberboard covered with melamine. And for the model base I chose extruded polystyrene foam (XPS), the kind used for insulation. Now, I was under the assumption that materials used for insulation were also good and used for sound-proofing... However, I found out after the fact that perhaps the XPS was the worst choice I could've made, soundwise, as the foam, contrary to what I expected from foam, at this density at least, becomes like the membrane of a drum and multiplies every noise! So now my mission is to quiet it down as much as possible.
At certain points the XPS sits right on top of the shelves. Here, I understand my best option is to glue it completely onto the melamine/fiberboard, thereby dampening its flexibility, which will prevent it from vibrating freely. Though here is where my knowledge of the concepts involved starts getting hazy... Would it be better to glue it entirely? Would it be better to glue it in certain parts and leave certain other parts unglued? Maybe even put some sound-absorbing material like cloth between the XPS and the shelf in those unglued parts? Is it better to glue it sparsely? Will any of this make a difference?
Then come other parts of the model where the foam needs to rise in an incline to meet another level of foam. I've got these set up as follows:
Where the incline is made by adding 3mm-thick pieces of MDF cut at intervals ranging from 0.5-4cm tall. In this case, my thougts are that leaving these empty "chambers" under the XPS will simply act as the body of a guitar and amplify everything even more. But what to do? Should I fill them with sound-absorbing material?
Should I glue in more incline intervals out of cardboard, for instance, to make it all more rigid?
Should I glue a more rigid base under the XPS? Like some MDF or even place some cloth?
What is my best option for achieving a good sound absorbtion here?
I can't get rid if the XPS because I already invested in a lot of it. I've already spentsoun way over what was planned, so I would greatly appreciate any solution that's rather on the budget side.
Thanks in advance for your input!