When you're trying to mitigate sound from an ASIC you need a) to reflect sounds back into the box and b) absorb sounds within the box. I've contructed a box from 25 mm MDF and lined it with 30 mm closed-cell foam marketed for vehicle sound-deadening but I'd like to do a better job and I was wondering what else I could construct the box from that would improve performance. I've read that bathroom tiles are good at reflecting sounds because they're hard and very smooth (not the textured ones, obviously) so I was considering attaching them to the inside of the box between the MDF and the foam to improve sound absorption. Does anyone think this makes sense or is a waste of time?

I'd actually really like to make something from concrete like this but it would be really heavy (kind of why I think it would be effective).