100 Polyurethane from Walmart ?

Etran, you're better off with high density fiberglass as sound absorber than most foam products. Both Owens Corning and John Mansfield make these panels in 4X8 feet and 1' to 6" thick.

This high density fiberglass is what my room is covered in and what most recording studio's use.

The down side is the cost of the rail system that allows for fine finish of acoustic cloth to cover it all up.

These mattress pads do make excellent packing material for components. I have sent 2 CDP's to europe using old pads cut to fit as packing. They arrived in pristine condition despite being handled bu US and European postal processors.

I have used the foam pads from walmart and they work great. Best value, twin size, I use them three thick. I use 1 by 5 inch pine frame backed by 1/4 inch luon. I wrap them with black twin bed sheets from walmart $2.65 each, stapled to the back luon. They are 6 ft by 3 ft and cost me $50.00. I mount them on ceilings and walls using simple brackets. Free standing panels are drilled from the back with a hole saw, opening the back. I roll full or queen size pads , like a cigarette, stappled around a wooden closet pole, wrapped in the same blk bed sheets and mount them in the corners of my room. I also use them hidden behind my wall hanging carpets and ta pastry. The panels are 1/4 of the price of finished( wrapped in fabric )sound panels.

Could be the same. Foams can be made several different ways, from several different materials. "Polyurethane" foams are cheap and relatively easy to work with.

Acoustic foams will be open cell, not closed cell. Could be polyurethane or other plastics, or even rubber. The formulation and type of processing will determine whether the cells remain open or close off on cure. There is also self skinning foams and open cell foams that you can make "skin" by how you process it, effectively closing the foams cell structure on the outside surface (not good for absorption).

Open cell polyurethane foam will allow sound energy (waves) to enter through the outer cells and decay (dissipate the energy)in the multiple voids present in the foam.

For some reason that I don't fully understand, foams absorb over much narrower frequency bands than fiberglass. and are also less effecient absorbers than fiberglass.

There you go, more than you cared to know about polyurethane foams. If you need more I will drag out the manufacturers data sheets.

P.S. 2nd question in 5 years that I actually knew a very little something about. Now I feel better.

Jim S.