Absolutely do NOT use any sort of
foam on your room's surfaces!! Imho that is.
Several reasons:
- it all burns with extremely toxic smoke and fumes
- it all outgasses nasty chemicals, including formaldehyde
- soon enough it crumbles off layers of nasty micro particles of foam that you breathe
- and even if you discount all of the above - it's a
very poor acoustic absorber
The foam that is sold that is made up of multiple surfaces is also sprayed with a latex paint type material (might be paint) so that it a) acts as a diffuse reflector (the painted surfaces) and b) acts as a multi frequency absorber (to spread the ratty absorption spectra).
Imho there are better ways to go.
The best commercial way to go is the stuff that Dow Corning (and others) sell for walls. It's been advertised on TV for basements recently. It's a fabric covered 2" or 4" thick "hard" fiberglass panel. If you look on their site you'll see how it absorbs relatively evenly with respect to frequency. The 4" works down to the bass regions. Fyi, the silly "eggcrate foam" stuff probably stops working by >1000Hz.
This stuff is also available as an unfinished "batt" without the fabric.
The same sort of stuff is used on the 2x4ft "acoustic tiles" for dropped ceilings, but it's only 1/2" thick, and it has usually plastic on the white side.
One can take the fiberglass stuff and enclose it in a simple "frame" and cover that with ur garden variety fabric and have a removable, jim dandy, and effective absorber. Make the frame up in sizes that are attractive and/or convenient for ur use. You do not not need to have 100% coverage of a wall or ceiling at all. 50% coverage of 4" thick will make the room reasonably dead at that.
Think of it this way - if the absorption is sufficiently good (in terms of dB) each area that is absorptive is like having a completely open window for the frequencies that the area absorbs well.
The other method that is also useful is to make the same frame deal up, and simply put a face and rear of mesh - window screen is one way to go - and fill the frame with regular 6" thick fiberglass house insulation or rock wool. Cover as before with a suitable looking fabric - open weave for max HF absorption, and something tighter for a bit less. You can pick colors and/or patterns to suit.
The fiberglass framed absorbers WORK.
The advantage of fiberglass over some other materials that are not foams is that the fiberglass is light and inexpensive. Polyester fiberfill works even better than fiberglass, btw. But costs more. There are things that absorb better than fiberglass but they weigh more.
Foam eggcrate stuff - not.
Fyi, there are various methods of making "bass absorbers" that use both Helmholtz methods and...geez what is that called now...adiabatic vs. iso-something ...ummm they use a membrane to convert LF energy into "heat" energy... you can find them online, if you need bass control too.
Skip the foam.
The carpet on the wall will work also - again the thickness will play a role in the lowest frequency that it will actually absorb - by LF the carpet tends to be invisible, so keep that in mind - the path length counts as you go lower in frequency. Carpet is better and safer than foam.
So, I vote for the carpet and/or the frames with absorptive material inside.
Foam sucks.
...Just my opinion on it.
_-_-WBear2GCR