My gosh. Another foam discussion.
Well, i don't have a Masters in Physics, but I gotta lotta Physics.
Let's start with two immutable truths that stand beyond the opinion of anyone on the internet.
1. it is possible to design and build something that only a very few, if any, can "hear beyond the space." That is, you can make it 'deader' than you can detect with most instruments and WAY beyond what your ears -- or the ears of anyone you've met -- can detect. If that's whatcha want.
2. Studio acoustic qualities are subject to the whims of fashion. The architectural requirements for decoupling and deadening have been known longer than anyone around here has been alive. Learned largely in the labs of the 1800s and simply refined when the Talkies showed up. In the 50s, they were scared of making rooms 'too dead'. Remember, this was when tube amps ruled and a Neuman 47 was no big collector's item. They had the circuits.
Then some pretentiousness showed up (with money) and it all became about copy-cat equipment. Golden Ears like Clearmountain and Nichols wanted rooms dead, dead, dead! Then, one day, somewhat mysteriously, Nichols started complaining about how rooms were just too darned dead and the trend started to reverse (1980? 82?) It has a tendency to see-saw.
So, that said, the life of foam is simple: it just hangs there until you want it different.
Sound is absorbed by Mass. Nothing more; nothing less. Foam has *some* mass, so it absorbs *some* sound, but as you might guess, not much. Shaped foam, like Sonex, clusters up the reflections and works well for that. After all, no matter HOW much mass your surfaces have, they will still reflect. If you want things dead - that means decoupled from the world - you're gonna need some mass in the form of many options. Lots of good books on this.
Rockwool is a favorite because it *sounds* like it works. It does. It sounds pretty good in the average studio - or even above average room. So that's why it's used in laboratory anechoic chambers at NASA and stuff, right? Nope. They don't use it. They use foam (with lots of lead behind it). Panels, however, do command an advantage, explained at the end.
There's been many materials in and out of favor in sound control including foam, wool, horsehair, cotton batting,fiberglass, etc. Obviously, wool is in-fashion right now. You can tell from the catty remarks that mention of the other materials receive. And it does work, certainly for project studios and limited budget installations. But it's far from alone. Heck, you can still get a LOT of the same effect, sometimes better, by simply hanging a carpet from your wall with a little air behind it. Just learn some basics and use your head -- then your ears.
I can argue theory about 'standing waves' and 'reflections' all day long, including rebound vector and phase cancellation with anyone, even the YouTube crowd. That's hardly the point. There's a few general rules that produce generally acceptable results and this list has plenty of expertise to guide you that way. There are NO hard-and-fast "gotta do this" rules; and darned few "don't do this" rules.
Oh, and I almost forgot the third immutable truth: No one, even with a Doctorate in Physics, can tell you what your treated space sounds like until they've been in it. You can harvest sweep data and timed reflections, and that might give the very-qualified expert solid ground for an absent opinion. But up to that, you can only count on getting comments like "it will sound small" or "it probably rings" which, duh, you probably already knew.
One bit of advice I'd give to you (or any other builder) is to go with changeable treatments. If you put up foam with a staple gun, great. If you put up hardwood frames of wool, great. If you put up lots of ceiling tiles in a random array, super. Now, after using it a week or two *change it*. Move the panels around. Don't get used to it... or you'll get used to it. Unless you can have someone (like my buds) come in and make acoustic datascapes of the entire volume, with people, gear, etc., which, okay, might be overkill, you don't REALLY know whatcha got but only what "sounds good". This is the fatal flaw of the "Bose Syndrome". But a few sweeps are not beyond anyone's expertise - if you're assembling a studio, anyway.
I'm gonna stick with that: Don't get used to it... or you'll get used to it. Seen that one many times. Your eyes can often fool your ears, believe it or not. Color alone. Had to have that one proved to me. Our senses are a fickle lot. Even the big money producers know this. Of course, they don't tear out treatment, they just move the goods to a studio down the road, and sometimes back again. Then an unfortunate side effect are things like Pro Tools being "required".
Oh, if we're still on the OP: I've got Sonex from 1983. Some of it is like new, other panels are eroding like sand. Why? Quien Sabe?? No idea. Manufacturing defect is all i got. But it does a lot in the right place so i always keep spares around. I've got 'pyramid' from 1990. The blue stuff is still solid - but never really worked well -- and the black stuff erodes like sand. Again, never really worked well, anyway. But i don't wanna burn it or put it in a landfill, so i put it up in the Generator Room to impress the uninitiated.
Candidly, that's what a LOT of gear seems to be about.