Use of Studio Foam

Posted: Fri Sep 14, 2007 4:04 am

Rod and Steve,

I'd like to ask if we can put this up as a sticky...

Ladies and Gentlemen,

Use of foam products in studio "construction" is a very popular misconception that is due some clarification.

Whether you are building a computer silencing box or a full blown 5 room facility, "acoustic" foam has it's place, but it isn't everywhere and just anywhere.

First off, let me say that there are some far more technically oriented folks than I around here, who can (and I hope will) add to this thread, about foam products.

Secondly, I would ask the moderators to please edit anything that is wrong with any of my statements, or to delete any posts (or partial post) which are not completely factual. My reasoning is that because the misconceptions and opinions usually end up superceding the facts as they are presented.

OK... to the heart of the matter...

All foams are NOT created equal. Essentially there are two types of foam; closed cell and open cell foam.
foam-tec.com has a very lay-oriented explanation and wikipedia's got the really tech stuff, that explains the differences in urethane based foams.

Generally, open cell foam is what is preferred for acoustical treatment. The open cell structure is what creates the friction with the sound energy, which in turn is what absorbs the sound energy. HOWEVER, there is little energy in the low frequency range, that is absorbed - in comparison to other types of material which have a greater mass.

It takes mass to stop low frequencies. If you were to make two identically shaped constructions; One of open cell foam, and one of concrete, I can with 100 percent guarantee, assure you that the foam will pass far more low frequencies than the concrete. AND, I can also guarantee you, that the concrete will not absorb the high frequencies as well as the foam.

Foam products are due their place in terms of acoustical treatment. But that place should really be as a fine tuning tool as opposed to a primary tool for sound insulation or isolation.

One thing that just scares the heck out of me are the folks that have a common misconception that ANY foam is the be all/end all for things like computer boxes. While I will not argue the point of far cheaper solutions for mass, I would instead prefer to focus on and point out the issues of safety.

Any type of foam that a user would select should be chosen with heat exposure in mind. If there is a constant heat source that will be in permanent proximity to the foam, it is EXTREMELY advisable to ensure that the foam product selected be at least treated professionally with a fire resistant or fire retardant substance. Failure to do so can (and does) result in catastrophic incidents. Examples of inappropriate foam types are; mattress toppers, seat cushions and packing materials.

This same reasoning should be observed when considering foam use in environments where exposure to momentary high high heat sources may occur. The Great White incident immediately comes to mind.

Again, this not intended to be an indictment against the use of foam products in a studio or entertainment application... but a clarification of common misconceptions.

Let's please keep things factual and up to the standards of this forum's truth and civility.

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