General confusion over polystyrene

[spitzer]

EDIT: VERY IMPORTANT:

NO ONE, AND I MEAN ABSOLUTELY NO ONE IN THIS THREAD HAS SAID YOU SHOULD USE POLYSTYRENE PRODUCTS FOR ANYTHING.

PLEASE DO NOT "line your studio walls" WITH POLYSTYRENE. IN CASE IT IGNITES, THE BURNING FUMES PRODUCED ARE TOXIC. YOU COULD DIE.

Thank you.

---

Hi.

Don't be alarmed. (and WARNING: scientific type question)

I've been reading (very) conflicting things, on several forums, about this for quite a while now. Some people will simply say "no, it will absolutely not work" while others will say "it could very well work, don't see why not (although haven't tried it)". All of these people are what most of you'd call experts.

I'm talking about using EPS sheets in sound reduction. Yes, you read that correctly. As far as I've been able to determine, EPS has a density that matches that of some types of mineral wool. So, let's say I would build some sort of isolation wall with a frame from 2x4's, then fill the gaps with 100 mm thick EPS sheets. Otherwise the construction would be fiberboard on the outside. Now. How exactly would the EPS "not work"? How would it, in principle, be different from mineral wool or fiberglass?

I am full aware of things like fire hazards etc. and I don't care. Also, I DO understand that EPS by itself will not do much because of it's light weight (note: fiberglass or mineral wool alone won't do much either!). The physics side of this however is that once the sound waves hit the fiberboard wall, they will then enter a completely different medium, the EPS, and I'm inclined to think the sound waves would then scatter or something. What would be different here compared to mineral wool of the same density (30 kg/m^3)? I can't understand how the EPS would do "nothing" like some claim.

If you're familiar with sound suppressors for firearms, their operating principle is NOT based on enourmous amounts of MASS, but instead on forcing the sound waves to "go somewhere else". (a mass-based design would be impossible because it would be hundreds of times too heavy to handle. However very effective suppressors do exist and have existed for a very long time.)

I've used EPS panels in the past, successfully, to deal with spaces that otherwise are unbearable echo chambers. The difference is VERY evident. I believe they can also be used to construct corner bass traps, that do in fact work (I'm not interested in whether some other material would be better or "more efficient", I don't care).

So to restate the main question, is EPS functionally equal and effective compared to mineral wool when used to fill gaps in an isolation wall? If not, why? (Have you tried such a construction?)

Thanks.

 

[miroslav]

So to restate the main question, is EPS functionally equal and effective compared to mineral wool when used to fill gaps in an isolation wall? If not, why? (Have you tried such a construction?)

Thanks.

You're talking about Styrofoam sheets, right?
I'm sure you would notice some difference between using nothing, and using some Styrofoam sheets...but they will never have the same effect for acoustic treatment as fiber panels of any kind.
Why...?...because the fiber is the key. Sound waves enter and excite each individual fiber, which is then transferred as heat, and that's what dissipates the sound waves.

Also...if Styrofoam was of any acoustical value...it would have been used already. No one uses it. There are people much smarter than you or I, who have worked all that stuff out scientifically, and they don't use it.

Oh...and it's a fire hazard....but you said you "don't care"...??? I mean, it won't combust on its own...but when it burns, it's bad, real bad.
Being a closed-cell foam product, it's great for thermal insulation (coffee cups and coolers), and is used in a lot of ways for that...but not something you would want to line your studio walls with.

 

[rob aylestone]

Well if you don't mind the styrene and benzine risks, and the additional risks from any form of heating - I guess it's up to you, but it's pretty poor at lower frequencies because of it's rigidity - it's surface is a hard medium as opposed to soft mediums, so that while the inner is fairly aerated, the hard edges reflect a good proportion of the sound that hits it. Mineral wool is much more open to approaching pressure waves. Loose polystyrene granules offer a more 'open' surface, but the stuff frankly is just plain nasty! While they do work as absorbers, the amount of absorption is much lower than mineral fibres, and of course at lower frequencies it's pretty ineffective, like the often mentioned egg boxes.

My studio has one entrance, and the idea of being stuck in there with such nasty stuff if there was a fire is quite worrying - and usually I don't worry much about these things. Oddly, fire risk is not now a major snag, as most building polystyrene has fire inhibitors. It's not that cheap though, is it?

 

[gecko zzed]

The only difference between the Blu-Ray Extended trilogy and DVD Extended trilogy is colour correction because Peter Jackson STILL wasn't done tweaking it! While accepting his academy award, he quipped that he must be the only director to win an oscar while still shooting principal scenes for the movie... because it was true, he was still shooting the Extended edition!

But did he use styrofoam?

 

[ecc83]

Decades ago a chap called Gilbert A Briggs did some pioneering work with loudspeakers (Wharfedale) he practically invented the roll surround and some of that work was trying out various 'stuffings'. Many things worked quite well and he fixed upon Bonded Acetate Fibre as the most practical and effective material. Expanded PS was found to have all the acoustic properties of brick! All it did was uselessly displace air from the cabinet.

Firearm moderators work on the same principle as a ICE silencer (muffler to yous folks across The Pond but we wear those here!) N.B. moderators are only really of use with sub-sonic rounds and pretty much FA use with a revolver due to the cylinder gap (don't stop Hollywood mind).

Dave.

 

[miroslav]

But did he use styrofoam?

Yes...I think the packaging had some.

 

[spitzer]

Guys,

just quickly to clear the possible misunderstanding: when I said "I don't care", that needs to be taken in context. I'm not planning on actually building anything like I described, like I said the question was purely scientific.

Also...if Styrofoam was of any acoustical value...it would have been used already. No one uses it. There are people much smarter than you or I, who have worked all that stuff out scientifically, and they don't use it.

I'm not sure that logic is completely valid. One of the reasons for my asking this whole thing is precisely that there are VERY few smart people who actually have worked anything out scientifically. I've read countless posts on forums saying the equivalent of "don't use polystyrene because of the fire hazard". That's everywhere. On the other hand, ANY explanation of whether or not, or WHY would it not work in conjunction with fiberboard to block, absorb or scatter sound waves... that information is nowhere to be found.

Also, regardless of the physics involved, there actually are comments from what I would assume to be very smart people who have commented that polystyrene CAN indeed be successfully used to build bass traps, for example. I remember it was mentioned that they won't be as effective as (probably heavier) rockwool, but they WILL work. That's what's puzzling me, I'm repeating myself now a whole lot, but: if the DENSITY of some particular styrofoam sheet is the same as some particular rockwool sheet, my common sense asks me what's the real difference then? It could even be 100 mm of cardboard, the sound waves would STILL have to travel through another layer of material and even "worse", something with a different density. The sound simply cannot penetrate straight through some solid material, whatever it is. I would say I'm sure we can at least agree on that, but I'm actually not sure.

BTW, as for "no one uses it"... I don't know about everyone else, but I said in my first post that I HAVE tried using EPS panels for acoustic treatment (echo reduction) and they DO work. No doubt. The difference is very obvious. (The reason I used a styrofoam panel here is that it's indoors, in the house, and I can't use rockwool there without some kind of covering... which I wasn't prepared to do just for an experiment, just to see whether it would work and where exactly is the correct position for the panel. Styrofoam, you can basically break the panel to the size you want with your bare hands and don't need to worry about getting sand in your eyes and cutting a million little slashes in your hands).

Again, I'm aware of the conventional wisdom that rockwool/fiberglass is most probably more effective and safer if you're worried about fires. The question was about the differences in physical properties between the given alternatives, nothing more. (also, don't forget it's not rockwool alone versus styrofoam ALONE, it would be fiberboard PLUS what's behind it. What happens to the sound waves once they hit the fiberboard layer and enter the styrofoam/rockwool)

Should this be moved to the noob forum or something so I won't get made fun of anymore for wanting to learn more about stuff?

Thanks guys.

 

[ecc83]

The 'science' that tells you EXPS is effectively soundproof is the fact that it has been used for woofer cones.

Briggs did this with a 12" speaker and reported that it cut down enclosure resonances that were heard through the cone. The paper cones of the day were not very soundproof.
The technique was also used for the famous KEF B139 elliptical woofer where its rigidity was also a useful property.

A sound TREATMENT material has to allow sound energy to enter in order to be dissipated. Sound PROOF materials, brick, steel, wood to a degree, just reflect it back.

Just saw you claim the stuff works as a treatment? I would say that is because a panel will be set in motion by the sound energy and in its tiny flexings dissipate some sound energy. I am confident a solid, rigid block of the same overall volume will act more 'brick-like'.

Should be easy enough to do some before and after recordings? Just need a waffle into the space.

Dave.

 

[sasquatch]

g

 

[TalismanRich]

That was an interesting read, Sasquatch. Thanks for posting it.

I was actually surprised by the relatively low absorption coefficient of sand. Its very even, broadband absorption, but not as effective as I would have expected. I remember when we were designing a laboratory, we had one room which would house a number of pieces of noisy equipment. To minimize the sound transmission to the other parts of the lab, it was specified that the concrete block walls would be filled with sand. It was pretty effective. Most of the noise that escaped into the other rooms came through the door.

From the study, you can clearly see that plastics, such as PS and PP, will absorb higher frequencies, but are not so good for bass frequencies. I would guess that is the reason that styrofoam is more often used for thermal insulation, but not so much as sound insulation.

 

[ecc83]

"I was actually surprised by the relatively low absorption coefficient of sand."

I think you are still confusing 'Absorption' with 'Obstruction'? A sand filled wall will have a very high mass, just what you need to stop sound travel. You can get EXPS clad with 3mm Hardboard and this is really a good sound proofing material of low overall weight. Not as good as plasterboard but easier to handle and can be portable.

Generally: If 'it' is dense and dose not move, stops sound. If 'it' is light and moves, absorbs sound.
If it moves and EMITS sound? Salute it.

Dave.

 

[miroslav]

I'm not sure that logic is completely valid. One of the reasons for my asking this whole thing is precisely that there are VERY few smart people who actually have worked anything out scientifically. I've read countless posts on forums saying the equivalent of "don't use polystyrene because of the fire hazard". That's everywhere. On the other hand, ANY explanation of whether or not, or WHY would it not work in conjunction with fiberboard to block, absorb or scatter sound waves... that information is nowhere to be found.

So then, by your logic...anything/everything that has NOT been clearly tested for acoustics, should have the potential to be good for acoustic treatment...???

I actually did give you a simple explanation that went beyond the "fire hazard thing". Styrofoam is closed cell foam...which HAS been proven not to be all that great for acoustics use. It's terrific for hot/cold insulation, but not much else. Things like fiberglass, etc...is open fiber construction, which dissipates sound energy into heat energy. That is how it works.

The simple point is this...you can knock yourself out and experiment with anything/everything that has not been formally tested (which is your logic)...or you can simply use the materials that HAVE been tested, and are known to be good for acoustic treatment. That goes in both home and pro studios.

Maybe there's a better way to make a wheel...?

 

[pcnj50a]

Yes, open cell foam is the best absorber. PS foam generally isn't.

A good acoustic foam will have high open cell content, high loss tangent for the matrix polymer, and high density. The surfaces need to be skived (skinned off) to minimize reflection, and cell sizes need to be relatively large, on the order of a couple millimeters. I've experimented with foaming some damping rubber compounds and am currently working on a 2K polyurethane system with a visco PUR.

For sound blocking, mass and hermetic seal are the two most important factors.

 

[spitzer]

So then, by your logic...anything/everything that has NOT been clearly tested for acoustics, should have the potential to be good for acoustic treatment...???

I actually did give you a simple explanation that went beyond the "fire hazard thing". Styrofoam is closed cell foam...which HAS been proven not to be all that great for acoustics use. It's terrific for hot/cold insulation, but not much else. Things like fiberglass, etc...is open fiber construction, which dissipates sound energy into heat energy. That is how it works.

The simple point is this...you can knock yourself out and experiment with anything/everything that has not been formally tested (which is your logic)...or you can simply use the materials that HAVE been tested, and are known to be good for acoustic treatment. That goes in both home and pro studios.

Maybe there's a better way to make a wheel...?

Miroslav... there's no need whatsoever to be so spiteful.

By "my logic"? What are you referring to? What I said boils down to: Just because "no one" does something, does not mean it does not or CAN not work. Similarly, there is absolutely no guarantee that if there's something already existing, someone or "everyone" would have found out what exactly it is and what are the possible uses for it.
Haven't you ever seen MacGyver? The point of that show is not that everything can be used to do everything, but instead it shows situations where you are forced to actually THINK how stuff actually works and whether or not some, whatever completely off the wall crazy thing COULD work.

I don't understand your constant conjecture. No one here said they want to "reinvent the wheel" or anything like that.

P. S. In the past, in another discussion, it took a long, long time for anyone to confirm my belief that a certain energy can not co-exist as BOTH sound and heat. That is VERY obvious to me. Do you feel there's a problem with my logical skills and if so, why?

 

[spitzer]

Just saw you claim the stuff works as a treatment? I would say that is because a panel will be set in motion by the sound energy and in its tiny flexings dissipate some sound energy. I am confident a solid, rigid block of the same overall volume will act more 'brick-like'.

Should be easy enough to do some before and after recordings? Just need a waffle into the space.

Dave.

The situation where an EPS sheet seemed to work as "treatment", although it's impossible to tell whether as a reflector or absorber (pure guess: both), was in a hard walled cavity holding the sound source. Aka echo chamber. As it was, it was difficult to understand speech, for example, as the sound bounced around. A small piece of EPS next to the source made a HUGE difference (the REALLY annoying echo was almost completely gone), and I suspect lining all sides would be even better.

Before/after recordings of this particular thing would actually require quite a bit of work... but I doubt it would be interesting. I once made that sort of A/B thing with numbers for different frequencies, showing you could make an effective low freq blocker/absorber from a shoebox and a doormat... guess how many gave a crap

 

[miroslav]

Do you feel there's a problem with my logical skills and if so, why?

The problem is that you set up a premise...that requires negative logic to prove something is true.
That's my problem...and when people insist on dismissing known facts and best practices, because they don't fit their personal expectations or beliefs.

You know what...just ignore my attempts at providing you with actual facts...and then go put up the Styrofoam, because NO ONE here is going to run out and do extensive testing for you, to prove that it's a lousy acoustic treatment choice (not to mention the fire hazard)...so just do it yourself, and be satisfied.

I really don't want to waste my time with this.
If people are here because they are looking for true solutions, and just need some guidance so they can got on with their studio construction and treatment...then I'm more than happy to be part of the conversations. I don't care about stuff that is well off the beaten path, because the science of audio and acoustics is not something we need to reexamine and reinvent here. It's quite safe to just accept the norm, and then get on with the business of making music, if that's what your goal really is...and I wonder about that sometimes here on the forums, because it seems like some people are just here to banter about topics, bot not so much to actually do anything with recording music.

Good luck with the Styrofoam.

 

[rob aylestone]

The thing here that is the constant and only rule is physics. Conservation of energy. Converting one form of energy into another. This is why there is no need to test products to predict basic behaviour. You can do the prediction simply. You need to test to determine how exactly the conversion performs, but you know something works or won't work - the variable is how much?

Polystyrene has very specific features. Its thermal performance is well know - to the touch it's always warm, but it's very hard - especially when cut via heated wires that cut and seal by melting the surface. Formed building foam being rougher on the outside than packing foam. Physics lets you determine that one will reflect similar to a hard panel, and the other will difuse because of the number of slightly different angles. The hard surfaces absorb very little and the polystyrene takes up very little of the sound energy as heat. On soft foam, the proportion of sound converted to heat is higher, but we know this is frequency dependent - bass goes right through largely unaffected, HF getting the heat conversion. A membrane absorber is quite hard, which should reflect, but it moves, and the sound is converted to kinetic energy - the vital bit being there's less sound left! Polystyrene because if the lack of mass/weight won't allow this conversion.

As an audio inexpert, my level of physics lets me predict the basic functions but I cannot quantify it, but I can understand what is happening. Plasterboard vs MDF is a good one. Plasterboard seems a good audio product because of how it responds to sound - some reflection, some absorbtion, plenty of mass, but MDF has a hard sealed surface, so has mass and reflection properties. How does painting plasterboard impact on the figures and performance? Don't know from doing it. Acousticians can read and really understand the specs. Less able people like me can only understand the lower tier of data. Good to learn though!

 

[miroslav]

How does painting plasterboard impact on the figures and performance? Don't know from doing it. Acousticians can read and really understand the specs. Less able people like me can only understand the lower tier of data. Good to learn though!

On a similar point...I've been preparing wood panels that will be spread out on the walls of my new studio (you can see details in my studio documentation thread)...some of it for aesthetics, as I do not want just the look of painted drywall...but also for acoustic treatment purposes, since the wood panels are on the rough/porous side.

Someone asked me if I was going to paint them...I said no, they were going to be only stained, and then no poly of any kind...so I could maintain the porous condition. If I painted them or added a poly finish over the stain...they would not be much better than the drywall for acoustics, and would only serve the aesthetics.
The panels will also get a liberal amount of elastomeric caulking between them and the drywall before I screw them to the walls...which will help deaden any vibrations and also for some additional sound reduction.

 

[spitzer]

The problem is that you set up a premise...that requires negative logic to prove something is true.
That's my problem...and when people insist on dismissing known facts and best practices, because they don't fit their personal expectations or beliefs.

That is indeed YOUR problem. Precisely no one on this entire thread has done what you're describing here.

You know what...just ignore my attempts at providing you with actual facts...and then go put up the Styrofoam, because NO ONE here is going to run out and do extensive testing for you, to prove that it's a lousy acoustic treatment choice (not to mention the fire hazard)...so just do it yourself, and be satisfied.

Go "put up the styrofoam" where? What styrofoam? I have not ignored any "actual facts", I just honestly don't understand roughly 50% of what your replies are about. You're answering stuff NO ONE asked in the first place.

It's EXTREMELY difficult to tell if you're indeed actually trying to be helpful. Honestly. I do not know.

I really don't want to waste my time with this.
If people are here because they are looking for true solutions, and just need some guidance so they can got on with their studio construction and treatment...then I'm more than happy to be part of the conversations. I don't care about stuff that is well off the beaten path, because the science of audio and acoustics is not something we need to reexamine and reinvent here. It's quite safe to just accept the norm, and then get on with the business of making music, if that's what your goal really is...and I wonder about that sometimes here on the forums, because it seems like some people are just here to banter about topics, bot not so much to actually do anything with recording music.

Then DO NOT reply! Is that too difficult for you? If you don't want to "waste your time", then DON'T.

Different people have different interests and different viewpoints. I personally DO care about stuff "well off the beaten path". If I was actually suggesting that I would actually build a studio and ACTUALLY use styrofoam in place of rockwool, I WOULD HAVE SAID SO. However instead, i specifically said this was a scientific type question.

Also, I indeed am just here to banter about topics. Making music, playing music, recording music is what I do regardless of anything else. I could post a thread here asking do you like your coffee black or with maple syrup in it. Who ever said everything here would need to be directly (and personally???) connected to "recording music"? This is just a forum. Just. A. Forum.

Good luck with the Styrofoam.

... (be nice, please.)

 

[spitzer]

On a similar point...I've been preparing wood panels that will be spread out on the walls of my new studio (you can see details in my studio documentation thread)...some of it for aesthetics, as I do not want just the look of painted drywall...but also for acoustic treatment purposes, since the wood panels are on the rough/porous side.

Someone asked me if I was going to paint them...I said no, they were going to be only stained, and then no poly of any kind...so I could maintain the porous condition. If I painted them or added a poly finish over the stain...they would not be much better than the drywall for acoustics, and would only serve the aesthetics.
The panels will also get a liberal amount of elastomeric caulking between them and the drywall before I screw them to the walls...which will help deaden any vibrations and also for some additional sound reduction.

Now THIS is interesting, and incidentally something that I researched (or tried to) a couple of years back. I also don't like the look of painted drywall. I also THINK I don't like the SOUND (reflections) of painted drywall. A million people told me that unpainted aka porous wood would sound the same as a painted wall. I flat out refused to believe them.

What's the "additional sound reduction" you're talking about there? Reduction through the wall?