New studio/set of rehearsal rooms based in Sheffield, UK!

xSpace wrote:

Soundman2020 wrote:

and also the amount of insulation in the air gap.

He has an existing rendered block wall. How does what you said apply to that?

I'm not sure I understand what you are questioning about my post! Yes, he has rendered "concrete block with plasterboard on top" outer leaf, then he has an air gap, then he has his plasterboard inner leaf. At least, that's the way I understand it when he says:

OUTER WALL (216mm concrete) - PLASTERBOARD (12.5mm) - AIR GAP (5 CM) - STUDS with 10 cm ROCKWOOL (with neoprene on the outer layer) - PLASTERBOARD (12.5 cm)

So, what I said applies the same as for any other air gap: If you DON'T put insulation in the air gap, then you'll run into the problems analyzed in detail in that paper. But he says he is already planning to fill part of that air gap with rockwool, so the basic construction looks fine, as far as I can see. If you read the paper, you'll see that the one possibility that they analyzed (insulation around the perimeter only) works reasonably well, but a much better solution is to use as much insulation as you can possibly afford, where the position of the insulation (up against the inner mass, up against the outer mass, in the middle, or all the way across) is not all that important, as long as you don't compress it so tightly as to create a flanking path. So I don't see why a rendered block outer leaf is going to make any difference at all to using (or not using) insulation in the air gap. The air gap and the insulation is just as important as for any other wall design, as far as I can see. - Stuart -

Sorry, I only had the last line in the paragraph. It should have the whole paragraph. btw, that document was compiled for The Department of Housing and Urban Development.

Soundman2020 wrote:

According to a rather old (but very valid) technical paper on acoustics, when using drywall for your mass, the optimum total thickness for the entire wall is 11.5 inches, with the mass being equally divided between the two leaves. However, even a couple of inches of airspace is good, and from about 4 or 5 inches upwards you are not really gaining an awful lot more. If you have the space, then shoot for 11.5 inches, but if not, then just go for as much separation as you can. The air gap is important, but much more important is the total amount of mass, and also the amount of insulation in the air gap.

Ok so what you're saying is that a 3 - 4 inch air gap will be effective? 11.5 inch air gap will not be possible unfortunately, we gotta save some space! I think our two leaf system will end up being; Solid concrete breezeblocks (8inch thick) - Plasterboard rendered to the concrete - 2x4 studs on the plasterboard filled with insulation - 4 inch air gap - 2x4 studs filled with insulation - plasterboard Does that sound right? According to rods book that is the two leaf system with the highest STC rating... Would there be any point in having two layers of plasterboard instead of just one? (In the places stated above) and also is it worthwhile investing in RC-2??

that document was compiled for The Department of Housing and Urban Development.

Correct. Does that make the findings any less valid? Does the science of acoustic measurement change, depending on who funds the study?

xSpace wrote:

btw, that document was compiled for The Department of Housing and Urban Development.

What is your point? It isn't exactly hidden with HUD in huge letters across the left side of the cover page. BTW it was not compiled. It is a major piece of research on sound isolation by one of the top acoustic firms in the world. Andre

DarkStorm wrote:

Ok so what you're saying is that a 3 - 4 inch air gap will be effective? 11.5 inch air gap will not be possible unfortunately, we gotta save some space! I think our two leaf system will end up being; Solid concrete breezeblocks (8inch thick) - Plasterboard rendered to the concrete - 2x4 studs on the plasterboard filled with insulation - 4 inch air gap - 2x4 studs filled with insulation - plasterboard

The 11.5 inch thickness is not just the air gap: It is for the entire wall, from the outer surface of one side, to the outer surface of the other, including everything in between, so it seems that your construction is about right, in total. Personally, I reckon that a 4" air gap is fine. Based on what you said, it seems that you actually have more than 4 inches in your case, since the way I understand it, the insulation between the studs also counts as air gap. So you have nearly 8 inches of air gap, in total. Maybe I'm wrong about that, depending on how you define "air gap", but from the detailed technical paper and from everyone's comments here, it seems that the entire space between the two chunks of "mass" is considered to be "air gap". You also get the best performance when you fill all of it with insulation (instead of just the stud space), as long as you don't jam it in tightly.

Does that sound right? According to rods book that is the two leaf system with the highest STC rating... Would there be any point in having two layers of plasterboard instead of just one? (In the places stated above) and also is it worthwhile investing in RC-2??

I think you can safely skip the RC! Everyone here says that it is a waste of money if you are already building separate walls for your leaves, which is what you are doing. And yes, I think it would be worthwhile adding a second layer of plasterboard on the inner leaf (the one attached to the studs), using Green Glue in between the two layers of plasterboard. Maybe even two extra layers (for a total of 3). I'm not an expert, but it seems to me that you don't need a second layer on the outer leaf (concrete block wall), as that already has plenty of mass. The more mass you can put into each leaf the better, and the paper does say that you get optimum isolation when both leaves have the same mass, so if you could go to three layers on your inner leaf, you'd be getting even closer to optimum, but I really don't understand the math well enough to calculate if it would be a huge increase going form 2 to 3, or just a tiny increase. Maybe Andre or Ro or one of the other experts can chip in, and give you their much more qualified opinion!

Soundman2020 wrote:

If you have the space, then shoot for 11.5 inches, but if not, then just go for as much separation as you can.

Bottom of page 87: It is therefore worthwhile to study more closely the practical combinations of panel mass and separation that will satisfy the 20dB requirement in order to determine the optimum configuration in terms of acoustic performance and cost. Top of page 90: The minimum overall thickness of a double wall with gypsumboard panels meeting the 20 dB requirement is slightly less than 11.5 inches. ...For all other combinations of panel mass and spacing - keeping the product constant - the overall thickness is greater than 11.5 inches. Top of page 92: "It is possible that a thickness of 11.5 inches is too great for a practical wall construction, although it would be satisfactory for floor and roof-ceilings. The parameter involved in the determination of the minimum thickness is the material density; therfore, it is useful to study the relationship between these two quantities in the hope that the use of alternative materials may result in a more practical construction." Is that what you saw Stuart? Your statement just doesn't read, to me, like it is an accurate presentation of this information. Air between walls is good, insulation to damp panels is also good.

AVare wrote:

What is your point? It isn't exactly hidden with HUD in huge letters across the left side of the cover page. BTW it was not compiled. It is a major piece of research on sound isolation by one of the top acoustic firms in the world. Andre

The document is not in question Andre. It was and still is a valid piece of research that applies directly to residential/commercial building first and foremost. In the event that this fact was over-looked, I simply reiterated. Please excuse my choice of words.

It was and still is a valid piece of research that applies directly to residential/commercial building first and foremost.

I guess you must be looking at a different document, then, because the one I'm looking at applies to acoustic research conducted on two-leaf and three-leaf walls, using drywall and stud construction, separated by insulation-filled airspace. In what way does that not apply to the construction techniques that Rod and numerous others recommend for studios? In what does the fact that the study was not commissioned by a builder of studios change the results? And why do you seem to always need to respond negatively to practically all of the posts I make in trying to help people with their questions? Did I step on your toe, or something?

xSpace wrote:

Please excuse my choice of words.

None needed. You can apologize the first week you see me make no errors. The clarification is appreciated and is helping a great discussion about the document. Andre

xSpace wrote:

Soundman2020 wrote:

If you have the space, then shoot for 11.5 inches, but if not, then just go for as much separation as you can.

Bottom of page 87: It is therefore worthwhile to study more closely the practical combinations of panel mass and separation that will satisfy the 20dB requirement in order to determine the optimum configuration in terms of acoustic performance and cost. Top of page 90: The minimum overall thickness of a double wall with gypsumboard panels meeting the 20 dB requirement is slightly less than 11.5 inches. ...For all other combinations of panel mass and spacing - keeping the product constant - the overall thickness is greater than 11.5 inches. Top of page 92: "It is possible that a thickness of 11.5 inches is too great for a practical wall construction, although it would be satisfactory for floor and roof-ceilings. The parameter involved in the determination of the minimum thickness is the material density; therfore, it is useful to study the relationship between these two quantities in the hope that the use of alternative materials may result in a more practical construction." Is that what you saw Stuart? Your statement just doesn't read, to me, like it is an accurate presentation of this information. Air between walls is good, insulation to damp panels is also good.

Yup, that's a small part of what I read, and yes what I said is most certainly an accurate representation of the above. Provided, of course, that you are referring to my ENTIRE statement, instead of just the carefully selected snippet that you choose. I'm having a really hard time trying to figure out what your point is, other than to split hairs and argue with me for the sake of arguing. For the record, the FULL CONTEXT of what I said was:

According to a rather old (but very valid) technical paper on acoustics, when using drywall for your mass, the optimum total thickness for the entire wall is 11.5 inches, with the mass being equally divided between the two leaves. However, even a couple of inches of airspace is good, and from about 4 or 5 inches upwards you are not really gaining an awful lot more. If you have the space, then shoot for 11.5 inches, but if not, then just go for as much separation as you can. The air gap is important, but much more important is the total amount of mass, and also the amount of insulation in the air gap.

I can't seem to find a single thing I said there that contradicts anything in the paper, unless you are concerned about the reference to 4 or 5 inches, which of course I got from numerous places on this site, and from Rod's book. Do you think Rod and other experts are wrong when they suggest that a 4 or 5 inch gap is sufficient in most cases? Do you know something that they don't about wall construction? And by the way, the purpose of insulation in the air gap is NOT to damp the panels. The insulation does not even need to touch the panels at all to be effective. It seems like you skipped over the pages where they explain how that works. You seem to be confusing wall construction with panel resonator construction.

xSpace wrote:

It was and still is a valid piece of research that applies directly to residential/commercial building first and foremost. In the event that this fact was over-looked, I simply reiterated.

I have been sitting on this for a couple of days. Why did you add "applies directly to residential/commercial building first and foremost?" Almost every studio we discuss here is in a residence or commercial building. It is of direct relevance to studio construction. It (Sharp) has become quite sought after since being referenced in Long, Architectural Acoustics, 2005. Yes, after over a quarter century it has been rediscovered! Confused, Andre

AVare wrote:

xSpace wrote:

It was and still is a valid piece of research that applies directly to residential/commercial building first and foremost. In the event that this fact was over-looked, I simply reiterated.

I have been sitting on this for a couple of days. Why did you add "applies directly to residential/commercial building first and foremost?" Almost every studio we discuss here is in a residence or commercial building. It is of direct relevance to studio construction. It (Sharp) has become quite sought after since being referenced in Long, Architectural Acoustics, 2005. Yes, after over a quarter century it has been rediscovered! Confused, Andre

I appreciate your presence in the forums that I know you are visiting and did not want my reply to seem curt. Also, it is outside of "studio building" so in my twisted search for clarity, this line was added. It existed at a time when I could have used it in residential/commercial building had I more interest in what the walls I placed did, the whys and what for. In that respect, to me, it was important to look at that part of the work. How, in a vertical and physically encroaching world, even then, keeping your neighbors 8 track out of your bedroom was important. If I am still digging a hole, will someone please just cover me up!