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post #1 of 568 Old 01-01-2014, 09:56 PM - Thread Starter
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Do you have a question about soundproofing your theater? Then this is the thread for you. It is a sister thread to the Acoustical Treatments Master Thread, but for soundproofing questions instead of acoustic questions.

Basic Q & A

Q. What is Soundproofing?

The goal of soundproofing is the reduction of sound leakage into or out of a room.

Q. Do I need soundproofing? I don't have close neighbors and everybody in my home watches movies at the same time!

Soundproofing refers to sound leakage both going out of the room (sound generated by your theater) and the sound entering the room. Arguably, controlling the sound entering a room might be more important than controlling it from leaving.

Q. Why? Who cares what happens outside the theater?

Sound leaking into the conditioned space of your theater adds to the noise floor in the room. This requires that in order to hear the quietest parts of a movie, you'd need to turn up the volume quite a bit just to hear over the noise from outside the room. How much? This quote by Desnnis Erskine says it all:
Quote:
Originally Posted by Dennis Erskine View Post

The softest sound on a sound track is 22dB. The typical noise floor in a quiet home in a quiet area is 33dB to 35dB. That is in the range of 6 to 7 times louder than the bottom of the sound track. Ok, so for whispers, and other low dB cues and voices on the sound track, that's no big deal...turn up the volume. But, now you run into problems. Normal speech is now 6-7 times louder ... talking is now yelling on the sound track. Next comes the louder sounds ... traffic, bombs, gun fire, etc. They are now 6-7 times louder as well ... too loud for comfort (or realistic listening). With the top of the dynamic range in a sound track at 105dB, that now must be 6-8 times louder. The problem is the vast majority of consumer equipment (amps/speakers) cannot handle that increase on the top end ... blowing out tweeters, clipping the amps, or amplifier distortion as you reach those levels.

Q. What's the difference between soundproofing and acoustics?

Technically, soundproofing is a form of acoustic control, but most people think of them as two different categories. Soundproofing is all about controlling the sound leakage in and out of the room. Acoustics is all about controlling the sound that is in the room. Think echos, reflections, reverberations, and the like. Both are important, if not at the same level. Soundproofing is likely important to many home theater builders -- acoustics is important to all of them.

Q. What are the fundamental basics of soundproofing?

There are four primary elements of soundproofing, roughly in order:
  1. Decoupling
  2. Adding Mass
  3. Damping
  4. Absorbing

All soundproofing methods will involve at least one of those elements.

Decoupling refers to creating gaps between solid surfaces. Sound is just a vibration and it travels very well on direct solid pathways. Decouple the solid materials and the pathway is broken.

Adding mass means to make the vibrating surfaces "heavier." Again, since sound is a vibration, it needs to actually vibrate any substance that it passes through. Heavier materials are simply harder to vibrate than lighter materials.

Damping is all about adding some material (usually a viscoelastic compound) to a surface to keep it from vibrating as much as it normally would. This is a relatively new development in soundproofing, but is so effective that it has become almost ubiquitous.

Absorbing is what you think it is - you add materials that can "trap" air and slow down resonating sound. This is an important step (and critical for acoustics) but for soundproofing, it is not as effective as the other four elements. That is, just adding a batt of fiberglass in your wall by itself will not do very much.

Q. How do I apply those elements, practically?

There are many ways to soundproof a room, and those elements can be adapted to fit many types of situations. Here are some high level thoughts:

First, address your walls. If you are able, consider decoupling them by creating a "room within a room". This is a separate 2x4 wall separated from your existing walls by an inch or so. If space is tight and it is new construction, then consider a staggered stud wall. Another alternative is to float the drywall by attaching the sheets to channels that are separated from the studs via clips. Add mass by layering at least two layers of 5/8" Type X drywall. Damp the drywall by putting Green Glue (or equivalent) between the sheets. Add absorption with insulation.

Then, do the same with the ceiling. Your ceiling is likely connected to either the floor above you or to the shared attic with the rest of the house. Decouple it by "floating" the ceiling, either using floating joists (in a "room within a room" concept) or via clips and channels. The former costs less from a materials perspective, but requires more room and is not always feasible. Add mass, damp, and add absorption the exact same way as the walls.

Now take care of your door. The door is typically the weakest link in the soundproofing chain, since it will be substantially thinner than the walls and will also need to be moveable. At the very least, get a 1 3/4" solid core door. Then add perimeter door seals (like weatherstripping). Consider an automatic door bottom to seal off the bottom of the door. If you need more soundproofing, then try adding more mass to the door using layers of MDF and damp with Green Glue. If even that is not enough, then (assuming you have room), create an "airlock" with two sealed solid core doors. That's the decoupling component.

You might also look at your floor, especially if it is on a concrete slab. Concrete transmits low frequencies very well and so it's possible for vibrations from air conditioning units or freezers or the like to intrude in your theater. Combat this by decoupling the floor via an additional layer of OSB or plywood laying on an underlayment. The underlayment adds mass and some absorption.

Essential Reading

Here are two links that give a great introduction to the topic of soundproofing:

Advice from Anthony Grimani (PMI) - Soundproofing 101: How to Keep Your Home Theater Quiet
Advice from Ted White (Soundproofing Company) - 4 Elements of Soundproofing

Quite a few articles on soundproofing quote from the original research done by the National Research Council of Canada. The most quoted white paper is here: Control of Sound Transmission through Gypsum Board Walls. If you ever hear references to "triple leaf", then this is where some of the key research concerning that was done. It's a very accessible paper.

In general, the articles on the Soundproofing Company website are excellent. The site is trying to sell soundproofing products, but the founder is an AVS Forum regular and the articles are very unbiased. Start with these articles: Soundproofing 101. Move on to these articles: Soundproofing Articles

Interesting Links in this Thread

Using OSB instead of Drywall as an initial layer
Should the "air gap" in a double wall be filled with insulation? (TL;DR - no)
Essential soundproofing links from BasementBob
Comparing soundproof door solutions
Solutions for temporarily "plugging" a window in a theater
OSB as first layer; Does next layer of drywall need to be screwed into channels or directly into the OSB? (TL;DR - channels)
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post #2 of 568 Old 01-02-2014, 09:26 AM - Thread Starter
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Notable Soundproofing Threads and Links

General Soundproofing Topics

Need help with soundproofing my new HT <-- Very good info!
New Construction Question Walls Sound Isolation Methods <-- Also good discussion
Sound proofing/insulation...Is it necessary??
Is there really any point in soundproofing? Is it a scam? Help me gain clarity please !!!

Construction Materials

Does OSB seem all that less dense...? - Excellent thoughts on OSB v Drywall (pros and cons)
Ceiling Insulation Thickness - Data from NRC research (IR-766 (PDF)) but in a very readable form
Technical papers on Green Glue - Green Glue is -- by far -- the most common damping agent and these technical papers illustrate why

Soundproofing Components

"Ultimate Studio Door" (PDF) - Custom door made of ply+2x4s+SAND. Fantastic read with tons of detail on all aspects of the door (include seals, jambs, framing, etc). Essential reading, even if you don't make this specific door. An associated forum thread about this is here. Concerns about using sand starts here.
Paul Woodlock's "Bank Vault" door - Custom door made of 5 layers of MDF + 5/8" Drywall; custom jamb; neoprene seals; and ball bearing hinges. Weighs over 200 lbs.
Several MDF doors
(Take 2 Theater) Mass-added door - Paneled solid core door leveled with heavy leveling compound; two layers of MDF with Green Glue; automatic door bottom.
(Desert Sunset Theater) Detailed Mass-added door - Solid core door with dual layers of MDF; Green Glue; automatic door bottom. LOTS of practical detail (even about threshold size).
(Cinemar Theater) Detailed door installation - Solid core door, but with custom jamb for double wall and TONS of very detailed instructions on how to install it all.

Projector hush box in several posts: One Two Three Four Five Six Seven Eight

(Retirement Theater) 200lb "removable" window plug - Very heavy, but it's at least possible to remove it
More typical removable window plug - Easily inserted and removed

Construction Examples

Room in a Room Examples

The "Bacon Race" Theater
Quote:
Originally Posted by damelon View Post

My "space" is 23'6" L x 16'4" W x 8'9" H. "room in a room" construction with a 1" gap between existing framed walls and concrete foundation walls. All side walls will connect to ceiling with RISC-DC04 clips. (The space inside of the "Inside" wall is 22'8" x 15'4" x 8'9" pre-drywall)

Ceiling is clipped & channeled from the existing ceiling joists.

All walls will be 2 layers of 5/8" drywall with green glue between.

28" wide, 1 3/4" thick solid coor door on the side wall. This is semi-hidden or hidden behind wall fabrics.

Staggered Studs Examples

I haven't found any, since most people with the space go with double walls and those without go with clips and channel.

Clips and Channels Examples

Bethesda Build
Clips and channels on walls and ceilings. Two layers of 5/8" drywall with Green Glue. At least one wall is a double wall. Single 1 3/4" solid core door installed on double wall with extra long jamb.

Another Erskine-designed masterpiece (if I don't screw it up)
Clips and channels. Roof with 5/8" OSB + GG + 5/8" DW; walls with two layers of 5/8" DW + GG. Floating OSB floor on membrane, over slab. Added mass to door. Projector "hush box"
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post #3 of 568 Old 01-02-2014, 09:26 AM - Thread Starter
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One more reservation, just in case
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post #4 of 568 Old 01-02-2014, 12:29 PM - Thread Starter
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First question! I am curious about people's experience with using OSB instead of drywall for at least one layer. Specifically, why was it done, and how was the soundproofing as a result?

Starting with "why". The two reasons I've heard so far is that OSB has better shear strength than drywall and thus is a better fit for freestanding "room in a room" walls AND that using OSB allows you to screw things (columns, soffits, acoustics treatments, etc) anywhere, without regard to studs. Are there more reasons?

OSB definitely has less mass than drywall for the same thickness but not by a huge amount. 5/8" Type X drywall tends to be around 2.2 lbs sq ft, while 19/32" OSB is around 2.0 lbs sq ft. The far more reasonable priced 15/32" OSB is 1.5 lbs sq ft. From a practical point of view, what kind of difference does this make in soundproofing?

I guess the meta question is: is it worth spending 2x the cost to use OSB?
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post #5 of 568 Old 01-02-2014, 06:47 PM
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On OSB the reasons why I've gone along with it on a few builds include:

1) it was already delivered and stacked in the basement when I got there or,
2) we intended to screw a lot of extra crap inside the room and wanted a good secure layer. Things like soffits, Coffered ceilings, tiered level ceilings etc.

We always used 5/8 because if you are going to put up with the splinters in your hands you might as well go all in.

There is one thing I almost always do and and that is to substitute at least one sheet of 5/8 in the projector mount location for the first layer of drywall then cover it with drywall.
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Quote:
Originally Posted by BIGmouthinDC View Post

On OSB the reasons why I've gone along with it on a few builds include:

1) it was already delivered and stacked in the basement when I got there or,
2) we intended to screw a lot of extra crap inside the room and wanted a good secure layer. Things like soffits, Coffered ceilings, tiered level ceilings etc.

Is the OSB more a convenience thing, even then? It seems like putting up soffits, coffered ceilings, and the like can be one "conventionally" using blocking attached to studs or joists. Is it that OSB makes it easier to not have to worry at all about placement OR is it that having to hit channels properly is that much more of a pain?
Quote:
Originally Posted by BIGmouthinDC View Post

We always used 5/8 because if you are going to put up with the splinters in your hands you might as well go all in.

There is one thing I almost always do and and that is to substitute at least one sheet of 5/8 in the projector mount location for the first layer of drywall then cover it with drywall.

That makes a lot of sense!

You've done at least a couple builds with floating joists, right? In that case, since the walls aren't attached to anything but themselves and their spanning joists, were you ever concerned that drywall wouldn't have enough shear support to keep the walls from moving?
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post #7 of 568 Old 01-03-2014, 04:30 AM
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This thread is one I read through since still in the planning phases of my build and discusses more of the performance and value end of the OSB vs drywall question. It is a little dated in terms of costs perhaps but a good read.

http://www.avsforum.com/t/1157120/does-osb-seem-all-that-less-dense

My two cents - I plan on using OSB for the ease of future use for all soffit and inside the soundproofed room construction. It allows more flexibility for sure.

An analogy from my unrelated experience - I resided my old house with vinyl siding (was aluminum). It was built in the 70's and they used this fiber board stuff which has the structural integrity of a greasy pizza box. So, I had to try and guess where there 16" studs were for the majority of the house siding since measuring from the last stud that I finally found would get you only within about 2" of the next stud center due to the builders having framed it up inconsistently spaced (I am sure this has never occurred in any of your houses!).

I have no desire to try and hit the studs and/or furring channel only and worry that all my $$$ devoted to clips and channel and general soundproofing could be short circuited by a few misplaced screws. Hope this is helpful.
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Yes rigidity of a totally floating structure was a reason for OSB in one case. When I talk about having a secure screwing surface I am reffering to walls and ceiling on a clips and channel system. Mostly all I ever do.

As for hitting channel on the ceiling. Let me know how that works out for you. I'd rather just screw anyplace I can. This is a four level tiered ceiling built inside the clip and channel ceiling with a layer of OSB and a layer of DW.

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post #9 of 568 Old 01-03-2014, 09:25 PM - Thread Starter
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Quote:
Originally Posted by PApilgrim View Post

This thread is one I read through since still in the planning phases of my build and discusses more of the performance and value end of the OSB vs drywall question. It is a little dated in terms of costs perhaps but a good read.

http://www.avsforum.com/t/1157120/does-osb-seem-all-that-less-dense

Oh, this thread is darn near perfect for my question! I love, too, that I get two direct quotes from Ted White himself:
Quote:
Originally Posted by Ted White View Post

The OSB first layer is a great idea. I would not worry about the small differences in density

and (emphasis added by me)
Quote:
Originally Posted by Ted White View Post

Mass is mass. True enough. There is the other factor of stiffness also. If, as the OP indicated, GG is involved, there is the matter of damping efficiency. Damping is optimized when the stiffness of each layer is the same.

So double 5/8" drywall is massive and equal in stiffness. Optimal. Small deviation in stiffness (no idea what that delta is) will reduce damping efficiency.

Having said all that, I would myself be inclined to use an initial layer of OSB for the sheer convenience of being able to stick a screw anywhere layer. The small variance in mass and stiffness is likely quite minimal to the point of being a non-issue.
Quote:
Originally Posted by PApilgrim View Post

My two cents - I plan on using OSB for the ease of future use for all soffit and inside the soundproofed room construction. It allows more flexibility for sure.

An analogy from my unrelated experience - I resided my old house with vinyl siding (was aluminum). It was built in the 70's and they used this fiber board stuff which has the structural integrity of a greasy pizza box. So, I had to try and guess where there 16" studs were for the majority of the house siding since measuring from the last stud that I finally found would get you only within about 2" of the next stud center due to the builders having framed it up inconsistently spaced (I am sure this has never occurred in any of your houses!).

I have no desire to try and hit the studs and/or furring channel only and worry that all my $$$ devoted to clips and channel and general soundproofing could be short circuited by a few misplaced screws. Hope this is helpful.

Yeah, I'm pretty convinced to use OSB based on the input here and on the quoted thread. I don't have to worry about accurate spacing in my theater, since I'm going to control every single stud and joist... but not having to worry about the spacing at all would make things so much easier. Outside of the theater, though... I try not to think about the building practices of whoever built my house back in 1980. Either there was no such thing as a building code back then (doubtful) or they paid off the inspector. Yeesh.
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post #10 of 568 Old 01-03-2014, 09:44 PM - Thread Starter
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(Moved from poor choice of initial thread)

I am trying to find an answer to an apparently esoteric acoustic question: does inserting insulation in between the walls in a double wall scenario either a) hurt the soundproofing b) increase the soundproofing or c) do nothing one way or another? I am finding directly contradictory info on this topic and am hoping that some acoustics experts here can set me straight.

Okay, to start, there appears to be two primary sources of info related to soundproofing with "double leaf" assembly. The original source was the Owens Corning study done by Geiger and Hamme in 1972. I find this referenced all over the place, but have not found the actual original research. The other primary source is the work done the National Research Council of Canada in the publication Control of Sound Transmission through Gypsum Board Walls. There is also secondary (excellent) information found on such sites as The SoundProofing Company.

From them, we have the canonical example of a "double leaf" wall assembly with an STC 63 rating.

Double Leaf with Partial Insulation

The documents all describe the "air gap" as being 8" in this example, since the insulation acts as air in a double leaf scenario. Therefore, the "air" is made up of 3.5" Batt + 1" empty space + 3.5" Batt

I'm going to dwell on the fact that "insulation = air" for a bit. On the SoundProofing Company website, we see this quote:
Quote:
For thermodynamic reasons, insulation essentially mimics a somewhat larger air cavity.

That's in support of the reasoning that adding insulation to this assembly will notably decrease sound leakage compared to having pure empty space. I take from that that "insulation = air" AND "insulation = better air than air".

The research done by NRC appears to say that same thing here:
Quote:
The optimal amount and type of soundabsorbing material for use in a cavity were investigated in a preliminary study in which seven different absorptive materials were used in a window-sized specimen formed from two layers of 3-mm-thick plastic. The study showed that:
  • sound reduction continuously improves as the thickness of sound-absorbing material covering the whole face of the specimen is increased.
  • there is no significant change when the sound-absorbing material is moved from the middle of the cavity to a position near one face.
  • partially filling the cavity from bottom to top, or from sides toward the middle, is less effective than having the same amount of material completely covering the whole inner face of the cavity.
  • the type of material used influences the sound reduction measured in frequencies ranging from 500 to 2000 Hz. The greater the airflow resistivity of the material, the greater the sound reduction. Because there is a direct correlation between the density of the materials and sound reduction in this frequency range, the sound reduction tends to increase as the density of the sound-absorbing material increases. However, in terms of the STC, no important acoustical differences were found among the sound-absorbing materials used in this preliminary investigation

I stressed that line, because to me, that is saying that the canonical example of a "double leaf" assembly actually is non-ideal, since the cavity is partially filled with insulation and NRC's research claims that the best results come from cavities that are completely filled with insulation (no empty space).

So let's take that "knowledge" and apply it thusly:

Double Leaf with Full Insulation

This is the exact same as the canonical example, but now we've replaced the empty air gap with insulation. If "insulation = air" and "insulation = better air than air" and "a full cavity is more efficient than a partially filled cavity", then it stands to reason that this assembly would be at least as good if not better than the typical assembly.

Right now, if you are reading this and know that I am completely wrong, then jump right in and tell me how wrong I am and why I'm wrong!

If I'm not wrong, then why can't I find any evidence that my conclusion is true? confused.gif In search after search on AV sites, studio forums, and the like, I keep hearing that the gap between the walls MUST be empty air and MUST NOT be insulation. But nobody says why and nobody references the above research one way or another.

So yeah, I'm really confused. If I'm wrong, then what am I missing? If I'm not wrong, then why isn't this talked about?
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Quote:
Originally Posted by BasementBob View Post

Insulation in the walls helps soundproofing.
Amongst other things, it dampens the resonance of the wall leafs.

If you're building walls, ceilings, around a home theatre, the rule of thumb is: insulation in the cavity is REQUIRED.

I don't regard Owens Corning as an expert in this area.
NRC is an expert. Very much an expert.

The stuff published by Brian at soundproofingcompany.com (aka Green Glue) is also really really good -- especially for us since it's mostly done from a home theatre point of view. Some of it gets dumbed down by the web guys there though, which isn't optimal.

This line by the NRC is correct,
  • partially filling the cavity from bottom to top, or from sides toward the middle, is less effective than having the same amount of material completely covering the whole inner face of the cavity.

but you've interpreted it incorrectly.
You're thinking of batts of fiberglass pink, or rigid Rockwool.
Consider what happens with blown in cellulose insulation in a wall cavity.

They're not talking about coupling the entirety of the leaves to each other by insulation as you drew.

What they mean is any of these are good:

WallInsulationGood1.png

WallInsulationGood2.png

WallInsulationGood3.png

but this is bad

WallInsulationBad1.png

Similarly batts that fall off one wall, or shrink with time, or blown in cellulose insulation, all break the rule:
The sound must go through insulation to be damped.
If there's a path around the insulation, (over it as would be the case with cellulose, or around it as shown in the above diagram), that's bad.

Note that Brian of soundproofingcompany.com did some tests and was surprised to find that

WallInsulationGood3.png

worked remarkably well, from a bang-for-the-buck point of view.
.

Thank you! That does, indeed, sound like a much more reasonable interpretation of the NRC data than I had.

I don't know that it fully answers my question, though. It shows that a fundamental pillar of my reasoning was flawed, but not necessarily that the conclusion was completely incorrect.

The key end question for me is if filling the empty air gap with a thin layer of fiberglass insulation will be detrimental at all? I get that the NRC data doesn't indicate that it would help, but they apparently don't address if it would hurt. Does anybody?

I wonder if small scale testing could actually work in cases like this. That is, what if I created some 2' x 2' walls with studs and drywall and insulation and the like, just like a full-size wall. I could separate the mini-walls with a 1" gap and then put speakers and/or a subwoofer on one side and a microphone on the other side. The speaker side could be completely incased with a couple feet of insulation. If I then ran one test with an empty air gap between the mini-walls and one test with insulation there, would I have an accurate representative sample of the differences? Or does some property of the sound negate all kinds of small scale tests?

I'm thinking that a small scale test definitely wouldn't work with acoustical treatment, since so much of treatment depends on the size of the sound waves per individual frequencies. I'm not sure if that translates to soundproofing or not.

(BTW, I just now realized that BasementBob is the one and the same as Bob Golds. I love your site! It's high up there on my "Google Suggests" URL bar)
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post #12 of 568 Old 01-04-2014, 04:04 AM
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Let's keep in mind that insulation doesn't do much on its very best day. Of the 4 Elements, it brings the least to the table. Interestingly, however, it's sometimes the most discussed.

What we see is that a bit of insulation does most of the work and the remaining insulation does little more. When they talk about the cavity being "filled" they are more referring to the side-to-side filling of the cavity. Insulation is filling the space between wall studs or joists.

Filling a cavity 50%-70% is about as good as it gets. Filling 100% doesn't get you anything audible. Keep in mind 3 STC points is audible. 2 STC point difference isn't perceivable by the human ear.

http://www.avsforum.com/t/1045780/ceiling-insulation-thickness

I have not and do not suggest completely filling the ceiling cavities beyond R13. I also don't spec filling that 1" insulation gap in a double stud wall. Not at all.

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Quote:
Originally Posted by Ted White View Post

Let's keep in mind that insulation doesn't do much on its very best day. Of the 4 Elements, it brings the least to the table. Interestingly, however, it's sometimes the most discussed.

What we see is that a bit of insulation does most of the work and the remaining insulation does little more. When they talk about the cavity being "filled" they are more referring to the side-to-side filling of the cavity. Insulation is filling the space between wall studs or joists.

Filling a cavity 50%-70% is about as good as it gets. Filling 100% doesn't get you anything audible. Keep in mind 3 STC points is audible. 2 STC point difference isn't perceivable by the human ear.

http://www.avsforum.com/t/1045780/ceiling-insulation-thickness

I have not and do not suggest completely filling the ceiling cavities beyond R13. I also don't spec filling that 1" insulation gap in a double stud wall. Not at all.

Thanks! This is quickly demolishing the entire framework for my hypothesis on the effectiveness of filling the space. The one remaining bit is that some people have asserted that any fiberglass in the air gap would actually create a sound bridge between the two walls, thus re-coupling them and making everything worse. What's your take on that?

Also, I added the Ceiling Insulation Thickness thread to the summary posts. I doesn't look like the NRC original research doc (IR-766) is online anymore, so it's handy that the table is quoted.
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post #14 of 568 Old 01-04-2014, 12:06 PM - Thread Starter
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Open question: What are the best build threads that go into detail on soundproofing aspects?

I'm having a tough time finding such threads, beyond the two I have already posted above. Most build threads I've bookmarked tend to spend lots of time on such things as risers and stages and screen walls and speakers and the like (all great, which is why they are bookmarked) but tend to gloss over the soundproofing bits.

What are some great threads on installing doors? Building a staggered wall? Building a dead vent? Floating a floor? Etc?

Really, any thread that goes into great detail on any aspect of soundproofing will be appreciated!
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I'm glad you mentioned Brian Ravnaas above. He is truly the soundproofing master. He developed the Green Glue and he and his brother founded the company. Was great to be part of all that way back in the day.

granroth, we have SIMs for all these construction aspects already. Fully illustrated.

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Quote:
Originally Posted by granroth View Post

Open question: What are the best build threads that go into detail on soundproofing aspects?

I'm having a tough time finding such threads, beyond the two I have already posted above. Most build threads I've bookmarked tend to spend lots of time on such things as risers and stages and screen walls and speakers and the like (all great, which is why they are bookmarked) but tend to gloss over the soundproofing bits.

What are some great threads on installing doors? Building a staggered wall? Building a dead vent? Floating a floor? Etc?

Really, any thread that goes into great detail on any aspect of soundproofing will be appreciated!

Check out Elill build he's getting into soundproofing and doing a lot around DIY vents ATM http://www.avsforum.com/t/1186799/downunder-theatre-mkii/250_50#post_24153073
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Quote:
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granroth, we have SIMs for all these construction aspects already. Fully illustrated.

Yes, I know. Right now, if I type 's' into Google Chrome, it automatically sends me to your website, since it knows that that's where I'm going. Why bother having me type out more if it knows for certain that that's where I'm going. Fully 90% of your website hits lately are probably from me! I'm definitely going to be calling you guys sometime in the next few weeks (hopefully; my build thread has more info).

But here's the deal -- all of those SIMs will be useful for me and for anybody else that is a customer, but since they are almost surely copyrighted, they can't be posted for general consumption. I'm really hoping that this thread will mirror the usefulness of the rest of AVS Forum and give people the info that they need, without having to become a customer of a specific company. For instance, I can get tons of info on acoustical treatments in the Acoustical Treatments Master Thread, without actually contracting with Erskine or GIK or MSR/PMI.

I know that so far this thread is just me asking a bunch of questions, but that's NOT my intent. I really want this to be both a central clearing house of proven soundproofing methods as well as an appropriate place to ask specific soundproofing questions. I've only been an AVS Forum member for a little while, but I've lurked for much longer... and I've seen so many of the same questions asked over and over. It really seems like there should be a thread like this (one way or another) for those. To make it truly effective, though, all of the info on it needs to be freely shared.
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Originally Posted by Ted White View Post

Filling a cavity 50%-70% is about as good as it gets.
Yep I'll agree with that.
Although I'd be willing to go as high as 87% (7" of an 8" cavity is both studs filled with a 1" air gap), but I don't complain about anything over 25% of the gap filled.
It's exponential diminishing returns for your dollar.

I like your NRC ir766 chart
IR-766.gif
although I was going by what Brian said too.
Quote:
Originally Posted by someone 
I'm wondering if putting insulation in between the walls will HURT the performance
What do you mean by performance?
- performance within the room, acoustically (absorb, diffuse, reflect)
- performance of the wall as a sound stopper, transmission/reflect

I'm assuming you know what the resonance dip and coincidence dip are in STC, from your travels to SoundproofingCompany (Green Glue).

If you mean stopping sound from going through the wall, then
a) a little insulation in a wall cavity is a good thing (1" thick) from "two perspectives".
b) more insulation up to 87% of the wall cavity is a good thing, with diminishing returns
c) coupling otherwise decoupled walls by having touching insulation, is probably a bad thing. In any event it's already a complete waste due to (b), so who cares.

"two perspectives"
- soundproofing, stopping sound from going through the wall. You want this for two reasons: to stop annoying the wife and sleeping kids and rattling dishes in the kitchen cupboards; and to keep the noise floor in the room low so you can hear the quiet scenes without raising the volume when trucks and airplanes go past your house or someone flushes the toilet or the furnace starts.
- acoustics, within the room itself. If you have a room mode that's the same frequency as the walls resonate, then the walls could help to damp that, but: (1) there are perhaps two people on the planet who can build such a wall and rebuild/tune it after the room is full of furniture and an average people load so odds are really good that any effort made on this technique will only make the room acoustics worse, and (2) doing so would completely defeat the purpose of the first perspective above as it would let a lot of sound through the walls at this frequency.

Build the walls according to the observations/recommendations of NRC and Green Glue.
Deal with in-the-room issues within the room, not with the walls.
Step 1: Decide what isolation you want, at each frequency, and pick a wall from the NRC/Green guys that matches. That's engineering.
Reduce the wall isolation if you've got other issues that would bypass it, or if the significant other refuses the cost. and redo step 1.

Understand a bit why it works, so that during construction you can avoid problems.
Why is nailing through a RISC clip bad?
If someone leaves a stick leaning from one decoupled wall to another decoupled wall within the wall cavity, why is this bad?
Where is acoustical caulking needed, and how long does it last?
What is receptacle putty?
etc

If green glue happens to damp some additional room modes, well that's cool too. A free benefit. But not a design consideration for the walls themselves.

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Quote:
Originally Posted by granroth View Post

. I doesn't look like the NRC original research doc (IR-766) is online anymore.

http://primaryacoustics.com/images/ir766.pdf

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Quote:
Originally Posted by granroth View Post

Open question: What are the best build threads that go into detail on soundproofing aspects?

What are some great threads on installing doors? Building a staggered wall? Building a dead vent? Floating a floor? Etc?

The book "Home Recording Studio: Build It Like the Pros" by Rod Gervais
There's nothing better than this. Answers everything you want to know, with practical advice.

Honourable mentions
- "How to Build a Small Budget Recording Studio from Scratch " by F. Alton Everest and Mike Shea
- "Noise Control in Buildings: A Practical Guide for Architects and Engineers" by Cyril M. Harris (the paperback version is cheaper. Nice stuff about concrete walls)


Combined with the NRC papers
and Brian's stuff (the website, and about 40+ papers),
and to a lesser extent the Resilient Sound Isolation Clip (RSIC-1) stuff,
And maybe Paul Woodlock's (his walls, his floating room, his hvac, and of course his door), and Galaxy Studios (Belgium) (with the unheard insulation value of plus 100 dB between 2 rooms 60cm apart) for over-the-top examples of floating rooms and doors and hvac.
that's all I needed to form an opinion.

Quote:
old NRC papers

ir772 Electrical Recepticals BackToBack.pdf
IRC - Institute for Research in Construction.htm
IRC 02-108.htm
IRC Avoiding Flanking Noise Transmission.htm
IRC BSI '85 - Noise Control in Buildings - Questions and Answers.htm
IRC BSI '85 - Sound Transmission Through Building Components.htm
IRC CBD-164_ Acoustical Effects of Screens in Landscaped Offices.htm
IRC CBD-186_ Office Partitions Acoustical Requirements for Design and Construction.htm
IRC CBD-236_ Introduction to Building Acoustics.htm
IRC CBD-239_ Factors Affecting Sound Transmission Loss.htm
IRC CBD-240_ Sound Transmission Through Windows.htm
IRC CBD-41_ Sound and People.htm
IRC concrete block ir586.pdf
IRC ctu01e Gypsum Board Walls.pdf
IRC ctu13e Concrete Block Walls.pdf
IRC ctu16e Sound Isolation and Fire Resistance firestop airgap.pdf
IRC ctu22e Floor Vibrations.pdf
IRC ctu25e Airborne Sound through Floors.pdf
IRC ctu27e Electrical Outlet.pdf
IRC ctu35e Impact Sound through Floors.pdf
irc electrical receptacles boxes nrcc43410.pdf
IRC Fire stops in walls can provide both fire resistance and sound isolation.htm
IRC flanking multi family dwellings rr218.pdf
irc flanking nrcc46629.pdf
irc flanking rr103.pdf
IRC flanking wood rr219.pdf
irc floating floor ir802.pdf
irc floor flanking nrcc45724.pdf
irc floor impact ctu35e.pdf
IRC floor rr169.pdf
IRC floor wall rr168.pdf
IRC How wall-floor details affect sound insulation in multi-family dwellings.htm
IRC ir693 walls.pdf
IRC ir760 airport.pdf
IRC ir761 walls.pdf
ir766.pdf
IRC ir811 floors.pdf
IRC ir826 test facility.pdf
IRC NRC's Institute for Research in Construction- Search.htm
IRC nrcc44692 resilient channel wall model.pdf
irc nrcc44764 brick.pdf
IRC rr103 flanking.pdf
IRC sand in walls cupboard door heard brn232.pdf
IRC Sound Transmission Through Concrete Block Walls.htm
IRC Thickness of Air Space in Double Glazing.htm
IRC Thirteen concert hall test data ir668.pdf
IRC Washing Machine, Dryer, Dishwasher, Counter, Toilet resonance resilient channel RC 125hz.htm
IRC Washing Machine, Dryer, Dishwasher, Counter, Toilet resonance resilient channel RC 125hz_files

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Quote:
Originally Posted by BasementBob View Post

What do you mean by performance?
- performance within the room, acoustically (absorb, diffuse, reflect)
- performance of the wall as a sound stopper, transmission/reflect

I'm assuming you know what the resonance dip and coincidence dip are in STC, from your travels to SoundproofingCompany (Green Glue).

If you mean stopping sound from going through the wall, then
a) a little insulation in a wall cavity is a good thing (1" thick) from "two perspectives".
b) more insulation up to 87% of the wall cavity is a good thing, with diminishing returns
c) coupling otherwise decoupled walls by having touching insulation, is probably a bad thing. In any event it's already a complete waste due to (b), so who cares.

Performance, in this context, refers to using the wall as a sound stopper. Your c) is the key bit in this -- does loosely packed fiberglass couple the two decoupled walls? That is, I know that any sort of rigid material like wood (2x4s), steel (screws, nails), foam (insulation), etc will definitely couple the walls. Fiberglass is used enough in a single 2x4 wall where it touches both sides that I wonder if it's considered a coupling agent at all. If it's not, then perhaps having it fill the air gap would not hurt the soundproofing performance.

It's a fair question to ask why you'd want to do it, if it's not helping at all (we've established that it definitely does not). Consider exterior walls and those with an attic above them. In the exterior wall case, that extra R-3.5 for the inch (vs R-0.68 for the empty air) could be appreciated. In the attic case, it could prevent all sorts of things (bugs, debris, etc) from falling down into the gap from the attic. That is, it doesn't have any soundproofing benefits, but if it doesn't hurt the soundproofing, then it still has benefit from other perspectives.
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Quote:
Originally Posted by BasementBob View Post

http://primaryacoustics.com/images/ir766.pdf

Yeah, I found that. I was a little leery about posting it, though, since the article was removed from the NRC website. Reposting copyrighted materials gets into some grey areas that I prefer to avoid. Of course, this is just linking to it but the US courts haven't always agreed that that's a worthwhile distinction.

As far as that goes, I also found a PDF of the Rod Gervais Home Recording Studio book. Same deal, though -- it's copyrighted material and providing a link to it might be more trouble than it's worth.

In general, lots of stuff is available in PDF form if you do an Advanced Search in Google and specify 'pdf' as the type (or add 'filetype: pdf' to the end of a search)
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Quote:
Originally Posted by granroth View Post

Yeah, I found that. I was a little leery about posting it, though, since the article was removed from the NRC website.
Ok, then this one
http://archive.nrc-cnrc.gc.ca/obj/irc/doc/pubs/ir/ir766/ir766.pdf

I'd be less worried about copyright on the NRC stuff.
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Originally Posted by granroth View Post

I also found a PDF of the Rod Gervais Home Recording Studio book.
That one copyright applies. People should really buy that book. And not just because I know the author.

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post #24 of 568 Old 01-05-2014, 02:57 PM - Thread Starter
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Thanks, Bob! I updated the summary posts with your links. And no, I wouldn't dream of posting a link to a copyrighted book that is currently available for sale.
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Quote:
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Performance, in this context, refers to using the wall as a sound stopper. Your c) is the key bit in this -- does loosely packed fiberglass couple the two decoupled walls?
Actually, the key is this

Step 1: Decide what isolation you want, at each frequency, and pick a wall from the NRC/Green guys that matches. That's engineering.

If you build something that hasn't been tested and measured, you're guessing. Why bother. Personally I wouldn't even consider it.

If on the other hand you have the NRC's or Green Glue's research budget, you can build the wall configuration you're curious about and test it at a rated facility.
But if you're not willing to do that, you won't get answers, unless someone else does.

Tweaking in your home with radical ideas, usually is just money wasted. When Brian started doing the green glue stuff, the big internet question was if limp mass in the walls really helped or not. (turns out not, sometimes it's just a 3 leaf wall which is bad)

When considering if filling that last inch with fluffy fiberglass pink is going to do any good,
you'd be much better off considering if you could use concrete instead of drywall, using a tested with published frequency loss measurements, design with concrete.

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Quote:
Originally Posted by BasementBob View Post

Actually, the key is this

Step 1: Decide what isolation you want, at each frequency, and pick a wall from the NRC/Green guys that matches. That's engineering.

If you build something that hasn't been tested and measured, you're guessing. Why bother. Personally I wouldn't even consider it.

If on the other hand you have the NRC's or Green Glue's research budget, you can build the wall configuration you're curious about and test it at a rated facility.
But if you're not willing to do that, you won't get answers, unless someone else does.

Tweaking in your home with radical ideas, usually is just money wasted. When Brian started doing the green glue stuff, the big internet question was if limp mass in the walls really helped or not. (turns out not, sometimes it's just a 3 leaf wall which is bad)

When considering if filling that last inch with fluffy fiberglass pink is going to do any good,
you'd be much better off considering if you could use concrete instead of drywall, using a tested with published frequency loss measurements, design with concrete.

I don't disagree with you, but I do think you are describing a form of the holy grail. Lab tested data is definitely what we all want to get, but it sometimes just doesn't exist. Sometimes the only answers we can get is "best guess" or anecdotal and that, I'd argue, is better than nothing.

For instance, as far as I know, there are no lab tests that compare OSB + GG + Drywall vs Drywall + GG + Drywall. But when Ted says that he thinks the damping impact would be too minimal to worry about, then that's as good as it'll get and good enough for me.

So what I'm looking for with the insulation question is just that -- an educated guess or some anecdotal evidence.
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post #27 of 568 Old 01-05-2014, 04:55 PM - Thread Starter
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Question: What are the prevailing opinions on the validity of small scale soundproofing tests?

I'm wondering if it's possible to perform some small scale tests to compare various soundproofing methods. I'm not even remotely suggesting that any small scale tests would even start to approach the reliability of a full lab test... but would they be at least a little useful?

The biggest reason I'm thinking that maybe they wouldn't be at all valid is because I'm 99% certain that small scale tests absolutely won't work for comparing acoustical treatment plans. Acoustical treatments are designed to work with specific wave lengths and so the actual size of a room matters a lot.

But is that true for soundproofing? If all I'm going to test is an overall DB drop, then would a small scale test at least approximate a result?
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Quote:
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I'm wondering if it's possible to perform some small scale tests to compare various soundproofing methods. I'm not even remotely suggesting that any small scale tests would even start to approach the reliability of a full lab test... but would they be at least a little useful?

Yes.
Brian once did an experiment like this:
Most of the noise through a wall is at resonance, and resonance can be tested with a small 1'x1' piece of material and an accelerometer.
As I recall, he used it to give him a better idea of what to build full scale and test in a real testing facility.

But resonance in a 2 leaf wall, is because of the leaf-air-leaf system, I'm not sure how to test that small scale off hand.

I think he even mused how to, although I don't know if he ever got around to it, make his own testing facility with thin concrete walls to test gypsum walls approximately.
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But is that true for soundproofing? If all I'm going to test is an overall DB drop, then would a small scale test at least approximate a result?
No.
Just good quick hints of what to really test; of what might give good results.

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post #29 of 568 Old 01-06-2014, 06:23 PM - Thread Starter
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Question: Is there qualitative data on the effectiveness of various door designs?

There's a decent amount of test data concerning the effectiveness of various forms of wall construction. I'm not finding any such data concerning doors, beyond the basic "hollow core" vs "solid core".

For instance, it makes intuitive sense that adding a layer of 3/4" MDF + Green Glue to a solid core door will make it more sound proof. But do we know the numbers? What about adding another layer?

Now compare that to single doors vs double doors. Will that approach the effectiveness of a double wall, if they are solid core? And what about a mass-added single door vs a conventional double door setup?
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post #30 of 568 Old 01-06-2014, 07:52 PM
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There's single doors: wood hollow core, steel hollow core, wood solid core, steel fire door (aka steel hollow core, thicker steel, filled with insulation, often with better seals), custom door, professional acoustical doors.
There's double doors: communicating doors (aka tandem doors, width of the double stud wall) , airlock doors (one man room), and lobby doors (a real room).

Back in 1994, BBC did a study of "door blanks" and "door seals" which included multi frequency test results, but it was mostly the types of doors they had handy which were kind of thin.

Most of the 'professional acoustical doors' or manufactured units specifically designed for sound isolation are sold with an STC rating only.
Steel doors going up to around STC 55, wood doors up to around STC 49.

Overly is nice enough to have frequency tests at the bottom of each of their products
http://door.overly.com/products.aspx?family=Acoustical&prodType=door&material=metal

An airlock, with a couple of heavy steel fire doors with decent seals, usually works well.

SAE used to have some very nice summary pages on acoustical isolation techniques, again over a decade ago. One of the things they recommended for airlocks was hanging thin open-cell foam on the side of the doors on the inside of the airlock. Given the study of walls above it should be obvious why this helps.

Doors are remarkably sensitive to the seals they have, so a simple study of door types while indicative is not predictive of installed results. I seem to recall a bunch of multi frequency test results for single doors, where they glued the door into a test frame.

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