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Old 03-20-2012, 03:16 PM   #1
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Sound attenuation; a surprise about insulation


As there are often questions about sound attenuation here, I thought I'd post this. I have NFI who compact dynmaics is, so take this fwiw.

http://www.compactdynamics.com/encyc-acoustics-0.html

Here is an excerpt from above:
It may appear, by analogy with heat insulation, that stuffing the wall with an insulating material such as glass fiber or rock wool will increase the transmission loss of the wall. Experience shows, however, that an insulating material increases the transmission loss by 2 or 3 dB at most. Insulation materials don’t work for the same reason that acoustical materials don’t—they are too light and porous. It is one of the great fallacies of modern home construction that stuffing an acoustical material in a partition will help prevent the transmission of sound through it. In addition, trying to increase the transmission loss of a wall, or a ceiling, by attaching acoustical tiles, insulation board, drapes, or a similar lightweight, porous material against one of the external surfaces is also a waste of money because the lightweight and porous nature of these materials makes them inherently incapable of preventing the transmission of sounds through themselves, much less through a wall or ceiling. However, it should be added that attaching an insulation material to one of the interior surfaces of a wall partition does help increase the transmission loss through the partition, if the installation is done correctly.

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Old 03-21-2012, 05:06 AM   #2
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Sound attenuation; a surprise about insulation


This is a good example of incorrect information one can find on the internet. Rock Wool for example: Roxul makes a sound deadening batt that works very well. I do a lot of sound attenuation projects and the sound is tested before and after always showing 50%-80% success. I also inject Retro Foam in exterior walls for insulation. This offers 80% reduction and is a very light product. Normally my client's first comment is that the outside sounds are no longer noticed unless they open a window.

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Old 03-21-2012, 09:28 AM   #3
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Sound attenuation; a surprise about insulation


From personal experience, any insulation in the wall seems to make a difference. Ever heard how easy sound goes through a hollow wall, versus one filled with something (not even things as good as Roxul). Reminds me of a former doctor's office I used to go to: all of the patient rooms had hollow partition walls between them, and you could clearly hear a conversation in the room next-door.
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Old 03-21-2012, 01:09 PM   #4
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Sound attenuation; a surprise about insulation


Ok here is a question along the same lines...

I want to sound proof (for the most part) a basement bedroom.

However the basement bedroom is going to have radiant heat and i'd like that heat to work its way up to the 1st floor to some extent.

Are there any acoustical insulating materials that also wouldn't be heat insulation materials?

Or are there any other cost/size effect solutions to reduce hearing steps from upstairs or music/noise from downstairs up. If we're talking about losing over 3"+ of headroom that would hurt....

Thanks guys!

Chris
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Old 03-21-2012, 01:43 PM   #5
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Sound attenuation; a surprise about insulation


Bob: Thanks for the info. Yes, one never knows what rumors are on the Net, which is why I said I don't know the source. I've been searching my butt off for unbiased info on this topic, and as yet have found little; most is from companies. This I did find:

http://www.fhwa.dot.gov/environment/...scape/al04.cfm

"Add acoustical blankets.
Also known as isolation blankets, these can increase sound attenuation when placed in the airspace. Made from sound absorbing materials such as mineral or rock wool, fiberglass, hair felt or wood fibers, these can attenuate noise as much as 10 dB.3They are mainly effective in relatively lightweight construction."

In your experience, how productive is dense packed cellulose for killing noise? And different from Roxul's sound blanket? There is no rock wool up here, (I could order it for an arm and leg) but I will be dense packing my exterior walls, so will have plenty of cellulose around. Thanks. john

Chris: sheet rock w/ the special "wiggly" connectors may be your best bet. Seal any cracks/openings, too.
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Old 03-21-2012, 02:28 PM   #6
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Sound attenuation; a surprise about insulation


Quote:
Originally Posted by CarlsonRower View Post
Ok here is a question along the same lines...

I want to sound proof (for the most part) a basement bedroom.

However the basement bedroom is going to have radiant heat and i'd like that heat to work its way up to the 1st floor to some extent.

Are there any acoustical insulating materials that also wouldn't be heat insulation materials?

Or are there any other cost/size effect solutions to reduce hearing steps from upstairs or music/noise from downstairs up. If we're talking about losing over 3"+ of headroom that would hurt....

Thanks guys!

Chris
Chris....we will get to your issue in a moment....but first a few facts...

Every 3db drop in noise represents a reduction of half....so, if something reduces noise by 6db...then your looking at about 1/4 of what you had before.

Noise is transmitted through something because it vibrates at the same frequency of the sound....the key to reducing noise is finding materials that do not vibrate....that is why a concrete block wall does such a good job and a typical wall of drywall and wood studs does a poor job. If you could make that wall so that the wood on one side was not touching wood on the other side and you could put a vacuum in between....you would have a very good sound blocker....

Acoustic foam does a good job of blocking noise due to it's low mass and random foam cell size. Because the foam is so flexible, sound waves do not propogate very well through it. Whereas, insulation is acutally made of a more dense material and the glass fibers tend to transmit the sound.

Now...the basement issue....heat is transfered in one of two ways...radiation and convection. Convection requires the movement of air. Radiation requires a material that has thermal conductivity. There 'tends' to be a direct relationship between mass and thermal conductivity. For examaple, steel transmits heat more readily than wood....which one is more dense?

The moment you insulate your floor to keep sound out...you are also preventing heat from moving....

Chris....if your going to insulate between the basement and 1st floor and have radiant heat....the basement is going to get warm....but then again, the 1st floor surface will not be cold....
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Old 03-21-2012, 02:34 PM   #7
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Sound attenuation; a surprise about insulation


I'm aware of this. My question is if there is a way to have the sound dampening without increasing the insulation between the two spaces.

I have been looking at the drywall option but I am curious if there is anything else out there or a building practice.
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Old 03-21-2012, 02:39 PM   #8
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Sound attenuation; a surprise about insulation


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Originally Posted by CarlsonRower View Post
I'm aware of this. My question is if there is a way to have the sound dampening without increasing the insulation between the two spaces.

I have been looking at the drywall option but I am curious if there is anything else out there or a building practice.
Cheaply? NO.
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Old 03-21-2012, 02:53 PM   #9
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Sound attenuation; a surprise about insulation


Dawg: I believe there are a couple of errors here.

"...heat is transfered in one of two ways...radiation and convection...." You forgot the important one; conduction, from one body to the adjacent, "touching" body. This is where thermal conductivity comes into play. Thermal bridges, like a slab open to the outside air, conduct like crazy.

"...Radiation requires a material that has thermal conductivity...." Oops. Radiation travels across any open space, even a vacuum. That is why the sun heats us up across many miles of (essentially) a vacuum. That is primarily how radiant heat works in a house; it warms objects, including us, more so than the less dense air.
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Old 03-21-2012, 03:30 PM   #10
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Sound attenuation; a surprise about insulation


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Originally Posted by jklingel View Post
Dawg: I believe there are a couple of errors here.

"...heat is transfered in one of two ways...radiation and convection...." You forgot the important one; conduction, from one body to the adjacent, "touching" body. This is where thermal conductivity comes into play. Thermal bridges, like a slab open to the outside air, conduct like crazy.

"...Radiation requires a material that has thermal conductivity...." Oops. Radiation travels across any open space, even a vacuum. That is why the sun heats us up across many miles of (essentially) a vacuum. That is primarily how radiant heat works in a house; it warms objects, including us, more so than the less dense air.
You are correct...but I was trying to keep it simple within the context of the application.

For quickness...I just copied this from Wikipedia...
Conduction or diffusion The transfer of energy between objects that are in physical contact Convection The transfer of energy between an object and its environment, due to fluid motion Radiation The transfer of energy to or from a body by means of the emission or absorption of electromagnetic radiation Mass transfer The transfer of energy from one location to another as a side effect of physically moving an object containing that energy In reality, what people call 'radiant heat' is actually a combination of Mass Transfer, Conduction and Convection...floor gets hot due to hot water or electric elements...hot floor heats the air next to it...warm air rises warming up what it comes in conact with it...hence, 'radiant heat' has not radiation in it...

So...within the context of the basement being discussed....we really don't have any radiation...or 'radiant heat'....but we do have a warm floor...air...and varing pieces of solid material between the basement and 1st floor. Hence, anything done to dampen the transfer of sound will also dampen the transfer of heat.

I do know of some passive methods to moving heat without moving sound....but they are expensive....one involves a special fluid in copper fin tubes....gets real expensive....
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Old 03-21-2012, 04:32 PM   #11
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Sound attenuation; a surprise about insulation


"...'radiant heat' has not radiation in it..." Not to squabble, but everything having a higher temperature radiates energy to any object having lower temperature, and radiant floor heat does just that. We radiate, the floor radiates, and so does the Dachshund. Sure, a heated slab conducts and convects (which is likely a word I just made up), but it also radiates nicely. That is one of the huge benefits of it. Even baseboard radiates, but you don't have the mass in a baseboard that you have in a floor, so the baseboard heats the air primarily. Radiant floors don't work by warming the air and having it rise. On the contrary, thermal stratification in radiant-heated homes is less of an issue than if heated otherwise. Radiant wall and ceiling heat works because of heating objects by radiation, not heating the air. We feel cold in front of a cheap window because we lose heat by radiation through the window. For ex: From http://www.greenbuildingadvisor.com/...-floor-heating

"The (radiant floor) heat is distributed over a large surface area, so it is delivered at a relatively low temperature. It’s uniform, and it warms people directly, rather than having to heat the air. This means that radiant heat can provide comfort at a lower air temperature than is required with forced-warm-air or baseboard hot water heat. You might be able to keep your thermostat lower—say 65 degrees—and be perfectly comfortable with radiant-floor heating, while 68 or even 70 degrees would be required with other systems." BTW: This covers what is NOT GREAT about in-floor radiant heat in some situations, and may be of interest to those who are thinking about installing it. I don't quite agree w/ all his points, but.... he is the pro, so....

BTW: Wth is "mass transfer"? Unless you are talking about literally transferring molecules, it sure sounds like radiant heat going from a warmer, high-mass object to something cooler.

Last edited by jklingel; 03-21-2012 at 04:50 PM.
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Old 03-21-2012, 05:17 PM   #12
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Sound attenuation; a surprise about insulation


This thread is a good example of what my first comment was. Bad and incorrect info. Sound attenuation and heat transfer are not in any way related. To clear things up.
three methods of heat transfer from fastest to slowest are 1: conduction heat transfer through a solid 2: convection heat transfer through fluid (air and water are both examples of a fluid) and 3: radiation where heat transfers across a space from a hot object to a cold object.

Now to you questions:
the idea of wanting heat to move upstairs is a bad one from the start. You are best to keep both areas in different zones. And nothing you do will completely stop heater air from getting to the upper floor. This is do to stack effect. The air in a home layers itself with colder air at the bottom and hotter air above it. PS.... heat does not rise.... it moves randomly in all directions.

Use Quietrock for the ceiling so you have a 10 fold sound reduction with minimal R-Value being added.

to all... jklingles response is all wrong.. so do not follow this.
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Old 03-21-2012, 07:51 PM   #13
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Sound attenuation; a surprise about insulation


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to all... jklingles response is all wrong.. so do not follow this.
Bob: I don't think anyone implied that heat transfer and sound attenuation were related. They were always separate issues in my mind, and of course they are not related; they completely different phenomena. The OP asked how to deaden sound w/ out blocking heat, ("My question is if there is a way to have the sound dampening without increasing the insulation between the two spaces. ") so I suggested sheet rock, as it does not impede heat transfer tremendously, but does deaden noise if installed correctly. There is nothing you can do to deaden noise w/out impeding heat flow somewhat. If you want to deaden noise, one of the suggested methods is to use heavy sheet rock (because it is cheap) and to install it w/ little wiggly fasteners. Mass is one of the commonly suggested mechanisms for deadening noise, is it not? QuietRock is another option. Now, exactly which response do you think is "all wrong"? thanks. john

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Old 03-21-2012, 07:53 PM   #14
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Sound attenuation; a surprise about insulation


I had issues with you stating only two methods of heat transfer and the explanation of radiant heat. A slab does not convect heat in any way. We feel cold by windows because a natural convection occurs here.
the lower temps of a radiant floor have no correlation to the large floor area...???
A radiant system allows a lower temp setting normally due to its not using air movement to warm the area. It is the moving air which we perceive as cold and set the temps higher. In homes that I air seal the temos are set at 65 and the occupants are comfortable. Stop the drafts and you are more comfortable.

and mass alone does not necessarily reduce sound. A steel floor will have more mass, yet allow much more sound through it. Quitrock reduces sound by decoupling the sound within the makeup of the sheets. Sort of two layers separated by a paper sheet, but this breaks up the wavelengths.

A cheaper way is to use channel and regular rock.... but only yeilds a reduction by 4 or so. QuietRock will yield a factor 0f 10 reduction.

leaving a space at the top and bottom are also important and to fill this with acoustical caulking.

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Old 03-21-2012, 09:23 PM   #15
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Sound attenuation; a surprise about insulation


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I had issues with you stating only two methods of heat transfer and the explanation of radiant heat. •• I corrected dawg for forgetting the conduction. He is the one who originally only mentioned two heat transfer methods.

A slab does not convect heat in any way.•• Yes it does, as does anything that has a fluid moving past it. It is not significant, sure, but it happens. Air is forced to move in a house with animals, etc, in it, and we touch slabs, so a slab conducts heat via all three methods. I believe radiant is the most significant of the three, but you can't discount the low temp of a slab in a super-insulated house. The slab may be as cool as 72-75 degrees F, below the 80-ish that our toes want. I think 83-85 is what feet consider confortable for a long exposure.

We feel cold by windows because a natural convection occurs here. •• We feel cold in front of a window in still air, too, and it is because we radiate. Our skin is one of the most sensitive materials on the planet to detect radiation loss. Sure, if the window is leaky or generates a convection, the felt loss will be pronounced.

the lower temps of a radiant floor have no correlation to the large floor area...??? •• I have no idea what this means. My comment was that the floor is large, so what it radiates is significant. A lit match radiates, too, and although very hot, it is not very big and can not radiate many btu's to us.

A radiant system allows a lower temp setting normally due to its not using air movement to warm the area. It is the moving air which we perceive as cold and set the temps higher. •• Certainly partially true, but, again, our skin is very sensitive to radiant losses/gains as well. No doubt about it; fluids moving past us rob us of heat via convection. Radiant floor heat can allow lower temps because our feet are happier at warmer temps than our heads, and floor-radiant-heated homes tend to (depending on the insulation of the house) have warmer floors. Plus, we get warmed without the air being warmed as much (it is less dense), so the thermo can be lower (sometimes).

In homes that I air seal the temos are set at 65 and the occupants are comfortable. Stop the drafts and you are more comfortable. •• Certainly.

and mass alone does not necessarily reduce sound. •• Within the context of the materials used in a normal house, sheet rock is one of the cheapest masses we can add. Most of us don't have steel floors.

Quitrock reduces sound by decoupling the sound within the makeup of the sheets. Sort of two layers separated by a paper sheet, but this breaks up the wavelengths. •• And apparently it is a tad better than other gypsum products, but it is expensive. I have not studied the charts enough to voice if the expense is worth it or not, but I know sheet rock is often recommended because it is available and cheap.
Bob: I think we are pretty much on the same wavelength, but I still don't agree with a couple of your points. Pls see after the bullets above. Some great reading can be had at http://www.nrc-cnrc.gc.ca/eng/projec.../gypsum-1.html, esp the second study. Also, healthyheating.com and greenbuildingadvisor.com go into great detail on a lot of stuff, if anyone wants to read for the next year or so... Bottom line: We are sensitive to heat loss in a variety of ways, and radiant needs to be considered when we build.

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