Sound Proofing with Blown-In Insulation

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Hi ted,

Agree with your statement “Any pre-damped drywall is simply layers of standard boards and damping compound.”
But this process of making them is time consuming. Quiet Solutions has full TL data by frequency available for their expensive drywall and not for the inexpensive panels. And I do not know why.

Without boring the larger audience with excessive details, let me say that I am familiar with the manufacturing of damping compounds at the molecular level, as well and the factory assembly of these pre-damped panels. I have been involved with the R&D of constrained layer damping materials and systems since 2003. I have consulted with 3 of the 4 manufacturers who make these pre-damped panels.

There is no time consuming aspect of this in any form. It's very fast. To add mystique to the process is simply misleading.

Due to expenses like freight costs, factory damped panels are naturally and understandibly more expensive, but also have more expensive waste, and have generally lower performance than a field assembled panel (due to either lack of mass, lack of damping or some combination thereof).

They are all fine products, however.
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Hi, I have the same problem with airborne noise coming from an upstairs apartment occupying the third floor of my home. My bf and I are looking for an easy solution to reduce this noise with minimal cost and damage to the exisiting ceiling. We just put the ceiling up and really don't want to take it down and start over. We hear everything, every creak, the ice machine, the phone ring, talking...everything, and the tenant says the same for us.

We have the soundproofing, thicker sheet rock that you guys discussed in previous threads throughout the house on all the walls and the ceilings. It acts as a great barrier for the walls but does absolutely nothing for the ceiling. There is no insulation in the ceilings, or soundproofing on the flooring in the apartment, just plywood flooring with click flooring on top, and the thicker sheet rock on the ceiling.

I'm curious to know what you did as a solution to your airborne noise problem, and how it's working for you.

Yes Ted,
It certainly did give me lots of food for thought. This whole site should provide a wealth of information while we renovate is old house of ours. It was built in 1904.
What I was asking was how RMD handled his problem with the noise and was it effective. in elininating or minimizing the problem.

Ted knows his stuff, his advice is sound. We talked about some of this in a podcast here Episode #54 – Keeping the noise out

Thanks. I would not suggest the concept of a suspended ceiling for sound isolation.
I would not suggest the concept of a suspended ceiling for sound isolation.
I don't like them either.

As has been said, just another drywall layer will do more than blown in insulation. Decoupled drywall would be even better.
This is almost certainly the one thing that you can do A LOT about at very little cost.


To be honest with you, I wish you would read the paper by Mr. Quirt of the Canadian National Research Council on reducing noise transmission through building components like walls, floors, ceilings, windows and doors.

Sound Transmission Through Building Components - NRC-CNRC

That will convince you that the noise reduction you're likely to get by blowing cellulose insulation into your ceiling joist space is gonna be a disappointing waste of money. There are two reasons for this:

1. The first one is that adding sound absorbing materials like insulation to a wall, floor or ceiling is pretty well a waste of time and money if there are studs or floor joists that connect the two sides of the wall, floor or ceiling. That's cuz any movement of one side of the wall or floor is going to result in the simultaneous and equal amount of movement on the other side of the wall or ceiling, so any sound wave hitting the wall or floor is going to be accurately reproduced by the other side of that wall or ceiling. Sound absorbing materials are only helpful when you don't have any mechanical linkage between your wall and your neighbors, or your ceiling and your neighbor's floor. You can do that by building two walls, or using a 2X6 as the bottom and top plates, and staggering the 2X4 studs so that half of them support the drywall on one side and the other half support the drywall on the other.

2. And the second reason why is that sound is a pressure wave in the air and behaves all the laws of physics just like any other wave does. It's the fact that sound is a wave that allows me to explain in simple terms why the cellulose insulation in the ceiling won't do very much good.

When a sound wave hits a wall, floor or ceiling what happens is that the wall, floor or ceiling moves in response to the changing pressure on one side of it. It is that movement of the wall, floor or ceiling that reproduces another sound wave on the other side of the wall, floor or ceiling. It is this second "reproduced" sound wave that that we hear, NOT the original.

And, I can prove that by showing how the Mass Law results in our hearing only a "BOOM-BOOM-BOOM" and not all of the music when someone is having a party late at night in the same building we're living in.

The "Mass Law" is one of the basic principles of accoustics. The Mass Law says that for every:

a) doubling of the mass per given area of the wall, floor or ceiling, or

b) doubling of the frequency of the sound waves hitting the wall, floor or ceiling, then

the sound pressure level of the "reproduced" sound wave on the other side of the wall, floor or ceiling will be reduced to 1/4 of it's initial value, or by 6 decibels.

And the reason why is that by doubling the mass of the wall, you also double it's inertia. When you do that, the wall simply doesn't move as fast or as far under the same applied force. The smaller and slower movement of the wall means that the reproduced sound wave is lower in amplitude, which our ears recognize as being "quieter".

Similarily, if you double the frequency of the sound waves hitting the wall, then the inertia of your existing wall makes it progressively harder and harder for your wall to change it's direction of movement fast enough to respond to the sound waves hitting it. Once the frequency is high enough that the inertia of the wall prevents it from moving in response to those sound waves, the wall simply stops moving in response to those sound waves, and that means the wall stops moving. Unless something else is making noise on the other side of the wall, it's quiet on the other side of the wall.

It is these simple principles of physics that explain why you hear BOOM-BOOM-BOOM when there's a party going on in your building late at night. What's happening is the midrange and treble frequencies are too high for the walls and ceilings to respond to, so you don't hear them. The only frequencies that are low enough for the walls and ceilings to respond to are the deep bass frequencies. Consequently, your walls and ceilings only move in respond to those low frequencies, and that's the only sound that is reproduced by the walls, floors and ceilings. This is why you only hear BOOM-BOOM-BOOM when they're playing a song you know well. You have to get close enough to the source of the sound so that there are no walls, floors or ceilings between you before you will hear the midrange and trebel and recognize the music being played.

OK, so if you blow this cellulose insulation into the space between the ceiling joists, the amount it's going to help is going to be directly proportional to the amount it increases the mass per square foot of what's there now. It's only going to help significantly if your neighbor's wall wasn't mechanically connected to your ceiling by the joists. That's because the joists connect both sides of the floor structure, and so movement of the neighbor's floor is going to result in exactly the same movement of your ceiling. So, you can consider the entire floor/joist/ceiling a single "wall" of uniform composition and density and apply the Mass Law. You can do a rough calculation on your own. You know wood floats, so it's density has to be less than that of water. 0.8 say. It shouldn't be hard to find out how much a 1/2 inch by 32 square foot sheet of drywall weights and you know the area of your ceiling (roughly). And, you can probably assume 2X12 fir joists on 16 inch centers. Now add to that 12 inches (say) of cellulose insulation at, what, 3 or 4 pounds per cubic foot say (?) to see how much of a percent difference you're gonna make in the mass of that "wall" over your head.

Here's my best advice:

1. Deal with the stereo first: Explain what I've explained to you to your neighbor, and make him an offer: You'll buy him a set of good quality ear phones (which he will return when either of you move) if he will agree to turn the bass control on his stereo (or music source) all the way down when he's not using the ear phones. Since the source of the low frequency sound is the movement of the walls and floors in response to the low frequeincy sound created by the woofers, by stopping the movement of the woofers, we eliminate the bass frequencies which cause the "BOOM-BOOM-BOOM" you hear in your condo.

2. Deal with the foot steps next: Make your upstairs neighbor another offer: If he installs carpet in his apartment, you'll go halfers on a thicker and better quality underpad to go under it. (I know this is killing you.) The reason why the footsteps are loud is because the whole floor/joist/ceiling structure moves in response to 175 pounds suddenly coming down on it in one spot and causing it to vibrate. That's called "impact loading". By having a thick underpad under the carpet, you slow the rate at which that load is applied to the floor, (cuz underpad foam rubber is a lot softer than shoe heel rubber so it compresses more over a longer period of time) and that slows the movement of the floor/joist/ceiling in response to footsteps. If the movement of your ceiling is slower, then the sound pressure wave created when it moves is weaker (which means that the air pressure doesn't change as much as fast), and that translates into "quieter" noise.

The problem, of course, is that he might not want to give up his hardwood floor.

I'd look up "Engineers, Accoustical" in your yellow pages and phone one of them up. Explain what you've learned from posting online and reading various papers and see if he agrees that the earphones/underpad will be both more effective and considerably less expensive than the insulating idea.

There are noise and vibration isolation devices but to retrofit a building with these, even around one condo is likely going to be cost prohibitive.

Also, you already know that increasing the MASS of your floor/joist/ceiling structure is the single biggest factor in determining how much noise comes through. So, spending $5000 to REPLACE the drywall on the ceiling with Quietrock (whatever that is) is likely to be less effective than spending $3000 to ADD a second layer of ordinary drywall to your existing ceiling. Obviously, your drywall contractor doesn't know much about accoustics.

Click on the link above and read through it before making any decisions.

(Aside: Also remember that our hearing isn't linear. We hear quiet sounds much better than louder ones. So, a 25% (or 6 dB) reduction in the sound pressure level won't seem to be only one quarter as loud as it was before. You'd probably perceive a 6 dB drop in the noise level to be "half as loud" as before (at best).)

PS: The Canadian National Research Council is a government funded research group that does research into problems pertinant to Canadians and the Canadian climate. They do a lot of research on insulation and energy savings. You can access all of the information available from the Canadian National Research Council on their web site at:
spray foam insulation
Then left click on Library and Publications
Then left click on NRC Publications
Then click on Browse by Subject
You should be able to find the paper by J. A. Quirt under the heading "Construction", but it may take a while since the NRC has issued 16,488 publications under that general heading. (Best to use the "Advanced Search" feature and type in part of the title.)
In case you hadn't thought of it, the NRC web site is an excellent tool to research just about any subject; as is Google itself.

This is extremely helpful... Great resources....Thanks again for the share.

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Just to refine a point or two. We have the following elements to help us isolate sound:

Decoupling- Staggered studs, double studs, resilient clips&channel, and resilient channel are all common methods to decouple walls and ceilings.

Absorption- Some material in a sealed air cavity (in our case) that increases the resistance to sound wave movement, thereby robbing the waves of energy. A very large volume of air can accomplish this, but our walls are limited in depth. We add a low-medium density insulation to increase the resistance without introducing conduction. This is a thermodynamic process, whereby the introduction of open-fiber insulation essentially mimics a system with a much bigger air cavity.

Mass- This is primarily the job of materials like drywall and plywood. Could be masonry if wer're looking at exterior walls. Wall / ceiling framing and insulation technically contribute to the overall mass of the partition as well as the resonance and TL calculations, however we don't look to increase the mass of either the framing or the insulation. This is a key point.

Damping- The panels used to build partitions are very resonant. This resonance facilitates the propogation (re-creation) of the sound wave. Effectively damping the panels increases TL dramatically.

So in general, as previously posted, mass is king, but it's what we do with the mass that allows us to exceed pure Mass Law calculations. By decoupling the massive leaves, introducing a larger air cavity and adding prudent insulation, we exceed Mass Law calculated performance in the mid and upper frequencies. Again, the answer is not simply mass.

The value of insulation isn't its contribution to the mass of the assembly. Lightweight insulation isn't contributing anything meaningful to the mass of the system, rather it offers absorption within the sealed air cavity. This is why low / medium density insulation performs better in the more problematic low frequencies. Refer to the NRC data as pointed out already. Massive / dense insulation is not what we want at all.

The value of framing isn't its contribution to the mass of the assembly. Indeed, less massive steel studs perform better than wood in a coupled assembly by allowing the panels to flex more. Similarly, 24" OC studs perform better than 16", which are better than 12". Obviously having studs placed 12" OC would yield the heaviest wall, yet the worst performance. Again, it's not all about the mass.

Another example discussed here: The Significance of Air Cavity Depth & the Triple Leaf Effect | Soundproofing Company demonstrates that adding a massive leaf in the middle of a decoupled system air cavity increases the mass of the partition significantly, yet TL performance essentially does not increase.

To Sum: Mass is a critical component of any sound isolating system, however it is the arreangement and deployment of the mass that yields increased results. Stick to a low / medium density insulation, typically exactly what you would use for thermal insulation (Home Depot). THe data says this is best.
To Nestor Kelebay:

Thank you for the scientific explanation! I'm having the same problem, and my upstairs neighbors were actually offering to split the cost but also worried about wasting money on insulation to get no results because it's a floor joist problem. Reading the science behind it has convinced me completely that insulation won't help our problem. I will talk to them about the carpet padding solution instead. Thanks!!! :)
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I'm having the same problem. But my annoyance from my upstairs neighbor is more that I can hear their voices and conversation rather than footstep vibrations. Would green glue and additional layers of drywall be a better option for muffle this acoustic disturbance?