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RMD 02-25-2010 12:41 PM

Sound Proofing with Blown-In Insulation
I'm going to be getting foam injection insulation for my exterior walls to help with energy loss, and I was told I couldn't use this product in my ceilings.

I live in the bottom two floors of a 5 story browstone condo, and my upstairs neighbors are very loud. I don't think there is any insulation of any kind between their floors (hardwood, of course) and my ceiling drywall. I was hoping I could spray some foam in there to deaden the sound a bit.

The insulation installer recommended blown-in rockwool. He said it would require 2.5" holes to be cut at various places, but would not require the removal of the existing drywall.

Should I go with his recommendation? Any solution that requires the removal of the ceiling drywall will likely be a no-go because of the cost.

Wuzzat? 02-25-2010 02:47 PM

You need to find out how the sound is being transmitted to your place.
If your ceiling acts like a diaphragm then insulating it or stiffening it seems the way to go.
Soundproofing - Noise Reduction - Noise Abatement

Acoustiblok Inc., Soundproofing, Soundproofing Materials, Sound Deadening

There also may be zoning restrictions on how much noise they can legally make; your county would have to send someone out with a sound level meter.
Quiet Enjoyment

A 3 to 5 decibel noise reduction seems practical.
Sound Insulation

psych1 02-25-2010 02:59 PM

you may get some small benefit from filling the cavity with rockwool, but probably not a huge one. The kind of sound you are getting floor to floor is different than what you get from outside. Most of it is probably from direct impact on the floor above and so is transmitted by vibration of the buidling materials. Insulating between the ceiling rafters blocks the sound transmitted through the air between the rafters, but not what is being transmitted through the rafters themselves and then through the drywall.

Even in terms of insulating the air space, blown rockwool is not very dense and so not the most effective. Foam would do better since it essentially glues everything together, effectively dampening vibration. Maybe you can't do the injection type, but you could do the blown on type. Even Rockwool batts (which are much denser than the blown in) would be better than blown in, but these solutions require removing the drywall.

The best bet would probably be some combination of air space insulation and a second layer of drywall, preferably separated from the first by spacers. Maybe a suspended ceiling would also help (although it might be ugly).

Why is it so expensive to repalce drywall? I would think that foam insulation would cost much more than drywalling - it would here.

You could also buy your upstairs neighbors carpet with a really thick underpad ;)

RMD 02-25-2010 03:59 PM

Thanks for the tips.

Sound is being transmitted multiple ways. Some sound is vibration transfer (footsteps, for instance), but I can also hear them talking. If they're playing music... forget it, no sleep for me.

I was given quotes in the $5000+ range for the removal of the existing ceiling drywall (< 200 sqft of ceiling) and replacing it with QuietRock. My ceiling is very "complex" (lots of cuts to be made).

Futhermore, not having the use of my bedroom even for a few days would be problematic given the size (small) of my condo.

Since I can get 75% off the cost of insullation installation, I thought it might be a cost effective way to at least partially fix the issue, plus the added thermal benefit. The idea of partially heating my jerk neighbor's apartment kills me.

inspectorD 02-25-2010 04:38 PM

Try the rockwool, better than what you have, and you can always install another dampening system over the existing sheetrock if that does not help.

There are channels and insulation boards and standoffs for soundproofing..done in home theaters allll the time.

The insulation for the the best way to go.
I use Nu-Wool :: Premium Cellulose Insulation :: Home Page on most jobs.

psych1 02-25-2010 08:55 PM


Originally Posted by RMD (Post 41453)
Thanks for the tips.

I was given quotes in the $5000+ range for the removal of the existing ceiling drywall (< 200 sqft of ceiling) and replacing it with QuietRock.


wow that must be a complex job. I would have guessed you could do it in oak for that ;)

I agree that it would be worth doing the rockwool as an initial step. Wuzzat, are you reccomending cellulose? I hadn't thought of that, but it is pretty dense and soundproof as well.

Nestor_Kelebay 02-25-2010 09:34 PM


If they're playing music... forget it, no sleep for me.
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:
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.

Wuzzat? 02-26-2010 08:04 AM


Originally Posted by psych1 (Post 41464)
Wuzzat, are you reccomending cellulose? I hadn't thought of that, but it is pretty dense and soundproof as well.

Whatever gives you the most decibel reduction per installed dollar.

RMD 02-26-2010 11:21 AM

Again, good tips from everybody.

Quiet rock is 5/8 drywall that has the same sound dampening as 8 sheets of normal drywall. That's why its so expensive.

In terms of the insulation not helping the sound very much, its gotta be better than what I have now, and will at least help my heating bill.

Nestor_Kelebay 02-26-2010 02:26 PM


Originally Posted by RMD (Post 41490)
Quiet rock is 5/8 drywall that has the same sound dampening as 8 sheets of normal drywall.

Is that what people that have had it installed say, or is that what the company that makes it says in their advertising? I expect that if you ask to talk to some "satisfied customers" you might hear sumthin diffrnt.


In terms of the insulation not helping the sound very much, its gotta be better than what I have now, and will at least help my heating bill.
I realize I'm telling you something you don't want to hear. The biggest step forward you can make would be to get on speaking terms with your upstairs neighbor so that he'd be open to co-operating with your efforts.

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