the worlds cheapest sound isolation tips

[Brian Dayton]

1.  use wider stud spacing as code allows.  Its generally always better to space studs 24"OC than 16"OC.  at www.nrc.ca the files IR818 and IR761 and some in IR693 have more than enough data to cement this in as a firm rule.  However, be wary of using spacing wider than the local authorities would allow.



2.  use normal boring, off-the-shelf, home depot low-density fiberglass insulation.    By my interpretation, the data from IR761 suggests that this material is preferable to higher density more expensive types.  It does not show higher tranmission loss at middle and high frequencies (indeed, it shows lower TL in those bands, generally), but it does seem to have a BETTER effect at lowering the frequency fo the mass-spring resonance.  



3.  don't use exotic esoteric, really expensive sealants.  Data presented by USG shows that when substituting their own sealant for a putty like sealant (heavier, higher damping), the only real penalty was at the coincidence dip, and the overall utility of the wall didn't decline.  If you wish to utilize a really flexible type of sealant, try Tremco Acoustic sealant.  This is a butyl, solvent-based material with extremely good properties.  But generally boring old latex type caulks are fine.  Believe it or not, alot of off-the-shelf latex caulks are more flexible than some marketed acoustic sealants.  

But do use alot of cualk.  Never rely on a single layer of caulk to seal the wall.  multiple layers (under top/bottom plates, each layer of drywall) back each other up in the instance that one isn't perfect, and this is worth alot.



4.  Don't feel compelled at all to float your floor over a concrete slab if you are on a budget.  I know that statement may spark alot of controversy, and someone might call me names, and without a doubt concrete slabs can be sources of flanking noise.  But the weight of the slab ensures that a very good level of performance can be attained before flanking -via- a slab becomes the problem.

Also, you risk making things worse when floating a floor.  It is no small challenge to get the MSM low enough in frequency to ensure that your efforts are positive, and the expense and/or labor won't ever be small to truly successfully float a floor.  

I know slabs can be problems, but for AIRBORNE (as opposed to impact sounds, where they are a real problem) noise, they aren't going to cause your whole project to be bad unless they are really cracked or something along those lines, allowing an air path under the walls.  


5.  Cut things.  When possible, just cutting structural connections can be a great help with flanking noise (mostly via floors).  Don't cut anything that would cause danger to yourself via water/mold or structural weakening, and always ask the local building inspector if at all in doubt.


6.   Cover your entire door with sound absorbing material.  Some foam or 703 or whatever.  Leave a space around the door knob if you need to, but cover the entire door.  (don't bother with this on walls)


7.  if your wall is decoupled (staggered studs, resilient channel, double studs, sound clips, etc.) then your wall will benefit from a deeper air cavity (such as using 2x6 studs -vs- 2x4 studs).  But if your wall is not decoupled (single wood stud or single rigid steel stud, and to an extent single flexible steel stud), depth is just wasted space and $$$.  IR818 from the NRC has sufficient data to justify this statement.


8.  $$$/lb.  Thats the most important factor when selecting what type of panel to use.  Plywood?  Drywall?  Cement board?  The best choice is basically always drywall because its least expensive per pound, and drywall is basically always the best choice or basically all walls or ceilings.  don't make a drywall floor or door.  

There is no magical nothing to wood or cement or whatever relative to gypsum.  None at all.

Is 5/8" plus 1/2" best?  is 3x1/2"?  whichever is cheapest in $$/lb


9.  don't risk weird decoupling schemes that aren't tested.  Things like little homemade brackets here or strips of foam there may - in at least some cases in my tseting experience - work against you as much as they help.  I know its easy to get caught up with the details of "caulk-vs-mudding my inner seams" or "do i need some foam here", but its really simpler than all that most of the time.


10.   When selecting a method of decuopling, alot of the work we have done has shed some light on how the different methods behave, and i summarize here.  This gets a bit long.

The data from IR761 would seem to show that thin-gauge (25 gauge) steel studs and resilient channel over wood or rigid steel studs perform largely the same.  And when looking at STC ratings, most of the historical data tends to favor either of those methods over staggered studs.  

However, the situation is this when scrutinized over a wider range of wall weights and frequencies:

-the properties of resilient channel in the market today are all over the place.  All over the place.  Widely different designs and even different gauges of metal are found, and the original USG channel appears to remain the best.  At minimum, you should ensure that your RC is 25 gauge.  You can do this with a ruler and some reference samples of steel from somewhere - just make sure the thickness is the same.  Or buy a micrometer somewhere.

all resilient, however, has an adverse effect on the location of the MSM when utilized because it adds a spring in parallel to the spring of the air cavity, raising MSM to a frequency above that predicted by a mass-air-mass calculation.


-steel stud walls, even thin gauge ones.  DO NOT CREATE a true mass-spring system.  some of the behavior of a wood stud system remains, and you cannot drive the MSM down and create a very low frequency decoupling point with any practical level of mass.  Both panel stiffness and a mass-air-mass factor into the location of the MSM in this system, and as weight goes up the stiffness factor becomes dominat and MSM stubbornly refuses to go down in frequency.  The single thin-gauge steel stud wall is an interesting thing.


-staggered stud walls DO create a true MSM with MSM falling quite close to the theoretical mass-air-mass resonance, BUT, they also suffer from mechanical resonance issues at slightly higher low frequencies that keep performance less htan ideal.

-double studs are just the best choice

But, the combination of these is more than any one together, as it were.  The use of thin gauge steel studs + resilient channel yields two springs in series (the sum of those being in parallel to the air spring), and allows you to create a true MSM that you can drive down in frequency with mass, and which will occur at a lower frequency than that of an RC wall with rigid studs.  Something else to think about is that if you short-circuit your RC on steel studs, the steel studs are still flexible and the results aren't likely to be as disastrous as they would be with wood studs.

So, considering the whole frequency range, the preferred decoupling methods are

1.  double studs
2.  sound clips (really, their advantages exceed the rest, but cost more)   OR thin steel studs plus RC
3.  stagg studs  (if using Green Glue these are as good as the sound clips)
4.  RC
5.  thin steel studs

That should be a good decision making guide.  Once decoupled, adding mass to a wall does MORE than it does on a non-decoupled wall as it both adds mass and lowers MSM.


11. the use of 1x4 wood furring strips or simple metal furring strips (even if not resilient) does help your cause.  They should be spaced 24" OC.  They sort of make a 16" OC wall into a 24" OC wall


12.  send me some sludgy authentic european beer.  I heard that makes your wall 5 dB better for every 6 pack you send.

[Rod Gervais]

Brian,

As usual a great post........  and as far as this goes:

4.  Don't feel compelled at all to float your floor over a concrete slab if you are on a budget.  I know that statement may spark alot of controversy, and someone might call me names, and without a doubt concrete slabs can be sources of flanking noise.  But the weight of the slab ensures that a very good level of performance can be attained before flanking -via- a slab becomes the problem.  

You won't get called anything by me - I've been in agreement with this for quite some time..........

Sincerely,

Rod

[Scott R. Foster]

Don't feel compelled at all to float your floor over a concrete slab if you are on a budget.

I love you man...  so glad to hear some one else saying it out loud.  

PS: Bob can get you a good deal on Canadian beer I think.

[jonessy]

Brian,

Thanks for the wonderful post.

Around here, we get two local beers: Goldstar and Maccabee.

Maccabee tastes like goat's piss, so I'd go with Goldstar.

2 x 6 packs =~ 10dB of TL... Sounds like a good deal to me.  :)

Eric, can you mathematically insert this new empirical value into the Mass-Law?

We'll call it - the Mass-Law Brian-Variation.

Another secret AES paper on the way...  :mrgreen:

[Scott R. Foster]

I vote to immediately shorten that to the "B3" resonance dip*

* Beer-Brian-Beer

Its a request, a cheer, and an imperative command all in one  

[Terry Montlick]

4.  Don't feel compelled at all to float your floor over a concrete slab if you are on a budget.  I know that statement may spark alot of controversy, and someone might call me names, and without a doubt concrete slabs can be sources of flanking noise.

I now agree with Rod on this one as well. In fact, from the calculations I did from our discussions, Brian, I would go further:

"Don't feel compelled at all to float your floor over a concrete slab even if your are not on a budget."

A good example is a certain commercial floating floor system which uses heavy compressed fiberglass isolation supports with light fiberglass batting between them. In typical applications, you actually introduce an audible low frequency resonance that makes the isolation worse. And this, from the high-priced solution!

Floating floor systems should be installed only after detailed engineering analysis. Entrapped air (further inhibited in lateral motion by light fiberglass) can render the resonant frequency from the static displacement of the compression elements practically useless in predicting field performance.

- Terry

[Bob]

Brian - great summary.
I might put your comments about caulk into my standard caulk post.

Re #4 -- that's what I was talking about when I was asking about drycore in the other thread. (Rod was curious).

[Eric Desart]

4.  Don't feel compelled at all to float your floor over a concrete slab if you are on a budget.  I know that statement may spark alot of controversy, and someone might call me names, and without a doubt concrete slabs can be sources of flanking noise.  But the weight of the slab ensures that a very good level of performance can be attained before flanking -via- a slab becomes the problem.

Also, you risk making things worse when floating a floor.  It is no small challenge to get the MSM low enough in frequency to ensure that your efforts are positive, and the expense and/or labor won't ever be small to truly successfully float a floor.  

Brian,

I don't call you names or whatever.  (  May I ....., may I ......?????)

I still think that you should be more carefull with how you put this.  What I see here is the reasoning from someone with lots of experience with drywall separations, but less with brick.

Since indeed for most people the mass-spring-spring of drywall will be the defining factor in the single number TL rating, and the concrete floor you describe will behave as a heavy single mass, the drywall double layer wall will be for long the weak link in the chain.
Making floating floors should be linked to to be obtained TL values, not available budgets.
It indeed has no sense to make an already stronger link in the chain even stronger.

Correct of course, and very often discussed is that you better have no floating floor than a wrong designed one.

The mass however doesn't tell it all.

Here is a saying: "Any Belgian is born with a brick in his stumach", meaning that every Belgian aims (or nowadays dreams about) to posses once its own house, and for us a house is standard build in bricks (close to synonym with bricks), inside out., with often/mostly (always for linked houses in roads/streets) concrete ceilings and floors.
Hence we DO have experience with heavy masses.

One of the main limitations in isolating towards neighbors is exactly this flanking via all these heavy masses.
It's a traditional story: People isolate the separation wall towards the neighbors with a perfect good designed resilient skin wall made from drywall on a cavity, and then are frustrated by the poor results that application brought.
Reason: Flanking.  And we only/mainly use heavy masses to build houses.

I think the way you formulate this is a bit confusing.  
Clear is that one doesn't need to reïnforce an already stronger link in the chain. But that's defined by acoustics and the desired TL, not low or high budgets.
Also clear is that when applying whatever it should be done correct, and indeed a floating floor is something often sinned against.

Note that floating floors are a STANDARD concept in building practices here when higher insulation is desired, and then I don't even speak about studio and home theater circumstances.
Therefore Rockwool and Isover will standard have Floating floor slabs in there catalogue. Aglofoam (bonded foam) sells related stuff. Etc.......  They all sell it specifically described AND tested for this purpose in more standard building practices. And that's not only meant for impact noise but also airborn sound.
Guys like CDM and Sylomer and the likes are more oriented to a more technical market..

I told I moved, so I'm new here in a 6 story high appartment building. Every single wall is brick,  every floor is concrete.
2 stories above me there lives someone , who thought his appartment was meant to be a disco or whatever.
I heard his music and beats coming THROUGH the whole structure (FLANKING) even with a buffer appartment directly above me (I know how to distinguish sound paths).  There's NO way this could be solved without a room in room system including floating floor.
And since that's impossible here I wrote an extensive note hanging it in the common corridor, gently, respectful but firm, directed to all inhabitants..
At least until now it had helped (cross my fingers here).
Cutting things is not always an option.
 If I cut the walls the only thing that happens is that all the above appartments will lower a few mm, and if I cut the floors, they all live in my appartement with an incredible high ceiling (I live lowest level).

KInd regards
Eric

PS: that saying about Belgians and the bricks becomes less and less valid due to the sickening rate income/building cost (+land), which as I recently heard causes banks to allow loans with a 40 years payback period (that wasn't possible in my time, 20 years was standard, 25 years concidered long already).

 Damned, it should have been much easier, shorter and faster just to call you names .......
.

[bert stoltenborg]

Move to Germany, Eric.
Big houses half the price you pay here, and it's only a couple of km away from the dutch coffeeshop.

[Zaphod]

Here is a saying: "Any Belgian is born with a brick in his stumach", meaning that every Belgian aims (or nowadays dreams about) to posses once its own house, and for us a house is standard build in bricks (close to synonym with bricks), inside out., with often/mostly (always for linked houses in roads/streets) concrete ceilings and floors.
Hence we DO have experience with heavy masses.

Well, it seems that Italians are a lot like Belgs regarding house wishing and building  :D

And since that's impossible here I wrote an extensive note hanging it in the common corridor, gently, respectful but firm, directed to all inhabitants..

Not to mention that note writing is much cheaper than floating a floor  :mrgreen:

PS: that saying about Belgians and the bricks becomes less and less valid due to the sickening rate income/building cost (+land), which as I recently heard causes banks to allow loans with a 40 years payback period (that wasn't possible in my time, 20 years was standard, 25 years concidered long already).

Same here
The raising interest rates are going to put a lot of people in deep troubles  

Anyway, on behalf of the living-in-concrete-brick-housings-where-structureborne-sound-is-the-problem,
i thank you  :mrgreen:

[Eric Desart]

Move to Germany, Eric.
Big houses half the price you pay here, and it's only a couple of km away from the dutch coffeeshop.

 I shoot anyone, trying to move me again for the next 250 years.

[Terry Montlick]

Good points, Eric. I was thinking more of the typical American application of basement home theater or 1st floor on slab in climates where basements are not used.

And we will make sure that nobody moves you for the next 250 years!

Regards,
Terry

[Ido]

Maccabee tastes like goat's piss, so I'd go with Goldstar.

:

I second that.

[Brian Dayton]

4.  Don't feel compelled at all to float your floor over a concrete slab if you are on a budget.  I know that statement may spark alot of controversy, and someone might call me names, and without a doubt concrete slabs can be sources of flanking noise.  But the weight of the slab ensures that a very good level of performance can be attained before flanking -via- a slab becomes the problem.

Also, you risk making things worse when floating a floor.  It is no small challenge to get the MSM low enough in frequency to ensure that your efforts are positive, and the expense and/or labor won't ever be small to truly successfully float a floor.  

Brian,

I don't call you names or whatever.  (  May I ....., may I ......?????)

I still think that you should be more carefull with how you put this.  What I see here is the reasoning from someone with lots of experience with drywall separations, but less with brick.

Since indeed for most people the mass-spring-spring of drywall will be the defining factor in the single number TL rating, and the concrete floor you describe will behave as a heavy single mass, the drywall double layer wall will be for long the weak link in the chain.
Making floating floors should be linked to to be obtained TL values, not available budgets.
It indeed has no sense to make an already stronger link in the chain even stronger.

Correct of course, and very often discussed is that you better have no floating floor than a wrong designed one.

The mass however doesn't tell it all.

Here is a saying: "Any Belgian is born with a brick in his stumach", meaning that every Belgian aims (or nowadays dreams about) to posses once its own house, and for us a house is standard build in bricks (close to synonym with bricks), inside out., with often/mostly (always for linked houses in roads/streets) concrete ceilings and floors.
Hence we DO have experience with heavy masses.

One of the main limitations in isolating towards neighbors is exactly this flanking via all these heavy masses.
It's a traditional story: People isolate the separation wall towards the neighbors with a perfect good designed resilient skin wall made from drywall on a cavity, and then are frustrated by the poor results that application brought.
Reason: Flanking.  And we only/mainly use heavy masses to build houses.

I think the way you formulate this is a bit confusing.  
Clear is that one doesn't need to reïnforce an already stronger link in the chain. But that's defined by acoustics and the desired TL, not low or high budgets.
Also clear is that when applying whatever it should be done correct, and indeed a floating floor is something often sinned against.

Note that floating floors are a STANDARD concept in building practices here when higher insulation is desired, and then I don't even speak about studio and home theater circumstances.
Therefore Rockwool and Isover will standard have Floating floor slabs in there catalogue. Aglofoam (bonded foam) sells related stuff. Etc.......  They all sell it specifically described AND tested for this purpose in more standard building practices. And that's not only meant for impact noise but also airborn sound.
Guys like CDM and Sylomer and the likes are more oriented to a more technical market..

I told I moved, so I'm new here in a 6 story high appartment building. Every single wall is brick,  every floor is concrete.
2 stories above me there lives someone , who thought his appartment was meant to be a disco or whatever.
I heard his music and beats coming THROUGH the whole structure (FLANKING) even with a buffer appartment directly above me (I know how to distinguish sound paths).  There's NO way this could be solved without a room in room system including floating floor.
And since that's impossible here I wrote an extensive note hanging it in the common corridor, gently, respectful but firm, directed to all inhabitants..
At least until now it had helped (cross my fingers here).
Cutting things is not always an option.
 If I cut the walls the only thing that happens is that all the above appartments will lower a few mm, and if I cut the floors, they all live in my appartement with an incredible high ceiling (I live lowest level).

KInd regards
Eric

PS: that saying about Belgians and the bricks becomes less and less valid due to the sickening rate income/building cost (+land), which as I recently heard causes banks to allow loans with a 40 years payback period (that wasn't possible in my time, 20 years was standard, 25 years concidered long already).

 Damned, it should have been much easier, shorter and faster just to call you names .......
.

hmmmm...  

I would re-phrase my statement to say, then, "if you are on a budget, floating a floor is very unlikely, or perhaps sure to not be, a cost-effective undertaking"

But I think that is might be good to add some comments, lest your statement be interpreted by a passer by as compulsion to float a floor over a slab ina  typical north america construction (or other constructions).   I don't think that was your intention, and if i was i would have to disagree.  

This thread and my comments herein related to cost-effective assemblies.  In no way do all-masonary room within a room constructiosn fall within that realm- budget sound isolation.  Block walls run into $10+/sq foot installed here int he US, and by the time one floats a slab (as per your discussion of standard practices outlined in cataloges above) and builds another block wall (or other wall) on top of it you could ahve built any degree of stud wall construction you wish.  You may have exceeded the total cost for studs, drywall, insulation, whatever products you want to use, and wahtever else you might wish for a normal "high peformance" room combined just to make this floating slab.  DIY skills could bring costs down alot if you have alot of time to devote, to be sure.  But in general, i think reducing the discussion to stud walls is fair and reasonable, but a comment that masonary assemblies should be treated differently may be in order.

For sound stemming from an impact on the concrete... that's another story, and some type of surface modification is almost compulsory.  But resonance in function of localized impact and more uniform stimulation with airborne sound is quite an interesting topic in and of itself, and its vastly easier to isolate nosie stemming from a local impact than from airborne sound.  Alot of why that is relates to MSM poitns being lower for local impact isolation than for airborne sound, often vastly lower.  And alot of the imprsesive improvements in IIC rendered by various floating systems hardly correlate to grand improvements in isolation from airborne sound (and many, perhaps, would prove just the opposite).


But, to my second point, basic law of conservation of energy and (if i cared to dig for an example) basic theory and the like of flanking noise would imply that the flanking that can be delivered to another area from any single given surface has to be lower than the airborne TL through that surface (except in odd cases involves resonances and such).

Basically, if "20 pieces" of vibrational energy are injected into a concrete slab

-some of those go left, some go right, some are dissipated by the (albeit very low) damping of the slab and wahtever its attached to, some go up, some go down, etc.
       -so no one direction has as much energy, as flanking noise, from this slab as was injected into the slab

-re-radiation of energy in any given poitn isn't total, as the process of shaking the air removes a proportional amount of energy from whatever surface is vibrating
     

So, flanking from a slab cannot exceed the TL of the slab when directly subjected to airborne sound.  And generally speaking it has to be at least somehwat lower than this.  So a very good level of performance can be attained  - probably Tennekes rating = 35 or 40 db anyway, maybe more - even while allowing full flanking fromt he slab.

(I only ask) is there any reason to believe that the statement above isn't correct?  - that flanking must be at least somewhat less than airborne TL?



And in general, when you review what calculations and theories exist for flanking noise, you find that damping (and also rigidity) become extremely important.  Stiffness helps define the rate at which sound waves travel through a system, and damping affects the rate at which they are dissipated.  So stiffness + damping = (less or more) the basic rate at which mechanical energy is removed from a system.  One big advantage of damping that doesn't translate in lab tests, but does reveal itself in the 3-dimensional real world, is the impact on flanking noise.   One slab-related flanking path that isn't so comonly talked about is slab-to-wall-sound-radiated-from-wall-not-from-slab.  This path is fairly efficient, and strongly affected by damping.

The great advantage of those European block walls is weight.  But basically everything else is at a great disadvantage relative to our simple little stud walls.  I would dearly love to one day go explore the UK sound problem situatiosn that we hear about alot - to try to gain a solid idea of the how's and why's and so forth.



So i stand by my statement in the context taht it was offered.  Flanking from a slab won't be your doom until a very high level of isolation is required, and for most budget applicatiosn, you would be better off to invest int he walls.

[Brian Dayton]

4.  Don't feel compelled at all to float your floor over a concrete slab if you are on a budget.  I know that statement may spark alot of controversy, and someone might call me names, and without a doubt concrete slabs can be sources of flanking noise.

I now agree with Rod on this one as well. In fact, from the calculations I did from our discussions, Brian, I would go further:

"Don't feel compelled at all to float your floor over a concrete slab even if your are not on a budget."

A good example is a certain commercial floating floor system which uses heavy compressed fiberglass isolation supports with light fiberglass batting between them. In typical applications, you actually introduce an audible low frequency resonance that makes the isolation worse. And this, from the high-priced solution!

Floating floor systems should be installed only after detailed engineering analysis. Entrapped air (further inhibited in lateral motion by light fiberglass) can render the resonant frequency from the static displacement of the compression elements practically useless in predicting field performance.

- Terry

GGCo is getting a new building and i beg daily for a section at the back to build big gg double stud walls and seperate ceiling joists and...  ... a naked slab that is continuous between the rooms.  Then one could test (even if not in some accredited 3rd party environment) flanking via the slab at the effect of different floors.

That would be alot of fun to do, alot of fun.  I'd float the bottom plates of the stud walls on springs & the whole 9 yards.

[Brian Dayton]

also - and somebody might call me names again - in my experience, i haven't ever found a big concrete bunker to really be bad for noise isolation (unless the concrete is cracked).

I did find one case with 12" concrete block seperating two rooms, and i measured int he field an STC of i think 44.  But just taking some caulk and getting a ladder and caulking alot of little cracks raised this to a 57 or so, and the good low-frequency isolation of the really heavy wall generally made for pretty darn good isolation.

This room is exposed to the elements here in North Dakota where it might be -45 deg F int he winter and 105 deg F in the summer, and more cracks pop up all the time, and if you visit these guy's place once in a while the STC may be back into the 40's, but more caulk fixes things again, until the next big temperature change, i guess.

And again, in general, i have not encountered sealed all-concrete rooms that really do have "bad" isolation.  Its pretty good.  STC=50 with really good low-freq isolation is pretty darn good isolation overall (and certainly one could build STC=60 walls with fairly crappy isolation due to awful low-freq TL, and i've heard some of those too).


But to Eric's point of my general unfamiliarity with masonary constructions, i am often perplexed by the tales of double-brick walls with an insulated air space that people can easily converse right through - Or listen to the neighbors snoring or watching TV or something similar - that come my way from Europe.  I tend to suspect something simpler, but perhaps less obvious, than structure-born flanking noise.  Like cracks int he masonary.



But for my own curiosity, have any of you folks heard a room built with big heavy concrete block walls that really could be said to have crappy isolation?  I'm not saying the best isolation ever, but actually crappy?  I have not.

[Brian Dayton]

Eric,

     i'll leave my first, rambling and disorganized, reply inact, and just offer this shorter one:


-the flanking TL of a slab cannot be lwoer than the airborne TL of the slab.

-as such, a very good level of performance can be attained before addressing this slab is necessary.


I'm not saying its never necessary, and my comments shouldn't be interpreted as such.  I simply offer that if one is on a budget you may find that money hurled at the slab would have been far better spent somewhere else, like adding weight to the walls.

[bert stoltenborg]

With a 160 mm thick slab and two normal 100 mm walls (common over here) between appartments you already won't have benefit from making the wall better. And that's only the flanking from the slab. At least conform theory.
And conform experience. In a lot of our houses, when they are coupled, you can clearly hear loud speaking and music.
The Germans do a better job, i'm told. And experience seems to be up with that.

[Brian Dayton]

With a 160 mm thick slab and two normal 100 mm walls (common over here) between appartments you already won't have benefit from making the wall better. And that's only the flanking from the slab. At least conform theory.
And conform experience. In a lot of our houses, when they are coupled, you can clearly hear loud speaking and music.
The Germans do a better job, i'm told. And experience seems to be up with that.

Just to clarify, your comment is that with a ~6 inch continuous slab, you can hear conversation int he next room through the slab?

[bert stoltenborg]

If you take a slab with a dividing wall on it the same weight of the slab (so you get a T-construction), and the slabs in both rooms
is the same surface, you get (theoretically) a 11 dB better isolation by the flanking than by the air borne noise.