John Sayers' Recording Studio Design Forum Archive

1. Are you building on a concrete slab?
   
   If you will be building on a concrete slab on grade or on a concrete basement slab, you automatically have the benefit of the dampening effect of earth against your concrete. The concrete is not going to be good conductor of energy because it's got the equivalent of thousands of "hands" pressing against it to keep it from "ringing."
   
   If your slab is of good quality and suitable for construction, then you should be able to build on it without much risk of the slab being a significant transmission (flanking) path of structure-borne noise.
   
   Rod Gervais, forum member and author of Home Recording Studio: Build it Like the Pros, writes about this in his book. On this forum he recently wrote:
   

   Rod Gervais wrote:Except for in very weird cases (i.e.: highly hydraulic earths with high water content - OR the inverse of that - both you and a neighbor have your foundations pinned to the same run of bedrock) the amount of transmission you receive in the upper level of the home or outside of the house - is VERY small coming from this slab. It just takes too much energy to move it that much....
   
   It's the airborne sound that transmits through the deck - deck assembly, windows, doors, ducts, pipes, holes, etc., etc., etc. that cause 99% of your problems.
   
   For existing slab on grade I am a firm advocate of leave it alone. (Source)

   So, if you're planning to build your studio on concrete that has firm connection with earth, you most likely don't need to float your floor(s)/room(s). But suppose you're building on an elevated surface, above a basement or above a ground floor of a building...
2. What will be the resonance frequency of your floor?
   
   Every object has a resonance frequency -- the tone at which the object will sympathetically vibrate.
   
   I live near an airport. During some takeoffs, a piece of artwork in my house vibrates after the jet has already passed my house. I can barely hear the jet anymore, but the framed art on my wall vibrates a little. That's because its resonance frequency is equal to the noise the jet engines generate at a particular point after flying overhead.
   
   When an object is not resonating, it's still and quiet. When it resonates, it rattles and makes noise.
   
   Imagine building something to prevent transmission of noise, only to have it be a source of noise instead!
   
   A dedicated minority of motivated people might be able to design a floating floor that will resonate at a frequency that is below what humans can hear. Unfortunately, doing so requires a huge amount of heavy mass.
   
   An efficient method of achieving the necessary amount of mass is concrete. It may be possible to use multiple layers of plywood/OSB or to do a sand-filled deck, but concrete is probably less expensive. Needless to say, the effort, time, materials, and strain of such a project is beyond most do-it-yourselfers, not to mention the knowledge or consultation required to design it to resonate at a frequency that is below human hearing or to dampen it effectively so that it doesn't ring uncontrollably.
   
   Arguably the most famously ambitious and successful do-it-yourself floating slab project would be that of Paul Woodlock in Peterborough, England. His home garage conversion project is quite impressive, requiring complete demolition of his garage slab, excavation of about two feet of soil, and the construction of two new slabs -- one underground and one floating on an industrial grade elastomer. Although he did practically all of the construction himself, he had the guidance of an engineer:
   

   Paul Woodlock wrote:My floor was as follows from lowest to highest layer....
   
   1] Concrete SUBFLOOR
   
   2] Elastomer Blocks (Sylomer) glued to concrete (special glue) with rockwool in between to damp any resonances
   
   3] 18mm waterproofed Plywood glued to Elastomer blocks (To hold concrete) while wet.
   
   4] 125mm Concrete Floating Floor (steel reinforced)
   
   5] 18mm Layer of MDF Screwed and glued to concrete (I sealed the concrete with PVA glue solution first)
   
   6] Top floor finish
   
   . . .
   
   you MUST however do the calculations for the resonant freqeuncy otherwise you will 99% certain make a very expensive mistake. (Source)

   I think Paul's Studio Build Diary is required reading for anyone seriously contemplating a floating slab. In my opinion, if one can't be bothered reading and learning about all he went through building one, then one has no business trying to build one.
   
   Now, assuming you're going to design one that is heavy enough not to make isolation worse than not floating at all...
3. Can you build it safely?
   
   Perhaps you are on an upper floor or ground floor above a basement or crawlspace, and you've determined with certainty that you need a floating floor/room.
   
   Can the structure handle the amount of weight you need to add to it?
   
   Unless you have some letters after your name, you're most likely not qualified to answer this question yourself. You probably need a structural engineer to evaluate the existing construction to determine the amount of additional weight you can safely add without risk of a catastrophic failure that could, at best, destroy all of your work and cause an extraordinary amount of damage, or at worst, kill people.
   
   This is not a time for guesswork, or even being almost certain. You need to be POSITIVE that it will be safe.
   
   Do the math, and you'll find that the amount of weight needed is often measured in tons.
   
   In general, buildings are built as inexpensively as possible, which means there's usually not a lot of margin for adding tremendous amounts of weight on elevated floors. The structure may have to be retrofitted in order to support the additional weight being proposed.
   
   Still with me? Wow... I'm impressed. Now, let's not build a useless floating floor...
4. How will you ensure that your floating floor will actually float?
   
   In order to connect two things to each other without the connection point being a bridge for energy to travel across, there must be an elastic polymer ("elastomer"), a spring-like rubber substance. DuPont's "Neoprene" and ethylene propylene diene monomer (EPDM) rubber are commonly referenced in floating floor designs and other engineered acoustic isolation construction devices.
   
   Imagine putting a 15 pound weight on a spring that "bottoms out" at 10 pounds. The spring is completely compressed. The weight is unable to bounce on this overloaded spring, and therefore is not isolated from the surface below.
   
   The same holds true of a lighter weight upon a heavier grade spring. Imagine a 10 pound weight on a spring that does not begin to compress until the weight reaches 15 pounds. The weight is too light to cause the spring to compress, so it too is unable to bounce, and is therefore again not isolated from the surface below.
   
   Now, imagine an entire room floating on springs made of rubber pucks. How do the rubber pucks deflect under the loads of the room? Are parts of the floor loaded more heavily than others? Are the walls erected on top of the floor, and if so, is the weight of the ceiling overhead transferred to those walls? If so, the perimeter of the room is much heavier than its unfurnished middle. How many pucks should be used? How far apart should they be positioned? Should they be closer around the perimeter to account for the additional weight of the walls and ceiling? How much closer? Should the elastomers around the perimeter be harder/stronger so as to handle the additional weight? What about the dynamic loads of the varying number of people and gear that will be inside the room? What about the lifespan of the elastomers under the loads -- how long will they last before they lose their elasticity and "bottom out," rendering them useless?
   
   These are not easy questions to answer! Yet we often see cases where people either do not think of these questions, do not take them seriously when asked, or resort to guesswork when attempting to answer them!
   
   The fact is, a floating floor that is not engineered to account for all of the above questions is most likely doomed to fail to meet its designer's intentions.
   
   Couple this issue with the resonance frequency issue described previously, and you would almost certainly end up in an unenviable position of being worse off than if you had not attempted to float at all.
   
   Let's close with my favorite -- the thing that stopped me from going forward with a floating floor plan...
5. Do the building codes in your area even allow you to do it?
   
   I live in California, which is prone to earthquakes. Even though my area is pretty stable, the fact is, my city has adopted California Building Code (CBC), which has very strict standards when it comes to building in a manner that will withstand seismic events.
   
   My first floating floor plan was summarily rejected by my city's plan checker before I even had a chance to submit it for review.
   
   This is not to say that all floating floors are illegal. Even in California, I'm sure it is possible to engineer one with seismic snubbers that would prevent lateral movement in an earthquake... But that only increases the expense and the complexity of the system.
   
   Indeed, anything is possible... But there's often a price to pay for it.

A floating floor should only really be considered if you design the room that sits upon it where the walls and ceiling have a low enough resonant frequency to stop bass. Which means they need to have a LOT MORE MASS than your current design.

I would advise putting the resources ( Time, effort and $$ ) that you've reserved for your floating floors into creating much heavier walls and ceilings instead.

A room within a room ( without a floating floor ) which is really heavy will give you much better TL than a lightweight room on a lightweight floating floor.

A Lightweight Floating floor is pointless with a lightweight room ( such as yours ), because your original floor already exceeds the TL specs of your walls and ceiling.

A lightweight floating floor is also pointless with a heavyweight room.

Even a heavyweight floating floor is pointless with a lightweight room in top of it.

IOW a lightweight floating floor is pointless period for room within a room designs.

See this discussion for more details http://forum.studiotips.com/viewtopic.php?t=1653

hope that helps

John Sayers wrote:OK - there are basically two issues here.

1. One is floating a floor to achieve isolation and to stop flanking through the concrete slab to the adjacent rooms or to stop the sound in the vertical direction, say a studio on the 3rd floor of an office building or on the ground floor with a subway running underneath..

2. The other option is cosmetic - i.e you would prefer the look and feel of a timber floor v a cold concrete slab and carpet is out as it's a really bad absorber as it only absorb the upper highs.

With regard to version 1. - most cases I read of floating floors are unnecessary IMO. Flanking from one room to another via the floor is really not a problem you'd normally worry about when you compare the cost and labour v the isolation achieved. To be honest I've never worked in a studio without a floating floor where I've gone "Hell listen to all the flanking coming through the floor!!!"

On the other hand should you build on the third floor of a commercial office block and want to record heavy metal all day it would be appropriate to float the floor, not to stop the sound of telephones ringing from downstairs but to stop your constant kick drum annoying the hell out of the people downstairs and upsetting your landlord.

Similarly with the subway underneath - if the train rumble vibrates throughout your building you will need to float the floor to isolate yourself and the whole framing for each room sits on this floor thus isolating the whole construction from the rest of the building..

The version 2 is a cosmetic factor, i.e you like the look and feel of a timber floor. Left Bank and Oasis studios are both examples of that. The timber floor is laid on battens on rubber and is only built where the floor is needed, i.e the outer walls don't sit on it and there is no timber floor under the front speaker section or in the rear trap section etc.

There is a "my dick is bigger than your dick" mentality being expressed in these forums recently - The - "I've added 3 layers of drywall, floated the floor etc for my garage studio where my neighbours are 100 yards away and I'm in the country!!"

If you look at Left Bank's ( http://johnlsayers.com/Studio/Mainpage/MP-Leftbank.htm ) construction you will see it has only 2 layers of 5/8 (16mm) drywall - one on the outer frame, one on the inner frame. The floors are cosmetic yet that studio has NO sound transmission problems. Similarly with Oasis - no sound transmission problems.

Check out the thread on Sideshow's studio - http://johnlsayers.com/phpBB2/viewtopic.php?t=6968

He lists his sound isolation method and also reports on the results - no problems.

I hope this helps


cheers
john

eruss wrote:. . . I read so many times here that raised floors were not needed.

rod gervais wrote:eruss,

not really - what you have read is that properly floated concrete slabs are generaly not really needed for home studios constructed in basements or in residential garages.........

In commercial ventures it's a different story altogether.

In new construction you can always use isolated slabs - giving you separation from direct contact with the foundation and other interior spaces.

But - in your case I will bet you a dozen donuts against a dollar that this isn't the case.

You have a case where the roadway sits about 30' from your building - and not isolation form the low frequency road sounds (125 to 250 Hz roughly) might very well be bringing sound in through the slab.

Personally- your best bet would be to hire a local acoustic engineer to visit your site and take some readings to determine exactly where your sound is coming from.

Everything on our end would be wild guess work to say the least.......... and we might well lead you in a bad direction without even knowing it....