Has anyone had great isolation on a floating concrete slab??

[Govinda]

"So would I get a good result with a thin slab on the isolation matting?? as you mentioned previously? "
sorry steve I was not being very clear!
What I meant was would I get a good result with the system you mentioned before which was:
"EPDM pucks resting on your 4" slab, then 4x2's on edge resting on the pucks, then 3/4" exterior grade plywood, a layer of poly sheeting (to keep the plywood from contact with the top layer) then pouring a 2.5" slab on top"

To be clear on what I was thinking was this: same method as above but instead of using 4x2's on epdm pucks I would lay isolation matting on the concrete then plywood then a poly layer then the slab...but in my situation it does not seem like a very practicle application to isolate loud sounds, like drums from my close neighbours!
Sorry for the confusion...it was all mine ..

Are the Kinetics lsms very expensive...I also have seen in joe egans studio that he used a kinetics K.I.P with a 5 inch cement slab...would that also be a possiblility for my situation?
In australia I dont think the kinetics product are sold or distrubited ,so I would have to ship them in which is fine...but I have no idea of the price of them...for instance we get ripped off majorly, the auralex u-boats cost aus$1000 for 200 u boats...thats alot of money for freakin rubber!
Thanks again,
Govinda

[knightfly]

The same physics apply to floors as to walls and ceilings, etc - so the more mass and the more air space between the two masses, the better - using a 6" bottom slab separated by 1" air space and a 5" top slab gets your mass-air-mass resonance down to around 32 hZ, gives a TL of 40 dB @ 50 hZ, and steadily climbs in isolation for a rough STC rating of around 70 dB - increasing the air gap to 2" only changes the STC by 1 dB, but improves the bottom to 44 dB @ 50 hZ. In doing this, the m-a-m resonance drops to about 22 hZ, which is why the low end improves by so much with the wider air space.

As to availability, maybe John can help you better with local options - you can PM him just in case he misses this... Steve

[Govinda]

As always steve some more great information!
thankyou so much!
Govinda

[knightfly]

Here's a case study of one of the "big boys" customers using the kinetics system, just for reference -

http://www.wsdg.com/portfolio/portfol.php?SL=ht&BL=2

BTW, if I had this guy's budget I'd probably be paying Philip Newell to write my answers here, while I was playing in my new TOWN, which would be the capital city of my new ISLAND, named New Zealand, or possibly Crete; still, the kinetics stuff wasn't the most expensive part of this install by far, so that's good news, right? Steve

[Govinda]

HAHAHAHA...omg that guy went "all" out! 2x2x1 inch rubber pucks! Thats what im talking about!
Steve, about total sprung weight: is this the total weight of each room? or is this the total weight of the whole structure including the outside wall slab etc?
Plans have been delayed (as usual) but I will soon have to deal with the engineer!
Thanks again,
Govinda

[knightfly]

Total sprung weight is as it sounds - if it's part of the mass that's supported on the springs, whether rubber, steel, fiberglass, whatever, then it's part of the total sprung weight -

Keep in mind that a spring is only a spring when it is NOT at either extreme of its travel - if it's fully compressed or fully expanded, then it's a SOLID coupling. Not good. What you're looking for is a ballpark of around 15-20% compression on springs with everything in place except people - this will depend on the spring rate/durometer of any elastomer supports, whichever you're using - it also, in the case of various types of rubber, depends on the cross-sectional area of each surface contact between supported frame members and rubber, with additional supports under heavier parts like walls (especially if the walls are ALSO supporting a ceiling that's part of the floated system) - and several other factors such as point loading calculations, etc - this is why an engineer needs to be involved in this without a doubt -

Companies like Kinetics can help along these lines, but having a local engineer such as you do is definitely a good plan... Steve

[ejbragg]

Guys,

This is a good discussion. Knightfly, your in-depth knowledge in isolation is impressive.

There is another step that occurred to me, Govinda, when you mentioned this building floating in space, so to speak, with drums being played within. Certainly, you guys have already agreed that the low end vibration is the real challenge, here, and it appears you have worked through the issue.

There is yet another step one can take in this situation: a platform for the drums. Since much of the power of the vibration is where the kick and stands are actually in contact with the floor, isolating the drums from the floor on which they sit will add to the insulatinve effects against sound leaking through.

A description I ran across once went something like this:
Build a sturdy but short platform, resting on rubber. Maybe use the pucs you are talking about (keep a few extra from the building construction). The platform's topside should resemble a floor, shaped like a circle, square, octagon - whatever shape you want. But put a (sealed) 1 inch wide, 1 inch tall lip around the outside. This makes for a very shallow bowl. Pour sand in, about 1/2 inch (doesn't take much). Sand is dense, yet if it's somewhat loose, it can soak up some of the vibration. Then put 1/2 inch flooring over it. Make sure the flooring makes contact with the sand, but not the sides - might resort to somekind of rubber gasket. Also, you could add to the sand, cork fibers, to help keep air in the space.

If the structure was very solid and sturdy, you may not need sand. You could just use shredded cork, which will retain its sponginess practically forever. This would keep the platform lighter, in cse you needed to remove it.

Playing the drums on top of this should help prevent structure-borne vibrations.

[knightfly]

Eric, good point on the riser - except for this; due to "triple leaf" physics, this should be an "either/or" situation - either you float your entire floor, OR you build a drum riser...

If you do both, you've just created a triple leaf barrier, which will work poorly for just the frequencies you're trying to stop - a third leaf/second air space doesn't have to be SEALED in order to cause problems; the air still can't escape quickly enough NOT to act as a spring, and again you have short circuited the mass-air-mass that works best for low frequency isolation.

IF you build an entirely floated drum room, with its inner floor slab, walls, and ceiling isolated from structure, and maintain the m-a-m envelope in ANY direction from the sound source toward the area to be protected, you can't improve on that design - you can only augment it with more mass in each leaf, more space between leaves, better decoupling between leaves, and/or better damping of the space between leaves... Steve

[ejbragg]

Really??!

Hmmm..... I squint my eyes, yet unconvinced!

I am not trying to stop low end sound pressure waves, mind you. What I'm trying to focus on is further isolation of the vibration coupling into the (inner) structure itself.

In my feeble mind, if the drums were set on the floor (as I suppose they shall be, on planet Earth), aside from the SPL, we have direct vibration coupling. If the drums were somehow floating in space in the middle of the room, the SPL within the room will be similar (apart from a shift in reverb characteristics and 'stuff'), yet there will be no direct coupling of the instrument to the building aside from the SPLs alone. Would this not lower the overall noise penetration?

Please convince me of my fallacy. My feelings will not be hurt - as long as you refrain from using naughty names!

[knightfly]

Again, no naughty names -

Basically, a floor, from a physics standpoint, is just a wall that's horizontal - when you add a third leaf and attending second air gap, you stiffen the coupling between the inner and outer leaf and allow more low frequency energy through - This is also true when placing a panel bass trap against an outer wall - the more efficient the trap, the more damage done to the containment of sound at that frequency (it has to go SOMEWHERE)

This mass-air-mass concept is one that has been drilled into my gray matter by Eric Desart, whose credentials are pretty much impeccable - he was the one responsible for the world's highest STC rating of any studio at Galaxy Studios - over 100 dB STC from room to room and to the outside. Although my math is in dire need of (and getting, even as we speak) a serious brushing up, I'm not about to challenge the word of someone with this serious an accomplishment to his credit -

Getting back, since low frequency is the hardest to stop and arguably the most obnoxious to others, this is the thrust of the design goal; the rest of the spectrum will pretty much take care of itself once this low frequency part is established.

For the best low frequency isolation, your mass-air-mass resonance needs to be below the lowest frequency you hope to stop - when you add a third leaf, you send this resonance back upwards in frequency, weakening the overall performance of the barrier in the lower range. This is exactly the wrong direction to go when trying to stop drums and bass... Steve

[ejbragg]

> since low frequency is the hardest to stop and arguably the most obnoxious to others

You want to know what's obnoxious? An STC of 100!! Now THAT's obNOXious! Are you serious?!! Holy moly.

Okay, sir, patience. Please humor me a little more. By nature, I tend to be a skeptic until I see the point driven into obliteration....

I see your point about the floor being the same as a wall. It's just a boundary, an ideally massive one, at that. If this boundary is truly suspended above the outer floor boundary, it still must be held up by some 'thing', as we all know. This thing, being added, is a non-rigid material, often in the form of rubber. The argument seems to be that if the vibrating object (drum) is placed directly on this floor, it should be decoupled from the outer boundary by the amount of 'cushion' provided by this pliant material, the vibration being only a product of the vibrational values of ths rubber when it has X amount of weight compressing it.

Correct me if I misrepresent you: You said that placing another boundary on more pliant material over the first floor will merely add to the compression of the original pliant material (yes, I buy this), and therefore, whatever is 'soaked up' by the upper platform, is now lost in the lower platform. In other words, the extra weight of the upper layer compresses more onto the layer below. I'm struggling with this reasoning because:

1) It seems to assume that the upper platform cannot be made light enough so as to not add to the compression between floors. What if, in a sense, the drums were (let's make this proposterous) floating on balloons? Assuming the drums were very light compared to the floor, how much compression would balloons add to the floor? Pretty much nothing. So in comparison to a 2.5" slab of concrete, how much compression is added by a lightweight platform?

2) It seems to assume that the upper platform cannot be made resilient enough so as to not add to the compression wave. If the platform were raised above ground and (let me renig on making it stiff) were resilient enough that low wavelengths merely bent the platform like a panel resonator. I can see that the amount of compression wave striking the outer floor may remain relatively unchanged merely because the upper platform may support the wave if it were stiff, actually adding to the noise below. But what if it gives as though it weren't there?

It all comes back to the "What if we can just float the drums?" theory.

I apologize to the originator of this thread . Forgive me for using this as a point of self education (and much interesting argument), especially if you are bored to tears!

I'm not challenging you, Steve, nor Mr. Desart's mathematics. I'm genuinely trying to understand the physics. I just can't quite buy it yet.

[knightfly]

OK, part of the problem seems to be that I didn't make clear my reasons for a third leaf NOT working - it has nothing (or very little) to do with more sprung weight, (since that can be compensated by different spring rates) and (nearly) everything to do with the extra air space and mass negatively affecting mass-air-mass resonance - this part would be true whether the different leaves were separated by anti-gravity generators, springs, rubber, dried cow patties, or rocks. The spring material, obviously, will make a difference in decoupling between leaves; I'm not saying it won't make a difference. Only that one would get better isolation by combining the masses of the second and third leaf, with corresponding increase in spring rate (or decrease in spacing) to compensate for the extra weight.

The rest of the problem is that I barely understand what I'm trying to explain, and have (in this particular case and time) essentially decided to take Eric's statements at face value, considering that only ONE of us has the distinction of being responsible for the worlds' quietest recording studio -

Since Eric drops in here from time to time, maybe the most practical way of increasing BOTH our understandings of the reasons why a third leaf isn't a good idea, would be for you to start a separate thread using Eric's name and specifically linking to this one - that way, the discussion can get as far afield as we all can stand, and not impact Govinda's thread for readability... Steve

[Govinda]

An stc of 100 is not obnoxious its AMAZING!
ej bragg thanks for the drum riser thing...The whole reason im going to the drama of pouring a floating concrete slab is "one reason" to stop sound getting to my neigbours!
I personally have allways liked the sound of drums directly on a wooden floor anyways!
Apologies accepted ej bragg!

Steve i'm not trying to boast but I have known for at least 10 years that tripple leaf walls are not very good for stopping extreme noise and music,
I dont need to know the complete science of why!!..read alot of data, quite straight forward when looking at the results!
I'm a musician not a studio building technician and all I know is the Guys with credit know and understand and teach! I have been very fortunate to come into contact with 2 great studio builders gunter wagner and john sayers! I never knew that eric had built the worlds quietest studio! Eric that is a really amazing achievement!! What I learnt from this topic and found very interesting was that a hollow core building block if not filled caused the tripple leaf effect, when building a room within those walls!
Thanks for all your help steve, right now my house plans are at the engineers I will keep you posted of the outcome!

BTW steve if I want a studio wall height of 3 metres (internal) am I looking at the outside shell walls being at say 3.6 meters?
Thanks again,
Govinda

[knightfly]

That would be minimum -more if you intend to do deep ceiling trapping with hangers, etc... Steve