Puck numbers and Placement

[Johnrg]

Hi Guys,
posted this on Sayers site but thought someone here nmight be able to help as well:

Well after alot more reading and info gathering I have found my room weight was slightly wrong due to a dodgy kg to pounds conversion.

My room will be 4700pounds including two people and the gear.

This room will be constructed with the inside out system with two layers of 13mm plasterboard, floated floor on 90x45mm etc.

If I work on another members tests one 90x45x25mm (3 1/2x 1 1/2 x 1) puck (Neoprene-60duro) will take about 300pounds of pressure to acheive 10/15% compression. This basically means I need approx 15pucks.

My floor aera is 11.04m2(118sqfeet).

So I need One puck every .736m2 (7.9sqfeet).

This is fine, and sounds OK in principle however the original wooden floor joists that I am building overtop off run at 600mm centers (23inchs) from the existing wall and I have been told many times that my new pucks must rest where the existing joists run in the existing floor.

Because I am starting my new floor and walls about 100mm out from this existing wall I cannot put them at .736m intervals and have them placed on the original timber joists. The first one nearest the wall will not be on top of the origianl joist and so on (domino effect!!)

So what's worse, or best!!

(a)pucks that do not rest on the original joists but are correctly placed at .736m2 intervals to generate the correct spring for the expected room weight.

(b)about 25% more pucks than I need, therefore not creating the correct spring, but they will lie on top of the existing joists at 600m with extra not on top of joists around the edge of the room.

(c) What about if I reduct the puck size (not thickness). Will that have any effect on the amount I need?

Help appreciated everyone:

JG

 

[RICK FITZPATRICK]

I have been told many times that my new pucks must rest where the existing joists run in the existing floor.

Hello Johnrg. In the unlikely event that Steve or otheres don't get to your post right away, I'll try to help a bit. But first, man you are building a floated room on an existing wood floor? Even if you could line these up, I think you need to re-evaluate some things first. There is another issue at stake here which may totally negate the need for a floated floor in the first place. And that is Low Frequency resonance. Let me state right now, that I'm no expert, but there are some things that you haven't even mentioned that are at the forefront of floating a floor in the first place and should be addressed.

Evidently, you have done some homework on this, but without knowing certain facts, no one should give you further encouragement towards your goal. At least at this point. And at least from my perspective. Let me explain.

First off, is the issue of structural integrity of the existing floor. What have you done to insure this existing floor will handle the weight, even if distributed properly, which it sounds from your post, you can not. Point loads of this type place directly on floor sheithing BETWEEN joists, is asking for trouble if not down right failure of the isolation system to perform. Not to mention failure of the flooring to support it. I'm not saying it will, only without knowing things, I would hesitate to offer any encouraging advice.

Second, is the fact that you already have an existing membrane(wood floor)
that will act as a drum head regardless if you float this floor. All membranes have a natural resonant frequency, and this floor is simply a damped membrane. Now you want to place another, although isolated membrane on top of the existing membrane. Without sounding like a negative so and so, I think you need to research a principle here before proceeding.

The fact is, unless your walls, and ceiling are designed with LOW FREQUENCY TRANSMISSION LOSS in mind, floating a room on a lightweight floor is useless IN MY OPINION. In fact, certain low frequencies may actually be amplified. Especially under these circumstances. The reason is simple. Walls and ceilings built as you have specified will have adequete mid and high frequency transmission loss. But when it comes to Low frequency. the Mass -Air Mass resonant frequency will not be low enough to justify floating the room, as the mass of the floor can NOT possibly be increased enough to prevent LF TL via resonance of the TWO floor membranes in the first place. This principle has just come to my attention and I by no means understand it completely.

However, it behooves me to bring it to YOUR attention as you are on a path to probable LF isolation failure. I'm sure Steve has had a chance to delve into this issue at length, but he's a busy guy, so he may not have had time to address your post yet. So, in the meantime, I'm going to link you to a discussion of this very issue at both Steves site, AND another.

However, they are discussing floating a WOOD floor on top of an existing CONCRETE slab, which in itself brings this principle into focus. But your plan is to build a floated wood floor on top of another which is a double whammy as far as LF transmission loss is concerned. I suggest you read these links in their ENTIRITY. You may save yourself some money as well as isolation disappointment. Let me add one thing though. Because we know very little of your circumstances, you prioritys, budget, skills, existing conditions, type of music, adjacent isolation concerns, and your isolation goals, my reply may be totally out of line. In that case, take my advice with a grain of salt and carry on. But if you are as serious as it sounds like you are, it would behoove you to at least check this information out.

This whole idea of floating rooms has underlying requirements to make it perform correctly, or you undermine its ability to do its job from the outset. This is why the success of floating a floor that supports a room requires ALL of the elements to be designed and built with LF TL in mind. Otherwise you are wasting your time and money. Well, thats my NON EXPERT .02.

http://forum.studiotips.com/viewtopic.php?t=1653

And this at Johns, which you may have already read.

http://www.johnlsayers.com/phpBB2/viewtopic.php?t=2921&start=0&sid=7ab263b66a97a57d689bfdb78f9dacb3

fitZ

 

[Johnrg]

Thanks Rick.

I have read through your post and also through the other links and have to admit the information is mind boggling to say the least.

My situation is that I have a stand alone 6mx5m building about 20feet from the nearest neighbours that I want to split in two as with the attached plan on my original post to house a small control room and small live room.

It is a personal facility, I am a drummer and I am on a very limited budget. I am also not totally isolation crazy. My neighbours will have there own STC and I will probally only track drums on weekends and not to late at night.

Floating the floor has always been a concern because (a) It will really eat into my room height (I am at 2.4m now), and (b) It will cost alot of extra money.

The reason I included a floated floor into my plan was two fold.

Firstly the existing rooms floor construction is relatively light weight (see attached drawing). When you jump up and down on it, it is "boomy". I was told I had to beef this up and the only way to do that was float the floor.

Secondly, I was told that because the control room and live room share this common floor I would have servere flanking problems unless I isoloated the live room from the existing floor.

I would love nothing better than not to float the floor because it would save me a few bucks and increase my room height by another 100mm atleast. The walls between the two rooms will be normal double stud wall with airgap, two layers of gib and I was planning to rest the new ceiling on these walls

To be honest, I really seem to be going around in circles. I am told to float one minute then not to float the next. Everyone is really helpful in these forums but I am at the stage where I need to get started and the more reading I do the more I am freaking out and getting confused.

I have thought about just adding another 20mm layer of flooring in the live room and building the walls on top of this (It would be alot easier) but the flanking noise into the control room is a concern.

One very confused kiwi!!

Anyhelp would be appreciated

ps - I had a builder look over the rooms and he said it can easily hold 4700 pounds,

Thanks

JG

 

[RICK FITZPATRICK]

I was told I had to beef this up and the only way to do that was float the floor.

Hello again. Thats the problem with "net fact" advice. Truely, the only thing I can say is if Steve or other experts told you to build this floating floor on an existing membrane, by all means carry on. I gave you MY opinion regarding what has come to light lately. I gave you a link to illustrate the concept. I don't know what else to tell you. The fact remains, unless your WHOLE room, meaning FLOORS, WALLS and CEILING address low frequency transmission via M-A_M resonance by adding mass to lower the resonant frequency, you will have TRANSMISSION at those as well as other frequencies. Whether or not it is critical to you or your neighbors, or even if the escaping sound is a problem, can only be determined by you. However, like Keith said in the link I provided, HE can't afford to take a chance. That is the issue here. Whether or not you can gamble with your money and time is your decision.

I am also not totally isolation crazy. My neighbours will have there own STC and I will probally only track drums on weekends and not to late at night.

Define "not totally isolation crazy"..thats one of the problems. If you CAN define it in absolutes, then you are on the way to meeting you goal. It is at that point that material and technique limitations will tell you which direction to go. If it doesn't fit within your means, then at least you haven't wasted it already and STILL not have it perform correctly.

Secondly, I was told that because the control room and live room share this common floor I would have servere flanking problems unless I isoloated the live room from the existing floor.

And I agree. However, if the walls/ceiling don't address the need for Low Frequency TL, whats the point? And THEN, you STILL have to address the MASS in the floated floor itself, which then places a bigger burden on the existing support floor. THat is why I was asking about your knowlege of the structure and what it will support.

I would love nothing better than not to float the floor because it would save me a few bucks and increase my room height by another 100mm atleast. The walls between the two rooms will be normal double stud wall with airgap, two layers of gib and I was planning to rest the new ceiling on these walls

I understand, believe me. I've already gone through a floating floor build only to have to tear it out. I never even got the walls built. And after it was removed, I discovered the weight of just the floor had cracked the existing concrete slab BAD!! And if that wasn't enough, because it was a rental, I had to have the floor REPAIRED!!

Johnrg, I am not TELLING you to NOT float it. Only that I believe you will get LF transmission period. At what frequency, and at what level at what distance I couln'd tell you. I think this is probably what defines a pro job from a home studio job. From what you have told me, MY GUESS was it wouldn't cut the mustard. And I just hate the thoughts of expecting isolation results that are a far cry from the end result after spending a ton of money and time. And just to protect myself from "net fact" accusations, I'm going to make it perfectly clear. I AM NO FUCKING EXPERT. So take my word with a grain of salt if you so choose. My whole point was new information had come to light in regards to the criteria the makes floating a ROOM worth the time and expense. Hence my links to the discussions of said criteria OPINIONS! The only way I know of to be ABSOLUTELY sure you are meeting your isolation goals is to hire an Acoustical Engineer who takes responsibility for the results.

To be honest, I really seem to be going around in circles. I am told to float one minute then not to float the next. Everyone is really helpful in these forums but I am at the stage where I need to get started and the more reading I do the more I am freaking out and getting confused.

What can I say but join the crowd At least the crowd that is concerned enough about their results that they take the time to address what IS KNOWN, and make informed descisions instead of relying solely on a few replies on a forum. And that is EXACTLY the problem here. This is a massive information problem on the net. My BEST advice, other than Steve knows much more than I do and to trust his word above mine, but also check those threads out in full. Lastly, I read about peoples success with the same sort of critera. Here is one from last month. Whether or not their ISOLATION results will meet YOUR criteria is another animal altogether.
http://www.homerecording.com/bbs/showthread.php?t=156184
fitZ

 

[Johnrg]

Thanks Rick,
maybe some others will chime in - your help is greatly appreciated.
JohnG