Asking the impossible?

Hi everyone, Firstly I would like to thank everyone on this site for the amazing amount of info supplied. If only I had gotten onto this sooner I would possibly in a different line of work. Ha Ha This is really interesting stuff!!! Secondly I apologize that this reads like a novel but I am trying to cover as much detail as I can. Anyway here is the story. I would like to convert a section of a demountable/ movable building into a jam/ rehearsal room. If we do any recording it will only be recording ideas so no need for control rooms etc. The building is movable however I don't see it ever leaving this address. Ideally I would love to have enough isolation for a 3 piece band IE: Guitar, bass and drums so I am thinking I would need around 100db of isolation. However its not a huge room so maybe that will mean less volume, but Im sure you all know what happens when the ”boys” get together! Correct me if I am wrong. The “shed” is pretty lightweight construction. I know I am asking the near impossible, but I already have this building in my backyard so I would love to come up with a solution. Half of the “shed” has been snavelled by my lovely wife and converted by us to an outdoor room with lounge/ spare bed, bar etc that opens up to an outdoor patio / barbecue area and onto our pool. The remaining room is mine to play with thus the dream of a “Jam Room” Details: The whole thing is 12mtrs x 3mtrs with a slight gabled roof starting at 2.5mtrs high at its lowest point (each end) raising to 2.8 mtrs high at the peak. The internal ceiling is 2.4 mtrs high. The whole thing sits on 2 steel RSJ steel beams that are 12mtrs x 200mm high x 135mm wide and are 2 mtrs apart so the floor joists over hang the RSJ‘s by 500mm each side. The floor joists are 70mm x 40mm, not sure of what timber they are and are at 600mm centres. There is also steel RSJ’s accross both ends and at every 4 mtrs. The RSJ’s sit 100mm off the ground sitting on concrete blocks putting the actual flooring 370mm OFF the ground. I have a mate who is a builder so I have covered what I need to do to support the joists to stop any sag with the added weight. The existing flooring is 20mm particle board. The existing walls are 45mm x 45mm studs at 400mm centres with 5mm ply internally and colourbond type steel cladding outside, all insulated with what looks to be standard fibreglass batts but is surprisingly cool inside so maybe they are higher spec. The wall in the centre that separates the rooms is made of 70mm x 45mm structural pine with 400mm centres The nearest neighbour is only 7 mtrs away. Told you I was asking the impossible Ha Ha Budget: I would like to get away with spending around $5000 if possible. I am quite handy with my hands (so is my wife-she can use a drop saw like a champion) so we can do all the construction needed. What I am Thinking: Basic layout. 2 leaf wall system, room within a room 100mm air gap between walls,ceiling and floor . Walls: existing walls and ceiling - add resilient channel and 1 layer of 13 mm frycheck Gyprock. Inner walls and ceiling: 2 layers of 16 mm frycheck Gyprock. First layer layed vertical, second layer glued or screwed off as per Steves suggestions here. viewtopic.php?t=598 Insulation: 48kg/m3 50 insulation in both walls. Floor: Here is where I get confused ! My first thoughts were a floating timber floor as per John’s or Knightflys instruction below. With 2 layers of particle board for each layer, Insulation, neoprene etc download/file.php?id=2182 http://johnlsayers.com/Recmanual/Images/Walls%202..gif However I than read this from Soundman2020:- basically, to get meaningful isolation from a floated floor, you need considerable mass, as in concrete slab. Putting a thin light-weight membrane over a cavity has another name: musicians refer to that as a "drum head". They like it, because when you impact a drum head with something, it resonates loudly and longly and musically. Drums are great when they are arranged as a kit and played by a musician, but not so great when arranged as a floor that you walk on... So now I am confused on which way to go. I am obviously missing something or am getting my wires crossed because this sounds contradictory to me??? Doors: 2 Solid doors with extra insulation as John’s instruction below. http://johnlsayers.com/Recmanual/Images/Doors.gif Ventilation: My sparky is also a registered A/C Tech so is researching Split system air conditioners that brings in fresh air. Short of that we'll include a totally separate isolated fan with inlet and outlet with self made sound baffles with insulation etc. Windows: Dont have any so no need to worry about this! Drums and possibly amps to be on a self made raisers. There was a great post on here somewhere about making raisers out of mdf and insulation similar to the Auralux ones below Questions: Can some one clear up the floor scenario please. What would be my best plan of attack? Are any of my other suggestions not valid? If the wooden floating floor is valid does anybody know where to get neoprene blocks in OZ Is there any validity in adding gyrock to to gap between flooring layers between the joists to beef up the mass or is that just a waste of time and money? Thanks again Rob

Hi Rob, and welcome to the forum! :)

I am thinking I would need around 100db of isolation.

There is only one single studio on this planet that gets 100 dB of isolation. That is Galaxy Studios in Belgium. They get 100.7 dB. It cost them millions of dollars, and took the best acousticians in the world several years to design and build. It basically consists of a giant reinforced concrete shell, with several giant reinforced concrete bunkers inside of it, each of which sits in several massive isolation mounts, like this: Not exactly portable! :) In other words, there's not a chance in hell that you'll get 100 dB of isolation from a dis-mountable structure. There's also the question of why you would even need that... Realistically, a typical studio isolation system will get maybe 50-60 dB of isolation. A really good one will get perhaps 70, if you invest a lot of money. But those are for fixed studios that don't come apart, and don't need to be transportable.

The “shed” is pretty lightweight construction. I know I am asking the near impossible, but I already have this building in my backyard so I would love to come up with a solution.

OK, lets' put this in perspective: You're effectively saying "I want to fly to the moon by strapping three tiny feathers to my wrists, and pumping my arms up and down incredibly fast. I know that is impossible, but I really have to do that, so show me how." :) :shock: :!: I'm trying to keep it light and be amusing in my response, but it really is like that. What you ask is not "near impossible": it is in fact completely, totally and absolutely impossible, no matter how much you want a solution. I want a solution for global hunger that costs less than US$ 5, but that isn't going to happen either! The issue is this: you said two hyphenated words that make this impossible: "dis-mountable" and "light-weight". Let's take the second one first: stopping sound requires mass. Huge amounts of mass: The more isolation you need, the more mass that takes, and it goes up exponentially, not linearly. There is no way around that: it is a simple consequence of the laws of physics. In fact, it is a simple consequence of one very specific law of physics, which (unsurprisingly) is knows as "Mass Law". It goes like this: TL(dB)= 20log(M) + 20log(f) -47.2 M is the surface density of the barrier, and f is the frequency That tells you how much isolation (Transmission Loss) you will get from any given single-leaf barrier. Do the math: to get 100 dB of isolation, you'd need a wall with a surface density of roughly one million kilograms per square meter. In other words, you'd have to build it so that each square meter of the wall weighs about one thousand metric tons... That kind of makes "dis-mountable" and "portable" into an amazing feat of engineering.... That would be for a single-leaf wall. A two-leaf wall is much better, since you are using the principle of resonance in your favor, so you can get really good isolation with less mass. You'd only need to have two walls that have a surface density of 300 kg/m2, separated by an air gap of about 50 cm. That's a little better, but still pretty darn hard to take apart and transport. You could get that type of mass from a pair of reinforced concrete walls, each about 30cm thick. Clearly you are going to have to lower your sights a bit on how much isolation you need. The basic issue is, as I mentioned: isolation requires a LOT of mass. If you want to have a dis-mountable room that can be transported reasonably easily on a realistic truck, then it cannot provide anywhere near 100 dB of isolation. Maybe 45. The other issue with "dis-mountable" is air-tight seals: that's pretty darn hard to do with a structure that has to come apart and be re-assembled. The basic issue here is that even a tiny crack, gap, or hole in one small part of the wall, can trash your isolation. The entire structure has to be sealed air-tight, at least twice over. If air can get through, then so can sound.

The RSJ’s sit 100mm off the ground sitting on concrete blocks putting the actual flooring 370mm OFF the ground.

:shock: So it does not even sit firmly on the ground? There's an air gap under it, and the floor is resonant? :ahh: I'm lowering my 45 dB isolation estimate to 35 dB... that's about all you can hope for with such a building, and even that is pushing it.

The existing flooring is 20mm particle board.

Then I'm lowering the estimate again: make it 30 dB, tops.

The existing walls are 45mm x 45mm studs at 400mm centres with 5mm ply internally and colourbond type steel cladding outside

So all you have is thin sheet metal on the outside, and 5mm ply on the inside, with a fully-coupled wall? The isolation estimate is now down to 25 dB: Actually, 26.2 dB. That's the theoretical isolation you would get from such a wall, except that it will only isolate frequencies above about 200 Hz: it won't isolate that well below 200 Hz, because that is the resonance-controlled region for such a wall, and also into the stiffness-controlled region, ... but there is no stiffness to thin sheet metal and thin plywood.

Told you I was asking the impossible Ha Ha

Yes you are, most certainly! There is no doubt about that... :)

Budget: I would like to get away with spending around $5000 if possible

That would buy you some nice finish flooring and a usable mini-split system, with some left over for very basic acoustic treatment inside the room, and one small hamburger at McDonalds. That's about it. Multiply by ten if you want serious isolation, in the region of 50 dB. Multiply by one hundred if you want extreme isolation, in the region of 70 dB. Multiply by one thousand if you want Galaxy Studios type isolation, at 100 dB.

2 leaf wall system, room within a room

You already HAVE a two-leaf wall system! You mentioned it: "45mm x 45mm studs at 400mm centres with 5mm ply internally and colourbond type steel cladding". Those are your two leaves. The sheet metal on the outside is your outer-leaf, and the 5mm plywood on the inside is your inner leaf. Anything you add to that will create a 3-leaf system. If you want to create a room-in-room here, then the plywood has to come off, and you'd have to beef up the outer-leaf (sheet metal) with substantial mass.

Walls: existing walls and ceiling - add resilient channel and 1 layer of 13 mm frycheck Gyprock

That would REDUCE isolation in the low frequency region of the spectrum, since it would create a 3-leaf system tuned to an even higher frequency than the current two-leaf system. Roughly, the tuned MSMSM resonances of that wall would be at 77 Hz (F-) and 110 Hz (F+). The wall would only isolate well, starting at about 250 Hz. Total isolation would be down by 2 dB, to roughly 24 dB.

Inner walls and ceiling: 2 layers of 16 mm frycheck Gyprock.

Whoaa! :shock: That would make a FOUR-leaf wall! so your low frequency isolation goes down once again, since you'd be setting an MSMSMSM resonance frequency even higher than for the previous scenario. 4-leaf resonance is a bit beyond my math skills: maybe Bert can figure it out for you. I'd hazard a guess that you'd lose another 2 dB or so there.

So now I am confused on which way to go. I am obviously missing something or am getting my wires crossed because this sounds contradictory to me???

No, you are not missing anything, nor getting your wires crossed. Here is how floated floors work: viewtopic.php?f=2&t=8173 Here's the saddening laboratory test report: http://archive.nrc-cnrc.gc.ca/obj/irc/d ... /ir802.pdf

Ventilation: My sparky is also a registered A/C Tech so is researching Split system air conditioners that brings in fresh air.

There's only a very, very few mini-split systems that also supply some fresh air. The vast majority don't: they only cool or heat the air. So you will need ducting for your ventilation, which implies silencer boxes and fans. And since you want extreme isolation, your ducts will need to be huge, as will your silencer boxes.

Short of that we'll include a totally separate isolated fan with inlet and outlet with self made sound baffles with insulation etc.

HVAC is just a little bit more complicated than that! :) There's a whole bunch of calculations you have to go through, to figure out what flow rate (volume per minute) and what flow velocity (distance per minute) your air needs to move at for your room with your occupancy in your area. That will define what duct size you need, and what type / capacity of fan you need. The fan musty be capable of handling that flow rate and that flow velocity when faced with the static pressure produced by your system. When you have figured all that out, then you can do the math for the HVAC system itself, calculation the latent heat load and sensible heat load that it needs to deal with in that room with the amount of gear, lighting, people, and climate heating that is going on, which will get you to the cooling capacity that you need. HVAC calculation is complex.

Can some one clear up the floor scenario please. What would be my best plan of attack?

For high isolation, the building cannot be raised off the ground, so your plan of attack is to figure out how to lower the building such that the floor is contact with the ground. Most studios are built at ground level for this vary reason: the floor is a simple "slab on grade".

If the wooden floating floor is valid does anybody know where to get neoprene blocks in OZ

It isn't valid in the way you imagine, but even for those cases where it is valid, there's a huge number of questions: How did you decide that you need neoprene? How thick did you calculate that your blocks need to be in order to get the resonant frequency of your floor down low enough? How big doe the blocks need to be (surface area) and how do they need to be distributed under the floor in order to correctly carry the load evenly) What type of neoprene will you be using, and what is the resiliency of that? How much static deflection does it need in order to float, and how much load is needed in order to produce that amount of static deflection? How will you account for the vastly different load conditions in different places on the floor that have different loads on them? What target frequency are you aiming for? Floating a floor is way, way, WAY harder than just shoving a couple of rubber pucks under a few bits of timber (despite what you see on YouTube...) This is what a properly floated floor looks like: That is several inches of reinforced concrete on a steel frame that is supported on carefully designed and tuned springs. Here's a close-up of one of the springs: Mason Industries makes floor isolation mounts that are a bit different but also work well. They look like this: Those are great, as they allow you to pour your inner-leaf slab on top of the outer-leaf slab (with a membrane in between, of course), then jack it up once the concrete has cured. But you still need to do the calculations to ensure that the floor actually will float correctly, or you'll run into the same issues in that link above: your floor wont' actually float, so you will have made the situation worse, not better.

Is there any validity in adding gyrock to to gap between flooring layers between the joists to beef up the mass or is that just a waste of time and money?

That applies to typical basement studios, and yes there's a huge amount of validity in that, provided that the floor is structurally capable of bearing the additional mass safely. Mass is what isolates, and the higher the isolation needed, the more mass you need. The amount of mass needed for even moderate isolation is pretty impressive, and can easily overload a typical floor structure. When you hire your structural engineer (yes, you do need one!), he can tell you how much extra mass your floor can take safely. That's what places the limit on how much isolation you can achieve.

There was a great post on here somewhere about making raisers out of mdf and insulation similar to the Auralux ones below

Two layers of 3/4" (19mm) plywood sitting on top of 2" of OC-703 will do that trick. But that's mostly for isolating impact noise and vibration: it wont' do anything for air-borne noise. I'm not trying to be insulting, demeaning, or a wet-blanket on your plans. I just being a realist, and generally this "in your face" approach wakes people up to the sad reality of the laws of physics and how they apply to the science of acoustics. I'm just pointing out why it is impossible to do what you say you want to do, even with a budget ten times what you want to spend here. It simply cannot be done, because the laws of physics are immutable, and they apply to your shed just as much as the do to Galaxy studios. It doesn't matter how much you "want" or "wish" or "hope" or "need" to have high levels of isolation with no mass, it just isn't going to happen. The reality is this: sound isolation requires mass. Lots of it. The more isolation you want, the more mass you need. Realistically, home studio builders can expect about 50 dB of isolation from their studios, maybe 60 dB if they are really lucky. And in the vast majority of cases, 50 to 60 dB is enough. A drum kit played normally produces around 110 to 115 dBC, so 60 dB of TL would bring that down to roughly 50 dB at 1m from your wall. Sound diminishes with distance on the inverse square principle, at about about 6 dB per distance doubling, in theory, but more like 4 to 5 dB in practice for typical urban situations. So at 2m you'd have 46 dB, at 4m it would be 42 dB, and at 8m (where your neighbors are) around 38 dB. Check your local noise ordinances (local municipality website) to see if that meets regulations. But that applies to a properly constructed studio built on the basis of a slab-on-grade floor. It does not apply to a flimsy, thin, light-weight shed that is elevated above ground level. I'm sorry, but that's just the way it is. I know this is NOT the answer you were expecting or hoping for, but it is the truth. I'm sure you were hoping I'd say "Just by some Magicustic paper to glue to your walls, and spread some HoodoSorb carpets on your floor, then you'll get 100 dB of isolation", but the sad truth is that there are no such magical materials: just ordinary ones that have to obey the laws of physics, which are not on your side. Realistically, the very best you can hope for with that shed on your budget and with your restrictions, is isolation in the region of 30 to 35 dB, tops. Drums would be about 85 dB outside your wall at 1m, and still around 70 dB at your neighbor's wall: That's loud, and likely unacceptable, but that's also reality. I wish I had better news for you, but there is none. You either have to greatly change your budget and building concept, or greatly lower your target. - Stuart -