Thanks for the reply....and holy hell, I didn't realize just how far up the creek I am haha!
Sometimes, a bucket of cold reality puts a different perspective on things...
One of the issues is that acoustics is not intuitive, at first glance. Sound does not actually behave the way we think it ought to, or assume it should. It is invisible, we can't see what it is actually doing, so we make assumptions about it that turn out to be wrong.
For example, most people don't "get" that the decibel scale is logarithmic, not linear, and have a hard time grasping that not all decibels are equal. The single decibel that goes between "99" and "100" on the scale is one hell of a lot bigger than the single decibel that goes between "9" and "10". People assume that since all kilograms are the same size, and all kilometers are the same size, and all seconds are the same size, then all decibels must also be the same size, but that isn't true. It's confusing, and not intuitive, and not obvious. But when you lay it out in real terms, the shock suddenly hits.... "Man, that 99-to-100 guy is HUGE! And that 9-to-10 guy is miniscule!".
That's just one of many aspects of "non-intuitive acoustics" that you'll come across as you design your place... Another one that confuses the hell out of many people is the 3-leaf issue: It sure isn't logical or intuitive to think that if you have a two leaf wall, with decent mass on both leaves, and then you add a third leaf of decent mass in the middle, between the existing two, then that can actually REDUCE your isolation, instead of increasing it! But it does. How can it be that adding an EXTRA layer inside the wall, with MORE mass, can make things WORSE? Because resonance is a son-of-a-so-and-so, and it will bight you every time, when you aren't looking! Not intuitive at all. But true.
Etc.
So welcome to the illogical, confusing, non-intuitive world of acoustics, where nothing is as it seems at first glance! And you aren't even sure any more if you took the blue pill or the red pill ....
So, what I got from your response is that I need to increase budget and decrease my goals...
Yup.
The band can play at lower levels (we rehearse on an in-ear system) so we can definitely bring the dB level down there and I can ask the drummer to not put his fists through the kit.
Great! Good start. Some drumsticks are quieter than others. I'm no expert on drumsticks, but I'm sure your drummer will know what I'm talking about. Tell him that if he can't get it down to 100 dBC, then you'll replace his drum heads with whale blubber, and switch his sticks for wet noodles....
I can't really know for sure how the roof is attached without pulling off the plasterboard,
It would be useful to know. Can you ask the builder/manufacturer? Maybe peek through a vent or gap someplace? That roof will be your third leaf, very likely, so it would be very useful to understand how it is built. At the very least to find out if it is a vented roof (probably), and if there is any insulation up there (perhaps), and most important, what the structure is, to see if it can safely handle any additional load. Assuming you will have to go with a 3-leaf roof, you will need to add additional mass to that existing ceiling, so you will need to know what the live and dead loads are right now, as well as what the design limits of live load and dead load, so you can figure out what thickness/how many layers of drywall you can add up there.
I work for an air conditioning company who call these High Wall Splits, no different to a split system.
Great! Then you already have half of your HVAC system. No extra cost there. Now you just need the other half: the "V" part of HVAC...
Yes I have experience in construction (was a landscape architect for 5 years). No, I don't have tools but have a separate budget for tools and some well armed tradie friends that will lend a nail gun for some cold ones etc.
Good! You will need things like a table saw, chop saw, circular saw, router, electric drill/screwdrivers, nail guns, hammer drill, compressor, pneumatic caulking gun, power plane, belt sander, as well as a good set of typical hand tools, and probably some unusual ones that you never thought of...
So you DO need to be rather concerned about the acoustic treatment that you WILL need inside your room.
Understood, I assume that this will be a separate conversation once the room is built
Not really: You should design your complete room from the start, including EVERYTHING, before you start building. Otherwise you'll end up finding out that some things can't fit in any more, because other things are in the way.... A studio is a system made up of numerous parts, and they all have to be there for it to work. So it's a good idea to consider treatment, HVAC, electrical, lighting, and perhaps even interior decoration, along with the actual structural and isolation issues.
One very well respected acoustician here on the forum has a signature tag line that goes something: "Building a studio is 90% design, 10% construction.". He's very, very right. The more time you spend on refining your design down to the last final minimal detail, the less time, money, and effort you'll spend on the actual build. Moving a wall or door on the computer screen costs you nothing at all. Moving a wall or door in real life is a little more complicated....
Ok so I guess I'm after some advice on what sort of isolation I can buy for $10,000. The space inside the room can come down to a width of 3,000mm if it absolutly has to.
OK, time to hit the theory books: Isolation depends mainly on mass, but not mass alone. Let's take a step back first:
There are four ways that you can stop sound:
1. Build a barrier so extremely massive that sound waves cannot move it.
2. Build a barrier so extremely stiff (rigid) that sound waves cannot move it.
3. Build a barrier so extremely absorptive that the sound wave can't get through to the other side (it gets absorbed completely along the way).
4. Remove all paths that could possible conduct sound.
That's it. Nothing else. No magical incantations, or secret materials, or bottles of snake oil. Just those four.
And it turns out that each of them is impossible!
1. Mass: There is no such barrier! Even the entire planet cannot stop a sufficiently powerful sound wave. If it could, there would be no earthquakes...
2. Stiffness: There is no such materials! No material that could possibly exist is perfectly rigid. All materials can and do vibrate.
3. Damping: There is no such material! Nothing can absorb a sound wave fully, not even hundreds of meters of thickness of the best acoustic absorber known to man.
4. Decoupling: There is no such solution! Only a perfect vacuum could do that, and even deep interstellar space is not a perfect vacuum.
OK, so we are up the proverbial creek without the proverbial paddle, and we don't even have the proverbial canoe to help!
Mass doesn't work. Stiffness doesn't work. Damping doesn't work. Decoupling doesn't work. Or rather, each of those does not work BY ITSELF.... but if you put them together in an intelligent manner, then you can get pretty darn decent isolation. Not perfect, but very good. All you need to do is to have two layers of rigid, massive materials, that are decoupled from each other and have acoustic damping in between. Because when you do that, you change the rules. You create a resonant system, and that's a different story entirely. You still can't get perfect isolation, but you can get really good isolation.
So your wall will be a resonant system, and resonant systems can be tuned. It is resonant in the exact same way that a heavy object hanging from a spring is resonant. The weight bounces up and down very easily for a long time, all by itself, "resonating" at its natural frequency, and it does NOT want to move at any other frequency. It is what physics refers to as a "Mass-Spring-Mass" system. In the wall, you have "mass" on one side (your outer-leaf), mass on the other side (your inner-leaf), a spring (the air trapped in between the two leaves), and then you also have a damper that hampers the resonance (the insulation in the gap). All of those work together to create isolation that none of them could produce on its own. You get much greater isolation than you could get from just using that same amount of mass, or that same stiffness, or that same amount of damping, or that same amount of decoupling on its own. The whole is greater than the sum of its parts, because resonance is a monster that can bight you, but you can also tame it and use it in your favor.
OK, so your wall is a tuned system. What does that mean? First, it means that when you play a note that happens to coincide with the natural resonant frequency that it is tuned to, it resonates, vibrates, rings, and yells out as loud as it can, and sends that note right through to the other side, even louder: resonant systems amplify. Which is what you DON'T want your wall to do! You don't want to play notes that get amplified by your wall! So you therefore have to tune the wall so that its resonant frequency is much lower than any note you will ever play in the room. It turns out that a good rule of thumb is to tune your wall at least one octave lower than the lowest note it will ever hear.
Second, even though your wall strongly amplifies its own note, it also strongly resists all other notes! Every frequency that is at least 1.414 times higher than the tuned frequency of the wall, is isolated greatly. Much more than you could get any other way.
If you were to build a wall from pure mass, then it would be governed by mass law, which basically says that as you go up the musical scale, you get a 6 dB increase in isolation each time you double the frequency (go up an octave). That's not much to start with, but in reality its not even that high: 6 dB is theoretical, but in the real world it is more like 4 or 5 dB. However, with an MSM wall, each time you go up an octave you get an increase of 18 dB! That's also theoretical, and in reality it's more like 15 dB per octave, but that's still huge. Way, way better than mass law.
Mass law also says something else: it says that each time you double the mass of your single-leaf wall, you get a tiny increase of just 6 dB in isolation (theoretical: 4 to 5 in reality). MSM says that each time you double the mass of your two-leaf wall, you get an increase of 18 dB in isolation (theoretical: 14 to 15 in reality).
Thus, MSM is the way to go! It's the reason why studios are built with fully-decoupled two-leaf MSM walls. It gives you the best "bang for the buck" of all possible methods.
Alright, so far so good! But how do you "tune" your wall?
The resonance of an MSM system depends on only a very few things. The most important are the mass (surface density) of each leaf, and the resilience of the spring. In this case, the spring is air, and you change the resilience by putting more or less of it between the leaves. In other words, you make the gap bigger or smaller. Small gap = high resilience = high frequency. Large gap = low resilience = low frequency. And since you want the lowest possible frequency you can get, you want a large gap. The same applies to mass: More mass = lower frequency, and since you want it low, you need lots of mass on each leaf.
It's that simple. There are equations that can predict the resonant frequency of a 2-leaf MSM wall, and all you need to do is to plug in the surface density of each leaf, and the size of the gap between them.
So far so good! But it turns out MSM resonance is not the only thing that governs the isolation of a wall. MSM resonance governs low frequency isolation, but rigidity governs even lower frequencies, and something called "coincidence" governs higher frequencies, and mass law also throws its hat in the ring, for good measure. So there's actually a set of equations that you use to predict the isolation, in decibels, for each of those frequency ranges, one equation for each region, then you can draw a graph, and you'll see exactly how your wall will isolate. Your graph will looks something like this:
random-IRC-MSM-TL-graph.jpg
I just chose one at random from a paper that shows hundreds of such graphs. Ignore the pink line, and look at the black line. You can see where the resonance of this wall occurs: around 63 Hz. That's the lowest dip in the isolation. You can also see the coincidence dip at around 3 kHz. Etc. Your wall will have a similar graph.
But it's not that simple.... That graphs shows the
mathematical isolation, assuming that we hear all frequencies at the same level. But we don't. Our ears are not linear, and not mathematical. They are more sensitive to some frequencies than to others. A couple of smart guys called Fletcher and Munson did some experiments on lots of people, many decades ago, and found out that not only do we not hear all frequencies at the same level, the relationship between how we perceive different frequencies changes for different volume levels! These guys came up with a set of graphs, now called the Fletcher-Munson curves, that show how we perceive all frequencies at different intensity levels. It looks like this:
fletcher-munson-with-absolute-threshold.jpg
Each curve represents one listening level, from 10 dB to 120 dB. As you can see, out ears are really sensitive at around 5 kHz, but not so much at 50 Hz. So your wall doesn't actually need to be so good at 50 Hz as it is at 5 kHz, for example....
So you need to take that into account when you design your wall.
Lot's to think about!
Right, now you have the basics of how isolation works in place, we can move on to your question:
I guess I'm after some advice on what sort of isolation I can buy for $10,000.
There's no simple answer to that! It's like saying "How much food can I buy for $100?". You can get a hell of a lot of lettuce for that price, but very little caviar. Lots of hamburger, but not much steak. A few cans of beer, but only a tiny splash of best champagne. It all depends on what you want!
OK, real world: To figure out what you can get for 10k, you start out by pricing "massive" building materials. The more mass each leaf has, the better it will isolate. So you want the most mass you can get for each $. In other words, you want to compare dollars per kilogram of mass, for several types of common building material. The best deal is usually plain old drywall. Brick and concrete block usually come in close behind, then things like OSB, plywood, MDF, fiber-cement board, steel, aluminium, glass, and other things. So you'll need to take a trip to your local building supply store, and start pricing materials, to find out what is the best value in YOUR area. My guess would be drywall, or concrete block. The advantage of concrete block is that you'd have to have several layers of drywall to get the same total mass, so you also need to figure in the time taken to build each wall, and since drywall also needs framing and nails, that might be a factor. Block walls go up fast. Drywall takes a bit longer. Block wall needs mortar, bricklayers, masonry sealant. Drywall needs caulk, backer rod, mud and tape. Etc. There are pros and cons all around.
OK, lets' say you figured out what your cheapest mass and method is: now you need to figure out how much of it you can afford. Let's say you figured out that you can afford to make your inner-leaf from two layers of 16mm drywall. So now you know one part of the equation: the "surface density" of your walls. Based on that, you can then calculate how big your air gap needs to be, in order to get the MSM resonant frequency down low enough (one octave below the lowest tone you need to isolate), and you are done!
So there's a method here, and even though there's no simple answer to your question, you can still use that method to get to the answer. So break out your pen, paper, and calculator, and have at it!
Is it better to rip out whats there and build besa block wall for starters?
It might be, but I doubt your budget could handle that. It might be just as good, and lower cost, to add an extra layer of drywall right on top of what you have already to complete your outer leaf, then build a block wall for your inner leaf. Concrete block is great stuff for isolation. Lots of mass, and rigid.
Yep got it (I think I read too much of your handbook in one day and got myself confused)
But you are only just getting started! There's a LOT more to go still! Acoustics is a big subject.... If you are confused, then that's a sure sign you are on the right track.
(If you would have said that you fully understand it all, then I'd be VERY worried!)
So I can use the existing reverse cycle?
Sure! Why not? You already have it, it works, I'm assuming the evaporator (indoor unit) is reasonably quiet... so there's no reason NOT to use it.
Won't there be issues with oxygen (as the reverse cycle recirculates air rather than using fresh?)
Right! Becuase it only covers the H and AC parts of HVAC. It does nothing for V, which is a completely different thing.
Or is the level of isolation that I can afford not going to be "that airtight"?
Oh, it's going to be very much airtight! Twice over, in fact. Each one is going to be a full hermetic seal. So yes, you certainly do need the V part: Ventilation is what feeds you fresh air (oxygen) and takes away the stale air (CO2), so that you can stay alive.
Now here's the problem: In order to get high isolation, you have to have those two fully airtight massive leaves around you. But in order to breath, you have to knock huge holes through the leaves to get enough airflow. Ooops! If only people didn't have to breathe, isolating a room would be so much easier....
But you do have to breathe, so you do need to knock huge holes in the walls.... so you need to do something to stop the sound getting in and out through those holes, while allowing the air to get through.... You need "silencer boxes". Same basic principle as the muffler on your car, but on a much larger scale. Silencer boxes in home studios usually look like this:
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http://www.johnlsayers.com/phpBB2/viewt ... 25&start=2
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http://www.johnlsayers.com/phpBB2/viewt ... =2&t=13821
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http://www.johnlsayers.com/phpBB2/viewt ... 2&start=16
It's just a large box, made from a couple of layers of massive material (often OSB or MDF), and with several baffles inside to force the air to take a long convoluted route while blocking sound, and lined with 1" duct liner all over.
There are rules of thumb and equations for figuring out how big to make your boxes, based on air flow volume, air flow velocity, static pressure, duct diameter, insertion loss, and other things. You'll get to doing all that fun math at some point in your design. And since you work in the industry, you probably already know some of it, so it won't be such a big issue for you as it is for many others. HVAC is a major part of studio design, and is often completely forgotten about initially... But it's rather important!
Again thanks, and please let me know anything to make this easier for you guys on your end. I'm new to the forum world
Photos of the location, diagrams of what you are working on, and an accurate model of what you plan to do, done in SkethUp, would be very useful. Then we can sort of "look over your shoulder" in the design process, and keep you on track.
- Stuart -
What part of the neighbor's house faces towards your roaring hurricane studio? Are there any windows in that side? Please don't tell me that it's their bedrooms facing you, and the like to sleep with their windows open, and they have a small child who wakes up at the drop of a pin.... That's about the only way you could make this worse than it already is....
That's a problem. Your PDF file shows the length as 5.9m but does not mention the width. I'll assume 4m. So you have about 24m2 that you need to isolate to massively extreme levels. That means you plan to spend no more than $400 per square meter, (give or take a few). I have designed a few studios for customers in Australia, and they tell me that it costs them around $1000 to get decent isolation with fairly good acoustics inside. So you are already budgeting less than half of the going rate in Oz. But those customers were only looking for around 50 to 60 dB isolation, and you need a hundred to a thousand times more. I think you see what the problem is...
Maybe you could climb through the ventilation ducts? 
From what I can see their dwelling is about 3 metres away from the back of the shed and I don't think it's a bedroom.