Hi
After many months of reading these wonderful forums, I’ve finally reached a point where I feel I need to get some input on my project.
I’m in the planning stage to have a 6m x 9m Colorbond steel shed built which I intend to use for an office/music room. It’s a portal frame shed with a wall height of 2.7m, rising to a peak height of 4.1m at the gable. It has a single 2.1m x 2.1m glass sliding door, and 4 1.5m x 0.9m windows. For my quote I’ve chosen the ‘fully insulated’ option, which is simply a foil thermal insulation specifically for sheds which conveniently also serves as quite a good condensation/moisture barrier. I’m also getting the vermin proofing option, which is a plastic channel which the sheeting sits in and which forms a good protective barrier from vermin and dirt getting in. I’ve asked if I can specify thicker glass for the windows, but I haven’t had that confirmed yet – and it’s probably a bit of a waste of money because they’re not airtight, and nor is the structure they’re attached to.
I’m well aware that a steel shed is one of the least ideal structures to try to isolate. Well, that’s not strictly true I suppose – I could ignore it and build whatever I wanted to inside. Sadly I don’t have enough money to do that, and also, I will use the shed as my office and living area easily as much as I will be making noise in it that needs containing. So I want my high ceilings. I want my windows. And I want to open them! To do all of that with a fully decoupled MSM is prohibitively expensive, and impractical for the type of room I’m planning/needing.
So how much noise are we talking? I play drums, bass guitar, electronic music. Also guitar etc, but the bass SPL is obviously the bigger problem. How loud? Drums max 115db, and rarely that. I would say 90 - 95db would be the loudest I’d feel like existing in for long. And an average high level sound would be 75 - 85db. Having been a demon for loud music when younger, I’m less inclined to inflict that sort of punishment on my eardrums these days.
What are my goals? I want to achieve 30db isolation outside the shed. Reason for this relatively low figure is that I live in a regional area, and the area is all half acre and acre blocks, and then farmland. Houses are staggered on the blocks too, so my nearest neighbour is close to 50m away, and their living area is on the other side of their house, about 65m away. There’s only about 6 - 8 houses that could physically hear anything before distance makes my noise practically ambient. I will record in my room, but not often or critically, and I don’t care if noise comes in. There’s no planes here – just birds, insects (can be incredibly loud) and rain, and the occasional car in the cul-de-sac. So my sound situation isn’t that bad, even despite the wonderful amplifier (shed) I’m planning to build. If I was a less considerate and less private person, I could probably get away without any isolation or complaints.
The shed will be fully detached from our house and built on its own slab. Our street is on a hill which seems to be made entirely of bluestone. Last year we had a carport installed and with a Bobcat drilling the holes in solid rock with a large diamond tipped post hole drill, we could neither hear anything or feel any vibrations from inside our ensuite which is 3m away from the hole that was being drilled. So I’m not concerned about ground borne vibration or noise. Also, the neighbour had an 18th party for their son with 100 guests drinking and partying in the back yard last year. We didn’t hear anything inside our house, and had to go outside to hear if the party was still going. Even then it was faint. So we’re pretty lucky that we don’t live in a big echo chamber. Not many reflections happening here.
I think that’s all the info I can give about the structure. I suppose I should say I’m located in Queensland, Australia. Near Toowoomba to be more specific.
I’ve had a few thoughts for what I want to do in terms of lining the shed, but I mostly come back to a single solution which ticks most boxes for me – sound isolation being only one of these boxes.
I plan on installing RSIC clips at 600mm centres on all the wall girts and roof purlins. There are 4 girts on each wall, and a similar number of purlins for the ceiling. I estimate using somewhere in the vacinity of 350 clips which should keep me well below the 26lb acoustic load capacity, even if I use 2 layers of 16mm firecheck. Furring channel will obviously go on the clips, and a single layer of 16mm firecheck will be attached to the furring channel with 32kg/m3 50mm poly batts going in behind the sheet. The portal c-channels will be sheeted around in a similarly decoupled manner. I will use acoustic caulk to seal everything. For the windows and door I will make removable plugs, with 2x16mm firecheck. These will only really be in place when I plan to make loud noises. When in place, the room will be airtight.
My budget for all of this is $7k.
Now for my questions:
1: Will this be enough isolation to achieve in the ballpark of 30db TL, or is it a case of ‘no chance’, back to drawing board?
2: Am I correct in thinking of this system as a partially decoupled dual leaf system?
I know I’ve read John’s and others’ suggestions that a steel shed is not airtight and can, for isolation purposes, be ignored as a leaf. That makes sense to me if the goal is 70+db isolation - just ignore it and create a structure inside it. I can’t help but think, however, that when we’re talking about 30 - 40db isolation, the mass of the steel boundary will have SOME effect, even if it’s not airtight. Whether it’s positive or negative impact, the structure will act as a system won’t it? After all, the Colorbond sheeting has a mass of ~4.5kg/m2, and that’s not including the structure supporting it. That’s 2000kg+ of mass for the sheeting alone.
I know that a bigger problem with the sheeting is its resonance in terms of sympathetic vibration and poor isolation, but will it actually function as mass in a MSM system? In my case it would go from the outside in: 4.5kg/m2 Mass > foil insulation > girts/purlins > 32kg/m3 poly batts > RSIC > Furring Channel > 16mm firecheck plasterboard. There will be an air gap between the firecheck and the colorbond – something around 100mm. It will have 50mm of poly insulation, but it will be kept against the firecheck, so there will still be an actual air gap of around 50mm. Which leads to another couple of questions.
3: Does 32kg/m3 insulation actually act to couple the firecheck to the structure if it touches the girts/purlins or portal frames? I’m primarly thinking of it as adding mass to the inner leaf, rather than as ‘air-gap-expanding’ lower density fibreglass insulation. I might be way off base there.
4: On that note, should I put lighter insulation in to fill the air gap completely (but not compressing it)? I believe the foil insulation prefers an air gap to work properly, and my thermal considerations are equal weight with isolation considerations. But if there’s 3 - 6db in it, maybe it’s worth it. I can’t see that though – it’s not like I have an ideal MSM system.
5: Should I even bother with the foil insulation on the shed? The acoustic insulation alone would have pretty decent thermal rating I expect, and the firecheck combined should provide adequate thermal insulation. Another bonus with this that I can add stiffening and damping/mass to the sheeting from the inside, which would drop its resonance significantly. I would save nearly $3k through omitting the foil, but it is also a good condensation barrier and will damp the metal to some extent. Sigh. Nothing is ever straightforward.
6: If the poly batts couple the wall completely and therefore negate any benefit of using RSIC clips, am I better off omitting the clips and just jamming as much mass into the wall space as I can fit, or am I better making certain the internal mass is de-coupled, perhaps at the expense of a little bit of mass. Given that I’d need to double the mass to make much difference, I think the latter is more logical. On the other hand, making it one big leaf of bulk would perhaps lower the resonance of the sheet metal and damp it reasonably well.
I know that I can always apply Green Glue and another layer of 16mm firecheck without overloading anything. As long as the window plugs match it and it’s airtight and decoupled, surely that’s got to have a reasonable chance at a halfway decent TL performance. Trouble is that to go this extra step bloats me $10+k without blinking. If it turns out I don’t need that, then I’d rather save the money. Of course, if I do one layer and find I need two, I’d rather know I CAN do that, so I’ll always engineer it for 2 x 16mm firecheck (and an extra 13mm standard sheet also probably :D ).
It’s just a balance of having adequate isolation and not spending improperly or wastefully. Besides, I’ve got to have some money left over for some sound treatment. Superchunks, broadband absorbers and a some clouds I think - but I’ll plan this once I get a better of what issues my space will present me. In any event, keeping less SPL contained in the room means there should be a bit less to deal with right?
Thanks for reading this. I tried to keep it concise and in-line with forum rules. So hopefully I haven’t omitted anything/ transgressed too badly. There are many more questions, of course, but they’re largely derivative of those above.
Any assistance anyone can give will be very much appreciated!
Thanks
Phill
Can I stop 30db from getting out of a three bay shed...
Originally posted at johnlsayers.com, topic 18693.
Hi Phil, and Welcome! :)
So you also want to eat your cake. And have it too! :)So I want my high ceilings. I want my windows. And I want to open them!
I think you are underestimating your drums, considerably! I've never met anybody that can play drums at 75 dB. Maybe just with soft wire brushes, very gently, on a very relaxed ballad... but I wouldn't call that typical "playing drums". I suspect your normal playing is more likely around 100, and your really quite playing around 90. Drums played quieter than that just don't sound much like drums... more like soggy cardboard boxes... :)Drums max 115db, and rarely that. I would say 90 - 95db would be the loudest I’d feel like existing in for long. And an average high level sound would be 75 - 85db.
The metal sheeting plus insulation will get you around 15 dB or so. So you need another 15 beyond that.What are my goals? I want to achieve 30db isolation outside the shed.
Work it backwards, using the typical decay of sound over distance: about 4-5 dB per distance doubling in the real world (6 dB, theoretically). Call it 5. So assuming 110 inside, less 30 gives you 80 dB at one meter from the wall. 75 at 2m. 70 at 4m. 65 at 8m, 60 at 16m. 55 at 32m. 50 at 64m. So is a level of 50 to 55 acceptable for your neighbors? That's the question. To answer it, set up a good full-range speaker, play drums through it loudly right where the shed will end up, and adjust the level until you get 55 dB at your neighbors front door, then ask them if that is OK. If not, then you might need more isolation.so my nearest neighbour is close to 50m away,
Theoretically, yes it should, provided that everything is done perfectly. From mass law alone, two sheets of 16mm drywall should get you 33 dB of isolation, plus a little bit extra from the tin, so maybe you'd be approaching 40 dB... EXCEPT at the resonant frequency of that MSM system. I'm not sure what that would be without knowing what type of metal the shed will be covered with, and how thick it is. Probably somewhere in the region of about 50 Hz to 150 Hz. Around that frequency, the isolation will be greatly reduced, practically zero.1: Will this be enough isolation to achieve in the ballpark of 30db TL, or is it a case of ‘no chance’, back to drawing board?
If you do it right, RSIC plus hat channel counts as "almost fully decoupled". The resilience of those rubber inserts in the clips is pretty good, so it can get you fairly decent decoupling.2: Am I correct in thinking of this system as a partially decoupled dual leaf system?
Yes it will. The cavity does not need to be sealed in order for the system to resonate. Sealing the cavity improves things greatly, of course, but even two sheets of drywall out in the open with no sealing at all will exhibit some low level of resonance, especially if the gap between them is small. So yes, the tin will have a slight effect on isolation: it will be negative at the resonant frequency, zero from there up to 1.414 times the resonant frequency, reasonable at about 2x resonance, and good above 3x resonance.Whether it’s positive or negative impact, the structure will act as a system won’t it?
Ahhh! That's what I needed to know :) So, for a 10cm air gap, resonance will be at 97 Hz, null isolation at 136 Hz, reasonable isolation at 194 Hz, good isolation at 292 Hz. If you fill the gap with insulation, then that changes to: Resonance = 69.6 Hz, null at 97 Hz, reasonable at 139 Hz, good at 208 Hz.After all, the Colorbond sheeting has a mass of ~4.5kg/m2, ... There will be an air gap between the firecheck and the colorbond – something around 100mm.
The supporting structure is not part of the resonance equation. It has an effect below resonance (due to stiffness), but the effect above resonance is negligible, since the boundary conditions are already assumed in the equations.and that’s not including the structure supporting it.
Yes, to a certain extent. The above calculations assume a sealed wall, and the resonant effect would be less for an unsealed wall (and therefore the isolation would also be less).but will it actually function as mass in a MSM system?
The insulation is ignored in the calculation of depth of the air gap, since it is mostly air anyway. However, it is still considered on the equations in a different place, since it changes the way the air behaves. So for the purposes of the cavity depth, forget about the insulation: your depth is 100mm.It will have 50mm of poly insulation, but it will be kept against the firecheck, so there will still be an actual air gap of around 50mm.
No. As long as you just lay it in normally, without compressing it, then you are fine. It would only form a bridge if you force it in, compressing it considerably, so that it is putting pressure on both leaves.3: Does 32kg/m3 insulation actually act to couple the firecheck to the structure if it touches the girts/purlins or portal frames?
The mass of the insulation is irrelevant for the purpose of calculating the resonant characteristics. It is considered in the sense that it changes the behavior of the air from adiabatic to isothermal, and increases the effective depth of the cavity, as well as damping various types of resonance inside the wall. The overall effect is quite substantial. The factor that matters most is not the mass or density of the insulation, but rather the gas flow resistivity. That's sort of a measure of how much it impedes air moving through it.I’m primarly thinking of it as adding mass to the inner leaf, rather than as ‘air-gap-expanding’ lower density fibreglass insulation. I might be way off base there.
If you use fiberglass insulation, the density should be about 30 kg/m3. If you use mineral wool, the density should be about 50 kg/m3. Once again, it's not the density per se that matters: it is the gas flow resistivity. Most manufacturers don't bother measuring or publishing that figure for their products, but fortunately there is somewhat of a relationship between mass and gas flow resistivity, that varies depending on the type of insulation.4: On that note, should I put lighter insulation in to fill the air gap completely (but not compressing it)? I believe the foil insulation prefers an air gap to work properly, and my thermal considerations are equal weight with isolation considerations. But if there’s 3 - 6db in it, maybe it’s worth it. I can’t see that though – it’s not like I have an ideal MSM system.
That's a good question! Not sure quite how to answer that. The issue with the vapor barrier is important, and you should take into account that the vapor barrier always goes on the warmer side of the wall, up against the leaf surface. For you, I guess that would be the outer leaf, up against the metal, whereas in a cold climate it goes up against the inner-leaf: So check with local building contractors and local code, to find out where that has to go, and what type of barriers are considered acceptable in your area. As to the question of whether or not you need the foil: Hmmm.... I would suggest asking around local contractors for that one as well.5: Should I even bother with the foil insulation on the shed? The acoustic insulation alone would have pretty decent thermal rating I expect, and the firecheck combined should provide adequate thermal insulation. Another bonus with this that I can add stiffening and damping/mass to the sheeting from the inside, which would drop its resonance significantly. I would save nearly $3k through omitting the foil, but it is also a good condensation barrier and will damp the metal to some extent. Sigh. Nothing is ever straightforward.
No!!! :shock: Definitely not. You have a workable MSM system, so keep it that way: fill the cavity with exactly enough insulation to do the job. If the cavity measures 100mm, then put in exactly 100mm of insulation, and make sure it doesn't get compressed more than about 10% to 20%.6: If the poly batts couple the wall completely and therefore negate any benefit of using RSIC clips, am I better off omitting the clips and just jamming as much mass into the wall space as I can fit,
Logic sometimes doesn't work too well with acoustics! :) Or it does, but only when you consider all the facts: With a single-leaf system you do, indeed, need to double mass to get any useful increase in isolation, and even then it is a measly 4 or 5 dB in the real world. But with an MSM system, doubling the mass can get you far more "bang for the buck", so to speak, since MSM isn't governed by mass law: Resonance plays a huge part. So you can get a large increase in isolation for a smaller increase in mass... but only at some frequencies! That's the thing with resonance: it throws in the factor of resonance. An MSM wall is actually WORSE than mass law at the point of resonance, but much better once you get higher up the scale. In fact, you can get between 12 and 18 dB increase in isolation for each mass doubling, and each frequency doubling, with MSM, but its only 6 dB per mass doubling or frequency doubling with mass law. Confusing! So it pays off big time to ensure that you really do have an MSM system, and that the resonant frequency is lower than the lowest you need to isolate.or am I better making certain the internal mass is de-coupled, perhaps at the expense of a little bit of mass. Given that I’d need to double the mass to make much difference, I think the latter is more logical.
Don't forget to take into account that mass is a two-way street with MSM: doubling the mass makes a much bigger difference than for mass law.... but then again, so does HALVING the mass.... the numbers I gave you above were for two layers of drywall: They are no nearly so exciting for just one layer........Of course, if I do one layer and find I need two, I’d rather know I CAN do that,
yup...so I’ll always engineer it for 2 x 16mm firecheck
... and also for your HVAC system. You can't live inside a hermetically sealed tin can for very long.... you kind of do need to breath in there, and also to control the temperature and humidity.Besides, I’ve got to have some money left over for some sound treatment.
Well, yes, that is true, but you also need to know what frequencies you are dealing with...Superchunks, broadband absorbers and a some clouds I think - but I’ll plan this once I get a better of what issues my space will present me. In any event, keeping less SPL contained in the room means there should be a bit less to deal with right?
:thu: - Stuart -Thanks for reading this. I tried to keep it concise and in-line with forum rules. So hopefully I haven’t omitted anything/ transgressed too badly.
Thanks very much Stuart - for both the welcome and the detailed response! So very much appreciated.Hi Phil, and Welcome! :)
Yup. I confess I wrote that to see if I could get a nibble from you. I think it was you (if not you then someone) said on a window plug thread something along the lines of... ‘next you’ll want to be able to OPEN the windows!’ So, yeah... sorry about that. :)So you also want to eat your cake. And have it too! :)So I want my high ceilings. I want my windows. And I want to open them!
Sorry – poorly worded on my part. I mean my drums will be 115db on average. 90 - 95db would be guitar/bass/synth/etc. 75-85db is just listening to music and mixing volume type stuff. I know drums aren’t that quiet. :) I hit 132db once, measured just on the port of the bass drum. But I’m not Dave Grohl... can’t keep hitting them that hard for long. So yes, I think about 110-15db for drums is a pretty reasonable estimate. If I go louder sometimes, I’m not worried about having isolation enough to cover it.I've never met anybody that can play drums at 75 dB.
The frequency where it won't isolate is a concern. Infrasonic frequencies aren't much bother to me here but 60hz is one of those boomy frequencies that travels a long way and annoys people. I also find 125hz a pest also. Naturally these two bands are prominent in kick, toms, and bass guitar so I want to try to tune the system to be isolating as much as possible there. ...And naturally, they’re close to the frequencies where my system will have least isolation. I need to shift that system resonance down. I can make more air gap – probably 200mm, maybe a little more if I get my thinking cap on. That’s definitely got to help, yes? (the extra air gap... not my thinking cap - it’s patently useless) Is there any merit to damping the sheet metal? I’m investigating vapour barriers/insulation at the moment. I’m not a fan of the aircell shed stuff they use a lot of for sheds in Aus. It’s great if you want a workshop, but becomes a waste of money for what I want to do. I’ve got a couple of options. First is to use Acousticon. To me this serves a few purposes. First, it’s marginally cheaper than aircell, though the wire mesh will probably bring it equal. Second, it should damp the resonance of the sheet metal quite well, shouldn’t it? Third, it will muffle the sound of rain on the tin. Fourth, it’s got a better R value than the aircell. So it’s an attractive option. The shed builder says he has used it before, but to be aware that because it’s so thick it can make the sheeting look ‘bulgy’ between the screws. I already want him to use more screws to increase the rigidity of the sheeting, so I’m not too overly about that and think it's potentially a good thing. Second option is much cheaper and is simply a foil sisalation (sarking/wallwrap/whatever it’s variously called throughout the world). It serves as a vapour barrier and gives a reflective R value. I don't think it will damp the sheet metal very well, however I’m not sure if it’s of huge benefit to damp the sheet metal anyway. Intuition tells me so, but I’m aware intuition is of zero value in acoustics. I have an idea that I could use in conjunction with the sisalation. Hard to explain, but if you have a sheet metal shed wall and rap it sharply with a knuckle, it reverberates a great deal. But if you press quite hard in the middle of the sheet and repeat the sharp rap, it is quite well damped as far as sympathetic vibration is concerned. Is there any merit to implementing points behind behind each ‘stud’ (channel) which place pressure on the sheet metal to stiffen and damp it? I know it would deaden the vibration, but is doing so going to have a useful effect on my MSM system? It’s easy to do, and if it isn’t harmful to my plan I’ll do it for the sake of quieting down the sheet metal. It may well give me most of the benefit of going the Acousticon route by doing this. Obviously it won’t make the rain quieter (not all that concerned to be honest), and it won’t have quite the same R value (there’s going to be 200mm of decent batts anyway so hardly an issue, unless I’m missing something?).So, for a 10cm air gap, resonance will be at 97 Hz, null isolation at 136 Hz, reasonable isolation at 194 Hz, good isolation at 292 Hz. If you fill the gap with insulation, then that changes to: Resonance = 69.6 Hz, null at 97 Hz, reasonable at 139 Hz, good at 208 Hz.
It’s pretty hard to research batts here in Aus. The fluffy type batts give you R value, but not density figures. Few give the total weight of the packed batts either. The ones that do give that figure I can calculate the m3 density. It’s definitely the m3 density that should be ~30kg right? All of the expensive high density commercial batts are in the vacinity of 20 - 30kg/m2, which is great for room treatment, but completely unnecessary for in-wall, if I understand what I’ve read so far on here. I’m basically just trying to find the cheapest fibreglass/mineral wool I can find that gives me 30/50 kg/m3. If anyone knows of a CSR Bradford or Fletcher product in Aus that is the ticket, I’d be much obliged if you'd let me know. I’ve read the topics that talk about the gas flow resistivity of such products, but it’s all a bit obtuse to my untrained eye.If you use fiberglass insulation, the density should be about 30 kg/m3. If you use mineral wool, the density should be about 50 kg/m3.
Remember that door and those windows? :) That’s my plan. Close and plug them when I want to play drums or loud other stuff. It’s not a major problem for me to unplug a window and do an air refresh whenever. Sounds silly, but it’s free and easier to design. It’s only a hobby space and I can live with doing it that way. Is that reasonable? I plan to install a split system air con, but I’d rather wait a while for that.... and also for your HVAC system. You can't live inside a hermetically sealed tin can for very long.... you kind of do need to breath in there, and also to control the temperature and humidity.Besides, I’ve got to have some money left over for some sound treatment.
I won’t really know those properly until I get the thing built and tested. I haven’t tried to ascertain whether the ratios of the room are going to be useful or not. 6mx9m with the vaulted ceilings is a reasonable space volume wise - around 6000 usable internal cubic feet. It’s worth trying to preserve the ambiance of that space, hence me wanting to isolate it rather than build a small drum room – even though I could more easily get excellent isolation by doing the latter. Big room is just so much nicer. I’m actually quite excited about the prospect of the room. Probably a huge challenge to make it a flat mixing environment, but it should make a good live room. Thanks again for your responses Stuart. They’ve helped me stop dashing between quite so many design concepts. I can concentrate on doing one properly now. PhillWell, yes, that is true, but you also need to know what frequencies you are dealing with...
Ahhhh! Ok, that makes more sense.So yes, I think about 110-15db for drums is a pretty reasonable estimate. If I go louder sometimes, I’m not worried about having isolation enough to cover it.
Don't you just love Murphy? I think he must be the patron saint of studio builders, or something... There must be several corollaries to Murphy's Law, specifically for us: things about the most prominent frequency always occurring at the most undesirable point, and stuff like that....Infrasonic frequencies aren't much bother to me here but 60hz is one of those boomy frequencies that travels a long way and annoys people. I also find 125hz a pest also. Naturally these two bands are prominent in kick, toms, and bass guitar so I want to try to tune the system to be isolating as much as possible there. ...And naturally, they’re close to the frequencies where my system will have least isolation.
Yep, it sure will help. A 20cm air gap is pretty decent: And I'm sure your thinking cap is nowhere near as useless as you imagine!I can make more air gap – probably 200mm, maybe a little more if I get my thinking cap on. That’s definitely got to help, yes? (the extra air gap... not my thinking cap - it’s patently useless)
It's probably worth doing if you can do it simply and inexpensively.Is there any merit to damping the sheet metal?
Do you have a link to that? I'm not familiar with it, and the first bunch of hits on Google turn up info on a drum manufacturer!First is to use Acousticon
Actually, that would not be a good idea! Yes, it will reduce some low frequency resonance, but my stretching it tighter, you are basically driving the resonance UP the scale, not down! So now the tin will resonate at higher frequencies, up there in the part of the spectrum where you have lots of stuff going on... I like the idea of damping the metal, but I'd suggest some type of rubber compound to do that. Perhaps some type of spray-on rubber might be worth experimenting with.But if you press quite hard in the middle of the sheet and repeat the sharp rap, it is quite well damped as far as sympathetic vibration is concerned. Is there any merit to implementing points behind behind each ‘stud’ (channel) which place pressure on the sheet metal to stiffen and damp it?
Right ! Kilogram per CUBIC meter. That's the real measure or density.The fluffy type batts give you R value, but not density figures. Few give the total weight of the packed batts either. The ones that do give that figure I can calculate the m3 density. It’s definitely the m3 density that should be ~30kg right?
That is SURFACE density, which isn't the same thing: It tells you how how much one square meter weight when installed in a wall, in the normal thickness. But I must say, 20-30 kg/m2 seems REALLY high! Assuming those batts are 10cm thick, that implies the true density is up around 200 to 300 kg/m3! That is MASSIVELY dense for insulation batts: That's more like density for the entire WALL; including the studs and drywall too! Are you sure you got those numbers right? But anyway, there's an easy way to figure out the density roughly: Measure the dimensions of the package so you can calculate the volume, and then weigh the package. For example, if you have a package that stands 80cm high, 1.2m long and 60 cm thick, that would be a volume of 0.576 m3. If the package weighed about 15kg, then the density would be roughly 26 kg/m3. Etc. Of course, if the package is round, then you figure the volume for a cylinder...All of the expensive high density commercial batts are in the vacinity of 20 - 30kg/m2
Right!I’m basically just trying to find the cheapest fibreglass/mineral wool I can find that gives me 30/50 kg/m3.
Gas Flow Resistivity ("GFR") is the actual physical property of the insulation that REALLY matters for acoustics, not the density. GFR just refers to how the insulation resists the flow of air moving through it. It's a relationship between the pressure applied across the sample and the amount of air that actually moves through it, and is measured in Ralys. It is somewhat analogous to resistance and impedance in electrical circuits, measure in ohms. But since most manufacturers never even bother measuring GFR for their products, it's really hard to find those numbers! Fortunately, it turns out that there's a rough relationship between the density of each type of insulation and the GFR, and even though it isn't a linear relationship, it's good enough for our purposes. There's a broad enough range of useful GFR values that covers a bunch of different densities, where 30 and 50 are the optimum points, bout you'd still be fine at 25 or 35 for fiberglass, or 45 to 55 for mineral wool. The performance tapers of gradually on each side, so as long as you are reasonably close to the optimal points, you'll still be OK.I’ve read the topics that talk about the gas flow resistivity of such products, but it’s all a bit obtuse to my untrained eye.
Ummmm.... the simple answer that you don't want to hear is "No, it ain't reasonable at all!". For several reasons. Musical instruments, some microphones, and some electronic gear MUST be kept at fairly constant temperature and humidity: If either of those changes, then so does the tone! Get two identical snares, tune them identically, then put one in the freezer and take the other into a hot, steam-filled bathroom. After ten minutes, take them both out and and play them.... compare the way they sound.... :shock: :!: You'd be surprised just how much changes in humidity and temperature can mess up your gear, mics and above all your instruments. If you are opening and closing doors and windows regularly to ventilate, then you will have wild swings in both temp and humidity. You'll never be able to get the drums, mics and gear sounding consistently the same. Ideal humidity for instruments is around 45% RH, and ideal temp around 21°C. If it swings too much from that, you'll be fighting the changes all the time. It makes much more sense to have a constant and controlled flow of air that is regulated to stay close to the ideal temp and humidity. Hence HVAC is rather important!That’s my plan. Close and plug them when I want to play drums or loud other stuff. It’s not a major problem for me to unplug a window and do an air refresh whenever. Sounds silly, but it’s free and easier to design. It’s only a hobby space and I can live with doing it that way. Is that reasonable?
Great, but a split system only takes care of part of the HVAC acronym. It handles the "H" and "AC", but does nothing for the "V": ventilation. In addition to just cooling and dehumidifying the air, you also need to replace it several times per hour: All of the air in the room needs to be exhausted to the outside, and replaced with fresh air from outside. You have to get rid of the CO2 and odors, and bring in O2 without odors! :) So in addition to your mini-split, you will also need some ducts, silencer boxes and fans. And they must be dimensioned correctly to get the right volume of air flow at the right speed, while also retaining the acoustic islation. HVAC is probably the single most overlooked aspect of home studio builds, and the single most important, form the point of view of staying alive, comfortable and in a good state to make music, as well as keeping the instruments, mics and gear sounding good and consistent, in a controlled environment.I plan to install a split system air con,
Welll..... that isn't really true: you can (and should!) predict the response and behavior of the room. That's a big part of what acoustic design is all about. I agree that you won't know precisely until the room is built, but you still can predict things in advance to get a good overall idea of where your problems will be, and make all possible adjustments to improve and optimize that, before you even lift the hammer for the first time. It's easy and dirt-cheap to correct modal issues while the room is still on paper, but really hard and expensive to fix them after the room is already built...I won’t really know those properly until I get the thing built and tested.
You really should to that! It's a very important aspect of your room. Bad modal response can make the room totally unusable... :shock:I haven’t tried to ascertain whether the ratios of the room are going to be useful or not.
Yes, but a lousy space, modal-wise... 6 and 9 are both multiples of 3, so all your third-order modes in length will line up perfectly with all your second-order modes in width, causing you endless headaches and leading you to continuously ask whey things just don't sound good, and why your mixes don't translate well ....6mx9m with the vaulted ceilings is a reasonable space volume wise
Absolutely! But it is also rather short-sighted to not want to make it as as good as it can be, by minimizing modal issues in the design stage, instead of trying to patch them up with heaps of layers of treatment afterwards. IMHO, at least.It’s worth trying to preserve the ambiance of that space,
Absolutely! Provided that it has no overlapping modal issues, and good modal spread. A perfect cube room with sides of 6m each would be even bigger than your room, in terms of volume, but it would be an acoustic disaster, and absolutely unusable as a studio, since all modes in all directions would line up perfectly with each other. Volume is not everything...Big room is just so much nicer.
If you don't check your ratio, shape, size and dimensions, it won't make a good live room OR control room! I was recently called in to fix the acoustics of a church under construction, that looked great on paper, with really nice architecture, but the church leaders were noticing that it was going to be terrible acoustically, before it was even finished. The architect admitted he didn't know much about acoustics, even though he was an expert on structures, shapes, forms, lines, styles, etc. But he made the stage wall semi-cylindrical, and the sanctuary square... it sounded terrible.Probably a huge challenge to make it a flat mixing environment, but it should make a good live room.
Great! - Stuart -They’ve helped me stop dashing between quite so many design concepts. I can concentrate on doing one properly now.