Is there a magic size?

Haha that makes sense. I’m going to try and get as much light in as possible. Thinking a couple of floor to ceiling or quite long panels of glass windows along the side where the door is. Probably not where the first reflection points will be though, I guess it would be wise to avoid putting a window where your first reflection points are?

elastic wrote:

Haha that makes sense. I’m going to try and get as much light in as possible. Thinking a couple of floor to ceiling or quite long panels of glass windows along the side where the door is. Probably not where the first reflection points will be though, I guess it would be wise to avoid putting a window where your first reflection points are?

Remember your glass will be very expensive, you'll probably need a pane 12-15mm thickness glass in each leaf. So I'd get a quote before you settle on anything. With regards to first reflection points, you caaaan have glass there but you will be to angle it so it redirects the sound to the rear wall, so it might not be feasible. I would have the windows just past the soffit wings (are you soffit mounting speakers?) and definitely not opposite each other on opposing walls. You could also have a window on the front wall above desk height in between the speaker soffits. You might notice that it's best to fully design your studio before putting the windows in the design, to prevent you making a mistake in the location. Dan

Yes will be soffit mounting the speakers. Another thing I need to figure out ha! Yeah I forgot to say I will have a window in between the soffits so I can look out there while I work. No windows on the left wall as it’s going to be quite close to a fence so pointless and no windows on the back wall either. So there’s no way of opening any windows in a two leaf system I imagine? I’ve ordered my spl meter today. Went for this one - https://www.amazon.co.uk/Handheld-Measurement-Analysis-Industry-Included/dp/B01M32WX3H

So I took my reading with my new spl meter, slow and c rating - In my current studio where I sit, it’s about 95dbc when I turn it up loud, generally I work between 80-90dbc but I will go with 95 as my reading as I do go to that level sometimes. In the garden where the new studio will be built it measured 50dbc at 9pm - fair few birds chirping around and faint distant car hum from roads. I’m in England and this is what the government website says - The permitted noise level using A-weighted decibels (the unit environmental noise is usually measured in) is: 34 dBA (decibels adjusted) if the underlying level of noise is no more than 24 dBA 10 dBA above the underlying level of noise if this is more than 24 dBA So would i be looking at about 35db isolation needed? (i did 50db plus 10 - then 95 - 60 = 35) That doesn't seem much isolation to me? Just struggling to get a grip on exactly what isolation I require. Apologies if this seems trivial or easy, I’m just not great at things like this. Thanks again

Did you measure on A-weighted or C-weighted, because the regulation says it needs to be measured using the A-weighted setting? If 50dBA is the quietest it gets on your area then you would indeed be legally able to produce noise of up to 60dBA at your border, so 35dB isolation, which is super easy to get. Whether or not that would be acceptable to you is up to you. You can basically pick the level you want to isolate. You may want to isolate more than that to keep your neighbours on side, even if there is no legal reason to do so. Dan

Ah I did dbc based on someone on here telling me to use ‘C’. Ok no probs, I’ll do another reading and report back. Yeah my goal is so that if I’m working at about 85db then my neighbours pretty much can’t uear it if they were to stand the other side of the fence. So I suppose my question is, how much isolation do I need for it to be barely audible at the fence (1m away the one side, 3m away the other end where the speakers will be)

Ah I did dbc based on someone on here telling me to use ‘C’. Ok no probs, I’ll do another reading and report back.

Right. That "someone" would be me! :) This is often confusing, so let me explain: "A" and "C" weighting are two different methods for adjusting the sensitivity of the meter to different frequencies. "C" is much more sensitive to low frequencies. There are other possible weightings too, but A and C are the most common. Here's a graph that shows the difference: As you can see, in the low end of the spectrum, "A" (green curve) is much lower than "C" (black curve). At 40 Hz, for example, "A" is about 26 dB less sensitive than "C". On the other hand, in the high end "A" is a slightly MORE sensitive than C, between about 2 and 6 kHz. The obvious question is: WHY? Simple: That's the way our ears work! Our ears have different sensitivities for loud sounds and quiet sounds. The "C" weighting curve closely mimics how our ears respond to loud sounds, and the "A" weighting curve closely mimics the way our ears respond to quiet sounds: our ears are a lot less sensitive to quiet low frequencies, than they are to loud low frequencies. So what does that mean for studios and isolation and legal regulations and sound level meters? Also very simple: In your studio, you will be playing loud music, and you want to isolate that loud music: Therefore, to see how loud you are and how much isolation you need, you MUST measure using "C" weighting, because that's the way people perceive sound. So you turn on loud music in your studio, set your meter to "C", and measure the level inside the room, then again outside the room. The difference is how much isolation are getting. Even though it is quiet outside, you CANNOT use "A" here, because you need to know the DIFFERENCE in levels, so you have to use the same scale for both: you cannot compare "A" and "C" readings, because they are in different scales. That would be like saying that you drove your car at 60 miles per hour in the USA, then drove it at 100 kilometers per hour in the UK, and since the difference is 40, you must have been going 40 cubic feet per minute faster.... :) You cannot compare readings on different scales, so when you are testing for isolation, you MUST do both on "C", even though one is quiet and one is loud. However, for measuring ambient sound (the low-level background noise around your building), you should measure using "A", since that's what is appropriate for quiet sounds. And also is the cops show up at your door with a noise complaint against you, you darn well better measure on "A", not on "C", because it gives you that 20 dB advantage in the low end, where drums and bass guitars live! So even if your music is loud outside, measuring on "A" will show it to be quieter than it really is... which probably helps you avoid a fine... :) Regulations for noise levels are almost always written for "A" weighting, often expressed as "dBA", because they are measuring low levels usually. Unfortunately, workplace noise exposure levels are also measured in "A", which is kinda dumb when you think about it, because the sounds in a factory are LOUD, and often have low frequency content in them (big machines making big "thumps" and "rumbles"). Realistically, there should be two scales for workplace exposure: one for loud sounds on "C", and one for low level sounds on "A". But the powers that be have decided that "A" is the only wya to measure, even at 100 dB.... go figure! So, getting back to your situation: if you want to check that you are legal, then measure using "A" weighting, and be thankful for the advantage it gives you. You must measure that way, because that's what the regulations use. But when measuring the isolation of your studio, and when calibrating your system, and when tuning your room, use only "C" weighting, because that's what your ears are really experiencing at typical studio levels. Hopefully, that clears up the confusion... If you want more details, then google "Fletcher-Munson curves", and also "equal loudness curves". Or ask, and I'll add some more info about that... :) - Stuart -

Thanks for such a detailed reply Stuart, thats great and easy to understand, appreciate it :D So, i work at about 90dbc in the current bedroom studio - Outside at home where my plot of land is, it reads 50dbc - So i require 40db isolation? What i'm after basically is that when I'm working in my new studio at between 80-90db, it will be barely audible or not all audible at by my neighbours fence (1m away)

elastic wrote:

Thanks for such a detailed reply Stuart, thats great and easy to understand, appreciate it :D So, i work at about 90dbc in the current bedroom studio - Outside at home where my plot of land is, it reads 50dbc - So i require 40db isolation? What i'm after basically is that when I'm working in my new studio at between 80-90db, it will be barely audible or not all audible at by my neighbours fence (1m away)

So filtering on from what Stuart says, measure again in the evening/night at on A weighting. This will give you a lower ambient level than 50dBC. Add 10dB to this for the legal limit. With regards to your question about being barely audible at the boundary, if you're producing 90dBC and outdoors is 50dBC then attaining 50dB of isolation will put you below the ambient levels and it should just blend into the background. I would just aim for 50dB isolation in your situation, which coincidentally is exactly the amount I'm aiming for myself. Dan

You were right - just measured at 11pm - Ambient noise in garden - 37dba / 45dbc I’m thinking a 2 leaf system will be the way to go. So going from out to in — 2 layers or gypsum, wood stud wall filled with a insulation like rock wool - air gap - studwall filled with rock wool, then 2 layers of gypsum again. Don’t know what density rock wool yet Don’t know what air gap size to leave yet I saw you mention a breathable membrane or something? Not sure where that slots in yet. Will re read your post tomorrow and try and work it out. I will make the 2 leaves a slightly different construction, I heard that helps. So the inner leaf could have different density rock wool or different thickness gypsum. Sound ok? Looking at using green glue to bond the 2 layers of gypsum together, again heard it was good stuff to dissipate sound waves. Feel free to add or hammer my thoughts! All help is welcome and appreciated. Willing to learn :) Thanks guys :D

So I’m thinking I need about 50db isolation. Now, my question is, do I actually need to do a room within a room system? Would I be better off using resilient channels or genie clips/RISC-1 clips, just like you said Dan before? What about doing 2 layers of acoustic plasterboard, stud wall with insulation, resilient bars with 2 more layers of acoustic plasterboard on the inside? Struggling to find out how much isolation that would give me. Some websites for acoustic plasterboard don’t tell you how much isolation they give you.

Now, my question is, do I actually need to do a room within a room system? Would I be better off using resilient channels or genie clips/RISC-1 clips,

I doubt you'd get 50 dB isolation like that. 40-something, probably, but getting over 50 with resilient connections is going to be problematic.

Some websites for acoustic plasterboard don’t tell you how much isolation they give you.

That's because plasterboard by itself is only part of the solution! It's how you use it, in combination with the rest of the building materials that you need, that defines what your isolation will be. One piece of plasterboard by itself can be tested to see how much isolation it will give, yes, but that won't tell you how much isolation the completed wall will give. Do yourself a favor: Forget "acoustic plasterboard", and just go with ordinary, common, fire-rated plasterboard. Sound waves cannot read the price tags on the materials you use, so they won't be impressed if you paid double the price for a certain amount of mass. Sound waves are stopped by mass, not by price tags. Don't be fooled by the fancy marketing hype put out by manufacturers who are only interested in selling really expensive products for questionable benefit. - Stuart -

Ah ok. Appreciate that advice. Back to the 2 wall method. And thanks for the heads up on the plasterboard! So, I’m thinking Wood cladding on the outside of the building - 2 layers of plasterboard held together with green glue 2x4” staggered stud with insulation Air gap - what size? 2x4” staggered stud with insulation 2 layers of plasterboard held together with green glue How does that sound? I still don't know the isolation values for each part of the wall, so i don't know if im overdoing it or undergoing it? E.g how much db reduction will standard fireproof plasterboard give me as part of this setup? Same with the air gap, the insulation, the wood cladding... As I understand it, it’s better to construct one of the walls a different density to the other? I have attached a pic of how i will build my walls. Thanks

elastic wrote:

Ah ok. Appreciate that advice. Back to the 2 wall method. And thanks for the heads up on the plasterboard! So, I’m thinking Wood cladding on the outside of the building - 2 layers of plasterboard held together with green glue 2x4” staggered stud with insulation Air gap - what size? 2x4” staggered stud with insulation 2 layers of plasterboard held together with green glue How does that sound? I still don't know the isolation values for each part of the wall, so i don't know if im overdoing it or undergoing it? E.g how much db reduction will standard fireproof plasterboard give me as part of this setup? Same with the air gap, the insulation, the wood cladding... As I understand it, it’s better to construct one of the walls a different density to the other? I have attached a pic of how i will build my walls.

Not preserved: IMG_2802.JPG

Thanks

You can use the MSM calculator http://www.johnlsayers.com/phpBB2/viewtopic.php?f=1&t=21770 to work out your estimated isolation with a fully decoupled wall. Don't include the cladding as part of your isolation calculation as it won't be sealed, as it requires a ventilation gap behind it. It may add a tiny bit of additional isolation but can't easily be calculated. Just find out the densities of the sheeting materials you will be using and drop them into the calculator. You don't need to have different densities really, you can add extra to one leaf if you want, but definitely don't reduce it on either. By the way you would usually replace the first layer of plasterboard with OSB3 or plywood, to provide structural support. If you don't you will need to provide many noggins and bracing. Also you can't have plasterboard on the outside of your outer leaf, it's not weather resistant. I've attached an image I found on the Internet of a standard cladded wall design. You'll see a breather membrane on the exterior sheathing, then battens screwed vertically to the face of it and cladding attached to the batten. In your case though you'll need to add a second timer frame wall on the inside to hold the inner sheathing (with its own structural sheathing or noggins / bracing), under the inner sheathing you put a vapour barrier in the UK, with this design. Dan

Great info. Thanks Re reading it many times to try and understand it. May I ask, what’s a ‘timer frame wall’? - edit - just re reading and guess you meant timber. Sorry haha That OSB you mention, should that just be on the outer leaf or both? In my head now, I’m going - Cladding / membrane / OSB / plasterboard / stud wall / air gap / stud wall / 2 layers of plasterboard My head is fried :horse: Haha! EDIT - oh so no plasterboard AT ALL on that outer leaf? Just sheathing and OSB then the stud wall?

Yep you're right, should be timber not timer :lol: You still need to beef up the outer leaf, but you have to use options that don't expose unsuitable materials to the elements. For example you could use a layer of cement board (cement board) on top of the OSB3 before the membrane. Or, a second layer of OSB3. Or as I chose to do, install plasterboard, but cut it to fit in between the studs of the timber framing, up tight against the back of the OSB3. This is cheapest in materials but takes an absolute ton of time. And boxes of caulk. I kind of regret doing it. I would go with cement board if I did the studio again. That would be: Cladding (on 50mm stand-off battens) / breather membrane / cement board / OSB3 / timber frame / cavity / timber frame / vapour barrier / OSB3 / plasterboard. Dan

Got you. I read somewhere that square edge board is better than tapered as tapered you need to fill them gaps where they join at corners? I will investigate Osb board and cement board. How come in Rod Gervais book he says it’s best practice to put 2 layers of plasterboard on the outside of each leaf? Can’t work that one out. Not doubting you at all, just interested. See pic[attachment=0] I need to learn how to use that MSM calculator. Will do that later and see how I get on :)

One important clarification...

2 layers of plasterboard held together with green glue

Despite the name, Green Glue is not actually glue, and cannot be used to "hold things together". I really wish they would have chosen a better name for their product! It's confusing... This is NOT an adhesive, and is not meant to stick things together. It has one very specific use, which is as a constrained layer damping compound. It damps certain types of resonance in the wall structure itself, and it does it very well when used correctly. So, you will still need to use nails or screws in the normal manner for your plasterboard, and following the approved fastening schedule provided in your local building code. - Stuart -

elastic wrote:

Got you. I read somewhere that square edge board is better than tapered as tapered you need to fill them gaps where they join at corners? I will investigate Osb board and cement board. How come in Rod Gervais book he says it’s best practice to put 2 layers of plasterboard on the outside of each leaf? Can’t work that one out. Not doubting you at all, just interested. See pic

Not preserved: 3948F9A2-7D7D-485E-9846-232A0654A051.png

[attachment=0] I need to learn how to use that MSM calculator. Will do that later and see how I get on :)

Square edge is better, tapered is used to allow to you to dry line the boards instead of skimming them. If you used tapered you would have to dry line (plaster over the joints) even if there was another layer being installed on top. With regards to Rod's book, that refers to internal walls. You can do two layers of plasterboard for the inner leaf, but you will have to put noggins and bracing in to prevent racking and twisting. It would be cheaper than an OSB3 layer, but takes more time cutting and installing the additional timber. A structural sheeting at least 9mm thick will provide all the support required without any noggins. The equivalent density of OSB3 to a plasterboard layer is the 18mm thickness. Dan

Duly noted sir :D Thanks! Maybe a silly question, but can I use regular screws, nails for construction? Just like on a normal building job. I realise the screws or nails can’t go through and make contact with the other leaf, just curious and want to do it right. Thanks

elastic wrote:

Duly noted sir :D Thanks! Maybe a silly question, but can I use regular screws, nails for construction? Just like on a normal building job. I realise the screws or nails can’t go through and make contact with the other leaf, just curious and want to do it right. Thanks

When building structural timber framing never use screws, only nails. The reason being, screws snap when they exceed their load, whereas nails bend. This is added protection in emergencies and if there are errors in construction. Ring shanked nails should be used for the framing, as these have a greater pull out resistance, 100mm where possible, or 75mm if the nail will go all the way through in certain places. To nail the OSB3 (if you use it) to the frame you need to use galvanised nails (they don't need to be ring shanked) and should be about 70mm long for 18mm OSB3. **EDIT** I was talking about the external OSB sheathing here, you don't need galvanised inside, but if you just buy a 25kg box you'll have loads spare. ********* Staple the membranes to the sheathing with stainless steel/aluminium staples so they don't rust. Bolt the frames to the floor (set J-bolts into the concrete, or drill and use resin and bolts once its set). Alternatively, hire a gun powder fired nail gun (Hilti gun) and shot fire through the soleplates into the concrete (get the max power cartridges) Dan

Maybe a silly question, but can I use regular screws, nails for construction? Just like on a normal building job.

Yup! For the drywall (plasterboard) they do make special nails/screws for this: in the USA and many other places, they are called "drywall screws" or "drywall nails". Might have a different name in the UK. One important thing: you need longer screws or nails for the second layer! You can use normal length screws/nails for the first layer of drywall (plasterboard), but for the second layer, then have to be long enough to go through BOTH layers, and deep into the studs.

I realise the screws or nails can’t go through and make contact with the other leaf,

You'd have to have insanely long screws/nails to do that! They would have to be long enough to go through both layers of drywall, and the full depth of the stud, and also the depth of the gap between your stud frames... - Stuart -

EDIT - Ah ok now i see! You mean internal walls as in if i was building a control room, live room and vocal booth, those partition internal walls? Super advice as always guys, reading and re-reading to take it all in!! Thanks! Now to tackle the MAM calculator

Guys this MSM calculator is SO COOL!!! What a great tool, thanks so much Gregwor and Audiomutt! Sure helpful! I have attached mine that i did for you guys to check out and just see if i've done it right. I couldn't see 'Cement Board' in the list? And couldn't see what type of insulation in the stud wall to choose? I decided on 30mm air gap - no idea what this should be? According to my calculations, if i did what i put in, i would get a total isolation of 68db - i think? Thoughts and feedback welcome :)

elastic wrote:

Guys this MSM calculator is SO COOL!!! What a great tool, thanks so much Gregwor and Audiomutt! Sure helpful! I have attached mine that i did for you guys to check out and just see if i've done it right. I couldn't see 'Cement Board' in the list? And couldn't see what type of insulation in the stud wall to choose? I decided on 30mm air gap - no idea what this should be? According to my calculations, if i did what i put in, i would get a total isolation of 68db - i think? Thoughts and feedback welcome :)

Not preserved: My MSM TL Calculator Version 2.03 - TL Calculator.pdf

You're on the right track, but you've not quite entered the correct values. When using "custom kg/m2" for thickness, you're telling the spreadsheet to ignore thickness and instead take the density you provide in kg/m2. So for 18mm thickness OSB3, I looked at the weight of a sheet online, which was listed at 35kg for a 1.2m x 2.4m sheet. This sheet is 2.88m2 in area, so 35 / 2.88 gives a density of 12.1kg/m2. So that goes in your box under OSB3. I did the same for 15mm standard plasterboard. The gap between the support structures is whatever space you will leave between your timber frames, I put 25 in there (for just 25mm between the inner and outer leaf frames) and selected mm in the custom units box at the top right of the spreadsheet. For cement board, just choose custom on a standard Gypsum board and work out the density online. I've attached the completed calculations for you: Dan