brick wall options...which one?

Hi,I'm planning to build a studio, on the outside the max permision is 45dBA so I need a very good isolation. which one of these wall options is better for isolate ? or other idea ? http://www.mamaproducciones.com/vaporstudio/images/A.jpg http://www.mamaproducciones.com/vaporstudio/images/B.jpg http://www.mamaproducciones.com/vaporstudio/images/C.jpg thanks,

Josep, I would go with the second drawing - for most efficient use of materials in wall/ceiling construction, you want ALL the mass to be in only TWO leaves, with as much air space as you can spare between the two. A leaf is defined as a center of mass, made up of any number of layers, as long as there's no air space it is still ONE leaf. I would also put as much insulation (spun fiberglas) as you can afford or fit between the two brick leaves; it will help sound proofing by about 12 dB over just plain air. If possible, you should also "render" both sides of the outer wall before building the inner one - Then render the inside of the inner wall as well. Rendering means plastering over the bricks with about 12-13mm layer of plaster/mortar. Bricks tend to be kind of porous, so the rendering will improve sound isolation by several dB. Between the insulation and rendering, you should gain at least 20 dB over plain, un-rendered brick walls with no insulation. With the mass of those brick walls, low frequency isolation should be several dB better than with just multi-layer drywall... Steve

sorry I forgot in the drawing...the outer wall is already rended on both sides and yes the inner wall will be redered inside also. with this second option and without insulation how many dB of reduccion I will have ? and with 80mm of fiberglas on the outer wall inside the air space? thanks,

Josep, I don't have exact figures available on double brick walls that have been laboratory tested - the only thing I can go on is this - http://www.saecollege.de/reference_mate ... 0Chart.htm A single, rendered brick wall tested at STC 45, and your brick are slightly thicker - I estimate maybe STC 48 for one wall, + 6 dB for doubling the mass, + about 8-9 dB for the air space and the same for insulation - I'd guess you're looking at about 68-70 dB if you use great care in building, getting everything hermetically sealed. Please keep in mind, though, that there are a LOT of variables here - any ONE of them chosen WRONG, and it screws up the whole thing... Steve

ok 8) if I need to put a window on this wall ,with 10 and 8mm glass I will respect the 68-70dB reduction ? and for the floor,instead of using fibergals as a insulation can I use fine sand that have density and don't transmit vibrations?

"with 10 and 8mm glass I will respect the 68-70dB reduction ?" - Sorry, no way will you be able to get that high isolation when glass is involved - check out this professional studio design/construction site's page on glass and you'll see what I mean - http://www.wsdg.com/resources/resour.php?SL=te&BL=2 -they're specing 1" laminated single glass (25mm!) at not quite 40 dB, so two spaced panes might reach 56-58 dB, and would cost about $1500 to $2000 for a 1 meter by 2 meter double glass studio window, just for the glass with no frame... Steve

thanks for the link very interesting 8) so I need to increase the separation between the two glases... do you know the formula to calculate the necesary separation between two leaves with a known STC to obtain one desired total STC ?

Josep, first of all I'm not sure from your questions, but I really HOPE that you're not trying to get the isolation from your neighbors AND still have an outer wall with a WINDOW in it? You do realize that STC takes NOTHING into account below 125 hZ, and that going by STC ratings you would probably need about STC 90 or 100 in order to keep noise below 45 outside when playing drums inside? That said, here's a helpful calculator (download it, then double-click the .exe file to run) - the demo is free, not sure what the real thing costs. http://www.insul.co.nz/download.html I just found this and havent had time to play with it yet, so you're on your own with it... Steve

thanks for the calculator I'm playing with it....really good I will try to draw what I'm thinking :roll:

the cost of the calculator is 1000€+VAT :shock: well ,if we only take a single brick wall with window like this: the red represent a single 140mm brick wall (STC54)and in green the double glass with 10+6 separated 240mm(STC50),we have a "similar" reduction also at low frequences! so if I double this wall at 250-300mm I will obtain a good total reduction.

Josep, is that going to be the wall between control room and tracking room? Should work pretty good. I figured that the full version of that calculator would be expensive - otherwise, there would have been a price and a "buy it" button on the site... Steve

between control room and tracking room I will have TWO of them separated 300mm,you could see it on this drawing it is only a initial sketch...

"between control room and tracking room I will have TWO of them separated 300mm" - Josep, is this what you mean? If so, don't start construction yet, please... Steve

yes this is, remember that the two panes on the wall are tuned to similar reduction as the brick wall(above graph)in order to have a more homogeneous reduction as the wall,then I now could consider wall+air+wall (medium mass+air +medium mass) because I can't separate the air for the brick and the glass. I 'm not sure if this is correct.....??

Josep, this is more what you'd want to do here - run the 600mm dimension through the Insul calculator with 6mm and 10mm glass; any time you use more than two leaves, even glass, in a wall, you LOSE... Steve

Steve,sorry If I'm doing a lot of questions... :roll: changing the separation from 240 to 600 only change the reducion 4-5 dB more (STC54 ) and the double brick wall is near STC96,I think that is enough with a single brick wall and the double galss. a theoretical question, you have three rooms A,B and C,each room is 10 metres long,between the room A and B there is a double glass with STC50 also as between the B and C rooms, if in the room A there is 120 dB in the B room it will be 70dB and 20dB on the C room ? and if it is true until what dimension could I diminish the longitude of the B without losing the reduction? thanks for All you are helping me a lot 8)

Josep, since decibels are a logarithmic value expressing a ratio, you can't just add 50 dB and 50 dB of STC value and come up with 100 dB of loss - If I remember correctly, it would be more like a total of 60-65 dB instead. Each time you double the mass, you only get 5-6 dB more Transmission Loss. Add to that the loss due to distance (which is not easy to figure except in free space) and you would probably get about 12 dB improvement with adding the second wall and room. Another thing to consider is REAL loss, as compared to theoretical loss. Field measurements of walls are ALWAYS worse performance than laboratory tests due to things like unforseen flanking noise (a very real problem in your case, unless you're prepared to slab saw the masonry floor between your two brick walls) poor caulking practices, blobs of masonry dropping between isolated surfaces, cracks and porosity of masonry not being taken care of, etc - I've not seen any specs on brick masonry walls, but here's some comment on double cement block walls that's kind of interesting - http://irc.nrc-cnrc.gc.ca/practice/noi1_E.html Another thing to remember when designing a studio - STC is nearly worthless as a measuring stick!!! You need to take things into consideration at least two full octaves BELOW where STC stops counting. The STC range of frequencies from 125 hZ to 4000 hZ was originally intended to be used for VOICE attenuation, not music. Today's music studios, if they're going to isolate well, need to consider down to at least 30 hZ for Transmission Loss. This is true both between studio and outside world, and between control room and tracking room if you want to hear what things sound like through your gear instead of through the walls/windows. It is a major pain in the ass to have to do test recordings of every little thing when setting up mics, especially for things like acoustic drums - it's much quicker if you only hear what's being sent to the board with little or no bleed through the structure of the studio. Take for example a STC 63 wall made of gypsum wallboard - by the time you get down to 30 hZ, that wall will be lucky to attenuate the sound by 30 dB, probably more like 25 or so. If you're kicking the crap out of an acoustic drum kit, the kick drum is at maybe 110 dB at the mic, 105 at the wall, and 80 dB on the other side of this so-called 62 dB wall - that level is only 5 dB down from where most knowledgeable engineers do most of their mixing; not much attenuation when you're trying to hear what's going on tape instead of what's bleeding into the Control Room... Gotta go for now, more posts to check out before bed time... Steve

what means "unforseen flanking noise" ? "..unless you're prepared to slab saw the masonry floor between your two brick walls." the second brick wall will be on a separate floating concrete floor. I understand that is better only two leaf and one air space,but imagine that you need to calculate the reduction through three or four leafs of glass,how could it be calculated ?

Josep, I had a long post ready for you and lost it in the crappy service provider I'm about to feed to the sharks... Here's the main parts; I don't have a calculator or formula for multi-leaf walls, it's just considered a no-no by nearly everyone. Go to this page, scroll to the bottom, and compare the 40 dB wall with the 57 dB wall. Now, imagine that the wallboard is glass. Same thing, except you can't see thru wallboard - http://www.domesticsoundproofing.co.uk/tloss.htm Now, for as good an explanation as I could give, from the mouth of a degreed acoustician - http://groups.yahoo.com/group/acoustics/message/5156 As far as my comment about "unforseen flanking noise" - flanking noise is anything that "flanks" or gets by your attempts at sound proofing. sound that travels along a concrete floor into another room and re-radiates there, becoming airborne noise, is "flanking noise" - sound that sneaks over a wall above a poorly built suspended ceiling is "flanking noise" - by "unforseen", I meant "not planned for", or something similar. "the second brick wall will be on a separate floating concrete floor." - Excellent. If you pay attention to the tiniest detail in all your construction, you should have a very quiet room... Steve

"...scroll to the bottom, and compare the 40 dB wall with the 57 dB wall" I see what you mean,but also you can compare the 36dB wall with the 50dB ,so if a double glass has a 50dB and I add a third leaf I will have minimum 50dB and maybe 60dB,I know I know only two leaf :D but take a look: http://www.mamaproducciones.com/vaporst ... es/B02.jpg

OK, I looked - what I saw could be improved by about 7 dB just by NOT using the intermediate glass. Why you would want to put it in, other than a need to spend more money, is beyond me. I know how counter-intuitive this particular concept is, because I also had a hard time accepting it until I saw more than one lab's tests on similar construction, and had Eric Desart explain it several times in several different ways - the fact remains that these are TESTED designs, and that you can, in this rare instance, have MORE for LESS. I don't know how to make this any clearer - if you feel you simply MUST put the extra pane of glass in, at least do it in such a way that you can open the window back up and REMOVE it when you find you're less than thrilled with the amount of bass bleed-thru. Keep in mind, too, that these high dB numbers you refer to are unrealistic for music. The extra two+ octaves below the STC rating's cutoff of 125 hZ get progressively worse, so drums and bass are nowhere NEAR as isolated as the numbers would make you think they are. Just look at ANY combination of materials in that Insul calculator, and you'll see that the TL gets really crappy at lower frequencies - If you plug your 4mm and 10mm glasses into the calculator with a 410mm gap, it comes up with STC 52 - however, look at the chart tab and see that at 50 hZ your TL is down by 22 dB, to only 30. This means that if you play a kick drum at 108 dB, the low energy will only be attenuated to about 78 dB, which is loud enough to be obnoxious to people who are NOT the drummers MOTHER... (and maybe even her too) I think the bottom line here is that you will do what you want - I've given you all the reasons I know NOT to, but in the end it will be your decision and you that has to live with it. I hope for your sake that you make the right choice... Steve

Don't take me wrong I'm with you and SURE that I will go with only two leafs. the thing is that the external window is in bad condition and I was trying to don't fix it and instead of put another one more,now I know that it is an error and it will be better to fix the existent and put only one new more.I will go with a 20mm laminated glass,410 mm air and the fixed 4mm. again thanks for your time PD:my english is not good and some times it is difficult to explain me correctly....

Josep, first of all if I had anywhere NEAR as good Spanish as you have English, I'd be dancing in the streets :lol: :lol: Second, it's hard to let go of things that seem right, or to accept things that DO NOT seem right, so I thought it was time for a little push, no big deal - Third, if you have to repair the outer window why not upgrade it at the same time, and increase thickness/change to laminated also? That would be the best thing to do acoustically... Steve