New rehearsal room/studio Transylvania

Hello. Location: Transylvania, Europe. Budget 10000 Euro, +/- 10%. I am doing it from scratch. So far the base is done, Monday the team will start to build the walls. I am sorry about SI units, but I am not familiar with the UK ones. Dimensions: Surface: 11x7x10x5 m (so no paralell walls), height (inside): 3m. Surface somewhat less than 60 square meters, volume (intended 180 m3 cubic meters). The base is of concrete, 1,4 x 0,5 m deep under the walls, and 20 cm layer of metal bars-enforced concrete floor, with hydro-isolation membrane on it; upon that 4 cm wide Rockwool Steprock ND mineral wool, (also perimetral) under a floating 6 cm wide metal-enforced concrete floor. On 0 m and 3 m height there will be a 20x20 cm layer of metal bars re-enforced concrete enforcement, and also 7 columns in the wall of the same content which will link the two concrete "belts". The wall itself beside the concrete columns and re-enforcements will be done of 30 cm wide bricks (bricks with air-holes - I know it should be compact, but this is what I can afford). On the outside of the wall there will be Frontrock (10cm) insulation. (In my district there are sometimes -40 Celsius, so I have to). Question nr. 1: Do I have to put the team to cover with 1-2 cm concrete the inner part of the wall, or not? I figure, that would add some weight to the wall, and close up all possible cracks etc. The inner side of the wall I intend to put a 10 cm wide glass/or rock wool as insulation (I was thinking without too many wood framing, to keep them close together without any air gaps and consolidate them using some fiberglass net. Then follows some 10 cm of air, and after that Isover akusto mineral wool, metal framing for gypsum board, aluminum based vapour barrier, and 2 layers of phonic gypsum board. This whole structure will be built on the floating floor, and will have no mechanical contact whatsoever with the brick wall. The ceiling will be done in the same way; from in towards up: 2 layers of phonic gypsum board, aluminum based vapour barrier(this has also small air-bubbles in it), 10 cm akusto mineral wool in the metal framing, 10 cm air gap, 10 cm stone wool between the ceiling wooden frames(mechanically connected to the roof and the brick wall), and covered with other 2 layers of phonic gypsum board. Upon which another 10 cm layer of glass wool. The roof is done by wooden structure, covered with(form out towards in): heavy concrete tiles, layer of air for ventilation, semi-permeable membrane. I don't intend to put any mineral wool at this point, I already have 30 cm of wool until the inner room and I don't think I need it. (warn me if I am wrong). Windows: there will be 2 sets of double windows(with vacuum approx 22mm wide), one in the brick wall (2x2 m ), and one identical in the inner wall. These are German made second-hand windows, which are hermetical, and impeccably manufactured. The distance between them will be presumably 40 cm (or more), and the gap between (the walls) them will be closed with double layer of drywall, and silicone caulk, in a manner that no mechanical contact will be between them(except flexible caulk). Question nr. 2: Should I angle them, or use them parallel? I guess parallel is not good, because of inner reverbs. What angle would You use? I can angle the window in the brick wall (because the inner one probably is more difficult to do - and also I may experience problems of the metal framework, which holds difficultly the 2x2m double window in weird angles. Would you angle upside down or laterally (left to right)? Doors: I also have some wide second hand doors. 15 cm wide, covered with mineral wool in cattle skin. The frames I will enforce heavily and add 2 different rubber layers to make them hermetical, and also on the inner door I intend to add 2 layers of phonic gypsum board, and an acoustic foam. Ventilation: I have considered 20 cm wide insulated flexible duct-work, and 2 ventilators (Solar&Palau Silent 120W) which does 20db noise only, and I want to install an input air system, and an exhaust system. The total length of each system is about 10 m. maybe 15 total of the exhaust system. Question nr. 3: Do You think I need mufflers? Can I do them of wooden boxes with layers of mineral wool? or it is enough to make a few turns and orient them away from the neighbor? The ducts are insulated with 2 layers of: fiberglass and some kind of foam, respectively. All windows, doors and ventilation ducts are oriented towards our yard (and the opposite direction from the neighbor, who is at 2,5 m from the back wall of my future studio, and about 8,5 form the front of the studio where everything opens). He is not too sensitive about noise, and the buildings are separated by almost flexible ground (not stiff). I am aware, that my DIY doors, and second-hand windows and also probably the ceiling are the weak points of my project. Question nr. 4: Is there a difference in various mineral and rock etc. wools in matter of sound insulation which would justify the difference in prices among them? Because I think in matter of bass frequencies, they all suck as isolators (as Gervais or Newel says). So this does mean or not that I can buy some less expensive wool with more or less the same results (as sound insulation) and save my money? Or I should go on the specs of the different products and pay more for more quality? Guestion nr. 5: The ceiling probably will be one of the weakest points in my project, especially since the team intends to do some ventilation holes which renders the roof air-communicative with the outside environment. Should I try to persuade them to do those holes only in the front of the building (oriented to our yard) and not the behind part (towards the neighbor)? Should I add some sand or bricks or anything over the 2 layers of gypsum board to make it more heavy? To try to pour concrete instead? My problem with this would be that the inner room would be sealed completely(which is good), but lacks ventilation of the space between the walls, and I may end up with a mice mushroom culture which may be tempted to do poetry (which I don't like). On the other hand, if I screw in the layers of gypsum well on the roof (attic) structure, I guess with the tiles and all, I have the necessary mass (this is somehow what I hope You will say). Since I arrived to the roof construction (no answer form You guys yet in over 2 weeks), I've decided to follow the A option (see drawing), but instead of the 2 layers of gypsum board from the inside part of the roof structure, I will add an 12mm OSB on the exterior part of the roof structure, under the anti-condense membrane, and caulk it airtight. This way, the OSB+structure+tiles will be the M, the attic with the wools will be the spring - and also more space to lose some 6db/quarter wavelength - and the metal profiled double gypsum board ceiling will be the second Mass. It will weight around 1,2 tones. This is the best I can come up with now. Question nr. 6: Please be critical and advise me to change all things which seem conceptual wrong in my idea. I have read Gervaise's and Newel's books, and I tried to adapt the ideas to my practical possibilities. Since I have time yet to improve and adapt things, I am able to put Your advice in practice yet. I also have additional 1000-1500 euros for acoustical treatment. My band produces around 95-100 dB of "noise" (A scale) (folk-rock, with occasional bass and drums) and despite the fact that my neighbor is not an asshole, I would like to keep Him as noise-protected as I can. I would use this room as a single live-room (at least at the beginning) and have no intention to become commercial or anything. There is no water, toilet, ducts, etc. I will use my house (which is at 15m). I also intend to mount all electrical stuff and switches on the floor or on the gypsum board, and not drill any holes in it. In case I overdid the insulation (which is unlikely) or You notice some problematic things in my project, please let me know. E.g. the air gap between the inner wall and the brick wall should be wider or less (than 10 cm). I trust that I gave the basic details on the project, but feel free to ask me anything else You may want to know. Thank You in advance, Tibi

Tibi, greetings and welcome to the website. Hopefully, you've made some time to go through some of the existing threads, as it will help to answer some similar questions you may have already had or will have soon during building. Looks like you have a lot going on. Maybe a few others can help too by chiming in here. I'm not going to answer in any particular order or to every question. There's a couple questions there beyond my knowledge or ability, but will help where I can. On question 2, are you referring to the glass being angled/parallel? If so, angled is usually best to reduce any 1st or direct reflections back to the listening position or into microphones. Typically for glass windows, you would want to have "window - air space - window". Use two different thicknesses so they don't resonate at the same frequencies. Example: One at 10mm and one at 15mm or something along those lines (sorry, I'm not good at metric measurements), but you get the point. Usually a laminated glass works well for achieving the different thickness and also reducing vibrations. The only way to get a true vacuum would be to have a concrete wall with the glass, which they did at Bad Animals studio in Seattle back in the 90's, but that's a whole different conversation. As far as angle, imagine looking at the assembly from the side. The glass would be in a "V" shape. In reference to the air system, yes, you want to be able to bring air in as well as a return to bring air out. They make a insulated duct board specifically for sound absorption to reduce transmitted sound. If I remember correctly, you want at least 10 or 15% fresh air intake from outside, since your rooms will be hermetically sealed. In reference to sound and your neighbors. Keep this in mind. MASS is what is going to keep or reduce the low frequencies from transferring to outside. If you have concrete block walls, you might consider filling them with concrete. Make sure you reinforce it with rebar though as the added weight could be hazardous. I would recommend a structural engineer for this. I am not one. But that aside, mass is your friend here. Mufflers? You may need to describe this a little better what you mean or where it's use is. For your doors, use magnetic seals and drop seals if you can. This will help keep the sound from leaking through. If you can, build a sound lock (a two door system: Door followed by a small room or chamber and another door). There are diagrams already on this forum for the construction of both windows and doors. Look around and you will find them. Part of this site is about spending time and researching the info already posted or listed. Question 4: Yes, there are different types of co-efficients of insulation. Rock/mineral wool comes in different thicknesses and compressions measured lb/ft2 or lb/m2 (I think - it's been a while since I've looked it up), but every insulation has a "co-efficient chart" to show the acoustical absorption rates for the rated product. As I mentioned earlier, mass is the only thing that really works well on reducing low frequencies. The rock wool/mineral wool or 703 products is more for the mid/high frequencies where it's useful. You can buy the cheaper stuff if the measurements are similar. There's different manufacturers out there, but it's mostly all similar stuff. But, keep in mind, those numbers also work as a complete wall system, including doors/windows isolation. It only takes one small hole to render the entire assembly useless. In other words, if you spend all this time and money building this great wall for sound absorption, but fail to put seals around your door, you've just completely wasted the time and money for it to be functional. This is one area, you really need to think about and is not the area to skimp on funds, but to do it right, no matter the cost. It all works together as a unit. I wouldn't put the electrical switches on the floor. You can however, if not putting holes in the drywall, you can surface mount all your electrical in conduit and metal boxes. Then you can hide all that with your acoustical treatments. Hopefully this is a start. Again, if you haven't yet, please take a few days and do lots of reading of existing threads on this forum. A lot of the info here will answer some of these questions for you. After that, if you still have some questions or need better clarification on something, post some more questions, and the members here will try and answer what we can to the best of our abilities, knowledge or experiences. And again, welcome to the forum. It's a great resource. Aaron

Dear Aaron, Thank You for Your answer. I will try to clarify the issues You've mentioned (I will convert the metric values to US ones, in attempt to make stuff easier for You; for the old drawings one can consider roughly 1 m=1 yard, in fact 0,9 m=1 yard): 1. I have 2 sets of windows. Basically the inner room will have an identical window and door with the outer brick wall. Both of the windows are double and have 22mm=somewhat less then 1 inch tickness (4mm=1 pica? glass-16mm(4 picas) vacuum-4mm glass) (really heavy wood framed). Between the two windows there will be a 40 cm (nearly 16 inch) air space - the same between the 2 walls (except that in the wall gap will be wool-air-wool space). I attach the sketchup I did to explain myself better. Obviously the space between the windows and the doors will be sealed from the gap between the walls, just like You've said, 2 doors with a small "room" between them. The question was: should I install those windows in paralell, or in angel between each other. And I guess the answer is yes, what angle? 2. Mufflers, I mean sound attenuators in the ventilation duct system. I read a lot on this site about all various issues, and clarified a lot a stuff, which I did not asked in my thread. I have seen dome DIY attenuators made of plywood, with the diameter at least twice as big as the duct's, with fiberglass glued on the inner walls etc. I will have a long duct system (more than 10m=32,4=11 yards or more) foot, using double (sound) insulated flexible ducts, and I will have a few turns to help mimicking that kind of an attenuator. Moreover, I will orient both the outer end of the input and the opening of the exhaust in an opposite direction from my neighbor (towards a 40 yards minimum until my other neighbor who is usually way noisier then my band and he's drunk all the time:)). Both the input and the exhaust ventilator fan is a Silent TD 1000 (Soler&Palau), which can carry 1000m3=1309 cubic yards/h on maximum speed, but produces only 21 db noise (and both will be mounted outside of the building); the fans also have a sound attenuating system, which absorbs the sound from the duct. I attached an excerpt from the specs. About electrical stuff: I agree, I will mount them on the wall, without drilling holes, in metal housing. About wool: OK. I will get the expensive ones, with certificate. Romania is famous of counterfeit stuff, so let's go securely on this one. It will be difficult to change it afterwards. The brick I am using it is heavy, 1 foot thick (called Weinberger Porotherm), and has some small air gaps vertically for thermal insulation. I cannot afford the compact ones or the concrete walls. But these holes were more or less filled with mortar. I will add then some inch of mortar on the wall surface too on both sides. This will add weight. Also on the outer side it will be a Rockwool thermal insulation (4 inches thick high density mineral wool), which adds somewhat both to the weight and the sound insulation. (I agree, not on bass frequencies). Thank You for Your time. It is already a big help, and also a good feeling being a part of such community. The roof is about to be finished this week. The guys are fast and precise. Guess I'm lucky. Best regards, Tibi

Hi. I am continuing my monologue. A month passed by. My external room is ready. Roof+wall+floating floor. Looks promising so far. I also had a very quick answer from John who explained me fast, that the reason why I am not getting replies is a. I am not bouncing my post (according to the rules you're are decreasing your chance if you do that) and beside that on my interface it is not nor ever been active b. my post is too long (according to the rules if you don't give details you won't get answer)(makes me also wonder why one needs all the details to able to build it - why would anyone wanna build my project?) c. everybody is tired. (which is understandable - I work as a volunteer in a health lab too. Sometimes it is overwhelming number of samples to process. But I TELL THEM: "listen - no chance this week. I will help you next Tuesday" I never ignored anyone. This is lack of respect. After all, I am a sort of contributor to this site too. Which makes me wonder, why are the rules enforced if one by obeying them deprives himself for the chance of getting some help? I understand, that this is not a free studio design site - nobody expected that - but then try sticking to the rules, because it is not fair to answer in the same week to somebody who has a short question (and ignores all the rules of the site), and neglect people who obeys them. Or it is a location-specific disregard? That's why one has to declare it? Back to the questions: I have only one, which remained relevant: The gap between the walls: will be filled according to the skechup drawing with 10 cm layer of wool, 10 cm air, another 10 cm of wool. Is this ok? Or useful? Thank You

Hi Tibi, and welcome to the forum! :) :) We don't have many members from Transylvania: I think you might even be the first!

I am sorry about SI units, but I am not familiar with the UK ones.

No problem: most of us can work in either metric or imperial measurements. I was lucky enough to grow up in Australia during the transition from imperial to metric, so I learned both at school.

Surface: 11x7x10x5 m (so no paralell walls),

OK, but is this a control room, or a live/tracking/rehearsal room? For a control room, you need symmetry, so at least two of the walls need to parallel. But for the other types of rooms, that isn't important.

This whole structure will be built on the floating floor,

Floating floor? Are you SURE you need that? You don't seem to have enough budget to do a floating floor properly. This might be interesting for you: viewtopic.php?f=2&t=8173

I don't intend to put any mineral wool at this point, I already have 30 cm of wool until the inner room and I don't think I need it. (warn me if I am wrong).

I would put some in there: you are basically building a three-leaf ceiling, so you do need insulation in both cavities, to damp the resonance.

Windows: there will be 2 sets of double windows(with vacuum approx 22mm wide), one in the brick wall (2x2 m ), and one identical in the inner wall

That sounds like typical double glazed windows? Two sheets of thin glass with a thin gap between them? They are not much use for studios. And having two of those next to each other creates a 4-leaf system, which means your low frequency isolation will be very poor.

Question nr. 2: Should I angle them, or use them parallel? I guess parallel is not good, because of inner reverbs.

For the windows? No, you do not need to angle them for acoustic purposes. Here's why:

Ventilation: I have considered 20 cm wide insulated flexible duct-work, and 2 ventilators (Solar&Palau Silent 120W) which does 20db noise only, and I want to install an input air system, and an exhaust system. The total length of each system is about 10 m. maybe 15 total of the exhaust system.

You need to do the calculations to make sure that you are moving enough air at the correct speed for your rooms. You also need silencer boxes at each point where the duct penetrates a wall.

Question nr. 3: Do You think I need mufflers? Can I do them of wooden boxes with layers of mineral wool? or it is enough to make a few turns and orient them away from the neighbor?

Yes, you will need silencer boxes, and you also need to calculate the dimensions for those. They should be lined on the INSIDE with proper duct liner, NOT with ordinary mineral wool or fiberglass.

The ducts are insulated with 2 layers of: fiberglass and some kind of foam, respectively.

same here: They should be lined on the INSIDE with proper duct liner, NOT with ordinary mineral wool or fiberglass.

Question nr. 4: Is there a difference in various mineral and rock etc. wools in matter of sound insulation which would justify the difference in prices among them?

Yes, there is a difference. If you use fiberglass, then it must have a density of about 30 kg/m3. If you use mineral wool, then the density should be about 50 kg/m3.

Because I think in matter of bass frequencies, they all suck as isolators

Right, but the purpose of fibrous insulation is NOT to isolate! That's not what it is meant for at all. Rather, it acts as a damping mechanism on the resonance on side the wall cavity, and it is VERY necessary. There can be as much as 16 dB of difference in isolation, comparing an empty wall (no insulation inside) with one that has a lot of insulation. You do need it, absolutely.

Guestion nr. 5: The ceiling probably will be one of the weakest points in my project, especially since the team intends to do some ventilation holes which renders the roof air-communicative with the outside environment. Should I try to persuade them to do those holes only in the front of the building (oriented to our yard) and not the behind part (towards the neighbor)?

Earlier, you described a three-leaf ceiling, and the ventilation will only be in between the outer leaf and middle leaf, so there is nor problem. As long as the middle leaf and inner leaf are sealed, then you are fine. I tried to open your Sketchup files to take a look at your design, but I can't open them: I get an error message saying that they were made with another version, but I have the latest version. So I don't know what's wrong there. Sorry.

I also had a very quick answer from John who explained me fast, that the reason why I am not getting replies is

Not sure about others, but in my case it is just over-load: there's a lot of activity on the forum lately, with lots of people asking questions, and not very many people replying. I have a list of threads that I need to answer, and I try to answer them in order. Especially when there are long posts with a lot of questions all together. Sometimes I see a post where I can give a quick answer right away, but I have to wait until I have enough time to answer longer posts. So yeah, sometimes I do answer threads out-of-sequence, although I try to keep that to a minimum. Sorry: that's just the way it is.

The gap between the walls: will be filled according to the skechup drawing with 10 cm layer of wool, 10 cm air, another 10 cm of wool. Is this ok? Or useful?

Yes, that's fine. - Stuart -

Thank You Stuart. You have no idea how much I appreciate Your answer. I WILL ANSWER WITH CAPITALS. I DID'T FIGURE OUT HOW THE QUOTE WORKS. SORRY. I AM A MORON. OK, but is this a control room, or a live/tracking/rehearsal room? For a control room, you need symmetry, so at least two of the walls need to parallel. But for the other types of rooms, that isn't important. THIS IS A LIVE ROOM. I WON'T DIVIDE THE ROOM IN ANY WAY. FOR ME IT IS IMPORTANT TO SOUND WELL AND KEEP MY NEIGHBORS MUSIC-FREE. I WILL USE IT FOR REHEARSAL AND OCCASIONALLY TO RECORD. I DON'T MIND IF COLORS A BIT THE SOUND.

This whole structure will be built on the floating floor,

Floating floor? Are you SURE you need that? You don't seem to have enough budget to do a floating floor properly. This might be interesting for you: IT IS ALREADY DONE. I HAVE 4 cm STEPROCK (ROCKWOOL) SPECIAL WOOL DESIGNED FOR UNDER CONCRETE, WHICH HOLDS UP TO 2 TONS/SQUARE METER WITHOUT SIGNIFICANT COMPRESSION. I AM AT SOME PORTIONS LESS THAN 2 METERS FROM MY NEIGHBOR(FOUNDATION TO FOUNDATION). THE GROUND IS SOMEWHAT WET. ALSO TEMPERATURES MAY DROP UNTER -35 IN WINTER, SO I NEED IT ALSO FOR THERMAL PURPOSES. THE ARMED CONCRETE UPON THIS WOOL WEIGHTS 8,8 TONS, AND DECOUPLES COMPLETELY (PERIMETRICALLY ALSO) THE INNER ROOM. IT IS NOT A DICK-SIZE CONTEST. I WANT TO BE SURE, THAT MY NEIGHBOR WON'T HEAR OR FEEL ANYTHING). SINCE THE INNER ROOM WILL BE BUILT ON THIS CONCRETE, IT WILL ADD ALL ITS WEIGHT TO IT. THE STRUCTURAL GUY SAID IT IS OK. 1440 KG CEMENT WAS USED AND 4MM IRON NET. IT IS HARD AND PORTANT.

I don't intend to put any mineral wool at this point, I already have 30 cm of wool until the inner room and I don't think I need it. (warn me if I am wrong).

I would put some in there: you are basically building a three-leaf ceiling, so you do need insulation in both cavities, to damp the resonance. I ATTACH BOTH THE JPG AND SKP VERSIONS OF THE FINAL ROOF. I ALSO ATTACH PHOTOS OF THE ROOF IN THE PDF FILE. I ADDED THE OSB DIRECTLY ON THE ROOF STRUCTURE AND ABOVE IT THERE IS THE TILE'S VENT SYSTEM. I WILL CAULK THE OSB AIRTIGHT. UNDER THE OSB WILL BE AIR, AND AS YOU CAN SEE ON THE DRAWING A LOT OF WOOL.

Windows: there will be 2 sets of double windows(with vacuum approx 22mm wide), one in the brick wall (2x2 m ), and one identical in the inner wall

That sounds like typical double glazed windows? Two sheets of thin glass with a thin gap between them? They are not much use for studios. And having two of those next to each other creates a 4-leaf system, which means your low frequency isolation will be very poor. THE GAP BETWEEN THE 2 DOUBLE WINDOWS WILL BE ALMOST 50 CM. THERE IS NO COMPANY IN ROMANIA WHICH PRODUCES ACOUSTIC GLASS. ALSO IS UTTERLY EXPENSIVE. BY THE WAY THERE ARE NO ACOUSTIC ENGINEERS EITHER AROUND HERE. THESE ARE REALLY HEAVY WINDOWS IN WOODEN FRAMES, UP TO 180 KG EACH, DOUBLE SEAL ON EACH FRAME. THE GAP BETWEEN THE INDIVIDUAL GLASSES IS 22MM. TOTAL THICKNESS OF THE SYSTEM 28MM. THIS IS THE BEST I CAN AFFORD.

Ventilation: I have considered 20 cm wide insulated flexible duct-work, and 2 ventilators (Solar&Palau Silent 120W) which does 20db noise only, and I want to install an input air system, and an exhaust system. The total length of each system is about 10 m. maybe 15 total of the exhaust system.

You need to do the calculations to make sure that you are moving enough air at the correct speed for your rooms. You also need silencer boxes at each point where the duct penetrates a wall. THESE FANS CAN CHANGE THE AIR COMPLETELY IN THE ROOM EACH 11 MINUTES IF THEY ARE MAXED. ON LOW SPEED IN ABOUT 18 MINUTES. I AM ALREADY STUDYING THE SILENCER BOXES ON THE SITE. THANK YOU.

Question nr. 3: Do You think I need mufflers? Can I do them of wooden boxes with layers of mineral wool? or it is enough to make a few turns and orient them away from the neighbor?

Yes, you will need silencer boxes, and you also need to calculate the dimensions for those. They should be lined on the INSIDE with proper duct liner, NOT with ordinary mineral wool or fiberglass. CAN YOU GIVE ME SOME CHARACTERISTICS OF THE DUCT LINER? NOBODY SEEMS TO SELL THIS STUFF AROUND HERE.

The ducts are insulated with 2 layers of: fiberglass and some kind of foam, respectively.

same here: They should be lined on the INSIDE with proper duct liner, NOT with ordinary mineral wool or fiberglass. THEY ARE CALLED SONOFLEX TUBES AND ARE FACTORY MADE FOR HIGH ACOUSTIC, MECHANICAL AND FIRE DEMANDS.THEY ALREADY HAVE THE DUCT LINER IN THEM IN 2 LAYERS, UNDER AND ABOVE SOME KIND OF MICROPERFORATED MEMBRANE TO ABSORB NOISE.THAT IS WHY I WAS WONDERING IF I NEED THE SILENCER BOXES AT ALL. BUT I GUESS IT IS BETTER IF I DO THE SILENCERS AS WELL. I tried to open your Sketchup files to take a look at your design, but I can't open them: I get an error message saying that they were made with another version, but I have the latest version. So I don't know what's wrong there. Sorry. I WILL TRY TO EXPORT THEM AS JPGs. UNTIL THEN I HAVE PREPARED A PDF WITH A NUMBER OF PHOTOS FROM THE ACTUAL WORK. I GUESS THEY WILL EXPLAIN STUFF BETTER THAN I CAN DESCRIBE. :) PLEASE LET ME KNOW IF YOU COULD IDENTIFY SOME MAJOR (OR MINOR) FLAWS IN THE DESIGN, SO I CAN CORRECT THEM IN TIME. ON THE EXTERIOR THERE WILL BE FRONTROCK MAXE 10 CM (ROCKWOOL) FOR THERMAL INSULATION (AND ALSO TO KEEP MOISTURE OUT OF THE GAP WINTERTIME - OFTEN -35 CELSIUS OUTSIDE). DO YOU THINK THIS ALSO HELPS SOMEWHAT THE SOUND INSULATION AS WELL? WHAT ATTENUATION YOU PREDICT TO THIS DESIGN ALLTOGETHER USING YOUR EXPERIENCE (RATHER THAN WASTING YOUR TIME WITH CALCULUS)? THANK YOU AGAIN STUART, TIBI

I WILL ANSWER WITH CAPITALS. I DID'T FIGURE OUT HOW THE QUOTE WORKS.

Highlight the text you want to quote by holding the left mouse button down while you drag over it. Release the mouse button, then click on the screen button that says "quote", just above the text window.

IT IS ALREADY DONE. I HAVE 4 cm STEPROCK (ROCKWOOL) SPECIAL WOOL DESIGNED FOR UNDER CONCRETE, WHICH HOLDS UP TO 2 TONS/SQUARE METER WITHOUT SIGNIFICANT COMPRESSION. I AM AT SOME PORTIONS LESS THAN 2 METERS FROM MY NEIGHBOR(FOUNDATION TO FOUNDATION). THE GROUND IS SOMEWHAT WET. ALSO TEMPERATURES MAY DROP UNTER -35 IN WINTER, SO I NEED IT ALSO FOR THERMAL PURPOSES. THE ARMED CONCRETE UPON THIS WOOL WEIGHTS 8,8 TONS, AND DECOUPLES COMPLETELY (PERIMETRICALLY ALSO) THE INNER ROOM. IT IS NOT A DICK-SIZE CONTEST. I WANT TO BE SURE, THAT MY NEIGHBOR WON'T HEAR OR FEEL ANYTHING). SINCE THE INNER ROOM WILL BE BUILT ON THIS CONCRETE, IT WILL ADD ALL ITS WEIGHT TO IT. THE STRUCTURAL GUY SAID IT IS OK. 1440 KG CEMENT WAS USED AND 4MM IRON NET. IT IS HARD AND PORTANT.

Excellent! It sounds like you did it correctly. The reason I mentioned it is because way too many people come here thinking they can "float" their floor with a sheet of plywood on top of some 2x4s and rubber pucks... :) In reality, floating a floor needs major mass, such as yours. I didn't check the math, but the concept is right.

I ATTACH BOTH THE JPG AND SKP VERSIONS OF THE FINAL ROOF. I ALSO ATTACH PHOTOS OF THE ROOF IN THE PDF FILE. I ADDED THE OSB DIRECTLY ON THE ROOF STRUCTURE AND ABOVE IT THERE IS THE TILE'S VENT SYSTEM. I WILL CAULK THE OSB AIRTIGHT. UNDER THE OSB WILL BE AIR, AND AS YOU CAN SEE ON THE DRAWING A LOT OF WOOL.

Good! It looks like you are doing that correctly too! :)

THE GAP BETWEEN THE 2 DOUBLE WINDOWS WILL BE ALMOST 50 CM. THERE IS NO COMPANY IN ROMANIA WHICH PRODUCES ACOUSTIC GLASS.

You don't need acoustic glass. Ordinary laminated glass is the best, but even if you can't get that, then plain old tempered glass is fine too, as long as it is thick enough. The problem with double-glazing is that it does not isolate well at low frequencies, does not have much mass, and also does not isolate well around its own critical frequency (coincidence dip). The 50 cm gap will help, of course, but there still might be problems with isolation at some frequencies...

THE GAP BETWEEN THE INDIVIDUAL GLASSES IS 22MM. TOTAL THICKNESS OF THE SYSTEM 28MM.

So the glass is only 3mm on each side? With those dimensions, the MAM resonant frequency is about 210 Hz. So those windows will not isolate sounds at 210 Hz, and will have greatly reduced isolation up to about 300 Hz. They only isolate well from about 420 Hz upwards.... The overall isolation of those windows should be around 40 dB, but only above 300 Hz. If you were to replace each of those double-glazed units with a single sheet of 12mm window glass, then the resonant frequency of the entire system would drop to 22 Hz, and it would isolate well from 43 Hz upwards. Overall isolation would be about 48 dB, starting at 30 Hz. That's a major difference in isolation! Three octaves lower, and nearly ten times better!

CAN YOU GIVE ME SOME CHARACTERISTICS OF THE DUCT LINER? NOBODY SEEMS TO SELL THIS STUFF AROUND HERE.

Call some local HVAC contractors: They must have it. This is what it looks like: Links: http://www.certainteed.com/products/ins ... ial/317381 http://www.industrialnoisecontrol.com/m ... -liner.htm http://www.kflexusa.com/HomePages/Marke ... 26&line=14 http://jm.com/insulation/performance_ma ... tic_rc.pdf - Stuart -

Hi Stuart, thank You again for the answer.

Soundman2020 wrote:

If you were to replace each of those double-glazed units with a single sheet of 12mm window glass, then the resonant frequency of the entire system would drop to 22 Hz, and it would isolate well from 43 Hz upwards. Overall isolation would be about 48 dB, starting at 30 Hz. That's a major difference in isolation! Three octaves lower, and nearly ten times better!

The external window must remain as it is because of thermal reasons.A single piece of glass at -40 winterstorm will be continuously full of ice on the inside, which is a bad idea. I will test it at the end, to see if attenuates enough for my purpose, and eventually can change the inner window's double glass to a 12 mm one. The windows are towards the other neighbor, and there is a considerable distance until him (30m+ trees etc.). Thank You for the calculus.

Soundman2020 wrote:

Call some local HVAC contractors: They must have it. This is what it looks like:

Image not preserved: AIR INPUT SYSTEM.jpg

I ordered it online. Italian K-flex, 25mm, 8m2, less than 100 euros. Now I am about to draw the silencer box. I will do 2 identical boxes, somewhat as shown in the picture. (I don't send You anymore skp files, since You cannot open them.) I was considering somewhat more than twice the surface of the tube, 5 baffles, and 90 grades entrance of the tubes. Both the input and the exhaust systems will be installed between the inner and outer wall. The exhaust system will have 3 entry holes in the room, and the closest 2 to the fan will have manual flux regulators. At the joint of the 3 tubes will be the fan, than the silencer box, crosses the external wall and I plan to introduce it in the wood shop which is beside the studio (for thermal reasons). I also consider to do 2 alternative routes for the input: a summer-circuit which uses the air from outside, and a winter circuit, which uses the air from the wood shop, which is huge, and not closed, but still somewhat warmer than the outside air. (I will have a studio similar to a passive house, but my heating system will by infrared panels - and I must minimize the heat loss to save on the electric bill). Please tell me if something is conceptually wrong. And now some additional questions: 1. The inner room will be double gypsum board on its metal framing. Since this will be built entirely on the floating floor, should I bolt the horizontal floor frame directly to the floating concrete, or better to use something like on the picture: a rubber piece, and and another L-frame beside, which come bolted into the concrete? (for an additional decoupling). The manufacturer of the profiles gives a foam-like stuff one supposed to put under the frame for acoustical reasons (it is missing from the drawing, but I will put it there) but then they say one supposed to bolt the frame through the isolator to the floor. This surely will "screw" the acoustics, and will trasmit all vibrations to the floor (1 bolt each 60 cm). In my case the floor is floating, so it may be ok. You tell me. :? 2. On the external wall there will be a 10 cm rockwool Frontrock MaxE for thermal insulation. Does that help according to You to the acoustical properties whatsoever? (this was one question You missed the last time :mrgreen: . I will add another set of pictures form the construction which continues the previous one. I hope is no problem that I add them in pdf. Due to the limit of upload (500kb), I have to work for hours to reduce the size of each photo, so I better include it in a ppt, and than transform it into a pdf. If You need more details, please let me know. Thank You again, Tibi

The external window must remain as it is because of thermal reasons.A single piece of glass at -40 winterstorm will be continuously full of ice on the inside, which is a bad idea.

Hmmmm... Good point! I didn't realize it gets that cold where you live. -40°! :shock: Wow! And I complain here if it hits -5° ... OK so definitely leave the double glazing for the outer one, and just use thicker laminate for the inner window, to compensate for the three-leaf system.

Now I am about to draw the silencer box. somewhat as shown in the picture

That looks about right. For your HVAC system, if it gets that cold outside then I would also consider putting a heat exchanger in the fresh air ducts, to recover most of the heat in the exhaust air and use it to warm the incoming fresh air. Otherwise you'll be wasting a LOT of heat (and therefor money), and run the risk of icing up the fresh air supply duct.

I was considering somewhat more than twice the surface of the tube, 5 baffles, and 90 grades entrance of the tubes.

That should be really good. Make the boxes of thick plywood or MDF.

At the joint of the 3 tubes will be the fan

Careful! If you put the fan inside the wall cavity, then you have no way of repairing it or replacing it if it fails, or cleaning it, or doing maintenance. The fan should be some place where you can get to it without having to break a hole in your wall.

1. The inner room will be double gypsum board on its metal framing. Since this will be built entirely on the floating floor, should I bolt the horizontal floor frame directly to the floating concrete, or better to use something like on the picture: a rubber piece, and and another L-frame beside, which come bolted into the concrete? (for an additional decoupling).

Just bolt it straight to the floor. The entire floor is properly floated, so there's no need to decouple the walls from the floor.

The manufacturer of the profiles gives a foam-like stuff one supposed to put under the frame for acoustical reasons (it is missing from the drawing, but I will put it there) but then they say one supposed to bolt the frame through the isolator to the floor. This surely will "screw" the acoustics, and will trasmit all vibrations to the floor (1 bolt each 60 cm). In my case the floor is floating, so it may be ok. You tell me.

That's fine, since your floor is already floated. No need for anything else.

2. On the external wall there will be a 10 cm rockwool Frontrock MaxE for thermal insulation. Does that help according to You to the acoustical properties whatsoever?

Yes, definitely! You need insulation in the wall cavity, and more is better. So if you are allowed to put more than 10cm in, then that would help with both acoustics and thermal insulation. - Stuart -

Dear Stuart,

Soundman2020 wrote:

For your HVAC system, if it gets that cold outside then I would also consider putting a heat exchanger in the fresh air ducts, to recover most of the heat in the exhaust air and use it to warm the incoming fresh air

Unfortunately they cost an absurd amount of money. Since most of the time I will play alone, and I have 170 cubic meters of air, I guess I will use the ventilation a couple of times/day for 11 minutes (which on max speed will completely replace the air - at least in theory). The IR panels heat the objects in the room, and so I won't lose too much heat (in theory again) except the air's temperature. Between the refreshing circles I will block completely the ducts at both ends.

Soundman2020 wrote:

Careful! If you put the fan inside the wall cavity, then you have no way of repairing it or replacing it if it fails, or cleaning it, or doing maintenance. The fan should be some place where you can get to it without having to break a hole in your wall.

I will have a visiting door (properly sealed) from the inside at the input vent. I plan to put the silencer box right at the entrance into the room (inner leaf) permanently (that is: no more access). I will glue it together anyway, and I don't foresee any problems there. Eventually I could mount some kind of removable panel between the two doors - between the leafs - so I can extract the box, if You think this is necessary). About the exhaust system, this will be in the "attick" so I will have full access to it. (It will be tight - less then 1m space- but I was an alpinist/speologist, so I will manage to do maintenance :mrgreen: .

Soundman2020 wrote:

That should be really good. Make the boxes of thick plywood or MDF.

As I read more of this topic (as foreseen) I get more and more frustrated. The in and out surfaces of the box will be the same as the sonoflex tube (20mm). Is this bad? Will the acceleration of the air create extra noise? I suppose, that the passage surface inside the silencer should be a twice or more than the tube's surface. Regardless of the shape? E.g. if I do a silencer box 40x40 cm it is the same if would do a 20x80 cm (in theory)? Because I have roughly 35 cm space between the leafs. I suppose, that one should also leave some space for the wool between the box and both leafs. Eventually if You have a link to a DIY silencer which according to You it is ok, and have sufficient data for me to transpose.

Soundman2020 wrote:

On the external wall there will be a 10 cm rockwool Frontrock MaxE for thermal insulation. Does that help according to You to the acoustical properties whatsoever? Yes, definitely! You need insulation in the wall cavity,

This is a wool which is applied on the building (outside) on the bricks, for thermal insulation. So from the outside to inside there is 10 cm Wool - 30 cm brick - 10 cm wool - 10 cm air - 10 cm wool - gypsum board (2x) on metal framing, as showed on the picture. This stuff will eat a lot of space from the room. Since now the outside is almost done, I will start to work on the ventilations and the inner leaf. Can I reduce somehow the distance between the leafs without losing significant sound insulation? Any ideas? (cause is almost sad how it will shrink the nice big room what I have today :)). :) Well, I guess I give up on that idea. Meantime I draw the silencer box. Is that too big? (I know, it is never too big, just like a dick), but I mean compared to the expectable attenuation of the wall assembly. Thank You Tibi

I suppose, that the passage surface inside the silencer should be a twice or more than the tube's surface.

Correct!

Regardless of the shape? E.g. if I do a silencer box 40x40 cm it is the same if would do a 20x80 cm (in theory)?

Right.

I suppose, that one should also leave some space for the wool between the box and both leafs. Eventually if You have a link to a DIY silencer which according to You it is ok, and have sufficient data for me to transpose.

Here are several examples of things people on the forum have done: viewtopic.php?f=2&t=1929&start=74 viewtopic.php?t=8425&start=2 viewtopic.php?f=1&t=11542&start=5 viewtopic.php?f=2&t=9761&start=0 viewtopic.php?f=2&t=11485&start=98 viewtopic.php?f=2&t=11508&start=157 viewtopic.php?f=2&t=13821 viewtopic.php?f=1&t=15378&start=44 viewtopic.php?f=2&t=18202&start=16

Can I reduce somehow the distance between the leafs without losing significant sound insulation? Any ideas?

Yes: You can put more mass on the leaves: Make them thicker, and/or user heavier materials. For example, add an extra layer of drywall to the inner leaf. (Some people even use lead sheeting! But that's really expensive.). You can also add Green Glue between the layers of drywall.

Meantime I draw the silencer box. Is that too big?

That looks fine to me! - Stuart -

Hello Stuart, Sorry for the delay, but I had major brain surgery which kind of kept me from writing and building. I had 50% chance to survive, 85% to become a ficus and 10 to survive complication free. I am ok now, part of the hair-loss due to X-ray fallout and I've become insensitive to taste which enables my girlfriend to feed me the crap she cooks. In fact I was walking around with a time-bomb in my head the last 3 years, hearing constantly and annoyingly loud my heart-beat. You can imagine how hard is that for one with integral hearing. Now is finally silence in my head and I am getting better, and will probably have a long and stupid life. Meanwhile winter arrived, and because of surgery I couldn't finish the inner wall and thermal insulation on the roof. So I've installed some IR panels inside and some lights (temporarily) and started working. They consume a lot of power..I had like 66 kWh in the first day (outside temp -15) , than 54 (meanwhile I caulked all the cracks and joints on the roof structure, even if sometime there was no crack, I still covered all the joints between elements with caulk. Consumption turned down to 36. Then I applied 10 cm of mineral wool on the roof. Consumption turned to 19 kWh. So it counts. Obviously as You'll see on the photos, there were 4 C inside. When the inner wall will be ready, with all that insulations I guess (hope) it will be less than 5 kWh/day. I have also covered with mortar all those "gaps" and cracks You'll see on the wall. Now I am building the silencer boxes. I've decided to do a big one for the influx of air (with 5 inner leafs) and 2 smaller ones for the exhaust, (5 and 3 leafs respectively), because in one piece they will be way too heavy for me installing them on the roof barns. This way I will gain more turns for the exhaust as well. I only have one question today: on the inner side of the exterior wall I want to install some Ursa P70 hidro-resistant acoustic wool, which is semi-rigid. I don't want to use wooden framing. I want to use those plastic holders which are mounted into the wall with plastic or metal bolts. Is that forbidden acoustically? Is it a mistake? It won't have any mechanical contact whatsoever with the inner wall. I added also a photo of the airedale - Frank - which denominates the future studio, and some winter photos. I hope You will enjoy them and come one day to visit me, obviously when the studio will be ready :) Happy Holidays Tibi

Well, looks like You guys did gave up on me :) I am not dead, on the contrary I will live a long live, because I don't have any more risks at all, so You may want to reply, if You care for me :) Meanwhile I can start building, the weather got warmer. Questions: 1. (from the last post) can I use plastic/metal bolts to hang the semirigid mineral wool on the inside of the brick wall? No mechanical contact between the inner and other leafs of course. It seem s to me more practical than wooden framing, since it is easier, cheaper and also the layer of wool will be complete. 2. I came up with some possible arrangements and speaker positions in the future room. On the first sketchup, I would use 2 pairs of speakers, not necessarily so close to each other (I am not very good in sketchup), the speakers may be in angle to each other or /and the wall, eventually separated by some bass absorbers or other. I plan to put bass traps in all corners of the room from the ceiling to the floor. Also some midrange absorbers in the early reflection zones, including on the ceiling. In the second sketchup I would use somewhat the old quadrophonic approach, with basstraps in the corners, and absorbers in the early reflection zones (which with a bit on angling may even coincide for both pairs). I would use 2 different amps for the 2 pair of loudspeakers, and the advantage would be, that no feedback in the mics in the rehearsal area, but also in the instrument free zone near the bookshelf we can set up some chairs for our friends to listen, or use it as a listening area of records and stuff when we're not playing. Tell me in I am particularly stupid or not. As You can see there are no parallel surfaces (walls more than 12 grades), including the ceiling which is angled from both directions. Surface 43 m2, dimensions: 3.77x9.7x5.71x8.76, height: in the middle diagonal: 3,71 at the bigger end, 3,51 at the smaller part, and at the lateral perimeter goes down to 3,2 m meeting all walls. Yet is not ready, I am starting to build. 3. Here they are selling some acoustic foam made of open cell polyurethane 23 kg/m3. According to You are they good for anything? Reading some controversial posts - some people say that they are waste of money, because they absorb only low mids and highs (no bass, and physics seem to agree with them), and worsen the bass issues of the room. They also say, that high density wool is much better, because it is broad band. If foam sucks, I won't buy any. You tell me. Thank You in advance. Tibi

Hi again Tibi, and I have NO idea how your thread managed to slip past! I just re-noticed it now. And WOW! That's about all I can say! Man, you sure have been through something incredibly tough. And I, for one, am incredibly glad that you are not a ficus! :)

I don't want to use wooden framing. I want to use those plastic holders which are mounted into the wall with plastic or metal bolts. Is that forbidden acoustically? Is it a mistake? It won't have any mechanical contact whatsoever with the inner wall.

If I'm understand your description correctly, those are generally called "impaling spikes". Some are plastic, some are metal. They are no problem at all, and will work just fine. Some can be glued to the wall surface.

In the second sketchup I would use somewhat the old quadrophonic approach,

It turns out that quadraphonic wasn't such a good idea after all. At least, not in the way it was done originally: generally with the four speakers in the room corners, and the rear ones facing the front ones. 5.1 is sort of an extension of that, but so very different in terms of how the speakers are set up, and what is sent to each one. If you are thinking quadraphonic, then I would suggest switching to 5.1.

3. Here they are selling some acoustic foam made of open cell polyurethane 23 kg/m3. According to You are they good for anything?

If it is open-cell then it should do something acoustically, and 23 kg/m3 is about right for fiberglass, so if the gas flow resistivity of this foam is similar to that of fiberglass, then chances are good that it will work. However, it would be good to see some technical data on the acoustic testing done on that stuff... and links?

Reading some controversial posts - some people say that they are waste of money, because they absorb only low mids and highs (no bass, and physics seem to agree with them),

Welll...... sort of, but not really. If the gas flow resistivity is in the correct range, then they should absorb reasonably well, but once again it would be good to see the test results. Do you have a link to the manufacturer's web site, showing the results of tests done on this product?

They also say, that high density wool is much better, because it is broad band.

Well, that particular "they" is just plain wrong. Contrary to popular belief, if you want to absorb low frequencies you do NOT need higher density: you need LOWER density. High density is good for absorbing highs and mids, but if you are looking to hit the low frequencies, then you need lower density insulation. - Stuart -

Hello Stuart, Thank You for Your answer. I've used the impaling spikes (plastic ones). The Ursa P70 wool seems to be awesome. Reading one of Your threads where You are talking about the distance between the leafs, You say that 8" gap between two walls made of double drywall would take care of all instruments including bass guitar and drums, and also 12" gap would be OK for space ships and canon rumble. My original plan was to leave 40 cm gap (almost 16"). So I am thinking about reducing the gap to 11" (28 cm). I must keep the 40 cm on the front (where the door and the windows are, and since this is the weak link, there is no point leaving all that precious space in the other 3 (continuous) walls. According to Your advice I still would have a decent attenuation. Since this is an urgent deal (If You say so, I will keep the 40 cm), please try to answer as fast as You can. I will get back with the info about the foams soon. Thank You in advance Tibi

Reading one of Your threads where You are talking about the distance between the leafs, You say that 8" gap between two walls made of double drywall would take care of all instruments including bass guitar and drums, and also 12" gap would be OK for space ships and canon rumble.

Right, provided that you also have a decent amount of mass on each leaf. Total isolation is a combination of both mass and air cavity depth. So assuming you have at least a couple of layers of 16mm drywall on each leaf, then yes, a 12" gap would be good. - Stuart -

Thank You for the prompt answer. 12" it is, and I have a massive brick wall, and 2 layers of heavy acoustic gypsum board (13 kg/m2). Gap filled with the best absorbing wool I could find. It is a challenge to do the metal profile-structure, I guess Eiffel would hang himself if He should do this. I probably would need an engineer from ancient Rome, who designed those underground water tanks with hundreds of columns of which none is identical in height. But I have 3 walls done, on left and the ceiling. Those foams of 23 kg/m3 which is found on our market seems to be done in some garage by some creeps. I've ordered some from a company, and paid for them 6 weeks ago, and still nothing. They do not have the specs for anything they sell, so they are of questionable quality at least. An also despicable service. Here is the link: http://www.materiale-izolatie-fonica.ro ... it-d20.htm they say that this stuff absorbs in the 32-225 Hz range with an alpha coefficient of 0,85 on all the range. http://www.materiale-izolatie-fonica.ro ... mm-d18.htm here it says that this stuff absorbs all frequencies and diffuses also. the perfect fit :). Well, I seriously doubt it. Today's question: I am trying to understand the theory behind gluing the two gypsum board layers with green glue. We don't have green glue here, but we have tapegum which is a hydro-insulation material which never gets rigid, and is designed for gypsum boards gap treatment. So my understanding so far is as follows: 1. forbidden to use gypsum for the gaps between the panels, because the whole structure gets too rigid, which is bad for both insulation and acoustics - so here I definitely will use elastic tapegum 2. one suppose to put green glue between the sheets of gypsum board (here is the part I don't understand), because you need then not to be glued, but elastic. this means the following: a. you need a shitload of green glue b. instead of gluing together the boards, you keep them apart, and this is good for insulation (I imagine this is a sort of panel absorber analogy). But this does not mean that in fact you are creating a multi-leaf system, with its own internal frequency, which is actually bad? (because you add a layer and instead of 2 leaf you will have 3 or 4 considering the glue layer). Also if I understood correctly, if one screws the layers together, all the dumping is inactivated (theoretically by one screw - and in this case there will be more that 36 screws per panel? So, is there any use to put green glue between the layers? Or I should caulk only the perimeter of each panel with it? Thank You, I really appreciate You precious help. I will add some photos later today. Here they are. You can see the gap between the windows, the airlock, the inner wool's first layer, the gypsum board arrived (4,1 tons that stack). and the metal framing as I started to build it. Before I added the wool and the second windows and door, I measured the the attenuation using REW. Looks like the brick wall does attenuate 30 db at 100 Hz, and 45 db at 1000Hz. (C scale). The waterfalls looks exactly the same in all corners as in the center, and as far as I can hear, I have only one corner with a slight bass buildup (not seen by the microphone however). I have a 180Hz leak at the windows, corresponding to a minimum in the waterfall (if I am doing the correct reasoning - the leak leaves less energy in the room at that frequency). Tibi

Those foams of 23 kg/m3 which is found on our market seems to be done in some garage by some creeps. I've ordered some from a company, and paid for them 6 weeks ago, and still nothing. They do not have the specs for anything they sell, so they are of questionable quality at least. An also despicable service.

Ahh yes! That reminds me a lot of the famous "foam by mail" people... Just one word here: As Dr Who would say: "RUN! Basically, just RUN!". Scary stuff, that. Stay away...

they say that this stuff absorbs in the 32-225 Hz range with an alpha coefficient of 0,85 on all the range.

:lol: :D :o :roll: :lol: :lol: Yep, for sure... :) And by the way, if anyone buys that, then I own nice bridge in New York that I can sell real cheap! :) If people really understood just how difficult it is to trap 32 Hz, they would NEVER make claims like that...

here it says that this stuff absorbs all frequencies and diffuses also. the perfect fit :). Well, I seriously doubt it.

You got that right! It probably also washes the windows and makes the coffee...

Today's question: I am trying to understand the theory behind gluing the two gypsum board layers with green glue.

Green Glue actually is NOT glue at all! I wish they would have used a different name for it, because it's confusing. It is not adhesive, and cannot be used to stick things together. In fact, it does the opposite! It keeps things apart. It is designed to decouple the two sheets of drywall, NOT to hold them together.

We don't have green glue here, but we have tapegum which is a hydro-insulation material which never gets rigid, and is designed for gypsum boards gap treatment.

Sorry, but that won't work. Or rather, it might work a little bit to some extent, but unless it is a proper visco-leastic polymer compound that is specifically designed to act as acoustic constrained layer damping (CLD), then it will not do what Green Glue does. There is no substitute for Green Glue that has been tested in independent laboratories to the same extent, and proven to work exactly as advertised. Green Glue Company has done extensive testing in their own labs and more importantly in independent labs, and they publish all the technical reports. Nobody else does that. So nobody else has a comparable product. (as far as I'm aware, anyway).

2. one suppose to put green glue between the sheets of gypsum board (here is the part I don't understand), because you need then not to be glued, but elastic. this means the following: a. you need a shitload of green glue b. instead of gluing together the boards, you keep them apart, and this is good for insulation (I imagine this is a sort of panel absorber analogy). But this does not mean that in fact you are creating a multi-leaf system, with its own internal frequency, which is actually bad? (because you add a layer and instead of 2 leaf you will have 3 or 4 considering the glue layer). Also if I understood correctly, if one screws the layers together, all the dumping is inactivated (theoretically by one screw - and in this case there will be more that 36 screws per panel?

Green Glue works like this: it damps sheer waves (bending waves that run along the surface of the panels). Those occur at all sorts of frequencies, but are most prominent in low frequencies. It damps the flexing, bending motion of the panels as they vibrate. Yes, the screws or nails do "short circuit" the panels to a certain extent, but GG is acting in the sheer plane mostly (not so much on normally incident sound), so the effect of green glue is much larger than the nails can counteract: it works, and it works very well. Yes, you need lots of it (two to three tubes per panel of drywall), and yes it is expensive. But yes it does work. And no, there is no substitute. If you can't afford it, then do not try to substitute something else: it won't work. If you don't use GG, then just put your two layers of drywall right on top of each other, with nothing in between: no air, no glue, no MLV, no nothing. If you need more isolation, then use thicker drywall, or an extra layer of drywall. Don't ever glue your panels together, or leave small air gaps in them, for the exact reasons you mention. - Stuart -

Here are the photos. I guess meanwhile the last time You answered to me I was editing the message. :) I am blocked by the asshole from proaudiostore.ro who non only did not delivered my ceiling hangers, but also kept my money which I paid 2 months ago. So I ordered them directly from his supplier from Greece, who is a really nice guy, and the shipment is on the road. Damned bank asked me 40 euro fee to transfer 160 euros to pay for it. No wonder banks rule the world. You can see the gap between the windows, the future airlock, the inner wool's first layer, the gypsum board arrived (4,1 tons that stack). and the metal framing as I started to build it. Before I added the wool and the second round of windows and door, I measured the the attenuation using REW. Looks like the brick wall alone does attenuate 30 db at 100 Hz, and 45 db at 1000Hz. (C scale). The waterfalls looks exactly the same in all corners as in the center, and as far as I can hear, I have only one corner with a slight bass buildup (not seen by the microphone however). I have a 180Hz leak at the windows, corresponding to a minimum in the waterfall (if I am doing the correct reasoning - the leak leaves less energy in the room at that frequency). Now, with the first layer of wool on the walls, and the second round of windows and door in place (as in the photos) I did a sound-check with my electric guitar and also with an active monitor (for drum-machine). The room is almost anechoic, and although one can hear it from outside, it is well attenuated. And I have no inner wall yet, and another layer of wool is to be added, and also a vapor barrier, which I bought one with small air bubbles and aluminum layer which according to the manufacturer will add some sound insulation too to the thermal one. The ventilation is fully functional, and changes the air in the room in 4 minutes. The sound boxes I made for both vent circuits work well, Thank You Stuart for the advice. I overdid them, but I am not sorry. Due to the fact, that the air input tube is the main wind direction, I have a slow convection of air input even if the fan is not functioning, and no sound escapes through the tube. So far I am pleased with the result. I won't use anything between the layers of drywall, but I will use the mapegum to caulk and cover the gaps between the drywall pieces within a layer. I guess that is a better idea than using gypsum, and rigidize the whole structure. If I'm wrong, please tell me. Thank You again Tibi

Damned bank asked me 40 euro fee to transfer 160 euros to pay for it. No wonder banks rule the world.

:shock: :!: Ouch! That's expensive! Have you tried using PayPal? It is all electronic between you and the seller (or buyer), no banks involved, and the fees are a lot more reasonable.

Here are the photos

Please post those on the forum itself, so they can be seen more easily, instead of in the PDF attachment.

You can see the gap between the windows, the future airlock, the inner wool's first layer,

On page 3, I see the outer wall (brick?), then a thin layer of insulation, then metal framing, then more insulation, an air gap, and another frame, also with insulation on it. So I'm not really sure what I'm seeing there! :) Why do you need TWO frames? Only one extra frame is necessary, for your inner-leaf wall. If you add two walls there, then you will have a 3-leaf system, which means that your isolation will be WORSE in low frequencies than for the same 2-leaf system.

Before I added the wool and the second round of windows and door, I measured the the attenuation using REW.

I think you are trying to use REW for something that it was not intended to be used for. REW is meant for analyzing the acoustic response inside a room, not for measuring isolation between one room and another. To measure isolation (Transmission Loss) just use a hand-held sound level meter.

Looks like the brick wall alone does attenuate 30 db at 100 Hz, and 45 db at 1000Hz. (C scale).

That sounds about right for thick brick.

And I have no inner wall yet, and another layer of wool is to be added, and also a vapor barrier, which I bought one with small air bubbles and aluminum layer which according to the manufacturer will add some sound insulation too to the thermal one.

Ummmm... that isn't a vapor barrier. Vapor barrier does not provide thermal insulation, nor sound isolation: it is normally just a sheet of polyethylene plastic attached to the framing right before you put the drywall on. It's only purpose is to retard the movement of water vapor through the wall, in order to prevent water condensing on the structural surfaces inside the wall.

The ventilation is fully functional, and changes the air in the room in 4 minutes. The sound boxes I made for both vent circuits work well, Thank You Stuart for the advice. I overdid them, but I am not sorry.

Excellent! It is MUCH better to overdo things, than to "under-do" them in studios! One room change in 4 minutes is more than you need, but that's good. One change every 6 minutes would be fine.

and no sound escapes through the tube. So far I am pleased with the result.

:thu: Then you did it right! :)

I won't use anything between the layers of drywall, but I will use the tapegum to caulk and cover the gaps between the drywall pieces within a layer.

I'm not sure what "tapegum" is, but you can either "tape and mud" the joints between drywall panels, or you can leave a slight gap between the panels as you put them up, then fill the gap with backer rod and acoustic caulk, if you want really good seals. - Stuart -

Soundman2020 wrote:

Ouch! That's expensive! Have you tried using PayPal

Of course, I am using paypal, but unfortunately the company only accepts bank transfer. Another fee is 50 for TNT "economy" shipment, which takes a week. Slowly it is more convenient to go by car and retrieve the hangers myself. Or, swim. Which is yet cheaper :mrgreen:

Soundman2020 wrote:

post those on the forum itself,

OK I will do so starting the next time. I have no novelties to show now. In fact I am amazed of those quick responses. Thank You a million times.

Soundman2020 wrote:

On page 3, I see the outer wall (brick?), then a thin layer of insulation, then metal framing, then more insulation, an air gap, and another frame, also with insulation on it

The additional frame is present only in the gap between the windows, and will sustain the drywall I will use to seal inner space between the windows from the gap between the walls. So it will sustain 2 vertical and 2 horizontal pieces of drywall, perpendicularly to the wall. There will be no 3 leaf system.

Soundman2020 wrote:

I think you are trying to use REW for something that it was not intended to be used for.

I used REW's sound generator through an active monitor, and measured the sound level inside and outside the studio with a professional handheld decibel-meter.

Soundman2020 wrote:

Ummmm... that isn't a vapor barrier

It is a multilayer membrane, which does the vapor stuff, and also has an aluminum layer to shield heat, and air bubbles for both sound and heat. Remember, here in winter there are sometimes -40 C and I will have electric heating...and since I will tape it hermetically together, I am sure there is no air-driven sound leak anywhere.

Soundman2020 wrote:

I'm not sure what "tapegum" is,

Tapegum [=mapegum] is a dedicated paste consistency stuff to caulk between drywall gaps, and it is very elastic, in fact it never becomes solid, and also hydro-insulator. I had surprising answers from two sound treatment companies ( I am not sure if I can write the names so I won't) - using their free room evaluation: they both said, that I almost do not need basstraps in my room, because I got the measurements right, and have no parallel surfaces nor 90 degree corners. In fact one of them said that I don't have any axial mode problem, and the tangential ones are 2-6dB only, so I will probably get away with some mid/high absorption and a certain degree of diffusion. Kind of flattering, but we will see after I will be ready. I guess, I will need yet some help. :oops: I will try not to bother You too much. ANYWAY, WITHOUT YOUR HELP MY STUDIO WOULD'T BE HALF AS GOOD SO FAR AS IT IS. I am just an MD, PhD and DIY. No idea of acoustics. As a read more, I am more and more convinced that I do not know jack about it. :) :lol: Tibi

Tapegum is a dedicated paste consistency stuff to caulk between drywall gaps, and it is very elastic, in fact it never becomes solid, and also hydro-insulator.

Sounds perfect! That should work well. Just leave a slight gap between the drywall panels as you put them up, maybe 2 or 3 mm or so, and force that tapegum stuff well down into the gap, to make sure you get a good seal. If you have long walls, you might need to adjust the framing so that the drywall is still centered on the studs: EG. 6 panels of drywall next to each other with an extra 4mm gap for each is 24mm, so that's off the edge of the stud!

The additional frame is present only in the gap between the windows, and will sustain the drywall I will use to seal inner space between the windows from the gap between the walls.

Don't seal that with drywall! That will connect your inner leaf to your outer leaf, defeating the decoupling. Just use Homasote board, add a piece of OC-703 insulation on top, then wrap that all in black fabric. Glue that to ONE side of the gap (probably the brick wall side), and let it float just a bit above the other side, without touching (or touching only very lightly).

I used REW's sound generator through an active monitor, and measured the sound level inside and outside the studio with a professional handheld decibel-meter.

Ahhhh! OK, then that's fine: You were just using it as a tone generator. When you mentioned waterfall plots, I though you were trying to measure the transmission loss through the walls with waterfall plots! :shock:

I had surprising answers from two sound treatment companies ( I am not sure if I can write the names so I won't) - using their free room evaluation:

They went there to your place for FREE, and evaluated your room with proper test equipment? At not cost? :) :!: :shock: If not, then I would not trust their assessment very much! If this is one of those services where they say "E-mail us your room dimensions and we will tell you which of you wonderful kits you need to buy", then be VERY aware... that's not a good way of determining what treatment your room needs. This is something that you CAN measure yourself with REW, then post the data files here.

because I got the measurements right, and have no parallel surfaces nor 90 degree corners.

Ummmm... well..... :) I would not trust what they said at all then! Good room measurement do NOT make room modes go away: they just spread the room modes a bit more evenly. Making the walls non-parallel does NOT eliminate modes: In fact, it multiplies them. Sure, the axial modes might get a bit weaker, but you have to angle the walls quite a bit before they disappear.... and at the same time, you are creating many new tangential and oblique modes, which replace the axial modes.... Also, by angling your walls you make it impossible to predict the modal behavior using simple room-mode calculators, and then the only method for doing that is by using expensive FEM/FEA software, and paying a good operator who knows what he is doing to set up the boundary conditions that simulate your room, and then interpret the results for you... I guarantee that the "free analysis" people did NOT do that, because it costs money. So if they knew that your room has no parallel walls, and they still told you that you have good modal response, and they did not actually go to your room and measure it acoustically, then sorry, but they were rather less than honest with you. Here's what you should do to find out for sure what the modal response of your room is, using REW: Place your speaker down on the floor in one corner of the room, right in the corner where the two walls meet the floor, with the speaker facing down the length of the room (the longest distance, not the shortest distance). Now place your measurement mic up in the exact opposite corner of the room, where the other two walls meet the ceiling. Point the mic right into the corner, as close as you can get it without it touching the walls or the ceiling. In other words, you have the mic and the speaker as far apart as it is physically possible to place them in that room, in digonally opposite corners. Now run REW, and post the resulting MDAT file here on the forum. It might be too big to post here, and in that case use a file sharing service such as Dropbox, and post the link here. Then I'll download that and analyze it for you. This is what REW is designed for: to measure room response. It is very good at doing this, and will certainly show the real modal behavior of your room. The reason for putting the mic and speaker in the corners, is because all room modes terminate in the corners, so by using the "tri-corners" of the room, you are triggering all possible modes, even down to the lowest frequencies, and also measuring them at the best point.

In fact one of them said that I don't have any axial mode problem,

:lol: We'll see if that is true or not... :) REW doesn't lie, and REW doesn't want to sell you a kit made up of pieces of foam.... :)

and the tangential ones are 2-6dB only,

That makes no sense: 2-6 dB ... with respect to WHAT? :shock: :roll: :idea: Theory says that tangential modes will be 3 dB lower than axial modes, and oblique modes will be 3 dB lower than tangentials. But that doesn't mean much: that is only the maximum INTENSITY of the mode. What is important about modes is not so much the maximum intensity but rather the decay: How long do they carry on ringing? Do they decay at the same frequency, or do the change to other frequencies? Does the decay rate change, or is it constant? That's what matters.

but we will see after I will be ready.

It's better to see now, so you can be prepared for the treatment in advance... :)

I guess, I will need yet some help.

No problem! That's what the forum is here for.... To help.

No idea of acoustics. As a read more, I am more and more convinced that I do not know jack about it.

Well, for somebody who doesn't know much, you seem to be doing a lot of things RIGHT! And it seems to be working out pretty well, so far!!! :thu: - Stuart -

Thank You for Your kind words. I have to do yet a lot of work. The hangers arrived from Greece. Now I wanted to jump and continue the profile mounting on the ceiling, but it turns out to be rather difficult due to the measurements of the room. Nothing is horizontal nor equal or parallel :) And a lot of thinking ahead (something like Karpov vs. Kasparov 20 moves ahead).

Soundman2020 wrote:

Don't seal that with drywall! That will connect your inner leaf to your outer leaf, defeating the decoupling. Just use Homasote board, add a piece of OC-703 insulation on top, then wrap that all in black fabric

I won't seal it. The extra framing You have seen on the photo will hold it in a way that it will have physical contact only with the inner window, and all the structure lays on the floating floor. With the external leaf will not touch, only through a layer of wool. I was thinking to seal the small gap with elastomer, or tapegum, but Your idea with the cloth is excellent. So I will use cloth.

Soundman2020 wrote:

Here's what you should do to find out for sure what the modal response of your room is, using REW:

I have measured the room with REW as You told me to. Here is the file. Hopefully it is ok. Somehow I couldn't inactivate completely the internal microphone of the laptop. I also had to "rar" it because the site did not accept the extension of the file. Hopefully it is no problem that the allover volume of the studio will be less than it is now, and the wool is on the wall...and the framing stands, there is a stack of drywall and some wool packages laying around. Thank You for everything, and now I go back to the drawing board and figure out the position of the hangers and the framing of the ceiling, which I am sure Eiffel would hang himself if he suppose to do it. Compared to my ceiling, the tower is simple :mrgreen: :lol: Tibi

Nothing is horizontal nor equal or parallel

:) Yup, that's normally the way things are...

And a lot of thinking ahead (something like Karpov vs. Kasparov 20 moves ahead).

Only 20??? Why so few? :) Seriously, yes, that's a very smart way of approaching studio design: Design the whole thing on paper or electronically first, then build it once you have thought of everything you possibly can.

I won't seal it. The extra framing You have seen on the photo will hold it in a way that it will have physical contact only with the inner window, and all the structure lays on the floating floor. With the external leaf will not touch, only through a layer of wool. I was thinking to seal the small gap with elastomer, or tapegum, but Your idea with the cloth is excellent. So I will use cloth

. Excellent. That will work fine.

I have measured the room with REW as You told me to.

The data looks OK, but you only measured up to 200 Hz! You need to measure the entire spectrum, from 20 Hz to 20,000 Hz. There are some modal issues apparent on that file, but I'd need to see the complete analysis. In the "measure" settings, make sure that you have "start" set to 20 hz (or lower) and "end" to 20,000 Hz. - Stuart -

Dear Stuart, I am really flattered by those fast responses. Seems like instead of working alone, I am working with You, which is excellent :yahoo: I remeasured 0-24000 Hz. Looks like if I set different intensities on the monitor, the graph looks different. So I attach both files. https://www.dropbox.com/s/0buf4l2jkdirh ... ements.rar You were right, it doesn't fit into 500 kb. Thank You Tibi