Thanks! It seems like the Nady is a better choice then. I'll get that :) I'm sorry, but I can't really put my mind to rest about floating my walls/floor... :shock: One "tiny" detail I might have forgotten to mention regarding the slab is that it's sharing the slab with the stairway next door to the studio going all the way up to through the house. Wouldn't the floor in the stairway then act as a large loudspeaker membrane transferring all the sounds that get into the concrete from the studio? If that's the case, what frequencies do I need to worry about with regards to a 5cm concrete slab (reinforced with 6mm steel in a 15x15cm pattern) resting on 20cm polystyrene then grade? If it's only impact noise (ex from the bass drum) I could easily fix that with a drum riser. But if we're talking most frequencies, then that would be an argument for floating the floor/walls, right? Here's some drawings of the house if that helps... The basement is as mentioned 90% under ground. Thanks, AndreasHere's an interesting article that compares several mics, in that respect: http://realtraps.com/art_microphones.htm
Littlewater Studio - Norway (Europe)
Originally posted at johnlsayers.com, topic 18085.
The slab is "on grade", right? Meaning that it is poured on top of the ground, with no other rooms or gaps below it? If so, then yo have the entire planet down there, acting as a damper on your slab.... :) It's as if you had thousands of people down there, all pressing their hands up against your slab to stop it from vibrating...One "tiny" detail I might have forgotten to mention regarding the slab is that it's sharing the slab with the stairway next door to the studio going all the way up to through the house.
If this is a bog concern for you, then just build a drum riser or amp riser for anything that might create impact noise in the slab. Airborne noise is not an issue, since concrete is extremely massive (a single square meter just 10cm deep weighs well over 200 kilograms), so airborne sound is not going to make it vibrate, especially considering the Planet Earth camping effect.... Now, if you REALLY want to float your floor, then go ahead! Nobody will stop you! Just make sure that you do it right, as in this thread: viewtopic.php?f=2&t=8173 And make sure that you have the budget to do it: It will cost you several thousand dollars. These are the floor jacks you will need: Or these: This is how you do it: As long as you know how to do all the calculations, and have the budget, then there's no problem in doing it.Wouldn't the floor in the stairway then act as a large loudspeaker membrane transferring all the sounds that get into the concrete from the studio?
You would need to build your floor such that the resonant frequency is below 10 Hz. That means that your floor will start isolating at about 14.1 Hz, and will isolate reasonably well at 20 Hz. From there, it gets better and better as you go up the spectrum. That's why you need the mass of concrete: to get the resonant frequency low enough. You cannot accomplish that with wood. Not even with a dozen layers of 3/4" plywood. Concrete is the only material at reasonable cost that can accomplish this.If that's the case, what frequencies do I need to worry about with regards to a 5cm concrete slab (reinforced with 6mm steel in a 15x15cm pattern) resting on 20cm polystyrene then grade?
For airborne sound, it would have to be EXTREMELY loud! How much energy do you think it takes to make the entire planet vibrate? :) - Stuart -But if we're talking most frequencies, then that would be an argument for floating the floor/walls, right?
Alright. I've done some measurements. I put on some pink noise playing at 105dbC (measured 1m from the speakers pointing the mic directly towards the speakers). Measuring at the top/2nd floor where my wife will be watching TV i got a 30dbC reduction. I left all the doors open, so the sound basically had free passage up the stairway. I also measured in my kids bedroom on the 1st floor which is right above the studio with the door to the bedroom closed and got a 35dbC reduction. I then lowered the volume so that my SPL meter was showing 55dbC 1m from the speakers. It seems almost too good to be true, but I could hardly hear anything on the 2nd floor. Measuring didn't give any results other than what I get from the background noise which is about 44dbC. Am I doing something wrong? In case this would be the expected noise I would hear when finished, 50dbC reduction should be more than enough for all my purposes.The only way to be sure is to measure it with a sound level meter
It seems impossible to get hold of 16mm in Norway. I can get 15mm fire rated plasterboard which weigh 12kg/m2 or 12,7mm Fermacell fibre gypsum board which weigh about 15kg/m2! The downsides to using the latter is that it would have to be plastered all over and it costs about twice as much. I'm thinking I could go for one layer of 12,4mm fibre gypsum and then a layer of 15mm fire rated plasterboard for the inner shell. Would that do the job? Does it matter in what order I place the two materials considering their density and weight? On the subject of drywall. I've beefed up the part of the wall facing the stairway with an additional layer of DW inbetween the studs and sealed it tight with caulk. Then remains the part of the wall facing into the technical/laundry room (called "Bod" in the basement floor plan). The problem is that it's kinda hard to fit any drywall inbetween the studs since there are lots of water pipes coming from the water supply cabinet mounted in this wall:Say I don't care that much about sound coming into this room, could I leave this wall as it is, only calking all edges so it becomes airtight and still get -50dbC in the stairway with the door to the laundry room closed (ps there is a 2cm airgap under this door for ventilation)? If I do need to add mass to this wall as well, are there other solutions I could use that would be easier to fit than drywall? I guess one solution would be to finish the room, then do some measurements and if needed add an additional layer on the laundry room side of the wall?definitely you want 16mm drywall! Always! Never thinner
Hi again Stuart, and sorry for bombarding you with questions, but I'm finally getting some momentum in the building process and the questions just keep coming... :)
I hired a carpenter to set up my inner framing which only point of contact is the concrete slab and a minimum of 3 cm from every part of the outer framing. As you can see from the picture below I've started putting in some insulation (fiber glass). So my first question is; Should I fill everything with insulation or should there be some gap of air between the inner and outer shell here as well? Ie, what is considered better; picture A or picture B (or non :))? If alternative B is the better option; Should I try to fasten the insulation somehow using some kind of string to make it slightly pressed to the drywall above and so it doesn't accidentally fall down on the inner joist? How about in the corners where there are no inner joists in between. Should I fill this hole with insulation or leave a bit of air there as well?The new ventilation ducts (which are attached to the outer framing) are in some places only 1 cm from the inner framing joists. Is this enough or should this distance also preferably be 3 cm or more? Should I put insulation between the inner joists and the ducts (making sure it's not compressed of course) or is the gap of air preferred?I guess all these questions really boil down to; How well does non compressed fiber glass transfer vs absorb sound and is fiber glass always preferred over a gap of air? :)
Thanks again for all your help Stuart. It's highly appreciated!
Cheers,
Andreas
"A" is better, for sure. But Rod has pointed out that you might not be allowed to do that, due to the quirks of some building code regulations. So check your local code to see if you can, and if so then fill the cavity completely, but without forcing the insulation in: you don't want it shoved in so tight that it creates a flanking path...:)what is considered better; picture A or picture B
Fill it completely.How about in the corners where there are no inner joists in between. Should I fill this hole with insulation or leave a bit of air there as well?
1cm is OK, but do fill that gap with acoustic caulk to make sure that the duct cannot touch the wood, or vibrate against it...The new ventilation ducts (which are attached to the outer framing) are in some places only 1 cm from the inner framing joists. Is this enough or should this distance also preferably be 3 cm or more? Should I put insulation between the inner joists and the ducts (making sure it's not compressed of course) or is the gap of air preferred?
Fiberglass is a porous absorber, just like mineral wool. It absorbs sound at the microscopic level when the vibrating air molecules transfer some of their energy to the fibers, which then convert it into low grade heat. Fiberglass insulation will only transmit sound (transfer it across the air gap due to flanking) if it is compressed. If it is just laid in place, even touching both sides, it won't actually transfer much sound like that. But if you force it in tightly, compressing it, then it will. - Stuart -How well does non compressed fiber glass transfer vs absorb sound and is fiber glass always preferred over a gap of air?
Cool, thanks! I'll check with my local code then :) Btw, did you see my post and questions from June 17th regarding the Fermacell gypsum-fibreboards? Do you have any experience using other types of drywall like this? Basically it's drywall made from 80% gypsum and 20% wood fibre and has a density of 1150 kg/m3. They come in 12,5mm and 15mm and are said to be equally good or better than two gypsum boards together.I'm thinking I could go for one layer of 12,4mm fibre gypsum and then a layer of 15mm fire rated plasterboard for the inner shell. Would that do the job? Does it matter in what order I place the two materials considering their density and weight? Here's some more data if you're interested: http://www.fermacell.com/en/docs/130606 ... amends.pdf Thanks! -Andreas"A" is better, for sure. But Rod has pointed out that you might not be allowed to do that, due to the quirks of some building code regulations.
That's pretty good density. I think that should work fine. - Stuart -Basically it's drywall made from 80% gypsum and 20% wood fibre and has a density of 1150 kg/m3.
Ok, thanks. They do however only come in 2400mm x 600mm. Won't that be a problem when attaching them to the wooden studs 60 c/c considering that I should avoid seams overlapping for the second layer? What would you consider good density? Would a 15.4mm thick fire rated plasterboard of 780kg/m3 also work okey? Also, does the size of the drywall plates matter for better sound isolation? Is bigger plates better or does smaller plates mean less flanking across studs and more "freedom" for the plates to vibrate and absorb energy? Thanks, AndreasThat's pretty good density. I think that should work fine.
Turn the boards sideways for the second layer, and/or offset them by one stud. OR change your studs to 40cm OC instead, and offset by one stud.Ok, thanks. They do however only come in 2400mm x 600mm. Won't that be a problem when attaching them to the wooden studs 60 c/c considering that I should avoid seams overlapping for the second layer?
Yep, that would be OK too. But if you want to be certain, then you should do the math: calculate the MSM resonant frequency of your wall, and the isolation.What would you consider good density? Would a 15.4mm thick fire rated plasterboard of 780kg/m3 also work okey?
The size of the panels makes no difference to how well they isolate. What matters is the density and the thickness. Thin drywall (less than 15mm) is too flexible for good isolation, the surface density is too low, the resonant characteristics are not so good, etc. As long as you are above about 10 kg/m2 on each layer, you should be fine. Use the equations to figure out how many layers you need, or rather, how much total mass you need. Other options include OSB, plywood, MDF, and even fiber-cement board. - Stuart -Also, does the size of the drywall plates matter for better sound isolation? Is bigger plates better or does smaller plates mean less flanking across studs and more "freedom" for the plates to vibrate and absorb energy?
Great. Bought 2400x900x15.3mm plasterboards and will put them sideways. :) What do you recommend to put between the separated windows in that 3cm gap between the frames? I guess it's a question of estetics while avoiding to create a flanking path between the two systems. I guess the same goes for the space between the frames for the double doors? Thanks, AndreasTurn the boards sideways for the second layer, and/or offset them by one stud.
That's where you need to put your desiccant! At the bottom, at least. One way is to make a light-weight "tray" with Homasote and put the beads in there. Or you could try to cut a small "bed" out of a piece of OC-703, or something similar. You then wrap that with black cloth, and fit it across the gap. For the sides and top, just 703 wrapped in black fabric. Some people glue those to one of the frames, and leave the other side floating freely, to avoid any possibility of flanking, but if you do it with 703 cut carefully to just the right size so it is a snug fit, then there shouldn't be any problems. Same concept for the gap between the doors: 703 wrapped in black fabric, press-fitted into place, or glued on one side. - Stuart -What do you recommend to put between the separated windows in that 3cm gap between the frames?
Good stuff! So, hopefully a quick and easy question; I've made these back boxes for the electrical boxes in order to seal them as airtight as legally possible. Should I fill the air within this box with something (like fiber glass or hardening foam)?Thanks, AndreasThat's where you need to put your desiccant!...For the sides and top, just 703 wrapped in black fabric.
Naah, that's fine. But do put some insulation in the ends of the conduit after the wiring is in, then seal that with caulk. And also make sure to caulk the front face of the framing around that box just before you put the drywall on, to make sure you have a good seal there to, around the edge of the box. - Stuart -Should I fill the air within this box with something (like fiber glass or hardening foam)?