How Much Isolation Do You Need? - part two - BLOCK WALLS

[@stephenborgovini]

Hi John, Thank you for these videos. You mention painting a concrete wall to seal it. What kind of paint do you recommend?

[@JHBrandt]

Use an exterior grade emulsion. We need an airtight seal because where air can go, so goes sound.

[@danieltapiamusica1]

Hi John, just found your channel and it's great! One question, if you decide to go with double solid concrete walls, would you need to do a floating floor? Or not necessarily...

[@mytommy]

what does resonance mean in the topic of soundproofing?

[@Espiritiv]

Hi John, Im trying to soundproof and isolate my daylight basement. My concrete back walls, i am going to put XPS foam, 3/4" airgap, then 2x4 wall with Rockwool. How do i finish my outside wall to have better isolation and soundproofing? On my outside wall, i have existing finished 2x6 walls with blow in insulation and 1/2" gypsum. DO i have to install another 2x4 wall/insulation with and airgap as well, or is there another method that works just as good, such as clips and channel, or just more mass(drywall?)

[@JHBrandt]

Without knowing how much isolation you need, I really can't recommend anything. Can you give me a noise spectrum and level at 1/3 octave bands? Go to my resources page and download the paper "Assess the Environment". And send me an email. [e-mail]

[@iLLerDiGGer]

Very interesing John, that info is hard to find thanks! So in an unfinished basement with ceiling joist filled with insulation left open for heigh reasons, and concrete foundation walls sealed with foam, adding layers of drywall to that will make low freq isolation worst? Thanks

[@alreddy13]

So will using channels, insulation material and one layer of drywall between floors, be counterproductive or productive when the goal is to minimize the sounds of footsteps, people talking and low music coming from the upstairs apt?!. I'm a little confused

[@JHBrandt]

I would not recommend channel because it doesn't isolate. Use either clips and channel or resilient channel. That will reduce impact noise and air-borne sound. If you need low frequency sound isolation, you'll need considerable mass.

[@alreddy13]

@@JHBrandt Yes sorry I meant to say I will be using resilient channels, insulation and one layer of drywall. One more question, just to clarify, Rockwool insulation will give me the same benefits as normal fiberglass insulation when coupled with resilient channels?? It's really the impact noises i'm trying to eliminate. Not too much low frequency sounds are being emmitted from the above apt.

[@JHBrandt]

@@alreddy13 The insulation type doesn't matter much that's why I recommend the cheapest. Rockwool insulation will do just fine. It's NOT the insulation that does the soundproofing, it's the mass and seal. The fiber insulation absorbs the cavity resonances and lowers the assembly resonance by damping and improves the STL thru that process.

[@Mythbuster42]

How about basement studio? With 20cm.concrete blockwall, is it needed to add 2 layers gypsum partition with gaps (12.5cm/no connection) to increase STC rating? Or just 20cm solid concrete is enough? Thanks

[@JHBrandt]

Panca, it depends on what you need. How much isolation do you need? Soundproofing is expensive, especially if you don't need it.

[@rezaachman299]

HI John, great video, thank you, if I may ask, cause I haven’t found the answer so far, if I am doing a double wall brick do I ned to fill the space gap with anything?, htank you

[@JHBrandt]

adding fiber or absorption in the gap will improve the STL... How much do you transmission loss do you need? And at what frequencies?

[@rezaachman299]

@@JHBrandt I’m not sure how much, as much as I can I get Iguess, each brick wall is about 14cm thick with the cement finish, and the air gap between them is 10cm and the will be use mostly for a drum kit, thank you John, sorry if I’m not very technical

[@aaronliddell5564]

I'm not positive about the other poster, but I also glued the gypsum to the outer sheathing form the inside. But it doesn't create a third leave beacuse from there you leave the stud wall open (with fluffy in it) then an air space then the next leaf which has 2 layers of gypsum on the room side of the new inner shell. So the two leafs are open to each other inside with 4" air gap and 8" of fluffy. Do you think that is alright?

[@glasgowguitarist3636]

At what point does a third leave stop being a third leave of the wall and become a corridor? Clearly there are lots of cases where there may be an internal corridor. Lets say the wall furthest from the external boundary is part of the control room and the corridor is 1m wide. Why does the control room wall not act like a third leave to the external wall and create a resonance that actually lowers the STC? Presumably there is a specific minimum air space which probably also depends on the mass of each leave?

[@JHBrandt]

Calculate the mass-air-mass resonance of each partition and space. If they differ by the square root of 2, it will add to the sound transmission loss. 😊

[@ssmith2019]

Good vid !

[@strongtowermuzik5440]

Hey John thanks for sharing your knowledge of acoustics with us. I'm working on a temporary space in my attic and I have a couple of questions. (1) I own a 1920's twin home with plaster and lathe construction and no firewall in between the two houses. Would it be beneficial to add a layer of drywall glued in between each cavity against my neighbors wall to increase isolation? (2) The space has two rooms, one larger than the other. I was thinking about adding a secondary wall next the existing wall that divides both rooms to help increase the separation between each room. It'll probably have a 6"-8" gap in between, insulation in between the studs and 2 layers of 5/8 drywall on both outer parts of the walls. My question is, should I completely fill that gap with insulation or leave it empty and just put the insulation between the cavities of the framed walls? Do you think it'll be worth doing? Or would there be a better solution to increase isolation without sacrificing so much space?

[@JHBrandt]

Good questions! If by adding the drywall (glued in between each cavity..) creates a THIRD partition, I would recommend against it. You are better off with only two partitions. It has been proven with testing that additional partitions can often REDUCE the sound isolation. So, I would recommend this if you need more isolation: Add another layer of drywall to your existing wall, taking care to apply it in such a manner as to eliminate any air space between the drywall layers. ok? What we're doing here is ADDING mass. If you are able to double the mass of your wall partition, it can improve STL by as much as 6 dB. (that's twice as much!) This becomes difficult if you need to add more than 6 dB, and starts to work like; two steps forward and one step back. :P If all you can add is one layer, use 5/8" (16mm) fire-rated drywall... and if you can afford it, use Green Glue as well. Of course, it's always best to test and see if you have adequate sound isolation. If not, add the drywall, if you do.. no need to spend the time or money. ;)

[@Mythbuster42]

Is hebel block good or bad for soundproofing?

[@JHBrandt]

Panca Tab, yes! Of course. It's heavy and heavy is what you need for Soundproofing.

[@Mythbuster42]

John Brandt does this material it self also good blocking low frequency noise, such as sub low noise coming from a big subwoofer? Thx for your reply.

[@JHBrandt]

As part of a system, yes. ONE layer of these won't block more than 56 dB at the most, assuming a 20 cm thickness. But the sound reduction does not extend to frequencies below 80 Hz. Not very much anyway. You need a resonant system like a sealed double wall to accomplish a good reduction of sound waves below 80 Hz.

[@Mythbuster42]

John Brandt I saw someone use perforated alumunium for soundproofing,how does it work?

[@JHBrandt]

Panca Tab, I have NO IDEA!! I would recommend that you ask them and get the testing data on that. To be honest, anything that is perforated will not block sound.

[@Jewdly]

Hi John, if I'm soundproofing a room constructed using hollow core block wall, is it normally better to only finish one side?

[@JHBrandt]

Finish as in what? do you mean a render or plaster? OR when building a room in a room do you mean doing a decoupled gypsum layer?

[@Jewdly]

Hi John, I just got my copy of Rod Gervais' book. As far as finishing, I know that the outside face of two walls will be gypsum, and have the space to create an air gap of moderate size. Two other walls are poured concrete foundation, so nothing on their outsides. The inside will be whatever works the best with the least amount of space.

[@roiad876]

I always imagined Isolation Clips with Mineral Wool would kill all the resonance withing behind the gypsum boards?

[@JHBrandt]

No, sir. Not all resonance. it's physics and not really a DIY thing. One size does not fit all. ;)