Another soundproofing question

This video:

https://www.youtube.com/watch?v=aFG-W9nvSrQ

by 'Max Troy' about turning a garage into a soundproof room was posted a while back on DW, and because it's very close to my situation I use it as a reference.

But I just started contracting the work for the inner and outer shell and looking for supplies and I have a quick, basic question.

Around 3:16 he mentions that he created a 'floating floor' by placing stone blocks on 100 mil wide by 4 mil thick rubber. Someone in the comments mentions that this seems really thin for the weight being placed on it, but nobody has replied.

I'm curious about the same thing. Where I live it's much easier and cheaper to build things from stone, concrete, and brick. So I'll have a block-and-concrete outer shell and probably a brick-and-wood or block-and-wood inner shell. With that much weight, is a strip of rubber of those dimensions truly sufficient to bear the weight of the inside room and effectively isolate it?

The ending recording of sound leakage (or lack thereof) doesn't really show how vibrations transmit, and I'm very concerned about that largely because the floor of these studios is probably the hardest part to re-do if you get it wrong.

Thanks for any help.
 

Pylot

Senior Member
Look up something called mass loaded vinyl.

I picked up a couple of rolls that I used to put between my existing wood floor and a particle board floor that I installed over it.

This stuff is really strange, a square foot weighs about 2 pounds. It will help isolate the sound above from the bearing surface below.

I think I paid 75 bucks for a roll that was about 30 inches wide and about 15 feet long. This was from craigslist so your mileage may vary.
 

Odd-Arne Oseberg

Platinum Member
His studio is just getting the most of the room he had and not loosing space.


If you don't have his restraints I'd just go for mass.
 
His studio is just getting the most of the room he had and not loosing space.


If you don't have his restraints I'd just go for mass.
Thanks, that actually raises another question. In the video it appears that the guy is filling the space between the inner shell walls and the outer shell walls with cement. That's mainly a byproduct of his pouring concrete over his wooden interior room ceiling.

Is that a sensible approach? I know you can't leave the space between the walls or ceilings empty because it will just reverberate, but if you fill it with cement it seems that creates full contact between the shells, making the shell separation kind of pointless.

Would it be better to fill the space with sand or fiberglass?
 

Morrisman

Platinum Member
Our school built a new theatre recently. I saw the stage floor going in - concrete slab, then matchbox sized blocks of black rubber spaced one foot apart. Then 3/4" plywood (then a thin, replaceable layer of masonite painted with thick black paint)

The half inch gap means the whole floor gives a little when dancers jump on it.

The plywood flooring had the rubber blocks stuck on before it was laid down, so they woukd be evenly spaced.
 
G

Ghostnote

Guest
Are you building on a slab on grade? If so, don't float a floor, it'll only use up space needlessly. Your walls will most likely not be as soundproof as a concrete slab directly on the ground, so floating a floor will serve no purpose. In some cases it actually reduces your amount of soundproofing depending on how you build it out.
 
So I bought a piece of property, 20 meters wide by 50 meters deep, that was at about a 20 degree slope front-to-back, then had a retaining wall built around it and the land leveled with refill. Over 5 years the elements have settled the refill enough that the engineers who built the house now say there's no need to dig down 5-6 meters to find the actual bedrock, the refill is firm enough to hold the smaller structures. So I'll be putting the cement foundation on top of a bunch of dirt and rock.

I plan to build a roughly 5mx5m outer shell of concrete block and cement, and then build a room-within-a-room inside that (probably about 4.5mx4.5m, since concrete blocks tend to be 20cm; that would let me leave about 10cm of space between the inner and outer walls).

If I don't need to float the inner room that's even better, I'm not sure I can buy things like mass loaded vinyl in Mexico (at least not without import and shipping fees). The real issue is lack of experience; I've never built this kind of room and none of the local builders have either. So I'd like to make it as simple as possible.

I'm thinking just build the outer shell, then either build the inner shell right inside or 'float' it on some kind of rubber lining, then stuff the space between the shells with fiberglass or sand or something else absorbent but not conductive. Ventilation can be done with baffle boxes or something similar, and entry would be with the standard double door.

But I would like it to be as sound 'proof' as possible, we live in a very quiet residential area and if I get a yen to bang out some tunes at 2am I would like to not wake the neighbors.
 
G

Ghostnote

Guest
So I bought a piece of property, 20 meters wide by 50 meters deep, that was at about a 20 degree slope front-to-back, then had a retaining wall built around it and the land leveled with refill. Over 5 years the elements have settled the refill enough that the engineers who built the house now say there's no need to dig down 5-6 meters to find the actual bedrock, the refill is firm enough to hold the smaller structures. So I'll be putting the cement foundation on top of a bunch of dirt and rock.

I plan to build a roughly 5mx5m outer shell of concrete block and cement, and then build a room-within-a-room inside that (probably about 4.5mx4.5m, since concrete blocks tend to be 20cm; that would let me leave about 10cm of space between the inner and outer walls).

If I don't need to float the inner room that's even better, I'm not sure I can buy things like mass loaded vinyl in Mexico (at least not without import and shipping fees). The real issue is lack of experience; I've never built this kind of room and none of the local builders have either. So I'd like to make it as simple as possible.

I'm thinking just build the outer shell, then either build the inner shell right inside or 'float' it on some kind of rubber lining, then stuff the space between the shells with fiberglass or sand or something else absorbent but not conductive. Ventilation can be done with baffle boxes or something similar, and entry would be with the standard double door.

But I would like it to be as sound 'proof' as possible, we live in a very quiet residential area and if I get a yen to bang out some tunes at 2am I would like to not wake the neighbors.
The point of building a room within a room is to not have one touch the other so as to limit the amount of sound transmitted through flanking paths. You don't want to fill the space with anything.
 

Odd-Arne Oseberg

Platinum Member
Thanks, that actually raises another question. In the video it appears that the guy is filling the space between the inner shell walls and the outer shell walls with cement. That's mainly a byproduct of his pouring concrete over his wooden interior room ceiling.

Is that a sensible approach? I know you can't leave the space between the walls or ceilings empty because it will just reverberate, but if you fill it with cement it seems that creates full contact between the shells, making the shell separation kind of pointless.

Would it be better to fill the space with sand or fiberglass?

Looks like insulation to me. You don't need anything really. The connections that don't transfer vibration is the thing but if you really want to a foot of sand should kill anything. Many ways. There's a studio in downtown Oslo that has their vocal booth hanging from a crane cable outside. That's getting out there, literally. lol

Either way, many sort of halfway things in that vid in many ways. Did he even use any armoring on that roof? Insane.
 

Pylot

Senior Member
What ghost note said, you don't have to fill the space between the inner and outer walls.

Are you going to use green glue and do two layers of interior drywall? I used that stuff and it is amazing.

You can cover the outer wall and fill it with rock wool but rock wool is really expensive and the benefit is not huge. If you use green glue between two inner layers of dry wall you wont need to fill the air gap.

One thing that is pretty interesting is at the green glue web site they advertise the use of a clip to actually stand the drywall off of the studs. If you are building a free standing room then you don't really need to do that. Anything you put through the wall, especially a screw into a stud for example, will transmit sound into the stud and on to the outside of the wall.

So you put the first layer of drywall up then green glue and another layer which you tack in place with drywall screws. Then once the green glue has set up for a few days you remove the screws and fill the holes.

Getting some air in there is interesting too. Obviously a hole lets sound out so you have to create a baffle in front of the hole that moves the air entrance point a few feet away. Easy enough to do. The trick is to get enough airflow in there to keep it comfortable. The green glue converts sound waves into heat and I have found my little room warms up pretty quickly with a couple of us in there jamming away.

One other thing that I wish I would have done, if you can slightly tilt or angle the walls so that you don't have two opposing walls that are square to each other you will reduce some of the standing wave that will set up otherwise.

Also plan on making some bass traps for the corners. You don't have to do all of the corners but you will find that a well soundproofed room will set up some reverb or echo and you will likely end up with some standing waves that need to be eliminated.
 
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