Filled 200 mm concrete block w 1/2" plaster both sid(N)

[hugo_inside]

I read about this kind of wall and its STC is 56. It's enough if I had a 100 mm floating floor, isn't it? How much dB could sound a death-metal band for example?

this is the link where I read it:http://www.angelusblock.com/noise.cfm[/b]

[knightfly]

You had me going for a second there; 20mm walls with STC 56!!?! You missed one zero, should be 200mm.

STC 56 sounds pretty good, til you realize that's at 500 hZ - as you drop in frequency, you also drop in sound transmission loss - that wall, even filled with sand, would have a transmission loss (TL) of around 34 dB at 50 hZ, rising to 56 dB at 500 hZ - what this means, is that if you have a death metal band they will be at about 110 dB spl, maybe a little more; if the kick drum and bass are that loud, they are (at 50-60 hZ) about 55-60 dB above the threshold of human hearing at that frequency (roughly 52-55 dB) - if you take the 52 dB hearing threshold at 50 hZ, then add the 34 dB of TL this wall gives at 50 hZ, you're still hearing about 25 dB of bass.

This is where mass-air-mass comes in - less mass, but with air space between, improves this low frequency performance (which is usually the most irritating when trying NOT to hear something)

If you use the exact same amount of mass, but put it in TWO leaves with 50mm air gap (100mm concrete/50mm air gap/100mm concrete) you end up with about STC 72, with a worst case LF TL of 50 dB instead of 34.

It's all physics... Steve

[hugo_inside]

so , plasterboard does not do nothing at all???

the construction starts on monday!!! and 20 mm block are in the place... Maybe I learn something about this bussines suicide.

Floating floor does nothing to?? So the idea to STC 72 is solid concrete block 100 mm with 50 mm air gap between?? Or hollow block filled? or without sand?

[knightfly]

Hugo, are you sure you don't mean 200 mm block, as in 8 inch?

Personally, I think you are rushing things to start construction when there is so much to learn about this type of building - everything you do will make a difference somehow. Adding mass to either leaf of a 2-leaf wall will change things, but not as much the more you do - for example, if you have 2 layers of gypsum wallboard on each side of a partition, and you want 6 dB better isolation, you have to put FOUR layers on each side - but 6 dB better than ONE layer each side, would only take TWO layers each side - you have to DOUBLE the mass on each side of a wall to get a 6 dB improvement. This is why really high soundproofing gets so expensive.

It's also why a wider air/insulation space between your two masses is cheaper way to get the same isolation - it comes back to the mass-air-mass calculation; the more air, the less mass for the same dB.

If you plan to FILL your (hopefuly) 200mm blocks, then that will be ONE mass - you will want one air/insulation gap and one more MASS between each area you want to isolate - so, from each area to each OTHER area, you want mass, air, mass - in other words, if you pretend you are a sound, imagine you are in one area - to get to the other area, you should have to travel through a mass, an air gap, and another mass to get to any OTHER area; this is the best use of materials and cost.

Any place these two masses come in solid contact with each other, makes them NOT WORK nearly as well.

I would strongly suggest that you stop construction until you fully understand these concepts and have a REAL WORKING PLAN of your facility - otherwise, you are headed for sad times... Steve

[hugo_inside]

Sorry, block size is 200 mm plastered both sides

After some weeks reading and questioning, I take into account some points:

1.- The more space in the rooms.
2.- The cheapest way, but it should complete in future. (If isolation is not enough we could put a gypsium + rock wool over the block, the floating floor will be made.)
3.- the isolation posible.

I think the way I choose collects this 3 points.

On the studio, there will be 2 block walls with 40 mm rock wool and 13 + 15 mm sheetrock and 150 mm jost for floating floor, here is more important the isolation.

Rehearsal rooms is not much important than in a recording room the coming in sound. And bands are unusual to coincide with othe band at the same time. And not all the bands plays death metal.

With all this points, you still think I'm in the wrong way??

[knightfly]

That can probably work for you; it just makes me nervous when someone says they're starting to build, and I haven't seen drawings with enough detail that I could build from them; I'm hoping you have some, and that whoever will build this for you knows sound proofing type construction.

If you build all your practice room walls from 20mm block, FILL it with sand, and put solid core doors in with good seals, your walls will have somewhere between 55 and 58 dB STC, with a low end TL of roughly 34 dB @ 60 hZ - with single doors, the walls will NOT be your weak link. Solid core single doors 44mm thick would be about STC 32, provided your seals are VERY good; at 60 hZ, this TL would only be about 25 dB, so a loud band would STILL be loud outside. If you added a second frame and door, 250mm inside the other one and hung on an interior frame (the one you would add 2 layers of gypsum wallboard to for the second walls) then your door would be about STC 60, (again, assuming GOOD seals) with TL at roughly 42 dB down at 60 hZ.

The tricky part of adding more walls LATER, is where do you put them? If you want to maintain the 2-leaf mode, then only every other practice room should have double walls inside; this would create a double leaf for the walls to the adjacent practice room WITHOUT adding anything inside it.

I don't see any way to do this in stages - anything you add later will mess up your separation of wall leaves somewhere. If you've figured out a way to put up part of your construction now and part later, and STILL keep each room's envelope having two separate and continuous leaves of mass all the way around each room, I'd like to see the plan... Steve

[hugo_inside]

this is an old plan, soon I'll post the new one. but the basical idea is that:

The door now open to outside, the oposite than in the floor plan. And the bigger room on the left side is where I build the studio. But there are some changes in the rooms sizes too.