Help! Soundproof room..... not soundproof.

[TequilaKez]

Hey guys,

A good friend of mine just converted half his garage space into a small rehearsal space where he imagined he could, amongst other things, play a drum kit without annoying neighbours or people inside the house. He had plans made up for a 'room within a room' and had it built to spec but it is still transferring a lot of sound and vibration into the house. Kick and snare especially are really quite loud. He asked me to take a look at it and I have a couple of ideas but before he goes spending any more money, I thought I'd see if anyone here might chime in with some useful advice. It could be something quite simple, or it may be that we are expecting too much. Here's a section of the plan and a few photos.

The first thing I noticed was the metal beams used to separate the two inner plasterboard layers. Not only are these layers connected via these metal beams, but they are attached with long screws, which I've read, can channel vibration quite readily. The whole structure is isolated from the garage space itself though, effectively creating the all important air gab should stop sound getting from one structure to the next.

Can anyone suggest a relatively inexpensive way to quiet this thing?

Thanks in advance,

Kez.

[TequilaKez]

--- the silver foil you see between the room and the garage wall is acoustic insulation and was placed there at the last minute in an attempt to stop some more of the sound getting to the house but it was the same when that space was just 'air'.

[gouge]

i guess we all have our preferences with regards detail, but i would not have designed it like that.

i would go back to your designer and ask them to visit site and help resolve the issues.

but that's just my opinion only.

ask them what sound transmission loss figure it's designed for and i'd do it prior to installing that next layer of internal lining.

[Sebg]

The relatively small airgap between the two sets of 2x13mm plasterboard will make sound insulation worse at low frequencies.

The Themotec stuff looks like a waste of money in this application.

Several elements of the design you have provided look like they are not cost effective.

What is the ceiling detail?

[boggy]

Originally Posted by TequilaKez

--- the silver foil you see between the room and the garage wall is acoustic insulation and was placed there at the last minute in an attempt to stop some more of the sound getting to the house but it was the same when that space was just 'air'.

If this is alumium foil, it cannot be used for acoustic isolation... or.. better... it may be used, but it cannot insulate anything acoustically, because it is too light.

For acoustic insulation (stopping sound waves and vibrations) it's always used a decoupled and heavy construction of "room within a room" where walls, ceiling and (floating) floor are much heavier than ordinary drywall, if you need to have (some) low frequency isolation (you already noted kick and snare).

I agree with gouge, ask designer to resolve problems... good isolation isn't an easy project.

[Chris_Nicks]

i think i would need more details on this.. Can you post the drawing plans?
i think it would have helped if the airgap between the garage and the room was wider. gap wid the foil too narrow and may cause resonance

[TequilaKez]

Thanks for your replies guys.

If this is alumium foil, it cannot be used for acoustic isolation... or.. better... it may be used, but it cannot insulate anything acoustically, because it is too light.

eh well of course it isn't plain old aluminium foil. It is 'Tontine' acoustic insulation (see plan), one side of which coated in a perforated foil, although I too don't see the point of the foil.

For acoustic insulation (stopping sound waves and vibrations) it's always used a decoupled and heavy construction of "room within a room" where walls, ceiling and (floating) floor are much heavier than ordinary drywall, if you need to have (some) low frequency isolation (you already noted kick and snare).

Well if you look at the photos and plans, it is in fact a room within a room. And almost, a room within a room within a room. Well it would be if the two double plasterboard layers were completely isolated from each other, but they are not because of those metal beams. None of the layers are particularly thick though, the thickest being the 2x13mm plasterboard. Can he expect a better result by doubling the inner plasterboard layer to say 4x13 = 52mm?

I agree with gouge, ask designer to resolve problems... good isolation isn't an easy project.

I am working with the designer now to see if we can find a way to improve the situation between us.

[TequilaKez]

i think i would need more details on this.. Can you post the drawing plans?

Ok Here's a better view of the plans.

[boggy]

Originally Posted by TequilaKez

.........
Well if you look at the photos and plans, it is in fact a room within a room. And almost, a room within a room within a room. Well it would be if the two double plasterboard layers were completely isolated from each other, but they are not because of those metal beams. None of the layers are particularly thick though, the thickest being the 2x13mm plasterboard. Can he expect a better result by doubling the inner plasterboard layer to say 4x13 = 52mm?
....

I mean heavy construction,... concrete, heavy brick walls, etc,... not ordinary drywall construction, it is too light for low frequencies. Room within a room isn't enough.... it's only a decoupling method.

You may use more layers of plasterboard sheets to build a much heavier wall and get better LF isolation if you like to improve existing situation.

[Chris_Nicks]

i see the problem.. i think there is a design flaw with the wall plans

[avare]

The resilient channel between the layers of gypsum is making low frequency isolation worse.

Andre

[Sebg]

Originally Posted by TequilaKez

Ok Here's a better view of the plans.

The design has some significant flaws in it. I am almost afraid to ask who did the construction plans. I am in Sydney if that helps your friend and he wants someone to look at it.

Detail 11 has a 5th layer of plasterboard. I presume this is not actually between the stud frame and the brick wall, as drawn, but rather as indicated, only on the stud frames which are exposed to the garage proper. He would have been better off covering that insulation with shadecloth from Bunnings rather than plasterboard. At least then the garage would have had significant acoustic absorption.

As to remediation ... I think it will involve major dismantling. I have never seen the Thermotec stuff used as vibration isolation as seems to be the case in Detail 11. Pretty sure it won't work very well in that role.

If your friend wants to try and salvage this mess then the first step would be to measure the noise levels coming into the house and to work out how many more dB of sound insulation are required to get a passable result (in at least octave frequency bands). If it is more than a small number, then a major rebuild is in order.

[TequilaKez]

Thanks again guys for shedding some light.

i see the problem.. i think there is a design flaw with the wall plans

Any suggestions?

The resilient channel between the layers of gypsum is making low frequency isolation worse.

Would tearing down the inner plasterboard layers and removing the metal beams and studs help?

Detail 11 has a 5th layer of plasterboard. I presume this is not actually between the stud frame and the brick wall, as drawn, but rather as indicated, only on the stud frames which are exposed to the garage proper. He would have been better off covering that insulation with shadecloth from Bunnings rather than plasterboard. At least then the garage would have had significant acoustic absorption.

Would taking this down help any? it would also make the gab between the room and the existing garage wall slightly larger, maybe reducing the possible resonance that Sebeg described.??

[gouge]

see what your designer comes up with, it's hard to know what conversations occurred between them and the client so i don't want to make assumptions. also, your designer might have an easy fix.

this is one option.

a partial dissmantle. you currently don't have a room within a room and as mentioned a 3 leaf system is not the best for bass frequencies.

you could remove all of the internal linings. ie. both layers of plasterboard and the resilient channel.

then fix the resilient channel to the stud frame and re-lay the 4 layers of plasterboard leaving a gap between the concrete slab and the bottom of the plasterboard. plasterboard has staggered joints. now you only have a double leaf wall. use fire mastic to all perimter edges and penetrations.

ceiling would be the same as the walls ie. double leaf construciton only, mastic to perimeter and penetrations.

you will need to make sure the resilient mounts you have will support the weight of the linings.

i'd use green glue between the layers of plasterboard also.

then i'd consider some kinetics type isolation pads and pour a concrete slab over your existing floor slab leaving a gap to the perimeter. at a minimum create a drum riser.

also, the details where the room touches the existing garage walls need some work and i'd consider sealing the cavity.

then look at the doors, typically they would be isolated from each other and fyrecheck used to add mass.

also your internal acoustic treatments may need some work. using the foil faced insulation helps improve some frequency ranges but it's no good for higher frequencies and you don't seem to have any bass traps.

it needs to be reconciled too i would think.

[Sebg]

Gouge, you will note that the insulation facing into the room will be "perforated foil" faced. So there shouldn't be an issue with reflecting high freqs (as would have been the case with plain foil).

edit: otherwise I agree that in general what you propose may be a reasonable "out". I don't see any benefit of sealing the wall cavity between the plasterboard and brickwork. Note that if the furring channels are run vertically and are supported at the bottom (eg sitting on the floor slab) then the Resilient Mounts won't be carrying any of the weight of the plasterboard so that won't be an issue. if the furrings are run horizontally then the plasterboard must be supported at the floor as those Resilient Mounts are not designed to be loaded in shear (structurally they will be fine but acoustically the rubber insert will be bridged). Also note that there may be no real benefit to using Resilient Mounts in this application anyway.

[Chris_Nicks]

The resilient channel between the layers of gypsum is making low frequency isolation worse.

+1 to andre. What your friend is constructing is a triple leaf system. You should make a real double wall construction. The resilient channel wont be necessary in a real double wall construction, you will just have to put more mass on the outer and inner walls. double insulation in between the walls would also help a lot. I think it would be best to float this room to reduce flanking noise. Are the garage walls made out of concrete?

[gouge]

Originally Posted by Sebg

Gouge, you will note that the insulation facing into the room will be "perforated foil" faced. So there shouldn't be an issue with reflecting high freqs (as would have been the case with plain foil).

edit: otherwise I agree that in general what you propose may be a reasonable "out". I don't see any benefit of sealing the wall cavity between the plasterboard and brickwork. Note that if the furring channels are run vertically and are supported at the bottom (eg sitting on the floor slab) then the Resilient Mounts won't be carrying any of the weight of the plasterboard so that won't be an issue. if the furrings are run horizontally then the plasterboard must be supported at the floor as those Resilient Mounts are not designed to be loaded in shear (structurally they will be fine but acoustically the rubber insert will be bridged). Also note that there may be no real benefit to using Resilient Mounts in this application anyway.

cheers sebg, i didn't think the holes made that big a difference to the high frequencies compared to non perforated. nice to know! :-)

[Sebg]

Gouge, sorry I am a bit lazy:

Just type "acoustisorb" into google (without quotes) and click on the first PDF that comes up. It will have some of Tontine's test data with plain and perf foil faced Acoustisorb. There is some drop-off of course but not that much.

[gouge]

thanks again sebg,

i had a look at the datasheet. think i'll sit on the fence now.

i notice the tontine datasheet stops at 2000hz and i think that above that the perforated insulation would drop away with the nrc value.

looking at the similar products from bradfords the perforated foil backed glass wool insulation looses out to the unfaced by about 10% at around 5000hz. i'd guess the tontine is similar.

somehting else worth mentioning is the room doesn't have any ceiling insulation. that's a tough space to play drums in. i'd guess listening fatigue will occur.

[Sebg]

sorry for going off-topic. CSR Bradford data for Supertel Glasswool plain, perf foil faced and plain foil faced.

[gouge]

that's an interesting table sebg, i had a look at the current datasheet for supatel and it's quite different.

http://www.bradfordinsulation.com.au...55d512969a.pdf

anyways, i take your point. i am surprised that the perf version performs as well as it does. but getting back to the op's problems.

my original point was that using all foil faced product is maybe not the best outcome and some unfaced insulation should be incorporated. i think which ever data is used this idea has some relevance.

the cheapest way is to reverse some of the foil faced batt's, wrap them in material to keep the fibres at bay and also hang some of the faced batts across the corners for bass trapping. i'd also consider at one end hanging the batts off the wall 50mm and hanging a curtain in front of them.

from the op's point of view it won't cost any extra money other than the small amount of additional material and the curtain.

[TequilaKez]

You may use more layers of plasterboard sheets to build a much heavier wall and get better LF isolation if you like to improve existing situation.

a partial dissmantle. you currently don't have a room within a room and as mentioned a 3 leaf system is not the best for bass frequencies.

The relatively small airgap between the two sets of 2x13mm plasterboard will make sound insulation worse at low frequencies.

What your friend is constructing is a triple leaf system. You should make a real double wall construction. The resilient channel wont be necessary in a real double wall construction, you will just have to put more mass on the outer and inner walls. double insulation in between the walls would also help a lot. I think it would be best to float this room to reduce flanking noise. Are the garage walls made out of concrete?

Thanks again guys for chiming in. Ok seems the gerenal consensus is taking down the inner plasterboard layer and furring channel and adding as much mass as possible to the other layers of pasterboard. As far as desired outcome, the sound transference is only an issue to the house and a small amount would be acceptable. It needs to drop from 'slightly annoying' to 'slightly audible' but i'm not sure how to quantify that in dBs.
As the doors and seals are the easiest fix, we will investigate them first. I'm not sure I understand completely though, is the airtightness important because soundwaves travel through air particles and therefore sound transmission localised to the area where there is a leak or does it average out more. For example, standing next to the room in the unocupied space in the garage, it sounds like the kickdrum and snare are coming directly through the wall itself and not from around the door or ceiling. In other words, would creating a better seal around the dooror created heavier doors effect the sound transmission going through to the house on the opposite side of the room?