DIY sound proofing

clarkyb

Established Member
Joined
Feb 2, 2005
Messages
266
Reaction score
58
Points
70
Age
34
Hi...is there a way to create really cheap but effective sound proofing, by say bunging 20cm of foam on the front and back walls of the home cinema and then carpeting the front of the foam..would this help in any way ? im not spending any/much money on sound proofing..also what can i put under the sub to decouple it from the floor because the bass can be heard from right the other end of the garden
thanks
 
The problem with any sound proofing is not just what you use but how you fit it, and more importantly if there are any 'gaps'. When i built my extension i had the sound insulation fitted when it was being built and this alone did not solve the whole problem of sound transmission. The key is isolation from the transmitting materials ie party walls, on the sub (bass) problem, i do not think there really is a solution to this, bass can seem to travel through just about anything, and only really expensive and well fitted isolation materials can even hope to diminish it by any significant way. Your idea will work to a degree but i am not too sure how it will look :eek: Mine had to be very wife friendly so not foam on the walls i am afraid. I think the golden rule is for the material to be as dense as possible and as isolatated as possible, but both of these and especially the latter on is not so easy to achieve, good luck.
 
just had a loft conversion done on my semi and i had a suspended floor and the stud walls were created away from the existing so as to create a 2 inch gap from the party wall even though i did it all the way round, not set up yet but will let you know how it is, the stud walls are plaster board then cellotex (kingspan compressed polystirein) within the studwork then plaster board again.
 
You'll need at least 1.5M of packed fiberglass insulation to absorb any meaningful low bass, so it's usually not very practicla to control low bass with wall treatments. You can use diaphragmatic absorbers, where you essentially have a wall section that can flex to absorb bass. With sound proofing, it is essential to avoid flanking paths, ie paths around the sound proofing, such as unsealed electrical outlets. These can negate up to 97% of you sound isolation efforts.
 
clarkyb said:
Hi...is there a way to create really cheap but effective sound proofing, by say bunging 20cm of foam on the front and back walls of the home cinema and then carpeting the front of the foam..would this help in any way ? im not spending any/much money on sound proofing..also what can i put under the sub to decouple it from the floor because the bass can be heard from right the other end of the garden
thanks

Hi Clarky, did you not get the email i sent you after our last contact? I went into some detail on cheap diy stuff for you, bit disappointed if you didnt!

You wont stop the bass being heard without some heavy duty soundproofing though im afraid!
 
mattym said:
Hi Clarky, did you not get the email i sent you after our last contact? I went into some detail on cheap diy stuff for you, bit disappointed if you didnt!

You wont stop the bass being heard without some heavy duty soundproofing though im afraid!

sorry i never got your email..i was quite disappointed because i though that you had forgotten me

thanks
 
clarkyb said:
sorry i never got your email..i was quite disappointed because i though that you had forgotten me

thanks

i try very hard not to forget anyone!:D

i will rummage back and find the email, and resend.:smashin:
 
thanks..i definitely never got that email before
 
clarkyb said:
thanks..i definitely never got that email before

it happens

i sent 3 emails on the same day and all 3 got lost, so a quick snotogram to the ISP is the best option :smashin:
 
clarkyb said:
Hi...is there a way to create really cheap but effective sound proofing, by say bunging 20cm of foam on the front and back walls of the home cinema and then carpeting the front of the foam..would this help in any way ? im not spending any/much money on sound proofing..also what can i put under the sub to decouple it from the floor because the bass can be heard from right the other end of the garden
thanks

to decouple the sub, you can try many options. some companies make specialized products such as these, which might be convenient.

if you wish for a DIY sub mount, the best bet would be to put some rubber pucks/pads/feet under something heavy - like a concrete block - and then mount the loudspeakers or sub on top of the block. For best results, you should get a tape or ruler, and make sure that the rubber pucks compress about 1-2 mm when you place the blocks on top of them (this ensures that the resonance of the system is very low, which is necessary as all decoupling schemes are worse than nothing around the resonance point). The weight of the blocks will help lower the resonance of the mass-spring system that you create, and it will provide inertial stability as well.

The cones of speakers/subs generate a fair amount of force when going forward/back, and sound quality can be impaired if they are placed on, for example, a stack of rockwool. The mass of the blocks keeps them stable.


As for the foam/carpet, that will absorb sound inside the room, which means there is less reverberant sonic energy inside the room = less noise outside of the room, but...

the absorption will fail at low frequencies, and the reduced noise at higher freq's will tempt you to turn up the volume, making even more LF noise, and as such solutions like this tend to make things worse as much as better. Room treatments/absorption do definitely make the room quieter, however, as in external noises won't bug you as much in such a room.


For a low cost method to improve sound isolation for home theater purposes, you might consider staggered stud walls. I don't recommend metal resilient channel for theater purposes as low frequency isolation from this type of assembly is not great.

don't look at Rw or Rw+Ctr for guidance on theater isolation systems, as that measure of performance only considers frequencies down to 100hz... which means it doesn't consider how well the wall performs in the subwoofer region.
 
Soundproofing was my main concern on my garage project as it linked to next doors living room:eek:
I built a room in a room or atleast as close to it as a could get,sealed every gap which took an age [like a 5000 piece jigsaw puzzle] used an acoustic sealant and for filling studs i used aucoustic boards from wicks [expensive] anyway the upshot is i told my neighbour what i was up to and if the noise bothered him please tell me!
No complaints a year later. And i don't skimp an the bass!:clap:
 
Not much to add to what's already been written but some years ago I discussed this with Bestobell Acoustics (don't know if they are still in business) and with Dunlop. The answer to bass frequencies is as follows:

It requires a very heavy, flexible "curtain'. They suggested I achieve this by glueing a very very low density foam to the wall (mostly air) and glueing a sheet of lead-powder filled PVC sheet onto the foam. However, the lead-filled PVC was incredibly expensive and I ended up using the thickest, heaviest solid rubber I could lay my hands on, which turned out to be a few dozen rubber foot mats. Tricky to glue in place I can tell you! To further cut down the high and mid-range frequencies (and for cosmetic purposes) you can build a plasterboard wall backed with 13mm coarse fibre underlay, leaving a small air gap between that and the rubber "curtain". This loses you around 40mm of room width per wall, which ain't too bad.
 
SamRadford said:
Not much to add to what's already been written but some years ago I discussed this with Bestobell Acoustics (don't know if they are still in business) and with Dunlop. The answer to bass frequencies is as follows:

It requires a very heavy, flexible "curtain'. They suggested I achieve this by glueing a very very low density foam to the wall (mostly air) and glueing a sheet of lead-powder filled PVC sheet onto the foam. However, the lead-filled PVC was incredibly expensive and I ended up using the thickest, heaviest solid rubber I could lay my hands on, which turned out to be a few dozen rubber foot mats. Tricky to glue in place I can tell you! To further cut down the high and mid-range frequencies (and for cosmetic purposes) you can build a plasterboard wall backed with 13mm coarse fibre underlay, leaving a small air gap between that and the rubber "curtain". This loses you around 40mm of room width per wall, which ain't too bad.

what was the TL on that method? I would be interested to see how that compares to modern solutions, Brians Green Glue is the best material ive seen so far, most impressive!
 
SamRadford said:
Not much to add to what's already been written but some years ago I discussed this with Bestobell Acoustics (don't know if they are still in business) and with Dunlop. The answer to bass frequencies is as follows:

It requires a very heavy, flexible "curtain'. They suggested I achieve this by glueing a very very low density foam to the wall (mostly air) and glueing a sheet of lead-powder filled PVC sheet onto the foam. However, the lead-filled PVC was incredibly expensive and I ended up using the thickest, heaviest solid rubber I could lay my hands on, which turned out to be a few dozen rubber foot mats. Tricky to glue in place I can tell you! To further cut down the high and mid-range frequencies (and for cosmetic purposes) you can build a plasterboard wall backed with 13mm coarse fibre underlay, leaving a small air gap between that and the rubber "curtain". This loses you around 40mm of room width per wall, which ain't too bad.

Hi SamRadford,

i hope your isolation works out for you, and please don't take my comments the wrong way, and i don't mean any disrespect to the expert you consulted...

But that is simply false. The logic is ... intuitive. it's easy to imagine a big, limp curtain absorbing all the low frequency sound and making much quiet on the other side. Similarly, sometimes you see someone toutint very stiff walls as the best way to stop low frequencies. And again, the logic is very intuitive - it's easy to imagine those cross-braced walls being so stiff that they resist being moved by low frequency noise.

but the former (limp mass) is false in every way, and the latter (stiff) is false on structures as large as walls. If you had a simple panel - like a 1m x 1m plasterboard panel - this panel would exhibit a strong resonance, and then below that resonance it's stiffness would in fact work for you and resist lower frqeuency noise. But on something as large as a wall, the panel would have to be about a meter thick before this stiffness could work in your advantage. a meter of solid plasterboard (a meter of layers of 16mm plasterboard wouldn't be nearly as stiff).

finally, stiffness helps us out only below that strong fundamental resonance in the panel, and so it's not that graet of an idea to ever try to use stiffness as a sound isolation tool because if you suceed in getting the wall stiff enough to resist sound at a relevant frequency, your wall will be very bad at higher frqeuencies around that resonance...


as for limp mass.... a simple mental experiment can help clarify that situation. Imagine that we got all the scientists at NASA together to develop the most amazingly limp material ever seen. so limp that it moved perfectly with the sound and absorbed it all...

well that would stop all of the sound, right? no, it would TRANSMIT all of the sound. sound = vibrating air, and sound makes its way through walls by vibrating the walls, which then vibrate air on the other side, making new sound. If you have this magical super-limp material that vibrates perfectly ... it offers no resistance to sound transmission at all. Indeed, the very nature of sound transmission is RESISTING vibration


but the point is moot. because a stiff mass (like plasterboard) and a limp mass (like the mass loaded vinyl) offer exactly the same performance for a given size over most of the frequency range because the resistance to motion is provided by mass, not by stiffness or by limpness. mass

and in real walls, resistance to vibration is a function of bascially two things

1) mass. the heavier the walls, the more they can resist vibration from airborne sound

2) resonance. the more the walls resonate, the easier it is for airborne sound to vibrate them.

Other things help sound isolation as well, like mechanical decoupling (resilient channel or double stud walls, etc.). Those function by helping prevent vibration from moving from one side of the wall to the other - by breaking the mechanical path.

Insulation in walls helps because (if the wall is decoupled and no mechanical path is available), then the sound has to try to make it to the other side via the air, and the insulation can absorb something.


But at low frequencies, most decoupling schemes are working against you, not working for you, and it is reasonable to view the low frequency behavior of most common walls as a function of mass and resonance.

good luck,

Brian
 
Now, i hope this is making good sense and not sounding like technobabble.

When you decouple a wall - like a double stud wlal or putting resilient channel on a normal stud wall - you create something called a "mass-spring system".

All mass-spring systems work like this:

1. there is a resonance defined by how stiff the spring is and how heavy the weight bouncing around on the spring is. at the resonance performance is much worse than a solid mass - MORE vibration is transferred

2. below the resonance the system has no effect and behaves like a solid mass

3. well above (about 1/2 octave) the resonance, performance starts becoming extremely good due to the decoupling action. Indeed, well above this resonance decoupling is a tremendously potent tool for sound isolation.


So, obviously, since decoupling works against us except well above the resonance, we should try to get the resonance as low as possible. these rules help quite a bit with that:

1. use as much weight on each side of the wall as you can. so 2x 16mm plasterboard on each side of the wall is much better than 1x 13mm plasterboard. more weight gives better performance due to mass AND it helps lower the resonance frequency = a double benefit

2. use as deep an air cavity as you can spare. above about 8" or so we start to get into diminishing returns for small changes. remember, it's big changes that make big differences, not adding an inch to an already deep wall.

3. use some insulation in the cavity. avoid excessively dense insulations.

4. if at all possible, avoid the use of what's called "resilient channel"in the US, and instead use double stud or staggered stud walls. the channel makes the "spring" stiffer, and worses low freq response. Modern sound clips or spring ceiling hangers are better than old fasionhed metal channel



Although masonary constructions are prone to a variety of sound isolationi problems, the weight of having brick or concrete on one side of a wall is always a nice starting point.
 
perhaps a couple sketches would help elaborate these points.

The first sketch shows something called mass law, which you can calculate easily enough. if anybody wants the formula i can oblige. It also shows a hypothetical stiff mass, and a hypothetical limp mass. the view is simplified in that only two resonances are shown.

in essence, limp mass will follow mass law, but stiff mass will exhibit problems due to these resonances.

the second graph shows the effect of decoupling - imagine splitting our mass in two and moving it apart with an air cavity in between.

When i ramble about the importance of - if you decouple - getting this resonance low, perhaps this graph shows why. the lower resonance moves the "weak" spot of the system lower in frequency where our ears can't hear it as well, and also improves things alot at more important frequencies slightly higher. the lower the better with respect to this resonance.


adding a limp mass with air in front of another mass won't create a magical sound stopping absorbing system, it will create a mass spring resonance as shown. the resonance may be better damped than the resonance of a stiff mass, which is a very good thing.
 

Attachments

  • stiff_limp_masslaw.gif
    stiff_limp_masslaw.gif
    7.5 KB · Views: 897
  • mass_spring_decoupling.gif
    mass_spring_decoupling.gif
    7.2 KB · Views: 859
Sorry to butt in.
I'm looking for a solution for a semi-detached house. I can spare about 8cm for sound insulation.
I have a solid brick party wall (useless sound proofing. Used to hear talking and music. Now hear talking, music and a screaming 1 month old)

I was going to try and go down the route of a new stud wall, 50mm of acoustic mineral wool (density 140kg/m3), then a sandwich of 12.5mm soundbloc pasterboard (denser than the normal stuff from the DIY sheds) + Green Glue + 12.5mm soundbloc

Questions for Brian.
Previously in this thread you stated "use some insulation in the cavity. avoid excessively dense insulations". What exactly is, 'excessively dense'? Is 140 kg/m3 too dense?
Various specialist 'sound proofing' web sites have what they call Dense Fibre Matting (DFM) with densities ranging from 20kg/m3 to over 140kg/m3. What sort of density should I be aiming for?

A few more for good measure.
If using green glue, is it absolutely necessary to decouple the studs of the new partition from the party wall? This makes the constrution that much harder. Could I get away with less deep studs, but with 1 or 2 point contacts up the wall, to stop the wall from flexing too much?

Is a green glue solution effective when only applied in the receiving room? (most people on the american forums seem to use it to stop sound escaping, not from entering a room)

Any idea if my proposal would be any good? If its a goer then I might think about all four rooms + lifting the upstairs floorboards and putting some DFM between the joists to cut down on some of the flanking noise as well.


Many thanks
 
Richard said:
Sorry to butt in.
I'm looking for a solution for a semi-detached house. I can spare about 8cm for sound insulation.
I have a solid brick party wall (useless sound proofing. Used to hear talking and music. Now hear talking, music and a screaming 1 month old)

I was going to try and go down the route of a new stud wall, 50mm of acoustic mineral wool (density 140kg/m3), then a sandwich of 12.5mm soundbloc pasterboard (denser than the normal stuff from the DIY sheds) + Green Glue + 12.5mm soundbloc

OK, the brick wall has it's problems, i know, but it's a good starting point as it's very heavy. That type of wall doesn't have all that good of middle and high frequency isolation, and can be just plain bad if it has cracks and the like, but the weight is a great starting point for low frequency isolation.

8cm is pretty thin... the 50mm studs, what type of studs would those be? would they be metal/flexible or wood/stiff?

about density of the insulation... in general, what i mean when i say that is don't ever use specialty type products as history basically shows that normal building fiberglass is the best choice. 140 kg/m^3 is too dense, yes, you'd be better served by something like common fiberglass (10-15 kg/m^3) or "normal" mineral fibers (30-50 kg/m^3). if you look here: http://irc.nrc-cnrc.gc.ca/fulltext/ir761/ir761.pdf , you can see low frequency performance degrade from excessively dense insulations (they tested up to ~100 kg/m^3)

insulation is very, very important, and every isolation project should use some. But it isn't the place to go dumping lots and lots of $$$. almost always cheap insulation + more drywall, for example, is a better plan.

1/2" high density board sounds really good.

Questions for Brian.
Previously in this thread you stated "use some insulation in the cavity. avoid excessively dense insulations". What exactly is, 'excessively dense'? Is 140 kg/m3 too dense?
Various specialist 'sound proofing' web sites have what they call Dense Fibre Matting (DFM) with densities ranging from 20kg/m3 to over 140kg/m3. What sort of density should I be aiming for?

Richard, without testing the specific material in question or seeing comparative tests of it -vs- something like common cheap building fiberglass, i can only speculate, but:

as i mentioned above, in historical studies high density insulations have been shown to cause LF performance that's worse than the cheap stuff. the BBC has a study that concludes along these lines, the NRC document above shows this clearly, and USG in US studies long ago (1980's) found that as density went up too high, performance at low freq suffered. So my guess is yes, that's too dense.

A few more for good measure.
If using green glue, is it absolutely necessary to decouple the studs of the new partition from the party wall? This makes the constrution that much harder. Could I get away with less deep studs, but with 1 or 2 point contacts up the wall, to stop the wall from flexing too much?

yes, that's fine. in the US, where wood stud walls are very very common, thta's probably the best-liked trait of Green Glue - it can make a good wall without decoupling. data is at audio alloys website for not-decoupled walls if you'd like to see it, or i can post some if you want. When using Green Glue (or similarly effective damping methods of whatever sort), decoupling is still helpful, but... but you do get this ability to make a good partition w/o decoupling.

Is a green glue solution effective when only applied in the receiving room? (most people on the american forums seem to use it to stop sound escaping, not from entering a room)

Any idea if my proposal would be any good? If its a goer then I might think about all four rooms + lifting the upstairs floorboards and putting some DFM between the joists to cut down on some of the flanking noise as well.


Many thanks

any idea how heavy that brick is? how thick? i'll estimate it's about 130 kg/m^2?

if flanking noise is controlled, and if the partition is well sealed (you might want to inspect the condition of the brick for severe cracks and the like before building the rest), this plan should be very solid.

i would consider using less dense insulation for the reasons given above & when time allows i can dig up some data on that (less dense insulation) as well.
 
Thanks Brian.

Lots of reading me thinks!
http://irc.nrc-cnrc.gc.ca/fulltext/ir761/ir761.pdf - Gypsum Board Walls: Transmission Loss Data
http://irc.nrc-cnrc.gc.ca/fulltext/ir832/ir832.pdf - Sound Insulation of Load Bearing Shear Resistant Wood and Steel Stud Walls

If anyone is interested I found a BBC report at http://www.bbc.co.uk/rd/pubs/reports/1995-06.pdf - Lightweight Partitions Having Improved Low Frequency Sound Insulations
+ more reports than you can shake a stick at! http://www.bbc.co.uk/rd/pubs/reports

Not too sure how to interpret everything for my circumstances, but I take on board your suggestion about the density of the insulation.
 
excellent links Richard, thank you!
 
i think i forgot to address one question:

it was asked if using GG is effective in both directions. Yes, and that applies to basically all other forms of sound isolation as well. For example, resilient channel is effective regardless of which side of the wall you put it on.


One important note has to be made, however:

imagine that we had a wall that was 10 feet of solid lead, studs, and a single layer of 1/2" plasterboard. The performance of that wall would be surrealistic, incredibly high. The weight of the lead would see to that. and regardles of which side the noise was on, it would perform the same.

But now imagine that we put that wall into a theater in an average house, in the real world, and switched between having the lead inside by the noise, and having the lead outside, with the plasterboard inside by the noise.

The lead inside would perform amazingly well.

But the plasterboard inside may not perform all that well at all. it is subject to resonance, etc., is light weight so the sound could easily stimulate it. And once it was stimulated, if it was attached to the rest of the structure, sound could easily escape here and there and isolation may not be all that good despite the 10' of lead. Flanking noise problems.

see? so, in general, it would seem reasonable to think that having the "best" side of the wall facing the noise is good practice for that reason.

If my story wasn't very clear, let me know and i can post a picture.

Brian
 
Hi Brian,

wondering if you knew anything about aerogel (they stuff they used to collect the space dust in NASA's recent mission)? I remember reading that it was a much better sound insulator than traditional insulators (lots of people are looking into it, including US Navy for sound insulation on aircraft carriers, so presumably good for broadband sound). Its made of silica fibres I think, but is about 99.9% air, and one of the least dense man-made materials available. Don't think you can just get it in b&q though. Any thoughts?

Tom
 
tek said:
Hi Brian,

wondering if you knew anything about aerogel (they stuff they used to collect the space dust in NASA's recent mission)? I remember reading that it was a much better sound insulator than traditional insulators (lots of people are looking into it, including US Navy for sound insulation on aircraft carriers, so presumably good for broadband sound). Its made of silica fibres I think, but is about 99.9% air, and one of the least dense man-made materials available. Don't think you can just get it in b&q though. Any thoughts?

Tom

Tom,

i'm a bit slow with the reply.

here's a link to a file from the Cabot Corporation about aerogel's sound absorption properties:

aerogel acoustic pdf file

looks similar to fiberglass

Brian
 
Brian, would it be possible to noticeably improve the sound proofing of a room without building a partition wall.

I was thinking of something like this http://www.customaudiodesigns.co.uk/soundproofing/rubbermat.htm and then adding Green Glue between two layers of plasterboard.

After months of detailed negotiations with my wife, I have not managed to persuade her to agree to losing some 5 inches of wall space around the room and therefore I need to find a compromise
 
Londondecca said:
Brian, would it be possible to noticeably improve the sound proofing of a room without building a partition wall.

I was thinking of something like this http://www.customaudiodesigns.co.uk/soundproofing/rubbermat.htm and then adding Green Glue between two layers of plasterboard.

After months of detailed negotiations with my wife, I have not managed to persuade her to agree to losing some 5 inches of wall space around the room and therefore I need to find a compromise

Well, yes. Are you starting from brick? Or from an existing stud-wall?

The latter is pretty easy to upgrade without a new row of studs. From GG to adding mass to removing drywall and trying decoupling products on the existing studs (like RC and so forth, although RC isn't so great for theater). Lots of options, and a very high level of performance can be attained.

For a brick wall... slight additions of mass won't do much, as they are such a small percentage of the mass that already exists.

As for the idea of adding rubber mat + plasterboard... this is commonly used here on floors (rubber mat + plywood) to help with flanking noise, but i don't have any lab data on such a test. It may do what you need, but w/o data i guess i can't offer a cocnrete answer.
 

The latest video from AVForums

Is Home Theater DEAD in 2024?
Subscribe to our YouTube channel
Back
Top Bottom