Sound proof plasterboards

[cedd]

I realise I'm swerving this topic massively in to the dom3stic world here, but with so many soundies on tap I thought I'd offer my household conundrum out to the wider Blue Room.

 

At our last house we had noisy neighbours, coupled with quite thin walls. We've now moved in to what we're planning on calling our "forever house" and are working around each room one by one redecorating, including plastering to remove the dado rails that are in every room.

With our last neighbours in mind I'm keen to do something while we're decorating to improve the soundproofing of the walls. It's hard to judge how thin they are as the current neighbour is a single, elderly lady who is very quiet. Nevertheless I'm keen to go for it and get something done about them now - never know who you're going to get next!

 

Wickes and the like have normal plasterboards that have acoustic deadening properties, but they're very sparse on the details. I'd love to see an attenuation figure but just can't see one anywhere.

Then there are places like this;

http://www.noisestopsystems.co.uk/

 

I'm particularly interested in these products;

http://www.noisestopsystems.co.uk/wall-soundproofing/nssw1-soundproofing-wall-board

which quotes 31dB reduction

 

http://www.noisestopsystems.co.uk/nssw1-plus-soundproofing-wall-board

which quotes 37dB

 

http://www.noisestopsystems.co.uk/wall-soundproofing/noisestop-acoustic-panel

which quotes 55dB

 

I can cope with the thicknesses of all of them, so it all comes down to the acoustic properties and money!

Oddly I find it pretty easy to imagine those figures in terms of gain, but in terms of reduction I'm finding it hard to imagine, or to work out which one I need. The 55dB panel is twice the price of the 31dB panel, which is still an awful lot more than a standard wickes-type plasterboard with a sound deadening label on it.

 

So the question is, has anybody used these in the day job (or at home) and can anyone shed some light on just what those figures might mean in easy to imagine terms? Or does anybody have a cheap home brew solution? Whatever I put on the walls will be on top of the existing plasterboard.

 

Thanks

Chris

[Brian]

You can find a pdf of the BBC acoustics guide online which has lots of practical information.

[timsabre]

The only thing really worth the effort is to build a floating wall separated from the original wall. Sticking more plasterboard onto the wall will help cut higher frequencies but will do nothing for bumping/banging and annoying bass.

[pjb304]

I'm wondering about doing a similar project in my place, so will be following this thread with interest.

 

In looking around I've seen this thick lining paper which claims a 35% reduction in noise in 3.2mm thickness. I was intrigued to convert this into a db figure and so found this table which offers conversions between db reductions and actual and percieved sound levels which might be helpful to you.

[paulears]

The book that seems to be recommended over and over again for the studio builders is Rod Gervais's Home Recording Studio - Build it like the Pros.

 

He's a very experienced guy and his book is full of very useful stuff - and often quite contra-common sense. He has all kinds of data comparing different techniques, and points out that very often the tiny gains people strive for get wrecked by other building errors - There's a bit about room within a room where adding a layer of plasterboard actually makes transmission worse. He talks about the benefits of an extra wall keeping sound out from the neighbours, and concludes the effectiveness depends on the floor and ceiling more than the new isolation wall.

 

Pretty much the theme is that the extra density and weight in the acoustic plasterboards only works if you can stop the flanking transmission from the floor and ceiling that is embedded in the wall. Sound goes over and under rather than through.

[bigclive]

I wonder what effect the acoustic foam panels designed to reduce reflection in a room would have on external sound coming in.

[paulears]

Good at the frequencies they work at - but most through wall sound has the HF seriously reduced anyway - so very little above 2K goes through even one layer of 12mm plasterboard. The foam treatment less than 50mm has very little impact down the bottom.

[kerry davies]

Friends of mine did a more than adequate job just by filling the stud partitioning with Rockwool insulation and fixing the plasterboard with plastic/nylon grommets rather than nails. In most domestic scenarios sound reduction can get very expensive very quickly for minimal benefit. Paul is right that you can spend an awful lot of time, effort and money only for the floor and ceiling transmission to undo any gains.

 

IMO the worst noise transmission comes from that lovely drum right above your head called a ceiling void.

[bruce]

I think this may just have been a west of scotland thing, but in many old Glasgow buildings - especially between tenement flats and in some victorian houses - it was common to fill the void between ceilings and the floorboards of the room above with 2 or 3 inches of ash or boiler clinker. Known as “deadening”, it was for sound and thermal insulation.

 

It was a lightweight, cheap insulation material. But very messy if you had a burst pipe upstairs and the ceiling collapsed!

[Barney]

In my day job as an acoustic consultant, we deal with this all the time :)

 

Tim's right - the best thing to do is a separate stud wall, set off the existing wall and with the void filled with mineral wool insulation. The overall performance will be limited by flanking sound via the other building elements (side walls, floor, etc). However you should be able to get around 10 dB improvement on the existing wall - perceptually this would correspond to a halving of the sound transfer.

 

Just lining an existing wall with an additional layer of direct-fix plasterboard (i.e. without a cavity) won't give you much improvement against intrusive noise transfer. Maybe 2-3 dB - which would be perceived as only just noticeable and do little to mitigate against LF and impact noise transfer.

 

You won't get the figures mentioned above (30 dB+) with a single additional lining onto an existing wall; if you could there would be no need for 500 mm thick wall constructions between cinema auditoria, and us noise consultants would be out of business!

 

For reference, 'acoustic' plasterboard in places like Wickes is just a slightly denser board than 'normal' plasterboard; it may give you a couple of dB improvement if you use it for the independent lining.

[sunray]

Dense materials are needed to stop sound travelling through, lead sheet sandwiched between ply wood is not uncommon as a roof.

 

The deadening described works better on a resilient bed such as Rockwool.

 

30 years ago we built a radio studio and as the plan was to have live bands the studio was a suspended box within a suspended box to isolate from the band with a total of 8 layers of the deadening plasterboard and 3 or 4 layers of heavy Rockwool batts, in total over 400mm thick. Sadly BT decided not to use the cable that had been laid in for them and drilled a 1/2" hole right through.

[paulears]

That brings back memories of one studio I did. Same thing, but the fire officer threw a fit when he realised a sound proof room had a single entrance/exit and when the fire alarm went off in the building he couldn't hear it. Two half inch holes for MI cable followed. Silicone is very happy letting sound through!

[boatman]

Loads of egg trays glued to the walls and ceiling have an amazing effect. Unfortunately it's not very pretty.

[Simon Lewis]

Chris,

 

The acoustic principles apply to both stage, industry and d0mo3t1c settings... so it's useful to discuss here!

 

Most people cite mass as being the important factor fro reducing noise transmission between rooms - and it is - to an extent, but it's more complicated than that,

 

Firstly - there's airborne and structure borne sound transmission. If there is a direct air path between the transmitting and receiving room, (even a keyhole) then a surprising amount of noise can pass between them. Hopefully in your setting there isn't direct airborne sound transmission...

 

Structure borne sound transmission can be directly through the separating wall or structure (direct transmission) or can be indirect through other connecting walls, floors, ceilings or building systems (flanking transmission). Sometimes systems like air handling ducts can give both types (airborne transmission by providing an air path between two rooms and structure borne by vibration passing along ductwork).

 

Getting good attenuation between two rooms involves investigating and understanding what the transmission path is. There is no point is having even a 1m thick concrete separating wall if there is a common void between two rooms above a flimsy ceiling structure.

 

The three techniques used are mass, isolation and sealing.

 

WRT mass, you should in theory get about an extra 6dB of attenuation each time you double the mass of the partition. However, due to partition stiffness, resonance and coincidence this rule of thumb does not hold true for all frequencies and constructions. A double brick wall with air gap and traditional plaster on both sides can provide very good transmission loss, but struggle to stop high level low frequency noise.

 

WRT isolation you will pragmatically get better reduction of transmitted sound than with mass law. A fairly standard 12.5mm gypsum board spaced from the existing wall may give around 25dB attenuation. Two layers with non coincident joints may give 30dB. Two double structures on non touching metal frames with acoustic treatment inside may give 60dB. In all cases, there will be benefit from using vibration isolation at the edges. All of these figures can be dramatically lowered through flanking and airborne transmission!

 

WRT sealing you are stopping air paths between the two spaces, whether direct or indirect.

 

Retrospectively applying noise control can be a difficult task, and as most of the posters here have stated your best route forward is a spaced partition, preferably floating on neoprene and only attached to the existing structure with resilient fixings and non setting sealants.

 

There is good information in the building regulations Part E, Resistance to the Passage of Sound.

 

Beyond this (and the wealth of related online material) is where acoustic consultants make their living - so why not support an Institute of Acoustics or Association of Noise Consultants member!

[Dave m]

I helped a mate convert a single skin garage into a home studio and it works great, far better than we hoped.

 

The 2x4 timber that made the stud wall was seated on 1/2" thick neoprene 4" wide cut for us by the supplier.

we took great care to construct the panels that made up the walls so that they were independent from the others, used two types of rock wool with a gap, then two sheets of plasterboard, staggered joints and skimmed.