I've been chatting to our architect and he suggests that an effective strategy for sound insulation is to erect a stud wall with a 1"/25mm air gap from the wall to the studs. This stud to be surfaced with ply (to support fixings) then plasterboard finish.
This gives a rough thickness of 25mm air gap, 50mm stud work, 25mm ply/pb cover or 100mm/4" in total
What does the team think?
Cheers
Dave R
should be pretty good. Hermetically seal it and possibly fill all air gaps with sand as well.
Ummm.....if they are filled with sand then they aren't air gaps. They are sand gaps. Won't the sand conduct sound?
It would help to an extent. If you have an inch or 2 to spare I'd up the timber size, 2" is very weedy. You can improve it a bit more by putting big lumps of masonry on the noggings, filling the cavity with dense insulation batts, and using soundproofing plasterboard.
NT
In article , David WE Roberts scribeth thus
Sort of, it will damp it down a bit but an Air gap is the better thing.
Most all radio and recording studios are a "Room in a room" and well isolated from each other by a decent Air gap...
The studwork is fixed top & bottom (not to existing wall), two layers of plasterboard are overlapped to eliminate any acoustic short-cuts. Often neoprene is added and works well, lead being far too costly these days.
If the space above ceiling or below floor have any holes around joists noise *will* simply bypass your acoustic studwork.
A wall with empty frogs (no mortar infill) has very poor acoustic performance. Usually noticed by drilling into mortar 3/4" only to find yourself flying against the wall as the drill collapses through an air filled frog to embed itself on what little mortar is the other side. Re-pointing can help, needs care re stability of the wall.
If this were noise through a bay window 3" studwork, I would suggest bonding 40-50mm Marmox with Mapei Keraflex (or its cheaper clones) to the wall. Whilst it is good thermal insulation with no mass, it has good acoustic dampening properties to traffic noise - like a pillow over your head.
You have a freestanding stud wall, so you may want to consider acoustic insulation between the studs.
If your problem is just general noise now, consider what it will be like if someone elderly moves in - with the TV turned full blast all the time. It can get very wearing and sound insulation is justifiably an important part of modern building regs.
David WE Roberts wrote on 3/20/2012 :
Air is a sound conduit, not an insulator. An air gap is dumb. A sound barrier must be a solid. The harder the better. Visit a radio station or a recording studio and you will see glass walls between the rooms. Add anything hard to the wall and you will make great strides. Do the same to the ceiling and fill all gaps. If you put a high density material on both sides of a stud wall, you have gone as far as you can without adding glass.
McGyver
The air gap is to stop the existing wall mechanically transmitting sound to the new stud wall, acoustic coupling.
Closed Cell materials absorb high frequency sound - clips the harshness re road traffic & speech. Materials of Mass absorbs low frequency sound, certain elements of speech, but also footfall & TV "drone".
Two layers of glass with air between them. For decent sound insulation that gap needs to be about 9". Which is why ordinary double glazing isn't much use for sound insulation. Secondary glazing is.
It would help to an extent. If you have an inch or 2 to spare I'd up the timber size, 2" is very weedy. You can improve it a bit more by putting big lumps of masonry on the noggings, filling the cavity with dense insulation batts, and using soundproofing plasterboard.
*****************************************************It is painful even to take 4" off the dimensions of the rooms. Less than 4" would be nice but we have budgetary constraints. I assumed (but didn't state) insulation material such as rockwool between the studs. Not sure if you have to have 2" sheets and maintain the clear air gap or if loose rockwool-style filling counts as air gap because of the air in between the fibres. Hmmm...puttting a blanket over your head is a reasonable sound insulator so rock wool blanket should be one as well. A use for old duvets?
If your problem is just general noise now, consider what it will be like if someone elderly moves in - with the TV turned full blast all the time. It can get very wearing and sound insulation is justifiably an important part of modern building regs.
*************************************************We will be the someone elderly eventually. :-) Noise downstairs has not been an issue because the hall and landing are central to the pair of semis. The lounge/living room is therefore well away from the party wall. Only the dining rooms adjoin. When the new downstairs is done noise from us to the neighbours may be more of an issue so we are taking the opportunity to put in some insulation during the build.
The current issue is upstairs where the toilets are side by side. Next door the bathroom has been joined with the toilet so we get all the bathroom sounds. We are going to join our bathroom and toilet and reclaim some of the bathroom for the back bedroom so in future all bathroom sounds may be transmitted. Again now seems the time to up the insulation.
The keys to sound insulation are airtightness, density, rigidity and weight. The densest rockwool you can find would be better than lightweight stuff, and a double layer of plasterboard separated by a layer of neoprene, or the type sold specially for sound insulation would help a lot. Almost all the sound can travel through a tiny hole, so you need to seal round the edges perfectly.
The new wall also needs to have a gap between it and the old wall to reduce transmission. If there's a wall eft projecting from the old wall, you also need to make a gap and run the soundproofing through the gap.
Old duvets are flammable & floppy, and you want dense & resilient. Fibre batts are effectiely an airgap, but with some added damping.
If it hurts to lose 4" I'd look at other options altogether, eg viscoelastic polymer.
Here is the dB(A) benefit of neoprene when stuck onto Marmox:
Here is the detailing of an acoustic wall...
Noise will walk through a single brick wall. It may be brick, but the mortar joints usually provide a weak acoustic barrier. Likewise it is a single leaf, having two free standing walls (cavity separated by air gap) greatly improves acoustic performance and is what they try to achieve above.
I believe neoprene can be sandwiched between two layers of plasterboard to good effect, but can not recall if it needs to be bonded rather than screwed through to get the best effect.
Here is a figure for plain Marmox. Impact Sound Reduction BS-ISO140-8, weighted reduction in impact sound (delta-Lw) = 21dB.
Plenty of other manufacturers of extruded polystyrene with bonded glass-fibre mesh & cement on both sides.
For 3"-stud bay windows near a highway, not the OPs application, it makes a very noticeable difference and quick to just bond on with Mapei Keraflex and flash finishing plaster skim over ready for paint/ wallpaper. Stiffens & dampens well, but I would PU sealant the joints or butt-slide tightly until the keraflex oozes out & wipe off to ensure no gaps etc. With thicknesses up to 60mm the thermal insulation benefit over 3"-stud with pebbledash is huge.
I've been following the Gyproc guide to domestic building renovation for the refurbishment of my Edwardian mid-terrace:
Thanks - useful.
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