Using sand for soundproofing

I'm toying with the idea of improving the soundproofing between my downstairs living room and the bedroom above it. At the moment the sound of the TV and people talking downstairs are annoyingly audible through the floor.
I'm thinking of the cheap old standby, sand (probably 50mm thereof). Looking back at some old threads the general reccommendation is (having taken up the floorboards) to create a 'platform' for the sand using batten and plywood between the joists rather then pouring the sand directly onto the ceiling below. The threads in question seem to be about saggy old lath and plaster ceilings. My ceiling is plasterboard - in fact a double thickness of plasterboard screwed into the joists in the conventional manner. Do the panel think I could pour sand directly onto the ceiling in this situation?
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Martin Pentreath wrote:

What does sand do in an egg timer? - this is what will occur in your house, unless you manage to make it so tightly fitting that a grain of sand cannot escape, and in any case, 50mm is next to useless - if you are going to go to the trouble of removing all the floorboards, it would be better to use insulation, probably rockwool or similar....this will be cheaper than plywood and battens.
Don't think about putting anything like sand on top of the p-board, unless you want the lounge ceiling to look like a ploughed field.
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Phil L wrote:

Hi Phil,
Many thanks for the reply.
There are two layers of tight-fitting plaster board, so I don't think the sand will percolate it's way downstairs. I'm not sure how I could end up with the ploughed field effect on the lounge ceiling! Perhaps I'm misundertanding you.
My understanding is that to deaden air-borne noise (like the TV) needs mass, and rockwool would not have much effect, but I stand to be corrected. Point taken about 50mm being insufficient.
Cheers!
Martin
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Martin Pentreath wrote:

You should in any case hermetically seal the ceiling - the sand is to deaden the muffled low frequencies that are transmitted by panel vibration, not the 'air borne' sounds. Hermetically sealing things gets rid of those.
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Martin Pentreath wrote:

It was done professionally to a chinese restraunt above a club a few years back, I wasn't involved with it but my brother was working on both buildings at the time...the firm came out and removed all floorboards, they then affixed battens to the insides of each joist and put plywood strips down, on top of this they put bags of soundproofing beads, still in their bags, laid flat on top of the plywood and on top of this they laid rockwool batts up to the top of the joists...above the lot of it went an acoustic blanket, which covered the tops of the joists, this was a foam rubber thing from what I can gather, and then 8 X 4 plywood flooring over everything, the results were impressive - the diners could eat without their tables vibrating away from them and the club didn't have to turn the racket down.
It was expensive though, I think the acoustic mat alone is about 15 per m2, hence my reccomendation for rockwool...the sound insulation now specified by building control between floors is just fibreglass or rockwool insulation.
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Phil L wrote:

Rockwool does not have the mass to do the job. Its a waste of time.
You must have MASS = you have to change the resonant frequency of the structure and increase the damping. Rockwool does nothing. Not to mid low frequencies - and the HF is attentuated by the floor and ceiling to a huge extent anyway.
The first limne of attack in soundproofing is to hermetically seal any air paths...otherwise you have a 'speaking trumpet' and sounds will carry really well. Think about e.g. opening a sealed DG window a crack..suddenly outside wounds are highly audible.
By and large what is left, is structural transmission. Its already lost the HF..it will be muffled and boomy, like a car stereo inside a car. Only the bass and lower middle really gets through. Its lost the HF because the panels themseves will be effective low pass filters..in this contexct material with low elasticity like plasterboard is far better than material like plywood. Make a box of plasterboard and tap it. A dull thump. Tap plywood box and it can sound like a drum. Tap a steel box and it ran ring like a steel drum or a bell..
Ideally what is really massive works bets. There is very little transmission through masonry and concrete. Wood is terrible.
The point of acoustic mats is to add weight by and large..sand is cheaper. That takes the panel resonances subsonic..you may get vibration, but not much audible sound.
Fill your plywoood box with sand and tap it. No 'bixiness' left. Just a dull thd at best, The sand rubs against itself forming a HUGE ebergy loss to any waves trying tp pass through it, leaving the studs themselves rather than the panels between as teh mnahort transmission, and they have very low reosnant frequencues.
Rockwool is designed to trap air, its full of air passages, Sure the path is long and complex, so short waves get reflected multiple times and decay, but long waves just move it as a complete mass and the rockwool does nothing to stop it.
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If you have none Rockwool works OK (the dense bats). It will not stop a disco but effective enough.

Very true. Sand, if the joists can take the weight, as sand is heavy. So work out the weight of the sand first, and then Rockwool over. Then making the ceiling floor air-tight will be quite effective. You can use a foam sprays where the ceiling meets the wall. This will air-tighten it up.
The German house maker Huf Haus, have suspended timber floors with cement screeds. You can have Rockwool between as well. Effective.
Sound is tranmitted by:
1. Impact (feet on floors) - Floating floor solves a lot of this as does sand (mass) 2. Air (TVs, voice) - Sand solves this (mass) 3. Flanking (down the walls) - Isolating the top floor layer from the walls, keeping skirting boards off the floors by a mm, etc)
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The Natural Philosopher wrote:

Obviously not if it's used by professionals who do it for a living.

Rockwool is made from rocks, hence it's name, so if you stuffed the box full of rockwool, fairly compressed, you are saying it wouldn't make any difference?

If it's a flimsy piece of rockwool, yes, not if it's compressed so that it has less air and more rock...it becomes similar to sand, but without the drawbacks
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Phil L wrote:

That is not what people mean by rockwool.
I am not sure that rockwool is made of rock either. Its more like glass fibres.
Acousting matting is very high density batts or an elastomer of high density. Take a look at a stripped out luxury car one day, and see what they use.
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What make, etc?

Rockwool is more dense.
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Doctor Drivel wrote:

I've no idea, this info is 3rd hand...the bags were filled with 'acoustic beads', I believe it was similar to black grit, possibly made of rubber, although how this would sit with the fire officer is open to debate, I'd wager they were fireproof or they wouldn't be allowed to install it.

This wasn't just ordinary rockwool that you buy for loft insulation, I think it was this stuff: http://www.rockwool.co.uk/graphics/RW-GB-implementation/brochures/SoundPro_E1_New.pdf
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http://www.rockwool.co.uk/graphics/RW-GB-implementation/brochures/SoundPro_E1_New.pdf
Dedicated acoustic stuff. Anything acoustic is expensive. I know one fella who built his own house and checked the specs and rigid Rockwool bats performed only slightly less than the dedicated stuff at a fraction of the price. This may be a new line.
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Doctor Drivel wrote:

It may have been just the normal batts, and I've remembered something else too, they stapled long strips of what looked like thick underlay along each joist prior to laying the final matting and boarding, this was similar in structure to the cushioned rubbery stuff, but thicker, about an inch, I'm told.
The overall difference was extremely effective, although I think it came to around 8K for a 80m2 approx area, but the club owner and the restaurant owner split this between them.
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Phil L wrote:

Yup. Thats the stuff they stick on car body panels to soundproof them Its sticky and its HEAVY. And expensive.
Th erockwool deals with the high frequencies reasonably, but that's all. You need MASS. and ideally mass with low elasticity..

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The Natural Philosopher wrote:

Even heavy foam underlay can make a difference, though not enough in real nuisance situations. Good for PC cases though if you've got noisy _internal_ fans.
Chris
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If you're happy to lift all the floorboards anyway, I've heard this is a good option:- http://www.british-gypsum.com/systems/system_selector/gypfloor_silent.aspx
Andy
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Martin Pentreath wrote:

Probably yes.
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"Martin Pentreath" wrote:

http://www.diydoctor.org.uk/projects/sound_proofing_in_the_home.htm http://www.domesticsoundproofing.co.uk/ceiling.htm http://www.soundreduction.co.uk / (no mention of sand)
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Martin Pentreath wrote:

What you really need is stiffness and decoupling. In lieu of that a LOT of sand will refuse to move, but a 2" layer isnt really going to do that.
Also cracks do occur, and when they do it'll be eggtimer time!
Try well fitted noggins, stressed box construction, and the other usual ways to stiffen up the floor. Then if you want even more soundproofing add a new ceiling on new 2x3 joists below the present one, not connected to it.
NT
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snipped-for-privacy@care2.com wrote:

the late Hope Bagnell, architect, once commented on the falling standrards of sound insulation in Glasgow. " In the old tenement buildings they used sand in the ceiling void and the sound insulation was so good that you could not even hear a baby being born in the room below. Nowadays [the 1950s it must have been] in these modern buildings, you can hear it being concieved."
Robert
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