Accoustic absorbing material

OK - house purchase has fallen through - turns out there were too many illegalities with the proposed purchase so to keep my sanity I'm reverting to finishing a project started a while bask: quietening my generator.

It's a 6 litre turbo charged diesel in a steel box with virtually no internal sound absorbing material - currently I've lifted off the box (2.6m x 1.5m x 1m) to do a bit of welding on rusty bits, and intend to line it before I crane it back on. Currently giving 90dBA @ 1 metre target is to reduce it to 70dBAor so.

Hunting around there seems to be a shortage of suitable materials at a reasonable price. I'm looking for a sandwich construction accoustic foam laminated with either lead foil or other dense material giving at least 32mm thick overall, preferably 45mm. Best so far seems to be

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but at a heck of a price.

So if anyone has about 14 sq metres of suitable fireproof, oil proof, rot proof and sound absorbing foam to hand or knows a better source please get in touch.

Regards,

Andrew

Reply to
Andrew Mawson
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Could thermal insulation sandwich board be adapted or suitable for the task?

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make this stuff at various thicknesses, foam core sandwich board with aluminium foil facing. Just a thought.

Peter

Reply to
Peter Neill

Does that mean you'll be asking for all your 'useful stuff' back??

Maybe a couple of layers of this sort of thing would be cheaper?

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Just a thought

Tim

Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

Reply to
Tim Leech

Boat builders use a fireproof acoustic material/lead sandwich for this job. I'll try and find out what its called.

Reply to
Tim Christian

I dunno what the box is like, but welding on a few bits of angle iron to stop the panels vibrating might help quieten the beast.

hth Guy

Reply to
Guy Griffin

We used Rockwool, held in place by perforated ali for the Film & TV generators that I used to build and look after.

63db(A) at 3metres was the target, which we achieved most of the time.

Peter

-- Peter A Forbes Prepair Ltd, Luton, UK snipped-for-privacy@easynet.co.uk

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Reply to
Prepair Ltd

These chaps do good quality sound insulation, but a bit pricey.

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These chaps do similar stuff but a bit cheaper
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and there's these chaps as well, but their prices are a bit scarey.
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HTH cheers, David

Reply to
penfold

proof,

Thanks chaps, some useful suggestions there that I'll follow up next week.

(Tim, it's ok you can keep the transformer !!!)

AWEM

Reply to
Andrew Mawson

Mass.

Our chief weapon is mass.

Mass - and hysteresis.

Our chief weapons are: mass, and hysteresis.

Mass, hysteresis and ...

So I can't see that rockwool would be much use.

Quickly surfing, I fell over this:

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Reply to
Charles Lamont

Fortunately the Navy could see it and used it on it's warships ! Rockwool is pretty good at soundproofing and I suspect that it is also relatively cheap.

The suggestion to use rockwool in conjunction with perforated aluminium is a good one, alternatively substitute fibreglass in place of the rockwool.... this was used on steel bulkheads in the engine rooms of ships.

I have also seen rockwool used for sound proofing in a paper mill which produced tissue at high speed. It did a good job when faced with very high noise levels at a wide range of frequencies.

Reg

Reply to
tux_powered

Sound studios also use masses of it 12 inches thick in all six directions with 6 layers plus of plasterboard either side of it.

Reply to
Neil Ellwood

Also fireproof

Perforated works equally well, but obviously heavier.

You have to get the sound waves into the absorbent material, hence the perf metal. We did line a few panels behind the perf with polythene to stop oil and fuel getting inside, but that made little sound deadening difference.

Interestingly, one of the last sets we had built was bad for cooling fan noise from the generator, as a join in the panels was opposite the fan vents on the front of the alternator (Markon 50kVA) so a sub-shield of steel sheet was placed by the joint and far enough away not to affect the cooling, and it took it out.

The best gennies for this were built by Mekanomatik in Stockholm, we had quite a few originals and a few UK-copies built by A Smith (Great Bentley) Ltd which were heavier and bulkier but did the job. I think the swedes used ali perf while the UK guys used steel as it was cheaper.

Peter

-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web:

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Reply to
Peter A Forbes

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