In our gorgeous basement flat we've had to install a positive ventilation system and although the efflux noise from the outlet is quite quiet the
fan makes a bit of noise (like a noisy PC). I'm planning on enclosing it in a MDF box to hide the fan unit (it's hardly pretty) so hopefully
the only noise will be the efflux. Thing is this- I want to line the MDF box with some sound-proofing material but does anyone know what's good
and what's not. I've heard of brown bread from car ICE circles but is that good or is it chavtastic? I can't use very thick material
otherwise the box will be too big IE 10-15mm thickness max...
Looking on the net there are blooming hundreds of different products but all I want is a self-adhesive foam product of about 10-15mm which absorbs
shed loads of fan type noise. Having a listen to the fan going round it's mostly quite low frequencies- great!!
Not asking for much then 
Thin cheap material capable of absorbing low frequencies....
Anyone had any experience with said products???? TIA!
We use it our machine at work for reducing noise but 15mm thick is not very much see the graph below
[img]Image deleted by owner[/img]
as you can see its not that effective unless its 30mm thick and it also depends on what you mean by low frequency.
we may have some off cuts available at work depending on how much you need. I don't know what thicknesses we have and I'm out on holiday for
2 weeks but drop me a u2u if your interested.
The foam is by caledonian ferguson timpsom and is called class 'o' foam
hope this helps
Pete
Dont know owt about it technically, as i've only just heard about it from my researching into building regs etc etc, but there's soundblock
plasterboard available which is a kind of dense insulated version of normal plasterboard just the thickness you require. As i say though - no
experience of it yet!
Liam
Oooh - another idea more in true locost fashion...
My vauxhall omega is super quiet inside - can barely hear the engine idling. That's in part cos it has some really thick sound deadening foam in
the footwells. Now you can bet GM and everyone else has put millions into fine tuning the composition of these materials, so get yourself down a
scrappy, rip up the carpet in an old executive barge and take advantage of their research!
Liam
Ben,
Drop Ben_Copeland a u2u 
HTH Fozzie
quote:
Originally posted by Liam
Oooh - another idea more in true locost fashion...
My vauxhall omega is super quiet inside - can barely hear the engine idling. That's in part cos it has some really thick sound deadening foam in the footwells. Now you can bet GM and everyone else has put millions into fine tuning the composition of these materials, so get yourself down a scrappy, rip up the carpet in an old executive barge and take advantage of their research!
Liam
look on eBay for accoustic foam. This stuff is used in sound studios to absorb sound and to stop reflections. The thicker the better is the rule,
particularly with low frequencies.
A heavy, very rigid box will contain the sound, lined with heavy non-rigid material to absorb the sound. Line a plywood (not MPF) box with 2 layers
of plasterboard, with an air gap between the board the the wood. Line that with the foam. Make sure there are no air gaps either in the wood or the
plasterboard.
Try dynamat spray?
play metallica turned up to 11?
Be careful of heat build up inside your box too.
quote:
Originally posted by grazzledazzle
Be careful of heat build up inside your box too.
Go to Sheffield Insulation in West London or any other company that sells insulation and use 25mm acoustict roll, they might sell you a part roll, How much do you need. U2U
Could you put something like a dimmer switch on your fan to turn it down to an acceptable noise level or use two smaller ones, one pulling in and one taking out? That's what I do with the computer and it seems to work for that.
quote:
Originally posted by Peteff
Could you put something like a dimmer switch on your fan to turn it down to an acceptable noise level or use two smaller ones, one pulling in and one taking out? That's what I do with the computer and it seems to work for that.