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Choosing the right acoustic foam

It is a well known fact that using acoustic foam in your studio will improve the sound quality of your studio. However with so many companies available selling acoustic foam it is easy to see why many producers venturing into acoustic treatment make the wrong decisions when looking for the right material to treat their rooms. This confusion is brought about by the fact that there are so many companies out there selling furniture foam passed off as acoustic foam. This foam is normally cheaper and is no wonder why every other question on our twitter feed is. “Why is acoustic foam so expensive?”

Acoustic foam has become the treatment material of choice for many home music producers for a number of reasons however the top three reasons are;

  • Acoustic foam offers great absorption for mid to high end frequencies.
  • Acoustic foam is relatively more affordable compared to high end options
  • Acoustic foam is easy to handle and shape into aesthetically pleasing and performance enhancing shapes

Broadly speaking, there are three types of open cell foam used for acoustic applications. These are, in order of increasing price.

  • Polyurethane polyether foam
  • Polyurethane polyester foam
  • Melamine foam

Polyurethane polyether foam

Polyurethane polyether foam has a large range of applications and comes in a variety of densities and colours. Acoustic applications are best suited to densities that are 29kg/m3 and above. Furniture foam converters generally tend to use the 25Kg/m3 foam or less and pass this off as acoustic foam. Whilst this foam may look similar to acoustic grade foam the performance shows that this foam falls below that of higher densities. This is basically down to physics. Although the structure of lower density polyether foams is the same as higher density foams lower density foam doesn’t have enough air pockets to absorb the sound waves impacting on them which reduces the observed performance.

Lower density foam whilst appearing cheaper may cost more in the long run because trying to get equivalent absorption values in your studio will mean purchasing more foam which is probably not a good idea because excess absorption can leave your room sounding flat.

If you are on a tight budget look for polyether foams that have higher densities 29Kg/m3 or greater, are darker coloured as these foams will tend to discolour with time and darker colours age gracefully. Also consider the fire rating UL 94 HF1 is the most stringent acoustic foam fire test and means you are not taking chances in your studio.

Polyurethane polyester

Polyurethane polyester foams are the Rolls Royce of acoustic foams and come at a premium which reflects the performance you can expect from these foams. Professional acoustic foam brands use polyester foams because the performance is guaranteed. Polyester foam is manufactured to very high standards because the applications these foams are used for require only the best foam.

Polyester foam lends its great performance to the greater percentage of open cells meaning more air pockets exist which soak up the energy of sound waves. Polyester foam is manufactured in blocks and tested for air resistance at intervals to ensure that the performance is uniform which ever part of the block is used. This precision led manufacturing process means that polyester foams aren’t riddled with blow holes leaving a shiny aesthetic surface that delivers performance time after time.

Polyester foams provide controlled absorption across the entire spectrum with thicker foams offering effective absorption down to 125Hz right through to the top end of the frequency spectrum. This wide band of performance means polyester foam is the choice for professionals looking to introduce absorption into their studios. Polyester foams take longer to discolour when compared to their polyether counterparts.

Melamine Foam

Whilst not traditionally used in music studios melamine foams are fast gaining recognition as an acoustic treatment option for studio acoustic treatment. Priced higher than polyester and polyether foams melamine foam offers the perfect combination of absorption and light weight.

Melamine foams achieve this extraordinary feat by exhibiting a true 3D filament structure. This structure means that melamine foam doesn’t have any closed cells but rather millions of air chambers which significantly increase its performance in the mid to high frequencies. Although thicker panels will shift the absorption down to the lower end of the spectrum for domestic purposes the cost doesn’t justify the performance.

So where then does melamine foam come in handy? The answer is simple. Firstly the extremely light weight nature of this foam means that melamine foam panels can be stuck on to ceilings of large buildings without any concern of the impact on roof loading. This property means that melamine baffles and blocks are used in large building, factories, gymnasiums, churches and swimming pools.

Secondly melamine foam is available in brilliant white and is the only type of foam which holds its colour without getting discoloured when exposed to UV rays. This lends it well to use for indoor applications where darker coloured tiles would present an aesthetic challenge. Melamine panels are handy for home cinemas and used for treating walls and ceilings at reflection points as well as treating home studios that double up as work offices.

Melamine foam can be cut into a number of shapes although most popular are flat panels with bevelled edges. Melamine comes in standard White, grey and light grey however the white panels may be spray painted using specialist equipment to any colour.

Finally melamine foam is class 0 fire rated which is lends it well to applications where building regulations mean only materials with high fire ratings can be used without impacting on the aesthetic of the room it is applied to. Other foams can be treated to make them class 0 rated but this involves impregnating them with graphite and carbon which results in black sheets. Not exactly the best for indoor use.

Melamine foam however is quite brittle and can easily get damaged so needs to be handled with caution.

I hope this helps you understand what to look out for when you are next shopping around for acoustic foam for your studio. Just remember if it looks like furniture foam and is priced like furniture foam then it most likely is furniture foam.