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VISUAL INSPECTION
As mentioned, MuteMat Plus is a composite with a base of high density foam
underneath a thick (~2cm) layer of micro-fibre material. The marketing material
also mentions a third layer: Viscoelastic Adhesive, but we're not sure whether
this is much different from ordinary adhesive. Each layer has a different function:
Layer 1: MuteMat Material
This layer is what makes MuteMat unique: As far as we know, no other company
sells damping material for computers based on micro-fibre material, although the material
is used in the audio industry to damp speaker enclosures. The claim is that
— thanks to its low density and fine pores compared to ordinary acoustic
foam — MuteMat is especially effective at absorbing sound. MuteMat should also help reduce cavity resonance inside the case.
Our experience with other damping materials has indicated that sound absorption
is usually not as important as vibration damping. Damping material work best in a sealed case so that there are no direct noise paths between the
noise sources (usually fans) and the listener. But in almost any fan cooled (or even convection cooled) case, there must be intake and exhaust vents. So, even if
the damping material can absorb some noise and cut down on the noise reflection
inside the case, it can't stop the noise from getting
out through those vents. This is the fundamental weakness that affects every brand of PC acoustic damping.
The MuteMat layer is soft, white and fluffy, almost the consistency
of fiberglass insulation but finer.
The black layer on top is a tough fabric that holds it all together —
a necessary feature given the looseness of the MuteMat material.
Layer 2: High Density Foam
The layer of high density foam was one of the features that set AcoustiPack
apart from its competitors. MuteMat Plus uses a very similar layer of foam.
The advantage of this extra layer is that is provides what is known as mass
damping. The essential idea is that a dense material is bonded to
the case panel, increasing its effective mass. This makes
it less prone to vibration, which is often the primary source of noise in
systems that use low-noise components. A side effect of this is that the resonant
frequency of the side panel is lowered, dropping it away from the range of
frequencies that humans are most sensitive to.
A secondary function of the high density layer is to reflect any noise that
makes it through the MuteMat layer back through it again, effectively doubling
the thickness of the material that the sound waves must travel through. Once
again, this is thanks to the increased density that makes it more difficult
for the side panels to vibrate, and thus transmit noise.
The high density foam is the upper black strip. The white layer on top
is a paper backing that protects the adhesive until it is ready for use.
Layer 3: Viscoelastic Adhesive
According to the MuteMat web site, the Viscoelastic Adhesive is meant to
provide a further layer of vibration damping. Personally, I find it difficult
to believe that it's anything other than adhesive, although it does seem thicker
and more rubbery than usual. If I had to make a guess, I'd say it's the same
gummy, silicone-based material that is sometimes used to attach extras to
magazines.
Most likely, the vibration-reducing qualities of this layer are minimal.
It's too thin to be of much help. Still, if the adhesive itself can contribute
even a bit, who am I to complain?
The "Viscoelastic" Adhesive is visible on the surface of the
black foam as a yellowish film.
It's thicker than standard adhesive, and can actually be peeled away from
the foam.
Standard MuteMat
The basic MuteMat package lacks both the high density foam and the special
adhesive, but is otherwise identical to the MuteMat Plus kit, both in the size
and number of pieces. The most noticeable difference is actually not visible
at all: MuteMat Plus weighs several times the standard MuteMat thanks to the
high mass of the high density foam. This is something to consider when shipping
MuteMat over long distances: International shipping for the basic MuteMat kit
is £3.50, but that cost almost quadruples to £13 for the Plus kit.
The standard MuteMat is missing the thicker dark foam layer.
Be careful: The backing sometimes peels away the adhesive from the MuteMat!
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