With BARRIER Ultra-dB acoustic insulation you get:
Superior noise reduction
with 48% less weight
While many materials
block sound - no single material blocks noise. The problem is the frequency
range. What we call "noise" nearly always consists of many different
frequencies. The sound spectrum analysis on the right (click for larger
image) shows a 3-cylinder diesel engine running at 2,800 rpms. The "noise"
it emits includes frequencies ranging from 22Hz to over 11kHz. No single
material can effectively block all these frequencies. The only way to
attenuate this kind of noise is to select a combination of materials which
work together to effectively control sound across a broad spectrum. In
practice this is harder than it may seem since different materials grouped
together change resonance characteristics and can respond in unexpected
The physics of multilayer acoustic insulation materials.
Multilayer "foam-vinyl-foam" type laminates are an attempt by manufacturers to try to attenuate a wider range of frequencies than would be possible with one material alone. The individual layers are often described by their functionality as the "absorption-damping-decoupling" layers. The "absorption" layer (nearest the noise source) is comprised of foam which is of a density that allows it to be moved (i.e. vibrated) by higher frequency sound waves. Energy is required to move the foam and this energy comes from the sound waves themselves. The frequency of sound which most effectively moves the foam the that particular material's "resonant" frequency. Consequently, it is the resonant frequency which is the one best attenuated by the material. Because they are located nearest the noise source, absorption layers also help to inhibit the formation of standing waves.
The resonant frequency of foam is quite high - above 250 - 500 Hz depending on thickness. Frequencies lower than that pass through virtually unaffected. Attenuating these lower frequencies is much more difficult and is the primary function of the "damping" layer. The damping layer used in conventional sound materials is very heavy (lead or a filled vinyl of similar density) and relies on high mass to provide a lower resonant frequency and harness the energy contained in these waves. The waves hit the damping layer and, as with the lighter foam, make it vibrate. Unfortunately, because of the weight of the damping layer, this vibration can create a new problem. If the vibrating mass is allowed to mechanically transfer energy to another surface (such as a wall or bulkhead) the noise is simply transferred through and radiated off the other surface. It is the job of the "decoupling" layer to prevent this from happening.
The BARRIER Ultra-dBtm
To accomplish this
is it was necessary to find a way to better attenuate low frequencies
without resorting to the high mass of conventional damping layers. What
was needed was a lightweight material which would resonate at low frequencies
and effectively dissipate that energy internally with a minimum of linear
solves the damping layer problem in a particularly ingenious way. Rather
than using a uniformly molded sheet, our damping layer is a composite
made up of randomly adhered elastomeric particles of varying sizes, shapes,
weights, densities and durometers. When sound waves strike, different
particles within the layer will resonate depending on the frequency of
the wave. At any given frequency only a fraction of the particles vibrate.
Each vibrating particle is loosely suspended between other particles,
most of which do not resonate at the same frequency. This permits the
energy contained within the vibrating particle to be dissipated into the
adjacent material rather than through movement of the entire layer.