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Acoustics 101
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Acoustics by means of Perforations, slots and
grooves
Wood as an Acoustic ProductFlat wood and wood veneer
products typically produce NRC values under .10. Based on a
theoretical maximum of 1.0 this translates into more than 90% of
the acoustical energy being reflected. In some cases this is
acceptable. When utilizing wood in the role of a diffuser,
reflective surfaces are necessary.
WoodTrends panels are
offered as non-perforated when reflection is the goal. Far more
often are the instances where the rich beauty and warmth of wood
is desired in a design without the accompanying echo and
reverberation. The answer to this is perforation. Allowing an
appropriate amount of open space on the face of the panels
allows absorptive material to be exposed to the noise. In the
case of large bore perforations in relatively thick base
materials, diffusion also increases as the angle of incidence
increases. This element of diffusion is especially beneficial in
performance spaces where too much absorption can create an
acoustically "dead" room.
Achieving transparency
The goal when putting a rigid, reflective material in front of
an acoustically absorptive material is to achieve acoustic
transparency. Fortunately, acoustic transparency is very
different from visual transparency. Some perforation patterns
actually improve the acoustic performance of the material behind
it. Certain perforation patterns, when combined with specific
thickness materials and air spaces can be "tuned" to achieve
maximum absorption at specified frequencies.
Acoustic materials underneath
Traditional acoustic material used behind perforated structural
materials has typically been mineral wood, spun glass blanket or
rigid fiberglass board of varying densities. All exhibiting good
acoustic properties, the choice tends to be driven by price,
installation and environmental conditions. In most case, the
thicker the absorber, the better the performance at the lower
frequencies and a better overall performance. In the typical
architectural applications, mid-range or speech pattern
frequencies are the main concern. For this reason, one inch of
any of the above materials is typically sufficient when
finishing an existing wall or ceiling. For those instances where
materials will be suspended from typical ceiling grid or where
panels will be mounted well off any reflective substrates, there
is another material to consider. |
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