C haptEr 9 design Environments and systems
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nanoporous sound insulation materials
Surprisingly few nanomaterials can be produced directly in the
large size or bulk form needed for many building-scale applications. Most are nanocomposites. Exceptions include the many thin
films, coatings, and nanoporous materials that have been developed. Few of these, however, have useful sound-related properties.
Nanoporous materials are exceptions. Aerogels are discussed extensively in Section 9.3 with regard to their important role as thermal
insulators. Of interest here are their interesting sound-insulating
properties. Aerogels have incredibly low densities. Sound waves
transmit through the air-filled part of the porous medium at a
reduced rate compared to normal air. There is little direct solid
phase vibration conducted through the solid matrix simply
because there is little solid material present and it is only
tenuously connected. Transmission reduction effects are most
evident at low frequencies (e.g., less than 400 mHz). They are
less effective at higher frequencies. Normally, in a building, the
aerogel product is contained within some other material assembly to protect and contain it, including fiber-reinforced panels,
double-walled polycarbonate glazing systems, or U-channeled
glass. Sound transmission losses for low frequencies have been
reportedly reduced as much as 25% for a polycarbonate glazing
system. Since this kind of system is translucent (polycarbonates
are highly transparent and aerogels translucent), it is highly interesting for use in many applications. Other kinds of highly porous
materials can also be expected to have similarly useful sound-loss
characteristics.
acoustical damping and isolation
As previously discussed, vibration isolation is a widely used soundcontrol technique. Vibrations might emanate from any of a number
of sources, but particularly from machines with moving or rotating
parts. Vibration control approaches normally assume one of two
primary forms, isolation and damping, or, as is often the case, some
combination of the two. Many passive vibration isolation devices
can be quite small and are manufactured as products. Vibration
damping can be achieved by affixing damping materials or devices
directly to the vibrating object, such as foam-type materials that are
inherently energy dissipating that can be glued directly to vibrating
panels.
Nanoporous materials and foams are being explored for use as
passive damping materials. The potential application of nano-
374
nanoporous sound insulation materials
Surprisingly few nanomaterials can be produced directly in the
large size or bulk form needed for many building-scale applications. Most are nanocomposites. Exceptions include the many thin
films, coatings, and nanoporous materials that have been developed. Few of these, however, have useful sound-related properties.
Nanoporous materials are exceptions. Aerogels are discussed extensively in Section 9.3 with regard to their important role as thermal
insulators. Of interest here are their interesting sound-insulating
properties. Aerogels have incredibly low densities. Sound waves
transmit through the air-filled part of the porous medium at a
reduced rate compared to normal air. There is little direct solid
phase vibration conducted through the solid matrix simply
because there is little solid material present and it is only
tenuously connected. Transmission reduction effects are most
evident at low frequencies (e.g., less than 400 mHz). They are
less effective at higher frequencies. Normally, in a building, the
aerogel product is contained within some other material assembly to protect and contain it, including fiber-reinforced panels,
double-walled polycarbonate glazing systems, or U-channeled
glass. Sound transmission losses for low frequencies have been
reportedly reduced as much as 25% for a polycarbonate glazing
system. Since this kind of system is translucent (polycarbonates
are highly transparent and aerogels translucent), it is highly interesting for use in many applications. Other kinds of highly porous
materials can also be expected to have similarly useful sound-loss
characteristics.
acoustical damping and isolation
As previously discussed, vibration isolation is a widely used soundcontrol technique. Vibrations might emanate from any of a number
of sources, but particularly from machines with moving or rotating
parts. Vibration control approaches normally assume one of two
primary forms, isolation and damping, or, as is often the case, some
combination of the two. Many passive vibration isolation devices
can be quite small and are manufactured as products. Vibration
damping can be achieved by affixing damping materials or devices
directly to the vibrating object, such as foam-type materials that are
inherently energy dissipating that can be glued directly to vibrating
panels.
Nanoporous materials and foams are being explored for use as
passive damping materials. The potential application of nano-