Note: Descriptions are shown in the official language in which they were submitted.
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"A PANEL AND RELATED WALL STRUCTURE"
TECI~CAL FIELD
The present invention relates to a panel and related wall structure and in
particular to a
sound absorbing panel and structure which although not essentially but,
preferably is used as a
building panel such as a wall or ceiling panel.
BACKGROUND ART
Wall and ceiling panels made of a gypsum based material are well known. Such
panels
are often also called plaster board panels and consist of a core of gypsum
material overlaid on
each side by a paper sheet. Such panels are used placed against framing timber
to provide a
lining for an interior surface of a mom of a house or building or the like.
Similarly suspended
ceilings may be provided wherein the plaster board is suspended from a framing
structure to
thereby reduce the degree of vibrational transmission of sound. - -
Such additional steps in providing a further sound proofing can however be
costly and it
is advantageous if a single sheet of a building panel can be provided wherein
significant or
adequate sound absorption effects are provided by that panel alone. It will be
appreciated that
the provision of intermediary sound absorbing members add steps to the
installation procedure
of lining a mom of a building.
The sound transmission loss of wall-barriers is determined by physical factors
such as
mass and stiffness. In double layer assembly, as in gypsum wallboard on non-
continuous wood
framing, the depth of air space, the presence of sound absorbing material and
the degree of
mechanical coupling between layers critically affect sound transmission losses
and therefore the
sound transmission class (STC).
Renewed interest in reducing noise in living chambers has motivated research
in
structural-acoustic analysis. Sound is generated by creating disturbance of
the air which sets up
a series of pressure waves fluctuating above and below the air's normal
atmospheric pressure.
These pressure waves propagate in all directions from the source of the sound.
There are many
sources of sound in buildings: voices, human activities, external noises such
as traffic,
entertainment devices and machinery. They all generate small rapid variations
in pressure
about the static atmospheric pressure. These propagate through the air as
sound waves. The
nature of excitation may be unique to each chamber. The sound transmission
loss of wall-
barriers is determined by physical factors such as mass and stiffness. In
double layer assembly,
as in gypsum wallboard on non-continuous wood framing, the depth of air space,
the presence
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of sound absorbing material and the degree of mechanical coupling between
layers critically
affect sound transmission losses and therefore the sound transmission class
(STC). The internal
sound field in the enclosed area is significantly affected by: the acoustic
modal characteristics,
the dynamic behaviour of the surrounding structure, and by the nature of the
coupling of these
two dynamic systems e.g. that created by wall and ceiling structures. In
addition, depending
upon the relative value of the wall panel and gap resonant frequencies, sound
transmitted from
one side of a wall to the other may be amplified rather than reduced.
It is common knowledge that for typical partitions, the transmission loss is
much smaller
for low frequency sounds than for high frequency sounds.
SUMMARY OF THE INVENTION
Accordingly it is an object of the present invention to provide a panel which
overcomes
the abovementioned disadvantages or which at least provides the public with a
useful choice.
It is also an object of the present invention to provide a wall structure
which has
improved acoustic transmission properties over single panelled wall
structures, or to at least
provide the public with a useful choice.
Accordingly the present invention consists in a panel comprising a unitary
wall or
ceiling panel comprising
a first layer predominantly of a solidified gypsum based material and of a non
cavity
defining structure, said first layer defining a first exterior major surface
of the panel and
a second layer of a solidified gypsum based material having a plurality of
preferably
substantially homogenously provided cavities, said second layer engaged with
the first layer
and disposed from the side of said first layer opposite to said first exterior
major surface,
said cavities each including anhydrate material of a kind having a water
content
dependent volumetric displacement, said cavities having been formed by the
volumetric
shrinking of said anhydrate material resultant from the dissipation of water
from said unitary
panel gypsum wet phase precursor during its curing to a solidified state.
Preferably said second layer is engaged directly to said first layer.
Preferably a third layer is provided as part of said panel capturing said
second layer
between said first and third layer, said third layer being of a solidified
gypsum based material of
a non cavity defining structure and defining a second exterior major surface
of said panel.
Preferably said third layer is substantially similar to said first layer.
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Preferably said first, second and third layers are coextensive.
Preferably at least one of said first and second major surface of said panel
is provided
with a patterned non planar surface.
Preferably at least one of said first and second major surface consists of a
plurality of
upstands.
Preferably each said upstand is prismatic in shape.
Preferably at least one of said first and second major surface of said panel
is a cobbled
surface.
Preferably said first and third layer is substantially of gypsum.
Preferably said third and first layers include EVA additive.
Preferably said first and third layers include a fibre re-enforcing material .
Preferably said anhydrate material is a polyacrylate.
Preferably said anhydrate material is a potassium polyacylate.
In a further aspect the present invention consist in a method of providing a
unitary wall
or ceiling panel which comprises the steps of
a) providing a layer of wet pre-solidified phase gypsum based material and
anhydrate material homogenous mixture, onto a layer of wet pre-solidified
phase gypsum based
material without said anhydrate,
b) allowing curing to a solidified phase of said gypsum to occur.
Preferably the method further includes the provision of a layer of wet pre-
solidified
phase gypsum based material onto to the exposed surface of the layer of pre-
solidified phase
based gypsum and anhydrate material homogenous mixture.
Preferably the method further includes the provision of a layer of gypsum
based
material onto the exposed surface of wet pre-solidified phase gypsum and
anhydrite material
homogenous mixture by the dispersing of a gypsum based power form material
onto the the
exposed surface of wet pre-solidified phase gypsum and anhydrite material
homogenous
mixture.
Preferably said third mentioned layer is absent of anhydrite material.
Preferably said anhydrite is a polyacrylate.
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Preferably said polyacrylate is potassium acrylate.
Preferably said third mentioned layer prior to it setting is screeded to
provide a planar
surface finish.
Preferably a fibrous material is provided in at least one of the first and
third mentioned
layers.
Preferably said fibrous material is fibreglass.
Preferably said second mentioned layer is applied onto a horizontal moulding
surface
which during the curing of said layers provides upward support to said layers.
Preferably said moulding surface has an patterned relief moulding surface to
impart a
non planar surface to said second mentioned layer.
In a fiu-ther aspect the present invention consist in a wall structure of a
building
comprising
a vertically extending frame work spanning between a floor and ceiling of said
building
a wall panel subassembly comprising a first panel and at least one other panel
said second panel engaged to said first panel in a substantially parallel
manner and
separated therefrom to define a space there between, said first and second
panels engaged to
each other in a separated manner by a compressible material spacer element,
wherein said subassembly is mounted from and affixed to said fi~ame work by
mechanical fastening means in a manner wherein said first panel is positioned
facing said frame
work and wherein a compressible material spacer element in provided
intermediate of said first
panel and said framework.
Preferably said first and second panels are coextensively engaged with each
other.
Preferably said first panel comprises
a first layer predominantly of a solidified gypsum based material and being of
a non
cavity structure, said first layer defining a first exterior major surface of
the panel and
a second layer of a solidified gypsum material having a plurality of
substantially
homogenously provided cavities, said second layer engaged with the first layer
and disposed
from the side of said first layer opposite to said first exterior major
surface,
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said cavities each including anhydrate material of a kind having a water
content
dependent volumetric displacement, said cavities having been formed by the
volumetric
shrinking of said anhydrate material resultant from the dissipation of water
from said unitary
panel gypsum wet phase precursor.
Preferably said second panel is of a homogenous gypsum based structure.
Preferably the surface of said first panel facing said frame structure side is
non planar.
Preferably said surface of said first panel facing said frame structure is of
a cobbled or
prismatic texture.
Preferably said compressible material spacer is a strip material and extends
at least
proximate to the perimeter of and between the first and second panels.
Preferably a second wall panel sub assembly is provided and disposed from the
other side
of said frame work, said second wall panel sub assembly comprising a first
panel and at least
one other panel
said second panel engaged to said first panel in a substantially parallel
manner and
separated therefrom to define a space there between, said first and second
panels engaged to
each other in a separated manner by a compressible material spacer element,
wherein said second subassembly is mounted from and affixed to said frame work
by
mechanical fastening means in a manner wherein said first panel is positioned
facing said frame
work and wherein a compressible material spacer element is provided
intermediate of said first
panel and said framework.
Preferably the distance between the first panel of said first wall panel
subassembly and
the first panel of the second wall panel sub assembly is approximately 170 mm.
Preferably said frame work comprises of vertically extending timber studs.
Preferably said frame work comprises two parallel and separated rows of studs
a first row
with which the first sub assembly is engaged and a second mw with which said
second sub
assembly is engaged.
Preferably said first panel of said first sub assembly and said first panel of
said second
sub assembly each included a cobbled or prismatic surface detail.
In still a further aspect the present invention consists in a wall or ceiling
panel assembly
comprising
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a first planar panel of a rigid sheet material
a second planar panel of a rigid sheet material affixed to said first wall
panel in a spaced
apart disposition from said first wall panel, wherein the major surfaces of
said first and second
planar panels are parallel and in at least a significant overlapping
relationship with each other
at least one resiliently flexible element disposed between the facing major
surfaces the
first and second panels and sealing engaged to the facing surfaces of each
panel,
wherein at least one of said first and second panels (hereinafter the "cavity
panel")
comprises
a first layer predominantly of a solidified gypsum based material and of a non
cavity
defining structure, said first layer defining a first exterior major surface
of the panel and
a second layer of a solidified gypsum based material having a plurality of
preferably
substantially homogenously provided cavities, said second layer engaged with
the first layer
and disposed from the side of said first layer opposite to said first exterior
major surface,
said cavities each including anhydrate material of a kind having a water
content
dependent volumetric displacement, said cavities having been formed by the
volumetric
shrinking of said anhydrate material resultant from the dissipation of water
from said unitary
panel gypsum wet phase precursor
a third layer predominantly of a solidified gypsum based material and of a non
cavity
defining structure, said third layer defining a second exterior major surface
of the panel.
Preferably at least one of the first or second exterior major surfaces of said
cavity
panels) is of a non planar surface consisting of plurality closely or
abuttingly spaced upstands.
Preferably one of the first or second exterior major surfaces of said cavity
panels) is of
a non planar surface consisting of plurality closely or abuttingly spaced
upstands.
Preferably only one of said first and second panels is a cavity panel.
Preferably the exterior (to said assembly) facing major surface of said cavity
panel is of
a non planar surface consisting of plurality closely or abuttingly spaced
upstands.
Preferably the major surface of said cavity panel facing the other of said
first and second
panels is of a non planar surface consisting of plurality closely or
abuttingly spaced upstands.
CA 02435052 2003-09-08
Preferably said resiliently flexible element is a strip material and is
provided between
the first and second panels at or immediately inwardly of the overlying
perimeter regions of
said first and second panels.
Preferably said first and second panels are affixed to each other in a
substantially
coextensive relationship.
BRIEF DESCRIPTION OF THE DRAWINGS
This invention may also be said broadly to consist in the parts, elements and
features
referred to or indicated in the specification of the application, individually
or collectively, and
any or all combinations of any two or more of said parts, elements or
features, and where
specific integers are mentioned herein which have known equivalents in the art
to which this
invention relates, such known equivalents are deemed to be incorporated herein
as if
individually set forth.
Figure 1 is a sectional view through a preferred form of the panel of the
present
invention,
Figure 2 is a side view of a panel of the present invention,
Figure 3 is a sectional view through an installation which includes the panel
of the
present invention to define a sound absorbing wall structure,
Figure 4 illustrates a means of joining adjacent panels,
Figure 5 illustrates an arrangement for supporting a panel from a vertical or
horizontal
surface,
Figure 6 illustrates a method of fixing a series of panels to a wall structure
wherein the
assembly provides enhanced soundproofing,
Figure 7 illustrates an example of an assembly of a wall utilising the panel
of the
present invention in conjunction with additional panels and framing,
Figure 8 illustrates a prismatic surface texture provided on the panel of the
present
invention,
Figure 9 is a view of the core of the panel of the present invention,
Figure 10 is an illustration of the setup of the acoustic testing room,
Figure 11 is a graph of results of the testing as hereinafter described,
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Figure 12 shows a test data sheet of the wall construction incorporating the
cavity
panel, and
Figure 13 shows a test data sheet of the wall construction incorporating the
cavity
panel.
DETAILED DESCRIPTION OF THE INVENTION
The wall or ceiling panel
The proposed panel of a first aspect of the inventions described provides a
convenient
way of absorbing noise transmission and is maintained within a standard panel
thickness (e.g.
l2.Smm) commonly used in building trades. With reference to Figure 1, the face
gauge
(exterior layers 4 and 1) consists of a gypsum based material and provides a
high density thin
layer. The exterior layers 1 and 4 are of a non-cavity structure and may hence
be considered of
a solid non porous structure. The face gauges 1 and 4consists of a gypsum
based material and
provides a substantially solid thin section to the panel of the present
invention. One face gauge
provides its exposed surface 2 to be provided in a condition in use to be
exposed into the room
but which can later be subjected to further treatment such as priming and
painting or for the
application by adhesion of a paper layer or similar cellulosic material.
Each face gauge 1 is preferably of a high density consistency. Each face gauge
is
preferably in a form to provide a high density thin section to the panel and
may be for example
be provided by a reasonably low water content wet mix of solidified gypsum pre-
cursor.
The body gauge (the interior layer 3) consists of a gypsum material mixed with
anhydrite gelling material.
The gelling material is a product, which upon contact with water, results in
rapid
swelling as a result of electrical forces pushing the inward structure of the
particle away from
the centre. When water is drawn away from the polymer the particle shrinks in
volume.
Post curing, cavities are formed within the body gauge. These cavities provide
sound
wave dissipation. Noise that flanks past the body gauge is in part
reverberated back to the
cavities from the backward high-density exterior surface face of the panel. As
a result of the
cavities within the body gauge, many entering sound waves are internally
reflected and
dissipated.
A first face gauge 1 is provided in a mould or onto a mould in its wet form
gypsum
based pre-cursor and is spread to a thickness of for example 2mm. Provided on
top of the face
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gauge (i.e. against the surface of the face gauge away from the to be exposed
surface 2 of the
face gauge is the body gauge 3. The body gauge consists of a gypsum material
which has been
mixed with a hydrated gelling material such as an anhydrate as potassium
polyacrylate. An
example of a potassium polyacrylate is that known by the trade mark TERAWETTM
which is a
S crosslinked potassium polyacrylate/polyacrylamide copolymer which comes in
the form of
white granules and has a bulk density of S40t 40 grams per cubic meter. Its Ph
value is
somewhere between 6-6.8. TerawetTM is a product which upon contact with water
results in
rapid swelling as a result of electrical forces pushing the inward structure
of the particle away
from the centre. Small spaces are created inside the particle which attract
water. When water is
drawn away from the polymer the particle shrinks in volume. With the provision
of hydrated
potassium polyacrylate with the gypsum to define the body gauge, a
substantially solid, in its
wet form, layer of material is applied to the (preferably still procured form)
inwardly facing
surface 10 of the face gauge 1.
The body gauge may be allowed to cure along with curing of the face gauge.
However
1 S preferably a third layer, a backing face gauge 4 is provided to the then
upwardly facing exposed
surface of the body gauge 3. The backing face gauge 4 is preferably made of a
substantially
similar material to the face gauge 1. The body gauge 3 may be provided in the
form of 8.Smm
layer intermediate of the backing face gauge 4 and face gauge. Further
intermediate layers may
be provided of a different kind however the most preferred form of the panel
is as shown, in
cross section in Figure 1.
Preferably said third layer 4 has a normal to the plane of its exterior
surface projecting
in the opposite direction away from said panel to the normal of the plane of
the exterior surface
of said first layer 1 so the panel is of a uniform thickness...
Upon the curing of the gypsum material moisture is drawn out from the wet
phase of the
2S face, backing and body gauges. As the potassium polyacrylate also contains
water, upon the
curing of the panel, that water is removed from the potassium polyacrylate.
The potassium
polyacrylate becomes dehydrated and reduces in volume. As it reduces in
volume, cavities are
formed within the body gauge such cavities being substantially of a size of
the wet or hydrated
phase of the potassium polyacrylate.
Once dehydrated, the swelled anhydrites at the core of the sheet shrinks to
form small
beads. The result is aerated cavities 30-40 times larger than the remaining
bead of anhydrate.
The dried anhydrites can re-swell to its original cavity mass when atmospheric
moisture
conditions are present. This phenomenon can occur repeatedly in a consistent
manner.
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The anhydrites within the panel will absorb and contain water ingress and
release it
when appropriate warm and dryer atmospheric conditions are present.
At the casting stage an anti-mould and fugal agent is added to at least the
body gauge to
combat the problems associated with water ingress such as product breakdown,
rot, mildew and
mould growth.
The application of the backing gauge to form part of the panel of the present
invention,
is achieved during the curing of the face and body gauge. As the curing of the
face and body
gauge takes place, moisture is floated to the surface of the body gauge. This
moisture can be
removed by the application of gypsum powder to the upper surface of the body
gauge as the
moisture is transferred therefrom. The application of gypsum powder to the
upper surface of
the body gauge provides the backing face gauge to the panel of the present
invention. In order
to achieve a smooth surface to the backing gauge the powdered gypsum that is
applied to the
surface of the body gauge is smoothed by for example a screed. The thickness
of the backing
gauge can be built up appropriately to cover the upper surface of the body
gauge and to thereby
define a panel which is of a desired thickness. By way of example, the
thickness of the panel
may be provided to approximately l2.Smm.
Cavities in the body gauge, provide a disruption of reverberation of sound
through the
panel. The panel allows for mild reverberation of the face gauge allowing for
a reasonably high
percentage of noise to pass through to the body gauge. The reverberation of
sound in the body
gauge can be captured in the cavities in providing a dissipating effect of the
noise. Noise that
flanks past the body gauge is in part reverberated back to the cavities from
the exterior layers.
As a result of the cavities within the body gauge of the panel of the present
invention, much
sound that enters therein is internally reflected and eventually some if not
most is absorbed.
To provide strength to the panel, fibre rovings may be provided throughout the
panel or
provided within at least one of the gauges and preferably within the body
gauge 3.
The panel of the present invention with the inclusions of a dehydrated
anhydrate will
also provide some degree of humidity or moisture absorption.
Further additives may be provided to the gypsum material for the purposes of
hardening
and such materials may include EPA and EP hardener and indeed anti-mould or
antifungal
agents may be added particularly considering the possibility of moisture
absorption being
provided by the anhydrates.
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In designing the wallboard several factors were taken into account. These
include the
right weight for swelled anhydrites, the right amount of a typical hardener
(EP hardener) which
is added to both the face and body gauges, the fibre-glass strands. Table 1
shows one example
of material detail. Table 2 shows an alternative. Table 2 gives weight values
of components
for the improved mix at a mass quantity gauge ratio of 100 : 60.
The panel of the present invention may further be provided with a surface
modification
to at least one of the outwardly facing surfaces of the face gauge or backing
face gauge 1,4.
Such a surface modification is by way of a pattern of upstands or
substantially the entire of the
surface and provides a disruption to the otherwise flat exterior surface of
the panel.
The panel of the present invention provides a convenient way of absorbing some
noise
transmission through the panel while still allowing it to be maintained within
a standard
thickness wall panel which are commonly used in the building trade.
With the provision of surface modifications to at least one and alternatively
to both of
the outwardly facing surfaces of the panel of the present invention, further
sound reducing
characteristics may be catered for. Surface upstands which may be provided as
a pattern to the
surface of the panel can provide further sound deflection. With reference to
Figure 3, the panel
is provided as part of a sound absorbing structure and the surface
modifications 12 may be
provided exposed into a cavity which is defined between the panel of the
invention and an other
like or other type of panel 13.
Wall Structure
The overall function of a wall, in conjunction with floors, and roofs, is to
provide a
barrier between two environments, so that one environment can be adjusted and
maintained
within acceptable limits.
A wall is a selective separator between two spaces where between an actual or
potential
flow of energy is involved. The greater the difference between the two spaces
the greater is the
stress of duty imposed on the wall. Thus, the elements of the wall must be
selected so that in
the first instance they impart the necessary resistance to keep noise levels
within acceptable
limits. The way they are arranged, however, is also important. This will
determine the
variation in conditions throughout the wall. Interaction between various
factors involved may
produce conditions within the wall structure that require special attention.
The panel 13 may be a standard plaster board sheet which is provided in
association
with the panel 14 of the present invention. The surface modifications 12 may
be provided
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preferably within the cavities provided between two panels 14, 13.
Alternatively the panel 14
may present the surface modifications outwardly for positioning facing a frame
structure. The
surface modifications will provide a disruption to the sound waves
endeavouring to travel into
the panel 14 from any sound transmitted from the inwardly facing surface of
the panel I3. To
prevent direct vibrational transmissions between the two panels a spacer 15 of
a low hardness
material such as a foam or rubber is provided to create a space lamination
such may be
provided at appropriate locations between the panels 13 and 14. This spacer
will reduce the
incidence of material vibrational transmission of sound.
The panel 14 is preferably mounted to a frame work structure 16 of a building
such as
timber framing directly, or with rubber or foam spaces in between or by way of
mounts 17.
Such mounts may be rails of an extruded or roll formed kind to which the panel
structure of the
panels 13, 14 are mounted. Rubber grommets 21 or strip material may be further
provided
intermediate of the structure 16 and the mounts 17 and/or between the mounts
17 and the panel
14. With reference to Figure 5, there is shown a detailed view of the
arrangement wherein the
panel is provided to a timber framing structure as for example shown in Figure
16.
A putty like material may be provided to overlay the positions where the
fastening
means 22 may be provided to secure the panel 14 to the rails 17. The
application of such a
putty 23 provides a sound seal to the migration of sound via the fastening
means 22 to or from
the other side of the panel 14 to which it is provided.
With reference to Figure 6, a wall utilising the panel construction of the
present
invention may be provided wherein a plurality of panels are provided adjacent
to each other.
Such a plurality of panels 20 are preferably engaged to adjacent like panels
as for example
shown in Figure 4. A sound sealing material 25 may be provided intermediate of
the panels to
thereby reduce transmission of vibration between adjacent abutting panels.
The spacer seal 15 may extend around or approximate to the formed perimeter of
the
plurality of panels. Intermediate of the spacer there may be provided a sound
absorbing putty
26. Such a sound absorbing may also be provided external of the seal 15.
The exterior panel 13 may preferably be adhered to the panel 14 by adhesive
regions 27
such as adhesive daubs. The adhesive is that which holds the facing panel 13
to the inner panel
14.
With reference to Figure 7 there is shown a double sided wall structure which
includes a
frame structure of a first row of studs 102 and a second row of studs 106. The
studs preferably
CA 02435052 2003-09-08
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extend from floor to ceiling of a building structure and nogs or dwangs may
extend between
adjacent studs in each row. However most preferably each row remains separated
from the
other row and accordingly a gap 107 is provided between the rows of studs. The
gaps will
reduce the possibility of solid mass sound transmission, between studs and
hence each side of
the wall.
On each side of the studs are provided a wall panel sub assembly. Each wall
panel sub
assembly preferably consists of a first panel 101 and a second panel 100. In a
most preferred
form the pane1.101 is of a kind as hereinbefore described which utilises the
cavity structure
defined by the anhydrate material therein. The first and second panels are
engaged to each
other but are separated by a space therebetween which is preferably defined by
a spacer element
104 which is of a flexible material such as a foam or rubber strip or strips.
The foam may for
example be a high density foam seal. As mentioned above, additional adhesive
daubs may be
provided intermediate of the two panels of each sub assembly to fix these
together. As a sub
assembly, the two panels are then fixed to the appropriate side of the fi~ame
structure to a
respective row of studs.
Preferably a high density foam seal is provided intermediate of the stud and
the facing
side of the first panel 102 to act as a vibration absorption spacer between
the studs and the
subassemblies. Fixing screws can then extend through the subassemblies
(through both panels
101 and 100 to further fix the sub assemblies to the frame work). Screws of a
sufficient length
and of a kind often used in a plaster board panels can be used
Intermediate of the two sub-assemblies of panels a thermal insulation material
such as a
fibre insulation mat can be positioned to further enhance sound absorption and
to provide
thermal insulation.
In the most preferred form the sub assemblies are positioned such that the non
planar
(e.g. the surface with the cobbled or prismatic upstands) panel of the sub
assemblies are
positioned engaged to the frame structure, facing the studs or facing the
cavity between the
studs. The non planar surface 108 positioned in this manner will encourage the
sound
dissipation within the cavity between the two facing sub assemblies, provided
on each side of
the frame structure.
It is perceived by the inventor that these wall structure as shown in Figure 7
may utilise
one only subassembly on one side only and the other side may be of a different
kind. A single
stud arrangement against which a single sub assembly is provided may also be
utilised.
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However it has been recognised in testing that a double wall structure as
shown in Figure 7 and
wherein the spacing between the interior facing surfaces of the wall sub
assemblies provided at
approximately 170mm apart, provides a very attractive absorption
characteristic of which
reference will hereinafter be made.
Tests
In order to achieve high STC valves it has been recognised by the inventor
that,
important factors, in addition to masses of the component layers, are the
depth of air space, the
use of sound absorbing materials within the air space and the rigidity of the
mechanical
coupling between the layers. This may be achieved by a wall assembly with no
significant rigid
mechanical connection between the two wall panel subassemblies on each side of
the frame
structure. The mechanical connection between the subassemblies of two panels
is reduced by
the use of separate rows of studs to support the subassemblies independently
of each other.
With reference to Figures 11, 12 and 13 test results indicate that the cavity
panel
incorporating sub-assembly of this invention reached an STC of 63 dB. This
value is higher
1 S than those reached with locally and internationally (Canada and USA)
produced acoustic panels
of solid (non cavity) configuration. The STC of Standard Commercial Wall
Boards is 54 dB.
For the wall assembly of Figure 7 the results also showed a significant
improvement to
the lower ranges of frequency {between 50 - 160 Hz). This effect can be
avoided by increasing
the air space between the non-continuous wooden frames to displace the facing
surfaces of the
two subassemblies. Tests were conducted to fmd the optimum airspace between
the facing
surfaces of the panel subassemblies on each side of the frame structure to
suppress resonance.
This was found to be optimum at 170mm.
It was shown by analysis that the core shear parameter has a significant
effect on the
noise transmission characteristics of the proposed panel, which has better
sound transmission
characteristics than a homogenous panel, for two reasons: first, the
coincidence frequencies are
shifted to higher frequency ranges, and second, the coincidence transmission
loss is
considerably increased due to the presence of the cavities on the layer
surface.
Tests were conducted on the new panel at the University of Auckland Acoustic
Laboratories. Sound transmission loss was measured by testing in two separate
rooms highly
reverberant not in solid contact with either of them. A loud speaker and
amplifier are used to
generate random sound in one of the rooms and sound energy passes through the
partition into
the second receiving room (Figure 10):
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The level in the receiving room is partly determined by the area of the
partition and the
total absorption of the receiving room. The larger the sound transmission
class (STC) value,
the better the partition (less sound energy passes through it).
The reverberation time in the echoic chambers was optimised. The reverberation
time is
directly related to the room volume and inversely related to total absorption
in the room. The
reverberation time is calculated using Sabine reverberation time equation:
RT=0.161 V/(aS+4mV)
where:
V is the room volume in cubic meters,
a is the mean absorption coefficient,
S is the total surface area of the room, in square meters,
m is the energy attenuation constant per meter due to air absorption.
An important improvement is achieved on the low frequency range (between 50 -
160
Hz). On curve of Figure 11, the variation of the transmission loss is shown
with frequency:
- For low values of frequency (between 50 - 160 Hz) the transmission loss
curve follow
the mass law. It shows significant improvement.
- At mid-ranged frequencies (between 200 - 630 Hz) a deviation from the mass
law takes
place. This is attributed to the fact that at this range the wave resonance
acts to increase
the frequency values. The larger the air space between the double layers or
the heavier
the materials, the lower the frequency at which resonance occurs.
- For higher frequency ranges, the transmission loss curve follows the mass
law again.
The curve shows that the TL is significantly higher at intermediate frequency
range
(1000 - 2000 Hz). This is mainly due to the fact that the coincidence
frequencies are
much higher than for the larger values of frequency. A sharp drop in LT is
noticed
between (2000 - 2500 Hz) to then increase rapidly with increase in frequency
(2500 -
4000 Hz).
To maximize the improvement due to airspace, frames should be designed so that
the
mass-air-mass resonance is at the lowest frequency as possible. Many common
frame designs
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do not meet this criterion. The air trapped in the space between the layers
acts as a spring
transferring vibration energy from one frame to the other.
The concept of sound transmission of prismatic surface cavitated core of a
wall burner
is of a significant importance in the research for more cost effective methods
related to
development of acoustic wallboards.
The sound transmission losses of a single or double layer walls are determined
by the
physical properties of the component materials and the method of assembly.
We believe that noise management of the whole system will dictate whether the
subsystems will perform satisfactorily. Furthermore, it is estimated that the
major failures can
be avoided by proper design and suitably implemented wall barriers. The rate
of noise failures
can be reduced effectively if corrective measures are taken by the whole
industry.
Summary of the measurement of airborne sound insulation of building elements
regarding the results of figures 11-13.
INSTALLATION OF TEST SAMPLE:
The wall under test is installed in the opening between two reverberation
chambers -
chambers C and A for a wall, chambers A and B for a floor. These chambers are
vibration
isolated from each other which results in a structural discontinuity at the
middle of the test
opening. This gap is covered over by a collar, which seals the gap and
provides for each of
fixing of samples. The wall sample is constructed by the client following the
techniques
normally used in practice for that type of wall or floor/ceiling, and is
sealed into the test
opening with perimeter seals of acoustic sealant. For each of removal, the
surfaces of the test
opening are covered with an adhesive, heavy fabric tape prior to the
construction of the building
element.
METHOD:
The measured transmission loss values are obtained in accordance with the
recommendations of ISO standard 140-3:1995(E) "Laboratory Measurement of
Airborne Sound
Insulation of Building Elements" using a B&K 2133 analyser. The measurements
were
repeated and checked by an independent measuring system, the B&K 2260 sound
level meter.
Essentially the transmission loss of a building element is measured by
generating sound
on one side of the building element (the source chamber) and measuring how
much sound is
transmitted into the receiving chamber. In the source chamber pink noise is
radiated from a
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loudspeaker. Time and space averaged sound pressure levels in both the source
and receiving
chambers are measured by using a rotating boom microphone, and the average
sound pressure
levels are obtained by sampling the sound pressure levels as the boom rotates
through one cycle
(taking 32 seconds). This is repeated for a different loudspeaker position in
the source
chamber.
Measurements of the background noise levels in the receiving chamber are also
made.
Then, should it prove necessary, the transmitted noise levels are corrected
for the influence of
background noise as prescribed in the standard.
The sound absorption of the receiving chamber is also determined by measuring
the
reverberation times (ISO-354:1985(E) "Measurement of Sound Absorption in a
Reverberation
Room")
RESULTS:
The third octave band sound reduction indices R are presented in both table
and graph
formats. Sometimes a highly reflective test sample means that the lower
frequency sound
pressure levels cannot be reliably measured; this is indicated by #N/A in the
table of results.
Additionally, if the specimen is highly insulating, sometimes the background
noise affects the
measurements, resulting in only an upper threshold being found; this is
indicated by a > sign
preceding the tabulated results.
Single figure ratings are also presented. The weighted sound reduction index
RW,
determined according to ISO 717-1, is presented along with spectrum adaptation
terms C~, and
C. RW is determined by fitting a reference curve to the third octave band
sound reduction
indices R from 100Hz to 3lSOHz, and gives a single figure rating of the sound
reduction
through the building element (higher is better). The spectrum adaptation terms
are added to RW
and are used to take into account the characteristics of particular sound
spectra. C is used for
living activity noise, children playing, railway traffic at medium and high
speed, highway
(>80km/h) road traffic, and jet aircraft at short distances. Cr, is used for
lower frequency noise
such as urban road traffic, low speed railway traffic, aircraft at large
distances, pop music, and
factories which emit low to medium frequency noise. C and C~, without further
subscripts are
applied to a frequency range of 100Hz to 3150Hz. Other spectrum adaptation
terms are
provided with enlarged frequency ranges (if measured), e.g. Ca,so-sooo is
applied to urban traffic
noise with a frequency range of SOHz to SOOOHz. For light timber constructions
Ct, will be
negative, indicating the poor sound insulation abilities of such constructions
at low frequencies.
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The sound transmission class (STC) determined according ASTM E413 is also
presented. This is determined by fitting a reference curve to the third octave
band sound
reduction indices R from 125Hz to 4000Hz, but in a slightly different way to
ISO 717-2. The
sound transmission class gives a single figure rating of the sound reduction
through the building
element so that higher is better.
TABLE 1
Gauge Type Weight Per Thickness
Body(B.Smm) Swelled anhydrates1.42 kg/m2
(i) Face (2mm) Hardened (EPA) l9mlt/m2
(ii) Backing Face 76 mtl/m2
(2mm)
(iii) Body (B.Smm)
Body gauge surface Fibre-glass strands220 gms/m2
TABLE 2
Gauge Type Weight Per Thickness
Body (8.Smm) Swelled anhydrites 1.54 kg/m2
(i) Face ((2 mm) Hardener (EPH) 61.7 mlt/m2
(ii) Body (O.Smm) 185.2 mlt/m2
(iii) Backing Face 61.7mlt/m2
(2mm)
(i)Face layer Fiber-glass strands24 gms/mz
(ii)Body layer 208 gms/m2
