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DESCRIPTION JP2015064594

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DESCRIPTION JP2015064594
Abstract: PROBLEM TO BE SOLVED: To provide a sound transmitting material having selfsupporting property and high performance sound transmitting property by using a material
formed by interlacing fibers. An acoustically transparent material which is a material in which
fibers are mutually entangled, Taber stiffness is 5 mN · m or more, bending resistance is 100 mN
or more, porosity is 50% or more, and thickness is 3 mm or less An acoustic control surface
structure, comprising: an acoustic control mechanism having a sound absorbing structure and /
or a reflective structure installed on the back surface thereof. [Selected figure] Figure 1
Sound transmitting material, sound adjusting surface structure including architectural use using
the material, windshield for microphone, protective grille, sound transmitting projection screen
and speaker
[0001]
The present invention relates to an acoustically transparent material in which fiber materials are
entangled, and more particularly to an acoustically transparent material having self-supporting
properties. Furthermore, the present invention relates to a sound control surface structure
including a construction application to which the sound transmitting material is applied, a
windshield for a microphone, a protective grill, a sound transmitting projection screen and a
speaker.
[0002]
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1
In various fields such as architecture and electronic devices, materials that transmit sound are
required. As the sound transmitting material, for example, a mesh structure such as a saran net
of a speaker, a perforated plate used for an architectural wall surface, and the like can be
mentioned.
[0003]
Unlike these conventional sound-transmissive materials, they appear to be hard because they
appear to be hard because they have a hard texture and can not be viewed with no or no
apertures, but they transmit almost completely through the sound. An acoustically transparent
plate-like member or sheet-like member has been proposed as a material (Patent Document 1).
[0004]
In addition, it has been reported that sound permeability can be obtained by providing a large
number of fine holes, which can not be visually recognized in appearance, in a hard plate as a
plate-like sound transmitting material (patent documents 1 and 2) Non Patent Literature 1).
Since a hard sound transmitting material can be obtained by the sound transmitting material, it
has been proposed to apply it as a screen of a movie and install a speaker on the back of the
screen to enhance the sense of reality.
[0005]
JP, 2010-59658, A JP, 2010-210778, A
[0006]
Nakai, Kawakami, Wada, Sano "Acoustic Characteristics of Perforated Plate", Architectural
Acoustics Research Institute of Japan Acoustics Society Material (AA2009-18), 2009.03.11
[0007]
In applications such as building materials, when an acoustically transparent material is erected,
self-supporting may be required to maintain a standing state by the strength of the acoustically
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2
transparent material itself without providing any auxiliary mechanism or the like.
According to the sound transmitting material of Patent Document 1, there is a problem that the
sound transmitting property is impaired when it is intended to give the sound transmitting
material a self-supporting property.
Moreover, according to the sound transmitting material of Patent Document 2 and Non-patent
Document 1, although it has self-supporting property, it is necessary to provide a large number
of fine holes, so there is a problem that the manufacturing cost becomes high by special drilling
technology or trained by skilled workers. there were. Therefore, an object of the present
invention is to provide an acoustically transparent material that is self-supporting and has highperformance acoustic transparency, using a material formed by interlacing fibers.
[0008]
As a result of examining the fiber material in which the self-supporting property and the sound
transmission are compatible, the present inventor made the density of the fiber too high and
increased the sound transmission by increasing the amount of fiber used for the fiber material in
order to secure the self-supporting property. It has been found that the problem lies in the
entanglement of fibers as densely as they are impeded.
[0009]
That is, the acoustic energy reflectance | r <2> | (here, r is the sound pressure reflectance) at the
material interface is expressed by the following equation (1).
[0010]
The acoustic energy reflectance | r <2> | is that the normal acoustic impedance Zn of the
material surface is Zn = ρc (ρc is the characteristic impedance of air) or the specific acoustic
impedance ζ (the value obtained by dividing Zn by cc) is ζ≡Zn When / (ρc) = 1, the minimum
value | r <2> | = 0, and all the incident sound energy enters the inside of the material, apparently,
the sound absorption coefficient α = 1− | r <2> | is the maximum value 1 (Koyasu Masaru
"Basics of sound absorption" Acoustics No. 71 / sep. 1990).
In this condition, Zn = cc means that the condition of the material is equal to air, the amount of
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3
air contained in the material, ie the porosity (porosity = porosity); the air contained internally to
the apparent volume of the material amount.
As the specific definition is described later), the amount of incident sound energy into the
material increases. Therefore, if the conditions inside the material, such as flow resistivity (unit
thickness flow resistance) and tortuosity (degree of labyrinth) (Hiroshi Nakagawa “About
acoustic materials (Part 3)” Nittobo Engineering Technology News), the conditions inside the
material are equal. The energy Eh absorbed by is also constant, and the larger the porosity, the
amount of acoustic energy coming back, ie, the transmittance τ (τ = | t | <2> = Et / Ei; the ratio
of the transmitted energy Et to the incident energy Ei . t is the sound pressure transmittance) at
maximum (τ 1 1), that is, the insertion loss (the difference in level between the absence and
presence of the sample (dB)) when placed immediately before the speaker or microphone can be
minimized. It turns out that conditions close to sound transmission can be realized (see FIG. 12).
[0011]
Furthermore, in the material having self-supporting property, in order to obtain sufficient sound
transmission, not only the porosity of the material used but also the relationship with the
thickness is found to be important, and furthermore, the porosity is high. It has been found that,
if the material has a thickness equal to or less than a predetermined value, sufficiently high
acoustic transparency is exhibited.
[0012]
That is, the present invention (1) is an acoustically transparent material in which fibers are
mutually entangled, and the acoustically transparent material has a Taber stiffness of 5 mN · m
or more, a bending resistance of 100 mN or more, and a porosity of 50% This is a sound
transmitting material characterized in that the thickness is 3 mm or less.
[0013]
The present invention (2) is the sound transmitting material according to the invention (1),
wherein the fiber is a metal fiber.
[0014]
The invention (3) is the sound transmitting material of the invention (1) or (2), wherein the
insertion loss is 5 dB or less in each 1/1 octave band of 63 Hz to 8 kHz.
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[0015]
The present invention (4) is the sound transmissive material according to any one of the present
inventions (1) to (3), wherein the sound transmissive material is a material obtained by
compression molding a metal fiber.
[0016]
The present invention (5) comprises the sound-transmissive material (for example, the soundtransmissive material 2 in FIG. 1) according to any one of the above-mentioned inventions (1) to
(4), and a sound absorbing structure and / or Or a sound control surface structure (e.g., sound
control surface structure 1 in FIG. 1) including a sound control mechanism (e.g., sound control
mechanism 3 in FIG. 1) having a reflective structure.
[0017]
The present invention (6) is the sound adjusting surface structure according to the invention (5),
wherein the sound adjusting mechanism is a variable sound adjusting mechanism capable of
changing the arrangement ratio of the sound absorbing structure and / or the reflective
structure.
[0018]
The present invention (7) is an acoustic control surface structure in an interior of a wall and / or
a ceiling of a building, wherein the acoustically transparent material forms a space between the
wall and / or the ceiling of the building. (For example, the sound transmitting material 2 in FIG.
3), and the variable sound adjusting mechanism (e.g., variable sound adjusting mechanism 610)
is disposed in the space, the curtain or sound absorbing blind configured to be openable and
closable. It is a sound control surface structure (for example, reverberation variable wall 600) of
the said invention (6) which has (for example, curtain 613) and adjusts the sound absorption
characteristic of a surface by opening and closing of the said curtain or a blind.
[0019]
The present invention (8) is an acoustic control surface structure in an interior of a wall and / or
a ceiling of a building, wherein the acoustically transparent material forms a space between the
wall and / or the ceiling of the building. (For example, the sound transmitting material 2 in FIG.
4), the sound adjusting mechanism has a sound absorbing structure and / or a reflective
structure (for example, the sound absorbing material 701, the air layer 702) arranged in the
space. Plywood 704, space A), the acoustic control surface structure (for example, reverberation
control wall 700) of the invention (5).
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[0020]
The present invention (9) is an interior structure of a building having the acoustic control surface
structure according to any one of the inventions (5) to (8).
[0021]
The present invention (10) is a windshield for a microphone for reducing wind noise of a
microphone, wherein the windshield has a sound transmitting material disposed at a position for
blocking the wind to the microphone, and the sound transmitting material is It is a windshield for
microphones which is an acoustically transparent material any one of the said invention (1)-(4).
[0022]
The present invention (11) is a protective grille disposed in front of a microphone or a speaker,
wherein the grill is made of the sound transmitting material according to any one of the
inventions (1) to (4). It is a grill for.
[0023]
The present invention (12) is an acoustically transmissive projection screen having a front
projection type projection and projection surface, wherein a speaker is disposed behind the
image projection surface so as to emit sound. It is a sound transmissive projection screen whose
image | video projection surface is comprised with the sound transmissive material in any one of
the said invention (1)-(4).
[0024]
The present invention (13) is a speaker having a speaker box and a woofer unit, wherein the
sound transmitting material according to any one of the above-mentioned inventions (1) to (4),
and a porous member disposed behind the sound transmitting material. A sound absorbing
structure made of a high quality sound absorbing material, and a sound absorbing structure
having an air layer disposed behind the sound absorbing material in the speaker box, and the
sound absorbing structure is provided on an inner wall of the speaker box It is a speaker.
[0025]
The present invention (14) is the speaker according to the invention (13), wherein the speaker is
a closed type.
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[0026]
According to the sound transmitting material of the present invention, the Taber stiffness is 5
mN · m or more, the bending resistance is 100 mN or more, the porosity is 50% or more, and the
thickness is 3 mm or less. A material with good sound transmission is obtained.
[0027]
Fig.1 (a) is sectional drawing of the sound control surface structure of this invention, FIG.1 (b) is
an exploded view of the sound control surface structure of this invention.
FIG. 2 is a schematic configuration view showing a case where the sound control surface
structure is used for building interiors.
FIG. 3 is a schematic block diagram of the reverberation variable wall 600 whose appearance
does not change.
FIG. 4 is a schematic block diagram of the reverberation adjustment wall 700 whose appearance
does not change.
FIG. 5 is a schematic configuration view of a spherical windshield (for a sound field microphone)
using an acoustically transparent material.
FIG. 6 shows a schematic configuration diagram of a microphone device for measuring surface
sound pressure with a cylindrical windshield.
FIG. 7 shows an outline of an insertion loss Δ (dB) measurement method for evaluating the
sound transmission in the measurement method 1.
FIG. 8 is an explanatory drawing of the measurement method 2.
FIG. 9 shows the result of a comparative test of the sound absorption coefficient α 0 of the back
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sound absorbing material (GW) with and without the sound transmitting material (TTP).
FIG. 10 shows the results of measuring the sound transmission of each sample in measurement
method 2.
FIG. 11 (A) shows an outline of a system on which the wind noise reduction test was performed,
and FIG. 11 (B) is a graph showing the results of the wind noise reduction test.
FIG. 12 is a supplementary explanatory view on the amount of acoustic energy that escapes
behind.
[0028]
The present invention is an acoustically transparent material in which fibers are entangled with
one another.
That is, the sound transmitting material of the present invention has a Taber stiffness of 5 mN ·
m or more and a bending resistance of 100 mN or more.
By being the said range, a sound transmissive material has self-supporting property.
In addition, as described above, by setting the porosity to 50% or more and the thickness to 3
mm or less in the sound transmitting material having self-supporting property, a material having
high sound transmitting property can be obtained.
[0029]
The Taber stiffness of the sound transmitting material of the present invention is 5 mN · m or
more, preferably 8 mN · m or more, and more preferably 10 mN · m or more.
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The upper limit value of Taber stiffness is not particularly limited, and is, for example, 100 mN ·
m.
By having the range of Taber stiffness, a material having self-sustainability can be obtained.
Taber stiffness is measured in accordance with JIS-P8125. The Taber stiffness value can be
adjusted based on the knowledge of those skilled in the art according to the hardness of the fiber
used, the density of the sound transmitting material, and the pressure in compression molding.
[0030]
The bending resistance of the sound transmitting material of the present invention is 100 mN or
more, preferably 150 mN or more, and more preferably 200 mN or more. The upper limit of
bending resistance is not particularly limited, and is, for example, 2000 mN. By having the range
of Taber stiffness, a material having self-sustainability can be obtained. The bending resistance is
a value obtained by measuring according to the Taber stiffness test of JIS-P8125. In addition, the
value of bending resistance can be adjusted with the hardness of the fiber to be used, the density
of an acoustically transparent material, and the pressure in compression molding based on the
knowledge of those skilled in the art.
[0031]
The porosity of the sound transmitting material of the present invention is 50% or more,
preferably 60 to 90%, and more preferably 70 to 90%. The upper limit of the porosity is not
particularly limited, and is, for example, 95%. In the material in which the fibers are entangled, by
selecting the material in which the porosity falls within the range, it is possible to achieve the
effect that the sound transmission is secured while having the self-sustaining property. Moreover,
since the porosity is not too high in a preferable range, more preferable range, even when used
as a wall material, it is possible to prevent the other side from being transparent through the
sound transmitting material.
[0032]
In consideration of the angular dependence of the sound transmission, the porosity of the sound
transmitting material is particularly preferably 80 to 90%. With such a range, it is possible to
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exhibit high acoustic transparency that is substantially independent of the incident angle of
sound on the material.
[0033]
The void ratio is calculated from the volume and weight of the sound transmitting material and
the specific gravity of the fiber material at the ratio of the space where no fiber exists to the
volume of the sound transmitting material. Porosity (%) = (1-weight of sound transmitting
material / (volume of sound transmitting material x specific gravity of fiber)) x 100 Note that the
value of porosity is the fiber used based on the knowledge of those skilled in the art The
thickness, the amount, the density of the material in which the fibers are entangled, and the
pressure in compression molding can be adjusted.
[0034]
Here, the thickness of the sound transmitting material is 3 mm or less, more preferably 50 μm
to 2000 μm, still more preferably 100 μm to 1500 μm, and particularly preferably 500 μm to
1000 μm. In the material having the above-described porosity, by setting the thickness in the
range, a material having high acoustic transparency can be obtained.
[0035]
The sound transmitting material according to the present invention is formed by interlacing
fibers. The fibers used for the sound transmitting material include metal fibers or fluorine fibers.
Among these, by using metal fibers, it becomes easy to secure the self-supporting property.
[0036]
The metal fiber is not particularly limited. One or a combination of two or more selected from
fibers made of metal materials such as stainless steel, aluminum, brass, copper, titanium, nickel,
gold, platinum, lead and the like can be mentioned.
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[0037]
The fluorine fiber is preferably selected from thermoplastic fluorine resins, for example,
polytetrafluoroethylene (PTFE), tetrafluoroethylene (TFE), perfluoroether (PFE),
tetrafluoroethylene and hexafluoropropylene. (FEP), copolymers of tetrafluoroethylene and
ethylene or propylene (ETFE), vinylidene fluoride resin (PVDF), polychlorotrifluoroethylene resin
(PCTFE), vinyl fluoride resin (PVF) Be
[0038]
Further, the diameter of the fiber used for the sound transmitting material of the present
invention is not particularly limited, but for example, 0.1 to 100 μm is suitable, 0.5 to 50 μm is
more preferable, and 1 to 40 μm is further preferable. It is suitable.
By setting the fiber diameter within such a range, it is possible to enhance the strength of the
fiber and to obtain appropriate sound transmission.
[0039]
The said sound-permeable material is obtained by the method of compression-molding a fiber,
and the papermaking of the raw material comprised including a fiber by the wet paper-making
method.
[0040]
In the case of producing the sound transmitting material of the present invention using metal
fibers or fluorine fibers by compression molding, first, the fibers are put together, and the web is
formed by preliminary compression.
Alternatively, a binder may be impregnated between the fibers to provide bonding between the
fibers. Such a binder is not particularly limited, but, for example, in addition to organic binders
such as acrylic adhesives, epoxy adhesives and urethane adhesives, inorganic adhesives such as
colloidal silica, water glass and sodium silicate It can be used. Note that, instead of impregnating
the binder, the surface of the fiber may be coated with a heat adhesive resin in advance, and the
metal fiber assembly may be laminated and then heated and adhered. The amount of the binder
to be impregnated is preferably 5 to 130 g, more preferably 20 to 70 g, with respect to the
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surface weight of 1000 g / m 2 of the sheet.
[0041]
The assembly of metal fibers is pressurized under heat to form a sheet. The heating conditions
are set in consideration of the drying temperature and the curing temperature of the binder and
heat adhesive resin to be used, but the heating temperature is usually about 50 to 1000 ° C.
The applied pressure is adjusted in consideration of the elasticity of the fiber, the thickness of the
sound transmitting material, and the light transmittance of the sound transmitting material. In
addition, when impregnating a binder by a spray method, it is preferable to shape | mold a metal
fiber layer to predetermined | prescribed thickness by press process etc. before spray-processing.
[0042]
The sound transmitting material in the case of using metal fibers can be formed into a sheet by a
wet sheet-forming method using a slurry containing metal fibers. When a slurry containing metal
fibers is produced, the dispersibility of the metal fibers in water may be deteriorated, so a
polymer aqueous solution such as polyvinyl pyrrolidone, polyvinyl alcohol, carboxymethyl
cellulose (CMC) having a thickening action is used. A small amount may be added. As the paper
making method, for example, various methods such as fourdrinier paper making, circular wire
making, inclined wire paper making, etc. can be adopted as needed.
[0043]
When using a wet sheet-making method, it is preferable to manufacture through a fiber
entanglement treatment step in which the metal fibers forming the sheet containing moisture on
the net are entangled with each other. Here, as the fiber entanglement treatment step, for
example, it is preferable to adopt a fiber entanglement treatment step in which a high-pressure
jet water stream is jetted on the metal fiber sheet surface after paper making. Specifically, a
direction orthogonal to the sheet flow direction By arranging a plurality of nozzles at the same
time and simultaneously injecting a high pressure jet stream from the plurality of nozzles, it is
possible to entangle metal fibers across the entire sheet.
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[0044]
In addition, the method for producing a metal fiber material may include a sintering step of
sintering the obtained metal fiber material in vacuum or in a non-oxidizing atmosphere at a
temperature equal to or lower than the melting point of metal fibers after the above-described
wet sheet-forming step. preferable. Since the metal fibers are entangled, it is possible to increase
the strength of the metal fiber material after sintering.
[0045]
In the case of using a fluorine fiber, the method of producing an acoustically transparent material
is a method of mixing a fluorine fiber and a substance having a self-adhesive function by a wet
paper making method and drying the fluorine fiber mixed paper material obtained by the
softening point of the fluorine fiber. After thermocompression bonding is performed to thermally
fuse the fibers of the fluorine fiber as described above, the substance having a self-adhesive
function is dissolved and removed with a solvent, and re-drying can be performed if necessary.
Here, as a substance having a self-adhesive function, natural pulp consisting of plant fibers such
as wood, cotton, hemp, straw and the like usually used for papermaking, polyvinyl alcohol (PVA),
polyester, aromatic polyamide, acrylic, polyolefin It is possible to use synthetic pulp and
synthetic fibers made of thermoplastic synthetic polymers of the present invention, and paperpaper strength agents made of natural polymers and synthetic polymers, etc. It is not limited to
these as long as it can be dispersed in water.
[0046]
(Physical Properties) Sound Transmissivity The sound transmissive material according to the
present invention is the difference in frequency characteristics measured according to the
following measurement method 1 (hereinafter referred to as “insertion loss”. Is preferably
within 5 dB (preferably within 2 dB) in each 1/1 octave band of center frequency 63 Hz to 8 kHz.
The sound transmitting material is preferably 6 dB or less (preferably 3 dB or less) in each 1⁄3
octave band with a center frequency of 31.5 Hz to 16 kHz. When using a continuous sine wave
sweep, it shall be based on the case where it evaluates in 1/3 octave band.
[0047]
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Various methods are assumed as an evaluation method regarding sound transparency. More
specifically, in an anechoic room or a room with high sound absorption, the microphone and the
speaker are direct sound areas to the former (the direct sound is a sound source near area
sufficiently larger than the indirect sound (reflection sound and reverberation sound)) Between
the microphone response to the speaker when the sample is placed at a right angle to the
reference line (the line connecting the microphone and the speaker) and when the sample is not
placed. ) Is evaluated as insertion loss Δ (dB). Incidentally, the signal generated from the speaker
may be any of sine wave, pink noise and tremor (FM sound), and the duration may be either
continuous or short sound. Furthermore, the filter for band-limiting is a sound source It may be a
side, a receiving side, a short tone or a continuous frequency sweep tone. At the same time, the
position of the sample may be either immediately before the speaker, immediately before the
microphone, or in the middle of both, and these are properties having substantially the same
result as long as the measurement system is regarded as a linear system. Incidentally, although
the sample is herein defined to be evaluated at a right angle to the reference line, the sample can
be placed at an angle to the reference line if necessary, and the angular dependence can also be
evaluated. In addition, when a difference arises in a result by a measuring method, in sound
transmission in a specification, the result obtained by the method of the following measuring
method 1 shall be prioritized.
[0048]
Measurement method 1: As the method of measuring insertion loss most simply, in an anechoic
chamber or a chamber of high sound absorption according to this, an axis connecting a speaker
and a microphone (hereinafter, “speaker-microphone axis”). And the angle θ = 0 ° between
the normal direction of the sound transmitting material (the state as shown in FIG. 7 is an angle
θ = zero). A continuous sine wave sweep sound (a sound of 20 dB or more in S / N ratio to
background noise) between 20 Hz and 20 kHz, and several tens of cm to several m (preferably
about 30 cm to 5 m) from this speaker When the member is installed immediately before or
between the speaker and the microphone, or between the two, after receiving sound with a
microphone installed at a distant position, or with a sound level meter, etc., and then recording
with a level recorder etc. The difference between the frequency response characteristics of is
measured, and this is taken as insertion loss Δ (dB).
[0049]
The sound transmitting material according to the present invention can be evaluated by the
insertion loss measured according to the following measurement method 2 to evaluate the
dependency of the incident angle of sound.
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[0050]
Measurement method 2: The angle θ between the speaker-microphone axis and the normal
direction of the sound transmitting material (the state as shown in FIG. 7 is an angle θ = zero.
And measure the insertion loss Δ (dB) at every arbitrary angle of θ = 0 to 90 degrees, or the
energy average value (n dB) of n insertion losses included in adjacent ± Δθ at every
representative angle θi The average insertion loss Δ (−) i (dB) can also be determined for each
angle based on the average) (FIG. 8). This makes it possible to evaluate the dependence of the
insertion loss on the angle. For example, in the case of taking an energy average value (dB
average) of i angles of 15 degrees, 45 degrees, and 75 degrees, and each of three angles adjacent
to ± 10 degrees, the following formulas (a) to (c) or (d) It can obtain | require by (f). (In the
above formulas (e) to (f), L′ 5, L5, etc. are the frequency response (dB) of the microphone when
the member is installed at θ = 5 °, and the frequency response (dB) before the installation) . 2.)
In this example, since it can be evaluated from various angles, it is suitable for evaluation of the
material according to the present invention.
[0051]
Wind noise reduction effect The windshield according to the present invention preferably has a
wind noise reduction effect of Δ20 dBA or more in a 1/1 octave band with respect to a wind
velocity of 2.7 m / s in the wind noise reduction effect evaluation method. It is. Here, in the wind
noise reduction effect evaluation test, a wind speed of 2.7 m / s (a range where generation of
wind noise is recognized or reduction of wind noise can be observed) from a blower or the like in
the anechoic chamber When the response measured with the windshield attached is S (dBA)
reduced by the noise level (dBA) relative to the microphone output response observed without
the windshield, the wind noise reduction effect ΔS (dBA) and Do.
[0052]
(Sound control surface structure used for the inner wall of a building) FIG. 1 is a schematic block
diagram of the sound control surface structure of the present invention. Fig.1 (a) is sectional
drawing of the sound control surface structure of this invention, FIG.1 (b) is an exploded view of
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the sound control surface structure of this invention. The sound control surface structure 1 of
the present invention comprises the above-mentioned sound transmitting material 2 formed into
a plate shape used as a decorative board, and a sound absorbing structure and / or a reflecting
structure disposed behind the sound transmitting material. And an acoustic adjustment
mechanism 3 having the following. By using the sound transmitting material of the present
invention as a decorative plate having a sound control surface structure, not only the
characteristics of sound transmission but also the surface itself exhibits the same texture as a
hard non-porous plate because the material itself has self-supporting properties It provides the
results of so-called "hard sound absorbing materials" and can be applied to the walls of museums
etc. to construct a quiet space. Further, if necessary, reinforcement may be performed by a
material / structure such as a honeycomb structure or a metal mesh such as expanded metal
which does not affect the sound transmission, behind the sound transmitting material.
[0053]
The sound absorbing structure in the sound adjusting mechanism 3 can be realized, for example,
by arranging a sound absorbing material. Although a well-known material can be used as a sound
absorbing material, For example, glass wool, a needle felt, a urethane foam, a sponge, a rock wool
board etc. can be used. Also, the sound absorbing structure may have a sound absorbing material
and an air layer disposed behind the sound absorbing material. By providing the air layer in this
manner, it is possible to extend the sound absorption to the low frequency range.
[0054]
The reflective structure in the sound adjustment mechanism 3 can be realized, for example, by
arranging nothing or a reflecting material. Although a well-known material can be used as a
reflector, For example, the board in which the hole is not formed, such as a plywood, a gypsum
board, a concrete board, a flexible board, is mentioned.
[0055]
These acoustic control surface structures support the structure, and thus a skeleton 4 having a
space 41 for housing the acoustic control mechanism 3 and a support 42 on which a fixing
surface 421 for fixing the sound transmitting material 2 is formed. It is preferable to further
include (Fig. 1 (b)). Such panelization makes it possible, for example, to simply retrofit it to a
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room in which a sound disorder such as a snail has occurred and solve the problem.
[0056]
When the skeleton 4 is provided, the sound adjustment surface structure 1 is mounted on the
fixation surface 421 of the skeleton 4, the sound adjustment mechanism 3 housed in the space
41 of the skeleton 4, and the support 42 of the skeleton. And an acoustically transparent
material 2. The frame 4 may be provided with a trunk 43 and a stud 44 in the middle as needed
to reinforce the whole (see FIG. 2). Also in this case, similarly to the above, an air layer may be
appropriately provided behind the sound absorbing material.
[0057]
As a function of the sound control surface structure of the present invention, sound reaches the
sound control surface structure of the present invention, transmits the sound transmitting
material, reaches the sound absorbing structure and is absorbed, or a reflective structure It
reaches and is reflected. At this time, by using the acoustically transparent material of the
present invention, it is possible to prevent the bounce of the sound on the wall surface, and it
becomes easy to reflect the acoustic characteristics of the object disposed behind the acoustically
transparent material, It can be effectively used as a sound improvement panel capable of easily
solving acoustic disturbances in a meeting room of an office building, or a sound field adjustment
panel in an audio room or an AV room of a house.
[0058]
The sound control surface structure 1 of the present invention provides, for example, a "hard
sound absorption surface" which has not been used conventionally by using it as an interior
structure of a building, and effectively absorbs a space requiring a flat hard surface. It can be
processed.
[0059]
FIG. 2 is a view showing a schematic configuration of an interior structure of a building using the
acoustic control surface structure 1 of the present invention.
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The interior structure 6 has a structure in which the sound control surface structure 1 is
arranged side by side, and if necessary, the trunk 43 and the stud 44 may be provided in the
middle to reinforce the whole, or sound absorption as described above. An air layer may be
provided behind the material to extend the sound absorption to the low frequency side.
[0060]
The interior structure 6 may, for example, constitute a wall surface, and the height of the sound
control surface structure 1 may be a length from the floor end F to the ceiling end R of the wall
surface. Even when the surface formed continuously in this way becomes large by using the
sound transmitting material of the present invention, it is easy to apply because it has selfsustaining ability, and wrinkles and / or sagging is formed even after the construction. It
becomes difficult.
[0061]
As a matter of course, the surface of the acoustic control surface structure may be continuous.
Reflective structure (see FIG. 9 (0)) having exactly the same surface using the sound transmitting
material of the present invention in the middle and having no sound absorbing material behind,
or the sound transmitting of the present invention as a surface dressing According to the
application of the room without changing the interior design at all by adjusting the total sound
absorption of the room by arranging the surface of the reflective structure with materials such as
plywood and gypsum board placed behind the insulating material, etc. Can provide optimal
reverberation characteristics.
[0062]
In addition, the sound absorbing material behind the interior structure 6 is omitted, and only the
surface material, ie, the sound transmitting material of the present invention as shown in FIG. 3,
is composed, and variable sound absorbing mechanism such as curtain or sound absorbing blind
(sound absorbing louver) is behind. The reverberation variable wall and the reverberation
variable ceiling may be configured without changing the interior design at all, and the
reverberation characteristics of the room may be freely changed. Since the room design does not
change, it does not give a sense of incongruity to the room occupant or the audience / player (in
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the case of a hall, etc.), so it is suitable as a variable means of sound effects.
[0063]
More specifically, FIG. 3 shows a reverberation variable wall 600 as an application example of an
acoustic control surface structure using the acoustically transparent material of the present
invention as a surface material. FIG. 3 shows an example of a reverberation variable wall
intended for use in an AV room of a hall or a house, or a recording studio or a music rehearsal
room. Since the sound transmitting member of the present invention is used as the surface
member, the sound absorbing power of the wall surface and the ceiling surface is changed by
operating the rear variable sound adjusting mechanism without changing the design of the
surface, and the reverberation time characteristics of the room It can be changed. According to
the structure, there is an effect that the design of the surface does not change even if the acoustic
condition changes.
[0064]
More specifically, FIG. 3 shows a schematic block diagram of the reverberation-variable wall 600,
which is a cross-sectional view as viewed from above the room. The reverberation variable wall
600 has the sound transmitting material 2 provided on the entire wall surface, and a variable
sound adjusting mechanism 610 disposed behind the sound transmitting material.
[0065]
The variable sound adjusting mechanism 610 includes, for example, a sound absorbing curtain
613 attached to a curtain rail provided on a ceiling of a space behind the sound transmitting
material 2, and a curtain box 615 for storing the curtain. And. The curtain 613 may have an
opening and closing mechanism that can be opened and closed electrically.
[0066]
The above-described variable acoustic adjustment mechanism 610 can change the acoustic
characteristics of the wall by opening and closing a curtain 613 disposed behind the acoustically
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transparent material. That is, the appearance of the wall surface does not change due to the
presence of the sound transmitting material, but the area occupied by the sound absorbing
material changes when the curtain is opened and closed. Changes. That is, conventionally, in
order to change the acoustic characteristics, it is necessary to install a sound absorbing material
and a reflecting material, and the appearance largely changes, but the acoustic characteristics
can be changed without changing the appearance. The reverberation-variable wall 600 exerts a
high effect particularly in a space restricted by the design of the appearance such as a concert
hall or a movie theater.
[0067]
A reverberation control wall is shown as an application example of the sound control surface
structure using the sound transmitting material of the present invention as a surface material.
FIG. 4 is a schematic block diagram of a reverberation control wall 700 according to the present
invention. According to the configuration, it is possible to provide from the complete reflection
surface to the complete sound absorption surface while unifying the design of the surface.
[0068]
The reverberation control wall 700 includes an acoustically transparent material 2 disposed to
form a space in front of the wall, and a sound absorbing structure and / or a reflective structure
disposed in the space formed behind the acoustically transparent material. And. For example, a
sound absorbing surface can be formed by arranging a sound absorbing structure consisting of a
sound absorbing material 701 and an air layer 702 behind the sound transmitting material 2. In
addition, by arranging a reflective structure made of plywood 704 behind the acoustically
transparent material 2, a strong reflective surface can be formed. Alternatively, by disposing a
space A (the back material is omitted) as a reflective structure behind the sound transmitting
material 2, a weak reflection surface can be formed. By selecting the material behind the sound
transmitting material in this manner, flexible sound absorption characteristics can be realized
without considering the design. Although the air layer may or may not be present behind the
sound absorbing surface, the sound absorbing property of the sound absorbing surface can be
further extended to a bass range by providing the air layer.
[0069]
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(Winding shield for microphones) The sound transmitting material of the present invention, due
to its special structure, effectively blocks the wind corresponding to the DC component of the
electric signal, and the sound signal corresponding to the AC signal follows the purpose and has
no loss Since there is a function like a high pass filter to pass through, it is possible to effectively
configure a windscreen for the microphone. The structure of the windshield for the microphone
is not particularly limited as long as it shields the wind to the microphone. The sound
transmitting material of the present invention can achieve both self-sustaining ability and sound
transmitting property because the Taber stiffness, bending resistance, porosity, and thickness are
within the predetermined ranges, but this effectively reduces wind noise. be able to. Furthermore,
because the material is self-supporting, the present invention is applied to surfaces in the form of
spheres, rectangular parallelepipeds, cones, spheres, streamlines, etc., instead of the conventional
(filled with sponge or urethane) windshield. By arranging the sound transmitting material of the
above, it is possible to constitute a windshield having a hollow structure.
[0070]
The schematic block diagram of the windshield 200 of a hollow structure is shown in FIG. The
hollow windshield 200 has a screen portion 210 made of the sound-transmissive material
according to the present invention, and a waterproof and protective cap portion 220. Thus, the
screen unit 210 and the waterproof and protective cap unit 220 are combined to constitute the
windshield 200 (FIG. 5 (b)). In this configuration, the microphone is inserted into the waterproof
protective cap 220 and used.
[0071]
The waterproof and protective cap part 220 is made of a tip cap part 221 covering the sound
collecting part of the microphone made of the sound transmitting material according to the
present invention, and a hard cylindrical material such as a metal cylinder, And a torso cap 222
in close contact with the body of the microphone. In addition, a circular ridge 223 may be
provided around the body cap 222 to determine the position of the screen 210.
[0072]
The microphone device 250 using the windshield has a cylindrical body portion 2511, and a
microphone 251 having a sound collecting portion 2512 formed at the tip of the body portion, a
waterproof protective cap portion 220 covering the microphone, and A hollow screen unit 210
covering at least the sound collecting unit 2512, the screen unit 210, an airtight rubber packing
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253 for providing airtightness inside the screen, the screen unit 210, and a waterproof cap 220
And a metal plate 254 fixing the rubber packing via the rubber packing (FIG. 5 (a)).
[0073]
Further, when the sound transmitting material according to the present invention is used, since a
hollow windshield having self-supporting property as described above can be configured, it is
used as a windshield of a microphone for measuring surface sound pressure, among others. Is
preferred.
By using the acoustically transparent material of the present invention, it is possible to effectively
reduce or block the penetration of the wind without allowing the windproof layer on the surface
to flow or resonate even under strong wind with a large wind speed, so in particular It is most
suitable to construct a low-range windshield or a windshield for use under strong winds.
[0074]
(Cylindrical windshield attached surface sound pressure measuring microphone device) FIG. 6 is
a schematic configuration view of a cylindrical windshield attached surface sound pressure
measuring microphone device 300 according to the present invention. A microphone device 300
for surface sound pressure measurement according to the present invention includes a
windshield 320 having a frame 321 and an acoustically transparent material 322 formed on the
upper surface of the frame, and a microphone 330 provided inside the windshield. And.
Moreover, in order to make a wind flow smoothly, the streamline edge part 323 may be provided
in the outer edge of the frame 321. As shown in FIG. Here, the shape of the frame body 321 is
not particularly limited, and examples thereof include a cylindrical shape and the like. Also, the
height h of the frame body 321 is not particularly limited, but researches up to now (Fukushi
Kawakami, Susumu Inamoto, Shinichi Terashima, Yasuo Inoue, Takayuki Sano "Development of
waterproof type windshield for low frequency sound measurement" Japan Acoustics Proceedings
of the Conference Presentations, 2011.03, p. 36, (1-12-23) From the circle (in the case of a
spherical body) and the diameter d of the cylinder there is an optimum balance and in the case of
height h = 10 mm It is known that around 70 mm is optimal. When it is desired to extend the
windshield effect to the lower region, the effects of d and h are extended by one octave (the
lower region) while maintaining this basic balance (height h: diameter d = 1: 7) unless there is
any other reason. It is preferable to increase in a doubled manner.
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[0075]
In a general application, the height h of the tube is preferably in the range of 1 mm to several 10
mm, more preferably in the range of 1 mm to 50 mm, and still more preferably in the range of
10 mm to 30 mm. When the height h is less than 1 mm, the wind noise preventing effect can not
be sufficiently obtained, which is not preferable. Also, if the height h is more than several tens
cm, new wind noise is generated due to air turbulence around the windshield, or the path
difference (so there is or does not have a barrier effect) in the so-called barrier effect
(soundproofing effect) This is not preferable because a difference in the distance from the sound
source to the sound receiving point in the case occurs, the insertion loss increases, or the sound
source position changes, that is, the incident angle changes and directivity occurs as a result. For
this reason, it is preferable that the shape of the peripheral part be a streamlined cross section as
shown by the streamline edge 323 in FIG. 6 by a filling type inclined material such as clay having
a right triangle or quarter circle cross section to caulking treatment. . If this measure is taken, in
particular, by setting the height of the frame to about 10 mm or more, an appropriate space is
formed between the microphone and the windshield, and the wind noise is significantly reduced.
That has been confirmed. Moreover, the said height can be adjusted by superimposing two or
more frame bodies 321 which concern on this invention (Fig.6 (a)-(c)).
[0076]
The shape of the frame is preferably cylindrical, and the diameter d of the cylinder is not
particularly limited. However, as described above, while maintaining the substantially similar
form according to the height h, the application (wind noise reduction in low region It is
preferable to change according to the limit). Generally, 5 mm or more is preferable, 30 mm or
more is more preferable, and 70 mm or more is more preferable, but it is preferable to increase
the height h according to the expansion of the diameter. The upper limit of the cylinder diameter
is not particularly limited, and is, for example, about 200 mm.
[0077]
The surface microphone device 300 according to the present invention can be attached to the
surface B of a vehicle or body such as an automobile or airplane or the like, and can measure
noise during movement, and can also be installed on the surface of a duct pipe wall to cut wind
noise. Since the duct propagation noise can be picked up without being affected by the noise,
effective control and large noise reduction effects can be provided when used for ANC (active
noise control) or the like.
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[0078]
The sound-transmissive material according to the present invention can be used as a protective
grill placed in front of a microphone or a speaker.
Moreover, when arrange | positioning to a front at a speaker, you may use not only a speaker but
a hole, such as a buffless port currently formed in the front baffle, and a decorative board which
hides the knob of a variable attenuator.
[0079]
In addition, the sound transmitting material according to the present invention can be used as a
screen for a movie by utilizing the sound transmitting property and the self-supporting property.
In this case, it is preferable to form a front projection type projection projection plane by the
sound transmitting material according to the present invention, and to use a speaker disposed
behind the sound transmitting material. In this manner, even if the speaker is disposed on the
back of the screen, the sound transmitting material according to the present invention is not used
for sound insulation and the sound is transmitted, thereby enhancing the localization of the
sound.
[0080]
The sound transmitting material according to the present invention can be used to construct a
sound absorbing structure in the low frequency range. That is, the sound absorbing structure has
the sound transmitting material of the present invention, a sound absorbing material made of a
porous sound absorbing material disposed behind the sound transmitting material, and an air
layer disposed behind the sound absorbing material. . Although it was difficult to absorb the low
frequency range with the conventional glass wool alone, by having such a structure, it is possible
to further absorb the low frequency range. Examples of porous sound absorbing materials
include glass wool and urethane foam.
[0081]
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In a speaker having a closed type or a speaker box having a form according to this, a hollow
structure made of the sound transmitting material of the present invention, instead of the sound
absorbing material in the box that conventionally contributes only to the sound absorption of
middle and high frequency range such as glass wool Alternatively, by adopting a structure in
which the inside is filled with a porous sound absorbing material such as glass wool, it has a
large sound absorbing power mainly in the low frequency range, and improves the quality (sound
quality) and volume (sound volume) of the sound emitted from the front. Can be Here, the lowpitched range refers to the sound emitted from the front of the speaker unit (for example, the
woofer unit) (here, assumed to be a normal phase sound) and the sound emitted from the back of
the speaker unit in the sound range of the sound emitted at the speaker. The term (here, assumed
to be a reverse phase sound) means a sound range where cancellation by interference is a
problem, and more specifically, means a sound range of, for example, 500 Hz or less. As
described above, in the low frequency range, it is said that the reverse phase sound emitted from
the rear of the speaker is emitted to the front through an element such as the cone of the speaker
unit in the closed speaker box by the reflection and wrap around of the sound. ing. In this case,
the normal phase sound emitted from the front of the speaker unit and the reverse phase sound
intersect with each other to cancel out the sound. By arranging the sound absorbing structure
according to the present invention in the speaker box, the reverse phase sound is absorbed, so
that cancellation by interference with normal phase sound can be prevented, and the volume
feeling and quality of the sound can be enhanced. Become.
[0082]
More specifically, in a speaker having a speaker box and a woofer unit, the sound transmitting
material of the present invention, a sound absorbing material comprising a porous sound
absorbing material disposed behind the sound transmitting material, and the sound absorption A
sound absorbing structure having an air layer disposed behind the material is provided in the
speaker box. The said sound absorption structure is provided in the inner wall of the said speaker
box, and is laminated | stacked in order of an air layer, a sound absorbing material, and a soundpermeable material from the inner wall of a speaker.
[0083]
In addition, the sound transmitting material according to the present invention can be used in
various fields by utilizing its sound transmitting property.
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[0084]
Example 1 Using a 30 .mu.m diameter fiber of stainless steel AISI 316L, it was laminated so as to
be uniform to form a cotton-like web.
The web was weighed so as to give a basis weight of 950 g / m 2 and compressed between the
flat plates to a thickness of 800 μm. The compacted plate was placed in a sintering furnace,
heated to 1100 ° C. in a vacuum atmosphere, and sintered to obtain a sample.
[0085]
Example 2 A web having a diameter of 6.5 μm and a diameter of 12 μm of stainless steel AISI
316L was prepared in the same manner as in Example 1. The web is brought to the front and
back in a weight ratio of 7: 3. The front and back web was weighed to give a basis weight of 850
g / m 2 and compressed between the flat plates to a thickness of 400 μm. A sample was
prepared in the same process as in Example 1 except for these conditions.
[0086]
Example 3 A web was made in the same manner as Example 1, using copper fibers with a wire
diameter of 30 μm. This web was weighed so that the basis weight became 1100 g / m <2>, and
compressed between the flat plates so that the thickness became 800 μm. The compacted plate
was placed in a sintering furnace, heated to 900 ° C. in a vacuum atmosphere, and sintered to
obtain a sample.
[0087]
Example 4 A web was made in the same manner as in Example 1 using aluminum fibers with a
wire diameter of 30 μm. The web was weighed so as to give a basis weight of 800 g / m 2 and
compressed between the flat plates to a thickness of 1000 μm. The compacted plate was placed
in a sintering furnace, heated to 800 ° C. in a hydrogen atmosphere, and sintered to obtain a
sample.
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[0088]
Comparative Example 1 Using aluminum as a raw material, a fiber having a wire diameter of 100
μm is formed by melt spinning method, and in the case of this fiber, the cotton-like one has a
basis weight of 1650 g / m 2. The sample was weighed to obtain a thickness of 5000 μm and
compressed between the rolls.
[0089]
Comparative Example 2 A web was prepared in the same manner as in Example 1 using
aluminum fibers with a diameter of 100 μm.
The web was weighed so that the basis weight was 1500 g / m 2 and compressed between the
flat plates so that the thickness was 1000 μm. The compacted plate was placed in a sintering
furnace, heated to 900 ° C. in a vacuum atmosphere, and sintered to obtain a sample.
[0090]
Comparative Example 3 A fluorine fiber sheet “Tomy Fileck F” R-250 (manufactured by ShinShinagawa Paper Mill) was used as a sample.
[0091]
Comparative Example 4 A stainless steel fiber sheet "Tomy Fileck SS" SS8-50M (manufactured by
Shinshogawa Paper Mill) was used as a sample.
[0092]
[0093]
(Self-supporting) The end of a 5 cm square sample was held up and the opposite end was lifted,
and when it was not bent, it was regarded as having "self-supporting", and when it was bent, it
was evaluated as "free".
[0094]
(Taber stiffness / bending resistance) Measured according to Taber stiffness test (JIS-P8125).
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[0095]
(Thickness) Measured by a micrometer.
[0096]
(Void ratio) The void ratio was calculated from the following equation from the volume calculated
from the outer dimension of the sample, the mass of the entire sample, and the specific gravity of
the fiber.
Porosity (%) = (1-weight of sound transmitting material / (volume of sound transmitting material
x specific gravity of fiber)) x 100
[0097]
(Acoustic Transmissivity) Measurement Method 1 The acoustic transparency was evaluated
based on the measurement method 1 described in the present specification.
There are various transmission frequency characteristics such as continuous sine wave sweep,
FM short sound, steady state pink noise, and FM vibration sound, but here, as shown in FIG. 7, a
speaker a having an effective diameter of 10 cm is used. A continuous sine wave sweep sound is
emitted from the attached sounding device of about 2250 cm <3>, and the sound transmitting
material b of each example and each comparative example is installed on the front surface, and
the position about 1500 mm from the front surface of the speaker a The effective value of the
sound pressure response measured by the microphone c installed in the above was recorded as a
transmission frequency characteristic on a level recorder or the like.
In that state, a change in the presence or absence of the sound transmitting material b was
measured and confirmed as an insertion loss Δ (dB).
As a sound source emitted from the speaker a, a continuous sine wave sweep without frequency
modulation was used as a signal from 20 Hz to 20 kHz.
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The sound used here is 20 dB or more in S / N ratio to background noise.
The insertion loss was determined by the following equation. Insertion loss Δ (dB) = frequency
response of microphone without sample (dB)-frequency response with sample placed (dB)
[0098]
Here, the sound transmission is performed when the insertion loss Δ (dB) is within 2 dB in each
1/1 octave band of center frequency 63 Hz to 8 kHz, or each 1/3 octave band of center
frequency 31.5 Hz to 16 kHz In the case of 3 dB or less, "good", respectively within 5 dB or 6 dB,
"slightly inferior", over 5 dB and 6 dB, respectively, "poor". Moreover, since continuous sine wave
sweep was used, it evaluated by the said 1/1 and 1/3 octave band.
[0099]
Measurement method 2 The above measurement method is used to evaluate the sound
transmission at angles θ = 0 ° and 15 ° between the speaker-microphone axis and the normal
direction of the sound transmission material, except that the FM short tone is used as the angle
and the sound source Under the same conditions as 1, the following sound transmitting materials
P to R were used. The results are shown in FIG. The details of the sound transmitting materials P
to R used here are as follows.
[0100]
P: The sound transmitting material of Example 1 was used. Q: A sound transmitting material
prepared by the same method as in Example 1 except that the porosity was 74% and the
thickness was 1.10 mm was used. S: The sound transmitting material of Example 2 was used. R: A
sound transmitting material prepared by the same method as in Example 1 except that the
porosity was 65% and the thickness was 1.03 mm was used.
[0101]
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In addition to the sound transmitting material, a material in which a metal mesh is attached and
reinforced is used for the samples described as Q and R described above.
[0102]
As a result of the sound transmission evaluation by the measurement method 2, it was found that
the sample P exhibits high sound transmission even when θ = 15 °.
That is, it was found that the material of Example 1 hardly shows the dependency of the incident
angle of sound on the sound transmission.
[0103]
(Implementation test of sound absorbing structure: Comparison of sound absorption coefficient
α 0 of the back sound absorbing material (GW) with and without sound transmitting material
(TTP)) The sample is a sound transmitting material of about 1 mm thickness (Example 4) and
glass wool ( The sound absorption test was performed using GW). The results are shown in FIG.
Here, the horizontal axis is the frequency (Hz), and the vertical axis is the normal normal
incidence sound absorption coefficient α 0. [A] indicates the measured value of α 0 of 30 mm
thick glass wool (GW) alone as a sound transmitting material (TTP) without (1) and with (2). [B]
represents the measured value of α 0 of 25 mm-thick glass wool (GW) alone, without TTP (1 ')
and with (2'). Here, in the present structure, an air layer of 5 mm was formed between TTP and
GW. According to these results, in both (2) and (2 ') in which the sound transmitting material
(TTP) of the present invention is disposed on the surface, values equal to or greater than (1) and
(1') of GW alone are obtained. It shows that it has all sound transmission. Incidentally, (0) is 0.2
or less at α 0 of TTP alone, and can be used as a variable reflection site as a reflective site.
[0104]
(Wind Noise Reduction Test) A wind noise reduction test was conducted on the system shown in
FIG. 11 (A). In addition, the wind speed was 2.7 m / s here. Here, in the wind noise reduction
effect evaluation test, the wind is sent from the fan (FAN) at a position away from the wall to an
extent that the wind bounce back in the room can be ignored, and the microphone output
response observed without the wind shield is The degree of reduction S (dB) of the response
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measured with the windshield made of the acoustically transparent material attached is
determined for each 1/1 octave band, and this is shown as the wind noise reduction effect ΔS
(dBA) did. The results are shown in FIG. Moreover, the wind noise reduction test was similarly
done by the system | strain shown to (b1) also in the sample of Examples 1-4 and Comparative
Examples 1-4. In the evaluation in Table 1, “excellent” is Δ30 dBA or more, “good” is Δ20
dBA or more, and “poor” is less than Δ20 dBA.
[0105]
According to the present invention, a material having high sound permeability can be obtained
while having self-supporting property, and therefore, it can be used as a surface member of a
sound absorbing wall structure or the like. As an example of industrial applicability, a windshield
for a microphone, a protective grill, an acoustically transmissive projection screen and a speaker
are shown.
[0106]
1: sound control surface structure 2: sound transmitting material 3: sound control mechanism 4:
frame 41: space 42: support 421: fixed surface 6: interior structure 300: microphone device 600
for measuring surface sound pressure 600: reverberation variable wall 700: Reverberation wall
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