JP2011039357A - Sound absorbing body and sound absorbing structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sound absorbing body having excellent sound absorbing performance in a lower frequency region. <P>SOLUTION: In the sound absorbing body 1 attached on a wall face 4 from which a sound absorbing effect is to be obtained, first and second film vibration type sound absorbing materials 11 and 21 are arranged approximately parallel to each other by pinching a closed space 13, and a second spacer 22 is provided for forming a second closed space 23 between the second film vibration type sound absorbing material 21 which is the closest side to the wall face 4 when attached on the wall face 4, and the wall face 4. A weight member 101 is provided in a center of gravity section of the second film vibration type sound absorbing material 21. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sound absorber and a sound absorbing structure using a membrane vibration type sound absorbing material.

Noise is a familiar problem with vibration, and the demand for sound absorbers is high. In addition, there are a wide range of required characteristics depending on the application and purpose, and recently, a sound absorber having high sound absorption performance in a low frequency region has been desired.
The sound absorption characteristics are represented, for example, by a graph with the frequency on the horizontal axis and the sound absorption rate on the vertical axis. In order to obtain a good sound absorption effect in the low frequency region, the frequency at which the sound absorption rate peaks (peak frequency) is low. It is preferable that the peak value of the sound absorption coefficient is high.

  As conventional sound-absorbing materials, for example, porous materials such as materials in which fibers are formed into a cotton or board shape, such as glass wool and rock wool, and materials in which a polymer material is foamed, such as polyurethane foam, are known. Yes. When sound waves are incident on these porous materials, the sound waves vibrate the air in the gaps in the materials, so some of the vibration energy is converted into heat energy and dissipated by the viscosity of the air itself and the friction with the surroundings. An effect is obtained.

  In addition, as a sound absorber capable of obtaining a good sound absorbing effect in a low frequency region of 500 Hz or less, the present inventors have previously made a membrane vibration type sound absorbing material having a specific storage elastic modulus with an opening provided in a frame. Has proposed a sound absorber having a configuration covered with (Patent Document 1).

JP 2008-96826 A

  However, the demand for the sound absorption effect in the low frequency region is high, and it is required to further reduce the peak frequency to lower the frequency region where the sound absorption effect can be obtained.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a sound absorbing body and a sound absorbing structure capable of exhibiting good sound absorbing performance in a lower frequency region.

  In order to solve the above-described problems, the sound absorber of the present invention is a sound absorber that is attached to a wall surface to obtain a sound absorption effect, and a plurality of membrane vibration type sound absorbers are arranged substantially in parallel with a closed space interposed therebetween. A plurality of membrane vibration type sound absorbing materials, wherein a spacer is provided to form a closed space between the wall surface and the membrane vibration type sound absorbing material that is closest to the wall surface when mounted on the wall surface. Of the materials, a weight member is provided at the center of gravity of at least one membrane vibration type sound absorbing material.

It is preferable that the weight member is provided in one or more of the membrane vibration type sound absorbing material that exists between the membrane vibration type sound absorbing material and the wall surface farthest from the wall surface side.
When the peak frequency of the sound absorption coefficient in the state where all of the membrane vibration type sound absorbing material existing between the wall vibration side farthest from the wall surface side and the wall surface and the weight member are removed is set as the single layer peak frequency, The single layer peak frequency is preferably 600 Hz or less.

  Further, the present invention provides a sound absorber in which a plurality of membrane vibration type sound absorbing materials are arranged substantially in parallel with a closed space between the wall surface and the membrane vibration type sound absorbing material on the wall surface on which a sound absorbing effect is to be obtained. It is attached so that a closed space is formed between them.

  ADVANTAGE OF THE INVENTION According to this invention, the sound absorber and sound absorption structure which can exhibit favorable sound absorption performance in the area | region where a frequency is lower are obtained.

An embodiment of the sound absorber of the present invention is shown, in which (a) is a plan view and (b) is a cross-sectional view taken along line BB in (a). It is sectional drawing which shows other embodiment of the sound-absorbing body of this invention. It is a perspective view which shows other embodiment of the sound-absorbing body of this invention. It is a graph which shows the sound absorption coefficient measurement result concerning an Example and a reference example. It is a graph which shows the sound absorption coefficient measurement result concerning an Example and a reference example. It is a graph which shows the sound absorption coefficient measurement result concerning an Example and a reference example. The other embodiment of the sound-absorbing body of this invention is shown, (a) is a top view, (b) is sectional drawing which follows the AA line in (a). It is a graph which shows the sound absorption coefficient measurement result concerning an Example and a reference example.

The value of the storage elastic modulus in the present invention is determined by the measurement method according to JIS K7244-4 (tensile vibration). The sample size is 40 mm in length, 10 mm in width, and 1 mm in thickness. The measurement conditions are a span distance of 20 mm and a strain amplitude of 6 μm. , 25 ° C., 20 Hz (unit: Pa). The measurement frequency of the storage elastic modulus is generally 20 Hz because it is closer to the actual sound absorption frequency within the measurable range (0.2 to 50 Hz). 20 Hz).
The storage elastic modulus is a value determined by the material. The storage elastic modulus was measured using a viscoelastic spectrometer EXSTAR6000 DMS, model name DMS6100, manufactured by SII Nano Technology.

  The sound absorption coefficient in this specification means “normal incidence sound absorption coefficient”, and is a value measured by a method according to JIS A 1405-2. The sound absorption rate is measured while changing the incident frequency, and the frequency at which the sound absorption rate shows a peak is called the peak frequency.

FIG. 1 shows an embodiment of a sound absorbing body of the present invention and a sound absorbing structure in which the sound absorbing body is mounted on a wall surface. FIG. 1 (a) shows a sound absorbing body and a wall surface to which the sound absorbing body is mounted (hereinafter referred to as mounting surface). The plan view seen from the side, (b) is a sectional view taken along line BB in (a). In the figure, reference numeral 1 denotes a sound absorbing body, 4 denotes a mounting surface (wall surface), 11 denotes a first membrane vibration type sound absorbing material (hereinafter sometimes simply referred to as a first sound absorbing material), 12 denotes a first spacer, 13. Is a first closed space, 21 is a second membrane vibration type sound absorbing material (hereinafter sometimes simply referred to as a second sound absorbing material), 22 is a second spacer, 23 is a second closed space, and 101 is It is a weight member. Hereinafter, for the front and back surfaces of the first and second sound absorbing materials 11 and 21 and the first and second spacers 12 and 22, the mounting surface 4 side is referred to as the back surface side, and the opposite surface side is referred to as the surface side. .
The sound absorber 1 of the present embodiment includes two membrane vibration type sound absorbing materials (first and second sound absorbing materials 11 and 21) disposed substantially in parallel with the first closed space 13 interposed therebetween, and the outermost film. There is a second spacer 22 that forms a closed space between the vibration type sound absorbing material (second sound absorbing material 21) and the mounting surface 4. A weight member 101 is provided integrally with the second sound absorbing material 21 on the back surface of the second sound absorbing material 21.

<Spacer>
The first and second spacers 12 and 22 have through holes 12a and 22a, respectively, and openings are formed on the front surface and the back surface, respectively. The surfaces 12b and 22b of the first and second spacers 12 and 22 are flat surfaces.
The first sound absorbing material 11 is laminated and fixed on the surface 12 b of the first spacer 12 so as to cover the through hole 12 a of the first spacer 12.
The second sound absorbing material 21 is fixed in a state sandwiched between the back surface 12c of the first spacer 12 and the front surface 22b of the second spacer 22, and the through holes 12a and the second spacers of the first spacer 12 are provided. The through holes 22a of the spacers 22 are simultaneously covered. Thereby, a space surrounded by the back surface of the first sound absorbing material 11, the surface of the second sound absorbing material 21 and the inner surface of the first spacer 12, that is, the first closed space 13 is formed.
The back surface 22 c of the second spacer 22 is bonded and fixed to the attachment surface 4. Thereby, a space surrounded by the back surface of the second sound absorbing material 21, the surface of the attachment surface 4, and the inner surface of the second spacer 22, that is, a second closed space 23 is formed.

The shape of the first spacer 12 is such that the first sound-absorbing material 11 and the second sound-absorbing material 21 fixed to the first spacer 12 are substantially parallel to each other and can oscillate in the membrane and form the first closed space 13. Any shape can be used. The first sound absorbing material 11 and the second sound absorbing material 21 are preferably parallel to each other, but if the distance between the two is parallel to each other as a set value, the difference from the set value is within ± 2 mm. In range, one may be inclined with respect to the other.
The shape of the second spacer 22 is such that the second sound absorbing material 21 fixed to the second spacer 22 can vibrate and a second closed space 23 can be formed between the second sound absorbing material 21 and the mounting surface 4. I just need it.
The material of the first and second spacers 12 and 22 may or may not have sound absorbing performance, and is not particularly limited. From the viewpoint of weight reduction, a material having a low specific gravity such as a resin is preferable.
The material, shape, or size of the first spacer 12 and the second spacer 22 may be the same or different from each other. However, the first spacer 12 and the second spacer 22 may be different from each other in the openings of the through holes 12a and 22a. The shape and size are preferably the same.
In the present embodiment, each of the first and second spacers 12 and 22 has a circular outer shape and a shape having concentric through holes 12 a and 22 a, and the first spacer 12 and the second spacer 22. The material and the sizes of the openings of the through holes 12a and 22a are the same.
In addition, the shape of the opening part of the through-holes 12a and 22a in the surface or back surface of the 1st and 2nd spacers 12 and 22 is not restricted circular but can be made into arbitrary shapes, such as a polygon.

The thicknesses t1 and t2 of the first and second spacers 12 and 22 correspond to the thicknesses of the first and second closed spaces, respectively. The thicknesses t1 and t2 are each preferably 3 mm or more, and more preferably 5 mm or more. When it is 3 mm or more, it is easy to obtain good vibrations of the first sound absorbing material 11 and the second sound absorbing material 21. Moreover, 50 mm or less is preferable and, as for the sum total (t1 + t2) of both thickness, 20 mm or less is more preferable. When it is 50 mm or less, it is easy to realize a reduction in size and weight.
When the thickness of the first spacer 12 or the second spacer 22 is not uniform in the circumferential direction of the through holes 12a and 22a, the average thickness is used as the thickness t1 or t2. The average thickness of the first spacer 12 is an average value of the distance from the first sound absorbing material 11 to the second sound absorbing material 21 in the region surrounded by the first spacer 12. The average value is obtained as an average value of distances between the two sound absorbing materials at all points by regarding the surfaces of the two sound absorbing materials as a set of points.
The average thickness of the second spacer 22 is an average value of the distance from the second sound absorbing material 21 to the mounting surface 4 in the region surrounded by the second spacer 12. The average value is obtained as an average value of the distance from the second sound absorbing material 21 to the mounting surface 4 at all points, regarding the surface of the second sound absorbing material 21 and the mounting surface 4 as a set of points.

As for the area of the opening part of the through-holes 12a and 22a in the surface side or back surface side of the 1st and 2nd spacers 12 and 22, 3800-20000 mm < ² > is preferable, More preferably, it is 5000-15800 mm < ² >.
When the opening has a circular diameter, the inner diameter D is preferably 70 to 160 mm, more preferably 80 to 142 mm. When it is 70 mm or more, the peak frequency tends to be low, and when it is 160 mm or less, it is preferable in terms of miniaturization. The smaller the number of openings, the greater the number of openings that can be provided in a certain area, and the sound absorbing performance in the certain area is improved.
In the present invention, when the opening is not circular, it is preferable that the inner diameter of a circle having the same area as the opening is in the range of D.
When the opening is a square, the length of one side is preferably 62 to 142 mm, and more preferably 71 to 126 mm.

<Membrane vibration type sound absorbing material>
The first and second sound absorbing materials 11 and 21 are made of a material that can generate a sound absorbing action by membrane vibration. Specifically, in order for the first and second sound absorbing materials 11 and 21 to generate a sound absorbing action by membrane vibration, the flow resistance in the sound absorbing material is preferably 1 × 10 ⁶ N · s / m ⁴ or more. . The value of the flow resistance in this specification is the surface and back surface of each sound absorbing material when a constant air flow is passed in the direction perpendicular to the surface of each single film of the first and second sound absorbing materials 11 and 21. Is a value obtained by dividing the pressure difference between the pressure and the pressure (the difference between the pressure on the front side and the pressure on the back side) by the velocity of the air flow. Since sound corresponds to a state where the flow velocity is very small, it is defined as a limit value when the flow velocity approaches zero. The measurement method conforms to the DC method of ISO 9053.
The materials of the first sound absorbing material 11 and the second sound absorbing material 21 may be the same as or different from each other.

The specific gravity G of each of the first and second sound absorbing materials 11 and 21 is preferably 0.86 to 1.65, and more preferably 0.9 to 1.6. When the specific gravity G is 0.86 or more, a good sound absorption effect in the low frequency region can be easily obtained. It is preferable from the point of weight reduction that it is 1.65 or less.
The specific gravity G of the first sound absorbing material 11 and the second sound absorbing material 21 may be the same or different.

In the present invention, the storage elastic moduli E1 and E2 of the first and second sound absorbing materials 11 and 21 are preferably 5 × 10 ^{7 to} 5 × 10 ⁹ Pa, and more preferably 1 × 10 ⁸ to 2 × 10 ⁹ Pa.
When the storage elastic moduli E1 and E2 are 1 × 10 ⁸ Pa or more, it is easy to obtain good vibration of the sound-absorbing material, and a good sound-absorbing effect in a low frequency region is easily obtained. When it is 2 × 10 ⁹ Pa or less, the peak frequency tends to be low.

  In the present specification, all of the membrane vibration type sound absorbing material (the first sound absorbing material 11 in the present embodiment) farthest from the attachment surface 4 side and the membrane vibration type sound absorbing material existing between the attachment surface 4 (the present embodiment). Then, the peak frequency of the sound absorption coefficient in a state where all of the second sound absorbing material 21) and the weight member provided on the sound absorbing body are removed is referred to as “single layer peak frequency”. The single layer peak frequency corresponding to the sound absorber 1 of the present embodiment is a closed layer having the same thickness as the total thickness (t1 + t2) of the closed space in the sound absorber 1 between the first sound absorber 11 and the attachment surface 4. This is the peak frequency measured in the presence of space.

The storage elastic modulus E1 of the first sound absorbing material 11 and the storage elastic modulus E2 of the second sound absorbing material 21 may be the same or different from each other. In any case, by providing the second sound absorbing material 21 between the mounting surface 4 and the first sound absorbing material 11, the peak frequency is made higher than the single layer peak frequency without changing the total thickness of the closed space. The peak frequency can be shifted to the low frequency side by providing a weight member. Accordingly, it is possible to make the total thickness of the closed space smaller than when measuring the single layer peak frequency while achieving a peak frequency equivalent to the single layer peak frequency.
In particular, E1 = E2 and t1 = t2, E1 <E2 and t1 = t2, E1 = E2 and t1 <t2, or E1> E2 is more preferable in that the peak frequency is likely to shift to the lower frequency side.

  In order to obtain a sound absorber that can realize a good sound absorbing effect in a lower frequency region, the single layer peak frequency is preferably 600 Hz or less, more preferably 500 Hz or less, and even more preferably 400 Hz or less. The value of the single layer peak frequency is the material, film thickness, and total thickness of the closed space (in this embodiment, the first sound absorbing material 11 in the present embodiment) farthest from the mounting surface 4 side. t1 + t2), the size of the through hole 12a in the first spacer 12, and the like.

Each of the first and second sound absorbing materials 11 and 21 may be made of a single material, or may be a mixture of two or more materials.
As a constituent material of the first and second sound absorbing materials 11 and 21, for example, a thermoplastic resin can be used. Specifically, EEA (ethylene ethyl acrylate), EVA (vinyl acetate copolymer), PE ( Polyethylene), CPE (chlorinated polyethylene), PVC (polyvinyl chloride), PP (polypropylene), EBR (ethylene butadiene rubber), SEBS (styrene ethylene butylene styrene block copolymer), styrene isoprene styrene block copolymer or its Hydrogenated products (hereinafter collectively referred to as SIS), SEPS (styrene ethylene propylene styrene block copolymer), PET (polyethylene terephthalate), acrylic resin, polymethylpentene, polybutene, PEEK (polyether ether ketone), cyclic olefin , Polylactic acid And one or more resins or these resins as a base resin, selected from, this inorganic filler and or mixture of organic filler appropriately added, and the like in.
Among the resins listed above, PE (particularly HDPE (high density polyethylene), LLDPE (linear low density polyethylene)), PP (polypropylene), CPE (chlorinated polyethylene), EBR, ethylene-α olefin copolymer , SIS or a mixed resin thereof is preferable.

Examples of the inorganic filler include mica, talc, calcium carbonate, magnesium hydroxide, barium sulfate and the like.
When the inorganic filler is blended, the blending amount is not particularly limited as long as the specific gravity G of the sound absorbing material and the favorable ranges of the storage elastic moduli E1 and E2 are obtained. In terms of mechanical strength, in each sound-absorbing material, the content is preferably 80% by mass or less, and more preferably 60% by mass or less.
Examples of organic fillers include 3,3 ′, 3 ″, 5,5 ′, 5 ″ -hexa-tert-butyl-a, a ′, a ″-(mesitylene-2,4,6-triyl ) Tri-p-cresol (for example, product name: ADK STAB AO-330, manufactured by ADEKA), tris (2,4 di-tert-butylphenyl) phosphite (for example, product name: Irg168, Ciba Specialty Chemicals) Product).
When the organic filler is blended, the blending amount is not particularly limited as long as the specific gravity G of the sound absorbing material and the good ranges of the storage elastic moduli E1 and E2 are obtained. From the viewpoint of mechanical strength, in each sound-absorbing material, the content is preferably 50% by mass or less, more preferably 30% by mass or less.

The film thicknesses of the first and second sound absorbing materials 11 and 21 are 0.5 to 3 mm, respectively, and preferably 0.6 to 2 mm. When the thickness is 0.5 mm or more, good primary vibration of the sound absorbing material is easily obtained. It is preferable from the point of weight reduction that it is 3 mm or less. If the film thickness is not uniform, the average value is used.
The film thicknesses of the first sound absorbing material 11 and the second sound absorbing material 21 may be the same or different from each other.

<Weight member>
The weight member 101 maintains a state in which the sound absorbing material (second sound absorbing material 21 in the present embodiment) integrated with the weight member 101 generates a sound absorbing action due to the membrane vibration, and at the center of gravity of the second sound absorbing material 21. Any material that can locally increase the mass may be used. For example, a sheet-like weight member 101 is preferably used.

The material of the weight member 101 is not particularly limited. For example, the weight member 101 may be formed using the thermoplastic resin mentioned as the material constituting the first and second sound absorbing materials 11 and 21 above, brass, copper, steel plate, galvanized steel plate, stainless steel plate. A metal material such as the above may be used. The material of the weight member 101 and the second sound absorbing material 12 provided integrally with the weight member 101 may be different from each other or the same. Further, the weight member 101 made of a composite material obtained by combining a plurality of different materials may be used.
The shape of the weight member 101 is not particularly limited, but a shape close to a cylinder (including a disk) is preferable, and a cylinder is most preferable.

If the mass of the weight member 101 is the same as the area of the surface where the weight member 101 and the second sound absorbing material 21 are in contact (the area of the weight member 101), the smaller the shift amount of the peak frequency to the lower frequency side is. There is a tendency to grow. That is, the smaller the area of the weight member 101, the larger the reduction amount of the peak frequency per unit mass. On the contrary, as the area of the weight member 101 increases, the reduction amount of the peak frequency per unit mass decreases. Therefore, in terms of efficiently reducing the peak frequency, the area of the weight member 101 is preferably 30% or less, and more preferably 20% or less when the area of the second sound absorbing material 21 is set as a reference (100%).
On the other hand, if the area of the weight member 101 is too small, the sound absorption rate may decrease. Accordingly, when the area of the second sound-absorbing material 21 is set as a reference (100%) in that a good sound absorption rate is easily obtained, the area of the weight member 101 is preferably 0.5% or more, and 1.0%. The above is more preferable.
In the present specification, the area of the second sound-absorbing material 21 serving as a reference (100%) is an area of a region where membrane vibration is possible, and is surrounded by a region surrounded by the first spacer 12 or the second spacer 22. It is the area of the smaller one of the areas. When two or more weight members 101 are provided, the total contact area between each weight member 101 and the second sound absorbing material 21 is defined as the area of the weight member 101.

As long as the weight member 101 has the same shape and size as the weight member 101, the weight of the weight member 101 tends to increase as the peak frequency shifts to the lower frequency side. On the other hand, if the mass of the weight member 101 is too large, the peak value of the sound absorption coefficient tends to be low.
Therefore, the mass of the weight member 101 is preferably 30% by mass or less, and more preferably 20% by mass or less, based on the mass of the second sound absorbing material 21 (100% by mass). The lower limit of the mass is not particularly limited, but in order to sufficiently obtain the effect of providing the weight member 101, it is preferably 2% by mass or more when the mass of the sound absorbing material is used as a reference (100%), and 4% by mass. % Or more is more preferable, and 8 mass% or more is more preferable.
In the present specification, the mass of the membrane vibration-type sound absorbing material serving as a reference (100% by mass) is the mass of a region where membrane vibration is possible, and is surrounded by the region surrounded by the first spacer 12 or the second spacer 22. Is the smaller of the two areas.
The mass of the weight member 101 is a mass including the mass of the fixing means for fixing the weight member 101 to the membrane vibration type sound absorbing material, and the mass from the second sound absorbing material 21 before the weight member 101 is attached. It corresponds to the increase.
The mass of the weight member 101 can be adjusted by the material and size of the weight member 101 and the specific gravity and thickness of the fixing member. Further, a plurality of weight members 101 may be superposed via fixing means.

The means for fixing the weight member 101 to the second sound absorbing material 21 is not particularly limited. For example, an adhesive means or an adhesive means may be used. The adhesion means refers to an apparatus that bonds and integrates a solid surface and a surface and exerts an adhesive force by itself changing phase from a liquid to a solid. On the other hand, the adhesive means is the same as the adhesive means in that the surfaces of the solid are bonded and integrated, but the adhesive means itself has adhesive strength in the solid state and changes phase from the solid. It means what is used for adhesiveness between surfaces. Further, the adhesive means can be peeled off from a hard smooth surface and is different from the adhesive means in that it has adhesive force even after peeling.
A commercially available adhesive can be used as the bonding means. One-pack type or two-pack type may be used.
A commercially available adhesive can be used as the adhesive means. A double-sided pressure-sensitive adhesive tape or the like in which a pressure-sensitive adhesive layer is provided on both surfaces of a substrate such as a nonwoven fabric in advance may be used. An agent may be used.
Further, the weight member 101 may be provided so as to locally increase the mass at the center of gravity of the second sound absorbing material 21, and the weight member 101 is fixed to a fixing means other than the adhesive means and the adhesive means, for example, heat fusion, weight in the film. Means such as sandwiching the members can be appropriately used.

The weight member 101 is provided at the center of gravity of the second sound absorbing material 21. In this specification, the center of gravity is the center of gravity in the smaller surface direction of the region surrounded by the first spacer 12 or the region surrounded by the second spacer 22, and the distance from the center of gravity. Is a region in the plane direction including a position that is within 12% of the smaller diameter (diameter D in the present embodiment) of the through hole of the first spacer 12 or the through hole of the second spacer 22. It is not necessary to consider the position of the center of gravity in the direction perpendicular to the surface of the second sound absorbing material 21 (thickness direction). The provision of the weight member 101 at the center of gravity means that the position of the center of gravity of the weight member 101 is within the center of gravity of the second sound absorbing material 21 when viewed from above in a direction perpendicular to the surface of the second sound absorbing material 21. Say something.
The weight member 101 may be provided at two or more different locations of the second sound absorbing material 21. When the plurality of weight members 101 are provided, the center of gravity position of the plurality of weight member 101 groups is provided so as to be located within the center of gravity of the second sound absorbing material 21.

When only one weight member 101 is provided, if the distance between the gravity center position of the weight member 101 and the gravity center position of the second sound absorbing material 21 is large, the peak value of the sound absorption coefficient is lowered and the average sound absorption coefficient is likely to be lowered. . Accordingly, the distance between the positions of the center of gravity is preferably 12% or less of the smaller diameter (diameter D in the present embodiment) of the through hole of the first spacer 12 or the through hole of the second spacer 22, and zero. Most preferred.
When a plurality of weight members 101 are provided, the distance between the center of gravity of the plurality of weight members 101 and the center of gravity of the second sound absorbing material 21 is 12% or less of the through hole diameter D for the same reason. Is preferred, with zero being most preferred.

  In the present embodiment, the weight member 101 is provided on the back surface of the second sound absorbing material 21, but not limited thereto, on the surface of the second sound absorbing material 21, on the back surface of the first sound absorbing material 11, Alternatively, the weight member 101 may be provided at any one of the surfaces of the first sound absorbing material 11 or at two or more locations thereof as in the present embodiment.

In the present embodiment, the peak frequency can be shifted to the low frequency side regardless of whether the first sound absorbing material 11 or the second sound absorbing material 21 is provided with a weight member.
In particular, the membrane vibration type sound absorbing material (first sound absorbing material 11 in the present embodiment) farthest from the mounting surface 4 side and the membrane vibration type sound absorbing material (first sound absorbing in the present embodiment) existing between the mounting surface 4. When a weight member is provided on the material 12), two peak frequencies are easily obtained in the low frequency band. Thereby, a good sound absorption effect can be obtained in two different 1/3 octave bands in the low frequency band. Specifically, as shown in the examples described later, for example, two 1/3 octave bands with central wavelengths of 250 Hz and 500 Hz, and two 1/3 octave bands with central wavelengths of 315 Hz and 400 Hz, 500 Hz, or 630 Hz. A good sound absorbing effect can be obtained in the belt.
The sound absorption characteristics after the weight member 101 is fixed vary depending on the material, shape, size (area), mass, fixing position to the membrane vibration type sound absorbing material, and fixing means. Therefore, by adjusting these, it is possible to realize various sound absorbers having desired sound absorption characteristics in the low frequency region.

<Sound absorber>
The sound absorber 1 fixes the weight member 101 to the second sound absorbing material 21, and the first sound absorbing material 11, the first spacer 12, the second sound absorbing material 21, and the second spacer 22 are shown in FIG. 1. Thus, it is obtained by stacking and integrating.
As a means for fixing the first and second sound absorbing materials 11 and 21 to the first and second spacers 12 and 22, an adhesive means such as an adhesive or a double-sided tape may be used. May be.

Further, another sound absorbing layer (not shown) may be laminated on the surface of the first sound absorbing material 11 (on the side opposite to the first spacer 12 side). Specifically, the other sound absorbing layer is formed of a layer having a flow resistance smaller than 1 × 10 ⁶ N · s / m ⁴ . As the other sound absorbing layer, a known sound absorbing material satisfying the above flow resistance range can be appropriately used. Specific examples include foamed resin, felt, fiber material, glass wool, rock wool, wood powder cement, and the like. Particularly preferred are foamed resin, felt, fiber material, and glass wool.
By laminating such other sound absorbing layers, the frequency range in which the sound absorbing effect can be obtained can be broadened as the sound absorber 1 as a whole.

The material of the mounting surface 4 is not particularly limited as long as the first and second sound absorbing materials 11 and 21 can undergo membrane vibration in a state where the sound absorber 1 is fixed on the mounting surface 4 via a closed space. Not. Examples of the material of the mounting surface 4 include metals, synthetic resins, ceramics, and the like.
As a means for fixing the sound absorber 1 to the mounting surface 4, an adhesive, or an adhesive means such as a double-sided adhesive tape or an adhesive can be used as appropriate.

  If the mounting surface 4 is a flat surface, the sound absorber 1 can be easily mounted. However, the present invention is not limited to this, and if the first and second sound absorbing materials 11 and 21 are capable of membrane vibration, the mounting surface 4 is a curved surface. There may be a rough surface. For example, as shown in FIG. 2, when the mounting surface 34 is a curved surface, the first and second sound absorbing materials 31 and 41 are not slackened with the sound absorber 30 fixed to the mounting surface 34. The shapes of the first and second spacers 32 and 42 are adjusted. In the figure, reference numeral 33 denotes a first closed space, 43 denotes a second closed space, and 102 denotes a weight member.

It is preferable to provide a plurality of sound absorbers 1 on the wall surface (attachment surface 4) where a sound absorbing effect is to be obtained. The plurality of sound absorbers 1 may be separate from each other. For example, as shown in FIG. 3, the spacers of adjacent sound absorbers 1 may be integrated.
In the sound absorber 50 shown in FIG. 3, the first spacer 52 and the second spacer 62 are both plate-shaped, and a plurality of through holes 52 a and 62 a are provided respectively. The first sound absorbing material 51 is laminated and fixed so as to collectively cover the plurality of through holes 52 a of the first spacer 52, and the second sound absorbing material 61 is formed of the plurality of through holes of the first spacer 52. The holes 52a and the plurality of through holes 62a of the second spacer 62 are stacked and fixed so as to cover them collectively. This figure is a perspective view of the sound absorber 50 viewed from the second spacer 62 side. Reference numeral 103 in the figure denotes a weight member. Although the arrangement of the plurality of through holes 52a and 62a is arbitrary, the efficiency of sound absorption in the sound absorber 50 increases as the distance P between adjacent through holes decreases.

In the above embodiment, the case where there are two membrane vibration type sound absorbing materials constituting the sound absorber 1 is described as an example. However, a configuration in which three or more membrane vibration type sound absorbing materials are stacked with a closed space interposed therebetween. The same effect can be obtained.
For example, when using the first to third membrane vibration type sound absorbing materials, the first membrane vibration type sound absorbing material, the first spacer, the second membrane vibration type sound absorbing material, the second spacer, and the third membrane vibration material. A mold sound absorbing material and a third spacer are laminated in order, and the third spacer is used as the attachment surface side.
The storage elastic moduli of the first, second, and third membrane vibration-type sound absorbing materials are respectively E1, E2, E3, and the thicknesses of the first, second, and third spacers (thicknesses of the respective closed spaces) are each t1. , T2, t3, E1 = E2 = E3 and t1 = t2 = t3, E1 <E2 <E3 and t1 = t2 = t3, E1 = E2 = E3 and t1 <t2 <t3, or E1>E2> E3 More preferred. Among these, it is more preferable that E1 = E2 = E3 and t1 <t2 <t3 from the viewpoint that the peak frequency is easily shifted to the lower frequency side.

Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited to these examples.
(Examples 1-7, Reference Examples 1-3, Comparative Examples 1-3)
Using the membrane vibration type sound-absorbing material shown in Table 1, a sound-absorbing body having the structure shown in Table 2 was prepared, and the sound-absorbing rate was measured by the following method to obtain the peak frequency. The results are shown in Table 2 and FIGS. 4 to 6, the horizontal axis represents frequency (unit: Hz) and the vertical axis represents sound absorption coefficient.
The following HD and A were used as the membrane vibration type sound absorbing material. Table 1 shows the specific gravity, storage elastic modulus (25 ° C., 20 Hz), film thickness, and mass (mass of a circular portion having a diameter of 90 mm). In the value of the storage elastic modulus in the table, for example, “1.6E + 09” represents 1.6 × 10 ⁹ .
The sound absorbers of Examples 1 to 7 and Reference Examples 1 to 3 are examples using two membrane vibration type sound absorbing materials as shown in FIG. 1, and Examples 1, 3, and 5 are the first sound absorbing materials. Examples in which the weight member 101 is provided on the back surface of the material 11, Examples 2, 4, 6, and 7 are examples in which the weight member 101 is provided on the back surface of the second sound absorbing material 21, and Reference Examples 1 to 3 are weights. This is an example in which no member is provided. The structure of the sound absorber in the table indicates “first sound absorbing material / first closed space thickness (mm) / second sound absorbing material / second closed space thickness (mm) / mounting surface”. The sound absorbing material + weight indicates that the weight member is integrally provided on the sound absorbing material.
The sound absorbers of Comparative Examples 1 to 3 are sound absorbers for measuring the single layer peak frequency, and the structure of the sound absorber in the table is “sound absorber / closed space thickness (mm) / mounting surface”. Is shown.

Each of the spacers used in these examples has a circular shape with an outer shape of 100 mm and has a circular through hole. The inner diameter D of the opening of the through hole is 90 mm on both the front surface and the back surface of the spacer. is there. The thickness of the closed space was changed by changing the thickness of the spacer.
As the weight member 101, a circular brass sheet having a diameter of 20 mm is used, and a double-sided adhesive tape (manufactured by Hose Care Products, product number: NoH100, tape having an adhesive layer on both sides of a nonwoven fabric) is used as the first sound absorbing material 11 or. Affixed to the center of the back surface of the second sound absorbing material 21. The mass of the weight member 101 was 1.85 g including the mass of the double-sided tape.
The mounting surface of the sound absorber is made of an aluminum plate.

Examples 1 and 2 and Reference Example 1 are examples in which E1 = E2 and t1 = t2.
Examples 3 and 4 and Reference Example 2 are examples in which E1 = E2 and t1 <t2.
Examples 5 and 6 and Reference Example 3 are examples in which E1> E2 and t1 = t2.
The seventh embodiment is an example where E1> E2 and t1> t2.
The table and each graph show the sound absorption characteristics of the sound absorbers of the examples and reference examples. The table also shows the measurement result (comparative example) of the single layer peak frequency corresponding to each example.

[Membrane vibration type sound absorbing material]
HD: HDPE, manufactured by Nippon Polyethylene Co., Ltd., product name: HY540.
A: 50% by mass of LLDPE (manufactured by Nippon Polyethylene, product name: UF240) and EBR (manufactured by Dow Chemical Japan, product name: ENR7270, specific gravity: 0.88, storage elastic modulus 2.4 × 10 ⁷ Pa) And 20% by mass of barium sulfate (manufactured by Sakai Chemical Industry Co., Ltd., product name: barium sulfate BA, specific gravity 4.50).
It was confirmed that the flow resistances of HD and A were both 1 × 10 ⁶ N · s / m ⁴ or more.

[Measurement method of sound absorption coefficient]
The “normal incidence sound absorption coefficient” was measured by a method according to JIS A 1405-2. For the measurement, a circular impedance tube (made of aluminum, thickness 15 mm) having an inner diameter of 100 mm was used.

  As shown in the graphs of FIGS. 4 to 6, the sound absorbers of Examples 1 to 7 having a configuration in which two or more sound absorbing materials are stacked with a closed space interposed therebetween and a weight member is provided on the sound absorbing material, Both have a peak frequency in a low frequency region of 350 Hz or less, and a sound absorption coefficient at the peak frequency is high.

As shown in FIG. 4 and Table 2, in the configuration of E1 = E2 and t1 = t2, the sound absorbers of Examples 1 and 2 in which the weight member is provided on the sound absorber have the peak frequency (single layer peak frequency). The peak frequency is shifted to the low frequency side as compared with the comparative example 1 shown and also with the reference example 1 in which the weight member is not provided.
Moreover, Example 2 which provided the weight member on the 2nd sound-absorbing material has another peak frequency in 570 Hz. Therefore, a sound absorbing effect can be obtained in two 1/3 octave band bands with center wavelengths of 315 Hz and 630 Hz.
The peak frequency shift amount from the single layer peak frequency to the low frequency side is larger in Example 1 in which the weight member is provided on the first sound absorbing material than in Example 2.

As shown in FIG. 5 and Table 2, in the configuration where E1 = E2 and t1 <t2, the sound absorbers of Examples 3 and 4 in which the weight member is provided on the sound absorber have the single layer peak frequency of Comparative Example 2 Compared to Reference Example 2 in which no weight member is provided, the peak frequency is shifted to the low frequency side.
Moreover, Example 4 which provided the weight member on the 2nd sound-absorbing material has another peak frequency at 489 Hz. Therefore, a sound absorbing effect can be obtained in two 1/3 octave band bands with central wavelengths of 250 Hz and 500 Hz.
There was no difference between Example 3 and Example 4 in the peak frequency shift amount from the single layer peak frequency to the low frequency side.

As shown in FIG. 6 and Table 2, in the configuration where E1> E2 and t1 = t2, the sound absorbers of Examples 5 and 6 in which the weight member is provided on the sound absorber have the single layer peak frequency of Comparative Example 1. Even compared with the reference example 3 in which the weight member is not provided, the peak frequency is shifted to the low frequency side.
Further, Example 6 in which the weight member is provided on the second sound absorbing material has another peak frequency at 522 Hz. Therefore, a sound absorbing effect can be obtained in two 1/3 octave band bands of center wavelengths 315 Hz and 500 Hz.
The peak frequency shift amount from the single layer peak frequency to the low frequency side is slightly larger in Example 5 in which the weight member is provided on the first sound absorbing material than in Example 6.

Further, in the configuration of E1> E2 and t1> t2, the sound absorber of Example 7 in which the weight member is provided on the second sound absorber has a peak frequency lower than the single layer peak frequency of Comparative Example 3. And has another peak frequency at 499 Hz. Therefore, a sound absorption effect can be obtained in the two 1/3 octave band bands of the center wavelengths of 315 Hz and 400 Hz.
Comparing Example 6 and Example 7, in Example 7, another peak frequency was obtained on the lower frequency side by increasing the thickness t1 of the first back air layer.

(Example 8, Reference Example 4)
The sound absorption characteristics on the surface where a plurality of sound absorbers are arranged side by side were examined.
7A and 7B show the sound absorber 70 of this example. FIG. 7A is a plan view seen from the mounting surface side, and FIG. 7B is a cross-sectional view taken along the line AA in FIG. In this example, the first and second spacers 72, 82 are provided with four square through holes 72a, 82a arranged in a lattice pattern. The shape and size of the through holes 72 a and 82 a are constant in the thickness direction of the first and second spacers 72 and 82. In the figure, reference numeral 71 denotes a first sound absorbing material, 81 denotes a second sound absorbing material, 73 denotes a first closed space, 83 denotes a second closed space, 74 denotes a mounting surface, and 104 denotes a weight member. Each dimension is as follows.
Length of one side of the opening: a = 107.5 mm.
The thickness of the first spacer 72: b1 = 20 mm.
The thickness of the second spacer 82: b2 = 10 mm.
HD of Table 1 was used as the first sound absorbing material 71, and A of Table 1 was used as the second sound absorbing material 81. That is, this example is an example of E1> E2 and t1> t2.
As the weight member 104, the same brass sheet as in Example 1 was used, and the same double-sided adhesive tape as in Example 1 was attached to the center of the back surface of the second sound absorbing material 81. The mass of the square part of one side of 107.5 mm of the second sound absorbing material 81 is 16.5 g.

Reference Example 4 is the same as Example 8 except that the weight member 104 is not provided.
The configuration of the sound absorber and the measurement results of the sound absorption characteristics are shown in Table 3 and FIG.
For the sound absorber of this example, the sound absorption rate was measured by the following method.
[Measurement method of sound absorption coefficient]
The “normal incidence sound absorption coefficient” was measured by a method according to JIS A 1405-2. Specifically, a square impedance tube (made of aluminum, thickness 15 mm) having an inner size of 240 mm × 240 mm was used. The sample installation surface was an aluminum plate, and the sound absorber of this example was fixed to the center of the plate with a double-sided adhesive tape, and measurement was performed.

  As shown in the results of Table 3 and FIG. 8, the sound absorber of Example 8 has a peak frequency (215 Hz) shifted to a lower frequency side than the peak frequency (271 Hz) of Reference Example 4 and is already at 324 Hz. It has one peak frequency. Therefore, a sound absorbing effect can be obtained in two 1/3 octave band bands with center wavelengths of 250 Hz and 315 Hz.

1, 30, 50, 70 ... sound absorber,
3, 34, 74 ... mounting surface (wall surface),
11, 31, 51, 71 ... the first membrane vibration type sound absorbing material,
12, 32, 52, 72 ... first spacer,
13, 33, 73 ... 1st closed space,
21, 41, 61, 81 ... second membrane vibration type sound absorbing material,
22, 42, 62, 82 ... second spacer,
23, 43, 83 ... second closed space,
101, 102, 103, 104 ... weight members.

Claims (4)

A sound absorber attached on the wall surface to obtain a sound absorbing effect,
A plurality of membrane vibration type sound absorbing materials are arranged substantially in parallel with a closed space therebetween, and a closed space is formed between the wall surface and the membrane vibration type sound absorbing material that is closest to the wall surface when mounted on the wall surface. A sound absorber, wherein a spacer is provided, and a weight member is provided at a center of gravity of at least one of the plurality of membrane vibration type sound absorbing materials.   The sound absorber according to claim 1, wherein the weight member is provided on one or more of the membrane vibration type sound absorbing materials existing between the film vibration type sound absorbing material farthest from the wall surface side and the wall surface.   When the peak frequency of the sound absorption coefficient in the state where all of the membrane vibration type sound absorbing material existing between the wall vibration side farthest from the wall surface side and the wall surface and the weight member are removed is set as the single layer peak frequency, The sound absorber according to claim 1 or 2, wherein the single layer peak frequency is 600 Hz or less.   A sound absorbing structure, wherein the sound absorbing body according to any one of claims 1 to 3 is mounted on a wall surface on which a sound absorbing effect is to be obtained.

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