JP6958830B2 - Composite sound absorbing material - Google Patents

Description

The present invention relates to a composite sound absorbing material, and more particularly to a composite sound absorbing material in which a plurality of sound absorbing layers are laminated.

Sound absorbing materials are used to improve the acoustic properties of the interior of buildings such as houses and public facilities, and the interior of vehicles such as automobiles, trains and airplanes. Further, a sound absorbing material is used to reduce noise generated from a machine tool or the like.

As a sound absorbing material, for example, Patent Document 1 below describes a structural laminated steel plate having a Helmholtz-type resonator structure in a vibration damping steel plate having a laminated structure in which a resin plate is sandwiched between a pair of steel plates. There is. Patent Document 2 describes a sound absorbing structure in which a Helmholtz sound absorbing device and a plate / membrane vibration sound absorbing structure are combined. Further, in Patent Document 3, a hole formed by at least three layers of a surface layer, a core layer, and a back layer and penetrating the bottom surface of the surface layer and the core layer, and a hole penetrating the surface surface are closed. A sound absorbing member for an interior is described in which a non-woven fabric is heat-welded in a state where the non-woven fabric is not used.

Japanese Unexamined Patent Publication No. 2011-221283 Japanese Unexamined Patent Publication No. 2010-97147 Japanese Patent No. 3103516

The conventional fibrous or porous sound absorbing material does not have a sufficient sound absorbing effect in the bass region, and in order to obtain a sufficient sound absorbing effect, the thickness of the sound absorbing material must be increased. Therefore, if it is indoors, the living space needs to be reduced, and if it is machinery, it is necessary to increase the size. Further, even in the sound absorbing materials having the Helmholtz resonator structure described in Patent Document 1 and Patent Document 2, sound of a specific frequency can be absorbed, but sound of a wide range of frequencies cannot be absorbed. rice field.

Further, the sound absorbing material described in Patent Document 3 is a combination of a non-woven fabric and a Helmholtz resonance structure, and can absorb sound having a wide range of frequencies. However, the through hole is formed by using a cutter after joining the skin material and the bottomed cylinder, and the strength of the tool for penetrating the skin material and the bottomed cylinder and the processing method are appropriately used. If it is not set, there is a problem that a through hole having a desired size is not formed and a desired sound absorbing characteristic cannot be obtained. In addition, the Helmholtz resonator has a rigidity similar to that of a honeycomb structure, which makes it difficult to bend, and it is difficult to mount the Helmholtz resonator on a flat surface other than a flat construction surface such as a wall. When the sound absorbing material was attached to the construction surface by making a notch in the resonator, the resonator did not work and the sound absorbing effect was significantly reduced.

The present invention has been made in view of such circumstances, and is a composite that can be flexibly bent and can be easily attached to the attached member without being limited by the shape of the attached member. An object of the present invention is to provide a sound absorbing material.

In order to achieve the above object, the present invention has a protrusion plate having a plurality of protrusions and each protrusion is hollow, and a shielding plate provided on the open side of the plurality of protrusions of the protrusion plate. At least one of the plate and the shielding plate is provided with a first sound absorbing layer provided with holes communicating with each other in a plurality of spaces formed by the cavities of the plurality of protrusions, and holes in the first sound absorbing layer. Provided is a composite sound absorbing material provided on a side surface and comprising a second sound absorbing layer made of a porous material or a fibrous material.

According to the present invention, a plurality of spaces are formed between a protrusion plate having a plurality of protrusions having a hollow inside of the protrusions and a shielding plate provided on the open side of the plurality of protrusions, and the space is communicated with each other. By providing the holes to be formed, a plurality of Helmholtz resonators are formed by the plurality of spaces and holes, and a first sound absorbing layer is formed. Thereby, the sound in the low frequency region can be absorbed by using the first sound absorbing layer. In addition, a second sound absorbing layer made of a porous material or a fibrous material can be used to absorb sound in a high frequency region. Therefore, it is possible to effectively absorb sound having a wide range of frequencies.

Further, since the composite sound absorbing material is composed of a laminated body in which the first sound absorbing layer and the second sound absorbing layer are laminated, the composite sound absorbing material can be flexibly bent. Therefore, for example, it can be easily installed and installed in a columnar pillar of a building or a vehicle interior composed of a curved surface in a train.

In another aspect of the invention, the holes are preferably provided in the shielding plate.

According to this aspect, the sound acting on the shielding plate side can be effectively absorbed.

In another aspect of the present invention, the first sound absorbing layer comprises the volume of the space, the perforated area of the hole, and the axial length of the hole so that the sound absorbing characteristics corresponding to the plurality of spaces are the same. Is preferably set.

According to this aspect, since the sound absorbing characteristics corresponding to the plurality of spaces of the first sound absorbing layer are set to be the same as each other, the first sound absorbing layer strongly absorbs the sound of a specific frequency. be able to. Therefore, it can be effectively used as a noise countermeasure for equipment that generates noise of a specific frequency.

In another aspect of the present invention, the first sound absorbing layer has the volume of the space, the opening area of the hole, and the hole so that the sound absorbing characteristics corresponding to the plurality of spaces are at least two types different from each other. It is preferable that the axial length is set.

According to this aspect, since the sound absorbing characteristics corresponding to the plurality of spaces of the first sound absorbing layer are set to be at least two types different from each other, the frequency of the sound absorbed by the first sound absorbing layer is set. The area of can be expanded. Therefore, sound absorption can be effectively performed for a sound including a plurality of peak frequencies.

In another aspect of the present invention, it is preferable that the holes are provided in the shielding plate and the protruding plate, respectively.

According to this aspect, by providing holes in each of the shielding plate and the protrusion plate, the space formed by the protrusions of the protrusion plate and the shielding plate is used as a Helmholtz resonator, and is a composite sound absorbing material and a construction surface. The space formed by the wall surface can also be used as a Helmholtz resonator. Therefore, it is possible to further obtain a sound absorbing effect in a low frequency region.

In another aspect of the present invention, it is preferable to have a film-like member between the first sound absorbing layer and the second sound absorbing layer.

According to this aspect, a film-like member is provided between the first sound-absorbing layer and the second sound-absorbing layer, and the first sound-absorbing layer and the second sound-absorbing layer are joined via the film-like member. Therefore, the first sound absorbing layer and the second sound absorbing layer can be adhered to a material that cannot be bonded by heat fusion. Further, by providing the film-like member, it is possible to prevent dust or moisture from entering the composite sound absorbing material through the holes, and it is possible to maintain the desired sound absorbing characteristics.

According to the present invention, it is possible to effectively absorb sound in a wide frequency range, and the composite sound absorbing material is composed of a laminated body in which a first sound absorbing layer and a second sound absorbing layer are laminated. The composite sound absorbing material can be flexibly bent, and can be easily attached to the attached member without being limited by the shape of the attached member.

It is a top view of the composite sound absorbing material of 1st Embodiment. It is sectional drawing which follows line 2-2 in FIG. It is a figure explaining the operation of a Helmholtz resonator. It is a graph which shows the relationship between the frequency and the sound absorption coefficient of each sound absorbing material. It is a graph which shows the relationship between the frequency and the sound absorption coefficient with respect to the change of the pore diameter of the 1st sound absorption layer. It is sectional drawing which shows the other structural example of a hole. It is a figure explaining the effect of this invention. It is a top view of the composite sound absorbing material of 2nd Embodiment. FIG. 5 is a cross-sectional view taken along the line 9-9 in FIG. It is a top view of the composite sound absorbing material of 3rd Embodiment. It is sectional drawing which follows the line 11-11 in FIG. It is sectional drawing of the composite sound absorbing material of 4th Embodiment.

Hereinafter, the composite sound absorbing material according to the present invention will be described with reference to the accompanying drawings.

<First Embodiment>
FIG. 1 is a plan view of the composite sound absorbing material 1 of the first embodiment. FIG. 2 is a cross-sectional view of the composite sound absorbing material 1 along line 2-2 in FIG.

The composite sound absorbing material 1 of the first embodiment is composed of a laminated body in which a first sound absorbing layer 18 and a second sound absorbing layer 14 are laminated. The first sound absorbing layer 18 is composed of a protrusion plate 10 made of resin and a shielding plate 12. The second sound absorbing layer 14 is provided on the surface of the first sound absorbing layer 18 on the side where the holes 16 are provided (the surface on the shielding plate 12 side), and is made of a porous material or a fibrous material.

The protrusion plate 10 includes a plurality of protrusions 22 having a hollow inside. As shown in FIGS. 1 and 2, the protrusion 22 is formed in a cylindrical shape formed in a circular shape in a plan view. The shape of the protrusion 22 is not particularly limited, and may be a triangular, quadrangular polygonal, or elliptical columnar structure in a plan view. It may also be spherical, and may have a shape that tapers toward the tip of the protrusion, such as a cone, a pyramid, a truncated cone, and a truncated cone.

As the resin material for forming the protrusion 10, for example, a polyolefin resin such as polypropylene or polyethylene, a polystyrene resin such as polystyrene, a polyester resin such as polyethylene terephthalate, or a polyamide resin such as nylon may be used. can.

The thickness (thickness) D ₁ of the protrusion plate 10 is preferably 350 μm or more and 1700 μm or less. The height H of the projection 22 is preferably 4mm or more 20mm or less, a diameter _{R 1} of the protrusion 22 is preferably set to 5mm or 25mm or less.

The shielding plate 12 is arranged on the open side (upper side in FIG. 2) of the protrusion 22 of the protrusion plate 10. A space 24 is formed by the protrusion 22 of the protrusion plate 10 and the shielding plate 12. As the resin material for forming the shielding plate 12, for example, a polyolefin resin such as polypropylene and polyethylene, a polystyrene resin such as polystyrene, a polyester resin such as polyethylene terephthalate, and a polyamide such as nylon are used as the resin material for forming the shielding plate 12. A system resin or the like can be used. The same resin material may be used for the protrusion plate 10 and the shielding plate 12, or different materials may be used.

The shielding plate 12 has a hole 16 that communicates the space 24 with the outside at a position corresponding to the protrusion 22 of the protrusion plate 10. That is, as shown in FIG. 1, the hole 16 is provided at a position overlapping the space 24 in a plan view. The number of holes 16 is not particularly limited, and at least one or more holes 16 may be provided at positions corresponding to one protrusion 22.

The thickness D ₂ of the shielding plate 12 is preferably 350 μm or more and 1700 μm or less. Further, the diameter R _{2 of the} hole 16 is at least smaller than the diameter of the protrusion 22, preferably 0.5 mm or more and 5.0 mm or less, more preferably 1.5 mm or more and 5.0 mm or less, and further preferably. Is 1.5 mm or more and 2.0 mm or less. By setting the diameter of the hole 16 in the above range, the processing for forming the hole 16 can be easily performed, and the rigidity of the composite sound absorbing material 1 in the thickness direction can be maintained.

The space 24 and the hole 16 allow a sound absorbing effect to be obtained using the Helmholtz resonator principle. The first sound absorbing layer 18 includes a small-diameter opening portion by the hole 16 and a space 24 as a cavity located behind the opening portion by allowing communication between the space 24 and the outside through the hole 16. Has a structure. The air existing in the opening becomes a lump, and the space 24 acts like a spring for this lump. In this way, the sound acting on the shielding plate 12 side on which the hole 16 is provided is directly guided into the space 24 and reflected on the inner wall of the space 24 to vibrate the protrusion 22 of the protrusion plate 10. As a result, the sound energy can be attenuated to obtain a sound absorbing effect. By arranging a large number of Helmholtz resonators, effective sound absorption can be performed.

The operation of the Helmholtz resonator will be described with reference to the schematic diagram shown in FIG. The Helmholtz resonator has a strong sound absorbing effect with respect to the opening direction of the opening. The Helmholtz resonator 30 has a space 32 and an opening 34 that communicates the space 32 with the outside. As shown in FIG. 3, the cross-sectional area S of the hole 34 (that is, the hole area of the hole 16), the actual length l of the hole 34 (that is, the axial length of the hole 16), and the space 32. The resonance frequency is determined from the following equation (1) by each element constituting the Helmholtz resonator such as the cavity volume V (volume of the space 24) and the sound velocity C of the acting sound, and the region near this resonance frequency. In, resonance vibration occurs, and a high sound absorption coefficient can be obtained.

Here, f is the resonance frequency (Hz), C is the speed of sound (m / s), S is the perforated cross-sectional area of the perforated portion 34 (m ² ), V is the cavity volume of the space 32 (m ³ ), and l is the cavity volume (m 3). The actual length (m) of the opening portion 34 and δ are correction values.

By using the Helmholtz resonator, the second sound absorbing layer 14 (see FIG. 2) such as urethane foam and glass wool can absorb low-frequency sound that is difficult to absorb. Further, it has a characteristic that sound of a frequency other than the resonance frequency is not absorbed. The sound absorption coefficient can be obtained by [100 − (energy of reflected sound <I _r > / energy of incident sound <I _i >) × 100] (%). The composite sound absorbing material 1 of the present embodiment is a Helmholtz resonator having characteristics that depend on the opening area of the hole 16, the axial length of the hole 16, and the volume of the space 24, and these values are appropriately set. This allows the resonance frequency of the Helmholtz resonator to match the major frequency of the noise. Therefore, it is possible to provide a sound absorbing material that matches the characteristics of the noise source.

Returning to FIG. 2, a second sound absorbing layer 14 made of a porous material or a fibrous material is provided on the surface of the first sound absorbing layer 18 on the side where the holes 16 are provided (the surface on the shielding plate 12 side). Be done. The second sound absorbing layer 14 can be joined to the shielding plate 12 by heat welding. Urethane foam or the like can be used as the second sound absorbing layer 14 made of a porous material. Further, as the second sound absorbing layer 14 made of a fibrous material, a material having a large number of gaps or open cells in the fibers such as cloth, felt, glass wool and rock wool can be used. By providing the second sound absorbing layer 14, it is possible to absorb sound in a high frequency region. Although the holes 16 are provided on the shielding plate 12 side in FIGS. 1 and 2, they may be provided on the protruding plate 10 side. In this case, the second sound absorbing layer 14 is preferably provided on the surface on the protruding plate 10 side where the holes 16 are provided. Further, the holes 16 can be provided in both the protrusion plate 10 and the shielding plate 12, and in this case, the second sound absorbing layer 14 is provided on either the protrusion plate 10 side surface or the shielding plate 12 side surface. It may be provided or both may be provided. By providing the second sound absorbing layer 14 on both the surface on the protrusion plate 10 side and the surface on the shielding plate 12 side, it is possible to absorb sound having a wide range of frequencies acting from both sides of the composite sound absorbing material 1. Further, by using different materials for the surface of the second sound absorbing layer 14 on the surface on the protruding plate 10 side and the surface on the shielding plate 12 side, different sound absorbing characteristics can be imparted on both sides of the composite sound absorbing material 1. ..

According to the present embodiment, the second sound absorbing layer 14 can absorb sound in a high frequency region. In addition, the first sound absorbing layer 18 can absorb sound in a low frequency region that cannot be absorbed by the second sound absorbing layer 14. As a result, effective sound absorption can be performed in a wide frequency range. In order to enhance the sound absorbing effect in the low frequency region of the second sound absorbing layer 14, it is necessary to increase the thickness of the second sound absorbing layer 14, that is, the volume of the second sound absorbing layer 14. According to the present embodiment, since the first sound absorbing layer 18 can absorb sound in a low frequency region, the thickness of the second sound absorbing layer 14 can be reduced, and the thickness of the composite sound absorbing material 1 as a whole can be reduced. be able to.

Such a composite sound absorbing material can be produced, for example, by the following method. First, the protrusion plate 10 and the shielding plate 12 are joined by heat welding to prepare a first sound absorbing layer 18 having a large number of spaces 24. Next, the second sound absorbing layer 14 is arranged on the surface of the first sound absorbing layer 18 on the side of the shielding plate 12 where the holes 16 are provided (that is, the surface of the shielding plate 12 opposite to the protruding plate 10), and then By pressing the heated needle-shaped tool, the holes 16 are formed in the shielding plate 12, and at the same time, the second sound absorbing layer 14 is heat-welded to the shielding plate 12 of the first sound absorbing layer 18. By pressing the heated needle-shaped tool in this way, the composite sound absorbing material 1 can be easily manufactured.

FIG. 4 shows (1) a porous material (second sound absorbing layer), (2) a fibrous material (second sound absorbing layer), (3) a resonance type sound absorbing device (first sound absorbing layer), and (4). Combination of porous material (second sound absorbing layer) and resonance type sound absorber (first sound absorbing layer), (5) fibrous material (second sound absorbing layer) and resonance type sound absorbing device (first sound absorbing layer) It is a graph which shows the relationship between the frequency and the sound absorption coefficient in 5 kinds of sound absorption materials of the combination of.

As shown in FIG. 4, when (1) a porous material and (2) a fibrous material are used, a high sound absorption coefficient is exhibited in a high frequency region. Further, when (3) a resonance type sound absorber is used, the highest sound absorption coefficient is shown in the vicinity of 1350 Hz to 1400 Hz, and a low frequency region is exhibited as compared with the case where (1) a porous material or (2) a fibrous material is used. Shows a high sound absorption coefficient. By combining the second sound absorbing layer and the first sound absorbing layer, the frequency is low, such as (4) a combination of a porous material and a resonance type sound absorber and (5) a combination of a fibrous material and a resonance type sound absorber. It can be confirmed that it has high sound absorption characteristics in a wide range from a region to a high region.

Further, FIG. 5 is a graph showing the relationship between the frequency and the sound absorption coefficient with respect to the change in the hole diameter of the holes 16 in the first sound absorbing layer 18. The cavity volume of the space 32 (V in FIG. 3) and the actual length of the opening 34 (l in FIG. 3) are the same conditions. Further, as a comparative example, urethane foam (thickness t = 25 mm), which is a porous material, is also shown. As shown in FIG. 5, by increasing the hole diameter of the hole 16, sound absorption in a high frequency region can be performed. That is, the sound absorption characteristics can be adjusted by changing the hole diameter. Further, although not shown in the graph, the sound absorption characteristic can be adjusted by changing the actual length l (the axial length of the hole 16) of the opening portion 34. That is, as shown in the equation (1), by lengthening the actual length l of the opening portion 34, resonance vibration occurs in a low frequency region, and low frequency sound can be absorbed. Further, by shortening the actual length l of the opening portion 34, resonance vibration occurs in a high frequency region, and high frequency sound can be absorbed.

In each resonance type sound absorber of the first sound absorbing layer 18, the opening area of the hole 16 (opening area S of the opening portion 34) and the axial length of the hole 16 (so that the sound absorbing characteristics are the same as each other) By setting the actual length l) of the opening portion 34 and the volume of the space 24 (cavity volume V), it is possible to impart a sound absorbing characteristic that strongly absorbs sound of a specific frequency. Therefore, as shown in FIGS. 1 and 2, by forming a Helmholtz resonator composed of a plurality of protrusions 22 under the same conditions, it is effectively used as a noise countermeasure for equipment that generates noise of a specific frequency. be able to.

Further, by changing at least one of the parameters of the Helmholtz resonator, it is possible to absorb two or more kinds of sounds having different frequencies. For example, the volume of the space 24 and the axial length of the hole 16 are made constant, and the opening area of the hole 16 is changed. As shown in FIG. 5, by increasing the hole diameter of the hole 16 (increasing the hole opening area), it is possible to absorb sound in a high frequency region, and reduce the hole diameter (decrease the hole opening area). ) Therefore, the sound in the low frequency region can be absorbed. Therefore, by installing Helmholtz resonators with different sound absorption characteristics, the frequency range in which the sound absorption effect appears can be expanded, and sound absorption can be effectively performed for sounds containing multiple peak frequencies. can. When holes 16 having a plurality of hole diameters different from each other are provided, the sound absorption characteristic with respect to the frequency of the sound to be absorbed can be adjusted by changing the ratio thereof.

The change of the parameter of the first sound absorbing layer 18 is not limited to (1) changing the opening area of the hole 16 described above, and (2) changing the shape of the hole 16 (to the area of the opening portion). (Relevant), (3) Change the axial length of the hole 16 (related to the actual length of the opening), (4) Change the diameter of the protrusion 22 (related to the volume of the space 24), ( 5) The shape of the protrusion 22 can be changed (related to the volume of the space 24), (6) the height of the protrusion 22 can be changed (related to the volume of the space 24), or a plurality of these can be combined. can.

Further, in FIGS. 1 and 2, the hole 16 is formed only in the shielding plate 12, but it can also be provided in the protrusion 22 of the protrusion plate 10. By providing the hole 16 in the protrusion 22, the sound acting from the protrusion plate 10 side can be sucked.

FIG. 6 is a cross-sectional view showing another configuration example of the hole 16. In FIG. 2, the holes 16 are provided parallel to the thickness direction of the shielding plate 12 (vertical direction in the drawing), but the direction in which the holes 16 are provided is not limited to this. As shown in FIG. 6A, the hole 16 may be inclined at an angle with respect to the thickness direction of the shielding plate 12. The hole 16 shown in FIG. 6A can be formed by arranging the second sound absorbing layer 14 on the shielding plate 12 and then obliquely pressing a heated needle-shaped tool.

By forming the holes 16 in the shielding plate 12 before joining the second sound absorbing layer 14, only the holes 16 may be inclined at an angle as shown in FIG. 6B. Further, the hole 16 is not limited to a configuration in which the front surface side (second sound absorbing layer 14 side) and the back surface side (projection plate 10 side) of the shielding plate 12 are linearly connected, and the hole 16 is bent in the middle. (FIG. 6 (c)), or the shielding plate 12 may be formed in a curved shape from the front surface side to the back surface side (FIG. 6 (d)). In the case of these configurations (FIGS. 6B to 6D), after forming the holes 16 in the shielding plate 12, the second sound absorbing layer 14 is arranged in the shielding plate 12, and the heated needle-shaped tool is pushed. By hitting the shield plate 12 and the second sound absorbing layer 14 by heat welding, the composite sound absorbing material 1 can be obtained. Further, the composite sound absorbing material 1 is formed by forming the holes 16 in the shielding plate 12 and forming the holes in the second sound absorbing material 14, then arranging the second sound absorbing layer 14 in the shielding plate 12 and heat welding. Can be obtained. The holes 16 can be formed by using various tools such as a drill and punching, or by tapping, in addition to forming by using a heated needle-shaped tool.

By making the cross-sectional shape of the hole 16 the shape shown in FIG. 6, the Helmholtz resonator is compared with the configuration shown in FIGS. 1 and 2 (a configuration in which the hole 16 is provided parallel to the thickness direction of the shielding plate 12). Since the actual length l (the axial length of the hole 16) of the opening portion 34 can be increased, the thickness of the shielding plate 12 (that is, the thickness of the entire composite sound absorbing material 1) can be increased without increasing the thickness. The resonance frequency can be lowered. Further, when the second sound absorbing layer 14 side is viewed from the front, the holes 16 can be made inconspicuous, so that the installed composite sound absorbing material 1 itself can be made inconspicuous.

In the present specification, the "axial length of the hole 16" corresponds to the actual length l of the above-mentioned opening portion 34, and specifically, a plurality of holes 16 are formed in the thickness direction of the shielding plate 12. When the straight line obtained by connecting the centers (positions of the center of gravity) of each opening when cut in a cross section is used as the central axis, it means the length of the hole in the direction of the central axis.

FIG. 7 is a diagram illustrating the effect of the present invention. The first sound absorbing layer 18 is composed of only the protrusions 10 and the shielding plate 12, and the region on the opposite side of the shielding plate 12 where the protrusions 22 are not formed is open. With such a configuration, the composite sound absorbing material 1 can be flexibly bent. For example, as shown in FIG. 7, the shielding plate 12 is bent (FIG. 7 (a)), is not bent (FIG. 7 (b)), is bent toward the protrusion 10 (FIG. 7 (c)), and the like. The shape of the composite sound absorbing material 1 can be freely designed. Thereby, for example, it is possible to facilitate construction and installation on a wall surface formed of a curved surface such as a columnar pillar of a building and a vehicle interior composed of a curved surface in a train.

<Second Embodiment>
FIG. 8 is a plan view of the composite sound absorbing material 50 of the second embodiment. FIG. 9 is a cross-sectional view of the composite sound absorbing material 50 along the line 9-9 in FIG. The composite sound absorbing material 50 of the second embodiment is different from the composite sound absorbing material 1 of the first embodiment in that the adhesive film 52 is provided as a film-like member between the first sound absorbing layer 18 and the second sound absorbing layer 14. It's different.

The composite sound absorbing material 50 of the second embodiment can be manufactured, for example, as follows. First, similarly to the composite sound absorbing material 1 of the first embodiment, the protruding plate 10 and the shielding plate 12 are joined by heat welding. Next, a heated needle-shaped tool is pressed against the space 24 of the shielding plate 12 to form a hole 16 in the shielding plate 12 to form a first sound absorbing layer 18 of the composite sound absorbing material 50. do. The composite sound absorbing material 50 is manufactured by attaching the adhesive film 52 to the surface of the first sound absorbing layer 18 produced in this manner on the side where the shielding plate 12 is provided, and further attaching the second sound absorbing layer 14. ..

According to the composite sound absorbing material 50 of the second embodiment, even when a material that cannot heat-seal the first sound absorbing layer 18 (shielding plate 12) and the second sound absorbing layer 14 is used, the composite sound absorbing material Can be produced. Further, by providing the adhesive film 52, it is possible to prevent dust and moisture from entering the space 24.

The thickness of the adhesive film 52 needs to be sufficiently small with respect to the diameter of the holes 16 so that the adhesive film 52 vibrates due to the sound waves reaching the adhesive film 52. For example, by setting the thickness of the adhesive film 52 to 1/50 or less of the diameter of the hole 16, even if the adhesive film 52 is provided, the composite sound absorbing material 50 is composite without affecting the sound absorbing characteristics. The sound absorbing material 50 can be manufactured. The thickness of the pressure-sensitive adhesive film 52 is the total thickness of the base film and the pressure-sensitive adhesive layer.

A thin-film resin film can be used as the base material constituting the adhesive film 52. Further, by using the adhesive film 52 as a nonflammable material such as a metal thin film (aluminum foil), flame retardancy can be imparted. In this case, it is preferable that the second sound absorbing layer 14 is made of a non-combustible material.

According to the composite sound absorbing material 50 of the second embodiment, since the adhesive film 52 can prevent stains such as dust and moisture, it is usually used as a floor material in addition to the wall and ceiling on which the sound absorbing material is installed. Can also be used. Therefore, the sound absorbing material can surround all four sides, and the sound absorbing effect can be improved.

Although the aspect in which the pressure-sensitive adhesive film 52 is used as the film-like member has been described, the film-like member is not limited to the pressure-sensitive adhesive film 52, and an adhesive may be applied to both surfaces of the film-like member.

<Third Embodiment>
FIG. 10 is a plan view of the composite sound absorbing material 100 of the third embodiment. FIG. 11 is a cross-sectional view of the composite sound absorbing material 100 along the line 11-11 in FIG. The composite sound absorbing material 100 of the third embodiment is different from the composite sound absorbing material 50 of the second embodiment in that the protrusion plate 10 and the shielding plate 12 are joined by using an adhesive 102.

According to the composite sound absorbing material 100 of the third embodiment, when the protrusion plate 10 and the shielding plate 20 are made of a material that cannot be heat-welded, they can be joined by using an adhesive 102, which is effective. Examples of the material that cannot be heat-welded include a metal material such as aluminum. The protrusion 22 is formed on the protrusion plate 10 by press working, embossing, or the like. Further, a hole 16 is formed in the shielding plate 12. The hole 16 can be formed by using various tools such as a drill, a needle, and punching, or by tapping. Next, the adhesive 102 is applied to at least one of the joint surfaces of the protrusion plate 10 and the shielding plate 12, and the other joint surface is joined to the one joint surface via the adhesive 102 to obtain the first first. The sound absorbing layer 18 is produced. After that, the first sound absorbing layer 18 and the second sound absorbing layer 14 are joined by joining the second sound absorbing layer 14 using the adhesive film 52 in the same manner as in the method of manufacturing the composite sound absorbing material 50 of the second embodiment. It is possible to obtain a composite sound absorbing material 100 made of a laminated body of.

<Fourth Embodiment>
FIG. 12 is a cross-sectional view of the composite sound absorbing material 150 of the fourth embodiment. The composite sound absorbing material 150 of the fourth embodiment is different from the composite sound absorbing material 1 of the first embodiment in that holes 16 formed in the space 24 are provided on both sides of the protrusion plate 10 and the shielding plate 12. There is.

According to the composite sound absorbing material 150 of the fourth embodiment, the sound acting on the shielding plate 12 side can be absorbed by the first sound absorbing layer 18. Further, by utilizing the space created between the wall surface on which the composite sound absorbing material 150 is installed and the composite sound absorbing material 150, a sound absorbing effect in a low frequency region can be expected.

The holes 16 can be formed by the same method as the method for forming the holes 16 in the first to third embodiments.

1, 50, 100, 150 ... Composite sound absorbing material, 10 ... Projection plate, 12 ... Shielding plate, 14 ... Second sound absorbing layer, 16 ... Hole, 18 ... First sound absorbing layer, 22 ... Projection, 24, 32 ... Space, 30 ... Helmholtz resonator, 34 ... openings, 52 ... adhesive film, 102 ... adhesive

Claims (6)

It has a protrusion plate having a plurality of protrusions and the inside of each protrusion is hollow, and a shielding plate provided on the open side of the plurality of protrusions of the protrusion plate, and at least one of the protrusion plate and the shielding plate. On one side, there is a first sound absorbing layer provided with holes communicating with each other in a plurality of spaces formed by the cavities of the plurality of protrusions.
A second sound absorbing layer provided on the surface of the first sound absorbing layer on the side where the holes are provided and made of a porous material or a fibrous material, and a second sound absorbing layer.
With
The region of the protruding plate where the protrusion is not formed is a composite sound absorbing material which is open in the direction opposite to the shielding plate. The composite sound absorbing material according to claim 1, wherein the hole is provided in the shielding plate. In the first sound absorbing layer, the volume of the space, the opening area of the hole, and the axial length of the hole are set so that the sound absorbing characteristics corresponding to the plurality of spaces are the same. The composite sound absorbing material according to claim 2. The first sound absorbing layer has a volume of the space, an opening area of the hole, and an axial length of the hole so that the sound absorbing characteristics corresponding to the plurality of spaces are at least two types different from each other. The composite sound absorbing material according to claim 2, wherein is set. The composite sound absorbing material according to claim 1, wherein the hole is provided in each of the shielding plate and the protruding plate. The composite sound absorbing material according to any one of claims 1 to 5, which has a film-like member between the first sound absorbing layer and the second sound absorbing layer.

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