Sound absorber and sound environment adjustment structure

Abstract

To construct a sound absorber with excellent designability capable of easily changing an indoor sound environment, and improve comfort of a room using the sound absorber.SOLUTION: A sound absorber 10 comprises: a self-supporting rectangular frame body 11 with a part of an outside surface serving as a bottom part; a first membrane body 12 closing a first opening 11a on one end side of the frame body 11; a second membrane body 13 closing a second opening 11b on the other end side of the frame body 11; and a sound absorption material 14 made of a porous material, which is arranged inside the frame body 11. The first membrane body 12 and the second membrane body 13 are made of different materials. The first and second membrane bodies 12, 13, together with the first and second openings 11a, 11b, integrally cover front end surfaces 15a, 16a and outside surfaces 15b, 16b of first and second frame members 15, 16, and their peripheral edge parts extend to inside surfaces 15d, 16d of the first and second frame members 15, 16, and are fixed to the inside surfaces 15d, 16d.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a sound absorber and a sound environment adjustment structure for use indoors. [Background technology]

[0002] Conventionally, in order to improve the sound environment in a house, office, etc., sound absorbers have been placed in the room to absorb voices and other sounds (see, for example, Patent Document 1 listed below).

[0003] In Patent Document 1, multiple plate-shaped or block-shaped sound absorbers made of sound-absorbing material are hung from the ceiling so as to surround the periphery of the booth, reducing sound leakage into and out of the booth and suppressing sound reverberation within the booth, making it easier to have conversations within the booth. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-034006 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the sound absorber used in Patent Document 1 is made of one type of sound-absorbing material and has a limited frequency band that it can absorb. Therefore, when it becomes necessary to change the sound environment in the room (such as the frequency band of sound to be absorbed) due to, for example, a change in the use of the room (changing a conference room used for face-to-face meetings into a conference room used for online meetings), it is necessary to remove the sound absorber suspended from the ceiling and replace it with a sound absorber with different sound absorption characteristics (different sound absorption coefficients for each frequency band), making it difficult to change the sound environment in the room.

[0006] The present invention has been made in view of the above points, and its object is to construct a sound absorber that can easily change the sound environment in a room, and to use this sound absorber to improve the comfort of the room. [Means for solving the problem]

[0007] In order to achieve the above object, in the present invention, a sound absorbing body whose sound absorbing characteristics change simply by changing its orientation is used to adjust the sound environment in a room.

[0008] Specifically, the first invention is a sound absorbing body that is installed in a room to adjust the sound environment in the room, and includes a frame body that is framed in a rectangular shape and that stands on its own with a part of its outer surface serving as a bottom, a first film body that closes a first opening at one end side of the frame body in the depth direction, a second film body that closes a second opening at the other end side of the frame body in the depth direction, and a sound absorbing material made of a porous material that is placed inside the frame body, and the frame body includes a cylindrical first frame member that forms the first opening and a cylindrical second frame member that forms the second opening, and the first frame The first membrane and the second membrane are made of different materials, and the first membrane, together with the first opening, integrally covers the front end face and outer surface of the first frame material on the first opening side, with its peripheral portion fixed to the back end face or inner surface of the first frame material, and the second membrane, together with the second opening, integrally covers the front end face and outer surface of the second frame material on the second opening side, with its peripheral portion fixed to the back end face or inner surface of the second frame material.

[0009] In the first aspect of the present invention, the sound absorber is configured such that a rectangular frame is self-supporting, and first and second membranes made of different materials are arranged horizontally facing each other with a porous sound-absorbing material sandwiched between them. A sound absorber configured in this way exhibits different sound absorption characteristics depending on whether sound is incident from the first membrane side or the second membrane side. Specifically, the first and second membranes made of different materials have different sound transmittances. Therefore, when sound is incident from the membrane side through which sound is easily transmitted, the sound easily enters the sound absorber, and the porous sound-absorbing effect of the sound-absorbing material is exerted. However, when sound is incident from the membrane side through which sound is less transmitted, the sound is less likely to enter the sound absorber, and the porous sound-absorbing effect of the sound-absorbing material is hardly exerted, while the membrane vibration of the membrane exerts a membrane-vibration sound-absorbing effect. Porous-type sound absorbers tend to have a high sound absorption coefficient from the mid-low to high frequencies, while membrane-vibration-type sound absorbers tend to have a high sound absorption coefficient only in a narrow frequency range from the mid-low to mid-range. In other words, the sound absorber according to the first invention has different sound absorption coefficients (different sound absorption characteristics) for each frequency band depending on whether the sound is incident from the first film side or the second film side. In this way, according to the first invention, it is possible to configure a sound absorber whose sound absorption characteristics change simply by changing its orientation, so that by installing such a sound absorber in a room and changing its orientation, it is possible to easily adjust the sound environment in the room.

[0010] However, when the frame body consists of a single frame material framed in a rectangular shape, the peripheral portions of the two membrane bodies that block the two openings of the frame body will be positioned on the outer surface of the frame body where they are easily visible, which may reduce the design value of the sound-absorbing body.

[0011] Therefore, in the first invention, the frame body is constructed from two frame materials (first and second frame materials), and each membrane integrally covers each opening and the front end face and outer surface of each frame material, with its peripheral edge fixed to the back end face or inner surface of each frame material. If the frame body were constructed from a single frame material, blocking each of the frame body's two openings with two membranes would likely result in the membrane's peripheral edge being located on the frame body's outer surface, which is easily visible, thereby reducing the design of the sound absorber. However, according to the first invention, the frame body is constructed from two frame materials, and the two membranes blocking the two openings are configured to cover not only the openings but also the back end face or inner surface of the frame materials. With this configuration, when the first and second frame materials are joined together with the first and second membranes fixed to them, the peripheral edges of the first and second membranes are sandwiched between the joint between the first and second frame materials and are not exposed on the frame body's outer surface, which is easily visible. That is, according to the first aspect of the present invention, it is possible to provide a sound absorber with excellent design.

[0012] As described above, according to the first invention, a sound absorber with excellent design that can easily change the sound environment in a room is provided, and by using this sound absorber, indoor comfort can be improved.

[0013] The second invention is a sound-absorbing body that is placed in a room to adjust the sound environment in the room, and is characterized in that it comprises a rectangular sound-absorbing material made of a porous material, a first membrane that covers a first side of the sound-absorbing body, and a second membrane that covers a second side of the sound-absorbing body that faces the first side, and the first membrane and the second membrane are made of different materials and are closed in a bag shape to cover the sound-absorbing material.

[0014] In a second aspect of the present invention, the sound absorber is configured to include a rectangular parallelepiped sound-absorbing material made of a porous material and first and second membranes covering opposing first and second side surfaces of the sound absorber. Furthermore, the first and second membranes are made of different materials and are closed in a bag-like shape to cover the sound-absorbing material. With this configuration, when the sound absorber is freestanding, the first and second membranes made of different materials are arranged horizontally opposite each other with the sound-absorbing material made of a porous material sandwiched between them. A sound absorber configured in this way exhibits different sound-absorbing characteristics depending on whether the sound is incident from the first membrane side or the second membrane side. Specifically, the first and second membranes made of different materials have different sound transmittances. Therefore, when sound enters from the membrane side through which sound is easily transmitted, it easily enters the sound absorber, and the porous sound-absorbing effect of the sound-absorbing material is exerted. However, when sound enters from the membrane side through which sound is less transmitted, it is difficult for sound to enter the sound absorber, and the porous sound-absorbing effect of the sound-absorbing material is hardly exerted, while the membrane vibration of the membrane exerts the membrane vibration sound-absorbing effect. Porous sound absorption tends to have a high sound absorption coefficient from the low-mid to high frequency ranges, while membrane vibration sound absorption tends to have a high sound absorption coefficient only in a narrow frequency band from the low-mid to mid ranges. In other words, the sound absorber according to the second invention has a different sound absorption coefficient (exhibited different sound absorption characteristics) for each frequency band depending on whether the sound is incident from the first membrane side or the second membrane side. In this way, according to the second invention, it is possible to construct a sound absorber whose exhibited sound-absorbing characteristics can be changed simply by changing the orientation. Therefore, by installing such a sound absorber in a room and changing its orientation, the sound environment in the room can be easily adjusted.

[0015] A third invention is characterized in that, in the first or second invention, the first film body and the second film body are configured to be distinguishable from each other.

[0016] In the third aspect of the present invention, the first film and the second film are configured to be distinguishable from each other, so that the orientation of the sound absorber can be easily changed to an orientation that matches the desired sound absorption characteristics.

[0017] The fourth invention is characterized in that, in the first or second invention, the first film body is made of woven fabric and the second film body is made of artificial leather.

[0018] In a sound absorber according to a fourth aspect of the present invention, the first membrane is made of woven fabric, and the second membrane is made of artificial leather, which has lower breathability than woven fabric. The first membrane, made of woven fabric, allows sound to pass through easily, while the second membrane, made of artificial leather, which has lower breathability than woven fabric, allows sound to pass through less easily than the first membrane. Therefore, in the sound absorber according to the fourth aspect of the present invention, when sound enters from the first membrane side, the sound easily passes through the first membrane and enters the sound absorber, and the porous sound absorption effect of the sound absorbing material is exerted. However, when sound enters from the second membrane side, the sound does not easily enter the sound absorber, and the porous sound absorption effect of the sound absorbing material is hardly exerted, while the membrane vibration of the second membrane exerts a membrane vibration sound absorption effect. Thus, according to the fourth aspect of the present invention, it is possible to easily construct a sound absorber whose sound absorption characteristics can be changed simply by changing its orientation.

[0019] The fifth invention is a sound environment adjustment structure for adjusting the sound environment in a room, characterized in that a plurality of sound absorbers according to the first or second invention are provided on a shelf installed in the room.

[0020] According to the fifth aspect of the present invention, a plurality of sound absorbing bodies whose sound absorption characteristics change simply by changing their orientation are placed on shelves in a room, and by changing their orientation, the sound environment in the room can be easily adjusted. [Effects of the Invention]

[0021] As explained above, according to the present invention, a sound absorbing body whose sound absorption characteristics change simply by changing its orientation is used to adjust the sound environment in a room, so that a sound absorbing body that can easily change the sound environment in a room can be provided, and the use of this sound absorbing body can also improve the comfort of the room. [Brief explanation of the drawings]

[0022] [Figure 1]FIG. 1 is an interior view showing an example of a sound environment adjustment structure according to a first embodiment of the present invention. [Figure 2] FIG. 2 is an explanatory diagram for explaining the structure of the sound absorber in the first embodiment. [Figure 3] FIG. 3 is a cross-sectional view of the sound absorber according to the first embodiment. [Figure 4] FIG. 4 is a graph showing the results of a sound absorption performance test carried out in the first embodiment. [Figure 5] FIG. 5 is a cross-sectional view of the sound absorber according to the second embodiment. [Figure 6] FIG. 6 is a cross-sectional view of a sound absorber according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following description of the embodiments is merely exemplary in nature and is not intended to limit the present invention, its applications, or uses.

[0024] First Embodiment of the Invention 1 is an interior view showing a sound environment adjusting structure 1 according to a first embodiment of the present invention. In this first embodiment, as an example of the sound environment adjusting structure 1, a sound absorbing body 10 according to the present invention is provided in a conference room of an office to adjust the sound environment of the conference room.

[0025] A plurality of shelves 2 are installed on a wall W in a conference room shown in Fig. 1. The sound environment adjusting structure 1 of the first embodiment is configured to adjust the sound environment in the conference room by providing a plurality of sound absorbers 10 on the plurality of shelves 2, the sound absorption characteristics of which change simply by changing the orientation of the plurality of sound absorbers 10.

[0026] Here, the change / different sound absorption characteristics means that the sound absorption coefficient changes / differently for each frequency band.

[0027] -Sound absorbing body composition- 2 and 3, sound absorber 10 includes a frame 11, first and second membranes 12 and 13, and sound-absorbing material 14. Frame 11 is made up of four plate-like bodies arranged in a rectangular shape, with a first opening 11a at one end in the depth direction closed by first membrane 12 and a second opening 11b at the other end closed by second membrane 13. Sound-absorbing material 14 is provided in internal space S inside frame 11, which is closed by first and second membranes 12 and 13.

[0028] The sound absorber 10 is self-supporting with part of the outer surface of the frame 11 as its bottom, and is configured so that the first film 12 and the second film 13 are arranged horizontally facing each other with sound-absorbing material 14 sandwiched between them. When the sound absorber 10 is installed (self-supporting with part of the outer surface of the frame 11 as its bottom), it has dimensions of approximately 400 to 500 mm in width, 300 to 400 mm in height, and 80 to 111 mm in depth. In this embodiment 1, the sound absorber 10 is formed to have dimensions of 448 mm in width, 320 mm in height, and 100 mm in depth.

[0029] (Frame) In the first embodiment, the frame body 11 is formed by a cylindrical body with a rectangular cross section that is framed in a rectangular shape. In the first embodiment, the frame body 11 is formed by joining first and second frame members 15, 16, each of which is a cylindrical body with a rectangular cross section. The first and second frame members 15, 16 are formed, for example, by framing four rectangular wooden boards (four rectangular plywood boards with a thickness of 12 mm in the first embodiment) into a rectangular shape. The first and second frame members 15, 16 are joined by a plurality of dowels 17. The dowels 17 join the first and second frame members 15, 16 by fitting their ends into dowel holes h formed in the rear end surfaces 15c, 16c of the first and second frame members 15, 16. The back end faces 15c, 16c of the first and second frame members 15, 16 in which the dowel holes h are formed are the end faces opposite the front end faces 15a, 16a on the first and second openings 11a, 11b sides of the two end faces of the frame body 11. The first frame member 15 forms the first opening 11a, and the second frame member 16 forms the second opening 11b.

[0030] (membrane body) The first film 12 and the second film 13 are made of different materials. The first and second films 12, 13 can be made of woven fabric, artificial leather, natural leather, resin film, etc. In the first embodiment, the first film 12 is made of woven fabric, and the second film 13 is made of artificial leather. As will be described in detail later, by making the first and second films 12, 13 of different materials, the sound absorber 10 is configured to exhibit different sound absorption characteristics depending on whether the sound is incident from the first film 12 side or the second film 13 side.

[0031] Furthermore, the first film 12 and the second film 13 are configured to be distinguishable. In the first embodiment, the colors of the first film 12 and the second film 13 are different enough to be distinguishable. In the first embodiment, the color of the first film 12 is gray, and the color of the second film 13 is black. The method of making the first film 12 and the second film 13 distinguishable is not limited to changing the color. They may be configured to be distinguishable by changing the patterns of the first film 12 and the second film 13, or by marking only one of them. Note that, as in the first embodiment, when the first film 12 and the second film 13 are made of different materials and the surface textures (gloss, unevenness, tactile feel, etc.) are different enough to be distinguishable, there is no need to change the color or pattern or mark them.

[0032] The first film 12 is formed to a size that integrally covers the first opening 11a and the front end surface 15a, outer surface 15b, rear end surface 15c, and at least the rear end portion of the inner surface 15d of the first frame member 15. The first film 12 is wrapped around the first frame member 15 so as to integrally cover the first opening 11a and the front end surface 15a, outer surface 15b, rear end surface 15c, and at least the rear end portion of the inner surface 15d of the first frame member 15, and its peripheral edge is fixed to the inner surface 15d of the first frame member 15 with a stapler, adhesive, or the like. Note that in this embodiment 1, the first film 12 has holes formed therein that correspond to the dowel holes h in the rear end surface 15c of the first frame member 15.

[0033] In addition, in this embodiment 1, the first membrane 12 is made of a rectangular woven fabric with rectangular cutouts formed in the four corners. The cutouts at the four corners of the first membrane 12 are formed by cutting out the portions that will become excess portions so that, when the first membrane 12 is fixed to the first frame member 15, excess portions (portions that do not abut the outer surface 15b) are not generated at the corners of the outer surface 15b of the first frame member 15. In this embodiment 1, at the four corners of the outer surface 15b of the first frame member 15, each of the two sides that form the edges of the cutouts of the first membrane 12 are sewn together.

[0034] The second film 13 is formed in the same manner as the first film 12. Specifically, the second film 13 is formed to a size that integrally covers the front end surface 16a, the outer surface 16b, the rear end surface 16c, and at least the rear end portions of the inner surface 16d of the second frame member 16, together with the second opening 11b. The second film 13 is wrapped around the second frame member 16 so as to integrally cover the second opening 11b and the front end surface 16a, the outer surface 16b, the rear end surface 16c, and at least the rear end portions of the inner surface 16d of the second frame member 16, and its peripheral edge is fixed to the inner surface 16d of the second frame member 16 with a stapler, adhesive, or the like. In this embodiment 1, the second film 13 has holes formed in it that correspond to the dowel holes h in the rear end surface 16c of the second frame member 16.

[0035] In addition, in this embodiment 1, the second membrane 13 is made of rectangular artificial leather with rectangular cutouts formed in the four corners. The cutouts at the four corners of the second membrane 13 are formed in advance to remove excess portions (portions that do not abut the outer surface 16b) from the corners of the outer surface 16b of the second frame member 16 when the second membrane 13 is fixed to the second frame member 16. In this embodiment 1, at the four corners of the outer surface 16b of the second frame member 16, each of the two sides that form the edges of the cutouts of the second membrane 13 are sewn together.

[0036] With the above-described configuration, when the first and second membrane bodies 12, 13 are fixed to the first and second frame members 15, 16 and the first and second frame members 15, 16 are joined with dowels 17, the peripheral portions of the first and second membrane bodies 12, 13 are sandwiched between the joints of the first and second frame members 15, 16 and are not exposed on the outer surface of the frame body 11, where they are easily visible to the public.

[0037] (sound absorbing material) The sound absorbing material 14 is made of a porous material and is formed in a rectangular parallelepiped shape. In the first embodiment, the sound absorbing material 14 is formed to have a thickness of 100 mm and a size equal to the inside dimensions of the frame 11.

[0038] The porous material constituting the sound-absorbing material 14 is not particularly limited as long as it is a fiber aggregate or resin foam with sound-absorbing properties. A fiber aggregate with sound-absorbing properties has numerous three-dimensionally continuous (interconnected) voids within it, allowing air to pass through the interior and exterior of the aggregate. This fiber aggregate has excellent breathability and soundproofing properties. Examples of such fiber aggregates include woven fabrics (fibrous materials), nonwoven fabrics, wood fiberboard, and inorganic fiberboard. Specific examples include inorganic fiber aggregate materials such as rock wool, glass wool, and soft fibers; and resin fiber aggregate materials such as polyethylene terephthalate (PET) fibers (recycled PET fibers, etc.) and polyester fibers. A resin foam with sound-absorbing properties is an open-cell foam with an open-cell structure in which air bubbles are connected within the foam, allowing air to pass through the interior and exterior of the foam. This foam has excellent breathability and soundproofing properties. Examples of open-cell foams include resin foam materials such as polyurethane foam (urethane foam) and acrylic resin foam (acrylic foam). In the first embodiment, a relatively lightweight polyethylene terephthalate (PET) nonwoven fabric is used as the sound absorbing material 14.

[0039] -How to adjust the sound environment- As shown in Fig. 1, sound absorbers 10 configured as described above are provided by freestanding them on a shelf 2 installed on a wall W of a room, with part of the outer surface of frame body 11 (long side or short side surface of first and second frame members 15, 16) forming the bottom. By freestanding sound absorbers 10 in this way, in each sound absorber 10, first film body 12 and second film body 13 made of different materials are arranged horizontally facing each other with sound-absorbing material 14 sandwiched between them. Then, the orientation of each sound absorber 10 is adjusted.

[0040] Specifically, when the sound absorber 10 is installed with the first film 12 facing the center of the room and the second film 13 facing the wall W, the woven fabric that makes up the first film 12 is relatively breathable and easily transmits sound. Therefore, most of the sound that occurs in the center of the room and enters the first film 12 passes through the first film 12, and the porous sound-absorbing effect of the sound-absorbing material 14 is exerted. Porous sound absorption tends to have a high sound absorption coefficient from the low-midrange to the high-frequency range. Therefore, when the sound absorber 10 is installed with the first film 12 facing the center of the room, sound enters from the first film 12 side, and the porous sound-absorbing effect of the sound-absorbing material 14 increases the sound absorption coefficient over a wide frequency range from the low-midrange to the high-frequency range (160 to 8000 Hz), effectively absorbing the sound.

[0041] On the other hand, if the sound absorber 10 is installed with the second membrane 13 facing the center of the room and the first membrane 12 facing the wall W, the artificial leather that makes up the second membrane 13 has relatively low breathability and is less susceptible to sound transmission than the first membrane 12, so most of the sound that occurs in the middle of the room and enters the second membrane 13 is reflected. As a result, the porous sound absorption effect of the sound absorbing material 14 is hardly exerted, but the sound hits the second membrane 13 and vibrates it, thereby exerting the membrane vibration sound absorption effect of the artificial leather that makes up the second membrane 13. Membrane vibration sound absorbers tend to have a high sound absorption coefficient only in a narrow frequency band from the low-mid range to the mid-range. Therefore, if the sound absorber 10 is placed with the second membrane 13 facing the center of the room, sound will enter from the second membrane 13 side, and due to the membrane vibration type sound absorption effect of the second membrane 13, the sound absorption coefficient will be high only in a narrow frequency band from the mid-low range to the mid-range (160 Hz to 315 Hz), and the sound will be effectively absorbed.

[0042] As a result, the orientation of each sound absorber 10 can be changed to match the frequency of the sound that is desired to be reduced among the sounds generated in the room, thereby adjusting the sound environment in the room to a desired state.

[0043] -Sound absorption performance test- In order to confirm that the sound absorption characteristics change when the orientation of the multiple sound absorbers 10 is changed, a sound absorption performance test was conducted with reference to the reverberation room sound absorption coefficient measurement method specified in JIS A 1409:1998.

[0044] Specifically, a large sound-absorbing material 14 measuring 100 mm thick and 1800 mm x 1800 mm was prepared, along with a first membrane 12 (woven fabric) and a second membrane 13 (artificial leather) also of similarly large size. Sound absorber I was fabricated by laminating the sound-absorbing material 14 and the first membrane 12 (woven fabric) in this order on the floor of a reverberation chamber, and sound absorber II was fabricated by laminating the sound-absorbing material 14 and the second membrane 13 (artificial leather) in this order. Sound absorption performance tests were then conducted on each of sound absorbers I and II to measure the sound absorption coefficient in a reverberation chamber. The results are shown in Figure 4.

[0045] As shown in Figure 4, the central frequency (peak central frequency) at which sound absorber I's reverberation room sound absorption coefficient reaches its maximum is around 500 Hz, and the reverberation room sound absorption coefficient is 1.0 or higher from 160 Hz to 8000 Hz (from mid-low to high frequencies), resulting in effective absorption of sound over an extremely wide frequency range from mid-low (100-300 Hz) to high frequencies (above 8000 Hz). Note that although Figure 4 does not show the reverberation room sound absorption coefficient at 8000 Hz for sound absorber I, the reverberation room sound absorption coefficient at 8000 Hz was also measured in the test, and was found to be 1.06.

[0046] In sound absorber I, sound is incident from the first film 12 side. However, because the woven fabric that makes up first film 12 has relatively high breathability and allows sound to pass through easily, most of the incident sound passes through first film 12 and enters sound absorber 10, where it is absorbed and attenuated by sound-absorbing material 14 (porous sound absorption). Porous sound absorption tends to have a high sound absorption coefficient from the low-midrange to the high-frequency range. Therefore, in sound absorber I, the porous sound-absorbing effect of sound-absorbing material 14 is exerted, and it is thought that the reverberation chamber sound absorption coefficient is high, at 1.0 or more, from the low-midrange to the high-frequency range (160 to 8000 Hz).

[0047] On the other hand, the center frequency (peak center frequency) at which the reverberation room sound absorption coefficient of sound absorber II is maximum is around 200 Hz, and the reverberation room sound absorption coefficient is 0.7 or higher only in a narrow frequency band (160-315 Hz) from the mid-low range (100-300 Hz) to the mid range (300-2000 Hz), resulting in effective sound absorption.

[0048] In sound absorber II, sound enters from the second membrane 13 side. However, because the artificial leather that constitutes second membrane 13 has relatively low breathability and is difficult for sound to transmit, most of the incident sound is reflected by second membrane 13 and does not enter sound absorber 10. As a result, the porous sound-absorbing effect of sound-absorbing material 14 in sound absorber 10 is hardly exhibited, while sound that enters sound absorber 10 is attenuated by hitting second membrane 13 and vibrating it (membrane vibration sound absorption). Membrane vibration sound absorption tends to have a high sound absorption coefficient only in a narrow frequency band from the low-mid to mid-range. Therefore, in the above-mentioned sound absorber II, the porous sound-absorbing effect of sound-absorbing material 14 is hardly exhibited, and the membrane vibration sound-absorbing effect of second membrane 13 is exhibited, which is thought to be why the reverberation chamber sound absorption coefficient is 0.7 or higher only in a narrow frequency band from the low-mid to mid-range (160 to 315 Hz).

[0049] From the results of the sound absorption performance tests described above, it can be inferred that sound absorber 10 of embodiment 1 exhibits excellent sound absorption effects (reverberation chamber sound absorption coefficient of 1.0 or more) in an extremely wide frequency range (160 to 8000 Hz) from the low-mid to high ranges for sounds incident from the side of first film 12 made of woven fabric, but exhibits excellent sound absorption effects (reverberation chamber sound absorption coefficient of 0.7 or more) only in a narrow frequency band (160 to 315 Hz) from the low-mid to mid ranges for sounds incident from the side of second film 13 made of artificial leather. In other words, it can be inferred that sound absorber 10 of embodiment 1 exhibits different sound absorption characteristics depending on whether the sound is incident from the side of first film 12 or the side of second film 13.

[0050] -Effects of the first embodiment- In the first embodiment, the sound absorber 10 is configured such that a rectangular frame 11 is self-supporting, and a first film 12 and a second film 13 made of different materials are arranged horizontally facing each other with a sound-absorbing material 14 sandwiched between them. The sound absorber 10 configured in this manner exhibits different sound absorption characteristics depending on whether the sound is incident from the first film 12 side or the second film 13 side. Specifically, the first and second films 12 and 13, which are made of different materials, have different sound transmittances. Therefore, when sound is incident from the first film 12 side, through which sound is easily transmitted, it easily enters the sound absorber 10, and the porous sound-absorbing effect of the sound-absorbing material 14 is exerted. However, when sound is incident from the second film 13 side, through which sound is less transmitted, it is difficult for sound to enter the sound absorber 10, and the porous sound-absorbing effect of the sound-absorbing material 14 is hardly exerted, while the membrane vibration of the second film 13 exerts a membrane vibration sound-absorbing effect. Porous sound absorbers tend to have a high sound absorption coefficient from the low-midrange to the high-midrange, while membrane vibration sound absorbers tend to have a high sound absorption coefficient only in a narrow frequency band from the low-midrange to the midrange. In other words, the sound absorber 10 of this embodiment 1 has a different sound absorption coefficient (developed sound absorption characteristics) for each frequency band depending on whether the sound is incident from the first film 12 side or the second film 13 side. In this way, according to this embodiment 1, it is possible to configure a sound absorber 10 whose developed sound absorption characteristics can be changed simply by changing its orientation, and therefore it is possible to easily adjust the sound environment in a room by installing such a sound absorber 10 in the room and changing its orientation.

[0051] However, when the frame body 11 is made up of a single frame material framed in a rectangular shape, the peripheral portions of the two membrane bodies 12, 13 that block the two openings 11a, 11b of the frame body 11 will be positioned on the outer surface of the frame body 11 where they are easily visible, which may reduce the design quality of the sound absorber 10.

[0052] Therefore, in this embodiment 1, the frame body 11 is composed of two frame materials (first and second frame materials 15, 16), and each membrane body 12, 13 is configured to integrally cover each opening 11a, 11b, the front end faces 15a, 16a, outer surfaces 15b, 16b, rear end faces 15c, 16c, and rear end portions of the inner surfaces 15d, 16d of each frame material 15, 16, and the peripheral portions are fixed to the inner surfaces 15d, 16d of each frame material 15, 16. If the frame body 11 is made up of a single frame material, and the two openings 11a, 11b of the frame body 11 are blocked by two membranes 12, 13, respectively, the peripheral portions of the membranes 12, 13 would be positioned on the outer surface of the frame body 11, which is easily visible to the public, and this could reduce the design appeal of the sound absorber 10. However, according to this embodiment 1, the frame body 11 is made up of two frame materials 15, 16, and the two membranes 12, 13 that block the two openings 11a, 11b are configured to cover not only the openings 11a, 11b but also the inner surfaces 15d, 16d of the frame materials 15, 16. According to this configuration, when the first and second frame members 15, 16 are joined together while the first and second membranes 12, 13 are fixed to them, the peripheral edges of the first and second membranes 12, 13 are sandwiched between the joints of the first and second frame members 15, 16 and are not exposed on the outer surface of the frame 11, which is easily visible to the public. In other words, according to this first embodiment, it is possible to provide a sound absorber 10 with excellent design.

[0053] As described above, according to the first embodiment, a sound absorber 10 with excellent design that can easily change the sound environment in a room is provided, and by using this sound absorber 10, the comfort of the room can be improved.

[0054] Furthermore, in this embodiment 1, the first film body 12 and the second film body 13 are configured to be distinguishable, so the orientation of the sound absorber 10 can be easily changed to an orientation that corresponds to the desired sound absorption characteristics.

[0055] Furthermore, in the sound environment adjusting structure 1 of the first embodiment, a plurality of the sound absorbers 10 are provided on a shelf 2 installed in the conference room to adjust the sound environment in the conference room. With this sound environment adjusting structure 1, the sound environment in the room can be easily adjusted simply by changing the orientation of the sound absorbers 10.

[0056] Furthermore, in the first embodiment, the first membrane 12 is made of woven fabric, and the second membrane 13 is made of artificial leather, which has lower breathability than woven fabric. The first membrane made of woven fabric allows sound to pass through easily, while the second membrane 13 made of artificial leather, which has lower breathability, allows sound to pass through less easily than the first membrane 12. Therefore, in the first embodiment, when sound enters from the first membrane 12 side, the sound easily passes through the first membrane 12 and enters the sound absorber 10, and the porous sound absorbing effect of the sound absorbing material 14 is exerted. However, when sound enters from the second membrane 13 side, the sound does not easily enter the sound absorber 10, and the porous sound absorbing effect of the sound absorbing material 14 is hardly exerted, while the membrane vibration of the second membrane 13 exerts a membrane vibration sound absorbing effect. In this way, according to the first embodiment, it is possible to easily construct a sound absorber whose sound absorbing characteristics can be changed simply by changing the orientation.

[0057] Furthermore, in this embodiment 1, a plurality of the above-mentioned sound absorbers 10 are provided on a shelf 2 installed in a room as a sound environment adjusting structure for adjusting the sound environment in the room. In this way, according to this embodiment 1, a plurality of sound absorbers 10, whose sound absorption characteristics are changed simply by changing their orientation, are provided on the shelf 2 in the room, and by changing their orientation, the sound environment in the room can be easily adjusted.

[0058] Second Embodiment of the Invention In the second embodiment, the sound absorber 10 of the first embodiment is partially modified. Specifically, as shown in Fig. 5, in the first embodiment, the first and second films 12 and 13 are formed so that their peripheral edges reach the inner surfaces 15d and 16d of the first and second frame members 15 and 16, whereas in the second embodiment, their peripheral edges reach the outer edges of the rear end faces 15c and 16c of the first and second frame members 15 and 16, respectively, and are fixed to the rear end faces 15c and 16c. This type of sound absorber 10 can also achieve the same effects as the first embodiment.

[0059] Third Embodiment of the Invention As shown in FIG. 6, the sound absorber 10 of the third embodiment is the same as the sound absorber 10 of the first embodiment except that the frame 11 is omitted.

[0060] Specifically, the sound absorber 10 of the third embodiment does not include a frame 11, but includes a rectangular parallelepiped sound absorbing material 14 and a cover member 20 for covering the sound absorbing material 14. The sound absorbing material 14 is configured in the same manner as in the first embodiment. The cover member 20 is formed by enclosing the first film body 12 and the second film body 13 in a bag shape.

[0061] As in the first embodiment, the first film 12 and the second film 13 are made of different materials. The first and second films 12, 13 can be made of woven fabric, artificial leather, natural leather, resin film, etc. As in the first embodiment, in the third embodiment, the first film 12 is made of woven fabric, and the second film 13 is made of artificial leather. Furthermore, by making the first and second films 12, 13 out of different materials in this way, the sound absorber 10 in the third embodiment is also configured to exhibit different sound absorption characteristics depending on whether the sound is incident from the first film 12 side or the second film 13 side.

[0062] In the third embodiment as well, the first film body 12 and the second film body 13 are configured to be distinguishable by making their colors different enough to distinguish them. Note that the method of making the first film body 12 and the second film body 13 distinguishable is not limited to changing their colors. They may be configured to be distinguishable by changing the patterns on the first film body 12 and the second film body 13, or by marking only one of them. Note that in the third embodiment as well, if the first film body 12 and the second film body 13 are configured from different materials and therefore the surface textures (gloss, unevenness, feel, etc.) are different enough to distinguish them, there is no need to change the color or pattern or mark them.

[0063] In the third embodiment, the first film 12 and the second film 13 are closed in a bag shape to cover the outer surfaces (all six sides) of the sound-absorbing material 14. The first film 12 covers the first side surface 14a of the sound-absorbing material 14, and the second film 13 covers the second side surface 14b opposite the first side surface 14a of the sound-absorbing material 14. The first film 12, together with the first side surface 14a of the sound-absorbing material 14, is formed to a size that covers half of the four side surfaces between the first side surface 14a and the second side surface 14b on the first side surface 14a side. The second film 13, together with the second side surface 14b of the sound-absorbing material 14, is formed to a size that covers half of the four side surfaces between the first side surface 14a and the second side surface 14b on the second side surface 14b side. The first film 12 and the second film 13 are, for example, sewn together, and an opening / closing means such as a zipper is provided on one side surface (for example, the surface that will be the bottom).

[0064] When the sound absorber 10 of the third embodiment is made to stand on its own, the first film 12 and the second film 13, which are made of different materials, are arranged horizontally facing each other with the sound-absorbing material 14 made of a porous material sandwiched between them, and the sound absorption characteristics exhibited differ depending on whether the sound is incident from the first film 12 side or the second film 13 side. Specifically, the first and second films 12 and 13, which are made of different materials, have different sound transmittances. Therefore, when the sound is incident from the side of the film through which sound is easily transmitted (the first film 12 made of woven fabric), the sound easily enters the sound absorber 10, and the porous sound-absorbing effect of the sound-absorbing material 14 is exhibited. However, when the sound is incident from the side of the film through which sound is less transmitted (the second film 13 made of artificial leather), the sound is less likely to enter the sound absorber 10, and the porous sound-absorbing effect of the sound-absorbing material 14 is hardly exhibited, while the membrane vibration of the membrane (the second film 13) exhibits a membrane vibration-type sound-absorbing effect. Porous-type sound absorbers tend to have a high sound absorption coefficient from the low-midrange to the high-midrange, while membrane vibration-type sound absorbers tend to have a high sound absorption coefficient only in a narrow frequency band from the low-midrange to the midrange. In other words, even with the sound absorber 10 of embodiment 3, the sound absorption coefficient for each frequency band will differ (the sound absorption characteristics that are exhibited will differ) depending on whether the sound is incident from the first film 12 side or the second film 13 side. Therefore, even with embodiment 3, it is possible to configure a sound absorber 10 whose exhibited sound absorption characteristics can be changed simply by changing its orientation, and so the sound environment in a room can be easily adjusted by installing such a sound absorber 10 in the room and changing its orientation.

[0065] Other Embodiments In the above first to third embodiments, the sound absorbing material 14 is made up of one porous member, but the sound absorbing material 14 may have a multi-layer structure in which two or more porous members made of porous materials are stacked on top of each other.

[0066] In addition, in the above-mentioned first and second embodiments, the first and second frame members 15, 16 constituting the frame body 11 are formed by framing four rectangular wooden boards in a rectangular shape, but the first and second frame members 15, 16 are not limited to the above-mentioned configuration as long as they are self-supporting when framed in a rectangular shape to constitute the frame body 11. The first and second frame members 15, 16 may be, for example, two rectangular boards arranged one above the other, with the left and right ends of the two rectangular boards connected by at least one pillar instead of boards. [Industrial Applicability]

[0067] The present invention is useful for sound absorbers and sound environment control structures. [Explanation of symbols]

[0068] 1 Sound environment adjustment structure 2 shelves 10 Sound absorber 11 Frame 11a 1st opening 11b 2nd opening 12 First membrane 13 Second membrane 14 Sound-absorbing material 14a: First side of sound-absorbing material 14 14b: second side of the sound absorbing material 14 15 1st frame material 15a Front end 15b External surface 15c Back side end 15d inner surface 16 Second frame material 16a Front end 16b External surface 16c Back end 16d inner surface 17 Dowel 20 Cover member

Claims

1. A sound absorbing body that is installed in a room to adjust the sound environment of the room, A rectangular frame body that is self-standing and has a part of its outer surface as a bottom, a first membrane body that closes a first opening at one end side of the frame body in a depth direction; a second membrane body that closes a second opening on the other end side of the frame body in the depth direction; a sound absorbing material made of a porous material and arranged inside the frame body, the frame body includes a cylindrical first frame material that forms the first opening and a cylindrical second frame material that forms the second opening, and is formed by joining the first frame material and the second frame material, the first film and the second film are made of different materials; the first film body integrally covers the front end face and outer surface of the first frame member on the first opening side together with the first opening, and a peripheral edge portion is fixed to the back end face or inner surface of the first frame member, The second film integrally covers the front end face and outer surface of the second frame member on the second opening side together with the second opening, and a peripheral edge portion is fixed to the back end face or inner surface of the second frame member. A sound absorber characterized by:

2. A sound absorbing body that is installed in a room to adjust the sound environment of the room, a rectangular parallelepiped sound absorbing material made of a porous material; a first film covering a first side surface of the sound absorber; a second film body covering a second side surface of the sound absorber that faces the first side surface, The first film and the second film are made of different materials and are closed in a bag shape to cover the sound absorbing material. A sound absorber characterized by:

3. The sound absorber according to claim 1 or 2, The first membrane and the second membrane are configured to be distinguishable from each other. A sound absorber characterized by:

4. The sound absorber according to claim 1 or 2, The first membrane is made of woven fabric, The second film body is made of artificial leather. A sound absorber characterized by:

5. A sound environment adjusting structure for adjusting the sound environment in a room, A plurality of sound absorbers according to claim 1 or 2 are provided on a shelf installed in the room. A sound environment adjustment structure characterized by:

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