Sound absorption structure

Abstract

To provide a sound absorption structure that can reduce a diffraction sound of a high speed railway like a linear motor car.SOLUTION: A sound absorption structure 1 of the present invention comprises: a reflection member 10 having a sound source front surface part 10a placed so as to be opposed to a sound source 50 and a sound source back surface part 10b as an opposite surface side of the sound source front surface part 10a, and reflecting the sound generated from the sound source 50; and a first sound absorption material 20 provided at the sound source back surface part 10b of the reflection member 10.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a sound absorbing structure. [Background technology]

[0002] The sound generated by trains is reflected multiple times between the soundproof wall and the train, leaking outside the wall and becoming noise. As train speeds increase, the sound pressure of the sound source tends to increase, and applying conventional sound-absorbing panels makes noise control insufficient. In order to reduce the noise of high-speed trains such as the Shinkansen, sound-absorbing panels have been proposed as sound-absorbing structures with built-in reflectors, and have been put to practical use as soundproof walls on the side walls of viaducts (see, for example, Patent Document 1). The sound-absorbing panel with built-in reflector described in Patent Document 1 is extremely suitable for efficiently absorbing directional sounds with a fixed sound source direction, such as the sound of a passing train. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-188394 A Summary of the Invention [Problem to be solved by the invention]

[0004] With the opening of the linear motor car, a high-speed railway, there is a need to install new soundproofing walls on viaducts. The noise emitted by linear motor cars is characterized by a lower frequency than conventional high-speed railways, and the sound pressure level is also high, so conventional sound-absorbing panels were insufficient to prevent noise. In particular, the noise emitted by linear motor cars is low-frequency, so it is prone to diffracting sound that goes around soundproofing walls, etc., and measures against diffracted sound have been insufficient.

[0005] Therefore, an object of the present invention is to provide a sound absorbing structure capable of reducing diffracted noise from high speed trains such as linear motor cars which have a speed range exceeding that of the Shinkansen. [Means for solving the problem]

[0006] The present invention has been made to solve the above problems, and the gist of the present invention is as follows. [1] A sound-absorbing structure having a sound-source front portion arranged to face a sound source, and a sound-source rear portion that is the opposite side of the sound-source front portion, comprising a reflective member that reflects sound emitted from the sound source, and a first sound-absorbing material provided on the sound-source rear portion of the reflective member. [2] The sound-absorbing structure described in [1], further comprising a second sound-absorbing material provided on the sound source front portion of the reflecting member. [3] The sound absorbing structure described in [1] or [2], wherein the reflective member extends from the rear portion of the sound source toward the front portion of the sound source, is inclined in the direction of sound propagation emitted from the sound source, and has a plurality of reflective plates arranged approximately parallel to each other. [4] The sound-absorbing structure described in [3], wherein the reflecting member includes a third sound-absorbing material filling the space between the reflecting plates. [5] The sound absorbing structure according to any one of [1] to [4], wherein the sound source is aerodynamic noise caused by the running of a linear motor car. [6] The sound absorbing structure according to any one of [1] to [5], which is used for a soundproof wall and an air vent provided around the running path of a linear motor car. [7] The sound-absorbing structure described in any one of [1] to [6], wherein the first sound-absorbing material, the second sound-absorbing material and the third sound-absorbing material are at least one selected from the group consisting of glass wool, rock wool, felt and urethane foam. Effect of the Invention

[0007] According to the present invention, it is possible to provide a sound absorbing structure capable of reducing diffracted sound from high speed trains such as linear motor cars. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing a sound absorbing structure according to a first embodiment of the present invention. [Diagram 2]FIG. 2 is a schematic diagram showing a sound absorbing structure according to a first modified example of the first embodiment of the present invention. [Diagram 3] FIG. 2 is a schematic diagram showing a sound absorbing structure according to a second modified example of the first embodiment of the present invention. [Figure 4] FIG. 4 is a schematic diagram showing a sound absorbing structure according to a second embodiment of the present invention. [Diagram 5] FIG. 11 is a schematic diagram showing a sound absorbing structure according to a first modified example of the second embodiment of the present invention. [Figure 6] FIG. 11 is a schematic diagram showing a sound absorbing structure according to Modification 2 of the second embodiment of the present invention. [Figure 7] FIG. 2 is a schematic diagram showing an acoustic analysis model used for measuring sound transmission loss in the examples and comparative examples. [Figure 8] 1 is a graph showing the measurement results of sound transmission loss at observation point A (0°) in the sound absorbing structures of the examples and the comparative examples. [Figure 9] 1 is a graph showing the measurement results of sound transmission loss at observation point B (−30°) in the sound absorbing structures of the examples and the comparative examples. [Figure 10] 1 is a graph showing the measurement results of sound transmission loss at observation point C (−45°) in the sound absorbing structures of the examples and the comparative examples. [Figure 11] 1 is a graph showing the measurement results of sound transmission loss at observation point D (−60°) in the sound absorbing structures of Examples and Comparative Examples. [Figure 12] 1 is a graph showing the measurement results of sound transmission loss at observation point E (−90°) in the sound absorbing structures of Examples and Comparative Examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The present invention will be described in more detail below with reference to embodiments.

[0010] [First embodiment] As shown in FIG. 1, the sound-absorbing structure 1 according to the first embodiment of the present invention has a sound-source front portion 10a arranged to face a sound source 50, and a sound-source rear portion 10b which is the opposite side of the sound-source front portion 10a, and is equipped with a reflecting member 10 that reflects sound emitted from the sound source 50, and a first sound-absorbing material 20 provided on the sound-source rear portion 10b of the reflecting member 10.

[0011] (Reflective material) The reflecting member 10 is a member having a function of reflecting sound emitted from the sound source 50. The shape of the reflecting member 10 may be any shape as long as it has a function of reflecting sound emitted from the sound source 50, and may be, for example, a simple plate shape or a shape provided with a reflecting functional material, but from the viewpoint of good reflection efficiency and improved soundproofing effect, a shape provided with a reflecting functional material is preferable.

[0012] The thickness T1 of the reflecting member 10 is preferably 5 mm or more, more preferably 10 mm or more, and even more preferably 15 mm or more. When the thickness T1 of the reflecting member 10 is equal to or more than the above-mentioned lower limit, the reflecting member 10 can efficiently reflect the sound pressure of the sound emitted from the sound source 50 without being deformed. Moreover, the thickness T1 of the reflecting member 10 is preferably 200 mm or less, more preferably 150 mm or less, and even more preferably 100 mm or less. When the thickness T1 of the reflecting member 10 is equal to or less than the above-mentioned upper limit, the reflecting member 10 can contribute to space saving and weight reduction of the sound absorbing structure 1.

[0013] The height H of the reflecting member 10 is preferably 500 mm or more, more preferably 600 mm or more, and even more preferably 700 mm or more. When the height H of the reflecting member 10 is equal to or more than the above-mentioned lower limit, it is possible to reduce the wraparound of the sound emitted from the sound source 50. In addition, the height H of the reflecting member 10 is preferably 3,000 mm or less, more preferably 2,500 mm or less, even more preferably 2,000 mm or less, even more preferably 1,500 mm or less, and particularly preferably 1.000 mm or less. When the thickness T1 of the reflecting member 10 is equal to or less than the above-mentioned upper limit, it is possible to improve the handling property when installing the reflecting member 10.

[0014] When the reflecting member 10 is simply a plate, in order to easily reflect the sound emitted from the sound source 50, it is preferable to use a hard and heavy material such as a metal material, a resin material, or a stone material that does not deform due to sound pressure.

[0015] When the reflecting member 10 is shaped to have a reflecting function material, the reflecting function material may be shaped to have a plurality of reflecting plates 12 as shown in FIG. 1. The plurality of reflecting plates 12 may be shaped to be contained within a hollow first housing 11 having a sound source front part 10a and a sound source rear part 10b facing each other. The shape of the first housing 11 may be a rectangular parallelepiped, a cube, a cylinder, a regular tetrahedron, or other shapes. The material of the first housing 11 may be a material having rigidity and durability, and examples of such materials include metals such as iron, steel, and aluminum, and resins such as polyethylene, polypropylene, and polybutene.

[0016] <Reflector> The multiple reflecting plates 12 extend from the sound source rear part 10b toward the sound source front part 10a, are inclined toward the traveling direction of the sound emitted from the sound source 50, and are arranged approximately parallel to each other. By providing multiple reflecting plates 12, the sound undergoes multiple reflections between the reflecting plates 12, thereby attenuating the sound during multiple reflections and reducing the volume of diffracted sound going around the sound absorbing structure 1. In this specification, "approximately parallel" does not mean only parallel in the strict sense, but rather means allowing an angle that can change the direction of the multiple reflections of the sound. Usually, it is sufficient for adjacent reflectors to be within ±10° of each other.

[0017] The reflecting plates 12 are not particularly limited as long as they are inclined in the traveling direction of the sound emitted from the sound source 50 and at least two adjacent plates can be arranged substantially parallel to each other. As a means for fixing the reflector 12, for example, a fixing member (not shown) may be provided on the sound source back portion 10b, and a means for fixing the reflector 12 to the fixing member may be employed. By employing a means for fixing the reflector 12 to the fixing member, it becomes easy to set and maintain the inclination angle of the reflector 12. 1, when the lower end 12a of the reflector 12 is fixed to a fixing member provided on the sound source rear part 10b, the angle θ between the reflector 12 and the fixing member is preferably 10° to 65°, more preferably 12° to 55°, and even more preferably 15° to 45°. When the angle θ between the reflector 12 and the fixing member is within the above range, the reflector 12 is provided at a predetermined angle with respect to the sound source 50, and the reflection efficiency can be improved.

[0018] The thickness W of the reflector 12 is preferably 0.1 mm to 3.2 mm, more preferably 0.3 mm to 2.3 mm, and even more preferably 0.4 mm to 1.6 mm. By keeping the thickness W of the reflector 12 within the above range, the sound reflection function can be maintained while the weight can be reduced, and both sound reflection efficiency and weight reduction effects can be achieved.

[0019] The surface density of the reflector 12 is 0.05 g / cm 2 More than 7g / cm 2 It is preferable that: When the surface density of the reflector 12 is equal to or greater than the lower limit, the amount of sound reflected is increased, improving the reflection efficiency. When the surface density of the reflector 12 is equal to or less than the upper limit, the sound absorbing structure 1 can be made lighter.

[0020] The material of the reflector 12 may be a material having rigidity and durability, and examples of the material include metals such as iron, steel, and aluminum, resins such as polyethylene, polypropylene, and polybutene, and wooden plywood. Metals are preferable as the material of the reflector 12, and plated steel sheets such as highly corrosion-resistant plated steel sheets and hot-dip galvanized steel sheets are particularly preferable. Specific examples of highly corrosion-resistant plated steel sheets include Super Dyma steel sheets (registered trademark) and ZAM steel sheets (registered trademark). The reflector 12 may be coated with paint or the like to improve corrosion resistance.

[0021] (First sound absorbing material) The first sound-absorbing material 20 is provided on the sound-source back surface 10b of the reflecting member 10, and is capable of absorbing diffracted sound emitted from the sound source 50 and going around the reflecting member 10. The first sound-absorbing material 20 may be integrally molded or may be formed by appropriately combining parts that have been molded in separate parts. The first sound-absorbing material 20 may be provided on the sound-source rear surface portion 10b of the reflecting member 10 by, for example, attaching it with an adhesive or the like.

[0022] The thickness T2 of the first sound-absorbing material 20 is preferably 5 mm or more, more preferably 10 mm or more, and even more preferably 15 mm or more. When the thickness T2 of the first sound-absorbing material 20 is equal to or more than the above-mentioned lower limit, the efficiency of absorbing the diffracted sound emitted from the sound source 50 and going around the reflecting member 10 can be improved. Moreover, the thickness T2 of the first sound-absorbing material 20 is preferably 200 mm or less, more preferably 150 mm or less, and even more preferably 100 mm or less. When the thickness T2 of the first sound-absorbing material 20 is equal to or less than the above-mentioned upper limit, the sound-absorbing structure 1 can be made more compact and lightweight.

[0023] The coverage rate of the first sound-absorbing material 20 on the sound source back portion 10b is preferably 70% or more, more preferably 80% or more, even more preferably 90% or more, and particularly preferably 100%, from the viewpoint of improving the efficiency of absorbing diffracted sound emitted from the sound source 50 and passing around the reflecting member 10. The coverage rate of the first sound-absorbing material 20 on the sound source back portion 10b is the ratio of the area of ​​the first sound-absorbing material 20 to the entire area of ​​the sound source back portion 10b when the sound source back portion 10b is viewed in plan.

[0024] The material of the first sound-absorbing material 20 is not particularly limited, and examples thereof include dry materials such as glass wool, rock wool, felt, synthetic fibers, and metal fibers, and wet materials such as urethane foam and putty. The material of the first sound-absorbing material 20 may be a dry material or a wet material used alone. Of the dry materials, those that deform when they absorb moisture, such as glass wool, are preferably water-repellent.

[0025] The density of the dry material of the first sound absorbing material 20 is 16 kg / m 3 More than 64kg / m 3 It is preferable that the thickness is less than 20 kg / m 3 More than 48kg / m 3 More preferably, it is 24 kg / m or less. 3 More than 32kg / m 3 It is more preferable that the density of the dry material of the first sound-absorbing material 20 is within the above range, so that both the sound absorbing effect and the reduction in manufacturing costs can be achieved.

[0026] The density of the wet material of the first sound absorbing material 20 is 20 kg / m 3 More than 100kg / m 3 It is preferable that the thickness is less than 25 kg / m 3 More than 80kg / m 3 More preferably, it is 30 kg / m or less. 3 More than 60kg / m 3It is more preferable that the density of the wet material of the first sound-absorbing material 20 is within the above range, so that both the sound absorbing effect and the weight reduction of the sound absorbing structure can be achieved.

[0027] It is preferable that the first sound-absorbing materials 20 are each independently covered with either a water-repellent or waterproof cloth or film. By covering the first sound-absorbing materials 20 with either a water-repellent or waterproof cloth or film, it is possible to impart water-repellency or waterproofness to the first sound-absorbing materials 20, prevent deformation due to moisture absorption, and improve durability. In addition, by independently covering the first sound-absorbing materials 20, it is possible to prevent the sound-absorbing materials from scattering, and it becomes easy to control the density, thickness, etc. of the first sound-absorbing materials 20. The glass cloth is not particularly limited, but it is preferable that the density and thickness are within the range of EP12D equivalent to EP18B equivalent (JIS R 3414:2012) in order to balance the sound absorbing performance and the shatterproof performance.

[0028] The sound absorbing structure according to the first embodiment can be used in an environment where the sound source is a low frequency and generates noise as diffracted sound that goes around the sound absorbing structure. For example, the sound absorbing structure can be suitably used for soundproof walls and ventilation openings provided around the running path of a linear motor car, where the sound source is aerodynamic noise caused by the running of the linear motor car.

[0029] According to the sound absorbing structure of the first embodiment, by providing a reflective member, sound emitted from a sound source can be reflected back toward the sound source, thereby reducing noise that leaks outside the sound absorbing structure where it is installed. Furthermore, according to the sound absorbing structure of the first embodiment, the first sound absorbing material is provided on the sound source rear part of the reflecting member, so that the diffracted sound that has gone around the reflecting member can be absorbed. In particular, when the sound source is aerodynamic sound caused by the running of a linear motor car, the aerodynamic sound is a low frequency sound that goes around the sound absorbing structure and becomes noise, but the noise can be reduced by absorbing the diffracted sound with the first sound absorbing material provided on the sound source rear part of the reflecting member.

[0030] [Modification 1 of the first embodiment] As a first modified example of the first embodiment, when the reflecting member 10 is provided with reflecting plates 12 as shown in FIG. 2, it may be provided with a third sound-absorbing material 13 that fills the space between the reflecting plates 12. In the case of a configuration including the third sound-absorbing material 13, the means for fixing the reflector 12 may be, for example, a means for fixing the reflector 12 by using the filled third sound-absorbing material 13.

[0031] (The third sound absorbing material) The material of the third sound-absorbing material 13 is not particularly limited, and examples thereof include dry materials such as glass wool, rock wool, felt, synthetic fiber, and metal fiber, and wet materials such as urethane foam and putty. The material of the third sound-absorbing material 13 may be a dry material or a wet material used alone. Of the dry materials, those that deform when they absorb moisture, such as glass wool, are preferably water-repellent.

[0032] The density of the dry material of the third sound absorbing material 13 is 16 kg / m 3 More than 64kg / m 3 It is preferable that the thickness is less than 20 kg / m 3 More than 48kg / m 3 More preferably, it is 24 kg / m or less. 3 More than 32kg / m 3 It is more preferable that the density of the dry material of the third sound-absorbing material 13 is within the above range, so that both the sound absorbing effect and the reduction in manufacturing costs can be achieved.

[0033] The density of the wet material of the third sound absorbing material 13 is 20 kg / m 3 More than 100kg / m 3 It is preferable that the thickness is less than 25 kg / m 3 More than 80kg / m 3 More preferably, it is 30 kg / m or less. 3 More than 60kg / m 3It is even more preferable that the density of the wet material of the third sound-absorbing material 13 is within the above range, so that both the sound absorbing effect and the weight reduction of the sound absorbing structure can be achieved.

[0034] It is preferable that the third sound-absorbing material 13 is covered independently with either a water-repellent or waterproof cloth or film. By covering the third sound-absorbing material 13 with either a water-repellent or waterproof cloth or film, the third sound-absorbing material 13 can be given water-repellent or waterproof properties, deformation due to moisture absorption can be prevented, and durability can be improved. In addition, by covering the third sound-absorbing material 13 independently, scattering of the sound-absorbing material can be prevented, and it becomes easy to control the density, thickness, etc. of the third sound-absorbing material 13. The glass cloth is not particularly limited, but it is preferable that the density and thickness are within the range of EP12D equivalent to EP18B equivalent (JIS R 3414:2012) in order to balance the sound absorbing performance and the shatterproof performance.

[0035] [Modification 2 of the first embodiment] As a second modification of the first embodiment, as shown in FIG. 3, a first sound absorbing material 20 may be provided inside a second housing 21. In the second modification, as shown in FIG. When the first sound-absorbing material 20 is disposed within the second housing 21, means for providing the first sound-absorbing material 20 to the sound source rear portion 10b of the reflecting member 10 include, for example, a means for fixing the second housing 21 to the sound source rear portion 10b using a fixing member such as an adhesive and a screw.

[0036] (Second housing) The shape of the second housing 21 is a hollow shape capable of housing the first sound-absorbing material 20 therein, and may be a rectangular parallelepiped, cube, cylinder, regular tetrahedron, or any other shape.

[0037] The surface constituting the second housing 21 is preferably provided with a large number of through holes, and examples of such materials include wire mesh, punched metal, and louvers. The surface constituting the second housing 21 is preferably a perforated plate such as punched metal with a large number of through holes, from the viewpoint of improving the absorption effect and obtaining rigidity and durability. The shape of the through holes may be any of a round hole, a square hole, and an elongated hole. By providing a large number of through holes on the surface constituting the second housing 21, the sound from the sound source 50 can easily enter the second housing 21, and the sound that enters the second housing 21 is absorbed by the first sound-absorbing material 20, thereby improving the sound absorption effect against the noise from the sound source 50.

[0038] The material of the second housing 21 may be a material having rigidity and durability, and examples of the material include metals such as iron, steel, and aluminum, resins such as polyethylene, polypropylene, and polybutene, and wooden plywood. Metals are preferred as the material of the second housing 21, and plated steel sheets such as highly corrosion-resistant plated steel sheets and hot-dip galvanized steel sheets are particularly preferred. Specific examples of highly corrosion-resistant plated steel sheets include Superdyma steel sheets (registered trademark) and ZAM (registered trademark) steel sheets. The second housing 21 may be coated with paint or the like to improve corrosion resistance.

[0039] The thickness of second housing 21 is preferably 0.8 mm or more and 9.0 mm or less, more preferably 1.2 mm or more and 6.0 mm or less, and even more preferably 1.6 mm or more and 4.5 mm or less. When the thickness of second housing 21 is within the above range, it has rigidity and durability, and can contribute to weight reduction.

[0040] [Second embodiment] The second embodiment differs from the first embodiment in that it further includes a second sound-absorbing material 30 provided on the sound source front portion 10a of the reflecting member 10, as shown in Fig. 4. The differences between the first embodiment and the second embodiment will be described below. In the following description of different embodiments, the same reference numerals will be used to designate members having the same configuration.

[0041] (Second sound absorbing material) The second sound-absorbing material 30 is provided on the sound source front portion 10a of the reflecting member 10, and is capable of absorbing sound emitted from the sound source 50 and sound reflected by the reflecting member 10. The second sound-absorbing material 30 may be integrally molded or may be formed by appropriately combining parts that have been molded in separate parts. The second sound absorbing material 30 may be provided on the sound source front portion 10a of the reflecting member 10 by, for example, attaching it with an adhesive or the like.

[0042] The thickness T3 of the second sound-absorbing material 30 is preferably 5 mm or more, more preferably 10 mm or more, and even more preferably 15 mm or more. When the thickness T3 of the second sound-absorbing material 30 is equal to or more than the above-mentioned lower limit, the efficiency of absorbing the sound emitted from the sound source 50 and the sound reflected by the reflecting member 10 can be improved. Moreover, the thickness T3 of the second sound-absorbing material 30 is preferably 200 mm or less, more preferably 150 mm or less, and even more preferably 100 mm or less. When the thickness T3 of the second sound-absorbing material 30 is equal to or less than the above-mentioned upper limit, it can contribute to saving space and reducing the weight of the sound-absorbing structure 1. The thickness T3 of the second sound-absorbing material 30 may be the same as the thickness T2 of the first sound-absorbing material 20, or may be different.

[0043] The coverage rate of the second sound-absorbing material 30 on the sound source front portion 10a is preferably 70% or more, more preferably 80% or more, even more preferably 90% or more, and particularly preferably 100%, from the viewpoint of improving the efficiency of absorbing the sound emitted from the sound source 50 and the sound reflected by the reflecting member 10. The coverage rate of the second sound-absorbing material 30 on the sound-source front portion 10a is the ratio of the area of ​​the second sound-absorbing material 30 to the area of ​​the entire sound-source front portion 10a when the sound-source rear portion 10b is viewed in plan.

[0044] The material of the second sound-absorbing material 30 is not particularly limited, and examples thereof include dry materials such as glass wool, rock wool, felt, synthetic fiber, and metal fiber, and wet materials such as urethane foam and putty. The material of the second sound-absorbing material 30 may be a dry material or a wet material used alone. Of the dry materials, those that deform when they absorb moisture, such as glass wool, are preferably water-repellent.

[0045] The density of the dry material of the second sound absorbing material 30 is 16 kg / m 3 More than 64kg / m 3 It is preferable that the thickness is less than 20 kg / m 3 More than 48kg / m 3 More preferably, it is 24 kg / m or less. 3 More than 32kg / m 3 It is even more preferable that the density of the dry material of the second sound-absorbing material 30 is within the above range, thereby making it possible to achieve both a good sound absorbing effect and reduced manufacturing costs.

[0046] The density of the wet material of the second sound absorbing material 30 is 20 kg / m 3 More than 100kg / m 3 It is preferable that the thickness is less than 25 kg / m 3 More than 80kg / m 3 More preferably, it is 30 kg / m or less. 3 More than 60kg / m 3 It is even more preferable that the density of the wet material of the second sound-absorbing material 30 is within the above range, so that both the sound absorbing effect and the weight reduction of the sound absorbing structure can be achieved.

[0047] It is preferable that the second sound-absorbing materials 30 are each independently covered with either a water-repellent or waterproof cloth or film. By covering the second sound-absorbing materials 30 with either a water-repellent or waterproof cloth or film, the second sound-absorbing materials 30 can be imparted with water-repellent or waterproof properties, and deformation due to moisture absorption can be prevented, and durability can be improved. In addition, by independently covering the second sound-absorbing materials 30, scattering of the sound-absorbing materials can be prevented, and it becomes easy to control the density, thickness, etc. of the second sound-absorbing materials 30. The glass cloth is not particularly limited, but it is preferable that the density and thickness are within the range of EP12D equivalent to EP18B equivalent (JIS R 3414:2012) in order to balance the sound absorbing performance and the shatterproof performance.

[0048] The sound absorbing structure according to the second embodiment can achieve the same effects as the sound absorbing structure according to the first embodiment. Moreover, the sound absorbing structure according to the second embodiment can absorb the sound emitted from the sound source 50 and the sound reflected by the reflecting member 10 by providing the second sound absorbing material on the sound source front portion of the reflecting member 10, thereby further reducing noise.

[0049] [Modification 1 of the second embodiment] As a first modified example of the second embodiment, as shown in FIG. 5, when the reflecting member 10 is provided with reflecting plates 12, it may be provided with a third sound-absorbing material 13 that fills the space between the reflecting plates 12. In the case of a configuration including the third sound-absorbing material 13, the means for fixing the reflector 12 may be, for example, a means for fixing the reflector 12 by using the filled third sound-absorbing material 13.

[0050] [Modification 2 of the second embodiment] As a second modification of the second embodiment, as shown in FIG. 6, a second sound absorbing material 30 may be provided inside a third housing 31. In the second modification, as shown in FIG. When the second sound-absorbing material 30 is disposed within the third housing 31, a means for providing the second sound-absorbing material 30 to the sound source front portion 10a of the reflecting member 10 may be, for example, a means for fixing the third housing 31 to the sound source front portion 10a using a fixing member such as an adhesive and a screw.

[0051] (Third housing) The shape of the third housing 31 is a hollow shape capable of housing the second sound-absorbing material 30 therein, and may be a rectangular parallelepiped, cube, cylinder, regular tetrahedron, or any other shape.

[0052] The surface constituting the third housing 31 is preferably provided with a large number of through holes, and examples thereof include wire mesh, punched metal, and louvers. The surface constituting the third housing 31 is preferably a perforated plate such as punched metal with a large number of through holes, from the viewpoint of improving the absorption effect and obtaining rigidity and durability. The shape of the through holes may be any of a round hole, a square hole, and a long hole. By providing a large number of through holes on the surface constituting the third housing 31, the sound from the sound source 50 does not easily enter the third housing 31, and the sound that enters the third housing 31 is absorbed by the second sound-absorbing material 30, and the sound absorption effect against the noise from the sound source 50 can be improved.

[0053] The material of the third housing 31 may be a material having rigidity and durability, and examples of the material include metals such as iron, steel, and aluminum, resins such as polyethylene, polypropylene, and polybutene, and wooden plywood. Metals are preferred as the material of the third housing 31, and plated steel sheets such as highly corrosion-resistant plated steel sheets and hot-dip galvanized steel sheets are particularly preferred. Specific examples of highly corrosion-resistant plated steel sheets include Superdyma steel sheets (registered trademark) and ZAM (registered trademark) steel sheets. The third housing 31 may be coated with paint or the like to improve corrosion resistance.

[0054] The thickness of the third housing 31 is preferably 0.8 mm or more and 9.0 mm or less, more preferably 1.2 mm or more and 6.0 mm or less, and even more preferably 1.6 mm or more and 4.5 mm or less. When the thickness of the third housing 31 is within the above range, it has rigidity and durability, and can contribute to weight reduction. EXAMPLES

[0055] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0056] (Measurement of sound transmission loss) The sound transmission loss of the sound absorbing structures according to the examples and the comparative examples was measured using an acoustic analysis using a general-purpose structural analysis solver ("Abaqus" manufactured by HKS) as analysis software (CAE). Specifically, the sound transmission loss of the sound absorbing structures according to the examples and the comparative examples was measured using an acoustic analysis model in which the far boundary is a semicircle with a diameter of 15 m as shown in FIG. 7. In the acoustic analysis model, the sound absorbing structures 1 according to the examples and the comparative examples were placed at a point 0.6 m away from the sound source 50, and a sound with a sound pressure of 100 dB was generated from the sound source 50. The acoustic intensity was measured at observation points A (0°), B (-30°), C (-45°), D (-60°), and E (-90°) 15 m away, and the sound transmission loss for each 1 / 3 octave band was calculated. The results of the sound transmission loss measured and calculated at observation points A to E are shown in FIGS. 8 to 12, respectively. In the acoustic analysis model, the sound absorbing structure 1 and the surface on which the sound absorbing structure 1 is placed are assumed to completely reflect sound, and no sound is transmitted.

[0057] [Example 1] As Example 1, a sound absorbing structure including a reflecting member and a first sound absorbing material provided on the rear surface of the reflecting member to a sound source as shown in FIG. 1 was prepared. The reflective member is a first housing (zinc-based alloy plated steel sheet, manufactured by Nippon Steel Corporation, product name "ZAM (registered trademark) steel sheet") having a thickness T1 of 50 mm and a height H of 850 mm, and the first housing is provided with a plurality of reflective plates (zinc-based alloy plated steel sheet, manufactured by Nippon Steel Corporation, product name "ZAM (registered trademark) steel sheet") inside. The surface density of the reflective plate is 0.31 g / cm 2 The thickness of the reflector was 0.4 mm, and the angle with the fixing member was 23°. The first sound-absorbing material (glass wool, manufactured by Mag-Isobel Co., Ltd.) had a thickness T2 of 100 mm. The density of the first sound-absorbing material was 32 kg / m 3 It was decided.

[0058] [Example 2] As Example 2, a sound absorbing structure was prepared, as shown in Figure 4, which included a reflecting member, a first sound absorbing material provided on the back side of the reflecting member facing the sound source, and a second sound absorbing material provided on the front side of the reflecting member facing the sound source. The reflective member is a first housing (zinc-based alloy plated steel sheet, manufactured by Nippon Steel Corporation, product name "ZAM (registered trademark) steel sheet") having a thickness T1 of 50 mm and a height H of 850 mm, and the first housing is provided with a plurality of reflective plates (zinc-based alloy plated steel sheet, manufactured by Nippon Steel Corporation, product name "ZAM (registered trademark) steel sheet") inside. The surface density of the reflective plate is 0.31 g / cm 2 The thickness of the reflector was 0.4 mm, and the angle with the fixing member was 23°. The first sound-absorbing material (glass wool, manufactured by Mag-Isobel Co., Ltd.) had a thickness T2 of 50 mm. The density of the first sound-absorbing material was 32 kg / m 3 It was decided. The second sound-absorbing material (glass wool, manufactured by Mag-Isobel Co., Ltd.) had a thickness T3 of 50 mm. The density of the second sound-absorbing material was 32 kg / m 3 It was decided.

[0059] [Comparative Example 1] A sound absorbing structure was produced in the same manner as in Example 1, except that the first sound absorbing material was provided on the sound source front portion of the reflecting member, and the sound transmission loss was calculated.

[0060] In Example 1, by providing a reflector and a first sound-absorbing material, the sound transmission loss results were better than those of Comparative Example 1 at observation points D and E, and an excellent soundproofing effect was achieved. In other words, the results of Example 1 and Comparative Example 1 show that the diffraction sound reduction effect was greater than the reverberation sound reduction effect of the sound source and the sound absorbing structure at observation points D and E. In Example 2, by providing a reflector, a first sound-absorbing material, and a second sound-absorbing material, the sound transmission loss results were all good at observation points A to E, and in addition to the reverberation sound between the sound source and the sound absorbing structure, it became possible to effectively reduce the diffraction sound that explains the sound absorbing structure, and an excellent soundproofing effect was achieved. [Explanation of symbols]

[0061] 1. Sound-absorbing structure 10 Reflective material 10a Sound source front section 10b Sound source rear part 11 First Case 12 Reflector 13 The third sound-absorbing material 20 The first sound absorbing material 21 Second Case 30 Second Sound-Absorbing Material 50 Sound Sources

Claims

1. a reflecting member having a sound source front portion disposed to face a sound source and a sound source rear portion on the opposite side of the sound source front portion, the reflecting member reflecting a sound emitted from the sound source; a first sound-absorbing material provided on the sound source rear surface of the reflecting member.

2. The sound absorbing structure according to claim 1 , further comprising a second sound absorbing material provided on the sound source front portion of the reflecting member.

3. 3. The sound absorbing structure according to claim 1, wherein the reflecting member extends from the rear portion of the sound source toward the front portion of the sound source, is inclined in the direction of sound propagation emitted from the sound source, and comprises a plurality of reflecting plates arranged approximately parallel to each other.

4. 4. The sound absorbing structure of claim 3, wherein the reflecting member comprises a third sound absorbing material filling the spaces between the reflecting plates.

5. 3. The sound absorbing structure according to claim 1, wherein the sound source is aerodynamic noise generated by a linear motor car running.

6. 3. The sound absorbing structure according to claim 1, which is used for a soundproof wall and an air vent provided around a running path of a linear motor car.

7. 3. The sound absorbing structure according to claim 1, wherein the first sound absorbing material, the second sound absorbing material and the third sound absorbing material are at least one selected from the group consisting of glass wool, rock wool, felt and urethane foam.

Images