JP2010061078A - Sound absorbing structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent degradation in sound absorbing performance. <P>SOLUTION: A perforated plate 6 is pinched by a plurality of first ribs 2b provided in parallel on a side facing a second frame 3 of a first frame 2, and a plurality of second ribs 3b provided in parallel on a side facing the first frame 2 of the second frame 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sound absorbing structure that reduces sound from a noise source.

  Conventionally, in a sound absorbing structure, a perforated plate having a large number of through holes and a plate not having a through hole are arranged to oppose each other to absorb the sound at the resonance frequency using the Helmholtz resonance principle and pass through the through hole. Some of them are configured to absorb a wide range of frequencies by producing a viscous damping effect on the air.

  Patent Document 1 discloses a sound absorbing structure having a configuration in which a perforated plate is sandwiched between each of a plurality of frame members provided inside a box member. According to this configuration, the four sides of the perforated plate are held back and forth in the traveling direction in which the sound from the sound source travels.

JP 2008-138505 A

  However, as in Patent Document 1, when the four sides of the perforated plate are sandwiched by the frame member, the portion of the perforated plate that is not sandwiched by the frame member is moved forward and backward in the sound traveling direction by the sound pressure. There is a problem that the sound absorption performance deteriorates.

  An object of the present invention is to provide a sound absorbing structure capable of preventing a decrease in sound absorbing performance.

Means and effects for solving the problems

  The sound absorbing structure of the present invention is a sound absorbing structure that absorbs sound from a sound source, wherein a box member having a space formed therein and having a porous surface with a plurality of through holes, and the inside of the box member A first frame and a second frame disposed opposite to each other, and a porous plate provided between the first frame and the second frame and having a number of through holes. The first frame body includes a first frame body and a plurality of first ribs arranged in parallel at a predetermined interval on a side of the first frame body facing the second frame body. And the second frame body includes a second frame main body and a plurality of second ribs arranged in parallel at a predetermined interval on a side of the second frame main body facing the first frame body. The perforated plate is sandwiched between the first rib and the second rib.

  According to the above configuration, the porous plate is held between the plurality of first ribs and the plurality of second ribs, so that the plurality of portions of the porous plate are held. The vibration of the plate is suppressed. Thereby, the fall of sound absorption performance can be prevented.

  In the sound absorbing structure of the present invention, the first rib and the second rib may be arranged at positions that do not face each other. According to said structure, the 1st rib and the 2nd rib are arrange | positioned in the position which does not mutually oppose, and it partitions off with the space partitioned off with 1st ribs, and 2nd ribs The space formed is shifted in the direction in which the ribs are juxtaposed. Here, in the space partitioned by the first ribs and the space partitioned by the second ribs, resonance phenomena occur in directions orthogonal to the direction in which the sound travels. However, since the space partitioned by the first ribs and the space partitioned by the second ribs are shifted in the direction in which the ribs are juxtaposed, the two are communicated with the perforated plate interposed therebetween. The resonance phenomenon is alleviated. Thereby, the sound absorption performance can be further improved.

  Further, in the sound absorbing structure of the present invention, the first frame body has first side walls at both ends of the first frame body facing the second frame body, When the perforated plate is sandwiched between the first rib and the second rib at both ends of the second frame body on the side facing the first frame, the second frame body The first rib may be longer in the direction perpendicular to the perforated plate than the first side wall. According to said structure, since the length of the 1st rib in the direction orthogonal to a perforated plate is longer than a 1st side wall, a perforated plate is pinched by the 1st rib and the 2nd rib, When the second side wall comes into contact with the first side wall, the perforated plate is deformed into a wave shape along the parallel arrangement direction of the ribs by the first rib. Thereby, since tension | tensile_strength arises in a perforated panel in the front-end | tip of a 1st rib, the vibration of a perforated panel can be suppressed further. Moreover, since the surface area facing the sound is increased by deforming the perforated plate into a wave shape by the first rib, the sound absorbing performance can be further improved.

  In the sound absorbing structure of the present invention, the length of the second rib in a direction orthogonal to the perforated plate may be longer than that of the second side wall. According to the above configuration, since the second rib is longer in the direction orthogonal to the porous plate than the second side wall, the porous plate is sandwiched between the first rib and the second rib, When the second side wall comes into contact with the first side wall, the perforated plate is further deformed in a wavy shape along the parallel arrangement direction of the ribs by the second rib. Thereby, since tension | tensile_strength arises in a perforated plate in the front-end | tip of a 2nd rib, the vibration of a perforated plate can be suppressed further. Further, since the perforated plate is deformed in a wave shape by the first rib and the second rib, the surface area facing the sound is further increased, so that the sound absorbing performance can be further improved.

  In the sound absorbing structure of the present invention, the first rib and / or the second rib may be arranged in parallel at random intervals. According to said structure, the 1st rib and / or the 2nd rib are arranged in parallel by the random space | interval, By the space partitioned by 1st ribs, and / or 2nd ribs, The partitioned space has a plurality of different sizes. Thereby, since the number of resonance frequencies that can be absorbed by the Helmholtz resonance principle increases, it is possible to absorb a wide range of frequencies.

  The sound absorbing structure of the present invention further includes one or more third frames provided between the first frame and the second frame, and the third frame. A third frame main body, a plurality of the first ribs arranged in parallel at a predetermined interval on a side of the third frame main body facing the second frame body, and the third frame main body A plurality of the second ribs arranged in parallel at a predetermined interval on the side facing the first frame body, and the plurality of the perforated plates, and sandwiching one perforated plate When the first rib and the second rib are a pair of ribs, each may be sandwiched between a pair of different ribs. According to said structure, the number of perforated plates can be increased / decreased easily by increasing / decreasing the number of 3rd frame bodies.

  In the sound absorbing structure of the present invention, the first frame body and the second frame body may be formed of a non-conductor. According to said structure, the electrolytic corrosion of the perforated plate pinched by the 1st rib and the 2nd rib is prevented by forming the 1st frame and the 2nd frame with a non-conductor. can do.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a configuration diagram of a sound absorbing structure 10 according to the first embodiment of the present invention. As shown in FIG. 1, the sound absorbing structure 10 of the present embodiment has a box member 1 in which a space is formed. The box member 1 has a porous surface 1b having a large number of through holes 1a on the sound source side with respect to the traveling direction of the sound from the sound source indicated by the arrow, and penetrates on the opposite side to the sound source side. It has the obstruction | occlusion surface 1c which does not have a hole. In addition, although the box member 1 of this Embodiment does not have many through-holes in a side surface, you may have many through-holes in a side surface. Further, the box member 1 is not limited to the configuration having the porous surface 1b on the sound source side.

  The sound absorbing structure 10 has a first frame body 2 and a second frame body 3 that are disposed to face each other inside the box member 1. In the sound absorbing structure 10 of the present embodiment, the first frame 2 is disposed on the sound source side, and the second frame 3 is disposed on the side opposite to the sound source side.

  The first frame body 2 includes a plurality of first frame bodies 2a arranged in parallel on the first frame body 2a and the side of the first frame body 2a facing the second frame body 3 (the side opposite to the sound source side). Rib 2b. In the present embodiment, the first rib 2b has a rectangular parallelepiped shape, the short direction of the first frame body 2a is the longitudinal direction, and the long direction of the first frame body 2a is the short direction, They are arranged at random intervals in the short direction. Each of the first ribs 2b is connected to each other by an intermediate rib 2c provided in parallel to the longitudinal direction of the first frame body 2a. In addition, a transversal direction is a direction orthogonal to a longitudinal direction. Further, the first rib 2b may be plate-shaped.

  The second frame 3 includes a second frame main body 3a and a plurality of second ribs 3b arranged in parallel on the side (sound source side) of the second frame main body 3a facing the first frame 2. have. In the present embodiment, the second rib 3b has a rectangular parallelepiped shape like the first rib 2b, the short direction of the second frame body 3a is the longitudinal direction, and the second frame body 3a The longitudinal direction is taken as the short direction, and they are arranged in parallel at random intervals in the short direction. Each of the 2nd rib 3b is mutually connected by the intermediate rib 3c provided in parallel with the longitudinal direction of the 2nd frame main body 3a. The second rib 3b may be plate-shaped.

  The sound absorbing structure 10 has a porous plate 6 provided between the first frame 2 and the second frame 3. The perforated plate 6 has a large number of through holes 6a on the entire surface. The perforated plate 6 is sandwiched between the first rib 2b and the second rib 3b. Specifically, the porous plate 6 is in a state in which tension is applied to both sides of the porous plate 6 while both ends are fixed, so that the first rib 2b and the second rib 3b It is held by.

  The first frame 2 has first side walls 2d at both ends of the first frame body 2a facing the second frame 3, and the second frame 3 is A second side wall 3d is provided at both ends of the second frame main body 3a on the side facing the first frame 2. The second side wall 3d is configured to come into contact with the first side wall 2d through the perforated plate 6 when the perforated plate 6 is sandwiched between the first rib 2b and the second rib 3b. .

  The through hole 1a of the porous surface 1b and the through hole 6a of the porous plate 6 are formed in a circular shape by punching, embossing, or any other process. The through holes 1a and 6a are not limited to a circular shape, and may be a slit shape. The diameter of the through hole 1 a of the porous surface 1 b is slightly larger than the diameter of the through hole 6 a of the porous plate 6.

  Here, the perforated plate 6 and the box member 1 are formed of a metal such as iron or aluminum, a synthetic resin, a fiber reinforced composite material, or the like. The perforated plate 6 and the box member 1 are preferably formed of the same material so that the separation process at the time of recycling is unnecessary. In the present embodiment, the perforated plate 6 and the box member 1 are formed of steel plates (for example, highly weather-resistant plated steel plates). Thereby, the manufacturing cost of the porous plate 6 and the box member 1 can be suppressed low.

  Moreover, although the porous plate 6, the porous surface 1b, and the obstruction | occlusion surface 1c have a rectangular flat plate shape, you may have a plane of circular shape, elliptical shape, and a triangular shape, for example. Further, the porous plate 6 may be a thin film instead of a flat plate, and for example, a metal thin film such as aluminum foil or a resin thin film such as vinyl chloride can be applied.

  Moreover, the 1st frame 2 and the 2nd frame 3 are formed with resin which is a nonconductor. Specifically, in the first frame 2, the first frame body 2a, the first rib 2b, the first side wall 2d, and the intermediate rib 2c are integrally formed of resin. The same applies to the second frame 3. Thereby, the electrolytic corrosion of the porous plate 6 pinched by the 1st rib 2b and the 2nd rib 3b can be prevented. In addition, the 1st frame 2 and the 2nd frame 3 may be formed with non-conductors other than resin.

  As shown in FIG. 2 which is an AA cross-sectional view of FIG. 1, the inside of the box member 1 is divided into a plurality of spaces by a perforated plate 6, first ribs 2b, and second ribs 3b. Yes. Specifically, the inside of the box member 1 includes a plurality of spaces 11a partitioned by two adjacent first ribs 2b, a porous surface 1b, and a porous plate 6, and two adjacent second ribs 3b. It is divided into a plurality of spaces 11b partitioned by the closed surface 1c and the perforated plate 6. These spaces 11a and 11b are configured to absorb the sound of the resonance frequency by the Helmholtz resonance principle. And the sound which passed the porous surface 1b advances the inside of the box member 1 by the frequency below the frequency which makes the space | interval of the 1st rib 2b or the space | interval of the 2nd rib 3b a half wavelength. become. Thereby, the spread of the sound after passing through the porous plate 6 is prevented.

  In addition, an air layer 12a is formed between the porous surface 1b and the porous plate 6, and an air layer 12b is formed between the porous plate 6 and the closing surface 1c. The parameters including the layer thicknesses d1 and d2 of the air layers 12a and 12b, the aperture ratios β1 and β2 of the porous surface 1b and the porous plate 6, the plate thicknesses t1 and t2, and the diameters φ1 and φ2 of the through holes 1a and 6a are porous. It is set so as to produce a viscous action on the air passing through the surface 1b and the through holes 1a, 6a of the porous plate 6. As a result, when a viscous damping action occurs in the air passing through the through holes 1a and 6a, the air vibration is converted into thermal energy, resulting in a damping property of the air vibration. As a result, a high sound absorption effect in a relatively wide frequency band. Will be demonstrated.

  Here, since the porous plate 6 is sandwiched by the plurality of first ribs 2b and the plurality of second ribs 3b, a plurality of portions of the porous plate 6 are sandwiched. The vibration of the plate 6 is suppressed. Thereby, the fall of sound absorption performance can be prevented.

  As shown in FIG. 2, the first rib 2b and the second rib 3b are provided at positions that do not face each other. Therefore, the space partitioned by the first ribs 2b (the space partitioned by the two adjacent first ribs 2b, the porous surface 1b and the porous plate 6) 11a and the second ribs 3b are partitioned. The space 11b (space partitioned by the two adjacent second ribs 3b, the blocking surface 1c, and the perforated plate 6) is shifted in the rib parallel direction. Thereby, the space 11a partitioned by the first ribs 2b and the space 11b partitioned by the second ribs 3b communicate with each other with the perforated plate 6 interposed therebetween.

  Here, in the space 11a partitioned by the first ribs 2b and the space 11b partitioned by the second ribs 3b, a resonance phenomenon occurs in a direction orthogonal to the direction in which the sound proceeds. However, since the space 11a partitioned by the first ribs 2b and the space 11b partitioned by the second ribs 3b are shifted in the direction in which the ribs are juxtaposed, the both sandwich the porous plate 6 therebetween. The resonance phenomenon is alleviated because of the communication. Thereby, the sound absorption performance can be further improved.

  Further, the length h1 of the first rib 2b in the direction orthogonal to the perforated plate 6 is longer than the length h3 of the first side wall 2d. Similarly, the length h2 of the second rib 3b in the direction orthogonal to the perforated plate 6 is longer than the length h4 of the second side wall 3d. For this reason, when the porous plate 6 is sandwiched between the first rib 2b and the second rib 3b, and the second side wall 3d comes into contact with the first side wall 2d via the porous plate 6, the porous plate 6 6 is deformed into a wave shape along the direction in which the ribs are juxtaposed. Thereby, tension is generated in the porous plate 6 at the tip of the first rib 2b, and tension is generated in the porous plate 6 at the tip of the second rib 3b, so that vibration of the porous plate 6 can be further suppressed. Moreover, since the surface area which opposes a sound is increased because the perforated plate 6 is deformed in a wave shape, the sound absorbing performance can be further improved.

  In the present embodiment, the length h1 of the first rib 2b is longer than the length h3 of the first side wall 2d, and the length h2 of the second rib 3b is equal to the length of the second side wall 3d. Although the length h1 is longer than the length h4, the length h1 of the first rib 2b is longer than the length h3 of the first side wall 2d, whereas the length h2 of the second rib 3b is longer. May be the same as or shorter than the length of the second side wall 3d. Similarly, the length h2 of the second rib 3b is longer than the length h4 of the second side wall 3d, whereas the length h1 of the first rib 2b is equal to the length of the first side wall 2d. It may be the same as the length or may be shortened.

  Further, as shown in FIG. 2, the first ribs 2b are arranged in parallel at random intervals. Specifically, the first ribs 2b are arranged in the order of the interval a, the interval b, and the interval a. On the other hand, the 2nd rib 3b is arranged in parallel by the fixed space | interval c. For this reason, the space 11a partitioned by the first ribs 2b has a plurality of different sizes.

  Here, the resonance frequency that can be absorbed by the Helmholtz resonance principle is determined by the size of the space 11a partitioned by the first ribs 2b and the size of the space 11b partitioned by the second ribs 3b. For this reason, since the space 11a partitioned by the first ribs 2b has a plurality of different sizes, the number of resonance frequencies that can be absorbed by the Helmholtz resonance principle increases, so that sounds of a wide range of frequencies are absorbed. be able to.

  Note that the second ribs 3b may also be arranged in parallel at random intervals, similarly to the first ribs 2b. In this case, since the space 11b partitioned by the second ribs 3b has a plurality of different sizes, the number of resonance frequencies that can be absorbed by the Helmholtz resonance principle is further increased. Can absorb sound.

  FIG. 3 is a graph showing the sound absorption rate of the sound absorbing structure 10 according to the present embodiment and the sound absorbing structure having a conventional configuration. From FIG. 3, it can be seen that the decrease in the sound absorption coefficient is suppressed around the frequency of 1000 Hz.

[Outline of First Embodiment]
As described above, the sound absorbing structure 10 according to the present embodiment is a sound absorbing structure 10 that absorbs sound from a sound source. The sound absorbing structure 10 includes a porous surface 1b that has a space therein and includes a large number of through holes 1a. Provided between the first frame body 2 and the second frame body 3, the first frame body 2 and the second frame body 3 disposed opposite to each other inside the box member 1. The first frame body 2 is a side opposite to the first frame body 2a and the second frame body 3 of the first frame body 2a. And a plurality of first ribs 2b arranged in parallel at a predetermined interval, and the second frame body 3 includes a second frame body 3a and a first frame body 2 of the second frame body 3a. And a plurality of second ribs 3b arranged in parallel at a predetermined interval on the side facing to each other, and the porous plate 6 is sandwiched between the first ribs 2b and the second ribs 3b. Has been.

  According to the above configuration, since the porous plate 6 is sandwiched between the plurality of first ribs 2b and the plurality of second ribs 3b, a plurality of portions of the porous plate 6 are sandwiched. The vibration of the porous plate 6 due to the sound pressure is suppressed. Thereby, the fall of sound absorption performance can be prevented.

  In the sound absorbing structure 10 of the present embodiment, the first rib 2b and the second rib 3b are arranged at positions that do not face each other. According to said structure, the 1st rib 2b and the 2nd rib 3b are arrange | positioned in the position which is not mutually opposed, The space 11a partitioned off by 1st rib 2b, and 2nd The space 11b partitioned by the ribs 3b is shifted in the rib parallel arrangement direction. Here, in the space 11a partitioned by the first ribs 2b and the space 11b partitioned by the second ribs 3b, a resonance phenomenon occurs in a direction orthogonal to the direction in which the sound proceeds. However, since the space 11a partitioned by the first ribs 2b and the space 11b partitioned by the second ribs 3b are shifted in the direction in which the ribs are juxtaposed, the both sandwich the porous plate 6 therebetween. The resonance phenomenon is alleviated because of the communication. Thereby, the sound absorption performance can be further improved.

  In the sound absorbing structure 10 according to the present embodiment, the first frame 2 has first side walls 2d at both ends of the first frame body 2a facing the second frame 3. In the second frame 3, the porous plate 6 is narrowed between the first rib 2b and the second rib 3b at both ends of the second frame body 3a on the side facing the first frame 2. The first rib 2b has a length h1 in a direction perpendicular to the perforated plate 6 as compared with the first side wall 2d. The second side wall 3d is in contact with the first side wall 2d when held. Has a long configuration. According to the above configuration, since the first rib 2b has a length h1 in the direction orthogonal to the porous plate 6 longer than the first side wall 2d, the porous plate 6 has the first rib 2b and the second rib. When the second side wall 3d comes into contact with the first side wall 2d, the perforated plate 6 is deformed into a wave shape along the rib parallel direction by the first rib 2b. become. Thereby, since tension is generated in the porous plate 6 at the tip of the first rib 2b, the vibration of the porous plate 6 can be further suppressed. Further, since the perforated plate 6 is deformed into a wave shape by the first rib 2b, the surface area facing the sound is increased, so that the sound absorption performance can be further improved.

  Further, in the sound absorbing structure 10 of the present embodiment, the second rib 3b is configured such that the length h2 in the direction orthogonal to the perforated plate 6 is longer than the second side wall 3d. According to the above configuration, since the second rib 3b has a length h2 in the direction orthogonal to the porous plate 6 longer than the second side wall 3d, the porous plate 6 has the first rib 2b and the second rib. 3b, and when the second side wall 3d comes into contact with the first side wall 2d, the perforated plate 6 is further deformed in a wavy shape along the parallel arrangement direction of the ribs by the second rib 3b. It will be. Thereby, since tension is generated in the porous plate 6 at the tip of the second rib 3b, the vibration of the porous plate 6 can be further suppressed. Further, since the perforated plate 6 is deformed into a wave shape by the first rib 2b and the second rib 3b, the surface area facing the sound is further increased, and therefore the sound absorbing performance can be further improved.

  In the sound absorbing structure 10 of the present embodiment, the first ribs 2b and / or the second ribs 3b are arranged in parallel at random intervals. According to said structure, the 1st rib 2b and / or the 2nd rib 3b are arranged in parallel by the random space | interval, Therefore The space 11a partitioned by 1st rib 2b and / or 2nd The spaces 11b partitioned by the ribs 3b are made into a plurality of different sizes. Thereby, since the number of resonance frequencies that can be absorbed by the Helmholtz resonance principle increases, it is possible to absorb a wide range of frequencies.

  Further, in the sound absorbing structure 10 of the present embodiment, the first frame 2 and the second frame 3 are configured to be formed of a non-conductor (resin or the like). According to said structure, the perforated plate 6 pinched by the 1st rib 2b and the 2nd rib 3b by forming the 1st frame 2 and the 2nd frame 3 with a nonconductor. Can prevent electric corrosion.

[Second Embodiment]
FIG. 4 is a cross-sectional view of the sound absorbing structure 20 according to the second embodiment of the present invention. As shown in FIG. 4, the sound absorbing structure 20 according to the present embodiment includes a first frame 2 and a second frame 3 in addition to the configuration of the sound absorbing structure 10 according to the first embodiment. A third frame 4 formed of a resin that is a non-conductor is further provided therebetween. A perforated plate 6 is provided between the first frame body 2 and the third frame body 4 and between the second frame body 3 and the third frame body 4.

  The third frame body 4 includes a third frame body 4a and a plurality of first ribs 2b arranged side by side on the side of the third frame body 4a facing the second frame body 3 (on the opposite side of the sound source). And a plurality of second ribs 3b arranged in parallel on the side (sound source side) facing the first frame 2 of the third frame body 4a. The first rib 2b included in the third frame 4 is the same as the first rib 2b included in the first frame 2, and the second rib 3b included in the third frame 4 is the second rib 2b. It is the same as the 2nd rib 3b which the frame 3 has.

  The third frame body 4 has first side walls 2d at both ends of the third frame body 4a facing the second frame body 3, and the third frame body 4a has a first side wall 2d. A second side wall 3d is provided at both ends on the side facing the first frame 2. The first side wall 2d of the third frame body 4 is the same as the first side wall 2d of the first frame body 2, and the second side wall 3d of the third frame body 4 is the second side wall 2d. This is the same as the second side wall 3d of the frame 3.

  If the first rib 2b and the second rib 3b sandwiching one porous plate 6 are a pair of ribs, each of the porous plates 6 is sandwiched by a different pair of ribs.

  As shown in FIG. 4, the inside of the box member 1 is divided into a plurality of spaces by two perforated plates 6, two first ribs 2b, and two second ribs 3b. Specifically, the inside of the box member 1 includes a space 11a partitioned by a porous surface 1b and two first ribs 2b adjacent to the porous plate 6, and two adjacent surfaces of the closed surface 1c and the porous plate 6. A space 11b partitioned by the second rib 3b, a space 11c partitioned by the two first ribs 2b adjacent to the two porous plates 6, and two second adjacent to the two porous plates 6. It is divided into a space 11d partitioned by the rib 3b. The space 11c and the space 11d are communicated with the third frame body 4a interposed therebetween. These spaces 11a, 11b, 11c, and 11d are configured to absorb sound having a resonance frequency based on the Helmholtz resonance principle. And the sound which passed the porous surface 1b advances the inside of the box member 1 by the frequency below the frequency which makes the space | interval of the 1st rib 2b or the space | interval of the 2nd rib 3b a half wavelength. become.

  In addition, an air layer 12a is formed between the porous surface 1b and the porous plate 6, and an air layer 12b is formed between the porous plate 6 and the closing surface 1c, and the two porous plates 6 An air layer 12c is formed between the two. The layer thicknesses d1, d2, and d3 of the air layers 12a, 12b, and 12c, the aperture ratios β1, β2, and β3 of the porous surface 1b and the porous plates 6 and 6, the plate thicknesses t1, t2, and t3, and the through holes 1a, 6a, The parameter composed of the diameters φ1, φ2, and φ3 of 6a is set so as to cause a viscous action on the air passing through the porous surface 1b and the through holes 1a, 6a, and 6a of the porous plates 6 and 6. As a result, when a viscous damping action is generated in the air passing through the through holes 1a, 6a, 6a, the air vibration is converted into thermal energy, resulting in a damping property of the air vibration. As a result, the air vibration is high in a relatively wide frequency band. The sound absorption effect will be exhibited.

  In the present embodiment, the number of the third frame bodies 4 is one, and thus the number of the perforated plates 6 is two, but one or more third frame bodies 4 are provided. It may be. In this case, the number of perforated plates 6 is the number obtained by adding “1” to the number of third frames 4.

  Thus, the number of the perforated plates 6 can be easily increased or decreased by increasing or decreasing the number of the third frame bodies 4.

  Other points are the same as those in the first embodiment.

[Outline of Second Embodiment]
As described above, the sound absorbing structure 20 according to the present embodiment further includes one or more third frames 4 provided between the first frame 2 and the second frame 3. The third frame body 4 includes a third frame body 4a and a plurality of first ribs 2b arranged in parallel at a predetermined interval on the side of the third frame body 4a facing the second frame body 3. And a plurality of second ribs 3b arranged in parallel at a predetermined interval on the side of the third frame body 4a facing the first frame 2, and a plurality of perforated plates 6 are provided. When the first rib 2b and the second rib 3b that sandwich the perforated plate 6 are a pair of ribs, each is sandwiched by a pair of different ribs. According to said structure, the number of the perforated plates 6 can be easily increased / decreased by increasing / decreasing the number of the 3rd frame bodies 4. FIG.

[Modification of each embodiment]
The embodiments of the present invention have been described above, but only specific examples have been illustrated, and the present invention is not particularly limited. Specific configurations and the like can be appropriately changed in design. Further, the actions and effects described in the embodiments of the invention only list the most preferable actions and effects resulting from the present invention, and the actions and effects according to the present invention are described in the embodiments of the present invention. It is not limited to what was done.

  For example, in the first embodiment, the perforated plate 6 is configured to be deformed in a wave shape along the juxtaposed direction of the ribs, but is not limited to this configuration, and as shown in FIG. In addition, the first rib 22b and the second rib 23b have a corrugated surface along the longitudinal direction of the rib, and the perforated plate 6 is sandwiched between the first rib 22b and the second rib 23b. When it is done, it may be configured to be deformed in a wave shape along the juxtaposing direction of the ribs and may be deformed in a wave shape along the longitudinal direction of the rib. Similarly, the first side wall 22d and the second side wall 23d may have wavy surfaces. In this case, since the tension is generated in the porous plate 6 also in the longitudinal direction of the rib, the vibration of the porous plate 6 can be further suppressed. Further, since the perforated plate 6 is deformed in a wave shape along the rib parallel direction and the rib longitudinal direction, the surface area facing the sound is further increased, so that the sound absorbing performance can be further improved.

The block diagram of a sound absorption structure. Sectional drawing of a sound absorption structure. The graph which shows a sound absorption coefficient. Sectional drawing of a sound absorption structure. The block diagram of a sound absorption structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Box member 1a, 6a Through-hole 1b Porous surface 2 1st frame 2a 1st frame main body 2b 1st rib 2d 1st side wall 3 2nd frame 3a 2nd frame main body 3b 2nd rib 3d 2nd side wall 4 3rd frame 4a 3rd frame main body 6 Perforated plate 10,20 Sound absorption structure

Claims (7)

A sound absorbing structure that absorbs sound from a sound source,
A box member having a porous surface with a space formed therein and having a large number of through holes;
A first frame body and a second frame body arranged to face each other inside the box member;
A perforated plate provided between the first frame and the second frame and having a large number of through holes;
Have
The first frame body includes a first frame body and a plurality of first ribs arranged in parallel at a predetermined interval on the side of the first frame body facing the second frame body. And
The second frame body includes a second frame body and a plurality of second ribs arranged in parallel at a predetermined interval on a side of the second frame body facing the first frame body. And
The sound absorbing structure according to claim 1, wherein the perforated plate is sandwiched between the first rib and the second rib.   The sound absorbing structure according to claim 1, wherein the first rib and the second rib are arranged at positions that do not face each other. The first frame body has first side walls at both ends of the first frame body on the side facing the second frame body,
In the second frame body, the porous plate is sandwiched between the first rib and the second rib at both ends of the second frame body on the side facing the first frame body. Having a second side wall abutting against the first side wall,
The sound absorbing structure according to claim 2, wherein the first rib has a length in a direction orthogonal to the perforated plate longer than that of the first side wall.   The sound absorbing structure according to claim 3, wherein the second rib has a length in a direction perpendicular to the perforated plate longer than the second side wall.   The sound absorbing structure according to any one of claims 1 to 4, wherein the first rib and / or the second rib are arranged in parallel at random intervals. One or more third frames provided between the first frame and the second frame;
The third frame body includes a third frame body, and a plurality of the first ribs arranged in parallel at a predetermined interval on the side of the third frame body facing the second frame body, A plurality of the second ribs arranged in parallel at a predetermined interval on the side of the third frame body facing the first frame body;
There are a plurality of the perforated plates, and when the first rib and the second rib sandwiching one perforated plate are a pair of ribs, each is sandwiched by a pair of different ribs. The sound absorbing structure according to any one of claims 1 to 5.   The sound absorbing structure according to any one of claims 1 to 6, wherein the first frame and the second frame are formed of a non-conductor.

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