Sound absorbing structure

Abstract

To suppress the occurrence of feelings such as displeasure, aggravation and fear depending on appearance.SOLUTION: The sound absorbing structure 1 includes an undulating structure 10. The uneven structure portion 10 has a plurality of protruding portions 20 protruding toward the sound source side. Each of the protruding portions 20 has an upper wall portion 21 and a side wall portion 25 that form the vibration film 2, and forms a space 22 on the fixed side opposite to the sound source side with respect to the upper wall portion 21. The side wall portion 25 is a tubular portion extending from a lateral end portion of the upper wall portion 21 to the fixed side, and surrounds the space 22 from the lateral side. The uneven structure portion 10 is a porous body having closed cells formed of a thermoplastic resin.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Conventionally, various soundproofing structures have been proposed for soundproofing. Among these soundproofing structures are plate-shaped soundproofing panels used for walls and the like. Some soundproofing panels have a sound-absorbing structure that exhibits sound-absorbing properties. For example, there is a sound-absorbing structure having an undulating structure in which multiple protrusions that define a sound-absorbing space are formed. Among such sound-absorbing structures having multiple protrusions, there is a sound-absorbing structure in which Helmholtz resonators of various shapes are formed side by side (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3306610 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to absorb sound, a Helmholtz resonator has holes formed therein for introducing vibrating air into the sound-absorbing space inside. Therefore, a sound-absorbing structure formed with a plurality of Helmholtz resonators arranged in a row as described above has a plurality of holes arranged in a row. When the plurality of Helmholtz resonators included in the sound-absorbing structure have various shapes, the Helmholtz resonators are irregularly arranged, and therefore the plurality of holes are also irregularly arranged. Such a plurality of holes may cause discomfort or disgust to people who see it, or may even provoke fear.

[0005] For this reason, conventional sound-absorbing structures formed with multiple Helmholtz resonators arranged side by side are required to have an appearance that can prevent feelings of discomfort, hatred, fear, etc. Thus, conventional sound-absorbing structures having multiple protrusions that form sound-absorbing spaces are required to have an appearance that can prevent feelings of discomfort, hatred, fear, etc.

[0006] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a sound-absorbing structure that can suppress the appearance from causing feelings of discomfort, hatred, or fear. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the sound-absorbing structure of the present invention comprises an undulating structure portion, which has a plurality of protruding portions protruding toward one side, each of which has an upper wall portion and a side wall portion forming a vibration membrane, and which forms a space on the other side of the upper wall portion opposite the one side, and the side wall portion is a cylindrical portion extending from the lateral end of the upper wall portion to the other side, surrounding the space from the side, and the undulating structure portion is a porous body having closed bubbles formed from a thermoplastic resin.

[0008] In the sound absorbing structure according to one aspect of the present invention, the side wall portion forms a plurality of vibration membranes.

[0009] In a sound-absorbing structure according to one embodiment of the present invention, the side wall portion forms four vibration membranes, two of which face each other across the space, and the other two of which face each other across the space in a direction intersecting the direction in which the two vibration membranes face each other.

[0010] In the sound absorbing structure according to one aspect of the present invention, the thermoplastic resin is any one of polypropylene, polyethylene, and polystyrene.

[0011] In the sound absorbing structure according to one aspect of the present invention, the foaming ratio of the porous body is 20 times or more and 30 times or less.

[0012] In the sound absorbing structure according to one aspect of the present invention, the thickness of the undulating structure is 3 mm or more and 7 mm or less.

[0013] In the sound absorbing structure according to one aspect of the present invention, the thickness of the diaphragm is not less than 3 mm and not more than 7 mm.

[0014] In the sound absorbing structure according to one aspect of the present invention, the plurality of protrusions include a plurality of types of protrusions.

[0015] In the sound absorbing structure according to one aspect of the present invention, the plurality of types of protrusions include at least one of the size of the protrusions and the shape of the protrusions. [Effects of the Invention]

[0016] The sound absorbing structure according to the present invention can prevent the appearance from causing feelings of discomfort, hatred, or fear. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is an exploded perspective view showing a schematic configuration of a sound absorbing structure according to an embodiment of the present invention. [Figure 2] FIG. 2 is a perspective cross-sectional view showing a part of a cut sound absorbing structure. [Figure 3] FIG. 2 is a perspective cross-sectional view showing a part of a cut sound absorbing structure. [Figure 4] FIG. 1 is a graph showing the sound absorption efficiency of a sound absorbing structure according to an embodiment of the present invention and the sound absorption efficiency of a conventional sound absorbing structure in which a plurality of Helmholtz resonators are arranged side by side. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that in the drawings, not all of the components are labeled with reference numerals, and some of the components may be omitted.

[0019] FIG. 1 is an exploded perspective view showing the schematic configuration of a sound-absorbing structure 1 according to an embodiment of the present invention, and FIGS. 2 and 3 are perspective cross-sectional views showing a cut portion of the sound-absorbing structure 1. Note that FIGS. 1 and 2 show the sound-absorbing structure 1 as viewed from the front, and FIG. 3 shows the sound-absorbing structure 1 as viewed from the rear. As shown in FIGS. 1 to 3, the sound-absorbing structure 1 includes an undulating structure 10. The undulating structure 10 has multiple protrusions 20 that protrude toward one side, the sound source side. Each protrusion 20 has an upper wall 21 and a side wall 25 that form a diaphragm, and also forms a space 22 on the other side, the fixed side, opposite the sound source side, of the upper wall 21. The side wall 25 is a cylindrical portion that extends from a lateral end of the upper wall 21 toward the other side, the fixed side, and laterally surrounds the space 22. The undulating structure 10 is a porous body having closed cells formed from a thermoplastic resin. The configuration of the sound absorbing structure 1 will now be described in detail.

[0020] The sound source side is one side of the virtual plane that faces the sound source of the sound to be absorbed when the sound absorbing structure 1 is in use. The fixed side is the other side of the virtual plane that faces the object to which the sound absorbing structure 1 is fixed when the sound absorbing structure 1 is in use.

[0021] As shown in FIGS. 1 to 3 , the undulating structure 10 of the sound-absorbing structure 1 has a shape similar to that of a known sound-absorbing structure in which, for example, a plurality of Helmholtz resonators are arranged side by side. In the undulating structure 10, the plurality of protrusions 20 are arranged along an imaginary plane. As described above, each of the plurality of protrusions 20 of the undulating structure 10 has an upper wall 21 that forms a vibration membrane and a side wall 25 that also forms a vibration membrane. The side wall 25 extends from the lateral end of the upper wall 21 toward the fixed side. The upper wall 21 and the side wall 25 form a recess that is recessed toward the sound source, and a space 22 is defined by the upper wall 21 and the side wall 25. The space 22 is open toward the fixed side. Note that the lateral side refers to the side perpendicular to the direction toward the sound source or the fixed side. The lateral end of the upper wall 21 is the end on the outer periphery of the upper wall 21.

[0022] As shown in FIGS. 1 to 3 , the upper wall portion 21 extends like a film and has a pair of surfaces, a front surface 23 and a back surface 24, facing back to back. The front surface 23 is the surface facing the sound source side, and the back surface 24 is the surface facing the fixed side. The thickness (thickness T1) of the upper wall portion 21 is uniform or approximately uniform. That is, in the upper wall portion 21, the distance between the front surface 23 and the back surface 24 is constant or approximately constant throughout. The upper wall portion 21 extends along a plane. For example, the front surface 23 extends parallel or approximately parallel to an imaginary plane, and similarly, the back surface 24 extends parallel or approximately parallel to this imaginary plane. The front surface 23 and the back surface 24 are, for example, parallel or approximately parallel. The upper wall portion 21 is not perpendicular to the direction toward the sound source side but is inclined, and the front surface 23 and the back surface 24 are not perpendicular to the direction toward the sound source side but are inclined. The upper wall portion 21 may be perpendicular to the direction toward the sound source side, and the front surface 23 and the back surface 24 may be perpendicular to the direction toward the sound source side. The front surface 23 may be flat or curved. Similarly, the back surface 24 may be flat or curved. The shape of the upper wall portion 21 as seen from the sound source side or the fixed side is rectangular or approximately rectangular, as shown in FIGS. 1 to 3, for example. The shape of the upper wall portion 21 as seen from the sound source side or the fixed side is not limited to a rectangle, and may be other polygons such as a triangle or an approximately triangle, or approximately other polygons, or a circle or an approximately circle, or other shapes.

[0023] As shown in FIG. 2, the side wall portion 25 has an opening 20b at its lower end 20a, which is the end on the fixed side, that opens the space 22 to the fixed side. The lower end 20a is the end on the fixed side of each protrusion 20. The side wall portion 25 has a shape corresponding to the shape of the upper wall portion 21 and has one or more membrane-like side wall pieces. The shape of the side wall portion 25 is, for example, a square tube or a roughly square tube with a rectangular or roughly rectangular cross section, as shown in FIGS. 1 to 3. The shape of the side wall portion 25 is not limited to a square tube or a roughly square tube with a rectangular or roughly rectangular cross section, and can be various shapes corresponding to the shape of the upper wall portion 21. The thickness (thickness T2) of the side wall portion 25 is, for example, uniform or roughly uniform. Furthermore, the thickness T2 of the side wall portion 25 is, for example, the same as or roughly the same as the thickness T1 of the upper wall portion 21. The thickness T2 of the side wall portion 25 does not have to be uniform, and the thickness T2 of the side wall portion 25 does not have to be the same as the thickness T1 of the upper wall portion 21. No through-holes are formed in the upper wall portion 21.

[0024] 1 to 3, the side wall portion 25 specifically has four side wall pieces 25a, 25b, 25c, and 25d. The side wall pieces 25a, 25b, 25c, and 25d extend from the respective lateral sides of the upper wall portion 21. The side wall pieces 25a, 25b, 25c, and 25d are connected in this order in the circumferential direction. Similar to the upper wall portion 21, the side wall pieces 25a, 25b, 25c, and 25d each have a pair of opposing surfaces: a front surface 25aa and a back surface 25ab, a front surface 25ba and a back surface 25bb, a front surface 25ca and a back surface 25cb, and a front surface 25da and a back surface 25db. The side wall pieces 25a, 25b, 25c, and 25d extend in a film-like shape, and have a uniform or approximately uniform thickness T2 throughout. The thickness of each of the side wall pieces 25a, 25b, 25c, and 25d is the distance between the surface 25aa and the back surface 25ab, the distance between the surface 25ba and the back surface 25bb, the distance between the surface 25ca and the back surface 25cb, and the distance between the surface 25da and the back surface 25db. The thickness T2 of each of the side wall pieces 25a, 25b, 25c, and 25d is the same as or approximately the same as the thickness T1 of the upper wall portion 21. The thickness T2 of each of the side wall pieces 25a, 25b, 25c, and 25d does not have to be the same as the thickness T1 of the upper wall portion 21.

[0025] The side wall pieces 25a, 25b, 25c, and 25d each extend along a plane. For example, the surfaces 25aa, 25ba, 25ca, and 25da each extend parallel or approximately parallel to an imaginary plane. Similarly, the back surfaces 25ab, 25bb, 25cb, and 25db each extend parallel or approximately parallel to these imaginary planes. The surfaces 25aa, 25ba, 25ca, and 25da and the back surfaces 25ab, 25bb, 25cb, and 25db are, for example, parallel or approximately parallel to each other. The side wall pieces 25a, 25b, 25c, and 25d are, for example, inclined with respect to the direction toward the sound source. The surfaces 25aa, 25ba, 25ca, and 25da and the back surfaces 25ab, 25bb, 25cb, and 25db are, for example, inclined with respect to the direction toward the sound source. The side wall pieces 25a, 25b, 25c, and 25d may be parallel to the direction toward the sound source, and the front surfaces 25aa, 25ba, 25ca, and 25da and the back surfaces 25ab, 25bb, 25cb, and 25db may be parallel to the direction toward the sound source. The front surfaces 25aa, 25ba, 25ca, and 25da and the back surfaces 25ab, 25bb, 25cb, and 25db may be flat or curved. The side wall pieces 25a, 25b, 25c, and 25 each have a rectangular or substantially rectangular shape, as shown in FIGS. 1 to 3. The shape of the side wall pieces 25a, 25b, 25c, and 25 is not limited to a rectangular shape and may be another shape.

[0026] As described above, the top wall 21 and the side wall 25 form a vibrating membrane. The vibrating membrane is a part that vibrates in a spring-mass resonance system, which will be described later. Specifically, the side wall 25 has a vibrating membrane formed on each of the side wall pieces 25aa, 25ba, 25ca, and 25da. In the top wall 21, the entire portion where the front surface 23 and the back surface 24 extend forms the vibrating membrane. Alternatively, a portion of the portion where the front surface 23 and the back surface 24 extend may form the vibrating membrane. For example, a portion of the portion where the front surface 23 and the back surface 24 extend, which has high rigidity, excluding the end portions, forms the vibrating membrane. Similarly, in the side wall piece 25a, the entire portion where the front surface 25aa and the back surface 25ab extend forms the vibrating membrane. Alternatively, a portion of the portion where the front surface 25aa and the back surface 25ab extend may form the vibrating membrane. For example, a portion of the portion where the front surface 25aa and the back surface 25ab extend, which has high rigidity, excluding the end portions, forms the vibrating membrane. Similarly, in side-wall piece 25b, the entire portion where front surface 25ba and rear surface 25bb extend forms a vibrating membrane. Also, a portion of side-wall piece 25b where front surface 25ba and rear surface 25bb extend may form a vibrating membrane. For example, the vibrating membrane may be formed by a portion of the portion where front surface 25ba and rear surface 25bb extend, which has high rigidity, excluding the end portions. Similarly, in side-wall piece 25c, the entire portion where front surface 25ca and rear surface 25cb extend may form a vibrating membrane. Also, the vibrating membrane may be formed by a portion of the portion where front surface 25ca and rear surface 25cb extend, which has high rigidity, excluding the end portions. Similarly, in side-wall piece 25d, the entire portion where front surface 25da and rear surface 25db extend forms a vibrating membrane. Also, the vibrating membrane may be formed by a portion of the portion where front surface 25da and rear surface 25db extend, which has high rigidity. For example, the portion where the front surface 25da and the back surface 25db extend, excluding the ends, which has high rigidity, forms the vibration membrane.

[0027] The multiple protrusions 20 of the undulating structure 10 include multiple types of protrusions 20. The multiple types of protrusions 20 include at least one of the sizes of the protrusions 20 and the shapes of the protrusions 20. As shown in FIGS. 1 to 3, the undulating structure 10 has multiple protrusions 20 that are different from each other, for example, in the size of the upper wall 21 and the size of the space 22. Specifically, for example, the undulating structure 10 has multiple protrusions 20 that are different from each other in at least one of the following: the size of the upper wall 21, the size of each of the side wall pieces 25a, 25b, 25c, and 25d, the height of the side wall 25, the shape of the upper wall 21, and the shape of each of the side wall pieces 25a, 25b, 25c, and 25d. Furthermore, the undulating structure 10 has multiple protrusions 20 of the same type. However, the undulating structure 10 does not necessarily have to have multiple protrusions 20 of the same type.

[0028] 1 to 3, the undulating structure 10 has, for example, a bottom 26. The bottom 26 is a portion that extends toward the fixed side, and the multiple protrusions 20 protrude from the bottom 26, with the openings 20b of each protrusion 20 being located at the bottom 26. The bottom 26 is a portion that extends along an imaginary plane and extends between adjacent protrusions 20. The bottom 26 extends, for example, at an angle with respect to the upper wall 21 of each of the multiple protrusions 20. Note that the bottom 26 may also extend parallel to the upper wall 21 of each of the multiple protrusions 20. The bottom 26 has a pair of opposing surfaces, an upper surface 26a and a bottom surface 26b, and the multiple protrusions 20 protrude from the upper surface 26a toward the sound source side, with the openings 20b of the multiple protrusions 20 being formed in the bottom surface 26b. The top surface 26a is, for example, a surface that extends on a plane or a substantially plane, and the bottom surface 26b is, for example, a surface that extends on a plane or a substantially plane. Note that the top surface 26a does not have to be a surface that extends on a plane, but may be, for example, a surface that extends on a curved surface, and similarly, the bottom surface 26b does not have to be a surface that extends on a plane, but may be, for example, a surface that extends on a curved surface.

[0029] The sound-absorbing structure 1 has the above-described structure, and each protrusion 20 forms a spring-mass resonator system. Specifically, in each protrusion 20, the top wall 21 and the side wall pieces 25a, 25b, 25c, and 25d of the side wall 25 form a vibrating membrane that absorbs sound through membrane vibration. In other words, the top wall 21 and the side wall pieces 25a, 25b, 25c, and 25d form a resonator that resonates at a specific frequency and acts as an inertial mass. In particular, the centers and their vicinity of the top wall 21 and the side wall pieces 25a, 25b, 25c, and 25d form a resonator and act as an inertial mass. When the sound-absorbing structure 1 is in use, the spaces 22 of each protrusion 20 are closed, and the air in the spaces 22 acts as an air spring against the upper wall portion 21 and side wall pieces 25a, 25b, 25c, and 25d of each protrusion 20, which vibrate as membranes. In this way, the sound-absorbing structure 1 forms a spring-mass resonance system and can absorb sound in a desired frequency range. The sound-absorbing structure 1 is attached to a fixed member such as a sound-insulating wall or a wall, and the bottom surface 26b of the bottom portion 26 faces the fixed member, thereby closing the spaces 22 of each protrusion 20. The sound-absorbing structure 1 may also have a closing member that closes the spaces 22 formed by each of the multiple protrusions 20. The closing member is, for example, a plate-shaped member having a surface facing the bottom surface 26b of the bottom portion 26. The closing member is attached to the undulating structure 10 and closes the spaces 22 formed by each of the multiple protrusions 20.

[0030] As described above, the sound-absorbing structure 1 does not have through holes in the upper wall portion 21 of the multiple protrusions 20, and is therefore less likely to cause feelings of discomfort, hatred, or fear in people who see the sound-absorbing structure 1, as is the case with conventional sound-absorbing structures in which multiple Helmholtz resonators are formed in a row.

[0031] As described above, the undulating structure 10 is a porous body having closed cells formed from a thermoplastic resin. In other words, the undulating structure 10 is a closed-cell body formed from a thermoplastic resin, and the cells inside the undulating structure 10 are closed cells. The thermoplastic resin forming the undulating structure 10 is, for example, polypropylene, polyethylene, or polystyrene. However, the thermoplastic resin forming the undulating structure 10 is not limited to these, and other thermoplastic resins may also be used. The expansion ratio of the undulating structure 10 is 20 times or more and 30 times or less. For example, the expansion ratio of the undulating structure 10 is 25 times.

[0032] The thickness T1 of the upper wall portion 21 of the undulating structure 10 is 3 mm or more and 7 mm or less. For example, the thickness T1 of the upper wall portion 21 of the undulating structure 10 is 5 mm or approximately 5 mm. For example, the thickness T2 of each of the side wall pieces 25a, 25b, 25c, and 25d of the side wall portion 25 is 3 mm or more and 7 mm or less. For example, the thickness T2 of each of the side wall pieces 25a, 25b, 25c, and 25d of the side wall portion 25 is 5 mm or approximately 5 mm. Thus, the thickness T1 of the upper wall portion 21 and the thickness T2 of each of the side wall pieces 25a, 25b, 25c, and 25d of the side wall portion 25 are, for example, the same or approximately the same. That is, the thickness of each of the multiple protrusions 20 is uniform or approximately uniform, and is 3 mm or more and 7 mm or less, for example, 5 mm or approximately 5 mm. The thickness of the bottom 26 may also be the same as or approximately the same as the thickness T1 of the upper wall 21 and the thickness T2 of each of the side wall pieces 25a, 25b, 25c, and 25d of the side wall 25. That is, the thickness of the undulating structure 10 may be uniform or approximately uniform. In this case, too, the thickness of the undulating structure 10 is, for example, 3 mm or more and 7 mm or less, and is, for example, 5 mm or approximately 5 mm.

[0033] Furthermore, the thickness T1 of the diaphragm of the upper wall portion 21 of the undulating structure 10 may be 3 mm or more and 7 mm or less. For example, the thickness T1 of the diaphragm of the upper wall portion 21 of the undulating structure 10 may be 5 mm or approximately 5 mm. For example, the thickness T2 of the diaphragm of each of the side wall pieces 25a, 25b, 25c, and 25d of the side wall portion 25 may be 3 mm or more and 7 mm or less. For example, the thickness T2 of the diaphragm of each of the side wall pieces 25a, 25b, 25c, and 25d of the side wall portion 25 may be 5 mm or approximately 5 mm. In this way, the thickness T1 of the diaphragm of the upper wall portion 21 and the thickness T2 of the diaphragm of each of the side wall pieces 25a, 25b, 25c, and 25d of the side wall portion 25 may be the same or approximately the same.

[0034] As described above, the undulating structure 10 is a porous body made of a thermoplastic resin, and the bubbles inside the undulating structure 10 are closed bubbles. This allows a vibrating membrane to be formed in the undulating structure 10, and also allows the undulating structure 10 to have high flexibility, resulting in a highly flexible vibrating membrane. This allows the upper wall 21 and the side wall pieces 25a, 25b, 25c, and 25d of each of the multiple protrusions 20 to have high flexibility, thereby widening the resonant frequency range of the membrane vibration that can be set for each of the upper wall 21 and the side wall pieces 25a, 25b, 25c, and 25d. In other words, the resonant frequency range of the membrane vibration of each of the upper wall 21 and the side wall pieces 25a, 25b, 25c, and 25d that can be set by adjusting the thickness of each of the upper wall 21 and the side wall pieces 25a, 25b, 25c, and 25d is wide.

[0035] Furthermore, the sound absorption coefficient of each protrusion 20 can be increased by setting the thickness of each protrusion 20, specifically the thicknesses T1 and T2 of the side wall pieces 25a, 25b, 25c, and 25d of the upper wall portion 21 and the side wall portion 25 of each protrusion 20, to 3 mm or more and 7 mm or less. The sound absorption coefficient of each protrusion 20 can be increased by setting the thickness of each protrusion 20, specifically the thicknesses T1 and T2 of the upper wall portion 21 and the side wall pieces 25a, 25b, 25c, and 25d of the side wall portion 25 of each protrusion 20, to 5 mm or approximately 5 mm.

[0036] The undulating structure 10 can be formed, for example, by vacuum molding a porous sheet having closed cells formed from a thermoplastic resin. The thermoplastic resin is, for example, polypropylene, polyethylene, or polystyrene. The expansion ratio of the closed-cell porous sheet formed from a thermoplastic resin is, for example, 20 times or more and 30 times or less. The closed-cell porous sheet formed from a thermoplastic resin is, for example, a sheet having a uniform or approximately uniform thickness, and the thickness of this porous sheet is, for example, 3 mm or more and 7 mm or less. The thickness of this porous sheet is, for example, 5 mm or approximately 5 mm.

[0037] FIG. 4 is a graph showing the sound absorption efficiency of the sound-absorbing structure 1 as a test example and the sound absorption efficiency of a conventional sound-absorbing structure formed with multiple Helmholtz resonators arranged side by side as a test example. The conventional sound-absorbing structure has a similar configuration to the undulating structure 10 of the sound-absorbing structure 1, but has through-holes formed in the upper wall of each protrusion, and the undulating structure is not porous. The thermoplastic resin forming the undulating structure 10 of the sound-absorbing structure 1 as a test example is polypropylene, the foaming ratio is 25 times, and the thickness of the undulating structure 10 is 5 mm. The measured sound absorption coefficient is the reverberation chamber sound absorption coefficient, and is a value measured based on the reverberation chamber sound absorption coefficient measurement method of JIS A 1409. The resin forming the conventional sound-absorbing structure as a test example is polypropylene, and the thickness of the undulating structure is 1 mm.

[0038] As shown in FIG. 4, it can be seen that the sound absorption efficiency of the sound absorbing structure 1 is higher than that of a conventional sound absorbing structure formed by arranging a plurality of Helmholtz resonators.

[0039] In this way, the sound absorbing structure 1 can be formed as a sound absorbing structure with high sound absorbing efficiency by using a spring-mass resonance system without using Helmholtz resonance.

[0040] As described above, the sound absorbing structure 1 according to the embodiment of the present invention can suppress the arousal of feelings of discomfort, hatred, fear, etc. due to its appearance. Furthermore, the sound absorbing structure 1 according to the embodiment of the present invention can achieve a high sound absorbing effect while suppressing the arousal of feelings of discomfort, hatred, fear, etc. due to its appearance.

[0041] Although the present invention has been described above through the above embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included within the technical scope of the present invention.

[0042] The above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the scope of the present invention. Furthermore, the above-described embodiments do not limit the scope of the present invention, and the present invention may include any and all applications. The components of the above-described embodiments, as well as their arrangement, materials, conditions, shape, size, etc., are not limited to those illustrated and may be modified as appropriate. For example, the present invention includes differences that arise during implementation due to manufacturing tolerances, etc. Furthermore, components illustrated in different embodiments may be partially substituted or combined within the scope of technical inconsistency. Furthermore, the various configurations may be selectively combined as appropriate to achieve at least some of the above-described problems and effects. [Explanation of symbols]

[0043] 1 sound absorbing structure, 10 undulating structure, 11 undulating surface, 12 undulating back surface, 13 lattice surface, 14 opening, 20 protrusion, 20a lower end, 20b opening, 21 upper wall portion, 22 space, 23 surface, 24 back surface, 25 side wall portion, 25a, 25b, 25c, 25d side wall piece portion, 25aa, 25ba, 25ca, 25da surface, 25ab, 25bb, 25cb, 25db back surface, 26 bottom portion, 26a upper surface, 26b bottom surface, T1, T21 thickness

Claims

1. Equipped with an undulating structure, The relief structure has a plurality of protrusions protruding toward one side, Each of the protrusions has an upper wall portion and a side wall portion that form a vibration membrane, and also forms a space on the other side opposite to the one side with respect to the upper wall portion, the side wall portion is a cylindrical portion extending from a lateral end of the upper wall portion to the other side and enclosing the space from a side, The undulating structure is a porous body having closed cells formed from a thermoplastic resin. Sound-absorbing structure.

2. The side wall portion forms a plurality of vibration membranes. The sound absorbing structure according to claim 1 .

3. The side wall portion forms four vibration membranes, two of the four vibration membranes face each other across the space, the other two of the four vibration membranes face each other across the space in a direction intersecting the direction in which the two vibration membranes face each other; The sound absorbing structure according to claim 2 .

4. The thermoplastic resin is any one of polypropylene, polyethylene, and polystyrene. The sound absorbing structure according to claim 1 .

5. The expansion ratio of the porous body is 20 times or more and 30 times or less. The sound absorbing structure according to claim 1 or 4.

6. The thickness of the undulating structure is 3 mm or more and 7 mm or less. The sound absorbing structure according to claim 5.

7. The thickness of the vibration membrane is 3 mm or more and 7 mm or less. The sound absorbing structure according to claim 5.

8. The plurality of protrusions includes a plurality of types of protrusions. The sound absorbing structure according to claim 1 .

9. The plurality of types of protrusions includes at least one of the size of the protrusions and the shape of the protrusions. The sound absorbing structure according to claim 1 .

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