Sound absorber

Abstract

The present invention provides a sound-absorbing material that improves sound absorption performance in the low-frequency range while suppressing sound absorption performance in the high-frequency range, thereby facilitating control of sound absorption performance and improving space efficiency. [Solution] The sound-absorbing body 11 of the present invention comprises a porous layer 20 made of a porous material and a non-permeable mass layer 30. The porous layer 20 has a plurality of holes 21. Each hole 21 opens on the surface of the porous layer 20 in the thickness direction facing the sound incidence side, extends toward the interior of the porous layer 20, and is closed within the porous layer 20. The porous layer 20 includes a through-layer portion 22 having through-portions 21a of the plurality of holes 21, and a bottom-side layer portion 23 having bottoms 21b of the plurality of holes 21. The mass layer 30 is disposed on the surface of the through-layer portion 21a in the thickness direction. The thickness of the mass layer 30 is smaller than the thickness of the through-layer portion 22 and the bottom-side layer portion 23 of the porous layer 20.

Description

Technical Field

[0001] The present invention relates to a sound absorber for absorbing sound.

Background Art

[0002] When dealing with sound in an indoor space, for example, when recording sound, due to the influence of the size, shape, and reflection characteristics of the boundary surface of the indoor space, the recorded sound includes, in addition to the direct sound from the sound source during recording, the unique timbre of the space, reflected sound, etc. As a result, various changes such as changes in the frequency characteristics (spectrum) occur in the recorded sound compared to the direct sound. On the other hand, if the space for dealing with sound is a free space where sound is not reflected at its boundary surface, that is, if a free sound field is realized, a recorded sound consisting only of the direct sound can be obtained.

[0003] When designing an indoor space for dealing with sound, depending on the use of the room, it may be required to actively utilize reflected sound or minimize the influence of reflected sound. In this case, what is important is to control the influence of the sound brought about by the indoor space according to the use of the room. In an indoor space for dealing with sound, since it is necessary to minimize the influence of the indoor space or avoid acoustic interference to meet the desired purpose, in most cases, sound-absorbing materials are used. There are various types of these sound-absorbing materials, but the most commonly used sound-absorbing materials are those using porous materials.

[0004] Porous materials used in sound-absorbing materials are typically processed into plates of a uniform thickness. It is known that the sound-absorbing performance of such processed porous materials is excellent in the high-frequency range, almost to the point of perfect absorption, but poor in the low-frequency range, almost to the point of perfect reflection. In other words, simply processing porous materials into plates and installing them along walls makes it difficult to control low-frequency sounds, and reverberation time, an indicator of how long sound resonates in a space, tends to be longer in the low-frequency range than in the high-frequency range. Therefore, when designing indoor spaces that deal with sound, it is an important challenge not only to use special structures for absorbing low-frequency sounds, but also to control low-frequency sounds by using methods such as devising the shape of the room.

[0005] In particular, in indoor spaces used for recording conversations, music, etc., such as studios, it is necessary to create an environment where the speaker, performer, etc., can comfortably hear the sound when recording sounds produced by vocalization, performance, etc. In this case, it is necessary to enhance sound absorption performance in the low-frequency range while suppressing sound absorption performance in the high-frequency range. For this reason, various sound absorption technologies have been proposed to enhance sound absorption performance in the low-frequency range while suppressing sound absorption performance in the high-frequency range.

[0006] For example, as an example of the above sound absorption technology, a sound insulation structure having a sound-absorbing layer (porous layer) made of thermoplastic felt, which is arranged to form an air layer between the body panel of an automobile, and a non-permeable sound-insulating layer made of rubber sheet, which is laminated to the sound-absorbing layer on the opposite side of the body panel in the thickness direction, wherein the body panel has a basis weight of 6.2 kg / m 2 It is configured such that the sound-absorbing layer has a basis weight of 1.0 kg / m 2 The sound insulation layer is configured to have a thickness of 20 mm and a basis weight of 5.0 kg / m 2 One example of a sound-insulating structure is one in which the sound absorption performance is controlled by utilizing the resonance of the sound-absorbing layer and the sound-insulating layer, and the thickness of the layer is set to 2.0 mm (see, for example, Patent Document 1, in particular Figure 12).

[0007] Another example of the above sound absorption technology is a sound absorption panel provided along a rigid wall facing a sound field, which includes a non-permeable airtight membrane positioned away from the rigid wall toward the sound field, a permeable porous sound-absorbing material (porous layer) having flow resistance positioned toward the sound field than the airtight membrane, and a micro-perforated sheet having multiple micro-perforations positioned toward the sound field than the porous sound-absorbing material (see, for example, Patent Document 2). [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2004-294619 [Patent Document 2] Japanese Patent Publication No. 2017-044796 [Overview of the project] [Problems that the invention aims to solve]

[0009] However, in the above example of sound absorption technology, the porous layer is merely processed into a plate shape with a constant thickness. Therefore, it is particularly difficult to improve sound absorption performance in the low-frequency range.

[0010] Furthermore, in the above example and another example of sound absorption technology, in order to shift the peak of sound absorption performance to a lower frequency, it is necessary to increase the thickness of the porous layer or increase the mass of the porous layer. In this case, it is difficult to clearly change the resonance frequency of the porous layer, etc., which affects sound absorption performance, and it is difficult to control the sound absorption performance in the low-frequency range to produce a peak in the sound absorption coefficient frequency characteristics in the low-frequency range, especially in the frequency range below approximately 100 Hz (see, for example, Figure 14(b) of Patent Document 1). In addition, there is the problem that the effective volume of the room in which the sound absorber is installed decreases due to the increase in the thickness of the porous layer. In other words, the example and another example of sound absorption technology have the problem of being difficult to control in terms of sound absorption performance and being space-inefficient.

[0011] In light of these circumstances, it is desirable to provide a sound-absorbing material that efficiently improves sound absorption performance in the low-frequency range while suppressing sound absorption performance in the high-frequency range, thereby facilitating control of sound absorption performance and improving space efficiency. [Means for solving the problem]

[0012] To solve the above problems, an acoustic absorber according to one embodiment comprises a porous layer made of a porous material and a non-permeable mass layer, wherein the porous layer has a plurality of holes, the plurality of holes open on the surface of the porous layer in the thickness direction facing the acoustic incidence side, extend toward the interior of the porous layer and are closed within the porous layer, the porous layer includes a through-layer portion having through portions of the plurality of holes and a bottom-side layer portion having the bottom of the plurality of holes, the through-layer portion is located on the acoustic incidence side within the porous layer, the bottom-side layer portion is laminated on the through-layer portion on the back side opposite to the acoustic incidence side in the thickness direction, the mass layer is laminated on the surface of the through-layer portion in the porous layer, and the thickness of the mass layer is smaller than the thickness of the through-layer portion and the bottom-side layer portion of the porous layer, respectively. [Effects of the Invention]

[0013] According to one embodiment of the sound-absorbing material, not only can the sound absorption performance in the low-frequency range be efficiently improved, but the sound absorption performance in the high-frequency range can be suppressed while the sound absorption performance in the low-frequency range is improved, making it easier to control the sound absorption performance and improving space efficiency. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a schematic exploded perspective view showing the case in the sound absorber according to the first embodiment in which the mass layer is placed in the middle of the thickness direction of the porous layer. [Figure 2] Figure 2 is a schematic perspective view showing the interior of a broadcasting studio including a sound-absorbing structure having a sound-absorbing material according to the first embodiment. [Figure 3]Figure 3 is a cross-sectional view showing a sound-absorbing structure having a sound-absorbing material according to the first embodiment, where the mass layer is placed on the surface of the perforating layer portion of the porous layer, as seen when the structure is cut along line XX in Figure 2. [Figure 4] Figure 4 is a cross-sectional view showing a sound-absorbing structure having a sound-absorbing material according to the first embodiment, where the mass layer is placed in the middle of the perforating layer portion of the porous layer, as seen when the structure is cut along a line corresponding to line XX in Figure 2. [Figure 5] Figure 5 is a cross-sectional view showing a sound-absorbing structure having a sound-absorbing material according to the first embodiment, where the mass layer is placed on the back surface of the perforating layer portion of the porous layer, as seen when the structure is cut along a line corresponding to line XX in Figure 2. [Figure 6] Figure 6 is a cross-sectional view showing a sound-absorbing structure having a sound-absorbing material according to the second embodiment, where the mass layer is placed in the middle of the perforating layer portion of the porous layer, as seen when the structure is cut along a line corresponding to line XX in Figure 2. [Figure 7] Figure 7 is a graph showing the relationship between frequency and normal incidence sound absorption coefficient in the sound absorption structures of Examples 1 to 6 and Comparative Example 1. [Figure 8] Figure 8 is a graph showing the relationship between frequency and normal incidence sound absorption coefficient in the sound absorption structures of Examples 7 to 13. [Figure 9] Figure 9 is a graph showing the relationship between frequency and normal incidence sound absorption coefficient in the sound absorption structures of Examples 14 to 20. [Figure 10] Figure 10 is a graph showing the relationship between frequency and normal incidence sound absorption coefficient in the sound absorption structures of Examples 21 to 27. [Figure 11] Figure 11 is a graph showing the relationship between frequency and normal incidence sound absorption coefficient in the sound absorption structures of Examples 28 to 34. [Figure 12] Figure 12 is a graph showing the relationship between frequency and normal incidence sound absorption coefficient in the sound absorption structures of Examples 35 to 41. [Figure 13] Figure 13 is a graph showing the relationship between frequency and normal incidence sound absorption coefficient in the sound absorption structures of Examples 42 to 48. [Figure 14]Figure 14 is a graph showing the relationship between frequency and normal incidence sound absorption coefficient in the sound absorption structures of Comparative Examples 2 to 9. [Figure 15] Figure 15 is a graph showing the relationship between frequency and normal incidence sound absorption coefficient in the sound absorption structures of Examples 49 to 54. [Figure 16] Figure 16 is a graph showing the relationship between frequency and normal incidence sound absorption coefficient in the sound absorption structures of Comparative Examples 10 to 15. [Figure 17] Figure 17 is a graph showing the relationship between the surface density of the mass layer and the peak frequency of the normal incidence sound absorption coefficient in the sound absorption structures of Examples 55 to 59. [Figure 18] Figure 18 is a graph showing the relationship between the surface density of the mass layer and the frequency at which the normal incidence sound absorption coefficient is approximately 0.75 in the sound-absorbing structures of Examples 55 to 59. [Modes for carrying out the invention]

[0015] The sound-absorbing body and sound-absorbing structure having the same according to the first and second embodiments will be described. The sound-absorbing structure according to each embodiment is a structure in which the sound-absorbing body according to that embodiment is installed in a predetermined installation location. The installation location of such a sound-absorbing body can be one surface (installation surface) or part or all of each of the multiple surfaces (installation surfaces) among the walls, ceiling, and floor surrounding the indoor space where sound is handled (for example, the space inside a broadcast studio). However, the installation location is not limited thereto.

[0016] In each embodiment, the direction defined by the sound incidence side (indicated by the single-sided arrow A) and the back side (indicated by the single-sided arrow B) relative to the sound absorber is defined as the thickness direction.

[0017] "First Embodiment" Referring to Figures 1 to 5, the sound-absorbing body 11 and the sound-absorbing structure 10 having the same according to the first embodiment will be described.

[0018] "Sound-absorbing material" The sound absorber 11 according to this embodiment will be described with reference to Figures 1 to 5. The sound absorber 11 according to this embodiment is generally configured as follows. The sound absorber 11 is capable of absorbing sound input from the sound incident side. The sound absorber 11 has a porous layer 20 made of a porous material.

[0019] The porous layer 20 has a plurality of holes 21. Each hole 21 opens on the surface of the porous layer 20 in the thickness direction facing the acoustic incidence side and extends toward the interior of the porous layer 20. The porous layer 20 includes a through-layer portion 22 having through-portions 21a of the plurality of holes 21. In this specification, a through-portion of a hole means a part or all of a hole that extends through the through-layer portion that forms it.

[0020] Furthermore, the sound-absorbing body 11 has a mass layer 30. The mass layer 30 is substantially impermeable. The mass layer 30 is positioned in any direction in the thickness direction of the through-layer portion 22. Specifically, the mass layer 30 is laminated at any position in the thickness direction of the through-layer portion 22 such that it is interposed at any position in the longitudinal direction of the plurality of holes 21. In such a sound-absorbing body, as shown in Figure 3, it is particularly preferable that the mass layer 30 is positioned on the surface in the thickness direction of the through-layer portion 22. It is also preferable that the thickness of the mass layer 30 is smaller than the thickness of the porous layer 20.

[0021] Figures 1 and 3-5 show a sound-absorbing body 11 that includes one mass layer 30 having two mass layer materials 30a (details of which will be described later). However, the sound-absorbing body may also have multiple mass layers. In this case, the multiple mass layers can be spaced apart from each other in the thickness direction of the through-layer portion.

[0022] The through-layer portion 22 has a plurality of through-layer materials 22a stacked in the thickness direction. When the mass layer 30 is positioned in the middle of the thickness direction of the through-layer portion 22 as shown in Figure 4, it is stacked between adjacent through-layer materials 22a.

[0023] Figures 1 and 3-5 show, as an example, a porous layer 20 including a perforated layer section 22 having six perforated layer materials 22a. However, the perforated layer section of a porous layer may also have one to five or seven or more perforated layer materials. In particular, when the perforated layer section has one perforated layer material, the perforated layer section may have a slit formed in the middle of the thickness direction of the perforated layer section so that a mass layer can be inserted. The mass layer can be positioned in the middle of the thickness direction of the perforated layer section by being inserted into such a slit in the perforated layer section. When the sound absorber has multiple mass layers, it is preferable to form multiple slits in the perforated layer section so that each of the multiple mass layers can be inserted.

[0024] The mass layer 30 is detachable so that its position in the thickness direction relative to the through-layer 22 can be changed. In particular, the mass layer 30 is detachably laminated to the through-layer 22 during the manufacturing stage of the sound absorber 11, or before the sound absorber 11 is installed in the sound-absorbing structure 10, which will be described in detail later. After the sound absorber 11 is manufactured, or after the sound absorber 11 is installed in the sound-absorbing structure 10, which will be described in detail later, the mass layer 30 can also be fixed to the through-layer 22.

[0025] In the sound-absorbing body 11 according to this embodiment, each hole 21 is further closed inside the porous layer 20. Based on this configuration, the sound-absorbing body 11 is configured as follows. The configuration in which each hole 61 penetrates the porous layer 60 will be explained later in the sound-absorbing body 51 according to the second embodiment.

[0026] The porous layer 20 includes a bottom layer 23 having a bottom 21b of a plurality of holes 21. The through layer 22 is located on the acoustic incidence side within the porous layer 20, and the bottom layer 23 is laminated on the through layer 22 on the back side opposite to the acoustic incidence side in the thickness direction. The surface of the through layer 22 forms the surface of the porous layer 20.

[0027] In such a sound-absorbing body 11, the mass layer 30 can be positioned on the surface, in the middle, or on the back of the through-layer portion 22 in the thickness direction. Figure 3 shows the case where the mass layer 30 is positioned on the surface in the thickness direction of the through-layer portion 22, Figure 4 shows the case where the mass layer 30 is positioned in the middle of the thickness direction of the through-layer portion 22, and Figure 5 shows the case where the mass layer 30 is positioned on the back of the through-layer portion 22 in the thickness direction.

[0028] Furthermore, the sound-absorbing body 11 according to this embodiment can be configured in detail as follows. The sound-absorbing body 11 has a surface material 40 arranged on its surface in the thickness direction. Although not particularly clearly shown in the illustrations, the surface material 40 can also be arranged along the entire outer surface of the sound-absorbing body 11.

[0029] The surface material 40 is used to prevent the scattering of fibers and other particles of the porous material and to protect the entire surface or outer surface of the porous layer 20. However, if the scattering of fibers and other particles of the porous material is not a problem and protection of the surface of the porous layer is unnecessary, the surface material can be omitted in the sound absorber.

[0030] In such a sound-absorbing body 11, the porous layer 20 is constructed using a porous material that has sound-absorbing properties. The porous material constituting the porous layer 20 should preferably have heat resistance that meets the requirements of the Building Standards Act. The air permeability resistance (also called flow resistance) per unit thickness of the porous material should be approximately 4000 Ns / m² from the viewpoint of ensuring that the porous material has sound-absorbing properties. 4 The above and approximately 120,000 Ns / m 4 The following range is acceptable. The airflow resistance shall be evaluated according to the measurement method specified in ISO 9053-1.

[0031] Such porous materials can be glass wool made from glass fibers. However, the porous materials used in the porous layer are not limited to this. For example, the porous material can also be rock wool, felt (especially felt made from recycled materials), etc. The porous material can also be a foam material made of resin, such as urethane foam or melamine foam. When selecting such a porous material, not only the acoustic performance but also the performance required for fire-resistant materials under the Building Standards Act should be a major factor.

[0032] The surface of the porous layer 20 can be formed into a smooth shape. Here, a smooth shape includes a planar shape, a curved shape, a smooth shape, a shape with gentle undulations, a shape with fine irregularities, and the like.

[0033] The porous layer 20 is configured with a through-layer portion 22 and a bottom-side layer portion 23 as separate components. However, the porous layer can also be configured with the through-layer portion and the bottom-side layer portion as an integrated unit. In this case, the porous layer may have a slit formed on the back surface in the thickness direction of the through-layer portion to allow the insertion of a mass layer. The mass layer can be positioned on the back surface in the thickness direction of the through-layer portion by being inserted into such a slit in the porous layer.

[0034] The porous material used in the through-layer 22 and the bottom-side layer 23 can be the same type. However, the porous material used in the through-layer and the bottom-side layer can also be different types.

[0035] Each hole 21 opens on the surface of the porous layer 20 in the thickness direction, extends toward the interior of the porous layer 20, and is then closed within the porous layer 20. Specifically, multiple holes 21 open on the surface of the through-layer portion 22, penetrate the through-layer portion 22, and are closed by the bottom-side layer portion 23.

[0036] The through-layer portion 22 is formed in layers. Each through-layer material 22a has a plurality of through-holes 21c that penetrate in the thickness direction. When the plurality of through-layer materials 22a are stacked, the plurality of through-holes 21c in the plurality of through-layer materials 22a form the through-ports 21a of the plurality of holes 21 in the through-layer portion 22.

[0037] The bottom layer 23 is formed in layers. The bottom layer 23 has multiple bottom layer materials 23a that are stacked in its thickness direction. In Figures 1 and 3-5, a bottom layer 23 having six bottom layer materials 23a is shown as an example. However, the bottom layer is not limited to this. For example, the bottom layer may have one to five or seven or more bottom layer materials.

[0038] The bottom layer 23 has bottom portions 21b of multiple holes 21 that close the through portions 21a of each of the multiple holes 21 in the through layer 22. The bottom portion 21b of each hole 21 is formed to be substantially flat. However, the shape of the bottom is not limited to being substantially flat. For example, the bottoms of some or all of the multiple holes can be formed to be concave.

[0039] In the porous layer 20, each hole 21 extends substantially linearly such that its cross-section is substantially constant in its longitudinal direction. In this case, the through-holes 21c of the multiple through-layer materials 22a corresponding to the through-ports 21a of each hole 21 are formed to have substantially the same cross-section. However, each hole can also extend such that its cross-section changes gradually, continuously, or in stages in its longitudinal direction. In this case, the through-holes of the multiple through-layer materials corresponding to the through-ports of each hole can be formed so that some or all of their cross-sections are different from each other.

[0040] Each hole 21 extends in a substantially straight line. Each hole 21 extends substantially parallel to the thickness direction. Multiple holes 21 also extend substantially parallel to each other. Furthermore, each hole 21 extends substantially parallel to the thickness direction of the porous layer 20. Multiple holes 21 are formed so that their cross-sections are substantially identical to each other. However, the shape of each hole is not limited to these. Some or all of the multiple holes may extend inclined with respect to the thickness direction. Some or all of the multiple holes may be formed to be curved. Multiple holes may be formed so that some or all of their cross-sections are different to each other.

[0041] The multiple holes 21 are arranged in a substantially matrix-like pattern when viewed in the thickness direction of the porous layer 20. However, the arrangement of the multiple holes is not limited to this. The multiple holes can be distributed regularly or randomly when viewed in the thickness direction of the porous layer.

[0042] The cross-sections of the multiple holes 21 are formed in a substantially circular shape. However, the cross-sections of the multiple holes are not limited to this. Some or all of the multiple holes can be formed in a substantially polygonal shape such as a substantially triangular shape, a substantially square shape, a substantially pentagonal shape, a substantially hexagonal shape, a substantially elliptical shape, a substantially semicircular shape, a substantially semielliptical shape, a substantially sector shape, etc.

[0043] The sound-absorbing element 11 and the sound-absorbing structure 10 including it according to this embodiment are characterized in that they have excellent sound absorption characteristics, particularly in the low-frequency range, and have excellent sound absorption performance over a wide frequency range.

[0044] The opening ratio of the multiple holes 21 that open on the surface of such a porous layer 20 can be set to approximately 10% or more from the viewpoint of improving sound absorption characteristics. The opening ratio can be set to a range of approximately 80% or less from the viewpoint of maintaining the shape of the porous layer 20. Therefore, the opening ratio can be set to a range of approximately 10% or more and approximately 80% or less.

[0045] Furthermore, the occupancy rate of the multiple holes 21 in the porous layer 20 can be set to approximately 10% or more from the viewpoint of improving sound absorption characteristics. The occupancy rate can be set to a range of approximately 80% or less from the viewpoint of maintaining the shape of the porous layer 20. Therefore, the occupancy rate can be set to a range of approximately 10% or more and approximately 80% or less.

[0046] The length of each hole 21 in the thickness direction, i.e., the depth of each hole 21 (especially its average value), can be set to approximately 5% or more of the length of the porous layer 20 in the thickness direction, i.e., the thickness of the porous layer 20, particularly from the viewpoint of improving sound absorption characteristics in the low frequency range. The depth of each hole 21 (especially its average value), can be set to approximately 95% or less of the thickness of the porous layer 20, particularly from the viewpoint of improving sound absorption characteristics in the low frequency range.

[0047] Therefore, the depth of each hole 21 (especially its average value) can be within the range of approximately 5% or more and approximately 95% or less of the thickness of the porous layer 20. In the sound absorber 51 according to the second embodiment described later, each hole 61 penetrates the porous layer 60, so the depth of each hole 61 (especially its average value) can be within the range of approximately 5% or more and approximately 100% or less of the thickness of the porous layer 60.

[0048] For example, from the viewpoint of maintaining the shape of the porous layer 20, the thickness of the through-layer portion 22 of the porous layer 20 can be approximately 50 mm or more, and the thickness of the bottom-side layer portion 23 of the porous layer 20 can be approximately 50 mm or more. For example, from the viewpoint of miniaturizing the sound absorber 11, the thickness of the porous layer 20 can be approximately 1000 mm or less. However, the thickness of the porous layer and its through-layer portion and bottom-side layer are not limited to these.

[0049] For example, in terms of maintaining the shape of the porous layer 20, the porous layer 20 has a density of approximately 10 kg / m³. 3 Preferably, about 16 kg / m 3It can be configured to exclude portions corresponding to the plurality of holes 21 from the porous material having the above volume density. For example, from the viewpoint of weight reduction of the sound absorber 11, the porous layer 20 has a volume density of about 100 kg / m 3 Hereinafter, preferably, about 96 kg / m 3 It can be configured to exclude portions corresponding to the plurality of holes 21 from the porous material having a volume density of hereinafter. However, the configuration of the porous layer is not limited to these.

[0050] The mass layer 30 is formed in a layer shape. The mass layer 30 has one mass layer material 30a or a plurality of mass layer materials 30a laminated in the thickness direction thereof. In FIGS. 1 and 3 to 5, as an example, a mass layer 30 having two mass layer materials 30a is shown. However, the mass layer is not limited to this. For example, the mass layer can also have one or three or more mass layer materials.

[0051] The material constituting the mass layer 30 is a substantially airtight material. The material constituting the mass layer 30 can be wood, stone, glass, plywood, vinyl chloride, acrylic, polypropylene, ceramics, carbon fiber reinforced plastic (CFRP), etc. Further, the material constituting the mass layer 30 can be a compressed high-density porous material, for example, compressed thermoplastic felt, thermosetting felt, glass wool, etc. However, the material constituting the mass layer is not limited to these.

[0052] For example, from the viewpoint of ensuring weight and rigidity so as to surely provide sound absorption performance, the thickness of the mass layer 30 can be about 0.2 mm or more, preferably about 0.3 mm or more, more preferably about 0.5 mm or more. For example, from the viewpoint of weight reduction, the thickness of the mass layer 30 can be about 5 mm or less. For example, from the viewpoints of enhancing sound absorption performance, particularly in the low-frequency region around about 100 Hz, and further weight reduction, the thickness of the mass layer 30 can be about 4 mm or less, preferably about 2 mm or less. However, the thickness of the mass layer is not limited to these.

[0053] For example, in terms of ensuring weight and rigidity to reliably provide sound performance, the surface density of the mass layer 30 is generally about 50 g / m². 2 The above can be achieved. For example, from the viewpoint of weight reduction, the surface density of the mass layer 30 is generally about 10,000 g / m³. 2 The following are possible. However, the surface density of the mass layer is not limited to these.

[0054] The surface material 40 is used to protect the porous layer 20, particularly its surface, and a wide variety of materials can be used for this surface material 40. The materials used for the surface material 40 can be cloth-like, sheet-like, MPP (microperforated plate or microperforated membrane), perforated plates such as punched metal, etc.

[0055] For example, the cloth-like or sheet-like material may contain aramid fibers, glass fibers, cellulose fibers, nylon fibers, vinylon fibers, polyester fibers, polyethylene fibers, polypropylene fibers, polyolefin fibers, rayon fibers, etc. The cloth-like or sheet-like material may also contain carbon fibers. Furthermore, the cloth-like or sheet-like material may also contain thermosetting resins. Examples of thermosetting resins include phenolic resin (PF), epoxy resin (EP), melamine resin (MF), unsaturated polyester resin (UP), polyurethane (PUR), and thermosetting polyimide (PI). In addition, the cloth-like or sheet-like material should have flame retardancy and heat resistance to meet the requirements for fire-resistant materials under the Building Standards Act. The surface material constructed using such materials may be a nonwoven fabric. However, the surface material may also be something other than a nonwoven fabric. For example, the surface material may be a woven fabric, etc.

[0056] For example, a perforated plate can be made from materials such as iron, stainless steel, aluminum, or wood, and can have numerous holes formed on it, such as round holes, square holes, or elongated holes.

[0057] As shown in Figure 3, when the mass layer 30 is positioned on the surface of the through-layer portion 22 in the thickness direction, the surface material 40 is positioned along the surface of the mass layer 30 in the thickness direction. In this case, the surface of the mass layer 30 is covered by the surface material 40. However, as described above, if the surface material is omitted, the surface of the mass layer will be exposed on the surface of the sound absorber.

[0058] As shown in Figure 4 or 5, when the mass layer 30 is positioned in the middle or on the back of the through-layer portion 22 in the thickness direction, the surface material 40 is positioned along the surface of the through-layer portion 22. In this case, the surface of the porous layer 20 is covered by the surface material 40. However, as described above, if the surface material is omitted, the surface of the porous layer, particularly the surface of the through-layer portion, will be exposed on the surface of the sound absorber.

[0059] Although not specifically shown in the figures, the sound absorber 11 may be configured to have a housing (not shown) that surrounds the sides of the porous layer 20 and the mass layer 30, or that surrounds the sides of the porous layer 20 and the mass layer 30 and the back surface of the porous layer 20. The sound absorber 11 may also have a skeletal member (not shown) that is formed to support the surface material 40 along the surface of the porous layer 20 or the mass layer 30. However, the sound absorber may also be configured without the housing. The sound absorber may also be configured to support the surface material by means other than the skeletal member.

[0060] For example, a sound-absorbing body can be configured to support its surface material by bringing the surface material into contact with the surface of a porous layer or mass layer. A sound-absorbing body can also be configured to have the material constituting the surface material applied to or integrally molded onto the surface of a porous layer or mass layer. When the material constituting the surface material is applied to or integrally molded onto the surface of a porous layer, the holes in the porous layer are not blocked on the surface of the porous layer but are exposed on the outside of the sound-absorbing body.

[0061] As described later, the sound-absorbing material 11 exhibits excellent sound-absorbing properties and can therefore be used as a substitute for existing sound-absorbing materials and sound-absorbing elements. For this reason, the thickness of the sound-absorbing material 11 can be approximately 25 mm or more and approximately 1200 mm or less, similar to the thickness range of typical sound-absorbing finishes. However, the thickness of the sound-absorbing material is not limited to this range.

[0062] As will be shown in the embodiments described later, the sound absorber 11 is preferably constructed based on the following ranges of thickness and surface density of the porous layer 20 and surface density of the mass layer 30, with respect to ensuring high sound absorption characteristics in the low-frequency range and setting the peak of the normal incidence sound absorption coefficient to approximately 150 Hz or less. When the thickness of the through-layer portion 22 of the porous layer 20 is approximately 50 mm or more, and the thickness of the bottom-side layer portion 23 of the porous layer 20 is approximately 50 mm or more, the porous layer 20 has a surface density of approximately 3200 g / m 2 The porous material has the above surface density, and the portions corresponding to the multiple holes 21 are removed, and the surface density of the mass layer 30 is approximately 5500 g / m². 2 That should be sufficient.

[0063] When the thickness of the through-layer portion 22 of the porous layer 20 is approximately 50 mm or more, and the thickness of the bottom-side layer portion 23 of the porous layer 20 is approximately 50 mm or more, the porous layer 20 has a density of approximately 4800 g / m². 2 The porous material has the above surface density, and is configured such that portions corresponding to the multiple holes 21 are removed, and the surface density of the mass layer 30 is approximately 3900 g / m². 2 That should be sufficient.

[0064] When the thickness of the through-layer portion 22 of the porous layer 20 is approximately 75 mm or more, and the thickness of the bottom-side layer portion 23 of the porous layer 20 is approximately 75 mm or more, the porous layer 20 has a density of approximately 4800 g / m². 2 The porous material has the above surface density, and is configured such that portions corresponding to the multiple holes 21 are removed, and the surface density of the mass layer 30 is approximately 2600 g / m². 2 That should be sufficient.

[0065] When the thickness of the through-layer portion 22 of the porous layer 20 is approximately 75 mm or more, and the thickness of the bottom-side layer portion 23 of the porous layer 20 is approximately 75 mm or more, the porous layer 20 has a density of approximately 7200 g / m². 2 The porous material has the above surface density, and is configured such that portions corresponding to the multiple holes 21 are removed, and the surface density of the mass layer 30 is approximately 1600 g / m². 2 That should be sufficient.

[0066] When the thickness of the through-layer portion 22 of the porous layer 20 is approximately 150 mm or more, and the thickness of the bottom-side layer portion 23 of the porous layer 20 is approximately 150 mm or more, the porous layer 20 has a density of approximately 9600 g / m². 2 The porous material has the above surface density, and is configured such that portions corresponding to the multiple holes 21 are removed, and the surface density of the mass layer 30 is approximately 240 g / m². 2 That should be sufficient.

[0067] "Sound-absorbing structure" The sound-absorbing structure 10 according to this embodiment will be described with reference to Figures 2 to 5. In Figure 2, a schematic representation of the wall surface of a broadcasting studio to which the sound-absorbing structure 10 having a sound-absorbing body 11 is applied is shown as an example. However, the sound-absorbing structure can also be applied to places other than broadcasting studios. For example, the sound-absorbing structure can be applied to recording studios, audio rooms, instrument practice rooms, etc. Furthermore, the sound-absorbing structure can be applied to anechoic chambers, semi-anechoic chambers, etc., for the purpose of low-frequency acoustic experiments.

[0068] In the sound-absorbing structure 10, the sound-absorbing body 11 is positioned adjacent to the installation surface W. The installation surface W faces the sound-absorbing body 11 on its rear side. Specifically, the back surface of the sound-absorbing body 11 is adjacent to the installation surface W. Although not shown in the figures, the sound-absorbing structure 10 may have a support member (not shown) that supports the sound-absorbing body 11 in an adjacent position to the installation surface W.

[0069] However, a gap can be left between the back of the sound absorber and the mounting surface to form an air layer. The sound-absorbing structure can also support the sound absorber by means other than support members. For example, the sound-absorbing structure can support the sound absorber by fixing it to the mounting surface.

[0070] "Method for manufacturing sound-absorbing materials" Referring to Figures 3 to 5, an example of a method for manufacturing the sound absorber 11 according to this embodiment will be described. First, a porous material is cut to form a layered through-layer portion 22 and a bottom-side layer portion 23, and multiple holes 21 through-parts 21a are drilled in the through-layer portion 22.

[0071] The through-layer 22 is laminated onto the bottom-side layer 23 such that the through-holes 21a of the multiple holes 21 in the through-layer 22 are closed from the back side by the bottoms 21b of the multiple holes 21 in the bottom-side layer 23. As a result, a porous layer 20 is created.

[0072] Next, a layered mass layer 30 is formed by cutting a plate-shaped material. By conducting simulations, experiments, and calculations in advance, the position of the mass layer 30 in the thickness direction relative to the porous layer 20 that will yield peak sound absorption performance at a desired frequency is predicted. In accordance with this prediction, the mass layer 30 is positioned at one of the positions in the thickness direction of the porous layer 20.

[0073] The surface material 40 is placed on the surface of the sound-absorbing body 11. Alternatively, the surface material 40 can be placed on the entire outer surface of the sound-absorbing body 11. As a result, the sound-absorbing body 11 is manufactured.

[0074] However, the method of manufacturing the sound absorber is not limited to this. For example, instead of cutting the porous material, the porous layer of the sound absorber, such as the perforated layer and the bottom layer, can also be manufactured by foaming a foam material in a mold corresponding to the shape of the porous layer having multiple holes.

[0075] The inventors have discovered that, as described above, the sound absorption coefficient of a porous layer made of porous material without a mass layer tends to saturate with little change even when the thickness of the porous layer is increased. Furthermore, the inventors have discovered that when a mass layer is added to the porous layer, the frequency selectivity of the frequency characteristics of the sound absorption coefficient is reduced, and a broad peak is obtained on the frequency axis. In such a configuration, the frequency width of the peak of the sound absorption coefficient becomes broad, and as a result, sound absorption performance can be improved over a wide frequency range, and effective sound absorption performance can be obtained for various sounds.

[0076] Furthermore, the inventors have discovered that the sound-absorbing material 11 exhibits sound absorption performance through the following mechanism. Specifically, sound incident on the sound-absorbing material 11 passes through the air in the multiple holes 21 and the porous material portion in the penetrating layer portion 22 of the porous layer 20, in the direction from the surface to the back in the thickness direction of the sound-absorbing material 11. At this time, the sound passing through the porous material portion has a greater energy loss and slower velocity compared to the sound passing through the air. Therefore, the interface between the sound passing through the air and the sound passing through the porous material portion becomes discontinuous in the penetrating layer portion 22, and as a result, friction occurs at this interface, and sound is absorbed.

[0077] As described above, the sound absorber 11 according to this embodiment provides the following functions and effects. The sound absorber 11 according to this embodiment comprises a porous layer 20 made of a porous material and a mass layer 30, wherein the porous layer 20 has a plurality of holes 21, each hole 21 opening on the surface of the porous layer 20 in the thickness direction facing the sound incident side and extending toward the interior of the porous layer 20, the porous layer 20 includes a through-layer portion 22 having through-ports 21a of the plurality of holes 21, and the mass layer 30 is positioned at any position in the thickness direction of the through-layer portion 22 such that it is interposed at any position in the longitudinal direction of the plurality of holes 21.

[0078] The sound-absorbing structure 10 according to this embodiment comprises a sound-absorbing body 11 according to this embodiment and an installation surface W in the room space located on the back side of the sound-absorbing body 11 opposite to the sound incidence side in the thickness direction, wherein the sound-absorbing body 11 is arranged so that its back side in the thickness direction faces the installation surface W.

[0079] With this sound-absorbing structure 10 and sound-absorbing body 11, the perforated layer portion 22 of the porous layer 20 having the perforated portions 21a of the plurality of holes 21 can improve the sound absorption performance in the low-frequency range. Furthermore, the reflection generated by the mass layer 30, which is positioned at any point in the thickness direction of the perforated layer portion 22, can be intentionally and efficiently controlled, and by such control, the sound absorption performance in the high-frequency range can be efficiently suppressed. If it is desired to keep the sound absorption rate in the high-frequency range low, it is preferable to place the mass layer 30 in a part close to the surface of the perforated layer portion.

[0080] Generally, porous materials exhibit high sound absorption performance in the high-frequency range. Therefore, in room sound field design, excessive sound absorption in the high-frequency range results in a poor balance with the low-frequency range where little effect is obtained, and the frequency balance of the recorded and reproduced sound is disrupted, often resulting in an unnatural sound field. In contrast, the sound absorber 11 according to this embodiment can selectively exhibit sound absorption performance in the low-frequency range, thus avoiding these problems.

[0081] Furthermore, in the sound-absorbing structure 10 and sound-absorbing body 11 according to this embodiment, by changing the position of the mass layer 30 in the thickness direction that is in contact with the through-layer portion 22 of the porous layer 20 relative to the through-layer portion 22, or by changing the surface density of the mass layer 30, the frequency of the peak of sound absorption performance can be easily shifted without changing the thickness of the porous layer 20, and the sound absorption frequency characteristics can be easily changed. As a result, it is possible to easily control the sound absorption performance and further improve space efficiency. Therefore, according to the sound-absorbing structure 10 and sound-absorbing body 11 according to this embodiment, it is possible to improve the sound absorption performance in the low-frequency range while suppressing the sound absorption performance in the high-frequency range, making it easy to control the sound absorption performance and improving space efficiency.

[0082] In the sound-absorbing structure 10 and sound-absorbing body 11 according to this embodiment, the through-layer portion 22 has a plurality of through-layer materials 22a stacked in the thickness direction, and when the mass layer 30 is placed in the middle of the through-layer portion 22 in the thickness direction, it is stacked between adjacent through-layer materials 22a.

[0083] With this sound-absorbing structure 10 and sound-absorbing body 11, even when the mass layer 30 is positioned in the middle of the thickness direction of the through-layer portion 22, the mass layer 30 can be easily installed between adjacent through-layer materials 22a. Therefore, the position of the mass layer 30 in the thickness direction relative to the through-layer portion 22 can be easily changed, and as a result, the sound absorption performance can be easily controlled.

[0084] In the sound-absorbing structure 10 and sound-absorbing body 11 according to this embodiment, the mass layer 30 is detachable so that its position in the thickness direction relative to the through-layer portion 22 can be changed. With such a sound-absorbing body 11, the position in the thickness direction of the detachable mass layer 30 relative to the through-layer portion 22 can be easily changed. Therefore, the sound absorption performance can be easily controlled.

[0085] In the sound-absorbing structure 10 and sound-absorbing body 11 according to this embodiment, each hole 21 is further closed inside the porous layer 20, the porous layer 20 includes a bottom-side layer 23 having the bottoms 21b of the multiple holes 21, the through-layer 22 is located on the sound incidence side within the porous layer 20, and the bottom-side layer 23 is laminated on the through-layer 22 on the back side opposite to the sound incidence side in the thickness direction.

[0086] With such a sound-absorbing structure 10 and sound-absorbing body 11, the through-layer portion 22 of the porous layer 20 having through-holes 21a and the bottom-side layer portion 23 having bottoms 21b of the multiple holes 21 can efficiently improve sound absorption performance in the low-frequency range.

[0087] In particular, the sound-absorbing body 11 according to this embodiment is preferably configured as follows. In other words, the sound absorber 11 according to this embodiment comprises a porous layer 20 made of a porous material and a mass layer 30 that is substantially impermeable, wherein the porous layer 20 has a plurality of holes 21, the plurality of holes 21 open on the surface of the porous layer 20 in the thickness direction facing the sound incidence side, extend toward the interior of the porous layer 20 and are closed within the porous layer 20, the porous layer 20 includes a through-layer portion 22 having through-portions 21a of the plurality of holes 21 and a bottom-side layer portion 23 having bottoms 21b of the plurality of holes 21, the through-layer portion 22 is located on the sound incidence side within the porous layer 20, the bottom-side layer portion 23 is laminated on the through-layer portion 22 on the back side opposite to the sound incidence side in the thickness direction relative to the through-layer portion 22, and the mass layer 30 is disposed on the surface of the through-layer portion 22 in the porous layer 20, and the thickness of the mass layer 30 is smaller than the thickness of the through-layer portion 22 and the bottom-side layer portion 23 of the porous layer 20, respectively. The sound-absorbing structure 10 according to this embodiment has such a sound-absorbing body 11.

[0088] Such a sound-absorbing structure 10 and sound-absorbing body 11 can efficiently improve sound absorption performance in the low-frequency range. In particular, within the range of thickness and surface density of the porous layer 20 and the surface density of the mass layer 30 described above, the peak of the normal incidence sound absorption coefficient can be set to approximately 150 Hz or less, ensuring high sound absorption characteristics in the low-frequency range.

[0089] "Second Embodiment" Referring to Figure 6, a sound-absorbing body 51 and a sound-absorbing structure 50 having the same according to the second embodiment will be described.

[0090] "Sound-absorbing materials and sound-absorbing structures" Referring to Figure 6, the sound-absorbing body 51 and the sound-absorbing structure 50 having the same according to this embodiment will be described. In the sound-absorbing body 51 according to this embodiment, each hole 61 penetrates the porous layer 60 and opens further on the back side of the porous layer 60, which faces the back side opposite in the thickness direction from the sound incidence side. Except for this configuration, the sound-absorbing body 51 according to this embodiment is the same as the sound-absorbing body 11 according to the first embodiment.

[0091] The porous layer 60 includes a through-layer portion 62 having through-holes 61a. Each hole 61 opens on the surface of the porous layer 60 in the thickness direction, extends toward the interior of the porous layer 60, and is then closed within the porous layer 60.

[0092] Specifically, the multiple holes 61 open on the surface of the through-layer portion 62, penetrate the through-layer portion 62, and then open on the back surface of the through-layer portion 62. The surface of the through-layer portion 62 forms the surface of the porous layer 60, and the back surface of the through-layer portion 62 forms the back surface of the porous layer 60.

[0093] The through-layer portion 62 is formed in layers. The through-layer portion 62 has a plurality of through-layer materials 62a stacked in its thickness direction. Each of the plurality of layer materials 62a in the porous layer 60 corresponds to one of these plurality of through-layer materials 62a. In Figure 6, as an example, a through-layer portion 62 having 12 through-layer materials 62a is shown. However, the through-layer portion is not limited to this. For example, the through-layer portion may have 1 to 11 or 13 or more through-layer materials.

[0094] Each through-layer material 62a has multiple through-holes 61b that penetrate in the thickness direction. When multiple through-layer materials 62a are stacked, the multiple through-holes 61b in the multiple through-layer materials 62a form the through-holes 61a of the multiple holes 61 in the through-layer portion 62.

[0095] In such a sound-absorbing body 51, the mass layer 30 can be placed on the surface, in the middle, or on the back of the through-layer portion 62 in the thickness direction. Figure 6 shows, as an example, a sound-absorbing structure 50 having a sound-absorbing body 51 in which the mass layer 30 is placed in the middle of the through-layer portion 62.

[0096] "Method for manufacturing sound-absorbing materials" Referring to Figure 6, an example of a method for manufacturing the sound absorber 51 according to this embodiment will be described. First, a layered through-layer portion 62 is formed by cutting a porous material, and multiple holes 61 through-parts 61a are drilled in the through-layer portion 62. As a result, a porous layer 60 is produced. The process for producing such a porous layer 60 is the same as the process for producing the porous layer 20 according to the first embodiment, except that the bottom layer portion 23 is not installed.

[0097] Next, a layered mass layer 30 is formed by cutting a plate-shaped material. By conducting simulations, experiments, and calculations in advance, the position of the mass layer 30 in the thickness direction relative to the porous layer 60 that will yield peak sound absorption performance at a desired frequency is predicted. In accordance with this prediction, the mass layer 30 is positioned at one of the positions in the thickness direction of the porous layer 60.

[0098] The surface material 40 is placed on the surface of the sound-absorbing body 51. Alternatively, the surface material 40 can be placed on the entire outer surface of the sound-absorbing body 51. As a result, the sound-absorbing body 51 is manufactured.

[0099] As described above, the sound-absorbing body 51 and the sound-absorbing structure 50 having the same according to this embodiment can be obtained, except for the functions and effects based on the configuration in which each hole 21 is closed inside the porous layer 20, which are the same as those of the sound-absorbing body 11 according to the first embodiment.

[0100] Although embodiments of the present invention have been described so far, the present invention is not limited to the embodiments described above, and the present invention can be modified and changed based on its technical concept. [Examples]

[0101] First, Examples 1-48 and Comparative Examples 1-9 will be described.

[0102] Examples 1-27 Examples 1 to 27 will now be described. In Examples 1 to 27, the sound-absorbing structure according to the first embodiment was used. Specifically, in each of the sound-absorbing structures in Examples 1 to 27, a sound-absorbing body was used that included a porous layer having a through-layer portion with a thickness of approximately 150 mm and a bottom-side layer portion with a thickness of approximately 150 mm, and a mass layer.

[0103] Furthermore, the porous layer had 12 layers. Specifically, the through-layer section had 6 through-layers with a thickness of approximately 25 mm. The bottom layer section had 6 bottom layers with a thickness of 25 mm. The porous material used in the through-layer and bottom layer sections of the porous layer had a volume density of approximately 32 kg / m³. 3 Glass wool was chosen for this purpose.

[0104] The mass layers in Examples 1-6 were fabricated using a mass layer material made of acrylic plates. The mass layers in Examples 7-27 were fabricated using a mass layer material made of polyvinyl chloride plates. The thickness of the mass layers in Examples 1-6 was approximately 0.5 mm, and the surface density of the mass layers was approximately 650 g / m². 2 The mass layers of Examples 1 to 6 each contained one mass layer material.

[0105] The mass layer thickness in Examples 7-13 is approximately 1.0 mm, and the surface density of the mass layer is approximately 1400 g / m². 2 The mass layers of Examples 7-13 each contained one mass layer material.

[0106] The mass layer thickness in Examples 14-20 is approximately 2.0 mm, and the surface density of the mass layer is approximately 2800 g / m². 2 The mass layers of Examples 14-20 had two mass layer materials stacked on top of each other.

[0107] The mass layer thickness in Examples 21-27 is approximately 2.0 mm, and the surface density of the mass layer is approximately 5600 g / m². 2 The mass layers of Examples 21-27 had four mass layer materials stacked on top of each other.

[0108] These porous layers, having through-layers and bottom layers, and the mass layer were formed into a roughly square shape of approximately 300 mm × 300 mm when viewed in the thickness direction. Multiple through-holes with circular cross-sections were formed in the through-layers. The multiple holes were arranged in a matrix. The diameter of each hole was approximately 40 mm. The pitch between adjacent holes was approximately 55 mm. The depth of each hole was approximately 150 mm.

[0109] In Examples 1, 7, 14, and 21, the mass layer was laminated on the surface of the porous layer. In Examples 2, 8, 15, and 22, the mass layer was laminated approximately 25 mm from the surface of the porous layer. In Examples 3, 9, 16, and 23, the mass layer was laminated approximately 50 mm from the surface of the porous layer. In Examples 4, 10, 17, and 24, the mass layer was laminated approximately 75 mm from the surface of the porous layer.

[0110] In Examples 5, 11, 18, and 25, the mass layer was laminated at a position approximately 100 mm from the surface of the porous layer. In Examples 6, 12, 19, and 26, the mass layer was laminated at a position approximately 125 mm from the surface of the porous layer. In Examples 13, 20, and 27, the mass layer was laminated at a position approximately 150 mm from the surface of the porous layer.

[0111] Furthermore, since there is little need to protect the porous layer, the surface material was omitted from the sound absorber. The component corresponding to the installation surface in the room space was installed adjacent to the back of the sound absorber.

[0112] Such a sound-absorbing structure was installed inside an acoustic impedance pipe having a roughly square cross-section of approximately 300 mm x 300 mm. Specifically, the sound-absorbing structure was installed inside the acoustic impedance pipe so that the surface of the sound absorber faced the opening on the sound-ingress side of the acoustic impedance pipe. In this installed state, sound was input into the acoustic impedance pipe from the sound-ingress opening, and the normal incidence sound absorption coefficient of the sound-absorbing structure for this sound was measured according to JIS A1405-2.

[0113] Examples 28-48 Examples 28 to 48 will now be described. In Examples 28 to 48, the sound-absorbing structure according to the second embodiment was used. Specifically, in each of the sound-absorbing structures in Examples 28 to 48, a sound-absorbing body was used that included a porous layer having a through-layer portion with a thickness of approximately 300 mm and a mass layer.

[0114] Furthermore, the porous layer had 12 layers. Specifically, the perforated layer had 12 perforated layers with a thickness of approximately 25 mm. The porous material used in the perforated layer of the porous layer had a volume density of approximately 32 kg / m³. 3 Glass wool was chosen for this purpose.

[0115] The mass layers in Examples 28-48 were fabricated using a mass layer material made of polyvinyl chloride board. The thickness of the mass layers in Examples 28-34 was approximately 1.0 mm, and the surface density of the mass layers was approximately 1400 g / m². 2 That was the case.

[0116] The mass layers in Examples 28-34 had one mass layer material. The mass layers in Examples 35-41 had a thickness of approximately 2.0 mm and a surface density of approximately 2800 g / m². 2 The mass layers of Examples 35-41 had two mass layer materials stacked on top of each other.

[0117] The mass layer thickness in Examples 42-48 is approximately 4.0 mm, and the surface density of the mass layer is approximately 5600 g / m². 2 The mass layers of Examples 42-48 had four mass layer materials stacked on top of each other.

[0118] These porous layers with perforations and the mass layer were formed into a roughly square shape of approximately 300 mm × 300 mm when viewed in the thickness direction. Multiple perforations with circular cross-sections were formed in the perforations. The multiple holes were arranged in a matrix. The diameter of each hole was approximately 40 mm. The pitch between adjacent holes was approximately 55 mm. The depth of each hole was approximately 300 mm.

[0119] In Examples 28, 35, and 42, the mass layer was laminated on the surface of the porous layer. In Examples 29, 36, and 43, the mass layer was laminated approximately 25 mm from the surface of the porous layer. In Examples 30, 37, and 44, the mass layer was laminated approximately 50 mm from the surface of the porous layer. In Examples 31, 38, and 45, the mass layer was laminated approximately 75 mm from the surface of the porous layer.

[0120] In Examples 32, 39, and 46, the mass layer was laminated at a position approximately 100 mm from the surface of the porous layer. In Examples 33, 40, and 47, the mass layer was laminated at a position approximately 125 mm from the surface of the porous layer. In Examples 34, 41, and 48, the mass layer was laminated at a position approximately 150 mm from the surface of the porous layer.

[0121] Furthermore, since there is little need to protect the porous layer, the surface material was omitted from the sound absorber. The component corresponding to the installation surface in the room space was installed adjacent to the back of the sound absorber.

[0122] The perpendicular incidence sound absorption coefficients of the sound-absorbing structures in Examples 28-48 were measured in the same manner as the perpendicular incidence sound absorption coefficients of the sound-absorbing structures in Examples 1-27.

[0123] "Comparative Examples 1-9" Comparative Examples 1 to 9 will now be described. In Comparative Example 1, a sound-absorbing structure was used which was obtained by removing the mass layer from each of the sound-absorbing structures in Examples 1 to 27. In the sound-absorbing structures in Comparative Examples 2 to 9, a sound-absorbing body was used which included a porous layer having a non-penetrating layer portion with a thickness of approximately 300 mm. Unlike the penetrating layers in Examples 1 to 48, the non-penetrating layer portion was configured not to have holes. In the structures in Comparative Examples 3 to 9, the sound-absorbing body was further configured to include a mass layer.

[0124] Furthermore, the porous layer had 12 layers. Specifically, the non-penetrating layer section had 12 non-penetrating layers with a thickness of approximately 25 mm. The porous material used in the non-penetrating layer section of the porous layer had a volume density of approximately 32 kg / m³. 3 Glass wool was chosen for this purpose.

[0125] The mass layers of Comparative Examples 3 to 9 were fabricated using a mass layer material made of acrylic plate. The thickness of the mass layers of Comparative Examples 3 to 9 was approximately 0.5 mm, and the surface density of the mass layers was approximately 650 g / m². 2 The mass layers of Comparative Examples 3 to 9 each had one mass layer material. These porous layers having non-penetrating layers and the mass layer were formed into a roughly square shape of approximately 300 mm × 300 mm when viewed in the thickness direction.

[0126] In Comparative Example 3, the mass layer was laminated on the surface of the porous layer. In Comparative Example 4, the mass layer was laminated approximately 25 mm from the surface of the porous layer. In Comparative Example 5, the mass layer was laminated approximately 50 mm from the surface of the porous layer. In Comparative Example 6, the mass layer was laminated approximately 75 mm from the surface of the porous layer.

[0127] In Comparative Example 7, the mass layer was laminated at a position approximately 100 mm from the surface of the porous layer. In Comparative Example 8, the mass layer was laminated at a position approximately 125 mm from the surface of the porous layer. In Comparative Example 9, the mass layer was laminated at a position approximately 150 mm from the surface of the porous layer.

[0128] Furthermore, since there is little need to protect the porous layer, the surface material was omitted from the sound absorber. The component corresponding to the installation surface in the room space was installed adjacent to the back of the sound absorber.

[0129] The perpendicular incidence sound absorption coefficients of the sound-absorbing structures in Comparative Examples 1 to 9 were measured in the same manner as the perpendicular incidence sound absorption coefficients of the sound-absorbing structures in Examples 1 to 27.

[0130] Based on the above measurements, the relationship between frequency and normal incidence sound absorption coefficient in the sound absorption structures of Examples 1-6 and Comparative Example 1 is as shown in Figure 7. In Figure 7, the horizontal axis F represents frequency (Hz), and the vertical axis α represents normal incidence sound absorption coefficient.

[0131] Furthermore, in Figure 7, the data for Example 1 is shown by a solid line E1, the data for Example 2 is shown by a dashed line E2, the data for Example 3 is shown by a dashed line E3, the data for Example 4 is shown by a dashed line E4, the data for Example 5 is shown by a dotted line E5, the data for Example 6 is shown by a thin solid line E6, and the data for Comparative Example 1 is shown by a thin dashed line C1.

[0132] The relationship between frequency and normal incidence sound absorption coefficient in the sound absorption structures of Examples 7 to 13 is shown in Figure 8. In Figure 8, the horizontal axis F represents frequency (Hz), and the vertical axis α represents normal incidence sound absorption coefficient.

[0133] Furthermore, in Figure 8, the data for Example 7 is shown by a solid line E7, the data for Example 8 is shown by a dashed line E8, the data for Example 9 is shown by a dotted line E9, the data for Example 10 is shown by a double dotted line E10, the data for Example 11 is shown by a dotted line E11, the data for Example 12 is shown by a thin solid line E12, and the data for Example 13 is shown by a thin dashed line E13.

[0134] The relationship between frequency and normal incidence sound absorption coefficient in the sound-absorbing structures of Examples 14-20 is shown in Figure 9. In Figure 9, the horizontal axis F represents frequency (Hz), and the vertical axis α represents normal incidence sound absorption coefficient.

[0135] Furthermore, in Figure 9, the data for Example 14 is shown by a solid line E14, the data for Example 15 is shown by a dashed line E15, the data for Example 16 is shown by a dashed line E16, the data for Example 17 is shown by a dashed line E17, the data for Example 18 is shown by a dotted line E18, the data for Example 19 is shown by a thin solid line E19, and the data for Example 20 is shown by a thin dashed line E20.

[0136] The relationship between frequency and normal incidence sound absorption coefficient in the sound absorption structures of Examples 21 to 27 is shown in Figure 10. In Figure 10, the horizontal axis F represents frequency (Hz), and the vertical axis α represents normal incidence sound absorption coefficient.

[0137] Furthermore, in Figure 10, the data for Example 21 is shown by a solid line E21, the data for Example 22 by a dashed line E22, the data for Example 23 by a dashed line E23, the data for Example 24 by a dashed line E24, the data for Example 25 by a dotted line E25, the data for Example 26 by a thin solid line E26, and the data for Example 27 by a thin dashed line E27.

[0138] The relationship between frequency and normal incidence sound absorption coefficient in the sound-absorbing structures of Examples 28 to 34 is shown in Figure 11. In Figure 11, the horizontal axis F represents frequency (Hz), and the vertical axis α represents normal incidence sound absorption coefficient.

[0139] Furthermore, in Figure 11, the data for Example 28 is shown by a solid line E28, the data for Example 29 is shown by a dashed line E29, the data for Example 30 is shown by a dashed line E30, the data for Example 31 is shown by a dashed line E31, the data for Example 32 is shown by a dotted line E32, the data for Example 33 is shown by a thin solid line E33, and the data for Example 34 is shown by a thin dashed line E34.

[0140] The relationship between frequency and normal incidence sound absorption coefficient in the sound-absorbing structures of Examples 35 to 41 is shown in Figure 12. In Figure 12, the horizontal axis F represents frequency (Hz), and the vertical axis α represents normal incidence sound absorption coefficient.

[0141] Furthermore, in Figure 12, the data for Example 35 is shown by a solid line E35, the data for Example 36 is shown by a dashed line E36, the data for Example 37 is shown by a dashed line E37, the data for Example 38 is shown by a dashed line E38, the data for Example 39 is shown by a dotted line E39, the data for Example 40 is shown by a thin solid line E40, and the data for Example 41 is shown by a thin dashed line E41.

[0142] The relationship between frequency and normal incidence sound absorption coefficient in the sound absorption structures of Examples 42 to 48 is shown in Figure 13. In Figure 13, the horizontal axis F represents frequency (Hz), and the vertical axis α represents normal incidence sound absorption coefficient.

[0143] Furthermore, in Figure 13, the data for Example 42 is shown by a solid line E42, the data for Example 43 is shown by a dashed line E43, the data for Example 44 is shown by a dashed line E44, the data for Example 45 is shown by a dashed line E45, the data for Example 46 is shown by a dotted line E46, the data for Example 47 is shown by a thin solid line E47, and the data for Example 48 is shown by a thin dashed line E48.

[0144] The relationship between frequency and normal incidence sound absorption coefficient in the sound absorption structures of Comparative Examples 2 to 9 is shown in Figure 14. In Figure 14, the horizontal axis F represents frequency (Hz), and the vertical axis α represents normal incidence sound absorption coefficient.

[0145] Furthermore, in Figure 14, the data for Comparative Example 2 is shown by the solid line C2, the data for Comparative Example 3 is shown by the dashed line C3, the data for Comparative Example 4 is shown by the dashed line C4, the data for Comparative Example 5 is shown by the double dashed line C5, the data for Comparative Example 6 is shown by the dotted line C6, the data for Comparative Example 7 is shown by the thin solid line C7, the data for Comparative Example 8 is shown by the thin dashed line C8, and the data for Comparative Example 9 is shown by the thin dashed line C9.

[0146] Referring to Figures 7-14, the following characteristics were observed in the low-frequency range, particularly around 100 Hz.

[0147] As shown in Comparative Examples 2 to 9, in sound absorbers containing a porous layer and a mass layer without through holes, the frequency width of the peak of the normal incidence sound absorption coefficient in the low-frequency range was narrow. In contrast, as shown in Examples 1 to 48, in sound absorbers containing a porous layer with through holes and a mass layer, the frequency width of the peak of the normal incidence sound absorption coefficient in the low-frequency range was wide. Therefore, it was confirmed that sound absorbers containing a porous layer with through holes and a mass layer can exhibit a high sound absorption effect across a wide range of frequencies in the low-frequency range.

[0148] Furthermore, as shown in Comparative Examples 2 to 9, in sound absorbers including a porous layer and a mass layer without through holes, the frequency width, magnitude, and shape of the peak of the normal incidence sound absorption coefficient in the low-frequency range remained almost constant even when the position of the mass layer was changed. In contrast, as shown in Examples 1 to 48, in sound absorbers including a porous layer with through holes and a mass layer, the frequency width, magnitude, and shape of the peak of the normal incidence sound absorption coefficient in the low-frequency range changed when the position of the mass layer was changed. Therefore, it was confirmed that the peak of the normal incidence sound absorption coefficient in the low-frequency range can be efficiently controlled in sound absorbers including a porous layer with through holes and a mass layer.

[0149] Referring to Figure 7, in sound absorbers having a through-hole layer and a bottom-side layer, when a mass layer was not provided as in Comparative Example 1, the peak of the normal incidence sound absorption coefficient in the low-frequency range did not appear, and sufficient sound absorption characteristics were not achieved. In contrast, when a mass layer was provided as in Examples 1 to 7, the normal incidence sound absorption coefficient in the low-frequency range appeared, and sufficient sound absorption characteristics were achieved. Therefore, it was confirmed that by providing a mass layer in a sound absorber having a through-hole, a high sound absorption effect can be achieved in the low-frequency range.

[0150] Regarding sound-absorbing materials including a porous layer having a through-layer and a bottom-side layer, and a mass layer, the following characteristics in the low-frequency range were confirmed by comparing Examples 1-6, Examples 7-13, Examples 14-20, and Examples 21-27.

[0151] The frequency width, magnitude, and shape of the peak of the normal incidence sound absorption coefficient in the low-frequency range changed depending on the position of the mass layer in the thickness direction. In particular, the closer the position of the mass layer in the thickness direction was to the surface in the thickness direction of the porous layer, the higher the normal incidence sound absorption coefficient in the low-frequency range tended to be.

[0152] Regarding a sound-absorbing material comprising a porous layer having a through-layer portion but lacking a bottom-side layer, and a mass layer, the following low-frequency characteristics were confirmed by comparing Examples 28-34, Examples 35-41, and Examples 42-48.

[0153] The frequency width, magnitude, and shape of the peak of the normal incidence sound absorption coefficient in the low-frequency range changed depending on the position of the mass layer in the thickness direction. In particular, the closer the position of the mass layer in the thickness direction was to the surface in the thickness direction of the porous layer, the higher the normal incidence sound absorption coefficient in the low-frequency range tended to be.

[0154] Therefore, in the sound absorbers and sound absorbing structures according to the first and second embodiments, it was confirmed that the presence of a mass layer and the change in the position of the mass layer in the thickness direction relative to the perforating layer portion of the porous layer can efficiently change the frequency width, magnitude, and shape of the peak of the normal incidence sound absorption coefficient in the low frequency region. In particular, it was confirmed that the closer the position of the mass layer in the thickness direction is to the surface in the thickness direction of the porous layer, the higher the normal incidence sound absorption coefficient in the low frequency region tends to be.

[0155] Furthermore, regarding sound-absorbing materials including a porous layer having a through-layer and a bottom-side layer, and a mass layer, the following characteristics were confirmed by comparing Examples 7, 14, and 21, Examples 8, 15, and 22, Examples 9, 16, and 23, Examples 10, 17, and 24, Examples 11, 18, and 25, Examples 12, 19, and 26, and Examples 13, 20, and 27.

[0156] The magnitude of the peak of the normal incidence sound absorption coefficient in the low-frequency range changed with changes in the thickness or surface density of the mass layer. In particular, as the thickness or surface density of the mass layer increased, the magnitude of the peak of the normal incidence sound absorption coefficient in the low-frequency range tended to decrease. Furthermore, as the thickness or surface density of the mass layer increased, the peak frequency of the normal incidence sound absorption coefficient in the low-frequency range tended to decrease.

[0157] Regarding a sound-absorbing material comprising a porous layer having a through-layer portion but lacking a bottom-side layer, and a mass layer, the following characteristics in the low-frequency region were confirmed by comparing Examples 28, 35 and 42, Examples 29, 36 and 43, Examples 30, 37 and 44, Examples 31, 38 and 45, Examples 32, 39 and 46, Examples 33, 40 and 47, and Examples 34, 41 and 48.

[0158] The magnitude of the peak of the normal incidence sound absorption coefficient in the low-frequency range changed with changes in the thickness or surface density of the mass layer. In particular, as the thickness or surface density of the mass layer increased, the magnitude of the peak of the normal incidence sound absorption coefficient in the low-frequency range tended to decrease. Furthermore, as the thickness or surface density of the mass layer increased, the peak frequency of the normal incidence sound absorption coefficient in the low-frequency range tended to decrease.

[0159] These results confirm that, in the sound absorbers and sound absorber structures according to the first and second embodiments, the magnitude of the peak of the normal incidence sound absorption coefficient in the low-frequency region changes according to the change in the thickness or surface density of the mass layer. In particular, it was confirmed that as the thickness or surface density of the mass layer increases, the magnitude of the peak of the normal incidence sound absorption coefficient in the low-frequency region tends to decrease. Furthermore, it was confirmed that as the thickness or surface density of the mass layer increases, the peak frequency of the normal incidence sound absorption coefficient in the low-frequency region tends to decrease.

[0160] Referring to Figures 7-14, the following characteristics were observed in the high-frequency range, particularly in the frequency band above approximately 150 Hz, and even in the high-frequency range above approximately 300 Hz.

[0161] Regarding sound absorbers comprising a porous layer having a through-layer and a bottom-side layer, and a mass layer, the normal incidence sound absorption coefficient in the high-frequency region in Examples 1 to 6 was lower than that in Comparative Example 1. Comparisons of Examples 1 to 6, Examples 7 to 13, Examples 14 to 20, and Examples 21 to 27 showed that the normal incidence sound absorption coefficient in the high-frequency region changed according to the positional change in the thickness direction of the mass layer.

[0162] In the high-frequency range, particularly as the position of the mass layer in the thickness direction moved from the back to the surface in the thickness direction of the perforating layer in the porous layer, the normal incidence sound absorption coefficient decreased in the high-frequency range. This trend is thought to be influenced by the sound absorption effect of the perforating layer when it is located on the surface side in the thickness direction relative to the mass layer.

[0163] Regarding sound-absorbing materials that include a porous layer having a through-layer portion but lacking a bottom-side layer, comparisons of Examples 28-34, Examples 35-41, and Examples 42-48 confirmed that the normal incidence sound absorption coefficient in the high-frequency range changes depending on the positional change in the thickness direction of the mass layer.

[0164] In particular, the normal incidence sound absorption coefficient in the high-frequency range increased as the position of the mass layer in the thickness direction relative to the through-layer moved from the surface to the back. This is thought to be due to the sound absorption effect of the through-layer, which was positioned on the surface side in the thickness direction relative to the mass layer.

[0165] These results confirm that, in the sound absorbers and sound absorber structures according to the first and second embodiments, the presence of a mass layer and the position of the mass layer in the thickness direction relative to the through-layer can easily change the frequency characteristics of the normal incidence sound absorption coefficient in the high-frequency range. In particular, it was confirmed that the normal incidence sound absorption coefficient in the high-frequency range increases as the position of the mass layer in the thickness direction relative to the through-layer moves from the surface to the back surface.

[0166] As described above, a remarkable feature of the sound absorber of the present invention is that by changing the position of the mass layer in the thickness direction, it is possible to efficiently induce changes in the characteristics of the normal incidence sound absorption coefficient in a way that is inversely related between the low-frequency and high-frequency regions. This remarkable feature is in contrast to Comparative Examples 2 to 9 (see Figure 14), where the characteristics of the peak of the normal incidence sound absorption coefficient in the low-frequency region do not change even when the position of the mass layer in the thickness direction is changed.

[0167] Next, Examples 49-54 and Comparative Examples 10-15 will be described.

[0168] Examples 49-54 Examples 49 to 54 will now be described. In Examples 49 to 54, the sound-absorbing structure according to the first embodiment was used.

[0169] Specifically, in each of the sound-absorbing structures of Examples 49 to 54, a sound-absorbing body was used that included a porous layer having a through-layer portion with a thickness of approximately 75 mm and a bottom-side layer portion with a thickness of approximately 75 mm, and a mass layer. The porous material used in the through-layer portion and bottom-side layer of the porous layer had a volume density of approximately 32 kg / m³. 3 Glass wool was chosen for this purpose.

[0170] The mass layer in Example 49 was made using a mass layer material consisting of a polypropylene plate. The mass layers in Examples 50 to 54 were made using a mass layer material consisting of a polyvinyl chloride plate.

[0171] The thickness of the mass layer in Example 49 was approximately 0.2 mm. The thickness of the mass layer in Example 50 was approximately 0.3 mm. The thickness of the mass layer in Example 51 was approximately 0.5 mm. The thickness of the mass layer in Example 52 was approximately 1.0 mm. The thickness of the mass layer in Example 53 was approximately 2.0 mm. The thickness of the mass layer in Example 54 was approximately 4.0 mm.

[0172] The surface density of the mass layer in Example 49 is approximately 180 g / m². 2 The surface density of the mass layer in Example 50 was approximately 420 g / m². 2 The surface density of the mass layer in Example 51 was approximately 700 g / m². 2 The surface density of the mass layer in Example 52 was approximately 1400 g / m². 2 The surface density of the mass layer in Example 53 was approximately 2800 g / m². 2 The surface density of the mass layer in Example 54 was approximately 5600 g / m². 2 That was the case.

[0173] In Examples 49-54, a porous layer having a through-layer and a bottom-side layer, and a mass layer were formed in a roughly square shape of approximately 300 mm × 300 mm when viewed in the thickness direction. Multiple holes with circular cross-sections were formed in the through-layer. The multiple holes were arranged in a matrix. The diameter of each hole was approximately 40 mm. The pitch between the centers of adjacent holes was approximately 55 mm. The depth of each hole was approximately 75 mm. The mass layer was laminated on the surface of the porous layer.

[0174] Furthermore, since there is little need to protect the porous layer, the surface material was omitted from the sound absorber. The component corresponding to the installation surface in the room space was installed adjacent to the back of the sound absorber.

[0175] The perpendicular incidence sound absorption coefficients of the sound-absorbing structures in Examples 49-54 were measured in the same manner as the perpendicular incidence sound absorption coefficients of the sound-absorbing structures in Examples 1-27.

[0176] "Comparative Examples 10-15" Comparative Examples 10 to 15 will now be described. In each of the sound-absorbing structures of Comparative Examples 10 to 15, a sound-absorbing material was used that included a porous layer having a non-penetrating layer portion with a thickness of approximately 150 mm and a mass layer. Unlike the penetrating layers in Examples 49 to 54 above, the non-penetrating layer portion was constructed without holes. The porous material used in the non-penetrating layer portion of the porous layer had a volume density of approximately 32 kg / m³. 3 Glass wool was chosen for this purpose.

[0177] The mass layers in Comparative Examples 10-15 were the same as those in Examples 49-54. In Comparative Examples 10-15, the porous layer having a non-penetrating layer and the mass layer were formed into approximately square shapes of about 300 mm × 300 mm when viewed in the thickness direction. The mass layer was also laminated on the surface of the porous layer.

[0178] Furthermore, since there is little need to protect the porous layer, the surface material was omitted from the sound absorber. The component corresponding to the installation surface in the room space was installed adjacent to the back of the sound absorber.

[0179] The perpendicular incidence sound absorption coefficients of the sound-absorbing structures in Comparative Examples 10-15 were measured in the same manner as the perpendicular incidence sound absorption coefficients of the sound-absorbing structures in Examples 1-27.

[0180] Based on the above measurements, the relationship between frequency and normal incidence sound absorption coefficient in the sound-absorbing structures of Examples 49 to 54 is shown in Figure 15. The relationship between frequency and normal incidence sound absorption coefficient in the sound-absorbing structures of Comparative Examples 10 to 15 is shown in Figure 16. In Figures 15 and 16, the horizontal axis F represents frequency (Hz), and the vertical axis α represents normal incidence sound absorption coefficient.

[0181] In Figure 15, the data for Example 49 is shown by a solid line E49, the data for Example 50 is shown by a dashed line E50, the data for Example 51 is shown by a dashed line E51, the data for Example 52 is shown by a dashed line E52, the data for Example 53 is shown by a dotted line E53, and the data for Example 54 is shown by a thin solid line E54.

[0182] In Figure 16, the data for Comparative Example 10 is shown by the solid line C10, the data for Comparative Example 11 is shown by the dashed line C11, the data for Comparative Example 12 is shown by the dashed line C12, the data for Comparative Example 13 is shown by the dashed line C13, the data for Comparative Example 14 is shown by the dotted line C14, and the data for Comparative Example 15 is shown by the thin solid line C15.

[0183] Referring to Figures 15 and 16, the following characteristics were observed regarding the peak of the normal incidence sound absorption coefficient in the low-frequency range.

[0184] The peak frequency of the vertical incidence sound absorption coefficient in Example 49 and Comparative Example 10 was approximately 130 Hz. The peak frequency of the vertical incidence sound absorption coefficient in Example 50 and Comparative Example 11 was approximately 150 Hz. The peak frequency of the vertical incidence sound absorption coefficient in Example 51 and Comparative Example 12 was approximately 180 Hz.

[0185] The peak frequency of the vertical incidence sound absorption coefficient in Example 52 and Comparative Example 13 was approximately 200 Hz. The peak frequency of the vertical incidence sound absorption coefficient in Example 53 and Comparative Example 14 was approximately 220 Hz. The peak frequency of the vertical incidence sound absorption coefficient in Example 54 and Comparative Example 15 was approximately 280 Hz.

[0186] These comparisons confirmed that, at least in the frequency range below approximately 280 Hz, the presence or absence of holes in the porous layer does not substantially change the peak frequency of the normal incidence sound absorption coefficient.

[0187] In the low-frequency range, particularly below approximately 180 Hz, the peak values ​​of the vertical incidence sound absorption coefficient in Examples 49-51 were higher than those in Comparative Examples 10-12. Furthermore, the difference between the peak values ​​of the vertical incidence sound absorption coefficient in Example 51 and Comparative Example 12, the difference between the peak values ​​of the vertical incidence sound absorption coefficient in Example 50 and Comparative Example 11, and the difference between the peak values ​​of the vertical incidence sound absorption coefficient in Example 49 and Comparative Example 10 increased in this order.

[0188] On the other hand, in the frequency range above approximately 200 Hz, the peak values ​​of the vertical incidence sound absorption coefficient in Examples 52-54 were virtually no different from the peak values ​​of the vertical incidence sound absorption coefficient in Comparative Examples 13-15.

[0189] These comparisons confirmed that, in the low-frequency range, particularly below approximately 180 Hz, the holes in the porous layer increase the peak value of the normal incidence sound absorption coefficient, meaning that the sound absorption performance is enhanced.

[0190] Furthermore, Examples 55 to 59 will be described.

[0191] "Example 55 (Examples 55-1 to 55-6)" Examples 55, specifically Examples 55-1 to 55-6, will be described below. In the following, when Examples 55-1 to 55-6 are referred to collectively, they will be called Example 55. In Example 55, the sound-absorbing structure according to the First Embodiment was used.

[0192] Specifically, the sound-absorbing structure of Example 55 used a sound-absorbing material comprising a porous layer having a through-layer portion with a thickness of approximately 50 mm and a bottom-side layer portion with a thickness of approximately 50 mm, and a mass layer. The porous layer had a density of approximately 3200 g / m². 2 The porous material, which has a surface density, was constructed by removing portions corresponding to multiple holes. The mass layer of Example 55 was made using a mass layer material consisting of a vinyl chloride plate.

[0193] The surface density of the mass layer in Example 55-1 is approximately 180 g / m². 2 The surface density of the mass layer in Example 55-2 was approximately 420 g / m². 2 The surface density of the mass layer in Example 55-3 was approximately 700 g / m². 2 The surface density of the mass layer in Example 55-4 was approximately 1400 g / m². 2 The surface density of the mass layer in Example 55-5 was approximately 2800 g / m². 2 The surface density of the mass layer in Example 55-6 was approximately 5600 g / m². 2 That was the case.

[0194] In Example 55, a porous layer having a through-layer and a bottom-side layer, and a mass layer were formed in a roughly square shape of approximately 300 mm × 300 mm when viewed in the thickness direction. Multiple holes with circular cross-sections were formed in the through-layer. The multiple holes were arranged in a matrix. The diameter of each hole was approximately 40 mm. The pitch between the centers of adjacent holes was approximately 55 mm. The depth of each hole was approximately 50 mm. The mass layer was laminated on the surface of the porous layer.

[0195] Furthermore, since there is little need to protect the porous layer, the surface material was omitted from the sound absorber. The component corresponding to the installation surface in the room space was installed adjacent to the back of the sound absorber.

[0196] The perpendicular incidence sound absorption coefficient of the sound-absorbing structure in Example 55 was measured in the same manner as the perpendicular incidence sound absorption coefficients of the sound-absorbing structures in Examples 1 to 27.

[0197] "Example 56 (Examples 56-1 to 56-6)" Examples 56, specifically Examples 56-1 to 56-6, will be described below. In the following, when Examples 56-1 to 56-6 are referred to collectively, they will be called Example 56. In Example 56, the sound-absorbing structure according to the First Embodiment was used.

[0198] Specifically, the sound-absorbing structure of Example 56 used a sound-absorbing material comprising a porous layer having a through-layer portion with a thickness of approximately 50 mm and a bottom-side layer portion with a thickness of approximately 50 mm, and a mass layer. The porous layer had a density of approximately 4800 g / m². 2 The porous material, which has a surface density, was constructed by removing portions corresponding to multiple holes. The mass layer of Example 56 was made using a mass layer material consisting of a vinyl chloride plate.

[0199] The surface density of the mass layer in Example 56-1 is approximately 180 g / m². 2 The surface density of the mass layer in Example 56-2 was approximately 420 g / m². 2 The surface density of the mass layer in Example 56-3 was approximately 700 g / m². 2 The surface density of the mass layer in Example 56-4 was approximately 1400 g / m². 2 The surface density of the mass layer in Example 56-5 was approximately 2800 g / m². 2 The surface density of the mass layer in Example 56-6 was approximately 5600 g / m². 2 That was the case.

[0200] In Example 56, a porous layer having a through-layer and a bottom-side layer, and a mass layer were formed in a roughly square shape of approximately 300 mm × 300 mm when viewed in the thickness direction. Multiple through-holes with circular cross-sections were formed in the through-layer. The multiple holes were arranged in a matrix. The diameter of each hole was approximately 40 mm. The pitch between the centers of adjacent holes was approximately 55 mm. The depth of each hole was approximately 50 mm. The mass layer was laminated on the surface of the porous layer.

[0201] Furthermore, since there is little need to protect the porous layer, the surface material was omitted from the sound absorber. The component corresponding to the installation surface in the room space was installed adjacent to the back of the sound absorber.

[0202] The perpendicular incidence sound absorption coefficient of the sound-absorbing structure in Example 56 was measured in the same manner as the perpendicular incidence sound absorption coefficients of the sound-absorbing structures in Examples 1 to 27.

[0203] "Example 57 (Examples 57-1 to 57-6)" Examples 57, specifically Examples 57-1 to 57-6, will be described below. In the following, when Examples 57-1 to 57-6 are referred to collectively, they will be called Example 57. In Example 57, the sound-absorbing structure according to the First Embodiment was used.

[0204] Specifically, the sound-absorbing structure of Example 57 used a sound-absorbing material comprising a porous layer having a through-layer portion with a thickness of approximately 75 mm and a bottom-side layer portion with a thickness of approximately 75 mm, and a mass layer. The porous layer had a density of approximately 4800 g / m². 2 The porous material, which has a surface density, was constructed by removing portions corresponding to multiple holes. The mass layer in Example 57 was made using a mass layer material consisting of a vinyl chloride plate.

[0205] The surface density of the mass layer in Example 57-1 is approximately 180 g / m². 2 The surface density of the mass layer in Example 57-2 was approximately 420 g / m². 2 The surface density of the mass layer in Example 57-3 was approximately 700 g / m². 2 The surface density of the mass layer in Example 57-4 was approximately 1400 g / m². 2 The surface density of the mass layer in Example 57-5 was approximately 2800 g / m². 2 The surface density of the mass layer in Example 57-6 was approximately 5600 g / m². 2 That was the case.

[0206] In Example 57, a porous layer having a through-layer and a bottom-side layer, and a mass layer were formed in a roughly square shape of approximately 300 mm × 300 mm when viewed in the thickness direction. Multiple holes with circular cross-sections were formed in the through-layer. The multiple holes were arranged in a matrix. The diameter of each hole was approximately 40 mm. The pitch between the centers of adjacent holes was approximately 55 mm. The depth of each hole was approximately 75 mm. The mass layer was laminated on the surface of the porous layer.

[0207] Furthermore, since there is little need to protect the porous layer, the surface material was omitted from the sound absorber. The component corresponding to the installation surface in the room space was installed adjacent to the back of the sound absorber.

[0208] The perpendicular incidence sound absorption coefficient of the sound-absorbing structure in Example 57 was measured in the same manner as the perpendicular incidence sound absorption coefficients of the sound-absorbing structures in Examples 1 to 27.

[0209] "Example 58 (Examples 58-1 to 58-6)" Examples 58, specifically Examples 58-1 to 58-6, will be described below. In the following, when Examples 58-1 to 58-6 are referred to collectively, they will be called Example 58. In Example 58, the sound-absorbing structure according to the First Embodiment was used.

[0210] Specifically, the sound-absorbing structure of Example 58 used a sound-absorbing material comprising a porous layer having a through-layer portion with a thickness of approximately 75 mm and a bottom-side layer portion with a thickness of approximately 75 mm, and a mass layer. The porous layer had a density of approximately 7200 g / m². 2 The porous material, which has a surface density, was constructed by removing portions corresponding to multiple holes. The mass layer of Example 58 was made using a mass layer material consisting of a vinyl chloride plate.

[0211] The surface density of the mass layer in Example 58-1 is approximately 180 g / m². 2 The surface density of the mass layer in Example 58-2 was approximately 420 g / m². 2 The surface density of the mass layer in Example 58-3 was approximately 700 g / m². 2 The surface density of the mass layer in Example 58-4 was approximately 1400 g / m². 2 The surface density of the mass layer in Example 58-5 was approximately 2800 g / m². 2 The surface density of the mass layer in Example 58-6 was approximately 5600 g / m². 2 That was the case.

[0212] In Example 58, a porous layer having a through-layer and a bottom-side layer, and a mass layer were formed in a roughly square shape of approximately 300 mm × 300 mm when viewed in the thickness direction. Multiple through-holes with circular cross-sections were formed in the through-layer. The multiple holes were arranged in a matrix. The diameter of each hole was approximately 40 mm. The pitch between the centers of adjacent holes was approximately 55 mm. The depth of each hole was approximately 75 mm. The mass layer was laminated on the surface of the porous layer.

[0213] Furthermore, since there is little need to protect the porous layer, the surface material was omitted from the sound absorber. The component corresponding to the installation surface in the room space was installed adjacent to the back of the sound absorber.

[0214] The perpendicular incidence sound absorption coefficient of the sound-absorbing structure in Example 58 was measured in the same manner as the perpendicular incidence sound absorption coefficients of the sound-absorbing structures in Examples 1 to 27.

[0215] "Example 59 (Examples 59-1 to 59-6)" Examples 59, specifically Examples 59-1 to 59-6, will be described below. In the following, when Examples 59-1 to 59-6 are referred to collectively, they will be called Example 59. In Example 59, the sound-absorbing structure according to the First Embodiment was used.

[0216] Specifically, the sound-absorbing structure of Example 59 used a sound-absorbing material comprising a porous layer having a through-layer portion with a thickness of approximately 150 mm and a bottom-side layer portion with a thickness of approximately 150 mm, and a mass layer. The porous layer had a density of approximately 9600 g / m². 2 The porous material, which has a surface density, was constructed by removing portions corresponding to multiple holes. The mass layer in Example 59 was made using a mass layer material consisting of a vinyl chloride plate.

[0217] The surface density of the mass layer in Example 59-1 is approximately 180 g / m². 2 The surface density of the mass layer in Example 59-2 was approximately 420 g / m². 2 The surface density of the mass layer in Example 59-3 was approximately 700 g / m². 2 The surface density of the mass layer in Example 59-4 was approximately 1400 g / m². 2The surface density of the mass layer in Example 59-5 was approximately 2800 g / m². 2 The surface density of the mass layer in Example 59-6 was approximately 5600 g / m². 2 That was the case.

[0218] In Example 59, a porous layer having a through-layer and a bottom-side layer, and a mass layer were formed in a roughly square shape of approximately 300 mm × 300 mm when viewed in the thickness direction. Multiple holes with circular cross-sections were formed in the through-layer. The multiple holes were arranged in a matrix. The diameter of each hole was approximately 40 mm. The pitch between the centers of adjacent holes was approximately 55 mm. The depth of each hole was approximately 150 mm. The mass layer was laminated on the surface of the porous layer.

[0219] Furthermore, since there is little need to protect the porous layer, the surface material was omitted from the sound absorber. The component corresponding to the installation surface in the room space was installed adjacent to the back of the sound absorber.

[0220] The perpendicular incidence sound absorption coefficient of the sound-absorbing structure in Example 59 was measured in the same manner as the perpendicular incidence sound absorption coefficients of the sound-absorbing structures in Examples 1 to 27.

[0221] Based on the above measurements, the relationship between the surface density of the mass layer and the peak frequency of the normal incidence sound absorption coefficient in the sound-absorbing structures of Examples 55-59 is shown in Figure 17. In Figure 17, the horizontal axis D represents the surface density of the mass layer (g / m³). 2 The data is shown in logarithmic form, with the vertical axis P representing the peak frequency (Hz) of the normal incidence sound absorption coefficient.

[0222] In Figure 17, the data for Examples 55-1 to 55-6 are shown by six circles arranged sequentially from left to right on the page, and the logarithmic approximation curve based on the data for Example 55 is shown by the solid line E55a. The data for Examples 56-1 to 56-6 are shown by six squares arranged sequentially from left to right on the page, and the logarithmic approximation curve based on the data for Example 56 is shown by the dashed line E56a.

[0223] The data for Examples 57-1 to 57-6 are indicated by six triangular marks arranged sequentially from left to right on the page, and the logarithmic approximation curve based on the data for Example 57 is shown by the dashed line E57a. The data for Examples 58-1 to 58-6 are indicated by six diamond marks arranged sequentially from left to right on the page, and the logarithmic approximation curve based on the data for Example 58 is shown by the dashed line E58a.

[0224] The data for Examples 59-1 to 59-6 are indicated by six "x" marks arranged sequentially from left to right on the page, and the logarithmic approximation curve based on the data for Example 59 is shown by the dotted line E59a.

[0225] Furthermore, the relationship between the surface density of the mass layer and the frequency at which the normal incidence sound absorption coefficient is approximately 0.75 in the sound-absorbing structures of Examples 55-59 is shown in Figure 18. In Figure 18, the horizontal axis D represents the surface density of the mass layer (g / m³). 2 The data is shown on a logarithmic scale, with the vertical axis Q representing the frequency (Hz) at which the normal incidence sound absorption coefficient is approximately 0.75.

[0226] In Figure 18, the data for Examples 55-1 to 55-6 are indicated by six circles arranged sequentially from left to right on the page, and the logarithmic approximation curve based on the data for Example 55 is shown by the solid line E55b. The data for Examples 56-1 to 56-6 are indicated by six squares arranged sequentially from left to right on the page, and the logarithmic approximation curve based on the data for Example 56 is shown by the dashed line E56b.

[0227] The data for Examples 57-1 to 57-6 are indicated by six triangular marks arranged sequentially from left to right on the page, and the logarithmic approximation curve based on the data for Example 57 is shown by the dashed line E57b. The data for Examples 58-1 to 58-6 are indicated by six diamond marks arranged sequentially from left to right on the page, and the logarithmic approximation curve based on the data for Example 58 is shown by the dashed line E58b.

[0228] The data for Examples 59-1 to 59-6 are indicated by six "x" marks arranged sequentially from left to right on the page, and the logarithmic approximation curve based on the data for Example 59 is shown by the dotted line E59b.

[0229] Referring to Figure 17, we were able to confirm the relationship between the peak frequency of the normal incidence sound absorption coefficient, the thickness and surface density of the porous layer, and the surface density of the mass layer, as shown below.

[0230] At all surface densities of the mass layers, the peak frequencies of the perpendicular incidence sound absorption coefficient decreased in the following order: Example 55, Example 56, Example 57, Example 58, and Example 59. Therefore, it was confirmed that at all surface densities of the mass layers, increasing at least one of the thickness and surface density of the porous layer reduces the peak frequency of the perpendicular incidence sound absorption coefficient.

[0231] In all of Examples 55-59, it was confirmed that increasing the surface density of the mass layer reduced the peak frequency of the normal incidence sound absorption coefficient.

[0232] In particular, the ratio of the decrease in the peak frequency of the normal incidence sound absorption coefficient to the increase in the surface density of the mass layer in Examples 55 and 56 was substantially the same. The ratio of the decrease in the peak frequency of the normal incidence sound absorption coefficient to the increase in the surface density of the mass layer in Examples 57 and 58 was substantially the same. Therefore, it was confirmed that when the thickness of the porous layer is substantially constant, even if the surface density of the porous layer changes, the ratio of the decrease in the peak frequency of the normal incidence sound absorption coefficient to the increase in the surface density of the mass layer is maintained substantially constant.

[0233] Furthermore, in Examples 55 to 59, it was confirmed that in order to reduce the peak frequency of the normal incidence sound absorption coefficient to approximately 150 Hz or less in order to exhibit high sound absorption characteristics in the low frequency range, it is preferable to set the thickness and surface density of the porous layer and the surface density of the mass layer as follows.

[0234] In Example 55, the thickness of the perforating layer of the porous layer was set to approximately 50 mm or more, the thickness of the bottom layer of the porous layer was set to approximately 50 mm or more, and the porous layer was made of approximately 3200 g / m 2 When constructing a porous material with the above surface density by removing portions corresponding to multiple holes, the surface density of the mass layer is set to approximately 5500 g / m³ based on the relationship between the peak frequency range of approximately 150 Hz or less and the logarithmic approximation curve. 2 It was confirmed that the above is preferable.

[0235] In Example 56, the thickness of the perforating layer of the porous layer was set to approximately 50 mm or more, the thickness of the bottom layer of the porous layer was set to approximately 50 mm or more, and the porous layer was made of approximately 4800 g / m². 2 When constructing a porous material with the above surface density by removing portions corresponding to multiple holes, the surface density of the mass layer is set to approximately 3900 g / m³ based on the relationship between the peak frequency range of approximately 150 Hz or less and the logarithmic approximation curve. 2 It was confirmed that the above is preferable.

[0236] In Example 57, the thickness of the perforating layer of the porous layer was set to approximately 75 mm or more, the thickness of the bottom layer of the porous layer was set to approximately 75 mm or more, and the porous layer was made of approximately 4800 g / m². 2 When constructing a porous material with the above surface density by removing portions corresponding to multiple holes, the surface density of the mass layer is set to approximately 2600 g / m³ based on the relationship between the peak frequency range of approximately 150 Hz or less and the logarithmic approximation curve. 2 It was confirmed that the above is preferable.

[0237] In Example 58, the thickness of the perforating layer of the porous layer was set to approximately 75 mm or more, the thickness of the bottom layer of the porous layer was set to approximately 75 mm or more, and the porous layer was made of approximately 7200 g / m². 2 When constructing a porous material with the above surface density by removing portions corresponding to multiple holes, the surface density of the mass layer is set to approximately 1600 g / m³ based on the relationship between the peak frequency range of approximately 150 Hz or less and the logarithmic approximation curve. 2 It was confirmed that the above is preferable.

[0238] In Example 59, the thickness of the perforating layer of the porous layer was set to approximately 150 mm or more, the thickness of the bottom layer of the porous layer was set to approximately 150 mm or more, and the porous layer was made of approximately 9600 g / m 2 When constructing a porous material with the above surface density by removing portions corresponding to multiple holes, the surface density of the mass layer is set to approximately 240 g / m³ based on the relationship between the peak frequency range of approximately 150 Hz or less and the logarithmic approximation curve. 2 It was confirmed that the above is preferable.

[0239] Referring to Figure 18, we were able to confirm the relationship between the frequency at which the normal incidence sound absorption coefficient is approximately 0.75, the thickness and surface density of the porous layer, and the surface density of the mass layer.

[0240] At all surface densities of the mass layers, the frequencies at which the perpendicular incidence sound absorption coefficient was approximately 0.75 decreased in the following order: Example 55, Example 56, Example 57, Example 58, and Example 59. Therefore, it was confirmed that at all surface densities of the mass layers, increasing at least one of the thickness and surface density of the porous layer reduces the frequencies at which the perpendicular incidence sound absorption coefficient was approximately 0.75.

[0241] In all of Examples 55 to 59, it was confirmed that as the surface density of the mass layer increased, the frequency at which the normal incidence sound absorption coefficient was approximately 0.75 decreased.

[0242] In particular, the ratio of the decrease in the frequency of a perpendicular incidence sound absorption coefficient of approximately 0.75 to the increase in the surface density of the mass layer in Examples 55 and 56 was substantially the same. The ratio of the decrease in the frequency of a perpendicular incidence sound absorption coefficient of approximately 0.75 to the increase in the surface density of the mass layer in Examples 57 and 58 was also substantially the same. Therefore, it was confirmed that when the thickness of the porous layer is substantially constant, even if the surface density of the porous layer changes, the ratio of the decrease in the frequency of a perpendicular incidence sound absorption coefficient of approximately 0.75 to the increase in the surface density of the mass layer is maintained substantially constant. [Explanation of Symbols]

[0243] 11…Sound absorber, 20…Porous layer, 21…Cavity, 21a…Through section, 21b…Bottom, 22…Through layer, bottom side layer…23, 30…Mass layer

Claims

1. A porous layer composed of porous material, A non-permeable mass layer and Equipped with, The porous layer has a plurality of holes, The plurality of holes open on the surface of the porous layer in the thickness direction facing the acoustic incidence side, extend toward the interior of the porous layer, and are closed within the porous layer. The porous layer includes a through-layer portion having through-holes and a bottom-side layer portion having bottoms of the multiple holes. The through-layer portion is located on the acoustic incidence side within the porous layer, The bottom layer is laminated to the through layer on the back side opposite to the acoustic incidence side in the thickness direction, The mass layer is laminated on the surface of the through-layer portion in the porous layer, A sound-absorbing material in which the thickness of the mass layer is smaller than the thickness of the perforating layer and the bottom layer of the porous layer, respectively.

2. The thickness of the perforated layer portion of the porous layer is 50 mm or more. The thickness of the bottom layer of the porous layer is 50 mm or more. The porous layer has a density of 3200 g / m². ２ The porous material having the above surface density is configured such that portions corresponding to the plurality of holes are removed. The surface density of the mass layer is 5500 g / m³ ２ The sound-absorbing body according to claim 1, as described above.

3. The thickness of the perforated layer portion of the porous layer is 50 mm or more. The thickness of the bottom layer of the porous layer is 50 mm or more. The porous layer has a density of 4800 g / m². ２ The porous material having the above surface density is configured such that portions corresponding to the plurality of holes are removed. The surface density of the mass layer is 3900 g / m³. ２ The sound-absorbing body according to claim 1, as described above.

4. The thickness of the perforated layer portion of the porous layer is 75 mm or more. The thickness of the bottom layer of the porous layer is 75 mm or more. The porous layer has a density of 4800 g / m². ２ The porous material having the above surface density is configured such that portions corresponding to the plurality of holes are removed. The surface density of the mass layer is 2600 g / m³ ２ The sound-absorbing body according to claim 1, as described above.

5. The thickness of the perforated layer portion of the porous layer is 75 mm or more. The thickness of the bottom layer of the porous layer is 75 mm or more. The porous layer has a density of 7200 g / m². ２ The porous material having the above surface density is configured such that portions corresponding to the plurality of holes are removed. The surface density of the mass layer is 1600 g / m³ ２ The sound-absorbing body according to claim 1, as described above.

6. The thickness of the perforated layer portion of the porous layer is 150 mm or more. The thickness of the bottom layer of the porous layer is 150 mm or more. The porous layer is made of a porous material having a surface density of 9600 g / m ２ or more, and is configured to exclude portions corresponding to the plurality of holes The surface density of the mass layer is 240 g / m³ ２ The sound-absorbing body according to claim 1, as described above.

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