Sound-absorbing material

Abstract

To provide a sound absorber that exhibits superior sound absorption effect in a broad frequency band including a low frequency band while having reduced thickness.SOLUTION: A sound absorber 10 has a sound absorber body 11 which has air permeability, and a sound shield part 12 which is disposed on a surface α1 on at least one side of the sound absorber body 11 and has non-permeability and diffracts a sound wave impinging on the sound absorber body 11. The sound absorber body 11 preferably has a flow resistance of equal to or less than 107 N s / m4, and the sound shield part 12 also preferably has a flow resistance of equal to or larger than 108 N s / m4.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a sound-absorbing material.

Background Art

[0002] Various sound-absorbing materials and sound-absorbing structures have been proposed so far. For example, as shown in FIG. 1, there is a porous sound-absorbing material formed of a porous material such as urethane foam, and as shown in FIG. 2, there is a perforated plate type sound-absorbing material formed of a plate having a large number of holes, and as shown in FIG. 3, there is an air layer intervening type sound-absorbing structure in which an air layer is interposed on the back side of a plate (see, for example, Patent Documents 1 to 3). These sound-absorbing materials and sound-absorbing structures are adopted in vehicles, buildings, road facilities, and the like.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, as shown in the graph on the right side of FIG. 1, the porous sound-absorbing material has a drawback that although a high sound absorption rate can be obtained in a relatively wide range in the high-frequency band, the sound absorption rate becomes low in the low-frequency band. However, even with this porous sound-absorbing material, if the thickness is increased, the sound absorption rate in the low-frequency band can be increased. However, in this case, there arises a problem that it becomes difficult to adopt this sound-absorbing material in an application where the thickness is limited.

[0005] On the other hand, in the case of a perforated plate type sound absorbing material or an air layer interposed type sound absorbing structure, as shown in the graphs on the right side of FIGS. 2 and 3, a high sound absorption rate can be obtained in the low frequency band. However, in the perforated plate type sound absorbing material or the air layer interposed type sound absorbing structure, there is a drawback that such a high sound absorption rate is obtained only in the vicinity of a specific frequency.

[0006] The present invention has been made to solve the above problems, and provides a sound absorbing material capable of exhibiting an excellent sound absorption effect in a wide frequency band including the low frequency band while suppressing the thickness of the sound absorbing material.

Means for Solving the Problems

[0007] The above problems are solved by providing a sound absorbing material characterized in that a sound shielding portion having non - permeability and diffracting incident sound waves to the sound absorbing material body is arranged on at least one surface of the sound absorbing material body having air permeability.

[0008] That is, in a general sound absorbing material (for example, the above - mentioned porous type sound absorbing material), when its thickness coincides with 1 / 4 of the wavelength of the incident sound wave, the sound absorption rate becomes high. By arranging a sound shielding portion having no air permeability on the surface of the sound absorbing material body having air permeability as in the sound absorbing material of the present invention, the incident sound wave to the sound absorbing material body is diffracted by the sound shielding portion. For this reason, the path length of the incident sound wave inside the sound absorbing material body can be lengthened (the apparent thickness of the sound absorbing material body can be increased), and the frequency band where the sound absorption rate is high can be shifted to the low frequency side. Therefore, it is possible to absorb sound from low frequencies without thickening the sound absorbing material body.

[0009] In the sound absorbing material of the present invention, the sound shielding portion may be arranged on at least one side (the side where sound is incident) of the sound absorbing material body, but it can also be arranged on both sides (the side where sound is incident and the side where sound is transmitted) of the sound absorbing material body. In the following, the surface of the sound absorbing material body on the side where the sound shielding portion is arranged (or the side where the sound shielding portion has been arranged) may be referred to as the "sound shielding portion arrangement surface".

[0010] In the sound-absorbing material of the present invention, the sound-insulating portion may be provided at at least one location on the sound-insulating portion arrangement surface of the sound-absorbing material main body. Thus, even with one sound-insulating portion, the above-described diffraction effect can be obtained, so that the frequency band where the sound absorption rate is high can be shifted to the low-frequency side. However, providing the sound-insulating portions at a plurality of locations makes it easier to obtain a uniform sound absorption effect regardless of the location of the sound-absorbing material main body. For this reason, it is preferable to provide the sound-insulating portions at a plurality of locations on the sound-insulating portion arrangement surface of the sound-absorbing material main body. In this case, it is more preferable to repeatedly arrange a plurality of sound-insulating portions on the sound-insulating portion arrangement surface while leaving a gap between them. The dimensional shapes of the sound-insulating portions may be the same for one type or a plurality of types, or may be different for each sound-insulating portion.

[0011] In the sound-absorbing material of the present invention, the flow resistance (ventilation resistance) of the sound-absorbing material main body is lower than the flow resistance (ventilation resistance) of the sound-insulating portion. The flow resistance of the sound-absorbing material main body (the flow resistance measured by the method defined in the standard "ISO 9053" by the International Organization for Standardization or the standard "ASTM C522" by the American Society for Testing and Materials. The same shall apply hereinafter.) is 10 7 N·s / m 4 It is preferably as follows. On the other hand, the flow resistance of the sound-insulating portion is preferably 10 8 N·s / m 4 or more. If the flow resistance of the sound-absorbing material main body is higher than the above value (10 7 N·s / m 4 ), sound is likely to be reflected by the sound-absorbing material main body, and the sound absorption performance of the sound-absorbing material may deteriorate. If the flow resistance of the sound-insulating portion is lower than the above value (10 8 N·s / m 4 ), the sound insulation performance of the sound-insulating portion may deteriorate, and the above-described diffraction may be less likely to occur.

[0012] In the sound-absorbing material of the present invention, the surface density of the sound-insulating portion is not particularly limited. However, generally, a material with a low surface density has low sound insulation. For this reason, if the surface density of the sound-insulating portion is low, there is a possibility that the above-described effects (the effect of shifting the frequency band where the sound absorption rate is high to the low-frequency side) are less likely to be achieved. Therefore, the surface density of the sound-insulating portion is 0.01 kg / m 2It is preferable to be as described above. As will be described later, the sound insulation part may or may not be integrated with the sound absorption material body. When the sound insulation part is not integrated with the sound absorption material body, the surface density of the sound insulation part is 0.1 kg / m 2 It is more preferable to be as described above.

[0013] Here, "integrating the sound insulation part with the sound absorption material body" means integrating the sound insulation part with the sound absorption material body so that the sound insulation part and the sound absorption material body vibrate as one. On the other hand, "not integrating the sound insulation part with the sound absorption material body" means that regardless of whether the sound insulation part is in close contact (contact) with the sound absorption material body, the sound insulation part and the sound absorption material body do not vibrate as one, and each vibrates independently (a state where they attach and separate without affecting each other's vibration. Ideally, it can be considered that there is a thin air layer (an air layer with an infinitesimal thickness) between the sound insulation part and the sound absorption material body), and the sound insulation part and the sound absorption material body are provided.

[0014] In the sound absorption material of the present invention, the material forming the sound absorption material body is not particularly limited as long as it has a desired air permeability (sound absorption property). Examples of the material (material having air permeability) forming the sound absorption material body include porous materials. Examples of the porous material include foamed resins (those with continuous air bubbles) such as urethane foam and polyethylene foam, and non-woven fabrics such as chemical fiber felt and natural fiber felt. The concept of "non-woven fabric" also includes glass wool and rock wool.

[0015] In the sound absorption material of the present invention, the material forming the sound insulation part is not particularly limited as long as it has a desired airtightness (sound insulation property). The sound insulation part can be a patch-like member (including not only planar ones but also long and narrow strip-like ones, etc.) attached to the surface of the sound absorption material body. Also, the sound insulation part can be formed by a paint-based material applied to the surface of the sound absorption material body. Further, the sound insulation part can be a molten film part formed on the surface of the sound absorption material body.

[0016] In the sound-absorbing material of the present invention, the ratio of the sound-insulating portions provided on the surface of the sound-absorbing material body where the sound-insulating portions are arranged is not particularly limited. However, if the ratio of the sound-insulating portions provided is too small, there is a risk that the above-described diffraction phenomenon is less likely to occur. For this reason, the area S 1 of the surface of the sound-absorbing material body where the sound-insulating portions are arranged, and the total area S 2 of the sound-insulating portions arranged on the same surface where the sound-insulating portions are arranged, the ratio S 2 / S 1 is preferably 0.1 or more.

[0017] In the sound-absorbing material of the present invention, it is also preferable to cover the surface of the sound-insulating portion on the side opposite to the sound-absorbing material body with a sound-absorbing covering material having air permeability. Thereby, not only the frequency band where the sound absorption rate is high is shifted further to the lower frequency side, but also the sound absorption rate in the high frequency band can be improved, and a sound absorption effect can be obtained in a wider frequency band. The sound-absorbing covering material can be formed of the same material as the above-described sound-absorbing material body. The sound-absorbing covering material may be thick (having a thickness similar to that of the sound-absorbing material body) or thin (film-like).

[0018] The above-described sound-absorbing material of the present invention can also be made into a laminated type sound-absorbing material by stacking a plurality of them in the thickness direction. Thereby, a sound absorption effect can be obtained in a wider frequency band, such as shifting the frequency band where the sound absorption rate is high further to the lower frequency side. In the laminated type sound-absorbing material, it is also preferable to arrange the sound-insulating portions of the sound-absorbing material forming one layer and the sound-insulating portions of the sound-absorbing material forming another layer arranged above the one layer so as not to overlap in the thickness direction.

Advantages of the Invention

[0019] As described above, according to the present invention, it is possible to provide a sound-absorbing material that can exhibit an excellent sound absorption effect in a wide frequency band including the low frequency band while suppressing the thickness of the sound-absorbing material.

Brief Description of the Drawings

[0020]

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Embodiments for Carrying Out the Invention

[0021] 1. Sound Absorbing Material of the Present Invention A preferred embodiment of the sound absorbing material of the present invention will be described more specifically with reference to the drawings. In the following, the sound absorbing materials of 18 embodiments from the first embodiment to the eighteenth embodiment will be taken as examples to describe the sound absorbing material of the present invention. However, the technical scope of the sound absorbing material of the present invention is not limited to these embodiments. The configuration of the sound absorbing material of the present invention can be appropriately changed without departing from the gist of the invention.

[0022] 1.1 Sound Absorbing Material of the First Embodiment First, the sound absorbing material of the first embodiment will be described. FIG. 4 is a perspective view showing the appearance of the sound absorbing material 10 of the first embodiment. FIG. 5 is a cross-sectional view showing the state where the sound absorbing material 10 of the first embodiment is cut along a cross-section perpendicular to its surface α 1 is shown. FIG. 6 is a photograph of the appearance of the sound absorbing material 10 of the first embodiment.

[0023] The sound absorbing material 10 of the first embodiment, as shown in FIG. 5, has a surface α 1It is configured to absorb the incident sound wave 50 that enters the sound absorption material main body 11 from the side. As shown in FIGS. 4 to 6, this sound absorption material 10 is composed of a sound absorption material main body 11 having air permeability (sound absorption property) and a sound insulation portion 12 having non-air permeability (sound insulation property).

[0024] The sound insulation portion 12 may be provided on both surfaces α 1 , α 2 of the sound absorption material main body 11. However, in the sound absorption material 10 of the first embodiment, it is provided only on one surface α 1 . In other words, out of the pair of surfaces α 1 , α 2 of the sound absorption material main body 11, only the surface α 1 on the side where the incident sound wave 50 enters serves as the "sound insulation portion arrangement surface". The sound insulation portion 12 is not arranged so as to cover the entire area of the surface α 1 of the sound absorption material main body 11, but is locally arranged so that at least a part of the area of the surface α 1 is exposed when viewed from the surface α 1 side.

[0025] The sound insulation portion 12 may be provided at only one location on the sound insulation portion arrangement surface α 1 in one sound absorption material 10. However, in the sound absorption material 10 of the first embodiment, a plurality of sound insulation portions 12 are repeatedly arranged on the sound insulation portion arrangement surface α 1 with a gap therebetween. By repeatedly providing such a plurality of sound insulation portions 12, the diffraction phenomenon described later can occur equally at every location on the sound insulation portion arrangement surface α 1 , and it becomes possible to obtain substantially uniform sound absorption characteristics over the entire sound absorption material 10.

[0026] In the sound absorption material 10 of the first embodiment, as shown in FIG. 5, the incident sound wave 50 that enters the sound absorption material main body 11 from the surface α 1 side can be diffracted by the sound insulation portion 12. For this reason, the path length of the incident sound wave 50 inside the sound absorption material main body 11 can be lengthened, and the apparent thickness of the sound absorption material main body 11 can be increased.

[0027] As described above, in a general sound-absorbing material, when the thickness thereof matches 1 / 4 of the wavelength of the incident sound wave, the sound absorption rate increases. In the sound-absorbing material 10 of the first embodiment and the sound-absorbing material 10 of the present invention, due to the above-described diffraction phenomenon, the apparent thickness of the sound-absorbing material main body 11 increases, so that the frequency band where the sound absorption rate increases can be shifted to the low-frequency side. Therefore, even if the sound-absorbing material main body 11 is not thickened, it is possible to effectively absorb sound in the low-frequency band. For example, although it also varies depending on the material of the sound-absorbing material main body 11, even if the thickness of the sound-absorbing material main body 11 is 40 mm or less or 30 mm or less, it is possible to effectively absorb sound in the low-frequency band.

[0028] Examples of the material (material having air permeability) for forming the sound-absorbing material main body 11 include foamed resins (those having interconnected air bubbles) such as urethane foam and polyethylene foam, and porous materials of non-woven fabrics such as chemical fiber felt and natural fiber felt. The form of the sound-absorbing material main body 11 is not particularly limited. In the sound-absorbing material 10 shown in FIGS. 4 to 6, the sound-absorbing material main body 11 is a flat plate member formed of urethane foam.

[0029] On the other hand, examples of the material (material having non-air permeability) for forming the sound insulation part 12 include plate materials or sheet materials made of rubber, resin, metal, or the like. The sound insulation part 12 can be provided as a patch-shaped member, or the sound insulation part arrangement surface α of the sound-absorbing material main body 11 1 A paint-based material applied thereto, or the sound insulation part arrangement surface α of the sound-absorbing material main body 11 1 It can also be provided in the form of a molten film part locally formed thereon. The shape (shape in plan view) of the sound insulation part 12 is not particularly limited, and various shapes such as polygons such as quadrilaterals, circles, and ellipses can be adopted. In the sound-absorbing material 10 shown in FIGS. 4 to 6, the sound insulation part 12 is a square (quadrilateral) sheet material formed of rubber.

[0030] As described above, the sound-absorbing material main body 11 is formed of a material having air permeability (a material having a small flow resistance). In this regard, considering the sound absorption property of the sound-absorbing material main body 11, the flow resistance (air permeability resistance) of the sound-absorbing material main body is 10 7 N·s / m 4It is preferably as follows. The flow resistance of the sound absorption material body is 10 6 N·s / m 4 It is more preferably as follows, and 10 5 N·s / m 4 It is even more preferably as follows.

[0031] However, if the flow resistance of the sound absorption material body is made too low, the sound absorption performance of the sound absorption material body may decrease. For this reason, the flow resistance of the sound absorption material body is preferably 10 N·s / m 4 or more. The flow resistance of the sound absorption material body is 10 2 N·s / m 4 or more is more preferable, and 10 3 N·s / m 4 or more is even more preferable. In the sound absorption material 10 shown in FIGS. 4 to 6, the flow resistance of the sound absorption material body 11 is 1.1×10 4 N·s / m 4 and is as such.

[0032] On the other hand, the sound insulation part 12 is formed of a non-ventilative material (a material with a large flow resistance). In this regard, considering the ease of diffraction in the sound insulation part 12, the flow resistance (ventilation resistance) of the sound insulation part 12 is preferably 10 8 N·s / m 4 or more. The flow resistance of the sound insulation part is 10 9 N·s / m 4 or more is more preferable, and 10 10 N·s / m 4 or more is even more preferable. If the sound insulation part is formed of a completely non-ventilative material, the flow resistance of the sound insulation part becomes infinite. In the sound absorption material 10 shown in FIGS. 4 to 6, the flow resistance of the sound insulation part 12 is 5.62×10 8 N·s / m 4 (the measurement limit value of the measuring instrument used) or more and is as such.

[0033] The acoustic properties of the sound absorption material body 11 are not particularly limited. However, if the porosity of the sound absorption material body 11 is too small, the flow resistance (ventilation resistance) will increase, and sound waves will not penetrate into the sound absorption material body 11, making it difficult to ensure the sound absorption performance of the sound absorption material body 11. Therefore, the porosity of the sound absorption material body 11 is preferably 0.7 or more. More preferably, the porosity of the sound absorption material body 11 is 0.8 or more, and even more preferably 0.9 or more.

[0034] However, if the porosity of the sound absorption material body 11 is too close to 1 (the value when it is all air), it will also be difficult to ensure the sound absorption performance of the sound absorption material body 11. Therefore, the porosity of the sound absorption material body 11 is preferably 0.999 or less. More preferably, the porosity of the sound absorption material body 11 is 0.998 or less, and even more preferably 0.994 or less. In the sound absorption material 10 shown in FIGS. 4 to 6, the porosity of the sound absorption material body 11 is 0.986.

[0035] On the other hand, the surface density of the sound insulation part 12 varies depending on whether the sound insulation part 12 is integrated with the sound absorption material body 11 or not, and is not particularly limited. This is because when the surface density of the sound insulation part 12 is small, the sound insulation part 12 vibrates greatly due to sound waves, and the sound is re-radiated to the opposite side from the vibration, making it easy for the sound to penetrate, and it becomes difficult to ensure the sound insulation performance of the sound insulation part 12. When the sound insulation part 12 is not integrated with the sound absorption material body 11, the mass and rigidity of the sound insulation part 12 itself must ensure the sound insulation performance, so it is necessary to increase the surface density of the sound insulation part 12. In contrast, when the sound insulation part 12 is integrated with the sound absorption material body 11, the sound insulation part 12 is less likely to vibrate due to the mass and rigidity of the sound absorption material body 11, so the surface density of the sound insulation part 12 can be reduced.

[0036] Considering the above, when the sound insulation part 12 is integrated with the sound absorption material body 11, the surface density of the sound insulation part is preferably 0.01 kg / m 2 or more. In this case, the surface density of the sound insulation part is more preferably 0.05 kg / m 2 or more, and even more preferably 0.1 kg / m 2It is more preferable to be as above.

[0037] On the other hand, when the sound insulation part 12 is not integrated with the sound absorption material main body 11, it is preferably 0.1 kg / m 2 or more. In this case, the surface density of the sound insulation part is more preferably 0.5 kg / m 2 or more, and even more preferably 1.0 kg / m 2 or more. The upper limit of the surface density of the sound insulation part 12 is not particularly limited, but is usually 50 kg / m 2 or less. In the sound absorption material 10 shown in FIGS. 4 to 6, the surface density of the sound insulation part 12 is 2.24 kg / m 2 and is so.

[0038] As already described, the sound insulation part 12 is locally provided on the sound insulation part arrangement surface α 1 of the sound absorption material main body 11. The ratio of how much of the sound insulation part 12 is provided on the sound insulation part arrangement surface α 1 of the sound absorption material main body 11 is not particularly limited. However, if the ratio of providing the sound insulation part 12 is too small, there is a possibility that the above-described diffraction phenomenon is less likely to occur. For this reason, it becomes difficult to shift the frequency band where the sound absorption rate is high to the low frequency side.

[0039] Therefore, the ratio S 1 of the total area S 1 of the sound insulation part 12 arranged on the sound insulation part arrangement surface α 1 of the sound absorption material main body 11 to the area S 2 of the sound insulation part arrangement surface α 2 / S 1 is preferably 0.1 or more. The ratio S 2 / S 1 is more preferably 0.2 or more, and even more preferably 0.3 or more.

[0040] However, the ratio S 2 / S 1If it is made too large, as will be explained by the experimental results described later, although the frequency band where the sound absorption rate increases shifts to the low frequency side, a sharp sound absorption peak is formed near that frequency, and the width of the frequency at which a high sound absorption rate can be obtained becomes narrow. This is the ratio S 2 / S 1 If it is made too large, it is considered that, rather than the diffraction phenomenon described above occurring, the same Helmholtz resonance as that of the perforated plate sound absorption structure occurs. Therefore, the ratio S 2 / S 1 is preferably suppressed to such an extent that Helmholtz resonance does not occur (for example, 0.99 or less).

[0041] Also, when a plurality of sound insulation portions 12 are repeatedly arranged as in the sound absorption material 10 of the first embodiment, the width of the gap between adjacent sound insulation portions 12 also affects the sound absorption characteristics of the sound absorption material 10. That is, if this gap is narrow, inevitably, the above-mentioned ratio S 2 / S 1 becomes large, and instead of diffraction, the above-mentioned Helmholtz resonance occurs, and the width of the frequency at which a high sound absorption rate can be obtained becomes narrow.

[0042] Therefore, the width of the gap between adjacent sound insulation portions 12 is usually set to 1 mm or more. The width of the gap between adjacent sound insulation portions 12 is preferably 3 mm or more, and more preferably 5 mm or more. There is no particular upper limit to the width of the gap between adjacent sound insulation portions 12, but it is usually up to about 100 to 300 mm.

[0043] Furthermore, as will be explained by the experimental results described later, the dimensions of the sound insulation portion 12 also affect the sound absorption characteristics of the sound absorption material 10. That is, when the dimensions of each sound insulation portion 12 become larger, sound can be effectively absorbed from a lower frequency. For this reason, it is preferable to make the dimensions of each sound insulation portion 12 somewhat larger.

[0044] The specific dimensions of the sound insulation part 12 vary depending on the material, shape, etc. of the sound insulation part 12, but the span (equivalent circle diameter) of each sound insulation part 12 is usually set to 10 mm or more. The span of each sound insulation part 12 is preferably 20 mm or more, more preferably 30 mm or more, and even more preferably 40 mm or more. There is no particular upper limit for the span of each sound insulation part 12, but it is usually up to about 500 mm.

[0045] 1.2 Sound Absorbing Material of the Second Embodiment Subsequently, the sound absorbing material of the second embodiment will be described. FIG. 7 is a perspective view showing the appearance of the sound absorbing material of the second embodiment. In the sound absorbing material 10 (FIG. 4) of the first embodiment described above, the sound insulation part 12 has a square shape, whereas in the sound absorbing material 10 of the second embodiment, as shown in FIG. 7, the sound insulation part 12 has a circular shape. Thus, the shape of the sound insulation part 12 can also adopt a shape other than a square shape. For the configuration not particularly mentioned in the sound absorbing material 10 of the second embodiment, the same configuration as that described in the sound absorbing material 10 of the first embodiment can be adopted.

[0046] 1.3 Sound Absorbing Material of the Third Embodiment Subsequently, the sound absorbing material of the third embodiment will be described. FIG. 8 is a perspective view showing the appearance of the sound absorbing material of the third embodiment. In the sound absorbing material 10 (FIG. 4) of the first embodiment and the sound absorbing material 10 (FIG. 8) of the second embodiment described above, the shape of the sound insulation part 12 is only one type, whereas in the sound absorbing material 10 of the third embodiment, as shown in FIG. 8, as the sound insulation part 12, a square-shaped one and a circular-shaped one are mixed. Thus, by combining a plurality of types of sound insulation parts 12 with different shapes, it is possible to give variations to the diffraction distance, and it becomes possible to increase the sound absorption rate not only around one frequency but also around a plurality of frequencies. For the configuration not particularly mentioned in the sound absorbing material 10 of the third embodiment, the same configuration as that described in the sound absorbing material 10 of other embodiments can be adopted.

[0047] 1.4 Sound Absorbing Material of the Fourth Embodiment Next, the sound absorbing material of the fourth embodiment will be described. FIG. 9 is a perspective view showing the appearance of the sound absorbing material of the fourth embodiment. In the sound absorbing material 10 (FIG. 4) of the first embodiment and the sound absorbing material 10 (FIG. 8) of the second embodiment described above, the dimensions of the sound insulation part 12 were only of one type. In the sound absorbing material 10 of the fourth embodiment, as shown in FIG. 9, as the sound insulation part 12, those with various dimensions (those with large dimensions and those with small dimensions) are mixed. In this way, by combining a plurality of types of sound insulation parts 12 with different dimensions, it is also possible to give variations to the diffraction distance, and it becomes possible to increase the sound absorption rate not only around one frequency but also around a plurality of frequencies. For the configurations not particularly mentioned in the sound absorbing material 10 of the fourth embodiment, the same configurations as those described in the sound absorbing materials 10 of other embodiments can be adopted.

[0048] 1.5 Sound Absorbing Material of the Fifth Embodiment Next, the sound absorbing material of the fifth embodiment will be described. FIG. 10 is a perspective view showing the appearance of the sound absorbing material of the fifth embodiment. In the sound absorbing materials 10 (FIGS. 4 and 7 to 9) from the first embodiment to the fourth embodiment described above, a plurality of sound insulation parts 12 were regularly arranged on the lattice points of a square lattice. In the sound absorbing material 10 of the fifth embodiment, as shown in FIG. 10, a plurality of sound insulation parts 12 are arranged irregularly (randomly). For the configurations not particularly mentioned in the sound absorbing material 10 of the fifth embodiment, the same configurations as those described in the sound absorbing materials 10 of other embodiments can be adopted.

[0049] 1.6 Sound Absorbing Material of the Sixth Embodiment Next, the sound-absorbing material of the sixth embodiment will be described. FIG. 11 is a perspective view showing the appearance of the sound-absorbing material of the sixth embodiment. In the sound-absorbing materials 10 (FIGS. 4 and 7 to 10) from the first to the fifth embodiments described above, the patch-shaped sound-insulating portions 12 were repeatedly arranged in two directions (vertical and horizontal). In the sound-absorbing material 10 of the sixth embodiment, as shown in FIG. 11, the sound-insulating portions 12 extending in a strip shape in one direction (vertical direction) are repeatedly arranged in the other direction (horizontal direction). The adjacent sound-insulating portions 12 are arranged substantially in parallel, and the gaps therebetween are formed in a slit shape. For the configurations not particularly mentioned in the sound-absorbing material 10 of the sixth embodiment, the same configurations as those described in the sound-absorbing materials 10 of the other embodiments can be adopted.

[0050] 1.7 Sound-absorbing material of the seventh embodiment Next, the sound-absorbing material of the seventh embodiment will be described. FIG. 12 is a perspective view showing the appearance of the sound-absorbing material of the seventh embodiment. In the sound-absorbing materials 10 (FIGS. 4 and 7 to 11) from the first to the sixth embodiments described above, a plurality of sound-insulating portions 12 were arranged on one sound-absorbing material main body 11. In the sound-absorbing material 10 of the seventh embodiment, as shown in FIG. 12, only one sound-insulating portion 12 is arranged for one sound-absorbing material main body 11. For the configurations not particularly mentioned in the sound-absorbing material 10 of the seventh embodiment, the same configurations as those described in the sound-absorbing materials 10 of the other embodiments can be adopted.

[0051] 1.8 Sound-absorbing material of the eighth embodiment Next, the sound-absorbing material of the eighth embodiment will be described. FIG. 13 is a cross-sectional view showing the appearance of the sound-absorbing material of the eighth embodiment. In the sound-absorbing materials 10 (FIGS. 4 and 7 to 12) from the first to the seventh embodiments described above, nothing was arranged on the surface of the sound insulation part 12 opposite to the sound-absorbing material main body 11. In the sound-absorbing material 10 of the eighth embodiment, as shown in FIG. 13, a thick breathable material (such as urethane foam) sound-absorbing coating material 13 is arranged on the surface of the sound insulation part 12 opposite to the sound-absorbing material main body 11. Thereby, as will be described in Experiment 3 below, it becomes possible to improve sound absorption in the high-frequency band. For the configuration not particularly mentioned in the sound-absorbing material 10 of the eighth embodiment, the same configuration as that described in the sound-absorbing material 10 of other embodiments can be adopted.

[0052] 1.9 Sound-absorbing material of the ninth embodiment Next, the sound-absorbing material of the ninth embodiment will be described. FIG. 14 is a cross-sectional view showing the appearance of the sound-absorbing material of the ninth embodiment. In the sound-absorbing materials 10 (FIGS. 4 and 7 to 12) from the first to the seventh embodiments described above, nothing was arranged on the surface of the sound insulation part 12 opposite to the sound-absorbing material main body 11. In the sound-absorbing material 10 of the ninth embodiment, as shown in FIG. 14, a thin breathable material (non-woven fabric film such as meltblown non-woven fabric) sound-absorbing coating material 13 is arranged on the surface of the sound insulation part 12 opposite to the sound-absorbing material main body 11. Thereby, as will be described in Experiment 4 below, it becomes possible to absorb sound from a lower frequency side. For the configuration not particularly mentioned in the sound-absorbing material 10 of the ninth embodiment, the same configuration as that described in the sound-absorbing material 10 of other embodiments can be adopted.

[0053] 1.10 Sound-absorbing material of the tenth embodiment Next, the sound-absorbing material of the tenth embodiment will be described. FIG. 15 is a cross-sectional view showing the appearance of the sound-absorbing material of the tenth embodiment. Among the sound-absorbing materials 10 (FIGS. 4 and 7 to 14) from the first to the ninth embodiments described above, excluding the sound-absorbing material 10 (FIG. 12) of the seventh embodiment (the one having a plurality of sound-insulating portions 12), the sound-absorbing material main bodies 11 overlapping one sound-insulating portion 12 and the sound-absorbing material main bodies 11 overlapping the other sound-insulating portions 12 were continuous. However, in the sound-absorbing material 10 of the tenth embodiment, as shown in FIG. 15, the sound-absorbing material main body 11 overlapping one sound-insulating portion 12 and the sound-absorbing material main body 11 overlapping the other sound-insulating portion 12 are separated. In other words, the sound-absorbing material main body 11 is arranged only around the portion overlapping the sound-insulating portion 12, and the sound-absorbing material main body 11 is not arranged at the portion overlapping the gap of the sound-insulating portion 12. For the configuration not particularly mentioned in the sound-absorbing material 10 of the tenth embodiment, the same configuration as that described in the sound-absorbing material 10 of other embodiments can be adopted.

[0054] 1.11 Sound-absorbing material of the eleventh embodiment Next, the sound-absorbing material of the eleventh embodiment will be described. FIG. 16 is a cross-sectional view showing the appearance of the sound-absorbing material of the eleventh embodiment. In the sound-absorbing material 10 of the tenth embodiment, as shown in FIG. 16, an air layer 14 is provided on the back side of the sound-absorbing material 10 (the surface α 2 side of the sound-absorbing material main body 11). Thus, an air layer 14 can also be provided on the surface α 2 side (transmission side) of the sound-absorbing material 10. For the configuration not particularly mentioned in the sound-absorbing material 10 of the eleventh embodiment, the same configuration as that described in the sound-absorbing material 10 of other embodiments can be adopted.

[0055] 1.12 Sound-absorbing material of the twelfth embodiment Next, the sound-absorbing material of the twelfth embodiment will be described. FIG. 17 is a cross-sectional view showing the appearance of the sound-absorbing material of the twelfth embodiment. In the sound-absorbing material 10 (FIG. 16) of the above-described eleventh embodiment, the sound-absorbing material main body 11 overlapping one sound insulation part 12 and the sound-absorbing material main body 11 overlapping the other sound insulation part 12 were continuous. In the sound-absorbing material 10 of the twelfth embodiment, as shown in FIG. 17, the sound-absorbing material main body 11 overlapping one sound insulation part 12 and the sound-absorbing material main body 11 overlapping the other sound insulation part 12 are separated. In other words, the sound-absorbing material 10 of the twelfth embodiment is a combination of the configuration of the sound-absorbing material 10 (FIG. 15) of the tenth embodiment and the sound-absorbing material 10 (FIG. 16) of the eleventh embodiment. For the configuration not particularly mentioned in the sound-absorbing material 10 of the twelfth embodiment, the same configuration as that described in the sound-absorbing material 10 of other embodiments can be adopted.

[0056] 1.13 Sound-absorbing material of the thirteenth embodiment Next, the sound-absorbing material of the thirteenth embodiment will be described. FIG. 18 is a cross-sectional view showing the appearance of the sound-absorbing material of the thirteenth embodiment. In the sound-absorbing materials 10 (FIGS. 4 and 7 to 17) from the first embodiment to the twelfth embodiment described above, the sound insulation part 12 was provided on the front side (surface α 1 side) of the sound-absorbing material main body 11 where the sound is incident. In the sound-absorbing material 10 of the thirteenth embodiment, as shown in FIG. 18, the sound insulation part 12 is provided on the back side (surface α 2 side) of the sound-absorbing material main body 11 where the sound passes through. For the configuration not particularly mentioned in the sound-absorbing material 10 of the thirteenth embodiment, the same configuration as that described in the sound-absorbing material 10 of other embodiments can be adopted.

[0057] 1.14 Sound-absorbing material of the fourteenth embodiment Next, the sound-absorbing material of the fourteenth embodiment will be described. FIG. 19 is a cross-sectional view showing the appearance of the sound-absorbing material of the fourteenth embodiment. In the sound-absorbing material 10 (FIG. 18) of the thirteenth embodiment described above, the sound-absorbing material main body 11 overlapping one sound insulation part 12 and the sound-absorbing material main body 11 overlapping the other sound insulation part 12 were continuous. In the sound-absorbing material 10 of the fourteenth embodiment, as shown in FIG. 19, the sound-absorbing material main body 11 overlapping one sound insulation part 12 and the sound-absorbing material main body 11 overlapping the other sound insulation part 12 are separated. In other words, the sound-absorbing material 10 of the fourteenth embodiment is a combination of the configuration of the sound-absorbing material 10 (FIG. 15) of the tenth embodiment and the sound-absorbing material 10 (FIG. 18) of the thirteenth embodiment. For the configuration not particularly mentioned in the sound-absorbing material 10 of the fourteenth embodiment, the same configuration as that described in the sound-absorbing material 10 of other embodiments can be adopted.

[0058] 1.15 Sound-absorbing material of the fifteenth embodiment Next, the sound-absorbing material of the fifteenth embodiment will be described. FIG. 20 is a cross-sectional view showing the appearance of the sound-absorbing material of the fifteenth embodiment. In the sound-absorbing materials 10 (FIGS. 4 and 7 to 19) from the first embodiment to the fourteenth embodiment described above, the sound-absorbing material main body 11 had a single-layer structure. In the sound-absorbing material 10 of the fifteenth embodiment, as shown in FIG. 20, the sound-absorbing material main body 11 has a multi-layer structure. Specifically, the sound-absorbing material main body 11 is constituted by laminating a plurality of types of sound-absorbing materials 11a, 11b, 11c having different flow resistances and the like. In the example shown in FIG. 20, the sound-absorbing material main body 11 has a three-layer structure, but the sound-absorbing material main body 11 can also be two layers or four or more layers. For the configuration not particularly mentioned in the sound-absorbing material 10 of the fifteenth embodiment, the same configuration as that described in the sound-absorbing material 10 of other embodiments can be adopted.

[0059] 1.16 Sound-absorbing material of the sixteenth embodiment Next, the sound-absorbing material of the sixteenth embodiment will be described. FIG. 21 is a cross-sectional view showing the appearance of the sound-absorbing material of the sixteenth embodiment. In the sound-absorbing material 10 of the sixteenth embodiment, as shown in FIG. 21, the sound-absorbing material main body 11 has a multilayer structure, and an air layer 14 is provided on the back side of the sound-absorbing material 10 (the surface α of the sound-absorbing material main body 11). 2 side). In other words, the sound-absorbing material 10 of the sixteenth embodiment is a combination of the configuration of the sound-absorbing material 10 (FIG. 20) of the fifteenth embodiment and the configuration of the sound-absorbing material 10 (FIG. 16) of the eleventh embodiment. For the configuration not particularly mentioned in the sound-absorbing material 10 of the sixteenth embodiment, the same configuration as that described in the sound-absorbing material 10 of other embodiments can be adopted.

[0060] 1.17 Sound-absorbing material of the seventeenth embodiment Next, the sound-absorbing material of the seventeenth embodiment will be described. FIG. 22 is a cross-sectional view showing the appearance of the sound-absorbing material of the seventeenth embodiment. The sound-absorbing material of the seventeenth embodiment is a laminated type in which two sound-absorbing materials 10 each composed of a sound-absorbing material main body 11 and a plurality of sound insulation parts 12 are stacked in the thickness direction as shown in FIG. 22. As in the sound-absorbing material of this seventeenth embodiment, a plurality of sound-absorbing materials 10 can be stacked and arranged. Thereby, it becomes possible to perform sound absorption from a lower frequency side. The number of sound-absorbing materials 10 stacked is not limited to two, and can also be three or more. For the configuration not particularly mentioned in the sound-absorbing material of the seventeenth embodiment, the same configuration as that described in the sound-absorbing material 10 of other embodiments can be adopted.

[0061] 1.18 Sound-absorbing material of the eighteenth embodiment Next, the sound-absorbing material of the eighteenth embodiment will be described. FIG. 23 is a cross-sectional view showing the appearance of the sound-absorbing material of the eighteenth embodiment. In the sound-absorbing material (FIG. 22) of the seventeenth embodiment described above, the sound insulation portions 12 constituting the sound-absorbing material 10 of different layers were arranged so as to overlap in the thickness direction of the sound-absorbing material 10. In the sound-absorbing material of the eighteenth embodiment, as shown in FIG. 23, the sound insulation portions 12 constituting the sound-absorbing material 10 of different layers are arranged alternately so as not to overlap in the thickness direction of the sound-absorbing material 10. As a result, it becomes possible to perform sound absorption from a lower frequency side. The sound insulation portions 12 constituting the sound-absorbing material 10 of different layers are more preferably arranged alternately not only in one direction (the left-right direction toward the plane of FIG. 23) but also in the other direction (the direction perpendicular to the plane of the figure). For the configuration not particularly mentioned in the sound-absorbing material of the eighteenth embodiment, the same configuration as that described for the sound-absorbing material 10 of other embodiments can be adopted.

[0062] 1.19 Others In the sound-absorbing materials 10 of the first to eighteenth embodiments described above, a plurality of sound insulation portions 12 (patch-shaped members) were arranged at intervals from each other. However, if the frequency band to be sound-absorbed can be shifted to the lower frequency side by diffracting the incident sound wave with the sound insulation portion 12 based on the principle described above, these sound insulation portions 12 can also be in a connected form. FIG. 39 is a diagram showing a modified example of the sound insulation portion 12. FIG. 40 is a diagram showing another modified example of the sound insulation portion 12. The sound insulation portions 12 shown in FIGS. 39 and 40 are formed by repeatedly arranging square portions in a checkered pattern. In the sound insulation portion 12 of FIG. 39, they are in a state of being connected dot-like at the corner vertices of each square portion, and in the sound insulation portion 12 of FIG. 40, they are in a state of being connected with the corners of each square portion slightly overlapping. In the examples shown in FIGS. 39 and 40, the unit forming the sound insulation portion 12 is a square portion, but the shape of the unit forming the sound insulation portion 12 can also be other than square (for example, circular, elliptical, etc.). Also, a plurality of types of shapes can be combined and arranged.

[0063] 2. Numerical Analysis and Experiments In order to confirm the effectiveness of the sound-absorbing material of the present invention, the following numerical analyses 1 to 4 and experiments 1 to 3 were conducted.

[0064] 2.1 Numerical Analysis 1 First, in the sound-absorbing material of the present invention, a numerical analysis 1 was performed to confirm how the incident sound wave propagates inside the sound-absorbing material main body. Including this numerical analysis 1, in the following numerical analyses 2 to 3 described later, they were performed by the FEM (Finite Element Method). As the acoustic analysis software, "Simcenter 3D" manufactured by Siemens was used. FIG. 24 is a diagram showing the finite element model of the sound-absorbing material used in the numerical analysis 1. In the numerical analysis 1, it was performed for two cases: when the thickness of the sound-absorbing material main body was set to 20 mm and when it was set to 60 mm.

[0065] FIG. 25 shows the sound pressure distribution and particle velocity distribution obtained in the numerical analysis 1. FIGS. 25(a) and (b) show the results when the thickness of the sound-absorbing material main body is 20 mm. Among them, FIG. 25(a) shows the sound pressure distribution, and FIG. 25(b) shows the particle velocity distribution. Also, FIGS. 25(c) and (d) show the results when the thickness of the sound-absorbing material main body is 60 mm. Among them, FIG. 25(c) shows the sound pressure distribution, and FIG. 25(d) shows the particle velocity distribution. Looking at FIG. 25, it can be seen that the incident sound wave diffracts at the edge of the sound insulation part and wraps around to the back side of the sound insulation part. Also, it can be seen that the diffraction is larger when the thickness of the sound-absorbing material main body is smaller (FIG. 25(b)) than when the thickness of the sound-absorbing material main body is larger (FIG. 25(d)). As already described, as the reason for the sound-absorbing material of the present invention to be able to absorb sound from low frequencies, it was mentioned that the path length of the incident sound wave inside the sound-absorbing material main body becomes longer due to the diffraction of the incident sound wave at the sound insulation part, and this phenomenon was verified from the results of the numerical analysis 1.

[0066] 2.2 Experiment 1 Subsequently, Experiment 1 was conducted to measure the normal incidence sound absorption coefficient of the sound absorption material according to the present invention. FIG. 26 is a cross-sectional view showing a state in which the normal incidence sound absorption coefficient measuring device used in Experiment 1 was cut in a plane including the center line of the acoustic tube. As shown in FIG. 26, a disc-shaped sample (sound absorption material) was placed in the middle part inside a cylindrical acoustic tube with an inner diameter of 100 mm, and sound waves were vertically incident on the sample (sound absorption material) from a sound source provided at one end of the acoustic tube. By detecting the intensity of the reflected wave with a microphone placed between the sound source and the sample (sound absorption material), the reflectivity of the sample (sound absorption material) was obtained, and the normal incidence sound absorption coefficient was calculated.

[0067] FIG. 27 is a perspective view showing the samples (samples of Comparative Example 1 and Examples 1.1 to 1.3) used in Experiment 1. As shown in FIG. 27, the sound absorption materials (samples of Examples 1.1 to 1.3) according to the present invention are all composed of a sound absorption material main body in the shape of a disc with an outer diameter of 100 mm and a thickness of 20 mm, and a circular sound insulation part provided at the center of one side (the surface on the side where sound waves are incident) of the sound absorption material main body. The diameter of the sound insulation part is 40 mm for the sample of Example 1.1, 60 mm for the sample of Example 1.2, and 80 mm for the sample of Example 1.3. The sound absorption material main body is formed of urethane foam, and the sound insulation part is formed of a rubber sheet. In Experiment 1, in order to confirm the effectiveness of the sound absorption material of the present invention, the same measurement was also performed on the sample of Comparative Example 1 without a sound insulation part. The dimensions and materials of the sound absorption material main body in the sample of Comparative Example 1 are the same as those of the sound absorption material main body used in Examples 1.1 to 1.3.

[0068] Fig. 28 shows graphs of the normal incidence sound absorption coefficients of each sample (samples of Comparative Example 1 and Examples 1.1 to 1.3) measured in Experiment 1. Looking at Fig. 28, it can be seen that the sound absorption materials according to the present invention (samples of Examples 1.1 to 1.3) have higher sound absorption coefficients in the low frequency band than the sample of Comparative Example 1. From this, it was found that the sound absorption material of the present invention can absorb sound in the low frequency band. Also, from Fig. 28, the sample of Example 1.2 with a sound insulation part diameter of 60 mm absorbs sound from a lower frequency band than the sample of Example 1.1 with a sound insulation part diameter of 40 mm, and further, the sample of Example 1.3 with a sound insulation part diameter of 80 mm absorbs sound from a lower frequency band than the sample of Example 1.2 with a sound insulation part diameter of 60 mm. From this, it was also found that by increasing the size of the sound insulation part, sound can be absorbed from a lower frequency band.

[0069] 2.3 Experiment 2 Subsequently, Experiment 2 was conducted to measure the reverberation room method sound absorption coefficient of the sound absorption material according to the present invention. The measurement of the reverberation room method sound absorption coefficient in Experiment 2 was carried out in accordance with the method standardized in JIS A1409 "Method for Measuring Sound Absorption Coefficient by Reverberation Room Method".

[0070] Fig. 29 is a photograph of the samples (samples of Comparative Example 2 and Examples 2.1 and 2.2) used in Experiment 2. The sound absorption materials according to the present invention (samples of Examples 2.1 and 2.2) are made of urethane foam with an area of 4 m 2 (=2 m × 2 m) and a thickness of 20 mm, and a plurality of rubber sound insulation parts are arranged on one side of the sound absorption material body at the lattice points of a square lattice. In the sample of Example 2.1, each sound insulation part has a square shape of 80 mm × 80 mm, and in the sample of Example 2.2, each sound insulation part has a square shape of 200 mm × 200 mm. The number and gaps of the sound insulation parts are set to be equal with the above ratio S 2 / S 1 being 0.64 in the samples of Examples 2.1 and 2.2. In Experiment 2, the same measurement was also carried out for the sample of Comparative Example 2 under the same conditions as the samples of Examples 2.1 and 2.2 except that no sound insulation part was provided.

[0071] Fig. 30 shows a graph of the reverberation room sound absorption rate of each sample (samples of Comparative Example 2 and Examples 2.1 and 2.2) measured in Experiment 2. From the results in Fig. 30, it can also be seen that the sound-absorbing material according to the present invention (samples of Examples 2.1 and 2.2) can absorb sound in the low-frequency band. Also, from the comparison of the measurement results for the samples of Examples 2.1 and 2.2, even when the ratio S 2 / S 1 is kept constant, it was found that increasing the dimensions of each sound insulation part can absorb sound in the low-frequency band. In Fig. 30, there are places where the sound absorption rate exceeds 1 (the absorbed energy is greater than the energy of the incident sound) (for example, in the 1000 Hz, 1250 Hz, and 1600 Hz bands in Example 2.1). This is due to the area effect caused by the test surface area being smaller than the 10 m 2 specified by the standard. If measurements are made with a larger test body, the sound absorption rate will be smaller than this measured value, but it is considered that the magnitude relationship between the test bodies will not change.

[0072] 2.4 Experiment 3 Subsequently, Experiment 3 was conducted to measure the reverberation room sound absorption rate similar to that in Experiment 2 for samples with two layers of urethane foam (the sound absorption material main body or the sound absorption coating material). FIG. 31 is a cross-sectional view showing the samples (samples of Comparative Example 3 and Examples 3.1 and 3.2) used in Experiment 3. The sample of Example 3.1 is configured by stacking two layers of urethane foam with a thickness of 20 mm as the sound absorption material main body, and sound insulation parts in the shape of a 200 mm × 200 mm square are arranged on the lattice points of the square lattice on the surface layer of the sound absorption material main body. Further, the sample of Example 3.2 has sound insulation parts in the shape of a 200 mm × 200 mm square arranged on the lattice points of the square lattice on the surface layer of a single sound absorption material main body made of urethane foam with a thickness of 20 mm, and the surface of the sound insulation part opposite to the sound absorption material main body is covered with a single sound absorption coating material made of urethane foam with a thickness of 20 mm. This sample of Example 3.2 can also be regarded as having the sound insulation part arranged between two layers of urethane foam (the intermediate layer). Furthermore, the sample of Comparative Example 3 is obtained by removing the sound insulation part from the sample of Example 3.1.

[0073] FIG. 32 shows a graph of the reverberation room sound absorption rate of each sample (samples of Comparative Example 3 and Examples 3.1 and 3.2) measured in Experiment 3. Looking at FIG. 32, it can be seen that the sample of Example 3.2 with the sound insulation part arranged in the intermediate layer has an improved sound absorption rate in the high-frequency band compared to the sample of Example 3.1 with the sound insulation part arranged on the surface layer. From this, it was found that by covering the surface of the sound insulation part opposite to the sound absorption material main body with a breathable sound absorption coating material (forming a structure in which the sound insulation part is sandwiched between materials having sound absorption properties), excellent sound absorption effects can be achieved in a wide range from the low-frequency band to the high-frequency band.

[0074] 2.5 Numerical Analysis 2 Subsequently, the ratio S with respect to the normal incidence sound absorption rate 2 / S 1Numerical analysis 2 for confirming the dependencies was performed. FIG. 33 is a perspective view showing the samples (samples of Examples 4.1 to 4.9) defined in numerical analysis 2. In the samples of Examples 4.1 to 4.9, the sound insulation parts are all defined in a square shape of 100 mm × 100 mm, and the sound absorption material main bodies are all defined by fibrous sound absorption materials with a thickness of 20 mm. In the samples of Examples 4.1 to 4.9, while keeping the area of the sound insulation part constant, by changing the area of the sound absorption material main body, the ratio S 2 / S 1 was made different. The value of the ratio S 2 / S 1 is approximately 0.995 for the sample of Example 4.1, approximately 0.990 for the sample of Example 4.2, approximately 0.980 for the sample of Example 4.3, approximately 0.943 for the sample of Example 4.4, approximately 0.907 for the sample of Example 4.5, approximately 0.640 for the sample of Example 4.6, approximately 0.503 for the sample of Example 4.7, approximately 0.401 for the sample of Example 4.8, and approximately 0.200 for the sample of Example 4.9. The sample of Comparative Example 4 is obtained by removing the sound insulation part from the sample of Example 4.1.

[0075] FIG. 34 shows a graph of the normal incidence sound absorption rate of each sample (the samples of Comparative Example 4 and Examples 4.1 to 4.9) obtained by numerical analysis 2. Looking at FIG. 34, it can be seen that the smaller the ratio S 2 / S 1 , the more the sound absorption effect occurs in a wider frequency band including the low frequency band. Specifically, in the samples of Examples 4.3 to 4.9 where the ratio S 2 / S 1 is less than 0.990, a sound absorption effect is obtained in a relatively wide frequency band. On the other hand, when the ratio S 2 / S 1 is large (for example, in the samples of Examples 4.1 and 4.2 where the ratio S 2 / S 1 is 0.990 or more), although an excellent sound absorption effect is obtained in the frequency band, it was found that the width of the frequency at which such an effect is obtained becomes narrow. The reason is considered to be that as the ratio S 2 / S 1 increases, the influence of Helmholtz resonance is stronger than the effect due to the diffraction phenomenon described above.

[0076] 2.6 Numerical analysis 3 Subsequently, numerical analysis 3 was performed to confirm the dependence of the dimensions of the sound insulation part and the sound absorption material body on the normal incidence sound absorption rate when the ratio S 2 / S 1 was kept constant. Fig. 35 is a perspective view showing the samples (samples of Examples 5.1 to 5.5) defined in numerical analysis 3. In the samples of Examples 5.1 to 5.5, the ratio S 2 / S 1 is kept constant at 0.5. All of the sound absorption material bodies are defined by fibrous sound absorption materials with a thickness of 80 mm. However, the dimensions of the sound insulation part and the sound absorption material body are gradually increased from the sample of Example 5.1 to the sample of Example 5.5. That is, in the sample of Example 5.1, the dimension of the sound insulation part is 100 mm × 100 mm, in the sample of Example 5.2, the dimension of the sound insulation part is 150 mm × 150 mm, in the sample of Example 5.3, the dimension of the sound insulation part is 200 mm × 200 mm, in the sample of Example 5.4, the dimension of the sound insulation part is 300 mm × 300 mm, and in the sample of Example 5.5, the dimension of the sound insulation part is 500 mm × 500 mm. Under these dimensions of the sound insulation part, the dimensions of the sound absorption material body are adjusted so that the ratio S 2 / S 1 becomes 0.5. The sample of Comparative Example 5 is obtained by removing the sound insulation part from the sample of Example 5.1.

[0077] Fig. 36 shows a graph of the normal incidence sound absorption rate of each sample (the sample of Comparative Example 5 and the samples of Examples 5.1 to 5.5) obtained by numerical analysis 3. Looking at Fig. 36, the ratio S 2 / S 1When [a certain parameter] is constant, it can be seen that as the dimensions of the sound insulation part and the sound absorption material body increase, the frequency band in which the sound absorption effect is obtained shifts to the lower frequency side. The reason is that, as already described, in a general sound absorption material, when its thickness matches 1 / 4 of the wavelength of the incident sound wave, the sound absorption rate becomes high. In the sound absorption material of the present invention in which the sound insulation part is arranged on the surface of the sound absorption material body, due to the diffraction phenomenon occurring at the edge of the sound insulation part, the path length of the incident sound wave inside the sound absorption material body is lengthened (the apparent thickness of the sound absorption material body increases), shifting the frequency band with a high sound absorption rate to the lower frequency side. It is considered that when the dimensions of the sound insulation part increase, the diffraction distance becomes longer and the apparent thickness of the sound absorption material body increases.

[0078] 2.7 Experiment 4 Finally, Experiment 4 was conducted to confirm the sound absorption effect when a non-woven fabric film was arranged as a sound absorption covering material on the surface of the sound insulation part opposite to the sound absorption material body. FIG. 37 is a perspective view showing the samples (samples of Comparative Example 6 and Examples 6.1 and 6.2) used in Experiment 4. The sample of Example 6.1 has a sound insulation part in the shape of a circle with a diameter of 80 mm provided at the center of one side of a sound absorption material body made of a urethane foam in the shape of a disk with a thickness of 20 mm. The sample of Example 6.2 is obtained by covering the upper side (the surface of the sound insulation part opposite to the sound absorption material body) of the sample of Example 6.1 with a sound absorption covering material made of a non-woven fabric film (meltblown non-woven fabric). The sample of Comparative Example 6 is obtained by removing the sound insulation part from the sample of Example 6.1.

[0079] FIG. 38 shows a graph of the normal incidence sound absorption rate of each sample (samples of Comparative Example 6 and Examples 6.1 and 6.2) measured in Experiment 4. Looking at FIG. 38, it can be seen that the sample of Example 6.2 having a sound absorption covering material made of a non-woven fabric film has a better sound absorption rate than the sample of Example 6.1 without a sound absorption covering material made of a non-woven fabric film from the lower frequency side. From this, it was found that in order to obtain a better sound absorption rate from the lower frequency side, it is effective to cover the sound insulation part with a sound absorption covering material made of a non-woven fabric film.

Explanation of Reference Signs

[0080] 10 Sound-absorbing material 11 Sound-absorbing material body 11a Sound-absorbing material 11b Sound-absorbing material 11c Sound-absorbing material 12 Sound-insulating part 13 Sound-absorbing covering material 14 Air layer 20 Wall 50 Incident sound wave α 1 Surface (surface where sound-insulating part is arranged) α 2 Surface

Claims

1. On at least one surface of a sound-absorbing material body having air permeability, a plurality of sound insulation parts having non-air permeability and diffracting incident sound waves to the sound-absorbing material body are repeatedly arranged in the longitudinal and transverse directions of the surface with a gap of 5 mm or more between them. The sound-absorbing material body is formed of a porous material having a flow resistance of 10 ７ N·s / m4 or less, The sound insulation part is made of rubber, resin or metal with a flow resistance of 10 ８ N·s / m ４ or more, and The area S of the surface in the sound-absorbing material body １ The total area S of the sound-insulating portions arranged on the surface with respect to ２ The ratio S ２ / S １ is set to be not less than 0.1 and less than 0.99 so that Helmholtz resonance does not occur A sound-absorbing material characterized by the above.

2. The areal density of the sound insulating part is 0.01 kg / m ２ or more. The sound absorbing material according to claim 1

3. The sound-absorbing material according to claim 1 or 2, wherein the sound insulation part is a patch-shaped member attached to the surface of the sound-absorbing material body.

4. The sound-absorbing material according to claim 1 or 2, wherein the sound insulation part is formed of a paint-based material applied to the surface of the sound-absorbing material body.

5. The sound-absorbing material according to claim 1 or 2, wherein the sound insulation part is a molten film part formed on the surface of the sound-absorbing material body.

6. The sound-absorbing material according to any one of claims 1 to 5, wherein the surface of the sound insulation part opposite to the sound-absorbing material body is covered with a sound-absorbing covering material having air permeability.

7. A laminated type sound-absorbing material in which a plurality of sound-absorbing materials according to any one of claims 1 to 6 are laminated in the thickness direction.

8. The laminated type sound-absorbing material according to claim 7, wherein the sound insulation part of the sound-absorbing material forming one layer and the sound insulation part of the sound-absorbing material forming another layer arranged above the one layer are arranged so as not to overlap in the thickness direction.

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