JP2008285857A - Porous sound-absorbing material and sound-absorbing structure using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous sound-absorbing material which is best suited to the manufacturing of a sound-absorbing structure with various sound-absorbing characteristics in accordance with an installation site and a usage environment, and an easy-to-design sound-absorbing structure using the porous sound-absorbing material which can extensively and easily control the sound-absorbing characteristics. <P>SOLUTION: The porous sound-absorbing material is obtained by molding a metallic material composed of metallic fibers and/or metal cutting chips in a prescribed shape. The porous sound-absorbing material has a low-sound-transmission portion with relatively-high bulk density, and one or more high-sound-transmission portions lower in bulk density than that of the low-sound-transmission portion. The sound-absorbing structure comprises a first sound-source facing member which is composed of the porous sound-absorbing material, and a layer forming member or a second sound-source facing member which is arranged at a predetermined interval from the sound-source facing member and forms an air space behind the sound-source facing member. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to noise barriers for railways, noise barriers for roads, walls and partitions of ordinary buildings and concert halls, ceiling surfaces of underground passages, and cowls (or skirts) of vehicles such as trains and monorails, engines for ships, etc. Porous sound-absorbing material used for sound-absorbing structures used for sound-proofing or sound-absorbing in various structures and buildings that require sound-absorbing performance, such as room partition walls, and sound-absorbing treatment parts such as vehicles And a sound absorbing structure using the same.

  For porous sound-absorbing materials used in various structures, buildings, and vehicles, in general, aluminum fibers made of aluminum or aluminum alloys, copper fibers made of copper or copper alloys, iron fibers such as stainless steel, Metal fiber molded bodies formed by molding metal fibers such as nickel fibers into a predetermined shape, and those formed by glass fibers (glass wool), mineral fibers (rock wool), metal sintered materials, metal foam materials, etc. (See, for example, Japanese Patent Publication Nos. 4-5,721, JP-A-5-209,241, and JP-A-11-3,082).

  However, the sound absorption characteristics of these porous sound absorbing materials are almost uniquely determined by the material, bulk density, thickness, and the like. For this reason, it is necessary to efficiently absorb noise in a specific frequency band depending on the installation location and use environment of the porous sound absorbing material, or absorb noise in a relatively wide frequency band in a low frequency band or a high frequency band. If there is a need to change the sound absorption characteristics, such as when it is necessary to absorb noise in a wide frequency band from a low frequency band to a high frequency band, etc., a specific material can be selected. It is necessary to form a porous sound-absorbing material having a specific bulk density and thickness, or to produce a plurality of types of porous sound-absorbing materials and to use them together, and to have a desired sound-absorbing characteristic. In producing quality sound-absorbing materials, we had to rely on experience and trial and error, and required a great deal of labor and cost.

  For example, in Japanese Patent Laid-Open No. 1-296,297, when metal cutting waste is compression-molded in the presence of a resin binder, a material that contributes to sound absorption such as glass wool is sandwiched, and the sound absorption characteristics of the metal cutting waste are set such as glass wool. A sound-absorbing material supplemented with sound-absorbing characteristics is disclosed, and JP-A-4-333,897 discloses laminating a cotton-like fibrous sound-absorbing material layer such as glass wool or rock wool and an aluminum-based porous plate. In addition, a sound absorbing panel is disclosed in which a sound absorption coefficient is increased and excellent sound absorbing characteristics are provided over a wide frequency band. Further, Japanese Patent Laid-Open No. 8-311,823 discloses that a binder is mixed into a metal fiber to obtain an integrated body. A porous sound-absorbing plate that is formed into a porous plate shape and can change the sound-absorbing characteristic by re-pressurization, and can thereby impart the sound-absorbing characteristic according to the place where it is installed Open It is.

  However, the sound absorbing material that supplements the sound absorbing property of metal cutting waste with the sound absorbing property such as glass wool has a problem that the recyclability is poor, and a sufficient sound absorption rate cannot always be obtained, and the cotton-like fibrous sound absorbing material layer The sound absorbing panel in which the aluminum-based porous plate is laminated is insufficient in strength and rigidity as a single panel, and the sound absorbing material can be changed by re-pressurization. There is a problem that it takes extra time to form an air layer behind the sound absorbing material, and there is a limit to the control of the frequency range where the sound absorbing material expresses the sound absorbing characteristics in any case .

  In addition, when performing sound absorption processing and soundproofing processing using such a porous sound absorbing material, the rigidity of the target object to which the porous sound absorbing material is attached is insufficient, and a certain degree of rigidity is required on the porous sound absorbing material side. In such a case, it is necessary to use a stiffener (frame material, rib material, etc.), and sufficient sound absorption characteristics cannot be obtained depending on the shape and dimensions of the stiffener. .

  Furthermore, as a method for coping with various sound absorption characteristics required depending on the installation location and use environment, for example, Japanese Patent Application Laid-Open Nos. 5-71,109 and 2000-276,178 disclose a first porous material layer. , A first air layer, a second porous material layer, a second air layer, and a back layer (sound insulating material and strength member), and the first and second porous material layers are the first porous A large number of small holes are provided in the material layer, or the surface density of the first porous material layer is made smaller than the surface density of the second porous material layer, and the first porous material layer and the air layer are used. Absorbing noise in the low frequency region and absorbing noise in the high frequency region by the second porous material layer and the air layer, thereby obtaining sound absorption performance from the low frequency region to the high frequency region. A sound absorbing structure is disclosed, and Japanese Patent Laid-Open No. 2001-166,780 and Japanese Patent Laid-Open No. 2001-318,679 are also disclosed. In between the pair of left and right porous sound absorbing materials, a corrugated plate or partition (a left and right sound absorbing space formed by a large number of horizontal plates and vertical plates and opening to the left and right porous sound absorbing materials is provided. Double-sided sound absorption structure that obtains sound absorption performance from the low frequency range to the high frequency range by changing the pitch of the corrugated plate and the depth dimension of the left and right sound absorption spaces formed by the partitions. The body is disclosed.

  However, in the former (JP-A-5-71,109 and JP-A-2000-276,178), the sound absorbing structure requires a five-layer structure as a whole. In the double-sided sound absorbing structure of the latter (Japanese Patent Laid-Open No. 2001-166,780 and Japanese Patent Laid-Open No. 2001-318,679), noise from both sides is suppressed while suppressing the overall thickness. However, it is possible to obtain sound absorption performance from the low frequency range to the high frequency range by changing the width and depth dimensions of the sound absorption space formed by the corrugated plate or partition. Therefore, there is a limit to the sound absorption characteristics that can be handled.

Therefore, the present inventors can solve various problems in these conventional sound absorbing structures, such as a sound source facing portion having a large number of sound transmission holes closed with a porous sound absorbing material, and the back of the sound source facing portion. A sound absorbing unit having a number of sound absorbing unit structures when each of the laminated structures formed corresponding to each sound transmission hole is a sound absorbing unit structure. A structure in which the air layer is continuous in a predetermined direction over a large number of sound absorbing unit structures with the same layer thickness and is orthogonal to the direction in which the same layer thickness continues in the same plane. A plurality of different thicknesses are formed, and for the above-mentioned many sound transmission holes, a plurality of types of sound transmission holes having different equivalent circle diameters along the length direction of the continuous air layer. Is further disposed, and the above porous sound absorbing material , The same layer thickness has proposed a strip the formed sound absorbing structure that continuously along the length of the air layer to be continuous (see JP 2004-37,582).
Japanese Patent Publication No. 4-5,721 JP-A-5-209,241 Japanese Patent Laid-Open No. 11-3,082 Japanese Unexamined Patent Publication No. 1-296,297 JP-A-4-333,897 JP-A-8-311,823 Japanese Patent Laid-Open No. 5-71,109 JP 2000-276,178 Japanese Patent Laid-Open No. 2001-166,780 JP 2001-318,679 A JP 2004-37,582 JP

  As a result of earnestly examining the further improvement of the previously proposed sound absorbing structure, the present inventors have surprisingly found that the sound absorbing part has a relatively high bulk density and a low sound transmitting part. By forming multiple types of sound-transmitting parts with different sound-transmitting properties ranging from high-sound transmitting parts with relatively low bulk density to high sound-transmitting properties, a wide range of sound-absorbing characteristics can be selected according to the installation location and usage environment. The present invention has been completed by finding that it can be easily controlled and not only easy to design, but also simplifies the structure of the sound absorbing structure to reduce its manufacturing cost.

  Accordingly, an object of the present invention is to provide a porous sound-absorbing material that is optimal for producing a sound-absorbing structure having various sound-absorbing characteristics in accordance with the installation location and use environment.

  Another object of the present invention is to broadly and easily control the sound absorption characteristics, and to facilitate its design, to efficiently absorb noise in a specific frequency band, etc. Depending on the installation location and usage environment, such as when absorbing noise in a relatively wide frequency band in a high frequency band, and further, absorbing noise in a wide frequency band from a low frequency band to a high frequency band, etc. An object of the present invention is to provide a sound absorbing structure that can easily cope with a change in sound absorption characteristics and can be easily manufactured at low cost.

  That is, the present invention is a porous sound-absorbing material obtained by molding a metal material made of metal fibers and / or metal cutting scraps into a predetermined shape, and a low sound-transmitting part having a relatively high bulk density and The porous sound-absorbing material is characterized in that one or two or more high sound-transmitting parts having a bulk density lower than that of the low sound-transmitting part are formed. According to the present invention, it is possible to select sound absorption characteristics in a plurality of wide frequency ranges, and it is possible to provide an effective porous sound absorbing material.

  The present invention also comprises a porous sound-absorbing material formed by molding a metal material made of metal fibers and / or metal cutting scraps into a predetermined shape, and a low sound transmission part having a relatively high bulk density and the low sound transmission part. A first sound source facing member having one or two or more high sound transmitting portions having a bulk density smaller than that of the sound transmitting portion, a predetermined distance from the sound source facing member, and an air layer behind the sound source facing member. A sound absorbing structure comprising a layer forming member to be formed or a second sound source facing member. According to the present invention, since the porous sound absorbing material can be disposed on the sound source side without using a masking material, it is possible to provide an effective sound absorbing structure capable of exhibiting sound absorbing characteristics over the entire sound source side.

  In the present invention, the low sound transmission part and the high sound transmission part formed in the porous sound absorbing material have one low sound transmission part having a relatively high bulk density and a lower bulk density than the low sound transmission part. It suffices that at least one high sound transmission part exists, and the number of types and the total number thereof due to the difference in the bulk density of the high sound transmission part, the bulk density (sound permeability) of the low sound transmission part and the high sound transmission part, The shape of the porous sound-absorbing material and the planar shape and arrangement of the low sound-transmitting part and the high sound-transmitting part are not particularly limited, and are based on the sound-absorbing characteristics required when designing the sound-absorbing structure. Can be set arbitrarily.

As for the bulk density (sound transmissivity) of the low sound transmission part and the high sound transmission part, for example, when the metal material is an aluminum material, the bulk density (Bd-H) of the low sound transmission part is 1.0 g. / cm ³ or more and 2.0 g / cm ³ or less, and the bulk density (Bd-L) of the high sound transmission part is 0.5 g / cm ³ or more and 1.0 g / cm ³ or less, more preferably. The bulk density ratio (Bd-H / Bd-L) between these low sound transmission parts and high sound transmission parts is preferably in the range of 1.25-4. If the bulk density (Bd-H) of the low sound transmission part is larger than 2.0 g / cm ³ , the sound is not transmitted and reflected, and the sound absorbing effect cannot be exhibited. Also, the bulk density (Bd If -L) is less than 0.5 g / cm ³ , the ventilation resistance is low, and the sound is transmitted without being absorbed, and the sound absorbing effect cannot be exhibited. Also, if the bulk density ratio (Bd-H / Bd-L) is less than 1.25, there will be no difference in the sound absorption performance between the low sound transmission part and the high sound transmission part. When used as a sound absorbing material as it is, it becomes difficult to make the sound absorption characteristics compatible with a wide frequency range, and when used as a sound absorbing structure, the sound transmission performance is required in order to configure the surface side opening of the sound absorbing structure. This difference is too small, making it difficult to design the opening shape. Furthermore, when the bulk density ratio (Bd-H / Bd-L) is larger than 4, there arises a problem that production becomes difficult.

  Furthermore, for the shape of the porous sound absorbing material, depending on the shape of the sound absorbing structure to which the porous sound absorbing material is applied, for example, an appropriate shape such as a rectangular shape, a square shape, a strip shape, a circular shape, an elliptical shape, etc. Can be adopted. Moreover, about the planar shape and arrangement | positioning, etc. of a low sound transmission part and a high sound transmission part, for example, the low sound transmission part with low sound transmission property is made into the sea, and one or two or more high sound transmission parts with high sound transmission property are used. The island is also used as an island, and a large number of high sound transmission parts that are islands are arranged in the low sound transmission part that is the sea. Furthermore, a large number of high sound transmission parts are arranged in the low sound transmission part. The size may be changed, and / or a plurality of types having different bulk densities (sound transmissivity) may be employed. By adopting such means for the shape of the porous sound-absorbing material and the planar shape and arrangement of the low sound-transmitting part and the high sound-transmitting part, each sound-transmitting part and the air layer behind it are configured. Sound absorption characteristics in the Helmholtz resonance structure can be easily designed. In this case, the sound transmission opening is formed by the high sound transmission portion, and the neck portion is constituted by the boundary portion between the low sound transmission portion and the high sound transmission portion.

  Furthermore, for the porous sound absorbing material of the present invention, in addition to the configuration in which the low sound-transmitting portion having low sound permeability is the sea and one or two or more high sound-transmitting portions having high sound permeability are the islands, By setting the shape and bulk density of the low sound-transmitting part to the shape and rigidity necessary for the porous sound-absorbing material to maintain its shape, it is necessary to reinforce and attach it to the peripheral part of the porous sound-absorbing material. There is no need to provide means, and the sound absorbing structure can be manufactured at a low cost.

  The porous sound-absorbing material of the present invention is manufactured by molding a metal material made of metal fibers and / or metal cutting scraps into a predetermined shape. Examples of the metal material include aluminum made of aluminum or an aluminum alloy. -Based materials, copper-based materials composed of copper or copper alloys, iron-based materials such as stainless steel, nickel-based materials composed of nickel or nickel alloys, etc., preferably aluminum-based materials from the viewpoint of weight reduction and corrosion resistance It is.

  Further, in the porous sound-absorbing material of the present invention, when the metal material used as the molding material, particularly when the metal material is metal cutting waste, the metal cutting waste is entangled with each other when formed into a predetermined shape. Part or all of the intersections of the combined metal cutting scraps should be joined by an inorganic adhesive or brazing means, thereby giving good shape maintenance to the molded porous sound absorbing material, Not only can the workability during the production of the sound absorbing structure be improved, but the bulk of the low sound transmission part and the high sound transmission part can be maintained while maintaining the mechanical strength such as tensile strength, bending strength, and compression strength within a practical range. The density can be adjusted, and the production of the porous sound absorbing material becomes easy.

  With respect to the method for producing the porous sound absorbing material of the present invention, any conventionally known method can be used as long as the porous sound absorbing material having the desired low sound transmitting portion and high sound transmitting portion can be manufactured. Well, although not particularly limited, a case where a porous sound-absorbing material having a low sound-transmitting part and a high sound-transmitting part is manufactured using aluminum cutting waste will be described as an example. Various methods can be illustrated.

  First, as a first method, aluminum cutting waste is first compression-molded to form a low bulk density molded plate having a relatively low bulk density that is the same as the bulk density of the high sound transmission part. A part of the density molded plate is subjected to second-stage compression molding to form a target low sound transmission part having a relatively high bulk density, and thereby a low sound transmission part having a relatively high bulk density and the low sound transmission part. This is a method for producing a porous sound-absorbing material having a high sound-transmitting part having a bulk density smaller than that of the sound part. In this case, a two-step molding process is required.

  The second method includes a part for forming a low sound transmission part having a relatively high bulk density and a part for forming a high sound transmission part having a bulk density lower than that of the low sound transmission part. A mold capable of simultaneously molding the low sound transmission part and the high sound transmission part is prepared, and the low sound transmission part having a relatively high bulk density by compression molding in one step and the bulk density higher than the low sound transmission part. This is a method for producing a porous sound-absorbing material having a small high sound-transmitting part, and in this case, it can be processed by a single molding step.

  More preferably, in the first and second methods described above, after the aluminum cutting waste is compression molded to produce a molded product having a predetermined low sound transmission part and high sound transmission part, In contrast, the adhesive is impregnated, and a part or all of the intersections of the tangled aluminum cutting scraps are joined, or the aluminum cutting brazing material made of aluminum or aluminum alloy as the aluminum cutting scraps After using the aluminum clad cutting scrap obtained by cutting the aluminum clad material clad with the clad, compression molding the micladding cutting scrap to produce a molded product having a predetermined low sound transmission portion and high sound transmission portion. Apply some flux, and use a brazing furnace or join some or all of the intersections of aluminum swarf that are entangled with each other in an inert gas (usually nitrogen gas) atmosphere Good it is.

  In addition, regarding a sound absorbing structure manufactured using the porous sound absorbing material of the present invention, when it is used as a sound absorbing structure using a Helmholtz resonance structure, for example, the sound absorbing structure is used for one sound absorbing chamber. A porous sound-absorbing material with a low-bulk-density high sound-transmitting part is attached at a position corresponding to the central part, and this sound-transmitting part is used as an opening (neck part) of the Helmholtz resonance structure to form a sound-absorbing structure Alternatively, a plurality of low-bulk-density porous sound-absorbing materials are attached to one sound-absorbing chamber, and the plurality of highly-sound-transmitting portions are opened in the Helmholtz resonance structure (neck portion). ) As a sound absorbing structure.

  In this case, the sound absorbing structure can be formed by simply disposing the porous sound absorbing material on the sound source side without using a masking material that has been conventionally used. The sound-absorbing structure formed in this way is a first sound source facing portion having a low sound-transmitting part having a relatively high bulk density and one or more high sound-transmitting parts having a bulk density lower than that of the low sound-transmitting part. The sound absorbing structure includes a member and a layer forming member or a second sound source facing member that is disposed at a predetermined interval from the sound source facing member and forms an air layer behind the sound source facing member. In the case of such a sound absorbing structure, by appropriately selecting the number of bulk sounding parts having a high bulk density and a low sounding part having a low bulk density, and the bulk density, sound absorption characteristics can be selected according to the installation location and the use environment. In addition to being easy to design, the structure of the sound absorbing structure can be simplified to reduce the manufacturing cost.

  In the sound absorbing structure of the present invention, preferably, the first and second sound source facing members are constituted by a plurality of band sound absorbing materials formed in a band shape with a porous sound absorbing material, and each band shaped sound absorbing material has a low sound transmission property. And one or two or more highly sound permeable parts, and the sound absorption characteristics can be adjusted over a wide range of sound, and a conventional perforated plate can also be used for sound waves incident on the low sound permeable parts. Unlike the above, sound absorption is performed while transmitting sound waves to some extent, so that the sound absorption efficiency is improved.

  In the sound-absorbing structure of the present invention, preferably, for the first and second sound source facing members, the low sound-transmitting portion with low sound transmission becomes the sea, and one or more high sound transmission with high sound transmission is provided. It is preferable to provide a structure in which the part becomes an island, and thereby the volume density of the low sound transmission part is set to a height necessary for the sound source facing member to maintain its shape by itself. The necessary shape and rigidity can be given to itself, and it can be manufactured inexpensively by reducing the number of parts that make up the sound absorbing structure, and sound absorption efficiency by transmitting sound waves in low sound transmission parts with low sound transmission Has the advantage of improving. A part of the energy of the sound wave that has not been absorbed in the sound absorbing chamber is transmitted again toward the sound source through the low sound transmission part and the high sound transmission part, but directly on the surface of the conventional perforated plate. It goes without saying that the amount of energy absorbed by reciprocating through the low sound transmission part and the high sound transmission part is larger than the energy reflected and propagated to the sound source side.

  In addition, a plurality of high sound transmission portions arranged as islands in the low sound transmission portion that becomes the sea are composed of a plurality of types of high sound transmission portions having different sound transmission characteristics, and each of these high sound transmission portions and the back thereof. By configuring the sound absorption unit structure constituted by the air layer to exhibit a plurality of different sound absorption characteristics, the sound absorption characteristics can be controlled more widely and more easily. Further, with respect to the first and second sound source facing members, by providing the low sound transmission part with the shape and rigidity necessary for maintaining the shape of the sound source facing member, a perforated plate and a perforated plate as in the past are provided. Since it is not necessary to dispose the sound-absorbing material redundantly, there is an advantage that the structure of the sound-absorbing structure can be simplified to reduce the manufacturing cost, and the design becomes easier.

  When the Helmholtz resonance structure is configured using the porous sound-absorbing material of the present invention, from the sound transmission characteristics of the low sound-transmitting portion and the high sound-transmitting portion, the high sound-transmitting portion is conceptually the neck portion and the low sound-transmitting property. The sound part is a neck forming part that forms this neck part. Since the neck part and the neck forming part are made of porous materials having different bulk densities, the neck part has no ventilation resistance. However, the porous sound-absorbing material of the present invention is formed of a highly sound-permeable portion having ventilation resistance, and the surrounding low-noise portion is also formed of a material having high ventilation resistance but allowing ventilation. In the Helmholtz resonance structure (sound-absorbing unit structure) formed in (1), the actually measured maximum sound absorption frequency does not match the expected value obtained from the Helmholtz calculation formula. Needless to say, it can be designed.

  The porous sound-absorbing material of the present invention is an optimal material for producing a sound-absorbing structure having various sound-absorbing characteristics in accordance with the installation location and use environment. In addition, the sound absorbing structure of the present invention manufactured using this not only improves the sound absorbing performance, but also allows the sound absorbing characteristics to be controlled extensively and easily, and its design is easy. Efficiently absorbs noise in the frequency band, absorbs noise in a relatively wide frequency band in the low frequency band or high frequency band, and further wide frequency band from low frequency band to high frequency band When it is necessary to change the sound absorption characteristics depending on the installation location and the use environment, such as when it is necessary to absorb the noise, it can be easily manufactured at a low cost.

  Hereinafter, preferred embodiments of the porous sound-absorbing material and the sound-absorbing structure of the present invention will be specifically described based on test examples and examples.

[Test Examples 1 to 4]
As shown in FIGS. 1D and 1E, a cylindrical press die 1 having an inner diameter of 87 mm and a recess 2 having a diameter of 25 mm × depth of 2.5 mm in the center of the inner surface of the bottom and a compressive load up to 500 kN are applied. A 500 kN universal testing machine equipped with an upper die 3 to be applied is used. In this press die 1, a width of 0.4 mm or more and 2.0 mm of a cross section produced by cutting an appropriate aluminum waste material with a milling machine or a shaper. Hereinafter, a predetermined amount (mass: about 20 g) of aluminum cutting waste 4 having a cross-sectional thickness of 0.1 mm to 0.6 mm, a length of 5 mm to 100 mm, an average of about 30 mm, and a curl height of 2.0 mm to 8.0 mm. ) And compression molding within a compression load range of 200 to 500 kN, a low sound-transmitting portion having a relatively high bulk density is formed in the periphery of the recess 2 in one molding step, and the recess 2 A high sound-transmitting part is formed with a relatively low bulk density in the central part corresponding to Four types of pressure-molded materials thus prepared were prepared. Table 1 shows the loading pressure (low sound transmission part loading pressure: kN / cm ² ) and thickness (low sound transmission part thickness: mm) at the periphery of the recess 2 at this time.

  In the above test example, the pressure-molded material was produced by a single molding process. For example, as shown in FIGS. 1 (a), (b) and (c), a cylindrical press die 1 having an inner diameter of 87 mm and Using a 500 kN universal testing machine equipped with an upper mold 3 for applying a compressive load of up to 500 kN, a predetermined amount of aluminum cutting waste 4 formed from appropriately scraped aluminum material in the same manner as described above (in the press mold 1 ( Target: 20 mass g) is filled, and first, press molding is performed by applying a first-stage pressing force so as to obtain a bulk density corresponding to a portion having a low bulk density, and then the upper die 3 is placed on the lower surface. The upper die 3a having a concave portion 2a having a diameter of 25 mm and a depth of 2.5 mm or more is exchanged at the center, and only the peripheral portion is pressurized by applying a second stage pressing force with the upper die 3a. In this way, a low sound transmission part having a relatively high bulk density is formed in the peripheral part by a two-stage molding process. You may produce the press-molding material in which the high sound-transmitting part with a comparatively small bulk density was formed in the center part.

  Next, an inorganic adhesive solution obtained by mixing an inorganic adhesive (trade name: Porcelain manufactured by Tope Co., Ltd.) and a diluent (isopropyl alcohol) at a ratio of 1: 2 is prepared and obtained first. Each pressure molding material (4 types) obtained was immersed in this inorganic adhesive solution, then placed in a baking oven, heated at 180 ° C. for 25 minutes and dried, as shown in FIG. A disk-shaped sound-absorbing material for testing (porous sound-absorbing material) having a high sound-transmitting portion 8 having a relatively low bulk density corresponding to the concave portion 2 and having a low sound-transmitting portion 7 having a relatively high bulk density in its peripheral portion. No. 1 to No. 4 were prepared as test sound-absorbing materials. For each of No.1 to No.4 test sound-absorbing materials, the bulk density (BD-H) of the low sound transmission part and the bulk density (BD-L) of the high sound transmission part were measured, and these low sound transmission parts The bulk density ratio (BD-H / BD-L) between the bulk density (BD-H) and the high sound transmission part bulk density (BD-L) was determined. The results are shown in Table 1.

[Test Example 5]
Moreover, as shown in FIGS. 1 (a) and 1 (b), a 500 kN universal testing machine equipped with a cylindrical press die 1 having an inner diameter of 87 mm without a recess and an upper die 3 for applying a compressive load up to 500 kN is used. The press die 1 is filled with a predetermined amount (target: 20 mass g) of aluminum cutting waste 4 formed from appropriately scraped aluminum material in the same manner as described above, and compressed under the condition of a loading pressure of 1.66 kN / cm ^2. Molded to produce a pressure-molded material having a thickness of 3.66 mm and a bulk density of 0.94 g / cm ³ in a single molding step. Next, a flat donut-shaped aluminum foil having an outer diameter of 87.5 mmφ, an inner diameter of 25 mmφ and a thickness of 0.5 mm was attached to one side of the pressure-molded material, and the test No. 5 was performed. A sound absorbing material was prepared.

Using the sound absorbing material for each test No. 1 to No. 5 (porous sound absorbing material) thus obtained, the thickness of the low sound transmission part (t) 2.01 to 3.66 mm, the high sound transmission part A Helmholtz resonance structure (sound absorption unit structure) with a diameter (d) of 25 mm and a back air layer thickness (L) of 30 mm is used, and a normal incident sound absorption coefficient measuring device (manufactured by Kobe Steel, Ltd.) is used. In accordance with the above, the normal incident sound absorption coefficient was measured and the sound absorption frequency characteristic was confirmed.
The results are shown in Table 1 and FIG.

[Example 1]
FIGS. 4 (a), 4 (b) and 5 show a single-sided sound absorbing structure according to Example 1 of the present invention formed using the porous sound absorbing material of the present invention.

  As shown in FIG. 5, the single-sided sound absorbing structure of Example 1 is composed of four porous sound absorbing materials 9a (see FIG. 4 (a)) and four porous sound absorbing materials. A sound source facing member 9 composed of a band-shaped sound absorbing material 9b made of a sound absorbing material (see FIG. 4 (b)) and the band-shaped sound absorbing materials 9a, 9b of the sound source facing member 9 are attached to The layer forming member 10a for forming the air layers 11a, 11b having a predetermined thickness and the plate thickness 1 for fixing the end portions of the respective band-shaped sound absorbing materials 9a, 9b to the layer forming member 10a together with the layer forming member 10a This is composed of a 6 mm aluminum-made pressed edge material 10d. The overall size of the sound absorbing structure is 800 mm wide × 1500 mm long × 45 mm thick.

  In this Example 1, each band-like sound absorbing material 9a is obtained by a method similar to the manufacturing method of the test sound absorbing material (porous sound absorbing material) by the above-described two-stage molding process, and similarly to the above, an appropriate aluminum material is used. It was formed using aluminum cutting waste formed from waste material. That is, in FIGS. 1 (a), (b) and (c), instead of the cylindrical press die 1, a square press die (not shown) with an inner dimension of 394 mm × 98.4 mm is used, and a concave portion is used. First, low-bulk density molding is performed with the upper mold without any of the above, and the second mold is then compressed with the upper mold having recesses for forming low-density portions on another lower surface. A pressure molding material in which a low sound transmission part having a relatively high bulk density is formed in the peripheral part and a high sound transmission part having a relatively low bulk density is formed in the central part by a two-stage molding process. Produced.

  Next, in the same manner as in Test Examples 1 to 4, the obtained pressure-molded material was immersed in an inorganic adhesive solution, then placed in a baking furnace and heated at 180 ° C. for 25 minutes to dry, The porous sound-absorbing material shown in FIG. 4 (a) was formed. This band-shaped sound absorbing material 9a has a size of width 98.4 mm × length 394 mm × thickness 2.4 mm, and has a low sound-transmitting portion 7 a having a relatively high bulk density and low sound-transmitting property as the sea. A total of eight circular high sound transmission portions 8a having a relatively low bulk density and a high sound transmission property are formed as islands at a central portion in the width direction with a distance of 50 mm between the centers. The sound portion 7a has a thickness of 2.4 mm, and the high sound transmission portion 8a has a diameter of 25 mmφ and a thickness of 3.66 mm.

  Each band-shaped sound absorbing material 9b is formed in the same manner as each band-shaped sound absorbing material 9a, has a width of 98.4 mm, a length of 394 mm, and a thickness of 2.1 mm, and has a relatively high bulk density. The low sound-transmitting part 7b with low sound transmission is the sea, and the central part in the width direction is 100mm away from each other. 8b is formed as an island, and the low sound transmission portion 7b has a thickness of 2.1 mm, and the high sound transmission portion 8b has a diameter of 25 mmφ and a thickness of 3.66 mm.

  As shown in FIG. 5, the layer forming member 10a is entirely formed of an aluminum material having a plate thickness of 1.6 mm, and is a flat plate having a width of 30 mm and 100 mm from each other. A horizontal portion 12 that is positioned in parallel with a gap (gap) therebetween, and a vertical portion that is formed along the longitudinal direction on the back side of the central portion in the width direction of each horizontal portion 12 and projects toward the back direction of each horizontal portion 12 Back surface portion 14a, which is constructed to be opposed to a gap formed between the horizontal portion 12 adjacent to each other on the protruding end side of the portion 13 and the vertical portion 13 adjacent to each other. 14b.

  Each of the band-shaped sound absorbing materials 9a and 9b is fixed by fixing the pressing edge material 10d to the horizontal portion 12 with screws or the like. The band-shaped sound absorbing material 9a is opposed to one of the back portions 14a to form an air layer 11a having a thickness of 30 mm, and the band-shaped sound absorbing material 9b is opposed to the other back portion 14b. In between, an air layer 11b having a thickness of 40 mm is formed. Accordingly, the combination (A) of the high sound transmission portion 8a and the air layer 11a and the high sound transmission portion 8b and the air layer corresponding to the high sound transmission portions 8a and 8b formed in the respective band-shaped sound absorbing materials 9a and 9b. Two types of sound-absorbing unit structures (Helmholtz resonance structures) A and B consisting of the combination (B) with 11b are configured.

Here, the values of each parameter in the sound absorbing structure having the two types of sound absorbing unit structures (Helmholtz resonance structures) A and B configured in Example 1 are as shown in Table 2 below.
About these, when the maximum sound absorption frequency and the average sound absorption coefficient are predicted for each of the sound absorbing structures of AB constituting the sound absorbing structure of Example 1 from the experimental values such as the measured values of the sound absorption coefficient of the normal incident sound described above, Table 2 and FIG. As shown. Further, when the average sound absorption coefficient of the sound absorbing structure having two types of sound absorbing unit structures A and B was estimated, it was 0.86.

In addition, the single-sided sound absorbing structure obtained in Example 1 is based on JIS A1409, using an internal volume of 251 m ³ , a surface area of 237 m ² and a reverberation box of 8 seconds or longer at a reverberation time of 63 Hz to 1 kHz Reverberation chamber method sound absorption was measured. The results are shown in FIG.

  As is clear from the results shown in FIG. 7, the single-sided sound absorbing structure of Example 1 has an average sound absorption coefficient of 0.85 at 500 to 2000 Hz, and the above two types of sound absorbing unit structures (Helmholtz resonance structure). ) And the predicted value 0.86 of the average sound absorption rate obtained by calculation from (1) well.

[Example 2]
8 and 9A, 9B, and 9C show a double-sided sound absorbing structure according to Embodiment 2 of the present invention. This double-sided sound absorbing structure is formed of the first sound source facing member 9A, which is formed of the porous sound absorbing material of the present invention and includes two kinds of band-shaped sound absorbing materials 9c and 9d, and the porous sound absorbing material of the present invention. The second sound source facing member 9B provided with four sets of a total of four sets of two kinds of band-shaped sound absorbing materials 9e, 9f arranged opposite to the band-shaped sound absorbing materials 9c, 9d forming the above set. And between the first and second sound source facing members 9A and 9B, and behind the respective band-shaped sound absorbing materials 9c and 9d constituting the first sound source facing member 9A and the second sound source facing members. A layer forming member 10a for forming air layers 11c, 11d, 11e, 11f having a predetermined layer thickness behind the respective band-shaped sound-absorbing materials 9e, 9f constituting 9B, and the first layer formed on each layer forming member 10a. A layer forming member 10b for fixing the respective band-shaped sound absorbing materials 9c, 9d constituting the sound source facing member 9A, and the second sound source facing member 9B disposed on the layer forming member 10a It is composed of a layer forming member 10c for fixing the band-shaped sound absorbing materials 9e, 9f together, and the band-shaped sound absorbing materials 9c, 9d and the second sound source facing member 9B constituting the first sound source facing member 9A. Each of the constituting band-shaped sound absorbing materials 9e and 9f has a sound absorbing unit structure that expresses different sound absorbing characteristics, and the low sound transmitting portion 7 and the high sound transmitting portion 8 are formed with a predetermined bulk density, respectively. ing.

  In Example 2, the layer forming member 10a is entirely formed of an aluminum alloy extruded shape as shown in FIGS. 8 and 9 (a), and is flat. Three horizontal portions 12a positioned parallel to each other with a gap (gap) between them, three horizontal portions 12b arranged opposite to each horizontal portion 12a, and the horizontal portions 12a opposite to each other There are a vertical portion 13 that connects the horizontal portion 12b with a predetermined interval, and two back portions 14 that are horizontally installed between the adjacent vertical portions 13 and that are positioned in steps. is doing.

  Further, as shown in FIGS. 8 and 9 (b), the layer forming member 10b is entirely formed by cutting out an aluminum extruded shape, or the horizontal pressing portion 16 is formed as an extruded shape. It is formed by fixing the erection part 15 so as to straddle the horizontal pressing part 16, and is arranged in the same positional relationship as each horizontal part 12a of the layer forming member 10a. As shown in FIGS. 8 and 9 (c), the layer forming member 10c has a horizontal holding portion 16 connected to each other. Formed or formed by fixing the erection part 15 so that the horizontal pressing part 18 is formed by an extruded profile and straddles the horizontal pressing part 18, and each horizontal part of the layer forming member 10a is formed. Arranged in the same positional relationship as 12a and connected to each other at the erection part 17. And a flat pressing portion 18. The layer forming member 10c is provided with positioning ribs 19 for positioning the layer forming member 10a fixed to the layer forming member 10c.

  Then, the layer forming member 10b is fixed to the layer forming member 10a by appropriate means so that the band-like sound absorbing materials 9c, 9d are sandwiched and fixed between the two layer forming members 10a and 10b, and the layer forming member 10c is also appropriately provided. By fixing to the layer forming member 10a, the band-like sound absorbing materials 9e and 9f are sandwiched and fixed between the two layer forming members 10a and 10c.

  Therefore, according to the double-sided sound absorbing structure of Example 2, the first sound source facing member 9A including the two types of band-shaped sound absorbing materials 9c and 9d and the two types of band-shaped sound absorbing materials 9e and 9f are provided. The second sound source facing member 9B and the layer forming member 10a disposed between the first and second sound source facing members 9A and 9B to form the air layers 11c, 11d, 11e, and 11f Therefore, it is possible to construct a sound absorbing unit structure that exhibits a sound absorbing characteristic, and to easily design the sound absorbing unit structure, and to easily cope with the case where the sound absorbing characteristic needs to be changed depending on the installation location and the use environment.

FIG. 1 is an explanatory diagram for explaining a method for producing a porous sound-absorbing material of the present invention.

FIG. 2 is a perspective explanatory view showing the porous sound-absorbing material (pressure-molded material) before the bonding process manufactured according to FIG.

FIG. 3 is a graph showing the measurement results of the normal incidence sound absorption coefficient measured for the test sound absorbing materials obtained in Test Examples 1 to 4 and Test Example 5 of the present invention.

FIG. 4 is a perspective explanatory view showing two types of porous sound absorbing materials ((a) and (b)) made of a porous sound absorbing material used as a sound source facing member in Example 1 of the present invention.

FIG. 5 is a partial perspective explanatory view showing a single-sided sound absorbing structure formed using the sound source facing member of FIG.

FIG. 6 is a graph showing the measurement results of the normal incident sound absorption coefficient measured for the two types of porous sound absorbing material strips ((a) and (b)) used as the sound source facing member of FIG. is there.

FIG. 7 is a graph showing the measurement results of the reverberation chamber method sound absorption coefficient measured for the single-sided sound absorbing structure of FIG.

FIG. 8 is a partial perspective explanatory view showing a double-sided sound absorbing structure according to Embodiment 2 of the present invention.

FIG. 9 is a perspective explanatory view showing layer forming members ((a), (b) and (c)) used in the double-sided sound absorbing structure of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Press die, 2 ... Recessed part, 3 ... Piston, 4 ... Aluminum cutting waste, 6 ... Test sound-absorbing material (porous sound-absorbing material), 7 ... Low sound-transmitting part, 8 ... High sound-transmitting part, 9 ... Sound source Opposing member, 9A ... first sound source facing member, 9B ... second sound source facing member, 9a, 9b, 9c, 9d, 9e, 9f ... strip-shaped sound absorbing material, 10, 10a, 10b, 10c ... layer forming member, 10d ... Pushing edge material, 11a, 11b, 11c, 11d, 11e, 11f ... Air layer, 12,12a, 12b ... Horizontal part, 13 ... Vertical part, 14,14a, 14b ... Back part, 15,17 ... Installation part, 16, 18 ... Horizontal presser part, 19 ... Positioning rib.

Claims (14)

  A porous sound-absorbing material obtained by molding a metal material composed of metal fibers and / or metal cutting scraps into a predetermined shape, and a low sound-transmitting part having a relatively high bulk density and a volume higher than that of the low sound-transmitting part. A porous sound-absorbing material, wherein one or two or more highly sound-transmitting portions having a low density are formed.   The porous sound-absorbing material according to claim 1, wherein the metal material is an aluminum-based material made of aluminum or an aluminum alloy.   The porous sound-absorbing material according to claim 2, wherein the aluminum-based material is aluminum cutting waste.   4. A part or all of the intersections of the metal cutting scraps entangled with each other when the metal cutting scraps are formed into a predetermined shape are joined by an inorganic adhesive or brazing means. Porous sound absorbing material. The bulk density (Bd-H) of the low sound transmission part is in the range of 1.0 to 2.0 g / cm ³ , and the bulk density (Bd-L) of the high sound transmission part is 0.5 to 1.0 g. / cm ³ in the range of, claims 1 to 4 bulk density ratio of these TeiToru sound part and high clef Metropolitan (Bd-H / Bd-L ) is within the range of 1.25 to 4 The porous sound-absorbing material according to any one of the above.   It consists of a porous sound-absorbing material formed by molding a metal material consisting of metal fibers and / or metal cutting scraps into a predetermined shape, and has a relatively low bulk sound density and a bulk density higher than this low sound permeability section. A first sound source facing member having one or two or more high sound-transmitting portions with a small size, and a layer forming member disposed at a predetermined interval from the sound source facing member and forming an air layer behind the sound source facing member, or A sound absorbing structure comprising a second sound source facing member.   The first and second sound source facing members are composed of a plurality of band-shaped constituent members formed in a band shape with a porous sound-absorbing material. Each band-shaped component member includes a low sound-transmitting portion and one or more high-permeability members. The sound absorbing structure according to claim 6, wherein a sound part is formed.   The first and second sound source facing members have a structure in which a low sound-transmitting portion with low sound transmission is the sea and one or two or more high sound-transmitting portions with high sound transmission are the islands. The sound absorbing structure described in 1.   A plurality of high sound transmission portions arranged as islands in a low sound transmission portion that becomes the sea are composed of a plurality of types of high sound transmission portions having different sound transmission characteristics. The sound-absorbing structure according to claim 8, wherein the sound-absorbing unit structure composed of the air layer exhibits a plurality of different sound-absorbing characteristics.   The sound absorbing structure according to any one of claims 6 to 9, wherein the first and second sound source facing members have a shape and rigidity necessary for the low sound transmission portion to maintain the shape of the sound source facing member.   The sound absorbing structure according to any one of claims 6 to 10, wherein the metal material is an aluminum-based material made of aluminum or an aluminum alloy.   The sound absorbing structure according to claim 11, wherein the aluminum-based material is aluminum cutting waste.   The part or all of the intersection of the metal cutting waste which became entangled mutually when shape | molding the metal cutting waste in the predetermined | prescribed shape is joined by the inorganic adhesive or the means of brazing. Sound absorption structure. The bulk density (Bd-H) of the low sound transmission part is in the range of 1.0 to 2.0 g / cm ³ , and the bulk density (Bd-L) of the high sound transmission part is 0.5 to 1.0 g. The volume density ratio (Bd-H / Bd-L) between the low sound transmission part and the high sound transmission part is in the range of 1.25 to 4 within the range of / cm ^3. The sound absorbing structure according to any one of the above.

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