JP2006153926A - Compound sound absorbing structure body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for improving a sound absorbing coefficient in a sound range of 500Hz to 1kHz without increasing thickness and air layer of a porous material, and to provide a compound sound absorbing structure body for practical use. <P>SOLUTION: The compound sound absorbing structure body is obtained by holding a film-like or a thin plate-like material C between a mesh structure body A transmitting acoustic waves and a mesh structure body B to obtain a double layer structure body by partly fixing D them to each other, and further, closely compounding the mesh structure body B of a compound structure body and the porous sound absorbing material E. Thus, it the compound sound absorbing structure body which can be increased in a sound absorbing coefficient in a not only middle and high sound range but also low sound range without increasing the thickness of the sound absorbing structure body can be obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sound absorption technique used for noise reduction and sound field adjustment.

  Examples of the porous material include inorganic fiber materials such as glass wool and rock wool, polymer fiber materials such as polyester, and resin foam materials such as foamed soft urethane. These porous materials are excellent sound absorbing materials as sound absorbing materials for middle and high sounds, but in order to increase the sound absorption coefficient in the low sound region in addition to the medium and high sound regions, the porous material is made thicker or the air layer. You have to take. However, when the composite sound absorbing structure cannot be made thick due to the space of the construction site, the sound absorption coefficient is often insufficient in the middle sound range. That is, there are many cases where the application is difficult in terms of sound absorption characteristics, structural design, weight, and cost due to various circumstances.

  The frequency band that is often a problem with noise is 500 to 2 KHz. For example, the sound absorption characteristic (normal incidence method) of a polyester fiber system (density 35 kg / m3) is 20% at 500 Hz and 40% at 1 KHz at a thickness of 35 mm. There is only about the sound absorption coefficient. In order to improve this, non-woven fabric is usually applied to the surface also for surface protection, but this also improves to about 70% at 1 KHz, but only to about 40% at 500 Hz. Is known.

  Furthermore, in order to improve the sound absorbing performance, as described above, it is conventional to increase the thickness of the polyester fiber, which is a porous material, or to provide an air layer behind the sound absorbing material. When the thickness of the sound absorbing structure is 50 mm or more and the space is limited, there is a situation in which it cannot be applied. This also causes the same situation for other porous materials such as glass wool and flexible urethane foam.

  The object is to provide a method for improving the sound absorption coefficient in the sound range of 500 to 1 KHz without increasing the thickness of the porous material or the air layer, and to provide a specific composite sound absorbing structure.

  The gist of the present invention is that a film-like or thin plate-like material C is sandwiched between a mesh structure A and a mesh structure B that transmit sound waves, and these are partially fixed to each other to obtain a multilayer structure. Furthermore, the present invention relates to a composite sound absorbing structure in which the network structure B of the composite structure and the porous sound absorbing material E are closely combined.

  The present invention has the above-described configuration, and is a composite that can increase the sound absorption coefficient in the low sound range without increasing the thickness of the sound absorbing structure, as well as the conventional middle and high sound ranges. A sound absorbing structure can be provided.

  Patent Document 1 is known as a composite sound absorbing structure. However, in this technology, a translucent sound absorbing material and a translucent sound insulating material are arranged in a frame member with a space therebetween, and the translucent sound absorbing material is disposed on the sound source side, and the translucent light transmitting material is separated from the space. The sound-insulating material and its surroundings are fixed by a frame material, and an internal sound-absorbing material is arranged inside the translucent soundproofing plate. Therefore, since translucency is assumed, the mesh is as large as possible (3 to 50 mm), and the film can move as freely as possible between the mesh structures. In other words, when excited by sound pressure, the membrane vibrates, a part of which comes into contact with a part of the network structure, is converted into thermal energy at that part, and produces sound absorption.

JP 2002-317408 A

  In the present invention, a network structure A, a film or thin plate material C, and a network structure B are laminated, and these are partially fixed to each other to obtain a composite structure, and a porous sound absorbing material E is adhered thereto. This is a composite sound-absorbing structure that has been combined, and the structural loss is increased by integrally combining the porous material.

  That is, when the entire structure is excited by the acoustic incident energy, bending vibrations cause thermal energy conversion by friction between each layer, partial resonance of the film or thin plate, fiber of porous material (glass wool, polyester fiber) Etc.) or thermal energy conversion by vibration of membranes (soft urethane foam etc.), without increasing the thickness of the porous material or providing an air layer, that is, without changing the thickness of the composite structure. The sound absorption performance in the range can be greatly improved.

  In particular, the difference from the above-mentioned Patent Document 1 is that a film or a thin plate is sandwiched by a network structure, and they are brought into close contact with each other as much as possible to vibrate together to increase the friction between the layers. As described above, the movement of a multi-mass point system is performed, the conversion efficiency of heat energy is increased, and high sound absorption characteristics are obtained in a wide band, and the basic technical idea is different.

  In the case where the composite sound absorbing structure of the present invention is configured by combining urethane foam having only a relatively rigid skeleton, polymer nonwoven fabric, solidified metal fibers, etc., the film itself The network structure contacting the latter of the multilayer structure can be removed so that the contacting surface and the film surface are sufficiently rubbed.

  Examples of metal materials in the mesh structures A and B include aluminum, iron, stainless steel, examples of polymer materials include various resins, and examples of wood materials include paper. The size of the openings of the structures A and B is preferably 0.5 to 5 mm.

  As the film-like or thin plate-like material C, a metal material, a polymer material, or a wood material in the mesh structures A and B can be applied. The thickness is preferably about 10 to 100 μm.

  Specific examples of laminating the network structure A, the film or thin plate material C, and the network structure B and partially fixing these to each other include stapler, rivet, welding, sewing, and the like. The fixed number is usually about 1 to 10 in 10 cm × 10 cm.

  Examples of the porous material E include glass wool, rock wool, polyester fiber, and flexible urethane foam. The material is relatively flexible, such as a relatively flexible material, a non-woven fabric, or a solidified metal fiber. It consists of something with. These porous materials exhibit sound absorbing performance by converting the incident acoustic energy into thermal energy when the incident energy of sound enters the material and vibrates or air enters and exits the material. Is. The density is preferably 20 to 100 kg / m 3.

  Hereinafter, the present invention will be described in more detail with reference to examples. For measuring the sound absorption coefficient, a 2-microphone method normal incidence sound absorption coefficient measuring apparatus using an acoustic tube was used.

(Comparative Example 1)
This is an example of a sound-absorbing structure made only of a porous material in which polyester fibers (density 35 kg / m 3, thickness 35 mm) are used alone. In this example, incident energy of sound enters the material, vibrates the fiber, and air enters and exits the material to convert incident acoustic energy into thermal energy, thereby exhibiting sound absorbing performance.

Example 1
As shown in FIG. 1, the composite sound absorbing structure of the present invention has an aluminum mesh structure (mesh 16) A + aluminum foil (thickness: 3 μ) C + aluminum mesh structure (mesh 16) B fixed with rivets D (5 A composite sound-absorbing structure is obtained by adhering a D / 100 mmφ) D to a polyester fiber sound absorber (density: 35 kg / m 3, thickness: 35 mm) E.

  In this example, the structural loss is increased by combining the network structure, membrane material, network structure, and porous material together, and the entire structure is excited by the incident acoustic energy, resulting in bending vibration. Therefore, the sound absorption performance in the mid-low range is improved by heat energy conversion by friction between layers, partial resonance of the film, and heat energy conversion by vibration of the fiber or film of the porous material.

  FIG. 2 shows the result of measuring the sound absorption coefficient of each test sample with the above-mentioned normal incidence method sound absorption coefficient measuring apparatus. As a result, according to the present invention, it was possible to demonstrate excellent sound absorption performance in the mid-low range that could not be realized only with porous materials, the sound absorption characteristics were greatly improved, and its effectiveness was proved. It is a thing.

  As described above, the composite sound-absorbing structure constituted by the present invention has an appropriate material type, mesh, etc. with respect to restrictions on usage such as sound absorption coefficient and allowable space required for each material constituting the structure. By selecting the size of the mesh (approximately 10 mesh or less), the thickness of the membrane or thin plate material (approximately 0.1 mm or less), the density and thickness of the porous material, etc., the sound absorption characteristics in the required frequency band It is possible to realize a composite sound absorbing structure suitable for the above.

  The composite sound-absorbing structure of the present invention includes a sound-absorbing structure part used in a sound insulation wall or tunnel in the railway / road field, a sound-absorbing structure part used for noise reduction in the building field, an engine area and a vehicle compartment for automobiles, construction machines, agricultural machines, etc. Widely applicable, such as sound absorbing structure part for reducing noise in cabin, sound absorbing structure part for reducing noise of household appliances and AV equipment, sound absorbing structure part for adjusting sound field characteristics of music room, hall, audio room, etc. It can be done.

FIG. 1 is a view showing a composite sound absorbing structure. FIG. 2 is a diagram showing the normal incidence sound absorption coefficient.

Explanation of symbols

A, B ... Aluminum mesh structure,
C. Aluminum foil,
D: Rivet fixing part,
E: Polyester fiber sound absorber.

Claims (5)

  A film-like or thin plate-like material C is sandwiched between a mesh structure A and a mesh structure B that transmit sound waves, and these are partially fixed D to each other to obtain a multilayer structure. A composite sound-absorbing structure characterized in that the network structure B of the body and the porous sound-absorbing material E are combined in close contact.   The composite sound absorbing structure according to claim 1, wherein a perforated plate or a louver is provided on a back surface of the composite structure.   2. The composite sound absorbing structure according to claim 1, wherein the mesh structures A and B are a metal material or a polymer material.   The composite sound absorbing structure according to claim 1, wherein the film-like or thin plate-like material is a metal material, a polymer material, or a wood material. The composite sound absorbing structure according to claim 1, wherein the mesh structure A, film-like or thin plate material, and mesh structure B are partially fixed D to each other by staples, rivets, welding, sewing, or the like.

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