JP2008008997A - Composite sound absorbing structural body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sound absorbing structural body capable of improving a sound absorbing characteristic of a wide frequency band without increasing the bulk density and thickness of porous material of a sound absorbing base material. <P>SOLUTION: In the sound absorbing structural body, the porous material or foamed material is used as the sound absorbing base material and one or more layers of nonwoven fabric are stuck to the surface of the sound absorbing base material by thermally melting a hot-melt material which does not hinder air-flow resistance, at least on the sonic wave incident side, whereby a sound absorbing performance excellent even in middle/low sound regions can be exhibited without deteriorating a sound absorbing characteristic in a high frequency band. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a composite sound absorbing structure constituting a sound absorbing technique which is one of key technologies for noise reduction and sound field control.

  Conventional sound-absorbing materials and sound-absorbing structures include porous materials, film / plate-like materials, and resonance structures. In general, the applied frequency band of the film / plate material system and the resonance structure system is a medium / low frequency band, the tuning frequency is narrow, and the sound absorption coefficient is not so high. In addition, the material (structure) is often thick or requires a space such as an air layer behind it, and it cannot be said that it is particularly easy to handle in the fields of industrial machinery, home appliances, automobiles, vehicles and the like.

  On the other hand, inorganic fiber type such as glass wool and rock wool, porous material type such as polymer fiber type such as polyester, resin foam type such as soft urethane foam, metal foam type such as aluminum These are excellent materials as sound-absorbing materials for medium and high sounds.

  However, in order to increase the sound absorption coefficient in the low range in addition to the mid / high range, it is necessary to increase the thickness of the material or provide an air layer as in the case of the film, plate, and resonance structure described above. , Requires considerable space. Furthermore, for this reason, it is often necessary to lower the sound absorption characteristics in the high sound range, and in the fields of industrial machines, household appliances, automobiles and vehicles, as in the above examples, the sound absorption characteristics, structural design, and weight In many cases, it is difficult to apply due to costs.

  On the other hand, the porous material is an excellent sound absorbing material as a sound absorbing material for the middle / high range, but if the thickness cannot be taken due to space, the sound absorption rate is often insufficient in the middle / low range. However, the frequency band that is often a problem with noise is 500 to 2 kHz. From the viewpoint of thickness, for example, a polyester fiber system (density 44 kg / m 3), and the sound absorption characteristic (normal incidence method) is 35 mm thick. In this case, the sound absorption coefficient is only about 20% at 500 Hz and about 40% at 1 kHz. For glass wool, flexible urethane foam, etc., the sound absorption coefficient is about the same at 35-50 mm. For this reason, measures such as increasing the thickness of the sound-absorbing base material and providing an air layer are taken, but this causes problems such as space, weight, and economy.

  However, as one of the porous materials, the polyester fiber-based sound absorbing material, which has been widely used recently, has a viscous resistance when the incident energy of sound enters a dense material and air enters and exits the material. The sound absorbing performance is exhibited by converting incident acoustic energy into thermal energy by generating friction, causing friction between fibers, or vibrating the fabric. This sound absorption performance is closely related to the flow resistance of the sound absorber, and the sound absorption characteristics can be controlled by adjusting the flow resistance. The polyester fiber-based sound absorbing material is obtained by combining a non-woven fabric with a non-woven fabric to adjust the flow resistance, thereby obtaining high sound absorption characteristics with a practical thickness.

  However, in order to further improve the sound absorption characteristics in the middle and low frequencies, methods such as thickening the sound absorbing matrix material made of polyester fiber, increasing the density, and providing an air layer behind can be considered. There are many cases that cannot be executed from the aspect. The same is true for glass wool and rock wool, which are other porous materials.

  Therefore, it would be very useful if there was a method to improve the sound absorption characteristics in a wide frequency band without increasing the bulk density and thickness of the porous material of the sound absorbing base material, and without providing an air layer in addition to the base material. The present invention seeks to provide a sound absorbing structure that enables this.

  The gist of the present invention is that a porous material or foamed material is used as a sound-absorbing base material, and a nonwoven fabric is used at least on the side on which sound waves are incident. The present invention relates to a composite sound absorbing structure characterized by being worn.

  According to the composite sound-absorbing structure of the present invention, a non-woven fabric is laminated on a surface on which sound waves are incident without changing the thickness of the sound-absorbing base material, and a plurality of layers are laminated with a hot-melt material that does not inhibit the airflow resistance. This makes it possible to exhibit excellent sound absorbing performance even in the mid- and low-frequency range without deteriorating the sound absorption characteristics in the high frequency band, which is difficult to realize with a system sound absorbing material.

  Further, according to the composite sound absorbing structure of the present invention, not only excellent sound absorbing performance is shown, but also the outermost nonwoven fabric on the sound wave incident side is subjected to treatment such as weather resistance, durability, waterproofness, chemical resistance and the like. Protects against various predisposing factors, and is also a great advantage in improving surface strength and flame retardancy (more enhanced with a metal-based multi-layer structure). large. In addition, when applied to a part with an air flow such as a duct, a part of the fiber is not taken away, and it is safe in terms of air cleaning.

  The composite sound-absorbing structure of the present invention comprises at least one non-woven fabric / hot melt material disposed on the sound wave incident side of a sound-absorbing base material made of a porous material, and is heat-fused to be integrated and combined. The present invention provides a composite sound absorbing structure in which ventilation resistance is controlled so as to match the sound absorbing performance and the sound absorbing characteristics in a wide frequency band are improved.

  According to this composite sound absorbing structure, it is possible to improve the sound absorbing characteristics in the middle and low frequency bands without deteriorating the sound absorbing characteristics in the high frequency band and without increasing the thickness, bulk density, etc. of the sound absorbing base material. It is. This is because the ventilation resistance of the composite structure can be controlled by laminating and heat-sealing at least one layer, preferably a plurality of layers of non-woven fabric / hot melt, on at least the sound wave incident side of the sound-absorbing base material. Yes, when the acoustic incident energy penetrates into the composite structure, first, the viscous resistance between the laminated nonwoven fabrics is increased, and further, the viscous resistance as a composite structure including the sound-absorbing base material is increased. Friction between laminated nonwoven fabrics and fibers of the sound-absorbing base material, resonance of the fibers, etc. are added, so that the conversion efficiency from acoustic energy to thermal energy can be improved overall, so that the sound absorption characteristics in the high frequency band are not deteriorated In addition, the sound absorption characteristics in the middle and low frequency band can be improved.

  First, in the above composite sound absorbing structure, typical examples of the sound absorbing base material are polymer materials such as polyester, inorganic fibers such as glass wool and rock wool, porous materials such as metal fibers, and soft materials. Examples thereof include porous materials such as polymer foams such as urethane foam and metal foams such as aluminum, or foam materials. And the ventilation resistance of the sound-absorbing base material is in a preferable range of 3 × 10 3 to 7 × 10 4 N · sec / m 4. Among them, recently, a polyester fiber-based porous material having excellent performance such as good sound absorption performance, friendly to the global environment and working environment, can be recycled, and has weather resistance and durability, is preferably used. When a polyester fiber system is used as the sound-absorbing base material, those having a bulk density of 20 to 80 kg / m 3 and a ventilation resistance of 4 × 10 3 to 2 × 10 4 N · sec / m 4 are often used in a practical range. Depending on the configuration of the non-woven fabric heat-bonded / laminated body with the hot melt material, the sound absorbing characteristics may be sufficiently exhibited even if only the air layer is formed instead of the above sound absorbing base material.

  Regarding airflow resistance, if the airflow resistance is too small, the sound pressure is vibrated and air moves easily in the base material, reducing the viscous resistance. Conversely, if the airflow resistance is too high, air is generated in the base material. The range of the airflow resistance optimum as the sound absorber is specified from the knowledge that the viscous resistance becomes small and the sound absorption rate shifts to the lower side in this case.

  The nonwoven fabric integrated with the sound-absorbing matrix is laminated by hot fusion with one or more layers through a hot melt material, but such nonwoven fabrics are polymer-based, for example polyester-based, polyethylene-based, nylon-based, The paper type is a non-woven fabric such as Japanese paper or wallpaper, and preferably a non-woven fabric made of polyester fibers. A nonwoven fabric having a surface weight of 20 to 200 g / m 2 and a ventilation resistance of 0.5 to 5 × 10 4 N · sec / m 4 is preferable. With respect to the target sound absorption characteristics, those having the same characteristics or different characteristics can be appropriately combined.

  In addition, for example, many spunbond nonwoven fabrics have a ventilation resistance of around 0.7 × 10 4 N · sec / m 4, and are combined with the ventilation resistance of the base material to provide a composite ventilation resistance. The sound absorption characteristics are optimized within a certain thickness. In the present invention, the aim is to control the airflow resistance by superimposing a nonwoven fabric on the surface (in the case of polyester fiber, many spunbond nonwoven fabrics) in multiple layers.

  Furthermore, the most important point of the present invention is that a non-woven fabric (for example, spunbond non-woven fabric) is composited with a base material by heat fusion with powdery hot melt in multiple layers, and an air layer may be used instead of the base material. It is in the point which can also show a characteristic by providing. Also in this case, the viscous resistance increases due to the flow of air in and out of the multilayer nonwoven fabric and between the front and back (air layers), acoustic energy is converted into thermal energy, and sound absorption characteristics are improved, of course. Needless to say, when a base material is used, the base material is naturally converted into thermal energy, and the sound absorption characteristics are improved accordingly.

  Non-woven fabrics and non-woven fabrics, hot melt materials for thermal fusion and composite of non-woven fabrics and sound-absorbing base materials are polyester-based, nylon-based, polypropylene-based, olefin-based polymer systems, etc. A powder, mesh, or fiber having a melting point of 70 to 180 ° C. is preferred.

  In the above composite sound absorbing structure, since the nonwoven fabric / hot melt material is laminated on the sound absorbing base material, water repellent treatment, flame retardant treatment, weather resistance / light treatment, antifouling treatment are applied to the outermost layer on the sound wave incident side as required. It goes without saying that practicality can be enhanced economically by applying the above and the like so as not to disturb the airflow resistance and imparting various characteristics.

  Hereinafter, an exemplary configuration of a sound absorbing structure according to the present invention will be described based on a cross-sectional view and a three-dimensional view. In the following examples, the effects of the present invention will be described with experimental examples using the normal incidence method.

  FIG. 1 shows the structure of a first embodiment of a composite sound absorbing structure according to the present invention. 1A is a cross-sectional view, and FIG. 1B is a three-dimensional view with a part broken away. A composite sound absorbing structure 101 shown in FIG. 1 shows a basic structure of the present invention in which a single layer of nonwoven fabric 1 is thermally fused to a sound absorbing base material 3 with a hot melt material 2. The sound-absorbing base material 3 used was a polyester fiber-based porous material, and the bulk density was 44 kg / m 3. The nonwoven fabric 1 and the nonwoven fabric described later are spunbond nonwoven fabrics having a surface weight of 100 g / m 2 and a ventilation resistance of 0.7 N · sec / m 4. The hot melt material 2 and the hot melt material 5 to be described later are nylon-based, and have a powder shape so as not to impede the airflow resistance, and have a melting point of 150 ° C.

  FIG. 2 shows the structure of a second embodiment in which a nonwoven fabric is laminated on the basis of the basic structure of FIG. 2A is a cross-sectional view, and FIG. 2B is a three-dimensional view. The composite sound-absorbing structure 102 shown in FIG. 2 is laminated on and bonded to the nonwoven fabric 1 / hot melt material 2 on the nonwoven fabric 101, and two layers (1, 1) of the nonwoven fabric are ventilated. An example of a structure in which the viscous resistance is effectively increased and the low and medium frequency bands are improved without substantially reducing the high frequency band.

  According to the present invention, the non-woven fabric is laminated as it is to increase the viscous resistance, and the ventilation resistance is controlled in a complex manner. Over time, the sound absorption characteristics can be improved to general.

  FIG. 3 is a graph showing the effectiveness of the present invention. As a sound absorbing base material, a polyester fiber type (bulk density: 44 kg / m 3, thickness: 35 mm) is selected, and the nonwoven fabric (polyester fiber type of the present invention is compared with the case of only the sound absorbing base material (Comparative Example: 100). A case where a spunbond nonwoven fabric having a surface density of 100 g / m 2 and a ventilation resistance of 0.7 × 10 4 N · sec / m 4 is heat-fused to a sound-absorbing base material (first embodiment) : 101), the case where the same nonwoven fabric is made into two layers and thermally fused to the sound-absorbing base material (second embodiment: 102) is shown. The sound absorption performance is considerably improved in the first embodiment in which the nonwoven fabric is a single layer, but it is understood that the sound absorption performance is further improved in the second embodiment in which the nonwoven fabric is formed in two layers, and the effectiveness of the present invention is recognized.

FIG. 4 is a diagram showing the effect of using two layers of non-woven fabric having different properties, and a composite sound absorbing structure (second embodiment: 102a) laminated and composited with each other and with a heat absorbing base material. ) And a composite sound absorbing structure (first example: 101a) in which the surface weight and the airflow resistance obtained by heat-sealing a single-layer nonwoven fabric to the sound absorbing base material are substantially the same as those of the second example. . It has been proved that 102a using two layers of nonwoven fabric is more effective than 101a in the case of one layer.

This is because the multilayer resistance is more effective in the multilayer, the overall ventilation and viscosity resistance including the sound-absorbing base material is increased, the acoustic energy is efficiently converted into thermal energy, and the sound-absorbing performance is greatly improved. is there. In addition, the structure of 1st Example (101a) in FIG. 4 made the nonwoven fabric into the polyester fiber type spunbonded nonwoven fabric (Area density: 200 g / m <2>, Ventilation resistance: 1.5 * 104 N * sec / m <4>), The second embodiment (102a) is the same as that of FIG. 3, and the surface density and the ventilation resistance are almost the same as each other.

  FIG. 5 shows an example in which the nonwoven fabric is further composed of a plurality of layers. In the figure, E is a three-layered (Example 3: 103), and F is a five-layered (Example 4: 104). It is a graph which shows an effect. All used the sound-absorbing base material, nonwoven fabric, and hot melt material used in Example 1.

  FIG. 6 shows the structure of a fifth embodiment 105 in which a plurality of non-woven fabrics are laminated with a powdered hot melt material, heat-sealed and composited, and the base material is replaced with an air layer. The nonwoven fabric 1 is a spunbond nonwoven fabric as in the previous example, the powdered hot melt material 2 is nylon, and the nonwoven fabric has a five-layer structure. The structure of the air layer 6 is an arbitrary means. For example, it may be supported and configured (105a) by the honeycomb 7 as shown in FIG. 6 (a), or as shown in FIG. 6 (b). It may be supported / configured by a polymer nonwoven fabric having no film, for example, saran net 8 (105b) or a polymer foam material without a film.

  FIG. 7 is a graph showing the effect of the fifth embodiment shown in FIG. That is, the case where the spunbonded nonwoven fabric is made into a five-layer composite structure with powdered hot melt and the air layer 6 is 0 mm (100a), 25 mm (105c), and 35 mm (105d) is illustrated. In the example (105a) in which the air layer is provided by the honeycomb 7, it can be seen that the sound absorption characteristics are remarkably improved. Thus, according to the present invention, it was found that excellent sound absorption characteristics can be obtained even when the base material 3 is replaced with the air layer 6.

  The object of application of the composite sound absorbing structure according to the present invention is various industrial machines such as construction machinery, agricultural machinery, and compressors, sound absorption processing of casings and openings of household electrical appliances, sound absorption ducts, automobiles, sound absorption processing inside vehicles, It can be widely used as a sound-absorbing structure such as a sound-insulating wall in the railway and road fields, and as a sound-absorbing material for noise reduction in the building field and indoor acoustic control.

It is a figure which shows the structure of 1st Example of the composite sound absorption structure by this invention. It is a figure which shows the structure of 2nd Example of the composite sound absorption structure by this invention. It is a graph which shows the effect of the composite sound absorption structure of the present invention. It is a graph which shows the effect which laminated | stacked the nonwoven fabric of the composite sound-absorbing structure of this invention. It is a graph which shows the effect of the 3rd and 4th example which laminated the nonwoven fabric of the composite sound-absorption structure of the present invention further. It is a figure which shows the structure of 5th Example of the composite sound absorption structure of this invention. It is a graph which shows the effect of 5th Example of the composite sound-absorbing structure of this invention.

Explanation of symbols

1. Nonwoven fabric,
2. Hot melt material
3. Sound absorbing base material
6. Air layer,
7. Honeycomb
8 ... Saran Net,
101, 102, 103, 104, 105... Composite sound absorbing structure.

Claims (11)

  A composite sound-absorbing structure comprising a porous material or a foam material as a sound-absorbing base material, and a non-woven fabric is thermally fused to the surface of the sound-absorbing base material with a hot-melt material that does not inhibit airflow resistance from the side on which sound waves are incident.   Sound absorbing base material is made of polymer such as polyester, inorganic fiber such as glass wool or rock wool, porous material such as metal fiber, polymer foam such as flexible urethane foam, metal foam such as aluminum, etc. The composite sound-absorbing structure according to claim 1, which is a porous material or a foam material.   The composite sound-absorbing structure according to claim 1 or 2, wherein the sound-absorbing base material has a ventilation resistance of 0.3 to 7 x 10 4 N · sec / m 4.   The composite sound-absorbing structure according to any one of claims 1 to 3, wherein the nonwoven fabric is heat-sealed and laminated by a single layer or a plurality of layers via a hot melt material.   The composite sound-absorbing structure according to any one of claims 1 to 4, wherein the one-layered or plural-layered nonwoven fabric on the incident side of the sound wave is a polymer-based or paper-based nonwoven fabric.   6. The composite sound absorbing structure according to claim 5, wherein the polymer nonwoven fabric is a polyester, polyethylene, or nylon polymer nonwoven fabric.   6. The composite sound absorbing structure according to claim 5, wherein the paper-based nonwoven fabric is a Japanese paper or wallpaper nonwoven fabric.   The composite sound-absorbing structure according to any one of claims 1 to 7, wherein the nonwoven fabric has a surface weight of 20 to 200 g / m 2 and a ventilation resistance of 0.5 to 5 × 10 4 N · sec / m 4.   The composite sound-absorbing structure according to any one of claims 1 to 8, wherein at least one layer of the nonwoven fabric on the sound wave incident side is subjected to water repellent treatment, flame retardant treatment, weather resistance / light treatment, antifouling treatment, and the like. The hot-melt material is in the form of a polymer, such as polyester, nylon, polypropylene, or olefin, powder, network, or fiber, and has a melting point of 70 to 180 ° C. Composite sound absorbing structure. The composite sound absorbing structure according to any one of claims 1 to 10, wherein an air layer is used as the sound absorbing base material.

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