JP2009157060A - Sound absorbing structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sound structure used for: reflection sound absorbing in an internal closed space such as a vehicle, an industrial mechanics, an air conditioner, a home electronics and a house; and reduction of external transmission sound as a result. <P>SOLUTION: In the sound absorbing structure in which a porous material is a sound absorbing base material, and a non-woven surface material is compounded in a face of the sound absorbing base material, a mass density in the inside of a sound absorbing base material is made large at a non-woven surface side and made gradually smaller toward the other side, and the non-woven surface side is set facing an entrance side of a sound wave. The sound absorbing base material 1, a hot melt material 2 and the non-woven fabric 3 are included in the sound structure 100. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sound-absorbing structure used for the purpose of absorbing reflected sound in an internal closed space of a vehicle, industrial machine, air conditioner, home electric appliance, house, etc., and reducing externally propagated sound as a result. .

  Sound absorbing materials that are generally used are classified according to materials and structures into a) membrane / plate-like materials, b) perforated plate materials, and c) porous materials. In (b), one vibration system is constituted by a plate-like material such as a plaster board, a film-like material such as a vinyl sheet, and a back air layer.

  In (b), a resonance structure is constituted by a perforated plate of various materials and a back air layer. When the frequency of the incident wave matches the resonance or resonance frequency of these systems, the acoustic energy is converted to resonance or resonance energy. Therefore, the frequency band of the acoustic energy absorbed by these sound absorbing structures is often a relatively narrow range of the mid-low range.

  C) The porous material system includes glass wool, rock wool, felt, foamed resin, fiber material, etc., and has a number of gaps and vesicles inside the material, and has air permeability. is there. The acoustic energy of the incident wave is converted into thermal energy due to the viscosity of the air, friction, resonance of the fibrous material, and the like when passing through the gap or vesicle.

  Unlike the above a) and b), the sound absorbing structure of the porous material system of c) absorbs acoustic energy in a relatively wide frequency band centering on the middle to high frequencies. Therefore, when the spectrum of the sound source covers a relatively wide frequency band, such as an engine of an industrial machine such as a construction machine or an air conditioning compressor, the sound absorbing structure of the porous material system is often used.

  The sound absorption performance of the porous material-based sound absorbing material is improved in all frequency bands by increasing the density of the sound absorbing base material. This is because viscosity resistance or the like when air moves inside the material is increased, and the conversion efficiency into heat energy per unit volume is increased. Further, increasing the thickness of the sound absorbing base material also increases the total viscous resistance when acoustic energy passes through the material, so that the sound absorbing performance is improved.

  As another method for improving the sound absorbing performance of the porous material-based sound absorbing material, there is a method of attaching a skin having air permeability to the surface of the sound absorbing base material (Patent Document 1). By increasing locally the ventilation resistance of the surface of the sound absorbing material, the overall ventilation resistance including the base material is increased to improve the sound absorbing performance. The mechanism is the high level of the sound absorbing base material described in the previous section. Although it is the same as densification, the thickness of the base material can be suppressed to some extent.

Japanese Patent Application No. 2006-177348

  Although the above-described porous material-based sound absorbing material is an excellent sound absorbing material, there are some aspects that must be improved. That is, if the base material density of the porous material-based sound absorbing material is increased, the amount of material used increases, resulting in an increase in cost. Further, since the heat insulation effect increases as the base material density increases, heat balance becomes a problem when used in an engine room or the like.

  In recent years, further noise reduction has been demanded for home appliances. However, on the other hand, due to the compactness of the product, there is often no room for mounting the sound absorbing material, and the thickness of the sound absorbing material to be used is limited.

  For this reason, there is a demand for means for making the sound absorption performance in the middle and low frequency bands higher, without limiting the amount of material used for the sound absorption base material, and without increasing the thickness of the sound absorption material.

  The gist of the present invention is that in a sound-absorbing structure comprising a porous material as a sound-absorbing base material and a non-woven skin material composited on the surface of the sound-absorbing base material, the bulk density inside the sound-absorbing base material is adjusted to The present invention relates to a sound absorbing structure characterized in that it is greatly reduced toward the other side, and the non-woven skin material side is set toward the incident side of the sound wave.

  The present invention creates a gradient structure of density distribution inside the base material of the porous sound-absorbing material, composites the non-woven skin material on the high density side, and installs the non-woven skin material surface facing the incident surface of the sound wave By doing so, it has been found that conventional problems can be improved.

  FIG. 1 shows a state when the porous sound absorbing material is attached to the rigid wall surface. 10 is a porous sound absorbing material, and 11 is a rigid wall. However, when sound waves are incident from the left side of FIG. 1, the velocity of air particles is 0 on the rigid wall surface, c / 4f from the rigid wall to the left (c: sound velocity in air [cm / s], f: frequency of incident sound wave [ Hz]) maximum at a distant position.

  Now, when the bulk density side of the porous sound-absorbing material (= portion where the ventilation resistance is large) is arranged at a position where the air moves violently, the conversion efficiency of acoustic energy into heat energy is higher. Therefore, in the present invention, the higher the bulk density, the greater the distance from the rigid wall, and the sound absorbing effect of the sound in the middle and low frequency band is improved. The bulk density distribution in the sound-absorbing base material can be changed sequentially, but can also be changed in stages.

  Further, by laminating the nonwoven fabric 12 having air permeability on the incident surface side of the sound wave, the ventilation resistance on the incident surface side is further increased. For this reason, the sound absorption effect in the middle and low frequency band is more excellent. Reference numeral 13 denotes a hot melt material.

  A preferred example of the sound-absorbing base material is a polyester fiber nonwoven material. The non-woven skin material disposed on the surface of the sound absorbing member is a polymer material such as polyester, polyethylene, or nylon, or a paper material such as Japanese paper or wallpaper.

  The sound-absorbing base material and the non-woven skin material are preferably heat-sealed via a hot-melt material that retains a powder-like or mesh-like air permeability, and examples of the hot-melt material include polyester, nylon, and polypropylene. A polymer material having a melting point of 70 to 200 ° C. as a main component is preferable.

  The means for attaching the sound-absorbing base material to the rigid wall is not particularly limited, but is preferably a sound-absorbing structure in which the sound-absorbing base material surface opposite to the non-woven skin material is subjected to double-sided tape or adhesive treatment. Is good.

  FIG. 2 shows the structure of an embodiment of a sound absorbing structure according to the present invention. 2A is a three-dimensional view with a part broken away, and FIG. 2B is a cross-sectional view. A sound absorbing structure 101 shown in the figure is produced by thermally fusing a nonwoven fabric 3 to a sound absorbing base material 1 of a polyester fiber porous material via a hot melt material 2.

The thickness of the sound-absorbing base material 1 used here was 35 [mm], the ventilation resistance was 0.7 [N · sec / m ⁴ ], and the bulk density as a whole material was 45 [kg / m ³ ]. However, the density distribution inside the material is not uniform, and the density increases from A to B (indicated by shading in the figure). This density gradient structure is formed by hitting a needle punch from the B surface side.

As the nonwoven fabric 3, a spunbond nonwoven fabric having a surface weight of 100 [g / m ² ] and a ventilation resistance of 0.7 [N · sec / m ⁴ ] was used.

The hot melt material 2 is nylon, has a melting point of 135 ° C., and a surface weight of 27 [g / m ² ]. The hot melt material 2 is applied to the nonwoven fabric 3 in a powder form and does not impair the breathability of the nonwoven fabric 3.

  FIG. 3 is a graph showing the effectiveness of the sound absorbing structure according to the present invention. The sound absorbing structure 100 having the same structure as the sound absorbing structure 101 was selected as a comparative example, but the thickness and bulk density of the sound absorbing base material were the same as those in Example 101, and the density distribution in the sound absorbing base material was uniform. It has become.

  When comparing both the sound absorbing structures 101, 100, the sound absorbing performance in the middle and low frequency band of the embodiment 101 of the present invention is considerably improved, and the sound absorbing performance in the high frequency band is hardly deteriorated. The effectiveness of the present invention is recognized, and it can be widely used as a reflection sound absorbing material in internal closed spaces such as vehicles, industrial machines, air conditioners, home appliances, and houses.

It is a figure which shows the effect of the sound absorption structure by this invention. It is a figure which shows the structure of the Example of the sound-absorbing structure by this invention. It is a graph which shows the effectiveness of the sound-absorbing structure by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Sound absorption base material 2 ... Hot melt material 3 ... Nonwoven fabric 100 ... Sound absorption structure

Claims (6)

  In a sound-absorbing structure in which a porous material is a sound-absorbing base material and a non-woven skin material is composited on the surface of the sound-absorbing base material, the bulk density inside the sound-absorbing base material is greatly increased from the non-woven skin material side to the other side. A sound-absorbing structure characterized by being gradually reduced in size and installed with the non-woven skin material side facing the sound wave incident side.   The sound absorbing structure according to claim 1, wherein the porous material is a polyester fiber.   The sound absorbing structure according to claim 1 or 2, wherein the non-woven skin material is a polymer material such as polyester, polyethylene or nylon, or a paper material such as Japanese paper or wallpaper.   The sound-absorbing structure according to any one of claims 1 to 3, wherein the sound-absorbing base material and the non-woven skin material are heat-sealed via a hot-melt material that maintains a powder-like or mesh-like breathability.   The sound absorbing structure according to claim 4, wherein the hot melt material is a polymer material having a melting point of 70 to 200 ° C mainly composed of polyester, nylon, polypropylene or the like.   The sound-absorbing structure according to any one of claims 1 to 5, wherein a surface of the sound-absorbing base material opposite to the non-woven skin material is subjected to double-sided tape or adhesive treatment.