JPH0659680A - Sound absorbing structure - Google Patents

Abstract

PURPOSE:To obtain a structure displaying an excellent sound absorbing characteristic over a wide frequency range, by holding at least two sheets with a large number of slits on holding members having a large number of through holes, and placing the sheets at a suitable interval. CONSTITUTION:Basically, at least two sheets which are held by holding members having a large number or through holes and which are provided with a large number of slits are placed at a suitable interval. In other words, a first sheet 16 having a large number of slits 14 is placed on the upper surface of a first holding member 12 having 'honeycomb structure', a second holding member 18 having similar 'honeycomb structure' is placed on the upper surface of the first sheet 16, and moreover a second sheet 20 having the similar slits 14 is placed on the upper surface of the second holding member 18. This structure is held by a rigid body serving as a sound absorbing body and, preferably, covered with a metallic mesh 24 in order to protect a sound absorbing body 10, especially the second sheet 20 that is arranged on the topmost surface of the body 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound absorbing structure which is inexpensive, has a simple structure, can be easily formed into a panel and can be installed, and can exhibit good sound absorbing efficiency from low frequencies to high frequencies.

[0002]

2. Description of the Related Art Conventionally, various porous materials have been used as sound absorbing materials. A typical example of the porous material used for the sound absorbing material is glass wool. Further, in recent years, aluminum fiber non-woven fabric and aluminum porous material using aluminum sintered body have also started to be widely used as sound absorbing materials. Inventing a sound-absorbing material made from the above, and previously proposed this (see Japanese Patent Publication No. 4-13142).

Of these various sound absorbing materials, glass wool is inexpensive, but has the problem that it scatters over time due to its properties, and the sound absorbing effect is reduced by absorbing water and the like. There is also a problem.
On the other hand, the aluminum porous material has good sound absorption characteristics,
It is lightweight and has excellent durability. However, although the aluminum porous material has such excellent characteristics, it has a drawback that it is relatively expensive.

[0004]

As described above, the conventional sound absorbing material has advantages and disadvantages, and is appropriately used by selecting an application in which the characteristics can be utilized.
It is desired to develop a sound absorbing material that has the advantages of conventionally known sound absorbing materials, that is, a sound absorbing material that is inexpensive, lightweight, and has good sound absorbing properties over a wide frequency range from low frequencies to high frequencies. There is.

An object of the present invention is to solve the above-mentioned problems of the prior art, and has excellent properties such as a simple structure, easy panelization and construction, light weight and low cost, and also from a low frequency range. It is an object of the present invention to provide a sound absorbing structure capable of exhibiting excellent sound absorbing characteristics over a wide frequency range up to a high frequency range.

[0006]

In order to achieve the above object, the sound absorbing structure of the present invention comprises a sheet having a large number of cuts, which is held by a holding member having a large number of through holes.
Provided is a sound absorbing structure characterized by having at least two sheets spaced apart.

Further, in the sound absorbing structure, on the upper surface,
It is preferable to have any one of expanded metal, mesh, and punching metal for protecting the sheet.

The sound absorbing structure of the present invention will be described in detail below. FIG. 1 shows a partially cutaway schematic perspective view of an example of the sound absorbing structure of the present invention, and FIG. 2 shows a schematic sectional view taken along line II-II of this sound absorbing structure.

The sound absorbing structure of the present invention basically has at least two sheets having a large number of cuts, which are held by a holding member having a large number of through holes, at intervals. Sound absorbing structure 10 (hereinafter, sound absorbing body 1
0) is the first holding member 1 having a so-called honeycomb structure
The first sheet 16 having a large number of notches (slits) 14 is arranged on the upper surface of 2, the second holding member 18 having the honeycomb structure is arranged thereon, and the second sheet having the similar slits 14 is formed on the upper surface thereof. The sheet 20 is arranged, and in the illustrated example, is supported by a rigid body 22 serving as a sound insulating material. Also, the sound absorber 1 in the illustrated example
0 has a metal mesh 24 for protecting the sound absorbing body 10, particularly for protecting the second sheet 20 disposed on the uppermost surface, as a preferable embodiment.

In the sound absorbing body 10 of the present invention, sheets having a large number of slits 14 and arranged at intervals, that is, the first sheet 16 and the second sheet 20 in the illustrated example.
Is a thin film body that vibrates (membrane vibration) by sound waves.

The material of the first sheet 16 and the second sheet 20 is not particularly limited, and various resin thin films can be used. Particularly, in terms of durability and weather resistance, ethylene fluoride resin and vinylidene resin are available. A resin is preferably used. Specifically, tetrafluoroethylene resin (Teflon), tetrafluoroethylene hexafluoropropylene copolymer, tetrafluoroethylene polyethylene copolymer, trifluoroethylene chloride resin, vinylidene difluoride, vinylidene cyana Examples thereof include tetraid ethylene resin. The material for forming the first sheet 16 and the second sheet 20 (even when the number of sheets is larger than this) does not have to be the same, and they may be formed of different materials.

Further, the thickness is not particularly limited, and the thickness of the sheet itself which receives a sound wave and the thickness at which the slit portion vibrates well may be appropriately determined depending on the rigidity and durability of the sheet material. In order to secure durability, obtain good film vibration and vibration of the slit portion, and exhibit excellent sound absorbing characteristics, the thickness is usually about 10 to 50 μm.

The sound absorbing body 10 in the illustrated example has two sheets, but the present invention is not limited to this, and the number of sheets may be three or more. Since the sound absorbing characteristic of the sound absorbing body of the present invention changes depending on the number of sheets, the number of sheets may be appropriately determined according to the application of the sound absorbing body and the like.

Such a sheet (first sheet 16 and second sheet 20) has a large number of slits. For example, slits (cuts) as shown in FIG.
Have 14. The slits 14 may be regularly formed as shown in FIG. 3, or may be completely irregularly formed. Further, the slits formed may be uniform or non-uniform. Further, the shape and the forming position are not limited at all, and it is sufficient that sufficient durability can be secured depending on the sheet material, the thickness of the sheet and the like. The sound absorbing characteristic of the sound absorbing body 10 of the present invention changes depending on the size, shape, forming position (state) of the slit 14, and so on.
It is preferably formed according to the intended use of 0 or the like. Also, the slits formed in each sheet need not be uniform,
Different slits may be formed for each sheet depending on the use of the sound absorber.

The sound absorbing body of the present invention is a holding member (first holding member 12 and second holding member 18) having a large number of through holes.
By holding the above-mentioned sheet (first sheet 1
6 and the second sheet 20), at least two of which are arranged at intervals. The sound absorbing body 10 of the illustrated example is a first holding member 12 having a so-called honeycomb structure having a large number of hexagonal tubular through holes as a holding member, which is an aggregate of hexagonal tubes (hexagonal cells) sharing one side. And the second holding member 18 is used.

The shape of the holding member used in the sound absorbing body 10 of the present invention is not limited to the honeycomb structure of the illustrated example, and is a collection of triangular tubes (triangular cells) sharing one side like the honeycomb. It may be present, and similarly, it may be an assembly of square cylinders, pentagonal cylinders, hexagonal cylinders, and the like. Alternatively, it may have a large number of cylindrical through holes, or may have a shape provided with a large number of linear partitions. Further, the through holes are not limited to the same shape and the same size, and may have two or more types of through holes or different size through holes. Furthermore, the through holes do not have to be uniform over the entire surface. That is, in the sound absorbing body of the present invention, this holding member holds the sheet and also has a role of forming an air layer behind the sheet.
Various types of sheets having a shape capable of holding the sheet entirely without disturbing the vibration of the sheet (and the slit) can be used.

The material for forming the holding members (holding member 12 and second holding member 18) is not particularly limited, and a holding member having a desired shape such as paper, various resin materials, various metal materials, etc. can be formed. Any of the various materials that can be used are available. In addition, it is preferable that the material is lightweight in consideration of workability and flame-retardant or non-combustible in consideration of disaster prevention after construction, and nonflammable (flame-retardant) paper developed in recent years, especially strength. In this respect, the honeycomb structure formed of such paper is particularly suitably used.

There is no particular limitation on the method of holding the sheet by such a holding member, and when the sheet is sandwiched by the first holding member 12 and the second holding member 18 like the first sheet 16, only by sandwiching. It may be held, or may be configured to hold a key portion with an adhesive, a jig, or the like as needed. Also, the second sheet 20
If the sheet having the mesh 24 as in the illustrated example is sandwiched between the second holding member 18 and the mesh 24, the sheet having the upper surface as shown in FIG. If the mesh 24 is not provided, the peripheral portion, the corner portion, or an appropriate portion may be held by an adhesive, a jig, or the like.

In the present invention, the thickness of each holding member, that is, the thickness b of the first holding member 12 shown in FIG. 2 (that is, the air layer behind the first sheet 16), and the second holding member 1
The thickness a of 8 (that is, the air layer behind the second sheet 20) may be the same or different.

Here, the thickness of each holding member, that is, the thickness of the air layer behind the sheet affects the sound absorbing characteristics of the sound absorbing body.
According to an experiment by the present inventor, for example, in the case of a two-layer structure such as the sound absorber 10 shown in the drawing, the thickness b of the first holding member 12 is
Is larger than the thickness a of the second holding member, that is, the back air layer of the first sheet 16 is larger than the back air layer of the second sheet 20, good sound absorbing characteristics can be obtained. . When the total thickness of the sound absorbing body 10 (that is, a + b) is determined, the thickness of the upper layer, that is, the second holding member 1
As the thickness of No. 8 is made smaller (the distance from the second layer to the rigid body 22 is made larger), it tends to have good sound absorption characteristics in the low frequency region. Therefore, in the sound absorbing body of the present invention, it is preferable that the thickness of each holding member be appropriately determined according to the application.

As a preferred embodiment, the sound absorbing material 10 of the illustrated example has a metallic mesh 24 for protecting the second sheet 20 provided on the upper surface. Such a mesh 24
By including such a protective member, a preferable result is obtained in terms of durability of the sound absorbing material. In the present invention, the protective member is not limited to the mesh 24 as shown in the illustrated example,
Expanded metal, punching metal and the like are also preferably used. These forming materials are not particularly limited, and any known material such as metal or alloy such as aluminum, iron and stainless, various resin materials and the like can be used. The sound absorbing body of the present invention is not limited to the one having such a mesh, and it goes without saying that it may have a structure having no mesh as in the example shown in FIG.

In the sound absorbing body 10 of the present invention as described above,
When a sound wave enters, the second sheet 20 vibrates due to the sound wave, and the vibration propagates to the first sheet 16 through the space of the second holding member 18 behind. Further, the vibration of the first sheet 16 is propagated to the space of the first holding member 12 behind. The sound absorbing body of the present invention exhibits a good sound absorbing effect over a wide frequency range due to the vibrations of the plurality of films, the slits formed in the films, and the action of the air layer behind the films.

That is, the sound absorbing body of the present invention comprises: a. When a sheet such as a vinyl sheet or canvas is stretched with an air layer between it and a rigid wall, when a sound wave enters, the air layer behind acts as a spring and the sheet vibrates.
Sound absorption due to membrane vibration in which sound waves are vibrationally absorbed, b. When the size of the cavity is small compared to the wavelength like a porous plate, the air inside acts as a spring. Therefore, the air in the constriction moves as a mass (weight), and when a sound wave is incident, the air in the constriction violently moves, and the frictional loss converts the sound wave energy into heat energy to absorb sound. , So-called resonance sound absorption, in addition to the sound absorption effects of a and b described above, since the slit is formed in the sheet, the sound absorption effect by vibrating the sheet around the slit due to the incidence of sound waves is large,
Academic elucidation is very difficult. However, in the case of the present invention, the sound absorbing effect due to this phenomenon is large. This will be proved by a later example.

In the sound absorbing body of the present invention, the second sheet 2
The vibration of 0 (and this slit portion) is transmitted to the first sheet 16 at a certain interval. Therefore, as described above, the distance between the two influences the sound absorbing characteristics of the sound absorbing body 10. Therefore, it is preferable to appropriately determine the back layer of each sheet according to the application.

When the sound absorbing body of the present invention is actually used as a sound absorbing material, a plurality of those having the same constitution may be arranged and constructed, and those having different constitutions, for example, FIG.
The sound absorbers 10A and 10B having different ratios of the thickness b of the first holding member 12 and the thickness a of the second holding member 18 may be alternately arranged (arranged) as shown in FIG. In this case, as a whole, it is possible to obtain sound absorbing characteristics having both characteristics of the sound absorbing bodies 10A and 10B.

Although the sound absorbing structure of the present invention has been described above in detail, the present invention is not limited to the above-mentioned examples, and various improvements and modifications can be made without departing from the scope of the present invention. Of course it's good.

[0027]

EXAMPLES The present invention will be described in more detail with reference to specific examples of the sound absorbing structure of the present invention. <Example 1>

The following materials were prepared for producing the sound absorbing structure of the present invention and the sound absorbing structure of the comparative example. a. A sheet F in which a notch (slit) 14 as shown in FIG. 3 is formed on a tetrafluoroethylene resin sheet having a thickness of 20 μm (in FIG. 3, the unit is mm). b. Height (thickness) 10 mm, 30 mm, 50 mm, 70 having a honeycomb structure with a cell size of 18 mm, respectively.
mm and 80 mm holding members.

The following sound absorbing structure (sound absorbing body) was produced using such a member. [Sound Absorber a (Comparative Example)] The sheet is held by a holding member having a thickness of 80 mm (see FIG. 6a) [Sound absorber b (Comparative Example)] The sheet is held by a holding member having a thickness of 50 mm Sound Absorber (See FIG. 6b) [Sound Absorber c (Invention Example)] A sheet F is placed on a holding member having a thickness of 50 mm, a holding member having a thickness of 30 mm, and a sheet F is placed thereon. Body (see FIG. 6c) [Sound Absorbing Body d (Invention Example)] A sheet F is placed on a holding member having a thickness of 70 mm, a holding member having a thickness of 10 mm, and a sheet absorbing body having the sheet F placed thereon ( (See FIG. 6d)

A sound absorption test by the vertical incidence method was conducted using such various kinds of sound absorbing bodies. The traveling direction of the sound wave is the direction shown by the arrow in FIG. The results are shown in Fig. 7. In addition,
Each sound absorber is indicated by an alphabet in FIG.

As shown in FIG. 7, both the sound absorbing bodies a and b having only one sheet can obtain a sound absorbing efficiency of 10% or less, but two sheets are arranged with a gap. Both the sound absorbing bodies c and d of the present invention exhibit excellent sound absorbing efficiency. With the sound absorbers a and b having only one sheet F, the sound waves that have passed through the sheet F are not dispersed and good sound absorption efficiency cannot be obtained. In contrast,
In the sound absorbers c and d of the present invention, the first sheet F
The sound wave that has passed through is incident on the next sheet F, and this sheet F
And by vibrating the air layers behind both seats,
Good sound absorption characteristics can be obtained. It is also shown in FIG. 7 that the distance between the two sheets affects the sound absorption characteristics, and the greater the distance from the second sheet F to the rigid body,
The sound absorption characteristics on the low frequency side become better (on the contrary, the smaller the sound absorption characteristics on the high frequency side become benign).

<Embodiment 2> The sound absorbing efficiency was measured by the reverberation chamber method using a total of 10 m ² of the sound absorbing body c and the sound absorbing body d described above which were formed into a panel of 1 × 5 m and two sheets were combined. did. As a result, it was possible to obtain an excellent sound absorption efficiency of 70% or more over a wide range of 500 Hz to 2 KHz.

From the above results, the effect of the present invention is clear.

[0034]

As described above in detail, according to the sound absorbing structure of the present invention, it has excellent characteristics such as simple structure, easy panelization and construction, light weight, low cost, and low frequency. It is possible to realize a sound absorbing structure capable of exhibiting excellent sound absorbing characteristics over a wide frequency range from a range to a high frequency range.

[Brief description of drawings]

FIG. 1 is a partially cutaway schematic perspective view showing an example of a sound absorbing structure of the present invention.

FIG. 2 is a schematic sectional view taken along line II-II of the sound absorbing structure shown in FIG.

FIG. 3 is a schematic plan view of an example of a sheet of the sound absorbing structure body shown in FIG.

FIG. 4 is a partially cutaway schematic perspective view showing another example of the sound absorbing structure of the present invention.

FIG. 5 is a view conceptually showing an example of construction of the sound absorbing structure of the present invention.

FIG. 6 is a conceptual diagram for explaining an example of the present invention.

FIG. 7 is a graph showing sound absorption coefficient by the vertical incidence method in the example of the present invention.

[Explanation of symbols]

 10 Sound Absorbing Structure 12 First Holding Member 14 Slit 16 First Sheet 18 Second Holding Member 20 Second Sheet 22 Rigid Body 24 Mesh

Claims (2)

[Claims] 1. A sound absorbing structure, comprising at least two sheets having a plurality of cuts, which are held by a holding member having a plurality of through holes, at intervals. 2. The sound absorbing structure according to claim 1, wherein the upper surface has any one of expanded metal, mesh, and punching metal for protecting the sheet.