JP2005098067A - Sound absorbing panel and sound absorbing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin and lightweight sound absorbing panel having good sound absorbing efficiency, and to provide a sound absorbing method. <P>SOLUTION: In the sound absorbing panel 1 including a plate body 2 in which a number of holes 3 going from one side to the other side are formed to constitute a number of closed-tube air column parts, the face having the opening parts of the holes 3 is brought into contact with a reflecting plate body (sound insulating wall) 7 to close the holes 3. The sound absorbing method is that the holes 3 are closed by bringing the face having the opening parts into contact with the reflecting panel body (sound insulating wall) 7, in the sound absorbing panel 1 including the plate body 2 in which the holes 3 going from one side to the other side are formed to constitute the closed-tube air column parts. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a sound-absorbing plate that effectively absorbs noise generated from railways, roads, power facilities, and the like and transmitted to downstairs of houses and buildings, and a sound-absorbing method using the same.

In buildings close to railways, noise barriers may be installed to avoid noise from railways. Generally, a railing is installed at a viaduct, but a method of reducing the influence of noise by attaching a soundproof wall to this is taken.

Conventionally, to install a soundproof wall, as described in “Calculation of sound attenuation due to dredging” (Pollution prevention technology and regulations, published by Industrial Environment Management Association, page 94), transmission loss of dredging (30 dB ~ 50d
If B) is 10 dB larger than the wraparound attenuation (limit value 25 dB), it is considered that there is no effect of improving the performance of the soundproof wall. For soundproof walls having a sound insulation performance that satisfies this condition, the performance is further improved. Was not done. Patent Document 1 describes a sound absorbing material using a sound absorbing principle by air column resonance. That is, the length of the air column tube is 1/4 of the wavelength, 3/4, 5 /
When a reflection plate is provided in the air column tube so as to be 4 etc., the sound that has entered the air column tube from one end travels in the tube, is reflected by the reflection plate, and travels in the reverse direction in the tube. . At this time, the incident wave sound traveling in the direction of the reflecting plate and the reflected wave sound traveling in the opposite direction interfere with each other and cancel each other.
Japanese Utility Model Publication No. 7-12650

However, in the conventional sound absorbing material using the sound absorption principle by air column resonance, it is necessary to increase the thickness in order to mute the low frequency sound. For example, at 250 Hz, the depth of the hole, that is, the air column When the length is 340 mm and 125 Hz, the length of the air column tube is 680 mm, and a large thickness is required.

In view of the above situation, it is an object of the present invention to provide a sound-absorbing plate that is thin, lightweight, and exhibits high sound-absorbing performance with respect to low-frequency sound, and a sound-absorbing method using the same.

The sound-absorbing plate according to the present invention is a sound-absorbing plate in which a large number of holes are formed from one surface side to the other surface side of the plate body to form a large number of closed tube air columns, and the surface on the hole opening side is for reflection. A large number of holes are blocked by being applied to the plate.

The sound absorbing method according to the present invention comprises a sound absorbing plate having a plurality of holes formed on one side of the plate body from the other surface side to form a number of closed tube air column portions, and a reflection plate body on the hole opening side surface. This is a method to close a large number of holes.

  A sound absorbing material may be interposed between the sound absorbing plate and the reflecting plate.

Some holes form a large number of closed air column parts by forming a large number of holes on the plate body from the other side to the one side, and / or a large number of through holes on both sides of the plate body And many open-tube air column parts may be comprised.

The sound absorbing plate constituting a large number of closed tube air column portions may be composed of a plate body having a large number of through holes and a hole closing member provided on one surface of the plate body. A sound absorbing material can also be interposed between a plate having a large number of through holes and a hole closing member provided on one side of the plate.

In the present invention, the material constituting the plate is preferably a foamed polymer resin such as foamed polystyrene, foamed polyurethane, foamed polypropylene, or foamed polyethylene,
It may be paper, non-foamed polymer resin, inorganic material, metal material such as aluminum, or the like. The holed portion and the holeless portion of the plate body, that is, the solid portion on one side, are usually made of the same material, but may be made of different materials. If the sound insulation is too high in the holeless portion, the sound is reflected and does not reach the closed air column, so the surface density of this portion is preferably 50 kg / m ² or less.
In addition, it is preferable to form irregularities on the surface of the holeless portion in terms of improving the high frequency sound absorption coefficient. This holeless portion may be provided with a hole that allows the closed tube air column portion to communicate with the outside so that the closed tube air column portion has air permeability. It is also preferable to perform fireproofing, waterproofing, weathering, etc. on at least the holeless portion of the plate.

The formation form of the hole is not particularly limited, and a fine hole may be provided so as to communicate between the closed air column portions. The method for forming the holes is not particularly limited, and examples thereof include use of a honeycomb material, mechanical processing, use of a mold, lamination molding such as stereolithography, processing by laser, and the like. Moreover, what bundled many straw (pipe) -like bodies may be used.

Reflective plates can be used for existing sound barriers (sound barriers) such as railways, roads, and power facilities,
It may be a floor or the like. The material and thickness of the reflection plate are not limited. The material of the reflection plate may be the same as or different from the material of the sound absorbing plate. The reflection plate may be integrated with the sound absorbing plate. When sound insulation is required in addition to sound absorption, the reflective plate is preferably made of a material with high sound insulation, i.e. high surface density, and good fire resistance, water resistance, and weather resistance. It is necessary to have a flexible board, a stainless steel plate, an aluminum plate, a rust-proof metal plate, or a laminated plate obtained by bonding these to the surface. The reflection plate may be composed of a closed-cell or open-cell foam or a non-foam. In the case of open cells, the cell diameter is preferably sufficiently smaller than the diameter of the closed tube column.

The sound absorbing material interposed between the sound absorbing plate and the reflecting plate is made of a material such as inorganic fiber, organic fiber, inorganic foam, or organic foam, or uses air column resonance. Good.

Since the sound absorbing plate of the present invention is constituted by the plate body in this way, the shape can be maintained without covering it with an auxiliary plate or the like. Therefore, it can be installed on the reflecting plate as it is with an appropriate mounting member such as a bolt or nut, and is very lightweight. And
In this sound absorbing plate, a large number of holes are formed in the plate body from one side to the other side to form a large number of closed tube air columns, and it is considered that resonance occurs in each closed tube air column, Effective sound absorption is performed.

As described above, in the present invention, sound absorption is achieved by resonance of the closed tube air column portion, and therefore the frequency band of the sound absorption target can be set by adjusting the length, that is, the depth of the hole constituting the closed tube air column portion. In order to adjust the depth of the hole, the depth of the hole is made different in a plate having a constant thickness (FIG. 4).
(See (a)), the plate body is integrally formed from a plurality of portions having different plate thicknesses and hole depths (see FIG. 4B), and the plate thickness and hole depth are gradually increased from one end to the other. (See FIG. 4C)
There are methods.

In the sound absorbing plate according to the present invention, the surface on the hole opening side is applied to the reflecting plate, and many holes are closed. By providing the sound absorbing plate on the reflection plate in this way, the soundproofing effect is further improved. Further, unlike the sound absorbing plate using a fibrous sound absorbing plate or an open air column tube, since there is no hole leading to the outer surface, there is no risk of deterioration due to clogging due to water absorption, dust, and dust.

The sound absorption frequency of the open air column tube is known to be a value obtained by dividing the sound velocity by 4 times the hole depth. However, the sound absorbing plate of the present invention is further provided with a number of closed tube air column portions. Sound absorption on the low frequency side is possible.

In the closed tube air column, the sound absorption frequency shifts to the low frequency side compared to the open tube, so the sound absorption rate on the high frequency side may decrease, but the sound absorbing material is between the sound absorbing plate and the reflecting plate. Or a plurality of holes are formed in the plate body from the other surface side to the one surface side to form a large number of closed air columns, and / or on both sides of the plate body By forming a large number of holes and forming a large number of open tube air column portions, such a problem of a decrease in the sound absorption coefficient can be solved.

A preferred sound absorbing plate is one in which at least one of the holes constituting the many closed tube air column portions has a different length from the other. In this way, by making the lengths of the holes constituting a large number of closed tube air column portions different, a plurality of frequency bands to be sound-absorbed can be set.

A preferred sound absorbing plate has a large number of holes formed in an oblique direction of the plate. By forming a large number of holes in the oblique direction of the plate body in this way, the length of the hole, and hence the closed tube column, can be reduced compared to the case of forming a large number of holes in a direction perpendicular to the expanding direction of the plate body. It is possible to increase the length of the holes to be formed, and therefore it is possible to adapt to a lower frequency band without increasing the thickness of the plate.

The sound absorbing plate may be a plate in which at least a front surface portion and a side surface portion of the plate body are covered with a protection plate, and communication portions corresponding to a large number of holes of the plate body are formed on the front surface portion of the protection plate. In applications that require fire resistance, weather resistance, and scratch resistance, it is preferable to cover the plate with the protective plate in this way. In this case as well, it is not necessary to cover the entire plate body, and it is sufficient to cover at least the front surface and the side surface. can do.

  It is also preferable to provide a wire mesh instead of the protective plate.

If the plate of the sound absorbing plate is covered with a protective plate, the plate and the protective plate may collide with each other due to vibration when the train passes and become a new sound source. In order to prevent this, it is necessary to firmly bond both of them. When the vibration state of the sound absorbing plate itself or the wall or floor to which the sound absorbing plate is attached changes and as a result the soundproofing performance deteriorates, the peak value 1 of the loss sine (tan δ) is used as the protective plate to deal with these points. It is preferable to use a vibration damping sheet made of an organic polymer material of 0.5 or more and a restraining member having a longitudinal elastic modulus of 1 GPa or more provided outside the vibration damping sheet. As a result, the plate body and the protection plate can be firmly bonded, and the soundproof performance can be prevented from being lowered by the excellent vibration damping performance. When a protective plate made of a damping sheet and a restraining member is provided on the hole opening surface side of the plate body, that is, on the entire surface portion, it is preferable that a communicating portion, that is, a through hole is also formed in the protective plate at a position corresponding to the hole of the plate body. As a restraining member, fire resistance and weather resistance,
It is preferable that it is metal from the point of abrasion resistance.

  Next, the vibration damping sheet and the restraining member constituting the protective plate will be described.

The organic polymer material of the vibration damping sheet is not particularly limited as long as the peak value of the loss sine (tan δ) measured at 100 Hz is 1.5 or more, but a polymer material having a polar group is preferable. Such polymer materials include chloroprene rubber, acrylonitrile-butadiene rubber, fluorine rubber, ethylene-vinyl acetate copolymer, polyvinyl butyral, chlorosulfonated polyethylene, chlorinated polyethylene, vinyl chloride resin, chlorinated vinyl chloride. The resin, vinylidene chloride resin, vinyl chloride-vinylidene chloride copolymer, halogenated polymer, fluorine polymer, bromine polymer, polyurethane thermoplastic elastomer, polyester thermoplastic elastomer, and polyamide thermoplastic elastomer are appropriately selected.

If the halogen content of the organic polymer material is too small, the vibration damping property is lowered, and if it is too large, the vibration damping sheet becomes too hard and it becomes difficult to mold, so it is preferably 20 to 70% by weight.

The method for producing a vibration damping sheet made of an organic polymer material is not particularly limited, and may be a general sheet molding method such as an extrusion molding method, a calendar molding method, a solvent casting method, or the like. The obtained sheet is cut into a required size and used for the construction of the soundproofing device. The organic polymer material constituting the vibration damping sheet is preferably composed of a chlorinated polymer material and chlorinated paraffin.

If necessary, a filler may be added to the resin composition containing the chlorinated paraffin mixture.

The restraining member provided on the vibration damping sheet preferably has a longitudinal elastic modulus of 1 GPa or more.

Examples of such restraining members include lead, iron, steel (including stainless steel), aluminum and other metal materials; concrete, gypsum board, marble, slate plate, sand plate, glass and other inorganic materials; polycarbonate, polysulfone, etc. Bisphenol A modified resin; poly (meth)
Acrylic resins such as acrylates; Chlorine resins such as vinyl chloride resins and chlorinated vinyl chloride resins; Rubber materials such as acrylonitrile-butadiene-styrene rubber; Saturated polyesters such as polyethylene terephthalate and polyethylene naphthalate; Styrene resins Olefin resin such as polyethylene and polypropylene; polyamide resin such as nylon 6, nylon 66 and aramid (aromatic polyamide); melamine resin; polyimide resin; urethane resin; thermosetting such as dicyclopentadiene and bakelite Resins; Cellulosic materials such as wood and paper; plate materials or sheets made of chitin, chitosan and the like.

These may be used alone or in combination of two or more. The restraining member may be reinforced with glass fiber, carbon fiber, liquid crystal or the like, may be a composite plate made of different materials, or may be a foam made of these materials.

The sound absorbing plate according to the present invention is such that the surface on the hole opening side is applied to the reflecting plate and many holes are blocked, so that it can exhibit high sound absorbing performance for low frequency sound. The thickness of the sound absorbing plate can be reduced.

  Next, embodiments of the present invention will be described with reference to the drawings.

Embodiment 1 of the Invention
1 and 2, the sound absorbing plate (1) has a number of holes (3) formed from one side of the polystyrene foam plate (2) to the other side, and a number of holes (3) are formed. It is configured as a closed tube air column. The openings of the numerous holes (3) are formed so as to be aligned vertically and horizontally as viewed in a plane, but they can be arranged in a staggered manner, randomly, or appropriately.

FIG. 3 shows an example in which the sound absorbing plate (1) shown in FIG. 1 and FIG. 2 is applied to the soundproof wall (7) on the surface of the hole opening side and many holes (3) are closed. Indicates. The sound wave reaches the sound absorbing plate (1) as indicated by an arrow.

FIG. 4 shows a modification of the sound absorbing plate. In the sound absorbing plate (1) of FIG. 4 (a), the length of the closed tube air column portion, that is, the length (depth) of the hole (3) is set to 20 mm, 3 mm, respectively, in the plate body (2) having a constant thickness.
0mm and 40mm are different from each other. In the sound absorbing plate (1) of FIG. 4 (b), the plate body (2) is integrally constructed from a plurality of portions having different plate thicknesses and depths of the holes (3). FIG. 4 (c)
In the sound absorbing plate (1), the plate thickness and the depth of the hole (3) are gradually increased from one end to the other end. Thus, the frequency band of the sound absorption target can be set by adjusting the length, that is, the depth of the hole constituting the closed tube air column.

FIG. 5 shows another modification of the sound absorbing plate. In the sound absorbing plate (1) in FIG.
A large number of holes (3) are formed in an oblique direction with respect to the thickness direction of the plate (2). In the sound absorbing plate (1) of FIG. 5 (b), a large number of holes (3) are formed obliquely with respect to the thickness direction of the plate (2) whose thickness is gradually increased. By forming a large number of holes in the oblique direction of the plate body in this way, the length of the hole, and hence the closed tube column, can be reduced compared to the case of forming a large number of holes in a direction perpendicular to the expanding direction of the plate body. It is possible to increase the length of the holes to be formed, and therefore it is possible to adapt to a lower frequency band without increasing the thickness of the plate.

Depending on the application requiring fire resistance, weather resistance, and scratch resistance, as shown in FIGS. 6 and 7, a plate body (2) having a large number of holes (3) open at both ends may be used as a protective plate (4). You may coat with. In FIG. 6, the hole opening on the front surface is closed with a protective plate (4). Even in this case, the covering with the protective plate (4)
It is not necessary to cover the whole plate body (2), and it is sufficient to cover at least the front surface portion (2a) and the side surface portion (2b) of the plate body (2). Accordingly, since it is not necessary to cover the entire plate as in the case of using glass wool as the sound absorbing material, the sound absorbing plate can be configured to be lighter. In FIG. 7, a large number of holes (3) are opened only on the rear surface, and the protective plate (4) is configured to cover the rear surface portion (2c) of the plate body (2).

FIG. 8 shows a damping sheet (5) made of an organic polymer material having a peak value of 1.5 or more as a protective plate (4), and a longitudinal elastic modulus provided outside the damping sheet. An example using a member composed of a restraining member (6) of 1 GPa or more is shown. Protective plate consisting of damping sheet and restraining member
(4) covers the front surface portion (2a) and the side surface portion (2b) of the plate body (2) as well as a part of the rear surface portion (2c). In the embodiment of the present invention, the hole opening on the front surface is closed by the protective plate (4) among the many holes (3) open at both ends. However, as shown in FIG. May be opened only on the rear surface.

The vibration damping sheet (5) is produced as follows. 100 parts by weight of chlorinated polyethylene (manufactured by Showa Denko KK, trade name “Elaslene 402NA”, chlorine content 40% by weight), chlorinated paraffin (manufactured by Asahi Denka Co., product number “E500”, chlorine content 50% by weight, average 1 carbon
4, 200 parts by weight of carbon number 12-16 = 99% by weight or more, chlorinated paraffin (manufactured by Ajinomoto Fine Techno Co., trade name “Empara 70”, chlorine content 70% by weight, average number of carbons 26,
200 parts by weight of carbon number 20-50 = 99% by weight or more) was kneaded with a roll kneader, and the obtained resin kneaded product was pressed at 120 ° C. to obtain a sheet having a thickness of 0.4 mm. This was cut to a required size to produce a vibration damping sheet having a thickness of 1.0 mm. The tan δ of the resin kneaded product is 3.5.
Met.

The restraining member (6) is a steel plate (longitudinal elastic modulus 25) of the same size as the vibration damping sheet (5) and having a thickness of 1.0 mm.
0 GPa), which is bonded to the vibration damping sheet (5) without an adhesive.

FIG. 9 shows a sound-absorbing plate (1) that requires fire resistance, weather resistance, and scratch resistance, and the front surface portion (2a), side surface portion (2b), and rear surface portion (2c) of the plate body (2), that is, the plate An example in which the entire body is covered with a protective plate (4) is shown. In the embodiment of the present invention, a large number of holes (3) are opened only on the front surface, and these hole openings are closed by the protective plate (4), but the large number of holes (3) are open at both ends. These are all protective plates
(4) may be closed.

Embodiment 2 of the Invention
In FIG. 10, a sound absorbing material (10) made of a polyester fiber sheet is interposed between a sound absorbing plate (1) having the same configuration as in FIG. 4 (c) and a reflecting plate (9) arranged on the opening side. It is installed.

Embodiment 3 of the Invention
In FIG. 11, a synthetic resin having a number of bottomed holes (21) between a sound absorbing plate (1) having the same configuration as in FIG. 4 (c) and a reflecting plate (9) arranged on the opening side thereof. A sound absorbing material (10) made of a plate is interposed. The many bottomed holes (21) of the sound absorbing material (10) are open on the surface opposite to the reflecting plate (9) and deviate from the many bottomed holes (3) of the sound absorbing plate (1). It is designed to utilize air column resonance.

Embodiment 4 of the Invention
In FIG. 12, in the sound absorbing plate formed by forming a large number of closed tube air column portions by forming a large number of holes in the plate body from one surface side to the other surface side, some holes are formed in a large number of through holes ( 23) to form a large number of open tube air column portions.

Embodiment 5 of the Invention
In FIG. 13, in the sound absorbing plate in which a large number of holes are formed in the plate body from one surface side to the other surface side to constitute a large number of closed tube air column portions, some of the holes are many from the other surface side to the one surface side. A plurality of closed-pipe air column portions are formed by forming a hole (24).

Embodiment 6 of the Invention
In FIG. 14, a sound absorbing plate (31) comprising a large number of closed tube air column portions is a plate body (32) having a large number of through holes (material: a single plate having a thickness of 5 mm is laminated to a thickness of 400). Corrugated plastic corrugated board, plate size: 400 mm x 700 mm, plate hole diameter: 4 mm, aperture ratio: 70%, surface area: 2.8 m ² ), and hole closing member (33) bonded to one side of the plate body Become. Hole closing member (33)
Is made of an aluminum thin plate having a thickness of 0.5 mm.

Embodiment 7 of the Invention
In FIG. 15, in the sound absorbing plate (31) having the configuration of the sixth embodiment of the present invention, a sound absorbing material (34) made of glass wool board having a thickness of 25 mm is provided on the side surface of the hole opening.

Embodiment 8 of the Invention
In FIG. 16, in the sound absorbing plate (31) having the configuration of the sixth embodiment of the invention, a plate body (32) having a large number of through holes and a hole closing member (33) bonded to one surface of the plate body. A sound absorbing material (34) made of glass wool board having a thickness of 25 mm is interposed therebetween.

Comparative form 1
In FIG. 17, the sound-absorbing plate (31) is a plate having a number of through-holes having the configuration of the sixth embodiment of the invention.
(32) only.

Example 1
1 and FIG. 2 (material: Styrofoam, plate size: 400 mm × 350
mm, plate thickness: 150 mm, number of sheets: 20, hole depth: 140 mm, hole diameter: 4 mm, hole pitch: 14 mm) with the hole opening side facing down on the floor of the residual sound chamber 1.5 m from the floor and many holes were blocked by the floor surface. With this structure, the sound absorption rate was measured by the method specified in JIS A 1409. That is, as a sound source, two speakers are installed in the vicinity of the wall in the residual sound room at intervals of 3.5 m, three microphones are 1.5 m from the sound absorbing plate, 1.5 m from the wall and the floor, and 2 from the sound source. It was installed in the residual sound chamber at a position 5 m away and the sound absorption coefficient was measured.
The measurement results are shown in the graph of FIG.

Comparative Example 1
The same sound absorbing plate as in Example 1 was placed on the floor with the hole opening side facing up. With this structure, the sound absorption rate was measured by the method specified in JIS A 1409. This measurement result is also shown in the graph of FIG.

As is apparent from FIG. 18, in Comparative Example 1, a high sound absorption coefficient is obtained at a frequency at which the length of the air column tube coincides with 1/4, 3/4, or 5/4 of the wavelength, and air column resonance occurs. The sound absorption due to. On the other hand, in Example 1, a high sound absorption rate was obtained with respect to low frequency (around 315 Hz) sound.

Example 2
As shown in FIG. 19, a sound absorbing plate having a large number of through holes (23) shown in FIG. 20 (material: corrugated board, plate size: 400 mm × 700 mm, plate thickness: maximum 140 mm to minimum 60 mm, number of sheets:
20 sheets, hole diameter: 4 mm, open area ratio: 70%, surface area: 2.8 m ² ) (11) The 10 mm thick polystyrene sheet (13) is bonded to the entire inclined surface (12), and a number of through holes ( 23) The opening on the inclined surface side was closed. Ten sound absorbing plates with a foamed polystyrene plate were placed on the floor of the residual sound chamber (volume: 200 m ² ) 1.5 m away from the wall so that each inclined surface (11) was on the top. With this structure, one speaker as a sound source is installed near the wall in the residual sound room at an interval of 3.5 m, three microphones are 1.5 m from the sound absorbing plate, 1.5 m from the wall and the floor, and the sound source (Pink noise) to 2.
Installed in the residual sound chamber at a position 5 m away and measured the sound absorption coefficient (temperature 20 ° C., relative humidity 50%)
. The measurement results are shown in the graph of FIG.

Example 3
As shown in FIG. 22, a number of through holes shown in FIG.
Styrofoam plate having a thickness of 10 mm on the thick side half of the inclined surface (12) of the sound absorbing plate (11) having (23)
(14) was pasted, and the openings on the inclined surface side of many through holes (23) in this portion were closed. The other points were performed in the same manner as in Example 2, and the sound absorption rate was measured. The measurement results are shown in the graph of FIG.

As can be seen from the comparison between FIG. 21 and FIG. 23, the configuration of FIG. 22 improved the sound absorption rate particularly in the high frequency range.

Example 4
As shown in FIG. 24, in the configuration of the second embodiment (see FIG. 19), the sound absorbing plate and the reflecting plate floor
(16) Sound absorbing material (polyester fiber sheet with a density of 13 kg / cm ³ and a thickness of 90 mm)
(15) was installed. The other points were performed in the same manner as in Example 2, and the sound absorption rate was measured. The measurement results are shown in the graph of FIG.

As can be seen from a comparison between FIG. 21 and FIG. 25, the configuration of FIG. 24 improved the sound absorption coefficient in the entire frequency range.

Comparative Example 2
A sound-absorbing plate without a polystyrene foam plate having a large number of through-holes (23) shown in FIG. 20 (material: corrugated board, plate size: 400 mm × 700 mm, plate thickness: maximum 140 mm to minimum 60 mm, number of sheets: 20, hole diameter: 4 mm The aperture ratio: 70%, the surface area: 2.8 m ² ) (11) was used in place of the sound absorbing plate with the foamed polystyrene plate shown in FIG. The measurement results are shown in the graph of FIG.

As can be seen from a comparison between FIG. 26 and FIG. 21 showing the measurement results of Example 2, the configuration of Example 2 shown in FIG. 19 improved the sound absorption rate particularly in the low frequency range.

Example 5
As the sound absorbing plate, the one in the sixth embodiment of the invention shown in FIG. 14 is used.
The sound absorption coefficient was measured in the same manner as in the above. The measurement results are shown in the graph of FIG.

Example 6
The sound absorbing plate is the same as that of the seventh embodiment of the invention shown in FIG.
The sound absorption rate was measured in the same manner as in the above. The measurement results are shown in the graph of FIG.

Example 7
As the sound absorbing plate, the eighth embodiment of the invention shown in FIG.
The sound absorption coefficient was measured in the same manner as in the above. The measurement results are shown in the graph of FIG.

Comparative Example 3
As the sound absorbing plate, the one in the comparative form 1 shown in FIG. 17 was used, and other points were performed in the same manner as in the operation of Example 1, and the sound absorption rate was measured. The measurement results are shown in the graph of FIG.

It is a top view which shows the sound-absorbing board of embodiment of invention. It is sectional drawing which follows the II-II line | wire in FIG. It is sectional drawing which shows the example which applied the sound-absorbing board to the sound-proof wall with the surface at the hole opening side. It is principal part sectional drawing which shows the modification of a sound-absorbing board. It is principal part sectional drawing which shows the modification of a sound-absorbing board. It is principal part sectional drawing which shows the modification of a sound-absorbing board. It is principal part sectional drawing which shows the modification of a sound-absorbing board. It is principal part sectional drawing which shows the modification of a sound-absorbing board. It is a partially notched top view which shows the modification of a sound-absorbing board. It is a principal part top view which shows the modification of a sound-absorbing board. It is principal part sectional drawing which shows the modification of a sound-absorbing board. It is principal part sectional drawing which shows the modification of a sound-absorbing board. It is sectional drawing which shows the sound-absorbing plate of Embodiment 2 of invention. It is sectional drawing which shows the sound-absorbing plate of Embodiment 3 of invention. It is sectional drawing which shows the sound-absorbing plate of Embodiment 4 of invention. It is sectional drawing which shows the sound-absorbing plate of Embodiment 5 of invention. It is sectional drawing which shows the sound-absorbing board of Embodiment 6 of invention. It is sectional drawing which shows the sound-absorbing plate of Embodiment 7 of invention. It is sectional drawing which shows the sound-absorbing plate of Embodiment 8 of invention. It is sectional drawing which shows the sound-absorption board of the form 1 of a comparison. It is a graph which shows the relationship between the frequency by Example 1 and the comparative example 1, and a sound absorption coefficient. It is sectional drawing which shows the sound-absorbing board used in Example 2. It is sectional drawing which shows the sound-absorbing board used in the comparative example 2. It is a graph which shows the relationship between the frequency by Example 2, and a sound absorption coefficient. It is sectional drawing which shows the sound-absorbing board used in Example 3. It is a graph which shows the relationship between the frequency by Example 3, and a sound absorption coefficient. It is sectional drawing which shows the sound-absorbing board used in Example 4. It is a graph which shows the relationship between the frequency by Example 4, and a sound absorption coefficient. It is a graph which shows the relationship between the frequency by the comparative example 2, and a sound absorption coefficient. It is a graph which shows the relationship between the frequency by Example 5, and a sound absorption coefficient. It is a graph which shows the relationship between the frequency by Example 6, and a sound absorption coefficient. It is a graph which shows the relationship between the frequency by Example 7, and a sound absorption coefficient. It is a graph which shows the relationship between the frequency by the comparative example 3, and a sound absorption coefficient.

Explanation of symbols

1,11 Sound absorbing plate 2 Plate body 2a Front surface portion 2b Side surface portion 2c Rear surface portion 3 Hole (closed tube air column portion)
4 Protection plate 5 Damping sheet 6 Restraining member 7 Soundproof wall 8 Through hole 12 Inclined surface 13, 14 Styrofoam plate 10, 15 Sound absorbing material 9, 16 Reflecting plate 21 Bottomed hole 23 Through hole 24 Hole 31 Sound absorbing plate 32 Plate Body 33 Hole closing member 34 Sound absorbing material

Claims (10)

A sound-absorbing plate in which a large number of holes are formed on one side of the plate from the other side to form a number of closed tube air columns, and the surface on the hole opening side is applied to the reflective plate. A sound-absorbing plate that closes the holes. A plate with a large number of holes from one side to the other side to form a large number of closed tube air column parts, and a hole on the surface of the hole is applied to the reflective plate with a number of holes. Sound absorption method to close. The sound absorbing plate according to claim 1, wherein a sound absorbing material is interposed between the sound absorbing plate and the reflecting plate. The sound absorbing method according to claim 2, wherein a sound absorbing material is interposed between the sound absorbing plate and the reflecting plate. Some holes form a large number of closed air column parts by forming a large number of holes on the plate body from the other surface side to the one surface side,
The sound absorbing plate according to claim 1, wherein a number of through holes are formed on both sides of the plate body to constitute a number of open tube air column portions. Some holes form a large number of closed air column parts by forming a large number of holes on the plate body from the other surface side to the one surface side,
The sound absorbing method according to claim 2, wherein a plurality of through holes are formed on both sides of the plate body to form a large number of open tube air column portions. 2. The sound absorbing plate according to claim 1, wherein the sound absorbing plate comprising a large number of closed tube air column portions comprises a plate having a large number of through holes and a hole closing member provided on one side of the plate. The sound absorbing method according to claim 2, wherein the sound absorbing plate comprising a large number of closed tube air column portions comprises a plate having a large number of through holes and a hole closing member provided on one side of the plate. The sound-absorbing plate according to claim 7, wherein a sound-absorbing material is interposed between a plate having a large number of through holes and a hole closing member provided on one side of the plate. The sound absorbing method according to claim 8, wherein a sound absorbing material is interposed between a plate having a large number of through holes and a hole closing member provided on one side of the plate.

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