JP2005200913A - Sound absorbing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sound absorbing plate stable in a wide frequency area, having a high sound absorbing rate, and superior in high strength, durability and weatherability. <P>SOLUTION: This sound absorbing plate has a porous ceramic sound absorbing plate 10 provided with a plurality of through-holes 13, a cement-based rigid body porous sound absorbing plate 20 sticking to or abutting on one surface 12 of the porous ceramic sound absorbing plate 10, and a panel 30 integrally combined with the porous ceramic sound absorbing plate 10 and the cement-based rigid body porous sound absorbing plate 20. The panel 30 has a panel frame 31 and a panel plate 32, and an air layer 40 is arranged between the panel plate 32 and the cement-based rigid body porous sound absorbing plate 20. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a sound absorbing plate, and more particularly to a sound absorbing plate that absorbs traffic noise in roads and tunnels.

Conventionally, sound-absorbing plates used as sound barriers for highways and reflective sound countermeasures for digging sections and tunnels are porous sound-absorbing materials made of sintered ceramics (hereinafter referred to as porous ceramic sound-absorbing materials). ), Porous sound-absorbing materials composed of rigid structures such as cement-based and calcium silicate-based materials (hereinafter referred to as cement-based rigid porous sound-absorbing materials), foamed sound-absorbing materials mainly composed of cement and calcium silicate (hereinafter referred to as cement-based foaming) And so on) formed into a plate shape.
The materials that make up these sound absorbing plates have certain inherent characteristics such as the chemical composition, porosity, and air gap structure that affects the air flow resistance (venting resistance), making it difficult to improve the sound absorbing performance. Met.
In the case of a porous ceramic sound-absorbing plate, since there are restrictions on weight and economy, for example, the thickness is set to about 20 mm and an air layer is provided on the back surface, so that the panel is made vulnerable to impact. There was a drawback of being easily damaged.
Further, the cement-based rigid porous sound-absorbing plate or the cement-based foam sound-absorbing plate has a drawback that the surface is easily scratched because of insufficient surface hardness.

Further, an invention has been disclosed in which a number of holes having different depths are formed in the thickness direction of the porous ceramic sound absorbing plate to exhibit excellent sound absorbing performance in a wide frequency range (see, for example, Patent Document 1). .
Further, an invention has been disclosed in which a non-penetrating groove is provided in the thickness direction of a porous ceramic sound absorbing plate to exhibit excellent sound absorbing performance in a wide frequency range (see, for example, Patent Document 2).
Furthermore, an invention has been disclosed in which a large number of concave grooves are formed on one surface of a cement-based foam sound-absorbing material, and a sound-insulating back plate is directly joined to the back surface to form a panel to improve sound absorption performance, mechanical strength and workability. (For example, see Patent Document 3).
JP-A-9-328833 (page 2-3, FIG. 1) Japanese Patent Laid-Open No. 10-30288 (page 2-4, FIG. 1) JP 2000-56776 A (page 4, FIG. 4)

However, the invention disclosed in Patent Document 1 is various in particular when trying to flatten the sound absorption rate (no peak) in a high frequency range (the frequency of road traffic noise is high in 400 Hz to 1000 Hz). It is necessary to drill a large number of holes with a sufficient depth, which makes it difficult to form a ceramic block, leading to an increase in manufacturing cost.
The invention disclosed in Patent Document 2 has a flat sound absorption characteristic over a high frequency range because the sound absorption characteristic shows a peak at a specific frequency, and a satisfactory sound absorption coefficient cannot be obtained.
Furthermore, although the invention disclosed in Patent Document 3 can obtain a high sound absorption coefficient in the entire high frequency range, it is easy to be damaged due to the use of cementitious foam.

  The present invention has been made to solve such problems, and provides a sound absorbing plate having a high sound absorption rate that is stable in a wide frequency range, high strength, durability, and weather resistance. With the goal.

(1) A sound absorbing plate according to the present invention includes a porous ceramic sound absorbing plate provided with a plurality of through holes;
A cement-based rigid porous sound-absorbing plate or a cement-based foam sound-absorbing plate affixed or abutted to one surface of the porous ceramic sound-absorbing plate;
A panel in which the porous ceramic sound-absorbing plate and the cement-based rigid porous sound-absorbing plate or the cement-based foam sound-absorbing plate are combined together;

  (2) The panel includes a panel frame and a panel plate, and an air layer is provided between the panel plate and the cementitious rigid porous sound absorbing plate.

  (3) Further, the total area of the opening areas of the plurality of through holes is 10 to 30% of the surface area of the porous ceramic sound absorbing plate.

Since the sound absorbing plate according to the present invention is as described above, the following effects are obtained.
(I) Since a back-side sound absorbing plate made of a cement-based rigid porous sound absorbing plate or a cement-based foamed sound absorbing plate is disposed at the bottom of the through hole of the front surface side sound absorbing plate, it can be used in a wide range from a low frequency range to a high frequency range. High sound absorption rate is demonstrated.
(Ii) Since a high-hardness porous ceramic sound-absorbing plate is disposed as the surface-side sound absorbing plate, the surface-side sound absorbing plate is hardly scratched.
(Iii) It becomes possible to wash the surface-side sound absorbing plate with water by hard brushing.
(Iv) Since the cement-based rigid porous sound-absorbing plate or the cement-based foam sound-absorbing plate is affixed or brought into contact as the back-surface-side sound absorbing plate, the front-side sound absorbing plate is hardly broken against bending due to impact or the like.
(V) Furthermore, since the surface side sound absorbing plate is provided with a through hole, the surface is not blank and has excellent design.

[Embodiment 1]
FIG. 1 is a cross-sectional view schematically showing a sound absorbing plate according to Embodiment 1 of the present invention.
In FIG. 1A, the sound absorbing plate 1 includes a front side sound absorbing plate 10 provided with a plurality of through holes 13, a back side sound absorbing plate 20 disposed on the back side of the front side sound absorbing plate 10, and a front side. A panel 30 that holds the sound absorbing plate 10 and the back side sound absorbing plate 20 is provided. In addition, the back surface 12 of the front surface side sound absorbing plate 10 and the front surface 21 of the back surface side sound absorbing plate 20 are bonded or abutted with each other without being bonded by an adhesive.

The panel 30 includes a panel frame 31 and a panel plate 32, and the panel frame 31 holds the outer peripheral end surfaces of the front surface side sound absorbing plate 10 and the back surface side sound absorbing plate 20, and the panel plate 32 contacts the back surface 22 of the back surface side sound absorbing plate 20. It touches.
In FIG. 1B, the sound absorbing plate 2 has the panel plate 32 separated from the back surface 22 of the back surface side sound absorbing plate 20 to form an air layer 40 having a predetermined thickness. In addition, the same code | symbol is attached | subjected to this and the same part as (a) of FIG.

2A and 2B are external views showing the surface-side sound-absorbing plate of the sound-absorbing plate according to Embodiment 1 of the present invention, wherein FIG. 2A is a plan view and FIG.
2A and 2B, the rectangular front surface side sound absorbing plate 10 is provided with through holes 13 in a staggered manner. The surface-side sound absorbing plate 10 is a rectangular plate having a row direction (horizontal direction in the figure) of 323 mm and a column direction (vertical direction in the figure) of 480 mm, and the through holes 13 are arranged at intervals of 30 mm in the row direction. They are arranged in a staggered manner at intervals of 32 mm (odd lines are displaced by 15 mm in the row direction with respect to even lines).

At this time, if the inner diameter (diameter) of the through hole 13 is set to 10 to 30 mm, the entire surface area of the surface-side sound absorbing plate 10 when the through hole 13 is not provided (hereinafter referred to as the surface area of the sound absorbing plate) is all through. The ratio of the total area of the openings of the holes 13 (hereinafter referred to as the opening ratio) is 5 to 20%.
In addition, as for the planar shape of the through-hole 13, a circle is the best from the viewpoint of manufacture, but it may be a triangle, a quadrangle, or an ellipse.

The surface-side sound-absorbing plate 10 is an inorganic porous sound-absorbing material (porous ceramic sound-absorbing material), and the inorganic particles that form it are singular products such as mullite, alumina, silica, cordierite, or a mixture thereof. Crushing stone particles such as ceramic particles, ceramic waste, and silica sand can be appropriately applied.
On the other hand, the back-side sound absorbing plate 20 is a cement-based rigid porous sound-absorbing material or a cement-based foam sound-absorbing material.
Moreover, although the panel 30 is formed with the steel profile (channel) and the steel plate, it is not limited to this, For example, concrete etc. may be sufficient.

  Therefore, since the surface-side sound absorbing plate 10 is a combination of inorganic particles, it is harder and less likely to be scratched than a fibrous one. It is possible to wash with water by brushing. Moreover, since the through-hole 13 is vacant in the surface side sound-absorbing plate 10, it is excellent also in the design property by combining the magnitude | size and arrangement | positioning pattern of the through-hole 13 compared with a flat surface.

Moreover, since the cement-type rigid porous sound absorbing plate is used in combination as the back surface side sound absorbing plate, the front side sound absorbing plate 10 is reinforced, so that it is difficult to break against bending due to impact or the like.
In addition, it demonstrates below that the sound-absorbing board 1 has a high sound absorption rate in a wide frequency range from a low sound range to a high sound range.

3 to 5 are experimental results showing the sound absorption characteristics of the sound absorbing plate according to the first embodiment of the present invention. The vertical axis represents normal incidence sound absorption coefficient (hereinafter referred to as sound absorption coefficient), and the horizontal axis represents frequency.
FIG. 3 shows the effect of a through hole provided in the surface side sound absorbing plate. The sound absorbing plate S is a porous ceramic sound absorbing plate having a thickness of 20 mm, which is a surface side sound absorbing plate, and a cement having a thickness of 50 mm. A sound-absorbing plate A is a surface-side sound-absorbing plate in which a through-hole having a diameter of 15 mm (opening ratio: 14%) is provided in a 20 mm-thick porous ceramic sound-absorbing plate. On the other hand, a cement-based rigid porous sound-absorbing plate having a thickness of 50 mm is bonded as a back-side sound-absorbing plate. In FIG. 3, the improvement effect of the sound absorption rate by providing a through-hole becomes remarkable, so that it becomes a high sound range.

  FIG. 4 shows the effect of the material of the back surface side sound absorbing plate that closes the bottom of the through hole for the porous ceramic sound absorbing plate provided with the through hole. The sound-absorbing plate A is a cement-based rigid porous sound-absorbing plate having a thickness of 50 mm, compared with a surface-side sound-absorbing plate in which a through-hole having a diameter of 15 mm (opening ratio: 14%) is provided in a porous ceramic sound-absorbing plate having a thickness of 20 mm. Adhered as a back-side sound absorbing plate (same as in FIG. 3), and sound-absorbing plate B was bonded with a 50 mm-thick porous ceramic sound-absorbing plate as a back-side sound-absorbing plate (that is, a 70 mm-thick porous ceramic sound-absorbing plate) The sound-absorbing plate C is obtained by contacting a 50 mm-thick concrete plate as a back-surface-side sound-absorbing plate.

In FIG. 4, the sound absorbing plate A (the cement-based rigid porous sound absorbing plate is used as the back side sound absorbing plate) is higher than the sound absorbing plate B (the porous ceramic sound absorbing plate is used as the back side sound absorbing plate). It has a high sound absorption coefficient in a wide frequency range over the sound range. Further, the sound absorbing plate C (concrete plate is the back side sound absorbing plate) has an extremely low sound absorbing rate compared to the sound absorbing plate B, and the sound absorbing rate is higher than the sound absorbing plate S (see FIG. 3) having no through holes. Is low.
That is, since the sound that has entered the through hole is absorbed or reflected by the material that closes the bottom of the through hole, in particular, the sound absorbing plate A has a cement-based rigid porous sound absorbing plate with excellent absorption performance at the bottom. The sound absorption rate is superior to that of the sound absorption plate B (corresponding to a blind hole) having a porous ceramic sound absorption plate at the bottom.
On the other hand, the sound absorbing plate C has a lower sound absorption rate than the sound absorbing plate S (see FIG. 3) that does not have a through hole, even though the surface side sound absorbing plate has a through hole. This is because the sound that has entered the through hole is reflected by the concrete that closes the bottom of the through hole and is radiated from the through hole again, so that the radiated sound has a surface area equivalent to the through hole of the surface-side sound absorbing plate. It is estimated that the sound is louder than the sound reflected at. That is, it is considered that the minus effect due to the reflected sound from the bottom becomes more prominent than the plus effect due to the provision of the through hole.
This indicates that one of the through holes needs to be closed with a material having a high sound absorption rate in order to provide the sound absorption plate with a through hole and obtain an improvement in the sound absorption rate of the sound absorption plate.

FIG. 5 shows the thickness of the back side sound absorbing plate and the effect of the air layer provided behind the back side sound absorbing plate. The thickness is 20 mm provided with a through hole having a diameter of 15 mm (opening ratio: 14%). The thickness of the back-side sound absorbing plate made of a cement-based rigid porous sound-absorbing plate and the support procedure behind the back-side sound-absorbing plate are changed using the porous ceramic sound-absorbing plate as the front-side sound absorbing plate.
The sound absorbing plate F is such that the thickness of the back side sound absorbing plate is 30 mm and an air layer having a thickness of 20 mm is provided behind it. In FIG. 5, the sound absorbing plate F has a higher sound absorption rate in the mid-high range than that of the sound absorbing plate A. That is, although the sound absorption performance is deteriorated by reducing the thickness of the back-side sound absorbing plate (decrease by 20 mm), the deterioration is complemented by providing an air layer. Better sound absorbing performance is obtained than when the back side sound absorbing plate is thick (50 mm).
Therefore, in addition to the improvement of the sound absorbing performance, the amount of the back surface side sound absorbing plate is greatly reduced, thereby reducing the weight of the sound absorbing plate and reducing the manufacturing cost. In addition, in order to obtain an equivalent sound absorption rate, the back side sound absorbing plate can be made thinner by providing an air layer. Therefore, the panel incorporating the back side sound absorbing plate is lightweight and inexpensive. As a result, the workability (handling property) is improved.

The above describes the case where a cement-type rigid porous sound-absorbing plate is used as the back-side sound-absorbing plate, but it goes without saying that a cement-type foamed sound-absorbing plate having the same level of sound-absorbing characteristics may be used.
Table 1 shows physical property values of the porous ceramic sound absorbing plate forming the front surface side sound absorbing plate 10, and Table 2 shows physical property values of the cement-based rigid porous sound absorbing plate forming the back surface side sound absorbing plate 20.

[Embodiment 2]
FIG. 6 schematically shows a sound-absorbing panel according to Embodiment 2 of the present invention, in which (a) is a front view and (b) is a cross-sectional view. In addition, the same code | symbol is attached | subjected to this same part as Embodiment 1 (FIG. 1, 2), and one part description is abbreviate | omitted.
6, the sound absorbing panel 3 includes a sound absorbing plate 2 (width 480 mm × height 323 mm, surface side sound absorbing plate thickness 20 mm, back surface side sound absorbing plate thickness 30 mm, air layer thickness 20 mm, FIG. 6) are arranged in a single panel.
The panel 30 includes a rectangular panel frame 31 formed by horizontal steels 31 a and 31 c and vertical steels 31 b and 31 d and a panel plate 32. The panel board 32 has two rows of recesses 32b and 32d, attachment portions 32a and 32e, and a central support portion 32c. The peripheral edge of the sound absorbing plate 2 is held by the panel frame 31, the center of the back surface 22 is supported by being in contact with the support portion 32c, and two rows of air layers 40 are formed on the back surface side by the recesses 32b and 32d. ing.

Therefore, since the sound absorbing plate 2 is protected by the panel 30 and can be fixed to the wall surface in units of the panel 30, the handling property is improved and the construction work is facilitated. By arranging the plurality of panels 3 in the horizontal direction and the vertical direction, it is possible to easily and quickly form a soundproof wall having a predetermined spread.
Note that a pressing material may be disposed around the front surface side sound absorbing plate 10 to directly hold the back surface side sound absorbing plate 20. Moreover, you may provide the support part 32c in several places, or may abbreviate | omit. Further, the sound absorbing plate 1 (without an air layer) may be incorporated in the sound absorbing panel 3.

  The present invention can be widely used for sound absorbing plates installed outdoors and indoors in structures.

Sectional drawing which shows typically the sound-absorbing board which concerns on Embodiment 1 of this invention. The external view which shows the surface side sound-absorption board of the sound-absorption board which concerns on Embodiment 1 of this invention. The experimental result which shows the sound absorption characteristic (effect of a through-hole) of a sound-absorbing board. The experimental result which shows the sound absorption characteristic (effect of the material of a back surface side sound absorption board) of a sound absorption board. The experimental result which shows the sound absorption characteristic (effect of an air layer) of a sound-absorbing board. The front view and sectional drawing which show typically the sound-absorbing panel which concerns on Embodiment 2 of this invention.

Explanation of symbols

1 sound absorbing plate, 2 sound absorbing plate, 3 sound absorbing panel,
10 surface side sound absorbing plate, 11 surface, 12 back surface,
13 through-holes, 20 back side sound absorbing plate, 21 surface,
22 back side, 30 panel, 31 panel frame,
32 panel boards, 40 air layers

Claims (3)

A porous ceramic sound absorbing plate provided with a plurality of through holes;
A cement-based rigid porous sound-absorbing plate or a cement-based foam sound-absorbing plate affixed or abutted to one surface of the porous ceramic sound-absorbing plate;
A sound-absorbing plate having the porous ceramic sound-absorbing plate and a panel integrally combining the cement-based rigid porous sound-absorbing plate or the cement-based foam sound-absorbing plate.   The sound absorbing plate according to claim 1, wherein the panel includes a panel frame and a panel plate, and an air layer is provided between the panel plate and the cement-based rigid porous sound absorbing plate. The sound absorbing plate according to claim 1 or 2, wherein the total area of the opening areas of the plurality of through holes is 10 to 30% of the surface area of the porous ceramic sound absorbing plate.

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