JPH0798590A - Sound absorbing material - Google Patents

Abstract

PURPOSE:To obtain a good shape retaining property, a large sound absorbing characteristic in a low frequency band and a high sound absorption rate in a wide frequency band from a low frequency to a high frequency by packing powders which develop sound absorbing performance by the vibrations of the powder particles themselves into the holes bored in a perforated sound absorbing material. CONSTITUTION:Rock wool 1 which is the perforated sound absorbing material is bored with the holes 6 and powder sealing containers 3 consisting of acrylic cylinders are arranged into these holes 6. The powders 2 which develop the sound absorbing performance by the vibrations of the powder themselves are packed into the these powder sealing containers 3. The upper and lower parts of the powder sealing containers 3 are capped with polyethylene(PE) films so as to prevent the spilling of the powders. Such thin PE films have sound wave transmittability and, therefore, the incident sound waves easily infiltrate the inside of the powder sealing containers 3 and excite a vibration mode. As a result, the sound absorption performance is high from the broad frequency band from the low frequency to the high frequency and the shape retaining property is obtd. as well.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound absorbing material.

[0002]

2. Description of the Related Art Conventionally, there is a sound absorbing material used in the following cases.

(1) Used as an interior material for listening rooms, musical instrument practice rooms, etc. In a room where the acoustic characteristics of the room are a problem, it is used as an interior finishing material to control the reverberation time characteristics and reflection characteristics of the room.

(2) Used as a filling material for walls and ceilings.
In a room where sound insulation performance is required, a double wall structure is often adopted to improve the sound insulation performance of walls and ceilings.
A sound absorbing material is filled between the double walls to further improve the performance.

(3) In addition, for attaching the sound absorbing duct inside,
It is also used for attaching the soundproof cover of equipment that generates noise.

Porous sound absorbing materials such as glass wool, rock wool, and urethane foam are used as one kind of the sound absorbing material used for the above-mentioned applications. When a sound wave is incident on the inside of communicating bubbles, these porous sound absorbing materials are continuous bubbles with a complicated cross-sectional shape, so viscous friction with the bubble wall surface during propagation of the sound wave. The sonic energy is absorbed by the material. The broken line in FIG. 3 shows the frequency characteristics of the normal incident sound absorption coefficient of rock wool (density 40 kg / m ³ , thickness 30 mm).

The sound absorption characteristics of glass wool and urethane foam are similar, but they have a small sound absorption coefficient in the low frequency band. If the thickness of the porous material is increased, the sound absorption coefficient in the low frequency band can be increased, but if the thickness is increased, the room becomes narrower when used as an interior material for the room. Further, when it is used as an inside attachment of a duct, there arises a problem that an air passage becomes narrow.

For sound waves in the low frequency band, there is a sound absorbing material utilizing the vertical vibration of the powder tank. Several μm to several hundred μ
When a sound wave is incident on a powder layer (sound absorbing material) made of m particles, the longitudinal vibration mode of the powder layer 10 as shown in FIG. 15 is excited, and the sound absorption coefficient increases in the frequency band in which the mode occurs. Reference numeral 11 is a rigid wall provided with the powder layer 10. In the primary mode, 1/4 of the wavelength in the powder layer 10 is
Although it occurs at a frequency that matches the thickness of the powder layer 10, the powder layer 1
Since the velocity of the elastic wave in 0 is generally as low as several tens of m / sec, the first-order mode occurs in a low frequency band of 500 Hz or less even in a thin layer with a thickness of about 30 mm. By using the powder layer 10 made of such powder particles, a sound absorbing material that efficiently absorbs sound waves in the low frequency band can be designed. Fig. 3 shows white carbon (average particle size 83 μm, bulk density 98 kg
/ M ³ and thickness 30 mm)
It can be seen that it has a high sound absorption coefficient in the low frequency band around 270 Hz. By changing the type of powder particles and the powder layer thickness, it is possible to change the frequency with a high sound absorption coefficient (sound absorption peak frequency) to match the frequency of the noise source. However, since the powder has fluidity, it must be enclosed in cells such as a honeycomb when it is actually used, which is very difficult to use. Further, there is a drawback that the sound absorption band is narrow.

[0009]

In view of the above-mentioned circumstances, the present invention has a shape-retaining property and has a large sound absorbing property in a low frequency band. Another object is to provide a sound absorbing material having a high sound absorption coefficient in a wide frequency band from low frequencies to high frequencies.

[0010]

Means for Solving the Problems The first aspect of the invention of this application
Is a porous sound absorbing material such as glass wool or rock wool 1
The sound absorbing material is characterized in that the perforations 6 pierced in the space are filled with the powder 2 that exhibits sound absorbing performance by vibration of the powder particles themselves.

As the porous sound absorbing material 1, glass wool,
A material having shape retention property is used, such as rock wool.

The perforations 6 formed in the porous sound absorbing material 1 preferably have a diameter of about 20 mm to 100 mm.

As the powder 2, a material such as mica, talc, permukilite or the like having a good sound absorbing material characteristic in a low frequency band due to vibration of self-excited particles is used.

The openings of the perforations 6 filled with the powder band 2 are preferably sealed with a polymer film 4 or the like.

The second aspect of the invention of this application is the porous sound absorbing material 1
The sound absorbing material according to claim 1, wherein a hard plate 5 made of plywood, a plastic plate, an iron plate, or the like is installed on a surface portion other than the perforations 2.

As the rigid plate 5, wood plywood, plastic plate, iron plate, or the like is used. A third aspect of the invention of this application is to use the sound absorbing material according to claim 1 or 2 for a plywood plate, an iron plate,
The sound absorbing box or the sound absorbing material panel has improved shape retention by being put in a box 7 or a frame 8 made of a plastic plate or the like.

The box 7 or the frame 8 is formed of plywood, plastic plate, iron plate or the like.

A fourth aspect of the invention of this application is a sound insulation in which the sound absorbing material or the sound absorbing panel according to claim 1, 2 or 3 is arranged in a gap between a double wall or a double floor to improve sound insulation. It has a double wall structure.

A fifth aspect of the invention of this application is that the sound absorbing material or the sound absorbing panel according to claim 1, 2 or 3 is arranged in a gap between a double wall or a double floor to improve the sound insulating property. It has a double floor structure.

[0020]

The sound absorbing material according to claim 1 has a high sound absorbing performance in a wide frequency band from a low frequency to a high frequency and also has a shape retaining property.

In the sound absorbing material according to the second aspect, the sound absorbing coefficient in the high frequency band is low, but the sound absorbing peak frequency in the low frequency band becomes low. That is, it is possible to provide a thinner and low-frequency sound absorbing material.

In the sound absorbing panel according to the third aspect, the shape retention of the sound absorbing material is enhanced. According to the sound absorbing structure of the fourth aspect, the sound insulation performance of the double wall is enhanced.

According to the sound absorbing structure of the fifth aspect, the sound insulation performance of the double floor is enhanced.

[0024]

【Example】

(Embodiment 1) Embodiment 1 of the present invention will be described with reference to FIGS. As shown in FIG. 1, rock wool 1 (density 40 kg / m ³ , thickness 30 mm, size 600 × 600 mm), which is a porous sound absorbing material, is provided with a hole 6 having a diameter of 60 mm, and the hole 6 is shown in FIG. Outer diameter 60 mm, inner diameter 58 mm
Then, the powder band enclosing container 3 made of an acrylic cylinder having a length of 30 mm is arranged. The powder zone 2 has an average particle size of 83 μm and a bulk density of 9
8 kg / m ³ of white carbon was used. The upper and lower parts of the container have a thickness of 250μ to prevent powder 2 from leaking.
Although the polyethylene film 4 of m 2 is covered, since such a thin polyethylene film 4 is sound-transmitting, the incident sound wave easily penetrates into the powder enclosure 3 and excites the vibration mode. . The sound absorption coefficient of rock wool 1 is α ₁ (τ), and the sound absorption coefficient of white carbon 2 is α ₂ (f)
Then, the sound absorption coefficient α (f) for each angular frequency in the first embodiment has a value approximately represented by the following equation.

Α (f) = (S ₁ α ₁ (f) + S ₂ α ₂
(f)) ÷ (S ₁ + S ₂ ), where S ₁ is the surface area of the rock wool portion of Example 1,
Similarly, S ₂ is the surface area of the powder portion of Example 1, S ₁ = 22
It is 15 cm ² , and S ₂ = 1385 cm ² . f represents the frequency.

The sound absorption coefficient characteristics of Example 1 are shown in FIG. 3 in comparison with those of rock wool and white carbon alone.

As shown in FIG. 3, the first embodiment exhibits high sound absorption coefficient characteristics in a wide frequency band. The porous sound absorbing material 1 is not limited to rock wool, but may be glass wool, urethane foam, or the like. Further, the powder 2 is not limited to white carbon, and any powder such as mica, talc, vermiculite that exhibits sound absorbing performance in a low frequency band due to vibration of the particles themselves may be used. Further, the dimensions, thickness, shape, size, number, etc. of the porous sound absorbing material 1 need to be changed according to the application. The material for the powder enclosing container 3 shown in FIG. 2 is not limited to acrylic and polyethylene films. (Second Embodiment) FIG. 4 shows a second embodiment according to the present invention.

The basic structure is the same as in Example 1, but the powder 2 was directly enclosed in the perforations of the rock wool 1 without using the powder enclosure 3 shown in FIG. Then, the entire surface is covered with the polyethylene film 4. In this case, although the structure is simpler than that of the first embodiment, since the pressure of the sound wave that has passed through the rock wool 1 is directly applied to the side surface of the powder cylinder, longitudinal vibration in the powder is less likely to occur and the low frequency band is generated. The sound absorption coefficient is slightly lower than in Example 1. The sound absorption coefficient characteristic of the first embodiment is shown in FIG. (Third Embodiment) A third embodiment according to the present invention is shown in FIG.

The basic structure of this embodiment is the same as that of the second embodiment, but in the case where the perforations 6 of the rock wool 1 do not penetrate as shown in the figure. The diameter of the perforations 6 is 60 mm and the depth is 20 mm.

Even in this case, the vertical vibration of the powder zone 2 occurs, and the sound absorption characteristics are almost the same as those of the second embodiment shown in FIG. (Fourth Embodiment) A fourth embodiment according to the present invention is shown in FIG. The structure is different from that of Example 2 in that only the surface of the rock wool 1 is covered with an acrylic plate (thickness 5 mm) that does not easily vibrate with respect to sound waves. The surface of the powder 2 is covered with a polyethylene film 4 having a thickness of 250 μm.

The opening of the hole 12 of the acrylic plate 5 is 60 mm.
And is the same as the outer diameter of the powder layer. With such a configuration, the sound absorption coefficient in the high frequency band is reduced, but the reflection of the pressure of the sound wave on the opening surface of the powder layer is reduced, and the frequency where the longitudinal vibration mode of the powder layer is generated is in the low range. Turn into. That is, the sound absorption coefficient increases in the low frequency band.

The sound absorption coefficient characteristic of the fourth embodiment is shown in FIG.
The thickness of the acrylic plate as the rigid plate 5 that covers one portion of the rock wool is not limited to 5 mm, but it is necessary to have a thickness of about 2 mm or more under the condition that it does not vibrate due to sound waves. As the rigid plate 5, it is necessary to have a thickness of about 0.5 mm in the case of an iron plate without using an acrylic plate and about 3 mm in the case of a wooden plywood. (Fifth Embodiment) A fifth embodiment according to the present invention is shown in FIG. In this example, the holes 1.2 of the acrylic plate 5 used in Example 4 were used.
The diameter is changed from 60 mm to 34 mm, and the other structure is similar to that of the fourth embodiment. By doing so, the longitudinal vibration mode of the powder layer is further generated on the low frequency band side, and the sound absorption peak frequency is lowered. The sound absorption coefficient characteristics of this example are shown in FIG. (Embodiment 6) An embodiment based on the present invention is shown in FIG. The sound-absorbing panel of Example 1 shown in FIG. 1 is put into a frame 8 made of plywood (thickness 3 mm) to form a sound-absorbing panel, which further enhances the shape retention. The sound absorbing characteristics of this sound absorbing panel are almost the same as those of the first embodiment. (Embodiment 7) Embodiment 7 of the present invention will be described with reference to FIGS.
Will be explained. As shown in FIG. 11, a 60 mm thick rock wool 1 having a large number of perforations 4 with a diameter of 84 mm is placed in a box 7 made of plywood, and sepiolite powder 2 is enclosed in the perforations 6 and the rock wool part Only the lid is covered with an acrylic plate 5 to form a sound absorbing box 18.

Sepiolite powder 2 (average particle size of about 50 μm
The bulk density of 250 kg / m ³ ) alone has a sound absorption peak at a frequency of about 130 Hz with a thickness of 60 mm, and the sound absorption performance can be enhanced in the low frequency band by configuring as shown in FIG. The sound absorbing box 18 of FIG. 11 is shown in FIG.
As shown in 2, it is arranged in the void portion of the double bed. Two
The structure of a heavy floor comprises a slab 17 and a floor board 15 in which a particle board 13, a plywood 14 and the like are laminated on a slab 17 via a bundle 16. The size of the floor plate of the double floor is 900 × 900 mm, but when six sound absorbing boxes 18 shown in FIG. 11 are placed under one floor plate 15, the heavy impact sound insulation performance is improved as shown in FIG. Especially, it is improved in the low frequency region of 250 Hz or less.

FIG. 13 is a graph comparing the floor impact sound level (L value defined in JIS) of the double floor using the sound absorbing box 18 with that without using the sound absorbing box 18. It can be seen that the case is improved. (Embodiment 8) An embodiment based on the present invention is shown in FIG. 2 holes of 90 mm thick sound absorbing material filled with white carbon powder 2 in perforations 6 of rock wool 1 (density 40 kg / m ³ ).
It is arranged in the void portion of the heavy wall 16.

The double wall 16 is 12 mm of the gypsum board 17.
It is formed by stacking two sheets having a thickness of 150 mm across a stud 18 of 150 mm square.

By adopting such a structure, the sound transmission loss of the wall can be improved.

[0037]

According to the sound absorbing material of the first aspect, it is possible to provide a sound absorbing material having a high sound absorbing performance in a wide frequency band from a low frequency to a high frequency and also having shape retention.

According to the sound absorbing material of the second aspect, it is possible to provide a sound absorbing material having a low sound absorbing peak frequency in the low frequency band, although the sound absorbing coefficient in the high frequency band is low.

In the sound absorbing panel according to the third aspect, shape retention of the sound absorbing material is enhanced. According to the sound absorbing structure of the fourth aspect, the sound insulation performance of the double wall is enhanced.

According to the sound absorbing structure of the fifth aspect, the sound insulation performance of the double floor is enhanced.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional perspective view showing a first embodiment of the present invention.

FIG. 2 is a perspective view of an essential part of the above.

FIG. 3 is a graph showing the sound absorption coefficient of the same.

FIG. 4 is a partial cross-sectional perspective view showing a second embodiment of the invention.

FIG. 5 is a graph showing the sound absorption coefficient of the same.

FIG. 6 is a partial sectional perspective view showing a third embodiment of the invention.

FIG. 7 is a partial cross-sectional perspective view showing Embodiment 4 of the present invention.

FIG. 8 is a graph showing the sound absorption coefficient of the same.

FIG. 9 is a partial cross-sectional perspective view showing a fifth embodiment of the invention.

FIG. 10 is a perspective view showing a sixth embodiment of the invention.

FIG. 11 is a perspective view showing a seventh embodiment of the invention.

FIG. 12 is a cross-sectional view showing a usage state of the same.

FIG. 13 is a graph showing the floor impact sound level of the above.

FIG. 14 is a sectional view showing an eighth embodiment of the invention.

FIG. 15 is a conceptual diagram illustrating the invention.

[Explanation of symbols]

 1 Porous Sound Absorbing Material (Rock Wool) 2 Powder (White Carbon) 3 Powder Encapsulation Container 4 Polymer Film (Polyethylene Film) 5 Rigid Plate (Acrylic Plate) 6 Perforation 7 Box 8 Frame 10 Powder Layer 11 Rigid Wall 12 Hole 18 sound absorbing box

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location E04B 1/86 C (72) Inventor Hideyuki Ando 1048 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Works Co., Ltd. (72) Inventor Yuriko Uegaki 1048 Kadoma, Kadoma-shi, Osaka Matsushita Electric Works Co., Ltd.

Claims (5)

[Claims] 1. A sound-absorbing material, characterized in that perforations 6 formed in a porous sound-absorbing material 1 such as glass wool and rock wool are filled with powder 2 which exhibits sound-absorbing performance by vibrating the powder particles themselves. 2. The sound absorbing material according to claim 1, wherein a rigid plate 5 made of plywood, a plastic plate, an iron plate, or the like is installed on a surface portion other than the perforations 2 of the porous sound absorbing material 1. 3. A sound-absorbing box or sound-absorbing material panel in which the sound-absorbing material according to claim 1 or 2 is put in a box 7 or a frame 8 made of plywood, an iron plate, a plastic plate or the like to improve shape retention. 4. A sound-insulating double-wall structure in which the sound-absorbing material or the sound-absorbing panel according to claim 1, 2 or 3 is disposed in a gap between a double wall or a double floor to improve sound insulation. 5. A sound-insulating double-floor structure in which the sound-absorbing material or sound-absorbing panel according to claim 1, 2 or 3 is disposed in a gap between a double wall or a double floor to improve sound insulation.