JPS5825280B2 - Sound-absorbing board structure with excellent weather resistance and mechanical strength, and good drainage - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention has excellent weather resistance, mechanical strength, and water drainage, and can efficiently absorb sound at extremely wide frequencies such as about 400 to 2,500 Hz, unlike those of automobiles. The present invention relates to the structure of a sound-absorbing plate suitable for absorbing sound from Shinkansen vehicles and the like that generate sounds ranging from low frequencies to high frequencies.

Glass and wool are examples of sound-absorbing materials with good sound-absorbing properties, but these fibrous materials have little weather resistance or mechanical strength, and when used as soundproof walls installed outside the building, aluminum or other materials are recommended. It is installed and used in a metal plate case.

For this reason, the present inventors researched and developed alternatives to fibrous sound absorbing materials, and first proposed and implemented metal sound absorbing materials.

This metal sound-absorbing material is made by bonding adjacent powder particles of metal or alloy at a portion to form communicating holes between the particles, and has good sound-absorbing properties. It had mechanical strength and weather resistance.

However, this sound absorbing material exhibits a high sound absorption coefficient in the high frequency range to the medium frequency range, for example, 700 Hz or higher, but
At about 0 Hz, the sound absorption coefficient rapidly decreases, and improvement is desired.

That is, Shinkansen vehicles emit extremely high-frequency sounds when running, but they also generate sounds of about 300 to 500 Hz, and it is desirable to absorb these sounds.

The present invention aims to solve the above-mentioned drawbacks and proposes a structure of a sound-absorbing plate that can satisfactorily absorb sounds of a wide range of frequencies.

Embodiments of the present invention will be described below with reference to the drawings.

Note that FIG. 1 is a cross-sectional view showing the structure of a sound-absorbing plate according to one embodiment of the present invention, and FIG. 2 is a cross-sectional view of the structure of a conventional sound-absorbing plate.

First, in FIG. 1, numeral 1 indicates a porous plate-like material,
A sound absorbing material 2, such as glass wool, is placed at a required distance S from the back surface 1a of this porous plate material.

This porous plate-like material 1 is made of powder of copper-aluminum or an alloy thereof, and the powder particles are bonded together, and pores 3 are formed between the particles.

Note that this porous plate-like material can be formed by bonding metal powder particles by a sintering method.

Further, the sound absorbing material 2 is made of fibrous material, that is, glass wool.

Next, the porous plate material 1 is placed at the required interval S as described above.
After arranging the sound absorbing material 2, the sheath tone plate 4 is further attached to the back surface 2a of the sound absorbing material 2.

It is usually sufficient for the sound plate 4 to be made of a steel plate or other metal plate, an asbestos cement board or other plate-like material, but it is also possible to use an insulated sound plate 4 if the purpose of the sound can be achieved. .

As mentioned above, by setting the interval S on the surface of the porous plate material 10,
A sound absorbing material 2 is arranged, and a sound plate 4 is further placed on the back side of the sound absorbing material 2.
When configured by attaching the porous plate material 1 and the sound absorbing material 2, and the effect of the spacing S between them, it is possible to increase the sound absorption coefficient over a wide frequency range up to the low frequency range, and the mechanical In addition, the porous sheet material 1 on the surface has excellent drainage ability, so even when exposed to the wind and rain, the sound absorbing material 2 can be left with sufficient spacing. Since rainwater does not reach the sound absorbing material 2 and the water retention time of the porous plate material 1 is short, the time for deterioration of sound absorbing properties due to water absorption is extremely short compared to other sound absorbing materials.

The sound absorption effect when sound is incident on a porous material can be attenuated by two mechanisms.

■When the air in a small hole or gap attempts to move due to sound, the air that is very close to the wall of the hole or the surface of the porous material becomes difficult to move due to the influence of the stationary wall, and the viscosity of this air causes the energy of the sound to move. Some of it is converted into thermal energy, causing sound attenuation.

■Heat loss due to heat conduction between the air inside the hole and the wall or porous material of the hole attenuates the sound energy.

The above is a qualitative explanation of the sound absorption effect of porous materials.

Therefore, in the sound absorbing plate according to the present invention, sound enters the porous plate material 1 from the direction of the arrow in FIG.

This porous plate-like material 1 is made of metal powder particles and alloy powder particles.
In particular, adjacent particles are bonded at the contact portion, and pores are formed in areas other than the bonded portion, and these pores form communicating holes 3 that communicate both in the horizontal and vertical directions.

In short, the pores are infinitely curved and connected.

Therefore, if the porous plate material has such a structure,
The sound that hits the surface enters the communication hole 3 and instead of traveling directly, it hits the metal powder particles infinitely and bends further, and the sound passes through the communication hole gap, and during this time, the sound is reduced by the viscosity of the air. Some of the energy is converted into thermal energy, causing sound attenuation.

In addition, a sound damping effect can be obtained due to heat loss due to heat conduction in small gaps.

This sound absorption effect is remarkable because the communication holes of the porous plate material are formed by being bent between the respective metal powder particles, and the communication holes communicate vertically and horizontally three-dimensionally.

As mentioned above, the sound is attenuated by the dusk passing through the porous plate material 1, but in order to increase the sound absorption effect in the low frequency range, the interval (
This sound-absorbing material takes an air layer) S, and furthermore, in order to improve the decrease in sound absorption coefficient in the mid-range sound range and obtain broadband sound-absorbing characteristics, a sound-absorbing material 2 is placed behind the porous plate material 1 at a distance S. 2 usually uses a sound absorbing material made of fibrous glass wool or the like.

Therefore, by setting the interval S, water absorption by the sound absorbing material 2 due to rainwater etc. can be avoided.

In addition, in relation to this interval S and the sound absorbing material 2, it is possible to adjust the sound absorption characteristics in the band, and in the case of a wide band, the interval S is 40
It is preferable to set it to about 150 mm.

As explained above about the three-stage θ and sound mechanism in the present invention, the porous plate material 1 and the sound absorbing material 2 are arranged at intervals, and the sound plate is heated at °C on the back side of the sound absorbing material 2. However, since the surface of the sound-absorbing plate with this structure is covered with a porous plate-like material, it is completely protected even if the internal sound-absorbing material 2 is made of fibers, and the porous plate-like material 1 is extremely It has good drainage, which also greatly increases its service life.

In other words, currently, fibrous materials such as glass wool are cited as materials with good sound absorption properties, but since these materials are fibrous, they do not have regular shape and cannot be formed into the desired shape. , which are adhered with phenol resin or the like.

However, even if glass wool is shaped using adhesive strength such as phenol resin, there is a problem in terms of weather resistance, and it is said that it is out of the question to discuss mechanical strength. In order to protect it from wind and rain, it is used by storing it in a protective case such as a box, and it is not used alone.

Even when housed in such a case, a metal plate 6 having a sound passage hole 5 is provided on the surface of the case, and a sound absorbing material 2 is attached to the back surface 6a of this metal plate 6. The sound absorbing material 2 is wrapped around the sound absorbing material 2.

However, even if the surface of the sound absorbing material 20 is covered with the metal plate 6, wind and rain cannot be completely prevented, and a considerable amount of material can easily enter the interior through the passage hole 5. It is protected by a coating layer 7 of resin.

For this reason, in conventional sound absorbing materials, the metal plate 6 on the surface does not contribute to sound absorption at all, and the film or coating layer 7 for waterproofing etc. deteriorates the sound absorbing properties of the sound absorbing material 2, making it difficult to obtain a good sound absorption coefficient. Usually there is no.

Furthermore, waterproofing is incomplete even with the film or coating layer 7, and water absorption by the sound absorbing material 2 is unavoidable, so when it rains, this water becomes an obstacle and reduces the sound absorption coefficient. In this case, the water retention time is very long and the performance as a sound absorbing material is also reduced.

In contrast, in the sound absorbing material according to the present invention, the porous plate-like material on the surface has excellent sound absorbing properties in itself, and furthermore, since the communication holes 3 are pores that communicate three-dimensionally, no rainwater can pass through. However, the water retention time is very short.

Therefore, a fibrous material can be used as the sound absorbing material 2 without any treatment, and the sound absorbing properties of the sound absorbing material 2 can be reduced to 1.
00%.

That is, as described above, the sound absorbed by the porous plate material has a frequency of 700 Hz or higher, particularly 100 OH2 or higher, and sounds with a frequency of about 500 to 300 Hz are difficult to absorb.

However, if the surface of glass wool is not treated (i.e., it is used in its fibrous form), this low frequency sound can be well absorbed, and furthermore, due to the presence of air gaps of 40 to 50 mm, it is possible to absorb low frequency sounds of 400 to 500 Hz. Sound can be absorbed by 0.8 or more.

The reason for this is that the sound absorption properties of the glass school alone are not sufficient to maintain a high sound absorption coefficient of 0.8 or higher in order to prevent noise from residents living along the railway. This is because it is necessary to absorb sound by glass wool on top.

Note that if the spacing is less than 40 mm, a sound absorption coefficient of 0.8 or more cannot be obtained, and if the spacing is more than 50 mm, sound absorption due to the air cushion effect due to air viscosity will not be achieved.

In addition, to make a porous plate-like material, select metal powder or alloy powder such as copper powder or its copper alloy powder, mix them under normal pressure, and form the particle shape of the metal powder or alloy powder. is preferably spherical or nearly spherical.

In addition, the metal powder or alloy powder used as a raw material may be copper, iron, aluminum, or an alloy thereof (any commercially available metal powder or alloy powder may be used; For example, a coated powder such as iron powder coated with copper can also be used.

Furthermore, after mixing as described above, this mixed powder is formed into a plate-shaped material such as stainless steel or graphite in an Ω mold, and when the plate-shaped material is sintered in this way, a porous plate-shaped material 1 is formed. is configured,
This surface has a hole 3 which passes through the plate-like material, and the through hole does not just pass straight through, but is completely irregularly bent.

Next, examples will be described.

First, bronze powder (Cu90wt%, isn.
(lowt%) were selected and mixed, and this mixed powder was placed in a graphite mold and molded into a plate material with a thickness of 3 mm under no pressure conditions.

After that, this plate material was placed in the atmosphere at 850°C for 1.5 hours.
The material was sintered under conditions of r 2 to produce a porous plate-like material in which pores were formed between adjacent alloy powder particles as shown in FIG.

Further, the diameter of this pore was determined to be approximately 100 microns.

Next, with respect to this porous plate material, the required interval Si-40
mm, a sound absorbing material made of glass wool (32 kg/i) with a thickness of 50 mm was arranged at this interval, and a steel plate was attached to the back side of the sound absorbing material to produce a sound absorbing board.

Next, the vertical ν incident sound absorption coefficient of this sound absorbing plate was determined by the standing wave method, and it was as shown in FIG. 4 O.

In addition, a porous plate material configured as described above (plate thickness 3++
m) was placed in water as it was, and the water retention time after being removed from the water was determined.

At this time, the water retention time, which was defined as the time from when the porous plate material was pulled out of the water until the water content in the porous plate material became zero, was approximately 10 hours.

Fibers such as glass wool require several days to retain water.

Therefore, the sound absorbing board has superior weather resistance and mechanical strength compared to sound absorbing materials conventionally used outdoors.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a sound absorbing plate according to one embodiment of the present invention,
Figure 2 is a sectional view of a conventional sound absorbing board for outdoor use;
The figure is an enlarged plan view of two parts of a porous plate material according to an embodiment of the present invention. This is a graph showing. Code 1: porous plate-like material, 2: sound absorbing material, 3: communication hole, 4: sound wave.

Claims (1)

[Claims] 1 40 to 50 mm from the surface of a porous plate material having infinitely curved communication holes between metal or alloy powder particles
The sound-absorbing material of the glass cooler is placed in the form of fibers at intervals of
A sound absorbing material that has good drainage and can absorb a wide range of sound over a frequency range of 400 to 2,500 Hz.