JPH04258998A - Sound absorbing material, powder for sound absorbing material and production thereof - Google Patents

Abstract

PURPOSE:To provide a sound absorbing material having satisfactory sound absorbing action in a very low frequency band without increasing the thickness of the powder packed layer. CONSTITUTION:This sound absorbing material is fitted with a sound absorbing body obtd. by packing with powder and this powder is composed of porous particles contg. a weight increasing substance 2 in the pores 1.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to sound absorbing materials, powders for sound absorbing materials, and methods for producing the same.

0002

2. Description of the Related Art As a sound absorbing material, there is a sound absorbing material in which a thin box having an open side is filled with powder and the opening is closed with an acoustically transparent sheet. The powder filled layer acts as a sound absorber and exerts a sound absorbing effect. Frequency characteristics of sound absorption (hereinafter referred to as “sound absorption characteristics”)
) is determined by physical property values such as the bulk density and Young's modulus of the powder packed bed.

FIG. 3 shows the sound absorption characteristics of a sound absorber made of porous calcium silicate powder. As shown in FIG. 3, this sound absorber exhibits sound absorption peaks around 500 Hz and 1400 Hz.

0004

[Problems to be Solved by the Invention] The above sound absorbing material has a
Although it is very effective against sounds in a constant frequency range around 0Hz and 1400Hz, it is not very effective against sounds in a frequency range lower than 500Hz. In listening rooms, musical instrument practice rooms, etc., there is a so-called booming phenomenon in which extremely low frequency sounds are emphasized and reverberate, but in order to prevent this booming phenomenon, lower frequency ranges (frequency ranges below 500Hz) are used. What is desired is something that can absorb enough sound.

[0005] Of course, increasing the thickness of the powder-filled layer increases the sound absorption effect, but the sound-absorbing material itself becomes too thick and the indoor space becomes narrow, so increasing the thickness of the powder-filled layer is not an appropriate solution. I can't say it's a method. In view of the above circumstances, the first object of this invention is to provide a sound absorbing material that exhibits a sufficient sound absorbing effect in a lower frequency range without increasing the thickness of the powder packed layer. The second objective is to provide a powder for a sound absorbing material that easily realizes the following, and the third objective is to provide a method for manufacturing this useful powder for a sound absorbing material.

[0006]

[Means for Solving the Problems] In order to solve the first problem, in the sound absorbing material according to the invention as set forth in claim 1, in the sound absorbing material, the powder has a strong sound absorbing effect in a specific frequency range. As particles, for example, as shown in Figure 1,
Powder particles are used in which weight-increasing substances 2 are contained in the pores 1 of porous particles having pores 1 therein.

[0007] In order to solve the second problem, the powder for a sound absorbing material according to the invention as claimed in claim 2 includes powder particles having a strong sound absorbing effect in a specific frequency range.
Powder particles are used in which a weight-increasing substance is contained in the pores of porous particles having pores inside. Furthermore, in order to solve the third problem, the method for producing a powder for sound absorbing materials according to the invention as claimed in claim 3 includes dispersing a weight increasing substance in obtaining the powder for sound absorbing materials as described in claim 2. After the porous particles are added to a solution consisting of porous particles and the solution is introduced into the pores of the porous particles, the solvent of the solution is removed by drying.

Examples of porous particles include porous calcium silicate particles. Before introducing ultrafine particles (for example, ultrafine silica particles), these calcium silicate particles had thin plate-like crystals gathered together irregularly, as seen in the scanning electron micrograph shown in Figure 5. It is a honeycomb-like material in which pores are formed, and a large number of pores of about 1 μm are connected through pores of about 0.1 μm. The average particle size of the calcium silicate particles is, for example, 5 to 6
They are highly porous particles with a diameter of approximately 0 μm and a porosity of approximately 96%.

[0009] Examples of weight-increasing substances in the pores include silica,
Ultrafine ceramic particles such as alumina and zirconia, ultrafine metal particles such as aluminum, zinc, and iron, ultrafine metal oxide particles such as iron oxide, magnesium oxide, and antimony oxide, barium sulfate, barium chloride, calcium carbonate, and magnesium carbonate. Inorganic compound-based ultrafine particles such as silicon-based polymer compounds, acrylic-based polymer compounds, and other polymer compound-based ultrafine particles (silicon powder and acrylic powder)
Alternatively, examples include acrylic resin, urethane resin, epoxy resin, silicone resin, oil and fat. Any material can be used as long as it can be inserted into the hole. In addition, in the case of solid ultrafine particles, for example, those having a particle size of about 0.01 to 0.02 μm can be mentioned.

[0010] The powder for a sound absorbing material of the present invention can be easily produced by the method of the invention described in claim 3 above. Even when the weight-increasing substance is generated directly within the pores of porous particles,
Porous particles are added to a solution in which a compound (resin, etc.) for producing a weight increasing substance is dissolved, and after the solution is introduced into the pores of the porous particles, only the solution solvent is removed by drying, etc. Causes weight gain substances to be produced.

When ultrafine silica particles are introduced into porous calcium silicate particles, a state as shown in the scanning electron micrograph of FIG. 4 is obtained. The ultrafine silica particles become attached not only inside the calcium silicate but also on the particle surface. The weight-increasing material within the pores results in a powder-filled layer (sound absorber)
This results in an increase in bulk density, and it goes without saying that the degree of increase in bulk density is proportional to the amount of substance introduced, and the larger the amount of substance introduced, the higher the rate of increase in bulk density. Usually, the bulk density ratio before and after introducing the weight-increasing substance (bulk density after introducing the weight-increasing substance/bulk density before introducing the weight-increasing substance) is 1.5.
The above should be maintained.

A specific form of the sound absorbing material includes a structure in which a thin box with an opening on one side is filled with powder into which a weight increaser has been introduced, and the opening is closed with an acoustically transparent sheet. Manufacturing is easy because the powder into which the weight-increasing substance has been introduced is simply used in place of the conventional powder. It goes without saying that the packed bed of powder exhibits a sound absorbing effect as a sound absorber.

[0013]

[Operation] The sound absorbing material of this invention has a weight-increasing substance in the pores of the porous particles constituting the sound absorbing body, so the bulk density of the powder increases, and as a result, it absorbs sound in a lower frequency range. The effect increases. The primary sound absorption peak frequency f of a sound absorber made of powder follows the following formula.

[0014] f=0.25×E1/2 ÷ρ1/2
÷L However, E is Young's modulus of the powder packed bed, ρ is the bulk density of the powder packed bed, and L is the powder packed bed thickness. The above formula is
The increase in bulk density due to the introduction of weight-increasing substances causes the primary sound absorption peak to shift to the lower frequency side without increasing the thickness L of the powder-filled layer, resulting in a sound absorption effect for sounds in a lower frequency range. This proves that it is an enhancement.

Furthermore, the amount of shift of the sound absorption peak depends on the degree of increase in bulk density. Since the degree of increase in bulk density is determined by the amount of weight-increasing material introduced, it is possible to control the shift amount of the sound absorption peak by adjusting the amount of weight-increasing material introduced. In other words, the sound absorption characteristics can be easily controlled.

[0016]

[Embodiments] Examples of the present invention will be described below. Of course, the sound absorbing material of the present invention is not limited to the following embodiments. As the porous particles, porous calcium silicate particles (Fluorite R manufactured by Tokuyama Soda, particle size 20 to 30 μm, porosity 95%) were prepared, and the particle size was 0.01 to 0.0.
A silica sol (manufactured by Nissan Chemical Industries, Ltd.) made by dispersing ultrafine silica particles of 2 μm in water was prepared.

[0017] Then, the powder was dispersed in silica sol at a ratio of 100 g of calcium silicate powder per liter of silica sol and placed under reduced pressure of 30 Torr or less,
Silica sol was impregnated into the pores of the powder. Then,
After evaporating water through filtration and drying to obtain a sound-absorbing powder in which ultrafine silica particles are introduced into the pores, this powder is filled into a thin box and the opening is covered with a thin sheet to absorb sound. I got the material.

In order to understand the characteristics of the sound absorbing material of the example, the sound absorbing characteristics, bulk density and Young's modulus of the calcium silicate particle packed bed (sound absorbing material) after introducing ultrafine silica particles were measured. Figure 2 shows the measurement results of the sound absorption properties. The measurement results of bulk density and Young's modulus are as follows. Bulk density: 315.0kg/m3 Young's modulus:
1.42×10 5 N/m 2 For comparison, the sound absorption properties, bulk density, and Young's modulus of a packed layer of calcium silicate particles (same thickness as in the example) before introduction of ultrafine silica particles were also measured. Figure 3 shows the measurement results of sound absorption characteristics. The measurement results of bulk density and Young's modulus are as follows.

Bulk density: 83.0 kg/m Young's modulus: 1.35×105 N/m 2 As shown in Figures 2 and 3, in the case of a packed bed of calcium silicate particles into which ultrafine silica particles are introduced, the primary Sound absorption peak from 505Hz to 265H
It is clearly seen that a sound absorbing body that exhibits a high sound absorbing effect in a very low frequency range of 500 Hz or less can be realized. The measurement results of bulk density and Young's modulus also well support that the shift in the sound absorption peak is due to an increase in bulk density.

[0020]

Effects of the Invention As described above, the sound absorbing material according to the invention as claimed in claim 1 has a stronger sound absorbing effect in a lower frequency range because the bulk density of the powder constituting the sound absorber increases. Moreover, since the sound absorbing material is made of powder,
Even if the thickness is thin, sufficient sound absorption coefficient can be ensured, making it highly adaptable to thin shapes.

[0021] By using the powder for a sound absorbing material according to the second aspect of the invention, the excellent sound absorbing material according to the first aspect can be easily realized. According to the method of the invention recited in claim 3, claim 2
The useful powder for sound absorbing materials described above can be easily obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the appearance of calcium silicate particles in which ultrafine silica particles are introduced into the pores.

FIG. 2 is a graph showing the sound absorption characteristics of a sound absorber using calcium silicate particles after the introduction of ultrafine silica particles.

FIG. 3 is a graph showing the sound absorption characteristics of a sound absorber using calcium silicate particles before introducing ultrafine silica particles.

FIG. 4 is an electron micrograph showing the particle structure of calcium silicate particles after introduction of ultrafine silica particles.

FIG. 5 is an electron micrograph showing the particle structure of calcium silicate particles before the introduction of ultrafine silica particles.

[Explanation of symbols] 1 Vacancy 2. Weight-increasing substances

Claims (4)

[Claims] 1. A sound absorbing material comprising a sound absorbing body made of powder that has a strong sound absorbing effect in a specific frequency range, wherein the powder particles are porous particles having voids inside, and a weight increasing substance is added to the pores of the porous particles. A sound-absorbing material characterized by using powder particles in which is incorporated. 2. In a powder for a sound absorber having a strong sound absorbing effect in a specific frequency range, the powder particles are porous particles having pores inside, and a weight increasing substance is present in the pores. A powder for sound-absorbing materials characterized by being body particles. 3. A method for producing a powder for a sound absorbing material according to claim 2, wherein porous particles are added to a solution in which a weight increasing substance is dispersed, and the solution is filled into the pores of the porous particles. A method for producing a powder for a sound absorbing material, which comprises removing the solvent of the solution by drying after introducing the powder. 4. The sound absorbing material according to claim 1, the powder for a sound absorbing material according to claim 2, and the powder for a sound absorbing material according to claim 3, wherein the porous particles are calcium silicate particles, and the weight increasing substance is solid ultrafine particles. A method for producing powder for sound absorbing materials.