JPH05313669A - Acoustic material and production of acoustic material - Google Patents

Abstract

PURPOSE:To improve acoustic absorptivity and to stabilize the acoustical effect in a low-frequency region by specifying the Young's modulus of a buffer material alone to a specific value or below. CONSTITUTION:The buffer material having <=10<5>N/m<2> Young's modulus of the buffer material alone is used as the buffer material. The more specific form of the acoustical material includes the form that powder 3 is filled in the respective holes 2 of the buffer material 1 of a three-dimensional grating structure having the holes 2... arraying in a checker shape and the form that the powder is filled in the holes of the buffer material having the many holes formed among the fibers intricately entangled with each other. The powder 3 having about the same size as the size of the respective holes 2 is used. Further, the constitution that the powder 3 is at least partly adhered to the buffer material is adopted. The acoustical material is produced by the method of introducing the powder into the buffer material layer by supplying the powder to one surface side of the buffer material layer and sucking the powder from the other surface side of the buffer material layer.

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 and a method for manufacturing the 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 in order to improve the sound insulation performance of walls and ceilings. However, sound absorption material should be filled between the double walls to further improve the performance. To do. (3) In addition, it is also used for attaching sound absorbing ducts inside, and for attaching soundproof covers of devices that generate noise.

The conventional sound absorbing materials used for the above applications, such as urethane foam and glass wool, are shown in FIGS.
As shown in Fig. 8, the porosity of the material is used. That is, as shown in FIGS. 27 and 28, when a sound wave enters into the bubble 92 or the hole 96 communicating with the urethane foam 91 or the glass wool 95, the sound wave is generated because it is an open cell having a complicated cross-sectional shape. During the propagation, the sound pressure is reduced due to viscous friction with the bubble wall surface, and as a result, the acoustic energy is absorbed in the material.

The normal incident sound absorption coefficients of urethane foam (density 20 kg / m ³ , thickness 24 mm) and glass wool (density 32 kg / m ³ , thickness 24 mm) are shown in FIGS. 29 and 30. The sound absorption coefficient of the porous material increases as the frequency of the sound wave increases and as the thickness increases. In other words, it has a low sound absorption coefficient for sound waves in the low frequency range. Increasing the thickness of the porous material can increase the sound absorption coefficient in the low frequency range. However, when the thickness is increased, there is a problem that the room becomes narrow when it is used as an interior material for a room, and the air passage becomes narrow when it is used as a duct inside. Therefore, the method of increasing the sound absorption coefficient in the low frequency region by increasing the thickness is not an appropriate measure. However, if it has a sufficient sound absorption coefficient in the low frequency range, it is a very useful sound absorbing material in any case of room acoustic characteristics of a listening room, sound insulation of walls and ceilings, and suppression of mechanical noise.

For example, in a space having a relatively small volume such as a listening room or a musical instrument practice room, there is a problem that a so-called booming phenomenon occurs in which a sound of a specific frequency is emphasized and sounds like a "bonbon". If there is a sufficient sound absorption coefficient in the frequency range, the booming phenomenon can be suppressed. The booming phenomenon is a phenomenon caused by the room resonating with the sound due to the relationship between the wavelength of the sound generated from the stereo device and the musical instrument and the size of the room.

That is, in the listening room, the musical instrument practice room, etc., the sound in the low frequency range (about 500 Hz or less) is particularly high among the wavelengths of the sound in the audible range of 20 to 20 kHz (that is, the wavelength of 17 m to 1.7 cm). Is caused by the fact that the wavelength of is approximately the same as the length of one side of the room. In the case of a large indoor space such as a concert hall, this is not a problem because the length of one side of the room is longer than the wavelength of the sound in the low frequency range. In the case of a listening room or a musical instrument practice room with a wavelength of, the unpleasant sound such as "the sound is muffled" or "the sound is not clean" is caused. A sound absorbing material having a sufficient sound absorption coefficient in a low frequency range well absorbs a sound in an extremely low low frequency range, and thus is suitable for eliminating the above-mentioned inconvenience.

[0007]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides a sound-absorbing material having good sound-absorbing performance in a low frequency range even though the thickness is thin, and having high utility, and such a useful sound-absorbing material. An object of the present invention is to provide a method capable of easily manufacturing a highly sound absorbing material.

[0008]

In order to solve the above-mentioned problems, the inventors have paid attention to the sound absorbing action due to powder vibration. The particle size of the powder when the interaction force between the powders (particles) and the gravity acting on the powder match is called the equilibrium particle size. The equilibrium particle size varies depending on the type of powder, but is in the range of several μm to several 100 μm. A powder having a particle size in the vicinity of the equilibrium particle size is very easy to vibrate, easily excited by a sound wave in the low frequency range, and has a good sound absorbing effect for sound in the low frequency range.

FIG. 22 shows the sound absorption coefficient versus frequency characteristic of the calcined calcium silicate powder layer (thickness 30 mm), and FIG. 23 shows the sound absorption coefficient versus frequency characteristic of the wet silica powder layer (thickness 30 mm). The sound absorption coefficient is a normal incidence sound absorption coefficient measured according to JIS A 1405 “Method for measuring normal incidence sound absorption coefficient of building materials by in-pipe method”. The measurement was performed using the A tube, but since it was a powder, it was measured by standing it up. The sound absorption coefficient was calculated by the standing wave ratio.

The particle diameter and the like in the powder layer are as follows. "Firing silicatizing average particle size: 25 [mu] m, true density: 2.52 g / cm ³ calcium powder" bulk density: 0.080 g / cm ³ porosity: 0.97 "wet silica" mean particle diameter: 150 [mu] m, a true density: 2.1 g / cm ³ bulk density: 0.282 g / cm ³ porosity: 0.87 as seen in FIG. 22 and 23, both a peak at 500Hz below (hereinafter, referred to as "sound absorption peak") is Has occurred,
High sound absorption in the low frequency range. As shown in FIG. 15, the sound absorption peak is generated when the powder layer P vibrates in the longitudinal vibration mode, thereby effectively absorbing the sound in the low frequency range.

The sound absorption coefficient vs. frequency characteristic of the powder is shown in FIG.
23, not only when the sound absorption peak is generated in the low frequency region, but when the powder is vermiculite, for example, as shown in FIG. There may be a case where the sound absorption coefficient is substantially constant at a frequency of fs or higher to 2000 Hz. The center frequency fr of the sound absorption peak appearing in the low frequency range, the sound absorption coefficient value at the center frequency fr, the (frequency) width of the sound absorption peak, and the lower limit frequency f of the constant sound absorption coefficient when there is no sound absorption peak in the low frequency range.
s and the like vary depending on the powder particle size, shape, powder bulk density in the powder layer, powder agglomeration state, and the like.

The usefulness will be further enhanced if a high sound absorption coefficient can be provided in a lower frequency range and the excellent sound absorbing performance of the powder can be stabilized over time. If the center frequency fr of the sound absorption peak in the sound absorbing material can be shifted to a lower side, or if the lower limit frequency fs of the constant sound absorption coefficient when there is no sound absorption peak in the low frequency range can be extended to the lower frequency range side, Sound absorption increases at low frequencies.

Therefore, the inventors have studied from various angles, and as a result, have found that the center frequency fr can be appropriately shifted to the lower side as follows. It has been experimentally confirmed that the center frequency fr of the peak in the low frequency region in the powder layer basically complies with the following equation (1).

Fr = 0.25 t ⁻¹ (E / ρ) ^0.5 (1) where t is the powder layer thickness, E is the Young's modulus of the powder layer, and ρ is the bulk density. The above equation (1) shows that an increase in the powder layer thickness t and the bulk density ρ causes a decrease in the center frequency fr. However, the increase of the powder layer thickness t brings about the inconvenience that the room is narrowed and the air passage in the duct is narrowed as described above, and the increase of the density ρ is accompanied by the suppression of the powder vibration, and therefore the sound absorption coefficient is increased. Inconvenience of deterioration is brought about, and neither is suitable. On the other hand, the above formula (1) also indicates that the center frequency fr can be reduced if the Young's modulus E of the powder layer is reduced. The Young's modulus E of the powder layer is usually much higher than 10 ⁵ N / m ² , and the lower the frequency, the lower the center frequency fr. Focusing on this point, the investigation was continued, and since the Young's modulus E of the powder layer is largely influenced by the spring constant between the contact particles, the buffer material having a Young's modulus less than the Young's modulus of the powder layer is used as the powder. If mixed, the Young's modulus of the powder layer can be substantially (apparently) lowered, and in this case, the Young's modulus of the powder layer is usually considerably higher than 10 ⁵ N / m ² . Therefore, less than 10 ⁵ N / m ² or less (preferably 5 × 10 ⁴ N
It was possible to find that the Young's modulus of the powder layer is sufficiently reduced by using the buffer material having the Young's modulus of less than / m ² ). As a result, the invention according to claim 1 could be completed.

Therefore, in the sound absorbing material according to the first aspect of the present invention, in the sound absorbing material in which the powder that exhibits a sound absorbing effect by vibration and the cushioning material are mixed, the Young's modulus of the cushioning material alone is used as the cushioning material. Of 10 ⁵ N / m ² or less is used. As a specific form of the sound absorbing material according to claim 1, as shown in FIG. 1, each hole 2 of the buffer material 1 having a three-dimensional lattice structure having holes 2 arranged in a grid pattern.
As shown in FIG. 2, the form in which the powder 3 is contained in the powder 3 and the powder 13 is contained in the holes 12 of the cushioning material 10 having a large number of holes 12 formed between the intricately entangled fibers 14. There is a form. The powders 3 and 13 are usually of the same size as the holes 2 and 12, respectively.

The cushioning material used here is, for example, a non-woven fabric, a fiber structure, an artificial pulp, a filter paper or the like, and a sheet-like porous material having a thickness of about 5 to 40 mm is suitable. Specifically, 2 × 10 ³
Examples thereof include a polyester-based non-woven fabric having a Young's modulus of about 3 × 10 ³ N / m, and a non-woven fabric made of a mixture of rayon, nylon and polyester having a Young's modulus of about 1.3 × 10 ⁴ N / m. In addition, polypropylene-based nonwoven fabric, polyurethane-based nonwoven fabric, nylon-based nonwoven fabric and the like can also be used. In the case where the thickness is thin, a plurality of layers may be stacked. The sheet-like porous material may be, in addition to the above-mentioned non-woven fabric, for example, a fiber base material such as glass wool or rock wool, or a foamed resin material such as urethane foam. When the cushioning material is a sheet-shaped porous material, the powder and the cushioning material are mixed because the powder is introduced into the voids in the porous material.

The cushioning material is preferably in the form of a sheet because it has excellent shape-retaining properties, but is not necessarily in the form of a sheet. In the case of the present invention, for example, a non-sheet-like (separate) fibrous body can be mixed with the powder to reveal a mixed state of the powder and the cushioning material,
A single Young's modulus of 10 ⁵ N / m ² or less (for example, non-sheet-shaped silicon carbide whiskers) may be used as the cushioning material.

The Young's modulus of a few cushioning materials will be specifically described below. “Glass wool 36k”: Young's modulus 7.8 × 10 ⁴ (N / m ² ): Density 3.6 × 10 ⁻² (g / cm ³ ) “Synthetic pulp”: Young's modulus 2.0 × 10 ³ (N / m ² ) (fiber length 100 μm): density 8.9 × 10 ^-2 (g / cm ³ ) “silicon carbide whisker”: Young's modulus 8.5 × 10 ⁴ (N / m ² ): density 3.6 × 10 ^-1 (g / cm ³ ) "Polypropylene fiber: Young's modulus 1.4 × 10 ² (N / m ² ) porous material": Density 2.4 × 10 ^-2 (g / cm ³ ) The invention according to claim 1. As the powder used in the above, in addition to the above-calculated calcined calcium silicate powder and wet silica, mica powder, vermiculite powder, leucite powder, acrylic ultrafine powder, spherical silica powder, etc. Can be mentioned. Specific examples of powder are given below. "Talc Powder" average particle size: 9.4 .mu.m, true density: 2.75 g / cm ³ Bulk density: 0.45 g / cm ³ porosity: 0.84 "Talc Powder" average particle size: 2.3 .mu.m, True density: 2.75 g / cm ³ Bulk density: 0.25 g / cm ³ Porosity: 0.91 “Spherical silica powder” Average particle size: 28 μm, True density: 2.23 g / cm ³ Bulk density: 0. 92 g / cm ³ Porosity: 0.59 As shown in FIG. 16, the Young's modulus E of the cushioning material is measured by filling the cylinder-shaped container 50 with the cushioning material 51 to be measured, and then adding the additional mass thereon. Place the piece 52. Then, the exciter 53 excites the vibration, and the transfer function between the vibration acceleration of the impedance head 56 and the vibration acceleration of the additional mass piece 52 is obtained by the FET analyzer 57 via the charge amplifiers 54 and 55. Finally, the Young's modulus E is calculated from the frequency of the peak of the transfer function by the personal computer 58. In addition, the Young's modulus E of the powder layer or the cushioning material containing the powder E
Can be similarly measured.

More specifically, the container 50 has an inner diameter of 85 mm.
3 mm thick with a cushioning material to be measured up to a height of 30 mm from the bottom and as an additional mass piece 52 thereon.
Place the iron plate of and measure. The following are specific examples of the main measuring instruments in FIG.

Charge amplifier: Type 2 manufactured by B & K
635, FFT analyzer: CF36 manufactured by Ono Sokki Co., Ltd.
0, noise generator: Type 270 manufactured by B & K
6, PC: 33 in the 9000 series made by hp
0. Further, if the excellent sound absorbing action by the powder vibration is stably exhibited, the practicality is high. If the powder does not flow and the mixed state of the powder and the cushioning material is kept constant, the sound absorbing action is stable and stable. Therefore, we continue to investigate for a way to keep the mixed state of powder and cushioning material constant.
It has been found that at least a part of the powder may be adhered to the cushioning material. Needless to say, the adhered powders are partially adhered to the cushioning material so that the powder vibration is not hindered.

Therefore, the sound absorbing material according to the second aspect of the present invention is a sound absorbing material in which powder and a buffer material exhibiting a sound absorbing effect by vibration are mixed, and at least a part of the powder is buffered. The material is adhered to the material. The type and form of the cushioning material used for the sound absorbing material of the invention of claim 2 are the same as those of the invention of claim 1, and of course, as in claim 3, the sound absorbing performance in the low frequency range. It is preferable that the buffer material has a Young's modulus E of 10 ⁵ N / m ² or less (more preferably 5 × 10 ⁴ N / m ² or less), which has a very high effect of improving The type of powder used in the invention of claim 2 is also the same as that of the invention of claim 1. It is not necessary that all the powders adhere to the cushioning material, and it may be that some of the powders exist in a separated state between the adhered powders.

As a concrete form of the sound absorbing material according to the second aspect, as shown in FIG. 3, the sound absorbing material has a plurality of holes 22 formed between the fibers 24 intricately entwined with each other. An example is a mode in which the powder 23 is contained and the powder 23 is partially bonded to the fibers 24 by the thermoplastic resin 25 applied to the surface. In addition, as shown in FIG. 4, adhesion between the powder 23 and the fibers 24 is made by the thermoplastic resin 25 applied to the surface of the fibers 24, and as shown in FIG. There is also a form in which the fiber itself is made of a thermoplastic resin and is made by the heat-sealing property of the fiber 24.

Furthermore, the inventors of the present invention
Using a fibrous body in which a thin thread with a small diameter is entwined with the core thread,
Even in the structure in which the powder and the cushioning material are mixedly present by allowing the powder that exhibits a sound absorbing effect to exist in the void formed by this fibrous body, the center frequency fr of the sound absorbing peak is shifted to a lower side. It has been found that it is effective in increasing the sound absorption coefficient to the low frequency side.

The powder used here is not particularly limited,
Although all of the examples in this specification can be used,
Usually, the particle size is about 0.1 to 1000 μm and the bulk density is about 1.0 g / cm ³ or less. Gold mica powder, silica powder, acrylic ultrafine powder, talc powder, calcium silicate. Examples of the powder include powder. More specifically, for example, the average particle size is 40 μm and the bulk density is 0.37 g.
/ Cm ³ gold mica powder, average particle size 1.7 to 7.5 μ
m, wet silica powder having a bulk density of 0.06 to 0.14 g / cm ³ , an average particle size of 23 to 28 μm, and a bulk density of 0.84 to
0.92 g / cm ³ spherical silica powder, average particle size 1-2
Acrylic fine powder with μm and bulk density of 0.30 g / cm ³ ,
Average particle size 1.5 to 3.2 μm, bulk density 0.25 g / c
Examples thereof include talc powder of m ³ and calcium silicate powder having an average particle size of 20 to 30 μm and a bulk density of 0.08 g / cm ³ .

As an example of the structure of a fibrous body in which thin yarns having a small diameter are entwined with each other (along the longitudinal direction), as shown in FIG. There is a fibrous body 121 entangled along. The fine yarn 123 is a yarn having a smaller diameter (diameter) than the core yarn 122, but specifically, the diameter of the fine yarn 123 is usually about 1/3 to 1/20 of the diameter of the core yarn 122. . The thicker core thread 122 is preferably elastic, such as polyurethane thread. As a specific fibrous body 121, for example, a polyurethane thread (polyurethane fiber) having a diameter of 100 μm is used as a core thread 122, and a nylon thread (nylon fiber) having a diameter of 10 μm is added to the core thread 122.
Entangled as thin yarn 123 (true density 1.19 g /
cm ³ ).

In the case of the sound absorbing material of the present invention, as the powder, a powder having a substantially constant sound absorption coefficient at a frequency higher than a specific frequency may be used. The vermiculite powder described above is a powder that exhibits a sound absorbing effect due to vibration, but as shown in FIG. 24, the sound absorption coefficient versus frequency characteristic of the vermiculite powder layer filled with a thickness of 30 mm is 300 Hz to 2000 Hz. Although it has a constant sound absorption coefficient of about 0.5 and a flat sound absorption characteristic, such vermiculite powder may be used.

The lower limit frequency fs having a constant sound absorption coefficient in FIG. 24 follows the following equation (2). fs = 0.25 t ⁻¹ (E / ρ) ^0.5 (2) where t is the powder layer thickness, E is the Young's modulus of the powder layer, and ρ is the bulk density. This expression (2) indicates that the specific frequency fs extends to the lower side as the Young's modulus E decreases. The Young's modulus E of the powder layer is 10 as shown in FIG.
It is well over ⁵ N / m ² . Since the Young's modulus E of the powder layer is greatly influenced by the spring constant between the contact particles, 10 ⁵
The Young's modulus E of the powder layer, which considerably exceeds N / m ^2, is 10 ⁵ N / m ² or less (preferably 5 × 10 ⁴ N / m ^2).
It has been found that the use of the Young's modulus buffer material (below) substantially (apparently) lowers the Young's modulus of the powder layer, and as a result, it is possible to provide sufficient and flat sound absorption characteristics from a lower frequency. As a result of the examination, I was able to obtain it. In this case, the lower limit of the required frequency for music playback is 3
It will be very useful in consideration of the point below 00Hz.

As the powder having a substantially constant sound absorption coefficient in a frequency range above a specific frequency, silica powder, talc powder, gold mica powder, in addition to the above-mentioned vermiculite powder, Examples of the powder include soft calcium carbonate powder and powders of calcined ferrite. Bulk density 0.1-3.0 g /
The above characteristics are obtained by filling the material with about ³ cm ³ (usually 0.1 to 1.0 g / cm ³ ). Specifically, the following modes are exemplified. A: Primary average particle size 7.5 μm, aggregate particle size 150 to 600
Wet silica powder of μm (preferably 400 to 500 μm) is filled at a bulk density of about 0.12 to 0.17 g / cm ³ . B: Talc powder having an average particle size of 1 to 3 μm was used, and a bulk density of 0.
Fill with about 23 to 0.28 g / cm ³ . C: Gold mica powder having an average particle size of 650 μm was filled at a bulk density of about 0.49 to 0.56 g / cm ³ . D: Average particle size 3 to 10 to 150 parts of linseed oil adhered
A wet silica powder having a size of 7.5 μm was added to have a bulk density of 0.12.
Filled with 0.42 g / cm ³ . E: Average particle size of 9.4μ with 20 parts of acrylic resin adhered
m talc with a bulk density of about 0.51 g / cm ³ . F: Filling powder such as vermiculite having an average particle diameter of 200 to 400 μm with a bulk density of about 0.19 g / cm ³ . G: A soft calcium carbonate powder having a particle size distribution in the range of 1 to 2 μm was filled at a bulk density of about 0.42 g / cm ³ . H: A calcined ferrite powder having a particle size distribution in the range of 1.3 to 1.5 μm is filled at a bulk density of about 1.00 g / cm ³ . I: Nylon powder (powder) having a particle size distribution in the range of 180 to 500 μm was filled at a bulk density of about 0.47 g / cm ³ .

In this case, the sound absorption coefficient of each sound absorber in the region exceeding 2000 Hz (the region of 2000 to 20000 Hz) usually tends to be slightly higher than that in the frequency range of fs to 2000 Hz. It is desirable that the sound absorption performance is as follows. Sound absorber frequency fs ~
The fluctuation range of the sound absorption coefficient in the frequency range of 2000 Hz is 0.
It is within 2 (more preferably within 0.1), and the sound absorption level is usually 0.35 or more (preferably 0.4 or more, more preferably 0.45 or more).

The sound absorption coefficient referred to here is also JIS A 1405.
It is the normal incident sound absorption coefficient measured according to the "method of measuring the normal incident sound absorption coefficient of building materials by the in-pipe method".
mm (filling thickness 30 mm for powder packed bed). The sound absorption coefficient is calculated using the standing wave ratio. As the powder, as shown in FIG. 6, a mixed powder of a powder 11 made of a granular material and a powder 15 made of a fine fibrous body is used, and this is used as a void 12 in the sheet-shaped porous material. It may be introduced or may be made to exist in a void made of a fibrous body in which a thin yarn having a small diameter is entwined with a core yarn.

The following are examples of the constitution of the mixed powder of the powder consisting of the granular material and the powder consisting of the fine fibrous body. "Average particle size 150μ as powder consisting of granules"
m silica powder "and" powder composed of silicon carbide whiskers (fine fibrous bodies) as a powder made of fibrous body (average particle diameter of the aggregated body is around 50 μm) "by volume ratio 1:
An example is the mixed powder mixed in 1. In addition,
The granular body is not limited to a spherical shape, but a plate (scale) shape,
Examples include various shapes other than fibrous shapes such as horns and lumps, and examples include those in which fine particles are aggregated to form a large particle aggregate. Of course, the fine fiber bodies may be individually separated without cohesiveness. As the whiskers themselves, those having an average length of 5 to 200 μm and an average diameter of 0.05 to 1.5 μm are usually used. In addition,
The shape of the microfiber body itself is not limited to the linear shape and may be, for example, a coil shape. Also, the microfiber body,
Young's modulus E measured by the method shown in FIG. 16 is 10 ⁵ N / m
Those of ² or less are preferable.

A concrete example of the structure of the sound absorbing material of the present invention will be described with reference to FIG. 7 in which the fibrous body 121 is used as a cushioning material. That is, in the sound absorbing material 101 of FIG. 7, in the thin flat box 102 in which the bottom plate 102b is attached to one opening surface of the frame body configured by the side plate 102a and the other opening surface is closed by the acoustically transparent sheet 104. ,
It has a panel structure in which the voids made of the fibrous bodies 121 which are randomly stacked and packed are filled with the powder 103 as exemplified above. In the sound absorbing material 101, the surface closed by the acoustically transparent sheet 104 is the sound absorbing side surface.
The voids formed by the fibrous body 121 include not only voids between the fibrous bodies 121 but also voids between the yarns forming the fibrous body 121. Normally, not all voids are densely packed with powder, and there are unfilled spaces.

The sound absorbing material 101 is, for example, a flat box 102.
The fibrous body 121 is irregularly stacked and housed inside, and the fibrous body 121 is supplied while supplying the powder 103 from above and vibrating.
It can be manufactured by introducing the powder 103 into the void formed in the above step. As the acoustically transparent sheet 104, for example, a breathable woven fabric (for example, saran cloth or glass cloth), a sheet having a thickness of about 0.05 mm or less (for example, polyethylene film, vinyl film, etc.), etc. Can be mentioned. This sheet is designed for the required frequency range (usually 2
It is preferable that the sound transmittance is 0.8 or more at 0 to 4 kHz).

As the flat box 102, wood, gypsum board, calcareous board, wood wool cement board, wood chip cement board, etc. are used, and the width: about 300 to about 900 m.
m, length: about 1800 to about 2400 mm. Of course, in the case of the sound absorbing material according to claims 1 to 3, a non-woven fabric containing powder is stored.

The sound absorbing material of the present invention is the invention according to claim 8, that is, a method for producing a sound absorbing material in which powder and a cushioning material exhibiting a sound absorbing action by vibration are mixed, and the sound absorbing material of the cushioning material layer is It can be manufactured by a method in which the powder is introduced into the buffer material layer by supplying the powder to one surface side and suctioning from the other surface side of the buffer material layer. First, as shown in FIG. 9, a sheet-like porous material (buffer material layer) 41 is arranged in the container 40 that can be evacuated from the bottom so as to partition the inside of the container 40 into upper and lower parts. The powder 43 is evacuated and sucked, and the powder 43 is gradually supplied from above to gradually introduce the powder 43 into the porous material 41.
The powder 43 is collected in the porous material 41 along the flow of the air flowing in from the air introduction port 45 or the like and is filled in a short time. By adjusting the supply amount of the powder 43 and the suction force by a vacuum pump (not shown), the porous material 41
The powder 43 can be filled therein in a uniform state.
The equipment is simple, inexpensive and simple. Even when making a large-scale sound absorbing material, it can be easily handled by securing the size of the container. When a cushioning material that is not in the form of a sheet is used, a layered body is formed of the cushioning material at the porous material 41 in FIG.
Do the same as above.

When the powder 43 is adhered to the porous material 41 as in the case of the sound absorbing material according to claim 2, for example, as shown in FIG. 10, a thermoplastic resin 46 is formed on the surface of the powder 43.
Is applied to form a heat-fusible surface on the powder 43 in advance, and after being introduced into the porous material 41, heat treatment is performed to melt the thermoplastic resin 46, and as shown in FIG. The fibers 48 of the porous material 41 are bonded at some positions A and B. Not limited to this, the thermoplastic resin 46
May be applied to form a heat-fusible surface in advance, or a fiber made of a thermoplastic resin may be used as the fiber 48 to form the heat-fusible surface. The heat-fusible surface may be formed on both the powder and the porous material. Further, the application form of the thermoplastic resin 46 on the surface of the powder 43 may be linear as shown in FIG. 12 or fine particles as shown in FIG. 13 instead of the scale-like form as shown in FIG. As the thermoplastic resin, polyvinyl resin, polyamide resin,
Examples include polyester resins and polyurethane resins.

In the sound absorbing material of the present invention, it is preferable that the powder is in a sufficient amount, but it is preferable not to exceed 90% by volume. This is because the amount of cushioning material should be too small. The cushioning material is, for example, about 5% by volume, and the rest is voids. In contrast, Figure 2
As shown in FIG. 5, it is possible to manufacture the sound absorbing material by placing the powder 43 on the porous material 41 and vibrating it with the vibrator 61. Requires a large shaker, and it takes a long time to fill the powder.
There is a tendency that uniform filling becomes difficult. In addition, FIG.
Although a method of manufacturing a sound absorbing material by using the sedimentation method as shown in FIG. 2 can be considered, it is difficult to uniformly disperse the powder because the sedimentation speeds of the powder 43 and the fiber 48 are different, and the solution 49 is usually used. Since it is an organic solvent, it is necessary to consider hygiene and safety, and the device tends to be complicated and expensive.

FIG. 14 shows the Young's modulus of various powders. The diagonal axis represents the frequency of the sound absorption peak. The measured powder layer thickness is 30 mm. In FIG. 14, a: electrofused magnesia powder, b: heavy calcium carbonate powder, c,
f: acrylic resin powder, d, y: fluororesin powder,
e: whole milk powder, g, α: calcined ferrite powder, h, m:
Shirasu balloon powder, i: carbon black powder, j:
Strong flour (wheat flour), k, l: chlorine method titanium oxide powder,
n: crystalline cellulose powder, o: soft flour (wheat flour), p:
Ishimatsuko, q, s: nylon powder, r: bainite powder, u, v: pearlite powder, t, w: silicon powder, x: natural earth graphite, β: vermiculite, γ:
Vinylidene fluoride powder, δ: soft calcium carbonate powder.

The sound absorbing material of the present invention is used in a listening room,
It can be used not only as an interior material for musical instrument practice rooms, but also as an inside sticker for sound absorbing ducts and as a soundproof cover for equipment that generates noise.

[0040]

The sound-absorbing material of the present invention uses powder that exhibits a sound-absorbing effect by vibration, so that it can have sufficient sound-absorbing performance even if it is thin. Moreover, the apparent Young's modulus of the powder is lowered by the buffer material mixed with the powder, and the sound absorption coefficient at a lower frequency is increased.

Particularly, the Young's modulus of the cushioning material alone is 10 ⁵ N /
In the case of m ² or less, for example, the center frequency of the sound absorption peak is lowered in an appropriate state, and an excellent sound absorption action is exhibited in a lower frequency range. For example, in the case of a sound absorbing material in which vermiculite powder having a sound absorbing characteristic shown by a broken line in FIG. 17 is contained in a nonwoven fabric as a cushioning material, as shown in FIG. The center frequency drops from 337.5 Hz to 250.0 Hz, which decreases to the low frequency side.
Further, in the case of a sound absorbing material in which wet silica powder having a sound absorbing characteristic shown by a broken line in FIG. 21 and silicon carbide whiskers as a cushioning material are mixed in an equal volume ratio, as shown in FIG. 21, the center frequency is 245.00 Hz. To 203.75Hz, the sound absorption coefficient value also increased from 0.85 to 0.92,
It can be clearly seen that the center frequency of the sound absorption peak is shifted to the low frequency side in an appropriate state without deteriorating the sound absorption coefficient.

When at least a part of the powder exhibiting the sound absorbing effect by vibration is contained in the form of being adhered to the cushioning material, the mixed state of the powder and the cushioning material is constant, and the low frequency range is maintained. Excellent sound absorption effect in the stable without changing. Good dimensional stability. When the cushioning material is a fibrous body in which a thin yarn having a small diameter is entwined with a core yarn, the Young's modulus of the cushioning material is sufficiently low and the sound absorption peak frequency shifts to a lower side. Even if it is not increased, the sound absorption performance in the low frequency range becomes higher. In other words, in the sound absorbing material, a soft spring is formed by the fibrous body, and the Young's modulus E of the whole becomes sufficiently small, and the sound absorbing peak frequency shifts to a lower side, so that in a lower frequency range. The sound absorption rate of is increased.

When the powder has a substantially constant sound absorption coefficient in the frequency range above a specific frequency fs, the sound absorbing material itself,
It becomes possible to have sufficient and flat (constant) sound absorption performance (sound absorption coefficient) in a frequency range from a very low frequency to 2000 Hz, which is more useful. When the powder is a mixed powder of a powder made of a granular material and a powder made of a fine fiber body, the sound absorption peak frequency tends to be lowered due to the buffering action of the powder made of the fine fiber body. Therefore, it is preferable.

According to the sound absorbing material manufacturing method of the eighth aspect, it is possible to easily obtain a useful sound absorbing material that exhibits a good sound absorbing action in a low frequency range. According to the method of manufacturing a sound absorbing material described in claim 9, the useful sound absorbing material described in claim 1 can be easily obtained. According to the method of manufacturing a sound absorbing material described in claim 10, the useful sound absorbing material described in claim 2 can be easily obtained.

[0045]

Embodiments of the present invention will be described below in detail with reference to the drawings. Of course, the present invention is not limited to the following embodiments. -Example 1- According to the method for producing a sound absorbing material according to claim 8, the sound absorbing material according to claim 1 was produced as shown in Fig. 9.

A sound absorbing material was obtained by combining the buffer material and the powder. As the cushioning material, a non-woven fabric (thickness 30 mm) made of polyester, which is a sheet-like porous material, was used. This non-woven fabric has a fiber diameter of 25 μm, a bulk density of 0.011 g / cm ³ ,
Young's modulus is 2.1 × 10 ³ N / m ² . Vermiculite classified powder (180 to 250 μm) was used as the powder.

In the sound absorbing material, the true proportion of the non-woven fabric is 0.8% by volume, and the true proportion of the powder is 7.1.
Volume% and the remaining 92.1 volume% are voids.
The sound absorption coefficient versus frequency characteristic of this sound absorbing material is shown by a solid line in FIG. In addition, FIG. 17 shows the sound absorption coefficient versus frequency characteristic of only the vermiculite classified powder (bulk density 0.171 g / cm ³ ) with a broken line. As shown in the figure, in the sound absorbing material of the embodiment, the peak frequency fr is 337.5 Hz to 25.
It has dropped to 0.0Hz. In addition, the Young's modulus is 1.62 × when 2.8 × 10 ⁵ N / m ^{2 of the} powder alone is compounded.
It has fallen to 10 ⁵ N / m ² , about half.

-Example 2- According to the method for producing a sound absorbing material according to claim 9,
The sound absorbing material described in 3 was produced. After all, a sound absorbing material was obtained by combining the types of buffer material and powder. Basically the same as in Example 1, except that wet silica pre-coated with vinyl acetate resin was used as the powder, and heat treatment was performed after filling the powder to adhere the powder to the buffer material. is there.

As a result of investigating the sound absorbing characteristics of the sound absorbing material of Example 2, it was confirmed that the sound absorbing effect in the low frequency region was improved. -Example 3-A sound absorbing material having a thickness of 30 mm was obtained in which vermiculite powder having an average particle diameter of 300 µm was vibrably contained in a polyester nonwoven fabric having an average pore diameter of 515 µm. The Young's modulus E of the nonwoven fabric is 2.6 × 10 ³ N / m.

FIG. 1 shows the sound absorption coefficient versus frequency characteristics of this sound absorbing material.
The solid line is shown in FIG. Further, FIG. 18 shows the sound absorption coefficient vs. frequency characteristic in the case of only vermiculite powder by a chain line.
As shown in the figure, in the sound absorbing material of the embodiment, the specific frequency fs is about 300 Hz to about 250 Hz as compared with the case of using only powder.
The sound absorption coefficient level is almost unchanged.

Example 4 The sound absorbing material of the example has the same structure as that shown in FIG. A powder having a peak in frequency characteristics of sound absorption coefficient has an average particle diameter of 150 μm and a bulk density of 0.2 in a natural state.
8 g / cm ³ of silica powder was used. On the other hand, as the fibrous body, a polyurethane thread having a diameter of 100 μm was used as a core thread, and a nylon thread having a diameter of 10 μm was entangled as a fine thread to have a true density of 1.19 g / cm ³ .

The fibrous bodies are randomly stacked and housed in a box body (porosity 98.6%, Young's modulus 7.56 × 10 ³ N / m).
² ) Then, the created voids were filled with powder. In the sound absorbing material, the true proportion of the non-woven fabric is 1.4.
The volume% and the ratio of the powder to the true are 13.2% by volume, and the remaining 85.4% by volume are voids. In order to know the sound absorbing performance of the obtained sound absorbing material, the sound absorbing layer composed of the fibrous body and powder of the example (thickness 30 mm) and the sound absorbing layer of equal thickness composed of only the powder used in the example The frequency characteristics of the rate were measured. The measurement results are shown in FIG. 19 by a solid line (sound absorbing layer of fibrous body and powder) and a broken line (sound absorbing layer of powder only).

As shown in FIG. 19, the sound absorbing layer made of the fibrous body and the powder of the embodiment is 20% thicker than the sound absorbing layer made of only the powder.
Since the sound absorption coefficient in a very low frequency range of 0 Hz or less is high, it can be clearly seen that the sound absorbing materials of the examples are very effective in suppressing the booming phenomenon. -Example 5-The sound absorbing material of Example 5 has a basic configuration as shown in Fig. 7.

As a powder, a mixture of silica powder having an average particle size of 150 μm and powder (secondary particle size of 50 μm) obtained by aggregating silicon carbide element whiskers (fine fiber bodies) in a volume ratio of 1: 1 is mixed. The powder is contained in the voids of a polyester non-woven fabric having a Young's modulus of 2.6 × 10 ³ N / m ² and is stored in the box. The frequency characteristic of the sound absorption coefficient of this sound absorbing material is shown by the solid line in FIG. The alternate long and short dash line shows the frequency characteristic of the sound absorption coefficient in the case of only the mixed powder without nonwoven fabric.

Referring to FIG. 20, the sound absorbing material of the embodiment is 20
Since the sound absorption coefficient is high in a very low frequency range below 0 Hz, it can be seen that the sound absorbing materials of the examples are also very effective in suppressing the booming phenomenon.

[0056]

Since the sound absorbing material according to claims 1 to 7 uses powder which exhibits a sound absorbing effect by vibration, it has sufficient sound absorbing performance even if it is thin, and moreover, it is powdered by the buffer material mixed with the powder. Has a lower apparent Young's modulus and a higher sound absorption coefficient at lower frequencies, and the Young's modulus of the cushioning material alone is 10 ⁵ N.
/ M ² or less, the effect of improving the sound absorption is remarkable, and if at least a part of the powder is adhered to the cushioning material, the excellent sound absorbing effect in the low frequency range is stable and does not change. ..

In addition to the above, in the case of using a fibrous body in which a small-diameter thin yarn is entwined with a core yarn as a cushioning material, Young's modulus of the cushioning material is sufficiently low, and a remarkable sound absorbing coefficient improving effect is expected. If the powder has a substantially constant sound absorption coefficient in a frequency range of a specific frequency fs or more, the sound absorbing material itself,
Since it is possible to have a sufficient and flat (constant) sound absorption performance (sound absorption coefficient) in a frequency range from an extremely low frequency to 2000 Hz, there is an advantage that it is more useful.

When the powder is a mixed powder of a powder made of a granular material and a powder made of a fine fibrous body, the frequency of the sound absorption peak is increased by the buffering action of the powder made of the fine fibrous body. It is preferable because it tends to be low. According to the method of manufacturing a sound absorbing material described in claim 8, it is possible to easily obtain a useful sound absorbing material that exhibits a good sound absorbing action in a low frequency range.

According to the manufacturing method of the sound absorbing material described in claim 9, the useful sound absorbing material described in claim 1 can be easily obtained. According to the method of manufacturing a sound absorbing material described in claim 10, the useful sound absorbing material described in claim 2 can be easily obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an internal configuration example of a sound absorbing material according to claim 1.

FIG. 2 is an explanatory diagram showing another internal configuration example of the sound absorbing material of claim 1.

FIG. 3 is an explanatory diagram showing an internal configuration example of the sound absorbing material of claim 2.

FIG. 4 is an explanatory diagram illustrating another internal configuration example of the sound absorbing material of claim 2.

FIG. 5 is an explanatory view showing another internal configuration example of the sound absorbing material of claim 2;

FIG. 6 is an explanatory diagram showing an internal configuration example of the sound absorbing material of claim 7;

FIG. 7 is a perspective view showing a specific configuration example of the sound absorbing material of claim 5.

FIG. 8 is an explanatory diagram showing a configuration example of a fibrous body in the sound absorbing material of claim 5;

FIG. 9 is an explanatory diagram showing a state when a sound absorbing material is produced by the invention according to claim 8.

FIG. 10 is a front view showing an example of powder used when making the sound absorbing material of claim 2.

FIG. 11 is an explanatory diagram showing a bonded state of the powder and the cushioning material in the sound absorbing material of claim 2.

FIG. 12 is a front view showing another powder example used when making the sound absorbing material of claim 2.

FIG. 13 is a front view showing another powder example used when the sound absorbing material according to claim 2 is produced.

FIG. 14 is a graph showing the bulk density and Young's modulus of powder.

FIG. 15 is an explanatory diagram showing a state when the powder layer vertically vibrates.

FIG. 16 is a block diagram showing a system for measuring Young's modulus.

FIG. 17 is a graph showing the sound absorption coefficient versus frequency characteristics of the sound absorbing material of Example 1.

FIG. 18 is a graph showing the sound absorption coefficient versus frequency characteristic of the sound absorbing material of Example 3;

FIG. 19 is a graph showing the sound absorption coefficient versus frequency characteristics of the sound absorbing material of Example 4.

FIG. 20 is a graph showing the sound absorption coefficient versus frequency characteristics of the sound absorbing material of Example 5.

FIG. 21 is a graph showing frequency characteristics of sound absorption coefficient of an example of the sound absorbing material of the present invention.

FIG. 22 is a graph showing frequency characteristics of sound absorption coefficient of a calcium silicate powder layer.

FIG. 23 is a graph showing the sound absorption coefficient versus frequency characteristics of the wet silica powder layer.

FIG. 24 is a graph showing the sound absorption coefficient versus frequency characteristic of the vermiculite powder layer.

FIG. 25 is an explanatory diagram showing a state of making a sound absorbing material by a vibration method.

[Fig. 26] Fig. 26 is an explanatory diagram showing a state when a sound absorbing material is produced by a sedimentation method.

FIG. 27 is a cross-sectional view showing the internal structure of urethane foam.

FIG. 28 is a cross-sectional view showing the internal structure of glass wool.

FIG. 29 is a graph showing frequency characteristics of sound absorption coefficient of urethane foam.

[Fig. 30] Fig. 30 is a graph showing the frequency characteristics of the sound absorption coefficient of glass wool.

[Explanation of symbols]

 1 buffer material 2 holes 3 powder 10 buffer material 12 holes 13 powder 20 buffer material 22 holes 23 powder

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[Procedure amendment]

[Submission date] June 19, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

[0009] silicic acid calcium powder layer 22 (thickness 3
The sound absorption coefficient vs. frequency characteristic of the 0 mm) is shown in FIG. The sound absorption coefficient is JIS A 140
5 "Measurement method for normal incidence sound absorption coefficient of building materials by in-pipe method"
Normal incident sound absorption coefficient measured in accordance with. The measurement was performed using the A tube, but since it was a powder, it was measured by standing it up. The sound absorption coefficient was calculated based on the acoustic impedance .

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

The particle diameter and the like in the powder layer are as follows. "Silicate Cal average particle size: 25 [mu] m, true density: 2.52 g / cm ³ Siumu powder" bulk density: 0.080 g / cm ³ porosity: 0.97 "wet silica" mean particle diameter: 150 [mu] m, a true density 2.1 g / cm ³ bulk density: 0.282 g / cm ³ porosity: 0.87 as seen in FIG. 22 and 23, both a peak at 500Hz below (hereinafter, referred to as "sound absorption peak") have occurs The sound absorption coefficient in the low frequency range is high. As shown in FIG. 15, the sound absorption peak is generated when the powder layer P vibrates in the longitudinal vibration mode, thereby effectively absorbing the sound in the low frequency range.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

The Young's modulus of a few cushioning materials will be specifically described below. “Glass wool 36k”: Young's modulus 7.8 × 10 ⁴ (N / m ² ): Density 3.6 × 10 ⁻² (g / cm ³ ) “Synthetic pulp”: Young's modulus 2.0 × 10 ³ (N / m ² ) (fiber length 100 μm): density 8.9 × 10 ⁻² (g / cm ³ ) “silicon carbide whiskers”: Young's modulus 8.5 × 10 ⁴ (N / m ² ): density 3.6 × 10 ^-1 (g / ^cm 3) "polypropylene fibers many: Young's modulus ^{1.4 × 10 2 (N / m} 2) porous material": density ^{2.4 × 10 -2 (g / cm} 3) the invention of claim 1, wherein As the powder used in the above ,
Other silicic acid calcium powder and wet silica, mica powder,
Vermiculite powder, A acrylic ultra fine powder, a spherical silica powder or the like may be mentioned. Specific examples of powder are given below. "Talc Powder" average particle size 9.4 .mu.m, true density: 2.75 g / cm ³ Bulk density: 0.45 g / cm ³ porosity: 0.84 "Talc Powder" average particle size: 2.3 .mu.m, true Density: 2.75 g / cm ³ Bulk density: 0.25 g / cm ³ Porosity: 0.91 “Spherical silica powder” Average particle size: 28 μm, True density: 2.23 g / cm ³ Bulk density: 0.92 g / Cm ³ Porosity: 0.59 The Young's modulus E of the cushioning material is measured by filling the cylinder-shaped container 50 with the cushioning material 51 to be measured and then adding the additional mass piece, as shown in FIG. Put 52. Then, the exciter 53 excites the vibration, and the transfer function between the vibration acceleration of the impedance head 56 and the vibration acceleration of the additional mass piece 52 is obtained by the FET analyzer 57 via the charge amplifiers 54 and 55. Finally, the Young's modulus E is calculated from the frequency of the peak of the transfer function by the personal computer 58. In addition, the Young's modulus E of the powder layer or the cushioning material containing the powder E
Can be similarly measured.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0030

[Correction method] Change

[Correction content]

The sound absorption coefficient referred to here is also based on JIS A
1405 is a vertical incident sound absorption coefficient measured in accordance with the “internal pipe method vertical incident sound absorption measuring method”, which is measured at a sound absorber thickness of 30 mm (filling thickness of powder packed layer: 30 mm). Sound absorption coefficient is calculated by acoustic impedance
Perform based on dance . Further, as a powder, as seen in FIG. 6, a mixed powder of the powder 1 3 and the powder 15 made of a micro-fibrous body consisting of granules, which, voids of the sheet-like porous material of 12 Or may be made to exist in a void made of a fibrous body in which a thin yarn having a small diameter is entwined with a core yarn.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction content]

FIG. 14 shows the Young's modulus of various powders. The diagonal axis represents the frequency of the sound absorption peak. The measured powder layer thickness is 30 mm. In FIG. 14, a: electrofused magnesia powder, b: heavy calcium carbonate powder, c,
f: acrylic resin powder, d, y: fluororesin powder,
e: whole milk powder, g, α: calcined ferrite powder, h, m:
Shirasu balloon powder, i: carbon black powder, j:
Strong flour (wheat flour), k, l: chlorine method titanium oxide powder,
n: crystalline cellulose powder, o: soft flour (wheat flour), p:
Lycopodium, q, s: nylon powder, r: base cement Night powder, u, v: perlite powder, t, w: silicon powder, x: natural soil-like graphite, β: vermiculite, γ:
Vinylidene fluoride powder, δ: soft calcium carbonate powder.

Claims (10)

[Claims] 1. A sound absorbing material in which powder and a cushioning material exhibiting a sound absorbing effect by vibration are mixed, and the Young's modulus of the cushioning material alone is 10 ⁵ N / m ² or less. Sound absorbing material. 2. A sound absorbing material in which powder and a cushioning material exhibiting a sound absorbing effect by vibration are mixed, and at least a part of the powder is adhered to the cushioning material. Material. 3. The Young's modulus of the buffer material alone is 10 ⁵ N / m ^2.
The sound absorbing material according to claim 2, which is as follows. 4. The cushioning material is a sheet-like porous material, and the powder and the cushioning material are present in a mixed state by introducing the powder into the voids in the porous material. The sound absorbing material according to any one of 3 to 3. 5. The sound absorbing material according to claim 1, wherein the cushioning material is a fibrous body formed by entwining a core thread with a thin thread having a small diameter. 6. The sound absorbing material according to any one of claims 1 to 5, wherein the powder has a substantially constant sound absorption coefficient at a frequency higher than a specific frequency. 7. The sound absorbing material according to any one of claims 4 to 6, wherein the powder is a mixed powder of a powder of a granular body and a powder of a fine fibrous body. 8. A method of manufacturing a sound absorbing material, which comprises a mixture of powder and a cushioning material exhibiting a sound absorbing effect by vibration, wherein the powder is supplied to one surface of the cushioning material layer and the other surface of the cushioning material layer is supplied. A method of manufacturing a sound absorbing material, wherein powder is introduced into a cushioning material layer by performing suction from the side. 9. The method for producing a sound absorbing material according to claim 8, wherein the cushioning material alone has a Young's modulus of 10 ⁵ N / m ² or less. 10. A powder having a heat-fusible surface is used as at least one of the powder and the cushioning material, and the powder is buffered by introducing the powder into the cushioning material layer and then performing heat treatment. The method for manufacturing a sound absorbing material according to claim 8 or 9, wherein the sound absorbing material is adhered to the material.