JP2008009014A - Porous soundproof structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous soundproof structure which can ample sufficient sound-absorbing performance in a wide frequency band, without having to excessively enlarge the sound-absorbing structure. <P>SOLUTION: The porous soundproof structure 100 is so constituted that a porous panel 2 with a large number of through-holes 2a is arranged to face a panel member 1 with a shut-off surface 1a, to intercept the air from passing therethrough, and is provided with a resonator 4, including frame bodies 4a, 4b which partition the space sandwiched between the panel member 1 and the porous panel 2, to form resonance chambers 4c, and hole parts 4d which allow the resonance chambers 4c to communicate with the outside of the resonance chambers 4c. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a porous soundproof structure installed for the purpose of reducing noise in railways, roadsides, around machines, or indoors.

Conventionally, for the purpose of noise reduction, porous sound absorbing materials such as glass wool, felt, and urethane have been used. These porous sound-absorbing materials are excellent in sound absorption in a high frequency band.
Also, a sound absorbing mechanism using a Helmholtz resonator, which is a mechanism that absorbs sound by a resonance phenomenon, is configured by a small cavity and a small opening that communicates with the outside of the cavity. The resonance frequency f of the Helmholtz resonator is
“F = (c / 2π) × {s / V (l + 0.8d)} ^1/2 “
Given in. Here, c is the speed of sound in the air, s is the opening area, V is the closed space volume, l is the plate thickness of the opening, and d is the diameter of the opening. The Helmholtz resonator can perform sound absorption at the resonance frequency obtained from the above equation by designing the opening area s as a parameter, and is excellent in sound absorption at a specific frequency. As a sound absorption mechanism using the principle of the Helmholtz resonator, there are those disclosed in Patent Document 1, Patent Document 2, and Patent Document 3, as shown below.

  The resonance type sound absorption / sound insulation panel described in Patent Document 1 is formed by adjoining a plurality of resonance chambers having different cross-sectional areas, and corresponds to a plurality of frequency bands that require sound absorption. . Thus, it has excellent sound absorption efficiency and sound insulation performance. In addition, the sound absorbing structure described in Patent Document 2 is a structure including a large number of hollow ridges that form a Helmholtz resonator, and a gap formed between the ridge and the mounting material by attaching the ridges to the mounting material. This prevents the strong wind from wrapping around the gap and prevents the sound absorbing structure from being peeled off from the mating material. Moreover, the sound-insulating sound absorbing plate described in Patent Document 3 has a two-degree-of-freedom by arranging a sound-insulating flat plate, a porous flat plate in which small holes are formed over the entire surface, and a flat plate in which slits are formed in parallel. A resonance system is formed and has a sound absorption effect for two resonance frequencies. Since this sound insulation sound absorbing plate can be easily manufactured by forming slits and holes in a flat plate, it can be made inexpensive.

  On the other hand, the porous soundproof structures described in Patent Document 4 and Patent Document 5 have a configuration in which an interior plate in which a large number of through holes are formed on the entire plate surface is arranged to face the surface member via an air layer. The sound absorption by the fine porous plate is performed. The sound absorption by the fine porous plate can be absorbed in a wide band by the viscous attenuation of the air by the fine hole portion as compared with the Helmholtz resonator.

JP-A-6-1229029 JP-A-10-245823 JP 2003-268728 A JP 2002-175083 A Japanese Patent Laid-Open No. 2003-50586

However, the sound absorption mechanisms described in Patent Document 1 and Patent Document 2 are provided with a plurality of resonators having different resonance frequencies, and since the sound absorption area of the resonator is small for each frequency, Since the sound absorption performance is reduced, there is a possibility that sufficient sound absorption cannot be performed. Further, the sound absorbing mechanism described in Patent Document 3 is a sound absorbing mechanism using a slit having a wide opening width, and it is difficult to make the opening area fine. For this reason, the sound absorption band may be narrowed.
On the other hand, the sound absorbing structures described in Patent Document 4 and Patent Document 5 can absorb sound in a wide frequency band, but the lower limit of the frequency at which sound can be absorbed is determined by the total thickness of the sound absorbing structure. In order to achieve this, it is necessary to increase the total thickness of the sound absorbing structure. In addition, it is possible to absorb sound in a lower frequency band by reducing the aperture ratio of the fine porous plate on the most surface side, but in this case, there is a problem that the sound absorption coefficient in the high frequency band decreases. is there.

  In view of the above circumstances, an object of the present invention is to provide a porous soundproof structure capable of exhibiting sufficient sound absorption performance in a wide frequency band without excessively increasing the total thickness of the sound absorption structure. To do.

Means and effects for solving the problems

  The present invention relates to a porous soundproof structure installed for the purpose of reducing noise in railways, roadsides, around machines, or indoors. And the porous soundproof structure which concerns on this invention has the following some characteristics, in order to achieve the said objective. That is, the porous soundproof structure according to the present invention includes the following features alone or in combination as appropriate.

  In order to achieve the above object, the first feature of the porous soundproof structure according to the present invention is that it has a large number of through holes and is opposed to a surface member having a blocking surface for blocking the passage of air. And a resonator having a perforated plate, a frame that partitions a space between the surface member and the perforated plate, and a hole that penetrates the frame.

According to this configuration, the energy of air vibration is converted into thermal energy by the friction of air in the through-hole formed in the perforated plate, and sound absorption in a high frequency broadband is possible.
Further, a space between the surface member and the perforated plate is defined by a frame having holes, and a closed space communicating with the outside is formed by the holes. Thereby, a resonator having the closed space as a resonance chamber is formed between the perforated plate and the surface member. With this resonator, it is possible to absorb sound in a low frequency band without increasing the distance between the surface member and the perforated plate. Since the inside and the outside of the resonator communicate with each other through a hole penetrating the frame body, the aperture ratio can be reduced by reducing the opening area of the hole or reducing the number of holes to be formed. The frequency band that can be absorbed by the resonator can be easily set to a lower frequency band without increasing the size of the resonator.
Therefore, it is possible to exhibit a sufficient sound absorbing performance in a wide frequency band without excessively increasing the total thickness of the sound absorbing structure.

  Further, the second feature of the porous soundproof structure according to the present invention is that a plurality of the porous plates are provided to be laminated via an air layer, and sound waves from the sound source all pass through the plurality of porous plates. By doing so, it reaches the blocking surface.

  According to this configuration, a resonance frequency corresponding to the number of perforated plates appears, and sufficient sound absorbing performance can be exhibited not only in the vicinity of a specific frequency but also in a wider frequency band.

  The third feature of the porous soundproof structure according to the present invention is that the resonator has a dimension in a direction parallel to the blocking surface larger than a dimension in a direction perpendicular to the blocking surface. Is formed.

  According to this configuration, the volume inside the resonator can be increased without increasing the length of the resonator in the direction perpendicular to the blocking surface, that is, in the thickness direction of the porous soundproof structure. Since the resonance frequency of the resonator can be lowered by increasing the volume inside the resonator, sound absorption in the low frequency band can be performed with a thinner porous soundproof structure.

  A fourth feature of the porous soundproof structure according to the present invention is that the hole is formed in the vicinity of the end of the resonator in a direction parallel to the blocking surface.

  According to this structure, the distance from the hole located near the end of the internal space of the resonator to the end opposite to the end where the hole is formed can be increased. Thereby, since it is possible to lower the resonance frequency of the second or higher order, it is possible to absorb sound in a wider frequency range in the low frequency band.

  A fifth feature of the porous soundproof structure according to the present invention is that the hole is formed on a surface perpendicular to the blocking surface of the frame.

  According to this configuration, the length of the air layer (back air length) in the direction of penetration of the hole in the resonator can be increased. When the back air length is increased, the frequency interval at which the sound absorption peak appears is reduced. Therefore, it is possible to include more frequencies at which the sound absorption peak is present in a certain frequency range. Therefore, sound absorption in a wider frequency range is possible.

  A sixth feature of the porous soundproof structure according to the present invention is that a porous sound absorbing material is disposed in a space between the face member and the porous plate.

  According to this configuration, since the air resistance in the space sandwiched between the surface member and the porous plate by the porous sound absorbing material increases, it is possible to increase the attenuation of air vibration. Therefore, the sound absorption performance of the porous soundproof structure can be improved.

  A seventh feature of the porous soundproof structure according to the present invention is that at least one of the porous plates has a concave shape or a convex shape on the surface.

  According to this configuration, it is possible to improve the sound absorption performance with respect to not only the sound wave perpendicularly incident on the porous soundproof structure but also the sound wave incident obliquely.

  Further, an eighth feature of the porous soundproof structure according to the present invention is that at least one of the porous plates is formed so that a cross section has a wave shape.

  According to this configuration, it is possible to improve the sound absorption performance with respect to not only a sound wave perpendicularly incident on the porous soundproof structure but also an obliquely incident sound wave with a simpler structure.

  A ninth feature of the porous soundproof structure according to the present invention is that at least one of the porous plates has an embossed surface.

  According to this configuration, it is possible to easily form irregularities on the surface by surface processing of the flat plate, and it is possible to improve the sound absorption performance for not only the sound wave incident perpendicularly to the porous soundproof structure but also the sound wave incident obliquely. .

  The tenth feature of the porous soundproof structure according to the present invention is that a porous sound absorbing material is disposed inside the resonator.

  According to this configuration, the air resistance inside the resonator is increased by the porous sound absorbing material, so that it is possible to increase the attenuation of the air vibration. Therefore, the sound absorption performance in the frequency band where sound is absorbed by the resonator can be improved. Moreover, since the sound speed in the porous sound-absorbing material is slow, it is possible to absorb lower frequencies.

  The eleventh feature of the porous soundproof structure according to the present invention is that the opening diameter of the hole is 3 mm or less.

  According to this configuration, the attenuation of the air vibration can be increased by increasing the air viscous resistance in the hole of the resonator, so that the sound absorption performance can be improved. Moreover, the width of the frequency band in which sound can be absorbed can be widened by the action of the viscosity of air in the hole.

  A twelfth feature of the porous soundproof structure according to the present invention is that the hole is formed as a cylindrical member having a flow path that communicates the inside of the resonator and the outside of the resonator. The cylindrical member is formed so as to protrude from the frame body toward at least one of the outside of the resonator and the inside of the resonator.

According to this configuration, the channel volume can be increased without increasing the cross-sectional area of the channel by increasing the length of the communication channel in the hole. Since the resonance frequency of the resonator becomes a lower frequency as the flow path volume increases, the porous soundproof structure enables sound absorption in a lower frequency band.
Further, when the hole is formed so as to penetrate the frame body in a direction parallel to the blocking surface of the surface member, the resonator is perpendicular to the blocking surface by the protruding hole, That is, it is possible to form a thinner porous soundproof structure without being elongated in the thickness direction of the porous soundproof structure.

  The thirteenth feature of the porous soundproof structure according to the present invention is that the size of the opening diameter of the through hole is 3 mm or less. Porous soundproof structure.

  According to this configuration, the attenuation of air vibration can be increased by increasing the viscous resistance of air in the through-hole formed in the perforated plate, so that the sound absorption performance can be improved. Moreover, the width of the frequency band in which sound can be absorbed can be increased by the action of the viscosity of air in the through hole.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. The porous soundproof structure according to the present embodiment can be similarly applied to a site where a conventional sound absorbing member is used. For example, as a structural panel of a soundproof range that realizes inner sound absorption and outer sound insulation. Used for a wide variety of noise sources such as motors and gears. Moreover, it is applicable also as a sound-absorbing board, such as a hall and a living room.

  FIG. 1 is a cross-sectional perspective view showing a schematic configuration of a porous soundproof structure according to an embodiment of the present invention. A porous soundproof structure 100 according to this embodiment includes an exterior plate 1 (surface member) having a blocking surface 1a that blocks air, a first porous plate 2 (porous plate), and a second porous plate 3 (porous plate). ) And the resonator 4, and a structure formed in a thin plate shape having a closed space inside.

  The porous soundproof structure 100 has a structure in which these plate materials are laminated via an air layer in the order of the first porous plate 2, the second porous plate 3, and the exterior plate 1 from the noise source side. 2, the 2nd porous board 3 and the exterior board 1 are being fixed to the side board 5 which forms the both sides | surfaces (both end surfaces in the X-axis direction in FIG. 1) of the porous soundproof structure 100. FIG. Further, both end portions in the longitudinal direction (Y direction in FIG. 1) of the porous soundproof structure 100 are not shown so that the space formed by the exterior plate 1, the first porous plate 2, and the side plate 5 is a closed space. It is blocked by a partition plate. The thickness of the porous soundproof structure 100 in the stacking direction (Z-axis direction in FIG. 1) is, for example, 60 mm.

  The exterior board 1 is a board | plate material formed so that attachment to the wall surface requested | required to interrupt noise, for example, and can be formed with metals, such as iron and aluminum, and synthetic resins. The wall surface itself that is required to block the noise is used as a blocking surface for blocking the passage of air, and the porous plate and the resonator are arranged on the wall surface without using the exterior plate 1. It is also possible to form a quality soundproof structure. In this case, a thinner structure can be provided as the soundproof structure including the wall surface.

  The first perforated plate 2 is a perforated plate having a plurality of through holes 2a, and can be formed of a metal such as iron or aluminum or a synthetic resin, for example. The thickness of the first porous plate 2 can be formed, for example, as 0.8 mm. The through holes 2a are formed so as to be uniformly distributed throughout the first perforated plate, and are formed as holes having a diameter of 0.8 mm, for example. By reducing the diameter of the through-hole 2a, the viscous action of the air passing through the through-hole 2a becomes remarkable, and the air vibration is more easily attenuated, so that the sound absorption performance can be improved. In addition, the hole shape of the through-hole 2a is not restricted to circular shape, It is also possible to form in polygonal shapes, such as a rectangle.

The second perforated plate 3 is a perforated plate having a plurality of through holes 3a, and can be formed of a metal such as iron or aluminum or a synthetic resin, for example. The thickness of the second porous plate 3 can be formed, for example, as 0.1 mm. Moreover, the through-hole 3a is uniformly formed in the whole 2nd perforated plate 3, for example, is formed so that it may become a diameter of 0.1 mm.
By making the diameter of the through hole 3a formed in the second porous plate 3 smaller than the diameter of the through hole 2a formed in the first porous plate 2, the viscosity attenuation of the air passing through the hole can be increased. It is possible to further widen the frequency band in which sound can be absorbed by the porous soundproof structure 100.

  By making the size of the opening diameter of the through hole formed in the first porous plate 2 or the second porous plate 3 to be a fine hole of 3 mm or less, the viscous attenuation of air can be increased as described above. When the sound absorption target sound source is 70 dB or more, the air passing through the through hole can be attenuated by pressure loss. The lower limit value of the opening diameter is preferably 0.05 mm. The reason for this is that when the opening diameter is 0.05 mm or less, the resistance to the air flow increases and the sound absorption performance decreases. In addition, it becomes difficult to process the perforated plate and the cost is increased, and depending on the use environment, the through hole is easily closed by dust or dust. Further, the aperture ratio of the perforated plate can be, for example, 3% or less, whereby sufficient sound absorption characteristics can be obtained, and the number of through holes can be reduced to shorten the perforated plate creation time.

The resonator 4 includes frames 4a and 4b that define a resonance chamber 4c by dividing a space between the outer plate 1 and the second porous plate 3. The frame includes a portion 4a (parallel portion) having a surface arranged in parallel with the exterior plate 1 and a portion 4b (vertical portion) having a surface arranged perpendicular to the exterior plate 1, and in the resonance chamber 4c. A direction perpendicular to the thickness direction (a direction parallel to the blocking surface 1a) rather than a dimension of the porous soundproof structure 100 in a thickness direction (a direction perpendicular to the blocking surface 1a, the Z-axis direction in FIG. 1), FIG. In the X-axis direction and Y-axis direction).
Further, in the vertical portion 4b of the frame body, a plurality of through holes 4d (hole portions) are opened side by side in the longitudinal direction (Y-axis direction in FIG. 1) of the vertical portion 4b, and the through holes 4d are porous. The soundproof structure 100 is formed so as to penetrate the vertical portion 4b of the frame body in a direction perpendicular to the thickness direction of the soundproof structure 100 (a direction parallel to the blocking surface 1a, the X-axis direction in FIG. 1). In other words, the through-hole 4d is formed at the end of the resonator 4 having the resonance chamber 4c which is a flat closed space (the end in the direction parallel to the blocking surface 1a (X-axis direction in FIG. 1)). Yes. The dimension of the opening diameter of the through hole 4d can be formed as 1 mm, for example. The frames 4a and 4b can be formed of, for example, a metal such as iron or aluminum or a synthetic resin. The resonator 4 faces the vertical portion 4b of the frame body in which the through-hole 4d is formed in the central portion (the central portion in the X-axis direction in FIG. 1) of the porous soundproof structure 100 with a certain interval. Two are provided. The resonance chamber 4c is closed by partition plates (not shown) at both ends in the longitudinal direction (Y direction in FIG. 1) of the porous soundproof structure 100.
Note that the shape of the hole formed by the through hole 4d is not limited to a circular shape, and may be a polygonal shape such as a rectangle. Moreover, it is also possible to comprise a hole part with a slit.

  FIG. 2 shows the sound absorption characteristics (examples) of the porous soundproof structure 100 according to the present embodiment and, as a comparative example, the sound absorption characteristics of a soundproof structure having a configuration in which the resonator 4 in the porous soundproof structure 100 is removed ( In the structure of Comparative Example 1) and Comparative Example 1, the sound absorption characteristics (Comparative Example 2) when the aperture ratio of the perforated plate is reduced in order to perform sound absorption in a lower frequency band are shown.

  As shown in FIG. 2, this embodiment (example) has a sound absorption characteristic with a sound absorption coefficient of 0.6 or more in a wide frequency band from 315 Hz to 4 kHz. On the other hand, in Comparative Example 1, the sound absorption coefficient is 0.6 or more in the frequency band from 630 Hz to 4 kHz, but the sound absorption coefficient in the frequency band of 500 Hz or less is 0.5 or less. Further, in Comparative Example 2 in which the aperture ratio of the surface perforated plate is reduced in order to absorb sound in a lower frequency band, the sound absorption coefficient is 0.6 or more in the frequency band from 400 Hz to 800 Hz, but the high frequency of 1 kHz or more. In the frequency band, the sound absorption rate is remarkably reduced, and the sound absorption rate is 0.6 or less. This is considered to be because sound waves are less likely to be transmitted into the soundproof structure by reducing the aperture ratio of the perforated plate.

  As described above, the porous soundproof structure 100 according to the present embodiment exhibits the sound absorption performance in the high frequency band by converting the energy of air vibration into thermal energy due to the friction of air in the through hole 2a and the through hole 3a. In addition, the resonator 4 provided inside the porous soundproof structure 100 is difficult to absorb sound in the structure formed by the exterior plate 1, the first porous plate 2, and the second porous plate 3. Band sound absorption is possible. Thus, sound absorption in a low frequency band where sound absorption is difficult in Comparative Example 1 is possible (see FIG. 2). Further, since the resonator 4 can be installed inside the structure without changing the aperture ratio of the first porous plate 2 and the second porous plate 3, the sound absorption coefficient in the low frequency band can be improved. This is advantageous because it does not deteriorate the sound absorption coefficient in the high frequency band as in FIG. 2 (see FIG. 2).

  Further, since the resonance chamber 4 and the outside of the resonance chamber 4 communicate with each other through the through hole 4d, the opening diameter of the through hole 4d is reduced or the number of the through holes 4d formed in the frame body 4a is reduced. Thus, it is possible to easily reduce the aperture area of the resonator 4 and reduce the aperture ratio. Thus, the frequency band that can be absorbed by the resonator 4 without changing the size of the resonance chamber 4a can be absorbed by the structure formed by the exterior plate 1, the first porous plate 2, and the second porous plate 3. It is possible to easily make the frequency band lower than the band. Therefore, a change in the size of the resonator 4 suppresses a decrease in sound absorption performance in a high frequency band where sound can be absorbed by the action of the first perforated plate 2 and the second perforated plate 3, and a lower frequency band. It is possible to perform sound absorption. Thus, it is possible to exhibit sufficient sound absorbing performance in a wide frequency band without increasing the size of the sound absorbing structure.

  In addition, when an opening is formed in the resonator 4 so as to have a predetermined opening ratio, it is possible to form the opening by dispersing the entire surface of the resonator 4 by using a through hole as the opening. And by locally concentrating the openings, it is possible to suppress the occurrence of bias in the sound absorption characteristics depending on the position where the sound wave is incident on the porous soundproof structure 100, and more uniformly in the plane where the openings are formed. It is possible to exhibit sound absorption characteristics.

  Further, the first perforated plate 2 and the second perforated plate 3 are provided so as to be laminated via an air layer, and sound waves from a sound source pass through the first perforated plate 2 and the second perforated plate 3. Therefore, at least two resonance frequencies appear in the porous soundproof structure 100. Therefore, high sound absorption performance can be exhibited not only in the vicinity of one frequency but also in a wider frequency band.

  The resonance chamber 4c in the resonator 4 has a thin flat shape (in the thickness direction dimension) extending in a plane (XY plane in FIG. 1) perpendicular to the thickness direction of the porous soundproof structure 100. (The shape having a large dimension in a plane perpendicular to the thickness direction), the volume of the resonance chamber 4a can be increased while suppressing the resonator 4 from increasing in the thickness direction. By increasing the volume of the resonance chamber 4a, the resonance frequency of the resonator 4 obtained from the formula for calculating the Helmholtz resonance frequency can be lowered. Therefore, sound absorption in the low frequency band can be performed with a thinner porous soundproof structure. It becomes possible.

  The through-hole 4d of the resonator 4 is formed so as to penetrate the vertical portion 4b of the frame body in a direction parallel to the blocking surface 1a. Since the dimension of the resonance chamber 4c in the penetration direction (X-axis direction in FIG. 1) of the through hole 4d is larger than the dimension of the resonance chamber 4c in the thickness direction (Z-axis direction in FIG. 1), the parallel portion of the frame body The length of the air layer (rear air length) existing in the penetration direction of the through hole 4d in the resonance chamber 4c can be made larger than when the through hole 4d is formed so as to penetrate in the thickness direction at 4a. . Here, the frequency interval Δf at which the sound absorption peak appears can be obtained by the following equation: Δf = c / (2L) (L: back air length, c: sound speed), and by increasing the back air length L, The frequency interval Δf can be reduced. That is, it is possible to include more frequencies at which the sound absorption peak by the resonator 4 is present in a certain frequency range. Therefore, the resonator 4 can absorb sound in a wide frequency range, and the sound absorbing performance of the porous soundproof structure 100 can be improved.

  Further, as shown in FIG. 3, a porous soundproof structure composed of an exterior plate 1, a first porous plate 2, and a resonator 4, in a space sandwiched between the exterior plate 1 and the first porous plate 2. For example, the porous soundproofing structure 101 in which the porous sound absorbing material 6 formed in a plate shape is provided can also be used. This is a configuration in which the second perforated plate 3 in the porous soundproof structure 100 (see FIG. 1) is replaced with a porous sound absorbing material 6, and the same members are denoted by the same reference numerals and description thereof is omitted.

  The porous sound absorbing material 6 may be formed by compressing a metal fiber such as aluminum or stainless steel or a strip-shaped metal, or may be formed of a nonwoven fabric. Moreover, the foam of a metal or a resin material may be sufficient. Furthermore, the porous sound absorbing material 6 may be made of the same metal so that good recyclability can be obtained if the exterior plate 1, the first porous plate 2, and the resonator 4 are made of metal. desirable. The porous sound-absorbing material 6 is not limited to being formed in a plate shape, and for example, a metal fiber, a nonwoven fabric, or the like may be filled in the space in the porous soundproof structure.

The porous sound-absorbing material 6 installed in this way can provide attenuation to sound waves in a wide frequency band, and can widen the sound absorption band of the porous soundproof structure.
The porous soundproof structure 101 has a configuration in which the second porous plate 3 in the porous soundproof structure 100 (see FIG. 1) is replaced with the porous sound absorbing material 6, but the second porous plate 3 is removed. The porous sound-absorbing material may be installed in the internal space in a porous sound-proof structure having a plurality of perforated plates such as the porous sound-proof structure 100 or the like.

  Moreover, a porous soundproof structure can also be formed using a porous plate having an uneven shape on the surface. For example, as shown in FIG. 4, the first perforated plate 2, the corrugated perforated plate 7 which is a plate material in which a large number of through-holes 7a are formed and has a corrugated cross section, and the exterior plate 1 are arranged in this order. The porous soundproof structure 102 may be configured to have a resonator 4 between the corrugated porous plate 7 and the exterior plate 1. In addition, the same code | symbol is attached | subjected to the same member as the porous soundproof structure 100 (refer FIG. 1), and description is abbreviate | omitted.

  In this way, by using a porous plate having an uneven shape on the surface, not only the sound absorption coefficient (perpendicular incident sound absorption coefficient) for a sound wave perpendicularly incident on the surface of the porous soundproof structure 102 but also from an oblique direction. The sound absorption coefficient for incident sound waves (oblique incident sound absorption coefficient) and the sound absorption coefficient for random sound waves (random incident sound absorption coefficient) can also be increased. Further, by using the corrugated porous plate 7, it is possible to form an uneven shape with a simple structure. Moreover, an uneven | corrugated shape can also be formed in the surface by embossing the surface of a flat porous plate. As a result, a porous plate having unevenness on the surface can be formed thinner.

  In the porous soundproof structure having a plurality of perforated plates such as the porous soundproof structure 102, not only when the uneven shape is formed on only one perforated plate, but also on the plurality of perforated plates. May be. It is also possible to form a concavo-convex shape on the porous plate (for example, the first porous plate 2 in the porous soundproof structure 102) that becomes the surface of the porous soundproof structure. Further, not only when the unevenness is formed by the above-described method, it is possible to increase the oblique incident sound absorption coefficient or the random incident sound absorption coefficient by forming an uneven shape on the surface of the porous plate.

  Moreover, as shown in FIG. 5, it can also be set as the porous sound-insulation structure 103 of the structure which has arrange | positioned the porous sound-absorbing material 6 in the resonance chamber 4c in the porous sound-insulation structure 100 (refer FIG. 1). In this configuration, the resistance when air flows in the resonance chamber 4c by the porous sound absorbing material 6 is increased, so that vibration energy is easily converted into heat energy, and attenuation of air vibration can be increased. Therefore, the sound absorption rate in the frequency band where sound is absorbed by the resonator 4 can be increased. Moreover, since the sound wave propagating through the porous sound absorbing material is slower than in the air, the wavelength is shortened, and the sound can be absorbed in a lower range.

  Further, as shown in FIG. 6, a porous body in which fine through-holes 4e are formed in the vertical part 4b of the frame so that the opening diameter of the through-holes 4e (holes) of the resonator 4 is 3 mm or less. The soundproof structure 104 may be used. In addition, the same code | symbol is attached | subjected to the same member as the porous soundproof structure 100 (refer FIG. 1), and description is abbreviate | omitted.

  In this case, the number of through-holes 4e is set so that the required aperture ratio allows sound absorption in the low frequency band. By reducing the opening diameter of the through hole 4e to 3 mm or less, the sound absorption peak can be obtained in the required low frequency band, the air resistance in the through hole 4e can be increased, and the attenuation of air vibration is increased. Can do. Further, since the influence of the viscosity of the air passing through the through hole 4e becomes significant, the width of the frequency band where sound can be absorbed can be widened. Further, by reducing the opening diameter, the number of through-holes is increased while maintaining the aperture ratio constant, and as shown in FIG. 6, the through-hole is formed in the thickness direction of the resonator 4 (Z-axis direction in FIG. 6). It is possible to make a configuration in which the holes 4e are arranged in two rows. Moreover, if the opening diameter of the through-hole 4e is 0.05 mm or more, while processing of a through-hole becomes easy, it will become difficult to obstruct | occlude an opening by the dust etc. in air | atmosphere, and it can suppress that sound absorption performance deteriorates.

  Further, as shown in FIG. 7, a cylindrical member 8 having a through hole 8a is used as a flow path that connects the resonance chamber 4c and the outside of the resonance chamber 4c, and is attached so as to penetrate the vertical portion 4b of the frame. Thus, the porous soundproof structure 105 can be formed. In addition, the same code | symbol is attached | subjected to the same member as the porous soundproof structure 100 (refer FIG. 1), and description is abbreviate | omitted.

  As described above, the cylindrical member 8 having the through-hole 8a protrudes from the frame body 4b to both the outside of the resonance chamber 4c and the inside of the resonance chamber 4c, so that the outside of the resonance chamber 4c and the resonance chamber 4c. The length of the flow path communicating with can be increased. As a result, the mass of the air that is housed in the flow path portion and vibrates increases due to the increase in volume of the flow path portion, and as a result, the resonance frequency of the resonator 4 becomes a lower frequency. As a result, the sound-absorbing structure 105 can absorb sound in a lower frequency band.

  Further, since the cylindrical member 8 is disposed so as to penetrate the vertical portion 4b of the frame body perpendicularly to the thickness direction of the porous soundproof structure 105, the dimensions of the resonator 4 are projected by the protruding cylindrical member 8. However, the thickness of the porous soundproof structure 105 does not increase in the thickness direction, and a thinner porous soundproof structure 105 can be formed.

  In the embodiment shown in FIG. 7, the cylindrical member 8 is formed so as to protrude from the vertical portion 4b of the frame body to both the outside of the resonance chamber 4c and the inside of the resonance chamber 4c. The cylindrical member 8 may be formed so as to protrude from the vertical portion 4b of the frame body to at least one of the outside of the resonance chamber 4c and the inside of the resonance chamber 4c. In particular, by forming so as to protrude only into the resonance chamber 4c, the protruding portion from the outer surface of the resonator 4 can be eliminated, and the space required for installing the resonator 4 can be reduced. Thus, the resonator 4 can be efficiently arranged by effectively using the space in the porous soundproof structure 105, and the sound absorption performance can be improved.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims.

  For example, as shown in this embodiment, when the through hole formed in the resonator 4 is formed so as to penetrate the vertical portion 4b of the frame body in the direction perpendicular to the thickness direction of the porous soundproof structure. Not limited to this, as shown in the porous soundproof structure 106 according to the modification in FIG. 8, in the parallel portion 4a forming the upper surface of the resonance chamber 4c, in the vicinity of the end in the direction parallel to the blocking surface 1a (close to the vertical portion 4b) A through hole 4f can be formed at the position). In this case, in the resonance chamber 4c, the distance from the position of the through hole 4f to the end portion (side plate 5) of the resonance chamber 4c can be increased, and the secondary or higher resonance frequency can be further lowered. Sound absorption in a wider frequency range is possible. In addition, when the resonator 4 has a shape in which the dimension in a plane perpendicular to the thickness direction is larger than the dimension in the thickness direction, the area of the surface on which the through hole 4f is formed can be increased, and the through hole 4f can be formed. This is effective in that it can be dispersed over a wide range.

It is a figure which shows schematic structure of the porous soundproof structure which concerns on embodiment of this invention. It is a graph which shows the sound absorption characteristic of the porous soundproof structure shown in FIG. It is a figure which shows schematic structure of the modification of the porous soundproof structure shown in FIG. It is a figure which shows schematic structure of the modification of the porous soundproof structure shown in FIG. It is a figure which shows schematic structure of the modification of the porous soundproof structure shown in FIG. It is a figure which shows schematic structure of the modification of the porous soundproof structure shown in FIG. It is a figure which shows schematic structure of the modification of the porous soundproof structure shown in FIG. It is a figure which shows schematic structure of the modification of the porous soundproof structure shown in FIG.

Explanation of symbols

1 Exterior plate (surface member)
2 First perforated plate (perforated plate)
3 Second perforated plate (perforated plate)
4 Resonator 4a, 4b Frame 4c Resonance chamber 4d, 4e, 4f Through hole (hole)
6, 9 Porous sound-absorbing material 7 Corrugated porous plate (porous plate)
8 Cylindrical members 100 to 106 Porous soundproof structure

Claims (13)

A perforated plate having a number of through-holes and disposed opposite to a surface member having a blocking surface for blocking the passage of air;
A resonator having a frame body defining a space sandwiched between the surface member and the porous plate, and a hole penetrating the frame body;
A porous soundproof structure comprising:   The plurality of the perforated plates are provided by being stacked through an air layer, and sound waves from a sound source reach the blocking surface by passing through all the perforated plates. The porous soundproof structure as described.   3. The resonator according to claim 1, wherein the resonator is formed so that a dimension in a direction parallel to the blocking surface is larger than a dimension in a direction perpendicular to the blocking surface. The porous soundproof structure as described.   The porous soundproof structure according to claim 3, wherein the hole is formed in the vicinity of an end of the resonator in a direction parallel to the blocking surface.   The porous soundproof structure according to claim 4, wherein the hole is formed on a surface perpendicular to the blocking surface of the frame.   The porous soundproof structure according to any one of claims 1 to 5, wherein a porous sound absorbing material is disposed in a space between the surface member and the porous plate. .   The porous soundproof structure according to any one of claims 1 to 6, wherein at least one of the porous plates has a concave shape or a convex shape on a surface thereof.   The porous soundproof structure according to claim 7, wherein at least one of the perforated plates is formed to have a corrugated cross section.   The porous soundproof structure according to claim 8, wherein at least one of the porous plates has an embossed surface.   The porous soundproof structure according to any one of claims 1 to 9, wherein a porous sound absorbing material is disposed inside the resonator.   The porous soundproof structure according to any one of claims 1 to 10, wherein a size of an opening diameter of the hole portion is 3 mm or less.   The hole is formed as a cylindrical member having a flow path that communicates the inside of the resonator and the outside of the resonator, and the cylindrical member extends from the frame to the outside of the resonator and the resonance. The porous soundproof structure according to any one of claims 1 to 11, wherein the porous soundproof structure is formed so as to protrude toward at least one of the inside of the vessel. The porous soundproof structure according to any one of claims 1 to 12, wherein an opening diameter of the through hole is 3 mm or less.

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