JP2023115604A - Structure and sound absorption material etc. including structure - Google Patents

Abstract

To provide a structure that exhibits high sound absorption performance in a low frequency range, such as, for example, in a 250 Hz band or lower with further efficiently arranged structure and a sound absorbing material etc. including the structure.SOLUTION: A structure 1 includes: a first sound-absorbing structure 10 comprising a perforated plate 11 perforated with holes 12 and a first void portion 13 formed on the rear side of the perforated plate 11; and a second sound-absorbing structure 20 comprising an opening 21 arranged around the holes 12, a hole portion 22 connected to the opening 21, and a second void portion 23 connected to the hole portion 22. At least a portion of the second void portion 23 is arranged behind the first void portion 13.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a structure, a sound absorbing material including the structure, and the like.

From the viewpoint of privacy protection and improvement of living space environment, high sound insulation is required for parting walls (walls that partition each dwelling unit) of housing complexes. As a means for achieving this, the use of concrete walls with a high surface density is the first conceivable method. Therefore, there are many double-walled structures in which studs are set up on both sides of the hollow layer as a base on the upper floor and runners attached to the floor, and interior materials such as gypsum boards and calcium silicate boards are attached there. adopted in case.

However, it is known that in such a double-wall structure as described above, the sound insulation performance deteriorates in a low frequency range due to a resonance phenomenon in which the hollow layer acts as an air spring. Therefore, in order to improve the sound insulation performance in the low frequency range, a method of absorbing sound energy by filling the hollow layer with a sound absorbing material such as glass wool or rock wool has been adopted. However, there is a limit to the amount of filling, since the hollow layer cannot be made thick due to the restriction on the thickness of the wall in order to utilize the space widely. In addition, the sound absorbing performance of these sound absorbing materials is high in the medium and high frequency range, but low in the low frequency range. Therefore, even if the sound absorbing material is arranged, there is a problem that the sound insulation performance in the low frequency range cannot be sufficiently improved.

Under such circumstances, one of the means conventionally used to solve such problems is MPP (abbreviation of Microperforated Panel Absorber, which means "microperforated panel sound absorber"). An MPP consists of a perforated plate in which fine holes with a diameter of about 0.5 mm are regularly arranged in a sheet or board with an opening ratio of about 1%. used as material. One of the characteristics of such MPPs is that the sound absorption coefficient changes according to the length of the micropores (perforation length) (see FIG. 4A). However, as can be seen from the figure, there is a region where sound absorption is difficult in the low frequency band below about 250 Hz.

Also, as a prior art, there is a Helmholtz resonator. A Helmholtz resonator has a shape like an urn or a bottle consisting of an open neck portion and a bulging body portion, and resonates sound waves of a predetermined frequency determined by the size of the neck portion and the volume of the body portion. It is used as a sound absorbing structure based on the principle of absorbing sound. Therefore, it is possible to shift the peak frequency of the sound absorption coefficient to a desired value by adjusting the size of the neck portion and the volume of the body portion.

Now, for example, Non-Patent Document 1 discloses a technique that combines the MPP and the acoustic metamaterial described above. Further, Patent Document 1 and Patent Document 2 also disclose such techniques.

Japanese Patent No. 6691521 Japanese Patent No. 6960469

L. Yuvaraj, et. al., “Sound absorption of Multilayer Micro perforated Panel with Helmholtz Resonator Mount,” Internoise 2019 Proceeding (June 16-19, 2019).

However, since the conventional technique as described above requires a thick sound-absorbing structure, it may be difficult to adopt it in a parting wall or the like where space is limited. For example, in Non-Patent Document 1, the housing of the Holmhertz resonator is arranged around the center of the MPP, which inevitably increases the height (see Non-Patent Document 1). (see Figure 1). Then, even if a conventional sound absorbing structure is adopted with the goal of improving the sound absorption characteristics of sound waves in the low frequency range of, for example, 250 Hz or lower, it is practically difficult to adopt as a result of a certain size. can be.

The inventors of the inventors, who have made intensive studies based on these points of view, have found that the above-described conventional techniques are not designed from the viewpoint of efficient arrangement, and that they can be arranged more efficiently from another viewpoint. We have found that it is possible to provide a structure with excellent space efficiency.

Based on such findings, the present invention provides a structure that exhibits high sound absorption performance in a low frequency range such as the 250 Hz band or less and is arranged more efficiently, and a sound absorbing material that includes the structure. intended to provide

One aspect of the present invention based on such findings is
a first sound absorbing structure composed of a perforated plate with holes and a first gap formed on the back side of the perforated plate;
a second sound absorbing structure including an opening arranged around the hole, a hole connected to the opening, and a second gap connecting to the hole;
wherein at least a portion of the second void is located behind the first void.

In the structure as described above, regarding the space that tends to be bulky, by arranging at least a part of the second space behind the first space, a three-dimensional structure that has not been realized in the conventional structure Effective arrangement is realized (three-dimensionally). According to this, it is possible to create a structure with a reduced height, which tends to be bulky. In addition, in the structure composed of the first sound absorbing structure and the second sound absorbing structure as described above, for example, by applying an MPP to one side and a Helmholtz resonator to the other side, it has not been realized in the past. For example, it is possible to exhibit high sound insulation performance in a low frequency range such as 250 Hz or lower.

A plurality of holes having different drilling lengths may be provided as the holes in the structure as described above.

In the structure as described above, a plurality of perforated plates having different perforation lengths may be provided.

In the structure as described above, a plurality of openings and holes may be provided.

In the structure as described above, the openings and the holes may have different diameters.

In the structure as described above, the second void may form a single space that communicates with all of the plurality of holes.

In the structure as described above, the second gap may be partitioned into a plurality of spaces corresponding to the plurality of holes.

In the structure as described above, the hole may be bent in the middle.

In the structure as described above, the hole may have a shape that bends along the radial direction of the structure.

In the structure as described above, the hole may have a shape that bends along the circumferential direction of the structure.

In the structure as described above, the hole may be bent in a crank shape.

In the structure as described above, the openings may be arranged substantially flush with the surface of the perforated plate.

Either or both of the first and second voids of the structure as described above may be partially or wholly filled with a porous material.

The structure as described above may be a structure in which the first sound absorbing structure and the second sound absorbing structure are built in a portable housing.

The structure as described above may be provided on the partition wall of an acoustic room or a soundproof room.

Another aspect of the invention is as follows. That is, a sound absorbing material including the structure as described above, a partition wall including the structure as described above, a floor structure including the structure as described above, a partition including the structure as described above, and a vehicle including the structure as described above. Members, aircraft members including structures as described above, housing members including structures as described above, building members including structures as described above, acoustic equipment including structures as described above, structures as described above audio equipment, including

According to the present invention, there is provided a structure that exhibits high sound absorption performance in a low frequency range such as the 250 Hz band or lower, and that is arranged more efficiently, and a sound absorbing material or the like including the structure. can be done.

It is a figure which shows an example of the structure which concerns on this invention. FIG. 3 is a perspective view showing the internal configuration of the structure with a part broken away; It is (A) the figure which shows the cross section of a fine perforated board sound absorber (1st sound-absorbing structure), and (B) the perspective view which shows an outline explaining the principle of sound absorption of a fine perforated board sound absorber (1st sound-absorbing structure). 4 is a graph showing the relationship between sound frequency and sound absorption efficiency, showing areas where sound absorption by the sound absorbing member of the microperforated plate (first sound absorbing structure) is difficult. FIG. 10 is a perspective view of another example of a structure having openings distributed among a plurality of holes such that the openings are arranged around the holes. FIG. 4 is a cross-sectional view showing an example of a structure in which a first gap and a second gap are filled with a porous material; 1 is a perspective view showing a structure according to a first embodiment of the invention; FIG. 1 is an exploded perspective view showing a structure according to a first embodiment of the invention; FIG. 1(A) is a side view showing a structure according to a first embodiment of the present invention, and FIG. 1(B) is a sectional view taken along line VII-VII in FIG. 1(A) is a top plan view showing a structure according to a first embodiment of the present invention, and FIG. 1(B) is a sectional view taken along line VIII-VIII in FIG. FIG. 5 is an exploded perspective view showing a structure according to a second embodiment of the invention; It is the figure seen from (A) side which shows the structure which concerns on the 2nd Embodiment of this invention, and (B) sectional drawing in the XX line in a figure. FIG. 8A is a top plan view showing a structure according to a second embodiment of the present invention, and FIG. FIG. 8 is an exploded perspective view showing a structure according to a third embodiment of the invention; It is the figure seen from the (A) side which shows the structure which concerns on the 3rd Embodiment of this invention, and (B) sectional drawing in the XIII-XIII line in a figure. (A) A top view showing the structure according to the third embodiment of the present invention, (B) a cross-sectional view along the XIVB-XIVB line in the figure, and (C) a cross-sectional view along the XIVC-XIVC line in the figure It is a sectional view. FIG. 11 is an exploded perspective view showing a structure according to a fourth embodiment of the invention; It is the figure seen from the (A) side which shows the structure based on the 4th Embodiment of this invention, and (B) sectional drawing in the XVI-XVI line in a figure. (A) A top view showing the structure according to the fourth embodiment of the present invention, (B) a cross-sectional view along the XVIIB-XVIIB line in the figure, and (C) a cross-sectional view along the XVIIC-XVIIC line in the figure It is a sectional view. FIG. 4 is a diagram showing an example in which a structure or a sound absorbing material composed of the structure is applied to a parting wall of an acoustic room or a soundproof room; 4 is a graph showing the profile of a sound absorbing material having a sound absorption peak at 250 Hz or less;

Preferred embodiments of the structure according to the present invention will be described in detail below with reference to the drawings. In the following, first, details of the structure and characteristics of the structure 1 according to the present invention will be described, and then four types of structures 1 having different detailed structures will be described as first to fourth embodiments. and

The structure 1 according to the present invention includes a first sound absorbing structure consisting of a microperforated plate sound absorbing body (MPP) 10, a second sound absorbing structure consisting of a Helmholtz resonator 20, and these microperforated plate sound absorbing body 10 and Helmholtz resonator 20. (see FIGS. 1 and 2).

The housing 30 is formed by a casing shaped to house the microperforated plate sound absorber 10 and the Helmholtz resonator 20 . The shape and material of the housing 30 are not particularly limited as long as the predetermined sound absorption characteristics described below are achieved. As a typical good example, in this example, the housing 30 is configured by a cylindrical resin casing having a space formed therein (see FIG. 2, etc.). The casing of this example is composed of a first casing 31 and a second casing 32 that are detachable along the central axis a (see FIG. 6, etc.). The first casing 31 is provided with the microperforated plate sound absorber 10 and the opening 21 and the hole 22 that constitute the Helmholtz resonator 20 . As will be described later, the first casing 31 is formed with an opening 31a, a stepped portion 31b, and a bottom portion 31c (see FIGS. 2, 6, etc.). The second casing 32 is provided with a second gap 23 that communicates with the hole 22 of the Helmholtz resonator 20 .

The size of the housing 30 is also not limited, but it is preferable that it is compact and small enough to be carried according to the application. The structure 1 composed of the miniaturized housing 30 can be widely used as a highly versatile device that can be retrofitted in a narrow space such as a vehicle interior.

The microperforated plate sound absorber 10 is provided in the housing 30 as a member constituting the first sound absorption structure for exhibiting sound absorption performance for sound waves in a specific frequency range, specifically, a frequency range of 250 Hz or higher. (See Figure 1, etc.). A fine perforated plate sound absorber 10 is composed of a perforated plate 11 in which fine holes 12 having a diameter d of about 0.5 mm are regularly arranged in a sheet or board with an aperture ratio of about 1%. A sound absorbing structure is formed by arranging an air layer with a predetermined space c in front of the portion 15 (see FIG. 3).

The sound absorption coefficient of the microperforated plate sound absorber 10 changes according to the length (perforation length) t of the holes 12 (see FIG. 3). Using such characteristics, a plurality of fine perforated plate sound absorbers 10 having different perforation lengths t may be provided in the housing 30 . As an example of such a mode, in this example, a first finely perforated plate sound absorber composed of a perforated plate 11 having holes 12 with a perforation length t of 0.001 m (a peak wavelength of 1300 Hz in sound absorption characteristics). (indicated as MPP1 in FIG. 1), a second fine perforated plate sound absorbing body (Fig. 1 indicated as MPP2 in FIG. 1), and a third fine perforated plate sound absorber (MPP3 in FIG. ), and a fourth microperforated plate sound absorber (indicated as MPP4 in FIG. 1) composed of a perforated plate 11 having holes 12 with a perforation length t of 0.004 m (a peak wavelength of 750 Hz in sound absorption characteristics). Four types of microperforated plate sound absorbers 10 are provided in the housing 30 (see FIG. 1). According to the structure 1 in which the plurality of fine perforated plate sound absorbers 10 are provided, the sound absorption performance of sound waves can be expressed in the frequency region of the band that overlaps and spreads around the respective peak wavelengths (Fig. 4A reference).

When a plurality of finely perforated plate sound absorbing bodies 10 are provided as described above, each of the finely perforated plate sound absorbing bodies 10 may be individually separated or integrated. In this example, four types of square-shaped microperforated plate sound absorbers (MPP1 to MPP4) are integrated in a manner arranged at four corners, and the integrated microperforated plate sound absorbers 10 are placed in the housing 30 at the 1 casing 31 (see FIGS. 2 and 6). On the other hand, the first casing 31 has an opening 31a that matches the size and shape of the integrated microperforated plate sound absorber 10, and a stepped portion that functions as a stopper for positioning the microperforated plate sound absorber 10 in the depth direction. 31b, and a bottom portion 31c facing the rear surface of the fine perforated plate sound absorber 10 (see FIGS. 2, 6, etc.). Although the opening 31a is formed substantially in the center of the first casing 31 (see FIG. 6, etc.), it may be arranged at a position shifted laterally from the center. The bottom portion 31 c functions as a wall portion ( 15 ) that forms a first cavity portion 13 consisting of an air layer with a predetermined gap c between the bottom portion 31 c and the back surface of the sound absorbing body 10 of the microperforated plate.

The first gap 13 may be partitioned into a plurality of spaces. In the structure 1 of this example, the first cavity 13 is partitioned into four spaces by the partitions 14 provided inside the first casing 31 (see FIG. 2). These four spaces are formed corresponding to the four perforated plates 11, respectively, so that four fine perforated plate sound absorbers 10 are individually formed. More specifically, the four perforated plates 11 function independently, and the four perforated plates 11 have It is possible to realize a sound absorption profile that looks like a superposition of sound absorption coefficient profiles. That is, by designing the four perforated plates 11 so as to have sound absorption peaks at different frequencies, a sound absorption profile having peaks at a plurality of frequencies can be realized. Therefore, it is possible to realize a sound absorbing material having high sound absorbing performance against noise having peaks at a plurality of frequencies. On the other hand, when there is no partition 14, the four perforated plates 11 interact and the sound absorption coefficient of the four perforated plates 11 has one peak at the average frequency position of the peak frequency. 4 shows a sound absorption profile. Therefore, the sound absorption performance for noise having peaks at multiple frequencies is low.

In this example, four types of square-shaped microperforated plate sound absorbing bodies (MPP1 to MPP4) are arranged at the four corners to form an integrated structure. This is just one example. The type of perforation length t may be increased or decreased, and each hole 12 (the perforated plate 11 having the perforation) may be arranged differently from the above. Further, each fine perforated plate sound absorbing body 10 or a fine perforated plate sound absorbing body 10 having a structure in which these are combined and integrated may have a shape other than square.

The Helmholtz resonator 20 is provided in the housing 30 as a member constituting a second sound absorbing structure for exhibiting sound absorbing performance for sound waves in a specific frequency range, specifically in a frequency range of 250 Hz or less. (See FIG. 1, etc.). The Helmholtz resonator 20 has a shape like an urn or a bottle consisting of an open neck portion and a bulging body portion, and resonates sound waves of a predetermined frequency determined by the size of the neck portion and the volume of the body portion. It is used as a sound absorbing structure based on the principle that sound is absorbed by The Helmholtz resonator 20 of this example has a configuration including an opening 21, a hole 21, and a second cavity 23 (see FIGS. 1 and 2).

The openings 21 are arranged around the holes 12 of the microperforated plate sound absorber 10 . Here, "arranged around the hole 12" includes various modes. In this example, which is a specific example, the opening 21 is arranged at a position outside the fine perforated plate sound absorbing body 10 arranged substantially in the center of the first casing, so that the opening 21 extends around the hole 12. , but this is only a preferred example. In addition, for example, openings 21 exist dispersedly in a plurality of holes 12 drilled in the fine perforated plate sound absorbing body 10, and as a result, the openings 21 are arranged around the holes 12. (see FIG. 4B). In short, as long as the sound absorption characteristics of the microperforated plate sound absorber 10 as the first sound absorption structure and the Helmholtz resonator 20 as the second sound absorption structure are fully exhibited, the single housing 30 can be used. The holes 12 of the sound absorber 10 of the fine perforated plate and the openings 21 of the Helmholtz resonators 20 are mixed in the structure, and as a result, the openings 21 can be said to be "arranged around the holes 12". Any structure is acceptable.

The hole portion 22 continues from the opening portion 21 to the second gap portion 23 and is formed so as to form a so-called neck portion of the Helmholtz resonator 20 . The hole portion 22 of this example is formed of a cylindrical hole that continues to the circular opening portion 21 and extends parallel to the central axis a (see FIG. 2 and the like). However, this is only a specific example of the holes 22 and the like. The hole 22 and the opening 21, which is the opening portion thereof, may have a shape other than a circular shape, and the hole 22 may have a structure in which the hole 22 is bent in the middle, as will be described in detail in an embodiment described later. good too. In short, the perforated plate 11, the holes 12, and the first voids, which are components of the fine perforated plate sound absorber 10, exhibit predetermined sound absorption characteristics as the second sound absorbing structure of the Helmholtz resonator 20. As long as it is arranged so as not to interfere with the portion 13, its specific structure is not limited.

A mode in which a plurality of openings 21 and holes 22 having different hole diameters are provided in the housing 30 by utilizing the characteristic that the sound absorption coefficient of the Helmholtz resonator 20 changes particularly according to the hole diameter of the hole 22. may be As an example of such a mode, in this example, the first Helmholtz resonator 20 (in FIG. 1 Helmholtz 1), a second Helmholtz resonator 20 (indicated as Helmholtz 2 in FIG. 1) composed of an opening 21 and a hole 22 having a hole diameter of 0.002 m (resonance peak in sound absorption characteristics is 307 Hz), A third Helmholtz resonator 20 (indicated as Helmholtz 3 in FIG. 1) composed of an opening 21 and a hole 22 having a hole diameter of 0.003 m (a resonance peak of 460 Hz in sound absorption characteristics), and a hole diameter of 0.004 m Four types of Helmholtz resonators 20 called fourth Helmholtz resonators 20 (indicated as Helmholtz 4 in FIG. 1) composed of openings 21 and holes 22 (resonance peak in sound absorption characteristic is 613 Hz) are mounted in the housing 30. provided (see Fig. 1). According to the structure 1 in which the plurality of Helmholtz resonators 20 are provided, sound waves are generated in a frequency range that overlaps and spreads around each peak wavelength so as to cover a frequency range of a low frequency band of 250 Hz or less. of sound absorption performance can be expressed (see FIG. 4A).

The second gap 23 is arranged behind the first gap 13 of the fine perforated plate sound absorber 10 and is formed by a gap portion formed so as to continue to the hole 22 . Such a second cavity 23 functions as a so-called trunk portion of the Helmholtz resonator 20 . In this example, a dish-shaped second casing 32 is attached to the back side of the first casing 31, so that the inside of the second casing 32 functions as the second space 23 (see FIG. 2, etc.). ). The structure in which at least a part of the second gap 23 is arranged behind the first gap 13 in this way is useful for making the structure 1, which has a limited space, particularly compact enough to be carried as described above. In the structure 1 where the problem of space becomes more pronounced when miniaturized, the first gap 13, which is indispensable for constructing the first and second sound absorbing structures but tends to increase the space, and This is effective in distributing the second gap 23 three-dimensionally (three-dimensionally) and as efficiently as possible. In other words, it can be said that the second sound absorbing structure is built on the side and back of the first sound absorbing structure. This makes it possible to realize the structure 1 with reduced thickness.

Further, as described above, the structure 1 composed of the fine perforated plate sound absorbing body 10 as the first sound absorbing structure and the Helmholtz resonator 20 as the second sound absorbing structure has a frequency band of, for example, 250 Hz, which has not been developed in the past. It is possible to exhibit high sound absorption performance in the low frequency range as described below (see FIG. 4). In addition, in the structure 1 such as this example, which aims to more effectively utilize the microperforated plate sound absorber (MPP) 10 and the Helmholtz resonator 20 within a limited region, the frequency region that can absorb sound by shape design It is possible to adjust the performance in a specific frequency range, and it is possible to express performance by shape design, so it is possible to improve sound absorption while using lightweight materials. be able to.

In addition, the second gap portion 23 may be partitioned into a plurality of spaces. In the structure 1 of this example, the interior of the second casing 32 is partitioned into four spaces by partitions 24 (see FIG. 2). These four spaces are respectively formed corresponding to four holes 22 (each hole 22 in Helmholtz 1 to 4), so that four Helmholtz resonators 20 are individually formed. It has a configuration. More specifically, the four Helmholtz resonators 20 function independently by combining the four hole portions 22 with the voids 23 partitioned by the partitions 24, and the sound absorption coefficient profiles of the four Helmholtz resonators 20 are adjusted. It is possible to realize a sound absorption profile that seems to be superimposed. That is, by designing the four Helmholtz resonators 20 so as to have sound absorption peaks at different frequencies, a sound absorption profile having peaks at a plurality of frequencies can be realized. Therefore, it is possible to realize a sound absorbing material having high sound absorbing performance against noise having peaks at a plurality of frequencies. On the other hand, when there is no partition 24, the four Helmholtz resonators 20 interact, and the sound absorption coefficient of the four Helmholtz resonators 20 has one peak at the average frequency position of the peak frequency. It shows a sound absorption profile such as Therefore, the sound absorption performance for noise having peaks at multiple frequencies is low.

Moreover, in the structure 1 of this example, the opening 21 of the Helmholtz resonator 20 is arranged substantially on the same plane as the surface of the perforated plate 11 of the fine perforated plate sound absorber 10, but this is also an example of a suitable configuration. It's nothing more than In this way, the surface of the structure 1 (the surface on which the perforated plate 11 and the openings 21 are provided) is made substantially smooth, so-called flat, so that it is easy to use as a product. Although it can be said to be preferable, a configuration in which these are not on the same plane, in other words, a configuration in which there is a step on the surface side is not excluded.

Moreover, a porous body may be provided in the void of the structure 1 . As an example, the structure 1 is shown in which the first gap 13 is filled with the porous body 16 and the second gap 23 is filled with the porous body 26 (see FIG. 4C). As the porous bodies 16 and 26, for example, foam, glass wool, felt, or the like can be used. Such a structure 1 can absorb noise in a wider range of frequencies by filling the porous bodies 16 and 17 and adding the sound absorbing effect of the porous bodies 16 and 17 themselves. The porous bodies 16 and 26 may be provided only in part of the gaps (the first gaps 13 and the second gaps 23), or may be filled in the entire gaps. may be provided in Moreover, the porous body may be provided in only one of the first gap portion 13 and the second gap portion 23, or may be provided in both the first gap portion 13 and the second gap portion 23 as illustrated and described. may be provided in

[First Embodiment]
5 to 8 show a structure 1 according to a first embodiment of the invention. In the structure 1 of the present embodiment, each of the plurality of holes 22 is a cylindrical hole extending parallel to the central axis a (see FIGS. 7 and 8). Further, since the inside of the second casing 32 is not partitioned, the second gap 23 formed inside the second casing 32 constitutes a single and common space that communicates with all the four holes 22. (See FIG. 6, etc.).

[Second embodiment]
9 to 11 show a structure 1 according to a second embodiment of the invention. In the structure 1 of the present embodiment, the first space 13 formed inside the first casing 31 is partitioned by the cross-shaped partitions 14 into four spaces communicating with the four perforated plates 11 ( 9, 10, etc.). In addition, a second space 23 formed inside the second casing 32 is partitioned by a cross-shaped partition 24 into four spaces respectively communicating with the four holes 22 (see FIGS. 9, 11, etc.). ).

[Third Embodiment]
12 to 14 show a structure 1 according to a third embodiment of the invention. In the structure 1 of this embodiment, the hole 22 has a shape that bends in the middle. Although there are various specific modes of bending, in this embodiment, the hole 22 extending along the central axis a is bent midway in a direction perpendicular to the central axis a, and then bent again to the central axis a. It has a crank shape that bends toward the direction (see FIGS. 13 and 14). At this time, the hole 22 is formed in the circumferential direction of the structure 1 (in other words, at the intersection of the line extending from the central axis a toward the central portion of the hole 22 and the outer edge of the housing 30). It is bent along the tangential direction of the housing 30 or the direction along the side of the rectangular perforated plate 11). However, although not shown, the hole portion 22 may have a shape that bends along the radial direction of the structure, or may bend along an oblique direction (a direction between the circumferential direction and the radial direction). It may have a curved shape.

[Fourth embodiment]
15 to 17 show a structure 1 according to a fourth embodiment of the invention. The structure 1 of this embodiment includes partitions 14 and 24 similar to those of the second embodiment, and a hole 22 that is bent in the middle, similar to that of the third embodiment.

Although the above-described embodiment is a preferred example of the present invention, it is not limited to this, and various modifications can be made without departing from the gist of the present invention. For example, in the above-described embodiment, it was explained that the structure 1 made up of the downsized housing 30 can be widely used as a highly versatile device that can be retrofitted in a narrow space such as a vehicle interior. , the vehicle described here is only one example of objects to which the structure 1 can be applied or used. In addition, it can be widely applied or used in vehicle members, aircraft members, housing members, building members, acoustic equipment, acoustic equipment, sound absorbing materials, parting walls, floor structures, partitions, and the like. Here, as an example, FIG. 18 shows one aspect of the boundary wall 300 when the structure 1 is applied to the boundary wall 300 of an acoustic room or a soundproof room (indicated by reference numeral 100). In this example, a sound absorbing material 200 composed of a plurality of regularly arranged structures 1 is provided inside the boundary wall 300 (see FIG. 18). In FIG. 18, reference numeral 302 denotes a frame constituting the partition wall 300, reference numeral 304 denotes a gypsum board, and reference numeral 306 denotes a wall cloth. Although not shown in particular detail, the floor structure 400 of a house or the like, the ceiling 500, the outer wall (partition wall in a narrow sense) 600, etc. are similarly provided with the structure 1 or the sound absorbing material 200 constituted by the structure 1. It is of course possible to apply (see FIG. 18).

A test was conducted to ascertain the profile of the structure 1 or the sound absorbing material 200 with different sound absorbing properties. Among the results obtained in the test, a graph showing the profile of a sound absorbing material having a sound absorption peak at 250 Hz or less is shown in the figure (see FIG. 19).

INDUSTRIAL APPLICABILITY The present invention can be suitably used in vehicles such as industrial vehicles, buildings such as houses, and various facilities including audio equipment.

1... Structure 10... MPP, microperforated plate sound absorbing body (first sound absorbing structure)
DESCRIPTION OF SYMBOLS 11... Perforated plate 12... Hole 13... First space part 14... Partition 15... Wall part 16... Porous body 20... Helmholtz resonator (second sound absorbing structure)
21... Opening 22... Hole 23... Second gap 24... Partition 26... Porous body 30... Housing 31... First casing 31a... Opening 31b... Stepped part 31c... Bottom 32... Second casing 100... Acoustic Room or soundproof room 200 Sound absorbing material 300 Parting wall 302 Frame 304 Gypsum board 306 Wall cloth 400 Floor structure 500 Ceiling 600 Outer wall a Central axis d Diameter of hole 12 t Length of hole 12 (drilling length)

Claims (25)

a first sound absorbing structure composed of a perforated plate with holes and a first gap formed on the back side of the perforated plate;
a second sound absorbing structure composed of an opening arranged around the hole, a hole connecting to the opening, and a second gap connecting to the hole;
wherein at least a portion of said second void is located behind said first void. 2. The structure according to claim 1, wherein a plurality of holes having different drilling lengths are provided as said holes. 3. The structure according to claim 1, wherein a plurality of said perforated plates having different perforation lengths of said holes are provided. 4. The structure according to any one of claims 1 to 3, wherein a plurality of said openings and said holes are provided. 5. The structure of claim 4, wherein said openings and said holes have different diameters. 6. The structure according to claim 4, wherein said second void forms a single space communicating with all of said plurality of holes. 6. The structure according to claim 4, wherein said second space is partitioned into a plurality of spaces corresponding to each of said plurality of holes. 8. The structure according to any one of claims 1 to 7, wherein the hole has a meandering shape. 9. The structure according to claim 8, wherein said hole has a shape that bends along the radial direction of said structure. 9. The structure according to claim 8, wherein said hole has a shape that bends along the circumferential direction of said structure. 11. A structure according to any one of claims 8 to 10, wherein said hole is bent in a crank shape. 12. A structure according to any preceding claim, wherein the openings are arranged substantially flush with the surface of the perforated plate. 12. The structure according to any one of claims 1 to 11, wherein either or both of said first and second gaps are partially or wholly filled with a porous material. 14. The structure according to any one of claims 1 to 13, wherein said first sound absorbing structure and said second sound absorbing structure are structures housed in a portable housing. 14. A structure according to any one of claims 1 to 13, provided in a parting wall of an acoustic or soundproof room. A sound absorbing material comprising a structure according to any one of claims 1-14. A boundary wall comprising a structure according to any one of claims 1 to 14. 15. A floor structure comprising a structure according to any one of claims 1-14. A partition comprising a structure according to any one of claims 1 to 14. A vehicle component comprising a structure according to any one of claims 1 to 14. Aircraft component comprising a structure according to any one of claims 1 to 14. A housing component comprising a structure according to any one of claims 1-14. A building component comprising a structure according to any one of claims 1-14. An acoustic device comprising a structure according to any one of claims 1-14. An acoustic installation comprising a structure according to any one of claims 1-14.

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