JP2017009759A - Sound absorbing structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sound absorbing structure capable of achieving improvement of sound absorbing performance and adjustable sounds, with a simple structure.SOLUTION: A sound absorbing structure (1) includes: a rear surface member (21) having a length in a predetermined direction; a front surface member (22) that is in parallel with the rear surface member (21) and is arranged to be separated forward from the rear surface member (21); a sound absorbing material (3) arranged inside a back area (25) located back of the front surface member (22); and a sound adjustable mechanism (5B). The sound adjustable mechanism (5B) makes sounds adjustable by changing an absorption coefficient of a sound entered from a predetermined direction end part of the back area (25). The sound adjustable mechanism (5B) typically includes a displacement member (54) provided so as to be able to change its position between a first position and a second position.SELECTED DRAWING: Figure 19

Description

  The present invention relates to a sound absorbing structure, and more particularly to a sound absorbing structure suitable for an audio room.

  In a room (audio room) whose main purpose is to play a musical instrument such as a piano or listen to music, not only soundproofing but also good sounding (sound) is required. One of the methods for producing good sound is “sound absorption”. Conventionally, there are sound-absorbing ceiling materials, sound-absorbing wall materials, wall-mounted or stationary sound-absorbing panels, and the like.

  For example, in Japanese Patent Application Laid-Open No. 2005-146650 (Patent Document 1), in order to absorb sound of a specific frequency in an air layer existing between double walls, a plurality of Helmholtz resonances are provided in a stud provided in a wall space. A sound absorbing structure that forms a vessel has been proposed. Specifically, the stud is composed of a hollow tube extending in the vertical direction, a plurality of openings that open to the space in the wall are provided on the side of the stud, and the periphery of the opening is the other part. Further, it is disclosed to form a cylindrical shape that protrudes more sideways.

  In addition, it is known in the architectural acoustics industry that it is effective to place a sound-absorbing material in the corner to reduce the acoustic disturbance of booming, where bass sounds accumulate in the corner of the room and the sound balance is poor. ing. For example, in Japanese Patent Application Laid-Open No. 2014-141822 (Patent Document 2), a substantially triangular prism-shaped sound absorber is arranged at a corner portion of a soundproof room, and a low-frequency sound is absorbed by a thick part, and a thin part. A technology for absorbing high-frequency sounds has been proposed. In addition, in this document, in order to make the sound variable, it is also proposed to add a variable mechanism that makes the exposed area of the sound absorption surface (surface) of the sound absorber variable.

  In JP-A-8-53887 (Patent Document 3), an opening is provided in the surface material of the wall of the acoustic chamber, and a sound absorbing box containing a sound absorbing material is inserted into the wall thickness from the opening. Thus, a wall structure that exhibits a sound absorbing effect by utilizing the thickness of the wall is disclosed. In the same document, it is also proposed that the sound absorption material that is thinner than the longitudinal length of the sound absorbing box is movable in the front-rear direction, so that the sound reverberation is adjusted by changing the sound absorption rate from low to mid-range.

JP 2005-146650 A JP 2014-141822 A JP-A-8-53887

  In order to improve the sound absorption performance of the substantially triangular prism-shaped sound absorber installed at the corner as in Patent Document 2, the size of the sound absorber may be increased. However, if the size of the sound absorber in the corner portion is too large, not only the space in the room is narrowed but also not desirable in terms of design, so that the practicality is poor. Moreover, since the technique of the said patent document 1 requires the pillar of a special structure, the technique which improves a sound absorption performance with a simple structure was calculated | required.

  Further, in the wall structure of Patent Document 3, since the sound absorbing material is disposed only behind the opening provided in the surface material, and the thickness of the sound absorbing material is reduced in order to make the sound variable, the wall structure. It is difficult to achieve a sufficient sound absorbing effect in

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a sound absorbing structure capable of realizing variable sound and improved sound absorbing performance with a simple structure. .

  A sound absorbing structure according to an aspect of the present invention is a sound absorbing structure for absorbing sound, and is disposed rearwardly with a length in a predetermined direction, parallel to the rearward surface member, and forwardly away from the rearward surface member. A front surface member, a sound absorbing material disposed in a rear region located behind the front surface member, and an acoustic variable mechanism. The sound variable mechanism changes the sound by changing the sound absorption rate of the sound entering from the end in the predetermined direction of the back region.

  Preferably, the acoustic variable mechanism includes a displacement member provided so that the position can be changed between the first position and the second position, and changes the size of the sound absorption region of the sound absorbing material according to the position of the displacement member. .

  Preferably, the displacement member is configured by a plate-like member.

  A plurality of displacement members may be provided. In this case, the plurality of displacement members may be arranged apart from each other.

  Preferably, a plurality of displacement members are provided at intervals from each other along the sound propagation direction.

  Alternatively, the displacement member may be provided so that its position can be changed along the sound propagation direction.

  The acoustic variable mechanism may further include an insertion hole provided in the front surface member for inserting and removing the displacement member.

  The displacement member may be rotatably arranged in the rear region.

  According to the present invention, it is possible to realize variable sound and improved sound absorption performance with a simple structure. Moreover, since it is not necessary to increase the thickness of the sound absorbing material, practicality can be improved.

It is sectional drawing which shows typically the soundproof room which concerns on Embodiment 1 of this invention. It is the figure which looked at the soundproof room which concerns on Embodiment 1 of this invention from the indoor side (from the direction of arrow II of FIG. 1). It is a figure which shows typically the cross-sectional structure of the sound-absorbing material contained in the sound-absorbing structure according to Embodiment 1 of the present invention. It is a figure which shows typically the structure of the sound absorption structure which concerns on Embodiment 1 of this invention. It is a graph which shows the experimental result about the sound absorptivity of the sound of a low frequency range which compared the sound absorption structure which concerns on Embodiment 1 of this invention, and another wall structure. It is a figure which shows the structure of the wall structure of a comparative example. It is a figure which shows the structure of the wall structure of a comparative example. It is a figure which shows the structure of the wall structure of a comparative example. It is a graph which shows the experimental result about the sound absorption characteristic from the low sound to the high sound which compared the sound absorption structure which concerns on Embodiment 1 of this invention, and another wall structure. It is a figure which shows the structure of the wall structure of a comparative example. It is a figure which shows the structure of the wall structure of a comparative example. It is a figure which shows typically an example of the base member of the sound absorption structure which concerns on Embodiment 1 of this invention. (A), (B) is a figure which shows typically the other example of the base | substrate member of the sound absorption structure which concerns on Embodiment 1 of this invention. It is a figure which shows typically a 125Hz sound wave. It is sectional drawing which shows typically the sound-absorption structure which concerns on Embodiment 2 of this invention, (A) shows the bass sound variable mechanism of a full open state, (B) shows the bass sound variable mechanism of a fully closed state. Show. It is a graph which shows the relationship between the material of the partition member which comprises a bass sound variable mechanism, and a sound absorption effect. It is sectional drawing which shows typically the sound absorption structure which concerns on the modification of Embodiment 2 of this invention. It is a graph which shows the relationship between the angle change of the partition member which comprises a bass sound variable mechanism, and the sound absorption property of a bass. It is sectional drawing which shows typically the bass sound variable mechanism in Embodiment 3 of this invention. (A)-(C) are the figures which show typically the sound-absorption area | region according to the position of the displacement member shown in FIG. (A), (B) is a figure which shows the structural example of the displacement member shown in FIG. (A), (B) is a figure which shows typically the sound absorption area | region according to the angle (position) of a displacement member, when changing the position of a displacement member by rotation. It is sectional drawing which shows typically the bass sound variable mechanism in the modification 1 of Embodiment 3 of this invention. It is a figure which shows typically the bass sound variable mechanism in the modification 2 of Embodiment 3 of this invention. (A), (B) is a figure which shows typically the sound absorption area according to the position of the displacement member shown in FIG. (A), (B) is a figure which shows typically the bass sound variable mechanism in the modification 3 of Embodiment 3 of this invention. It is a figure which shows typically the sound absorption structure which concerns on Embodiment 4 of this invention. It is a figure which shows typically the soundproof room which concerns on Embodiment 5 of this invention. It is the figure which looked at the soundproof room which concerns on other embodiment of this invention from the room inner side. It is a perspective view which shows the sound absorbing device which concerns on other embodiment of this invention. It is sectional drawing which shows typically the sound absorption structure which concerns on other embodiment of this invention. It is sectional drawing which shows typically the sound absorption structure which concerns on other embodiment of this invention. It is sectional drawing which shows typically the sound absorption structure which concerns on other embodiment of this invention.

  Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

<Embodiment 1>
First, the outline of the soundproof room according to the present embodiment will be described. In the present embodiment, the side closer to the sound source (the center side of the room) is called “front”, and the far side is called “rear”.

  1 and 2, the soundproof room 9 is a room surrounded by a floor 91, side walls 92 to 95, and a ceiling 96. In the present embodiment, for example, one side wall 92 has a sound absorbing structure 1 for absorbing sound generated indoors. The sound absorbing structure 1 includes a rear surface member 21, a front surface member 22, and a sound absorbing material 3 for absorbing sound.

  The rear surface member 21 has a rectangular shape and has a length in the vertical direction and the horizontal width direction. The rear surface member 21 is orthogonal to the side walls 93 and 95 of the soundproof room 9. The front surface member 22 is disposed in parallel with the rear surface member 21 and spaced forward from the rear surface member 21. The front surface member 22 is also rectangular and has a length in the vertical direction and the horizontal width direction. An arrow A1 in FIG. 2 indicates the horizontal width direction.

  The rear surface member 21 and the front surface member 22 have rigidity, and the front surface member 22 and the rear surface member 21 constitute a double wall. That is, both the rear surface member 21 and the front surface member 22 constitute the side wall 92.

  However, the lateral width of the front surface member 22 is shorter than the rear surface member 21. Therefore, an opening 23 is formed at a position in front of the rear surface member 21 and adjacent to the front surface member 22 in the lateral width direction. That is, the front region of the rear surface member 21 is configured by a first region 24 located behind the opening 23 and a second region 25 located behind the front surface member 22.

  The sound absorbing material 3 is provided in the first region 24 exposed from the opening 23 and extends to the second region 25 sandwiched between the rear surface member 21 and the front surface member 22. That is, the sound absorbing material 3 is located in the first region 24 and is exposed in the room (hereinafter referred to as “exposed sound absorbing part”) 31 and in the second region 25 and is hidden by the front surface member 22. It is comprised by the part (henceforth "back sound absorption part") 32.

The sound absorbing material 3 may be composed of a general sound absorbing body such as glass wool or rock wool, or may be composed of a layered sound absorbing body composed of a plurality of layer members as shown in FIG. In FIG. 3, a plurality of layer members are arranged so that layers are formed in the thickness direction in both the exposed sound absorbing portion 31 and the back sound absorbing portion 32. Each layer member is formed by, for example, intricately intertwining PET (Polyethylene terephthalate) fibers, and the density thereof is, for example, 30 kg / m ³ .

  According to the present embodiment, since the surface of the front surface member 22 and the surface of a part of the sound absorbing material 3 (exposed sound absorbing portion 31) are exposed in the room (soundproof room 9), A part of the sound generated in the above is reflected on the front surface member 22, and the other part is incident on the exposed sound absorbing part 31 of the sound absorbing material 3 through the opening 23 and is absorbed.

  Here, in the present embodiment, since the sound absorbing material 3 has the back sound absorbing portion 32 adjacent to the exposed sound absorbing portion 31 in the lateral width direction, the sound in the high sound range (hereinafter also simply referred to as “high sound”) is A sound in the low sound range (hereinafter also simply referred to as “low sound”) absorbed by the exposed sound absorbing portion 31 can be diffracted into the second region 25 and absorbed by the back sound absorbing portion 32. Therefore, the sound absorbing material 3 can absorb a wide range of sounds while suppressing the thickness of the sound absorbing material 3.

  Next, the configuration (size or ratio) of the sound absorbing structure 1 that can appropriately absorb low sounds in the sound absorbing material 3 and can absorb sound in a balanced manner from low to high sounds will be described. FIG. 4 is a diagram illustrating a configuration example of the sound absorbing structure 1 according to the present embodiment.

  As shown in FIG. 4, in the present embodiment, the opening dimension D1 of the opening 23 is 0.5P, and the lateral width dimension (hereinafter also referred to as “reflection wall dimension”) D2 of the front surface member 22 is 1 .5P. 1P represents one module in the design of the building, and indicates 910 mm or 1000 mm. The opening dimension (D1) of the opening 23 is read as the width dimension of the first region 24 (the length dimension of the first region 24 in a predetermined direction), and the width dimension (D2) of the front surface member 22 is the second region 25. May be read as the horizontal width dimension (the length dimension of the second region 25 in the predetermined direction).

  The thickness D3 of the sound absorbing material 3 is, for example, 100 mm. The thickness dimension D3 is also equal to the depth dimension of the first region 24 and the second region 25. In FIG. 4, the thickness is shown large for convenience. In the present embodiment, the exposed sound absorbing portion 31 and the back sound absorbing portion 32 have the same thickness, but the exposed sound absorbing portion 31 may protrude forward by the thickness of the front surface member 22. A decorative panel (not shown) may be attached to the surface of the exposed sound absorbing portion 31.

  The sound absorbing performance of the sound absorbing structure 1 having such a configuration will be described with reference to experimental results using a comparative example. In the experiment, a layered sound absorber as shown in FIG. 3 is used as the sound absorber 3.

  First, with reference to FIGS. 5 to 8, the sound absorption performance (sound absorption power) of the sound absorption structure 1 will be described. FIG. 5 shows a result of an experiment on the sound absorption of the sound in the low frequency range, comparing the sound absorbing structure 1 according to the present embodiment with another wall structure. 6 to 8 show configurations of wall structures 101 to 103 of comparative examples, respectively. In this experiment, the lateral width of the rear surface member 21 is fixed to 2P, and only the opening dimension D1 of the opening 23 is changed.

  The sound absorbing structure 1 according to the present embodiment is a “¼ sound absorbing” wall structure because the opening dimension D1 is 0.5P. The wall structure 101 shown in FIG. 6 has a “1/2 sound absorption” wall structure because the opening dimension D1 is 1P. The wall structure 102 shown in FIG. 7 is a “total sound absorption” wall structure because the front surface member 22 is not provided and the opening dimension D1 is 2P. The wall structure 103 shown in FIG. 8 is a “no sound absorption” wall structure because the opening 23 is not provided.

  In the graph of FIG. 5, compared with the “no sound absorption” wall structure 103 of FIG. 8, the sound level of the low to medium sound (125 to 1000 Hz) is shown for each of the sound absorption structure 1 and the wall structures 101 and 102. It is shown as a sound pressure level (unit: dB).

  In the “total sound absorption” wall structure 102 in FIG. 7, the low sound absorption coefficient is considerably lower than the medium sound absorption coefficient. Further, in the “1/2 sound absorption” wall structure 101 of FIG. 6, the sound absorption coefficient of the bass is slightly improved as compared with the wall structure 102, but the sound absorption coefficient of the medium sound is still higher. On the other hand, the sound absorption structure 1 of “¼ sound absorption” according to the present embodiment is further improved in the sound absorption rate of the low sound, and is similar to the sound absorption rate of the medium sound.

  From the above results, it can be seen that the sound absorbing structure 1 having the opening dimension D1 of 0.5P has excellent bass sound absorbing performance.

  Next, the sound absorption balance of the sound absorbing structure 1 will be described with reference to FIGS. FIG. 9 shows a result of an experiment on sound absorption characteristics from low to high, by comparing the sound absorption structure 1 according to the present embodiment with another wall structure. 10 and 11 show the structures of the wall structures 104 and 105 of the comparative example, respectively. From the above experimental results on the sound absorption of bass, it has been found that the opening dimension D1 is preferably 0.5P. In this experiment, the opening dimension D1 is fixed to 0.5P, and the opening dimension D1 and the reflection are reflected. Only the ratio with the wall dimension D2 is changed.

  In the sound absorbing structure 1 according to the present embodiment, the ratio between the opening dimension D1 and the reflecting wall dimension D2 is 1: 3. In the wall structure 104 shown in FIG. 10, the ratio of the opening dimension D1 to the reflecting wall dimension D2 is 1: 1, and openings 23 having an opening dimension of 0.5P are provided on both sides of the front surface member 22, respectively. It has been. In the wall structure 105 shown in FIG. 11, the ratio of the opening dimension D1 to the reflection wall dimension D2 is 1: 2.

  In the graph of FIG. 9, compared with the “no sound absorption” wall structure 103 of FIG. 8, the sound intensity of the sound absorption structure 1 and the wall structures 104 and 105 is from low to high (125 to 4000 Hz). It is shown as a sound pressure level (unit: dB).

  In the wall structure 104 of “sound absorption 1: reflection 1” in FIG. 10, the sound pressure level decreases as the sound becomes higher, and the sound absorption balance is not good. Further, in the “sound absorption 1: reflection 2” wall structure 105 of FIG. 11, the sound absorption balance is improved as compared with the wall structure 101, but the sound pressure level of the high sound is still lower. On the other hand, the sound absorbing structure 1 of “sound absorption 1: reflection 3” according to the present embodiment shows a substantially constant sound pressure level from low to high and has a flat sound absorption characteristic.

  From the above results, it can be seen that the sound absorbing structure 1 in which the ratio of the opening dimension D1 to the reflecting wall dimension D2 is 1: 3 can absorb sound in a balanced manner from low to high.

  In order to allow sound to pass through the second region 25 (back sound absorbing portion 32) in the lateral width direction, the base member that supports the rear surface member 21 and the front surface member 22 has a portion that penetrates in the lateral width direction. Need to be. Specifically, for example, the base member 4 as shown in FIG. 12 or the base member 4A as shown in FIG. 13 may be employed. In FIGS. 12 and 13, the illustration of the sound absorbing material 3 is omitted.

  The base member 4 has a plurality of cutouts 40 penetrating in the lateral width direction at intervals in the vertical direction. In FIG. 12, the notch 40 faces the front surface member 22 side, but the notch 40 may face the rear surface member 21 side.

  As shown in FIG. 13B, the base member 4A has a plurality of vertical bars 41 and a plurality of horizontal bars 42, and is formed in a sword shape. In this case, as shown in FIG. 13A, for example, the vertical rail 41 is in contact with the front surface member 22 and the horizontal rail 42 is in contact with the rear surface member 21.

  As described above, according to the sound absorbing structure 1 of the present embodiment, the back sound absorbing portion 32 is configured to absorb bass, so that the thickness of the sound absorbing material 3 can be suppressed. Therefore, since the space in the soundproof room 9 can be widely used, practicality and design can be improved. In addition, an excellent sound absorbing performance can be realized with a simple structure. As a result, in the soundproof room 9 provided with the sound absorbing structure 1, it is possible to create a comfortable sound, so that the soundproof room 9 can be provided as a comfortable audio room.

  In addition, the following structures may be sufficient as the structure (size or ratio) of the sound absorption structure 1 with which the soundproof room 9 is equipped.

  The ratio between the opening dimension D1 of the opening 23 and the reflecting wall dimension D2 may be 1: 2. That is, when the opening dimension D1 is 1, it is desirable that the reflection wall dimension D2 is 2 or more. In the experimental result shown in FIG. 9, even the wall structure 105 of “sound absorption 1: reflection 2” showed a relatively well-balanced sound absorption characteristic. Alternatively, the reflection wall dimension D2 may simply be longer than the opening dimension D1.

  Although it is considered that the sound absorption coefficient of each sound range varies depending on the material and density of the sound absorbing material 3, the horizontal width dimension of the back sound absorbing portion 32, that is, the reflection wall dimension D2, is 1 / th of the sound wave in the low frequency range (125 Hz). Two or more wavelengths are sufficient. FIG. 14 shows the length (1/2 wavelength) W1, specifically about 1.5P. Further, it is desirable that the thickness dimension (D3) of the back sound absorbing portion 32, that is, the depth dimension of the second region 25 is 100 mm or more.

  However, even when the depth dimension of the second region 25 (and the first region 24) is larger than 100 mm, the lateral width dimension of the back sound absorbing portion 32 that absorbs low sounds, that is, the reflection wall dimension D2, is at least an exposure that absorbs high sounds. It is longer than the thickness dimension D3 of the sound absorbing portion 31, that is, the depth dimension of the first region 24 (and the second region 25).

<Embodiment 2>
Next, the sound absorbing structure of the soundproof room according to Embodiment 2 of the present invention will be described. In the present embodiment, the sound absorbing structure has a function of changing the sound in the low sound range.

  15A and 15B are cross-sectional views schematically showing a sound absorbing structure 1A according to the second embodiment. The basic configuration of the sound absorbing structure 1A is the same as that of the sound absorbing structure 1 shown in the first embodiment. Therefore, only differences from the sound absorbing structure 1 of the first embodiment will be described below.

  The sound absorbing structure 1 </ b> A includes a bass sound variable mechanism 5. The bass sound variable mechanism 5 changes the sound absorption coefficient of the bass by adjusting the opening area (hereinafter referred to as “passage area”) of the low-frequency sound passage from the first region 24 into the second region 25. Can do. That is, the sound in the low sound range can be made variable.

  The bass sound variable mechanism 5 can be typically realized by a plate-shaped partition member 51. The partition member 51 has, for example, a width equal to or greater than the depth dimension of the first region 24 and the second region 25, and substantially the same length as their height dimension (the height from the floor 91 to the ceiling 96 shown in FIG. 2). Have Such a partition member 51 is inserted from the end of the opening 23 on the front surface member 22 side into the boundary surface 26 between the first region 24 and the second region 25 or in the vicinity thereof so as to divide the sound absorbing material 3. As a result, the bass passage area can be reduced. In this case, the sound absorbing material 3 is provided with a cut or a gap for inserting the partition member 51 in the thickness direction.

  In the state of FIG. 15A, since the partition member 51 is not inserted into the boundary surface 26, the passage area of the bass is the maximum and is in a fully opened state. In this case, as shown in the first embodiment, the low sound is sufficiently absorbed similarly to the high sound. On the other hand, in the state of FIG. 15B, since the partition member 51 is completely inserted into the boundary surface 26, the passage area of the bass is zero (minimum) and is in a fully closed state. In this case, since the sound absorption rate of the low sound is reduced, the low sound is increased indoors. In order to allow the partition member 51 to be easily inserted and removed, rails (not shown) may be provided on the floor 91 and the ceiling 96 of the soundproof room 9, for example. Alternatively, in order to facilitate insertion and removal of the partition member 51, the partition member 51 may be divided into a plurality of parts in the vertical direction.

  In order for the partition member 51 to effectively block or reduce the passage of bass to the second region 25, the partition member 51 is preferably a rigid plate-like member. This will be described with reference to the experimental results shown in FIG.

  FIG. 16 is a graph showing the relationship between the material of the partition member 51 and the sound absorption effect. In this experiment, the material of the partition member 51 was changed, and the partition member 51 was completely inserted as shown in FIG.

  From the experimental results shown in FIG. 16, it can be seen that the low sound absorption coefficient is not so low with a rigid vinyl sheet, but the low sound absorption coefficient is low with a rigid plywood or styrene board as intended. In addition, it is clear from this experimental result that, even if the partition member 51 has rigidity, even if the low-passage passage is fully closed by the partition member 51, it does not affect the sound absorption property of high frequencies of 1000 Hz or higher. It has become.

  As described above, according to the present embodiment, the low-frequency sound can be made variable, so that the sound absorption structure 1A can function like a woofer or a subwoofer by intentionally lowering the low-frequency sound absorption rate. it can. Therefore, comfortable sound can be created according to the type of musical instrument used.

  Although the vertical length of the partition member 51 is substantially the same as the height dimension of the boundary surface 26, it may be shorter than that. That is, the partition member 51 may be configured to partially open the bass passage even in the fully closed state.

  Further, the bass sound variable mechanism 5 may have other configurations. A modification of the bass sound variable mechanism 5 will be described.

(Modification)
FIG. 17 is a cross-sectional view schematically showing a sound absorbing structure 1B according to a modification of the second embodiment. The sound absorbing structure 1B includes a bass acoustic variable mechanism 5A. The bass acoustic variable mechanism 5 </ b> A includes a partition member 51 as in the bass acoustic variable mechanism 5. However, the arrangement position and the way of adjusting the passage area are different from those of the bass acoustic variable mechanism 5.

  In the bass acoustic variable mechanism 5 </ b> A, the partition member 51 is built in the second region 25. In this case, the bass passage area can be adjusted by rotating the partition member 51. That is, the partition member 51 is provided such that the angle with respect to the lateral width direction is variable. The partition member 51 is desirably provided near the entrance of the second region 25 (near the boundary surface 26 described above).

  In this case, in order to open and close the low-pass passage, the partition member 51 only needs to be able to rotate 90 ° with its center line as the rotation axis. A state in which the direction of the partition member 51 is 90 ° with respect to the lateral width direction (a state in which the partition member 51 is disposed in parallel with the thickness direction as shown in FIG. 15B) is a fully closed state. On the other hand, as shown in FIG. 17, the state in which the direction of the partition member 51 is 0 ° with respect to the lateral width direction is the fully open state.

  FIG. 18 is a graph showing the relationship between the angle change of the partition member 51 and the sound absorption of bass. In this experiment, a plywood having a thickness of 2.5 mm is used as the partition member 51. From the experimental results of FIG. 18, it can be seen that even if the partition member 51 is built in the vicinity of the entrance of the second region 25, the sound absorbing structure 1 </ b> B exhibits a sound absorption characteristic proportional to the angle change of the partition member 51.

  In the bass sound variable mechanism 5 </ b> A, the sound absorbing material 3 may not be provided in the rotation range of the partition member 51 in order to enable the partition member 51 to rotate within the second region 25. That is, as shown in FIG. 17, the second region 25 may be disposed in the cavity 250. The hollow portion 250 is, for example, a region where both sides thereof are separated by a partition bar 52 provided with a space in the vertical direction.

  Further, in order to easily rotate the partition member 51 from the indoor side, the bass acoustic variable mechanism 5 </ b> A may include an operation lever 53 coupled to the rotation shaft of the partition member 51. In this case, a part of the front surface member 22 located in front of the cavity part 250 may be provided with an operation opening 220 for exposing the tip part of the operation lever 53 in part.

  In the case where the cavity portion 250 is provided in the second region 25 as in this modification, in order to avoid a slight decrease in the low-frequency sound absorption force in the fully opened state, the width of the cavity portion 250 is reduced. The lateral width of the rear surface member 21 and the front surface member 22 may be increased. By doing so, the horizontal width dimension of the back sound absorption part 32 can be made the same as the dimension in the said Embodiment 2. FIG.

<Embodiment 3>
In the second embodiment, the bass sound is variable by adjusting the passage area of the bass from the first region 24 to the second region 25. On the other hand, in the present embodiment, the sound is made variable by changing the sound absorption rate of the sound that enters from the lateral width direction end of the second region 25.

  FIG. 19 shows a bass sound variable mechanism 5B in the present embodiment. The bass acoustic variable mechanism 5 </ b> B includes a displacement member 54. The displacement member 54 is a rigid plate-like member similar to the partition member 51 described above, and is disposed so as to partition (divide) the sound absorbing material 3 (the back sound absorbing portion 32) in the second region 25.

  The displacement member 54 is positioned between the first position (initial position) and the second position (partition position) at a position away from the boundary surface with the first area 24 (the end in the width direction of the second area 25). It is provided so that it can be changed. Depending on the position of the displacement member 54, the size (volume) of the sound absorbing region of the sound absorbing material 3 (the back sound absorbing portion 32) in the second region 25 changes. The “sound absorption region” indicates a region that contributes to the sound absorption of the sound that enters from the first region 24 side in the sound absorbing material 3 (back sound absorption unit 32) arranged in the second region 25.

  In the present embodiment, the displacement member 54 is inserted into the insertion position (shown by a solid line) drawn from the insertion hole 221 of the front surface member 22 and the insertion hole 221 and completely partitions the sound absorbing material 3 in the lateral width direction. It can be displaced between the insertion position (the position indicated by the imaginary line). In this case, the drawing position corresponds to the first position (initial position), and the insertion position corresponds to the second position (partition position). The displacement member 54 is disposed at the insertion position, for example, at the center position in the lateral width direction of the second region 25.

  In the bass sound variable mechanism 5B, a change in the sound absorption region of the sound absorbing material 3 in the second region 25 will be described with reference to FIG. An arrow A <b> 3 shown in FIG. 20A is the thickness direction of the second region 25. On the paper surface, the sound propagation direction is the direction from the right side to the left side of the second region 25. In FIG. 20, it is assumed that the sound absorbing material 3 is disposed in the entire second region 25. In the second region 25, a cavity (gap) 251 may be provided in the insertion range of the displacement member 54, or a cut may be provided in the sound absorbing material 3.

  FIG. 20A is a cross-sectional view schematically showing the sound absorption region 27 when the displacement member 54 is at the extraction position. In this case, since there is no displacement member 54 in the second region 25, the sound absorbing region 27 is the entire second region 25. Therefore, in this case, the sound absorption coefficient of the bass is maximum.

  FIG. 20B is a cross-sectional view schematically showing the sound absorption region 27a when the displacement member 54 is at the insertion position. In this case, the sound absorbing material 3 is divided into left and right by the displacement member 54. Therefore, in the sound absorbing material 3 in the second region 25, the region located on the right side (sound entrance side) of the paper with respect to the displacement member 54 is the sound absorption region 27 a, and the region located on the left side of the paper with respect to the displacement member 54 is not. A sound absorption region 28 is formed. Thereby, the sound absorption coefficient of the bass is lower than that at the extraction position.

  The displacement member 54 can be displaced to an intermediate position between the drawing position and the insertion position. FIG. 20C is a cross-sectional view schematically showing the sound absorption region 27b when the displacement member 54 is at the intermediate position. The displacement member 54 is inserted into the second region 25 from one end side (front side) in the thickness direction, and is inserted up to about half the thickness of the second region 25. In this case, in the thickness range where the displacement member 54 does not exist in the second region 25, the entire region from the right end to the left end of the second region 25 can be included in the sound absorption region 27b. Becomes larger than the sound absorption region 27a. As described above, the size of the sound absorption region may be changed stepwise by adjusting the degree of insertion of the displacement member 54.

  The displacement member 54 may be composed of one plate-like member as shown in FIG. 21 (A), or is arranged at intervals in the vertical direction as shown in FIG. 21 (B). A plurality of plate-like members 540 may be used. In the latter case, the plurality of insertion holes 221 are provided in a line in the vertical direction. The plurality of plate-like members 540 can be inserted into and removed from the respective insertion holes 221. In this case, in addition to a usage pattern in which all the plate-like members 540 are inserted and a usage pattern in which all the plate-like members 540 are pulled out, a usage pattern in which only some of the plate-like members 540 are inserted are possible. Even in this case, the size of the sound absorption region can be changed stepwise.

  Here, the first position as the initial position is described as being outside the second area 25, but the first position may also be within the second area 25. Specifically, for example, similarly to the bass acoustic variable mechanism 5A shown in the modified example of the second embodiment, the displacement member 54 is rotated in the second region 25 to thereby change the first position and the second position. It may be displaced. In this case, the position of the displacement member 54 (hereinafter referred to as “parallel position”) when the angle along the lateral width direction is 0 degrees is the first position, and the position of the displacement member 54 when the angle along the lateral width direction is 90 degrees. (Hereinafter referred to as “orthogonal position”) is the second position.

  The change of the sound absorption region in this case will be described with reference to FIG. Also in FIG. 22, the sound propagation direction is a direction from the right side to the left side of the second region 25.

  FIG. 22A is a cross-sectional view schematically showing the sound absorption region 27c when the displacement member 54 is in the parallel position. In this case, the volume of the non-sound absorbing region 28 is very small, and substantially the entire second region 25 becomes the sound absorbing region 27c. The size of the sound absorption region when the displacement member 54 is positioned at the orthogonal position is the same as that of the sound absorption region 27a of FIG.

  FIG. 22B is a transverse cross-sectional view schematically showing the sound absorption region 27d when the displacement member 54 is at an oblique position, for example, when the angle along the lateral width direction is about 45 degrees. Even in this case, in the thickness range in which the displacement member 54 does not exist in the second region 25, the entire region from the right end to the left end of the second region 25 can be included in the sound absorption region 27d. It becomes larger than the sound absorbing region 27a at the position.

(Modification 1)
In the first modification of the third embodiment, the plurality of displacement members 54 are provided at intervals from each other along the sound propagation direction. In this case, the position where the sound absorbing material 3 is partitioned can be changed by selecting the displacement member 54 to be displaced to the second position (partition position) from among the plurality of displacement members 54. That is, the size of the sound absorption region can be changed in stages.

  In the bass acoustic variable mechanism 5 </ b> C shown in FIG. 23, the front surface member 22 is provided with a plurality of insertion holes 221. The plurality of insertion holes 221 are arranged away from each other in the lateral width direction. The second region 25 is provided with a plurality of cavities (gap) 251 for receiving the displacement member 54.

  When all the displacement members 54 are brought into the drawing position, the sound absorbing region is the entire sound absorbing material 3 in the second region 25. The closer the position in the lateral direction of the displacement member 54 whose position has been changed from the state to the insertion position is closer to the sound entrance side, the lower the sound absorption rate of the bass.

  The displacement member 54 closest to the first region 24 (sound entrance side) may be disposed near the boundary position with the first region 24. In this case, when the displacement member 54 is displaced from the first position to the second position, the sound entering the second region 25 is blocked near the entrance, so that the sound absorbing region of the sound absorbing material 3 in the second region is blocked. Is almost equal to zero. Therefore, in this case, the bass sound can be maximized.

  When the displacement member 54 is provided so that its position can be changed along the sound propagation direction, the size of the sound absorption region can be changed stepwise even if there is only one displacement member 54. For example, a plurality of insertion holes 221 for inserting and removing the displacement member 54 may be provided along the sound propagation direction (lateral width direction).

(Modification 2)
In the above description, the displacement member 54, which is a plate-like member, is arranged vertically (along the vertical direction). However, the displacement member 54 may be arranged inclined or horizontally (along the lateral width direction). ) May be arranged. FIG. 24 shows an example in which the displacement member 54 is horizontally disposed at the center position in the vertical direction. In this case, the sound absorbing material 3 in the second region 25 is partitioned in the vertical direction by the displacement member 54.

  The sound (sound wave) that enters from the end of the second region 25 on the first region 24 side does not travel straight along the lateral width direction (sound propagation direction), but in the upward direction, the downward direction, or the thickness direction. Will continue. Therefore, as shown in FIG. 25B, even when the displacement member 54 is disposed in the second region 25 along the lateral width direction, the non-sound absorbing region 28 is formed in the vicinity of the displacement member 54. Therefore, the sound absorption region 27e is smaller than the sound absorption region 27 in the initial state shown in FIG. 25A, that is, in the state where the displacement member 54 is not located in the second region 25. Therefore, also in such a form, the sound absorption coefficient of the bass can be made variable by inserting and removing the displacement member 54. Note that an arrow A4 illustrated in FIG. 25A indicates the vertical direction.

  Note that the two displacement members 54 may be arranged so as to cross in the vertical direction and the horizontal width direction.

(Modification 3)
As shown in FIG. 10, even when the openings 23 are provided on both sides of the front surface member 22, a bass sound variable mechanism may be employed. In this case, by changing the arrangement position of the displacement member 54, it is possible to change the low sound absorption coefficient incident from one opening 23 and the low sound absorption coefficient incident from the other opening 23.

  For example, as shown in FIG. 26 (A), it is assumed that the displacement member 54 is disposed slightly to the left of the page with respect to the center position of the second region 25. In this case, the sound absorption coefficient of the low sound incident from the left opening 23 and the sound absorption coefficient of the low sound incident from the right opening 23 are slightly smaller in the former.

  As shown in FIG. 26B, it is assumed that the displacement member 54 is arranged further to the left on the paper surface than the center position of the second region 25. In this case, since the sound absorption coefficient of the low sound incident from the left opening 23 is considerably reduced, the sound absorption coefficient of the low sound incident from the right opening 23 is larger than that in the case of FIG.

  The change of the arrangement position of the displacement member 54 can be realized by the same method as in the second modification.

  As described above, in the form in which bass is absorbed from both sides of the second region 25, the displacement members 54 are arranged at different distances from the left and right end portions of the second region 25, so that sounds in different frequency ranges on the left and right are arranged. Can be realized. In this case, the arrangement position of the displacement member 54 can also be adjusted according to the positional relationship with the sound source.

  In the present embodiment, the displacement member 54 is a plate-like member, but is not limited. In the case of the form in which the displacement member 54 is inserted and removed, for example, the tip shape of the displacement member 54 is made into a semicircular shape, and pressed while being abutted against the sound absorbing material 3 in the second region 25 (the sound absorbing material 3 is compressed and deformed). The size of the sound absorption area may be changed.

  Further, the size of the sound absorbing region of the sound absorbing material in the second region 25 may be changed using a member other than the displacement member 54.

<Embodiment 4>
Next, the sound absorbing structure of the soundproof room according to Embodiment 4 of the present invention will be described. In the present embodiment, the sound absorbing structure has a function of changing the sound in the entire sound range.

  FIG. 27 is a diagram schematically illustrating a sound absorbing structure 1C according to the fourth embodiment. The basic structure of the sound absorbing structure 1C is the same as that of the sound absorbing structure 1 of the first embodiment. Therefore, only the points different from the sound absorbing structure 1 of the first embodiment will be described here.

  The sound absorbing structure 1 </ b> C includes an acoustic variable mechanism 6. The sound variable mechanism 6 can change the sound absorption rate of the entire sound by adjusting the exposed area of the sound absorbing surface exposed from the opening 23 (that is, the surface of the exposed sound absorbing portion 31 or the surface of the decorative panel).

  Specifically, the acoustic variable mechanism 6 is provided in the opening 23, and is composed of a plurality of wing plates 61 like a louver, for example. Each slat 61 extends in the horizontal width direction and can change the angle in the vertical direction. Therefore, the exposed area of the sound absorbing surface of the sound absorbing material 3 can be adjusted by changing the angle of the slat 61. That is, when the entire or part of the sound absorbing surface is closed with the wing plate 61, the sound absorption coefficient of the entire sound is lowered, so that the sound in the entire sound range is increased.

  Therefore, also in the present embodiment, comfortable sound can be created according to the type of musical instrument used.

  The acoustic variable mechanism 6 is not limited to the configuration as shown in FIG. 27 and may be configured by one or a plurality of doors.

<Embodiment 5>
In the first to fourth embodiments described above, the soundproof room having a side wall with a width of 2P has been described as an example. . A configuration example of the soundproof room in this case will be described.

  FIG. 28 is a diagram schematically showing a soundproof room 9A according to the fifth embodiment. The soundproof room 9A has side walls 92, 94 having a width of 3P and side walls 93, 95 having a width of 4P.

  In each of the 4P side walls 93 and 95, for example, the sound absorbing structure 1 shown in the first embodiment is set as one unit, and two sound absorbing structures 1 are arranged in the lateral width direction. In the present embodiment, the two units are arranged so that the left-right positional relationship between the front surface member 22 and the opening 23 is the same. In this case, a partition member 71 for blocking the passage of sound may be provided between the units.

  Alternatively, even if the two sound absorbing structures 1 are arranged so that the positional relationship between the front surface member 22 and the opening 23 is symmetric so that the opening 23 is arranged near the corner of the soundproof room 9A. Good. In any case, the rear surface member 21 may be continuous.

  Moreover, the 3P side wall 92 is comprised by the sound absorption structure 1D, for example. The sound absorbing structure 1D has an opening 23 with an opening size of 0.5P in front of the center of the rear surface member 21 having a width of 3P, and a pair of front surface members 22 are provided on both sides thereof. Also in this case, the thickness dimension D3 of the sound absorbing material 3 may be 100 mm or more.

  Thus, when the lateral width of the side wall is larger than 2P, the lateral width dimension D2 of the front surface member 22 may be larger than 1.5P.

<Other embodiments>
In the sound absorbing structures of the above-described embodiments, the front surface member 22 and the opening 23 are arranged so as to be adjacent to each other in the lateral width direction. In this case, like the side wall 92 shown in FIG. 29, the opening 23 may be provided at the center in the vertical direction.

  In each of the above embodiments, the rear surface member 21 and the front surface member 22 of the sound absorbing structure constitute the side wall of the soundproof room. However, as shown in FIG. 29, these are the floor 91 of the soundproof room. Alternatively, the ceiling 96 may be configured. That is, the rear surface member 21 and the front surface member 22 of the sound absorbing structure may constitute at least one of the side walls 92 to 95, the floor 91, and the ceiling 96 of the soundproof room.

  Alternatively, only the rear surface member 21 of the sound absorbing structure may constitute at least one of the side walls 92 to 95, the floor 91, and the ceiling 96 of the soundproof room. That is, the front surface member 22 may be disposed simply as a reflective panel in front of the component surface (rear surface member 21) of the soundproof room.

  Alternatively, the sound absorbing structure shown in each embodiment may not be incorporated in the soundproof room in advance. That is, the sound absorbing structure may be realized as a portable sound absorbing device as shown in FIG.

  Referring to FIG. 30, sound absorbing device 10 has a sound absorbing structure 1 </ b> E in which a sound absorbing structure 1 </ b> B according to a modification of the second embodiment and a sound absorbing structure 1 </ b> C according to the fourth embodiment are combined. Therefore, the sound absorbing device 10 includes, as an example, a bass sound variable mechanism 5 </ b> A (FIG. 17) and a sound variable mechanism 6. Therefore, the sound absorbing device 10 can change the sound for each sound range (for each frequency). In addition, in FIG. 30, the state in which the sound variable mechanism 6 is fully closed is shown.

  In this case, the rear surface member 21 and the front surface member 22 constitute a part of the housing of the sound absorbing device 10. In addition to the rear surface member 21 and the front surface member 22, the sound absorbing device 10 may be surrounded by surface members 81 to 84 that respectively block the upper end surface, the lower end surface, and both side surfaces of the sound absorbing material 3.

  Also in the sound absorbing device 10, the rear surface member 21 and the front surface member 22 are both rectangular. Assuming that a predetermined direction (a direction in which the front surface member 22 and the opening 23 are adjacent to each other) indicated by an arrow A2 in FIG. 30 is one direction, the length of the rear surface member 21 in one direction is 2P. On the other hand, the length in the direction is preferably 1.5P. The length of the rear surface member 21 and the front surface member 22 in the other direction (a direction orthogonal to the one direction) is desirably 1P or more.

  By installing the sound absorbing device 10 as described above at a desired position in the room, the room can be used like an audio room. The sound absorbing device 10 can also function as an audio tune because the sound can be changed for each sound range. The sound absorbing device 10 may be installed such that the predetermined direction matches the lateral width direction of the side wall of the room, or may be installed so that the predetermined direction matches the vertical direction of the room.

  In the example of the sound absorbing device 10 in FIG. 30, the shape of the rear surface member 21 and the front surface member 22 is a rectangular shape, but is not limited to such a shape. The rear surface member 21 and the front surface member 22 have at least a length in a predetermined direction, and the front surface member 22 and the opening 23 may be disposed adjacent to each other in the predetermined direction.

  Moreover, in the said Embodiment 2, 3, when providing the bass sound variable mechanism, it demonstrated that the sound-absorbing material 3 may be divided | segmented through the clearance gap or the cavity part, However, regardless of the presence or absence of a bass sound variable mechanism. Instead, the sound absorbing material 3 may be divided. That is, it is only necessary that the sound absorbing material 3 is provided in both the first region 24 and the second region 25 that constitute the front region of the rear surface member 21, and the sound absorbing material 3 is provided from the first region 24 to the second region. It does not have to extend to 25. For example, one or more cavities may be provided in the second region 25.

  In addition, in the second region 25, when a hollow portion is provided so as to extend in the horizontal direction, the displacement member 54 (or the partition member 51) having a short vertical length is slidably disposed along the hollow portion. May be.

  Further, in each of the above embodiments, the length of the front surface member 22 along the predetermined direction (for example, the lateral width direction) is shorter than the rear surface member 21, and the opening 23 is adjacent to the front surface member 22 in the predetermined direction. explained. However, the lengths along the predetermined direction of the rear surface member 21 and the front surface member 22 may be the same, and the opening 23 may be partially provided in the front surface member 22. In this case, a region located behind the portion (reflection wall portion) excluding the opening 23 in the front surface member 22 corresponds to the above-described second region. The first region is a region located behind the opening 23 as in the above embodiments.

  Even when the front surface member 22 has the opening 23, the opening 23 is disposed at one end of the front surface member 22 in a predetermined direction and extends in a direction intersecting (orthogonal) with the predetermined direction. It is desirable to exist. More specifically, when the predetermined direction is the lateral width direction, the opening 23 may extend from the upper end position of the front surface member 22 to the lower end position.

  As shown in FIG. 31, the front surface member 22 </ b> A may have a plurality of openings 23. In this case, the reflection wall portions 222 and the openings 23 of the front surface member 22A are alternately arranged along a predetermined direction. The above-described opening dimension D1 may be considered to correspond to the sum of the length dimensions along the predetermined direction of all the openings 23 (or the first region 24). The reflection wall dimension D2 may also be considered to correspond to the sum of the length dimensions along the predetermined direction of all the reflection wall portions 222 (or the second region 25).

  Moreover, in each said embodiment, although the sound-absorbing material 3 was provided in both the 1st area | region 24 and the 2nd area | region 25, as shown by the sound-absorbing structure 1G of FIG. May be provided only. That is, it is sufficient that the sound absorbing material 3 is disposed at least behind the front surface member 22.

  In the sound absorbing structure 1 </ b> G, a part of the sound incident on the first region from the opening 23 is reflected by the rear surface member 21, and the remaining part reaches the second region 25. In this case, most of the high sound is reflected, and the low sound is incident on the sound absorbing material 3 provided in the second region 25 from the side surface and absorbed. That is, in the sound absorbing structure 1G, the side surface of the sound absorbing material 3 is a sound absorbing surface. According to such a sound absorbing structure 1G, compared with the sound absorbing structure 1 of the first embodiment, it is possible to increase the sound pressure level of the high sound while maintaining the sound absorbing performance of the low sound. Therefore, by adopting the sound absorbing structure 1G, it is possible to realize a construction method that absorbs only low frequencies and absorbs low frequencies effectively. In addition, in the sound absorbing structure 1G, when an opening / closing mechanism (for example, a door) for enabling the opening 23 to be closed is provided, the sound absorption rate of the low sound can be changed by opening / closing the opening / closing mechanism.

  When the sound absorbing material 3 is provided only in the second region 25, as in the sound absorbing structure 1H of FIG. 33, the opening 23 is provided at both ends in the width direction of the front surface member 22, and the sound absorbing material 3 is sounded from both side surfaces. May be able to absorb sound.

  Alternatively, when such a sound absorbing structure is adopted in the sound absorbing device as shown in FIG. 30, the length dimension of the front surface member 22 in the lateral width direction may be the same as that of the rear surface member 21. In this case, for example, the surface members 83 and 84 that block the both side surfaces of the sound absorbing material 3 may be eliminated, the both side surfaces of the sound absorbing material 3 may be sound absorbing surfaces, or the surface member 81 that blocks the upper end surface of the sound absorbing material 3 may be eliminated. The upper end surface of the material 3 may be a sound absorbing surface.

  As mentioned above, although embodiment of this invention was described, you may combine each said embodiment and modification suitably.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1, 1A, 1B, 1C, 1D, 1E, 1G, 1H Sound absorbing structure, 3 sound absorbing material, 4, 4A Underlying member, 5, 5A, 5B, 5C Low sound variable mechanism, 6 Sound variable mechanism, 9, 9A Soundproof room DESCRIPTION OF SYMBOLS 10 Sound absorption device, 21 Back surface member, 22, 22A Front surface member, 23 Opening part, 24 1st area | region, 25 2nd area | region, 26 Boundary surface, 27, 27a-27e Sound absorption area | region, 28 Non-sound absorption area | region, 31 Exposure Sound absorbing part, 32 Back sound absorbing part, 41 Vertical beam, 42 Horizontal beam, 51 Partition member, 52 Partition beam, 53 Operation lever, 61 Blade, 71 Partition material, 81-84 Surface member, 91 Floor, 92-95 Side wall, 96 ceiling, 101-105 wall structure, 220 operation opening, 221 insertion hole, 222 reflecting wall part, 250 cavity part, 540 plate-like member.

Claims (8)

A sound absorbing structure for absorbing sound,
A rear surface member having a length in a predetermined direction;
A front surface member disposed parallel to the rear surface member and spaced forward from the rear surface member;
A sound absorbing material disposed in a rear region located behind the front surface member;
A sound absorbing structure comprising: an acoustic variable mechanism for changing sound by changing a sound absorption rate of sound entering from the end portion in the predetermined direction of the rear region.   The acoustic variable mechanism includes a displacement member provided so that the position can be changed between the first position and the second position, and changes the size of the sound absorbing region of the sound absorbing material according to the position of the displacement member. The sound absorbing structure according to claim 1.   The sound absorbing structure according to claim 2, wherein the displacement member is configured by a plate-like member.   The sound absorbing structure according to claim 3, wherein a plurality of the displacement members are provided, and the plurality of displacement members are arranged apart from each other.   The sound absorbing structure according to any one of claims 2 to 4, wherein a plurality of the displacement members are provided at intervals from each other along a sound propagation direction.   The sound-absorbing structure according to claim 2, wherein the displacement member is provided so that a position thereof can be changed along a sound propagation direction.   The sound-absorbing structure according to any one of claims 2 to 6, wherein the acoustic variable mechanism further includes an insertion hole provided in the front surface member for inserting and removing the displacement member.   The sound absorbing structure according to claim 2, wherein the displacement member is rotatably arranged in the rear region.

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