CN211714198U - Noise reduction device for road construction - Google Patents

Abstract

The utility model relates to a road construction equipment technical field provides a device of making an uproar falls for road construction. The noise reduction device comprises a plurality of sound insulation assemblies which are sequentially connected to jointly enclose a construction space; the sound insulation assembly comprises two stand columns, a sound insulation board and a first horizontal rod, wherein the sound insulation board and the first horizontal rod are arranged between the two stand columns; the bottom surface of the first horizontal rod is provided with a plurality of trundles, two ends of the top surface of the first horizontal rod are provided with first plugs protruding upwards, and the bottom surface of the upright post is provided with first jacks for inserting the corresponding first plugs; two columns between two adjacent acoustic panels can be detachably connected. The utility model discloses convenient to detach, economic environmental protection not only can utilize acoustic celotex board refraction, absorb the noise that the construction produced, and the noise reduction decibel can freely carry out the combination installation according to the construction region size moreover.

Description

Noise reduction device for road construction

Technical Field

The utility model relates to a road construction equipment technical field especially relates to a device of making an uproar falls for road construction.

Background

At present, in order to ensure smooth traffic in daytime, road construction is usually arranged to be carried out at night. The most commonly used equipment in the road construction process is an excavator, and a breaking hammer of the excavator generates large noise when the breaking hammer strikes the ground, so that great trouble is caused to residents and passing people nearby a construction site.

SUMMERY OF THE UTILITY MODEL

The present invention aims at least solving one of the technical problems existing in the prior art or the related art. Therefore, the utility model provides a simple structure, convenient to detach, size adjustable are used for the device of making an uproar that falls of road construction.

According to the embodiment of the utility model, the noise reduction device for road construction comprises a plurality of sound insulation components which are connected in sequence to form a construction space through common enclosure; the sound insulation assembly comprises two upright posts, a sound insulation board and a first horizontal rod, wherein the sound insulation board and the first horizontal rod are arranged between the two upright posts; the bottom surface of the first horizontal rod is provided with a plurality of trundles, two ends of the top surface of the first horizontal rod are provided with first plugs protruding upwards, and the bottom surface of the upright post is provided with a first jack for inserting the corresponding first plug; two between two adjacent acoustic celotex board the stand can be dismantled and connect.

According to the utility model discloses a device of making an uproar falls for road construction not only can utilize the acoustic celotex board refraction, absorb the noise that the construction produced, the noise reduction decibel, application scope is wide moreover, can freely carry out the combination installation according to the construction region size.

In addition, according to the utility model discloses a device of making an uproar falls for road construction, can also have following additional technical characteristics:

according to an embodiment of the present invention, the top surface of the first horizontal bar is formed with a second insertion groove for inserting the lower edge of the baffle.

According to the utility model discloses an embodiment, first horizon bar includes the U-shaped channel-section steel and locates respectively two connecting rods at U-shaped channel-section steel both ends with first plug, the one end of connecting rod with the bottom surface of U-shaped channel-section steel is connected, the other end of connecting rod with first plug connection.

According to the utility model discloses an embodiment, adjacent two between the acoustic celotex board the stand passes through bolted connection, the stand transversely runs through and sets up the first through-hole that is used for wearing to establish the bolt, the axis of first through-hole with the acoustic celotex board is perpendicular or parallel.

According to the utility model discloses an embodiment the axis of first through-hole with under the parallel condition of acoustic celotex board, first through-hole is located first slot orientation one side of acoustic celotex board.

According to the utility model discloses an embodiment, the stand includes the rectangular pipe, the rectangular pipe orientation one side of acoustic celotex board is equipped with the extension board of two relative settings, the rectangular pipe encloses with two extension boards jointly and establishes formation first slot.

According to the utility model discloses an embodiment, the subassembly that gives sound insulation still include with the connection piece of stand one-to-one, the first end of connection piece with the lateral wall at the top of stand is connected, the second end of connection piece is stretched out the stand, the second through-hole has been seted up to the second end of connection piece, the lateral wall of the bottom of stand seted up with the third through-hole that the second through-hole corresponds.

According to an embodiment of the present invention, the sound insulation assembly further comprises a second horizontal rod disposed between the two vertical columns, wherein a second plug protruding downwards is formed at two ends of the bottom surface of the second horizontal rod, and a third slot for inserting the upper edge of the sound insulation board is formed in the bottom surface of the second horizontal rod; and a second jack used for inserting the corresponding second plug is formed in the top surface of the upright post.

According to the utility model discloses an embodiment, the top surface of second horizon bar is equipped with the refraction board that extends along its length direction, the refraction board orientation the center slope of construction space.

According to the utility model discloses an embodiment, the acoustic celotex board includes puigging, damping layer and the layer of absorbing sound that sets gradually from outside to inside.

The embodiment of the utility model provides an in above-mentioned one or more technical scheme, one of following technological effect has at least:

the utility model has simple structure and convenient operation, and each sound insulation component is assembled in sequence during construction, namely the first horizontal rod is horizontally placed on the ground; then sliding the edges of the left side and the right side of the sound insulation board into first slots of the two upright posts respectively; and finally, inserting the first jacks of the two upright posts into the first plugs at the two ends of the first horizontal rod respectively. After all the sound insulation assemblies are assembled, the relative positions of the sound insulation assemblies are adjusted to enable the sound insulation assemblies to jointly enclose to form a construction space, and two stand columns between two adjacent sound insulation boards are connected together. Therefore, noise generated by the construction equipment in the operation of a construction area is greatly reduced after being refracted and absorbed by the sound insulation board, and normal work and rest life of nearby residents and passing people can be further guaranteed. Furthermore, the utility model discloses not only be convenient for installation dismantlement, reuse, economic environmental protection, application scope is wide moreover, can freely carry out the composite mounting according to the construction region size.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is an axial view of a noise reduction device for road construction according to an embodiment of the present invention;

fig. 2 is a schematic partial top view of a noise reducer for road construction according to an embodiment of the present invention;

FIG. 3 is a schematic top view of a baffle assembly in an embodiment of the present invention;

FIG. 4 is a schematic front view of a first horizontal bar in an embodiment of the present invention;

FIG. 5 is a cross-sectional view at A-A of FIG. 4;

fig. 6 is a schematic top view of a first horizontal bar in an embodiment of the invention;

fig. 7 is a schematic top view of a column in an embodiment of the invention;

fig. 8 is a schematic top view of another embodiment of a column according to the present invention;

fig. 9 is a schematic top view of two horizontally adjacent columns according to an embodiment of the present invention;

fig. 10 is a schematic top view of another connection mode of two horizontally adjacent columns in the embodiment of the present invention;

fig. 11 is a schematic side view of a connection mode of two vertically adjacent columns in the embodiment of the present invention;

fig. 12 is a schematic bottom view of a second horizontal rod according to an embodiment of the present invention.

Reference numerals:

100: a sound insulating assembly; 110: a column; 111: a rectangular tube; 112: an extension plate;

113: a first slot; 114: a first through hole; 115: connecting sheets; 116: a second through hole;

117: a third through hole; 120: a sound insulating board; 130: a first horizontal bar;

131: a first plug; 132: a second slot; 133: a caster wheel; 134: u-shaped channel steel;

135: a connecting rod; 140: a second horizontal bar; 141: a second plug;

142: a third slot; 150: a refracting plate; 160: advertising cloth; 170: a bolt;

171: and a nut.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly described below with reference to the accompanying drawings of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. Based on the embodiments in the utility model, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the utility model.

In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of describing the embodiments of the present invention and simplifying the description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the embodiments of the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the embodiments of the present invention, it should be noted that, unless explicitly stated or limited otherwise, the terms "connected" and "connected" should be interpreted broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; may be directly connected or indirectly connected through an intermediate. The specific meaning of the above terms in the embodiments of the present invention can be understood in specific cases by those skilled in the art.

In embodiments of the invention, unless expressly stated or limited otherwise, the first feature may be directly on or directly under the second feature or indirectly via intermediate members. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of an embodiment of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

With reference to fig. 1 to 6, an embodiment of the present invention provides a noise reduction device for road construction, which includes a plurality of sound insulation assemblies 100, wherein the plurality of sound insulation assemblies 100 are connected in sequence to jointly enclose a construction space; the sound insulation assembly 100 comprises two upright posts 110, a sound insulation board 120 and a first horizontal rod 130, wherein the sound insulation board 120 and the first horizontal rod 130 are arranged between the two upright posts 110, one side of each upright post 110, which faces the sound insulation board 120, is longitudinally penetrated and provided with a first slot 113, and the left side and the right side of each sound insulation board 120 are respectively slidably inserted into the corresponding first slots 113; a plurality of casters 133 are disposed on the bottom surface of the first horizontal rod 130, a first plug 131 protruding upwards is formed at two ends of the top surface of the first horizontal rod 130, and a first jack for inserting the corresponding first plug 131 is disposed on the bottom surface of the upright post 110; two pillars 110 between two adjacent baffles 120 are detachably connected. Wherein the caster 133 may be, but is not limited to, a universal wheel.

Before construction, a constructor can transport a corresponding number of the soundproof assemblies 100 to a construction area according to the size of the construction area. All of the acoustic baffle assemblies 100 may be the same size or different sizes. When all the soundproof assemblies 100 are the same in size, the number of soundproof assemblies 100 required for construction is proportional to the area of the construction area, that is, the greater the area of the construction area, the greater the number of soundproof assemblies 100 required.

The following description will be made of the method of using the noise reduction device for road construction according to the embodiment of the present invention, taking 3 sound insulation assemblies 100 required for construction as an example:

first step, assembling one of the acoustic assemblies 100, in particular: first, the first horizontal rod 130 is horizontally placed on the ground; then, as shown in fig. 3, the left and right side edges of the baffle 120 are respectively slid into the first slots 113 of the two pillars 110; finally, the first insertion holes of the two vertical posts 110 are inserted into the first plugs 131 at both ends of the first horizontal bar 130, respectively.

The second step, the remaining two acoustic baffle assemblies 100 are assembled in sequence in the order of the first step.

And thirdly, pushing the 3 sound insulation assemblies 100 to adjust the relative positions of the sound insulation assemblies so that the construction area is positioned in a T-shaped construction space formed by the 3 sound insulation assemblies 100 in a surrounding mode.

And a fourth step of connecting the two pillars 110 between the adjacent two soundproof plates 120 together. It should be noted that the two pillars 110 between two adjacent baffles 120 can be connected in various ways, such as by tying them together with ropes, or by fastening them together with bolts 170. When two vertical columns 110 between two adjacent baffle-panels 120 are connected by bolts 170, as shown in fig. 7 and 8, first through holes 114 for passing the bolts 170 are transversely formed through the vertical columns 110, and the axes of the first through holes 114 are perpendicular or parallel to the baffle-panels 120. As shown in fig. 10, when two adjacent sound insulation modules 100 enclose a corner forming a construction space, that is, two adjacent sound insulation panels 120 are perpendicular to each other, the pillar 110 of one sound insulation module 100 is provided with a first through hole 114 perpendicular to the sound insulation panel 120, and the pillar 110 of the other sound insulation module 100 is provided with a first through hole 114 parallel to the sound insulation panel 120. As shown in fig. 9, when two adjacent baffles 120 are parallel, the pillars 110 of two sound insulation assemblies 100 are respectively opened with first through holes 114 parallel to the baffles 120, and the first through holes 114 are disposed on one side of the first slots 113 facing the baffles 120. For the two cases, the first through hole 114 of one of the upright posts 110 is aligned with the first through hole 114 of the other upright post 110, and then one end of the bolt 170 is sequentially inserted through the two first through holes 114 and then screwed into the nut 171.

From this, noise that construction equipment produced when the construction area operation reduces by a wide margin through acoustic celotex board 120 refraction, its decibel after absorbing, adopts through experimental discovery the utility model provides an in the embodiment of make an uproar device of falling can effectively reduce noise 15 ~ 25 decibels, and then just can ensure near resident and the normal work and rest life of past crowd. It should be noted that all the sound insulation assemblies 100 may be connected end to end in sequence to enclose a construction space forming a ring shape when construction noise is large. For example, 4 sound insulation assemblies 100 are connected end to form a rectangular construction space. Therefore, the noise generated in the construction area can be prevented from generating a standing wave effect in the construction space, and the sound insulation quantity is enabled to have a low valley. Of course, in order to further reduce noise pollution, the top of the construction space may be covered with an acoustic panel 120 to form a closed space.

Further, in order to improve the coupling strength of the baffle 120 and prevent the baffle 120 from shaking, as shown in fig. 6, the top surface of the first horizontal bar 130 is formed with a second insertion groove 132 for inserting the lower edge of the baffle 120. As shown in fig. 12, the soundproof assembly 100 further includes a second horizontal bar 140 provided between the two pillars 110, both ends of a bottom surface of the second horizontal bar 140 are formed with second plugs 141 protruding downward, and a bottom surface of the second horizontal bar 140 is further formed with third insertion grooves 142 for inserting upper edges of the soundproof plates 120; the top surface of the upright post 110 is opened with a second jack for inserting a corresponding second plug 141.

When the sound insulation assembly 100 is assembled, the first horizontal bar 130 is horizontally placed on the ground; then, the left and right side edges of the sound insulation board 120 are respectively slid into the first slots 113 of the two upright posts 110; next, the first insertion holes of the two upright posts 110 are aligned with the first plugs 131 at both ends of the first horizontal bar 130, respectively, and the lower edges of the baffle plates 120 are aligned with the second insertion grooves 132; next, the baffle 120 is moved downward, i.e., toward the first horizontal bar 130, until the first insertion hole is inserted into the corresponding first plug 131, and the lower edge of the baffle 120 is inserted into the second insertion groove 132. Next, the second horizontal bar 140 is fastened to the top end of the baffle 120, and the second plugs 141 of the second horizontal bar 140 are inserted into the second insertion holes of the two upright posts 110, respectively, and the upper edge of the baffle 120 is inserted into the third insertion groove 142.

As shown in fig. 4 to 6, the first horizontal bar 130 includes a U-shaped channel 134, and two connecting bars 135 and a first plug 131 respectively disposed at two ends of the U-shaped channel 134, wherein one end of the connecting bar 135 is connected to a bottom surface of the U-shaped channel 134, and the other end of the connecting bar 135 is connected to the first plug 131. At this time, the groove of the U-shaped channel 134 is the second slot 132. Of course, the first horizontal bar 130 may also be a straight bar with a rectangular longitudinal cross section, and the top surface of the first horizontal bar 130 may be turned to form the second slot 132.

As shown in fig. 7 and 8, the pillar 110 includes a rectangular tube 111, two opposite extending plates 112 are disposed on one side of the rectangular tube 111 facing the baffle 120, and the rectangular tube 111 and the two extending plates 112 together form a first slot 113. When the sound insulation assembly 100 is assembled, the first horizontal bar 130 is horizontally placed on the ground; then, the left and right side edges of the sound insulation board 120 are respectively slid into the first slots 113 of the two upright posts 110; finally, the rectangular tubes 111 of the two upright posts 110 are respectively inserted into the first plugs 131 at the two ends of the first horizontal rod 130, and at this time, the tube openings of the rectangular tubes 111 are the first insertion holes.

In addition, considering that some construction equipment such as an excavator has a high height, in order to be capable of adapting to the heights of different construction equipment and realize the height adjustment of the sound insulation assembly 100, as shown in fig. 11, the sound insulation assembly 100 further includes a connecting piece 115 corresponding to the upright column 110 one to one, a first end of the connecting piece 115 is connected with a side wall of the top of the upright column 110, a second end of the connecting piece 115 protrudes out of the upright column 110, a second end of the connecting piece 115 is provided with a second through hole 116, and a side wall of the bottom of the upright column 110 is provided with a third through hole 117 corresponding to the second through hole 116.

The assembly method of the soundproof assembly 100 comprising four vertical posts 110, two soundproof plates 120 and a first horizontal bar 130 will be described below as an example, and for convenience of description, the four vertical posts 110 will be referred to as a first vertical post, a second vertical post, a third vertical post and a fourth vertical post in this order:

first, the left and right edges of one of the soundproof plates 120 are slid into the first slots 113 of the first pillar and the second pillar, respectively.

Then, the bottom end of the third upright post is tightly attached to the top end of the first upright post, so that the second end of the connecting piece 115 of the first upright post is attached to the outer wall of the third upright post; and simultaneously adjusting the position of the third upright relative to the first upright in the horizontal direction until the third through hole 117 of the third upright is aligned with the second through hole 116 of the connecting piece 115 of the first upright, i.e. the second through hole 116 and the third through hole 117 are coaxial.

Then, one end of the bolt is threaded through the third through hole 117 and the second through hole 116 in sequence and then screwed into the nut.

Next, the bottom end of the fourth upright post is attached to the top end of the second upright post, so that the second end of the connecting piece 115 of the second upright post is attached to the outer wall of the fourth upright post; and simultaneously adjusting the position of the fourth upright relative to the second upright in the horizontal direction until the third through hole 117 of the fourth upright is aligned with the second through hole 116 of the connecting piece 115 of the second upright, i.e. the second through hole 116 and the third through hole 117 are coaxial.

Then, one end of another bolt is threaded through the third through hole 117 and the second through hole 116 in sequence, and then the nut is screwed in.

Next, the left and right edges of the remaining one of the sound insulation panels 120 are slid into the first slots 113 of the third and fourth pillars, respectively.

Finally, the first horizontal bar 130 is horizontally placed on the ground, and the first insertion holes of the first vertical column and the second vertical column are respectively inserted into the first plugs 131 at both ends of the first horizontal bar 130. At this time, the height of the assembled soundproof assembly 100 is greater than or equal to the height of the two soundproof plates 120.

In addition, in order to further reduce noise and absorb noise, as shown in fig. 1, a refracting plate 150 is provided on the top surface of the second horizontal rod 140 to extend in the longitudinal direction thereof, and the refracting plate 150 is inclined toward the center of the construction space. Therefore, the transmission direction of the noise transmitted to the top of the construction space is changed after the noise is refracted for many times through the refraction plate 150, most of the noise returns to the construction space again and cannot be transmitted outwards, and the noise decibels heard by nearby residents and passing people are greatly reduced.

Further, the soundproof plate 120 includes a soundproof layer, a damping layer, and a sound absorption layer, which are sequentially disposed from the outside to the inside. Of course, the soundproof panel 120 may be composed of only the soundproof layer, only the soundproof layer and the damping layer, or only the soundproof layer and the sound absorbing layer. When the baffle 120 includes an acoustic insulating layer and a sound absorbing layer, the acoustic insulating layer and the sound absorbing layer correspond to forming a plurality of helmholtz resonators capable of absorbing medium and high frequency noise. In addition, an advertisement cloth 160 may be attached to a side of the soundproof plate 120 facing away from the construction space.

The sound insulation layer is used for reducing the noise in the construction space and preventing the transmission of the solid-borne sound, and is preferably a galvanized aluminum plate or a high-molecular-density foam board. The damping layer is used for preventing the mechanical vibration generated by construction and the resonance generated by sound wave, and the damping layer is preferably a high-molecular damping layer, and the thickness of the damping layer is preferably 3 mm. The sound absorption layer is used for absorbing noise, and is preferably made of waterproof high-flame-retardant wave crest cotton materials. It should be noted that the sound insulation layer, the damping layer and the sound absorption layer can be integrally formed, and can also be bonded together by screws or glue.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (10)

1. The noise reduction device for road construction is characterized by comprising a plurality of sound insulation assemblies, wherein the sound insulation assemblies are sequentially connected to jointly enclose to form a construction space; the sound insulation assembly comprises two upright posts, a sound insulation board and a first horizontal rod, wherein the sound insulation board and the first horizontal rod are arranged between the two upright posts; the bottom surface of the first horizontal rod is provided with a plurality of trundles, two ends of the top surface of the first horizontal rod are provided with first plugs protruding upwards, and the bottom surface of the upright post is provided with a first jack for inserting the corresponding first plug; two between two adjacent acoustic celotex board the stand can be dismantled and connect.

2. The noise reducer for road construction according to claim 1, wherein the top surface of the first horizontal bar is formed with a second insertion groove for inserting the lower edge of the soundproof plate.

3. The noise reducer for road construction according to claim 2, wherein the first horizontal rod comprises a U-shaped channel, and two connecting rods and the first plug which are respectively arranged at two ends of the U-shaped channel, one end of each connecting rod is connected with the bottom surface of the U-shaped channel, and the other end of each connecting rod is connected with the first plug.

4. The noise reduction device for road construction according to claim 1, wherein two of the pillars between two adjacent acoustic panels are connected by bolts, a first through hole for passing through a bolt is transversely formed through each pillar, and an axis of the first through hole is perpendicular to or parallel to the acoustic panel.

5. The noise reducer for road construction according to claim 4, wherein the first through hole is provided on a side of the first insertion groove facing the baffle plate in a state where an axis of the first through hole is parallel to the baffle plate.

6. The noise reducer for road construction according to claim 1, wherein the pillar comprises a rectangular tube, one side of the rectangular tube facing the acoustic panel is provided with two oppositely arranged extension panels, and the rectangular tube and the two extension panels jointly enclose to form the first slot.

7. The noise reduction device for road construction according to claim 1, wherein the sound insulation assembly further comprises a connecting piece in one-to-one correspondence with the upright post, a first end of the connecting piece is connected with a side wall of the top of the upright post, a second end of the connecting piece protrudes out of the upright post, a second through hole is formed in the second end of the connecting piece, and a third through hole corresponding to the second through hole is formed in a side wall of the bottom of the upright post.

8. The noise reducer for road construction according to any one of claims 1 to 7, wherein the sound insulation assembly further comprises a second horizontal rod disposed between the two uprights, wherein a second plug protruding downward is formed at both ends of a bottom surface of the second horizontal rod, and a third slot for inserting an upper edge of the sound insulation board is further formed in the bottom surface of the second horizontal rod; and a second jack used for inserting the corresponding second plug is formed in the top surface of the upright post.

9. The noise reducer for road construction according to claim 8, wherein the top surface of the second horizontal rod is provided with a refracting plate extending in a length direction thereof, the refracting plate being inclined toward the center of the construction space.

10. The noise reduction device for road construction according to any one of claims 1 to 7, wherein the acoustic panel comprises an acoustic insulating layer, a damping layer and a sound absorbing layer, which are sequentially disposed from outside to inside.

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