A bidirectional low-frequency sound-absorbing metamaterial imitating bamboo shoot snail and its additive manufacturing method
A bidirectional low-frequency sound-absorbing metamaterial mimicking the bamboo shoot's spiral cavity structure addresses the inefficiencies of traditional materials by achieving effective two-way sound absorption and mechanical support through adjustable parameters, enhancing noise reduction capabilities.
Patent Information
- Application Number
- CN202210161374.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-02-22
- Publication Date
- 2024-12-27
- Estimated Expiration
- 2042-02-22
AI Technical Summary
Existing sound-absorbing materials struggle to effectively absorb low-frequency noise in multiple directions due to their design limitations, particularly in traditional porous materials and micro-perforated sound absorbers, which are inefficient and difficult to implement in practice.
A bidirectional low-frequency sound-absorbing metamaterial is designed to mimic the spiral cavity structure of a bamboo shoot, incorporating two intertwined spiral cavities within a unit cell, each connected to the outside air at opposite ends, with a support column and partitions to enhance sound absorption and mechanical strength, allowing for adjustable sound absorption performance.
The metamaterial achieves broadband sound absorption in two directions by adjusting structural parameters, providing high sound absorption coefficients even at frequencies smaller than the working wavelength, while maintaining mechanical integrity.
Smart Images
Figure CN114550682B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field related to acoustic metamaterials, and more specifically, relates to a bamboo shoot-like bidirectional low-frequency sound-absorbing metamaterial and an additive manufacturing method thereof. Background Art
[0002] Noise is widely present in all areas of life. Long-term exposure to high-intensity noise will cause serious damage to human health. Therefore, it is necessary to reduce noise to provide a more comfortable environment. Traditional sound-absorbing materials such as sponges have a large number of micropores inside, which have a strong dissipation effect on the energy of sound waves and have good absorption effects on medium and high frequency noise. However, for low-frequency noise, the energy dissipation coefficient is very low, and traditional porous materials are difficult to absorb. Sound insulation materials follow the sound insulation quality law and are also difficult to effectively block low-frequency noise. The micro-perforated sound absorber consists of a micro-perforated plate and the cavity behind it. The local resonance effect can absorb low-frequency sound absorption effects. However, this method requires a large cavity size and is difficult to be applied in practice. The emergence of metamaterials helps to solve this problem. Metamaterials refer to artificially designed periodic / quasi-periodic design structures with functions that natural materials do not have. They can realize some functions such as negative Poisson's ratio / negative refractive index, and have broad prospects for engineering applications. Among them, the sound-absorbing material realizes the function of absorbing low-frequency sound waves at a scale much smaller than the working wavelength through structural design. However, the sound-absorbing materials currently developed can only have a good absorption effect on sound waves in a certain direction, and have obvious deficiencies in multi-directional sound absorption.
[0003] After a long period of natural evolution, biological materials have developed various functions or structures that can adapt to complex environments. By learning from nature, humans have developed a variety of widely used engineering materials or structures. There is a support column in the middle of the shell of the bamboo snail, which provides a certain strength to resist external impact. There is a spiral cavity with a gradient of size around the support column. The ends of the shell are closed, and only a small space at the mouth of the screw is connected to the outside air, which can effectively resist the invasion of natural enemies. The internal cavity is a natural Helmholtz resonator, which can realize a longer cavity size in a limited space by surrounding the spiral cavity of the support column. Summary of the invention
[0004] In view of the above defects or improvement needs of the prior art, the present invention provides a bidirectional low-frequency sound-absorbing metamaterial imitating a bamboo shoot spiral and an additive manufacturing method thereof. The metamaterial imitates the spiral cavity structure inside the bamboo shoot spiral, and couples two spiral cavities in a limited space. The spiral cavity effectively increases the length of the resonance cavity, and can achieve low-frequency sound absorption under conditions far less than the working wavelength. The two coupled cavities can respectively achieve low-frequency sound absorption effects in two directions.
[0005] To achieve the above-mentioned purpose, according to one aspect of the present invention, there is provided a bidirectional low-frequency sound-absorbing metamaterial imitating a bamboo snail, the metamaterial comprising a plurality of unit cells, the plurality of unit cells being arranged in an array; the unit cells forming a first spiral cavity and a second spiral cavity intertwined with each other, one end of the first spiral cavity and the second spiral cavity are both closed, and the other ends are both connected to the outside air, and the end of the first spiral cavity connected to the outside air and the end of the second spiral cavity connected to the air are respectively located at two opposite ends of the unit cell; at the same time, the first spiral cavity and the second spiral cavity are both bionic structures of the spiral cavity in the shell of the bamboo snail.
[0006] Furthermore, the unit cell includes a support column, an outer shell, a plurality of partitions, an upper cover plate and a lower cover plate, the outer shell is cylindrical, the support column is arranged in the outer shell, and the upper cover plate and the lower cover plate are respectively arranged at two opposite ends of the outer shell; a first cavity is formed between the support column, the outer shell, the upper cover plate and the lower cover plate, and the plurality of partitions are respectively arranged between the support column and the inner wall of the outer shell, and divide the first cavity into a first spiral cavity and a second spiral cavity, and the first spiral cavity and the second spiral cavity are arranged around the support column.
[0007] Furthermore, the upper cover plate is provided with a first through hole, and the lower cover plate is provided with a second through hole; one end of the first spiral cavity is connected to the lower cover plate and closed by the lower cover plate, and the other end is connected to the first through hole; one end of the second spiral cavity is connected to the upper cover plate and closed by the upper cover plate, and the other end is connected to the second through hole.
[0008] Furthermore, the multiple partitions include through partitions, multiple horizontal partitions and multiple vertical partitions. The edges of the horizontal partitions are connected to the inner walls of the outer shell, and the multiple horizontal partitions are arranged at intervals to divide the first cavity into multiple layers of horizontal cavities that are not connected to each other; the opposite sides of the through partitions are respectively connected to the support columns and the inner walls of the outer shell to separate the horizontal cavities from the middle; the vertical partitions are respectively arranged in the multiple layers of horizontal cavities, and the vertical partitions and the through partitions respectively form multiple connecting cylinders distributed on the opposite sides of the through partitions, and the multiple connecting cylinders are alternately distributed between the multiple layers of horizontal cavities, and the two ends of the connecting cylinder are respectively connected to the two horizontal partitions at the two ends of the cavity where it is located or one horizontal partition and the upper cover plate or the lower cover plate, and the area of the horizontal partition corresponding to the connecting cylinder is hollowed out to connect the two separated horizontal cavities, thereby forming the first spiral cavity and the second spiral cavity.
[0009] Furthermore, the cross-section of the unit cell perpendicular to its own height direction is a square, with a side length of A, and the value range of A is 1 / 20 to 1 / 5 of the working wavelength of the unit cell; the height of the unit cell is H, and the value range of H is 1 / 20 to 1 / 8 of the working wavelength; the cross-section of the support column perpendicular to its own height direction is a square, with a side length of a, and the value range of a is A / 20 to A / 2; the width of the first through hole is s11, the value range of s11 is 0.1 to 5 mm, and the length is the distance from the edge of the support column to the inner wall of the outer shell; the width of the second through hole is s21, the value range of s21 is 0.1 to 5 mm, and the length is the distance from the edge of the support column to the inner wall of the outer shell.
[0010] Furthermore, the depths of two adjacent horizontal cavities along the central axis direction of the support column are not completely the same.
[0011] Furthermore, the number of the horizontal partitions is an odd number.
[0012] Furthermore, the thickness of the shell is b, and the value range of b is 0.5mm to 3mm.
[0013] Furthermore, the structures of the plurality of unit cells are not completely the same.
[0014] According to another aspect of the present invention, there is provided a method for additive manufacturing of the above-mentioned bamboo shoot-like bidirectional low-frequency sound-absorbing metamaterial.
[0015] In general, compared with the prior art, the above technical solutions conceived by the present invention mainly have the following beneficial effects:
[0016] 1. By imitating the rotating cavity structure of the conch, a spiral cavity sound-absorbing metamaterial was designed, which can absorb low-frequency noise at a scale much smaller than the working wavelength.
[0017] 2. The support column is introduced to imitate the structure of bamboo shoots, which has the function of low-frequency sound absorption while maintaining high strength, and different mechanical support properties can be obtained by adjusting the side length of the support column.
[0018] 3. In the present invention, under the premise of keeping the overall size of the metamaterial unit cell unchanged, different sound absorption performance curves can be obtained by adjusting parameters such as the partition spacing, the slit (through hole) size of the upper and lower cover plates, and the side length of the support column. By combining unit cells with different sound absorption performances, the sound absorption performances of different unit cells will complement each other, and a broadband sound absorption effect can be obtained.
[0019] 4. Under the premise of keeping the overall size of the unit cell unchanged, different sound absorption performance and load-bearing performance can be obtained by adjusting the position of the partition and other dimensional parameters. The acoustic impedance of the metamaterial is mainly determined by the volume of the horizontal cavity. When the position of the partition is changed, the volume of each horizontal cavity will change, thereby affecting the acoustic impedance of the metamaterial, which is easy to adjust.
[0020] 5. One end of the first spiral cavity connected to the outside air and one end of the second spiral cavity connected to the air are respectively located at opposite ends of the unit cell, that is, the two spiral cavities of the unit cell are respectively connected to the outside air in two directions, thereby achieving noise absorption in two opposite directions. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 This is a schematic diagram of the internal structure of a bamboo snail, where the black curve is the spiral direction of the internal cavity of the bamboo snail;
[0022] Figure 2 This is a schematic diagram of a unit cell of a bidirectional low-frequency sound-absorbing material imitating a bamboo snail;
[0023] Figure 3 yes Figure 2 A schematic diagram of the partition plate and support column of a unit cell of the bamboo shoot-like snail bidirectional low-frequency sound-absorbing material;
[0024] Figure 4 yes Figure 2 Schematic diagram of the structure of the two coupled acoustic channels of the unit cell;
[0025] Figure 5 is a schematic diagram of a three-dimensional model of the first spiral cavity (i.e., the first coupled acoustic channel);
[0026] Figure 6 is a schematic diagram of a three-dimensional model of the second spiral cavity (i.e., the second coupled acoustic channel);
[0027] Figure 7 It is a schematic diagram of the sound absorption performance curve of the bamboo shoot-like snail bidirectional low-frequency sound absorption material provided by the present invention.
[0028] In all drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1 - stud, 2 - housing, 3 - cavity, 4 - support column, 5 - shell, 6 - partition, 7 - first spiral cavity, 8 - second spiral cavity. DETAILED DESCRIPTION
[0029] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
[0030] See also Figure 1 The bamboo snail includes a stud 1 and a shell 2. The stud 1 is arranged in the shell 2, and its central axis coincides with the central axis of the conical shell 2. A spiral cavity with a gradient size and a spiral shape is formed between the shell 2 and the stud 1. The spiral cavity is arranged around the stud 1, and one end is closed, and only a small space at the other end is connected to the outside air, which can effectively resist the invasion of natural enemies. The inside of the bamboo snail is a natural Helmholtz resonator, and the spiral cavity around the support column 1 realizes a longer cavity size in a limited space.
[0031] See also Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 The internal sound absorption channel of a bidirectional low-frequency sound absorption metamaterial imitating a bamboo snail provided by the present invention is an imitation structure of the spiral cavity inside the bamboo snail, that is, an imitation bamboo snail internal spiral cavity structure. The sound absorption metamaterial couples two spiral sound absorption channels in a limited space, and the spiral cavity effectively increases the length of the resonance cavity, and can achieve low-frequency sound absorption under the condition of a size much smaller than the working wavelength. The two sound absorption channels can respectively achieve low-frequency sound absorption effects in two directions.
[0032] The sound-absorbing metamaterial includes a plurality of unit cells arranged in an array. A first spiral cavity 7 and a second spiral cavity 8 intertwined with each other are formed in the unit cell, and the first spiral cavity 7 and the second spiral cavity 8 are sound-absorbing channels of the unit cell. The unit cell includes a support column 4, an outer shell 5, a plurality of partitions 6, an upper cover plate and a lower cover plate, the outer shell is cylindrical, the support column 4 is arranged in the outer shell 5, and the upper cover plate and the lower cover plate are respectively arranged at two opposite ends of the outer shell 5. A first cavity is formed between the support column 4, the shell 5, the upper cover plate and the lower cover plate, and a plurality of partitions are respectively arranged between the inner walls of the support column 4 and the shell 5, and the first cavity is divided into a first spiral cavity 7 and a second spiral cavity 8. The first spiral cavity 7 and the second spiral cavity 8 are arranged around the support column 4, and one end of the first spiral cavity 7 and the second spiral cavity 8 is closed by the upper cover plate or the lower cover plate, and the other end passes through the lower cover plate or the upper cover plate, that is, the lower cover plate or the upper cover plate has a through hole in the area corresponding to the other end of the first spiral cavity 7 and the second spiral cavity 8, so that the first spiral cavity 7 and the second spiral cavity 8 are connected to the outside air. Among them, the first spiral cavity 7 and the second spiral cavity 8 are not directly connected to each other, and the first spiral cavity 7 and the second spiral cavity 8 are bionic structures of the spiral cavity in the shell of the bamboo snail.
[0033] In this embodiment, the height of the shell 5 is equal to the height of the support column 4; the upper cover plate and the lower cover plate are respectively provided with a first through hole and a second through hole, the first through hole is connected to one end of the first spiral cavity 7, and the other end of the first spiral cavity 7 is closed by the lower cover plate; the second through hole is connected to one end of the second spiral cavity 8, and the other end of the second spiral cavity 8 is closed by the upper cover plate.
[0034] The plurality of partitions include through partitions, a plurality of horizontal partitions and a plurality of vertical partitions. The edges of the horizontal partitions are connected to the inner wall of the shell 5, and the plurality of horizontal partitions are arranged at intervals to divide the first cavity into multiple layers of mutually incommunicable horizontal cavities. The length of the through partition is equal to the height of the support column 4, and its two opposite sides are respectively connected to the support column 4 and the inner wall of the shell 5 to separate the layers of horizontal cavities from the middle, so that the layers of horizontal cavities cannot circulate around the support column 4. The vertical partitions are respectively arranged in the multi-layer horizontal cavities, and the vertical partitions are respectively surrounded by the through partitions to form a plurality of connecting cylinders distributed on the opposite sides of the through partitions, and the plurality of connecting cylinders are alternately distributed between the multi-layer horizontal cavities, and the two ends of the two connecting cylinders adjacent to the upper cover plate and the lower cover plate are respectively connected to the upper cover plate and the horizontal partition adjacent to the upper cover plate, the lower cover plate and the horizontal partition adjacent to the lower cover plate, and are respectively connected to the first through hole and the second through hole, and the area of the horizontal partition corresponding to the connecting cylinder is hollowed out, that is, a through hole is opened; the other two ends of the connecting cylinders opposite to each other are respectively connected to the two horizontal partitions corresponding to the horizontal cavity where they are located, and the areas corresponding to the horizontal partitions and the connecting cylinders are hollowed out, so that the corresponding connecting cylinders and the connected horizontal cavities are connected to form the first spiral cavity 7 and the second spiral cavity 8.
[0035] In this embodiment, the shape of the cross section of the shell 5 perpendicular to its own length direction is the same as the shape of the cross section of the support column 4 perpendicular to its own length direction; the cross section of the unit cell perpendicular to its own height direction is a square, the side length is A, and its value range is 1 / 20 to 1 / 5 times the working wavelength of the unit cell, and the height of the unit cell is H, and its value range is 1 / 20 to 1 / 8 times the working wavelength; the cross section of the support column 4 perpendicular to its own height direction is a square, and its side length is a, and its value range is A / 20 to A / 2; the width of the first through hole on the upper cover plate is s11, and its value range is 0.1 to 5 mm, and its length is It is the distance from the edge of the support column 4 to the inner wall of the outer shell 5; the channel width between the two layers of horizontal cavities corresponding to the first spiral cavity 7 is s12, with a value range of 0.1 to 5 mm, and a length of 1 / 5 to 4 / 5 times the distance from the edge of the support column to the inner wall of the outer shell; the width of the second through hole on the lower cover plate is s21, with a value range of 0.1 to 5 mm, and a length of the distance from the edge of the support column to the inner wall of the outer shell; the channel width between the two layers of horizontal cavities of the second spiral cavity 8 is s12, with a value range of 0.1 to 5 mm, and a length of 1 / 5 to 4 / 5 times the distance from the edge of the support column to the inner wall of the outer shell.
[0036] In this embodiment, the distance between two adjacent layers of horizontal partitions is not completely the same; the number of horizontal cavities separated by horizontal partitions in the unit cell is an even number, that is, the number of horizontal partitions is an odd number; the wall thickness of the outer shell 5 and the thickness of the partition are both b, and the value range is 0.5mm to 3mm; the volumes of multiple unit cells are the same or completely different.
[0037] In this embodiment, there are three horizontal partitions to divide the first cavity into four layers of horizontal cavities that are not connected to each other, which are called the first horizontal cavity, the second horizontal cavity, the third horizontal cavity and the fourth horizontal cavity from top to bottom. The depth of the first horizontal cavity along the support column 4, the depth of the second horizontal cavity along the support column 4, the depth of the third horizontal cavity along the support column 4 and the depth of the fourth horizontal cavity along the support column 4 are not exactly the same, and the edge of the horizontal partition is connected to the inner wall of the outer shell 5. The corresponding vertical partitions respectively form four connecting cylinders with the through partitions, and the four connecting cylinders are distributed on the opposite sides of the through partitions, and are respectively located in the first horizontal cavity, the second horizontal cavity, the third horizontal cavity and the fourth horizontal cavity, and the areas corresponding to the horizontal partitions and the connecting cylinders are hollowed out, so that the first horizontal cavity is connected to the third horizontal cavity, and the second horizontal cavity is connected to the fourth horizontal cavity, thereby forming two spiral cavities; wherein, the second horizontal cavity and the fourth horizontal cavity and the corresponding connecting cylinders form a first spiral cavity 7, and the first horizontal cavity, the second horizontal cavity and the corresponding connecting cylinders are interconnected to form a second spiral cavity 8; of course, in other embodiments, the number of horizontal partitions can be changed according to actual needs to obtain sound absorption effects of different frequencies.
[0038] Correspondingly, the upper cover plate and the lower cover plate are both square, with a thickness of b and a side length of A, and the edges completely overlap with the edges of the shell. The width of the first through hole is s11, with a value range of 0.1 to 5 mm, and a length of the distance from the edge of the support column to the inner wall of the shell; the width of the second through hole is s21, with a value range of 0.1 to 5 mm, and a length of the distance from the edge of the support column to the inner wall of the shell; the first spiral cavity 7 and the second spiral cavity 8 form two Helmholtz resonance cavities with the upper cover plate and the lower cover plate respectively provided with the first through hole and the second through hole, and the two Helmholtz resonance cavities can absorb low-frequency noise in two opposite directions respectively, and achieve a two-way low-frequency sound absorption effect.
[0039] The present invention also provides an additive manufacturing method for the above-mentioned bamboo snail-like bidirectional low-frequency sound-absorbing metamaterial, the additive manufacturing method adopted can be laser selective melting technology (SLM), laser selective sintering technology (SLS), fused deposition modeling technology (FDM) or photo-stereolithography technology (SLA), and the materials used can be selected according to the process and actual application requirements.
[0040] The present invention is further described in detail below with reference to a specific embodiment.
[0041] Example 1
[0042] When designing the structure of the bidirectional low-frequency sound-absorbing metamaterial imitating bamboo shoots, it is necessary to first determine the target sound absorption frequency range, then select the appropriate material according to the load-bearing requirements, and continuously modify the size parameters to achieve the set goals. The following are the manufacturing steps:
[0043] (1) Setting the sound absorption frequency band: The target sound absorption frequency is set to about 245 Hz. This frequency belongs to the low-frequency noise band and is difficult to be absorbed by traditional sound-absorbing materials.
[0044] (2) Optimization of sound absorption performance: The designed structural model is constructed using COMSOL. The side length of the unit cell section is first preset to 50 mm, and the other parameters are taken as arbitrary values within the constraints. The sound absorption effect is simulated and calculated. If the set sound absorption effect is not achieved, the size parameters are quantitatively modified and recalculated. The optimization calculation is iterated in this way until the target sound absorption effect is obtained.
[0045] (3) Optimization calculation results: Through optimization calculation, when the following size parameters are obtained, the unit cell achieves the optimal sound absorption effect at 345Hz: the side length A of the unit cell section is 50mm, the thickness H of the unit cell is 40mm, the side length a of the support column section is 5mm, the width s11 of the first through hole on the upper cover is 1.0mm, the length is 21.5mm, the width s12 of the channel between the two layers of cavities corresponding to the first spiral cavity 7 is 2.0mm, and the length is 10.25mm. The width s21 of the second through hole on the lower cover is 1.0mm, the length is 21.5mm, the width s22 of the channel between the two layers of cavities corresponding to the second spiral cavity 8 is 1.0mm, and the length is 10.25mm, and all wall thicknesses b are 1mm.
[0046] (4) Model export: Export the optimized model to STL format.
[0047] (5) Metamaterial forming: Slicing is performed in slicing software based on the exported model file, and the designed structure is formed using photosensitive resin material and SLA technology.
[0048] In order to verify the performance of the manufactured metamaterial, a sound absorption performance test was also carried out. The test results are as follows: Figure 7As shown, there are two absorption peaks, among which the sound absorption coefficient at 245 Hz reaches 1.0, and the sound absorption coefficient at 640 Hz reaches 0.91.
[0049] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.
Claims
1. A bidirectional low-frequency sound-absorbing metamaterial imitating bamboo shoots and snails, characterized in that: The sound absorbing metamaterial comprises a plurality of unit cells, and the plurality of unit cells are arranged in an array; The unit cell is formed with a first spiral cavity and a second spiral cavity intertwined with each other, one end of the first spiral cavity and the second spiral cavity are both closed, and the other end is connected to the outside air, and the end of the first spiral cavity connected to the outside air and the end of the second spiral cavity connected to the air are respectively located at two opposite ends of the unit cell; at the same time, the first spiral cavity and the second spiral cavity are both bionic structures of the spiral cavity in the shell of a bamboo snail; The unit cell includes a support column, an outer shell, a plurality of partitions, an upper cover plate and a lower cover plate, the outer shell is cylindrical, the support column is arranged in the outer shell, and the upper cover plate and the lower cover plate are respectively arranged at two opposite ends of the outer shell; a first cavity is formed between the support column, the outer shell, the upper cover plate and the lower cover plate, and a plurality of partitions are respectively arranged between the support column and the inner wall of the outer shell, and divide the first cavity into a first spiral cavity and a second spiral cavity, and the first spiral cavity and the second spiral cavity are arranged around the support column; The upper cover plate is provided with a first through hole, and the lower cover plate is provided with a second through hole; one end of the first spiral cavity is connected to and closed by the lower cover plate, and the other end is communicated with the first through hole; one end of the second spiral cavity is connected to and closed by the upper cover plate, and the other end is communicated with the second through hole; The multiple partitions include through partitions, multiple horizontal partitions and multiple vertical partitions. The edges of the horizontal partitions are connected to the inner walls of the outer shell, and the multiple horizontal partitions are arranged at intervals to divide the first cavity into multiple layers of horizontal cavities that are not connected to each other; the opposite sides of the through partitions are respectively connected to the support columns and the inner walls of the outer shell to separate the horizontal cavities from the middle; the vertical partitions are respectively arranged in the multiple layers of horizontal cavities, and the vertical partitions and the through partitions respectively form multiple connecting cylinders distributed on the opposite sides of the through partitions, and the multiple connecting cylinders are alternately distributed between the multiple layers of horizontal cavities, and the two ends of the connecting cylinder are respectively connected to the two horizontal partitions at the two ends of the cavity where it is located or one horizontal partition and the upper cover plate or the lower cover plate, and the area of the horizontal partition corresponding to the connecting cylinder is hollowed out to connect the two separated horizontal cavities, thereby forming the first spiral cavity and the second spiral cavity.
2. The bamboo shoot-like snail bidirectional low-frequency sound-absorbing metamaterial according to claim 1, characterized in that: The cross section of the unit cell perpendicular to its own height direction is a square, with a side length of A, and the value range of A is 1 / 20~1 / 5 of the working wavelength of the unit cell. The height of the unit cell is H, and the value range of H is 1 / 20~1 / 8 of the working wavelength; the cross section of the support column perpendicular to its own height direction is a square, with a side length of a, and the value range of a is A / 20~A / 2; the width of the first through hole is s11, the value range of s11 is 0.1~5 mm, and the length is the distance from the edge of the support column to the inner wall of the shell; the width of the second through hole is s21, the value range of s21 is 0.1~5 mm, and the length is the distance from the edge of the support column to the inner wall of the shell.
3. The bamboo shoot-like snail bidirectional low-frequency sound-absorbing metamaterial according to claim 1, characterized in that: The depths of two adjacent horizontal cavities along the central axis direction of the support column are not completely the same.
4. The bamboo shoot-like snail bidirectional low-frequency sound-absorbing metamaterial according to claim 1, characterized in that: The number of the horizontal partitions is an odd number.
5. The bamboo shoot-like snail bidirectional low-frequency sound-absorbing metamaterial according to claim 1, characterized in that: The thickness of the shell is b, and the value range of b is 0.5 mm ~3 mm.
6. The bamboo shoot-like snail bidirectional low-frequency sound-absorbing metamaterial according to any one of claims 1 to 5, characterized in that: The structures of the plurality of unit cells are not completely the same.
7. An additive manufacturing method for the bamboo shoot-like bidirectional low-frequency sound-absorbing metamaterial according to any one of claims 1 to 6.