Modular noise-reducing metamaterials based on spatially curled structures

Abstract

This invention discloses a modular noise-reducing metamaterial based on a spatially curled structure. The core structure consists of spatially curled modular blocks, including phase-control functional blocks and refraction-control functional blocks. The phase-control functional blocks control the phase of sound waves as they pass through the blocks, creating a phase difference without altering the propagation direction. The refraction-control functional blocks control the refraction of sound waves as they pass through the blocks, changing their propagation direction. By assembling these functional blocks, sound waves undergo refraction, deflection, and phase shift after passing through the metamaterial. These effects are superimposed in a designated intersection region behind the metamaterial, and combined with the metamaterial's acoustic bandgap characteristics, form a noise-reducing region, achieving noise reduction. A key advantage of this invention is the ability to easily and quickly adjust the noise-reducing frequency band of the metamaterial through the assembly of different types and numbers of blocks. It also has wide applicability, and the manufactured blocks are reusable.

Description

Technical Field

[0001] This invention belongs to the field of noise control technology, specifically relating to a modular noise reduction metamaterial based on a spatially curled structure that can be quickly assembled and reused. Background Technology

[0002] Noise is ubiquitous in various industrial equipment and people's daily lives. Noise suppression is a critical issue that needs to be considered in residential buildings, the automotive industry, ships, submarines, and aircraft. Traditional sound-absorbing materials have complex structures and large volumes, and their production and manufacturing processes may also cause environmental pollution, limiting their practical applications. In recent years, acoustic metamaterials, through the artificial design of unit cell structures, have exhibited anomalous properties not found in naturally occurring materials, showing potential applications in many fields.

[0003] Currently, acoustic metamaterials are mainly classified into three types: dielectric-filled, resonant, and spatially curled, as well as some composite metamaterials. Among them, spatially curled metamaterials have the advantages of being lightweight and small in size. Under the generalized law of refraction, the deflection angle of sound waves can be accurately designed and controlled, and the design method is simple and easy to implement. Furthermore, the acoustic bandgap characteristics of spatially curled metamaterials are also attracting attention. A bandgap refers to the physical phenomenon where sound waves cannot propagate within a specific frequency band. Studies have shown that the bandgap of spatially curled metamaterials can effectively block the propagation of sound waves. Research on spatially curled metamaterials is still in its early stages, and much work remains to be done in both expanding the understanding of their mechanisms and exploring their practical applications.

[0004] The functions and properties of metamaterials typically remain unchanged once their structure is determined. If adjustments to the operating frequency band are required for practical applications, the metamaterial must be redesigned and manufactured, limiting its practical application from economic and efficiency perspectives. Considering the convenience and repeatability of modular construction, if acoustic metamaterials could be constructed using this method, their functions could be easily reconstructed to adjust their functionality. Furthermore, effective design methods could even enable broadband noise reduction and control capabilities, which would have significant practical application value. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the present invention aims to provide a modular noise reduction metamaterial based on a spatially curled structure. This metamaterial, combined with the spatially curled structure, has many advantages such as light weight, small size, easy sound wave modulation and wide acoustic bandgap characteristics. Moreover, it has the advantages of quick splicing, reusability and adjustable noise reduction frequency band.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A modular noise-reducing metamaterial based on a spatially curled structure is constructed by assembling a spatially curled phase control functional block 1, a first spatially curled refraction control functional block 2, and a second spatially curled refraction control functional block 3. The spatially curled phase control functional block 1 and the first spatially curled refraction control functional block 2 are arranged parallel to each other horizontally, while the second spatially curled refraction control functional block 3 is positioned below the first spatially curled refraction control functional block 2. Based on the acoustic wave phase and propagation direction modulation functions of the spatially curled building blocks, this simple arrangement allows for the creation of a designated noise-reducing area behind the metamaterial. This assembly method leverages the acoustic wave modulation functions of each building block, facilitating the modular assembly and reuse of the metamaterial.

[0007] The spatial curl phase control functional block 1 is composed of multiple identical spatial curl structure unit cells arranged longitudinally. The first spatial curl refraction control functional block 2 and the second spatial curl refraction control functional block 3 are composed of multiple different spatial curl structure unit cells arranged longitudinally. The spatial curl structure unit cells in the first spatial curl refraction control functional block 2 and the second spatial curl refraction control functional block 3 are symmetrically arranged facing each other. Blocks of the same size are easy to splice and allow the sound waves to deflect in opposite directions without generating unnecessary phase differences, thus ensuring the noise reduction performance of the metamaterial.

[0008] The spatial curling phase control functional block 1 has a phase control function, causing the sound wave to undergo a designed phase change after passing through the block, which is used to construct the phase difference of the sound wave without changing the direction of sound wave propagation; the first spatial curling refraction control functional block 2 and the second spatial curling refraction control functional block 3 have a refraction control function, causing the sound wave to undergo a designed refraction after passing through the block, changing the direction of sound wave propagation; by splicing together the different functional blocks, the sound wave undergoes refraction deflection and phase shift after passing through the metamaterial, and superimposed in the designated intersection area behind the metamaterial. Combined with the acoustic bandgap characteristics of the metamaterial, a noise reduction area is formed to achieve the purpose of noise reduction.

[0009] The spatial curl phase control functional block 1, the first spatial curl refraction control functional block 2, and the second spatial curl refraction control functional block 3 have equal longitudinal lengths. Blocks of the same longitudinal length are easy to assemble and correspond to the same number of spatial curl channels, ensuring that the sound waves passing through the first spatial curl refraction control functional block 2 have the same phase difference, thus guaranteeing noise reduction performance. Blocks of the same longitudinal length are also beneficial for reuse; by assembling multiple spatial curl phase control functional blocks, the noise reduction frequency band can be adjusted.

[0010] Compared with the prior art, the present invention has the following advantages: 1. The present invention is a modular noise reduction metamaterial that utilizes the advantages of lightweight and small size of spatially curled metamaterials. It also utilizes the characteristic that it can easily change the propagation phase and direction of sound waves to cause sound waves to superimpose and cancel noise in a designated area behind the metamaterial.

[0011] 2. The modular noise reduction metamaterial of this invention utilizes the acoustic bandgap characteristics of the metamaterial itself, combined with its superposition noise reduction mechanism, to enhance the noise reduction effect within the bandgap frequency band.

[0012] 3. The modular noise-reducing metamaterial of this invention, through its modular design, enables the metamaterial to have the advantages of quick assembly, reusability, and adjustable noise reduction frequency band. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the modular noise reduction metamaterial of the present invention.

[0014] Figure 2 This is a schematic diagram of the spatially coiled unit cell structure in this invention.

[0015] Figure 3 This is an enlarged schematic diagram of the phase control building block and its unit cell structure in this invention.

[0016] Figure 4 This is an enlarged schematic diagram of the refraction control block and part of its unit cell structure in this invention.

[0017] Figures 5(a) and 5(b) are schematic diagrams of the spatial curl phase control functional block PCB and the spatial curl refraction control functional block RCB in this invention, respectively.

[0018] Figure 6 This is a schematic diagram illustrating the effect of the acoustic bandgap on the phase control functional building block in this invention.

[0019] Figure 7 This is a schematic diagram illustrating the effect of the acoustic bandgap on the refraction control functional building block in this invention.

[0020] Figure 8 This is a schematic diagram illustrating the application of the modular noise reduction metamaterial of this invention. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings.

[0022] like Figure 1As shown, this invention is a modular noise-reducing metamaterial based on a spatially curled structure, comprising a spatially curled phase control functional block 1, a first spatially curled refraction control functional block 2, and a second spatially curled refraction control functional block 3. The metamaterial can be viewed as being composed of multiple parts assembled together. The number of units in the spatially curled phase control functional block 1, the first spatially curled refraction control functional block 2, and the second spatially curled refraction control functional block 3 can be changed according to the noise reduction frequency band requirements, offering advantages such as convenience, wide applicability, reusability, and adjustable noise reduction frequency band.

[0023] The spatially coiled structure is composed of multiple spatially coiled unit cells spliced ​​together. A schematic diagram of the spatially coiled unit cell structure is shown below. Figure 2 As shown, the structure can be achieved through... a , b , c , d and t b Five parameters accurately describe it. a The total length of the spatially coiled unit cell structure. b The total width of the spatially coiled unit cell structure. c The width of the spatial curling channel. d The length of the spatially curled channel. t b The wall thickness is for a spatially coiled unit cell structure.

[0024] Within a certain frequency range, sound waves will propagate approximately along the slender channels within the unit cell of a spatially coiled structure. The lower limit of this frequency range is determined by… a Decide, a It should be greater than three times the wavelength of the sound wave; its upper frequency limit is determined by d To decide, d It should be less than one-third of the sound wave wavelength. The channel length of the sound wave through the unit cell of the spatially coiled structure. L Approximately: (1) Phase changes that occur when sound waves pass through a spatially coiled unit cell ΔΦ Approximately (2) In the formula, λ The wavelength of the sound wave within the spatially coiled structure.

[0025] According to the generalized Snell's law, by arranging and combining multiple spatially curled unit cells in a reasonable manner, spatially curled metamaterial building blocks with phase control and refraction control functions can be designed.

[0026] Designing multiple identical spatially curled unit cells arranged longitudinally, such as... Figure 3As shown, the Phase Control Block (PCB) constitutes the spatial curl phase control functional block 1 of this invention. A Cartesian coordinate system is established on a two-dimensional plane. OXY The corresponding position coordinates are used x and y Indicates. Sound waves originate from A ( x a , y a ) is transmitted to B through the spatially curled structure of the single-cell metasurface. x b , y b The phase change of the sound wave after passing through the spatial curl phase control function block 1 can be expressed as: (3) In the formula, ψ p ( y () represents the sound wave in the PCB coordinate system OXY median coordinate y Phase at that point, λ a Let be the wavelength of the sound wave in the medium at point A, the incident point. λ b Let λ be the wavelength of the sound wave in the medium at point B, the point of emission.

[0027] like Figure 4 As shown, arranging multiple different spatially curled structural unit cells longitudinally can construct a Refraction Control Block (RCB), namely, the first spatially curled refraction control functional block 2 and the second spatially curled refraction control functional block 3 of this invention. This arrangement can create a phase gradient behind the metamaterial, and the phase gradient has a definite relationship with the incident and refraction angles of the sound wave. (4) In the formula, ψ r ( y () represents the sound wave in the RCB coordinate system OXY median coordinate y Phase at that point, θ i and θ t These are the angle of incidence and the angle of refraction of the sound wave, respectively.

[0028] Based on the frequency modulation method described above, corresponding building blocks were designed. The spatial curl phase control function building block 1 has the same geometric dimensions for each channel, while the first spatial curl refraction control function building block 2 and the second spatial curl refraction control function building block 3 each have 9 different spatial curl channels. These 9 channels are named C1-C9 according to the sound wave path length from shortest to longest. The corresponding designed building blocks are shown in Figures 5(a) and 5(b). The detailed geometric dimensions of each channel of the building blocks are listed in Table 1. Wall thickness t b All are 2 mm.

[0029] Table 1. Geometric dimensions of each channel of the building block The acoustic bandgap is one of the most important properties of metamaterials. The bandgap prevents sound waves from passing through the metamaterial. The range of the bandgap can be calculated using the finite element method.

[0030] like Figure 6 As shown, the presence of the acoustic bandgap in the spatially curled phase control functional block 1 prevents sound waves of the corresponding frequency band from passing through the block. If the required frequency band is within the acoustic bandgap of the spatially curled phase control functional block 1, the blocks can be arranged symmetrically to prevent sound waves from passing through the metamaterial, thus achieving noise reduction. Otherwise, it is necessary to adjust the size of the spatially curled structural unit cell to avoid the acoustic bandgap when designing the block.

[0031] For the first spatial curling refraction control functional block 2 and the second spatial curling refraction control functional block 3, due to the uniformly varied design of their channel structures, the acoustic bandgap frequency bands of each channel will also gradually change. The existence of the acoustic bandgap will prevent sound waves of the corresponding frequency band from passing through part of the curling channel, thereby reducing the sound pressure value behind the channel, but it will not affect the sound wave refraction function, such as... Figure 7 As shown. Therefore, the acoustic bandgap of the spatially curled refraction-controlled functional building block does not generate more noise, but only reduces the overall sound pressure level. If the acoustic bandgap is close to the noise reduction frequency band of the metamaterial to be designed, it will help improve the noise reduction performance of the metamaterial.

[0032] like Figure 8As shown in the schematic diagram of the application of the modular noise reduction metamaterial of the present invention, the position of the designated noise reduction region 4 is determined by the refraction angle designed by the first spatial curling refraction control functional block 2 and the second spatial curling refraction control functional block 3, and the longitudinal length of the metamaterial. Based on the acoustic wave phase control function of the spatial curling phase control functional block 1, the acoustic wave passing through the first spatial curling refraction control functional block 2 and the acoustic wave passing through the second spatial curling refraction control functional block 3 will have a phase difference of half a cycle after passing through the metamaterial. Based on the acoustic wave refraction control function of the refraction control block, the acoustic wave passing through the first spatial curling refraction control functional block 2 and the acoustic wave passing through the second spatial curling refraction control functional block 3 will be refracted after passing through the blocks. The symmetrically arranged first spatial curling refraction control functional block 2 and second spatial curling refraction control functional block 3 cause the acoustic waves to deflect towards each other and superimpose. Because the sound wave passing through the first spatial curling refraction control functional block 2 and the sound wave passing through the second spatial curling refraction control functional block 3 have a phase difference of half a cycle constructed by the spatial curling phase control functional block 1, the sound waves on both sides undergo destructive interference, and after superposition and elimination, a noise reduction region is generated. The refraction angle and longitudinal length designed by the first spatial curling refraction control functional block 2 and the second spatial curling refraction control functional block 3 determine the intersection region of the sound waves. After the sound waves intersect and superimpose, the sound pressure value becomes very small, which can be regarded as a noise reduction region, and the location of the noise reduction region 4 is thus determined.

Claims

1. A modular noise-reducing metamaterial based on a spatially curled structure, characterized in that: The modular noise reduction metamaterial is constructed by splicing together a spatial curl phase control functional block (1), a first spatial curl refraction control functional block (2), and a second spatial curl refraction control functional block (3). The spatial curl phase control functional block (1) and the first spatial curl refraction control functional block (2) are arranged parallel to each other on the left and right, and the second spatial curl refraction control functional block (3) is arranged below the first spatial curl refraction control functional block (2). The spatial curl phase control functional block (1) is composed of multiple identical spatial curl structure units arranged longitudinally. The first spatial curl refraction control functional block (2) and the second spatial curl refraction control functional block (3) are composed of multiple different spatial curl structure units arranged longitudinally. The spatial curl structure units in the first spatial curl refraction control functional block (2) and the second spatial curl refraction control functional block (3) are symmetrical towards each other. The spatial curl phase control functional block (1) has a phase control function, which causes the sound wave to undergo a designed phase change after passing through the block, and is used to construct the phase difference of the sound wave without changing the direction of sound wave propagation; the first spatial curl refraction control functional block (2) and the second spatial curl refraction control functional block (3) have a refraction control function, which causes the sound wave to undergo a designed refraction after passing through the block, and changes the direction of sound wave propagation; by splicing different functional blocks, the sound wave undergoes refraction deflection and phase shift after passing through the metamaterial, and is superimposed in the designated intersection area behind the metamaterial. Combined with the acoustic bandgap characteristics of the metamaterial, a noise reduction area is formed to achieve the purpose of noise reduction.

2. The modular noise-reducing metamaterial based on a spatially curled structure according to claim 1, characterized in that: The longitudinal lengths of the spatial curl phase control functional block (1), the first spatial curl refraction control functional block (2), and the second spatial curl refraction control functional block (3) are equal.

3. The modular noise-reducing metamaterial based on a spatially curled structure according to claim 1, characterized in that: The spatially curled unit cell is defined by the total length of the spatially curled unit cell structure. a Total width of spatially curled unit cell structure b Spatial Curved Channel Width c Spatial curl channel length d and the wall thickness of the spatially coiled unit cell structure t b Five parameters describe it; Within a certain frequency range, sound waves will propagate approximately along the slender channels within the spatially coiled unit cell. The lower limit of this frequency range is determined by the total length of the spatially coiled unit cell. a The total length of the spatially curled unit cell structure is determined. a It should be greater than three times the wavelength of the sound wave; Its upper frequency limit is determined by the length of the spatially curled channel. d To determine the length of the spatial curling channel d It should be less than one-third of the sound wave wavelength; the channel length of the sound wave through the spatially coiled unit cell. L Approximately: (1) Phase changes that occur when sound waves pass through a spatially coiled unit cell ΔΦ for (2) In the formula, λ The wavelength of the sound wave within the spatially coiled structure.

4. The modular noise-reducing metamaterial based on a spatially curled structure according to claim 1, characterized in that: The change in the acoustic wave phase after using the spatial curl phase control function block 1 is represented as follows: (3) In the formula, ψ p ( y (This refers to the spatial phase control function of sound wave curvature in a modular coordinate system.) OXY median coordinate y Phase at that point, λ a The wavelength of the sound wave in the medium at the point of incidence. λ b The wavelength of the sound wave in the medium at the exit point. a The total length of the spatially coiled unit cell structure.

5. The modular noise-reducing metamaterial based on a spatially curled structure according to claim 1, characterized in that: In the first spatial curl refraction control functional block (2) and the second spatial curl refraction control functional block (3), the phase gradient has the following relationship with the incident and refraction angles of the sound wave: (4) In the formula, ψ r ( y (This refers to the coordinate system of functional building blocks for controlling the curling and refraction of sound waves in space.) OXY median coordinate y Phase at that point, θ i and θ t These are the angle of incidence and the angle of refraction of the sound wave, respectively. λ a The wavelength of the sound wave in the medium at the point of incidence. λ b λ is the wavelength of the sound wave in the medium at the point of emission.

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