Multifunctional Acoustic Metamaterials with Multi-Path Integrated Noise Reduction and Their Application Methods

Abstract

The present invention provides a multi-functional acoustic metamaterial for multi-path integrated noise reduction and its application method, including a plurality of resonant frequency units; each of the resonant frequency units is spliced and combined to form the multi-functional acoustic metamaterial for multi-path integrated noise reduction; each of the resonant frequency units includes a top perforated plate, a bottom panel, and multiple groups of double-chain helical structures located between the top perforated plate and the bottom panel. The multi-functional acoustic metamaterial for multi-path integrated noise reduction proposed by the present invention not only has sound absorption and vibration isolation performance in the low-frequency range, but also can exhibit vibration damping performance of vibration energy propagation attenuation and mechanical compressibility, and at the same time has the stability of acoustic performance when the material deforms, reflecting excellent multi-functional characteristics of the acoustic metamaterial.

Description

Technical Field

[0001] The present invention belongs to the technical field of noise reduction and vibration reduction, and particularly relates to a multi-functional acoustic metamaterial for multi-path integrated noise reduction and an application method thereof. Background Art

[0002] Noise and vibration problems, as an unsolved environmental pollution problem, have long existed in daily life. Strong noise pollution not only harms people's physical and mental health, but also affects people's quality of life and work efficiency.

[0003] Common noise reduction methods mainly include: sound absorption and sound insulation treatment at the sound source, air-borne sound and structure-borne sound absorption in the propagation path, and sound insulation treatment at the receiver position. Common acoustic materials, such as porous materials, damping materials, etc., all have good high-frequency noise reduction performance. However, due to the long wavelength and strong penetration ability of low-frequency sound waves, they cannot be effectively controlled, and low-frequency noise is more harmful to people's physical and mental health. Therefore, low-frequency noise reduction technology has always been a difficult point in noise reduction control.

[0004] As an artificially designed structural material, acoustic metamaterials have characteristics that ordinary natural materials do not have, such as extraordinary refraction, wave focusing, etc. Due to the excellent properties exhibited by acoustic metamaterials, they have attracted extensive attention in the field of noise and vibration, providing a new way to solve low-frequency noise.

[0005] Since the development of acoustic metamaterials to date, they include local resonance type, sound absorption type, wave control type, etc., involving many novel structures such as flexural wave band gaps, resonance sound insulation, tortuous cavities, thin film sound absorption, and periodic arrangement wave control. However, in the face of the actual complex working environment, acoustic metamaterials are developing towards the direction of multi-functional integration. For example, on the basis of having the ability of sound absorption or elastic wave attenuation resonance, the structure of acoustic metamaterials also has a certain stiffness. However, for such materials with multiple functions of acoustics and mechanics, their vibration and noise reduction performance mostly focuses on the high-frequency stage, and the acoustic modes of the internal cavity and the external structure modes are also prone to coupling, thus affecting their vibration and noise reduction performance.

[0006] Therefore, how to design a material that has integrated vibration and noise reduction in the low-frequency band, has multiple functions such as mechanics at the same time, and can solve the technical problem of the change of acoustic performance under the deformed state of the acoustic material is the problem that needs to be solved emphatically at present. Summary of the Invention

[0007] In view of the defects existing in the prior art, the present invention provides a multi-functional acoustic metamaterial for multi-path integrated noise reduction and an application method thereof, which can effectively solve the above problems.

[0008] The technical solution adopted by the present invention is as follows:

[0009] The present invention provides a multifunctional acoustic metamaterial for multi-path integrated noise reduction, including a plurality of resonant frequency units; each of the resonant frequency units is spliced and combined to form the multifunctional acoustic metamaterial for multi-path integrated noise reduction;

[0010] Each of the resonant frequency units includes a top perforated plate (1), a bottom panel (2), and multiple groups of double-stranded helical structures located between the top perforated plate (1) and the bottom panel (2); the groups of double-stranded helical structures are arranged at a set spatial relative position; the helical structure parameters of the groups of double-stranded helical structures are the same or different.

[0011] Preferably, each group of double-stranded helical structures includes two single helical structures; the two single helical structures are wound around the same axis in a reverse parallel manner to form the double-stranded helical structure.

[0012] Preferably, each single helical structure has a cavity, the top end of the single helical structure is communicated with a perforation (1-1) opened at a corresponding position on the top perforated plate (1), and the size and shape of the perforation (1-1) are the same as those of the cavity of the single helical structure;

[0013] The bottom end of the single helical structure is fixed to the bottom panel (2), and the bottom panel (2) does not have a through hole at the corresponding position and is a sealed structure.

[0014] Preferably, the helical structure parameters of the two single helical structures are the same, and the helical structure parameters include: the cross-sectional area S of the cavity r , the helical length l, the helical radius R, the pitch p, the helical wall thickness d', the number of turns n' of the helical structure, the cross-sectional radius r, and the base material properties.

[0015] Preferably, the cross-sectional shape of the cavity of each single helical structure is circular, elliptical, rectangular, or rhombic.

[0016] Preferably, the shape and size of the top perforated plate (1) are the same as those of the bottom panel (2);

[0017] The shapes of the top perforated plate (1) and the bottom panel (2) are circular, rectangular, square, or parallelogram.

[0018] Preferably, the materials of the top perforated plate (1), the bottom panel (2), and the double-stranded helical structure are the same or different.

[0019] The present invention also provides an application method for a multifunctional acoustic metamaterial for multi-path integrated noise reduction, including the following steps:

[0020] Step 1, determine the design requirements of the acoustic metamaterial, including: the noise control frequency band, the material mechanical elastic deformation requirement δ0, the target value f0 of the resonance frequency of the metamaterial, and the target value f of the elastic wave of the metamaterial r0 ;

[0021] Among them, the noise control frequency band includes n absorption frequencies, arranged in ascending order, which are: absorption frequencies F1, F2,..., F n ;

[0022] Step 2, for any absorption frequency F j , j = 1, 2,...., n, set a corresponding set of double - helix structures D_screw j , the double - helix structure D_screw j includes each single - helix structure S_screw j designed in the following way:

[0023] Step 2.1, give the initial structural parameter values, including: the cavity cross - sectional area S r , the perforation diameter d of the top perforated plate (1), and the thickness t of the top perforated plate (1);

[0024] Step 2.2, according to the following formula, obtain the helical length l of the single - helix structure S_screw j :

[0025] l = 4c / F j

[0026] Where:

[0027] c is the speed of sound;

[0028] Step 2.3, according to the following formula, obtain the cavity impedance Z j of the single - helix structure S_screw c :

[0029]

[0030] Where:

[0031] ρ e is the cavity equivalent density related to the cavity cross - sectional area S r ;

[0032] c e is the cavity equivalent sound speed related to the cavity cross - sectional area S r ;

[0033] k e is the cavity equivalent wave number related to the cavity cross - sectional area S r ;

[0034] i is the imaginary unit;

[0035] S is the area of the top perforated plate (1), i.e., the sound energy incident area, and is a known value;

[0036] ρ is the air density;

[0037] Step 2.4, according to the following formula, obtain the orifice impedance Z of the top perforated plate (1) of the single spiral structure S_screw j : t :

[0038]

[0039] Where:

[0040] m u is the air kinematic viscosity coefficient;

[0041] φ is the porosity related to the perforation diameter d of the top perforated plate (1);

[0042] K is the acoustic characteristic parameter related to the perforation diameter d of the top perforated plate (1);

[0043] ω is the circular frequency;

[0044] Step 2.5, determine whether the following functional relationship is satisfied:

[0045]

[0046] Where:

[0047] Re is the real part of the sum of Z c +Z t ;

[0048] Im is the imaginary part of the sum of Z c +Z t ;

[0049] If not satisfied, adjust the initial structural parameter values in Step 2.1 and return to Step 2.1; if satisfied, execute Step 2.6;

[0050] Step 2.6, give the initial structural parameter values, including: spiral radius R, pitch p, spiral wall thickness d', and thickness t' of the bottom panel (2);

[0051] Step 2.7, according to the following formula, obtain the number of turns n' of the spiral structure of the single spiral structure S_screw j :

[0052]

[0053] Where:

[0054] R' is the radius of the transition section, which is a known value;

[0055] Step 2.8, according to the cavity cross-sectional area S r and the spiral wall thickness d', obtain the cross-sectional radius r of the single spiral structure S_screw j ;

[0056] Step 2.9, according to the number of turns n', pitch p and cross-sectional radius r of the spiral structure of the single spiral structure S_screw j , obtain the maximum compression stroke δ of the material mechanics deformation:

[0057] δ = (p - 2r)2n'

[0058] Step 2.10, determine whether the following functional relationship is satisfied:

[0059] δ - δ0 ≥ 0

[0060]

[0061] If not satisfied, adjust the spiral radius R, pitch p and spiral wall thickness d', and return to Step 2.6; if satisfied, execute Step 2.11;

[0062] Step 2.11, given the basic material properties of the single spiral structure S_screw j , including: Poisson's ratio v0, Young's modulus E0 and density ρ0;

[0063] Step 2.12, determine whether the following functional relationship is satisfied:

[0064]

[0065] Where:

[0066] m is the mass of the vibration-isolated object, which is a known value;

[0067] k(v0, E0, ρ0, R, n', d) is the overall stiffness of the single spiral structure S_screw j , which is related to Poisson's ratio v0, Young's modulus E0, density ρ0, spiral radius R, number of turns n' of the spiral structure and spiral wall thickness d';

[0068] If not satisfied, adjust the spiral radius R, number of turns n' of the spiral structure and spiral wall thickness d', and return to Step 2.6; if satisfied, execute Step 2.13;

[0069] Step 2.13, thus design and obtain the double-chain spiral structure D_screw j ;

[0070] Step 3, for n absorption frequencies, design and obtain n groups of double-chain spiral structures D_screwj , together with the bottom panel (2) and the top perforated panel (1), constitutes an acoustic metamaterial;

[0071] Step 4: For the designed acoustic metamaterial, through two-dimensional Brillouin zone sweeping, obtain the elastic wave stopband range f of the metamaterial e1 ~f e2 ;

[0072] Where:

[0073] f e1 is the upper edge point of the bandgap;

[0074] f e2 is the lower edge point of the bandgap;

[0075] Step 5: Determine whether the elastic wave target value f of the metamaterial r0 is within the elastic wave stopband range f of the metamaterial e1 ~f e2 . If not, execute Step 6; if so, execute Step 7;

[0076] Step 6: Adjust the thickness t′ of the bottom panel (2), the spiral radius R, the spiral wall thickness d', and the spatial relative positions of each group of double-stranded spiral structures D_screw j , and return to Step 2.6;

[0077] Step 7: Output the designed multifunctional acoustic metamaterial.

[0078] The multifunctional acoustic metamaterial for multi-path integrated noise reduction and its application method provided by the present invention have the following advantages:

[0079] The multifunctional acoustic metamaterial for multi-path integrated noise reduction proposed by the present invention not only has sound absorption and vibration isolation performance in the low-frequency range, but also can exhibit vibration damping performance of vibration energy propagation attenuation and mechanical compressibility, and at the same time has the stability of acoustic performance when the material deforms, reflecting excellent multifunctional characteristics of the acoustic metamaterial. Description of the Drawings

[0080] Figure 1 is a three-dimensional schematic diagram of the multifunctional acoustic metamaterial provided by an embodiment of the present invention;

[0081] Figure 2 is a top view of the multifunctional acoustic metamaterial provided by an embodiment of the present invention;

[0082] Figure 3 is a front view of the multifunctional acoustic metamaterial provided by an embodiment of the present invention;

[0083] Figure 4The cavity structure model diagram of the multifunctional acoustic metamaterial provided by the embodiment of the present invention;

[0084] Figure 5 The sound absorption coefficient curve diagram of the acoustic performance of the multifunctional acoustic metamaterial provided by the embodiment of the present invention;

[0085] Figure 6 The sound absorption coefficient curve diagram when the multifunctional acoustic metamaterial provided by the embodiment of the present invention is deformed;

[0086] Figure 7 The uniaxial compression stress-strain curve diagram of the multifunctional acoustic metamaterial provided by the embodiment of the present invention;

[0087] Figure 8 The vibration isolation model diagram of the multifunctional acoustic metamaterial provided by the embodiment of the present invention;

[0088] Figure 9 The vibration isolation performance diagram of the multifunctional acoustic metamaterial provided by the embodiment of the present invention;

[0089] Figure 10 The periodic arrangement model diagram of the multifunctional acoustic metamaterial provided by the embodiment of the present invention;

[0090] Figure 11 The vibration damping performance diagram of the multifunctional acoustic metamaterial provided by the embodiment of the present invention;

[0091] Figure 12 The vibration propagation model diagram of the periodic arrangement model outside the bandgap frequency;

[0092] Figure 13 The vibration propagation model diagram of the periodic arrangement model within the bandgap frequency.

[0093] Wherein:

[0094] 1 - top perforated plate, 1-1 - perforation; 2 - bottom panel; 3-1 - the first single spiral structure, 3-2 - the second single spiral structure; 4-1 - the third single spiral structure, 4-2 - the fourth single spiral structure; 5 - vibration-isolated object. Specific embodiments

[0095] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clear, the present invention will be further described in detail below with reference to 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 used to limit the present invention.

[0096] In order to achieve integrated vibration reduction and noise reduction in the low-frequency band within a limited space, a multifunctional integrated acoustic metamaterial is required to comprehensively reduce noise in fields such as aviation, ships, and vehicles through multiple channels. Therefore, aiming at the demand for integrated vibration reduction and noise reduction in the low-frequency band in the existing noise reduction field and solving the technical problem that the acoustic performance will change under the deformed state of the structure, the present invention provides a multifunctional acoustic metamaterial combining sound and vibration, and the sound absorption effect can also remain stable and unchanged when the material is deformed. This material not only has the low-frequency sound absorption function of an acoustic material, but also can return to its initial form after being compressed, and can efficiently absorb mechanical vibration energy in the low-frequency range. Therefore, the multifunctional acoustic metamaterial for multi-channel integrated noise reduction proposed by the present invention not only has sound absorption and vibration isolation performance in the low-frequency range, but also can exhibit the vibration reduction performance of the attenuation of vibration energy propagation and the mechanical compressibility, and at the same time has the stability of acoustic performance when the material is deformed, reflecting the excellent multifunctional characteristics of the acoustic metamaterial.

[0097] The present invention provides a multifunctional acoustic metamaterial for multi-channel integrated noise reduction, including a plurality of resonant frequency units; each of the resonant frequency units is spliced and combined to form the multifunctional acoustic metamaterial for multi-channel integrated noise reduction; by arranging multiple groups of resonant frequency units in parallel, the bandwidth of the sound absorption frequency can be expanded.

[0098] Each of the resonant frequency units includes a top perforated plate 1, a bottom panel 2, and multiple groups of double-chain spiral structures located between the top perforated plate 1 and the bottom panel 2; as Figure 1 、 Figure 2 and Figure 3 shown, it is a specific schematic diagram of a single resonant frequency unit. In Figure 1 、 Figure 2 and Figure 3 , a total of two groups of double-chain spiral structures are included. Among them, the first single spiral structure 3-1 and the second single spiral structure 3-2 form a group of double-chain spiral structures; the third single spiral structure 4-1 and the fourth single spiral structure 4-2 form another group of double-chain spiral structures.

[0099] The double-chain spiral structures in each group are arranged at a set relative spatial position; the spiral structure parameters of the double-chain spiral structures in each group are the same or different.

[0100] In the present invention, each group of double-chain spiral structures includes two single spiral structures; the two single spiral structures are wound around the same axis in a reverse parallel manner to form the double-chain spiral structure, that is: the two single spiral structures are symmetrically distributed at 180°. And each single spiral structure has a cavity, and the cavity length is related to the resonance frequency of sound absorption. By adjusting the spiral length of the spiral structure, the designability of the acoustic absorption frequency can be achieved.

[0101] The top end of the single spiral structure communicates with the perforation 1-1 formed in the corresponding position of the top perforated plate 1. Moreover, the size and shape of the perforation 1-1 are the same as those of the cavity of the single spiral structure. According to the sound absorption principle, sound waves are incident from the top perforated plate 1, pass through the perforations 1-1 at the top, and enter the cavities inside each single spiral structure. According to the noise reduction design requirements, the sound absorption frequency can be determined by the length of the single spiral structure.

[0102] The bottom end of the single spiral structure is fixed to the bottom panel 2. Moreover, the bottom panel 2 does not have through holes at the corresponding positions and is a sealing structure.

[0103] In the present invention, the spiral structure parameters of the two single spiral structures are the same. The spiral structure parameters include: the cross-sectional area S of the cavity r , the spiral length l, the spiral radius R, the pitch p, the spiral wall thickness d', the number of turns n' of the spiral structure, the cross-sectional radius r, and the base material properties.

[0104] The cross-sectional shape of the cavity of each single spiral structure is circular, elliptical, rectangular, rhombic, etc.

[0105] The shape and size of the top perforated plate 1 are the same as the shape, size, and thickness of the bottom panel 2. The shapes of the top perforated plate 1 and the bottom panel 2 are circular, rectangular, square, parallelogram, etc. As a preferred method, the shape of the top perforated plate 1 is square, and the shape of the perforation 1-1 is circular.

[0106] The materials of the top perforated plate 1, the bottom panel 2, and the double spiral structure are the same or different. As a specific embodiment, the top perforated plate 1, the bottom panel 2, and the double spiral structure are integrally processed and manufactured using the same material.

[0107] In the present invention, a plurality of double spiral structures are designed between the top perforated plate 1 and the bottom panel 2. The total length of the double spiral structure is comprehensively determined by the spiral radius, the number of turns, and the height. By adjusting the spiral line parameters, the mechanical elastic deformation range of the required metamaterial can be obtained. Using the spiral structure can meet the corresponding mechanical property requirements and has the advantage of load-bearing stability.

[0108] In addition, the spiral lengths of the individual double spiral structures can be different, which can increase the sound absorption frequency band range.

[0109] As a usage method, the top perforated plate 1 can place the object to be vibration-isolated, and the bottom panel 2 can be fixed to the ground or the vibration source. The bottom panel 2 is a hard boundary, and the shape can be selected as circular, rectangular, square, parallelogram, etc. The vibration energy is dissipated after propagating through the double spiral pipeline. Within the vibration isolation range, the object to be vibration-isolated can be protected.

[0110] The metamaterial can be used as a unit and arranged periodically. The periodic arrangement can be a quadrilateral arrangement, a hexagonal arrangement, etc. The metamaterial with a multi-period finite arrangement can be used for vibration propagation attenuation (solid sound propagation attenuation).

[0111] The basic material of the metamaterial can be selected as a polymer material with certain stiffness and elasticity, such as nylon material, etc. Materials such as aluminum alloy and stainless steel can also be selected according to the requirements of the working environment.

[0112] The manufacturing of the metamaterial can process each part separately. For example, the upper and lower panels can be processed by stamping, bonding, etc. The cavity spiral structure cavity can be processed by casting, injection molding, etc. The connection between the cavity structure and the two side panels can be in forms such as welding and bonding.

[0113] The manufacturing of the metamaterial can also adopt advanced manufacturing technologies, such as additive manufacturing, etc., to achieve one-piece molding.

[0114] Therefore, the multifunctional acoustic metamaterial provided by the present invention can be used as a single cell unit for periodic arrangement. The multifunctional acoustic metamaterial has perfect sound absorption, vibration isolation and bending wave (solid sound) attenuation effects in the low-frequency range, can maintain stable sound absorption performance when the structure undergoes tensile or compressive deformation, and at the same time the metamaterial has deformation recoverability. Specifically, it can be designed and controlled specifically according to noises and vibrations of different frequencies, and the noise reduction frequency band can be further broadened by combining multiple different resonant frequency units. The multifunctional acoustic metamaterial has good application prospects and provides a new idea and application for solving low-frequency noise and vibration problems.

[0115] The present invention provides an application method of a multifunctional acoustic metamaterial for multi-path integrated noise reduction, including the following steps:

[0116] Step 1, determine the design requirements of the acoustic metamaterial, including: the noise control frequency band, the material mechanical elastic deformation requirement δ0, the target value f0 of the resonance frequency of the metamaterial, and the target value f of the elastic wave of the metamaterial r0 ;

[0117] Among them, the noise control frequency band includes n sound absorption frequencies, arranged from small to large, which are: sound absorption frequencies F1, F2,..., F n ;

[0118] Step 2, for any sound absorption frequency F j , j = 1, 2,...., n, set a corresponding group of double-chain spiral structures D_screw j , the double-chain spiral structure D_screw j includes each single spiral structure S_screw jDesigned in the following way:

[0119] Step 2.1, give the initial structural parameter values, including: the cavity cross-sectional area S r , the perforation diameter d of the top perforated plate 1 and the thickness t of the top perforated plate 1;

[0120] Step 2.2, according to the following formula, obtain the spiral length l of the single spiral structure S_screw j :

[0121] l = 4c / F j

[0122] Where:

[0123] c is the speed of sound;

[0124] Step 2.3, according to the following formula, obtain the cavity impedance Z of the single spiral structure S_screw j : c :

[0125]

[0126] Where:

[0127] ρ e is the cavity equivalent density related to the cavity cross-sectional area S r ;

[0128] c e is the cavity equivalent sound speed related to the cavity cross-sectional area S r ;

[0129] k e is the cavity equivalent wave number related to the cavity cross-sectional area S r ;

[0130] i is the imaginary unit;

[0131] S is the area of the top perforated plate 1, that is, the sound energy incident area, which is a known value;

[0132] ρ is the air density;

[0133] Step 2.4, according to the following formula, obtain the orifice impedance Z of the top perforated plate 1 of the single spiral structure S_screw j : t :

[0134]

[0135] Where:

[0136] m u is the air kinematic viscosity coefficient;

[0137] φ is the porosity related to the perforation diameter d of the top perforated plate 1;

[0138] K is the acoustic characteristic parameter related to the perforation diameter d of the top perforated plate 1;

[0139] ω is the circular frequency;

[0140] Step 2.5, determine whether the following functional relationship is satisfied:

[0141]

[0142] where:

[0143] Re is the real part of the sum of Z c +Z t ;

[0144] Im is the imaginary part of the sum of Z c +Z t ;

[0145] If not satisfied, adjust the initial structural parameter value in Step 2.1 and return to Step 2.1; if satisfied, execute Step 2.6;

[0146] Step 2.6, give the initial structural parameter values, including: helix radius R, pitch p, helix wall thickness d', and thickness t' of the bottom panel 2;

[0147] Step 2.7, obtain the number of helix turns n' of the single helix structure S_screw j according to the following formula:

[0148]

[0149] where:

[0150] R' is the transition section radius, which is a known value;

[0151] Step 2.8, obtain the cross-sectional radius r of the single helix structure S_screw r according to the cavity cross-sectional area S j and the helix wall thickness d';

[0152] Step 2.9, obtain the maximum compression stroke δ of the material mechanics deformation according to the number of helix turns n', pitch p, and cross-sectional radius r of the single helix structure S_screw j :

[0153] δ = (p - 2r)2n'

[0154] Step 2.10, determine whether the following functional relationship is satisfied:

[0155] δ - δ0 ≥ 0

[0156]

[0157] If not satisfied, adjust the helix radius R, pitch p, and helix wall thickness d', and return to step 2.6; if satisfied, execute step 2.11;

[0158] Step 2.11, specify the base material properties of the single helix structure S_screw j including: Poisson's ratio v0, Young's modulus E0, and density ρ0;

[0159] Step 2.12, determine whether the following functional relationship is satisfied:

[0160]

[0161] where:

[0162] m is the mass of the vibration-isolated object, which is a known value;

[0163] k(v0, E0, ρ0, R, n', d) is the overall stiffness of the single helix structure S_screw j related to Poisson's ratio v0, Young's modulus E0, density ρ0, helix radius R, number of turns n' of the helix structure, and helix wall thickness d';

[0164] If not satisfied, adjust the helix radius R, number of turns n' of the helix structure, and helix wall thickness d', and return to step 2.6; if satisfied, execute step 2.13;

[0165] Step 2.13, thus design the double helix structure D_screw j ;

[0166] Step 3, for n sound absorption frequencies, design n groups of double helix structures D_screw j , which together with the bottom panel 2 and the top perforated plate 1 form a metamaterial;

[0167] Step 4, for the designed metamaterial, through two-dimensional Brillouin zone sweeping, obtain the elastic wave stopband range f e1 ~f e2 ;

[0168] where:

[0169] f e1 is the upper edge point of the bandgap;

[0170] f e2 is the lower edge point of the bandgap;

[0171] Step 5, determine whether the target value f r0 of the elastic wave of the metamaterial is within the elastic wave stopband range f e1~f e2 If not, perform step 6; if yes, perform step 7.

[0172] Step 6: Adjust the thickness t′ of the bottom panel 2, the spiral radius R, the spiral wall thickness d', and the spatial relative positions of each group of double-stranded spiral structures D_screw j and return to step 2.6.

[0173] Step 7: Output the designed multifunctional acoustic metamaterial.

[0174] Next, the performance of the multifunctional integrated acoustic metamaterial provided by the present invention is detected:

[0175] Detection example 1:

[0176] In this detection example, the acoustic performance of the multifunctional integrated acoustic metamaterial is detected.

[0177] Detection object:

[0178] Taking Figure 1 the shown acoustic metamaterial as the detection object, its structural parameters are:

[0179] The top perforated plate 1 and the bottom panel 2 are square panels with a side length of 0.05 m and a thickness of 0.001 m. The radius of the perforation 1-1 provided on the top perforated plate 1 is 0.0024 m. The cavity cross-sectional radius of the single-stranded spiral structure is 0.0043 m.

[0180] The first single spiral structure 3-1 and the second single spiral structure 3-2 form a group of double-stranded spiral structures with 2.1 turns and a height of 0.058 m. The third single spiral structure 4-1 and the fourth single spiral structure 4-2 form another group of double-stranded spiral structures with 2 turns and a height of 0.058 m.

[0181] The acoustic performance is characterized by the sound absorption coefficient. The measurement of the sound absorption coefficient is based on "ISO 10534-2-1998 Measurement of sound absorption coefficient and specific impedance in acoustic impedance tubes - Part 2: Transfer function method" and is measured using two microphones.

[0182] The test system emits a plane wave from a speaker, and the sound wave is vertically incident on the top perforated plate 1 and enters the cavity inside the spiral structure through the perforation 1-1. The cavity structure is a hard acoustic boundary condition, which plays a role of total reflection. By measuring the sound pressure function in the impedance tube with two microphones, the sound absorption effect of the acoustic metamaterial can be obtained. As Figure 5 shown, it is the sound absorption coefficient curve graph of the acoustic performance of the multifunctional acoustic metamaterial. From Figure 5It can be seen that in this embodiment, due to the parallel arrangement of two groups of double-stranded helical structures with different lengths, the corresponding sound absorption resonance peaks are at two positions, and the maximum sound absorption coefficient is above 0.97. In addition, for the overall acoustic metamaterial, the sound absorption frequency band is also correspondingly broadened compared with that of a single group of helical structures.

[0183] In this test example, the change in the acoustic performance of the multifunctional acoustic metamaterial during structural deformation is further detected.

[0184] The measurement of the sound absorption coefficient is also based on "ISO 10534-2-1998 Acoustics - Measurement of sound absorption coefficient and specific impedance in impedance tubes - Part 2: Transfer function method". As Figure 6 shown, it is the sound absorption coefficient curve diagram when the multifunctional acoustic metamaterial deforms; it can be seen that in the tensile and compressive states of material deformation, the sound absorption coefficient is the same as that when there is no deformation, and the overall sound absorption peak position, the magnitude of the sound absorption peak, and the sound absorption bandwidth all remain unchanged.

[0185] For conventional acoustic materials, such as porous foams and lattice structures, they rely on internal micropores to resonate and dissipate sound energy through friction. In the case of structural deformation, the sound energy dissipation effect will inevitably be affected by the change of internal micropores. Therefore, this test example proves that the multifunctional acoustic metamaterial of the present invention has stable sound absorption performance after deformation, which helps to solve the negative connection between the acoustic performance and structural deformation of existing materials. This characteristic enables the multifunctional acoustic metamaterial to be more widely applied.

[0186] As Figure 7 shown, it is the uniaxial compression stress-strain curve diagram of the multifunctional acoustic metamaterial, that is, the uniaxial compression test response diagram of the multifunctional acoustic metamaterial under external force. It can be seen from the stress-strain curve diagram of the multifunctional acoustic metamaterial that its compression curve as a whole shows a linear deformation stage. In addition, due to the design of the double-stranded helical structure, the load-bearing has stability and does not tilt or the like. The existence of the loading-unloading hysteresis loop indicates the recoverability of the deformation of the multifunctional acoustic metamaterial, and there is also a certain amount of energy loss.

[0187] Test Example 2:

[0188] In this test example, the vibration energy attenuation performance of the multifunctional integrated acoustic metamaterial is detected.

[0189] The test object is the same as that in Test Example 1.

[0190] In this test example, the multifunctional acoustic metamaterial is used as a separate vibration isolator, but it is not limited thereto. It can also be used as a unit, and several units can be combined to form a vibration isolator together. As an illustrative example, as Figure 8As shown in the figure, it is a vibration isolation analysis model. The bottom panel 2 of the multifunctional acoustic metamaterial is fixed on the vibration source, and a heavy object is placed above to represent the object to be vibration-isolated. The vibration signal is generated by the vibration source and input into the bottom panel 2, denoted as a in . The vibration signal is transmitted to the top perforated plate 1 through the double-helix pipeline and then to the object to be vibration-isolated 5. The acceleration response measured on the object to be vibration-isolated is denoted as a out . By performing frequency function analysis on the input acceleration response and the output acceleration response, the vibration isolation effect of the multifunctional acoustic metamaterial as a vibration isolator can be observed. The vibration isolation effect is represented by the acceleration transmissibility T:

[0191]

[0192] As Figure 9 shown, it is the vibration isolation performance diagram of the multifunctional acoustic metamaterial provided by the embodiment of the present invention, which is the acceleration transmission spectrum of the multifunctional acoustic metamaterial as a vibration isolator. The vibration isolation curve first rises in the initial stage and then begins to decline after reaching the first-order resonance peak. In the frequency range after 96 Hz, the acceleration transmissibility is less than 0, indicating that the acceleration response of the object to be vibration-isolated is significantly attenuated compared with that at the vibration source. The vibration isolation mechanism of the multifunctional acoustic metamaterial comes from the elastic effect of the double-helix cavity structure to produce the function of a spring. In addition, the polymer material has certain viscoelasticity, which is equivalent to the effect of damping and dissipates the vibration energy, thus achieving the vibration isolation effect.

[0193] According to the elastic wave propagation characteristics, the waves propagating in the periodic structure will undergo Bragg scattering band gaps. Furthermore, by introducing local resonance units, local resonance band gaps are generated. The elastic waves within the band gap frequencies will be attenuated and thus difficult to propagate in the plate. Traditional sound-absorbing wall panels such as perforated plates can only play a simple sound-absorbing role, but vibrations can also transmit sound waves. Suppressing the propagation of vibrations in the panel can achieve the corresponding isolation of solid sound propagation. In the present invention, the multifunctional acoustic metamaterial is regarded as a unit cell and arranged in a quadrilateral periodic pattern, and the flexural wave band gap is shown through the band dispersion relationship. The vibration attenuation performance verification model is as Figure 10 shown. The unit cells are arranged in two directions, and the total size is 0.8 m × 0.1 m. Point excitation is applied on one side of the model, and at the same time, the acceleration response is extracted as the input acceleration response value a in , and a point is selected on the other side of the model as the vibration output acceleration response point a out . The vibration attenuation performance is characterized by the vibration transmission characteristic TL:

[0194]

[0195] As Figure 11As shown, it is the vibration damping performance diagram of the multifunctional acoustic metamaterial provided by the embodiment of the present invention. The vibration transmission spectrum diagram shows the vibration attenuation performance of the multifunctional acoustic metamaterial. When the transmission characteristic is less than 0, it indicates that the vibration propagating in the panel is attenuated. It can be seen that there is an obvious vibration attenuation bandgap near 250 Hz, and the maximum attenuation reaches -88 dB. Figure 12 and Figure 13 respectively show the vibration propagation cloud diagrams at 168 Hz outside the bandgap frequency range and 260 Hz inside the bandgap frequency range. It can be seen that within the bandgap frequency, vibration only occurs near the excitation point, and the bending wave on the panel is difficult to propagate. In contrast, the entire panel vibrates outside the bandgap frequency. This excellent vibration damping performance benefits from the vibration mode of the metamaterial. For example, the vibration of the spiral pipeline dissipates a large amount of vibration energy, so the vibration of the panel is relatively small, thus reflecting the excellent low-frequency vibration damping ability of the multifunctional metamaterial.

[0196] In practical engineering applications, the multifunctional acoustic metamaterial can be arranged to act as wall sound absorption while also attenuating the propagation of elastic waves, achieving vibration damping and noise reduction in multiple ways.

[0197] Compared with the existing technologies, the present invention has the following beneficial technical effects:

[0198] (1) The multifunctional acoustic metamaterial designed by the present invention can achieve the attenuation of sound energy propagating in air and in structures. In the low-frequency range, by designing the spiral structure shape and adjusting the three-dimensional structure parameters of the spiral line, sound absorption at different frequencies can be achieved.

[0199] (2) The acoustic metamaterial can maintain stable acoustic performance under tensile and compressive states, preventing the influence on the acoustic performance of the acoustic metamaterial in the case of structural deformation and excessive vibration amplitude.

[0200] (3) The acoustic metamaterial has compressibility recoverability and energy absorption effect, and can meet different stiffness usage requirements by selecting different manufacturing materials.

[0201] (4) The acoustic metamaterial has vibration isolation ability and can achieve vibration isolation in the low-frequency range according to the vibration isolation frequency requirements.

[0202] (5) The acoustic metamaterial described in the present invention, as a unit, can achieve the attenuation of low-frequency vibration and sound propagating in the structure through periodic arrangement, with an energy bandgap effect. By adjusting the structure model parameters and materials, etc., the frequency range of the elastic wave bandgap can be regulated, showing good structural designability.

[0203] The multi-functional acoustic metamaterial design method provided by the present invention can design an integrated structure that meets various vibration and noise reduction functions such as acoustics, mechanics, and vibration for the vibration and noise reduction frequency band targets required by actual engineering, realizing the high efficiency and compactness of material design, improving the space utilization rate, and being widely applicable to various engineering application fields.

[0204] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. An application method of a multi-functional acoustic metamaterial for multi-path integrated noise reduction, characterized in that, It includes the following steps: Step 1, determine the design requirements of the acoustic metamaterial, including: the noise control frequency band, the requirement δ0 for the mechanical elastic deformation of the material, the target value f0 of the resonance frequency of the metamaterial, and the target value f of the elastic wave of the metamaterial r0 ; Among them, the noise control frequency band includes n absorption frequencies, arranged in ascending order, namely: absorption frequencies F1, F2,..., F n ; Step 2, for any sound absorption frequency F j , where j = 1, 2,...., n, set a corresponding set of double helix structures D_screw j , the double helix structure D_screw j Each single helix structure S_screw included j is designed in the following way: Step 2.1, give the initial structural parameter values, including: the cross-sectional area S of the cavity r , the perforation diameter d of the top perforated plate (1) and the thickness t of the top perforated plate (1); Step 2.2, obtain the helical length l of the single helix structure S_screw according to the following formula j : l = 4c / F j Wherein: c is the speed of sound; Step 2.3, obtain the single helix structure S_screw according to the following formula j of the cavity impedance Z c : Wherein: ρ e is the equivalent density of the cavity related to the cross-sectional area S of the cavity r ; c e is the equivalent sound speed of the cavity related to the cross-sectional area S of the cavity r of the cavity; k e is the equivalent wave number of the cavity related to the cross-sectional area S of the cavity r ; i is the imaginary unit; S is the area of the top perforated plate (1), which is the sound energy incident area and is a known value; ρ is the air density; Step 2.4, obtain the single helix structure S_screw according to the following formula j of the orifice impedance Z of the top perforated plate (1) t :[[]]END]] Wherein: m u is the kinematic viscosity coefficient of air; φ is the porosity related to the perforation diameter d of the top perforated plate (1); K is the acoustic characteristic parameter related to the perforation diameter d of the top perforated plate (1); ω is the circular frequency; Step 2.5, determine whether the following functional relationship is satisfied: Wherein: The real part of Re is Z c +Z t The sum of the real parts; The imaginary part of Im is Z c +Z t the sum of; If not satisfied, adjust the initial structural parameter values in Step 2.1 and return to Step 2.1; if satisfied, execute Step 2.6; Step 2.6, give the initial structural parameter values, including: the spiral radius R, the pitch p, the spiral wall thickness d', and the thickness t' of the bottom panel (2); Step 2.7, obtain the number of turns n' of the helical structure of the single helical structure S_screw according to the following formula j of the helical structure: Wherein: R' is the transition section radius and is a known value; Step 2.8, according to the cross-sectional area S of the cavity r and the spiral wall thickness d', obtain the cross-sectional radius r of the single spiral structure S_screw j ; Step 2.9, according to the number of turns n', pitch p and cross-sectional radius r of the spiral structure of the single spiral structure S_screw j the maximum compression stroke δ of the mechanical deformation of the material is obtained: δ = (p - 2r)2n' Step 2.10, determine whether the following functional relationship is satisfied: δ - δ0 ≥ 0 If not satisfied, adjust the spiral radius R, the pitch p, and the spiral wall thickness d' and return to Step 2.6; if satisfied, execute Step 2.11; Step 2.11, given the basic material properties of the single helix structure S_screw j including: Poisson's ratio v0, Young's modulus E0, and density ρ0; Step 2.12, determine whether the following functional relationship is satisfied: Wherein: m is the mass of the vibration-isolated object and is a known value; k(v0, E0, ρ0, R, n', d) is the overall stiffness of the single helix structure S_screw j and is related to the Poisson's ratio v0, Young's modulus E0, density ρ0, helix radius R, number of turns n' of the helix structure, and helix wall thickness d'. If not satisfied, adjust the spiral radius R, the number of turns n' of the spiral structure, and the spiral wall thickness d' and return to Step 2.6; if satisfied, execute Step 2.13; Step 2.13, the double-stranded helical structure D_screw is designed therefrom j ; Step 3: For n absorption frequencies, n groups of double-chain helical structures D_screw are designed j , which form a metamaterial with the bottom panel (2) and the top perforated plate (1); Step 4: For the designed acoustic metamaterial, obtain the elastic wave stopband range f of the metamaterial through two-dimensional Brillouin zone sweeping e1 ~f e2 ; Wherein: f e1 is the upper edge point of the bandgap; f e2 is the lower edge point of the bandgap; Step 5, determine whether the target value f of the elastic wave of the metamaterial r0 is within the bandgap range f e1 ~f e2 of the elastic wave of the metamaterial. If not, execute Step 6; if so, execute Step 7; Step 6, adjust the thickness t' of the bottom panel (2), the spiral radius R, the spiral wall thickness d', and the spatial relative positions of each group of double-stranded spiral structures D_screw j and return to Step 2.6; Step 7, output the designed multifunctional acoustic metamaterial.

2. A multifunctional acoustic metamaterial for multi-path integrated noise reduction, characterized in that, The multifunctional acoustic metamaterial for multi-path integrated noise reduction is the material used in the application method of a multifunctional acoustic metamaterial for multi-path integrated noise reduction as described in Claim 1; the multifunctional acoustic metamaterial for multi-path integrated noise reduction includes multiple resonance frequency units; each of the resonance frequency units is spliced and combined to form the multifunctional acoustic metamaterial for multi-path integrated noise reduction; Each of the resonance frequency units includes a top perforated plate (1), a bottom panel (2), and multiple groups of double-chain spiral structures located between the top perforated plate (1) and the bottom panel (2); the groups of double-chain spiral structures are arranged according to the set spatial relative positions; the spiral structure parameters of the groups of double-chain spiral structures are the same or different.

3. The multifunctional acoustic metamaterial for multi-path integrated noise reduction according to claim 2, characterized in that, Each group of double-chain spiral structures includes two single spiral structures; the two single spiral structures are wound around the same axis in opposite parallel directions to form the double-chain spiral structure.

4. The multifunctional acoustic metamaterial for multi-path integrated noise reduction according to claim 3, characterized in that, Each single spiral structure has a cavity, the top end of the single spiral structure is communicated with the perforation (1-1) opened at the corresponding position on the top perforated plate (1), and the size and shape of the perforation (1-1) are the same as those of the cavity of the single spiral structure; The bottom end of the single spiral structure is fixed to the bottom panel (2), and the bottom panel (2) does not have a through hole at the corresponding position and is a sealed structure.

5. The multifunctional acoustic metamaterial for multi-path integrated noise reduction according to claim 4, characterized in that, The spiral structure parameters of the two single spiral structures are the same, and the spiral structure parameters include: the cavity cross-sectional area S r , the spiral length l, the spiral radius R, the pitch p, the spiral wall thickness d', the number of turns n' of the spiral structure, the cross-sectional radius r, and the base material properties.

6. The multifunctional acoustic metamaterial for multi-path integrated noise reduction according to claim 3, characterized in that, The cross-sectional shape of the cavity of each single spiral structure is circular, elliptical, rectangular, or rhombic.

7. The multifunctional acoustic metamaterial for multi-path integrated noise reduction according to claim 2, characterized in that, The shape and size of the top perforated plate (1) are the same as those of the bottom panel (2); The shapes of the top perforated plate (1) and the bottom panel (2) are circular, rectangular, square, or parallelogram.

8. The multi-path integrated noise reduction multi-functional acoustic metamaterial according to claim 2, characterized in that, The materials of the top perforated plate (1), the bottom panel (2), and the double-stranded helical structure are the same or different.

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