Sound absorption metamaterial with perforated beveled foamed aluminum composite micro-perforated plate

Abstract

The invention belongs to the technical field of noise control, and discloses a sound absorption metamaterial of a beveled foamed aluminum composite micro-perforated plate with perforations, which comprises beveled foamed aluminum with a beveled top, the beveled foamed aluminum is downwards provided with perforations from the beveled surface, the bottom surface of the beveled foamed aluminum is provided with a gradually-changed micro-perforated plate, and the beveled foamed aluminum is provided with a plurality of through holes. The gradually-changed micro-perforated plate is provided with gradually-changed micro-perforated holes, the small ends of the gradually-changed micro-perforated holes face upwards, the large ends of the gradually-changed micro-perforated holes face downwards, a cylindrical micro-perforated plate is arranged below the gradually-changed micro-perforated plate, a space between the gradually-changed micro-perforated plate and the cylindrical micro-perforated plate is a first rear-mounted cavity, and a second rear-mounted cavity is formed below the cylindrical micro-perforated plate. Through the unique perforation design and the beveling process, the sound absorption frequency band is remarkably widened, high-performance broadband sound absorption is achieved, the characteristics of saving materials and improving the machining efficiency and cost effectiveness are achieved, and the remarkable innovativeness and practicability advantages are shown.

Description

Technical Field

[0001] The invention belongs to the technical field of noise control, and in particular relates to a sound-absorbing superstructure material having a perforated oblique-cut foam aluminum composite micro-perforated plate. Background Art

[0002] Sound-absorbing materials mainly include two types: porous sound-absorbing materials and resonant sound-absorbing materials. As a porous sound-absorbing material, foamed aluminum has unique advantages in the field of sound absorption due to its excellent physical and chemical properties, efficient sound absorption and sound insulation effects, high strength and durability, environmental sustainability, wide range of applications and aesthetics, and easy processing and installation. However, it generally has the problem of poor low-frequency sound absorption. In order to enhance the sound absorption performance, invention patent CN202011288419.3 proposes a foamed aluminum sound absorber, but the structure is relatively complex.

[0003] The micro-perforated plate structure has significant advantages in resonant sound-absorbing materials due to its high peak sound absorption, controllable performance, durability and environmental protection, beautiful and practical appearance, and wide applicability. However, it can only show high sound absorption performance at the resonant peak frequency, and the sound absorption bandwidth is narrow. In order to broaden the sound absorption bandwidth of the micro-perforated plate structure, the invention patent CN201910770054.9 proposes a multi-unit coupled micro-perforated plate low-frequency broadband sound absorption structure and its design method. The structure is complex, puts forward higher requirements on the preparation process, and has excellent sound absorption performance only in the range of 400 to 2400 Hz.

[0004] Porous sound-absorbing materials and resonant sound-absorbing materials complement each other in terms of sound absorption performance. In order to combine the sound absorption advantages of both, invention patent CN201810791875.6 proposes a hybrid sound-absorbing structure in which a porous sound-absorbing material is connected in parallel with a resonant structure. The structure is relatively complex and only studies the sound absorption performance of 0 to 1600 Hz.

[0005] It can be seen that the composite design of porous sound-absorbing materials and resonant sound-absorbing materials in current patents is often limited by problems such as narrow sound absorption frequency band, incomplete material performance and high processing complexity. Summary of the invention

[0006] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a sound-absorbing super-structure material with a perforated beveled foam aluminum composite micro-perforated plate. The present invention, through a unique perforation design and bevel cutting process, not only significantly broadens the sound absorption frequency band and achieves high-performance broadband sound absorption, but also has the characteristics of saving materials, improving processing efficiency and cost-effectiveness, showing significant innovation and practical advantages.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] A sound-absorbing meta-structure material with a perforated beveled aluminum foam composite micro-perforated plate comprises a beveled aluminum foam with a beveled top, the top surface of the beveled aluminum foam is a beveled surface, the beveled aluminum foam is provided with perforations downward from the beveled surface, the perforations are blind holes, a gradient micro-perforated plate is provided on the bottom surface of the beveled aluminum foam, gradient micro-perforations are evenly provided on the gradient micro-perforated plate, the small end of the gradient micro-perforations is upward and the large end is downward, a cylindrical micro-perforated plate is provided below the gradient micro-perforated plate, cylindrical micro-perforations are provided on the cylindrical micro-perforated plate, the space between the gradient micro-perforated plate and the cylindrical micro-perforated plate is a first rear cavity, and a second rear cavity is provided below the cylindrical micro-perforated plate.

[0009] Preferably, the shape of the gradual micro-perforation is a truncated cone, the thickness of the gradual micro-perforation plate is 0.6-1 mm, the aperture of the gradual micro-perforation small diameter section is 0.5-0.8 mm, the aperture of the gradual micro-perforation large diameter section is 0.8-1.0 mm, the porosity on the upper surface of the gradual micro-perforation plate is 0.36%-0.68%, and the porosity on the lower surface of the gradual micro-perforation plate is 0.91%-1.07%; the thickness of the cylindrical micro-perforation plate is 0.6-1.0 mm, the aperture of the cylindrical micro-perforation is 0.8-1.0 mm, and the perforation rate of the cylindrical micro-perforation plate is 0.68%-0.77%.

[0010] Preferably, the depth of the first rear cavity is 6-10 mm, and the depth D2 of the second rear cavity is 6-10 mm.

[0011] Preferably, the diameter of the bevel-cut aluminum foam is 28 to 30 mm, the height is 20 to 30 mm, and the tangent value of the angle between the normal line of the beveled surface and the axis line of the bevel-cut aluminum foam in the up-down direction is 18 / 29 to 22 / 29.

[0012] Preferably, the pore structure of the oblique cut aluminum foam is uniform, satisfying the flow resistance of 103254 to 145936 Pa·s / m 2 .

[0013] Preferably, the number of perforations is 2 or 3, all perforations are arranged in sequence along the long axis of the beveled surface, the bottom surfaces of all perforations are flush, the cross-section of the perforations is circular, the diameter of the perforations is 4 to 6 mm, and the depth of the perforations is 15 to 25 mm.

[0014] Preferably, the sound-absorbing metamaterial having a perforated oblique-cut aluminum foam composite micro-perforated plate has two perfect sound absorption peaks at 0 to 3000 Hz;

[0015] The parameter determination process of the sound-absorbing metamaterial having a perforated oblique-cut aluminum foam composite micro-perforated plate comprises the following steps:

[0016] S1, calculating the acoustic impedance of the gradient micro-perforated plate according to the preset structural parameters of the gradient micro-perforated plate;

[0017] S2, calculating the acoustic impedance of the cylindrical micro-perforated plate according to the preset structural parameters of the cylindrical micro-perforated plate;

[0018] S3, calculating the total acoustic impedance of the double-layer microperforated plate sound absorption structure consisting of the gradient microperforated plate and the first rear cavity and the cylindrical microperforated plate and the second rear cavity according to the acoustic impedance of the gradient microperforated plate and the acoustic impedance of the cylindrical microperforated plate;

[0019] S4, using the total acoustic impedance, verifying whether the sound-absorbing meta-structure material having the perforated oblique-cut aluminum foam composite micro-perforated plate has perfect sound absorption at the resonant frequency;

[0020] S5, when perfect sound absorption exists, the preset structural parameters of the gradient micro-perforated plate, the preset structural parameters of the cylindrical micro-perforated plate, the depth of the first rear cavity, and the depth of the second rear cavity are used as the final parameters;

[0021] S6, if perfect sound absorption does not exist, adjust the preset structural parameters of the gradient micro-perforated plate, the preset structural parameters of the cylindrical micro-perforated plate, the depth of the first rear cavity, and the depth of the second rear cavity, and repeat S1 to S5.

[0022] Preferably, the preset structural parameters of the gradient micro-perforated plate include: the aperture d1 of the gradient micro-perforated small diameter section, the aperture d2 of the gradient micro-perforated large diameter section, the thickness t of the gradient micro-perforated plate, the perforation rate p1 on the upper surface of the gradient micro-perforated plate, and the perforation rate p2 on the lower surface of the gradient micro-perforated plate;

[0023] The process of calculating the acoustic impedance of the gradient micro-perforated plate includes: dividing the gradient micro-perforated plate into M equal parts along the height direction, and considering each part as a cylindrical hole with a thickness of t / M. Then the acoustic impedance Z of the gradient micro-perforated plate is 渐变型 as follows:

[0024] Z 渐变型 =r+jωm

[0025]

[0026]

[0027] Among them, r is the relative acoustic resistance; m is the relative acoustic mass; from the linear relationship, we can know that the diameter of the i-th hole is Thickness t i =t / M, the perforation rate of the i-th hole is The perforation constant is X is the correction coefficient of the cross-sectional perforation constant; ρ0 represents the density of air; ω is the angular frequency of the incident sound wave; η is the dynamic viscosity of air;

[0028] The preset structural parameters of the cylindrical micro-perforated plate include: the aperture d of the cylindrical micro-perforation, the plate thickness T of the cylindrical micro-perforated plate and the perforation rate ρ;

[0029] Acoustic impedance Z in cylindrical micro-perforated plate 圆柱型 as follows:

[0030]

[0031] Where k is the perforation constant, K is the perforation correction factor;

[0032] The total acoustic impedance of the double-layer micro-perforated plate sound absorption structure is as follows:

[0033]

[0034] Z Di =-jρ0ccot(ωDi / c),i=1,2

[0035] Among them, Z D1 is the acoustic impedance of the first rear cavity, the depth of the first rear cavity is D1, Z D2 is the acoustic impedance of the second rear cavity, the depth of the second rear cavity is D2; c is the speed of sound;

[0036] Verify that perfect sound absorption exists, including: when Re(Z 总 / Z0)=1,Im(Z 总 / Z0)=0, it indicates that there is perfect sound absorption. At this time, the sound absorption coefficient of the sound-absorbing metamaterial with perforated beveled aluminum foam composite micro-perforated plate is greater than or equal to 0.95; otherwise, there is no perfect sound absorption, wherein Z0 is the characteristic impedance of air.

[0037] Preferably, the sound-absorbing superstructure material having the perforated oblique-cut aluminum foam composite micro-perforated plate has an average sound absorption coefficient of greater than or equal to 0.8 at 3000 to 6300 Hz;

[0038] The parameter determination process of the sound-absorbing metamaterial having a perforated oblique-cut aluminum foam composite micro-perforated plate comprises the following steps:

[0039] S1, based on the finite element method, a finite element model of the beveled aluminum foam is established according to preset parameters in the pressure acoustics module in the multi-physics field simulation software, the beveled aluminum foam is defined using the DB model in the porous medium acoustic model, and a plane wave with an amplitude of 1Pa is introduced to simulate the vertical incidence of the sound wave;

[0040] S2, based on S1, establishes a finite element model of the chamfered aluminum foam with perforations according to preset parameters, and defines the perforations using the viscous acoustics module;

[0041] S3, calculate the sound absorption coefficient of the beveled aluminum foam with perforations;

[0042] S4, verify whether the sound absorption curve of the perforated beveled aluminum foam meets the average sound absorption coefficient at 3000-6300Hz

[0043]

[0044] S5, when the average sound absorption coefficient When the parameters of the sound-absorbing meta-structure material having the perforated oblique-cut aluminum foam composite micro-perforated plate are determined as the final parameters;

[0045] S6, when the average sound absorption coefficient , then repeat S1 to S5.

[0046] Preferably: in S1, the preset parameters when establishing the finite element model of the beveled aluminum foam include: the thickness of the beveled aluminum foam and the tangent value of the bevel angle;

[0047] In S2, the preset parameters for establishing the finite element model of the chamfered aluminum foam with perforations include: a perforation diameter and a perforation depth;

[0048] In S3, the calculation process of the sound absorption coefficient of the oblique-cut aluminum foam with perforations includes:

[0049] Surface acoustic impedance Z at the incident interface s And the sound pressure reflection coefficient R is as follows:

[0050]

[0051] Among them, p t It represents the average sound pressure when the sound is incident on the surface of the material; u represents the average normal vibration speed of the particles in the air when the sound is incident on the surface of the material; p r and p i denote the reflected sound pressure and the incident sound pressure respectively;

[0052] The sound absorption coefficient α is as follows:

[0053] α=1-|R| 2 .

[0054] The present invention has the following beneficial effects:

[0055] In the sound-absorbing meta-structure material of the perforated oblique-cut aluminum foam composite micro-perforated plate of the present invention, the traditional aluminum foam is designed as an oblique-cut structure. This design not only increases the surface area of ​​the aluminum foam on the sound wave incident surface, provides more interaction interfaces for the sound waves, and thus enhances the absorption capacity of the aluminum foam to the sound waves; moreover, the oblique-cut structure also forms a front oblique-cut cavity. When the sound wave is incident on the surface of the oblique-cut aluminum foam, the sound wave is first reflected on the interface of the front cavity, which increases the interaction time between the sound wave and the aluminum foam material, and helps to convert more sound wave energy into heat energy and dissipate it. Therefore, the oblique-cut aluminum foam proposed in the present invention has the advantage of saving materials while improving the sound absorption performance of medium and high frequencies. The oblique-cut aluminum foam is perforated, which significantly increases the viscous dissipation of sound energy and further improves the sound absorption of medium and high frequencies. In order to improve the sound absorption performance of medium and low frequencies, based on the principle of impedance matching, the structural parameters of the gradient micro-perforated plate and the cylindrical micro-perforated plate are optimized to produce a perfect sound absorption peak (sound absorption coefficient α≥0.95). In the process of structural optimization, the perforation constant k of the gradient micro-perforated plate was corrected based on the deviation between the experimental measurement results and the simulation results. i On the one hand, the aperture of the micropores in the gradient microperforated plate gradually changes in the direction of the incident sound wave. This structural characteristic makes its impedance no longer conform to the prediction results of the classical model. The gradient micropores will change the propagation path and reflection characteristics of the sound wave in the microperforated plate, thereby affecting the perforation constant k. i On the other hand, the arrangement and density distribution of cylindrical micropores will change the propagation path and interaction mode of sound waves in the double-layer micro-perforated plate structure, thereby affecting the perforation constant k. Therefore, in order to accurately describe the impedance characteristics of the double-layer micro-perforated plate structure, the perforation constant k of the gradient micro-perforated plate is calculated. i The perforation constant k of the cylindrical micro-perforated plate is modified to enhance the effectiveness of structural optimization. In general, the present invention can comprehensively utilize the excellent mid- and high-frequency sound absorption performance of foam aluminum and the excellent low-frequency sound absorption performance of the micro-perforated plate structure, and achieve the purpose of adjusting the resonance sound absorption peak by using the double-layer micro-perforated plate structure composed of the gradient micro-perforated plate and the cylindrical micro-perforated plate, and adjusting the mid- and high-frequency sound absorption performance by using the oblique-cut foam aluminum with perforations, solving the problems of the current sound absorption structure with limited sound absorption effect, complex structure, high production cost, and material consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is a schematic structural diagram of the sound-absorbing meta-structure material of the present invention having a perforated oblique-cut foam aluminum composite micro-perforated plate.

[0057] Figure 2 Schematic diagram of the structure of the gradual micro-perforations in the gradual micro-perforated plate in an embodiment of the present invention.

[0058] FIG. 3( a ) is a schematic diagram of the structure of Example 1 of the present invention; FIG. 3( b ) is a diagram of the sound absorption coefficient of Example 1 of the present invention.

[0059] FIG. 4( a ) is a schematic diagram of the structure of Example 2 of the present invention; FIG. 4( b ) is a diagram of the sound absorption coefficient of Example 2 of the present invention.

[0060] FIG. 5( a ) is a schematic diagram of the structure of Example 3 of the present invention; FIG. 5( b ) is a diagram of the sound absorption coefficient of Example 3 of the present invention.

[0061] In the figure, 1-front beveled cavity, 2-perforation, 3-first rear cavity, 4-first rear cavity, 5-beveled foam aluminum, 5-1-beveled surface, 5-2-bottom surface, 6-gradual micro-perforated plate, 7-cylindrical micro-perforated plate. DETAILED DESCRIPTION

[0062] The present invention is further described below in conjunction with the embodiments, but it should not be understood that the above subject matter of the present invention is limited to the following embodiments. Without departing from the above technical ideas of the present invention, various substitutions and changes are made according to the common technical knowledge and customary means in the art, which should all be included in the protection scope of the present invention.

[0063] See also Figure 1 The present invention provides a sound-absorbing meta-structure material with a perforated beveled aluminum foam composite micro-perforated plate, comprising a beveled aluminum foam 5 beveled at the top, the top surface of the beveled aluminum foam 5 being a beveled surface 5-1, the upper left space of the beveled aluminum foam 5 being a front beveled cavity 1 of the beveled aluminum foam 5, a perforation 2 being provided downward from the beveled surface 5-1 on the beveled aluminum foam 5, the perforation 2 being a blind hole, a gradient micro-perforated plate 6 being provided on the bottom surface 5-2 of the beveled aluminum foam 5, gradient micro-perforations being uniformly provided on the gradient micro-perforated plate 6, the small end of the gradient micro-perforations being upward and the large end being downward, a cylindrical micro-perforated plate 7 being provided below the gradient micro-perforated plate 6, cylindrical micro-perforations being provided on the cylindrical micro-perforated plate 7, the space between the gradient micro-perforated plate 6 and the cylindrical micro-perforated plate 7 being a first rear cavity 3, and a second rear cavity 4 being provided below the cylindrical micro-perforated plate 7.

[0064] In the above scheme of the present invention, the beveled aluminum foam 5 is in the shape of a cylinder before beveled, and after beveled from the beveled surface, the cut-off portion on the upper left is removed to form a front beveled cavity 1 of the beveled aluminum foam 5, wherein the beveled surface 5-1 is elliptical. The perforations 2 are circular holes opened downward from the beveled surface 5-1, and the axes of all the perforations 2 are distributed in sequence from left to right along the long axis of the beveled surface 5-1, and the bottoms of all the perforations 2 are on the same horizontal plane.

[0065] In order to realize that the sound-absorbing metamaterial has two perfect sound absorption peaks (sound absorption coefficient α≥0.95) at 0-3000 Hz, the present invention optimizes the parameters of the structure of the gradient micro-perforated plate 6 and the cylindrical micro-perforated plate 7, specifically comprising the following steps:

[0066] Step 1: Calculate the acoustic impedance of the gradient micro-perforated plate 6 according to the preset structural parameters of the gradient micro-perforated plate 6; Figure 2 , wherein the gradual micro-perforations of the gradual micro-perforated plate 6 are in the shape of a truncated cone with a small top and a large bottom, and the preset structural parameters of the gradual micro-perforated plate 6 include: the upper surface aperture d1 (i.e., the small end diameter of the gradual micro-perforations), the lower surface aperture d2 (i.e., the large end diameter of the gradual micro-perforations), the thickness t of the gradual micro-perforated plate 6, the perforation rate p1 of the upper surface (i.e., the perforation rate of the small end of the gradual micro-perforations), and the perforation rate p2 of the lower surface (i.e., the perforation rate of the large end of the gradual micro-perforations);

[0067] In this step, the gradual micro-perforations are formed along the axial direction (i.e. Figure 2 The vertical direction shown in the figure is divided into M equal parts, each of which can be approximately regarded as a cylindrical hole with a thickness of t / M. Then the acoustic impedance Z of the gradient micro-perforated plate 6 is 渐变型 It is expressed as:

[0068] Z 渐变型 =r+jωm

[0069]

[0070] Among them, r is the relative acoustic resistance; m is the relative acoustic mass; from the linear relationship, we can know that the diameter of the i-th hole is Thickness t i =t / M, the perforation rate of the i-th hole is The perforation constant is X is the correction coefficient of the cross-sectional perforation constant, and its value is related to the cross-sectional change, and its value range is 0.6 to 1.4; ρ0 represents the density of air; ω is the angular frequency of the incident sound wave; η is the dynamic viscosity of air;

[0071] Step 2: Calculate the acoustic impedance of the cylindrical micro-perforated plate 7 according to the preset structural parameters of the cylindrical micro-perforated plate 7; the preset structural parameters of the cylindrical micro-perforated plate 7 include: the aperture d, the plate thickness T and the perforation rate ρ of the cylindrical micro-perforated plate 7;

[0072] In this step 2, the acoustic impedance Z in the hole of the cylindrical micro-perforated plate 7 圆柱型 It is expressed as:

[0073]

[0074] Where k is the perforation constant, K is the perforation correction coefficient, which is related to the distribution of cylindrical micropores and ranges from 0.7 to 1.2;

[0075] Step 3, according to the acoustic impedance of the gradient micro-perforated plate 6 and the acoustic impedance of the cylindrical micro-perforated plate 7, the total acoustic impedance of the double-layer micro-perforated plate sound absorption structure composed of the gradient micro-perforated plate 6 and its first rear cavity 3 and the cylindrical micro-perforated plate 7 and its second rear cavity 4 is calculated;

[0076] In this step three, the total acoustic impedance of the double-layer micro-perforated plate structure is:

[0077]

[0078] Z Di =-jρ0ccot(ωDi / c),i=1,2

[0079] Among them, Z D1 is the acoustic impedance of the rear cavity (i.e., the first rear cavity 3) of the gradient micro-perforated plate 6, the depth of the first rear cavity 3 is D1, Z D2 is the acoustic impedance of the rear cavity (i.e., the second rear cavity 4) of the cylindrical micro-perforated plate 7, and the depth of the second rear cavity 4 is D2; c is the sound velocity;

[0080] Step 4: Verify whether there is perfect sound absorption (sound absorption coefficient α ≥ 0.95) at the resonant frequency. If not, return to step 1 and optimize again until there is perfect sound absorption at the resonant frequency.

[0081] In this step, only when the acoustic reactance reaches 1 and the acoustic resistance reaches 0, that is, Re(Z 总 / Z0)=1,Im(Z 总 / Z0)=0, perfect sound absorption can be achieved, where Z0 is the characteristic impedance of air.

[0082] In order to achieve an average sound absorption performance of the sound-absorbing metamaterial of greater than or equal to 0.8 at 3000-6300 Hz, the present invention performs structural design on the perforated oblique-cut aluminum foam, including the following steps:

[0083] Step 1: Based on the finite element method, in the pressure acoustics module in the multi-physics simulation software COMSOL Multiphysics 6.1, a finite element model of the beveled aluminum foam 5 is established according to preset parameters, and the beveled aluminum foam 5 is defined using the DB model in the porous medium acoustic model. At the same time, a plane wave with an amplitude of 1Pa is introduced to simulate the vertical incidence of the sound wave; in this step, the preset parameters include: the thickness of the beveled aluminum foam and the tangent value of the bevel angle;

[0084] Step 2: Based on step 1, a finite element model of the beveled aluminum foam with perforations is established according to preset parameters, and the perforation 2 is defined using the viscous acoustic module to consider the attenuation effect of heat conduction and viscous damping in the perforation 2 on the sound wave; in this step, the improvement effect of the perforation 2 on the sound absorption performance of 3000-6300 Hz is mainly considered, and the preset parameters include the aperture and perforation depth of the perforation 2;

[0085] Step 3: Calculate the sound absorption coefficient of the oblique-cut aluminum foam with perforations. In this step, the surface acoustic impedance Z at the incident interface is s And the sound pressure reflection coefficient R is expressed as:

[0086]

[0087] Among them, p t It represents the average sound pressure when the sound is incident on the surface of the material; u represents the average normal vibration speed of the particles in the air when the sound is incident on the surface of the material; p r and p i represent the reflected sound pressure and the incident sound pressure respectively.

[0088] In this step, the sound absorption coefficient α is expressed as

[0089] α=1-|R| 2

[0090] Step 4: Verify whether the sound absorption curve of the perforated beveled aluminum foam meets the average sound absorption coefficient between 3000 and 6300 Hz. If it is not satisfied, return to step 1 and optimize again until the sound absorption curve meets the average sound absorption coefficient between 3000 and 6300 Hz.

[0091] As a preferred embodiment of the present invention, in this embodiment, the thickness t of the gradient micro-perforated plate 6 is 0.6-1 mm, the pore size d1 is 0.5-0.8 mm, the pore size d2 is 0.8-1.0 mm, the number of micropores is 9-12, the porosity p1 is 0.36%-0.68%, and the porosity p2 is 0.91%-1.07%; the thickness T of the cylindrical micro-perforated plate 7 is 0.6-1.0 mm, the pore size d is 0.8-1.0 mm, the number of micropores is 6-9, and the perforation rate ρ is 0.68% to 0.77%; the rear cavity depth D1 of the gradient micro-perforated plate 6 is 6 to 10 mm, and the rear cavity depth D2 of the cylindrical micro-perforated plate 7 is 6 to 10 mm; the diameter of the beveled aluminum foam 5 is 28 to 30 mm, and the tangent value of the bevel angle is 18 / 29 to 22 / 29; the thickness (i.e., height) of the beveled aluminum foam 5 is 20 to 30 mm; the pore structure of the beveled aluminum foam 5 is uniform, and the flow resistance is 103254 to 145936 Pa·s / m 2The number of perforations 2 is 2 or 3, the diameter is 4 to 6 mm, and the perforation depth is 15 to 25 mm.

[0092] It can be seen from the above scheme that the present invention adjusts and optimizes the parameters of the double-layer micro-perforated plate structure to make the sound-absorbing meta-material have two perfect sound absorption peaks (sound absorption coefficient α≥0.95) at 0-3000Hz, thereby improving the mid- and low-frequency sound absorption performance. Secondly, by adjusting the structural parameters of the perforated bevel-cut aluminum foam, the sound absorption curve of the sound-absorbing meta-material has an average sound absorption coefficient of 3000-6300Hz. In order to improve the mid- and high-frequency sound absorption performance, the overall purpose of using double-layer micro-perforated plates to adjust the resonance sound absorption peak and using perforated beveled foam aluminum to adjust the mid- and high-frequency sound absorption performance is achieved.

[0093] In the following embodiments of the present invention, the gradual micro-perforations of the gradual micro-perforated plate 6 are all in the shape of a truncated cone that is small at the top and large at the bottom.

[0094] Embodiment 1:

[0095] Referring to FIG. 3( a ), the thickness of the gradient micro-perforated plate 6 is t=0.6 mm, the pore size of the upper surface is d1=0.5 mm, the pore size of the lower surface is d2=0.8 mm, the number of gradient micropores is 12, p1=0.36%, p2=0.91%; the thickness of the cylindrical micro-perforated plate 7 is T=0.6 mm, the pore size is 0.8 mm, the number of cylindrical micropores is 9, and the porosity is ρ=0.68%; the depth of the rear cavity of the gradient micro-perforated plate 6 is 6 mm; the depth of the rear cavity of the cylindrical micro-perforated plate 7 is 6 mm; the tangent value of the bevel angle of the beveled aluminum foam 5 is 18 / 29, the thickness (i.e., height) of the beveled aluminum foam 5 is 20 mm, the diameter is 28 mm, and the flow resistance is 103254 Pa·s / m 2 ; The number of perforations is 2, the perforation diameter is 4mm, and the perforation depth is 15mm.

[0096] Embodiment 2:

[0097] Referring to Fig. 4(a), the thickness of the gradient micro-perforated plate 6 is t=0.8 mm, the pore size of the upper surface is d1=0.6 mm, the pore size of the lower surface is d2=0.9 mm, the number of gradient micropores is 10, p1=0.43%, p2=0.96%; the thickness of the cylindrical micro-perforated plate 7 is T=0.8 mm, the pore size is 0.9 mm, the number of cylindrical micropores is 8, and the porosity is ρ=0.77%; the depth of the rear cavity of the gradient micro-perforated plate 6 is 8 mm; the depth of the rear cavity of the cylindrical micro-perforated plate 7 is 8 mm; the tangent value of the bevel angle of the beveled aluminum foam 5 is 20 / 29, the thickness of the beveled aluminum foam 5 is 25 mm, the diameter is 28 mm, and the flow resistance is 114368 Pa·s / m 2 ; The number of perforations is 3, the perforation diameter is 5mm, and the perforation depth is 20mm.

[0098] Embodiment 3:

[0099] Referring to FIG. 5( a ), the thickness of the gradient micro-perforated plate 6 is t=1.0 mm, the pore size of the upper surface is d1=0.8 mm, the pore size of the lower surface is d2=1.0 mm, the number of gradient micropores is 9, p1=0.68%, and p2=1.07%; the thickness of the cylindrical micro-perforated plate 7 is T=1.0 mm, the pore size is 1.0 mm, the number of cylindrical micropores is 6, and the porosity is ρ=0.71%; the depth of the rear cavity of the gradient micro-perforated plate 6 is 10 mm; the depth of the rear cavity of the cylindrical micro-perforated plate 7 is 10 mm; the tangent value of the bevel angle of the beveled aluminum foam 5 is 22 / 29, the thickness of the beveled aluminum foam 5 is 30 mm, the diameter is 28 mm, and the flow resistance is 145936 Pa·s / m 2 ; The number of perforations is 3, the perforation diameter is 6mm, and the perforation depth is 25mm.

[0100] It can be seen from the sound absorption curves of Figures 3(b), 4(b) and 5(b) that the sound absorption curves of the three groups of embodiments are composed of two parts: a resonant sound absorption domain and a porous damping sound absorption domain. Before 3000 Hz, the sound absorption performance is mainly dominated by the double-layer micro-perforated plate structure, which mainly reflects the resonant sound absorption performance, which is called the resonant sound absorption domain; at 3000-6300 Hz, the sound absorption curve does not reflect the resonant performance, and the sound absorption effect depends on the sound energy dissipation caused by the porous damping effect in the perforated beveled foam aluminum, and this frequency band is called the porous damping sound absorption domain.

[0101] Specifically, the perfect sound absorption peaks of Example 1 are located at 700 Hz and 2100 Hz, with sound absorption coefficients of 0.96 and 0.97, respectively. The average sound absorption coefficient in the entire study frequency band is 0.64, the average sound absorption coefficient in the resonance sound absorption domain is 0.45, and the average sound absorption coefficient in the porous damping sound absorption domain is 0.81; the perfect sound absorption peaks of Example 2 are located at 900 Hz and 2100 Hz, with sound absorption coefficients of 0.97 and 0.99, respectively. The average sound absorption coefficient in the entire study frequency band is 0.68, and the average sound absorption coefficient in the resonance sound absorption domain is 0.45. The average sound absorption coefficient in the vibration sound absorption domain is 0.47, and the average sound absorption coefficient in the porous damping sound absorption domain is 0.88; the perfect sound absorption peaks of Example 3 are located at 700Hz and 1800Hz, with sound absorption coefficients of 0.99 and 0.96 respectively, the average sound absorption coefficient in the entire research frequency band is 0.75, the average sound absorption coefficient in the resonance sound absorption domain is 0.55, and the average sound absorption coefficient in the porous damping sound absorption domain is 0.91; while the average sound absorption coefficient of foam aluminum of the same thickness at 0-6300Hz is about 0.48,

[0102] It can be seen that the sound absorption coefficients of the three embodiments are excellent, with two obvious perfect sound absorption peaks, obvious broadband sound absorption effect, and the average sound absorption coefficient of the resonance sound absorption domain is significantly lower than the average sound absorption coefficient of the porous damping sound absorption domain. This is because the sound absorption characteristics of the resonance material are high peak value but narrow frequency band, and the sound absorption peak is relatively sharp, showing excellent sound absorption effect at the resonance frequency, while the sound absorption effect at the non-resonance frequency is poor, which significantly reduces the overall average sound absorption coefficient. In contrast, Example 3 has more excellent sound absorption performance, and the average sound absorption coefficient in the resonance sound absorption domain and the porous damping sound absorption domain is higher, mainly because the thickness of the bevel-cut aluminum foam in Example 3, the perforation depth in the bevel-cut aluminum foam, and the depth of the rear cavity of the two layers of micro-perforated plates are all large. The thickness of the bevel-cut aluminum foam directly affects the number of times the sound wave passes through the material. The greater the thickness of the bevel-cut aluminum foam, the more sound waves it absorbs, the greater the sound absorption amount, and the better the sound absorption effect. Secondly, according to the 1 / 4 wavelength principle, as the thickness of the beveled aluminum foam increases, the sound absorption peak will move to the low frequency, thereby broadening the sound absorption frequency range of the material. The increase in perforation depth can increase the contact area and contact time between the sound wave and the hole wall, thereby enhancing the friction consumption and viscous resistance of the sound wave and improving the low-frequency sound absorption effect. The rear cavity of the micro-perforated plate is an important part of the sound absorption structure of the micro-perforated plate. The rear cavity can provide sufficient propagation space and damping effect for the sound wave. As the depth of the rear cavity increases, the resonance absorption peak of the micro-perforated plate structure in the low-frequency range will be enhanced, which helps to absorb more low-frequency sound waves.

[0103] The specific embodiments of the present invention are described in detail above. It should be understood that ordinary technicians in the field can make many modifications and changes based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by technicians in the technical field through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection of the claims of the present invention.

Claims

1. A sound-absorbing metamaterial having a perforated oblique-cut aluminum foam composite micro-perforated plate, characterized in that: The invention comprises a beveled aluminum foam (5) with a beveled top, wherein the top surface of the beveled aluminum foam (5) is a beveled surface (5-1), a perforation (2) is provided on the beveled aluminum foam (5) from the beveled surface (5-1) downward, the perforation (2) is a blind hole, a gradient micro-perforated plate (6) is provided on the bottom surface (5-2) of the beveled aluminum foam (5), gradient micro-perforated plates (6) are evenly provided with gradient micro-perforations, the small ends of the gradient micro-perforations are upward and the large ends are downward, a cylindrical micro-perforated plate (7) is provided below the gradient micro-perforated plate (6), cylindrical micro-perforations are provided on the cylindrical micro-perforated plate (7), a space between the gradient micro-perforated plate (6) and the cylindrical micro-perforated plate (7) is a first rear cavity (3), and a second rear cavity (4) is provided below the cylindrical micro-perforated plate (7).

2. The sound-absorbing metamaterial having a perforated oblique-cut aluminum foam composite micro-perforated plate according to claim 1, characterized in that: The shape of the gradual micro-perforation is a truncated cone, the thickness of the gradual micro-perforation plate (6) is 0.6-1 mm, the aperture of the gradual micro-perforation small diameter section is 0.5-0.8 mm, the aperture of the gradual micro-perforation large diameter section is 0.8-1.0 mm, the porosity of the upper surface of the gradual micro-perforation plate (6) is 0.36%-0.68%, and the porosity of the lower surface of the gradual micro-perforation plate (6) is 0.91%-1.07%; the thickness of the cylindrical micro-perforation plate (7) is 0.6-1.0 mm, the aperture of the cylindrical micro-perforation is 0.8-1.0 mm, and the perforation rate of the cylindrical micro-perforation plate (7) is 0.68%-0.77%.

3. The sound-absorbing metamaterial having a perforated oblique-cut aluminum foam composite micro-perforated plate according to claim 1, characterized in that: The depth of the first rear cavity (3) is 6 to 10 mm, and the depth D2 of the second rear cavity (4) is 6 to 10 mm.

4. The sound-absorbing metamaterial having a perforated oblique-cut aluminum foam composite micro-perforated plate according to claim 1, characterized in that: The diameter of the beveled aluminum foam (5) is 28-30 mm, the height is 20-30 mm, and the tangent value of the angle between the normal line of the beveled surface (5-1) and the axis line of the beveled aluminum foam (5) in the up-down direction is 18 / 29-22 / 29.

5. The sound-absorbing metamaterial having a perforated oblique-cut aluminum foam composite micro-perforated plate according to claim 1, characterized in that: The pore structure of the oblique cut aluminum foam (5) is uniform, and the flow resistance is 103254-145936 Pa·s / m 2 .

6. The sound-absorbing metamaterial having a perforated oblique-cut aluminum foam composite micro-perforated plate according to claim 1, characterized in that: The number of perforations (2) is 2 or 3, all perforations (2) are arranged in sequence along the long axis of the beveled surface (5-1), the bottom surfaces of all perforations (2) are flush, the cross-section of the perforations (2) is circular, the diameter of the perforations (2) is 4 to 6 mm, and the perforation depth is 15 to 25 mm.

7. A sound-absorbing metamaterial having a perforated oblique-cut aluminum foam composite micro-perforated plate according to any one of claims 1 to 6, characterized in that: The sound-absorbing metamaterial having a perforated oblique-cut aluminum foam composite micro-perforated plate has two perfect sound-absorbing peaks at 0 to 3000 Hz; The parameter determination process of the sound-absorbing metamaterial having a perforated oblique-cut aluminum foam composite micro-perforated plate comprises the following steps: S1, calculating the acoustic impedance of the gradient micro-perforated plate (6) according to preset structural parameters of the gradient micro-perforated plate (6); S2, calculating the acoustic impedance of the cylindrical micro-perforated plate (7) according to preset structural parameters of the cylindrical micro-perforated plate (7); S3, calculating the total acoustic impedance of the double-layer microperforated plate sound absorption structure consisting of the gradient microperforated plate (6) and the first rear cavity (3) and the cylindrical microperforated plate (7) and the second rear cavity (4) according to the acoustic impedance of the gradient microperforated plate (6) and the acoustic impedance of the cylindrical microperforated plate (7); S4, using the total acoustic impedance, verifying whether the sound-absorbing meta-structure material having the perforated oblique-cut aluminum foam composite micro-perforated plate has perfect sound absorption at the resonant frequency; S5, when perfect sound absorption exists, the preset structural parameters of the gradient micro-perforated plate (6), the preset structural parameters of the cylindrical micro-perforated plate (7), the depth of the first rear cavity (3) and the depth of the second rear cavity (4) are used as the final parameters; S6, if perfect sound absorption does not exist, adjust the preset structural parameters of the gradient micro-perforated plate (6), the preset structural parameters of the cylindrical micro-perforated plate (7), the depth of the first rear cavity (3) and the depth of the second rear cavity (4), and repeat S1 to S5.

8. The sound-absorbing metamaterial having a perforated oblique-cut aluminum foam composite micro-perforated plate according to claim 7, characterized in that: The preset structural parameters of the gradual micro-perforated plate (6) include: the aperture d1 of the gradual micro-perforated small diameter section, the aperture d2 of the gradual micro-perforated large diameter section, the thickness t of the gradual micro-perforated plate (6), the perforation rate p1 of the upper surface of the gradual micro-perforated plate (6), and the perforation rate p2 of the lower surface of the gradual micro-perforated plate (6); The process of calculating the acoustic impedance of the gradient micro-perforated plate (6) includes: dividing the gradient micro-perforated plate (6) into M equal parts along the height direction, and considering each part as a cylindrical hole with a thickness of t / M. Then, the acoustic impedance Z of the gradient micro-perforated plate (6) is 渐变型 as follows: WITH 渐变型 =r+jωm Among them, r is the relative acoustic resistance; m is the relative acoustic mass; from the linear relationship, we can know that the diameter of the i-th hole is Thickness t i =t / M, the perforation rate of the i-th hole is The perforation constant is X is the correction coefficient of the cross-sectional perforation constant; ρ0 represents the density of air; ω is the angular frequency of the incident sound wave; η is the dynamic viscosity of air; The preset structural parameters of the cylindrical micro-perforated plate (7) include: the hole diameter d of the cylindrical micro-perforations, the plate thickness T of the cylindrical micro-perforated plate (7) and the perforation rate ρ; The acoustic impedance Z in the hole of the cylindrical micro-perforated plate (7) 圆柱型 as follows: Where k is the perforation constant, K is the perforation correction factor; The total acoustic impedance of the double-layer micro-perforated plate sound absorption structure is as follows: Z Di =-jρ0ccot(ωDi / c),i=1,2 Among them, Z D1 is the acoustic impedance of the first rear cavity (3), the depth of the first rear cavity (3) is D1, and Z D2 is the acoustic impedance of the second rear cavity (4), the depth of the second rear cavity (4) is D2; c is the speed of sound; Verify that perfect sound absorption exists, including: when Re(Z 总 / Z0)=1,Im(Z 总 / Z0)=0, it indicates that there is perfect sound absorption. At this time, the sound absorption coefficient of the sound-absorbing metamaterial with perforated beveled aluminum foam composite micro-perforated plate is greater than or equal to 0.95; otherwise, there is no perfect sound absorption, wherein Z0 is the characteristic impedance of air.

9. A sound-absorbing metamaterial having a perforated oblique-cut aluminum foam composite micro-perforated plate according to any one of claims 1 to 6, characterized in that: The sound-absorbing superstructure material having the perforated oblique-cut aluminum foam composite micro-perforated plate has an average sound absorption coefficient of greater than or equal to 0.8 at 3000 to 6300 Hz; The parameter determination process of the sound-absorbing metamaterial having a perforated oblique-cut aluminum foam composite micro-perforated plate comprises the following steps: S1, based on the finite element method, a finite element model of the beveled aluminum foam is established according to preset parameters in the pressure acoustics module in the multi-physics field simulation software, the beveled aluminum foam is defined using the DB model in the porous medium acoustic model, and a plane wave with an amplitude of 1Pa is introduced to simulate the vertical incidence of the sound wave; S2, based on S1, a finite element model of the chamfered aluminum foam with perforations is established according to preset parameters, and the perforations are defined using a viscous acoustic module (2); S3, calculate the sound absorption coefficient of the beveled aluminum foam with perforations; S4, verify whether the sound absorption curve of the perforated beveled aluminum foam meets the average sound absorption coefficient at 3000-6300Hz S5, when the average sound absorption coefficient When the parameters of the sound-absorbing meta-structure material having the perforated oblique-cut aluminum foam composite micro-perforated plate are determined as the final parameters; S6, when the average sound absorption coefficient , then repeat S1 to S5.

10. The sound-absorbing metamaterial having a perforated oblique-cut aluminum foam composite micro-perforated plate according to claim 9, characterized in that: In S1, the preset parameters when establishing the finite element model of the beveled aluminum foam include: the thickness of the beveled aluminum foam and the tangent value of the bevel angle; In S2, the preset parameters for establishing the finite element model of the chamfered aluminum foam with perforations include: a perforation diameter and a perforation depth; In S3, the calculation process of the sound absorption coefficient of the oblique-cut aluminum foam with perforations includes: Surface acoustic impedance Z at the incident interface s And the sound pressure reflection coefficient R is as follows: Among them, p t It represents the average sound pressure when the sound is incident on the surface of the material; u represents the average normal vibration speed of the particles in the air when the sound is incident on the surface of the material; p r and p i denote the reflected sound pressure and the incident sound pressure respectively; The sound absorption coefficient α is as follows: α＝1-|R| 2 。

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