Multistage low-frequency sound absorption device and parameter value method thereof

Abstract

The application discloses a multistage low-frequency sound absorption device, which comprises a microporous plate, an intermediate layer and a back plate. The intermediate layer is arranged between the microporous plate and the back plate to form a cavity. The intermediate layer is provided with at least one cavity module. Each cavity module comprises a plurality of parallelly arranged cavities with multiple stages. The microporous plate is provided with a plurality of through holes which are respectively communicated with the cavities. Cavities of the same stage have the same cross-sectional area, and cavities of different stages have different cross-sectional areas. The cross-sectional area difference of the cavities causes a scale effect. The cavities have different resonance frequencies under the scale effect, and each cavity obtains low-frequency broadband excellent sound absorption through coherent coupling effect under under-damping. The multistage low-frequency sound absorption device has the characteristics of low working frequency, large working bandwidth and continuous sound absorption peak. The cavities of the multistage low-frequency sound absorption device are expanded in the plane direction, and the height direction size is not increased, so that the height is small and the mass is light. The application also provides a parameter value method of the multistage low-frequency sound absorption device.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sound absorption and noise reduction, in particular to a multi-stage low-frequency sound absorption device and a parameter value method thereof. BACKGROUND

[0002] With the continuous improvement of the operating speed of various vehicles in railway and highway transportation systems, noise, as one of the typical problems, has become a key factor affecting "environmental friendliness" and even restricting the development of rail transportation. Currently, various vehicles have adopted sound absorption devices to reduce the noise in the vehicle and improve the comfort of the driver and passengers.

[0003] Early sound absorption devices usually use sound-absorbing foam or fiber materials to reduce indoor noise and improve sound quality, but they have the problems of poor sound absorption performance in the medium and low frequency range and cannot withstand mechanical load. With the continuous progress of science and engineering, sound-absorbing metamaterials have been developed, and their fundamental concept is to design and build microstructures with special acoustic properties to achieve sound absorption performance beyond natural materials. These materials are usually composed of complex structural units, whose scale is much smaller than the wavelength of sound waves, so that sound waves propagate multiple reflections and interferences, eventually leading to efficient sound absorption.

[0004] Existing research mainly uses micro-perforated panel resonant sound absorption devices to enhance the structural sound quality by changing the geometric conditions of structural holes, cavities, etc. to achieve high sound absorption coefficient. However, in the low frequency range, the wavelength of sound waves is relatively long, and the traditional micro-perforated panel sound absorption device has a narrow working frequency band in the low frequency range, or there is a large absorption valley between the absorption peaks, which cannot achieve continuous and accurate absorption of sound waves in a wide frequency band.

[0005] A common technique is to combine several components with quasi-perfect sound absorption characteristics together to form a wideband sound absorption band, however, the absorption peak of such a combination is low, and these designs require sound absorption components to work perfectly at a specified frequency, which greatly limits the wideband sound absorption characteristics.

[0006] In summary, in actual engineering applications, due to limitations such as space size, processing and manufacturing technology, and manufacturing cost, existing sound absorption materials and structures often have difficulty in achieving low-frequency wideband sound absorption effect. At present, the problem of low-frequency wideband high-efficiency sound absorption is a prominent problem that researchers in the field of noise control are facing and need to solve urgently. SUMMARY

[0007] To solve the above technical problems, the purpose of the present application is to provide a multi-stage low-frequency sound absorption device with excellent low-frequency wideband sound absorption effect and a parameter value method thereof.

[0008] The technical solutions provided by the present application are as follows:

[0009] A multi-stage low-frequency sound absorption device, comprising a microporous plate, an intermediate layer and a back plate, the intermediate layer is sandwiched between the microporous plate and the back plate, the intermediate layer is provided with at least one cavity module, each cavity module comprises a plurality of parallelly arranged and multi-stage cavities, the microporous plate is provided with a plurality of through holes respectively communicating with each cavity, cavities of the same stage have the same cross-sectional area, and cavities of different stages have different cross-sectional areas.

[0010] Preferably, the intermediate layer comprises a plurality of cavity modules, and adjacent cavity modules are integrally spliced with each other.

[0011] Preferably, the material of the back plate is metal, rigid composite material or rigid polymer.

[0012] Preferably, the through holes of each stage structure have different perforation rates, but are uniformly distributed.

[0013] Preferably, the cavity module is formed by replacing four vertices of a square initial cavity structure with square structures with smaller side length, and the replacement number is the stage number i, thereby forming a plurality of Helmholtz resonance cavities with different resonance frequencies.

[0014] Preferably, the size of the through hole on the microporous plate matches the square cavity of different stage number, so as to obtain different stage Helmholtz resonance cavities with weak resonance effect, i.e. low sound absorption coefficient, and the sound absorption coefficients of these weak resonance cavities are distributed at different frequencies, and low-frequency continuous broadband sound absorption is realized through parallel connection by coherent coupling effect.

[0015] A parameter value method of the multi-stage low-frequency sound absorption device, comprising:

[0016] Step 1, obtaining a sound absorption coefficient related index of the multi-stage low-frequency sound absorption device;

[0017] Step 2, obtaining a sound absorption coefficient optimization target of the multi-stage low-frequency sound absorption device in a certain low-frequency frequency range;

[0018] Step 3, determining the side length l0 of the initial square cavity, the stage number i and the scale factor λ according to the expected low-frequency sound absorption frequency range i , i is a natural number greater than or equal to 2;

[0019] Step 4, selecting a sound impedance calculation method, constructing a sound resistance calculation model of each stage of the multi-stage low-frequency sound absorption device, and constructing a whole sound absorption coefficient calculation model of the multi-stage low-frequency sound absorption device;

[0020] Step 5, extracting the geometric parameters of the microporous plate which determine the sound absorption coefficient of each stage of the multi-stage low-frequency sound absorption device;

[0021] Step 6, determining the range of the geometric parameters of the micro-perforated panel when the acoustic resistance value is less than 1 according to the acoustic resistance calculation model of each level of the multi-level low-frequency sound absorption device, and determining the lower limit of the number and aperture of the through holes of the micro-perforated panel;

[0022] Step 7, setting the upper and lower limits of the optimized values of the thickness, the number of through holes and the aperture of the micro-perforated panel;

[0023] Step 8, selecting an optimization algorithm, setting the tolerance and the upper limit of iterations for the optimization algorithm solver;

[0024] Step 9, setting the objective function in the multi-objective optimization algorithm, wherein the objective function includes all the optimization objectives of the sound absorption coefficient;

[0025] Step 10, performing iterative calculation of the optimization algorithm to obtain the preset parameters of the micro-perforated panel of the multi-level low-frequency sound absorption device;

[0026] Step 11, verifying the sound absorption coefficient performance of the multi-level low-frequency sound absorption device under the preset parameters of the micro-perforated panel by using the sound absorption coefficient calculation model;

[0027] Step 12, determining whether the multi-level low-frequency sound absorption device meets the design target, if yes, outputting the preset parameter values and completing the parameter value determination of the multi-level low-frequency sound absorption device, if not, returning to Step 3 to adjust the side length l0 and the level i of the initial square cavity, and then performing Steps 4 to 11 again.

[0028] Preferably, in Step 3, the scale factor λ i is any value in the interval of 0.1 to 0.9.

[0029] Preferably, in Step 5, the geometric parameters of the upper micro-perforated panel of each level of the square cavity, i.e. the number of through holes and the aperture size, are determined by the real part Real(Z s ) of the impedance of each level structure, and Real(Z s ) < 1 at the resonant frequency of each level structure.

[0030] Preferably, in Step 10, the optimization algorithm is a brute-force search algorithm, a gradient-based optimization algorithm, an evolutionary algorithm or a local search algorithm.

[0031] The multistage low-frequency sound absorption device and the parameter value method thereof have the following advantages over the prior art: a plurality of parallelly arranged multistage chambers are arranged in the middle layer, chambers of the same stage have the same cross-sectional area, chambers of different stages have different cross-sectional areas, the cross-sectional areas of the chambers cause a scale effect, the chambers have different resonance frequencies under the scale effect, and each chamber obtains low-frequency wideband excellent sound absorption through coherent coupling effect under underdamping, and the sound absorption device has the characteristics of low working frequency, large working bandwidth and continuous sound absorption peak. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0033] Figure 1 It is a structural schematic diagram of the multistage low-frequency sound absorption device of the embodiment of the present application.

[0034] Figure 2 It is a structural schematic diagram of the multistage low-frequency sound absorption device of the embodiment of the present application. Figure 1 It is a structural schematic diagram of a chamber module in the multistage low-frequency sound absorption device shown in the figure.

[0035] Figure 3 It is a structural schematic diagram of a chamber module in the multistage low-frequency sound absorption device shown in the figure. Figure 2 It is a structural schematic diagram of a chamber module in the multistage low-frequency sound absorption device shown in the figure.

[0036] Figure 4 It is a structural schematic diagram of a chamber module in the multistage low-frequency sound absorption device shown in the figure. Figure 3 It is a structural schematic diagram of a chamber module in the multistage low-frequency sound absorption device shown in the figure.

[0037] Figure 5 It is a structural schematic diagram of a chamber module in the multistage low-frequency sound absorption device shown in the figure. DETAILED DESCRIPTION

[0038] In order to make those skilled in the art better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0039] It should be noted that when an element is referred to as being "fixed" or "set" on another element, it can be directly on the other element or indirectly set on the other element; when an element is referred to as being "connected" to another element, it can be directly connected to the other element or indirectly connected to the other element.

[0040] It should be understood that the terms "length", "width", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0041] In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" or "several" is two or more, unless otherwise explicitly specified.

[0042] It should be understood that the structure, proportion, size, etc. shown in the drawings of the present application are only used to cooperate with the content disclosed in the description, so that those skilled in the art can understand and read, and are not used to limit the implementation conditions of the present application, and therefore do not have technical significance. Any modification of the structure, change of the proportion relationship or adjustment of the size, without affecting the effect and purpose that can be achieved by the present application, should still fall within the scope of the technical content disclosed by the present application.

[0043] As shown in Figures 1 to 4 , the embodiment of the present application provides a multi-stage low-frequency sound absorption device, which comprises a microporous plate 1, an intermediate layer 2 and a back plate 3. The intermediate layer 2 is arranged between the microporous plate 1 and the back plate 3, and the intermediate layer 2 is provided with at least one cavity module (such as Figure 1 There are 6 cavity modules, and adjacent cavity modules are spliced into one body). Each cavity module comprises a plurality of parallelly arranged and multi-stage cavities, cavities of the same stage have the same cross-sectional area, and cavities of different stages have different cross-sectional areas, and the microporous plate is provided with a plurality of through holes respectively communicating with the cavities.

[0044] In the embodiment, the cavity module is formed by replacing the four vertices of the square initial cavity structure with square structures with smaller side lengths, and the number of replacements is the number of stages i (the number of stages in the embodiment is 2), to form a plurality of Helmholtz resonance cavities with different resonance frequencies. As Figure 2 , Figure 3As shown in the embodiment, the expansion number is 2, and each chamber module forms unit I 21, unit II 22, and unit III 23.

[0045] The micro-hole plate 1 has a uniform thickness, and the through holes 11 of the micro-hole plate 1 are distributed above each chamber. The number and aperture of the through holes of the micro-hole plate are different under different levels of chambers. The size of the through holes on the micro-hole plate matches the square chambers of different levels to obtain different levels of Helmholtz resonators with weak resonance effect, i.e., low sound absorption coefficient. The sound absorption coefficients of the weak resonators are distributed at different frequencies, and low-frequency continuous broadband sound absorption is realized through coherent coupling effect in parallel.

[0046] In the embodiment, the main technical features of the intermediate layer are described as follows.

[0047] (1) The side length l0 of the initial square chamber determines the size of the expandable level i of the square chamber. When the side length l0 is large enough, the square chamber can be expanded infinitely.

[0048] (2) The expansion level i of the square chamber is determined according to the actual low-frequency sound absorption range. In order to realize low-frequency broadband sound absorption in the low-frequency range of 100 Hz to 1000 Hz, the expansion level i is required to be ∈ [2, +∞), that is, at least two absorption peaks are coupled in parallel.

[0049] (3) Scale factor λ i The size of the new level square chamber at the vertex of the square chamber is controlled by the scale factor λ i , and the side length l i of the new level square chamber can be calculated from the scale factor λ

[0050]

[0051] (4) The cross-sectional area of each level of the square chamber is different, and the cross-sectional area is controlled by the scale factor λ i . Under the expandable design, the cross-sectional area of each level of the square chamber is different, and the cross-sectional area of each level of the square chamber is different.

[0052] (5) The number and aperture of the through holes of the upper micro-hole plate of each level of the square chamber are different, and the number and aperture of the through holes exist within a reasonable range to make the perforation rate of each level structure different and uniformly distributed.

[0053] (6) The number of through holes of the upper micro-hole plate of each level of the square chamber is at least 1, and the aperture size needs to be smaller than the side length of the square chamber of the level;

[0054] (7) The number and aperture of the through holes of the upper micro-hole plate of each level of the square chamber are determined by the real part Real(Z sdetermining Real(Z s )<1 to ensure that the sound resistance of each stage structure is low, and there is a weak absorption peak.

[0055] The back plate 3 has a planar size consistent with the intermediate layer and is connected to the intermediate layer. The back plate has a uniform thickness and is made of a rigid material such as metal, rigid composite material, or rigid polymer, and cannot be made of a soft material such as natural fiber, rubber, or sponge.

[0056] As shown in Figure 5 , the embodiment also provides a parameter value method of the multi-stage low-frequency sound absorption device as described above, comprising:

[0057] Step 1: obtaining sound absorption coefficient related indexes of the multi-stage low-frequency sound absorption device, such as the number of sound absorption coefficients greater than 0.5 and greater than 0.9 in 50-1000 Hz under a thickness of not more than 50 mm being the maximum;

[0058] Step 2: obtaining a sound absorption coefficient optimization target of the multi-stage low-frequency sound absorption device in a certain low-frequency frequency range;

[0059] Step 3: determining the side length l0 of the initial square cavity, the stage number i, and the scale factor λ i , i being a natural number greater than or equal to 2;

[0060] Step 4: selecting a sound impedance calculation method, constructing a sound resistance calculation model of each stage of the multi-stage low-frequency sound absorption device, and constructing a whole sound absorption coefficient calculation model of the multi-stage low-frequency sound absorption device;

[0061] Step 5: extracting the micro-hole plate geometric parameters that determine the sound absorption coefficient of each stage of the multi-stage low-frequency sound absorption device;

[0062] Step 6: determining the micro-hole plate geometric parameter range when the sound resistance value is less than 1 according to the sound resistance calculation model of each stage of the multi-stage low-frequency sound absorption device, and determining the lower limit of the value of the number of through holes and the aperture of the micro-hole plate;

[0063] Step 7: setting the optimization value upper and lower limits of the thickness, the number of through holes, and the aperture of the micro-hole plate;

[0064] Step 8: selecting an optimization algorithm, performing optimization algorithm solver setting, setting the tolerance and the upper limit of iteration;

[0065] Step 9: setting a target function in the multi-objective optimization algorithm, the target function including all optimization targets of the sound absorption coefficient;

[0066] Step 10: implementing iterative calculation of the optimization algorithm to obtain the preset parameters of the micro-hole plate of the multi-stage low-frequency sound absorption device;

[0067] Step 11, the sound absorption coefficient of the multi-stage low-frequency sound absorption device under the preset parameters of the microwell plate is verified by using a sound absorption coefficient calculation model;

[0068] Step 12, whether the multi-stage low-frequency sound absorption device meets the design target is judged, if yes, the pre-design parameter value is output, and the parameter value of the multi-stage low-frequency sound absorption device is completed; if not, return to step 3, adjust the side length l0 of the initial square chamber and the number i, and then perform steps 4 to 11 again.

[0069] In step 3, the scale factor λ i Any value in the interval of 0.1-0.9 can be taken.

[0070] In step 10, the optimization algorithm can be a brute force search algorithm, a gradient-based optimization algorithm, an evolutionary algorithm or a local search algorithm. In this embodiment, the optimization algorithm is specifically a NSGA-II genetic algorithm.

[0071] Compared with the prior art, the embodiment provides a multi-stage scalable low-frequency sound absorption device and an efficient design method. In this embodiment, the structure is designed by multi-stage iteration at the four vertices of the square, and square chambers with different areas are constructed. The difference in the areas of the square chambers of different stages is large, and the corresponding micro-hole plate geometric parameters are different, so that the perforation rate is uniformly and monotonously arranged, and the square Helmholtz resonance units of different stages have different sound absorption coefficients. Through the scalable design of the square chamber, new square Helmholtz resonance units can be continuously constructed, so that the weak sound absorption peaks in the low frequency can be continuously increased. The weak sound absorption peaks have a coherent coupling effect under parallel coupling, and together form a low-frequency broadband continuous sound absorption of the overall sound absorption device. The parallel coupling of the weak sound absorption peaks ensures the uniformity and robustness of the peak distribution of the sound absorption coefficient of the overall sound absorption device, and the absorption trough of the traditional material is not easy to appear.

[0072] In combination with the above technical features, the embodiment ingeniously constructs weak resonance Helmholtz units with different resonance frequencies through self-similar iteration of the square vertices, and then realizes low-frequency broadband continuous sound absorption of the overall structure through the coherent coupling effect of the Helmholtz units, and greatly weakens the anti-resonance effect that is prone to occur in traditional system structures. The overall sound absorption coefficient of the sound absorption device has no significant absorption trough. The structure of the invention is simple and very low in cost, and can be densely laid in all parts where low-frequency noise problems need to be solved, such as high-speed rail, urban rail, subway and ship cabin interiors.

[0073] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and that the appended claims are intended to cover all such modifications that do not depart from the true spirit and scope of the application. Therefore, the application is not limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A multi-stage low-frequency sound absorbing device, characterized in that: The invention comprises a microporous plate, an intermediate layer and a back plate, wherein the intermediate layer is sandwiched between the microporous plate and the back plate, and the intermediate layer is provided with at least one chamber module, each of the chamber modules comprises a plurality of chambers arranged in parallel and having multiple levels, the microporous plate is provided with a plurality of through holes respectively communicating with the chambers, chambers of the same level have the same cross-sectional area, and chambers of different levels have different cross-sectional areas; the chamber module is a square initial chamber structure, in which the four vertices of the square are replaced with square structures with smaller side lengths, and the number of replacements is the number of levels, thereby forming a plurality of Helmholtz resonance chambers with different resonance frequencies; the size of the through holes on the microporous plate matches the square chambers of different levels, so as to obtain different levels of Helmholtz resonance cavities with weaker resonance effects, i.e., lower sound absorption coefficients, the sound absorption coefficients of these weak resonance cavities are distributed at different frequencies, and low-frequency continuous broadband sound absorption is achieved after being connected in parallel through the coherent coupling effect.

2. The multi-stage low-frequency sound absorbing device according to claim 1, characterized in that: The middle layer includes a plurality of chamber modules, and adjacent chamber modules are spliced ​​together into one.

3. The multi-stage low-frequency sound absorbing device according to claim 1, characterized in that: The back plate is made of metal, rigid composite material or rigid polymer.

4. The multi-stage low-frequency sound absorbing device according to claim 1, characterized in that: The through-hole perforation rates on the microplate matched with each level of square chamber are different, but are evenly distributed.

5. The parameter determination method of the multi-stage low-frequency sound absorbing device according to claim 1, characterized in that: include: Step 1: Obtain relevant indicators of the sound absorption coefficient of the multi-stage low-frequency sound absorption device; Step 2: obtaining an optimization target of the sound absorption coefficient of the multi-stage low-frequency sound absorbing device within a certain low-frequency range; Step 3: Determine the side length l0, the number of stages i, and the scale factor λ of the initial square chamber according to the expected low-frequency sound absorption frequency range. i , i is a natural number greater than or equal to 2; Step 4: Select an acoustic impedance calculation method, construct an acoustic impedance calculation model for each stage of the multi-stage low-frequency sound absorbing device, and construct an overall sound absorption coefficient calculation model for the multi-stage low-frequency sound absorbing device; Step 5, extracting the geometric parameters of the microporous plate that determine the sound absorption coefficient of each stage of the multi-stage low-frequency sound absorbing device; Step 6: Determine the range of geometric parameters of the microporous plate when the acoustic resistance value is less than 1 based on the acoustic resistance calculation model of each stage of the multi-stage low-frequency sound absorbing device, and determine the lower limits of the number of through holes and the aperture of the microporous plate; Step 7, setting the upper and lower limits of the optimized values ​​of the microplate thickness, number of through holes and pore diameter; Step 8: Select the optimization algorithm, set the optimization algorithm solver, and set the tolerance and iteration limit; Step 9, setting an objective function in a multi-objective optimization algorithm, wherein the objective function includes all optimization objectives of the sound absorption coefficient; Step 10, performing iterative calculations using an optimization algorithm to obtain preset parameters of the microporous plate of the multi-stage low-frequency sound absorbing device; Step 11, using the sound absorption coefficient calculation model to verify the sound absorption coefficient performance of the multi-stage low-frequency sound absorption device under the preset parameters of the microporous plate; Step 12 determines whether the multi-stage low-frequency sound absorbing device meets the design objectives. If so, the preset parameter values ​​are output, completing the parameter setting for the multi-stage low-frequency sound absorbing device. If not, the process returns to step 3, adjusts the side length l0 of the initial square chamber and the number of stages i, and repeats steps 4 to 11.

6. The parameter determination method of the multi-stage low-frequency sound absorbing device according to claim 5, characterized in that: In step 3, the scale factor λ i Take any value in the range of 0.1~0.

9.

7. The parameter determination method of the multi-stage low-frequency sound absorbing device according to claim 5, characterized in that: In step 5, the geometric parameters of the upper microporous plate of each level of the square chamber, namely the number of through holes and the size of the aperture, are the real part of the impedance of each level structure (Real(Z s ) Determine the Real(Z s )<1.

8. The parameter determination method of the multi-stage low-frequency sound absorbing device according to claim 5, characterized in that: In step 10, the optimization algorithm is a brute force search algorithm, a gradient-based optimization algorithm, an evolutionary algorithm, or a local search algorithm.

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