Open noise-reducing acoustic metamaterial structure and acoustic barrier

Abstract

The utility model discloses an open noise reduction formula acoustic metamaterial structure, this open noise reduction formula acoustic metamaterial structure includes noise reduction unit and sound absorption unit, noise reduction unit and sound absorption unit are hollow cylinder, noise reduction unit is set on sound absorption unit, noise reduction unit includes a plurality of sub -units of lamination, be provided with the pipe cavity in each sub -unit, the opening of pipe cavity is located and is close to the one side of sound absorption unit of noise reduction unit, sound absorption unit is porous material. The utility model discloses a sound barrier. The utility model discloses through hollow structure of setting makes open noise reduction formula acoustic metamaterial structure in the process of noise reduction and has the ventilation function simultaneously, utilizes a plurality of sub -units resonance sound absorption and the coupling noise reduction between the hollow structure construction continuum of discrete state and the middle of sound wave in the process of propagation simultaneously, does not influence even improve the structure noise reduction performance, and the influence that the wind pressure of train brings simultaneously is greatly reduced greatly.

Description

Technical Field

[0001] This utility model relates to the fields of acoustic engineering, materials science and noise control engineering technology, and in particular to an open noise-reducing acoustic metamaterial structure and sound barrier. Background Technology

[0002] High-speed rail has experienced rapid and sustained development in my country in recent years due to its advantages such as safety, reliability, high speed, large transport capacity, and low energy consumption. In Sichuan Province alone, the operational mileage of high-speed rail reached 1705 km by the end of 2022, and is projected to reach 3000 km by 2035. High-speed rail plays a crucial role in improving the quality of residents' travel, promoting the sustained and coordinated development of the economy and society, and optimizing the layout of productive forces. However, the environmental noise induced by high-speed rail seriously affects the physical and mental health of residents along the lines, and also hinders the healthy and sustainable development of high-speed rail. High-speed rail noise pollution has become a pressing issue for the industry. In particular, the formal implementation of the "Noise Pollution Prevention and Control Law of the People's Republic of China" in 2022 and the formal promulgation of the "14th Five-Year Plan Action Plan for Noise Pollution Prevention and Control" jointly issued by multiple departments have elevated the prevention and control of high-speed rail noise to an unprecedented level.

[0003] To reduce the impact of high-speed railways on noise-sensitive targets along the line, sound barriers are typically installed when high-speed railways pass through sensitive sections. Sound barriers are the most widely used noise reduction infrastructure in high-speed railways both domestically and internationally. The basic idea is to dissipate sound wave energy or change the sound wave propagation path to achieve noise reduction. In my country, sound barriers have been installed at large noise-sensitive targets within 80 meters of the outer centerline of high-speed railway lines. Statistics from the installation of sound barriers on several completed high-speed railways show that the average length of sound barriers is approximately 17% of the line length, with the main structural form being the insert-type vertical sound barrier. Existing research indicates that existing vertical sound barriers have low insertion loss values ​​below 315Hz, resulting in negligible noise reduction effects. In some low-frequency bands, they even exhibit negative insertion loss values ​​due to coincident resonance. Low-frequency noise travels long distances and is highly bothersome, often leading to complaints. In high-frequency bands, sound leakage occurs due to sound wave diffraction at the top of the sound barrier. Overall, the average noise reduction effect of sound barriers is approximately 6dB(A), which is insufficient for sections with higher noise reduction requirements, leading to numerous noise complaints in areas where sound barriers are installed. Therefore, it is necessary to conduct research on high-speed railway sound barriers with low noise reduction starting frequencies and wide noise reduction bandwidths with significant amplitude.

[0004] Traditional sound barrier panels are primarily flat, perforated plates, with some having tiny openings, offering negligible ventilation and load reduction capabilities. Trains passing over these barriers exert significant wind pressure, and as train speed increases, the air pressure on the barrier surface undergoes abrupt changes, exhibiting pulsating characteristics with consecutive positive and negative pressure peaks, leading to resonance. The steel columns primarily vibrate laterally, exhibiting typical bending member characteristics, while the unit panels primarily move in a reciprocating lateral motion, with amplitude significantly affected by installation conditions. These vibrations can cause fatigue failure of sound barrier components and loosening of bolts at connection points, amplifying environmental noise and, in severe cases, threatening train safety. For existing sound barriers, ventilation performance becomes a challenge. When trains travel at high speeds, pulsating air pressure is generated by disturbances in the surrounding air. Under this force, the sound barriers on both sides of the railway experience strong compressive and suction loads. Therefore, the design of sound barriers must consider the dynamic response of the structure, ensuring both structural safety and smooth train operation. Thus, the poor ventilation performance of existing high-speed railway sound barriers urgently needs to be addressed.

[0005] The above content is only used to help understand the technical solution of this utility model and does not represent an admission that the above content is prior art. Utility Model Content

[0006] The main purpose of this utility model is to solve the technical problem of insufficient ventilation performance of existing high-speed railway sound barriers.

[0007] Firstly, to achieve the above objectives, this utility model provides an open noise-reducing acoustic metamaterial structure, which includes a noise-reducing unit and a sound-absorbing unit. The noise-reducing unit and the sound-absorbing unit are hollow cylinders. The noise-reducing unit is sleeved on the sound-absorbing unit. The noise-reducing unit includes multiple stacked sub-units. Each sub-unit has a cavity. The opening of the cavity is located on the side of the noise-reducing unit close to the sound-absorbing unit. The sound-absorbing unit is a porous material.

[0008] In one embodiment, the subunit is provided with multiple baffles.

[0009] In one embodiment, the number of baffles in the subunit is one less than the number of layers in the subunit where the cavity is located.

[0010] In one embodiment, the distance between any two adjacent baffles within the sub-unit is different.

[0011] In one embodiment, the location of the lumen opening of each of the sub-units is different.

[0012] In one embodiment, the open noise-reducing acoustic metamaterial structure further includes a fixing unit, wherein the noise-reducing unit is embedded in the fixing unit.

[0013] In a second aspect, the present invention also provides a sound barrier, the sound barrier comprising a plurality of open noise-reducing acoustic metamaterial structures, the open noise-reducing acoustic metamaterial structures being as described in any one of the first aspects.

[0014] In this invention, by setting a hollow structure in the open noise-reducing acoustic metamaterial structure, the open noise-reducing acoustic metamaterial structure can also have a ventilation function during the noise reduction process. At the same time, by utilizing the resonant sound absorption of each cavity (i.e., multiple intervals of the open noise-reducing acoustic metamaterial structure) and the coupling noise reduction between the discrete state of the sound wave during propagation and the continuous state constructed by the hollow structure, the noise reduction performance of the structure is not affected or even improved. This solves the problems of noise that cannot be reduced due to excessive wind pressure from trains and the easy loosening of sound barrier parts made of acoustic metamaterial structure. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of an open noise-reducing acoustic metamaterial structure in one embodiment of the present invention;

[0017] Figure 2 This is a top view schematic diagram of the noise reduction unit in an open noise reduction acoustic metamaterial structure according to one embodiment of the present invention;

[0018] Figure 3 This is a schematic diagram of the internal structure of the noise reduction unit in an open noise reduction acoustic metamaterial structure according to an embodiment of the present invention;

[0019] Figure 4 This is a detailed schematic diagram of the sound-absorbing unit in an open noise-reducing acoustic metamaterial structure according to one embodiment of the present invention;

[0020] Figure 5 This is a front view schematic diagram of a sound barrier according to one embodiment of the present invention;

[0021] Figure 6 This is a top view of a sound barrier according to one embodiment of the present invention;

[0022] Figure 7 This is a left-side view of a sound barrier in one embodiment of the present invention;

[0023] Figure 8 This is a schematic diagram of a simulation model of an open noise-reducing acoustic metamaterial structure in one embodiment of this utility model;

[0024] Figure 9 This is a schematic diagram of sound wave propagation in a simulation model of an open noise-reducing acoustic metamaterial structure according to an embodiment of the present invention;

[0025] Figure 10 This is a cross-sectional schematic diagram of multiple sound-absorbing units with varying thicknesses in one embodiment of the present invention;

[0026] Figure 11 This is a comparison diagram of sound transmission loss between the noise reduction unit and the addition of a sound absorption unit in one embodiment of this utility model;

[0027] Figure 12 This is a schematic diagram comparing the sound transmission loss curves of multiple thickness sound-absorbing units at the macroscopic level in one embodiment of this utility model.

[0028] Figure 13 This is a schematic diagram comparing the sound transmission loss curves of multiple porosity sound-absorbing units at the microscopic level in one embodiment of this utility model.

[0029] Figure 14 This is a schematic diagram comparing the sound transmission loss curves of sound-absorbing units with multiple fiber diameters at the microscopic level in one embodiment of the present invention.

[0030] Figure 15 This is a schematic diagram showing the characteristic modes (sound pressure level, sound power, sound pressure) of sound waves passing through a noise reduction unit without sound absorption units at various frequencies in one embodiment of the present invention.

[0031] Figure 16 This is a schematic diagram of the acoustic metasurface parameter design of the noise reduction unit in one embodiment of the present invention;

[0032] Figure 17 This is a schematic diagram of the deep learning model process in one embodiment of the present invention;

[0033] Figure 18 This invention serves as a verification of the structural fitness curve, evolution rate curve, and finite element method (FE) calculation results of particle swarm optimization-deep neural network (PSO-DNN) in one embodiment of the present invention.

[0034] Figure 19 The present invention includes the sound transmission loss curve of a train sound barrier model in one embodiment of the present invention, as well as the sound radiation mode diagrams of the sound barrier, the two-dimensional cross-sectional diagram of the sound energy distribution at the maximum noise reduction frequency, and the acoustic equipotential surface diagram of the sound barrier under the four sound propagation modes.

[0035] Figure 20 This is a comparison chart of the sound transmission loss results of the train-track-sound barrier coupling model in a laboratory test and simulation calculation in one embodiment of this utility model;

[0036] Figure 21 This is a schematic diagram illustrating the application of a sound barrier in one embodiment of the present invention;

[0037] Figure 22 This is a schematic diagram comparing the sound transmission loss of the sound barrier of this application and an existing sound barrier in one embodiment of the present invention;

[0038] Figure 23 This is a schematic diagram of the sound field distribution of the sound barrier at various frequencies in one embodiment of the present invention, and a partial enlarged view of the sound field distribution of the core noise reduction unit at each frequency.

[0039] Figure 24 This is a schematic diagram of the design method of an open noise-reducing acoustic metamaterial structure in one embodiment of the present invention;

[0040] Figure 25 This is a schematic diagram of the design method of an open noise-reducing acoustic metamaterial structure in one embodiment of the present invention;

[0041] Figure 26 This is a schematic diagram of the design method of an open noise-reducing acoustic metamaterial structure in one embodiment of the present invention;

[0042] Figure 27 This is a schematic diagram of the design method of an open noise-reducing acoustic metamaterial structure in one embodiment of the present invention;

[0043] Component symbols in the diagram:

[0044] 1. Noise reduction unit; 2. Sound absorption unit; 3. Fixing unit; 4. Pores; 5. Aggregate. Detailed Implementation

[0045] To better understand the above technical solutions, exemplary embodiments of this disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art.

[0046] It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0047] It should be noted that, in the embodiments of this utility model, the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the coordinate system shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0048] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0049] In this utility model, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0050] This utility model provides an open noise-reducing acoustic metamaterial structure, referring to... Figures 1-4 In one embodiment, the open noise-reducing acoustic metamaterial structure includes: a noise-reducing unit 1 and a sound-absorbing unit 2, wherein the noise-reducing unit 1 and the sound-absorbing unit 2 are hollow cylinders, the noise-reducing unit 1 is sleeved on the sound-absorbing unit 2, the noise-reducing unit 1 includes multiple stacked sub-units, each sub-unit having a cavity, the opening of the cavity being located on the side of the noise-reducing unit 1 near the sound-absorbing unit 2, and the sound-absorbing unit 2 being a porous material.

[0051] It is important to note that when sound waves pass through a medium with a periodic structure, phonons at certain frequencies will form band gaps or band barriers in the structure, preventing phonons from propagating at those frequencies. This will result in the sound wave energy being confined within the medium, with the discrete state and the periodic structure coupling with each other.

[0052] In acoustics, discrete states typically refer to phonon energy levels in a medium with a periodic structure, while continuous states constructed with hollow structures refer to the propagation state of sound waves in a continuous medium. In this embodiment, the noise reduction unit 1 is made of polyvinyl chloride, and the sound absorption unit 2 is made of melamine sponge. Different materials can be selected as needed.

[0053] Specifically, after the sound waves enter the metamaterial structure, part of the sound waves enter the interior of the acoustic metamaterial (noise reduction unit 1), while the other part passes directly through the hollow tube. At this time, the two will undergo Fano resonance.

[0054] In this embodiment, a hollow structure is incorporated into the open noise-reducing acoustic metamaterial structure, enabling it to function as a ventilation system during noise reduction. Simultaneously, the resonance absorption of each cavity (i.e., multiple sub-units of the open noise-reducing acoustic metamaterial structure) and the coupling noise reduction between the discrete state and the continuous state constructed by the hollow structure in the middle during sound wave propagation are utilized. This approach does not affect, and may even improve, the structure's noise reduction performance while significantly reducing the problem of excessive wind pressure from trains causing unavoidable noise reduction and the issue of sound barrier components made of the open noise-reducing acoustic metamaterial structure being prone to loosening.

[0055] In one embodiment, reference Figure 3 and Figure 16 The subunit is provided with multiple baffles.

[0056] The baffle is made of the same material as the noise reduction unit 1, and the height of the baffle is less than the height of the cavity in the subunit.

[0057] Specifically, the open noise-reducing acoustic metamaterial structure includes: a noise-reducing unit 1 and a sound-absorbing unit 2. The noise-reducing unit 1 and the sound-absorbing unit 2 are hollow cylinders. The noise-reducing unit 1 is sleeved on the sound-absorbing unit 2. The noise-reducing unit 1 includes multiple stacked sub-units. Each sub-unit has a cavity. The opening of the cavity is located on the side of the noise-reducing unit 1 near the sound-absorbing unit 2. Multiple baffles are provided in the sub-unit. The sound-absorbing unit 2 is a porous material.

[0058] In this embodiment, by setting multiple baffles in the sub-unit, the sound waves are made to propagate in the expected manner and direction, causing multiple refractions and attenuations of the sound waves, thereby improving the noise reduction effect of the open noise-reducing acoustic metamaterial structure.

[0059] In one embodiment, reference Figure 3 and Figure 16 The number of baffles in each of the sub-units is different.

[0060] Specifically, the open noise-reducing acoustic metamaterial structure includes: a noise-reducing unit 1 and a sound-absorbing unit 2. The noise-reducing unit 1 and the sound-absorbing unit 2 are hollow cylinders. The noise-reducing unit 1 is sleeved on the sound-absorbing unit 2. The noise-reducing unit 1 includes multiple stacked sub-units. Each sub-unit has a cavity. The opening of the cavity is located on the side of the noise-reducing unit 1 near the sound-absorbing unit 2. Each sub-unit has multiple baffles. The number of baffles in each sub-unit is different. The sound-absorbing unit 2 is a porous material.

[0061] In this embodiment, by setting the number of baffles in each subunit, a better sound absorption effect can be achieved in different frequency ranges, and sound waves of different modes can be absorbed and eliminated, thus achieving multi-level isolation of noise.

[0062] In one embodiment, reference Figure 3 and Figure 16 The number of baffles in the subunit is one less than the number of layers in the subunit where the cavity is located.

[0063] Among them, reference Figure 3 The stacked sub-units of the open noise-reducing acoustic metamaterial structure are arranged from top to bottom as 1st, 2nd, 3rd, 4th and 5th order. The number of baffles in the 1st order is 0, the number of baffles in the 2nd order is 1, the number of baffles in the 3rd order is 2, the number of baffles in the 4th order is 3, and the number of baffles in the 5th order is 4.

[0064] Specifically, the open noise-reducing acoustic metamaterial structure includes: a noise-reducing unit 1 and a sound-absorbing unit 2. The noise-reducing unit 1 and the sound-absorbing unit 2 are hollow cylinders. The noise-reducing unit 1 is sleeved on the sound-absorbing unit 2. The noise-reducing unit 1 includes multiple stacked sub-units. Each sub-unit has a cavity. The opening of the cavity is located on the side of the noise-reducing unit 1 near the sound-absorbing unit 2. Multiple baffles are provided in the sub-unit. The number of baffles in the sub-unit is one less than the number of layers in the sub-unit where the cavity is located. The sound-absorbing unit 2 is a porous material.

[0065] In this embodiment, the design of each sub-unit is regular, and the sound absorption performance in a specific frequency range can be adjusted as needed. The design regularity in this embodiment enables the open noise-reducing acoustic metamaterial structure to have excellent noise reduction effect in a wide frequency band of 300Hz-4000Hz.

[0066] In one embodiment, reference Figure 3 and Figure 16 The distance between any two adjacent baffles within the subunit is different.

[0067] Specifically, the open noise-reducing acoustic metamaterial structure includes: a noise-reducing unit 1 and a sound-absorbing unit 2. The noise-reducing unit 1 and the sound-absorbing unit 2 are hollow cylinders. The noise-reducing unit 1 is sleeved on the sound-absorbing unit 2. The noise-reducing unit 1 includes multiple stacked sub-units. Each sub-unit has a cavity. The opening of the cavity is located on the side of the noise-reducing unit 1 near the sound-absorbing unit 2. Multiple baffles are provided in each sub-unit. The distance between each pair of adjacent baffles in the sub-unit is different. The sound-absorbing unit 2 is a porous material.

[0068] In this embodiment, the different distances between the baffles cause sound waves of different frequencies to resonate at different levels, thereby providing a wider frequency response range, achieving a better frequency-selective sound absorption effect, realizing the absorption of multiple sound wave modes, thereby improving the metamaterial's adaptability to complex sound fields, increasing the dispersion of sound wave propagation paths, resulting in the dissipation and attenuation of sound wave energy, and helping to improve the damping effect of the sound-absorbing material.

[0069] In one embodiment, reference Figure 3 and Figure 16 The location of the lumen opening is different for each of the sub-units.

[0070] The opening of the fourth sub-unit is close to the fifth sub-unit, while the openings of the other units are close to the previous unit. The specific position of the lumen opening of each sub-unit can be set according to the requirements.

[0071] Specifically, the open noise-reducing acoustic metamaterial structure includes: a noise-reducing unit 1 and a sound-absorbing unit 2. The noise-reducing unit 1 and the sound-absorbing unit 2 are hollow cylinders. The noise-reducing unit 1 is sleeved on the sound-absorbing unit 2. The noise-reducing unit 1 includes multiple stacked sub-units. Each sub-unit has a cavity. The opening of the cavity is located on the side of the noise-reducing unit 1 near the sound-absorbing unit 2. The opening position of the cavity of each sub-unit is different. The sound-absorbing unit 2 is a porous material.

[0072] In one embodiment, reference Figure 1 The open noise-reducing acoustic metamaterial structure also includes a fixed unit 3, in which the noise-reducing unit 1 is embedded.

[0073] Among them, the fixing unit 3 can be made of aluminum alloy plate. Aluminum alloy plate has the advantages of being lightweight, corrosion resistant, highly malleable, strong and easy to maintain. It is also convenient to process and install, and is suitable for long-term use in outdoor environments.

[0074] Specifically, the open noise-reducing acoustic metamaterial structure includes: a noise-reducing unit 1, a sound-absorbing unit 2, and a fixing unit 3. The noise-reducing unit 1 is embedded in the fixing unit 3. The noise-reducing unit 1 and the sound-absorbing unit 2 are hollow cylinders. The noise-reducing unit 1 is sleeved on the sound-absorbing unit 2. The noise-reducing unit 1 includes multiple stacked sub-units. Each sub-unit has a cavity. The opening of the cavity is located on the side of the noise-reducing unit 1 near the sound-absorbing unit 2. The sound-absorbing unit 2 is a porous material.

[0075] In this embodiment, the fixing unit 3 fixes the noise reduction unit 1 of the open noise reduction acoustic metamaterial structure according to requirements (e.g., a specific angle), and the material properties used by the fixing unit 3 can also make the effect of the open noise reduction acoustic metamaterial structure better.

[0076] In one embodiment, reference Figure 1 The noise reduction unit 1 has an outer ring radius of 10cm, an inner ring radius of 5cm, and a height of 12cm. The fixed unit 3 has a side length of 10cm, and the radius of the inscribed circle of the fixed unit 3 is the same as the outer ring radius of the noise reduction unit 1, which is 10cm. The fixed unit 3 has a thickness of 4cm.

[0077] In this embodiment, the open noise-reducing acoustic metamaterial structure is thin, lightweight, has good ventilation performance, and excellent noise reduction performance.

[0078] In one embodiment, reference Figure 3 and Figure 16 The cavity opening of each subunit of the noise reduction unit 1 is located near the next subunit, and the cavity opening is smaller than the height of the subunit.

[0079] In one embodiment, reference Figure 3 and Figure 16 Except for the fourth subunit of the noise reduction unit 1, the cavity opening of each subunit is located near the next subunit, and the cavity opening is smaller than the height of the subunit.

[0080] This invention provides a design method for an open noise-reducing acoustic metamaterial structure, such as... Figure 24 As shown, the design method includes:

[0081] S1100, based on the size requirements of the sound barrier design, yielded the first acoustic metamaterial structure;

[0082] Specifically, by performing parametric scanning in COMSOL software and combining it with the size requirements of the sound barrier design, the first acoustic metamaterial structure was preliminarily designed.

[0083] S1200, by changing the thickness and porosity of the sound-absorbing unit 2, the second acoustic metamaterial structure is obtained through calculation and analysis;

[0084] Among them, the sound-absorbing unit 2 is a porous material, and its material properties are controlled by microscopic properties such as porosity, material density and aggregate diameter.

[0085] Specifically, the first acoustic metamaterial structure is placed inside an impedance tube at a hard acoustic field boundary, such as... Figure 8 As shown, the left end of the first acoustic metamaterial structure is the sound wave input port, and the right end is the sound wave output port. A schematic diagram of the sound wave flow is shown below. Figure 9 As shown, by changing the thickness and porosity of the sound-absorbing unit, the acoustic transmission loss curves of the acoustic metamaterial structure at different thicknesses and porosities are calculated. The method for calculating the acoustic transmission loss curve (STL) is as follows:

[0086]

[0087] Among them, P out P represents the output acoustic power. in The acoustic power at the incident end is given, and the unit of the acoustic transmission loss curve (STL) is dB. Based on these acoustic transmission loss curves, the thickness and porosity of the sound-absorbing unit of the acoustic metamaterial structure are obtained, and the second acoustic metamaterial structure is determined.

[0088] S1300, Obtain the dataset, which includes multiple parameter combinations of the noise reduction unit of the second acoustic metamaterial model;

[0089] Specifically, a combination of multiple random parameters that satisfy the constraint conditions is obtained, and acoustic calculations are performed using a program-controlled finite element method. Finally, multiple sets of data are obtained as a dataset.

[0090] S1400 obtains the optimal parameter combination in the dataset through a deep learning model;

[0091] Specifically, the dataset is input into the deep learning model, and the optimal parameter combination in the dataset is obtained based on the acoustic transmission loss curve output by the deep learning model and the average acoustic transmission loss within the target frequency range.

[0092] S1500, a third acoustic metamaterial structure is obtained according to the optimal parameter combination, wherein the third acoustic metamaterial structure is the open noise-reducing acoustic metamaterial structure described in any one of the first aspects.

[0093] In this embodiment, through forward design and module reverse optimization design, a joint algorithm is proposed to control the deep neural network model of metamaterials using particle swarm optimization. This algorithm can conveniently combine and optimize acoustic metamaterials according to different scenarios and needs to obtain the most suitable acoustic metamaterial structure.

[0094] In one embodiment, reference Figure 25 S1200, the steps of changing the thickness and porosity of the sound-absorbing unit and obtaining the second acoustic metamaterial structure through calculation and analysis include:

[0095] S1201, the sound transmission loss curves of the acoustic metamaterial structure with and without sound-absorbing units were calculated respectively, and the importance of the sound-absorbing unit was determined.

[0096] Specifically, refer to Figure 11 The second acoustic metamaterial structure exhibits strong sound attenuation in the 380Hz to 1040Hz range, with a noise reduction of over 15dB. After adding the sound-absorbing unit, the overall sound transmission loss curve shows even more significant effects, especially with a significant increase in the average noise reduction in the high-frequency range after 1000Hz.

[0097] S1202, set the thickness of various sound-absorbing units, calculate the sound transmission loss curve of the acoustic metamaterial structure for each thickness, and obtain the optimal thickness.

[0098] Specifically, refer to Figure 10 and Figure 12 The greater the thickness of the sound-absorbing unit, the greater the noise reduction of the acoustic metamaterial structure's sound transmission loss curve, and the more obvious the high-frequency noise reduction effect.

[0099] S1203, by changing the porosity of the sound-absorbing unit, the sound transmission loss curves at different porosities are calculated to obtain the optimal porosity.

[0100] Specifically, refer to Figure 13 Where P0 is the porosity of the acoustic metamaterial structure, as the porosity of the sound-absorbing unit gradually increases, the noise reduction of the acoustic transmission loss curve of the acoustic metamaterial structure after 380Hz increases and gradually becomes smoother.

[0101] S1204, by changing the fiber diameter of the sound-absorbing unit, the sound transmission loss curves for different fiber diameters are calculated to obtain the optimal fiber diameter.

[0102] Specifically, refer to Figure 14 T p The porosity of the acoustic metamaterial structure is given. As the fiber diameter of the sound-absorbing unit gradually decreases, the noise reduction of the sound transmission loss curve of the acoustic metamaterial structure increases after 380Hz and gradually becomes smoother.

[0103] S1205 determined the parameters of the sound-absorbing unit by optimizing the thickness, porosity, and fiber diameter.

[0104] In one embodiment, reference Figure 15To investigate the acoustic radiation characteristics of an open noise-reducing acoustic metamaterial structure with only a core noise-reducing unit, the acoustic radiation fields and acoustic power streamlines of the characteristic wave modes from Mode A to Mode E in this case were extracted. It can be found that in the high attenuation frequency range, such as Figure 15 As shown, at frequencies of 500Hz, 760Hz, and 1040Hz, the sound radiation field intensity at the output end of the sound wave after passing through the barrier composed of the open noise-reducing acoustic metamaterial structure is much smaller than that at the input end. This is precisely because the overall Fano resonance effect of the open noise-reducing acoustic metamaterial structure forms a standing wave, which prevents sound energy from propagating, resulting in a wave resistance (Stop) state and a large sound transmission loss. And as... Figure 15 The sound power flow at frequencies of 2000Hz, 3000Hz, and 4000Hz exhibits local Fano resonance. Some of the sound energy can pass through the barrier composed of the open noise-reducing acoustic metamaterial structure, resulting in a small difference in sound energy between the input and output ends, creating a wave pass state. Therefore, a small sound transmission loss value occurs, but it still has a sound attenuation value of about 15dB.

[0105] In one embodiment, reference Figure 26 S1400, the step of obtaining the optimal parameter combination in the dataset through a deep learning model, also includes:

[0106] S1410: Obtain multiple random parameters that meet the constraint conditions and perform acoustic calculations using program-controlled finite element methods to obtain the input dataset;

[0107] Specifically, by using the wave finite element method in conjunction with a self-developed stochastic iterative function program, the range of conditions satisfying the constraints is obtained, such as... Figure 16 The combination of 39 random parameters shown was used to perform acoustic calculations using a program-controlled finite element method, ultimately obtaining 30,000 sets of data as the dataset for the deep learning model.

[0108] S1420, Extract the training set of the input dataset, and train a deep learning model using the training set. The deep learning model includes a joint algorithm that uses particle swarm optimization to control a metamaterial deep neural network model.

[0109] Among them, deep learning models such as Figure 17 As shown, it consists of an input layer, an output layer, and several hidden layers.

[0110] Specifically, the geometric parameters from 30,000 datasets serve as the input layer, while the output consists of the acoustic transmission loss curve and the mean acoustic transmission loss within the target frequency range. Hidden layers between these layers learn features and perform intensive computation on the data to establish a mapping between the input and output layers. This includes two-dimensional convolutional layers, flattening layers, and dense layers. Flattening layers flatten the output of the convolutional layers into a single long feature vector. This single feature vector is then fed into the dense layers to extract complex features. As the number of layers increases, the features processed by the architecture become increasingly complex. The number of neurons in each dense layer decreases progressively from top to bottom, with the number of neurons in the final layer being the same as the number of output acoustic transmission loss values.

[0111] S1430, Extract the validation set of the input dataset to adjust the parameters of the deep learning model and evaluate the model;

[0112] Of the dataset, 80% is the training set and 20% is the validation set.

[0113] S1440, Use the test dataset to evaluate the final performance of the model, and optimize and adjust the deep learning model based on the evaluation results to obtain the optimized deep learning model.

[0114] The deep learning model uses the metrics Mean Relative Error (MRE) and Mean Accuracy (MAR) to evaluate its performance.

[0115] Specifically, the formula for this indicator is:

[0116]

[0117] MAR = (1-MRE) × 100%

[0118] Where n is the number of data points, and j is the j-th data point.

[0119] S1450 obtains the optimal parameter combination in the dataset through an optimized deep learning model.

[0120] In this embodiment, a deep neural network model is trained to efficiently replace the finite element method for optimization calculations, thereby quickly and accurately obtaining the optimal open noise-reducing acoustic metamaterial design.

[0121] In one embodiment, reference Figure 27 and Figure 17 S1420, Extract the training set of the input dataset, and train a deep learning model using the training set. The deep learning model includes a joint algorithm that uses particle swarm optimization to control a deep neural network model of metamaterials, including:

[0122] S1421, extracting features of the training set, flattening the features to obtain a feature vector;

[0123] S1422, extracting complex features of the feature vector, and mapping the complex features to an output.

[0124] In one embodiment, with reference to Figure 18 , A, B, C and D are the structural evolution processes randomly selected after 2nd, 8th, 16th and 30th optimizations, respectively. As shown in the figure, the structure spontaneously evolves once every iteration. As the number of iterations increases, the fitness curve of the structure continues to tend to be stable. When the number of iterations reaches 30, the evolution speed of the deep learning model becomes 0, and the training and optimization of the learning model are completed.

[0125] In this embodiment, the more the number of iterations within the target range, the better the noise reduction effect; in terms of the noise reduction effects of the four structures A, B, C and D, the noise reduction effect satisfies A < B < C < D, which is exactly because D has the largest number of iterations and a more optimal structure.

[0126] In one embodiment, with reference to Figure 19 , the sound transmission loss curve of the highway barrier acoustic model (HBAM_RO) in the frequency range of 100Hz-4000Hz is shown, where four acoustic radiation modes at 110Hz, 790Hz, 1630Hz and 4000Hz and the acoustic equipotential maps of these four acoustic propagation modes are extracted respectively. It can be determined that the sound insulation amounts at 110Hz, 790Hz, 1630Hz and 4000Hz are 8dB, 55dB, 17dB and 22dB respectively. Meanwhile, it can be seen from the acoustic radiation modes of the four that the noise reduction effect is achieved exactly due to the barrier effect of the structure of the present invention.

[0127] Wherein 790Hz is the maximum noise reduction frequency of the highway barrier acoustic model, as Figure 19 shows a two-dimensional cross-section of the sound energy distribution at this frequency. It can be seen that the sound energy flow has a strong coupling effect with the noise reduction unit, and the sound energy is confined in the channel and each cavity and cannot propagate, thereby realizing the dual functions of ventilation, load reduction and noise reduction.

[0128] In one embodiment, with reference to Figure 20 , the results of indoor acoustic tests have high consistency with the simulation results in terms of sound transmission loss trend, overall sound insulation and peak frequency. In addition, due to interference factors such as idealized boundary conditions of simulation, sealing or installation errors of tests, and actual damping effect of sample materials, there will be some errors between simulation and measured results in some frequency bands, especially in the peak frequency band. However, to sum up, the test results of the sample are generally consistent with the simulation results, which verifies the correctness of the simulation model and the calculation results of this paper.

[0129] This utility model also provides a sound barrier, as shown in the reference. Figure 5 The sound barrier includes multiple open noise-reducing acoustic metamaterial structures as described in any of the above embodiments.

[0130] Specifically, after noise enters the sound barrier, part of the noise enters the open noise-reducing acoustic metamaterial structure inside the sound barrier, while the other part of the noise will pass directly through the hollow pipe. At this time, the two will undergo Fano resonance, making it difficult for the noise energy to pass through the sound barrier.

[0131] In this embodiment, the beneficial effects of the sound barrier are the same as those of the open noise-reducing acoustic metamaterial structure described above, and will not be elaborated further here.

[0132] In one embodiment, reference Figures 5-7 Multiple open noise-reducing acoustic metamaterial structures are arranged in a regular array.

[0133] The sound barrier consists of multiple open noise-reducing acoustic metamaterial structures arranged in parallel to form a 5×10 unit panel.

[0134] In one embodiment, reference Figure 5-7 The sound barrier is 100cm long, 50cm wide, and 12cm thick, with each column being 110cm high.

[0135] In one embodiment, reference Figure 21 The sound barrier also includes a fixing structure, and multiple open noise-reducing acoustic metamaterial structures are fixed through grooves in the fixing structure.

[0136] In one embodiment, the sound barrier is installed as follows: Figure 21 In the environment shown.

[0137] In one embodiment, reference Figure 21 The fixed structure is an H-shaped steel column.

[0138] In one embodiment, the noise reduction effects of wheel-rail noise passing through a sound barrier and an existing vertical sound barrier are simulated and calculated respectively. The noise attenuation curves of the two are shown below. Figure 22 As shown, the sound barrier achieves a weighted noise reduction of 30-40 dB in the 500-4000 Hz range, while exhibiting a weaker noise reduction effect below 500 Hz. Existing vertical sound barriers achieve a weighted noise reduction of 15-25 dB in the same 500-4000 Hz range. Under the same noise source excitation, the sound barrier's average noise reduction is 9.4 dB higher than that of existing vertical sound barriers, with a peak noise reduction of 15.4 dB, indicating that sound barriers have a better noise reduction effect for noise control in engineering applications.

[0139] In one embodiment, reference Figure 23 This study explores the broadband noise reduction mechanism of metamaterial sound barriers, analyzing the sound field distribution patterns at frequencies of 1000Hz, 2000Hz, 3000Hz, and 4000Hz. Figure 23 As shown at f = 1000Hz, it can be observed that due to the "multi-level gradient siphon effect" in the core noise reduction region, the acoustic energy of the incident wave is confined within the multi-level noise reduction cavity of the sound barrier, making it difficult for noise to propagate to the receiving end. Similarly, as... Figure 23 As shown at f = 2000Hz, the energy of the sound wave is trapped in the multi-gradient noise reduction cavity and exhibits the same characteristics as... Figure 23 The different "gradient siphon effect" at f=1000Hz. For incident sound waves at 3000Hz and 4000Hz, the presence of multi-level noise reduction regions in the sound barrier creates a strong "impedance effect" under multiple gradients. This effect leads to a large amount of sound wave reflection, thus hindering sound energy from reaching the receiver through the sound barrier. The local amplification effect of the sound field distribution at each frequency is shown in the figure. Figure 27 As shown. In summary, the "multi-level gradient siphon effect" and "impedance effect" of sound barriers can effectively block the input of sound energy, thereby reducing engineering noise pollution.

[0140] Among them Figure 23 In the diagram, red and blue represent the phase direction of the sound wave, with red being positive and blue being negative. The darker the color, the greater the sound energy; the lighter the color, the smaller the sound energy.

[0141] In one embodiment, several pre-designed open noise-reducing acoustic metamaterial structures are arranged and combined to form a sound barrier unit panel, with a certain length of overlap reserved, such as... Figure 5 and Figure 21 As shown, in this embodiment, 50 open noise-reducing acoustic metamaterial units are used to construct a sound barrier unit panel, arranged in a 10-row, 5-column configuration. The assembled sound barrier unit panel is 1m high and 0.5m wide. The metamaterial sound barrier is obtained by connecting the assembled sound barrier unit panels with H-beam steel columns.

[0142] For specific construction methods, please refer to the relevant sound barrier construction plan specifications in the "Interim Provisions for the Design of Railway Sound Barrier Engineering".

[0143] In this embodiment, the assembled sound barrier has the advantages of being thin, lightweight, well-ventilated, and having excellent noise reduction performance, making it more suitable for noise reduction requirements in railway environments.

[0144] The above are merely preferred embodiments of this utility model and do not limit the patent scope of this utility model. Any equivalent structural or procedural transformations made based on the description and drawings of this utility model, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this utility model.

Claims

1. An open-type noise-reducing acoustic metamaterial structure, characterized in that, The open noise-reducing acoustic metamaterial structure includes a noise-reducing unit and a sound-absorbing unit. The noise-reducing unit and the sound-absorbing unit are hollow cylinders. The noise-reducing unit is sleeved on the sound-absorbing unit. The noise-reducing unit includes multiple stacked sub-units. Each sub-unit has a cavity. The opening of the cavity is located on the side of the noise-reducing unit close to the sound-absorbing unit. The sound-absorbing unit is a porous material.

2. The open-type noise-reducing acoustic metamaterial structure as described in claim 1, characterized in that, The subunit is equipped with multiple baffles.

3. The open-type noise-reducing acoustic metamaterial structure as described in claim 2, characterized in that, The number of baffles in the subunit is one less than the number of layers in the subunit where the cavity is located.

4. The open-type noise-reducing acoustic metamaterial structure as described in claim 2, characterized in that, The distance between any two adjacent baffles within the sub-unit is different.

5. The open-type noise-reducing acoustic metamaterial structure as described in claim 1, characterized in that, The location of the lumen opening is different for each of the sub-units.

6. The open-type noise-reducing acoustic metamaterial structure as described in claim 1, characterized in that, The open noise-reducing acoustic metamaterial structure also includes a fixed unit, in which the noise-reducing unit is embedded.

7. A sound barrier, characterized in that, The sound barrier comprises multiple open noise-reducing acoustic metamaterial structures, as described in any one of claims 1-6.

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