CN113216025B - Road sound barrier noise reduction device and structural design method thereof - Google Patents
Road sound barrier noise reduction device and structural design method thereof Download PDFInfo
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01F—ADDITIONAL WORK, SUCH AS EQUIPPING ROADS OR THE CONSTRUCTION OF PLATFORMS, HELICOPTER LANDING STAGES, SIGNS, SNOW FENCES, OR THE LIKE
- E01F8/00—Arrangements for absorbing or reflecting air-transmitted noise from road or railway traffic
- E01F8/0005—Arrangements for absorbing or reflecting air-transmitted noise from road or railway traffic used in a wall type arrangement
- E01F8/0017—Plate-like elements
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01F—ADDITIONAL WORK, SUCH AS EQUIPPING ROADS OR THE CONSTRUCTION OF PLATFORMS, HELICOPTER LANDING STAGES, SIGNS, SNOW FENCES, OR THE LIKE
- E01F8/00—Arrangements for absorbing or reflecting air-transmitted noise from road or railway traffic
- E01F8/0005—Arrangements for absorbing or reflecting air-transmitted noise from road or railway traffic used in a wall type arrangement
- E01F8/0023—Details, e.g. foundations
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
- G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
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- G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
- G06F2119/10—Noise analysis or noise optimisation
Abstract
The invention provides a road sound barrier noise reduction device and a structural design method thereof. The device is by making an uproar single cell of falling follow the road trend repeated arrangement in the space, arrange two-layerly and form along perpendicular road trend direction simultaneously, the single cell of making an uproar is made an uproar by two "protruding in concave outside" type thin-walled structure reverse combination form, the single cell of making an uproar falls central symmetry in the plane, constitute "protruding composite construction in concave outside" by two inside and outside sheet metal structures, the outer sheet metal of the protruding composite construction in concave outside is "concave" type, the inlayer sheet metal is "protruding" type, constitute two sound wave channels that the width is the same between outer sheet metal and the inlayer sheet metal, set up the interval of two sound wave channel entries according to air current coupling and sound wave transmission loss. The acoustic performance of the noise reduction unit cell can be effectively adjusted by changing the size of the 'outer concave inner convex composite structure' so as to adapt to various target noise reduction ranges. The noise reduction device for the road sound barrier has double-sided efficient noise reduction performance, and reduces the influence of the road on the external noise and the interference of the external noise on the road.
Description
Technical Field
The invention relates to the technical field of road traffic noise reduction, in particular to a road sound barrier noise reduction device and a structural design method thereof.
Background
With the increase of the quantity of motor vehicles kept in China, the influence of road traffic noise on the sound environment along the road is increasingly serious. The long-term noise exposure can cause serious physiological and psychological symptoms, such as nausea, headache, fatigue, insomnia and the like, and particularly, low-frequency sound waves in traffic noise have strong penetrating power and are difficult to attenuate in the transmission process, and even easily resonate with human organs to cause more serious harm to the body. Therefore, the technology for reducing noise in the road environment is researched and developed to have important application value.
Aiming at road noise reduction, the traditional sound insulation material mostly belongs to a linear material, even if damping is added, the low-frequency sound absorption capacity is still weak, and the traditional sound insulation material is limited by a mass action law, so that the performance requirements of light mass and effective noise reduction are difficult to meet simultaneously in practical application. Patent CN108978504A proposes a composite sound-insulating barrier, which has good sound-absorbing and sound-insulating effects, and also has the characteristics of high mechanical strength, low density, light weight, good cutting adhesion construction performance and the like in construction application, and does not contain any harmful substances such as heavy metals and the like. However, the sound absorption material particles required by the composite sound insulation barrier are complex, the requirements for material manufacturing are strict, and the actual application effect is limited. In order to weaken the dependence of the sound barrier on the acoustic performance of the material, from the structure configuration of the sound barrier, the researchers have proposed an acoustic metamaterial structure.
The acoustic metamaterial obtains high energy density by utilizing local resonance of a sub-wavelength thickness structure, shows the characteristics of negative effective bulk modulus, negative effective refractive index, wave manipulation and the like, and has great potential in the aspect of low-frequency noise attenuation. Conventional acoustic metamaterial noise reduction structures require reflectors, i.e., aluminum or other rigid plates placed behind the sound absorbing structure to reduce sound transmission, and once the reflector is removed, the sound absorbing performance of the sound absorbing structure is greatly reduced. At the same time, the conflict between the acoustic performance and the ventilation efficiency limits the application potential in various environments.
In order to realize the coordination of the ventilation function and the sound insulation function of the sound barrier, the students further propose ventilation type metamaterials. The ventilation type structure has high noise reduction characteristics in certain specific frequency bands while allowing air to flow. Patent CN105845121A proposes an acoustic metamaterial structural unit related to sound insulation through-flow and enhanced heat transfer, which has sound insulation capability superior to that of a common perforated plate or a micro-perforated plate in a wide frequency band, and at the same time, ensures sufficient heat flow, air flow or liquid flow to pass through smoothly. However, this structure has a poor sound loss effect with respect to low frequency sound waves (e.g., 100 Hz). Patent CN110822206A has proposed a super open high-efficient ventilation sound absorption unit, including the first, second split tube resonant cavity that two front and back side by side symmetry set up, every split tube resonant cavity comprises inside casing, frame, wholly is "the" font of returning ", and every sound absorption unit constitutes a rigid loss oscillator similar to the spring, and the sound absorber is used for installing in open airflow channel, can realize the high-efficient absorption (> 95%) and the ventilation (> 80% wind speed ratio) of low frequency (<1000 Hz). However, this structure has poor noise reduction effect on low frequency noise (100 Hz).
In summary, the noise reduction structure of the road sound barrier in the prior art has the following disadvantages:
1. aiming at road noise reduction, most of traditional sound insulation materials belong to linear materials, even if damping is added, the low-frequency sound absorption capacity is still weak, and the traditional sound insulation materials are limited by mass action laws, so that the performance requirements of light mass and effective noise reduction are difficult to meet in practical application.
2. Most acoustic metamaterial noise reduction structures require reflectors, i.e., aluminum or other rigid plates placed behind the sound absorbing structure to reduce the transmission of sound, and once the reflectors are removed, the sound absorbing performance of the sound absorbing structure is greatly reduced, and the conflict between acoustic performance and ventilation efficiency limits their potential for use in a variety of environments, and thus is limited in practical significance.
3. For a few of the prior ventilated metamaterial noise reduction structures, high-efficiency absorption is usually only suitable for one side, and for the other side, absorption is usually minimized, so that the requirement of noise reduction on two sides of a sound barrier cannot be met, and for low-frequency sound waves on urban roads, the optimal sound absorption coefficient of the ventilated metamaterial structure is small, and the resonance frequency is difficult to accurately control.
Disclosure of Invention
The embodiment of the invention provides a road sound barrier noise reduction device and a structural design method thereof, which are used for effectively reducing the influence of the road on the external noise.
In order to achieve the purpose, the invention adopts the following technical scheme.
The invention provides a noise reduction device of a road sound barrier, which is formed by repeatedly arranging noise reduction unit cells in a space along the direction of the road and arranging two layers of noise reduction unit cells in the direction vertical to the direction of the road, wherein the noise reduction unit cells are formed by reversely combining an outer concave and inner convex composite structure which is centrosymmetric in a plane and consists of an inner layer of thin plate and an outer layer of thin plate.
Preferably, the outer layer thin plate of the noise reduction unit cell is concave, the inner layer thin plate is convex, and the reflection distance of oblique incident sound waves on the outer surface of the composite structure is prolonged while the length of a sound wave channel is increased; the outer layer thin plate and the inner layer thin plate form double channels with the same width, and the distance between the inlets of the sound wave channels is set according to air flow coupling and sound wave transmission loss.
Preferably, the device is arranged on both sides of a road, and the bottoms of the inner and outer thin plates of the composite structure are fixed on a concrete/steel structure guard rail.
Preferably, the noise reduction unit cell is made of polycarbonate.
In another aspect, the present invention provides a method for designing a structure of a noise reduction device for a road sound barrier, comprising the following steps:
(1) the urban road traffic noise is mainly concentrated at 200-250Hz, so that two noise reduction targets for noise reduction unit cell configuration optimization are determined: a) the sound absorption coefficient at the center frequency of 225Hz is as large as possible; b) the frequency band with the sound absorption coefficient of more than 50 percent is as wide as possible;
(2) establishing a two-dimensional finite element model, considering the interaction of sound and heat adhesiveness, and carrying out numerical simulation research on the noise reduction effect of the double-layer sound barrier under the incidence of 100-Hz low-frequency sound waves; taking a background pressure field as a sound source, and enabling sound waves to enter along the vertical direction in a plane; applying Floquet period boundary conditions in the other direction in the plane, and applying a perfect matching layer in the incident direction; setting the propagation speed, density, dynamic viscosity, bulk viscosity, heat conductivity coefficient and constant-pressure heat capacity of sound waves in air;
(3) initially optimizing the unit cell configuration based on a Monte Carlo method, taking the sound wave incidence angle as 0 degrees, the thickness t of the inner and outer thin plates as a constant of 2mm, taking the maximum sound absorption coefficient at the central frequency of 225Hz as an optimization target, and taking the width a of one-half of the noise-reducing unit cell, the thickness b of the noise-reducing unit cell, the gap c of the same-row noise-reducing unit cell, the layer spacing d, the width w of the sound wave channel and the inlet spacing L of the sound wave channel as1Length L of inner concave2Setting the value ranges of all variables and geometric constraint conditions based on penalty functions for controlling the variables, optimizing once to obtain an initial optimization model, floating up and down for a certain range around the parameters a and b of the initial optimization model, and keeping the value ranges of other control variables unchanged;
(4) setting sound wave incidence angles of 0 degree, 15 degrees, 30 degrees, 45 degrees and 60 degrees for parametric scanning, maximizing the sum of sound absorption coefficients corresponding to the center frequency of 225Hz under 5 different sound wave incidence conditions as an objective function, randomly selecting a relative optimal value by applying a Monte Carlo method, obtaining average optimal values of the parameters a and b after multiple optimization, and simultaneously floating the average optimal values of other parameters up and down within a certain range to obtain initial value ranges of other parameters;
(5) changing the frequency domain setting into a range of 200Hz-250Hz, keeping the incident angle parametric scanning setting unchanged, taking the frequency bandwidth with the sound absorption coefficient more than 50% as an objective function, taking the a and b obtained in the step (4) as fixed values, taking the initial value ranges of other parameters as variable value ranges, and carrying out multiple optimization to obtain the optimal value averaging of each parameter as a relatively optimized solution, thereby obtaining the geometric dimension of the sound barrier with excellent noise reduction effect. According to the technical scheme provided by the embodiment of the invention, the road sound barrier noise reduction device provided by the embodiment of the invention has double-sided efficient noise reduction performance, can be applied to noise reduction of lower-frequency sound waves of roads, and reduces the influence of the roads on external noise and the interference of the external noise on the roads.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a three-dimensional perspective view and a two-dimensional plan view of a novel sound barrier and noise reduction unit cell provided by an embodiment of the invention;
FIG. 2 is a comparison graph of an example noise reduction simulation for verifying the correctness of the study method used in the present invention;
fig. 3 is a 3D printed noise reduction unit cell diagram in the embodiment of the present invention;
FIG. 4 is a comparison graph of the acoustic performance simulation of a novel sound barrier and melamine acoustic foam provided by an embodiment of the present invention;
fig. 5 is a numerical simulation diagram for investigating the influence of the number of layers on the noise reduction performance of the novel sound barrier provided by the embodiment of the present invention;
fig. 6 is a numerical simulation diagram for investigating the influence of interlayer spacing on the sound transmission loss performance of the novel sound barrier provided by the embodiment of the present invention;
FIG. 7 is a numerical simulation chart for investigating the influence of oblique incidence of sound waves on the noise reduction performance of a novel sound barrier provided by an embodiment of the present invention;
fig. 8 is a numerical simulation diagram for exploring the trade-off relationship between noise reduction performance and ventilation efficiency of the novel sound barrier provided by the embodiment of the invention;
FIG. 9 is a diagram illustrating the acoustic channel entrance spacing L1A numerical simulation diagram of the influence of the sound transmission loss performance of the novel sound barrier provided by the embodiment of the invention;
FIG. 10 is a graph illustrating the length L of the indent2A numerical simulation diagram of the influence of the sound transmission loss performance of the novel sound barrier provided by the embodiment of the invention;
FIG. 11 is a numerical simulation for investigating the effect of one-half noise reduction unit cell width a on the sound transmission loss performance of a novel sound barrier provided by an embodiment of the present invention;
fig. 12 is a numerical simulation diagram for investigating the influence of noise reduction unit cell thickness b on the sound transmission loss performance of the novel sound barrier provided by the embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. Further, "connected" or "coupled" as used herein may include wirelessly connected or coupled. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
For the convenience of understanding the embodiments of the present invention, the following description will be further explained by taking several specific embodiments as examples in conjunction with the drawings, and the embodiments are not to be construed as limiting the embodiments of the present invention.
The embodiment of the invention provides a novel Ventilated Metamaterial sound Barrier (VMB) with double-sided efficient noise reduction performance by taking the urban road traffic noise frequency (100-400Hz) as a practical application background, which is used for reducing noise of low-frequency sound waves of a road and reducing the influence of the road on external noise and the interference of the external noise on the road. Meanwhile, the ventilation structure of the road ventilation structure can adapt to various road weather environments, and wind-induced damage is avoided. In addition, the structure is beautiful.
Example one
The noise reduction device for the road sound barrier provided by the embodiment of the invention is formed by combining two noise reduction unit cells, the sizes of the noise reduction unit cells are completely the same, gaps exist among the noise reduction unit cells on different layers to allow air to flow relatively freely, and the noise reduction unit cells can be made of polycarbonate (PC material).
Fig. 1 is a three-dimensional perspective view and a two-dimensional plan view of a novel sound barrier and noise reduction unit cell provided by an embodiment of the invention. The noise reduction unit cell is formed by reversely combining two 'external concave and internal convex composite structures'. The 'external concave and internal convex composite structure' is centrally symmetrical in a plane and consists of an internal thin plate and an external thin plate. Compared with the prior noise reduction structure, the 'external concave and internal convex composite structure' mainly has the following three innovations: the outer layer thin plate is concave, the inner layer thin plate is convex, the length of the sound wave channel is increased, and the reflection distance of oblique incident sound waves on the outer surface of the composite structure is prolonged; the outer thin plate and the inner thin plate form double channels with the same width, and the proper distance between the inlets of the sound wave channels is set by considering double factors of air flow coupling and sound wave transmission loss; the acoustic performance can be effectively adjusted to adapt to various target noise reduction ranges by changing the length and width dimensions of the 'outer concave and inner convex' composite structure.
The noise reduction unit cells are arranged on two sides of a road, and the inner thin plate and the outer thin plate can be fixed by bottom cement concrete or additionally provided with fixed bases.
The structural parameters of the noise reduction unit cell are mainly as follows: thickness t of inner and outer thin plates, unit cell half width a, unit cell thickness b, acoustic channel width w, acoustic channel entrance spacing L1Length L of inner concave2The units are mm, and the following constraint conditions are required to be met when the structural parameters meet the basic type of the composite structure with the outward concave and inward convex structure:
a-L1-3w-6t>2
L1-w-2t>1
L1+3w+2t+1>0
b-3t-w-L2>1
the structural parameters (including unit cell structure size, unit cell gaps and layer intervals) of the double-layer sound barrier are determined by using a Monte Carlo optimization solver in COMSOL, and the structural parameter values which enable the target function to be relatively optimal can be obtained through continuous sampling tests by setting the range of the structural parameter variables of the double-layer sound barrier and related constraint conditions.
The structural design method of the road sound barrier noise reduction device comprises the following steps:
(1) the urban road traffic noise is mainly concentrated at 200-250Hz, so that two noise reduction targets for optimizing the noise reduction unit cell configuration are determined: a) the sound absorption coefficient at the center frequency of 225Hz is as large as possible; b) the frequency band with the sound absorption coefficient of more than 50 percent is as wide as possible;
(2) establishing a two-dimensional finite element model, considering the interaction of sound and heat adhesiveness, and carrying out numerical simulation research on the noise reduction effect of the double-layer sound barrier under the incidence of 100-400Hz low-frequency sound waves; taking a background pressure field as a sound source, and enabling sound waves to enter along the vertical direction in a plane; applying Floquet period boundary conditions in the other direction in the plane, and applying a perfect matching layer in the incident direction; setting the propagation speed, density, dynamic viscosity, bulk viscosity, heat conductivity coefficient and constant-pressure heat capacity of sound waves in air;
(3) performing initial optimization on the unit cell configuration based on a Monte Carlo method, taking the sound wave incidence angle as 0 degrees, the thickness t of the inner and outer sheets as a constant, taking the maximum sound absorption coefficient at the central frequency of 225Hz as an optimization target, and taking the width a of one-half of the noise-reducing unit cell, the thickness b of the noise-reducing unit cell, the gap c of the same-row noise-reducing unit cell, the layer spacing d, the width w of the sound wave channel and the inlet spacing L of the sound wave channel as1Length L of inner concave2Controlling variables (specifically defined in the attached figure 1), setting the value ranges of the variables and geometric constraint conditions based on penalty functions, optimizing once to obtain an initial optimization model, floating up and down to a certain range around the parameters a and b of the initial optimization model, keeping the value ranges of other parameters unchanged, and obtaining the initial value ranges for the optimization in the step (4);
(4) setting sound wave incidence angles of 0 degree, 15 degrees, 30 degrees, 45 degrees and 60 degrees for parametric scanning, maximizing the sum of sound absorption coefficients corresponding to the center frequency of 225Hz under 5 different sound wave incidence conditions as an objective function, randomly selecting a relative optimal value by applying a Monte Carlo method, obtaining average optimal values of the parameters a and b after multiple optimization, and simultaneously floating the average optimal values of other parameters up and down to a certain range to obtain initial value ranges of other parameters for the optimization in the step (5).
(5) Further changing the frequency domain setting into a range of 200Hz-250Hz, keeping the incident angle parameterization scanning setting unchanged, taking the frequency bandwidth with the sound absorption coefficient more than 50% as an objective function, taking the a and b obtained in the step (4) as fixed values, taking the initial value range of other parameters as a variable value range, and carrying out optimization for multiple times to obtain the average value of the optimal values of all the parameters as a relatively optimal solution, thereby obtaining the geometric dimension of the sound barrier with excellent noise reduction effect;
(6) aiming at other application scenes of the novel sound barrier, the design idea can refer to the steps (1) to (5).
The invention mainly adopts a scheme of numerical simulation and experimental research. The method specifically comprises the following steps:
(1) firstly, in order to verify the scientificity of the numerical simulation technology adopted by the invention, a double-elliptical-pipe noise reduction model based on split pipe resonance is selected, COMSOL software is used for simulating the sound absorption coefficients of two samples under 200Hz-500Hz, and the sound absorption coefficients are compared with the original experimental test results. As shown in fig. 2, the trend of the numerically simulated sound absorption coefficient curve of the embodiment of the present invention is substantially consistent with that of the corresponding experimental operation effect curve, and the peak value of the curve has a better matching effect in both the sound absorption coefficient and the sound absorption frequency, wherein the inset is a two-dimensional model of two samples, and sound waves are incident along the y-axis direction in fig. 2. The scientificity and correctness of the numerical simulation research method used in the embodiment of the invention are illustrated.
(2) Based on the method, the Monte Carlo method is used for designing the ventilating sound barrier structure. The geometrical size of the sound barrier which has better noise reduction effect on road traffic noise (100Hz-400Hz), especially on the frequency range of 200Hz-250Hz, is considered. The physical simulation effect is as shown in figure 1a, and the double-layer ventilation ultrasonic material sound barrier is arranged on two sides of the road. Polycarbonate may be selected for practical use. The gaps between adjacent noise reduction cells allow air to flow relatively freely, with sound waves incident normal to the surface of the sound barrier, being reflected, transmitted and absorbed (as shown in FIG. 1 b); fig. 1c shows a three-dimensional perspective view of a noise reduction unit cell of a sound barrier, wherein the noise reduction unit cell is formed by reversely arranging two 'external concave and internal convex composite structures', and the noise reduction principle mainly comes from cavity local resonance, thermal friction loss of a sound wave channel and weak coupling between the two 'external concave and internal convex composite structures'. The two-dimensional plane of the double layer sound barrier is shown in figure 1 d. The noise reduction unit cell test model in figure 3 is obtained by 3D printing of polylactic acid plastic, and a thin layer (shown as a black frame in the figure) is arranged at the bottom of the noise reduction unit cell and used for fixing an inner thin plate and an outer thin plate.
(3) A numerical model of the ventilation metamaterial sound barrier unit is built by using finite element software COMSOL, the sound-thermal viscosity acoustic interaction is considered, and the noise reduction effect of the sound barrier when low-frequency sound waves enter plane waves (100Hz-400Hz) along the cross section direction of a road is researched by adopting frequency domain analysis. The incident plane wave has a background pressure field as a sound source. Periodic boundary conditions are applied in the direction of the road heading to account for the infinite periodic arrangement of the direction. A perfect matching layer is applied in the road cross-section direction to simulate open boundary conditions. And (5) carrying out comparative analysis to simulate the noise reduction effect of the traditional porous material.
(4) Laminar flow analysis explores the ventilation properties of a single layer sound barrier in free space. The boundary condition of the inlet is set as 'fully developed flow', the boundary condition of the outlet is set as 'pressure', the constitutive relation of the fluid property is 'Newton', the initial fluid speed is 0.5m/s, and the road trend direction is a periodic flow condition. Flow resistivity R with single layer sound barrierSAs a key basis for evaluating ventilation performance, the larger the flow resistivity is, the larger the air blocking effect of the model structure is, and the formula of the variable is defined as follows:
in the formula, P1-P2Representing the pressure drop of air across a single layer of the sound barrier, V representing the average flow rate of air, b representing the sound barrier sheetThe thickness of the element.
Example two
Considering the sound absorption performance and sound transmission loss effect of a sound barrier (specific dimensions obtained by the monte carlo method, as shown in table 1) consisting of one layer of noise reduction unit cells; the noise reduction unit cell in figure 3 is obtained by 3D printing of polylactic acid plastic, and a thin layer (shown as a black frame in the figure) is arranged at the bottom of the noise reduction unit cell and used for fixing an inner thin plate and an outer thin plate.
TABLE 1 geometric parameters (mm)
The simulation effect of the acoustic performance of the novel ventilation metamaterial sound barrier and the Melamine Foam (MF) with the same thickness specification is shown in figure 4, wherein figure 4a shows that the single-layer sound barrier reaches a sound absorption peak value of 92.5% at 227Hz, the bandwidth with the absorption rate of more than 50% is 33Hz, the wavelength of sound waves at 227Hz is 151cm, and the wavelength is about 14 times as long as a noise reduction unit cell (11.2cm) and 24 times as long as the thickness of the noise reduction unit cell (6.2 cm); fig. 4b shows that the sound transmission loss of the novel sound barrier provided by the invention is the largest at 230Hz and reaches 12.6dB, while the sound transmission loss of the melamine foam material is about 5-6dB in the frequency range of 100Hz-400Hz, and it can be seen that the optimal sound absorption effect and the optimal sound transmission loss of the novel ventilation ultrasonic material sound barrier provided by the invention are far higher than the related parameters of the melamine sound absorption foam.
Fig. 5 is a numerical simulation diagram for investigating the influence of the number of layers on the noise reduction performance of the novel sound barrier provided by the embodiment of the present invention. When the absorption coefficient reaches the maximum value, the reflection coefficient (reflection) is less than 1.5%, the transmission coefficient (transmission) is 6%, and the reflection coefficient is smaller, so that the sound absorption peak value can be improved by increasing the number of unit layers of the sound barrier; in the numerical simulation phase, the spacing between the layers was assumed to be 20 mm. As can be seen from fig. 5a, when the number of layers is gradually increased, the peak of the sound transmission loss curve is gradually moved upwards, the frequency bandwidth with the sound transmission loss greater than 10dB is also obviously increased, and the peak frequency is still stabilized around 230 Hz; fig. 5b shows the sound pressure level around the sound barrier under four noise reduction cells, corresponding to the sound transmission loss. FIG. 5c shows that when the number of layers is 2, the peak of the absorption coefficient is 98.5%, and the bandwidth of the absorption rate at 50% or more is 49 Hz; when the number of layers is 3 or 4, the peak value of the absorption coefficient is more than 99%, the bandwidth of the absorption rate is more than 50% and 60Hz, and the number of layers is 2 under comprehensive consideration because the more the number of layers, the greater the economic cost.
Fig. 6 is a numerical simulation diagram for investigating the influence of interlayer spacing on the sound transmission loss performance of the novel sound barrier provided by the embodiment of the present invention. Figure 6 further studies the effect of the interlamellar spacing on the overall sound absorption, considering that the interlamellar spacing is 10mm, 20mm, 30mm, 40mm, 50mm respectively. The layer spacing is found to have little effect on the sound absorption peaks and the corresponding frequencies, so that in this respect the actual road factors can be taken into account sufficiently to set a practically optimum layer spacing.
Fig. 7 is a numerical simulation diagram for investigating the influence of oblique incidence of sound waves on the noise reduction performance of the novel sound barrier according to the embodiment of the present invention. Since the noise on the road is generated by a vehicle traveling on the road surface, i.e., a moving sound source. In most cases, sound waves are obliquely incident at a certain angle, so that the sound absorption effect and sound transmission loss of the novel sound barrier at the oblique incidence of the sound waves need to be further researched. As shown in fig. 7a, when the incident angle is changed from 0 ° to 60 °, the sound absorption peak of the novel sound barrier is not significantly weakened, the frequency corresponding to the sound absorption peak is still in the vicinity of 227Hz, and the frequency bandwidth with the absorption rate of more than 50% is robust in the case of oblique incidence of sound waves; fig. 7b shows that the sound transmission loss performance of the novel sound barrier in the higher frequency (300Hz-400Hz) range is slightly better than the sound transmission loss effect in the lower frequency (100Hz-200Hz) range.
Fig. 8 is a numerical simulation diagram for studying a trade-off relationship between noise reduction performance and ventilation efficiency of the novel sound barrier according to the embodiment of the present invention. The ventilation performance of the sound barrier proposed by the present invention was further explored. The distance c between the noise reduction unit cells is set as an independent variable so as to explore the influence on the low-frequency sound absorption effect, the low-frequency sound transmission loss and the ventilation performance. FIG. 8a shows that as the distance c increases, the frequency bandwidth with sound absorption coefficient above 50% decreases gradually, but both above 27Hz, and the peak sound absorption frequency and peak sound transmission loss frequency are respectivelyThe method is basically stable around 227Hz and 230Hz, and has stronger robustness; FIG. 8b shows that as the distance c increases, the peak sound absorption coefficient, the peak sound transmission loss and the flow resistivity all decrease, but the peak sound absorption coefficient is still above 0.85, the peak sound transmission loss is still above 9dB, and the flow resistivity is much smaller than that of the conventional porous material (2000--2). Research results show that the distance c between adjacent noise reduction unit cells is within a size range ensuring that the novel sound barrier has excellent noise reduction performance, and the obstruction effect on air fluid is negligible.
FIG. 9 is a diagram illustrating the acoustic channel entrance spacing L1Fig. 10 is a diagram illustrating a numerical simulation of an influence of sound transmission loss performance of a novel sound barrier according to an embodiment of the present invention, in which an indent length L is explored2Fig. 11 is a numerical simulation diagram for studying the influence of one-half noise reduction unit cell width a on the novel sound barrier sound transmission loss performance provided by the embodiment of the present invention, and fig. 12 is a numerical simulation diagram for studying the influence of noise reduction unit cell thickness b on the novel sound barrier sound transmission loss performance provided by the embodiment of the present invention. Finally, in order to verify that the novel sound barrier has good industrial adaptability, the influence of four geometric parameters of the sound barrier provided by the invention on the noise reduction effect is researched: acoustic channel entrance spacing L of noise reducing unit cell1(FIG. 9) concave length L2(FIG. 10), one-half noise reduction unit cell width a (FIG. 11) and noise reduction unit cell thickness b (FIG. 12), and the remaining parameters are as in Table 1. The results show that the parameters a and b are the determining factors influencing the sound transmission loss of the sound barrier, and the length L of the indent2Second, the acoustic channel entrance spacing L1The influence of the new sound barrier is minimum, and the influence analysis of four geometric parameters proves that the geometric dimension of the new sound barrier can be designed specifically according to the specific range (such as 100Hz-400Hz) of the main noise on the actual road, and the new sound barrier has good industrial adaptability.
In summary, the noise reduction device for the road sound barrier provided by the embodiment of the invention has double-sided efficient noise reduction performance, can be applied to noise reduction of low-frequency sound waves of roads, and reduces influence of the roads on external noise and interference of the external noise on the roads. Meanwhile, the ventilation structure of the road ventilation device can adapt to various road weather environments, and wind-induced damage is avoided. In addition, the structure has certain aesthetic property.
Specifically, aiming at the low-frequency traffic noise (100Hz-400Hz) of the urban road, the invention has the following beneficial effects:
(1) the single-layer sound barrier reaches a sound absorption peak value of 92.5% at 227Hz, the bandwidth with the absorption rate of more than 50% is 33Hz, the sound transmission loss of the single-layer sound barrier at 230Hz is the largest and reaches 12.6dB, and the noise reduction effect is good.
(2) The noise reduction performance and the economic cost are comprehensively considered, the novel sound barrier formed by the double-layer noise reduction unit cells is most suitable for practical application, and the interlayer spacing has almost no influence on the noise reduction performance, so that the actual road factor can be fully considered, the actual optimal interlayer spacing is set, and the actual applicability is strong.
(3) The sound barrier can keep satisfactory sound absorption performance and sound transmission loss performance under the oblique incidence of free space sound waves, and has robustness.
(4) The distance between noise reduction unit cells is within a size range ensuring excellent sound absorption performance of the model, the obstruction effect on air fluid is negligible, and the flow resistivity is 38.8Pa · s · m-2Far smaller than that of the traditional porous material (2000-4000Pa s-m)-2)。
(5) The working frequency and the sound insulation performance of the noise reduction unit cell are irrelevant to the material performance to a great extent, and can be further adjusted by adjusting the geometric parameters, so that the industrial applicability is strong, the use of steel is reduced, and the noise reduction unit cell is economical and has certain aesthetic property.
Those of ordinary skill in the art will understand that: the figures are merely schematic representations of one embodiment, and the blocks or flow diagrams in the figures are not necessarily required to practice the present invention.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for apparatus or system embodiments, since they are substantially similar to method embodiments, they are described in relative terms, as long as they are described in partial descriptions of method embodiments. The above-described embodiments of the apparatus and system are merely illustrative, and the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (4)
1. A road sound barrier noise reduction device is characterized in that a noise reduction unit cell is repeatedly arranged in a space along the direction of a road and is simultaneously formed by arranging two layers along the direction vertical to the direction of the road, the noise reduction unit cell is formed by reversely combining two outer concave and inner convex composite structures, and the noise reduction unit cell is centrosymmetric in a plane; each outer concave and inner convex composite structure is formed by mutually reversely sleeving two concave thin plate structures; the concave sheet structure positioned on the outer layer is sunken towards the interior of the outer concave-inner convex composite structure along one side of the width direction of the road, and the other side of the concave sheet structure is open; the concave sheet structure positioned on the inner layer protrudes towards the outside of the outer concave-inner convex composite structure along one side of the width direction of the road, and the other side of the concave sheet structure is open; the concave edge of each outer concave-inner convex composite structure is consistent with the direction of a road, and two sides of the convex edge of each outer concave-inner convex composite structure are respectively provided with a split with the same width; a gap is formed between the concave sheet structure of the outer layer and the concave sheet structure of the inner layer, so that two sound wave channels which take the two cracks as starting points and extend along the inner side edge of the concave sheet structure of the outer layer are formed, and the width of each sound wave channel is equal to that of each crack; the end points of the sound wave channel correspond to the two ends of the concave edge of the concave sheet structure of the outer layer;
setting the distance between the inlets of the two sound wave channels according to the air flow coupling and the sound wave transmission loss, prolonging the reflection distance of oblique incident sound waves on the outer surface of the composite structure while increasing the length of the sound wave channel by the external concave-internal convex composite structure, and adjusting the acoustic performance of the noise reduction unit cell by changing the size of the external concave-internal convex composite structure; the dimensions of the outer concave inner convex composite structure include: the width of a noise reduction unit cell is one half a, the thickness of the noise reduction unit cell is b, the same row noise reduction unit cell gap is c, the interlayer spacing is d, the width of a sound wave channel is w, and the inlet spacing of the sound wave channel is L1Length L of inner concave2。
2. The device of claim 1, wherein the device is installed on both sides of a road, and the bottoms of the inner and outer sheets of the composite structure are fixed to a concrete/steel guard rail.
3. The device of claim 1, wherein the noise reducing unit cell is made of polycarbonate.
4. A structural design method of the noise reduction device for the road sound barrier based on any one of claims 1 to 3 is characterized by comprising the following steps:
(1) the urban road traffic noise is concentrated at 200-250Hz, and two noise reduction targets optimized by the noise reduction unit cell configuration are determined: a) the sound absorption coefficient at the center frequency of 225Hz is as large as possible; b) the frequency band with the sound absorption coefficient of more than 50 percent is as wide as possible;
(2) establishing a two-dimensional finite element model, considering the interaction of sound and heat adhesiveness, and numerically simulating and researching the noise reduction effect of the double-layer sound barrier under the incidence of sound waves; taking a background pressure field as a sound source, and enabling sound waves to enter along the vertical direction in a plane; applying Floquet period boundary conditions in the other direction in the plane, and applying a perfect matching layer in the incident direction; setting the propagation speed, density, dynamic viscosity, bulk viscosity, heat conductivity and constant-pressure heat capacity of sound waves in air;
(3) performing initial optimization on the unit cell configuration based on a Monte Carlo method, taking the sound wave incidence angle as 0 degrees, the thickness t of the inner and outer sheets as a constant of 2mm, taking the maximum sound absorption coefficient at the central frequency as an optimization target, and taking the width a of a noise-reducing unit cell, the thickness b of the noise-reducing unit cell, the gap c of the noise-reducing unit cells in the same row, the layer spacing d, the width w of a sound wave channel and the inlet spacing L of the sound wave channel1Length L of inner concave2Setting the value ranges of all variables and geometric constraint conditions based on penalty functions for controlling the variables, optimizing once to obtain an initial optimization model, floating up and down for a certain range around the parameters a and b of the initial optimization model, and keeping the value ranges of other control variables unchanged;
(4) setting sound wave incidence angles of 0 degree, 15 degrees, 30 degrees, 45 degrees and 60 degrees for parametric scanning, maximizing the sum of sound absorption coefficients corresponding to the center frequency of 225Hz under 5 different sound wave incidence conditions as an objective function, randomly selecting a relative optimal value by applying a Monte Carlo method, obtaining average optimal values of the parameters a and b after multiple optimization, and simultaneously floating the average optimal values of other parameters up and down within a certain range to obtain initial value ranges of other parameters;
(5) changing the frequency domain setting into a range of 200Hz-250Hz, keeping the incident angle parametric scanning setting unchanged, taking the frequency bandwidth with the sound absorption coefficient more than 50% as an objective function, taking the a and b obtained in the step (4) as fixed values, taking the initial value ranges of other parameters as variable value ranges, and carrying out multiple optimization to obtain the optimal value averaging of each parameter as a relatively optimized solution, thereby obtaining the geometric dimension of the sound barrier with excellent noise reduction effect.
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