Sound barrier unit plate based on periodic structure, sound barrier and rail transit noise reduction structure

Abstract

The invention relates to a sound barrier unit plate based on a periodic structure, a sound barrier adopting the sound barrier unit plate and a rail transit noise reduction structure adopting the sound barrier, the sound barrier unit plate comprises a unit plate body, and at least one face of the unit plate body is provided with a sound absorption structure. The sound absorption structure comprises a plurality of sound absorption layers which are sequentially arranged from bottom to top; each sound absorption layer comprises a plurality of same sound absorption units, each sound absorption unit comprises a base body and a plurality of Helmholtz resonators embedded in the base body, and the sound absorption units in each sound absorption layer are periodically arranged in the horizontal direction so as to attenuate noise of a preset frequency band through the acoustic band gap effect. According to the sound barrier, the multiple sound absorption layers are arranged on the sound barrier unit plates in the vertical direction, the sound absorption layers adopt the mode that the sound absorption units are arranged periodically, the sound absorption layers can strongly attenuate noise of a specific frequency band, especially low-frequency noise through the acoustic band gap effect formed by periodic arrangement of the Helmholtz resonators, and the noise reduction effect of the sound barrier is guaranteed; the multiple sound absorption layers are vertically arranged so that the noise reduction frequency band coverage of the sound barrier can be more complete, and higher noise reduction pertinence can be achieved, for example, different sound absorption layers focus different frequency bands, and the problems of insufficient local noise reduction and the like caused by universal design are solved.

Description

Technical Field

[0001] This invention belongs to the field of rail transit noise control technology, specifically relating to a sound barrier unit plate based on a periodic structure, a sound barrier using the sound barrier unit plate, and a rail transit noise reduction structure using the sound barrier. Background Technology

[0002] Among the noise from passing vehicles on rail transit bridges, low- and mid-frequency noise (typically referring to frequencies below 1000Hz) is a major source of noise pollution affecting the quality of life of residents along the railway line due to its long propagation distance and strong penetrating power. The existing sound barriers along both sides of the railway bridges have three prominent problems:

[0003] First, the sound absorption performance is limited: low and medium frequency noise in rail transit is difficult to attenuate through conventional acoustic structures. Most existing sound barrier unit panels use a single conventional porous sound-absorbing material. These materials have a certain absorption effect on mid and high frequency noise, but their sound absorption coefficient for low frequency noise is generally low, which cannot effectively weaken the propagation of low frequency noise, resulting in an unsatisfactory overall noise reduction effect.

[0004] Secondly, the noise reduction efficiency is limited: the arrangement on both sides does not directly block the wheel-rail noise radiated in the middle area of ​​the track, and the sound waves are easy to diffract and propagate. Especially in the open space of the bridge section, the actual noise reduction is often lower than the design value.

[0005] Third, there is a significant conflict between cost and space: to achieve the same noise reduction effect, the height of the sound barriers on both sides needs to be significantly increased, leading to increased material usage and construction difficulty. In urban sections where space is narrow on both sides of the bridge, excessively high barriers can easily cause safety hazards due to wind loads, while also increasing the cost of reinforcing the bridge and pushing up the overall project cost. Summary of the Invention

[0006] The present invention relates to a sound barrier unit plate based on a periodic structure, a sound barrier using the sound barrier unit plate, and a noise reduction structure for rail transit using the sound barrier, which can at least solve some of the defects of the prior art.

[0007] This invention relates to a sound barrier unit panel based on a periodic structure, comprising a unit panel body, at least one side of which is provided with a sound-absorbing structure, the sound-absorbing structure comprising a plurality of sound-absorbing layers arranged sequentially from bottom to top; each sound-absorbing layer comprising a plurality of identical sound-absorbing units, each sound-absorbing unit comprising a matrix and a plurality of Helmholtz resonators embedded in the matrix, the sound-absorbing units in each sound-absorbing layer being periodically arranged in the horizontal direction to attenuate noise in a preset frequency band using the acoustic bandgap effect.

[0008] As one implementation method, from bottom to top, the attenuation domains of each sound-absorbing layer are sequentially connected in the frequency domain and cover the target noise reduction frequency band.

[0009] As one implementation method, at least one set of two adjacent sound-absorbing layers are coupled through a resonant mode;

[0010] Considering the coupling with the (i+1)th sound-absorbing layer, the coupling resonant frequency f of the ith sound-absorbing layer 0i The following relationship must be satisfied:

[0011]

[0012] Where c is the speed of sound in air at room temperature; S i V is the cross-sectional area of ​​the neck of the Helmholtz resonator in the i-th sound-absorbing layer; i L represents the cavity volume of the Helmholtz resonator in the i-th sound-absorbing layer; eq,i The equivalent neck length of the Helmholtz resonator in the i-th sound-absorbing layer; k is the coupling coefficient; C i(i+1) The acoustic coupling stiffness between the two sound-absorbing layers; m i =ρ·Si·L eq,i , where is the equivalent mass of the neck air column of the Helmholtz resonator in the i-th sound-absorbing layer, and ρ is the air density.

[0013] As one implementation method, the structural parameters between the two sound-absorbing layers coupled via resonant modes are configured such that the coupling coefficient k is approximately equal to the acoustic coupling stiffness C. i(i+1) To satisfy the preset matching relationship, so as to achieve seamless connection of the attenuation domains of the two sound-absorbing layers in the frequency domain and eliminate the sound absorption trough;

[0014] Specifically:

[0015]

[0016]

[0017] Where d is the width of the acoustic gap between the two sound-absorbing layers.

[0018] As one implementation method, the lower limit frequency of the acoustic bandgap of the sound-absorbing layer is calculated according to the following formula:

[0019]

[0020] Where c is the speed of sound in air at room temperature; S i V is the cross-sectional area of ​​the neck of the Helmholtz resonator in the i-th sound-absorbing layer; i L represents the cavity volume of the Helmholtz resonator in the i-th sound-absorbing layer; eq,i denoted as , where is the equivalent neck length of the Helmholtz resonator in the i-th sound-absorbing layer; a is the periodic lattice constant of the i-th sound-absorbing layer.

[0021] As one implementation method, sound-absorbing structures are provided on both sides of the unit board body.

[0022] The present invention also relates to a sound barrier, which is assembled from multiple sound barrier unit panels, at least some of which are sound barrier unit panels as described above.

[0023] The present invention also relates to a noise reduction structure for rail transit, including a near-rail sound barrier arranged close to the wheel and rail, wherein the near-rail sound barrier adopts the sound barrier described above; when the near-rail sound barrier is installed between two sets of wheel and rail, both sides of the unit plate body are provided with sound-absorbing structures.

[0024] The present invention has at least the following beneficial effects:

[0025] In this invention, the sound barrier unit panel is vertically arranged with multiple sound-absorbing layers, and the sound-absorbing layers are arranged in a periodic manner. The acoustic bandgap effect formed by the periodic arrangement of Helmholtz resonators can make the sound-absorbing layers strongly attenuate noise in specific frequency bands, especially low-frequency noise, thus ensuring the noise reduction effect of the sound barrier. The vertical arrangement of multiple sound-absorbing layers can make the noise reduction frequency band coverage of the sound barrier more complete, and can achieve stronger noise reduction targeting. For example, different sound-absorbing layers focus on different frequency bands, avoiding problems such as insufficient local noise reduction caused by general-purpose design. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the composition of the sound-absorbing structure provided in an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the structure of a sound barrier unit panel provided in an embodiment of the present invention;

[0029] Figure 3 for Figure 2 A sectional view along AA. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] like Figure 1 This invention provides a sound barrier unit panel 1 based on a periodic structure, comprising a unit panel body, at least one side of which is provided with a sound-absorbing structure, the sound-absorbing structure comprising a plurality of sound-absorbing layers 100 arranged sequentially from bottom to top; each sound-absorbing layer 100 includes a plurality of identical sound-absorbing units 101, each sound-absorbing unit 101 including a substrate and a plurality of Helmholtz resonators embedded in the substrate, the sound-absorbing units 101 in each sound-absorbing layer 100 being periodically arranged in the horizontal direction to attenuate noise in a preset frequency band using the acoustic bandgap effect.

[0033] Preferably, the sound-absorbing structure is provided on both sides of the unit panel body, so that the sound barrier unit panel 1 is configured as a unit panel with sound absorption effect on both sides, which can be conveniently arranged between two adjacent sets of wheel rails, for example, it can be arranged in the middle of the rail transit bridge section to ensure the sound absorption and noise reduction effect on both sides of the wheel rails.

[0034] Each sound-absorbing layer 100 is preferably designed to correspond to a different preset frequency band. Through the design of each sound-absorbing layer 100, the energy of different sub-frequency bands in the mid-low frequency sound energy can be captured by the sound-absorbing layer 100 in the corresponding attenuation domain. When the sound wave frequency matches the inherent resonant frequency of the Helmholtz resonator in the sound-absorbing layer 100, the air column in the neck of the Helmholtz resonator resonates violently. The sound energy is converted into heat energy through the friction between the air column and the neck wall and the compression and expansion of the air inside the cavity, thus achieving targeted dissipation.

[0035] In one embodiment, the attenuation domains of each sound-absorbing layer 100 are sequentially connected in the frequency domain from bottom to top, covering the target noise reduction frequency band. The attenuation domain of each sound-absorbing layer 100 is determined by the geometric parameters of its internal Helmholtz resonator. By designing the attenuation domains of different sound-absorbing layers 100 to be sequentially connected in the frequency domain, a continuous coverage from low to high frequencies can be formed, creating a stepped frequency band coverage system and avoiding the problem of excessively narrow bandwidth of a single resonant structure. Preferably, the attenuation domains between adjacent sound-absorbing layers 100 are designed to partially overlap, which not only ensures the reliability of the stepped frequency band coverage but also lays the foundation for acoustic coupling between the sound-absorbing layers 100.

[0036] The natural resonant frequency of a single-type Helmholtz resonator is designed according to the following formula:

[0037]

[0038] In the formula, c is the speed of sound in air at room temperature, c = 340 m / s; S is the cross-sectional area of ​​the neck of the Helmholtz resonator; V is the cavity volume of the Helmholtz resonator; L eq L is the equivalent length of the neck of the Helmholtz resonator.eq =L+0.8d, where L is the actual length of the neck and d is the equivalent diameter of the neck.

[0039] As can be seen from the above formula, by adjusting the structural parameters such as S, V, and L, each sound-absorbing layer 100 can correspond to each target sub-frequency band within the target noise reduction frequency band, thereby achieving full-dimensional coverage of the core frequency band of wheel-rail noise.

[0040] In one embodiment, at least one set of two adjacent sound-absorbing layers 100 are coupled via a resonant mode; specifically, considering the coupling resonant frequency f of the i-th sound-absorbing layer 100 after coupling with the (i+1)-th sound-absorbing layer 100. 0i The following relationship must be satisfied:

[0041]

[0042] Where c is the speed of sound in air at room temperature; S i V is the cross-sectional area of ​​the neck of the Helmholtz resonator in the i-th sound-absorbing layer 100; i L represents the cavity volume of the Helmholtz resonator in the i-th sound-absorbing layer 100; eq,i The equivalent neck length of the Helmholtz resonator in the i-th sound-absorbing layer 100; k is the coupling coefficient; C i(i+1) The acoustic coupling stiffness between the two sound-absorbing layers 100; m i =ρ·Si·L eq,i , where is the equivalent mass of the neck air column of the Helmholtz resonator in the i-th sound-absorbing layer 100, and ρ is the air density.

[0043] Furthermore, the structural parameters between the two sound-absorbing layers 100 coupled via resonant mode are configured such that the coupling coefficient k is proportional to the acoustic coupling stiffness C. i(i+1) To satisfy the preset matching relationship, the attenuation domains of the two sound-absorbing layers 100 are seamlessly connected in the frequency domain, eliminating sound absorption troughs;

[0044] Specifically:

[0045]

[0046]

[0047] Where d is the width of the acoustic gap between the two sound-absorbing layers 100.

[0048] The physical mechanism of the aforementioned resonance mode coupling is as follows: the acoustic energy in the overlapping region of the attenuation domains of two adjacent sound-absorbing layers 100 simultaneously excites the neck air column resonance of the Helmholtz resonators of the two sound-absorbing layers 100, forming a resonance superposition effect, which merges the single resonance peak into a continuous resonance band; the periodic coupling effect expands the narrow acoustic bandgap of a single sound-absorbing layer 100 into a wide bandwidth of the target noise reduction frequency band (e.g., 200Hz~4000Hz), achieving full-band sound absorption without valleys. Mid-to-low frequency acoustic energy undergoes multiple reflections and scatterings between adjacent sound-absorbing layers 100, and is transmitted between sound-absorbing layers 100 through acoustic gaps, forming a multi-level resonance dissipation channel. The acoustic energy not completely consumed by a single sound-absorbing layer 100 can be continuously captured and attenuated by the corresponding sound-absorbing layers 100 along the way, thus significantly improving the acoustic energy dissipation efficiency.

[0049] Optionally, the overlap rate of the attenuation domains of two adjacent sound-absorbing layers 100 shall not be less than 10%, including but not limited to being controlled within the range of 10% to 30%. Further, for high-frequency layers with a wider bandwidth, a smaller overlap rate (10% to 20%) shall be adopted; for low-frequency layers with a narrower bandwidth, a larger overlap rate (20% to 30%) shall be adopted.

[0050] Preferably, the target noise reduction frequency band is 200~4000Hz. In one embodiment, for this target noise reduction frequency band, such as... Figure 1 The design incorporates five sound-absorbing layers 100. From bottom to top, the attenuation range of the first sound-absorbing layer 100 is 200~300Hz, the attenuation range of the second sound-absorbing layer 100 is 250~600Hz, the attenuation range of the third sound-absorbing layer 100 is 500~1200Hz, the attenuation range of the fourth sound-absorbing layer 100 is 1000~2200Hz, and the attenuation range of the fifth sound-absorbing layer 100 is 2000~4000Hz.

[0051] In one embodiment, the lower limit frequency of the acoustic bandgap of the sound-absorbing layer 100 is calculated according to the following formula:

[0052]

[0053] Where c is the speed of sound in air at room temperature; S i V is the cross-sectional area of ​​the neck of the Helmholtz resonator in the i-th sound-absorbing layer 100; i L represents the cavity volume of the Helmholtz resonator in the i-th sound-absorbing layer 100; eq,i denoted as the neck equivalent length of the Helmholtz resonator in the i-th sound-absorbing layer 100; a is the periodic structure lattice constant of the i-th sound-absorbing layer 100.

[0054] Through the structural design of the corresponding sound-absorbing layer 100, its acoustic bandgap lower limit frequency f is achieved. bgTo meet design requirements and ensure effective attenuation of low- and mid-frequency noise, targeted noise reduction of low-frequency noise in bridge sections can be achieved; for example, by designing the parameters of the first sound-absorbing layer 100, its f bg = 200Hz; the second sound-absorbing layer has an f of 100. bg = 250Hz; etc.

[0055] Optionally, such as Figure 1 Each sound-absorbing layer 100 includes multiple sound-absorbing groups arranged horizontally in sequence. Each sound-absorbing group includes multiple sound-absorbing units 101 that are in contact with each other end to end. There is a certain interval between each two adjacent sound-absorbing groups. In this structure, the lattice constant of the above-mentioned periodic structure is the periodic distance between groups (for example, the distance between the first sound-absorbing unit 101 of the first sound-absorbing group and the first sound-absorbing unit 101 of the second sound-absorbing group).

[0056] In one embodiment, the inlet side of the Helmholtz resonator is further covered with a porous sound-absorbing plate. The incident sound wave first contacts the porous sound-absorbing plate, passes through it, and then enters the corresponding Helmholtz resonator. This forms a composite coupled sound absorption system of resonant sound absorption and porous sound absorption, which can effectively improve noise reduction. Furthermore, the porous sound-absorbing plate primarily absorbs high-frequency noise above 2000Hz, compensating for the Helmholtz resonator's shortcoming in high-frequency sound absorption. Additionally, the porous structure of the plate provides buffering and guidance for mid-to-low frequency sound energy, allowing it to be more accurately incident on the neck of the Helmholtz resonator, enhancing its mid-to-low frequency sound absorption effect. Moreover, the porous sound-absorbing plate can reduce acoustic crosstalk between adjacent Helmholtz resonators, thereby improving the overall acoustic sealing and preventing sound leakage from the unit gaps.

[0057] Optionally, the porous sound-absorbing board can be a polyurethane foam board; however, it is not limited to this method, and melamine foam board, urea-formaldehyde foam board, etc. are also feasible.

[0058] In one embodiment, the substrate may also be made of porous sound-absorbing material to form a structure that covers the Helmholtz resonator, thereby further improving the noise reduction effect; furthermore, the substrate is preferably made of the same material as the porous sound-absorbing plate.

[0059] Furthermore, the plurality of sound-absorbing layers 100 are designed such that the total sound absorption coefficient of the sound-absorbing structure within the target noise reduction frequency band is within a preset range, and the total sound absorption coefficient is calculated according to the following formula:

[0060]

[0061] Where, α total The total sound absorption coefficient is α; n is the total number of sound-absorbing layers 100, n≥2; iS is the sound absorption coefficient of a single Helmholtz resonator in the i-th sound-absorbing layer 100; i ξ is the effective sound absorption area of ​​the i-th sound-absorbing layer 100; i(i+1) α is the coupling loss coefficient between adjacent sound-absorbing layers 100; p S is the sound absorption coefficient of the porous sound-absorbing panel. p S is the effective coverage area of ​​the porous sound-absorbing panel; total The total sound-absorbing area of ​​the sound-absorbing structure.

[0062] Where, ξ i(i+1) The optimal design is close to 0, so that the sound energy transmission between each sound-absorbing layer 100 is almost lossless, thus optimizing the overall sound absorption performance of the unit board.

[0063] The above formula for calculating the total sound absorption coefficient fully considers the coupling loss between the 100 sound absorption layers, ensuring the stability of the sound absorption coefficient within the target noise reduction frequency band.

[0064] More preferably, such as Figure 2 The sound-absorbing structure also includes a porous panel 102, which is located on the incoming sound side of the corresponding Helmholtz resonator and covers each sound-absorbing layer 100 in the corresponding sound-absorbing structure. The porous panel 102 not only effectively protects the internal sound-absorbing components but also forms the first acoustic impedance layer, thereby improving the noise reduction effect of the sound barrier unit panel 1. The aforementioned porous panel 102 includes, but is not limited to, using aluminum alloy plates; its openings include, but are not limited to, a honeycomb distribution.

[0065] For cases where sound-absorbing structures are provided on both sides of the unit panel body, optionally, such as Figure 2 The sound-absorbing structures on both sides are separated by a partition 105.

[0066] In one embodiment, such as Figure 2 and Figure 3 The unit panel body includes two end vertical supports 103, and the side panels 102 are fixedly connected to the two end vertical supports 103 respectively, enclosing and embedding each sound-absorbing unit 101 inside. For cases where the unit panel has a long span, a middle vertical support 104 can be further provided. The middle vertical support 104 and the end vertical supports 103 can be connected by a connecting rod. When a partition 105 is provided, the partition 105 can be used to connect the middle vertical support 104 and the end vertical supports 103. For cases where there are end vertical supports 103 and partitions 105, the end vertical supports 103 can be designed in a mountain-shaped structure to facilitate connection with the partitions 105. For cases where there are middle vertical supports 104 and partitions 105, the middle vertical support 104 can be designed in a king-shaped structure to facilitate connection with the partitions 105.

[0067] Example 2

[0068] This invention provides a sound barrier assembled from multiple sound barrier unit panels 1. At least some of the sound barrier unit panels 1 are the sound barrier unit panels 1 provided in the first embodiment above, and preferably all the sound barrier unit panels 1 are the sound barrier unit panels 1 provided in the first embodiment above.

[0069] Example 3

[0070] This invention provides a noise reduction structure for rail transit, including a near-rail sound barrier arranged close to the wheel and rail. The near-rail sound barrier adopts the sound barrier provided in Embodiment 2 above. When the near-rail sound barrier is installed between two sets of wheel and rail, both sides of the unit plate body are provided with sound-absorbing structures.

[0071] Sound barriers installed near the rail have a better noise reduction effect than those installed far from the rail.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A sound barrier unit panel based on a periodic structure, comprising a unit panel body, characterized in that: At least one side of the unit panel body is provided with a sound-absorbing structure, the sound-absorbing structure includes a plurality of sound-absorbing layers arranged sequentially from bottom to top; each sound-absorbing layer includes a plurality of identical sound-absorbing units, the sound-absorbing unit includes a matrix and a plurality of Helmholtz resonators embedded in the matrix, and each sound-absorbing unit in each sound-absorbing layer is arranged periodically in the horizontal direction to attenuate noise in a preset frequency band by utilizing the acoustic bandgap effect.

2. The sound barrier unit panel as described in claim 1, characterized in that: From bottom to top, the attenuation domains of each sound-absorbing layer are sequentially connected in the frequency domain and cover the target noise reduction frequency band.

3. The sound barrier unit panel as described in claim 1, characterized in that: At least one set of two adjacent sound-absorbing layers are coupled through a resonant mode; Considering the coupling with the (i+1)th sound-absorbing layer, the coupling resonant frequency f of the ith sound-absorbing layer 0i The following relationship must be satisfied: Where c is the speed of sound in air at room temperature; S i V is the cross-sectional area of ​​the neck of the Helmholtz resonator in the i-th sound-absorbing layer; i L represents the cavity volume of the Helmholtz resonator in the i-th sound-absorbing layer; eq,i The equivalent neck length of the Helmholtz resonator in the i-th sound-absorbing layer; k is the coupling coefficient; C i(i+1) The acoustic coupling stiffness between the two sound-absorbing layers; m i =ρ·Si·L eq,i , where is the equivalent mass of the neck air column of the Helmholtz resonator in the i-th sound-absorbing layer, and ρ is the air density.

4. The sound barrier unit panel as described in claim 3, characterized in that, The structural parameters between the two sound-absorbing layers coupled via resonant modes are configured such that the coupling coefficient k is related to the acoustic coupling stiffness C. i(i+1) To satisfy the preset matching relationship, so as to achieve seamless connection of the attenuation domains of the two sound-absorbing layers in the frequency domain and eliminate the sound absorption trough; Specifically: Where d is the width of the acoustic gap between the two sound-absorbing layers.

5. The sound barrier unit panel as described in claim 1, characterized in that, The lower limit frequency of the acoustic bandgap of the sound-absorbing layer is calculated using the following formula: Where c is the speed of sound in air at room temperature; S i V is the cross-sectional area of ​​the neck of the Helmholtz resonator in the i-th sound-absorbing layer; i L represents the cavity volume of the Helmholtz resonator in the i-th sound-absorbing layer; eq,i denoted as , where is the equivalent neck length of the Helmholtz resonator in the i-th sound-absorbing layer; a is the periodic lattice constant of the i-th sound-absorbing layer.

6. The sound barrier unit panel as described in any one of claims 1 to 5, characterized in that, Both sides of the unit panel body are provided with sound-absorbing structures.

7. A sound barrier, assembled from multiple sound barrier unit panels, characterized in that, At least some of the sound barrier unit panels are made of the sound barrier unit panels as described in any one of claims 1 to 6.

8. A noise reduction structure for rail transit, characterized in that: The system includes a near-rail sound barrier arranged close to the wheel rails, wherein the near-rail sound barrier adopts the sound barrier as described in claim 7; when the near-rail sound barrier is installed between two sets of wheel rails, both sides of the unit plate body are provided with sound-absorbing structures.

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