Ventilated acoustic baffle

Abstract

The present application belongs to the technical field of acoustic metamaterials, and more particularly to a ventilation sound insulation ring with a spatially coiled structure. The sound insulation ring is mainly composed of a ring-shaped main pipeline and a plurality of fan-shaped spatially coiled structure sandwich units. The specific structure is that a plurality of spatially coiled structure sandwiches are excavated in the pipe wall of the ring-shaped pipeline, and the spatially coiled structure sandwich units are distributed in a circumferential array around the central axis of the ring-shaped pipeline. Compared with existing sound insulation structures, the spatially coiled structure sandwich units have a smaller size in the subwavelength size, are convenient to integrate, and realize low-frequency broadband ventilation sound insulation function under the joint action of sound absorption and reflection.

Description

Technical Field

[0001] This invention belongs to the technical field of acoustic metamaterials, specifically, it relates to a ventilation and sound insulation ring with a spatial coiled structure. Background Technology

[0002] Acoustic metamaterials are a new type of material with artificially periodic structures, possessing extraordinary physical properties that natural materials cannot achieve, such as acoustic cloaking and sound absorption, and have enormous application potential. Among them, labyrinth-type acoustic metamaterials have always been a research hotspot. Labyrinth-type sound-absorbing structures achieve sound absorption by increasing the sound wave's propagation path and thus increasing sound wave loss in the air.

[0003] Traditional porous sound-absorbing materials exhibit low energy density, typically resulting in weak dissipation of low-frequency sound waves. In recent years, acoustic metamaterials have utilized the high energy density achieved through local resonance in subwavelength thick structures, providing an alternative solution for mid-to-low frequency sound insulation. Several methods have been proposed in this regard, such as Fabry-Perot (FP) resonators, Helmholtz resonators, microperforated plates (MPPs), thin-film resonators, and gradient exponential structures. However, acoustic insulation units based on local resonance require complex geometries with a quarter-wavelength dimension and relatively narrow bandwidths.

[0004] Incident sound waves are confined within a coiled channel of subwavelength cross-section, resulting in remarkable acoustic properties such as binegativity and a near-zero effective refractive index per unit cell. Several types of spatial coil structures have been demonstrated for low-frequency sound absorption, such as coplanar helices, axially coupled circular tubes, coiled air chambers, helical metasurfaces, and labyrinth structures. Among these, labyrinth metamaterials have proven to be most effective for broadband sound absorption. These structures allow sound waves to propagate within folded, narrow channels, multiplying the effective path length and slowing the propagating wave velocity due to the viscous-thermal effect at the air channel wall interfaces.

[0005] Ventilation components are commonly used in various equipment that requires ventilation, which often generates noise that can have adverse effects on public health and quality of life.

[0006] Current ventilation and sound insulation structures have the following shortcomings:

[0007] 1. Narrow sound insulation frequency range: Existing sound insulation structures rely on internal thermal dissipation or resonance, resulting in a narrow usable sound insulation frequency range;

[0008] 2. Poor low-frequency sound insulation: Traditional sound insulation materials themselves have poor sound insulation performance. They can reduce sound to a certain extent in the high-frequency range, but their sound insulation performance is poor in the low-frequency range.

[0009] 3. Large volume of sound insulation structure: The sound insulation of some building materials is proportional to the logarithm of their mass (or surface density) per unit area; the sound energy is large at low frequencies, requiring a larger volume to meet the needs of sound insulation or sound absorption, which limits the application of traditional materials in sound insulation.

[0010] The purpose of this invention is to realize a low-frequency ventilation and sound insulation structure at the subwavelength level. Summary of the Invention

[0011] In view of this, the present invention proposes a sound insulation ring structure with ventilation function. By installing this ventilation sound insulation ring structure in front of the noise source, and at the same time optimizing the structural parameters of the ventilation sound insulation ring, it is beneficial to improve the sound insulation of noise over a wide frequency range, reduce noise, and reduce noise radiation outward while achieving good ventilation effect.

[0012] The sound insulation ring mainly consists of a ring-shaped main pipe and a spatial coiled structure interlayer. Specifically, a spatial coiled structure interlayer is carved out in the wall of the ring-shaped pipe. The ring-shaped pipe of the sound insulation ring contains multiple spatial coiled structure interlayer units, which are distributed in a circular array around the central axis of the ring-shaped pipe.

[0013] Furthermore, the spatial coiled structure unit is connected to the outside world only at the interlayer entrance and exit through the pipe incident surface and exit surface, respectively.

[0014] Furthermore, multiple spatial coiled structural interlayer units have the same shape and are evenly distributed along the central axis of the annular pipe in the annular pipe wall.

[0015] Furthermore, the number of folds n in each spatial coiled structure sandwich unit is ≥4 and is an even number.

[0016] Furthermore, the overall structure of each spatial coiled interlayer unit is fan-shaped, and the distance between the inner and outer diameters of the fan and the inner and outer diameters of the annular pipe structure is t1 = 0.5~2mm.

[0017] Furthermore, the spacing between adjacent pipes in the inner ring of each spatial coiled structure sandwich unit is t2≥0.5mm.

[0018] Advantages of this invention compared to existing technologies:

[0019] 1. The sound insulation ring structure in this invention, due to its unique ring structure, allows some fluid to pass through its interior.

[0020] 2. Thin-element structure design is not common, and the overall volume of this structure is relatively small. The thickness of this sound insulation ring structure unit can be as low as t≤40mm.

[0021] 3. The structural parameters of the sound insulation ring of the present invention are adjustable. By adjusting the structural parameters (the number of folds, thickness, etc. of the spatial coiled structure sandwich layer), the sound insulation frequency band can be adjusted. Moreover, the tube thickness of different spatial coiled sandwich structure units does not need to be exactly the same. Spatial coiled sandwich structure units with different parameters correspond to different sound insulation frequency ranges. Multiple spatial coiled structures with different parameter sizes influence each other. By setting reasonable structural parameters, the sound insulation frequency range can be effectively widened, which provides operability for designing specific sound insulation frequency bands.

[0022] 4. The sound insulation ring structure of the present invention can achieve different sound insulation effects by changing the various structural parameters of the sound insulation ring. By adjusting the various structural parameters of the sound insulation ring, a more ideal sound insulation effect can be obtained with the combination of different structural parameters. Attached Figure Description

[0023] Figure 1 a and 1b are schematic diagrams of the sound insulation ring with ventilation function and the space coiled structure sandwich unit provided by the present invention, respectively.

[0024] Figure 2 yes Figure 1 A schematic diagram of the sound insulation ring with ventilation function in direction A;

[0025] Figure 3 It is Figure 1 A schematic diagram of a sound-insulating ring with ventilation function placed inside a cylindrical waveguide;

[0026] Figure 4A This is a schematic diagram of the sound insulation coefficient versus frequency for each spatial coiled structure with a pipe thickness of w = 6 mm and a folding number of n = 4 in one embodiment of the present invention.

[0027] Figure 4B This is a schematic diagram of the sound insulation coefficient versus frequency for each spatial coiled structure with a pipe thickness of w = 3 mm and a folding number of n = 4 in one embodiment of the present invention.

[0028] Figure 4C This is a schematic diagram of the sound insulation coefficient versus frequency for each spatial coiled structure with a pipe thickness of w = 3 mm and a folding number of n = 6 in one embodiment of the present invention.

[0029] Figure label:

[0030] 1. Soundproof ring duct; 2. Spatial coiled sandwich structure unit; 3. Cylindrical waveguide Detailed Implementation

[0031] To make the objectives, advantages, and technical solutions of this invention clearer and more intuitive, the invention will be further described below in conjunction with embodiments and related drawings. It should be understood that the embodiments described below are only for explaining the invention and should not be construed as limiting the invention.

[0032] Please see Figure 1 and Figure 2 The ventilation and sound insulation ring structure described in this invention requires a smaller structural size to achieve the same sound insulation frequency as traditional sound insulation metamaterials, making it easier to meet practical application needs.

[0033] like Figure 3 As shown, a ventilation and sound insulation ring structure is placed inside a cylindrical air waveguide with a diameter of 80 mm and a length of 160 mm. The material of the sound insulation ring structure of this invention is photosensitive resin, and the model can be printed using 3D printing technology. The two ends of the cylindrical air waveguide are open, and the remaining boundaries are acoustically rigid. The determined dimensional parameters of the ventilation and sound insulation ring structure are: annular pipe thickness t = 40 mm, annular pipe inner diameter d = 40 mm, annular pipe outer diameter D = 80 mm, and the distances from the inner and outer ends of the spatial coiled sandwich structure inside the annular pipe wall to the inner and outer diameters of the pipe are both t1 = 2 mm. The sound insulation ring structure of this invention is placed between the inlet and outlet of the air waveguide, with air as the background medium. The two ends of the cylindrical waveguide are port boundaries, and the remaining boundaries are hard acoustic field boundaries. Frequency domain analysis is performed using the pressure acoustic module of the finite element software COMSOL MULTIPHYSICS to calculate the ratio of the sound waves at the inlet to the outlet of the air waveguide, i.e., the transmission coefficient S.

[0034] Example 1:

[0035] The sound insulation ring structure proposed in this invention has many dimensional parameters. Since this invention primarily examines the impact of the spatial coiled structure on the sound insulation effect, the external dimensions of the circular pipe must be determined first. Additionally, some structural parameters (such as the distance from the internal coiled structure to the outer wall) have a relatively small impact on the sound insulation effect and should be determined first. However, for structural parameters that have a significant impact on the sound insulation effect (such as the number of coiled structure units, the thickness of the coiled structure pipe, and the number of folds in the coiled structure units), some parameters should also be determined first to achieve a relatively ideal sound insulation effect. The specific design steps are as follows:

[0036] The structure of this invention has a thickness of 40mm; the inner radius of the annular main pipe is 20mm, and the outer radius is 40mm; the number of spatial coiled structure sandwich units is 6, and the number of folds in the coiled structure is 4. Compared with existing sound insulation structures, it has the following advantages at the subwavelength scale:

[0037] 1. Small structural size, easy to integrate;

[0038] 2. The hollow center of the structure allows for a certain degree of ventilation.

[0039] 3. It has a wide sound insulation frequency range, which broadens the sound insulation frequency domain, with an average bandwidth of 1kHz;

[0040] 4. The sound insulation frequency range is adjustable, and the sound insulation frequency range can be adjusted by adjusting the parameters of the coiled sandwich structure inside the pipe.

[0041] For example Figure 1 The ventilation and sound insulation ring structure shown was simulated using finite element analysis (FEM) software, COMSOLMULTIPHYSICS. The structure was placed in an air duct, with a plane wave incident perpendicularly from its left side. First, a SOLIDWORKS model was constructed as follows... Figure 1 a and Figure 3 The model shown is imported into the simulation software. Boolean operations are used to remove the solid outer shell of the structure, resulting in the acoustic channel model, whose material is set to air. Next, a pressure acoustics module is added, in which narrow acoustics and thermoviscous boundary impedance interfaces are added to simulate the acoustic-thermal coupling environment. An incident port is added to the left side of the acoustic channel interface as a sound source. A port is added to the right side of the acoustic channel interface to represent the non-reflective conditions at the exit. Then, frequency domain analysis is performed on the structure to calculate its transmission coefficient. The curve of the transmission coefficient as a function of frequency is shown below. Figure 4A and 4B As shown; from Figure 4A As can be seen, the transmission coefficient of the structure has two valleys within the selected frequency range, with a valley coefficient Smin ≤ 0.15. Between adjacent valleys, the transmission coefficient of the structure increases, but still maintains a low transmission coefficient (S < 0.3), effectively isolating sound waves. Figure 4A and 4B The comparison shows that as the thickness of the spatially coiled sandwich structure increases, the sound insulation frequency gradually shifts from 1580Hz to a lower frequency of 1390Hz. The average transmission coefficient within the sound insulation frequency range also decreases. The advantages of the spatially coiled sandwich structure are: wide low-frequency bandwidth and ease of adjustment. (Observation...) Figure 4A and 4B It can be observed that the thicker the channel of the spatial coiled sandwich structure, the lower its sound insulation frequency and the lower the transmission coefficient, resulting in better sound insulation.

[0042] Example 2:

[0043] In this embodiment, the thickness of the sound insulation ring structure is 40mm; the inner radius of the annular main pipe is 20mm and the outer radius is 40mm; the number of interlayer units of the spatial coiled structure is 6, and the pipe thickness of the coiled structure is w=3mm.

[0044] refer to Figure 4B and4C When the number of folds in the spatial coil structure is 4, its lowest sound insulation frequency is 1390Hz. When the number of folds in the spatial coil structure becomes 6, the lowest sound insulation frequency shifts to 900Hz. This shows that as the number of folds increases (i.e., the sound channel path becomes longer), the sound insulation frequency gradually decreases, while the sound transmission amplitude remains basically unchanged. Therefore, by increasing the number of folds in the spatial coil structure, the desired sound insulation frequency can be obtained, while maintaining a transmission coefficient below 0.4.

[0045] By adjusting the thickness and number of folds of the spatially coiled structure of this ventilation sound insulation ring, sound insulation with stable bandwidth and low-frequency ventilation can be achieved. The use of the ventilation sound insulation ring structure significantly reduces the lateral thickness of the sound insulation structure while maintaining the sound insulation efficiency of an equivalent long duct. The ventilation sound insulation ring structure offers a lower sound insulation frequency, a wider sound insulation frequency band, and greater flexibility in low-frequency ventilation sound insulation, contributing to the realization of ultra-thin, widely tunable, and highly efficient broadband sound insulation structures for low-frequency ventilation.

[0046] Finally, it should be noted that the embodiments described above are only used to explain the technical solutions of the present invention and cannot be used to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that any equivalent substitutions or modifications made within the spirit and scope of the technical solutions of the present invention should still be included within the protection scope of the present invention.

Claims

1. A ventilation and sound insulation ring structure, characterized in that: The ventilation and sound insulation ring structure includes a ring-shaped main duct and multiple independent spatial coiled structure sandwich units. These spatial coiled structure sandwich units are distributed circumferentially around the central axis of the ring-shaped main duct. Each spatial coiled structure sandwich unit communicates with the outside world at the inlet and outlet of the coiled duct via the incident and exit surfaces of the ring-shaped main duct, respectively. The overall shape of each spatial coiled structure sandwich unit is fan-shaped, and the path shape of the duct within the spatial coiled structure sandwich unit is maze-shaped, with each unit having a folding number n greater than or equal to 4. The distance between the inner and outer diameters of each spatial coiled structure sandwich unit and the inner and outer diameters of the ring-shaped main duct structure is t1 = 0.5~2 mm. The spacing between adjacent ducts within the inner ring of each spatial coiled structure sandwich unit is t2 ≥ 0.5 mm.

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