A perforated panel absorber with axially periodically rough surfaces and annular micropores

Abstract

The present invention provides a micro-perforated panel sound absorber with an axially periodically rough surface annular micropore, which includes a micro-perforated panel, a rigid backing, and a cavity between the micro-perforated panel and the rigid backing. An annular sound absorption through-hole is provided on the micro-perforated panel, and the opening directions of the annular sound absorption through-holes are all perpendicular to the micro-perforated panel. The axially periodically rough surface morphology of the annular sound absorption through-holes provided on the micro-perforated panel is controlled by a function. The structure of the present invention is simple, light in weight, and has a high sound absorption coefficient in the mid-low frequency band. Through reasonable design of the structure, the sound absorption frequency band can be flexibly and effectively adjusted, and the sound absorption performance in the corresponding frequency band can be improved, having a wide range of engineering application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of vibration and noise control, and particularly to a microperforated panel sound absorber with axially periodically rough-surfaced annular micropores. Background Art

[0002] Due to characteristics such as simple structure, light weight, and good sound absorption effect without the need to fill porous sound-absorbing materials, microperforated panels have been widely used in industries such as construction, transportation, aerospace, etc. The perforation morphology of traditional microperforated panels is straight holes with smooth circular cross-sections, and the sound absorption frequency is mainly concentrated in the medium and high frequency bands, with a relatively narrow sound absorption bandwidth. With the acceleration of the industrial modernization process and the rapid development of the building materials field, the requirements for a healthy and harmless acoustic environment are getting higher and higher. The defects of traditional microperforated panels, such as difficult adjustment of the sound absorption frequency band, weak absorption of medium and low frequency noise, and difficult improvement of sound absorption performance, have become more and more prominent, which has greatly affected the application performance of microperforated panels in modern engineering practice.

[0003] Therefore, it is necessary to improve the existing technology to solve the deficiencies of the existing technology. Summary of the Invention

[0004] The present invention provides a microperforated panel sound absorber with axially periodically rough-surfaced annular micropores. In order to improve the deficiencies in the existing technology, annular sound-absorbing through holes with axially periodically rough surfaces are introduced. Through reasonable design of the structure, the sound absorption frequency band is flexibly and effectively adjusted, and the sound absorption performance in the corresponding frequency band is improved to solve the problems of the existing technology.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A microperforated panel sound absorber with axially periodically rough-surfaced annular micropores includes a microperforated panel and a rigid backing. The microperforated panel and the rigid backing are connected by rigid rods or a rigid frame, and there is a cavity between the microperforated panel and the rigid backing. Among them, a plurality of annular sound-absorbing through-hole members are provided on the microperforated panel. The opening direction of the annular sound-absorbing through-hole members is perpendicular to the microperforated panel. The central ring body of the annular sound-absorbing through-hole members is fixedly arranged on the rigid backing or the microperforated panel. The inner wall surface and / or the outer wall surface of the annular sound-absorbing through-hole members is an axially periodically rough surface, and the axially periodically rough surface morphology is controlled by the function r(z) = r0 + εsin(αz), where r0 is the hydraulic radius of the inner / outer wall surface of the axially periodically rough surface of the annular sound-absorbing through-hole members, ε is the amplitude of the axially periodically rough surface, α is the wave number of the axially periodically rough surface, and z is the coordinate with the opening direction of the annular sound-absorbing through-hole members as the axis.

[0007] Furthermore, the minimum distance between the inner wall surface and the outer wall surface of the annular sound-absorbing through-hole members is greater than the viscous boundary layer thickness, and the viscous boundary layer thickness d visCalculated through the sound absorption frequency band: where f min is the lowest frequency in the sound absorption frequency band.

[0008] Furthermore, the thickness of the micro-perforated panel is 2 - 12 mm.

[0009] Furthermore, the cross-section of the annular sound absorption through-hole member is an annular shape. The hydraulic radius of the inner wall surface of the annular sound absorption through-hole member is 0.2 - 0.5 mm, and the hydraulic radius of the outer wall surface of the annular sound absorption through-hole member is 0.5 - 0.9 mm.

[0010] Furthermore, the annular sound absorption through-hole members on the micro-perforated panel are evenly distributed.

[0011] Furthermore, the depth of the cavity between the micro-perforated panel and the rigid backing is 0 - 100 mm.

[0012] Furthermore, the cavity between the micro-perforated panel and the rigid backing is filled or not filled with porous sound absorption materials.

[0013] Furthermore, the micro-perforated panel is made of wood-based boards, metal sandwich panels, resin materials or porous fibers.

[0014] The beneficial effects of the present invention are as follows:

[0015] 1. The present invention has a sound absorption peak in the medium and low frequency range of 0 - 1000 Hz. Compared with the traditional micro-perforated panel sound absorber of the same size, the peak value of the sound absorption coefficient is greatly improved, the frequency at which the peak value is located is reduced, the bandwidth of the high-efficiency sound absorption frequency band is greatly broadened, and it has an excellent sound absorption effect on specific medium and low frequency band noises;

[0016] 2. The minimum distance between the inner wall surface and the outer wall surface of the annular sound absorption through-hole of the present invention is greater than the viscous boundary layer size calculated from the sound absorption frequency band, so as to ensure that there is sufficient viscous action between the air particles and the wall surface of the annular sound absorption through-hole, and it has sufficient loss ability for the sound wave energy, while ensuring the smooth flow of air particles in the annular sound absorption through-hole.

[0017] 3. When the present invention is in use, the micro-perforated panel faces the sound source. Under the excitation of the incident sound wave, the air in the cavity vibrates. When the wavelength of the incident sound wave matches the acoustic impedance of the micro-perforated panel sound absorber with axially periodic rough surface annular micropores, resonance occurs. Due to the existence of viscosity, the friction between the inner and outer wall surfaces of the annular sound absorption through-hole and the air particles during the vibration process converts the sound energy into other forms of energy, thus generating a large amount of loss and achieving the sound absorption effect. In addition, since the annular sound absorption through-hole increases the wall surface in contact with the air particles compared with the circular sound absorption through-hole, the rough surface enhances the friction between the wall surface and the air particles, further improving the sound absorption performance of the micro-perforated panel sound absorber with axially periodic rough surface annular micropores.

[0018] 4. The present invention is light in weight, simple in structure and easy to install. It has excellent sound absorption effect without using porous sound-absorbing materials. By adjusting parameters such as the shape function of the axially periodic rough surface, the depth of the cavity between the micro-perforated panel and the rigid backing, and the size of the annular sound-absorbing through-holes, the sound absorption frequency band and sound absorption effect of the overall structure can be adjusted to meet the sound absorption and noise reduction requirements in different working environments.

[0019] In summary, the micro-perforated panel sound absorber with an axially periodic rough surface and annular micro-holes of the present invention can be used for efficient absorption of medium and low frequency noise. By adjusting the design of the rough surface shape function and structural size of the sound-absorbing through-holes, the sound absorption frequency band of the overall structure can be adjusted specifically, and it has broad engineering application prospects. Description of the Drawings

[0020] Figure 1 is a schematic structural diagram of an embodiment of the present invention;

[0021] Figure 2 is a partial enlarged view of the annular sound-absorbing through-hole of an embodiment of the present invention;

[0022] Figure 3 is a sound transmission loss curve diagram of an embodiment of the present invention;

[0023] Wherein: 1 - micro-perforated panel, 2 - rigid backing, 3 - annular sound-absorbing through-hole. Detailed Embodiments

[0024] The present invention will be further described below with reference to the drawings.

[0025] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0026] In the description of the present invention, it should be noted that, unless otherwise clearly defined and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection or an integral connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0027] Schematic diagrams of various structures according to the disclosed embodiments of the present invention are shown in the accompanying drawings. These figures are not drawn to scale, where for the purpose of clear illustration, some details are enlarged and some details may be omitted. The shapes of various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary. In practice, there may be deviations due to manufacturing tolerances or technical limitations, and those skilled in the art can design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0028] Please refer to Figure 1 , the present invention provides a microperforated panel sound absorber with axially periodically rough-surfaced annular micropores, including a microperforated panel 1 and a rigid backing 2. There is a cavity between the microperforated panel 1 and the rigid backing 2, and the two are connected by rigid rods or a rigid frame; the microperforated panel 1 faces the sound source and backs the rigid backing 2; a plurality of annular sound-absorbing through-holes 3 with opening directions perpendicular to the microperforated panel 1 are evenly distributed on the microperforated panel 1. The inner ring of the annular sound-absorbing through-hole 3 is fixed to the rigid backing 2 by a rigid rod, and the inner and outer wall surfaces of the annular sound-absorbing through-hole 3 are both axially periodically rough surfaces.

[0029] Please refer to Figure 2 , when the inner wall surface of the annular sound-absorbing through-hole 3 has a sinusoidal axially periodically rough surface while the outer wall surface is still an axially smooth surface, the inner wall surface morphology of the annular sound-absorbing through-hole 3 is controlled by the function r(z) = r0 + εsin(αz), where z is the axial coordinate, r0 is the hydraulic radius of the inner wall surface, ε is the amplitude of the periodically rough surface, and α is the wave number of the periodically rough surface.

[0030] The microperforated panel 1 is made of a wooden board or a metal sandwich panel or a resin material or porous fibers to ensure that the structure is lightweight and has a certain load-bearing capacity.

[0031] The thickness of the microperforated panel 1 is 2 - 12 mm so that the noise entering the microperforated panel sound absorber with axially periodically rough-surfaced annular micropores can be fully absorbed.

[0032] The cross-section of the annular sound-absorbing through-hole 3 on the microperforated panel 1 is circular. The hydraulic radius of the inner wall surface of the annular sound-absorbing through-hole 3 is 0.2 - 0.5 mm, and the hydraulic radius of the outer wall surface is 0.5 - 0.9 mm to ensure the smooth flow of air particles in the annular sound-absorbing through-hole 3 and sufficient viscous action between the air particles and the wall surface of the annular sound-absorbing through-hole 3.

[0033] The depth of the cavity between the microperforated panel 1 and the rigid backing 2 is 0 - 100 mm, and the cavity is filled or not filled with porous sound-absorbing materials to adjust the sound-absorbing frequency band according to requirements or further enhance the sound-absorbing performance of the microperforated panel sound absorber with axially periodically rough-surfaced annular micropores.

[0034] Materials for Examples:

[0035] Air: Characterized by a density of 1.205 kg / m 3 , and a sound speed of 343 m / s.

[0036] Aluminum: Characterized by a density of 2700 kg / m 3 , a Young's modulus of 69 GPa, and a Poisson's ratio of 0.33.

[0037] Structural dimensions of the examples:

[0038] The thickness of the microperforated panel 1: t1 = 12 mm, the cavity thickness: t2 = 100 mm. The hydraulic radius of the inner wall of the annular sound-absorbing through-hole 3: r0 = 0.5 mm, the radius of the outer wall of the annular sound-absorbing through-hole 3: r1 = 0.9 mm. The amplitude ε of the periodic rough surface ranges from [0, 0.2], and the wave number α of the periodic rough surface ranges from [0, 4π]. The perforation rate is 14%, and the cavity between the microperforated panel 1 and the rigid backing 2 is not filled with porous sound-absorbing materials.

[0039] Control Example 1 is a traditional microperforated panel absorber with smooth circular micropores that is similar in structure and has the same perforation rate as the example. Except for the pore shape and pore diameter of the circular micropores being different from those of the example, the other structural dimensions are kept the same. To ensure the objectivity of the comparison, the material parameters are also the same as those of the example.

[0040] Control Example 2 is a microperforated panel absorber with smooth annular micropores that is similar in structure and has the same perforation rate as the example. Except for the pore shape and pore diameter of the circular micropores being different from those of the example, the other structural dimensions are kept the same. To ensure the objectivity of the comparison, the material parameters are also the same as those of the example.

[0041] Using the above materials and structural dimensions for numerical simulation, the sound absorption coefficients of the example and Control Examples 1 and 2 within 0 - 1000 Hz are given as follows:

[0042] Please refer to Figure 3 , where the solid line represents the sound absorption coefficient curve of the microperforated panel absorber with smooth circular micropores, the dashed line represents the sound absorption coefficient curve of the microperforated panel absorber with smooth annular micropores (ε = 0, α = 2π in the inner wall surface morphology function of the annular sound-absorbing through-hole), the dotted line represents the sound absorption coefficient curve of the microperforated panel absorber with axially periodic rough surface annular micropores (ε = 0.2, α = 2π in the inner wall surface morphology function of the annular sound-absorbing through-hole), and the short dashed line represents the sound absorption coefficient curve of the microperforated panel absorber with axially periodic rough surface annular micropores (ε = 0.2, α = 4π in the inner wall surface morphology function of the annular sound-absorbing through-hole).

[0043] From Figure 3It can be seen that, compared with the traditional perforated panel absorber with smooth circular micropores, the perforated panel absorber with axially periodically rough-surfaced annular micropores proposed by the present invention has significantly improved sound absorption performance in a specific frequency band within 0 - 1000 Hz. Specifically, compared with the perforated panel absorber with smooth circular micropores, which reaches a peak sound absorption coefficient of 0.601 at 470 Hz and has a bandwidth of only 225 Hz where the sound absorption coefficient is above 0.5, the perforated panel absorber with axially periodically rough-surfaced annular micropores (in the wall surface morphology function of the annular sound-absorbing through-hole, ε = 0.2, α = 4π) has its peak sound absorption coefficient increased to 0.998, the frequency at which the peak sound absorption coefficient is located decreased by 13.8%, and the bandwidth where the sound absorption coefficient is above 0.5 widened by 177.8%; for the perforated panel absorber with axially periodically rough-surfaced annular micropores (in the wall surface morphology function of the annular sound-absorbing through-hole, ε = 0.2, α = 2π), the peak sound absorption coefficient is also increased to 0.987, the frequency at which the peak sound absorption coefficient is located decreased by 9.6%, and the bandwidth where the sound absorption coefficient is above 0.5 widened by 157.8%; even for the perforated panel absorber with smooth annular micropores (in the wall surface morphology function of the annular sound-absorbing through-hole, ε = 0, α = 2π), the peak sound absorption coefficient is increased to 0.718, the frequency at which the peak sound absorption coefficient is located decreased by 1.1%, and the bandwidth where the sound absorption coefficient is above 0.5 widened by 53.3%.

[0044] The results show that the present invention can significantly enhance the absorption ability of mid- and low-frequency noise and greatly broaden the bandwidth of the high-efficiency sound absorption frequency band by adjusting the axially periodic rough-surface morphology function of the wall surface of the annular sound-absorbing through-hole; at the same time, by adjusting parameters such as the depth of the cavity and the size of the annular sound-absorbing through-hole, the frequency at which the sound absorption peak is located and the high-efficiency sound absorption frequency band can be adjusted to meet the noise reduction requirements in different working environments and achieve the purpose of improving the sound absorption performance.

[0045] The above is only the preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the concept of the present invention belong to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, several improvements and refinements made without departing from the principle of the present invention should be regarded as within the protection scope of the present invention.

Claims

1. A micro-perforated panel absorber with an axially periodically rough surface and annular micro-holes, comprising a micro-perforated panel (1) and a rigid backing (2), wherein the micro-perforated panel (1) and the rigid backing (2) are connected by rigid rods or a rigid frame, and there is a cavity between the micro-perforated panel (1) and the rigid backing (2), and it is characterized in that, A plurality of annular sound-absorbing through-hole members (3) are provided on the micro-perforated panel (1). The opening direction of the annular sound-absorbing through-hole members (3) is perpendicular to the micro-perforated panel (1). The central ring body of the annular sound-absorbing through-hole members (3) is fixedly arranged on the rigid backing (2) or the micro-perforated panel (1). The inner wall surface and / or the outer wall surface of the annular sound-absorbing through-hole members (3) is an axially periodic rough surface. The morphology of the axially periodic rough surface is controlled by the function r(z) = r0 + εsin(αz), where r0 is the hydraulic radius of the inner / outer wall surface of the axially periodic rough surface of the annular sound-absorbing through-hole member (3), ε is the amplitude of the axially periodic rough surface, α is the wave number of the axially periodic rough surface, z is the coordinate with the opening direction of the annular sound-absorbing through-hole member (3) as the axis, and the minimum distance between the inner wall surface and the outer wall surface of the annular sound-absorbing through-hole member (3) is greater than the viscous boundary layer thickness, and the viscous boundary layer thickness d vis Calculated through the sound absorption frequency band: where f min is the lowest frequency in the sound absorption frequency band.

2. The microperforated panel absorber with an axially periodically rough-surfaced annular micropore according to claim 1, wherein The thickness of the micro-perforated panel (1) is 2 - 12 mm.

3. The microperforated panel absorber with an axially periodically rough-surfaced annular micropore according to claim 1, characterized in that, The cross-section of the annular sound-absorbing through-hole member (3) is circular. The hydraulic radius of the inner wall surface of the annular sound-absorbing through-hole member (3) is 0.2 - 0.5 mm, and the hydraulic radius of the outer wall surface of the annular sound-absorbing through-hole member (3) is 0.5 - 0.9 mm.

4. The microperforated panel absorber with an axially periodically rough-surfaced annular micropore according to claim 1, characterized in that, The annular sound-absorbing through-hole members (3) on the micro-perforated panel (1) are evenly distributed.

5. The microperforated panel absorber with an axially periodically rough surface annular micropore according to claim 1, characterized in that, The depth of the cavity between the micro-perforated panel (1) and the rigid backing (2) is 0 - 100 mm.

6. The micro-perforated panel absorber with an axially periodically rough surface and annular micro-holes according to claim 1, characterized in that, The cavity between the micro-perforated panel (1) and the rigid backing (2) is filled or not filled with a porous sound-absorbing material.

7. The microperforated panel absorber with an axially periodically rough surface annular micropore according to claim 1, characterized in that, The micro-perforated panel (1) is made of a wood board, a metal sandwich panel, a resin material, or a porous fiber.

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