A composite broadband noise reduction superstructure

Abstract

The present invention relates to the field of noise control and specifically provides a composite broadband noise reduction superstructure, comprising a mid-high frequency noise reduction body and a low-frequency broadband noise reduction body; the mid-high frequency noise reduction body comprises an incident perforated plate and a second sound absorber; the low-frequency broadband noise reduction body comprises a plurality of parallel sound absorbing units, each comprising a top perforated plate, a back closed plate, a side closed plate, and a closed partition; at least one internal perforated plate is disposed within the cavity of the sound absorbing unit, the top perforated plate being connected to the second sound absorber of the mid-high frequency noise reduction body; the internal perforated plate divides the sound absorbing unit into two or more series-connected sound absorbing chambers, each of which is provided with a first sound absorber; the sound absorbing chambers comprise a rearmost sound absorbing chamber and a front sound absorbing chamber, into which sound waves enter via the incident perforated plate, the second sound absorber, and the top perforated plate. This solution is applicable to broadband noise sources of various frequency domains or multi-order harmonic noise sources, can reduce the effective sound absorption frequency, and achieve full-band noise reduction through the composite mid-high frequency noise reduction body and low-frequency broadband noise reduction body superstructure.

Description

Technical Field

[0001] The present invention relates to the technical field of noise control, and in particular to a composite broadband noise reduction superstructure. Background Art

[0002] With the rapid development of the economy, the noise pollution caused by production and life is increasing, and sound-absorbing and noise-reducing structures play an indispensable role. Currently, sound-absorbing and noise-reducing structures can be generally divided into two categories based on their sound absorption principles. One type is porous material sound absorption, where the noise reduction principle is as follows: when sound waves enter the porous material, friction and viscosity convert a considerable portion of the sound energy into heat energy, thereby attenuating the sound waves and achieving the purpose of sound absorption. This type of sound absorption is characterized by significant noise reduction effects in the mid- and high-frequency bands and a wide effective noise reduction bandwidth, but poor noise reduction effects in the low-frequency band. The other type of sound absorption is resonant sound absorption, which is based on the Helmholtz resonator principle and uses a perforated plate, micro-perforated plate, or resonant cavity structure with a cavity of a certain depth behind it. The resonance between the holes in the perforated plate, micro-perforated plate, or resonant cavity and the air layer in the cavity behind it effectively absorbs sound. This type of sound absorption is characterized by the fact that the noise reduction frequency band can be specifically designed according to the characteristics of the noise source, achieving good low-frequency sound absorption. However, the effective noise reduction frequency band is generally narrow, and the lower the frequency, the larger the cavity behind it. At a certain point, even using the maximum cavity depth cannot achieve the required lower resonant sound absorption frequency, and thus cannot meet the low-frequency noise reduction requirements.

[0003] Meanwhile, for resonant noise reduction structures such as perforated plates, microperforated plates, or resonant cavities, a single-layer structure generally produces only one effective resonant sound absorption peak. Although the peak sound absorption coefficient can reach above 0.9, the absorption frequency band is relatively narrow. To broaden the sound absorption frequency band, a double-layer structure of perforated plates, microperforated plates, or resonant cavities can be employed to generate two effective resonant sound absorption peaks by increasing the degree of freedom. However, due to the limitations of the structural parameters, the noise reduction frequency band can only cover two to three octaves, and there is a significant trough between the two resonant peaks. Furthermore, if a three-layer or more microperforated plate structure is employed, while increasing the number of layers compared to a two-layer structure can broaden the sound absorption frequency band, it will reduce the average sound absorption coefficient within the original absorption frequency band (i.e., reduce the noise reduction effect within the effective frequency band), and the thickness, spatial dimensions, processing difficulty, and cost will all increase significantly. Therefore, for broadband noise sources or multi-order harmonic noise sources, satisfactory noise reduction effects are difficult to achieve with either a double-layer or multi-layer structure.

[0004] In order to solve the above problems, the following sound absorption and noise reduction technologies have emerged in the prior art:

[0005] 1. The invention patent with the patent number "202011380001.5" and the patent name "A noise reduction device and range hood" includes a back cavity shell, a micro-perforated plate and a guide plate assembly. The back cavity shell is formed with a cavity, and a plurality of microholes connected to the cavity are formed on the micro-perforated plate. The guide plate assembly is arranged in the cavity. The guide plate assembly includes a main board and a guide plate. The guide plate is connected to the through hole of the main board. The guide plate is spaced apart from the back cavity shell so that the sound waves of the noise can enter the cavity through the channels from the multiple microholes, and after reaching the back cavity shell, they return from between the channels and propagate toward the main board, which can achieve the effect of extending the propagation length of the sound waves, thereby reducing low-frequency noise and improving the noise reduction effect.

[0006] 2. Patent number "201820991506.7," titled "Partially Perforated Plate Silencing Unit, Combined Perforated Plate Silencing Unit, Composite Silencing Sheet, Composite Silencing Device, and Piping System," is a utility model patent. The patent includes a bottom plate, side plates, and a partially perforated plate. The partially perforated plate and bottom plate together form a silencing cavity. The partially perforated plate includes a perforated area and a non-perforated area, and the perforated area includes multiple silencing holes. The partially perforated plate silencing unit and the combined perforated plate silencing unit are suitable for controlling low-frequency noise and can also be used to control broadband noise.

[0007] 3. The invention patent application with the patent number "202210049291.8" and the patent name "A resonant coupling metamaterial structure and manufacturing process" includes a cover plate, a coupling cavity body and a bottom plate. The coupling cavity body is tightly connected to the cover plate and the bottom plate to form a sound absorption unit, which can achieve wider frequency and efficient sound absorption under thinner conditions.

[0008] 4. The patent number is "201811528044.6", and the patent name is "Built-in perforated plate Helmholtz resonator and low-frequency broadband sound absorption structure based thereon". The built-in perforated Helmholtz resonator is provided with one or more partitions to be used in conjunction with an ordinary Helmholtz resonator, which can more flexibly adjust the peak position and obtain continuous sound absorption broadband within a certain range.

[0009] However, the above prior art has the following problems:

[0010] Only perforated plates or the same type of units connected in series are used for single resistive sound absorption. Regardless of whether porous materials or resonance sound absorption are used, it is difficult to meet the requirements of good sound absorption performance under low frequency (such as below 200Hz) and wide frequency (greater than 2~3 1 / 3 octaves) conditions.

[0011] Under the premise of limited overall cavity depth, the noise reduction structure in the existing technology has limited noise reduction effect for the entire frequency band and it is difficult to achieve noise reduction in the entire frequency band.

[0012] To sum up, for noise sources in the full frequency band, how to effectively reduce low-frequency noise and widen the sound absorption band within a limited height range to achieve a good composite broadband full-band noise reduction effect is an urgent problem to be solved. Summary of the Invention

[0013] To address the above-mentioned issues, the present invention provides a composite broadband noise reduction superstructure, comprising a mid- and high-frequency noise reduction body and a low-frequency broadband noise reduction body. The low-frequency broadband noise reduction body comprises a plurality of parallel-connected sound absorption units and a sound absorption cavity arranged in parallel within the sound absorption units. The sound absorption cavity is provided with a first sound absorption body. This solution can reduce the resonant sound absorption frequency, enhance energy dissipation, and achieve full-band noise reduction in the range of 25 to 20,000 Hz.

[0014] To achieve the above-mentioned objectives, the present invention proposes the following technical solutions: a composite broadband noise reduction superstructure, comprising a mid-high frequency noise reduction body close to a sound source and a low-frequency broadband noise reduction body located behind the mid-high frequency noise reduction body; the low-frequency broadband noise reduction body comprises a plurality of sound absorbing units arranged in parallel, the sound absorbing unit comprising a top perforated plate located at an end of the mid-high frequency noise reduction body away from the sound source and at least one internal perforated plate located in a cavity of the sound absorbing unit; the top perforated plate is connected to the mid-high frequency noise reduction body, and the internal perforated plate divides the sound absorbing unit into two or more sound absorbing cavities connected in series, each sound absorbing cavity being provided with a sound absorbing body; full-band noise reduction is achieved through the composite structure of the mid-high frequency noise reduction body and the low-frequency broadband noise reduction body.

[0015] Preferably, the low-frequency broadband noise reduction body includes a back closing plate arranged opposite to the top perforated plate. After the multiple sound absorbing units are assembled in parallel, the peripheral sides of the top perforated plate and the back closing plate are enclosed and connected by the side closing plates; the multiple sound absorbing units are separated and formed by closed partitions arranged in the top perforated plate, the back closing plate and the side closing plates along the depth direction.

[0016] Preferably, the sound absorbing body 1 is arranged in the rearmost sound absorbing cavity away from the mid-high frequency noise reduction body, and the thickness of the sound absorbing body 1 is ≤ the cavity depth of the rearmost sound absorbing cavity.

[0017] Preferably, the front sound absorbing cavity between the rearmost sound absorbing cavity and the top perforated plate does not include the first sound absorbing body; the rear end of the first sound absorbing body in the rearmost sound absorbing cavity contacts the back closing plate, the front end does not contact the inner perforated plate, and a sound absorbing gap is left between the first sound absorbing body and the inner perforated plate; that is, the thickness of the first sound absorbing body in the rearmost sound absorbing cavity is less than the cavity depth of the rearmost sound absorbing cavity.

[0018] Preferably, the mid- and high-frequency noise reduction body includes an incident perforated plate and a second sound absorber from front to back, and the top perforated plate is in contact with and connected to the second sound absorber; the sound waves enter the second sound absorber, the top perforated plate, the front sound absorption cavity, the internal perforated plate and the rearmost sound absorption cavity from the incident perforated plate in sequence.

[0019] Preferably, the perforation rate of the perforations in the incident perforated plate is greater than the perforation rate of the perforations in the top perforated plate and the internal perforated plate; the apertures of the perforations in the incident perforated plate, the top perforated plate and the internal perforated plate, the perforation rates and apertures of the perforations in the top perforated plates or the internal perforated plates in different sound absorbing units, the perforation rates and apertures of the perforations in the top perforated plates and the internal perforated plates in the same sound absorbing unit, and the perforation rates and apertures of the perforations in different internal perforated plates in the same sound absorbing unit are the same or different and are set according to actual needs.

[0020] Preferably, the diameter of the perforations in the top perforated plate or the inner perforated plate is 1 to 5 mm, and the perforation rate is 5% to 15%; the diameter of the perforations in the incident perforated plate is 1 to 5 mm, and the perforation rate is 25% to 35%.

[0021] Preferably, the internal perforated plates in different sound absorbing units are not aligned and staggered, that is, the internal perforated plates in different sound absorbing units are arranged at different heights; when there are more than two internal perforated plates in the same sound absorbing unit, the internal perforated plates are arranged at unequal intervals, that is, the cavity depths of the rearmost sound absorbing cavity and the front sound absorbing cavity in the same sound absorbing unit are different.

[0022] Preferably, the material or thickness of the sound absorbing body 1 in different sound absorbing units is the same or different; the thickness of the sound absorbing body 1 is 40-180 mm; the sound absorbing body 1 is a low sound velocity sound absorbing material; and the sound absorbing body 2 is a porous sound absorbing material.

[0023] Preferably, the perforations on the incident perforated plate, the top perforated plate or the inner perforated plate are evenly arranged in the transverse and longitudinal directions; the number and arrangement of the perforations on the incident perforated plate, the top perforated plate or the inner perforated plate are set according to actual needs; the thickness of the top perforated plate or the inner perforated plate in different sound absorbing units, the thickness of the top perforated plate and the inner perforated plate in the same sound absorbing unit, and the thickness of different inner perforated plates in the same sound absorbing unit are the same or different.

[0024] The beneficial effects of the present invention are:

[0025] 1. The composite noise reduction superstructure of the present invention comprises a mid-high frequency noise reduction body and a low-frequency broadband noise reduction body, which has excellent sound absorption and noise reduction performance for both mid-high frequency and low frequency noise. By combining the mid-high frequency noise reduction body and the low-frequency broadband noise reduction body into a composite structure, broadband noise reduction can be achieved, even in the full frequency range of 25 to 20,000 Hz.

[0026] 2. The low-frequency, broadband noise reduction structure includes multiple sound-absorbing units connected in parallel. The resonant sound absorption peaks of the multiple parallel sound-absorbing units can be coupled, thereby raising the valleys and widening the effective sound absorption frequency band. Each sound-absorbing unit includes a top perforated plate and an internal perforated plate. The internal perforated plate divides the inner cavity of the sound-absorbing unit into multiple series-connected sound-absorbing cavities with the same or different sound absorption peaks. This enables the noise-reducing superstructure to have excellent sound absorption performance in the frequency range of 25 to 350 Hz.

[0027] 3. The present invention provides a porous sound-absorbing material in the mid- and high-frequency noise reduction body, and a low-sound-velocity sound-absorbing body 1 in the sound-absorbing cavity of the low-frequency broadband noise reduction body. The sound-absorbing body 1 maximizes the acoustic resistivity of the noise reduction structure within the design target frequency band, reduces the sound velocity, lowers the resonant sound absorption frequency, enhances energy dissipation, and reduces the overall thickness of the structure, which is conducive to meeting the requirements of limited installation space. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of an exploded view of the noise reduction superstructure provided in the first embodiment of the present invention.

[0029] Figure 2 Schematic diagram of the overall structure of the noise reduction superstructure provided in Example 1 of the present invention.

[0030] Figure 3 Schematic diagram of the structure of the low-frequency broadband noise reduction body provided in the first embodiment of the present invention.

[0031] Figure 4 This is a parameter table of the noise reduction superstructure provided in the first embodiment of the present invention.

[0032] Figure 5 This is a sound absorption performance curve diagram of the low-frequency broadband noise reduction body provided in Example 1 of the present invention.

[0033] Figure 6 This is a curve diagram of the sound absorption coefficient of the mid- and high-frequency noise reduction body provided in Example 1 of the present invention.

[0034] Figure 7 Schematic diagram of the structure of a low-frequency broadband noise reduction body provided in the second embodiment of the present invention.

[0035] Figure 8 Schematic diagram of the structure of the low-frequency broadband noise reduction body provided in the third embodiment of the present invention.

[0036] Figure 1: mid- and high-frequency noise reduction body 1, low-frequency broadband noise reduction body 2, sound absorbing unit 1 3, sound absorbing unit 2 4, sound absorbing unit 3 5, sound absorbing unit 4 6, top perforated plate 7, internal perforated plate 8, incident perforated plate 9, sound absorbing body 1 10, sound absorbing body 2 11, back closing plate 12, side closing plate 13, closed partition 14, rearmost sound absorbing cavity 15, front sound absorbing cavity 16, sound absorbing gap 17, perforation 18. Implementation Method

[0037] In order to make the purpose, technical solutions and advantages of the present invention more clear, the following Figure 1-8 It should be understood that the specific embodiments described herein are only used to illustrate the present invention and do not constitute a limitation of the present invention. Example 1

[0038] A composite broadband noise reduction superstructure, such as Figure 1 、 2 As shown, it includes a mid-high frequency noise reduction body 1 close to the sound source and a low-frequency broadband noise reduction body 2 located at the rear of the mid-high frequency noise reduction body 1; the mid-high frequency noise reduction body 1 includes an incident perforated plate 9 and a second sound absorbing body 11 from front to back, the incident perforated plate 9 is the incident surface of the sound wave, and the incident perforated plate 9 includes perforations 18, and the second sound absorbing body 11 is a porous sound absorbing material, such as a porous foam sound absorbing material or a porous fiber sound absorbing material; the low-frequency broadband noise reduction body 2 includes a plurality of sound absorbing units arranged in parallel, and in this embodiment, a total of four sound absorbing units are evenly arranged, such as Figure 3 As shown, the four sound absorbing units are sound absorbing unit 1 3 , sound absorbing unit 2 4 , sound absorbing unit 3 5 and sound absorbing unit 4 6 .

[0039] The sound absorbing unit includes a top perforated plate 7 located at the end of the mid- and high-frequency noise reduction body 1 away from the sound source and at least one internal perforated plate 8 located in the cavity of the sound absorbing unit. The top perforated plate 7 and the internal perforated plate 8 include perforations 18. The top perforated plate 7 is connected to the sound absorber 2 11 in the mid- and high-frequency noise reduction body 1. The internal perforated plate 8 divides the sound absorbing unit into two or more sound absorbing cavities connected in series. In this embodiment, each sound absorbing unit is provided with an internal perforated plate 8, which divides the cavity of the sound absorbing unit into two sound absorbing cavities connected in series. Those skilled in the art may also set other numbers of internal perforated plates 8 in the sound absorbing unit according to actual conditions. A sound absorber 10 is provided in the sound absorbing cavity.

[0040] like Figure 1-3 As shown, the low-frequency broadband noise reduction body 2 includes a back closing plate 12 arranged opposite to the top perforated plate 7. After the multiple sound absorbing units are assembled in parallel, the top perforated plate 7 and the back closing plate 12 are surrounded and connected by the side closing plates 13; the multiple sound absorbing units are separated by the closed partitions 14 arranged in the top perforated plate 7, the back closing plate 12 and the side closing plates 13 along the depth direction (in order to clearly express the internal structure of the noise reduction superstructure, a side closing plate 13 on the front side is not shown); the depth direction is as shown in FIG. Figure 3As shown in the S direction; the closed partition 14, the back closed plate 12 and the side closed plate 13 are all solid plate structures; the incident perforated plate 9 can be a flat or curved surface structure to adapt to the installation surface requirements of the flat or curved surface, to adapt to ordinary no airflow environment and high wind pressure, high airflow environment, and improve the applicability of the noise reduction super structure.

[0041] The sound absorber 10 is disposed in the rearmost sound absorption cavity 15 away from the mid- and high-frequency noise reduction body 1. The front sound absorption cavity 16 between the rearmost sound absorption cavity 15 and the top perforated plate 7 does not include the sound absorber 10. The thickness of the sound absorber 10 is less than or equal to the depth of the rearmost sound absorption cavity 15. In this embodiment, the rear end of the sound absorber 10 in the rearmost sound absorption cavity 15 contacts the back closing plate 12, the front end does not contact the inner perforated plate 8, and a sound-absorbing gap 17 is left between the inner perforated plate 8. That is, the thickness of the sound absorber 10 in the rearmost sound absorption cavity 15 is less than the depth of the rearmost sound absorption cavity 15. Sound waves enter the sound absorber 2 11, the top perforated plate 7, the front sound absorption cavity 16, the inner perforated plate 8, and the rearmost sound absorption cavity 15 in sequence from the incident perforated plate 9.

[0042] The perforation rate of the perforations 18 in the incident perforated plate 9 is greater than the perforation rate of the perforations 18 in the top perforated plate 7 and the internal perforated plate 8; the apertures of the perforations 18 in the incident perforated plate 9, the top perforated plate 7, and the internal perforated plate 8, the perforation rates and apertures of the perforations 18 in the top perforated plates 7 or the internal perforated plates 8 in different sound absorbing units, the perforation rates and apertures of the perforations 18 in the top perforated plates 7 and the internal perforated plates 8 in the same sound absorbing unit, and the perforation rates and apertures of the perforations 18 in different internal perforated plates 8 in the same sound absorbing unit are the same or different and are set according to actual needs; specifically, the aperture of the perforations 18 in the top perforated plate 7 or the internal perforated plate 8 is 1 to 5 mm, and the perforation rate is 5% to 15%; the aperture of the perforations 18 in the incident perforated plate 9 is 1 to 5 mm, and the perforation rate is 25%. ~35%, the aperture of the incident perforated plate 9 is preferably 3 mm, and the perforation rate is preferably 30%; the perforations 18 on the incident perforated plate 9, the top perforated plate 7 or the inner perforated plate 8 are evenly arranged in the horizontal and vertical directions, and the number and arrangement of the perforations 18 on the incident perforated plate 9, the top perforated plate 7 or the inner perforated plate 8 are set according to actual needs; Figure 3 As shown in the M direction, the longitudinal direction is as Figure 3 Shown in the N direction.

[0043] The internal perforated plates 8 in different sound absorbing units are arranged in an uneven and staggered manner, that is, the internal perforated plates 8 in different sound absorbing units are arranged at different heights. When there are two or more internal perforated plates 8 in the same sound absorbing unit, the internal perforated plates 8 are arranged at unequal intervals, that is, the depths of the rearmost sound absorbing cavity 15 and the front sound absorbing cavity 16 in the same sound absorbing unit are different. In this embodiment, the internal perforated plates 8 of each sound absorbing unit are arranged at different heights, so that the depths of the two sound absorbing cavities in each sound absorbing unit are different, and the depths of the sound absorbing cavities in different sound absorbing units are also different, thereby further reducing low-frequency noise and widening the sound absorption frequency band.

[0044] The material or thickness of the sound absorbing body 10 in different sound absorbing units is the same or different; the thickness of the sound absorbing body 10 is 40 to 180 mm, and the sound absorbing body 10 is a low sound velocity sound absorbing material; the thickness of the top perforated plate 7 or the internal perforated plate 8 in different sound absorbing units, the thickness of the top perforated plate 7 and the internal perforated plate 8 in the same sound absorbing unit, and the thickness of different internal perforated plates 8 in the same sound absorbing unit are the same or different.

[0045] The parameter table of the noise reduction superstructure in this embodiment is as follows: Figure 4 As shown, the thickness of the top perforated plate 7 in the sound absorbing unit 1 is t 11 , the perforation diameter is d 11 , the perforation rate is p 11 , the thickness of the internal perforated plate 8 is t 12 , the perforation diameter is d 12 , the perforation rate is p 12 , the depth of the front sound absorption cavity 16 is l 11 , the depth of the rearmost sound absorption cavity 15 is l 12 , the thickness of the sound absorbing body 10 is h 1; the thickness of the top perforated plate 7 in the sound absorbing unit 2 4 is t 21 , the perforation diameter is d 21 , the perforation rate is p 21 , the thickness of the internal perforated plate 8 is t 22 , the perforation diameter is d 22 , the perforation rate is p 22 , the depth of the front sound absorption cavity 16 is l 21 , the depth of the rearmost sound absorption cavity 15 is l22 , the thickness of the sound absorbing body 10 is h 2; The thickness of the top perforated plate 7 in the sound absorbing unit 3 5 is t 31 , the perforation diameter is d 31 , the perforation rate is p 31 , the thickness of the internal perforated plate 8 is t 32 , the perforation diameter is d 32 , the perforation rate is p 32 , the depth of the front sound absorption cavity 16 is l 31 , the depth of the rearmost sound absorption cavity 15 is l 32 , the thickness of the sound absorbing body 10 is h 3; The thickness of the top perforated plate 7 in the sound absorbing unit 4 6 is t 41 , the perforation diameter is d 41 , the perforation rate is p 41 , the thickness of the internal perforated plate 8 is t 42 , the perforation diameter is d 42 , the perforation rate is p 42 , the depth of the front sound absorption cavity 16 is l 41 , the depth of the rearmost sound absorption cavity 15 is l 42 , the thickness of the sound absorbing body 10 is h 4.

[0046] The thickness of the top perforated plate 7 and the inner perforated plate 8, i.e. t 11 、 t 12 、 t 21 、 t 22 、 t 31 、 t 32 、 t 41 、 t 42 The diameter of the perforation 18 in the top perforated plate 7 and the inner perforated plate 8 is 0.8 mm to 1.2 mm, preferably 1 mm; d 11 、 d12 、 d 21 、 d 22 、 d 31 、 d 32 、 d 41 、 d 42 is 1 ~ 5 mm; the perforation rate of the top perforated plate 7 and the perforation 18 in the inner perforated plate 8, that is, p 11 、 p 12 、 p 21 、 p 22 、 p 31 、 p 32 、 p 41 、 p 42 5% to 15%; the depth of the front sound absorption cavity 16 and the rear sound absorption cavity 15, that is, l 11 、 l 21 、 l 31 、 l 41 、 l 12 、 l 22 、 l 32 、 l 42 50 ~ 200 mm; the thickness of the sound absorbing body 10, ie h1, h2, h3, h4 is 40 ~ 180 mm; the sound absorption performance curve of the low-frequency broadband noise reduction body 2 in this embodiment is as shown Figure 5 As shown, the sound absorption coefficient curve of the mid-high frequency noise reduction body 1 is as follows Figure 6 shown.

[0047] In this embodiment, the main sound absorption frequency band of the mid-to-high frequency noise reduction body 1 is 200 ~ 20000 Hz, which is mainly used for mid-to-high frequency noise reduction. The main sound absorption frequency band of the low-frequency broadband noise reduction body 2 is 25 ~ 370 Hz, which is mainly used for low-frequency noise reduction. The composite structure of the mid-to-high frequency noise reduction body 1 and the low-frequency broadband noise reduction body 2 achieves full-band noise reduction of 25 ~ 20000 Hz. Example 2

[0048] like Figure 7As shown, the difference between this embodiment and the first embodiment is that each sound absorbing unit is provided with two internal perforated plates 8, and the cavity of the sound absorbing unit is divided into three sound absorbing cavities connected in series by the internal perforated plates 8. Example 3

[0049] like Figure 8 As shown, the difference between this embodiment and the first embodiment is that this embodiment includes eight sound absorbing units connected in parallel, some sound absorbing units have one internal perforated plate 8, some sound absorbing units have two internal perforated plates 8, and some sound absorbing units have three internal perforated plates 8; at the same time, the aperture, number, and arrangement of the perforations 18 in some top perforated plates 7 of different sound absorbing units are the same, while the aperture, number, and arrangement of the perforations 18 in some top perforated plates 7 are different.

[0050] Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art may make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

[0051] The above specific embodiments of the present invention do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A composite broadband noise reduction superstructure, characterized in that: The invention comprises a mid-high frequency noise reduction body (1) close to the sound source and a low-frequency broadband noise reduction body (2) located at the rear of the mid-high frequency noise reduction body (1); the low-frequency broadband noise reduction body (2) comprises a plurality of sound absorbing units arranged in parallel, the sound absorbing unit comprising a top perforated plate (7) located at one end of the mid-high frequency noise reduction body (1) away from the sound source and at least one internal perforated plate (8) located in the cavity of the sound absorbing unit; the top perforated plate (7) is connected to the mid-high frequency noise reduction body (1), and the internal perforated plate (8) divides the sound absorbing unit into two or more sound absorbing cavities connected in series. A sound absorbing body (10) is provided in the sound absorbing cavity; full-band noise reduction is achieved through a composite structure of a mid-high frequency noise reduction body (1) and a low-frequency broadband noise reduction body (2); the low-frequency broadband noise reduction body (2) includes a back closing plate (12) arranged opposite to the top perforated plate (7); after a plurality of sound absorbing units are connected in parallel, the top perforated plate (7) and the back closing plate (12) are surrounded and connected by side closing plates (13); a plurality of sound absorbing units are provided along the depth direction on the top perforated plate (7), the back closing plate (12) and the side closing plates (13) The sound absorbing body (10) is separated by a closed partition (14) inside the middle and high frequency noise reduction body (1); the sound absorbing body (10) is arranged in the rearmost side sound absorbing cavity (15) away from the middle and high frequency noise reduction body (1), and the thickness of the sound absorbing body (10) is ≤ the cavity depth of the rearmost side sound absorbing cavity (15); the front side sound absorbing cavity (16) between the rearmost side sound absorbing cavity (15) and the top perforated plate (7) does not include the sound absorbing body (10); the rear end of the sound absorbing body (10) in the rearmost side sound absorbing cavity (15) contacts the back closed plate (12), and the front end does not contact the internal perforated plate (8) and contacts the internal perforated plate (8) A sound-absorbing gap (17) is left between them; that is, the thickness of the sound-absorbing body 1 (10) in the rearmost sound-absorbing cavity (15) is less than the cavity depth of the rearmost sound-absorbing cavity (15); the mid-high frequency noise reduction body (1) includes the incident perforated plate (9) and the sound-absorbing body 2 (11) from front to back, and the top perforated plate (7) is in contact with and connected to the sound-absorbing body 2 (11); the sound waves enter the sound-absorbing body 2 (11), the top perforated plate (7), the front sound-absorbing cavity (16), the internal perforated plate (8) and the rearmost sound-absorbing cavity (15) from the incident perforated plate (9) in sequence.

2. The composite broadband noise reduction superstructure according to claim 1, characterized in that: The perforation rate of the perforations (18) in the incident perforated plate (9) is greater than the perforation rate of the perforations (18) in the top perforated plate (7) and the inner perforated plate (8); the apertures of the perforations (18) in the incident perforated plate (9), the top perforated plate (7) and the inner perforated plate (8), the perforation rates and apertures of the perforations (18) in the top perforated plate (7) or the inner perforated plate (8) in different sound absorbing units, the perforation rates and apertures of the perforations (18) in the top perforated plate (7) and the inner perforated plate (8) in the same sound absorbing unit, and the perforation rates and apertures of the perforations (18) in different inner perforated plates (8) in the same sound absorbing unit are the same or different and are set according to actual needs.

3. The composite broadband noise reduction superstructure according to claim 2, wherein: The aperture of the perforated hole (18) in the top perforated plate (7) or the inner perforated plate (8) is 1 to 5 mm, and the perforation rate is 5% to 15%; the aperture of the perforated hole (18) in the incident perforated plate (9) is 1 to 5 mm, and the perforation rate is 25% to 35%.

4. The composite broadband noise reduction superstructure according to claim 3, characterized in that: The internal perforated plates (8) in different sound absorbing units are not aligned and staggered, that is, the internal perforated plates (8) in different sound absorbing units are all arranged at different heights; when there are more than two internal perforated plates (8) in the same sound absorbing unit, the internal perforated plates (8) are arranged at unequal intervals, that is, the cavity depths of the rearmost sound absorbing cavity (15) and the front sound absorbing cavity (16) in the same sound absorbing unit are different.

5. The composite broadband noise reduction superstructure according to claim 4, characterized in that: The material or thickness of the sound absorbing body 1 (10) in different sound absorbing units is the same or different; the thickness of the sound absorbing body 1 (10) is 40 ~ 180 mm; the sound absorbing body 1 (10) is a low sound velocity sound absorbing material; the sound absorbing body 2 (11) is a porous sound absorbing material.

6. The composite broadband noise reduction superstructure according to claim 5, characterized in that: The perforations (18) on the incident perforated plate (9), the top perforated plate (7) or the inner perforated plate (8) are evenly arranged in the transverse and longitudinal directions; the number and arrangement of the perforations (18) on the incident perforated plate (9), the top perforated plate (7) or the inner perforated plate (8) are set according to actual needs; the thickness of the top perforated plate (7) or the inner perforated plate (8) in different sound absorbing units, the thickness of the top perforated plate (7) and the inner perforated plate (8) in the same sound absorbing unit, and the thickness of different inner perforated plates (8) in the same sound absorbing unit are the same or different.

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