Sound absorbing unit and sound absorbing device

Abstract

The present application provides a sound absorbing unit and a sound absorbing device. The sound absorbing unit includes at least one quarter-wavelength tube array and at least one Helmholtz resonator array stacked in a preset direction; the quarter-wavelength tube array includes a plurality of quarter-wavelength tubes arranged side by side, each quarter-wavelength tube having a first open end and a first closed end arranged oppositely; the Helmholtz resonator array includes a plurality of Helmholtz resonators arranged side by side, each Helmholtz resonator having a second open end and a second closed end arranged oppositely; each first open end and each second open end together form a sound wave incident surface of the sound absorbing unit; and within a preset frequency band, the overall acoustic impedance of the sound absorbing unit matches the acoustic impedance of air. The above-mentioned sound absorbing unit can achieve better sound absorption effect in the low frequency band, and can save space, reduce preparation costs, and reduce environmental pollution.

Description

Technical Field

[0001] The present invention relates to the technical field of sound absorbing devices, and in particular to a sound absorbing unit and a sound absorbing device. Background Art

[0002] Traditional sound-absorbing materials include porous sound-absorbing materials. Porous sound-absorbing materials are materials with a network structure consisting of interconnected or closed holes, and the boundaries or surfaces of the holes are formed by pillars or plates. A typical pore structure can be a two-dimensional structure formed by a large number of polygonal holes gathered on a plane. This type of polygonal hole is similar to the hexagonal structure of a honeycomb and is called a "honeycomb" material. More commonly, a three-dimensional structure formed by a large number of polyhedral holes gathered in space is usually called a "foam" material. If the holes are connected, it is called an open hole; if each hole is completely separated from the surrounding holes, it is called a closed hole; in addition, some holes are semi-open and semi-closed. The physical structure characteristics of porous sound-absorbing materials are that there are a large number of micropores inside the material that are interconnected and open to the outside, that is, the material has a certain air permeability.

[0003] Sound absorption mechanism of porous sound absorbing materials: When sound waves are incident on porous sound absorbing materials, the air in the pores vibrates. Due to friction and the viscous resistance of air, part of the sound energy is converted into heat energy. In addition, the heat conduction between the air in the pores and the pore walls and fibers will also cause heat loss and attenuate the sound energy. Porous sound absorbing materials have good sound absorption characteristics for medium and high frequencies. The sound absorption coefficient increases with the increase of sound frequency. The sound absorption coefficient α can reach 0.5 to 0.9 above 500Hz.

[0004] However, due to its physical properties, the thickness of traditional porous sound-absorbing materials is at least one-fourth of the sound wave. If porous sound-absorbing materials are used to eliminate low-frequency noise, the required thickness will also be larger, which will greatly increase the cost. For example, for noise in the frequency band below 50Hz, the thickness of the porous sound-absorbing material must be at least 1.5m.

[0005] In addition, depending on the preparation materials, traditional porous sound absorbing materials have the following disadvantages:

[0006] (1) Plastic foam porous materials are prone to aging and cannot be used in outdoor environments;

[0007] (2) Glass or rock fiber porous materials are prone to pulverization and failure under outdoor conditions, and are prone to produce carcinogenic debris;

[0008] (3) Foamed porous materials will release toxic gases during the on-site construction phase. Summary of the invention

[0009] Based on this, it is necessary to provide an improved sound absorbing unit to address the problems of high low-frequency sound absorption cost, short life, and easy environmental pollution and health hazards in the preparation process of traditional porous sound absorbing materials.

[0010] A sound absorbing unit comprises at least one quarter-wavelength tube array and at least one Helmholtz resonator array stacked in a preset direction;

[0011] The quarter-wavelength tube array comprises a plurality of quarter-wavelength tubes arranged side by side, each of the quarter-wavelength tubes having a first open end and a first closed end arranged opposite to each other;

[0012] The Helmholtz resonator array comprises a plurality of Helmholtz resonators arranged side by side, each of the Helmholtz resonators having a second open end and a second closed end arranged oppositely;

[0013] Each of the first opening ends and each of the second opening ends together form a sound wave incident surface of the sound absorbing unit; and, within a preset frequency band, the overall acoustic impedance of the sound absorbing unit matches the acoustic impedance of air.

[0014] The above-mentioned sound absorption unit, by introducing a Helmholtz resonator and matching the overall acoustic impedance with the acoustic impedance of air, is conducive to having a larger sound absorption coefficient, thereby achieving a better sound absorption effect in the low frequency band; and, in the same low-frequency sound absorption band, the above-mentioned sound absorption unit requires a small installation space, and when arranging such sound absorption units, there is no need to arrange a cavity structure separately, which can greatly save space and reduce preparation costs. In addition, by using a Helmholtz resonator in combination with a quarter-wavelength tube, the sound absorption effect of the sound absorption unit can be effectively improved through the sound absorption frequency doubling characteristics of the quarter-wavelength tube.

[0015] In one embodiment, the quarter-wavelength tube array and the Helmholtz resonator array each have two or more.

[0016] In one embodiment, in each of the quarter-wavelength tube arrays, the length of each of the quarter-wavelength tubes decreases sequentially; and, in each of the Helmholtz resonator arrays, the length of each of the Helmholtz resonators decreases sequentially; and / or, the opening area of ​​the second opening end of each of the Helmholtz resonators decreases sequentially.

[0017] In one embodiment, the length of any one of the quarter-wavelength tubes is less than the length of any one of the Helmholtz resonators.

[0018] In one embodiment, each of the first opening ends and each of the second opening ends are located in the same plane, and the overall acoustic impedance Z of the sound absorbing unit satisfies: Among them, Z QW represents the acoustic impedance of each of the quarter-wavelength tubes, ZHH represents the acoustic impedance of each of the Helmholtz resonators, m represents the ordinal number of the quarter-wavelength tube, and n represents the ordinal number of the Helmholtz resonator.

[0019] In one embodiment, the quarter-wavelength tube includes: a first tube body having a first end and a second end arranged opposite to each other, and a first through hole passing through the first end and the second end along the axis of the first tube body; and a first blocking block arranged at the opening of the second end for closing the second end.

[0020] In one embodiment, the overall acoustic impedance of the sound absorbing unit includes the acoustic impedance Z of the quarter-wavelength tube. QW , the acoustic impedance Z of the quarter-wavelength tube QW satisfy:

[0021]

[0022] Among them, ρ0 represents the density of air under natural conditions, L p represents the vertical distance from the first end to the inner surface of the first block, A QW represents the cross-sectional area of ​​the first tube, r QW represents the hydraulic radius, ν represents the kinematic viscosity, γ represents the specific heat capacity of air, η represents the viscosity coefficient of air, ω Q represents the terminal correction coefficient, Pr represents the Prandtl constant, ξ Q represents the pressure loss coefficient, represents the equivalent mass flow rate, and ω represents the angular frequency.

[0023] In one embodiment, the Helmholtz resonator includes: a second tube body, having a third end and a fourth end arranged opposite to each other, and a second through hole passing through the third end and the fourth end along the axis of the second tube body, the second through hole including a neck hole and a base hole connected to the neck hole from the third end to the fourth end in sequence; and a second blocking block, arranged at the opening of the fourth end, for closing the fourth end.

[0024] In one embodiment, the overall acoustic impedance of the sound absorbing unit includes the acoustic impedance Z of the Helmholtz resonator. HH , the acoustic impedance Z of the Helmholtz resonator HH satisfy:

[0025]

[0026] Wherein, A represents the area of ​​the entire third end, S a represents the opening area of ​​the neck hole, l represents the equivalent length of the neck hole, L represents the vertical distance from the third end to the inner surface of the second block, VHH represents the resonance cavity volume of the Helmholtz resonator, ρ cc 、c cc and k cc represent the density, sound speed and wave number of the air in the resonance cavity, respectively, k ca , va and ha They represent the wave number, viscosity term and thermal term of the neck hole under narrow acoustics, γ represents the specific heat capacity of air, δ Ω represents the sound quality terminal correction term, τ Ω represents the correction factor, ω represents the angular frequency, η represents the viscosity coefficient of air, ρ0 represents the density of air under natural conditions, and c0 represents the propagation speed of sound in the outside air.

[0027] In one of the embodiments, the preset frequency band is 300 Hz to 4000 Hz.

[0028] The present application also provides a sound absorbing device.

[0029] A sound absorbing device comprises a plurality of the sound absorbing units as described above.

[0030] The above-mentioned sound absorbing device can achieve a better elimination effect on low-frequency noise without occupying a large space, and the preparation cost is also low. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the structure of an embodiment of the present application;

[0032] Figure 2 for Figure 1 AA surface structural diagram of the embodiment shown

[0033] Figure 3 A structural schematic diagram of another perspective of an embodiment of the present application;

[0034] Figure 4 A side view schematic diagram of an embodiment of the present application;

[0035] Figure 5 for Figure 4 A schematic diagram of the structure at section BB of the illustrated embodiment;

[0036] Figure 6 for Figure 4 A schematic diagram of the structure at section CC of the illustrated embodiment;

[0037] Figure 7 This is a schematic structural diagram of a blocking device according to an embodiment of the present application;

[0038] Figure 8is a schematic structural diagram of a sound absorbing device composed of an embodiment of the present application;

[0039] Fig. 9 is a schematic structural diagram of another sound absorbing device composed of an embodiment of the present application;

[0040] Fig.10 Schematic diagram of the structure of another sound absorbing device composed of an embodiment of the present application.

[0041] The reference numerals of the components in the figure are as follows:

[0042] 100. Sound absorbing unit;

[0043] 9. a quarter-wavelength tube array, 11. a quarter-wavelength tube, 111. a first tube body, 1110. a first through hole, 1111. a first end, 1112. a second end, 112. a first blocking block;

[0044] 20. Helmholtz resonator row body, 21. Helmholtz resonator, 211. second tube body, 2110. second through hole, 21101. neck hole, 21102. base hole, 2111. third end, 2112. fourth end, 212. second blocking block;

[0045] 30. Blocking device, 31. Blocking block, 32. Connecting strip, 33. Pull strip. DETAILED DESCRIPTION

[0046] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to understand the disclosure of the present invention more thoroughly and comprehensively.

[0047] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may also be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right", "upper", "lower", "front", "rear", "circumferential" and similar expressions used herein are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0049] When traditional porous sound-absorbing materials are used to eliminate low-frequency noise, they occupy a large space volume, which is not conducive to reducing the preparation cost. In addition, traditional porous sound-absorbing materials are usually made of plastic foam, glass or rock fiber and foaming materials, which are easy to pollute the environment and endanger people's health.

[0050] In view of the defects of traditional porous sound-absorbing materials, the present application designs an improved sound-absorbing unit 100 by using a quarter-wavelength tube and a Helmholtz resonator.

[0051] Please refer to Figures 1 to 6 The sound absorbing unit 100 includes at least one quarter-wavelength tube array 10 and at least one Helmholtz resonator array 20 stacked in a preset direction. The quarter-wavelength tube array 10 includes a plurality of quarter-wavelength tubes 11 arranged side by side, each of which has a first open end 1111 and a first closed end 1112 arranged oppositely; the Helmholtz resonator array 20 includes a plurality of Helmholtz resonators 21 arranged side by side, each of which has a second open end 2111 and a second closed end 2112 arranged oppositely; each first open end 1111 and each second open end 2111 jointly form a sound wave incident surface of the sound absorbing unit 100; and, within a preset frequency band, the overall acoustic impedance of the sound absorbing unit 100 matches the acoustic impedance of air.

[0052] Specifically, a quarter-wavelength tube is an acoustic element that performs noise reduction treatment on the intake and exhaust systems of automobiles based on acoustic principles. Its basic structure is a T-shaped tube with one end open and the other end closed. When the sound wave enters the T-shaped pipe, part of the sound wave enters the closed-end pipe, and then reflects back, meets the incident sound wave to form a standing wave, and achieves sound elimination. The length of the quarter-wavelength tube is one-quarter or a multiple of one-quarter of the incident sound wave. The quarter-wavelength tube array 10 may include a plurality of quarter-wavelength tubes 11, for example, 6, 7, 8, 9 or 10, etc., which is conducive to absorbing sound waves of different frequencies. The opening shapes of the first open ends 1111 of different quarter-wavelength tubes 11 may be different, for example, they may be square, circular, triangular, etc., and the present application does not impose any restrictions on this.

[0053] On the other hand, a Helmholtz resonator refers to a muffler whose air in the cavity can be regarded as a "spring system". When the frequency of the incident sound wave is the same as the natural frequency of the Helmholtz resonator, the air in the cavity will resonate, so that the sound wave energy can be dissipated by the friction of the air to achieve muffler. In addition, the Helmholtz resonator has a sub-wavelength sound absorption characteristic (i.e., the sound absorption frequency is not completely limited by the quarter-wavelength theory). Under similar characteristic lengths, the sound absorption frequency of the Helmholtz resonator is much smaller than the sound absorption frequency of the quarter-wavelength tube. The Helmholtz resonator array 20 can include a plurality of Helmholtz resonators 21, for example, 6, 7, 8, 9 or 10, etc., which is also conducive to absorbing sound waves of different frequencies. The opening shape of the second opening end 2111 of the Helmholtz resonator 21 can be different, for example, it can be square, circular, triangular, etc., and the present application does not limit this.

[0054] Preferably, the number of the Helmholtz resonator array bodies 20 is greater than or equal to the number of the quarter-wavelength tube array bodies 10. More preferably, the number of the Helmholtz resonator array bodies 20 is greater than the number of the quarter-wavelength tube array bodies 10. In this way, the sound absorbing unit 100 can achieve a better low-frequency absorption effect.

[0055] Furthermore, according to the calculation formula of the sound absorption coefficient α in acoustics (Z represents the overall acoustic impedance of the sound absorbing unit 100, and Z0 represents the impedance of air) It can be seen that for the target working frequency band, when the overall acoustic impedance Z of the sound absorbing unit 100 matches the impedance Z0 of air, the sound absorption coefficient α can take a maximum value, for example, it can be a value close to 1 such as 0.95 to 0.999. At this time, it can be considered that the sound absorption efficiency of the quarter-wavelength tube 11 and the Helmholtz resonator 21 for the sound waves of the corresponding sound absorption frequency reaches the highest, and the sound absorption effect is the best. The acoustic impedance Z0 of air can be expressed as Z0 = ρ0c0, where ρ0 represents the density of air under natural conditions, and c0 represents the propagation speed of sound in the outside air. The overall acoustic impedance of the sound absorbing unit 100 can be calculated based on the arrangement of the quarter-wavelength tube 11 and the Helmholtz resonator 21, combined with the respective acoustic impedances of the quarter-wavelength tube 11 and the Helmholtz resonator 21. Furthermore, in order to achieve the maximum efficiency of sound attenuation of the sound absorbing unit 100, the structural parameters (such as length, width, height, opening area, etc.) of the quarter-wavelength tube 11 and the Helmholtz resonator 21 can be calculated and adjusted through calculation software to adjust the respective acoustic impedances, and the parameters when the overall acoustic impedance of the sound absorbing unit 100 matches the acoustic impedance of air are selected as the actual preparation parameters of the sound absorbing unit 100.

[0056] The above-mentioned sound absorption unit 100, by introducing the Helmholtz resonator 21 and matching the overall acoustic impedance with the acoustic impedance of air, is conducive to having a larger sound absorption coefficient, thereby achieving a better sound absorption effect in the low frequency band; and in the same low-frequency sound absorption band, the above-mentioned sound absorption unit 100 requires a small installation space. When arranging such a sound absorption unit 100, there is no need to arrange a cavity structure separately, which can greatly save space and reduce the preparation cost. Further, the quarter-wavelength tube 10 and the Helmholtz resonator array 20 are arranged along a preset direction (such as Figure 1 The stacked arrangement (in the x direction shown) can minimize the length or width of the sound absorbing unit 200, thereby facilitating the arrangement and application of the sound absorbing unit 100. In addition, since the sound absorption frequency of the quarter-wavelength tube 11 has a certain frequency doubling characteristic, the combined use of the quarter-wavelength tube 11 and the Helmholtz resonator 21 can compensate for the single-frequency sound absorption (too narrow frequency) problem of the Helmholtz resonator 21 to a certain extent, thereby improving the sound absorption effect of the sound absorbing unit 100.

[0057] In an exemplary embodiment, Figure 1 As shown, each first open end 1111 and each second open end 2111 are located in the same plane. Specifically, the plane can be a plane or a curved surface. At this time, each quarter-wavelength tube 11 and each Helmholtz resonator 21 are connected in parallel, and sound waves can be incident on each quarter-wavelength tube 11 and each Helmholtz resonator 21 at the same time for noise elimination, so that the overall acoustic impedance Z of the sound absorbing unit 100 satisfies: Among them, Z QW represents the acoustic impedance of each quarter-wavelength tube 11, Z HH represents the acoustic impedance of each Helmholtz resonator 21 , m represents the ordinal number of the quarter-wavelength tube 11 , and n represents the ordinal number of the Helmholtz resonator 21 .

[0058] In an exemplary embodiment, there are two or more quarter-wavelength tube array bodies 10 and Helmholtz resonator array bodies 20. By providing a plurality of quarter-wavelength tube array bodies 10 and Helmholtz resonator array bodies 20, on the one hand, the sound absorption frequency range of the sound absorption unit 100 can be widened, and on the other hand, it is also beneficial to set more dense sound absorption frequency points according to a given target sound absorption frequency range, thereby improving the sound absorption effect within the target sound absorption frequency range.

[0059] In an exemplary embodiment, please refer to Figures 1 to 3 (in Figure 3 The length of each quarter-wavelength tube 11 in each quarter-wavelength tube array 10 is reduced successively; and the length of each Helmholtz resonator 21 in each Helmholtz resonator array 20 is reduced successively; and / or the opening area of ​​the second opening end 2111 of each Helmholtz resonator 21 is reduced successively (such as Figure 2The above method can be used to make each quarter-wave tube 11 and each Helmholtz resonator 21 have different sound absorption frequencies according to the target sound absorption frequency band, thereby improving the sound absorption effect of the target frequency band. In addition, while the length of the quarter-wave tube 11 is reduced in sequence, the opening area of ​​the quarter-wave tube 11 can be controlled to be the same, so as to facilitate the adjustment of the acoustic impedance of the quarter-wave tube; similarly, the structure of the Helmholtz resonator 21 can also be set in this way to control variables, so as to facilitate the adjustment of the acoustic impedance of the Helmholtz resonator 21, which is beneficial to adjust the overall acoustic impedance of the sound absorption unit 100 and achieve the matching of the overall acoustic impedance with the acoustic impedance of air.

[0060] In an exemplary embodiment, the length of any quarter-wavelength tube 11 is less than the length of any Helmholtz resonator 21. In this way, the frequency doubling characteristics of the quarter-wavelength tube 11 can be fully utilized to further broaden the sound absorption frequency range of the sound absorption unit 100.

[0061] In an exemplary embodiment, if Figure 4 and Figure 5 As shown, the quarter-wavelength tube 11 includes: a first tube body 111, having a first end 1111 and a second end 1112 arranged opposite to each other, and a first through hole 1110 passing through the first end 1111 and the second end 1112 along the axis of the first tube body 111; and a first blocking block 112, which is arranged at the opening of the second end 1112 and is used to close the second end. In this case, the characteristic length of the quarter-wavelength tube 11 can be the vertical distance from the first end 1111 to the inner surface of the first blocking block 112. In another embodiment, the quarter-wavelength tube 11 can also be prepared by opening a hole at one end of the cylindrical cover.

[0062] Furthermore, the acoustic impedance Z of the quarter-wavelength tube 11 is QW satisfy:

[0063]

[0064] Among them, L p represents the vertical distance from the first end 1111 to the inner surface of the first block 112, A QW represents the cross-sectional area of ​​the first tube 111, r QW represents the hydraulic radius, ν represents the kinematic viscosity, γ represents the specific heat capacity of air, η represents the viscosity coefficient of air, ω Q represents the terminal correction coefficient, Pr represents the Prandtl constant, ξ Q represents the pressure loss coefficient, represents the equivalent mass flow rate, and ω represents the angular frequency.

[0065] The above formula is obtained by equating the quarter-wavelength tube 11 to a mass-spring system. Through the above formula, the length of each quarter-wavelength tube 11 can be quantitatively optimized, which is conducive to more accurately matching the acoustic impedance of the sound absorbing unit 100 with the acoustic impedance of air, thereby improving the sound absorption effect of the sound absorbing unit 100.

[0066] In an exemplary embodiment, Figure 4 and Figure 6 As shown, the Helmholtz resonator 21 includes: a second tube body 211, having a third end 2111 and a fourth end 2112 arranged opposite to each other, and a second through hole 2110 passing through the third end 2111 and the fourth end 2112 along the axis of the second tube body 211, the second through hole 2110 sequentially including a neck hole 21101 and a base hole 21102 communicating with the neck hole 21101 from the third end 2111 to the fourth end 2112; and a second blocking block 212, which is arranged at the opening of the fourth end 2112 and is used to close the fourth end 2112. At this time, the characteristic length of the Helmholtz resonator can be the vertical distance from the third end 2111 to the inner surface of the second blocking block 212. Considering the actual hole opening process, the neck hole 21101 is usually a tapered hole, so the equivalent length of the tapered hole can be selected to represent the characteristic length of the neck hole 21101. In another embodiment, a hole may be opened at one end of the cylindrical housing to prepare the Helmholtz resonator 21 .

[0067] Furthermore, the acoustic impedance Z of the Helmholtz resonator 21 is HH satisfy:

[0068]

[0069] Where A represents the area of ​​the entire third end 2111, S a represents the opening area of ​​the neck hole 21101, l represents the equivalent length of the neck hole 21101, L represents the vertical distance from the third end 2111 to the inner surface of the second blocking block 212, V HH represents the resonance cavity volume of the Helmholtz resonator 21, ρ cc 、c cc and k cc Respectively represent the density, sound speed and wave number of the air in the resonance chamber, k ca , va and ha They represent the wave number, viscosity term and thermal term of the neck hole 21101 under narrow acoustics, γ represents the specific heat capacity of air, δ Ω represents the sound quality terminal correction term, τ Ω represents the correction factor, ω represents the angular frequency, and η represents the viscosity coefficient of air. The resonance cavity is the through hole portion from the third end 2111 to the inner surface of the second block 212 .

[0070] Through the above formula, the parameters such as the length, opening area, and neck hole length of each Helmholtz resonator 21 can be quantitatively optimized, so that the acoustic impedance of the sound absorbing unit 100 can be more accurately matched with the acoustic impedance of air, thereby improving the sound absorption effect of the sound absorbing unit 100.

[0071] In an exemplary embodiment, the rows of sound absorbing units 100 are connected by ultrasonic welding or epoxy resin adhesive layer, which is conducive to improving the connection strength between the rows.

[0072] In an exemplary embodiment, the preset frequency band is 300 Hz to 4000 Hz. Figures 1 to 6 The sound absorbing unit 100 shown has eight Helmholtz resonator arrays 20 and two quarter-wavelength tube arrays 10 stacked in sequence along the x direction, each Helmholtz resonator array 20 has ten side-by-side Helmholtz resonators 21, and each quarter-wavelength tube array 10 has ten side-by-side quarter-wavelength tubes 11. Figure 3 As shown in the figure, the lengths of the two rows of Helmholtz resonators 21 at the bottom are the same, the opening area of ​​the last row of Helmholtz resonators decreases successively, the length and opening area of ​​the penultimate row of Helmholtz resonators are basically the same, and the lengths of the quarter-wavelength tubes 11 in the top two rows decrease successively. The sound absorbing unit 100 can have a sound absorption coefficient of more than 50% within 300Hz to 4000Hz, and further, the sound absorbing unit 100 can have a sound absorption coefficient of more than 90% within 800Hz to 4000Hz, thereby greatly improving the sound absorption effect in the low frequency band compared to the traditional porous sound absorbing material.

[0073] In an exemplary embodiment, each row of bodies in the sound absorbing unit 100 can be made of a material with low pollution and good environmental tolerance, thereby avoiding the use of plastic foam porous materials, glass or rock fiber porous materials, and foamed porous materials, which is beneficial to reducing pollution to the environment and extending the service life of the sound absorbing unit 100.

[0074] In an exemplary embodiment, Figure 7 As shown, a blocking device 30 can also be used to close the second end 1112 and the fourth end 2112. Specifically, the blocking device 30 includes a connecting strip 32 and a plurality of blocking blocks 31 arranged at intervals on the connecting strip 32. A pull strip 33 is also arranged at one end of the lower surface of the connecting strip 32. One blocking device 30 is used for each row body. Each end to be closed on a row body corresponds to the position of the blocking block 31. The outer wall of the blocking block 31 is connected to the inner wall of the first through hole 1110 or the second through hole 2110. By providing the blocking device 30, the first tube body 111 and the second tube body 211 are conveniently closed, which is conducive to the rapid installation of the sound absorbing unit 100.

[0075] The present application also provides a sound absorbing device.

[0076] A sound absorbing device, comprising a plurality of sound absorbing units 100 as described above, the specific arrangement of the plurality of sound absorbing units 100 can be referred to Figures 8 to 10 When applying, you can choose the most suitable arrangement method for installation according to the installation environment, and this application does not limit this.

[0077] The above-mentioned sound absorbing device can achieve a better elimination effect on low-frequency noise without occupying a large space, and the preparation cost is also low, and it has broad application prospects.

[0078] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0079] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A sound absorbing unit, characterized in that: It comprises at least one quarter-wavelength tube array and at least one Helmholtz resonator array stacked in a preset direction; The quarter-wavelength tube array comprises a plurality of quarter-wavelength tubes arranged side by side, each of the quarter-wavelength tubes having a first open end and a first closed end arranged opposite to each other; The Helmholtz resonator array comprises a plurality of Helmholtz resonators arranged side by side, each of the Helmholtz resonators having a second open end and a second closed end arranged oppositely; Each of the first opening ends and each of the second opening ends together form a sound wave incident surface of the sound absorbing unit; and within a preset frequency band, the overall acoustic impedance of the sound absorbing unit matches the acoustic impedance of air; Each of the first opening ends and each of the second opening ends are located in the same plane, and the overall acoustic impedance Z of the sound absorbing unit satisfies: Among them, Z QW represents the acoustic impedance of each of the quarter-wavelength tubes, Z HH represents the acoustic impedance of each of the Helmholtz resonators, m represents the ordinal number of the quarter-wavelength tube, and n represents the ordinal number of the Helmholtz resonator; The Helmholtz resonator comprises: The second tube body has a third end and a fourth end that are oppositely disposed, and a second through hole that passes through the third end and the fourth end along the axis of the second tube body, wherein the second through hole includes a neck hole and a base hole that communicates with the neck hole in sequence from the third end to the fourth end; and A second blocking block is provided at the opening of the fourth end and is used to close the fourth end; The overall acoustic impedance of the sound absorbing unit includes the acoustic impedance Z of the Helmholtz resonator. HH , the acoustic impedance Z of the Helmholtz resonator HH satisfy: Wherein, A represents the area of ​​the entire third end, S a represents the opening area of ​​the neck hole, l represents the equivalent length of the neck hole, L represents the vertical distance from the third end to the inner surface of the second block, V HH represents the resonance cavity volume of the Helmholtz resonator, ρ cc 、c cc and k cc represent the density, sound speed and wave number of the air in the resonance cavity, respectively, k ca , va and ha They represent the wave number, viscosity term and thermal term of the neck hole under narrow acoustics, γ represents the specific heat capacity of air, δ Ω represents the sound quality terminal correction term, τ Ω represents the correction factor, ω represents the angular frequency, η represents the viscosity coefficient of air, ρ0 represents the density of air under natural conditions, and c0 represents the propagation speed of sound in the external air; The quarter-wavelength tube array and the Helmholtz resonator array each have two or more; In each of the quarter-wavelength tube arrays, the lengths of the quarter-wavelength tubes decrease in sequence; and the quarter-wavelength tube array comprises a plurality of quarter-wavelength tubes, and the opening shapes of the first opening ends of different quarter-wavelength tubes are different; In each of the Helmholtz resonator arrays, the length of each of the Helmholtz resonators decreases sequentially; and / or the opening area of ​​the second opening end of each of the Helmholtz resonators decreases sequentially.

2. The sound absorbing unit according to claim 1, characterized in that: The length of any one of the quarter-wavelength tubes is shorter than the length of any one of the Helmholtz resonators.

3. The sound absorbing unit according to claim 1, characterized in that: The quarter-wavelength tube comprises: A first tube body has a first end and a second end that are oppositely disposed, and a first through hole that passes through the first end and the second end along the axis of the first tube body; and The first blocking block is arranged at the opening of the second end and is used for closing the second end.

4. The sound absorbing unit according to claim 3, characterized in that: The overall acoustic impedance of the sound absorbing unit includes the acoustic impedance Z of the quarter-wavelength tube QW , the acoustic impedance Z of the quarter-wavelength tube QW satisfy: Among them, ρ0 represents the density of air under natural conditions, L p represents the vertical distance from the first end to the inner surface of the first block, A QW represents the cross-sectional area of ​​the first tube, r QW represents the hydraulic radius, ν represents the kinematic viscosity, γ represents the specific heat capacity of air, η represents the viscosity coefficient of air, ω Q represents the terminal correction coefficient, Pr represents the Prandtl constant, ξ Q represents the pressure loss coefficient, represents the equivalent mass flow rate, and ω represents the angular frequency.

5. The sound absorbing unit according to any one of claims 1 to 2, characterized in that: The preset frequency band is 300 Hz to 4000 Hz.

6. A sound absorbing device, characterized in that: The method comprises a plurality of sound absorbing units according to any one of claims 1 to 5.

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