Composite absorption device for enhancing low-frequency sound absorption

Abstract

The utility model discloses a composite absorption device for enhancing low frequency sound absorption, which belongs to the technical field of pipeline acoustics black holes, and comprises a sound tube, a plurality of micro-perforated plates and a Helmholtz sound absorber, the micro-perforated plates are distributed at equal intervals along the axial direction of the inlet end of the sound tube and are arranged from large to small according to the perforated distribution area, and the Helmholtz sound absorber is arranged on the sound tube. Micro-pores are uniformly distributed in each micro-perforated plate; every two adjacent micro-perforated plates are connected through a separation ring; the Helmholtz sound absorbers are distributed at equal intervals in the axial direction of the outlet end of the sound tube, the diameters of the gradually-changed embedded necks are gradually reduced, the center of each Helmholtz sound absorber is provided with a gradually-changed embedded neck, and the inner diameter of each gradually-changed embedded neck is gradually reduced from the inlet end to the outlet end; every two adjacent Helmholtz sound absorbers are connected through a sound absorber cavity. According to the utility model, through the combination of the composite gradually-changed micro-perforated plate and the gradually-changed cascaded Helmholtz sound absorbers which are embedded in the neck part, low-frequency sound absorption and medium-high frequency broadband sound absorption are realized under the sub-wavelength length.

Description

TECHNICAL FIELD

[0001] The utility model relates to pipeline acoustic black hole technical field especially relates to a kind of composite absorption device for enhancing low-frequency sound absorption. BACKGROUND

[0002] Pipeline acoustic black hole (Sonic black hole-SBH) is used to manipulate sound waves propagating in air, by periodically embedding a large number of circular rings with gradually decreasing inner radius in a circular sound wave pipeline, it can be designed as a perfect sound wave trapping structure. When sound waves enter SBH, their propagation speed will gradually decrease, resulting in a shortened wavelength, and this phenomenon of wavelength compression will continue until the wave speed drops to zero, so that the incident wave cannot propagate to the end of the structure. Once the sound wave enters the SBH, it will be trapped and completely absorbed, without any reflection.

[0003] However, in practical applications, the discrete SBH structure with a limited number of built-in circular rings cannot achieve perfect sound absorption effect, it has good mid-high frequency broadband sound absorption performance, but the sound absorption capacity for sound waves below 200Hz is weak. Although the current combination of acoustic black holes or combined with traditional sound absorption structures, there are still problems of complex structure and poor deep subwavelength absorption performance. UTILITY MODEL CONTENT

[0004] Technical problem solved: In view of the technical problems existing in the application process of the pipeline acoustic black hole in the prior art, the utility model provides a composite absorption device for enhancing low-frequency sound absorption, which combines a composite gradually changing micro-perforated panel and a neck-embedded and gradually changing cascade Helmholtz absorber to realize low-frequency sound absorption (below 200Hz) and mid-high frequency broadband sound absorption (500-3000Hz) in subwavelength length.

[0005] Technical scheme: The utility model discloses a composite absorption device for enhancing low-frequency sound absorption, which comprises:

[0006] Sound pipe;

[0007] Micro-perforated panel, including a plurality of pieces distributed equidistantly along the sound pipe inlet end axis, each micro-perforated panel is uniformly distributed with micro-holes for sound waves to pass through, and the plurality of micro-perforated panels are arranged in order of decreasing perforation distribution area; adjacent two micro-perforated panels are connected by a partition ring;

[0008] The Helmholtz absorber comprises a plurality of Helmholtz absorbers which are distributed equidistantly along the axis of the sound tube outlet end, each of the Helmholtz absorbers is provided with a gradually-changing embedded neck, the gradually-changing embedded neck has a gradually-reduced inner diameter from the inlet end to the outlet end, and the gradually-changing embedded necks of the plurality of Helmholtz absorbers have gradually-reduced diameters; the Helmholtz absorbers are connected by the absorber cavities between adjacent two Helmholtz absorbers, and the absorber cavities at the ends of the Helmholtz absorbers are of a bottom-sealed structure.

[0009] Preferably, the micro-perforated plate has a micro-hole diameter D of 0.2 mm, a thickness of 0.2 mm, and a region area radius R of the micro-holes of the micro-perforated plate of 15.8-30 mm.

[0010] Preferably, the gradually-changing embedded neck has a diameter L of 1.0-2.4 mm and a neck length of 5 mm.

[0011] Preferably, a separation ring is arranged between the micro-perforated plate close to the inner side and the adjacent Helmholtz absorber, the plurality of separation rings have the same thickness, and the thickness H of the separation ring is 10 mm.

[0012] Preferably, the ends of the absorber cavities connecting the adjacent two Helmholtz absorbers are open, and the plurality of absorber cavities have the same thickness, and the thickness A of the absorber cavity is 20 mm.

[0013] Preferably, the micro-perforated plate comprises five pieces, i.e., a first micro-perforated plate, a second micro-perforated plate, a third micro-perforated plate, a fourth micro-perforated plate, and a fifth micro-perforated plate; and the separation ring comprises five pieces, i.e., a first separation ring, a second separation ring, a third separation ring, a fourth separation ring, and a fifth separation ring, which are arranged correspondingly to the first micro-perforated plate, the second micro-perforated plate, the third micro-perforated plate, the fourth micro-perforated plate, and the fifth micro-perforated plate.

[0014] Preferably, the Helmholtz absorber comprises three pieces, i.e., a first Helmholtz absorber, a second Helmholtz absorber, and a third Helmholtz absorber, and the first Helmholtz absorber, the second Helmholtz absorber, and the third Helmholtz absorber are provided with a first gradually-changing embedded neck, a second gradually-changing embedded neck, and a third gradually-changing embedded neck, respectively; and the absorber cavity comprises three pieces, i.e., a first absorber cavity, a second absorber cavity, and a third absorber cavity, which are arranged correspondingly to the first Helmholtz absorber, the second Helmholtz absorber, and the third Helmholtz absorber.

[0015] Preferably, the first Helmholtz absorber is supported at the rear end of the fifth separation ring, the first absorber cavity and the second absorber cavity are of an open structure at both ends, and the end of the third absorber cavity is of a closed structure.

[0016] Preferably, the plurality of micro-perforated plates, the separation rings, the Helmholtz absorbers, and the absorber cavities have the same outer diameter which is adapted to the inner diameter of the sound tube.

[0017] Compared with the prior art, the composite absorption device has the following beneficial effects:

[0018] 1、The composite absorption device has excellent deep subwavelength absorption performance, and the first absorption peak thickness is only one thirty of the corresponding sound wave length.

[0019] 2、The composite absorption device is convenient to install or disassemble, and different sound absorption structures can be assembled and designed according to different working conditions, so that sound absorption applications in multiple scenes are realized. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is an axial structural section view of the composite absorption device of the utility model;

[0021] Figure 2 It is Figure 1 It is a connecting structure schematic view of the middle micro-perforated plate and the separation ring;

[0022] Figure 3 It is Figure 1 It is a connecting structure schematic view of the Helmholtz sound absorber and the sound absorber cavity.

[0023] Reference signs: 100, composite absorption device; 1, sound pipe; 2, first micro-perforated plate; 3, second micro-perforated plate; 4, third micro-perforated plate; 5, fourth micro-perforated plate; 6, fifth micro-perforated plate; 7, first Helmholtz sound absorber; 8, second Helmholtz sound absorber; 9, third Helmholtz sound absorber; 10, first gradually-changing embedded neck; 11, second gradually-changing embedded neck; 12, third gradually-changing embedded neck; 13, first separation ring; 14, second separation ring; 15, third separation ring; 16, fourth separation ring; 17, fifth separation ring; 18, first sound absorber cavity; 19, second sound absorber cavity; 20, third sound absorber cavity. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the embodiments of the utility model clearer, the following will be combined with the drawings of the utility model to clearly and completely describe the technical scheme of the embodiments of the utility model. Figures 1-3 The technical scheme of the embodiments of the utility model is clearly and completely described. Obviously, the described embodiments are part of the embodiments of the utility model, rather than all the embodiments. Based on the described embodiments of the utility model, all other embodiments obtained by those skilled in the art belong to the scope of protection of the utility model.

[0025] As Figures 1-3As shown, the composite absorption device for enhancing low-frequency sound absorption, the composite absorption device 100 includes sound tube 1, micro-perforated plate and Helmholtz absorber, the micro-perforated plate includes along the sound tube 1 import end axial equidistant distribution multiple, the Helmholtz absorber includes along the sound tube 1 export end axial equidistant distribution multiple. Each micro-perforated plate is uniformly distributed with the micro hole for sound wave, and the micro hole diameter D of the micro-perforated plate is 0.2mm, its thickness is 0.2mm, and the area radius R of the micro-perforated plate setting micro hole region is 15.8~30mm, and multiple micro-perforated plates are arranged according to the distribution area from big to small. Adjacent two micro-perforated plates are connected through the separation ring;The micro-perforated plate close to the inside and adjacent Helmholtz absorber are provided with separation ring, and multiple separation rings have the same thickness, and the thickness H is 10mm. Sound wave is transmitted into the composite absorption device through the left side of sound tube 1, first passes through the micro-perforated plate of micro hole area area gradient absorption most of high-frequency sound wave;At the same time, the annular cavity formed by micro-perforated plate and separation ring around micro-perforated plate also has certain loss effect to sound wave.

[0026] Each Helmholtz absorber center is provided with gradually changing embedded neck, the gradually changing embedded neck inner diameter gradually reduces from import end to export end, and the gradually changing embedded neck diameter of multiple Helmholtz absorbers gradually reduces, and the gradually changing embedded neck diameter L is 1.0~2.4mm, and the neck length is 5mm. Adjacent two Helmholtz absorbers are connected through absorber cavity, and the both ends of absorber cavity connecting adjacent two Helmholtz absorbers are provided with open, and the absorber cavity at the end of Helmholtz absorber is the bottom sealing structure;Multiple absorber cavities have the same thickness, and the thickness A is 20mm. When sound wave passes through multiple micro-perforated plates and enters the neck embedded and gradually changing cascade Helmholtz absorber, the low-frequency sound wave is further lost through the resonance of gradually changing embedded neck and circumferential absorber cavity, so as to realize low-frequency sound absorption and high-frequency broadband sound absorption under subwavelength thickness.

[0027] In a specific embodiment, as Figures 1-3As shown, the micro-perforated plate includes five pieces, respectively, the first micro-perforated plate 2, the second micro-perforated plate 3, the third micro-perforated plate 4, the fourth micro-perforated plate 5, the fifth micro-perforated plate 6;The corresponding separation ring includes five, respectively, the first micro-perforated plate 2, the second micro-perforated plate 3, the third micro-perforated plate 4, the fourth micro-perforated plate 5, the fifth micro-perforated plate 6 Corresponding first separation ring 13, second separation ring 14, third separation ring 15, fourth separation ring 16, fifth separation ring 17 are arranged;Helmholtz absorber includes three, respectively, the first Helmholtz absorber 7, the second Helmholtz absorber 8, the third Helmholtz absorber 9 and the first gradually changing inner embedded neck 10, the second gradually changing inner embedded neck 11, the third gradually changing inner embedded neck 12 arranged in the center;The sound absorber cavity corresponds to include three, respectively, the first Helmholtz absorber 7, the second Helmholtz absorber 8, the third Helmholtz absorber 9 corresponding first sound absorber cavity 18, second sound absorber cavity 19, third sound absorber cavity 20;Among them, the first Helmholtz absorber 7 is supported at the rear end of the fifth separation ring 17, the first sound absorber cavity 18, the second sound absorber cavity 19 are both open structure, the end of the third sound absorber cavity 20 is closed structure. A plurality of micro-perforated plates, separation rings, Helmholtz absorbers and sound absorber cavities have the same outer diameter adapted to the inner diameter of the sound tube 1. Each micro-perforated plate and the corresponding separation ring constitute a unit, each gradually changing Helmholtz absorber and the corresponding sound absorber cavity constitute a unit, according to different working conditions, the structure quantity and geometric parameters of different units can be adjusted to realize multi-scene high-performance sound absorption.

[0028] The composite absorption device of the utility model adds micro-perforated plate and Helmholtz absorber to obtain matched low-frequency acoustic impedance;Meanwhile, the structure effectively reduces the dependence on the length of the structure through the slow wave effect;Helmholtz absorber as an excellent subwavelength sound absorber can realize high-efficiency sound absorption performance in subwavelength length. The composite absorption device has excellent deep subwavelength absorption performance, and the thickness of the first absorption peak is only one thirty-first of the corresponding sound wave length;And has excellent absorption performance at low frequency, the first peak is at 102 Hz and has three higher peaks within 500 Hz;The structure also has good broadband sound absorption performance at medium and high frequencies, and the average sound absorption coefficient after 500 Hz is 0.8730. The composite absorption device is convenient to install or disassemble, and different sound absorption structures can be assembled and designed according to different working conditions to realize multi-scene sound absorption application.

[0029] The above is the preferred embodiment of the utility model, it should be pointed out, for ordinary technical personnel in the prior art, without departing from the principle of the utility model, can make a number of improvements and refinements, these improvements and refinements also should be regarded as the protection scope of the utility model.

Claims

1. A composite absorption device for enhancing low frequency sound absorption, characterized by, The composite absorption device (100) comprises: a sound tube (1); a plurality of micro-perforated plates distributed equidistantly along the sound tube (1) in the axial direction, each micro-perforated plate being provided with micro-holes for sound wave to pass through, and the plurality of micro-perforated plates being arranged in descending order of the perforated area; a plurality of Helmholtz absorbers distributed equidistantly along the sound tube (1) in the axial direction, each Helmholtz absorber being provided with a tapered inner neck in the center, the inner diameter of the tapered inner neck gradually decreasing from the inlet end to the outlet end, and the diameters of the tapered inner necks of the plurality of Helmholtz absorbers gradually decreasing in sequence; and 2. The composite absorption device for enhancing low frequency sound absorption of claim 1, wherein, the sound absorber cavities between the adjacent two Helmholtz absorbers being connected, and the sound absorber cavity at the end of the Helmholtz absorber being a bottomed structure.

3. The composite absorption device for enhancing low frequency sound absorption of claim 1, wherein, The micro-holes of the micro-perforated plate have a diameter D of 0.2 mm, a thickness of 0.2 mm, and an area radius R of the region provided with the micro-holes of 15.8-30 mm.

4. The composite absorption device for enhancing low frequency sound absorption of claim 1, wherein, The diameter L of the tapered inner neck is 1.0-2.4 mm, and the neck length is 5 mm.

5. The composite absorption device for enhancing low frequency sound absorption of claim 1, wherein, The micro-perforated plate close to the inner side and the adjacent Helmholtz absorber are provided with a partition ring, and the plurality of partition rings have the same thickness, with a thickness H of 10 mm.

6. The composite absorption device for enhancing low frequency sound absorption according to any one of claims 1 to 5, wherein The sound absorber cavities connecting the adjacent two Helmholtz absorbers are provided with open ends, and the plurality of sound absorber cavities have the same thickness, with a thickness A of 20 mm.

7. The composite absorption device for enhancing low frequency sound absorption of claim 6, wherein, The micro-perforated plate comprises five micro-perforated plates, i.e., a first micro-perforated plate (2), a second micro-perforated plate (3), a third micro-perforated plate (4), a fourth micro-perforated plate (5), and a fifth micro-perforated plate (6); and the partition ring comprises five partition rings, i.e., a first partition ring (13), a second partition ring (14), a third partition ring (15), a fourth partition ring (16), and a fifth partition ring (17) corresponding to the first micro-perforated plate (2), the second micro-perforated plate (3), the third micro-perforated plate (4), the fourth micro-perforated plate (5), and the fifth micro-perforated plate (6), respectively. The Helmholtz absorber comprises three Helmholtz absorbers, i.e., a first Helmholtz absorber (7), a second Helmholtz absorber (8), and a third Helmholtz absorber (9), and the central part is provided with a first tapered inner neck (10), a second tapered inner neck (11), and a third tapered inner neck (12); and the sound absorber cavity comprises three sound absorber cavities, i.e., a first sound absorber cavity (18), a second sound absorber cavity (19), and a third sound absorber cavity (20) corresponding to the first Helmholtz absorber (7), the second Helmholtz absorber (8), and the third Helmholtz absorber (9), respectively.

8. The composite absorption device for enhancing low frequency sound absorption of claim 7, wherein, The first Helmholtz absorber (7) is supported at the rear end of the fifth partition ring (17), the first sound absorber cavity (18) and the second sound absorber cavity (19) are both open at both ends, and the end of the third sound absorber cavity (20) is closed. The plurality of micro-perforated plates, partition rings, Helmholtz absorbers, and sound absorber cavities have the same outer diameter as the inner diameter of the sound tube (1).

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