Silencer and silencing system

Abstract

The invention relates to a silencer and a silencing system. The silencer comprises a shell part, a low-frequency silencing assembly, a medium-frequency silencing assembly and a high-frequency silencing assembly. The shell part extends in the first direction, and a silencing cavity of the silencer is defined by the shell part. The shell part comprises an air inlet end and an air outlet end which are oppositely arranged in the first direction. The low-frequency silencing assembly, the medium-frequency silencing assembly and the high-frequency silencing assembly are arranged in the silencing cavity. And in the direction from the air inlet end to the air outlet end, the low-frequency silencing assembly, the medium-frequency silencing assembly and the high-frequency silencing assembly are sequentially arranged, so that sound is allowed to leave the silencing cavity from the air outlet end through the air inlet end, the low-frequency silencing assembly, the medium-frequency silencing assembly and the high-frequency silencing assembly.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sound attenuation equipment, and in particular to a muffler and a sound attenuation system. BACKGROUND

[0002] A fan or a compressor as a device for discharging gas is widely used in industry. However, the noise problem of such a device seriously affects the industrial application experience. Therefore, a corresponding muffler needs to be designed for such a device to reduce its aerodynamic noise.

[0003] The muffler currently has a narrow sound attenuation bandwidth. A corresponding muffler needs to be designed for each type and speed. Due to the lack of universality of such design, a large amount of time is required for debugging of the sound cavity each time, and there are also a large number of invalid spaces in the sound cavity, resulting in problems of narrow application range, long design period, poor sound attenuation performance, and high processing cost of such a muffler. SUMMARY

[0004] The present application provides a muffler and a sound attenuation system to solve some or all of the deficiencies in the related art.

[0005] The first aspect of the present application provides a muffler, comprising:

[0006] A housing portion extends in a first direction and surrounds to form a sound attenuation cavity of the muffler; the housing portion comprises an air inlet end and an air outlet end arranged opposite in the first direction;

[0007] A low-frequency sound attenuation assembly is arranged in the sound attenuation cavity;

[0008] A medium-frequency sound attenuation assembly is arranged in the sound attenuation cavity;

[0009] A high-frequency sound attenuation assembly is arranged in the sound attenuation cavity;

[0010] Wherein, in the direction from the air inlet end to the air outlet end, the low-frequency sound attenuation assembly, the medium-frequency sound attenuation assembly and the high-frequency sound attenuation assembly are arranged in sequence to allow sound to exit the sound attenuation cavity from the air outlet end via the air inlet end, the low-frequency sound attenuation assembly, the medium-frequency sound attenuation assembly and the high-frequency sound attenuation assembly.

[0011] Further, the low-frequency sound attenuation assembly comprises a first low-frequency sound attenuation portion; the first low-frequency sound attenuation portion comprises a first support plate and a first low-frequency sound attenuation hole arranged on the first support plate; the first support plate is connected with the housing portion and is arranged spaced apart from the air inlet end; the aperture of the first low-frequency sound attenuation hole is smaller than the aperture of the air inlet of the air inlet end.

[0012] Further, the spacing between the first support plate and the air inlet end in the first direction is greater than or equal to 25 mm and less than or equal to 75 mm; and / or,

[0013] The ratio of the diameter of the first low-frequency sound hole to the diameter of the shell part is greater than or equal to 0.25 and less than or equal to 0.75.

[0014] Further, the low-frequency sound-absorbing assembly comprises a second low-frequency sound-absorbing part; the second low-frequency sound-absorbing part comprises a second support plate and a first sound-absorbing pipe arranged on the second support plate; the second support plate is connected to the shell part on the side away from the air inlet end and is arranged in a spaced manner with the first support plate; and the first sound-absorbing pipe is arranged on the side of the second support plate facing the first support plate and surrounds to form a second low-frequency sound-absorbing hole of the second low-frequency sound-absorbing part.

[0015] Further, the size of the first support plate and the second support plate in the first direction is greater than or equal to 75 mm and less than or equal to 125 mm; and / or,

[0016] The ratio of the size of the first sound-absorbing pipe in the first direction to the size of the first support plate and the second support plate in the first direction is greater than or equal to 0.25 and less than or equal to 0.75; and / or,

[0017] The ratio of the diameter of the second low-frequency sound hole to the diameter of the shell part is greater than or equal to 0.25 and less than or equal to 0.75.

[0018] Further, the low-frequency sound-absorbing assembly comprises a third low-frequency sound-absorbing part; the third low-frequency sound-absorbing part comprises a third support plate and a second sound-absorbing pipe arranged on the third support plate; the third support plate is connected to the shell part on the side away from the air inlet end and is arranged in a spaced manner with the second support plate; and the second sound-absorbing pipe is arranged on the side of the third support plate facing the second support plate and surrounds to form a third low-frequency sound-absorbing hole of the third low-frequency sound-absorbing part.

[0019] The size of the second sound-absorbing pipe in the first direction is greater than the size of the first sound-absorbing pipe in the first direction.

[0020] Further, the size of the second support plate and the third support plate in the first direction is greater than or equal to 125 mm and less than or equal to 275 mm; and / or,

[0021] The ratio of the size of the second sound-absorbing pipe in the first direction to the size of the second support plate and the third support plate in the first direction is greater than or equal to 0.125 and less than or equal to 0.875; and / or,

[0022] The ratio of the diameter of the third low-frequency noise-absorbing hole to the diameter of the housing portion is greater than or equal to 0.25 and less than or equal to 0.75.

[0023] Furthermore, the intermediate frequency noise reduction assembly includes an intermediate frequency support plate and an expansion tube; the intermediate frequency support plate includes a front intermediate frequency support plate, a rear intermediate frequency support plate, and an intermediate frequency noise reduction hole penetrating the intermediate frequency support plate; the front intermediate frequency support plate and the rear intermediate frequency support plate are spaced apart along the first direction and connected to the housing portion; the expansion tube is connected between the front intermediate frequency support plate and the rear intermediate frequency support plate; the inner diameter of the expansion tube is larger than the aperture of the intermediate frequency noise reduction hole.

[0024] Furthermore, the number of the intermediate frequency noise-absorbing holes corresponds one-to-one with the number of the expansion tubes; the number of intermediate frequency noise-absorbing holes includes multiple holes; the multiple intermediate frequency noise-absorbing holes are evenly distributed around the central axis of the housing portion; and / or,

[0025] The ratio of the aperture of the mid-frequency noise-absorbing hole to the diameter of the housing portion is greater than or equal to 0.125 and less than or equal to 0.375; and / or,

[0026] The expansion tube has a dimension in the first direction that is greater than or equal to 25 mm and less than or equal to 70 mm; and / or,

[0027] The ratio of the inner diameter of the expansion tube to the diameter of the shell portion is greater than or equal to 0.25 and less than or equal to 0.5.

[0028] Furthermore, the high-frequency noise reduction assembly includes a high-frequency support plate and a porous tube; the high-frequency support plate includes a high-frequency front support plate, a high-frequency rear support plate, and a high-frequency noise reduction hole penetrating the high-frequency support plate; the high-frequency front support plate and the high-frequency rear support plate are spaced apart along the first direction and connected to the housing portion; the porous tube is connected between the high-frequency front support plate and the high-frequency rear support plate, and the inner cavity of the porous tube communicates with the high-frequency noise reduction hole;

[0029] The porous tube further includes multiple transmission holes distributed on its outer peripheral surface; sound enters the space between the high-frequency front support plate and the high-frequency rear support plate through the transmission holes via the inner cavity of the porous tube.

[0030] Furthermore, the high-frequency noise reduction assembly also includes a resistive material; the resistive material fills the space between the high-frequency front support plate and the high-frequency rear support plate.

[0031] Furthermore, the filling density of the resistive material is greater than or equal to 400 kg / m³. 3 And less than or equal to 1000 kg / m 3 ; and / or,

[0032] The resistive material is metal fiber or glass fiber cotton.

[0033] Further, the number of the high-frequency sound-absorbing holes corresponds to the number of the porous tubes one by one; the number of the high-frequency sound-absorbing holes comprises a plurality; the plurality of the high-frequency sound-absorbing holes are uniformly distributed around the central axis of the shell part; and / or,

[0034] The ratio of the aperture of the high-frequency sound-absorbing hole to the diameter of the shell part is greater than or equal to 0.125 and less than or equal to 0.375; and / or,

[0035] The distribution rate of the transmission hole on the outer peripheral surface of the porous tube is greater than or equal to 20% and less than or equal to 35%; and / or,

[0036] The aperture of the transmission hole is greater than or equal to 0.2mm and less than or equal to 0.5mm; and / or,

[0037] The size of the porous tube in the first direction is greater than or equal to 100mm and less than or equal to 500mm.

[0038] Further, the sound absorber further comprises a blocking plate; the blocking plate is arranged in the sound-absorbing cavity and connected with the shell part; the blocking plate is arranged between the high-frequency sound-absorbing assembly and the medium-frequency sound-absorbing assembly; the blocking plate comprises a communication hole penetrating along the first direction.

[0039] The second aspect of the present application provides a sound-absorbing system, comprising a fan or a compressor and the sound absorber of the foregoing embodiments; the air outlet of the fan or the compressor is connected with the air inlet end of the sound absorber.

[0040] The technical scheme provided by the embodiments of the present application can include the following beneficial effects:

[0041] As can be seen from the above embodiments, the sound absorber of the present application enables the airflow to enter the sound-absorbing cavity through the air inlet of the air inlet end, and sequentially pass through the low-frequency sound-absorbing assembly, the medium-frequency sound-absorbing assembly and the high-frequency sound-absorbing assembly for sound absorption, and then exit the cavity through the air outlet of the air outlet end. The low-frequency sound-absorbing assembly, the medium-frequency sound-absorbing assembly and the high-frequency sound-absorbing assembly can eliminate low-frequency noise, medium-frequency noise and high-frequency noise, respectively, thereby widening the effective sound-absorbing frequency band of the sound absorber, and further allowing the sound absorber to be used in different noise scenes for sound absorption without the need to design a new sound absorber for each noise scene. It can be seen that the generalization of the sound absorber of the present application is improved, and therefore the design cost and production cost can be effectively reduced.

[0042] It should be understood that the foregoing general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 The diagram shows a cross-sectional perspective view of one embodiment of the muffler of this application;

[0045] Figure 2 The diagram shown is a cross-sectional schematic of one embodiment of the muffler of this application;

[0046] Figure 3 The diagram shows the noise reduction effect of the low-frequency noise reduction component of the muffler of this application;

[0047] Figure 4 The diagram shows the noise reduction effect of the low-frequency noise reduction component and the medium-frequency noise reduction component of the muffler of this application;

[0048] Figure 5 The diagram shows the noise reduction effect of the low-frequency noise reduction component, the medium-frequency noise reduction component, and the high-frequency noise reduction component of the muffler of this application.

[0049] Explanation of reference numerals in the attached figures:

[0050] 100 silencer;

[0051] 1. Housing section; 11. Air inlet end; 12. Air outlet end; 13. Air inlet; 14. Air outlet.

[0052] 2. Silencing cavity;

[0053] 3 Low-frequency silencing component, 31 First low-frequency silencing part, 311 First support plate, 312 First low-frequency silencing hole, 32 Second low-frequency silencing part, 321 Second support plate, 322 First silencing pipe, 323 Second low-frequency silencing hole, 33 Third low-frequency silencing part, 331 Third support plate, 332 Second silencing pipe, 333 Third low-frequency silencing hole;

[0054] 4. Intermediate frequency noise reduction assembly; 41. Intermediate frequency support plate; 411. Intermediate frequency front support plate; 412. Intermediate frequency rear support plate; 42. Expansion tube;

[0055] 5. High-frequency noise reduction assembly, 51. High-frequency support plate, 511. High-frequency front support plate, 512. High-frequency rear support plate, 513. High-frequency noise reduction hole, 52. Multi-hole tube, 521. Transmission hole.

[0056] 6 barrier plates, 61 connecting holes;

[0057] X first direction, A axis. DETAILED DESCRIPTION

[0058] The technical solutions in the embodiments (or, modes of implementation) of the present application will be clearly and completely described herein with reference to the accompanying drawings. When the following description refers to the accompanying drawings, identical numbers in different drawings represent identical or similar elements unless otherwise indicated.

[0059] If the application embodiments involve directional indications or positional relationships (such as up, down, left, right, front, back, inner, outer, top, bottom, center, vertical, horizontal, longitudinal, transverse, length, width, counterclockwise, clockwise, axial, radial, circumferential, etc.), such terms are only used to explain the relative positional relationship, movement, etc. between the components in a certain posture (as shown in the drawings); if the posture changes, the directional indications or positional relationships will also change accordingly. In addition, the terms "first", "second", etc. in the application embodiments are only used for convenience of description, and cannot be understood as indicating or implying relative importance.

[0060] Reference Figure 1 and Figure 2 The present application provides a muffler 100. The muffler 100 comprises a housing part 1, a low-frequency sound-absorbing assembly 3, a medium-frequency sound-absorbing assembly 4, and a high-frequency sound-absorbing assembly 5. The housing part 1 extends along a first direction X and encloses a sound-absorbing cavity 2 of the muffler 100. The housing part 1 comprises an air inlet end 11 and an air outlet end 12 arranged opposite in the first direction X. The low-frequency sound-absorbing assembly 3, the medium-frequency sound-absorbing assembly 4, and the high-frequency sound-absorbing assembly 5 are arranged in the sound-absorbing cavity 2, respectively. Among them, in the direction from the air inlet end 11 to the air outlet end 12, the low-frequency sound-absorbing assembly 3, the medium-frequency sound-absorbing assembly 4, and the high-frequency sound-absorbing assembly 5 are arranged in sequence to allow sound to exit the sound-absorbing cavity 2 from the air outlet end 12 via the air inlet end 11, the low-frequency sound-absorbing assembly 3, the medium-frequency sound-absorbing assembly 4, and the high-frequency sound-absorbing assembly 5.

[0061] By such an arrangement, sound entering the sound-absorbing cavity 2 via the air inlet 13 of the air inlet end 11 can be sequentially absorbed by the low-frequency sound-absorbing assembly 3, the medium-frequency sound-absorbing assembly 4, and the high-frequency sound-absorbing assembly 5, and then exit the cavity via the air outlet 14 of the air outlet end 12. The low-frequency sound-absorbing assembly 3, the medium-frequency sound-absorbing assembly 4, and the high-frequency sound-absorbing assembly 5 can eliminate low-frequency noise, medium-frequency noise, and high-frequency noise, respectively, thereby widening the effective sound-absorbing frequency band of the muffler 100, and allowing the muffler to be used in different noise scenarios without the need to design a new muffler for each noise scenario. It can be seen that the generalization of the muffler of the present application is improved, thus effectively reducing the design and production costs.

[0062] The second aspect of the application further provides a silencer system. The silencer system comprises a fan or compressor and the silencer 100 of the application. The outlet of the fan or compressor is connected to the air inlet end 11 of the silencer 100. In this way, the silencer 100 can eliminate the noise generated by the outlet of the fan or compressor, achieving effective noise reduction. Moreover, due to the generalization of the silencer 100, different models of fans or compressors can use the same silencer 100, which is conducive to reducing the unit price of the silencer 100.

[0063] In addition, the air inlet end 11 and the air outlet end 12 of the application are oppositely arranged in the first direction X, and the shell part 1 extending along the first direction X surrounds to form the silencer cavity 2 extending along the first direction X. Therefore, when the external gas enters the silencer cavity 2, it enters along the extension direction of the air inlet 13 of the silencer 100. This arrangement can effectively avoid the problem of resonance of the shell part 1 compared to the embodiment in which the gas enters the air inlet 13 of the shell part 1 perpendicularly.

[0064] The arrangement of the low-frequency sound-absorbing assembly 3, the medium-frequency sound-absorbing assembly 4, and the high-frequency sound-absorbing assembly 5 will be described below. However, it should be understood that the embodiments of the low-frequency sound-absorbing assembly 3, the medium-frequency sound-absorbing assembly 4, and the high-frequency sound-absorbing assembly 5 can be combined for use without conflict.

[0065] In an optional embodiment, the low-frequency sound-absorbing assembly 3 comprises a first low-frequency silencer part 31. The first low-frequency silencer part 31 comprises a first support plate 311 and a first low-frequency silencer hole 312 arranged on the first support plate 311. The first support plate 311 is connected to the shell part 1 and is arranged spaced apart from the air inlet end 11. The aperture D1 of the first low-frequency silencer hole 312 is smaller than the aperture of the air inlet 13 of the air inlet end 11. The aperture D1 of the first low-frequency silencer hole 312 is smaller than the aperture of the air inlet 13, so that when the gas enters the first low-frequency silencer hole 312 through the air inlet 13, the flow area is reduced, the local flow rate is increased, and turbulence and friction are generated. At this time, the sound energy is converted into heat energy, thereby achieving noise elimination.

[0066] In this embodiment, the size of the first low-frequency silencer part 31 in the first direction X is only the size of the first support plate 311 in the first direction X, which is conducive to controlling the size of the low-frequency sound-absorbing assembly 3 in the first direction X, and further optimizing the overall volume of the silencer 100. In addition, the first low-frequency silencer part 31 is simple to arrange, which is conducive to reducing production costs.

[0067] Further optionally, the distance H1 between the first support plate 311 and the air inlet end 11 in the first direction X is greater than or equal to 25 mm and less than or equal to 75 mm. For example, the distance H1 can be 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, 65 mm, 70 mm, 75 mm or any value therebetween. The distance H1 between the first support plate 311 and the air inlet end 11 in the first direction X defines the volume of the space between the air entering the air inlet 13 and exiting from the first low-frequency sound elimination hole 312. The volume increases, and the corresponding eliminated sound wave length increases, so that the sound elimination frequency further decreases. Therefore, those skilled in the art can reasonably set the distance H1 according to the actual noise frequency to be eliminated.

[0068] Further optionally, the ratio of the hole diameter D1 of the first low-frequency sound elimination hole 312 to the diameter D of the shell portion 1 is greater than or equal to 0.25 and less than or equal to 0.75. For example, the ratio of the hole diameter D1 to the diameter D of the shell portion 1 can be 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75 or any value therebetween. According to the Helmholtz resonance formula, the resonance frequency is inversely proportional to the square root of the hole diameter D1, so the smaller the ratio of the hole diameter D1 to the diameter D of the shell portion 1, the higher the frequency of the noise that can be eliminated. The larger the ratio of the hole diameter D1 to the diameter D of the shell portion 1, the lower the frequency of the noise that can be eliminated. Those skilled in the art can select the ratio within the above range according to the noise frequency to be eliminated. Since the sound eliminator 100 of the present application is provided with the low-frequency sound elimination assembly 3, the medium-frequency sound elimination assembly 4 and the high-frequency sound elimination assembly 5, the above ratio range can ensure effective low-frequency sound elimination effect without worrying about the sound elimination effect of medium-frequency noise and high-frequency noise, while ensuring the overall volume of the sound eliminator 100.

[0069] The diameter D of the shell portion 1 can be adjusted according to the scene in which the sound eliminator 100 is applied and the size of the fan or compressor matched. In some optional embodiments, the diameter D is greater than or equal to 100 mm and less than or equal to 650 mm, so as to control the overall volume of the sound eliminator while avoiding excessive processing difficulty.

[0070] In some optional embodiments, the low-frequency muffling assembly 3 comprises a second low-frequency muffling portion 313. The second low-frequency muffling portion 313 comprises a second support plate 321 and a first muffling pipe 322 arranged on the side of the second support plate 321 facing the first support plate 311. The second support plate 321 is connected to the housing portion 1 on the side of the first support plate 311 away from the air inlet end 11, and is arranged spaced apart from the first support plate 311. The first muffling pipe 322 is arranged on the side of the second support plate 321 facing the first support plate 311, and surrounds the second low-frequency muffling hole 323 of the second low-frequency muffling portion 313. The arrangement of the first muffling pipe 322 can increase the path of the airflow flowing through the second low-frequency muffling hole 323, thereby increasing the friction path between the airflow and the hole wall of the second low-frequency muffling hole 323, and further increasing the friction loss to consume sound energy. As can be seen, the second low-frequency muffling portion 313 is provided with the first muffling pipe 322, so that the muffling frequency of the low-frequency muffling assembly 3 can be adjusted by adjusting the size H5 of the first muffling pipe 322. The cooperation of the first low-frequency muffling portion 31 and the second low-frequency muffling portion 313 can improve the effect of the low-frequency muffling assembly 3 on the elimination of low-frequency noise.

[0071] Optionally, the size H2 of the first support plate 311 and the second support plate 321 in the first direction X is greater than or equal to 75 mm and less than or equal to 125 mm. For example, the size H2 can be 75 mm, 80 mm, 85 mm, 90 mm, 95 mm, 100 mm, 105 mm, 110 mm, 115 mm, 120 mm, 125 mm or any value therebetween. The size H2 is greater than the size H1, so that the first muffling pipe 322 can be arranged on the side of the second low-frequency muffling portion 313 facing the first support plate 311. In addition, according to the foregoing, the first support plate 311 and the second support plate 321 define the muffling space of the second low-frequency muffling portion 313 in the muffling cavity 2. The volume increases, and the corresponding eliminated sound wave length increases, so that the muffling frequency is further reduced. As can be seen, the second low-frequency muffling portion 313 can eliminate noise in a frequency band lower than the first low-frequency muffling portion 31, thereby further improving the muffling effect of the muffler 100 on low-frequency noise.

[0072] Optionally, the ratio of the size H5 of the first muffler pipe 322 in the first direction X to the size H2 of the first support plate 311 and the second support plate 321 in the first direction X is greater than or equal to 0.25 and less than or equal to 0.75. For example, the ratio of the size H5 to the size H2 is 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75 or any value therebetween. According to the Helmholtz resonance formula, the resonance frequency is inversely proportional to the square root of the size H5, and thus the resonance frequency decreases as the size H5 increases. It can be seen that when the ratio of the size H5 to the size H2 decreases, the second low-frequency muffling part 313 can eliminate higher noise frequencies. When the ratio of the size H5 to the size H2 decreases, the second low-frequency muffling part 313 can eliminate lower noise frequencies. Those skilled in the art can adjust the size H5 of the first muffler pipe 322 according to the noise frequencies to be eliminated, so that the cooperation of the first low-frequency muffling part 31 and the second low-frequency muffling part 313 can cover a wider low-frequency range.

[0073] Optionally, the ratio of the hole diameter D2 of the second low-frequency muffling hole 323 to the diameter D of the housing part 1 is greater than or equal to 0.25 and less than or equal to 0.75. For example, the ratio of the hole diameter D2 to the diameter D is 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75 or any value therebetween. According to the foregoing, the smaller the ratio of the hole diameter D2 to the diameter D of the housing part 1, the higher the frequency of the noise that can be eliminated. The larger the ratio of the hole diameter D2 to the diameter D of the housing part 1, the lower the frequency of the noise that can be eliminated. Those skilled in the art can select the ratio within the above range according to the noise frequencies to be eliminated. Since the muffler 100 of the present application is provided with the low-frequency muffling assembly 3, the medium-frequency muffling assembly 4 and the high-frequency muffling assembly 5, the above ratio range can ensure effective low-frequency muffling effect without worrying about the muffling effect of medium-frequency noise and high-frequency noise, while ensuring the overall volume of the muffler 100.

[0074] Optionally, the low frequency muffling assembly 3 comprises a third low frequency muffling section 33. The third low frequency muffling section 33 comprises a third support plate 331 and a second muffling pipe 332 disposed on the third support plate 331. The third support plate 331 is connected to the housing section 1 on a side of the second support plate 321 away from the air inlet end 11, and is disposed apart from the second support plate 321. The second muffling pipe 332 is disposed on a side of the third support plate 331 facing the second support plate 321, and encloses a third low frequency muffling hole 333 of the third low frequency muffling section 33. The second muffling pipe 332 has a dimension H6 in the first direction X that is greater than a dimension H5 of the first muffling pipe 322 in the first direction X. As mentioned above, the resonance frequency is inversely proportional to the square root of the dimension of the muffling pipe in the first direction X. Since the dimension H6 of the second muffling pipe 332 is greater than the dimension H5 of the first muffling pipe 322, the third low frequency muffling section 33 is able to eliminate noise at a lower frequency than the second low frequency muffling section 313. It can be seen that the cooperation of the first low frequency muffling section 31, the second low frequency muffling section 313 and the third low frequency muffling section 33 can further broaden the low frequency noise that can be eliminated by the low frequency muffling assembly 3, thereby improving the noise elimination effect and versatility of the muffling section.

[0075] Optionally, the second support plate 321 and the third support plate 331 have a dimension H3 in the first direction X that is greater than or equal to 125 mm and less than or equal to 275 mm. For example, the dimension H3 can be 125 mm, 130 mm, 135 mm, 140 mm, 145 mm, 150 mm, 155 mm, 160 mm, 165 mm, 170 mm, 175 mm, 180 mm, 185 mm, 190 mm, 195 mm, 200 mm, 205 mm, 210 mm, 215 mm, 220 mm, 225 mm, 230 mm, 235 mm, 240 mm, 245 mm, 250 mm, 255 mm, 260 mm, 265 mm, 270 mm, 275 mm or any value therebetween. The second support plate 321 and the third support plate 331 define a muffling space of the third low frequency muffling section 33 in the muffling cavity 2. The volume increases, and the corresponding eliminated sound wave length increases, so that the muffling frequency is further reduced. It can be seen that the third low frequency muffling section 33 is able to eliminate noise at a lower frequency than the first low frequency muffling section 31 and the second low frequency muffling section 313, thereby further improving the noise elimination effect of the muffler 100 on low frequency noise.

[0076] Optionally, the ratio of the size H6 of the second muffler pipe 332 in the first direction X to the size H3 of the second support plate 321 and the third support plate 331 in the first direction X is greater than or equal to 0.125 and less than or equal to 0.875. For example, the ratio of the size H6 to the size H3 can be 0.125, 0.175, 0.225, 0.275, 0.325, 0.375, 0.425, 0.475, 0.525, 0.575, 0.625, 0.675, 0.725, 0.775, 0.815, 0.875 or any value therebetween. Similar to the first muffler pipe 322, the size H6 increases, and the resonance frequency decreases. It can be seen that when the ratio of the size H6 to the size H3 decreases, the third low-frequency muffling part 33 can eliminate higher noise frequencies. When the ratio of the size H6 to the size H3 decreases, the third low-frequency muffling part 33 can eliminate lower noise frequencies. Those skilled in the art can adjust the size of the second muffler pipe 332 H6 according to the noise frequencies to be eliminated, so that the cooperation of the first low-frequency muffling part 31, the second low-frequency muffling part 313 and the third muffling part can cover a wider low-frequency range.

[0077] Optionally, the ratio of the hole diameter D3 of the third low-frequency muffling hole 333 to the diameter D of the housing part 1 is greater than or equal to 0.25 and less than or equal to 0.75. For example, the ratio of the hole diameter D3 to the diameter D is 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75 or any value therebetween. According to the foregoing, the smaller the ratio of the hole diameter D3 to the diameter D of the housing part 1, the higher the frequency of the noise that can be eliminated. The larger the ratio of the hole diameter D3 to the diameter D of the housing part 1, the lower the frequency of the noise that can be eliminated. Those skilled in the art can select the ratio within the above range according to the noise frequencies to be eliminated. Since the muffler 100 of the present application is provided with the low-frequency muffling assembly 3, the medium-frequency muffling assembly 4 and the high-frequency muffling assembly 5, the above ratio range can ensure effective low-frequency muffling effect without worrying about the muffling effect of medium-frequency noise and high-frequency noise, while ensuring the overall volume of the muffler 100.

[0078] In an optional embodiment, the hole diameter D1 of the first low-frequency muffling hole 312, the hole diameter D2 of the second low-frequency muffling hole 323 and the hole diameter D3 of the third low-frequency muffling hole 333 can be set to be the same, thereby avoiding the influence of the difference in hole diameter on the muffling frequency.

[0079] As Figure 3As shown, in the embodiment in which the low-frequency muffling assembly 3 simultaneously includes the first low-frequency muffling part 31, the second low-frequency muffling part 313, and the third low-frequency muffling part 33, by taking values in the above-mentioned respective numerical ranges, the sound elimination peak value range of the first low-frequency muffling part 31 is 500-2000 Hz, the sound elimination peak value range of the second low-frequency muffling part 313 is 360-1200 Hz, and the sound elimination peak value range of the third low-frequency muffling part 33 is 240-600 Hz. It can be seen that the low-frequency muffling assembly 3 of the muffler 100 of the present application has a wider frequency coverage for noise and a good sound elimination effect, and can be widely applied in different low-frequency noise environments.

[0080] In some optional embodiments, the intermediate-frequency muffling assembly 4 includes an intermediate-frequency support plate 41 and an expansion pipe 42. The intermediate-frequency support plate 41 includes an intermediate-frequency front support plate 411, an intermediate-frequency rear support plate 412, and intermediate-frequency muffling holes penetrating through the intermediate-frequency support plate 41. The intermediate-frequency front support plate 411 and the intermediate-frequency rear support plate 412 are arranged in the first direction X and connected with the shell part 1. The expansion pipe 42 is connected between the intermediate-frequency front support plate 411 and the intermediate-frequency rear support plate 412. The inner cavity diameter D4 of the expansion pipe 42 is greater than the hole diameter of the intermediate-frequency muffling holes.

[0081] The intermediate-frequency muffling holes penetrate through the intermediate-frequency front support plate 411 and the rear support plate, and the inner cavity diameter D4 of the expansion pipe 42 is greater than the hole diameter of the intermediate-frequency muffling holes. That is, when the airflow enters the expansion pipe 42 through the intermediate-frequency muffling holes from one side of the low-frequency muffling assembly 3, and then exits the intermediate-frequency muffling assembly 4 through the intermediate-frequency muffling holes, the cross-sectional area through which the airflow can flow first decreases, then increases, and finally decreases again and exits the intermediate-frequency muffling assembly 4. In this way, the acoustic impedance of the airflow changes multiple times, causing part of the sound waves to reflect towards the sound source direction, and another part to continue to propagate. The reflected sound waves and the incident sound waves superimpose in the inner cavity of the expansion pipe 42. If the phase difference between the two columns of sound waves is 180°, the amplitudes are equal and the directions are opposite, destructive interference occurs, and the sound energy is significantly attenuated. In addition, the sound waves are reflected and scattered multiple times in the expansion chamber, so that part of the sound energy is converted into heat energy, thereby further reducing the noise intensity. As shown in the figure, Figure 4 As shown, in the embodiment in which the low-frequency muffling assembly 3 simultaneously includes the first low-frequency muffling part 31, the second low-frequency muffling part 313, and the third low-frequency muffling part 33, by taking values in the above-mentioned respective numerical ranges, the sound elimination peak value range of the first low-frequency muffling part 31 is 500-2000 Hz, the sound elimination peak value range of the second low-frequency muffling part 313 is 360-1200 Hz, and the sound elimination peak value range of the third low-frequency muffling part 33 is 240-600 Hz. It can be seen that the low-frequency muffling assembly 3 of the muffler 100 of the present application has a wider frequency coverage for noise and a good sound elimination effect, and can be widely applied in different low-frequency noise environments.

[0082] In some optional embodiments, the number of the mid-frequency sound holes corresponds to the number of the expansion tubes 42. The number of the mid-frequency sound holes includes a plurality. The plurality of the mid-frequency sound holes are evenly distributed around the central axis A of the housing part 1. In this embodiment, the gas flow can be understood as flowing through the expansion tubes 42 arranged in parallel. That is, after the gas flow leaves the low-frequency sound reduction assembly 3, it needs to be divided into multiple gas flows to enter the mid-frequency sound reduction assembly 4, and then combined into one gas flow after leaving the mid-frequency sound reduction assembly 4. This arrangement can effectively utilize the internal space of the sound reduction cavity 2 and avoid affecting the gas flow rate. Alternatively, the number of the mid-frequency sound holes can be two, three, four or more.

[0083] Alternatively, the ratio of the aperture of the mid-frequency sound hole to the diameter D of the housing part 1 is greater than or equal to 0.125 and less than or equal to 0.375. For example, the ratio of the aperture of the mid-frequency sound hole to the diameter D can be 0.125, 0.175, 0.225, 0.275, 0.325, 0.375 or any value therebetween. If the aperture of the mid-frequency sound hole is too small, it will increase the acoustic impedance and enhance the reflection of incident sound waves at the inlet of the expansion tube 42. However, too small aperture will increase the airflow resistance and induce turbulent noise. However, if the aperture is too large, the sound reflection effect may be weakened. Those skilled in the art can select according to the actual noise reduction needs.

[0084] Alternatively, the ratio of the inner cavity diameter D4 of the expansion tube 42 to the diameter D of the housing part 1 is greater than or equal to 0.25 and less than or equal to 0.5. The ratio of the diameter D4 and the diameter D4 can be 0.25, 0.30, 0.35, 0.40, 0.45, 0.50 or any value therebetween. The inner cavity diameter D4 of the expansion tube 42 is related to its expansion ratio. The inner cavity diameter D4 affects the frequency of the noise it can eliminate. If the ratio of the inner cavity diameter D4 to the diameter D of the housing part 1 is too large, the maximum sound reduction frequency will move to low frequency, thereby reducing the sound reduction effect of the mid-frequency noise. And the ratio of the inner cavity diameter D4 to the diameter of the housing part 1 is too small, which affects the sound reduction amount of the mid-frequency noise. Those skilled in the art can select within the above value range according to the frequency range of the mid-frequency noise to be eliminated.

[0085] Optionally, the size H4 of the expansion tube 42 in the first direction X is greater than or equal to 25mm and less than or equal to 75mm. For example, the size H4 can be 25mm, 30mm, 35mm, 40mm, 45mm, 50mm, 55mm, 60mm, 65mm, 70mm, 75mm or any value therebetween. An excessively long expansion tube 42 can easily cause airflow separation and vortex, resulting in secondary broadband noise and affecting the noise elimination effect of the mid-frequency noise. An excessively short expansion tube 42 is not good for the noise elimination effect. The size H4 in this range can balance the noise elimination effect of the mid-frequency noise and the overall volume of the mid-frequency noise elimination assembly 4, thereby optimizing the size of the muffler 100.

[0086] Optionally, the high-frequency noise elimination assembly 5 comprises a high-frequency support plate 51 and a porous tube 52. The high-frequency support plate 51 comprises a high-frequency front support plate 511, a high-frequency rear support plate 512 and high-frequency sound elimination holes 513 penetrating through the high-frequency support plate 51. The high-frequency front support plate 511 and the high-frequency rear support plate 512 are spaced apart along the first direction X and connected to the housing part 1. The porous tube 52 is connected between the high-frequency front support plate 511 and the high-frequency rear support plate 512, and the inner cavity of the porous tube 52 communicates with the high-frequency sound elimination holes 513. The porous tube 52 further comprises a plurality of transmission holes 521 distributed on the outer peripheral surface. Sound enters the space between the high-frequency front support plate 511 and the high-frequency rear support plate 512 through the inner cavity of the porous tube 52 via the transmission holes 521.

[0087] The high-frequency sound wave has a short wavelength and can easily penetrate into the fine transmission holes 521. In the transmission holes 521, the air molecules rub against the hole wall violently, generating viscous resistance, which in turn converts sound energy into heat energy, thereby achieving the elimination of high-frequency noise. Figure 5 As shown, the airflow can achieve the elimination of high-frequency noise under the action of the porous tube 52 when passing through the high-frequency noise elimination assembly 5. After the airflow enters the muffling cavity 2 from the air inlet end 11, passes through the low-frequency noise elimination assembly 3, the mid-frequency noise elimination assembly 4 and the high-frequency noise elimination assembly 5 in turn, the elimination of low-frequency noise, mid-frequency noise and high-frequency noise can be achieved. It can be seen that the muffler 100 of the present application can cover multiple noise frequency bands, thereby being applicable to different noise scenes.

[0088] Optionally, the high-frequency noise elimination assembly 5 further comprises a resistive material. The resistive material fills the space between the high-frequency front support plate 511 and the high-frequency rear support plate 512. After the sound wave enters the gaps of the resistive material after leaving the porous tube 52 through the transmission holes 521. In these gaps, the air molecules rub against the material violently, and the sound energy is converted into heat energy due to viscous resistance. Since the high-frequency sound wave has a short wavelength and can easily penetrate into the gaps of the resistive material, the elimination effect of the resistive material on high-frequency noise is particularly significant.

[0089] Further, the filling density of the resistive material is greater than or equal to 400kg / m3 and less than or equal to 1000 kg / m 3 For example, the filling density of the resistive material is 400 kg / m 3 , 500 kg / m 3 , 600 kg / m 3 , 700 kg / m 3 , 800 kg / m 3 , 900 kg / m 3 , 1000 kg / m 3 or any value between them. If the filling density is too small, the effect of gas friction inside the resistive material is reduced. If the filling density is too large, it is difficult for the sound wave to enter the gap of the resistive material.

[0090] Further, the resistive material is metal fiber or glass fiber cotton. The metal fiber will not be blown away by the gas after a long time of use. The glass fiber cotton is lower in cost and the filling process is simpler.

[0091] In some optional embodiments, the number of high-frequency sound-absorbing holes 513 corresponds to the number of porous tubes 52 one-to-one. The number of high-frequency sound-absorbing holes 513 includes a plurality. The plurality of high-frequency sound-absorbing holes 513 are uniformly distributed around the central axis A of the shell part 1. By such an arrangement, the plurality of porous tubes 52 are also arranged in parallel. In this way, the flow-through area of the gas is increased, so that the effect of the porous sound-absorbing assembly on the flow rate of the gas flow is further reduced. At the same time, the gas flow can be high-frequency sound-absorbed in the transmission holes 521 of the plurality of porous tubes 52, thereby improving the sound-absorbing effect of the high-frequency sound-absorbing assembly 5 on high-frequency noise.

[0092] Optionally, the ratio of the hole diameter D5 of the high-frequency sound-absorbing hole 513 to the diameter D of the shell part 1 is greater than or equal to 0.125 and less than or equal to 0.375. The ratio of the hole diameter D5 to the diameter D is 0.125, 0.175, 0.225, 0.275, 0.325, 0.375 or any value between them.

[0093] Optionally, the distribution rate of the transmission hole 521 on the outer peripheral surface of the porous tube 52 is greater than or equal to 20% and less than or equal to 35%. For example, the distribution rate is 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35% or any value between them. If the distribution rate is too small, the number of transmission holes 521 that can be passed by the gas flow is reduced, thereby affecting the friction between the gas flow and the transmission hole 521. If the distribution rate is too high, the structural strength of the porous tube 52 is affected.

[0094] Optionally, the diameter of the transmission hole 521 is greater than or equal to 0.2 mm and less than or equal to 0.5 mm. For example, the diameter of the transmission hole 521 is 0.2 mm, 0.25 mm, 0.30 mm, 0.35 mm, 0.40 mm, 0.45 mm, 0.5 mm or any value within the range. If the diameter of the transmission hole 521 is too small, the flow area of the airflow is reduced, the airflow is difficult to enter the transmission hole 521 for noise reduction, and the processing difficulty is increased. The larger the diameter of the transmission hole 521, the larger the flow area, and the smaller the airflow friction with the hole wall of the transmission hole 521. The diameter in the above range can better balance the high-frequency noise reduction effect.

[0095] Optionally, the size of the perforated pipe 52 in the first direction X is greater than or equal to 100 mm and less than or equal to 500 mm. For example, the size of the perforated pipe 52 in the first direction X is 100 mm, 120 mm, 140 mm, 160 mm, 180 mm, 200 mm, 220 mm, 240 mm, 260 mm, 280 mm, 300 mm, 320 mm, 340 mm, 360 mm, 380 mm, 400 mm, 420 mm, 440 mm, 460 mm, 480 mm, 500 mm or any value within the range. The size of the perforated pipe 52 increases, and the available space of the transmission hole 521 increases, which is beneficial to improve the noise reduction effect of the high-frequency noise reduction assembly 5. However, if the size of the perforated pipe 52 is too long, it will affect the overall size of the muffler. Those skilled in the art can select a value within the above range according to the actual space and the noise frequency band to be eliminated.

[0096] In some optional embodiments, the muffler 100 further comprises a blocking plate 6. The blocking plate 6 is arranged in the muffling cavity 2 and connected with the shell part 1. The blocking plate 6 is arranged between the high-frequency noise reduction assembly 5 and the medium-frequency noise reduction assembly 4. The blocking plate 6 comprises a communication hole 61 extending in the first direction X. When the airflow passes through the medium-frequency muffling hole, it enters the space between the medium-frequency noise reduction assembly 4 and the blocking plate 6, at which time the flow area increases. Then the airflow passes through the communication hole 61 with a reduced flow area, and then enters the space between the blocking plate 6 and the high-frequency noise reduction assembly 5 with an increased flow area. By changing the flow area multiple times, the sound energy of the noise can be effectively dissipated, thereby further ensuring the noise reduction effect of the muffler 100.

[0097] In the above embodiments, the connection between the low-frequency noise reduction assembly 3, the medium-frequency noise reduction assembly 4 and the high-frequency noise reduction assembly 5 and the shell part 1 can be achieved by welding, bonding, clamping and the like. The present application is not limited thereto.

[0098] It should be noted that the technical solutions or technical features described in the above embodiments can be combined or supplemented with each other without conflict. The scope of protection of the present application is not limited to the precise structure described in the above embodiments and shown in the accompanying drawings; any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the scope of protection of the present application.

Claims

1. A silencer, characterized in that, include: The housing portion extends along a first direction and encloses a silencing cavity forming the muffler; the housing portion includes an air inlet end and an air outlet end disposed opposite to each other in the first direction; A low-frequency noise reduction component is disposed in the noise reduction cavity; A mid-frequency noise reduction component is disposed in the noise reduction cavity; A high-frequency noise reduction component is disposed in the noise reduction cavity; In this configuration, the low-frequency silencing component, the mid-frequency silencing component, and the high-frequency silencing component are sequentially arranged in the direction from the air inlet to the air outlet, so as to allow sound to leave the silencing cavity from the air outlet via the air inlet, the low-frequency silencing component, the mid-frequency silencing component, and the high-frequency silencing component.

2. The silencer according to claim 1, characterized in that, The low-frequency silencing component includes a first low-frequency silencing part; the first low-frequency silencing part includes a first support plate and a first low-frequency silencing hole disposed on the first support plate; the first support plate is connected to the housing part and is spaced apart from the air inlet end; the diameter of the first low-frequency silencing hole is smaller than the diameter of the air inlet of the air inlet end.

3. The silencer according to claim 2, characterized in that, The distance between the first support plate and the air intake end in the first direction is greater than or equal to 25 mm and less than or equal to 75 mm; and / or, The ratio of the diameter of the first low-frequency noise-absorbing hole to the diameter of the housing portion is greater than or equal to 0.25 and less than or equal to 0.

75.

4. The silencer according to claim 2, characterized in that, The low-frequency silencing component includes a second low-frequency silencing part; the second low-frequency silencing part includes a second support plate and a first silencing pipe disposed on the second support plate; the second support plate is connected to the housing part on the side of the first support plate away from the air inlet end, and is spaced apart from the first support plate; the first silencing pipe is disposed on the side of the second support plate facing the first support plate, and surrounds a second low-frequency silencing hole forming the second low-frequency silencing part.

5. The silencer according to claim 4, characterized in that, The dimensions of the first support plate and the second support plate in the first direction are greater than or equal to 75 mm and less than or equal to 125 mm; and / or, The ratio of the dimension of the first silencer pipe in the first direction to the dimensions of the first support plate and the second support plate in the first direction is greater than or equal to 0.25 and less than or equal to 0.75; and / or, The ratio of the diameter of the second low-frequency noise-absorbing hole to the diameter of the housing portion is greater than or equal to 0.25 and less than or equal to 0.

75.

6. The silencer according to claim 4, characterized in that, The low-frequency silencing assembly includes a third low-frequency silencing section; the third low-frequency silencing section includes a third support plate and a second silencing pipe disposed on the third support plate; the third support plate is connected to the housing portion on the side of the second support plate away from the air inlet end, and is spaced apart from the second support plate; the second silencing pipe is disposed on the side of the third support plate facing the second support plate, and surrounds a third low-frequency silencing hole forming the third low-frequency silencing section; The dimension of the second silencer in the first direction is greater than the dimension of the first silencer in the first direction.

7. The silencer according to claim 6, characterized in that, The dimensions of the second support plate and the third support plate in the first direction are greater than or equal to 125 mm and less than or equal to 275 mm; and / or, The ratio of the dimension of the second silencer pipe in the first direction to the dimensions of the second support plate and the third support plate in the first direction is greater than or equal to 0.125 and less than or equal to 0.875; and / or, The ratio of the diameter of the third low-frequency noise-absorbing hole to the diameter of the housing portion is greater than or equal to 0.25 and less than or equal to 0.

75.

8. The silencer according to claim 1, characterized in that, The intermediate frequency noise reduction assembly includes an intermediate frequency support plate and an expansion tube; the intermediate frequency support plate includes an intermediate frequency front support plate, an intermediate frequency rear support plate, and an intermediate frequency noise reduction hole penetrating the intermediate frequency support plate; the intermediate frequency front support plate and the intermediate frequency rear support plate are spaced apart along the first direction and connected to the housing portion; the expansion tube is connected between the intermediate frequency front support plate and the intermediate frequency rear support plate; the inner diameter of the expansion tube is larger than the aperture of the intermediate frequency noise reduction hole.

9. The silencer according to claim 8, characterized in that, The number of intermediate frequency noise-absorbing holes corresponds one-to-one with the number of expansion tubes; the number of intermediate frequency noise-absorbing holes includes multiple holes; the multiple intermediate frequency noise-absorbing holes are evenly distributed around the central axis of the housing portion; and / or... The ratio of the aperture of the mid-frequency noise-absorbing hole to the diameter of the housing portion is greater than or equal to 0.125 and less than or equal to 0.375; and / or, The expansion tube has a dimension in the first direction that is greater than or equal to 25 mm and less than or equal to 75 mm; and / or, The ratio of the inner diameter of the expansion tube to the diameter of the shell portion is greater than or equal to 0.25 and less than or equal to 0.

5.

10. The silencer according to claim 1, characterized in that, The high-frequency noise reduction assembly includes a high-frequency support plate and a porous tube; the high-frequency support plate includes a high-frequency front support plate, a high-frequency rear support plate, and a high-frequency noise reduction hole penetrating the high-frequency support plate; the high-frequency front support plate and the high-frequency rear support plate are spaced apart along the first direction and connected to the housing portion; the porous tube is connected between the high-frequency front support plate and the high-frequency rear support plate, and the inner cavity of the porous tube communicates with the high-frequency noise reduction hole; The porous tube further includes multiple transmission holes distributed on its outer peripheral surface; sound enters the space between the high-frequency front support plate and the high-frequency rear support plate through the transmission holes via the inner cavity of the porous tube.

11. The silencer according to claim 10, characterized in that, The high-frequency noise reduction assembly also includes a resistive material; the resistive material fills the space between the high-frequency front support plate and the high-frequency rear support plate.

12. The silencer according to claim 11, characterized in that, The resistive material has a filling density greater than or equal to 400 kg / m³. 3 And less than or equal to 1000 kg / m 3 ; and / or, The resistive material is metal fiber or glass fiber cotton.

13. The silencer according to claim 10, characterized in that, The number of high-frequency silencing holes corresponds one-to-one with the number of porous tubes; the number of high-frequency silencing holes includes multiple holes; the multiple high-frequency silencing holes are evenly distributed around the central axis of the housing portion; and / or... The ratio of the aperture of the high-frequency silencing hole to the diameter of the housing portion is greater than or equal to 0.125 and less than or equal to 0.375; and / or, The distribution rate of the transfer holes on the outer peripheral surface of the porous tube is greater than or equal to 20% and less than or equal to 35%; and / or, The diameter of the transfer hole is greater than or equal to 0.2 mm and less than or equal to 0.5 mm; and / or, The porous tube has a dimension in the first direction that is greater than or equal to 100 mm and less than or equal to 500 mm.

14. The silencer according to claim 1, characterized in that, The muffler further includes a baffle plate; the baffle plate is disposed in the muffler cavity and connected to the housing portion; the baffle plate is disposed between the high-frequency muffler assembly and the mid-frequency muffler assembly; the baffle plate includes a through hole extending along the first direction.

15. A noise reduction system, characterized in that, It includes a fan or compressor, and a silencer as described in any one of claims 1-14; the air outlet of the fan or compressor is connected to the air inlet of the silencer.

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