A composite silencer with multiple slits connecting a Helmholtz resonant cavity

Abstract

A composite silencer with multiple slits connecting a Helmholtz resonator cavity relates to the field of noise control technology. It addresses the problem that traditional sound-absorbing Helmholtz resonators, whether using a single cavity and single neck or simply enlarging the neck cross-section, suffer from limited sound absorption and affect the frequency corresponding to the final absorption peak. A slit-type neck Helmholtz resonator assembly unit includes a hollow straight ventilation channel and four silencer units. The four silencer units surround the hollow straight ventilation channel. Each silencer unit includes seven L-shaped slits and a cuboid cavity. The lateral ends of the seven L-shaped slits are connected to the sides of the cuboid cavity in ascending order of length. The composite silencer with multiple slits connecting a Helmholtz resonator cavity comprises four sets of assembly units that differ only in the cuboid cavity. This invention is applicable to noise control.

Description

Technical Field

[0001] This invention relates to the field of noise control technology. Background Technology

[0002] With the rapid development of modern industry, noise has become one of the harmful environmental pollutants. Unlike other types of pollution, noise pollution is localized and disappears immediately after the source stops emitting sound. Therefore, effective noise control requires solutions considering the sound source, the propagation path, and the receiver. The operational space for effective noise control at the sound source and receiver itself is very limited. Therefore, considering practical feasibility, common noise control methods involve using sound absorption or sound insulation along the propagation path to achieve a certain noise control effect. Based on practical applications, new requirements have been placed on sound-absorbing and sound-insulating structures: adding a certain degree of ventilation while ensuring effective noise control. According to existing technology, ensuring a certain amount of ventilation space within the structure significantly reduces the overall sound absorption effect, posing a challenge to structural design and presenting dimensional limitations in practical applications. To ensure that the structure has a certain sound absorption and insulation effect under ventilated conditions, corresponding design improvements are necessary.

[0003] Traditional sound-absorbing structure designs rely on fundamental structural principles including Helmholtz resonators, micro-perforated plates, and folded channels. However, for traditional Helmholtz resonators, the sound absorption effect of a single-cavity, single-neck resonator in a ventilated environment is quite limited, even at its peak. In an attempt to improve sound absorption, excessively increasing the neck cross-sectional area beyond a certain limit would drastically reduce the sound energy consumed by the neck. Furthermore, different neck cross-sectional areas, neck lengths, and back cavity volumes all affect the frequency corresponding to the final absorption peak.

[0004] In summary, traditional sound-absorbing Helmholtz resonators, under the condition of ensuring a certain ventilation space, will have limited sound absorption effect regardless of whether a single cavity and single neck are used or a single enlarged neck cross-sectional area is chosen, and will affect the frequency corresponding to the final absorption peak. Summary of the Invention

[0005] This invention addresses the problem that traditional sound-absorbing Helmholtz resonators, whether using a single cavity and single neck or choosing to enlarge the cross-sectional area of ​​a single neck, result in limited sound absorption and affect the frequency corresponding to the final absorption peak.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] This invention provides a slit-type neck tube Helmholtz resonator assembly unit, the assembly unit comprising a hollow straight ventilation channel and four noise reduction units;

[0008] The four silencing units surround the hollow direct ventilation channel;

[0009] Each silencing unit includes seven L-shaped slits and a cuboid cavity;

[0010] The lateral ends of the seven L-shaped slits are connected to the side of the cuboid cavity in ascending order of length.

[0011] Furthermore, in a preferred embodiment, the hollow straight ventilation channel is a cuboid, the cross-section of which is a square, and the side length of which is 28mm.

[0012] Furthermore, in a preferred embodiment, the wall thickness of the aforementioned hollow direct ventilation channel is 1.5 mm.

[0013] Furthermore, in a preferred embodiment, the cuboid cavity in the first of the four silencing units has a length of 7mm, a width of 8.5mm, and a height of 20mm.

[0014] The rectangular cavity in the second anechoic unit is 9mm long, 8.5mm wide, and 20mm high.

[0015] The rectangular cavity in the third anechoic unit is 11mm long, 8.5mm wide, and 20mm high.

[0016] The rectangular cavity in the fourth anechoic unit is 13mm long, 8.5mm wide, and 20mm high.

[0017] Furthermore, in a preferred embodiment, the distance between the longitudinal slit and the edge of the seven L-shaped slits is 2mm, and the distance between the transverse slit and the edge of the seven L-shaped slits is 2mm.

[0018] The slit width between the seven L-shaped slits is 1.5 mm.

[0019] Furthermore, in a preferred embodiment, each of the L-shaped slits described above includes a longitudinal slit and a transverse slit;

[0020] The first L-shaped slit has a longitudinal slit length of 72 mm and a transverse slit length of 19.5 mm.

[0021] The second L-shaped slit has a longitudinal slit length of 69 mm and a transverse slit length of 16.5 mm.

[0022] The third L-shaped slit has a longitudinal slit length of 66 mm and a transverse slit length of 13.5 mm.

[0023] The fourth L-shaped slit has a longitudinal slit length of 63 mm and a transverse slit length of 10.5 mm.

[0024] The fifth L-shaped slit has a longitudinal slit length of 60 mm and a transverse slit length of 7.5 mm.

[0025] The sixth L-shaped slit has a longitudinal slit length of 57 mm and a transverse slit length of 4.5 mm.

[0026] The seventh L-shaped slit has a longitudinal slit length of 54 mm and a transverse slit length of 1.5 mm.

[0027] The present invention also provides a composite silencer with a multi-layer slit connecting a Helmholtz resonant cavity, the composite silencer being composed of a combination unit of a multi-layer slit connecting a Helmholtz resonant cavity as described in any one of the above claims, the composite silencer comprising four sets of combination units.

[0028] Furthermore, in a preferred embodiment, the cuboid cavity in the first silencing unit of the second group of the above four combined units has a length of 8mm, a width of 8.5mm, and a height of 34mm.

[0029] The rectangular cavity in the second anechoic unit has a length of 9.2 mm, a width of 8.5 mm, and a height of 34 mm.

[0030] The rectangular cavity in the third anechoic unit has a length of 10.4 mm, a width of 8.5 mm, and a height of 34 mm.

[0031] The rectangular cavity in the fourth anechoic unit has a length of 11.6 mm, a width of 8.5 mm, and a height of 34 mm.

[0032] Furthermore, in a preferred embodiment, the cuboid cavity in the first silencing unit of the third group of the above four combined units has a length of 9mm, a width of 8.5mm, and a height of 50mm.

[0033] The rectangular cavity in the second anechoic unit has a length of 10.2 mm, a width of 8.5 mm, and a height of 50 mm.

[0034] The rectangular cavity in the third anechoic unit has a length of 11.4 mm, a width of 8.5 mm, and a height of 50 mm.

[0035] The rectangular cavity in the fourth anechoic unit has a length of 12.6 mm, a width of 8.5 mm, and a height of 50 mm.

[0036] Furthermore, in a preferred embodiment, the cuboid cavity in the first silencing unit of the fourth group of the above four combined units has a length of 10mm, a width of 8.5mm, and a height of 68mm.

[0037] The rectangular cavity in the second anechoic unit is 11mm long, 8.5mm wide, and 68mm high.

[0038] The rectangular cavity in the third anechoic unit is 12mm long, 8.5mm wide, and 68mm high.

[0039] The rectangular cavity in the fourth anechoic unit is 13mm long, 8.5mm wide, and 68mm high.

[0040] The beneficial effects of this invention are as follows:

[0041] 1. This invention provides a composite silencer with a multi-layered slit-connected Helmholtz resonator. By changing the neck of the ordinary Helmholtz resonator to a gradient L-shaped slit, the single-peak width of the absorption peak of the Helmholtz resonator is widened. The absorption effect at different frequencies is obtained by utilizing the influence of the cavity volume of the Helmholtz resonator on the absorption peak frequency. Through the above structural design, the problem of the sound absorption effect of traditional structures being greatly reduced under ventilation conditions is solved. It achieves a good sound absorption band with a sound absorption coefficient of above 0.65 in the frequency range of 528Hz-850Hz, i.e., within 322Hz, under ventilation conditions. Furthermore, among the 16 peaks formed by the 4 combined units (a total of 16 units), 11 peak values ​​are above 0.85, and 2 peak values ​​are above 0.9.

[0042] 2. This invention provides a composite silencer with a multi-layer slit-connected Helmholtz resonant cavity, which can achieve sound absorption effects at different frequencies simply by adjusting the cavity volume in each small unit.

[0043] 3. This invention provides a composite silencer with a multi-layered slit-connected Helmholtz resonant cavity, which has no specific requirements for the material and can be realized with just a solid rigid structure.

[0044] This invention is applicable to noise control. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the structure of a slit-type neck tube Helmholtz resonator assembly unit as described in Embodiment 1;

[0046] Figure 2 This is a cross-sectional schematic diagram of the slit-type neck tube Helmholtz resonator assembly unit described in Embodiment 1.

[0047] Figure 3 This is a schematic diagram of the hollow straight ventilation channel described in Embodiment 2;

[0048] Figure 4 This is a cross-sectional schematic diagram of the hollow straight ventilation channel of the slit-type neck Helmholtz resonator assembly unit described in embodiments two and three.

[0049] Figure 5 This is a schematic diagram of the structure of the first noise reduction unit described in Embodiment 4;

[0050] Figure 6 This is a schematic diagram of the structure of the second noise reduction unit described in Embodiment 4;

[0051] Figure 7 This is a schematic diagram of the structure of the third noise reduction unit described in Embodiment 4;

[0052] Figure 8 This is a schematic diagram of the structure of the fourth noise reduction unit described in Embodiment 4;

[0053] Figure 9 This is a parameter diagram corresponding to the slit size of each group as described in Implementation Method Six;

[0054] Figure 10 This is a cross-sectional schematic diagram of a composite silencer with a multi-layer slit-connected Helmholtz resonant cavity as described in Embodiment 7.

[0055] Figure 11 This is a sound absorption effect diagram of a composite silencer with a multi-layered slit-connected Helmholtz resonant cavity as described in Embodiment 7. Detailed Implementation

[0056] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

[0057] Implementation Method 1. See Figure 1 and Figure 2 This embodiment describes a slit-type neck tube Helmholtz resonator assembly unit, which includes a hollow straight ventilation channel and four noise reduction units.

[0058] The four silencing units surround the hollow direct ventilation channel;

[0059] Each silencing unit includes seven L-shaped slits and a cuboid cavity;

[0060] The lateral ends of the seven L-shaped slits are connected to the side of the cuboid cavity in ascending order of length.

[0061] In practical applications, this embodiment designs the neck of a traditional Helmholtz resonator as multiple parallel slits, which then connect the back cavities of Helmholtz resonators of different volumes. Ultimately, four sets of combined units, differing only in cavity volume, achieve a good sound absorption frequency band under ventilation conditions. One set of combined units includes a hollow straight ventilation channel and four silencing units; for example... Figure 1 and Figure 2 As shown, four silencing units surround the hollow straight ventilation channel; each silencing unit includes seven L-shaped slits and a cuboid cavity, with the lateral ends of the seven L-shaped slits connected to the side of the cuboid cavity in ascending order of length. This solves the problem that traditional structures suffer a significant decrease in sound absorption when a certain amount of ventilation space is ensured. This embodiment achieves good sound absorption within a certain frequency range while maintaining a certain amount of ventilation space.

[0062] Implementation Method 2. See also Figure 3 and Figure 4 This embodiment is described by way of example of a hollow straight ventilation channel in a slit-type neck Helmholtz resonator assembly unit as described in Embodiment 1. The hollow straight ventilation channel is a cuboid with a square cross-section and a side length of 28mm.

[0063] In practical applications, this implementation method, such as Figure 3 and Figure 4 As shown, the hollow straight ventilation channel is a cuboid, and the cross-section of the cuboid is a square with a side length of 28mm.

[0064] Implementation Method 3. See also Figure 4 This embodiment is described by way of example of a hollow straight ventilation channel in a slit-type neck tube Helmholtz resonator assembly unit as described in Embodiment 1. The wall thickness of the hollow straight ventilation channel is 1.5 mm.

[0065] In practical applications, this implementation method, such as Figure 4 As shown, the wall thickness of the hollow direct ventilation channel is 1.5mm.

[0066] Implementation Method Four. See also Figures 5 to 8 This embodiment is illustrated by taking four noise reduction units in a slit-type neck tube Helmholtz resonator assembly unit as described in Embodiment 1 as an example. The first noise reduction unit has a cuboid cavity with a length of 7mm, a width of 8.5mm, and a height of 20mm.

[0067] The rectangular cavity in the second anechoic unit is 9mm long, 8.5mm wide, and 20mm high.

[0068] The rectangular cavity in the third anechoic unit is 11mm long, 8.5mm wide, and 20mm high.

[0069] The rectangular cavity in the fourth anechoic unit is 13mm long, 8.5mm wide, and 20mm high.

[0070] In practical applications, this implementation method, such as Figure 5 As shown, at 840Hz, the main sound-absorbing component is a rectangular cavity with a volume of 7mm in length, 8.5mm in width, and 20mm in height, corresponding to a sound-absorbing unit with a sound absorption coefficient of 0.82. Figure 6 As shown, at 816Hz, the main sound-absorbing component is a cuboid cavity with a volume of 9mm in length, 8.5mm in width, and 20mm in height, corresponding to a sound-absorbing unit with a sound absorption coefficient of 0.86. (See diagram below.) Figure 7 As shown, at 790Hz, the main sound-absorbing component is a cuboid cavity with a volume of 11mm in length, 8.5mm in width, and 20mm in height, corresponding to a sound-absorbing unit with a sound absorption coefficient of 0.87. (See diagram below.) Figure 8 As shown, the rectangular cavity in the fourth silencing unit has a length of 13mm, a width of 8.5mm, and a height of 20mm.

[0071] Implementation Method 5. This implementation method illustrates the seven L-shaped slits in a slit-type neck tube Helmholtz resonator assembly unit as described in Implementation Method 1. The distance between the longitudinal slits and the edge of the seven L-shaped slits is 2mm, and the distance between the transverse slits and the edge of the seven L-shaped slits is 2mm.

[0072] The slit width between the seven L-shaped slits is 1.5 mm.

[0073] In practical applications, the longitudinal slits of the seven L-shaped slits are all 2mm from the edge, and the transverse slits of the seven L-shaped slits are all 2mm from the edge; the width of the slits between the seven L-shaped slits is 1.5mm. This results in good sound absorption.

[0074] Implementation method six. See also Figures 5 to 9 This embodiment is described by way of example for each L-shaped slit in a slit-type neck tube Helmholtz resonator assembly unit as described in Embodiment 1. Each L-shaped slit includes a longitudinal slit and a transverse slit.

[0075] The first L-shaped slit has a longitudinal slit length of 72 mm and a transverse slit length of 19.5 mm.

[0076] The second L-shaped slit has a longitudinal slit length of 69 mm and a transverse slit length of 16.5 mm.

[0077] The third L-shaped slit has a longitudinal slit length of 66 mm and a transverse slit length of 13.5 mm.

[0078] The fourth L-shaped slit has a longitudinal slit length of 63 mm and a transverse slit length of 10.5 mm.

[0079] The fifth L-shaped slit has a longitudinal slit length of 60 mm and a transverse slit length of 7.5 mm.

[0080] The sixth L-shaped slit has a longitudinal slit length of 57 mm and a transverse slit length of 4.5 mm.

[0081] The seventh L-shaped slit has a longitudinal slit length of 54 mm and a transverse slit length of 1.5 mm.

[0082] In practical applications, this implementation method, such as Figure 9 As shown, 'a' represents the longitudinal slit length of the L-shaped slit, and 'b' represents the transverse slit length of the L-shaped slit. The first L-shaped slit has a longitudinal slit length of 72 mm and a transverse slit length of 19.5 mm; the second L-shaped slit has a longitudinal slit length of 69 mm and a transverse slit length of 16.5 mm; the third L-shaped slit has a longitudinal slit length of 66 mm and a transverse slit length of 13.5 mm; the fourth L-shaped slit has a longitudinal slit length of 63 mm and a transverse slit length of 10.5 mm; the fifth L-shaped slit has a longitudinal slit length of 60 mm and a transverse slit length of 7.5 mm; the sixth L-shaped slit has a longitudinal slit length of 57 mm and a transverse slit length of 4.5 mm; and the seventh L-shaped slit has a longitudinal slit length of 54 mm and a transverse slit length of 1.5 mm.

[0083] Implementation Method Seven. See also Figure 10 and Figure 11 This embodiment describes a composite silencer that connects a multi-layered slit to a Helmholtz resonant cavity. The composite silencer is composed of a combination unit of a multi-layered slit to a Helmholtz resonant cavity as described in any one of embodiments one to six. The composite silencer includes four sets of combination units.

[0084] In practical application, the cross-sectional schematic diagram of the composite silencer connecting the multi-layered slit Helmholtz resonant cavity in this embodiment is shown below. Figure 10As shown, this embodiment demonstrates a good sound absorption frequency band under ventilation conditions achieved by combining four sets of units with different cavity volumes. Firstly, the single neck was changed to a multi-neck design. To complement the overall square structure and extend the sound propagation path, the single neck was further modified into a multi-neck slit channel. Then, back cavities of different volumes were selected to obtain absorption peaks at different frequencies. Each unit includes four small units with different back cavity volumes in four sets of identical multi-neck slit channels, plus a hollow ventilation channel. A total of four units contain sixteen small units with different back cavity volumes in the same multi-neck slit channels. Combining these four units achieves multi-frequency absorption peaks, and the combined effect of the four ventilation and sound-absorbing units creates a sound absorption frequency band of a certain width. This ensures effective sound absorption within a specific frequency range while maintaining ventilation conditions.

[0085] This embodiment provides a composite silencer with a multi-layered slit connecting a Helmholtz resonator cavity. By replacing the neck of a conventional Helmholtz resonator cavity with a gradient L-shaped slit, the single-peak width of the absorption peak of the Helmholtz resonator cavity is widened. The absorption effect at different frequencies is obtained by utilizing the influence of the cavity volume of the Helmholtz resonator cavity on the absorption peak frequency. Through the above structural design, the problem of the sound absorption effect of traditional structures being greatly reduced under ventilation conditions is solved. It achieves a good sound absorption band with a sound absorption coefficient of above 0.65 in the frequency range of 528Hz-850Hz, i.e., within 322Hz, under ventilation conditions. Furthermore, among the 16 peaks formed by the 4 combined units (a total of 16 units), 11 peak values ​​are above 0.85, and 2 peak values ​​are above 0.9.

[0086] This embodiment provides a composite silencer with multiple slits connecting a Helmholtz resonant cavity, which can achieve sound absorption effects at different frequencies simply by adjusting the cavity volume in each small unit.

[0087] This embodiment provides a composite silencer with multiple slits connecting a Helmholtz resonant cavity. There are no specific requirements for the material; a solid rigid structure is sufficient.

[0088] Implementation Method 8. This implementation method is an example of the second group of four combined units in the composite silencer with a multi-layer slit-connected Helmholtz resonant cavity described in Implementation Method 7. The cuboid cavity in the first silencer unit of the second group of four combined units has a length of 8mm, a width of 8.5mm, and a height of 34mm.

[0089] The rectangular cavity in the second anechoic unit has a length of 9.2 mm, a width of 8.5 mm, and a height of 34 mm.

[0090] The rectangular cavity in the third anechoic unit has a length of 10.4 mm, a width of 8.5 mm, and a height of 34 mm.

[0091] The rectangular cavity in the fourth anechoic unit has a length of 11.6 mm, a width of 8.5 mm, and a height of 34 mm.

[0092] In practical applications, at 762Hz, the primary sound-absorbing element is a sound-absorbing unit with a back cavity volume of 8mm (length), 8.5mm (width), and 34mm (height), with a sound absorption coefficient of 0.92. At 738Hz, the primary sound-absorbing element is a sound-absorbing unit with a back cavity volume of 9.2mm (length), 8.5mm (width), and 34mm (height), with a sound absorption coefficient of 0.90. At 700Hz, the primary sound-absorbing element is a sound-absorbing unit with a back cavity volume of 11.6mm (length), 8.5mm (width), and 34mm (height), with a sound absorption coefficient of 0.89.

[0093] Implementation Method Nine. This implementation method is an example of the third group of four combined units in the composite silencer with a multi-layer slit-connected Helmholtz resonant cavity described in Implementation Method Seven. The cuboid cavity in the first silencer unit of the third group of four combined units has a length of 9mm, a width of 8.5mm, and a height of 50mm.

[0094] The rectangular cavity in the second anechoic unit has a length of 10.2 mm, a width of 8.5 mm, and a height of 50 mm.

[0095] The rectangular cavity in the third anechoic unit has a length of 11.4 mm, a width of 8.5 mm, and a height of 50 mm.

[0096] The rectangular cavity in the fourth anechoic unit has a length of 12.6 mm, a width of 8.5 mm, and a height of 50 mm.

[0097] In practical applications, at 672Hz, the primary sound-absorbing element is a sound-absorbing unit with a back cavity volume of 9mm (length), 8.5mm (width), and 50mm (height), with a sound absorption coefficient of 0.88. At 648Hz, the primary sound-absorbing element is a sound-absorbing unit with a back cavity volume of 10.2mm (length), 8.5mm (width), and 50mm (height), with a sound absorption coefficient of 0.87. At 626Hz, the primary sound-absorbing element is a sound-absorbing unit with a back cavity volume of 11.4mm (length), 8.5mm (width), and 50mm (height), with a sound absorption coefficient of 0.87. At 608Hz, the primary sound-absorbing element is a sound-absorbing unit with a back cavity volume of 12.6mm (length), 8.5mm (width), and 50mm (height), with a sound absorption coefficient of 0.86.

[0098] Implementation Method 10. This implementation method illustrates the fourth group of four combined units in the composite silencer with a multi-layer slit-connected Helmholtz resonant cavity described in Implementation Method 7.

[0099] The cuboid cavity in the first silencing unit of the fourth group of the four combined units is 10mm long, 8.5mm wide, and 68mm high.

[0100] The rectangular cavity in the second anechoic unit is 11mm long, 8.5mm wide, and 68mm high.

[0101] The rectangular cavity in the third anechoic unit is 12mm long, 8.5mm wide, and 68mm high.

[0102] The rectangular cavity in the fourth anechoic unit is 13mm long, 8.5mm wide, and 68mm high.

[0103] In practical applications, at 582Hz, the primary sound-absorbing element is a sound-absorbing unit with a back cavity volume of 10mm (length), 8.5mm (width), and 68mm (height), with a sound absorption coefficient of 0.86. At 566Hz, the primary sound-absorbing element is a sound-absorbing unit with a back cavity volume of 11mm (length), 8.5mm (width), and 68mm (height), with a sound absorption coefficient of 0.85. At 548Hz, the primary sound-absorbing element is a sound-absorbing unit with a back cavity volume of 12mm (length), 8.5mm (width), and 68mm (height), with a sound absorption coefficient of 0.84. At 536Hz, the primary sound-absorbing element is a sound-absorbing unit with a back cavity volume of 13mm (length), 8.5mm (width), and 68mm (height), with a sound absorption coefficient of 0.79.

[0104] Implementation Method 11. This implementation method verifies and illustrates the composite silencer with a multi-layer slit-connected Helmholtz resonator cavity described in Implementation Methods 7 to 10. This implementation method widens the single-peak width of the absorption peak of the Helmholtz resonator cavity by changing the neck of the ordinary Helmholtz resonator cavity to a gradient L-shaped slit. It also utilizes the influence of the cavity volume of the Helmholtz resonator cavity on the absorption peak frequency to obtain absorption effects at different frequencies. This structural design solves the problem of significantly reduced sound absorption effect in traditional structures under ventilated conditions, and achieves a good sound absorption band with an absorption coefficient of over 0.65 within the frequency range of 528Hz-850Hz (i.e., within 322Hz) under ventilated conditions. Figure 11 As shown.

[0105] According to the formula for calculating the absorption frequency of a Helmholtz resonator:

[0106]

[0107] Where the speed of sound c = 340 m / s, s is the cross-sectional area of ​​the neck, V is the volume of the dorsal cavity, and l is the length of the neck.

[0108] The formula for the sound absorption coefficient of a structure under unventilated conditions is:

[0109]

[0110] Where α is the sound absorption coefficient, E α To absorb sound energy, E i For incident sound energy, E r To reflect sound energy.

[0111] The sound absorption coefficient under ventilated conditions has a greater amount of sound energy transmitted through the structure compared to the sound absorption coefficient under unventilated conditions.

[0112] α = 1 - |r| 2 -|t| 2 ;

[0113] Where α is the sound absorption coefficient, |r| 2 To reflect part of the sound energy, |t| 2 This refers to the transmitted portion of sound energy.

[0114] The overall dimensions of this embodiment are 50×50×74mm. It achieves a sound absorption band with a sound absorption coefficient of 0.65 or higher within the frequency range of 528Hz-850Hz (i.e., 322Hz) while maintaining a 25% ventilation area. This sound absorption band with a sound absorption coefficient of 0.65 or higher is achieved through a combined structure in a ventilated environment.

[0115] Therefore, it can be seen that the composite silencer with multi-layer slits connecting the Helmholtz resonator cavity described in this embodiment has a good sound absorption frequency band under ventilation conditions, consisting of four sets of combined units with only different cavity volumes. The composite silencer with multi-layer slits connecting the Helmholtz resonator cavity described in this embodiment first changes the single neck to a multi-neck design. Simultaneously, to match the overall square structure and to extend the sound propagation path, the single neck is further changed to a multi-neck slit channel. Then, back cavities of different volumes are selected to obtain absorption peaks at different frequencies. One unit includes four small units with different back cavity volumes in four sets of identical multi-neck slit channels and a hollow ventilation channel. A total of four units contain sixteen small units with different back cavity volumes in the same multi-neck slit channels. Combining the four units together achieves multi-frequency absorption peaks, and under the combined action of the four ventilation and sound-absorbing units, a sound absorption frequency band with a certain width is formed. This achieves effective sound absorption within a certain frequency range while ensuring ventilation conditions.

[0116] This embodiment provides a composite silencer with a multi-layered slit connecting a Helmholtz resonator cavity. By replacing the neck of a conventional Helmholtz resonator cavity with a gradient L-shaped slit, the single-peak width of the absorption peak of the Helmholtz resonator cavity is widened. The absorption effect at different frequencies is obtained by utilizing the influence of the cavity volume of the Helmholtz resonator cavity on the absorption peak frequency. Through the above structural design, the problem of the sound absorption effect of traditional structures being greatly reduced under ventilation conditions is solved. It achieves a good sound absorption band with a sound absorption coefficient of above 0.65 in the frequency range of 528Hz-850Hz, i.e., within 322Hz, under ventilation conditions. Furthermore, among the 16 peaks formed by the 4 combined units (a total of 16 units), 11 peak values ​​are above 0.85, and 2 peak values ​​are above 0.9.

[0117] This embodiment provides a composite silencer with multiple slits connecting a Helmholtz resonant cavity, which can achieve sound absorption effects at different frequencies simply by adjusting the cavity volume in each small unit.

[0118] This embodiment provides a composite silencer with multiple slits connecting a Helmholtz resonant cavity. There are no specific requirements for the material; a solid rigid structure is sufficient.

[0119] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0120] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0121] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A slit neck tube Helmholtz resonator combination unit, characterized by, The combination unit comprises a hollow straight-through air passage and four sound absorbing units; The four sound absorbing units surround the hollow straight-through air passage; Each sound absorbing unit comprises seven gradient L-shaped slits and a cuboid cavity; The transverse ends of the seven gradient L-shaped slits are sequentially connected to the side of the cuboid cavity in ascending order of length, and the gradient L-shaped slits serve as the neck of a Helmholtz resonator, so that the slits connect Helmholtz resonator back cavities of different volumes, thereby widening the single-peak width of the Helmholtz resonator absorption peak.

2. A slit neck tube Helmholtz resonator combination unit according to claim 1, characterized in that The hollow straight-through air passage is a cuboid, and the cross section of the cuboid is a square with a side length of 28 mm.

3. A slit neck tube Helmholtz resonator combination unit according to claim 1, characterized in that The wall thickness of the hollow straight-through air passage is 1.5 mm.

4. A slit neck tube Helmholtz resonator combination unit according to claim 1, characterized in that The length, width and height of the cuboid cavity in the first sound absorbing unit of the second combination unit are 8 mm, 8.5 mm and 34 mm, respectively. The length, width and height of the cuboid cavity in the second sound absorbing unit are 9.2 mm, 8.5 mm and 34 mm, respectively. The length, width and height of the cuboid cavity in the third sound absorbing unit are 10.4 mm, 8.5 mm and 34 mm, respectively. The length, width and height of the cuboid cavity in the fourth sound absorbing unit are 11.6 mm, 8.5 mm and 34 mm, respectively.

5. A slit neck tube Helmholtz resonator combination unit according to claim 1, characterized in that The distance between the longitudinal slits of the seven L-shaped slits and the longitudinal edges of the sound absorbing unit shell is 2 mm, and the distance between the transverse slits of the seven L-shaped slits and the side edges of the cuboid cavity is 2 mm. The slit width between the seven L-shaped slits is 1.5 mm.

6. A slit neck tube Helmholtz resonator combination unit according to claim 1, characterized in that Each L-shaped slit comprises a longitudinal slit and a transverse slit. The length of the longitudinal slit of the first L-shaped slit is 72 mm, and the length of the transverse slit is 19.5 mm. The length of the longitudinal slit of the second L-shaped slit is 69 mm, and the length of the transverse slit is 16.5 mm. The length of the longitudinal slit of the third L-shaped slit is 66 mm, and the length of the transverse slit is 13.5 mm. The length of the longitudinal slit of the fourth L-shaped slit is 63 mm, and the length of the transverse slit is 10.5 mm. The length of the longitudinal slit of the fifth L-shaped slit is 60 mm, and the length of the transverse slit is 7.5 mm. The length of the longitudinal slit of the sixth L-shaped slit is 57 mm, and the length of the transverse slit is 4.5 mm. The length of the longitudinal slit of the seventh L-shaped slit is 54 mm, and the length of the transverse slit is 1.5 mm.

7. A composite muffler of multiple-layer slotted-port communicating Helmholtz resonators, characterized by, The composite sound absorber is composed of the combination unit of a multi-layer slit connected Helmholtz resonator cavity according to any one of claims 1-6, and the composite sound absorber comprises four combination units.

8. A composite muffler of a multi-layer slotted-port cross-Helmholtz resonator according to claim 7, characterized by The length, width and height of the cuboid cavity in the first sound absorbing unit of the second combination unit are 8 mm, 8.5 mm and 34 mm, respectively. The length, width and height of the cuboid cavity in the second sound absorbing unit are 9.2 mm, 8.5 mm and 34 mm, respectively. The length, width and height of the cuboid cavity in the third sound absorbing unit are 10.4 mm, 8.5 mm and 34 mm, respectively. The length, width and height of the cuboid cavity in the fourth sound absorbing unit are 11.6 mm, 8.5 mm and 34 mm, respectively.

9. A composite muffler of a multi-layer slotted-port cross-Helmholtz resonator according to claim 7, characterized by, The length of the cuboid cavity in the first muffling unit of the third set of combination units in the four sets of combination units is 9mm, the width is 8.5mm, and the height is 50mm; The length of the cuboid cavity in the second muffling unit is 10.2mm, the width is 8.5mm, and the height is 50mm; The length of the cuboid cavity in the third muffling unit is 11.4mm, the width is 8.5mm, and the height is 50mm; The length of the cuboid cavity in the fourth muffling unit is 12.6mm, the width is 8.5mm, and the height is 50mm.

10. A composite muffler of a multi-layer slotted-port communicating Helmholtz resonator according to claim 7, characterized by, The length of the cuboid cavity in the first muffling unit of the fourth set of combination units in the four sets of combination units is 10mm, the width is 8.5mm, and the height is 68mm; The length of the cuboid cavity in the second muffling unit is 11mm, the width is 8.5mm, and the height is 68mm; The length of the cuboid cavity in the third muffling unit is 12mm, the width is 8.5mm, and the height is 68mm; The length of the cuboid cavity in the fourth muffling unit is 13mm, the width is 8.5mm, and the height is 68mm.

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