Perforated Plate-based Ventilation Muffler

Abstract

The present invention discloses a ventilation silencer based on a perforated plate, which relates to the field of noise control and solves the problem that the existing ventilation perforated plate silencer has a high sound absorption peak frequency, a low sound absorption coefficient, a narrow bandwidth, and affects ventilation. The present invention includes a plurality of back cavities, a plurality of baffles, a plurality of micro-perforated plates, and a folded channel, wherein the baffles include an upper baffle, a plurality of lower baffles, and a plurality of side baffles; a plurality of micro-perforated plates, an upper baffle, and a plurality of lower baffles are vertically installed at both ends of a plurality of side baffles to form a back cavity; a plurality of back cavities are arranged in an enclosed manner, and the enclosed central area is a ventilation channel, wherein two back cavities are connected by a folded channel. The present invention can produce a sound absorption effect on medium and low frequency sound waves through the cooperation of the back cavity and the micro-perforated plate under the condition of maintaining ventilation, has good sound absorption performance, and has a good sound absorption bandwidth, and can use any rigid material to achieve an ideal sound absorption effect.

Description

Technical Field

[0001] The present invention relates to the field of noise control, and specifically to a ventilation muffler based on a perforated plate. Background Art

[0002] Currently, with the rapid development of the industrialization process, the noise hazards in life are accelerating, and noise reduction has become a key issue that people pay attention to and strive to solve. Based on the need to improve the acoustic environment and reduce noise pollution, many noise reduction structures have emerged in recent years, such as micro-perforated plates, Helmholtz resonators, porous sound-absorbing materials, etc.

[0003] In daily life, perforated plates are widely used. It can be used as a decorative panel for decoration, and at the same time, porous sound-absorbing materials can be added to the perforated plate to enhance the sound-absorbing performance. The sound-absorbing coefficient of traditional perforated plates is relatively low, and due to the small acoustic resistance of the perforated plate, the sound-absorbing bandwidth generated by the perforated plate is also relatively narrow. Compared with traditional perforated plates, the plate thickness of micro-perforated plates is generally less than 2 mm, the diameter of the perforations is generally less than 1 mm, and the perforation rate is less than 15%. Due to the good acoustic impedance of micro-perforated plates, they have good sound-absorbing performance by themselves, and their sound-absorbing frequencies are mainly in the middle and high frequencies. At the same time, the sound-absorbing structure of perforated plates has the characteristics of simple structure, light weight, and resistance to harsh environments, and has been widely used in the construction and industrial fields. However, due to its structure, the perforated plate can only produce good sound-absorbing performance at its resonance frequency, and the resonance frequency is generally in the middle and high frequency bands. And currently, in many cases, it is necessary to maintain ventilation conditions while reducing noise. Therefore, it is necessary to design a muffler that can achieve broadband sound absorption in the middle and low frequency bands under the condition of ensuring ventilation. Summary of the Invention

[0004] In order to solve the problems mentioned above that the existing ventilation perforated plate muffler has a relatively high sound absorption peak frequency, a relatively low sound absorption coefficient, a relatively narrow bandwidth, and affects ventilation, the present invention hereby provides a ventilation muffler based on a perforated plate. The ventilation muffler based on a perforated plate proposed by the present invention selects a perforated plate as the basic structure. By selecting suitable combination parameters, while ensuring perfect ventilation, the purpose of achieving broadband sound absorption in the middle and low frequencies is realized; it has a sound absorption effect on middle and low frequency sound waves, has good sound absorption performance, and can maintain a good sound absorption bandwidth; there are no specific requirements for the materials used in the present invention, and any rigid material can be used to achieve ideal results.

[0005] The present invention proposes a ventilation silencer based on a perforated plate, which specifically includes a plurality of back cavities, a plurality of baffles, a plurality of micro-perforated plates and a folded channel, wherein the baffles include an upper baffle, a plurality of lower baffles and a plurality of side baffles, and the plurality of micro-perforated plates, the upper baffle and the plurality of lower baffles are vertically installed at both ends of the plurality of side baffles to form a back cavity; the plurality of back cavities are arranged in an enclosed manner, and the enclosed central area is a ventilation channel, wherein two back cavities are connected by a folded channel; and sound absorption is achieved by the cooperation of the plurality of back cavities and the plurality of micro-perforated plates.

[0006] Furthermore, the depth of the back cavity is 30mm-200mm.

[0007] Furthermore, the back cavity has a size of 18 mm×10 mm×50 mm.

[0008] Furthermore, the back cavity includes a back cavity 1 and a back cavity 2, the back cavity 1 is surrounded by an upper baffle, a lower baffle and a side baffle, and the folded channel connects the back cavity 1 and the back cavity 2.

[0009] Furthermore, the size of the folded channel is 1.5 mm×10 mm×5 mm.

[0010] Furthermore, the number of the micro-perforated plates is 4-8, and the plate thickness is 0.5mm-1.5mm.

[0011] Furthermore, the diameter of the through hole of the micro-perforated plate is calculated based on the target sound wave frequency, and the calculation formula is:

[0012]

[0013] t′=t+0.8d+1 / 3PD

[0014] Where f r is the sound absorption frequency, t is the thickness of the micro-perforated plate, P is the perforation rate, D is the depth of the cavity behind the plate, d is the perforation diameter, and c is the sound velocity.

[0015] Furthermore, the diameter of the through holes of the micro-perforated plate is 0.5 mm-1.5 mm.

[0016] Furthermore, the perforation rate of the micro-perforated plate is 1.0%-15%.

[0017] Furthermore, the baffle has a thickness of 1.5 mm.

[0018] The beneficial effects of the ventilation silencer based on the perforated plate described in the present invention are:

[0019] (1) The ventilation muffler based on a perforated plate according to the present invention overcomes the problems of the existing ventilation perforated plate muffler, such as a relatively high peak absorption frequency, a relatively low absorption coefficient, a relatively narrow bandwidth, and affecting ventilation. Under the condition of maintaining ventilation, the muffler can produce an absorption effect on medium and low-frequency sound waves through a number of back cavities, has good sound absorption performance, and can maintain a good sound absorption bandwidth.

[0020] (2) For the ventilation muffler based on a perforated plate according to the present invention, there is no specific requirement for the materials used, and any rigid material can be used to achieve an ideal effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0022] In the drawings:

[0023] Figure 1 is a schematic diagram of the overall structure of a ventilation muffler based on a perforated plate according to the present invention;

[0024] Figure 2 is a perspective view of the overall structure of a ventilation muffler based on a perforated plate according to the present invention;

[0025] Figure 3 is a schematic diagram of the top view structure of a ventilation muffler based on a perforated plate according to the present invention;

[0026] Figure 4 is a schematic diagram of the front view structure of a ventilation muffler based on a perforated plate according to the present invention;

[0027] Figure 5 is a schematic diagram of the left view structure of a ventilation muffler based on a perforated plate according to the present invention;

[0028] Figure 6 is a schematic diagram of the structure of a bent channel connecting two cavities of a ventilation muffler based on a perforated plate according to the present invention;

[0029] Figure 7 is a graph of the sound absorption characteristics of a ventilation muffler based on a perforated plate according to the present invention;

[0030] Wherein: 1 - back cavity, 11 - first back cavity, 12 - second back cavity, 13 - third back cavity, 14 - fourth back cavity, 15 - fifth back cavity, 16 - sixth back cavity, 17 - seventh back cavity, 18 - eighth back cavity, 2 - baffle, 3 - micro-perforated plate, 4 - bent channel, L - structural length and width, h - structural height, a - back cavity length, b - back cavity width, c - back cavity depth, t - micro-perforated plate thickness, t1 - baffle thickness, h1 - bent channel height. DETAILED DESCRIPTION

[0031] The specific implementation of the present invention is further described in detail below with reference to the accompanying drawings:

[0032] Specific implementation method 1: See Figures 1-6 The present embodiment is described in detail. A ventilation silencer based on a perforated plate described in the present embodiment includes a plurality of back cavities 1, a plurality of baffles 2, a plurality of micro-perforated plates 3 and a folded channel 4, wherein the baffle 2 includes an upper baffle, a plurality of lower baffles and a plurality of side baffles, and a plurality of micro-perforated plates 3, an upper baffle and a plurality of lower baffles are vertically mounted at both ends of a plurality of side baffles to form a back cavity 1; a plurality of back cavities 1 are arranged in a closed arrangement, and the enclosed central area is a ventilation channel; a folded channel 4 is arranged between two back cavities 1, and the two back cavities 1 are connected through the folded channel 4; the size of the folded channel 4 is 1.5 mm (t1) × 10 mm (b) × 5 mm (h1).

[0033] like Figure 3 , Figure 4 and Figure 5 As shown, the overall size of the ventilation silencer structure is 52mm (L) × 52mm (L) × 52.5mm (h), the size of the middle ventilation channel is 26mm × 26mm; the depth of the back cavity 1 is 30mm-200mm; in this embodiment, the structure has a total of 8 back cavities, and the size of each back cavity is 18mm (a) × 10mm (b) × 50mm (c).

[0034] The back cavity 1 is surrounded by a plurality of baffles 2 and a plurality of micro-perforated plates 3 or by a plurality of baffles 2 , and different back cavities 1 are separated by baffles 2 . The thickness t1 of the baffles 2 between different back cavities 1 is 1.5 mm.

[0035] The ventilation muffler is a mouth-shaped structure, and two back cavities 1 are connected in series and then connected in parallel with the remaining back cavities 1 and are evenly distributed on the outer circle of the ventilation channel.

[0036] The back cavity 1 includes a first back cavity 11, a second back cavity 12, a third back cavity 13, a fourth back cavity 14, a fifth back cavity 15, a sixth back cavity 16, a seventh back cavity 17, and an eighth back cavity 18. The first back cavity 11 is formed by an upper baffle, a lower baffle, and several side baffles. The remaining back cavities 1 are formed by a micro-perforated plate 3, a lower baffle, and several side baffles. The folded channel 4 connects the first back cavity 11 and the second back cavity 12, thereby forming an integral back cavity and increasing the depth of the back cavity. The remaining six back cavities are independent of each other and are separated by a baffle 2. For the connected first back cavity 11 and second back cavity 12, since their depth is increased, they have a lower resonance frequency compared to the other six independent back cavities 1, and a better sound absorption effect in the low-frequency band is obtained. In this way, the first back cavity 11 and the back cavity 12 are connected in series and then in parallel with the remaining back cavities 1, which can generate different absorption peaks at different resonance frequencies without affecting each other. Through the parallel connection form, their absorption peak values are combined together to form a broadband absorption peak value.

[0037] The number of the micro-perforated plates 3 is 4 - 8, and the plate thickness is 0.5 mm - 1.5 mm; in this embodiment, the plate thickness t of the micro-perforated plate 3 is 1 mm.

[0038] For the selection of the through-hole diameter on the micro-perforated plate 3, it is calculated according to the target sound absorption frequency; for the sound absorption frequency, according to the theory, the sound absorption frequency of the micro-perforated plate 3 is mainly related to its four parameters, and the calculation formula is as follows:

[0039]

[0040] t′ = t + 0.8d + 1 / 3PD (2)

[0041] In the formula: f r - Sound absorption frequency; t - Micro-perforated plate thickness; P - Perforation rate; D - Cavity depth behind the plate; d - Perforation diameter; c - Sound velocity.

[0042] The cross-section of the through-holes of the micro-perforated plate 3 is circular, and the range of the diameter of the circular through-holes is 0.5 mm - 1.5 mm.

[0043] As Figure 3 shown, in this embodiment, the number of through-holes of the micro-perforated plate 3 is 12. The diameter R1 of the first micro-perforated plate 3 is 0.6 mm; the diameter R2 of the second micro-perforated plate 3 is 0.7 mm; the diameter R3 of the third micro-perforated plate 3 is 0.8 mm; the diameter R4 of the fourth micro-perforated plate 3 is 1.0 mm; the diameter R5 of the fifth micro-perforated plate 3 is 1.2 mm; the diameter R6 of the sixth micro-perforated plate 3 is 1.3 mm; the diameter R7 of the seventh micro-perforated plate 3 is 1.4 mm. To ensure that the resonance frequencies of the structures of each micro-perforated plate 3 are different, different through-hole diameters are selected.

[0044] The perforation rate of the micro-perforated plate 3 is 1.0% - 15%; in this embodiment, the perforation rate of the several micro-perforated plates 3 is calculated based on the through-hole diameter and the number of through-holes on each micro-perforated plate 3. The perforation rate of the first micro-perforated plate 3 is 1.88%; the perforation rate of the second micro-perforated plate 3 is 2.56%; the perforation rate of the third micro-perforated plate 3 is 3.35%; the perforation rate of the fourth micro-perforated plate 3 is 5.23%; the perforation rate of the fifth micro-perforated plate 3 is 7.53%; the perforation rate of the sixth micro-perforated plate 3 is 8.12%; the perforation rate of the seventh micro-perforated plate 3 is 8.83%.

[0045] As Figure 7 shown, the finite element simulation analysis of the sound absorption characteristics of a ventilation muffler based on a perforated plate is carried out. It can be seen from the figure that in the case of maintaining perfect ventilation, the overall sound absorption performance of a ventilation muffler structure based on a perforated plate is good, and a total of 4 absorption peaks are generated, at frequencies of 645 Hz, 875 Hz, 1150 Hz, and 1135 Hz respectively.

[0046] Regarding the sound absorption coefficient, for a traditional perforated plate, when sound waves are incident on the perforated plate, part of the sound waves will enter the interior of the perforated plate and be dissipated and absorbed, and part of the sound waves will be reflected and cannot be absorbed. Therefore, the sound absorption coefficient formula for a traditional perforated plate is:

[0047] A = 1 - R 2 (3)

[0048] In the formula: A is the sound absorption coefficient; R is the reflection coefficient.

[0049] And the present invention is a ventilation muffler structure based on a perforated plate designed on the basis of a traditional perforated plate. For the ventilation muffler structure, when sound waves are incident, part of the sound waves will enter the interior of the perforated plate and be dissipated and absorbed, part of the sound waves will be reflected and cannot be absorbed, and part of the sound waves will pass directly through the ventilation channel and also cannot be absorbed. Therefore, the sound absorption coefficient calculation formula for the ventilation muffler based on a perforated plate is:

[0050] A = 1 - R 2 - T 2 (4)

[0051] In the formula: R is the reflection coefficient, and T is the transmission coefficient.

[0052] The sound absorption coefficient of the present invention at different frequency bands can be obtained through formula (4).

[0053] In the frequency band of 631 Hz-1162 Hz, the overall sound absorption coefficient of the present invention exceeds 0.6; the corresponding sound absorption coefficients at frequencies of 645 Hz, 875 Hz, 1150 Hz, and 1135 Hz are 0.69, 0.89, 0.925, and 0.86, respectively.

[0054] The specific working principle of the ventilation silencer based on the perforated plate described in the present invention is explained as follows:

[0055] When the sound wave enters the micro-perforated plate 3 along the incident direction, when the incident wavelength is the same as the natural frequency of the micro-perforated plate 3, the sound wave and the perforated plate 3 will resonate, and the sound wave will vibrate violently in the hole and the back cavity 1. The sound wave needs to overcome friction resistance during transmission, thereby consuming sound energy to achieve the effect of sound absorption; at the same time, when the sound wave enters the back cavity 1 from the micro-perforated plate 3, due to the friction and thermal viscosity effect between the sound wave and the wall, part of the sound energy will also be consumed, thereby improving the overall sound absorption performance of the structure. Usually, a single micro-perforated plate 3 corresponds to a resonant frequency, and the sound absorption curve will only produce one peak, and the sound absorption bandwidth is narrow. However, by connecting multiple micro-perforated plates 3 in parallel, there will be coupling between the micro-perforated plates 3, generating multiple coupled resonance absorption peaks, thereby widening the sound absorption bandwidth.

[0056] To summarize the above implementation cases, the ventilation silencer based on a perforated plate described in the present invention can produce a sound absorption effect on medium and low frequency sound waves by setting up a number of back cavities 1 while maintaining ventilation. It has good sound absorption performance and can maintain a good sound absorption bandwidth. The ventilation silencer based on a perforated plate described in the present invention has no specific requirements on the materials used, and any rigid material can be used to achieve the ideal effect.

[0057] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the invention. It can also be a reasonable combination of the features recorded in the above implementation methods. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A ventilation muffler based on a perforated plate, characterized in that: The invention comprises a plurality of back cavities (1), a plurality of baffles (2), a plurality of micro-perforated plates (3) and a folded channel (4), wherein the baffles (2) comprise an upper baffle, a plurality of lower baffles and a plurality of side baffles; the plurality of micro-perforated plates (3), the upper baffle and the plurality of lower baffles are vertically mounted at both ends of the plurality of side baffles to form a back cavity (1); the plurality of back cavities (1) are arranged in a closed arrangement, and the central area formed by the closed arrangement is a ventilation channel, wherein two back cavities (1) are connected by a folded channel (4); and sound absorption is achieved by means of the plurality of back cavities (1) and the plurality of micro-perforated plates (3); The back cavity (1) comprises a back cavity one (11) and a back cavity two (12); the back cavity one (11) is surrounded by an upper baffle, a lower baffle and a side baffle; a folded channel (4) connects the back cavity one (11) and the back cavity two (12).

2. The ventilation muffler based on a perforated plate according to claim 1, characterized in that: The depth of the back cavity (1) is 30 mm-200 mm.

3. The ventilation muffler based on a perforated plate according to claim 2, characterized in that: The back cavity (1) has a size of 18 mm×10 mm×50 mm.

4. The ventilation muffler based on a perforated plate according to claim 1, characterized in that: The size of the folded channel (4) is 1.5 mm×10 mm×5 mm.

5. The ventilation muffler based on a perforated plate according to claim 1, 2, 3 or 4, characterized in that: The number of the micro-perforated plates (3) is 4-8, and the plate thickness is 0.5 mm-1.5 mm.

6. The ventilation muffler based on a perforated plate according to claim 1, 2, 3 or 4, characterized in that: The diameter of the through hole of the micro-perforated plate (3) is calculated based on the target sound wave frequency, and the calculation formula is: where f r is the absorption frequency, is the thickness of the micro-perforated panel, is the perforation ratio, is the depth of the cavity behind the panel, is the perforation diameter, and c is the speed of sound.

7. The ventilation muffler based on a perforated plate according to claim 6, characterized in that: The diameter of the through holes of the micro-perforated plate (3) is 0.5 mm to 1.5 mm.

8. The ventilation muffler based on a perforated plate according to claim 7, characterized in that: The micro-perforated plate (3) has a perforation rate of 1.0%-15%.

9. The ventilation muffler based on a perforated plate according to claim 8, characterized in that: The baffle (2) has a thickness of 1.5 mm.

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