A low-frequency broadband ventilation duct muffler based on a rough neck Helmholtz resonator

Abstract

The present invention belongs to the field of noise control, and discloses a low-frequency broadband ventilation duct muffler based on a rough necked Helmholtz resonator. The low-frequency broadband ventilation duct muffler includes a cylindrical shell (1), a ventilation hole (2) and a sound absorption unit (3). A ventilation hole (2) is arranged at the center of the cylindrical shell (1), and the sound absorption unit (3) is uniformly arranged between the ventilation hole (2) and the cylindrical shell (1), and the sound absorption unit (3) is annular; the sound absorption unit (3) includes a rough neck (3-1) and a cavity (3-2), the bottom end of the rough neck (3-1) is connected to the top end of the cavity (3-2), and the cavity (3-2) is arranged at the lower end of the whole low-frequency broadband ventilation duct muffler. The present invention is used to solve the problems that the existing ventilation duct muffler has a relatively high sound absorption peak frequency, a single sound absorption peak, and a relatively low sound absorption coefficient in the low-frequency range.

Description

Technical Field

[0001] The invention belongs to the field of noise control, and in particular relates to a low-frequency broadband ventilation duct muffler based on a rough neck tube Helmholtz resonator. Background Art

[0002] Ventilation is a problem often faced in actual sound absorption applications, especially in limited space environments where airflow is required. This has important practical significance in pipeline noise control and electronic equipment design. In order to achieve good sound absorption effects, general sound absorption structures usually adopt closed structures to prevent sound waves from transmitting outward. This also leads to the fact that ordinary sound absorption structures are at the expense of air circulation, and it is difficult to take into account both ventilation and sound absorption in one structure. However, so far, although ventilation is crucial in many important scenarios, the existing sound absorber manufacturing scheme will inevitably sacrifice ventilation performance. For resonant ventilated sound absorption structures, in order to obtain low-frequency broadband and efficient sound absorption, the existing problems of large structural size, narrow sound absorption bandwidth and low sound absorption efficiency still need to be solved. Broadband sound absorption is another focus of sound absorption, and the most commonly used solution is to use damping structures and multi-unit parallel connection. Using damping structures in the structure, such as rubber and other materials, can achieve the purpose of increasing the sound absorption bandwidth. However, in order to obtain a satisfactory sound absorption bandwidth, the performance of damping materials still needs to be further improved. The multi-unit parallel structure is to set multiple units with continuous sound absorption peaks in parallel, and form broadband sound absorption in the target sound absorption frequency band through coupling between units. This multi-unit parallel connection will inevitably lead to a linear increase in the area of ​​the sound absorption panel with the number of units, resulting in changes in the surface impedance of the structure, a deterioration in the multi-unit coupling effect, and a decrease in the sound absorption coefficient. In addition, the excessively large area of ​​the sound absorption panel also brings difficulties to practical applications. The mechanism of achieving efficient broadband sound absorption while maintaining efficient ventilation in a compact structure remains to be explored. In order to solve the above problems and realize the structural design that meets broadband ventilation and low-frequency effective sound absorption, we will design a low-frequency broadband ventilation sound absorber based on the rough neck tube Helmholtz resonator by optimizing structural parameters and combining structures. Under ventilation conditions, the goal of achieving excellent low-frequency sound absorption while also achieving broadband sound absorption can be achieved. Summary of the invention

[0003] The invention provides a low-frequency broadband ventilation duct silencer based on a rough neck tube Helmholtz resonator, which is used to solve the problems of high sound absorption peak frequency, single sound absorption peak and low sound absorption coefficient in the low frequency range of the existing ventilation duct silencer.

[0004] The present invention is achieved through the following technical solutions:

[0005] A low-frequency broadband ventilation duct muffler based on a rough neck Helmholtz resonator. The low-frequency broadband ventilation duct muffler includes a cylindrical shell 1, ventilation holes 2 and sound absorption units 3. A ventilation hole 2 is provided at the center of the cylindrical shell 1, and a plurality of sound absorption units 3 are evenly arranged between the ventilation hole 2 and the cylindrical shell 1. Each sound absorption unit 3 is annular;

[0006] Each sound absorption unit 3 includes a rough neck 3-1 and a cavity 3-2. The bottom end of the rough neck 3-1 is connected to the top end of the cavity 3-2, and the cavity 3-2 is arranged at the lower end of the entire low-frequency broadband ventilation duct muffler.

[0007] A low-frequency broadband ventilation duct muffler based on a rough neck Helmholtz resonator. The radius of the cylindrical shell is 50 mm and the height is 100 mm.

[0008] A low-frequency broadband ventilation duct muffler based on a rough neck Helmholtz resonator. The radius of the ventilation hole 2 is R = 15 mm.

[0009] A low-frequency broadband ventilation duct muffler based on a rough neck Helmholtz resonator. The distance of the sound absorption unit 3 from the central rotation axis is Rc.

[0010] A low-frequency broadband ventilation duct muffler based on a rough neck Helmholtz resonator. The surface of the rough neck 3-1 is a standard cosine curve. The period of the rough neck 3-1 is b, the amplitude is δ, the neck length is l, and the relative width is d.

[0011] A low-frequency broadband ventilation duct muffler based on a rough neck Helmholtz resonator. Two adjacent rough necks 3-1 are placed out of alignment, that is, the phase difference is 90°.

[0012] A low-frequency broadband ventilation duct muffler based on a rough neck Helmholtz resonator. The back cavity height of the cavity 3-2 is h, and the back cavity width of the cavity 3-2 is m. According to the placement position of the rough neck 3-1:

[0013] m = w + d + (k + 1)δ.

[0014] A low-frequency broadband ventilation duct muffler based on a rough neck Helmholtz resonator. When the number of the sound absorption units 3 is odd, k is 1; when the number of the sound absorption units 3 is even, k is -1.

[0015] A low-frequency broadband ventilation duct sound silencing device applied to a pipeline. The sound silencing device is based on the low-frequency broadband ventilation duct muffler based on a rough neck Helmholtz resonator.

[0016] A low-frequency broadband ventilation duct silencing device applied to a pipeline, and the muffler of the silencing device is applied to the sound insulation of a pipeline with a radius of 50 mm.

[0017] The beneficial effects of the present invention are as follows:

[0018] On the premise of keeping the same volume, the present invention realizes the purpose of reducing the peak absorption frequency and increasing the absorption bandwidth.

[0019] On the premise of ensuring the same volume size, the present invention greatly reduces the peak absorption frequency.

[0020] Compared with the traditional resonator, the present invention can achieve an absorption coefficient of more than 0.8 in the range of 400 - 1200 Hz and a relative bandwidth of 800 Hz for broadband absorption on the premise of unchanged volume. And the designed muffler has no specific requirements on the material, and only a solid rigid structure can achieve it. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Structural schematic diagram of the present invention.

[0022] Figure 2 Symmetric sectional view of the present invention.

[0023] Figure 3 Schematic diagram of a single sound absorption unit of the present invention.

[0024] Figure 4 Comparison diagram of the sound absorption coefficients between the present invention and a smooth neck Helmholtz resonator with the same volume. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] The present invention provides a composite low-frequency broadband ventilation duct muffler with a rough neck Helmholtz resonator. When sound waves reach the upper surface of the cylindrical muffler, a part of the incident sound generates transmitted sound through the central ventilation hole to meet the ventilation requirements; another part enters the muffler to generate resonance silencing. The proposed low-frequency broadband ventilation duct muffler based on a rough neck Helmholtz resonator is as Figure 1 shown.

[0027] A low-frequency broadband ventilation duct muffler based on a rough-necked Helmholtz resonator, the low-frequency broadband ventilation duct muffler comprising a cylindrical shell 1, ventilation holes 2 and sound absorption units 3. A ventilation hole 2 is arranged at the center of the cylindrical shell 1, and a plurality of sound absorption units 3 are evenly arranged between the ventilation hole 2 and the cylindrical shell 1. Each sound absorption unit 3 is annular;

[0028] There are 8 sound absorption units 3, specifically including a first sound absorption unit 3-11, a second sound absorption unit 3-12, a third sound absorption unit 3-13, a fourth sound absorption unit 3-14, a fifth sound absorption unit 3-15, a sixth sound absorption unit 3-16, a seventh sound absorption unit 3-17 and an eighth sound absorption unit 3-18.

[0029] Each sound absorption unit 3 comprises a rough neck 3-1 and a cavity 3-2. The bottom end of the rough neck 3-1 is connected to the top end of the cavity 3-2, and the cavity 3-2 is arranged at the lower end of the entire low-frequency broadband ventilation duct muffler.

[0030] A low-frequency broadband ventilation duct muffler based on a rough-necked Helmholtz resonator, the radius of the cylindrical shell is 50 mm and the height is 100 mm.

[0031] A low-frequency broadband ventilation duct muffler based on a rough-necked Helmholtz resonator, the radius of the ventilation hole 2 is R = 15 mm.

[0032] A low-frequency broadband ventilation duct muffler based on a rough-necked Helmholtz resonator, the distance of the sound absorption unit 3 from the central rotation axis of symmetry is Rc; the central rotation axis of symmetry is the axis of the ventilation hole 2.

[0033] A low-frequency broadband ventilation duct muffler based on a rough-necked Helmholtz resonator, the surface of the rough neck 3-1 is a standard cosine curve, the period of the rough neck 3-1 is b, the amplitude is δ, the length of the neck is l, and the relative width is d.

[0034] A low-frequency broadband ventilation duct muffler based on a rough-necked Helmholtz resonator, two adjacent rough necks 3-1 are placed out of alignment, that is, the phase difference is 90°, so that the wave crest and the wave trough are adjacent.

[0035] A low-frequency broadband ventilation duct muffler based on a rough-necked Helmholtz resonator, the back cavity height of the cavity 3-2 is h, the back cavity width of the cavity 3-2 is m, and according to the placement position of the rough neck 3-1:

[0036] m = w + d + (k + 1)δ.

[0037] A low-frequency broadband ventilation duct muffler based on a rough-necked Helmholtz resonator, where k = 1 when the number of the sound absorption units 3 is odd, and k = -1 when the number of the sound absorption units 3 is even.

[0038] Through the parallel combination of 8 designed sound absorption units, multiple consecutive sound absorption peaks can be connected into one piece, forming broadband sound absorption while maintaining a relatively high sound absorption peak.

[0039] A low-frequency broadband ventilation duct muffling device applied to a duct, where the muffler of the muffling device is based on the low-frequency broadband ventilation duct muffler based on a rough-necked Helmholtz resonator.

[0040] A low-frequency broadband ventilation duct muffling device applied to a duct, where the muffler of the muffling device is applied to the noise reduction of a duct with a radius of 50 mm.

[0041] In a further solution, the overall geometric dimensions are defined as 11 parameters, which are respectively:

[0042]

[0043] In a further solution, the sound absorption performance of the low-frequency broadband ventilation duct muffler based on a rough-necked Helmholtz resonator is verified through simulation calculation.

[0044] The present invention realizes that under the dimensions of a radius of 50 mm and a height of 100 mm, the optimized low-frequency broadband ventilation muffler has 8 relatively continuous absorption peaks located at 439 Hz, 472 Hz, 531 Hz, 606 Hz, 702 Hz, 817 Hz, 957 Hz, and 1109 Hz respectively, which are connected into one piece and combined together to form a broadband absorption with a sound absorption coefficient of more than 0.8 in the range of 400 - 1200 Hz and a relative width of 800 Hz. At the same time, as Figure 4 shown, for the traditional smooth-necked Helmholtz resonator muffler without adding a rough neck, the sound absorption coefficient can reach more than 0.8 in the range of 500 - 1100 Hz under the same volume size. In comparison, the optimized low-frequency broadband ventilation muffler with a rough-necked Helmholtz resonator has better low-frequency effect, which is reduced from 500 Hz to 400 Hz, and a wider sound absorption bandwidth, which is increased from a range of 600 Hz with a sound absorption coefficient of more than 0.8 to a range of 800 Hz, achieving the purpose of low-frequency broadband ventilation noise reduction.

[0045] Figure 1 As shown in the figure, the low-frequency broadband ventilation duct muffler based on a rough-necked Helmholtz resonator is composed of a ventilation hole in the center and a muffler main body as a whole. When sound waves reach the upper surface of the cylindrical muffler, a part of the incident sound generates transmitted sound through the ventilation hole in the center to meet the ventilation requirement; another part enters the muffler to generate resonance noise reduction.

[0046] The low-frequency broadband ventilation duct muffler based on the rough neck Helmholtz resonator is composed of Figure 2 the 8 designed sound-absorbing units shown in the figure, Figure 3 and the specific dimensions of each sound-absorbing unit shown in the figure are determined by the geometric parameters defined in the table. It is expected that the parallel combination of the 8 designed sound-absorbing units can connect the continuous sound-absorbing peaks into one piece, forming broadband sound absorption while maintaining ventilation.

[0047] The sound-absorbing performance of the designed structure is calculated. When the radius is 50 mm and the height is 100 mm, a broadband absorption with a sound absorption coefficient above 0.8 in the range of 400 - 1200 Hz and a relative bandwidth of 800 Hz is achieved. At the same time, compared with the traditional smooth neck Helmholtz resonator, the low-frequency broadband ventilation duct muffler of the present invention has better low-frequency effect with the low-frequency being reduced from 500 Hz to 400 Hz and a wider sound absorption bandwidth, with the range of sound absorption coefficient above 0.8 increasing from 600 Hz to 800 Hz while the volume remains unchanged.

[0048] There is no specific requirement for the material used in this structure, and any rigid material can achieve an ideal effect.

[0049] In summary, by combining and optimizing the design of multiple rough neck Helmholtz resonators, calculating the structure through finite element method, and simulating the sound absorption effect of the structure, the purpose of designing a low-frequency broadband ventilation duct muffler can be achieved.

Claims

1. A low-frequency broadband ventilation duct muffler based on a rough neck Helmholtz resonator, characterized in that, The low-frequency broadband ventilation duct muffler includes a cylindrical shell (1), ventilation holes (2), and sound absorption units (3). A ventilation hole (2) is provided at the center of the cylindrical shell (1), and a plurality of sound absorption units (3) are evenly arranged between the ventilation hole (2) and the cylindrical shell (1). Each sound absorption unit (3) is annular; Each sound absorption unit (3) includes a rough neck tube (3-1) and a cavity (3-2). The bottom end of the rough neck tube (3-1) is connected to the top end of the cavity (3-2), and the cavity (3-2) is arranged at the lower end of the entire low-frequency broadband ventilation duct muffler.

2. The low-frequency broadband ventilation duct muffler according to claim 1, characterized in that, The radius of the cylindrical shell is 50 mm and the height is 100 mm.

3. The low-frequency broadband ventilation duct muffler according to claim 1, characterized in that, The radius of the ventilation hole (2) is R = 15 mm.

4. The low-frequency broadband ventilation duct muffler according to claim 1, characterized in that, The distance of the sound absorption unit (3) from the central rotation axis is Rc.

5. The low-frequency broadband ventilation duct muffler according to claim 1, characterized in that, The surface of the rough neck tube (3-1) is a standard cosine curve. The period of the rough neck tube (3-1) is b, the amplitude is δ, the length of the neck tube is l, and the relative width is d.

6. The low-frequency broadband ventilation duct muffler according to claim 5, characterized in that, Two adjacent rough neck tubes (3-1) are placed out of alignment, that is, the phase difference is 90°.

7. The low-frequency broadband ventilation duct muffler according to claim 6, characterized in that, The back cavity height of the cavity (3-2) is h, and the back cavity width of the cavity (3-2) is m. According to the placement position of the rough neck tube (3-1): m = w + d + (k + 1)δ.

8. The low-frequency broadband ventilation duct muffler according to claim 1, characterized in that, When the number of the sound absorption units (3) is odd, k is 1; when the number of the sound absorption units (3) is even, k is -1.

9. A low-frequency broadband ventilation duct noise elimination device applied to a duct, characterized in that, The noise elimination device is based on the low-frequency broadband ventilation duct muffler based on a rough neck Helmholtz resonator according to any one of claims 1-7.

10. The low-frequency broadband ventilation duct noise elimination device according to claim 9, characterized in that, The muffler of the noise elimination device is applied to the noise elimination of a pipe with a radius of 50 mm.

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