CN210627893U - Helmholtz resonator of ultra-thin low frequency - Google Patents
Helmholtz resonator of ultra-thin low frequency Download PDFInfo
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- CN210627893U CN210627893U CN201921521736.8U CN201921521736U CN210627893U CN 210627893 U CN210627893 U CN 210627893U CN 201921521736 U CN201921521736 U CN 201921521736U CN 210627893 U CN210627893 U CN 210627893U
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Abstract
The utility model discloses a helmholtz resonator of ultra-thin low frequency, including closed cavity and space beta structure, having a snakelike air passage in the space beta structure, this air passage's one end is as the sound wave incident port, the other end with closed cavity's inner chamber intercommunication, air passage with the neck pipe of helmholtz resonator is enclosed into to space beta structure's inner wall. The utility model discloses a Helmholtz resonator is an ultra-thin structure, constitute by closed cavity and front end space beta structure, design through snakelike air duct, under the condition that does not increase Helmholtz resonator thickness, fold the neck pipe of Helmholtz resonator along sound wave incident direction, compare in linear distance, the distance that the sound wave propagated in folding pipeline will increase several times or tens of times even, the length increase of being equivalent to the neck pipe is several times or tens of times even, reach the effect of low frequency sound absorption, small in structure and compact characteristics.
Description
Technical Field
The utility model relates to a noise control technical field specifically is a Helmholtz resonator who relates to an ultra-thin low frequency.
Background
A helmholtz resonator is a basic acoustic unit consisting of a closed resonance chamber and a connected neck. When sound waves are incident, the air in the neck tube can be regarded as a mass to vibrate integrally, and the air in the closed cavity undergoes expansion and contraction changes due to the vibration of the air in the neck tube, so that the Helmholtz resonator can be regarded as a spring-mass system with a damping term. When the incident frequency of the sound wave reaches the natural frequency of the system, the resonator resonates, and the sound absorption effect is good. Helmholtz resonator units are widely used in duct silencing systems and in architectural acoustic structures because of their simple structure.
In real life, the low-frequency noise has the characteristics of ultra-strong penetrating power and difficult absorption, and is a difficult problem of engineering technology. The traditional sound absorption material or structure is used, the thickness of the traditional sound absorption material or structure can be compared with the sound wave wavelength to achieve the sound absorption purpose, and for the low-frequency sound wave wavelength up to several meters, the traditional sound absorption material or structure cannot be controlled under the condition that a plurality of spaces are limited, such as the low-frequency noise of submarines and spacecrafts.
For the Helmholtz resonator unit, the sound absorption frequency depends on the volume of the closed cavity, the length of the neck pipe and the cross-sectional area of the neck pipe, and measures such as increasing the volume of the closed cavity, lengthening the length of the neck pipe, reducing the cross-sectional area of the neck pipe and the like can be taken to obtain low-frequency sound absorption. In general, it is difficult to freely change the volume of the resonant cavity in practical situations due to the limitation of the space used; while at the same time, changing the neck characteristics of the resonator is easier to handle and also enables the resonant frequency and resonant sound absorption coefficient to be changed simultaneously. Many researchers have worked to study the effect of neck characteristics on the sound absorption characteristics of helmholtz resonators, for example, Tang and Sirignano found that the sound absorption coefficient was greatest when the resonator neck length was comparable to the acoustic wavelength by varying the resonator neck length. Selamet and Lee investigated the extension of the neck of the resonator into the interior of the resonant cavity, and their conclusion indicates that the extension of the neck into the interior of the resonant cavity can reduce the resonant frequency of the resonator without increasing the volume of the resonant cavity. The shape of the neck has been studied by the scholars and it has been found that the cross-section of the neck is circular, square, oval or other shape and has little effect on the sound absorption of the resonator. However, in all the above studies, in order to realize low-frequency sound absorption, the length of the neck is increased along the incident direction of sound waves, so that the overall thickness of the helmholtz resonator is still large.
Disclosure of Invention
The purpose of the invention is as follows: the utility model aims to provide a Helmholtz resonator of ultra-thin low frequency to prior art's not enough, utilize the sound wave can propagate this characteristic freely in crooked air duct, adopt the folding technique in space, fold the neck of Helmholtz resonator along sound wave incident direction and be snakelike bend to under the unchangeable prerequisite of assurance Helmholtz resonator thickness, reach the purpose of low frequency sound absorption.
The technical scheme is as follows: helmholtz resonator of ultra-thin low frequency, including closed cavity and space beta structure, have a snakelike air passage in the space beta structure, this air passage's one end is as the sound wave incident port, the other end with closed cavity's inner chamber intercommunication, air passage with the neck pipe that Helmholtz resonator was enclosed into to space beta structure's inner wall.
The utility model discloses further preferred technical scheme does, and this helmholtz resonator's resonant frequency and operating bandwidth are confirmed through the number of times of buckling of neck pipe and air duct's cross sectional dimension.
Preferably, the closed cavity is regularly or irregularly shaped.
Preferably, the closed cavity is one of cylindrical, square, spherical or elliptical.
Preferably, the shape of the space folding structure is identical to the shape of the closed cavity.
Preferably, the cross-sectional shape of the air passage is one of circular, square, or oval.
Preferably, the closed cavity is provided with an opening, the shape of the opening is consistent with the cross-sectional shape of the air channel, and the air channel is communicated with the inner cavity of the closed cavity through the opening.
Preferably, the closed cavity and the spatial fold structure are made of metal, plastic, concrete or glass material.
Has the advantages that: the utility model discloses a Helmholtz resonator is an ultra-thin structure, by closed cavity and front end space folded structure constitution, through snakelike air duct's design, under the condition that does not increase Helmholtz resonator thickness, fold the neck pipe of Helmholtz resonator along the sound wave incident direction, compare in straight-line distance, the distance that the sound wave propagated in folding pipeline will increase several times or even tens of times, be equivalent to the length increase several times or even tens of times of neck pipe, reach the effect of low frequency sound absorption, have the characteristics that the structure is little and compact; furthermore, the utility model discloses in can be according to the frequency of falling the target of making an uproar, through the folding number of times of adjustment air channel to change the length of neck pipe, accomplish the absorption to the target noise, have with strong points, design nimble characteristics.
Drawings
FIG. 1 is an outline view of a Helmholtz resonator as described in the example;
FIG. 2 is a cross-sectional view of a Helmholtz resonator as described in the examples;
FIG. 3 is a dimension diagram of the Helmholtz resonator of the embodiment;
FIG. 4 shows the effect of different channel numbers on the acoustic frequencies in an embodiment;
in the figure, 1-Helmholtz resonator, 2-closed cavity, 3-space folded structure, A-air channel inlet, B-air channel outlet.
Detailed Description
The technical solution of the present invention is described in detail below with reference to the accompanying drawings, but the scope of the present invention is not limited to the embodiments.
Example (b): an ultra-thin low frequency Helmholtz resonator 1, which can be one of cylindrical, square column, spherical or elliptical in shape, or can be a special-shaped structure customized according to the requirement. In the present embodiment, a cylindrical shape is taken as an example. The closed cavity and the space folding structure are made of metal, plastic, concrete or glass materials.
Comprising a closed cavity 2 and a spatial fold structure 3. The space folding structure 3 has a serpentine air channel therein, and the cross-sectional shape of the air channel can be one of circular, square or oval, in this embodiment, the closed cavity 2 has an opening, and the shape of the opening is consistent with the cross-sectional shape of the air channel.
One end of the air channel is used as a sound wave incident port, the other end of the air channel is communicated with the inner cavity of the closed cavity 2 through the open hole of the closed cavity 2, and the air channel and the inner wall of the space folding structure 3 enclose a neck pipe of the Helmholtz resonator.
The resonance frequency and the operating bandwidth of the helmholtz resonator 1 are determined by the number of times the neck is bent and the cross-sectional dimensions of the air passage. As shown in FIG. 3, the thickness and width of the neck respectivelytAndadefinition ofnN =4 in this example for its number of channels, the straight-line distance of the sound wave propagating from the air channel inlet a to the air channel outlet B in free space istWhen the folding structure is introduced, the sound wave enters the structure from the air channel inlet A and then propagates along the folding air channel, and finally, the sound wave is discharged from the air channel outletBEmission, compared to straight-line distancetThe propagation distance is greatly extended, however, the thickness of the folded structure is stilltThe path of air propagation in the folded pipe is thus the length of the neckl eff . While changing the number of channels of the structurenLength of toothlThe equivalent path can be changed, and the length of the neck tube can be changedl eff . According to fig. 3, the specific calculation formula of the equivalent neck length is as follows:
therefore, the utility model relates to a helmholtz resonator 1's resonant frequency does:
in the formula:c 0 in order to be the speed of sound of the background medium,S 0 is the cross-sectional area of the neck tube opening at the closed cavity,wis the width of the neck tube,Vis the volume of the closed cavity.
In order to verify the utility model discloses an air channel's folding number has designed three kinds of helmholtz resonators 1 samples to sound absorption coefficient's influence in helmholtz resonator 1, and its thickness h keeps unchanged with the volume V of closed cavity 2, adopts 3D printing material to make:
the thickness of the helmholtz resonator 1,h=180 mm. Closed cavity2 outer diameter of 100mm, inner diameter of 80mm, cavity depthD=60mm, wall thicknessd=10mm, width of neck openingw=10mm, width of air passage of folding spacewLength of teeth =10mml=70mm。
For the sake of comparison, the thickness of the folded space of the Helmholtz resonator 1 remains unchanged, i.e. it ist=110 mm. When in usen=0、n=2、nIf =4, the length of the neck of the corresponding helmholtz resonator 1l eff =110mm，l eff =250mm，l eff =460mm, and the measured sound absorption coefficient is shown in fig. 4.
nThe sound absorption coefficient of a sample of =4 reaches a maximum of 0.955 at a frequency of 126Hz,nsample with an acoustic absorption coefficient of 0.92 at a frequency of 188Hz reaches a maximum value,nsample with =0 achieved a maximum sound absorption coefficient of 0.988 at a frequency of 256 Hz. Obviously, the number of channels in the folding space is increased, which is equivalent to the increase of the length of the neck tube, so that the resonance frequency of the Helmholtz resonator 1 is shifted to low frequency, the Helmholtz resonator has good sound absorption coefficient in a low frequency band, and the purpose of reducing noise in low frequency is achieved.
Most importantly, under the condition that 2 volumes V of closed cavity keep unchangeable, if make traditional Helmholtz resonator have the biggest sound absorption coefficient in 126Hz department, required thickness h =530mm, and the utility model discloses a Helmholtz resonator 1's thickness h =180mm, only is 1/3 times of traditional Helmholtz resonator, has thickness thin, sparingly the characteristics of usage space.
As mentioned above, although the present invention has been shown and described with reference to certain preferred embodiments, it should not be construed as limiting the invention itself. Various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (8)
1. The Helmholtz resonator is characterized by comprising a closed cavity and a space folding structure, wherein a snake-shaped air channel is arranged in the space folding structure, one end of the air channel is used as a sound wave incident port, the other end of the air channel is communicated with an inner cavity of the closed cavity, and a neck pipe of the Helmholtz resonator is surrounded by the air channel and the inner wall of the space folding structure.
2. Ultra thin low frequency Helmholtz resonator as claimed in claim 1, characterized in that the resonance frequency and the operating bandwidth of the Helmholtz resonator are determined by the number of bends of the neck and the cross-sectional dimensions of the air passage.
3. Ultra thin low frequency Helmholtz resonator according to claim 1, characterized in that the closed cavity is regular or irregular shaped.
4. An ultra-thin low frequency Helmholtz resonator as claimed in claim 3, wherein said enclosed cavity is one of cylindrical, square, spherical or elliptical.
5. Ultra thin low frequency Helmholtz resonator according to claim 3 or 4, characterized in that the shape of the spatial fold structure coincides with the shape of the closed cavity.
6. An ultra-thin low frequency Helmholtz resonator as claimed in claim 1, wherein the cross-sectional shape of said air passage is one of circular, square or oval.
7. An ultra-thin low frequency Helmholtz resonator as claimed in claim 6, wherein said enclosed cavity has an opening therein having a shape conforming to the cross-sectional shape of said air passageway, said air passageway communicating with the interior cavity of the enclosed cavity through the opening.
8. Ultra thin low frequency Helmholtz resonator according to claim 1, characterized in that the closed cavity and the spatial fold structure are made of metal, plastic, concrete or glass material.
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| CN201921521736.8U CN210627893U (en) | 2019-09-09 | 2019-09-09 | Helmholtz resonator of ultra-thin low frequency |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111739499A (en) * | 2020-06-01 | 2020-10-02 | 南京航空航天大学 | Underwater Helmholtz resonance cavity with rough inner insertion pipe |
| IT202100002015A1 (en) | 2021-02-01 | 2021-05-01 | Aprea Vincenzo | OPTIMIZED SOUND-INSULATION DEVICE |
| CN113192481A (en) * | 2021-04-29 | 2021-07-30 | 大连理工大学 | Coiled Helmholtz resonator for controlling low-frequency noise |
| CN113327568A (en) * | 2021-05-01 | 2021-08-31 | 西北工业大学 | Perforated plate structure and low-frequency broadband sound absorption device with variable-section bent cavity applying same |
| CN113362797A (en) * | 2021-05-10 | 2021-09-07 | 西安交通大学 | Coarse folding type sub-wavelength low-frequency sound absorption structure |
| CN113593510A (en) * | 2021-07-31 | 2021-11-02 | 吉林大学 | Composite sound absorption and noise reduction structure and preparation method thereof |
| CN115597088A (en) * | 2022-11-03 | 2023-01-13 | 中国科学院工程热物理研究所（Cn） | Combustion chamber structure and combustion regulation and control method |
-
2019
- 2019-09-09 CN CN201921521736.8U patent/CN210627893U/en not_active Expired - Fee Related
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111739499A (en) * | 2020-06-01 | 2020-10-02 | 南京航空航天大学 | Underwater Helmholtz resonance cavity with rough inner insertion pipe |
| CN111739499B (en) * | 2020-06-01 | 2023-09-29 | 南京航空航天大学 | Coarse interpolation type underwater Helmholtz resonance cavity |
| IT202100002015A1 (en) | 2021-02-01 | 2021-05-01 | Aprea Vincenzo | OPTIMIZED SOUND-INSULATION DEVICE |
| CN113192481A (en) * | 2021-04-29 | 2021-07-30 | 大连理工大学 | Coiled Helmholtz resonator for controlling low-frequency noise |
| CN113192481B (en) * | 2021-04-29 | 2023-11-24 | 大连理工大学 | Coiled Helmholtz resonator for low-frequency noise control |
| CN113327568A (en) * | 2021-05-01 | 2021-08-31 | 西北工业大学 | Perforated plate structure and low-frequency broadband sound absorption device with variable-section bent cavity applying same |
| CN113362797A (en) * | 2021-05-10 | 2021-09-07 | 西安交通大学 | Coarse folding type sub-wavelength low-frequency sound absorption structure |
| CN113593510A (en) * | 2021-07-31 | 2021-11-02 | 吉林大学 | Composite sound absorption and noise reduction structure and preparation method thereof |
| CN113593510B (en) * | 2021-07-31 | 2022-03-18 | 吉林大学 | Composite sound absorption and noise reduction structure and preparation method thereof |
| CN115597088A (en) * | 2022-11-03 | 2023-01-13 | 中国科学院工程热物理研究所（Cn） | Combustion chamber structure and combustion regulation and control method |
| CN115597088B (en) * | 2022-11-03 | 2024-03-19 | 中国科学院工程热物理研究所 | Combustion chamber structure and combustion regulation and control method |
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Effective date of registration: 20201118 Address after: No.28 Liming Road, Laian Economic Development Zone, Chuzhou, Anhui Province Patentee after: Chuzhou Monte tech Environmental Protection Technology Co.,Ltd. Address before: Nanjing City, Jiangsu province 210037 Longpan Road No. 159, Nanjing Forestry University Patentee before: NANJING FORESTRY University |
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Granted publication date: 20200526 Termination date: 20210909 |
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