CN109300464B - Design method of low-frequency sound absorber with gradually-changed cross section - Google Patents
Design method of low-frequency sound absorber with gradually-changed cross section Download PDFInfo
- Publication number
- CN109300464B CN109300464B CN201811340120.0A CN201811340120A CN109300464B CN 109300464 B CN109300464 B CN 109300464B CN 201811340120 A CN201811340120 A CN 201811340120A CN 109300464 B CN109300464 B CN 109300464B
- Authority
- CN
- China
- Prior art keywords
- sound
- frequency
- sound absorber
- sound absorption
- channel
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/172—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using resonance effects
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Acoustics & Sound (AREA)
- Multimedia (AREA)
- Building Environments (AREA)
Abstract
The invention discloses a design method of a low-frequency sound absorber with a gradually-changed cross section. Compared with the traditional uniform channel sound absorber, the sound absorber constructed by the method can reach lower sound absorption frequency under the same volume, and the sound absorption frequency can be changed without changing the shape. By installing a plurality of sound absorbers with different peak sound absorption frequencies in parallel, the invention can realize low-frequency broadband sound absorption under the sub-wavelength scale. In conclusion, the sound absorber constructed by the method has the characteristics of simple structure, low processing difficulty and easiness in installation and use.
Description
Technical Field
The invention belongs to the field of noise control and architectural acoustics, relates to a design method of a low-frequency sound absorber, and particularly relates to a method for strongly absorbing low-frequency sound waves by utilizing gradient structure resonance and air thermal adhesion effect.
Background
Noise has a great negative impact on humans and human productive life, and constant noise may affect the human auditory and nervous systems to varying degrees. For many years, many relevant noise reduction technologies have been developed, and in the passive technology field, there are traditional porous sound absorption materials and micro-perforated plates, but because of the weak acoustic energy loss at long wavelength, in order to attenuate the energy of low frequency sound wave (< 500 Hz), their thickness will reach the size corresponding to the wavelength, which limits the application range of such sound absorbers; in the field of active technology, a series of technologies represented by active noise control can effectively control low-frequency sound waves, but the principle of the technology is complex and the cost is high, and the technology has not been popularized all the time.
In recent years, materials with resonant properties have been found to be effective in achieving better low frequency sound absorption at sub-wavelength thicknesses, and this has been achieved by constructing a wide variety of resonant sound absorbers. For example, widely studied decorative film resonators [ Mei, j., et al, nat. Commun.3 (2): 756 ] composed of flexible films and additional small mass blocks, can achieve good sound absorption in the frequency band of 100Hz to 1000Hz, but are complicated in pre-stress addition during processing and adhesion of decorative quality, increasing the difficulty of practical production and manufacturing. Compared with the folded helmholtz resonator [ Cai, x., et al, applied Physics Letters,105 (12): 1901 ] and the folded Fabry-P rot sound absorber [ Zhang, c.and x.hu, and phys.rev.applied.6 (6) ] are simpler in structure and can be processed and manufactured only by a 3D printer, but the structures used in the prior art are uniform channels, so that the space cannot be effectively utilized, the sound absorption of lower frequency is realized, and the shape of the sound absorber is inevitably changed when the sound absorption frequency of the sound absorber is changed, which is a problem to be solved in practical installation and use.
Disclosure of Invention
The technical problem is as follows: the invention provides a design method of a low-frequency sound absorber with a gradually-changed cross section, which can realize low-frequency and broadband sound absorption in a simple mode.
The technical scheme is as follows: the invention relates to a method for designing a low-frequency sound absorber with a gradually-changed section, which comprises the following steps of:
firstly, determining the sound absorption frequency of a sound absorber by measuring the noise frequency f in the environment;
step two, designing a sound absorber with a gradually-changed section corresponding to the sound absorption frequency according to the noise frequency f measured in the step one, and specifically comprising the following steps:
(1) Determining the gradual change type to be adopted according to the actual processing precision and the sound absorption frequency range, and calculating the area ratio m and the length l of the tail end inlet of a group of gradual change section sound absorbers according to a formula obtained by a finite element method;
(2) Calculating the number of folds required in combination with the thickness W of the sound absorber to be designed
Here, the
Rounding up the result of l/W;
(3) Substituting the area ratio m and the folding number N into a channel size recurrence formula corresponding to the gradual change type, calculating to obtain a gradual change coefficient g, and further calculating the width w of each channel in the sound absorber i ；
(4) Wall thickness of the combined pseudo-designed sound absorberDetermining the length and height of the external shape of the sound absorber, wherein the length L = (N + 1) D + w 1 +w 2 +…+w N The height is determined according to the size of the actual installation position, wherein w 1 ,w 2 …w N Respectively refer to the width of the ith channel;
step three, calculating a sound absorption coefficient curve of the sound absorber with the gradually-changed section according with the geometric parameters determined in the step two by using a transmission matrix method, judging whether the sound absorption coefficient curve meets the actual use requirement, if so, entering the step four, otherwise, abandoning m and l and returning to the step two;
and step four, processing the sound absorber with the gradually-changed section according to the geometric parameters determined in the step two, evaluating the actual sound absorption performance of the sound absorber with the gradually-changed section by comparing the actual sound absorption performance with a theoretical value, finishing the design of the sound absorber if the actual sound absorption performance meets the requirement, and finely adjusting the channel width and the gradual-change coefficient to meet the requirement if the actual sound absorption performance does not meet the requirement.
Further, in the method of the present invention, the formula obtained by the finite element method in step (1) is:
in the formula: m = S 1 /S 2 Is the ratio of the area of the end of the sound absorber to the area of the inlet channel, c eq To account for the effect of thermal viscosity and equivalent sound velocity of air in a uniform cross-section tube of the same number of channels, f lin And f exp The sound absorption frequencies of the linear and exponential gradient channel sound absorbers, respectively.
Further, in the method of the present invention, the channel size recurrence formula in step (3) is determined according to the gradual change type, specifically:
for the linear channel gradual change type, the channel size recurrence formula is as follows:
g＝mw 1 /(N-1)
wherein w 1 Is the first of initial presettingA width of each channel;
for the exponential channel formula gradual change type, the channel size recurrence formula is:
g＝ln(m)/(N-1)。
further, in the method of the present invention, in the third step, the method for judging whether the sound absorption coefficient curve meets the actual use requirement includes: if the sound absorption coefficient at the frequency f is smaller than the expected sound absorption coefficient, the sound absorption coefficient is not met, otherwise, the sound absorption coefficient meets the actual use requirement.
Furthermore, in the method, the channel width and the gradient coefficient are finely adjusted in the fourth step, namely the initial channel width is increased or decreased by taking 1/100 of the wavelength corresponding to the sound absorption frequency as a step length, and then the sound absorber is processed according to other channel widths calculated by the recursion relation.
Further, in the method of the present invention, when there are a plurality of noise frequencies in the environment measured in the step one, the sound absorption frequency of the sound absorber is determined for each frequency noise, the sound absorber is designed according to the flow of the step two to the step four, and the obtained plurality of sound absorbers are assembled in parallel into one body.
Furthermore, in the method of the present invention, the actual sound absorption performance of the sound absorber with gradually changed cross section is evaluated by comparing the peak sound absorption frequency actual value with the theoretical value in the fourth step, if the error is less than 5% compared with the theoretical value, the requirement is met, otherwise, the requirement is not met; here, the error is a relative error, i.e., (actual frequency-theoretical frequency)/theoretical frequency ".
Or comparing the actual value of the peak sound absorption coefficient with the theoretical value, if the error is less than 5 percent compared with the theoretical value, the requirement is met, otherwise, the requirement is not met. Here, the error is an absolute error, i.e., "actual coefficient — theoretical coefficient".
The sectional structure of one of the sound absorbers with gradually changed sections designed by the design method is shown in fig. 2 a. The structure is composed of a plurality of folding channels, and the cross-sectional dimension of each channel is different. In the case where the outer shape is not changed and the number of folds (i.e., the number of channels) N is constant, the inner structure of the structure may be formed by the thickness D and the equivalent length l of each channel i Width w i And (6) determining. Here the retaining wallThickness is constant by varying the initial channel width w 1 And the channel gradual change coefficient g is subjected to structural design, and the widths of the rest channels can pass through w 1 A recursive relationship with g is obtained. E.g. for the ith channel, w i ＝w 1 + g (i-1) and w i ＝w 1 e g(i-1) Corresponding to the widths of the linearly graded and exponentially graded channels, respectively. Fig. 2b is a schematic view of the external shape of the absorber, the dimensions of which can be determined by the external height H, the length L and the width W.
The designed structure is subjected to space uncoiling, and an equivalent coaxial straight channel structure equivalent to the designed structure can be obtained, as shown in fig. 2 c. The sound absorption properties of the structure in fig. 2a can therefore also be modelled on the basis of the transmission matrix method. The theoretical model is composed of two parts, namely impedance calculation from the channel tail end to the channel inlet and radiation correction from the channel inlet to the external space. For the first part, the sound pressure and volume velocity at the inlet of the initial channel are set to p E And U E The final sound pressure and volume velocity of the last channel are p F And U F . According to the transmission matrix theory, the following relationship can be obtained:
in the formula (1)
Is the transmission matrix of the ith channel and can be written as
Here, the
k i ＝ω(ρ i /C i ) 1/2 、l i Respectively, the characteristic impedance, equivalent wave number and equivalent propagation distance of the ith channel. Rho i And C i Is taking into accountThe equivalent density and compression function of the pipe due to thermal viscosity are respectively expressed as
Wherein alpha is k ＝(2k+1)π/w i And beta n = (= (2n + 1) pi/H) independent of frequency, the value of which is given by the channel dimension w i And H and expansion coefficients n and k. P 0 And γ is the air pressure and the ideal gas specific heat ratio. Wherein ν = μ/ρ 0 ，ν’＝κ/ρ 0 C v μ, κ and C v Respectively air viscosity, heat conduction and equivalent volumetric heat capacity.
When the reflected sound wave is radiated from the slit at the entrance of the structure to free space, there is a radiation end modification corresponding to a transmission matrix of
For a periodic arrangement of slits, the radiation end correction length can be expressed as
Wherein ψ = w 1 and/L is the perforation rate of the sound absorber.
Let the sound pressure on the surface of the sound absorber be p S And U S Since the velocity of the rigid wall at the end is zero, the united type (1) can be obtained
So that the surface acoustic impedance at the entrance of the structure is
The reflection coefficient r and the sound absorption coefficient alpha of the sound absorber can be calculated by the following two formulas
α＝1-|r 2 |, (10)
Wherein Z 0 Is the surface air characteristic impedance.
To achieve ease of design, the present study considered linear and exponential gradient absorbers as discretized approximations of the slowly varying section tubes shown in the upper and lower graphs of fig. 3, respectively, and analyzed the relationship between the resonant frequency and the geometric parameters of these two types of slowly varying section tubes using the two-endpoint finite element method. In the coordinate system shown in fig. 3, assuming that the acoustic wave propagating in the tube is only a plane wave in the x direction, the end points 1 and 2 are located at x =0 and x = L, respectively eq Then the sound pressure at different positions in this two-endpoint finite element can be expressed as
Wherein p is 1 And p 2 Sound pressure, L, at endpoint 1 and endpoint 2, respectively eq The equivalent length of the sound absorber channel after the pipe end correction is considered. The sound pressure at the end point 2 is equal to zero due to the inverse superposition of the incident wave and the reflected wave in the slowly-variable cross-section tube during resonance, and the kinetic energy and the potential energy of the finite element are equal at the moment, so that the following formula can be obtained
Where S (x) is the cross-sectional area of the tube of gradual change cross-section, k reso Is the wave number of the sound wave at resonance. By combining the formula (11) and the formula (12), the resonance frequency of the gradually-varied section tube can be solved, and the corresponding gradual variation can be predictedPeak sound absorption frequency of the cross-sectional sound absorber. For the linear and exponentially tapered tubes discussed above, the resonant frequencies are shown below
In the above formula, m = S 1 /S 2 Is the ratio of the area of the end of the absorber to the area of the inlet passageway. Considering that the formula (12) only accounts for the kinetic energy and the potential energy of the sound wave in the slowly-varying cross-section tube and does not consider the heat energy loss caused by thermal viscosity, the invention takes the sound velocity in the formula (13) and the formula (14) as the equivalent sound velocity c of the air in the uniform cross-section tube which takes the thermal viscosity effect into consideration and has the same number of channels eq 。
Compared with the traditional uniform-section sound absorber, the sound absorber with the gradually-changed section can achieve lower sound absorption frequency under the condition of the same shape. The structure shown in fig. 2a-2b is only one of the sound absorber structures that the present invention can achieve, and the actual structure is not limited thereto. There may also be forms of three-dimensional channel sound absorbers (three-dimensional tapered section tube composition) and coplanar channel sound absorbers (tapered section tubes wound in a coplanar manner), and the like. Therefore, if the person skilled in the art receives the teaching, without departing from the spirit of the invention, the person skilled in the art shall not inventively design the similar structural modes and embodiments to the technical solution, but shall fall within the scope of the invention.
Has the beneficial effects that: compared with the prior art, the invention has the following remarkable advantages:
(1) The existing theoretical research shows that the perfect absorption of low-frequency sound waves can be realized at the sub-wavelength or deep sub-wavelength scale by adopting the resonance structure with additional loss. Based on the theory, researchers construct resonators with various sub-wavelength dimensions, mainly including a decorative film resonator, a folded Helmholtz resonator, and a folded Fabry-Perot resonator. The attachment of prestress and the adhesion of decorative quality of the decorative film in the processing process are complex, which increases the difficulty of actual manufacturing; the folded type resonator essentially provides the acoustic impedance required for resonance through the folded channels, which can be conveniently produced by 3D printing technology, but the folded channels used at present are all uniform channels, which is not favorable for realizing acoustic absorption of lower frequencies in a limited space. The design method of the sound absorber with the gradually-changed section has the characteristics of convenience in processing and manufacturing as the folding sound absorber, and can absorb sound waves with lower frequency in a limited space by using the characteristic of faster impedance transmission of the channel with the gradually-changed section;
(2) The existing folding type resonance sound absorber has constant channel section, and the shape of the sound absorber is inevitably changed when the sound absorption frequency of the resonance body needs to be greatly changed. The sound absorber with the gradually-changed section can adjust the sound absorption frequency of the sound absorber within a very wide frequency range (about 200 Hz) by changing the gradually-changed type of the gradually-changed section, and meanwhile, the sound absorption coefficients are all more than 90 percent, so that the convenience in actual installation and use is improved;
(3) Because the sound absorbers designed by the method have the same shape, a plurality of sound absorbers with different resonant frequencies can be installed in parallel to realize broadband sound absorption under the condition of broadband noise.
Drawings
FIG. 1 is a flow chart of the design of the sound absorber of the present invention of the progressive cross-section system;
FIG. 2a is a schematic three-dimensional structure of a graduated-section sound absorber of the present invention;
FIG. 2b is a schematic structural view of the XY interface of the present invention;
FIG. 2c is an equivalent structure after the present invention is disassembled;
FIG. 3 is a corresponding continuous gradual change section tube of the present invention;
FIG. 4 shows theoretical values and measured values of the sound absorption coefficient versus frequency curves of three sound absorber samples according to example 1 of the present invention;
FIG. 5a is a schematic cross-sectional view of two sound absorbers according to example 2 of the present invention;
fig. 5b is a graph of sound absorption coefficient versus frequency for two sound absorbers in example 2 of the present invention after coupling.
Detailed Description
For a further understanding of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings and examples.
Example 1
In order to compare the advantages of the sound absorbers with the gradient cross sections, the present embodiment designs three sound absorbers (exponential, linear and uniform) with different gradient types according to the design flow shown in fig. 1, and compares the sound absorption performance of the sound absorbers with the three different gradient types. The method comprises the following specific steps:
step one, determining sound absorption frequency. Since the present embodiment aims to compare the advantages of the graduated-section sound absorbers, the sound absorber profile is set in advance to be L × W × H =60mm × 20mm × 50mm, and the graduated-section sound absorber which can achieve the lowest sound absorption frequency with the same sound absorption coefficient (more than 99%) for each type of graduation is designed under the condition of the profile.
And step two, determining the gradual change type according to the processing precision and the frequency range to be absorbed. Specifically, in terms of sound absorption frequency, the exponential type gradual change is lower than the lowest sound absorption frequency of the linear channel at the beginning, but the initial width of the exponential type gradual change is narrower than the initial channel width of the linear channel, so that the exponential channel can reach lower frequency if the processing precision is high. However, if the adjustable sound absorption range of the linear gradient channel is wider than that of the exponential gradient channel in terms of the adjustable sound absorption frequency range, the linear gradient channel is more beneficial to multi-frequency sound absorption. Therefore, the two factors need to be considered together for selection, if the design aim is to use as small a volume as possible to absorb low-frequency single-frequency or low-frequency narrow-band noise, the exponential gradient sound absorber is recommended, and if the design aim is to absorb low-frequency multi-frequency or low-frequency wide-band noise as much as possible, the linear gradient sound absorber is recommended. This example aims to compare the advantages of the graduated-section sound absorber, and therefore determines the geometric parameters of the three graduated-section sound absorbers required to reach the frequency in step one, using the finite element method (equations (7) and (8));
and step three, judging whether the obtained parameters meet the design requirements or not by using the formula (1-6). In the embodiment, three sound absorbers A, B and C listed in table 1 are obtained by repeating the step two and the step three, and the three sound absorbers are respectively an exponential gradient sound absorber, a linear gradient sound absorber and a traditional uniform cross section sound absorber, and specific parameters are shown in table 1.
TABLE 1 geometric parameters of three experimental samples
And step four, processing the corresponding sound absorber according to the obtained structural parameters, and evaluating the actual sound absorption performance by comparing with a theoretical value.
Samples A, B and C correspond to the exponential gradient sound absorber, the linear gradient sound absorber and the uniform channel sound absorber, respectively, which are white Polylactide (PLA) sound absorber samples manufactured by 3D printing process with a processing precision of ± 0.1mm.
Figure 4 compares the sound absorption coefficient of three samples in combination with theoretical and experimental results. The absorption peaks of the three samples are respectively found at 315Hz, 325Hz and 365Hz, and the peak sound absorption coefficients are 95.0%,91.7% and 94.1%; the measured Q values are 0.159,0.154 and 0.144, respectively, which agree well with theoretical predictions (0.153,0.147 and 0.139). Slight deviations between experimental and theoretical results may be caused by processing errors. Compared with the common uniform channel sound absorber, the sound absorber with the gradually-changed section can effectively utilize space to shift the absorption peak down by 40-50Hz under the condition of not changing the appearance. The thickness W of each sample was only about 1/55 of the wavelength, meaning that the absorber had a depth sub-wavelength scale.
The present invention and its embodiments have been described above schematically, and the description is not intended to be limiting, and what is shown in the drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto. This example shows only the implementation of the sound absorber with two kinds of exponential and linear gradient sections, and any other section variation type conforming to some functional relationship can be used to design such sound absorber. Therefore, if the person skilled in the relevant art receives the teaching, the similar structural modes and embodiments to those of the technical solution should be designed without creativity without departing from the spirit of the invention, and the invention shall fall into the protection scope of the invention.
Example 2
In different acoustic environments, the noise frequencies are not identical. Therefore, the sound absorber with fixed appearance and different peak sound absorption frequencies has high practical value in installation and application. Under the application scene of broadband noise, a single narrow-band sound absorber cannot achieve an ideal sound absorption effect, and the sound absorption bandwidth can be further expanded by installing two or more sound absorbers which are fixed in appearance and different in peak sound absorption frequency side by side.
In the embodiment, two sound absorbers with gradually changed sections, which have different peak sound absorption frequencies but the same appearance, are designed by using the steps shown in fig. 1, and specific parameters are shown in table 2. Fig. 5a is a schematic cross-sectional view of two sound absorbers installed in parallel, and fig. 5b shows the variation relationship between the absorption coefficient and the frequency when the two sound absorbers are used independently and installed in parallel. The dotted line in the figure is a sound absorption coefficient curve when the sound absorbers are used alone, and the solid line is a sound absorption coefficient curve when the sound absorbers are installed side by side. The calculations show that the peak absorption frequencies of the absorbers when used alone are 273Hz and 314Hz, respectively, with bandwidths of 15.1% and 13.7%. After the two sound absorbers are installed side by side, the 50% sound absorption bandwidth of the coupled sound absorber can reach 30.1%, and the bandwidth with the sound absorption coefficient larger than 0.8 is 20.4%. The thickness W =25mm of the acoustic absorber combination is still on the deep sub-wavelength scale. It is contemplated that the bandwidth of the coupled sound absorbers may be further expanded when a plurality of sound absorbers are installed in parallel. This provides the possibility of its application in practical noise reduction engineering.
TABLE 2 Acoustic absorber parameters
Claims (6)
1. A method for designing a low-frequency sound absorber with a gradually-changed cross section is characterized by comprising the following steps:
firstly, determining the sound absorption frequency of a sound absorber by measuring the noise frequency f in the environment;
step two, designing a gradually-changed section sound absorber corresponding to the sound absorption frequency according to the noise frequency f measured in the step one, and specifically comprising the following steps:
(1) Determining the gradual change type to be adopted according to the actual processing precision and the sound absorption frequency range, and calculating the area ratio m and the length l of the tail end inlet of a group of gradual change section sound absorbers according to a formula obtained by a finite element method; the formula obtained by the finite element method in the step (1) is as follows:
in the formula: m = S 1 /S 2 Is the ratio of the area of the end of the sound absorber to the area of the inlet channel, c eq To account for the effect of thermal viscosity and equivalent sound velocity of air in a uniform cross-section tube of the same number of channels, f lin And f exp Sound absorption frequency, L, of the linear and exponential gradient channel sound absorbers, respectively eq The equivalent length of the sound absorber channel after the pipe end correction is considered;
(2) Calculating the number of folds required in combination with the thickness W of the sound absorber to be designed
Here, the
Rounding up the result of l/W;
(3) Substituting the area ratio m and the folding number N into a channel size recurrence formula corresponding to the gradual change type, calculating to obtain a gradual change coefficient g, and further calculating the width w of each channel in the sound absorber i ；
(4) Determining the length and height of the sound absorber in combination with the wall thickness D of the sound absorber to be designed, wherein the length L = (N + 1) D + w 1 +w 2 +…+w N Height according to realityThe size of the actual mounting position, w 1 ,w 2 …w N Respectively refer to the width of the ith channel;
step three, calculating a sound absorption coefficient curve of the sound absorber with the gradually-changed section according with the geometric parameters determined in the step two by using a transmission matrix method, judging whether the sound absorption coefficient curve meets the actual use requirement, if so, entering the step four, otherwise, abandoning m and l and returning to the step two;
and step four, processing the sound absorber with the gradually-changing section according to the geometric parameters determined in the step two, comparing the actual sound absorption performance of the sound absorber with a theoretical value, finishing the design of the sound absorber if the actual sound absorption performance meets the requirement, and finely adjusting the width of the channel and the gradual-changing coefficient to meet the requirement if the actual sound absorption performance does not meet the requirement.
2. The method for designing a low-frequency sound absorber with a gradually-changed section as claimed in claim 1, wherein the channel size recurrence formula in the step (3) is determined according to a gradual change type, and specifically comprises:
for the linear channel gradual change type, the channel size recurrence formula is as follows:
g＝mw 1 /(N-1)
wherein w 1 A first channel width which is initially preset;
for the exponential channel formula gradual change type, the channel size recurrence formula is:
g＝ln(m)/(N-1)。
3. the method for designing a low-frequency sound absorber with a gradually-changing section as claimed in claim 1 or 2, wherein in the third step, the method for judging whether the sound absorption coefficient curve meets the actual use requirement comprises the following steps: if the sound absorption coefficient at the frequency f is smaller than the expected sound absorption coefficient, the sound absorption coefficient is not met, otherwise, the sound absorption coefficient meets the actual use requirement.
4. The method for designing a low-frequency sound absorber with a gradually-changed cross section as claimed in claim 1 or 2, wherein the fine adjustment of the channel width and the gradual-change coefficient in the fourth step is to increase or decrease the initial channel width by taking 1/100 of the wavelength corresponding to the sound absorption frequency as a step length, and then process the sound absorber according to other channel widths calculated by a recursion relationship.
5. The method for designing a low-frequency sound absorber with a gradually-changed cross section as claimed in claim 1 or 2, wherein when the noise frequency in the environment measured in the first step is multiple, the sound absorption frequency of the sound absorber is determined for each frequency noise, the sound absorber is designed according to the flow from the second step to the fourth step, and the multiple sound absorbers are assembled in parallel into a whole.
6. The method for designing a low-frequency sound absorber with a gradually-changing section according to claim 1 or 2, wherein the step four is to compare the theoretical value with the actual value of the sound absorption performance of the sound absorber with the gradually-changing section, and the actual value of the peak sound absorption frequency is compared with the theoretical value, if the error is less than 5% compared with the theoretical value, the requirement is met, otherwise, the requirement is not met;
or comparing the actual value of the peak sound absorption coefficient with the theoretical value, if the error is less than 5% compared with the theoretical value, the requirement is met, otherwise, the requirement is not met.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811340120.0A CN109300464B (en) | 2018-11-12 | 2018-11-12 | Design method of low-frequency sound absorber with gradually-changed cross section |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811340120.0A CN109300464B (en) | 2018-11-12 | 2018-11-12 | Design method of low-frequency sound absorber with gradually-changed cross section |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN109300464A CN109300464A (en) | 2019-02-01 |
| CN109300464B true CN109300464B (en) | 2022-12-09 |
Family
ID=65146534
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201811340120.0A Active CN109300464B (en) | 2018-11-12 | 2018-11-12 | Design method of low-frequency sound absorber with gradually-changed cross section |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN109300464B (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110503936B (en) * | 2019-08-13 | 2021-10-12 | 安徽建筑大学 | Adjustable sub-wavelength low frequency sound absorption structure |
| CN111145715B (en) * | 2019-12-27 | 2020-08-25 | 汉得利（常州）电子股份有限公司 | Active noise control system and control method for fan |
| CN112185327A (en) * | 2020-09-16 | 2021-01-05 | 西安交通大学 | Micro-seam low-frequency sound absorption unit and nested broadband sound absorption structure with same |
| CN112344544A (en) * | 2020-10-30 | 2021-02-09 | 南京大学 | Natural ventilation sound insulation structure applied to transformer noise control |
| CN112347594A (en) * | 2020-10-30 | 2021-02-09 | 南京大学 | Broadband noise reduction structure applied to natural ventilation sound insulation window and design method thereof |
| CN113077777A (en) * | 2021-03-19 | 2021-07-06 | 南京大学 | Ultra-thin low frequency ventilation acoustics sound absorption unit and sound absorber |
| EP4315315A1 (en) * | 2021-03-29 | 2024-02-07 | BAE SYSTEMS plc | Acoustic absorbing structures |
| EP4068276A1 (en) * | 2021-03-29 | 2022-10-05 | BAE SYSTEMS plc | Acoustic absorbing structures |
| 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 |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4243117A (en) * | 1978-10-27 | 1981-01-06 | Lord Corporation | Sound absorbing structure |
| CN101139822A (en) * | 2007-08-09 | 2008-03-12 | 同济大学 | Gradual-change cavity microperforated broad band sound absorption type sound barrier |
| CN101194077A (en) * | 2005-06-14 | 2008-06-04 | 金永玉 | The sound-absorbing panel |
| CN105427853A (en) * | 2015-10-30 | 2016-03-23 | 东南大学 | Broadband micro-perforated board sound absorber, absorber performance prediction method and absorber structure design method |
| CN107408378A (en) * | 2015-02-27 | 2017-11-28 | 富士胶片株式会社 | The manufacture method of noise reduction structure and noise reduction structure |
| CN108615521A (en) * | 2018-04-12 | 2018-10-02 | 湖南大学 | A kind of sound topological insulator |
-
2018
- 2018-11-12 CN CN201811340120.0A patent/CN109300464B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4243117A (en) * | 1978-10-27 | 1981-01-06 | Lord Corporation | Sound absorbing structure |
| CN101194077A (en) * | 2005-06-14 | 2008-06-04 | 金永玉 | The sound-absorbing panel |
| CN101139822A (en) * | 2007-08-09 | 2008-03-12 | 同济大学 | Gradual-change cavity microperforated broad band sound absorption type sound barrier |
| CN107408378A (en) * | 2015-02-27 | 2017-11-28 | 富士胶片株式会社 | The manufacture method of noise reduction structure and noise reduction structure |
| CN105427853A (en) * | 2015-10-30 | 2016-03-23 | 东南大学 | Broadband micro-perforated board sound absorber, absorber performance prediction method and absorber structure design method |
| CN108615521A (en) * | 2018-04-12 | 2018-10-02 | 湖南大学 | A kind of sound topological insulator |
Also Published As
| Publication number | Publication date |
|---|---|
| CN109300464A (en) | 2019-02-01 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN109300464B (en) | Design method of low-frequency sound absorber with gradually-changed cross section | |
| WO2021082706A1 (en) | Helmholtz resonator, and low-frequency broadband sound-absorbing and noise-reducing structure based on same | |
| EP3706114B1 (en) | Low-frequency coupling sound absorbing structure | |
| WO2018047153A1 (en) | Acoustic metamaterial sound absorber | |
| CN110503936B (en) | Adjustable sub-wavelength low frequency sound absorption structure | |
| Li et al. | An acoustic impedance structure consisting of perforated panel resonator and porous material for low-to-mid frequency sound absorption | |
| JP2010087174A (en) | Silencer for electronic equipment | |
| CN113035166A (en) | Ventilating sound-absorbing metamaterial | |
| CN113793586A (en) | Low-frequency ultra-wideband acoustic black hole acoustic material structure | |
| Herrin et al. | A guide to the application of microperforated panel absorbers | |
| CN114446271A (en) | Sub-wavelength multi-slit sound absorption superstructure with broadband sound absorption performance | |
| CN117316136A (en) | Sound absorber based on microperforated film and Helmholtz multi-cavity coupling structure | |
| JP6914004B2 (en) | Noise reduction device | |
| KR101643689B1 (en) | Method for manufacturing acoustic absorbent and acoustic absorbing structure having the same | |
| CN107563065B (en) | Design method and structure of broadband sound absorption structure of medium-low frequency cavity tube | |
| KR101330462B1 (en) | Pair glass having wide band width noise reduction effect | |
| CN107610688A (en) | A kind of compound sound insulating structure of lumen | |
| Setaki et al. | New sound absorption materials: using additive manufacturing for compact size, broadband sound absorption at low frequencies | |
| Mizukoshi et al. | A tunable open planar acoustic notch filter utilizing a pneumatically modulated Helmholtz resonator array | |
| CN212874037U (en) | Double-layer honeycomb-micro-perforated structure with adjustable back cavity height | |
| CN207397275U (en) | Middle low frequency lumen broad band sound absorption structure | |
| CN113123261A (en) | Bionic sound absorption structure based on conch cavity structure and sound absorption unit plate thereof | |
| CN111816151A (en) | Double-layer honeycomb-micro-perforated structure with adjustable back cavity height and design method thereof | |
| CN113192481A (en) | Coiled Helmholtz resonator for controlling low-frequency noise | |
| Mosa et al. | Micro-perforated panel absorber arrangement technique: A review |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |