CN110517659B - Multi-unit coupling type micro-perforated plate low-frequency broadband sound absorption structure and design method thereof - Google Patents
Multi-unit coupling type micro-perforated plate low-frequency broadband sound absorption structure and design method thereof Download PDFInfo
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- G—PHYSICS
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- 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
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- 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
- G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
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Abstract
The invention relates to a multi-unit coupling type micro-perforated plate low-frequency broadband sound absorption structure and a design method thereof, wherein the structure comprises a plurality of sound absorption units which are continuously arranged in parallel, and each sound absorption unit comprises a micro-perforated plate and a back cavity; the front end of the back cavity is provided with an opening, a micro-perforated plate is arranged, and the rear end of the back cavity is sealed to form a cavity; the micro-perforated plates of all the sound absorption units are arranged in a coplanar manner, the first-order peak values of all the sound absorption units and at least one high-order peak value of at least one sound absorption unit are uniformly and continuously distributed, and a continuous multi-peak sound absorption broadband is formed in a medium-low frequency range. By arranging a plurality of different sound absorption units, a plurality of peak value bandwidths are formed, and simultaneously, high-order peak values of partial sound absorption units are added for continuous sound absorption, so that sound absorption peak values with different frequencies are obtained; and through space folding, under the prerequisite that does not increase structure thickness, utilize a plurality of peak values that each unit can provide, the peak value bandwidth is wider, in limited size range, realizes expanding and the combination of bandwidth.
Description
Technical Field
The invention relates to the field of low-frequency vibration and noise reduction, in particular to a multi-unit coupling type micro-perforated plate low-frequency broadband sound absorption structure and a design method thereof.
Background
Noise pollution is one of four pollution sources in the world at present, great harm is caused to human health, the quality of daily life of people is seriously influenced, and the harm caused by low-frequency noise (200 Hz-1500 Hz) is the largest. The traditional sound absorption materials (such as micro-perforated plates, porous materials and the like) have low dissipation efficiency on low-frequency sound waves, and the traditional sound absorption materials cannot be applied to engineering because the traditional sound absorption materials are large in structural thickness (more than 20 cm) to completely absorb the low-frequency sound waves. Therefore, it is important to design a sound absorption structure with a small size (less than 10 cm) to effectively absorb low-frequency sound waves.
In recent years, rapid development of acoustic metamaterials has provided a new approach to solving the problem of low-frequency noise, and spatial folded metamaterials have attracted attention of researchers by virtue of excellent low-frequency characteristics. The space folding type metamaterial is a resonance type metamaterial, and is characterized in that a partition plate and the like are added in a back cavity of the metamaterial, so that a propagation path is bent and folded, the sectional area of the propagation path is reduced, the path length of the propagation path is increased, the equivalent spring stiffness of the back cavity is reduced, and finally, a sound absorption peak value can be moved to a low frequency greatly under the condition of ensuring the volume of the back cavity of the structure. However, due to the limitation of resonance characteristics, the peak bandwidth is narrow, and the requirement of broadband sound absorption cannot be met. At present, the most effective method for realizing broadband sound absorption is to introduce a plurality of sound absorption units, and then obtain a continuous sound absorption broadband consisting of a plurality of peak values. However, the number of units is limited by the average impedance of the structure, and can only be taken within a certain range, the number of peaks and the sound absorption bandwidth are also limited, and the problem of low-frequency broadband sound absorption within a limited size range still cannot be well solved.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a multi-unit coupling type micro-perforated plate low-frequency broadband sound absorption structure and a design method thereof, wherein the structure is compact, the design is reasonable, the sound absorption bandwidth is large, the broadband is continuous, and the sound absorption requirement is met.
The invention is realized by the following technical scheme:
a multi-unit coupling type micro-perforated plate low-frequency broadband sound absorption structure comprises a plurality of sound absorption units which are continuously arranged in parallel, wherein each sound absorption unit comprises a micro-perforated plate and a back cavity;
the front end of the back cavity is provided with an opening, a micro-perforated plate is arranged, and the rear end of the back cavity is sealed to form a cavity;
the micro-perforated plates of all the sound absorption units are arranged in a coplanar manner, the first-order peak values of all the sound absorption units and at least one high-order peak value of at least one sound absorption unit are uniformly and continuously distributed, and a continuous multi-peak sound absorption broadband is formed in a medium-low frequency range.
Preferably, the back cavity of the sound absorption unit with larger thickness in the adjacent sound absorption units is folded in space, and the rear end of the sound absorption unit is bent and extends to the lower part of the sound absorption unit with smaller thickness.
Preferably, the perforations on the microperforated panel are uniformly distributed.
Furthermore, the shape of the perforation of the micro-perforated plate is circular, square, triangular or oval, the diameter of the perforation is 0.5 mm-1 mm, the perforation rate of the perforation is 1% -15%, and the thickness of the micro-perforated plate 10 is 0.5 mm-2 mm; when the perforations are non-circular, the diameter refers to the diameter of the circumscribed circle of the perforation.
Preferably, 4-12 sound absorption units are arranged in parallel in succession.
Preferably, the cross section of the back cavity is a multi-deformation, round or irregular closed curve, and the cross section area of the back cavity of the sound absorption unit is 100mm2～1×104mm2。
Preferably, the sound absorption structure also comprises a structural frame formed by intersecting unit partition plates and used for isolating each sound absorption unit; the structural frame is provided with a closed shell, and one end of the shell, corresponding to the micro-perforated plate, is provided with openings in one-to-one correspondence with the micro-perforated plate.
Preferably, the structural frame and the micro-perforated plate are made of metal, rigid plastic and resin and are manufactured by 3D printing or die processing.
A design method of the multi-unit coupling type micro-perforated plate low-frequency broadband sound absorption structure comprises the following steps,
each sound absorption unit of the sound absorption structure is equivalent to a mass spring system, wherein equivalent mass is derived from the mass of air in a perforation hole of the micro-perforated plate, equivalent damping is derived from the damping effect of a perforation wall, and the equivalent spring stiffness is the air stiffness in the back cavity; obtaining sound absorption peak values of different frequencies by adjusting the structural parameters of different sound absorption units; the structural parameters comprise parameters of the micro-perforated plate and parameters of the back cavity; parameters of the microperforated panel include the diameter, depth of the perforations and the rate of perforations on the microperforated panel; the parameters of the back cavity comprise back cavity volume determined by two parameters of cross section area and depth;
according to all sound absorption peaks of the m sound absorption units in a target frequency band (f)A～fB) The requirement of continuous and uniform distribution is required to obtain the peak value n ═ (f)A-fB) Δ B, where Δ B is the peak bandwidth;
first, the structural parameters of a sound-absorbing unit are determined such that its first-order peak frequency is fAAnd corresponding high-order peak value frequency in the target frequency band, then designing other units, and obtaining the number m of the sound absorption units as n-s according to the number s of all high-order peak values in the target frequency band;
secondly, under the condition of keeping the sectional areas of the units the same, the back cavity depth of the sound absorption unit i is obtained in turn as follows,
wherein, the value range of i is 1 to m, s' is the number of high-order peak values provided by the existing unit, and the range is 0 to s, l1Is the back cavity thickness of the first sound-absorbing unit, /)iThe thickness of a back cavity of the ith sound absorption unit; the high-order peaks are in turn provided by the determined sound absorption unit.
Step 4, spatial folding arrangement of the absorption units;
and continuously arranging the determined absorption units in parallel, folding the back cavity of the sound absorption unit with larger thickness in the adjacent sound absorption units in space within the design thickness of the sound absorption structure, and bending and extending the rear end of the sound absorption unit to the lower part of the sound absorption unit with smaller thickness.
Preferably, the first-order peak frequency of the sound absorption unit is related to the perforation size and the back cavity size of the micro-perforated plate, and the smaller the perforation diameter, the larger the equivalent mass of the micro-perforated plate, and the lower the peak frequency; the greater the perforation depth, i.e. the greater the thickness of the microperforated plate, the lower the peak frequency; the smaller the perforation rate of the perforation, the lower the peak frequency; the larger the cavity volume is, the smaller the equivalent rigidity is, and the sound absorption peak value moves to low frequency;
the peak bandwidth of the sound absorption unit is mainly related to the size of the perforation and the number m of the sound absorption units, the smaller the diameter of the perforation is, the more obvious the damping effect is, and the wider the peak bandwidth is; the larger the perforation depth, the wider the peak bandwidth; the larger the number of sound absorption units, the smaller the peak bandwidth gradually decreases.
Compared with the prior art, the invention has the following beneficial technical effects:
according to the sound absorption structure provided by the invention, a plurality of different sound absorption units are arranged, a plurality of peak value bandwidths are formed, meanwhile, high-order peak values of part of the sound absorption units are added for continuous sound absorption, sound absorption peak values with different frequencies are obtained, and finally, a continuous sound absorption frequency band is realized; and through space folding, under the prerequisite that does not increase structure thickness, utilize a plurality of peak values that each unit can provide, the peak value bandwidth is wider, further increases the structure sound absorption bandwidth to in limited size range, realize the expansion and the combination to the bandwidth, be significant to the engineering application of structure.
Drawings
Fig. 1 is a schematic structural view of a sound absorbing structure according to example 1 of the present invention.
Fig. 2 is a schematic front side view of the internal structure of the sound absorbing structure according to example 1 of the present invention.
Fig. 3 is a schematic backside view of the internal structure of the sound absorbing structure according to example 1 of the present invention.
Fig. 4 is a negative Y-axis sectional view of the internal structure of the sound absorbing structure according to example 1 of the present invention.
Fig. 5 is an experimental test sound absorption coefficient of the sound absorbing structure according to example 1 of the present invention.
Fig. 6 is a schematic view showing the internal structure of a sound absorbing structure according to example 2 of the present invention.
In the figure: 1-8: first to eighth sound absorbing units, 9: structural frame, 10: microperforated panel, 11: back cavity, 12: and a cell partition plate.
Detailed Description
The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.
Aiming at the problem that the low-frequency-band noise absorption bandwidth in the air is too narrow, the small-size multi-unit coupled low-frequency broadband sound absorption structure is designed by utilizing the broadband characteristic of a micro-perforated plate and the low-frequency characteristic of a space folding type material, and comprises 4-12 sound absorption units which are continuously arranged in parallel, wherein each sound absorption unit consists of a micro-perforated plate 10 and a back cavity 11, the micro-perforated plates 10 are arranged at the opening ends of the back cavities 11, and the micro-perforated plates 10 of all the sound absorption units are arranged in a coplanar manner; by adjusting the parameters of the microperforated panel 10 and the back cavity 11, each cell has multiple sound absorption peaks and a wider bandwidth of peaks than a helmholtz resonator structure; wherein the parameters of the microperforated panel 10 include the diameter, depth, and rate of perforation on the microperforated panel 10; the parameters of the back cavity 11 include the volume of the back cavity 11, which is determined by two parameters, the cross-sectional area and the depth. On the basis, a plurality of strict coupling units are designed, so that the first-order peak value and the high-order peak value of the sound absorption unit are uniformly and continuously distributed as much as possible, a continuous multi-peak sound absorption broadband is formed in a medium-low frequency range, and the peak value number and the total sound absorption bandwidth are increased. Meanwhile, when the structure is designed, the back cavity of the sound absorption unit with larger thickness is subjected to space folding, namely, the rear end of the sound absorption unit is extended to the lower part of the sound absorption unit with smaller thickness, the structure space is fully utilized, and the total thickness of the structure is reduced. Finally, by strictly adjusting the parameters and peak positions of all units, when the structure thickness is 6cm, the continuous sound absorption can be realized within the range of 550Hz-2500Hz, and the average sound absorption coefficient is as high as more than 90%.
The micro-perforated plate 10 has evenly distributed perforations, and the cross section of the back cavity can be square, rectangular, circular, triangular and other shapes.
The sound absorption structure also comprises a structural frame 9 formed by unit partition plates 12 and used for isolating each sound absorption unit and avoiding the sound-solid coupling phenomenon; the frame adopts modes such as 3D printing or mould to process, and structural framework 9 is provided with confined shell, and the one end that the shell corresponds microperforated panel 10 is provided with the opening with microperforated panel 10 one-to-one.
Each sound absorption unit of the sound absorption structure can be equivalent to a mass spring system, wherein the equivalent mass is derived from the air mass in the perforation of the micropunch plate 10, the equivalent damping is derived from the damping effect of the perforation wall, and the equivalent spring stiffness is the air stiffness in the back cavity; by adjusting the structural parameters of different sound absorption units, sound absorption peak values with different frequencies can be obtained, and finally, a continuous sound absorption frequency band is realized.
The first-order peak value and the higher-order peak value of the sound absorption unit are caused by the first-order resonance and the higher-order resonance mode of the system, and the relation of the peak frequency can be approximately expressed as fp＝(2p-1)×f1P is the order of the peak value; it can be seen that the lower the first order peak frequency of the sound-absorbing element, the lower the corresponding higher order peak frequency.
All sound absorption peaks of the m sound absorption units are in a target frequency band (f)A～fB) The internal demand is continuously and uniformly distributed, and the number of peak values n is equal to (f)A-fB) Δ B, where Δ B is the peak bandwidth; determining structural parameters of a sound-absorbing unit so that its first-order peak frequency is fAAnd corresponding high-order peak value frequency in the target frequency band, then designing other units, and determining the number of the sound absorption units according to the number s of all high-order peak values in the target frequency band, namely m is n-s; the back cavity thickness l is the most direct parameter for regulating the peak frequency of the sound absorption unit, and under the condition of keeping the same unit sectional area, the back cavity depth of the sound absorption unit i can be according to the formula
Where s' is the number of higher-order peaks provided by the existing cell, l1Is the back cavity thickness of the first sound-absorbing unit,/iThe thickness of a back cavity of the ith sound absorption unit; the sound absorption peak value of the sound absorption units is irrelevant to the relative arrangement mode among the sound absorption units, and each sound absorption unit can be arranged in one line or multiple lines as long as the sound absorption units are closely and continuously arranged. The method has the advantages that the sequence of the sound absorption units has no corresponding relation with the final arrangement sequence, the determination sequence of the sound absorption units is determined according to the sound absorption peak value, the thickness of the first determined sound absorption unit is the largest, and then the thicknesses of the first determined sound absorption unit are sequentially reduced according to the determination sequence; the arrangement sequence of the sound absorption units is determined according to the thickness size.
The first-order peak frequency of the sound absorption unit is mainly related to the perforation size of the micro-perforated plate 10 and the size of the back cavity 11, and the smaller the perforation diameter is, the larger the equivalent mass is, and the lower the peak frequency is; the greater the perforation depth, i.e. the greater the thickness of the microperforated plate, the lower the peak frequency; the smaller the perforation rate of the perforation, the lower the peak frequency; the larger the cavity volume is, the smaller the equivalent stiffness is, and the sound absorption peak value is shifted to low frequency.
The peak bandwidth of the sound absorption unit is mainly related to the size of the perforation and the number m of the sound absorption units, the smaller the perforation diameter is, the more obvious the damping effect is, and the wider the peak bandwidth is; the larger the perforation depth, the wider the peak bandwidth; the larger the number of sound absorption units, the smaller the peak bandwidth gradually decreases.
The perforations of the micro-perforated plate 10 of the sound absorption unit are uniformly distributed, the shapes of the perforations can be circular, square, triangular or oval, and the like, when the perforations are non-circular, the diameter refers to the diameter of a circumscribed circle of the perforations, namely the maximum width of the perforations, and the number of the perforations is more than or equal to 1; the perforated diameter is recommended to be 0.5 mm-1 mm, and it is noted that when the diameter of the small hole is too small (less than 0.5mm), not only the processing difficulty is increased, but also the engineering application is not facilitated due to easy blockage, when the diameter of the small hole is too large (more than 1mm), the peak bandwidth is reduced, and the high-order sound absorption peak value is reduced or even disappears; the perforation rate can be 1% -15%; the thickness of the plate is not too thin to ensure the structural strength, and can be 0.5 mm-2 mm.
The sectional area of a back cavity 11 of the sound absorption unit can be 10mm multiplied by 10 mm-100 mm multiplied by 100mm, when the sectional area is too small (less than 10mm multiplied by 10mm), the damping on the wall surface of the back cavity 11 can destroy the sound absorption performance of the structure to generate influence, and the expected effect can not be achieved; the back cavity 11 of each cell may have a different cross-sectional area; the back cavity 11 may have different shapes, such as square, rectangular, circular, and other shapes; during the structural design, the back cavity 11 with larger thickness is folded, and the rear end of the back cavity extends to the lower part of the back cavity 11 with smaller thickness, so that the structural space is fully utilized, and the total thickness of the structure is reduced as much as possible.
The partitions 12 between the units form a structural frame 9, which has a certain rigidity to avoid the acoustic-solid coupling effect from affecting the target peak frequency of the units. The structural frame 9 and the micro-perforated plate 11 may be made of metal, rigid plastic, resin, etc.
Compared with the traditional structure or material, the sound absorption structure provided by the invention has great superiority, and when the thickness of the sound absorption structure is 6cm (in the z direction in fig. 1), the sound absorption structure can have a continuous average sound absorption coefficient of more than 90 percent within the range of 550Hz-2500Hz of medium and low frequencies. The suggested value range of the unit number m is 4-12, and when the unit number is more than 12, the sound absorption bandwidth of each unit is narrowed, which is not beneficial to the formation of a broadband; when the number of the units is less than 4, the total sound absorption frequency band is narrow or a valley appears in the middle of the frequency band, and a satisfactory continuous broadband cannot be obtained.
Example 1
The sound absorption structure consists of 8 units, the cross section size of a back cavity of each unit is 10mm multiplied by 10mm, the thickness of the micro perforated plate is 1mm, the thickness of the partition plate 12 in the structural frame 9 is 2mm, and other parameters are shown in table 1. In order to reduce the structural thickness, the second sound absorption unit 2, the third sound absorption unit 3, the seventh sound absorption unit 7 and the eighth sound absorption unit 8 with thicker back cavities are subjected to spatial folding treatment, the second sound absorption unit 2 is respectively extended to the lower part of the first sound absorption unit 1, the third sound absorption unit 3 is extended to the lower part of the fourth sound absorption unit 4, the eighth sound absorption unit 8 is extended to the lower part of the sixth sound absorption unit 6, and the seventh sound absorption unit 7 is sequentially extended to the lower parts of the eighth sound absorption unit 8, the sixth sound absorption unit 6 and the fifth sound absorption unit 5. The structure is integrally manufactured by 3D printing, and the material is photosensitive resin or tough resin and the like.
TABLE 1 concrete parameters of the sound absorption units
Note: d is the perforation diameter of the microperforated plate,. phi is the perforation rate of the perforation, and l is the depth of the back cavity.
As shown in fig. 5, is the measured sound absorption coefficient in the preferred embodiment of the present invention. It can be seen that the structure obtains a continuous nearly perfect absorption broadband in the frequency range 550Hz to 2500 Hz. The sound absorption frequency band consists of 10 sound absorption peaks, wherein two peaks are second-order peaks of the seventh sound absorption unit 7 and the third sound absorption unit 3, and the existence of the second-order peaks can be seen to increase the structural bandwidth by about 25%. In fact, there are high-order peaks of other cells at higher frequencies, but due to the frequency dispersion, the high-order peaks cannot be distributed continuously in the high frequency range, and thus cannot form a continuous wide band. It is confirmed that if the number of cells is increased, more peaks can be introduced, and then the range of the broadband is widened, and more high-order sound absorption peaks can be covered.
Example 2
The sound-absorbing structure in this preferred embodiment of the invention consists of 5 sound-absorbing cells, all arranged in a row. Also, to save space, the thicker cells of the back cavity are folded to extend under the thinner cells. The sound absorption unit d is extended to the lower part of the sound absorption unit e, the sound absorption unit b is sequentially extended to the lower parts of the sound absorption unit c and the sound absorption unit d, and the sound absorption unit a is sequentially extended to the lower parts of the sound absorption unit b, the sound absorption unit c, the sound absorption unit d and the sound absorption unit e.
The above-mentioned embodiments are further detailed to explain the purpose and technical solutions of the present invention, but do not limit the scope of the present invention, and any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (9)
1. A design method of a multi-unit coupling type micro-perforated plate low-frequency broadband sound absorption structure is characterized in that,
step 1, setting a model;
each sound absorption unit of the sound absorption structure is equivalent to a mass spring system, wherein equivalent mass is derived from the mass of air in a perforation of the micropunch plate (10), equivalent damping is derived from the damping effect of a perforation wall, and the equivalent spring stiffness is the air stiffness in the back cavity; obtaining sound absorption peak values of different frequencies by adjusting the structural parameters of different sound absorption units; the structural parameters comprise parameters of the micro-perforated plate (10) and parameters of the back cavity (11); the parameters of the microperforated plate (10) include the diameter, depth of the perforations and the rate of perforations on the microperforated plate (10); the parameters of the back cavity (11) comprise a back cavity volume determined by two parameters of a cross section and a depth;
step 2, determining the quantity of absorption peaks;
according to all sound absorption peaks of the m sound absorption units in a target frequency band (f)A～fB) The requirement of continuous and uniform distribution is required to obtain the peak value n ═ (f)A-fB) Δ B, where Δ B is the peak bandwidth;
step 3, determining the structural parameters of the absorption unit;
first, the structural parameters of a sound-absorbing unit are determined such that its first-order peak frequency is fADetermining corresponding high-order peak value frequency in a target frequency band, designing other units, and obtaining the number m of sound absorption units as n-s according to the number s of all high-order peak values in the target frequency band;
secondly, under the condition of keeping the sectional areas of the units the same, the back cavity thicknesses of the sound absorption units i are sequentially obtained as follows,
wherein, the value range of i is 1 to m, s' is the number of high-order peak values provided by the existing unit, and the range is 0 to s, l1Is the back cavity thickness of the first sound-absorbing unit,/iThe thickness of a back cavity of the ith sound absorption unit; the high-order peak values are provided by the determined sound absorption units in sequence;
step 4, spatial folding arrangement of the absorption units;
and continuously arranging the determined absorption units in parallel, folding the back cavity of the sound absorption unit with larger thickness in the adjacent sound absorption units in space within the design thickness of the sound absorption structure, and bending and extending the rear end of the sound absorption unit to the lower part of the sound absorption unit with smaller thickness.
2. The method for designing a low frequency broadband sound absorbing structure of a multi-unit coupled micro-perforated plate according to claim 1,
the first-order peak frequency of the sound absorption unit is related to the perforation size of the micro-perforated plate (10) and the size of the back cavity (11), and the smaller the perforation diameter is, the larger the equivalent mass is, and the lower the peak frequency is; the greater the perforation depth, i.e. the greater the thickness of the microperforated plate, the lower the peak frequency; the smaller the perforation rate of the perforation, the lower the peak frequency; the larger the cavity volume is, the smaller the equivalent rigidity is, and the sound absorption peak value moves to low frequency;
the peak bandwidth of the sound absorption unit is mainly related to the size of the perforation and the number m of the sound absorption units, the smaller the diameter of the perforation is, the more obvious the damping effect is, and the wider the peak bandwidth is; the larger the perforation depth, the wider the peak bandwidth; the larger the number of sound absorption units, the smaller the peak bandwidth gradually decreases.
3. A multi-unit coupling type micro-perforated plate low-frequency broadband sound absorption structure prepared by the design method of claim 1 is characterized by comprising a plurality of sound absorption units which are arranged in parallel and continuously, wherein each sound absorption unit consists of a micro-perforated plate (10) and a back cavity (11);
the front end of the back cavity (11) is provided with an opening, a micro-perforated plate (10) is arranged, and the rear end of the back cavity is sealed to form a cavity;
the micro-perforated plates (10) of all the sound absorption units are arranged in a coplanar manner, the first-order peak values of all the sound absorption units and at least one high-order peak value of at least one sound absorption unit are uniformly and continuously distributed, and a continuous multi-peak sound absorption broadband is formed in a medium-low frequency range;
the perforation diameter of the micro-perforated plate (10) is 0.5 mm-1 mm, the perforation rate of the perforation is 1% -15%, and the thickness of the micro-perforated plate (10) is 0.5 mm-2 mm.
4. A multi-unit coupled micro-perforated plate low frequency broadband sound absorbing structure according to claim 3, wherein the perforations on the micro-perforated plate (10) are evenly distributed.
5. The multi-unit coupled micro-perforated plate low frequency broadband sound absorbing structure according to claim 3 or 4, wherein the perforated plate (10) is circular, square, triangular or elliptical in shape; when the perforations are non-circular, the diameter refers to the diameter of the circumscribed circle of the perforation.
6. The multi-cell coupled micro-perforated panel low frequency broadband sound absorbing structure of claim 3, wherein 4-12 sound absorbing cells are arranged in series in parallel.
7. The multi-unit coupled micro-perforated plate low-frequency broadband sound absorption structure as claimed in claim 3, wherein the cross-section of the back cavity (11) is a polygon, a circle or an irregular closed curve, and the cross-sectional area of the back cavity (11) of the sound absorption unit is 100mm2～1×104mm2。
8. The multi-cell coupled micro-perforated panel low frequency broadband sound absorbing structure according to claim 3, further comprising a structural frame (9) formed by crossing cell partitions (12) for isolating each sound absorbing cell; the structural frame (9) is provided with a closed shell, and one end of the shell, corresponding to the micro-perforated plate (10), is provided with openings corresponding to the micro-perforated plate (10) one by one.
9. The multi-unit coupled micro-perforated plate low frequency broadband sound absorbing structure according to claim 3, wherein the structural frame (9) and the micro-perforated plate (10) are made of metal, hard plastic and resin by 3D printing or die processing.
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