CN111816151A - Double-layer honeycomb-micro-perforated structure with adjustable back cavity height and design method thereof - Google Patents
Double-layer honeycomb-micro-perforated structure with adjustable back cavity height and design method thereof Download PDFInfo
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- CN111816151A CN111816151A CN202010778971.4A CN202010778971A CN111816151A CN 111816151 A CN111816151 A CN 111816151A CN 202010778971 A CN202010778971 A CN 202010778971A CN 111816151 A CN111816151 A CN 111816151A
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- G—PHYSICS
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- 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
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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
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Abstract
The invention relates to a double-layer honeycomb-micro-perforated structure with adjustable back cavity height, which comprises an upper panel, a lower panel and a honeycomb core clamped between the upper panel and the lower panel. The invention realizes the absorption of the structure to the noise with different frequencies by changing the height of the micro-perforated plate contained in the honeycomb core, improves the sound absorption effect and simultaneously improves the application of the honeycomb-micro-perforated plate structure in noise reduction.
Description
Technical Field
The invention belongs to a medium-low frequency and broadband noise reduction structure and a method which are designed by utilizing a honeycomb-micro perforated plate composite structure, and particularly relates to a double-layer honeycomb-micro perforated plate structure with adjustable back cavity height and a design method thereof.
Background
The sound absorption structure of the micro-perforated plate is developed on the basis of a common perforated plate structure, and is mainly characterized in that the diameter of a perforated hole is reduced to be less than millimeters, and the relative sound resistivity of the sound absorption structure is controlled by using the sound resistance of the perforated hole, so that a sound absorption material behind the perforated plate can be cancelled, and the sound absorption structure is greatly simplified. The honeycomb sandwich structure has the characteristics of high specific strength, large specific rigidity, good fatigue resistance, flat and smooth surface and the like, is widely used in the field of aviation and the like, and the honeycomb-micro perforated plate structure combining the honeycomb sandwich structure and the micro perforated plate structure has excellent mechanical property and good sound absorption effect.
The sound absorption coefficient of the single-layer micro-perforated plate sound absorption structure is low except a sound absorption peak value, the effective sound absorption frequency band is narrow, the requirement of practical application cannot be well met sometimes, the double-layer micro-perforated plate sound absorption structure can be regarded as two mutually-coupled resonance sound absorption structures, and the double-layer micro-perforated plate sound absorption structure can be used for obtaining higher sound absorption coefficient and wider sound absorption frequency band.
According to the sound absorption principle of the micro-perforated plate, the depth of the plate thickness cavity of the micro-perforated plate structure directly influences the sound absorption performance of the structure, namely the sound absorption frequency and the sound absorption coefficient. In order to improve the sound absorption performance of the structure, one layer of micro-perforated plate of the double-layer honeycomb-micro-perforated structure only keeps vertical up-down freedom and is arranged to be adjustable up and down. Therefore, the height of the board thickness cavity of the micro-perforated board can be changed by changing the position of the layer of micro-perforated board, so that the noise of different frequencies can be absorbed.
Disclosure of Invention
The invention designs a double-layer honeycomb-micro perforated structure with adjustable back cavity height aiming at a honeycomb-micro perforated structure sound absorption structure, and realizes the absorption of the structure to different frequency noises by changing the height of a perforated plate contained in a honeycomb core, thereby improving the sound absorption effect and simultaneously improving the application of the honeycomb-micro perforated structure in noise reduction.
The invention is realized by the following technical scheme.
A double-layer honeycomb-micro-perforated structure with adjustable back cavity height comprises an upper panel, a lower panel and a honeycomb core clamped between the upper panel and the lower panel, and is characterized in that the upper panel is a micro-perforated panel, a micro-perforated plate with adjustable height is arranged in the honeycomb core, an adjusting boss is arranged on the micro-perforated plate, an adjusting screw is arranged in the honeycomb core, external threads and internal threads which are matched with each other are arranged in the adjusting screw and the adjusting boss, one end of the adjusting screw penetrates through the lower panel, an adjusting knob used for controlling the adjusting screw is arranged at the end of the adjusting screw, a raised line is arranged on the inner wall of the honeycomb core, a groove matched with the raised line is arranged on the outer side of the micro-perforated plate, the raised line is parallel to the axis of the honeycomb core, the distance between the upper panel and the micro-perforated plate is changed by rotating the adjusting knob, absorbing noise at different frequencies.
Preferably, the lower honeycomb core is arranged in a close-packed circle.
Preferably, the bottom of the adjusting screw penetrates through the lower panel, the bottom of the adjusting screw is in clearance fit with the lower panel to form a self-locking structure, and the middle of the self-locking structure is narrow and the two ends of the self-locking structure are wide.
Preferably, the thread of the adjusting screw is a right-hand rectangular thread.
Preferably, a dial is arranged on the adjusting knob.
A design method of a double-layer honeycomb-micro-perforated structure with adjustable back cavity height is characterized by comprising the following steps:
firstly, verifying the influence of the change of the cavity height on the sound absorption effect of the micro-perforation according to the theory of the micro-perforation plate of the university of Ma 29495 and computer simulation, wherein the sound absorption coefficient when sound waves vertically enter is as follows:
the sound absorption coefficient of the micro-perforated sound absorber reaches the maximum value when the micro-perforated sound absorber resonates, and the maximum sound absorption coefficient value is as follows:
resonant frequency f0Satisfies the following conditions:
2πf0m-cot(2πf0D/c)＝0 (3)
wherein the respective acoustic resistance r and acoustic mass m are:
in the above formulas, k is a perforated plate constant
Mu is kinematic viscosity coefficient of air (1.48X 10)-5m2T is the plate thickness, D is the perforation diameter, D is the cavity height, p is the perforation rate, f is the acoustic frequency, the acoustic resistivity of the cavity behind the plate is
ZD＝-jρccot(ωD/c) (7)
Two-layer microperforated panel m with double-layer microperforated sound absorber1，r1And m2，r2With rear cavities each being D1And D2The relative acoustic impedance of the double-layer series structure can be obtained according to the equivalent circuit
From the above theoretical formula, the resistance of the double-layer micro-perforated plate is determined by the parameters of the micro-perforated plate and the height D of the cavity1、D2Assuming that the microperforated panel parameters are determined, D1And D2The resistance value of the structure is directly influenced, namely, the sound absorption performance of the micro-perforated plate structure can be adjusted by changing the cavity height D of the micro-perforated plate.
Second, based on the above impedance value with the cavity height D1And D2The change rule of (2) designs a double-layer honeycomb-micro-perforated knot with adjustable back cavity heightThe structure adopts the closely-arranged circular honeycomb core, and the purpose of changing the acoustic impedance of the cavity behind the plate is achieved by changing the position of the micro-perforated plate inside the honeycomb core, so that the noise with different frequencies is absorbed.
Compared with the prior art, the invention has the advantages that:
1. the double-layer honeycomb-micro-perforated structure can realize the best absorption of noise by changing the resonant frequency of the structure by changing the height of the back cavity aiming at the noise with different frequencies;
2. compared with a single-layer honeycomb-micro-perforated structure, the double-layer honeycomb-micro-perforated structure has a better sound absorption effect;
3. the double-layer honeycomb-micro-perforated structure is simple to manufacture and operate, and has wide application prospect in the field of noise reduction.
Drawings
FIG. 1 is a conventional close-packed circular honeycomb-microperforated structure;
fig. 2 is a schematic diagram of the structure of a honeycomb core cell of the present invention;
fig. 3 is a schematic diagram of the internal structure of a honeycomb core cell of the present invention;
FIG. 4 is a schematic view of the self-locking structure of the present invention:
FIG. 5 is a top view of a honeycomb core sidewall of the present invention;
FIG. 6 is a top view of an internal microperforated panel in accordance with the present invention;
FIG. 7 is a schematic view of a boss of the present invention;
FIG. 8 is a schematic view of the screw configuration of the present invention;
FIG. 9 is a schematic view of the knob structure for controlling the rotation of the screw according to the present invention;
FIG. 10 is a honeycomb-microperforated structure of modified adjustable back cavity height;
FIG. 11 is a graph of sound absorption effect of an embodiment;
in the figure: 1. the honeycomb core comprises an upper panel, 2, a honeycomb core, 3, a lower panel, 4, a screw, 5, a micro-perforated plate, 6, a boss, 7, a knob, 8, a convex strip, 9 and a groove.
Detailed Description
The invention is further described with reference to the following drawings and specific examples, which are not intended to be limiting.
As shown in fig. 1, a common densely-arranged circular honeycomb-micro-perforated plate is composed of an upper panel 1, a densely-arranged circular honeycomb core 2 and a lower panel 3, wherein the upper panel is a micro-perforated plate with a certain perforation rate, the honeycomb core is in a densely-arranged circular structure, and the lower panel is a common metal sheet.
The invention improves the common honeycomb core sandwich structure, and the honeycomb core structure is set into a structure containing a screw and a micro-perforated plate.
As shown in fig. 2 to 10, a double-layer honeycomb-micro-perforated structure with adjustable back cavity height, an upper panel 1, a lower panel 3, and a honeycomb core 2 sandwiched between the upper panel 1 and the lower panel 3, wherein the upper panel 1 is a micro-perforated panel, a micro-perforated plate 5 with adjustable height is arranged in the honeycomb core 2, an adjusting boss 6 is arranged on the micro-perforated plate 5, an adjusting screw 4 is arranged in the honeycomb core 2, external threads and internal threads which are mutually matched are arranged in the adjusting screw 4 and the adjusting boss 6, one end of the adjusting screw 4 passes through the lower panel 3 and is provided with an adjusting knob 7 for controlling the adjusting screw 4, a raised strip 8 is arranged on the inner wall of the honeycomb core 2, a groove 9 matched with the raised strip 8 is arranged on the outer side of the micro-perforated plate 5, and the raised strip 8 is parallel to the axis of the honeycomb core 2, the distance between the upper panel 1 and the micro-perforated plate 5 is changed by rotating the adjusting knob 7, so that the structural resonance frequency is changed, and noises with different frequencies are absorbed. The ridges 8 and grooves 9 limit the degree of freedom of the microperforated plate 5 so that the microperforated plate 5 can only move up and down along the screw and cannot rotate with the screw.
In a preferred embodiment, the lower honeycomb core 2 is arranged in a close-packed circle.
As a preferred embodiment, the bottom of the adjusting screw rod 4 penetrates through the lower panel 3, the bottom of the adjusting screw rod 4 and the lower panel 3 are in clearance fit to form a self-locking structure, and the middle of the self-locking structure is narrow and the two ends of the self-locking structure are wide.
As a preferred embodiment, the thread of the adjusting screw 4 is a right-hand rectangular thread.
In a preferred embodiment, the adjusting knob 7 is provided with a dial.
A single adjustable back cavity height two-layer honeycomb-microperforated structure cell is shown in fig. 2 and 3. Fig. 2 is a schematic structural diagram of a single cell with a double-layer honeycomb-micro-perforated structure and adjustable back cavity height, and the honeycomb core 2 is arranged in a close-packed circular manner. Fig. 3 is a schematic diagram of the internal structure of a cell with a dual-layer honeycomb-micro-perforated structure and adjustable back cavity height. Fig. 4 is a schematic diagram of the self-locking structure of the invention, and during installation, the screw 4 is only required to be pushed into the honeycomb core 2 to form the self-locking structure, so that the screw 4 can be ensured not to fall out. Fig. 5 is a top view of the honeycomb core of the present invention, and fig. 6 is a top view of the inner microperforated plate of the present invention, and the grooves on the outer side of the microperforated plate 5 are fitted with the protrusions on the inner wall of the honeycomb core 2 to restrict the degree of freedom of the microperforated plate 5 so that the microperforated plate 5 can only move up and down along the screw. FIG. 7 is a schematic view of a boss of the present invention, FIG. 8 is a schematic view of a screw of the present invention, and a threaded hole is provided in the boss 6 below the micro-perforated plate 5, and the threaded hole is sized to be threadedly engaged with the screw 4. Fig. 9 is a schematic view of the knob of the present invention, and the elevation of the micro-perforated plate 5 inside the honeycomb core can be controlled by the above scale.
A design method of a double-layer honeycomb-micro-perforated structure with adjustable back cavity height is characterized by comprising the following steps:
firstly, verifying the influence of the change of the cavity height on the sound absorption effect of the micro-perforation according to the theory of the micro-perforation plate of the university of Ma 29495 and computer simulation, wherein the sound absorption coefficient when sound waves vertically enter is as follows:
the sound absorption coefficient of the micro-perforated sound absorber reaches the maximum value when the micro-perforated sound absorber resonates, and the maximum sound absorption coefficient value is as follows:
resonant frequency f0Satisfies the following conditions:
2πf0m-cot(2πf0D/c)＝0 (3)
wherein the respective acoustic resistance r and acoustic mass m are:
in the above formulas, k is a perforated plate constant
Mu is kinematic viscosity coefficient of air (1.48X 10)-5m2T is the plate thickness, D is the perforation diameter, D is the cavity height, p is the perforation rate, f is the acoustic frequency, the acoustic resistivity of the cavity behind the plate is
ZD＝-jρccot(ωD/c) (7)
Two-layer microperforated panel m with double-layer microperforated sound absorber1，r1And m2，r2With rear cavities each being D1And D2The relative acoustic impedance of the double-layer series structure can be obtained according to the equivalent circuit
From the above theoretical formula, the resistance of the double-layer micro-perforated plate is determined by the parameters of the micro-perforated plate and the height D of the cavity1、D2Assuming that the microperforated panel parameters are determined, D1And D2The resistance value of the structure is directly influenced, namely, the sound absorption performance of the micro-perforated plate structure can be adjusted by changing the cavity height D of the micro-perforated plate.
Second, based on the above impedance value with the cavity height D1And D2The change rule of (2) is to design a double-layer honeycomb-micro-perforated structure with adjustable back cavity height, wherein the structure adopts densely-arranged round honeycomb cores and through holesThe purpose of changing the acoustic impedance of the cavity behind the honeycomb core is achieved by changing the position of the micro-perforated plate inside the honeycomb core, so that noise with different frequencies is absorbed.
Example (b):
a single adjustable back cavity height two-layer honeycomb core cell is shown in fig. 3, 4 and 5. Wherein each structure size is as follows: the outer diameter of the honeycomb core 2 is 29mm, the inner diameter is 28mm, and the height is 60 mm; the screw rod 4 is a right-handed rectangular thread with a large diameter of 4mm, a small diameter of 2mm and a thread pitch of 4 mm; the thickness of a micro-perforated plate 1 is 1mm, the aperture is 0.5mm, and the perforation rate is 1%; the microperforated plate 5 had a plate thickness of 1mm, a hole diameter of 0.5mm and a perforation rate of 1%. The microperforated plate 5 has a thickness of only 1mm, and a boss 7 having a height of 5mm and a diameter of 5mm is provided thereunder. The boss 7 is internally provided with a threaded hole, and the size of the threaded hole is matched with the screw rod 4 in a threaded manner. In the present embodiment, the sound absorption coefficients of the three cases, that is, the height of the microperforated panel 5 from the bottom of the honeycomb core is 10mm, the height of the microperforated panel 5 from the bottom of the honeycomb core is 30mm, and the height of the microperforated panel 5 from the bottom of the honeycomb core is 50mm, are calculated, and the structure is set in a cylindrical shape with a diameter of 29mm so as to facilitate measurement in an impedance tube.
FIG. 11 shows the sound absorption effect of the structure in the first case, i.e., the sound absorption coefficient of the structure in which the height of the microperforated panel 5 from the bottom of the honeycomb core is 10mm, and D in this case1And D250mm and 10mm respectively; in the second case, the sound absorption coefficient of the structure with the height of the microperforated panel 5 being 30mm from the bottom of the honeycomb core, D of the structure at this time1And D2Are all 30 mm; third case microperforated panel 5 has a sound absorption coefficient of the structure at 50 f from the height of the honeycomb core bottom, when D of the structure1And D210mm and 50mm respectively. The figure shows that the double-layer honeycomb-micro-perforated structure with the adjustable back cavity height has good noise absorption effects at low frequency, medium frequency and medium-high frequency, and the best absorption of the structure to different frequencies is realized by changing the height of the micro-perforated plate in the honeycomb core from the bottom of the honeycomb core.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.
Claims (6)
1. A double-layer honeycomb-micro perforation structure with adjustable back cavity height comprises an upper panel (1), a lower panel (3) and a honeycomb core (2) clamped between the upper panel (1) and the lower panel (3), and is characterized in that the upper panel (1) is a micro perforation panel, a micro perforation plate (5) with adjustable height is arranged in the honeycomb core (2), an adjusting boss (6) is arranged on the micro perforation plate (5), an adjusting screw rod (4) is arranged in the honeycomb core (2), external threads and internal threads which are matched with each other are arranged in the adjusting screw rod (4) and the adjusting boss (6), one end of the adjusting screw rod (4) penetrates through the lower panel (3) and is provided with an adjusting knob (7) used for controlling the adjusting screw rod (4), a raised strip (8) is arranged on the inner wall of the honeycomb core (2), a groove (9) matched with the raised strip (8) is arranged on the outer side of the micro perforation plate (5), the convex strips (8) are parallel to the axis of the honeycomb core (2), and the distance between the upper panel (1) and the micro-perforated plate (5) is changed by rotating the adjusting knob (7), so that the structural resonance frequency is changed, and noises with different frequencies are absorbed.
2. The double-layered honeycomb-microperforation structure with adjustable back cavity height of claim 1, characterized in that the lower honeycomb core (2) is in a close-packed circular arrangement.
3. The double-layer honeycomb-micro perforated structure with the adjustable back cavity height of claim 1, characterized in that the bottom of the adjusting screw (4) penetrates through the lower panel (3), the bottom of the adjusting screw (4) and the lower panel (3) are in clearance fit to form a self-locking structure, and the self-locking structure is narrow in the middle and wide at two ends.
4. The double-layered honeycomb-microperforation structure with adjustable back cavity height of claim 1, characterized in that the thread of the adjusting screw (4) is a right-hand rectangular thread.
5. Double-layered honeycomb-microperforation structure with adjustable back cavity height according to claim 1, characterized in that a dial is provided on the adjusting knob (7).
6. A design method of a double-layer honeycomb-micro-perforated structure with adjustable back cavity height is characterized by comprising the following steps:
firstly, verifying the influence of the change of the cavity height on the sound absorption effect of the micro-perforation according to the theory of the micro-perforation plate of the university of Ma 29495 and computer simulation, wherein the sound absorption coefficient when sound waves vertically enter is as follows:
the sound absorption coefficient of the micro-perforated sound absorber reaches the maximum value when the micro-perforated sound absorber resonates, and the maximum sound absorption coefficient value is as follows:
resonant frequency f0Satisfies the following conditions:
2πf0m-cot(2πf0D/c)＝0 (3)
wherein the respective acoustic resistance r and acoustic mass m are:
in the above formulas, k is a perforated plate constant
Mu is kinematic viscosity coefficient of air (1.48X 10)-5m2/s), t is the plate thickness, D is the perforation diameter, D is the cavity height, p is the perforation rate, f is the audio frequencyRate, specific acoustic impedance of the cavity behind the plate of
ZD＝-jρccot(ωD/c) (7)
Two-layer microperforated panel m with double-layer microperforated sound absorber1，r1And m2，r2With rear cavities each being D1And D2The relative acoustic impedance of the double-layer series structure can be obtained according to the equivalent circuit
From the above theoretical formula, the resistance of the double-layer micro-perforated plate is determined by the parameters of the micro-perforated plate and the height D of the cavity1、D2Assuming that the microperforated panel parameters are determined, D1And D2The resistance value of the structure is directly influenced, namely, the sound absorption performance of the micro-perforated plate structure can be adjusted by changing the cavity height D of the micro-perforated plate.
Second, based on the above impedance value with the cavity height D1And D2The change rule of (2) designs a double-layer honeycomb-micro-perforated structure with adjustable back cavity height, the structure adopts a densely-arranged circular honeycomb core, and the purpose of changing the acoustic impedance of the cavity behind the plate is achieved by changing the position of a micro-perforated plate in the honeycomb core, so that the absorption of noise with different frequencies is realized.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113470605A (en) * | 2021-06-10 | 2021-10-01 | 西安交通大学 | Continuously adjustable sound absorption structure |
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| CN109584855A (en) * | 2019-01-11 | 2019-04-05 | 南昌航空大学 | Honeycomb-microperforated panel composite structural design method of adjustable sound absorption frequency |
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| CN212874037U (en) * | 2020-08-05 | 2021-04-02 | 南昌航空大学 | Double-layer honeycomb-micro-perforated structure with adjustable back cavity height |
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2020
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| US20020061110A1 (en) * | 2000-11-20 | 2002-05-23 | National Aerospace Laboratory Of Japan | Actively-controlled sound absorption panel system using movement-controlled reflective plate |
| CN108346421A (en) * | 2018-05-02 | 2018-07-31 | 南昌航空大学 | A kind of honeycomb interlayer sound absorption structure of built-in microperforated panel |
| CN208164418U (en) * | 2018-05-02 | 2018-11-30 | 南昌航空大学 | A kind of honeycomb interlayer sound absorption structure of built-in son back chamber |
| WO2020098477A1 (en) * | 2018-11-15 | 2020-05-22 | 中车株洲电力机车有限公司 | Low-frequency coupling sound absorbing structure |
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| CN113470605A (en) * | 2021-06-10 | 2021-10-01 | 西安交通大学 | Continuously adjustable sound absorption structure |
| CN113470605B (en) * | 2021-06-10 | 2024-05-24 | 西安交通大学 | Continuously adjustable sound absorption structure |
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| CN111816151B (en) | 2024-11-08 |
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