CN113808563A - Low-frequency sound absorption covering layer containing cylindrical scatterer with gradient parameters - Google Patents
Low-frequency sound absorption covering layer containing cylindrical scatterer with gradient parameters Download PDFInfo
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- CXQXSVUQTKDNFP-UHFFFAOYSA-N octamethyltrisiloxane Chemical compound C[Si](C)(C)O[Si](C)(C)O[Si](C)(C)C CXQXSVUQTKDNFP-UHFFFAOYSA-N 0.000 claims abstract description 23
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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
- G10K11/162—Selection of materials
- G10K11/168—Plural layers of different materials, e.g. sandwiches
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B15/00—Layered products comprising a layer of metal
- B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
- B32B15/06—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of natural rubber or synthetic rubber
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B15/00—Layered products comprising a layer of metal
- B32B15/18—Layered products comprising a layer of metal comprising iron or steel
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B25/00—Layered products comprising a layer of natural or synthetic rubber
- B32B25/20—Layered products comprising a layer of natural or synthetic rubber comprising silicone rubber
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- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar form; Layered products having particular features of form
- B32B3/02—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar form; Layered products having particular features of form characterised by features of form at particular places, e.g. in edge regions
- B32B3/08—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar form; Layered products having particular features of form characterised by features of form at particular places, e.g. in edge regions characterised by added members at particular parts
- B32B3/085—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar form; Layered products having particular features of form characterised by features of form at particular places, e.g. in edge regions characterised by added members at particular parts spaced apart pieces on the surface of a layer
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- B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar form; Layered products having particular features of form
- B32B3/26—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar form; Layered products having particular features of form characterised by a particular shape of the outline of the cross-section of a continuous layer; characterised by a layer with cavities or internal voids ; characterised by an apertured layer
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- B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
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- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63C—LAUNCHING, HAULING-OUT, OR DRY-DOCKING OF VESSELS; LIFE-SAVING IN WATER; EQUIPMENT FOR DWELLING OR WORKING UNDER WATER; MEANS FOR SALVAGING OR SEARCHING FOR UNDERWATER OBJECTS
- B63C11/00—Equipment for dwelling or working underwater; Means for searching for underwater objects
- B63C11/52—Tools specially adapted for working underwater, not otherwise provided for
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
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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
- G10K11/161—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general in systems with fluid flow
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Abstract
The invention relates to a low-frequency sound absorption covering layer containing cylindrical scatterers with parameters changing in a gradient mode. The sound absorption layer is formed by the periodic arrangement of the same cuboid unit of several, and the front surface of sound absorption layer is pasted and is sealed the layer and guarantee the water proofness, and the basic unit pastes the shell that simulates the structure under water at the sound absorption layer lower surface. In each unit of the sound absorption layer, three cylindrical scatterers are arranged from top to bottom. Each cylindrical scatterer is formed by wrapping two layers of elastic rubber with the same thickness and different modulus on the side surface of a cylindrical cavity. The sealing layer and the sound absorption layer are both made of PDMS polydimethylsiloxane silicone rubber, and the base layer is made of steel materials. The invention overcomes the problem of poor low-frequency sound absorption performance caused by adopting a single material, and can effectively reduce the frequency range of a sound absorption frequency band and improve the sound absorption coefficient by adopting the design that the modulus and the thickness of the cladding layer in the cylindrical scatterer are in gradient change. The invention has strong designability and is suitable for application in the aspects of low-frequency vibration reduction and noise reduction.
Description
Technical Field
The invention relates to a low-frequency sound absorption covering layer containing cylindrical scatterers with parameters in gradient change, in particular to a low-frequency sound absorption covering layer with a cavity and a plurality of layers of elastic materials coated outside the cylindrical scatterers.
Background
The sound absorption covering layer is widely applied to cover on an underwater vehicle shell, and the acoustic performance of the sound absorption covering layer is an important index for judging the sound hiding capability of the underwater vehicle. The function of the sound-absorbing covering layer is mainly realized in two aspects: firstly, the radiation noise level of the aircraft is reduced to reduce the probability of being found by an enemy passive sonar and the action distance of the enemy passive sonar; and secondly, the detection distance of the active sonar of the enemy is increased by reducing the intensity of the acoustic target of the aircraft. At present, most of sound absorption covering layers applied at home and abroad are made of rubber materials with certain damping performance, periodic cavity structures such as horn-shaped, spherical and cylindrical structures are embedded in the rubber layers, and the sound waves are effectively absorbed mainly by using the mechanisms of cavity resonance, wave mode conversion and relaxation effect. However, the sound absorption frequency band of the sound absorption covering layer based on the cavity resonance principle is generally narrow, and underwater broadband sound absorption is difficult to realize.
The existing solutions include: (1) the cylindrical cavity is coated with a layer of viscoelastic soft material as a scatterer structure, and the scatterers are periodically transversely arranged and embedded in rubber materials to form a sound absorption layer (Yanhai shore, Liyue, hong and gang, temperature shock and hong, temperature and Xisen, a viscoelastic material low-frequency sound absorption mechanism research containing a cylindrical resonance scatterer, Physics report 2013). The structure can obtain two higher absorption peaks in a frequency band range lower than 3000Hz, the first absorption peak is caused by the integral coupling resonance of the sound absorption layer and the steel backing, and the second absorption peak is closely related to the resonance characteristic of a single scatterer and multiple scattering among the scatterers. The two absorption peaks are connected together to form a broadband absorption peak with the sound absorption coefficient of more than 0.6 within the frequency band range of 1000-3000Hz, but no absorption peak appears below 1000Hz, and the sound absorption coefficient is lower. (2) Two types of cylindrical cavities with different sizes are embedded into two different rubber layers, and the better sound absorption performance can be obtained by integrally optimizing the material and the structural parameters of the rubber layers (Dan ZHao, honggan ZHao, Haibiin Yang, Jihong Wen. optimization and mechanism of acoustic absorption of elastomer coatings on a steel plate in water. applied. Acoust.2018,140: 183-) 187.). The optimization result shows that the sound absorption layer has a broadband sound absorption effect in the frequency band range of 1.3kHz-10kHz, the sound absorption performance of the broadband can be effectively improved by laying sound absorption layers with different parameters, but the sound absorption coefficient in the frequency band range of 1000-2000Hz is lower.
Disclosure of Invention
Aiming at the prior art, the invention aims to provide a low-frequency broadband sound absorption covering layer embedded with a cylindrical scatterer, which can effectively reduce the frequency range of a sound absorption frequency band and improve the low-frequency sound absorption performance.
In order to solve the technical problem, the invention relates to a low-frequency sound absorption covering layer containing a cylindrical scatterer with gradient parameters, which comprises a sealing layer, a sound absorption layer, a cylindrical scatterer and a base layer. The sound absorption layer is formed by a plurality of same cuboid units which are periodically arranged, and the front surface section and the rear surface section of the sound absorption layer are rectangular. The sealing layer is a cuboid plate and is used for sealing the sound absorption layer, and the rear surface of the sealing layer is mutually attached to the front surface of the sound absorption layer; the base layer is a cuboid plate which is a shell of a simulated underwater structure and is generally a steel shell, and the upper surface of the base layer is attached to the lower surface of the sound absorption layer. The cylindrical scatterer is formed by wrapping two layers of elastic rubber materials with different physical parameters outside a cylindrical cavity.
The invention also includes:
1. the sealing layer and the sound absorption layer are both made of PDMS polydimethylsiloxane silicone rubber, and the density of the PDMS polydimethylsiloxane silicone rubber is 1000kg/m3Complex Young's modulus is (1.879+0.540i) MPa, Poisson's ratio is 0.4997; the base layer is made of steel material and has a density of 7890kg/m3Young's modulus was 210GPa, and Poisson's ratio was 0.3.
2. The sound absorption layer is formed by a plurality of identical cuboid units which are periodically arranged, the sections of the front surfaces of the units are rectangular, and the side surfaces of the units are mutually attached. For the front surface of each unit in the sound absorption layer, the length d is 150mm, and the width a is 40 mm; the length of the side surface of each cell was 1 m.
3. The thickness of the sealing layer is 30 mm; the thickness s of the base layer was 20 mm. The sealing layer, the sound absorption layer and the base layer are bonded together through an adhesive and are integrally cold-pressed and molded.
4. In each unit in the sound absorption layer, a first layer of cylindrical scatterer, a second layer of cylindrical scatterer and a third layer of cylindrical scatterer are distributed from top to bottom, and the axes of the first layer of cylindrical scatterer, the second layer of cylindrical scatterer and the third layer of cylindrical scatterer are respectively parallel to the upper surface, the lower surface, the left side surface and the right side surface of the unit. 1 cylindrical scatterer is distributed on the first layer of cylindrical scatterer, the second layer of cylindrical scatterer and the third layer of cylindrical scatterer, and the length of each cylindrical scatterer is equal and is 1 m.
5. Every cylindrical scatterer that the sound absorption layer contains comprises two-layer different composition's elastic rubber of cylinder cavity side parcel, is full of the air in the cylinder cavity, radially is first layer cladding and the second layer cladding from inside to outside along cylindrical scatterer in proper order.
6. For three layers of cylindrical scatterers in the sound absorption layer, the Young modulus of a first layer of coating layer of the first layer of cylindrical scatterer is 0.1 time of that of the sound absorption layer, and the Young modulus of a second layer of coating layer of the first layer of cylindrical scatterer is 0.55 time of that of the sound absorption layer; the Young modulus of the first coating layer of the second layer of cylindrical scatterer is 0.1 time of that of the sound absorption layer, and the Young modulus of the second coating layer of the second layer of cylindrical scatterer is 0.55 time of that of the sound absorption layer; the Young modulus of the first coating layer of the third layer of cylindrical scatterers is 0.1 time of that of the sound absorption layer, and the Young modulus of the second coating layer of the third layer of cylindrical scatterers is 0.55 time of that of the sound absorption layer; namely, for each cylindrical scatterer, the Young modulus of the cladding layer changes in a positive gradient from inside to outside.
7. For three layers of cylindrical scatterers in the sound absorption layer, the radius r of a cylindrical cavity in the first layer of cylindrical scatterer11.5mm, radius r of the cylindrical cavity in the second layer of cylindrical diffuser2Radius r of cylindrical cavity in the third layer of cylindrical scatterer of 3.5mm35.5mm, that is, the radius of the three-layer cylindrical cavity is changed in a positive gradient (r)1＜r2＜r3)。
8. For three layers of cylindrical scatterers in the sound absorption layer, the first layer of coating layer of the first layer of cylindrical scatterer has the thickness c112mm, second layer coating thickness c of the first cylindrical diffuser 122 mm; first layer of cladding thickness c of second layer of cylindrical scatterers21Second layer coating thickness c of second layer cylindrical diffuser of 3mm223 mm; first layer coating thickness c of third layer cylindrical scatterer314mm, second layer coating thickness c of the third layer of cylindrical scattering body 324 mm; i.e. for a three-layer cylindrical diffuser, the thickness of the cladding varies with a positive gradient (c)11＜c21＜c31And c is and c11＝c12，c21＝c22，c31＝c32)。
9. For each unit in the sound absorption layer, the distance from the circle center of the cylindrical scatterer to the left boundary and the right boundary of the unit in the first layer of cylindrical scatterer is equal and is 20 mm; in the second layer of cylindrical scatterers, the distance from the circle center of each cylindrical scatterer to the left boundary and the right boundary of each unit is equal and is 20 mm; in the third layer of cylindrical scatterers, the distance from the circle center of the cylindrical scatterer to the left and right boundaries of the unit is equal and is 20 mm.
10. In each cell of the sound-absorbing layer, the clear distance d between the upper boundary of the cell and the cylindrical cavity of the first layer1The clear distance d between the first layer of cylindrical cavity and the second layer of cylindrical cavity is 29mm270mm, the clear distance d between the second layer of cylindrical cavity and the third layer of cylindrical cavity3The clear distance d between the third layer of cylindrical cavities and the lower boundary of the unit is 20mm410mm, i.e. the clear distance has a negative gradient (d)2＞d3＞d4)。
The invention has the beneficial effects that:
the invention can obtain higher sound absorption performance through a simpler structure, is suitable for application in the aspect of underwater low-frequency vibration and noise reduction, and has better underwater low-frequency sound absorption effect. The invention has the characteristics of simple structure, simple manufacturing process and strong designability. The invention overcomes the problem of poor low-frequency sound absorption performance caused by adopting a single material, can effectively reduce the frequency range of a sound absorption frequency band and effectively improve the sound absorption coefficient by adopting the design that the modulus and the thickness of the cladding layer in the cylindrical scatterer are in gradient change, and is suitable for application in the aspects of vibration reduction and noise reduction of a low-frequency broadband.
Drawings
FIG. 1 is a schematic structural view of a sound-absorbing cover layer of the present invention, taken through a section of the sound-absorbing cover layer of the present invention, comprising 6 cells;
FIG. 2 is a schematic representation of the elements of the acoustical layer of the acoustical cover layer of the present invention;
FIG. 3 is a schematic front view of a unit of the sound absorbing layer in the sound absorbing cover layer of the present invention;
FIG. 4 is a schematic view of a cylindrical diffuser of the sound absorbing layer in the sound absorbing overlay of the present invention;
FIG. 5 is a plot of the sound absorption coefficient for example 1 of the sound absorbing cover layer of the present invention;
FIG. 6 is a plot of the sound absorption coefficient of example 2 of the sound absorbing cover layer of the present invention.
In the drawings, the reference numerals denote: 1-sealing layer, 2-sound absorption layer, 3-base layer, 4-first layer cylindrical scatterer, 5-second layer cylindrical scatterer, 6-third layer cylindrical scatterer, 7-cylindrical cavity, 8-first layer coating layer and 9-second layer coating layer.
Detailed Description
The invention is further illustrated with reference to the following figures and examples.
As shown in fig. 1 and 2, a low frequency sound absorption covering layer containing cylindrical scatterers with parameters changing in a gradient manner comprises a sealing layer 1, a sound absorption layer 2 and a base layer 3. The sound absorption layer 2 is composed of 6 units, cylindrical scatterers in a certain arrangement mode are distributed in the units, the sealing layer 1 and the sound absorption layer 2 are both made of PDMS polydimethylsiloxane silicone rubber, the base layer is made of steel materials, and the cross sections of the cylindrical scatterers are round surfaces. As shown in fig. 3, a sealing layer is disposed on each cylindrical cavity. In each cell, the first, second and third layers all contain 1 cylindrical scatterer. The three layers of cylindrical scatterers are the same in length and are 1m in length. The thickness d of the selected sound absorption layer 2 is 150mm, the thickness of each unit is equal, the thickness d is 150mm, the width is equal, and the width a is 40 mm. The thickness of the sealing layer 1 is 30 mm. The thickness s of the base layer 3 is 20 mm. The sealing layer 1, the sound absorption layer 2 and the base layer 3 are bonded through an adhesive and are integrally cold-pressed and molded.
Example 1
The sound absorption layer and the sealing layer in the sound absorption covering layer are made of PDMS silicone rubber, and the density of the PDMS silicone rubber is 1000kg/m3The complex Young's modulus was (1.879+0.540i) MPa, and the Poisson's ratio was 0.4997. The density of the base layer is 7890kg/m3Young's modulus was 210GPa, and Poisson's ratio was 0.3. Three layers of cylindrical cavities are distributed in the sound absorption covering layer.
The invention relates to a low-frequency sound absorption covering layer containing cylindrical scatterers with parameters changing in a gradient manner and a sound absorption covering layer containing cylindrical cavities with parameters changing in a gradient mannerAnd comparing the low-frequency sound absorption covering layer containing the cylindrical scatterer with the parameters changing in negative gradient. For the sound-absorbing covering layer of the invention containing cylindrical diffusers with gradient parameters: in each unit, the first, second and third layers all contain 1 cylindrical scatterer. The radius of the selected first layer of cylindrical scatterers is r11.5mm, radius r of the second layer of cylindrical scatterers23.5mm, radius of the third layer cylindrical scatterer is r35.5 mm. The cylindrical scatterer in each unit is formed by wrapping two layers of elastic rubber with the same thickness but different modulus on the side surface of a cylindrical cavity, a first layer of coating layer and a second layer of coating layer are sequentially arranged from inside to outside along the radial direction of the cylindrical scatterer, and the thickness c of the first layer of coating layer of the first layer of cylindrical scatterer11And thickness c of the second cladding layer122mm, thickness c of the first cladding layer of the second cylindrical scatterer21And thickness c of the second cladding layer223mm, thickness c of the first cladding layer of the third cylindrical diffuser31And thickness c of the second cladding layer32Is 4 mm; the density and Poisson's ratio of the first coating layer and the second coating layer are the same as the corresponding physical values of the PDMS silicone rubber, the modulus of the first coating layer is 0.1 times of the modulus of the PDMS silicone rubber, and the modulus of the second coating layer is 0.55 times of the modulus of the PDMS silicone rubber. The clear distance between the upper boundary of the sound absorption layer in the selected sound absorption covering layer and the first layer of cylindrical cavity is d1The clear distance between the first layer of cylindrical cavity and the second layer of cylindrical cavity is d which is 29mm2The clear distance between the second layer of cylindrical cavity and the third layer of cylindrical cavity is d3The clear distance between the third layer of cylindrical cavity and the lower boundary of the unit is d which is 20mm410 mm. For the low-frequency sound absorption covering layer containing the cylindrical scatterer with the parameters in negative gradient change, other physical parameters and geometric parameters are the same as those of the low-frequency sound absorption covering layer containing the cylindrical scatterer with the parameters in gradient change, and only the modulus of the sound absorption layer and the sealing layer is different from that of the covering layer of the three cylindrical scatterer layers: the Young's modulus of the sound absorption layer is 0.1 times of the modulus of PDMS silicone rubber, and the modulus of a first layer coating layer of the first layer of cylindrical scatterer is equal to that of the PDMS silicone rubberThe modulus of the glue, the modulus of the second layer coating of the first layer of cylindrical scatterers is equal to 0.55 times of the modulus of the PDMS silicone rubber; the modulus of the first coating layer of the second layer of cylindrical scatterers is equal to the modulus of PDMS silicon rubber, and the modulus of the second coating layer of the second layer of cylindrical scatterers is equal to 0.55 times of the modulus of PDMS silicon rubber; the modulus of the first coating layer of the third layer of cylindrical scatterers is equal to the modulus of PDMS silicon rubber, and the modulus of the second coating layer of the third layer of cylindrical scatterers is equal to 0.55 times of the modulus of PDMS silicon rubber. For the sound absorption covering layer containing the cylindrical cavities with gradient parameters, 3 layers of cylindrical cavities are distributed in each unit, and 1 cylindrical cavity is distributed in each layer; the radius of the selected first layer of cylindrical cavity is r11.5mm, the radius of the second layer cylinder cavity is r23mm, the radius of the third layer of cylindrical cavity is r35.5 mm. The clear distance between the upper boundary of the unit in the sound absorption covering layer and the first layer of cylindrical cavity is d1The clear distance between the first layer of cylindrical cavity and the second layer of cylindrical cavity is d which is 29mm2The clear distance between the second layer of cylindrical cavity and the third layer of cylindrical cavity is d3The clear distance between the third layer of cylindrical cavity and the lower boundary of the unit is d which is 20mm4＝10mm。
Figure 5 is a comparison of the sound absorption characteristics of three sound absorbing overlays. It can be seen that for an acoustically absorbent covering comprising a cylindrical cavity with a gradient of parameters, three absorption peaks occur within the frequency band. The frequency of the first absorption peak is 160Hz, and the peak value is 0.86; the frequency of the second absorption peak was 780Hz, the peak was 0.89 Hz, the frequency of the third absorption peak was 1090Hz, and the peak was 0.94 Hz. The starting frequency of the half sound absorption frequency band (the difference of the frequencies corresponding to half of the peak value of the sound absorption coefficient) of the wide sound absorption frequency band formed by the second absorption peak and the third absorption peak is 630Hz, the cut-off frequency is 1450Hz, and the half sound absorption frequency band width is 820 Hz. The sound absorption covering layer containing the cylindrical scatterer with the parameters changing in a gradient manner is adopted, the frequency of the first absorption peak is 111Hz, and the peak value of the absorption peak is 0.84; the frequency of the second absorption peak is 540Hz, and the peak value is 0.93; the third absorption peak has a frequency of 750Hz and a peak value of 0.92. The second and third absorption peaks form a broad sound absorption band with an initial frequency of 470Hz, a cut-off frequency of 870Hz, and a frequency bandwidth of 400 Hz. Through calculation, compared with the sound absorption covering layer with the same number and the same distance of the cylindrical cavities, the first absorption peak frequency of the sound absorption covering layer with the gradient change of the number and the distance of the cylindrical cavities is reduced by 31.2 percent, and the peak value is reduced by 2.3 percent; the frequency of the second absorption peak is reduced by 30.2 percent, and the peak value is improved by 3.3 percent; the frequency of the third absorption peak is reduced by 31.2%, and the peak value is reduced by 2.1%. For the sound absorption covering layer containing the cylindrical scatterer with the parameters changing in a negative gradient manner, the frequency of the first absorption peak is 151Hz, and the peak value of the absorption peak is 0.92; the frequency of the second absorption peak is 590Hz, and the peak value is 0.99; the third absorption peak had a frequency of 950Hz and a peak value of 0.64. Through calculation, compared with the sound absorption covering layer with the same number and the same distance of the cylindrical cavities, the first absorption peak frequency of the sound absorption covering layer with the gradient change of the number and the distance of the cylindrical cavities is reduced by 31.2 percent, and the peak value is reduced by 2.3 percent; the frequency of the second absorption peak is reduced by 30.2 percent, and the peak value is improved by 3.3 percent; the frequency of the third absorption peak is reduced by 31.2%, and the peak value is reduced by 2.1%. It can be seen that although the first and third absorption peak peaks are somewhat lower in the case of a cylindrical diffuser with a gradient of parameters than in the case of a cylindrical cavity with a gradient of parameters, this is accompanied by a large shift of the three absorption peaks towards lower frequencies, which results in a significant reduction of the sound absorption band. Moreover, the sound absorption frequency band of the sound absorption covering layer containing the cylindrical scatterer with the parameters changing in the gradient manner is lower than the sound absorption frequency band of the sound absorption covering layer containing the cylindrical scatterer with the parameters changing in the negative gradient manner, and the whole sound absorption coefficient is higher, so that the sound absorption covering layer containing the cylindrical scatterer with the parameters changing in the gradient manner can obtain better low-frequency sound absorption effect.
Example 2
The sound absorbing layer and the sealing layer in the sound absorbing covering layer of the embodiment are made of PDMS silicone rubber, and the density of the PDMS silicone rubber is 1000kg/m3The complex Young's modulus was (1.879+0.540i) MPa, and the Poisson's ratio was 0.4997. The density of the base layer is 7890kg/m3Young's modulus was 210GPa, and Poisson's ratio was 0.3. Three-layer cylindrical scattering distributed in sound-absorbing covering layerAnd (3) a body.
Compared with the sound absorption covering layer of the invention, the sound absorption covering layer of the invention has the advantages that the sound absorption covering layer has different thicknesses of the covering layers in two cylindrical scatterers with parameters changing in a gradient manner. For the sound-absorbing covering layer of the invention containing cylindrical diffusers with gradient parameters: in each unit, the first layer, the second layer and the third layer respectively contain 1 cylindrical scatterer; the radius of the selected first layer of cylindrical cavity is r11.5mm, the radius of the second layer cylindrical cavity is r23.5mm, the radius of the third layer of cylindrical cavity is r35.5 mm. The cylindrical scatterer in each unit is formed by wrapping two layers of elastic rubber with the same thickness but different modulus on the side surface of a cylindrical cavity, a first layer of coating layer and a second layer of coating layer are sequentially arranged from inside to outside along the radial direction of the cylindrical scatterer, and the thickness c of the first layer of coating layer of the first layer of cylindrical scatterer11And thickness c of the second cladding layer122mm, thickness c of the first cladding layer of the second cylindrical scatterer21And thickness c of the second cladding layer223mm, thickness c of the first cladding layer of the third cylindrical diffuser31And thickness c of the second cladding layer32Is 4 mm; the density and Poisson's ratio of the first coating layer and the second coating layer are the same as the corresponding physical values of the PDMS silicone rubber, the modulus of the first coating layer is 0.1 times of the modulus of the PDMS silicone rubber, and the modulus of the second coating layer is 0.55 times of the modulus of the PDMS silicone rubber. Clear distance d between upper boundary of sound absorption layer in selected sound absorption covering layer and first layer of cylindrical cavity1Is 29mm, and the clear distance d between the first layer of cylindrical cavities and the second layer of cylindrical cavities2Is 70mm, and the clear distance d between the second layer of cylindrical cavity and the third layer of cylindrical cavity320mm, the clear distance d between the third layer of cylindrical cavities and the lower boundary of the unit4Is 10 mm. For the sound absorption covering layer (the thickness distribution of the covering layer is 2-3-4mm) of the cylindrical scatterer containing parameters with gradient change, which has different distribution, the sound absorption covering layer with the thickness of the covering layer in the two cylindrical scatterers has the same distribution in the distribution condition 1 (the thickness distribution of the covering layer is 3-3-3 mm): thickness of first cladding layer of first cylindrical scattererDegree c11And thickness c of the second cladding layer123mm, thickness c of the first cladding layer of the second cylindrical scatterer21And thickness c of the second cladding layer223mm, thickness c of the first cladding layer of the third cylindrical diffuser31And thickness c of the second cladding layer32Is 3 mm; the distribution 2 (the thickness distribution of the coating layer is 4-3-2mm) is a negative gradient distribution: thickness c of first cladding layer of first cylindrical scatterer11And thickness c of the second cladding layer124mm, thickness c of the first cladding layer of the second cylindrical scatterer21And thickness c of the second cladding layer223mm, thickness c of the first cladding layer of the third cylindrical diffuser31And thickness c of the second cladding layer32Is 2 mm.
Figure 6 is a comparison of the sound absorption characteristics of three sound absorbing overlays. It can be seen that 3 absorption peaks appear in the frequency band range of 1-2000 Hz in all three cases, the frequencies of the three absorption peaks are similar, but the peak value of the third absorption peak has a more obvious difference. The third absorption peak value is 0.92 under the condition that the thickness distribution of the coating layer is 2-3-4 mm; the third absorption peak value is 0.86 under the condition that the thickness distribution of the coating layer is 3-3-3 mm; the third absorption peak had a value of 0.77 for a clad thickness distribution of 4-3-2 mm. It can be shown that when the coating thickness of the three-layer cylindrical scatterer is in positive gradient distribution, the peak value of the absorption peak is relatively equal and the peak value in negative gradient distribution is relatively high, so that the sound absorption effect is better when the coating thickness of the three-layer cylindrical scatterer is in positive gradient distribution.
Claims (10)
1. A low frequency sound absorbing cover layer containing cylindrical scatterers with gradient parameters is characterized in that: comprises a sealing layer (1), a sound absorption layer (2) and a base layer (3); the sound absorption layer (2) is formed by periodically arranging a plurality of same cuboid units, and the sections of the front surface and the rear surface of the units in the sound absorption layer (2) are rectangular; the sealing layer (1) is a cuboid plate and is used for sealing the sound absorption layer (2), and the rear surface of the sealing layer (1) is mutually attached to the front surface of the sound absorption layer (2); the base layer (3) is a cuboid plate, is a shell of a simulated underwater structure, is generally a steel shell, and the upper surface of the base layer (3) is mutually attached to the lower surface of the sound absorption layer (2); in each unit of the sound absorption layer (2), a first layer of cylindrical scatterer (4), a second layer of cylindrical scatterer (5) and a third layer of cylindrical scatterer (6) are distributed from top to bottom: 1 cylindrical scatterer is distributed on the first layer of cylindrical scatterer (4), the second layer of cylindrical scatterer (5) and the third layer of cylindrical scatterer (6); each cylindrical scatterer is formed by wrapping two layers of elastic rubber with the same thickness and different modulus on the side surface of a cylindrical cavity (7).
2. A low frequency sound absorbing cover layer containing cylindrically shaped scatterers having a gradient of parameters as set forth in claim 1 wherein: the sealing layer (1) and the sound absorption layer (2) are both made of PDMS polydimethylsiloxane silicone rubber, and the density of the PDMS polydimethylsiloxane silicone rubber is 1000kg/m3Complex Young's modulus is (1.879+0.540i) MPa, Poisson's ratio is 0.4997; the base layer (3) is made of steel material and has the density of 7890kg/m3Young's modulus was 210GPa, and Poisson's ratio was 0.3.
3. A low frequency sound absorbing cover layer containing cylindrically shaped scatterers having a gradient of parameters as set forth in claim 1 wherein: the front surface of each unit in the sound absorption layer (2) has the length d of 150mm and the width a of 40 mm; for the side surface of each cell in the sound absorption layer (2), the length thereof is 1 m; the thickness of the sealing layer (1) in the front and back surface directions is 30 mm; the thickness s of the base layer (3) in the front and rear surface directions is 20 mm. The sealing layer (1), the sound absorption layer (2) and the base layer (3) are bonded together through an adhesive and are integrally cold-pressed and molded.
4. A low frequency sound absorbing cover layer containing cylindrically shaped scatterers having a gradient of parameters as set forth in claim 1 wherein: each unit in the sound absorption layer (2) is distributed with a first layer of cylindrical scatterer (4), a second layer of cylindrical scatterer (5) and a third layer of cylindrical scatterer (6) from top to bottom, and the axes of the first layer of cylindrical scatterer (4), the second layer of cylindrical scatterer (5) and the third layer of cylindrical scatterer (6) are respectively parallel to the upper surface, the lower surface, the left side surface and the right side surface of the unit; 1 cylindrical scatterer is distributed on the first layer of cylindrical scatterer (4), the second layer of cylindrical scatterer (5) and the third layer of cylindrical scatterer (6), and the length of each cylindrical scatterer is equal and is 1 m.
5. A low frequency sound absorbing cover layer containing cylindrically shaped scatterers with gradient parameters as claimed in claim 4 wherein: every cylindrical scatterer that sound absorption layer (2) contained comprises two-layer different composition's elastic rubber of cylindrical cavity (7) side parcel, is full of the air in cylindrical cavity (7), is first layer cladding (8) and second layer cladding (9) from inside to outside in proper order along cylindrical scatterer's radial.
6. A low frequency sound absorbing cover layer containing cylindrically shaped scatterers with gradient parameters as claimed in claim 4 wherein: the Young modulus of a first coating layer (8) of the first cylindrical scatterer layer (4) is 0.1 time of that of the sound absorption layer (2), and the Young modulus of a second coating layer (9) of the first cylindrical scatterer layer (4) is 0.55 time of that of the sound absorption layer (2); the Young modulus of a first coating layer (8) of the second layer of cylindrical scatterer (5) is 0.1 time of that of the sound absorption layer (2), and the Young modulus of a second coating layer (9) of the second layer of cylindrical scatterer (5) is 0.55 time of that of the sound absorption layer (2); the Young modulus of a first coating layer (8) of the third layer of cylindrical scatterers (6) is 0.1 time of that of the sound absorption layer (2), and the Young modulus of a second coating layer (9) of the third layer of cylindrical scatterers (6) is 0.55 time of that of the sound absorption layer (2); namely, for each cylindrical scatterer, the Young modulus of the cladding layer changes in a positive gradient from inside to outside.
7. A low frequency sound absorbing cover layer containing cylindrically shaped scatterers with gradient parameters as claimed in claim 4 wherein: the first layer of the three-layer cylindrical scatterer in the sound absorption layer (2)Radius r of a cylindrical cavity (7) in a cylindrical diffuser11.5mm, radius r of cylindrical cavity (7) in second layer cylindrical scatterer23.5mm, radius r of cylindrical cavity (7) in the third layer of cylindrical scatterer3The radius of the three-layer cylindrical cavity is changed in a positive gradient way, namely 5.5 mm.
8. A low frequency sound absorbing cover layer containing cylindrically shaped scatterers with gradient parameters as claimed in claim 4 wherein: three layers of cylindrical scatterers in the sound absorption layer (2), namely a first layer of coating layer (8) of the first layer of cylindrical scatterer (4) with the thickness c112mm, the thickness c of the second layer coating (9) of the first cylindrical scattering body (4)122 mm; thickness c of the first cladding layer (8) of the second cylindrical scatterer (5)21A second layer coating (9) thickness c of the second cylindrical scattering body (5) of 3mm223 mm; thickness c of the first cladding layer (8) of the third cylindrical scatterer (6)314mm, the thickness c of the second layer coating (9) of the third cylindrical scattering body (6)324 mm; i.e. for a three-layer cylindrical diffuser, the thickness of the cladding varies with a positive gradient.
9. A low frequency sound absorbing cover layer containing cylindrically shaped scatterers with gradient parameters as claimed in claim 4 wherein: three layers of cylindrical scatterers in the sound absorption layer (2), wherein in the first layer of cylindrical scatterers (4), the distances from the circle center of each cylindrical scatterer to the left boundary and the right boundary of each unit are equal and are 20 mm; in the second layer of cylindrical scatterers (5), the distance from the circle center of each cylindrical scatterer to the left boundary and the right boundary of each unit is equal and is 20 mm; in the third layer of cylindrical scatterers (6), the distance from the circle center of each cylindrical scatterer to the left boundary and the right boundary of each unit is equal and is 20 mm.
10. A low frequency sound absorbing cover layer containing cylindrically shaped scatterers having a gradient of parameters as set forth in claim 2 wherein: for each cell in the sound-absorbing layer (2), the net boundary of the cell with the first layer cylindrical cavity (7)Distance d1The clear distance d between the first layer of cylindrical cavities (7) and the second layer of cylindrical cavities (7) is 29mm270mm, the clear distance d between the second layer of cylindrical cavity (7) and the third layer of cylindrical cavity (7)3The clear distance d between the third layer of cylindrical cavities (7) and the lower boundary of the unit is 20mm410mm, i.e. the clear distance has a negative gradient.
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