CN110808023A - Omnidirectional sound absorption material and device suitable for fluid and preparation method - Google Patents
Omnidirectional sound absorption material and device suitable for fluid and preparation method Download PDFInfo
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- CN110808023A CN110808023A CN201911126442.XA CN201911126442A CN110808023A CN 110808023 A CN110808023 A CN 110808023A CN 201911126442 A CN201911126442 A CN 201911126442A CN 110808023 A CN110808023 A CN 110808023A
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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
- G10K11/161—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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- 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
Abstract
The application relates to an omnidirectional sound absorption material and device suitable for fluid and a preparation method. The omnidirectional sound absorption material comprises a substrate, a sound absorption layer and a sound absorption layer, wherein the substrate has mass density within a first preset range and bulk modulus within a second preset range, and is used for collecting sound waves incident from the outside; and at least one sound absorption unit embedded in the substrate, wherein the sound absorption unit is used for absorbing sound waves collected by the substrate. Above-mentioned acoustic material of qxcomm technology through with at least one sound absorption unit embedding to the substrate, can all realize the absorption effect of preferred to the sound wave of equidirectional incident simultaneously, just the substrate shape can be arbitrary, and the embedding position of sound absorption unit also can be arbitrary, and consequently this acoustic material of qxcomm technology's application scope is also comparatively extensive.
Description
Technical Field
The invention relates to the technical field of acoustic materials, in particular to an omnidirectional sound absorption material and device suitable for fluid and a preparation method.
Background
Acoustic wave research has been conducted for centuries. Among them, the research on sound wave absorption has been a hot spot in the acoustic field, which is very important in both engineering applications and defense and military.
The impedance of conventional sound absorbing materials cannot be directly matched to the background medium (e.g., air, water, etc.), and thus, they absorb sound while reflecting sound. In order to reduce the reflected sound wave to achieve a better sound wave absorption effect, researchers have proposed many methods. For example:
(1) the reflection is eliminated by realizing impedance matching by designing an antireflection film with the thickness of a quarter wavelength or designing a microstructure on the surface and the like, so that the sound wave absorption rate is improved;
(2) better absorption of sound waves is achieved by using a porous material (such as a sound absorbing sponge);
(3) based on the characteristics of the acoustic metamaterial, the acoustic wave absorption is realized.
However, the three methods have a relatively narrow application range because the absorption rates of the sound waves incident in different directions are not uniform, and the absorption effects of the sound waves are only good for the sound waves meeting the conditions of specific incident directions.
Disclosure of Invention
Based on this, it is necessary to provide an improved omnidirectional sound absorption material suitable for fluid, aiming at the problem that the absorption effect of the traditional sound absorption material for the sound waves incident from different directions is different.
An omnidirectional sound absorbing material suitable for use with a fluid, comprising:
the acoustic wave sensor comprises a substrate, a sensor and a sensor, wherein the substrate has mass density within a first preset range and bulk elastic modulus within a second preset range and is used for collecting acoustic waves incident from the outside; and the number of the first and second groups,
the sound absorption unit is embedded in the substrate and used for absorbing sound waves collected by the substrate.
Above-mentioned acoustic material of qxcomm technology, through with at least one sound absorption unit embedding to the substrate, can all realize the absorption effect of preferred to the sound wave of equidirectional incident simultaneously, just the substrate shape can be arbitrary, the embedding position of at least one sound absorption unit also can be arbitrary, and application scope is wide, and technical staff can adjust the shape of this acoustic material of qxcomm technology and the embedding position of acoustic material according to practical application to make it satisfy the adaptation demand of device.
In one embodiment, the mass density of the substrate is less than or equal to one tenth of the mass density of the ambient fluid, and the inverse of the bulk modulus of elasticity of the substrate is less than or equal to one tenth of the inverse of the bulk modulus of elasticity of the ambient fluid.
In one embodiment, the omnidirectional sound absorbing material satisfies the following relationship:
wherein N represents the total number of sound waves incident to the omnidirectional sound absorbing material, ρinDenotes the mass density, κ, of the ambient fluidinRepresenting the bulk modulus of elasticity, omega, of the surrounding fluidnIs the width of the n-th incident sound wave, udIndicating a displacement unit, phi u, on the boundary of the sound-absorbing unitdDl denotes the displacement unit udLine integrals along the boundary of the sound-absorbing unit.
In one embodiment, the substrate comprises a dielectric phononic crystal formation.
In one embodiment, the sound absorbing material comprises at least one of sound absorbing sponge, rock wool, rubber, or perforated sound absorbing sheet.
In one embodiment, when the number of incident sound waves is greater than or equal to 2, the phase difference of the omnidirectional sound absorption material is equal to or less than
To
The absorption of incident sound waves in the range is greater than 95%.
In one embodiment, when the number of incident sound waves is greater than or equal to 2, the absorption rate of the omnidirectional sound absorption material to incident sound waves with the same phase is greater than 99%.
The application also provides an omnidirectional sound absorption device.
An omnidirectional sound absorption device comprises a shell, wherein the shell is made of the omnidirectional sound absorption material.
Above-mentioned omnidirectional sound absorption device can all realize the absorption of preferred to the incident sound wave of external different directions simultaneously to need not to set up a plurality of sound absorbing material in the equidirectional incident sound wave of absorbing different directions respectively, alright will treat the sound insulation object and isolated with incident sound wave, the preparation cost of omnidirectional sound absorption device that has significantly reduced.
In one embodiment, the housing has a cavity for receiving an object to be insulated.
The application also provides a preparation method of the omnidirectional sound absorption material suitable for the fluid.
A method of making an omnidirectional sound absorbing material suitable for use with a fluid, comprising:
providing a substrate with mass density within a first preset range and bulk modulus within a second preset range for collecting external incident sound waves;
at least one sound absorbing element is embedded within the substrate.
According to the preparation method, at least one sound absorption unit is embedded into the substrate for collecting external incident sound waves, so that better absorption effects can be realized on the incident sound waves in different directions.
In one embodiment, providing a substrate having a mass density in a first predetermined range and a bulk modulus of elasticity in a second predetermined range specifically includes:
providing a dielectric phononic crystal;
and adjusting the size, the mass density and the bulk modulus of each material in the dielectric photonic crystal so as to enable the equivalent mass density of the dielectric photonic crystal to be within the first preset range and the equivalent bulk modulus to be within the second preset range.
In one embodiment, the mass density of the substrate is less than or equal to one tenth of the mass density of the ambient fluid, and the inverse of the bulk modulus of elasticity of the substrate is less than or equal to one tenth of the inverse of the bulk modulus of elasticity of the ambient fluid.
Drawings
FIG. 1 is a schematic structural diagram of an embodiment of the present application;
FIG. 2 is a sound pressure field diagram of two incident sound waves in different directions incident on another embodiment of the present application;
FIG. 3 is a sound pressure field diagram of three incident sound waves in different directions incident on the embodiment of FIG. 2;
FIG. 4 is a graph showing the variation of the acoustic absorption rate with the phase difference when two incident acoustic waves with different directions are incident on the embodiment of FIG. 2;
fig. 5 is a sound pressure field diagram of two incident sound waves with different directions incident on another embodiment of the present application.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. As used herein, the terms "vertical," "horizontal," "left," "right," "upper," "lower," "front," "rear," "circumferential," and the like are based on the orientation or positional relationship shown in the drawings for ease of description and simplicity of description, and do not indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the present invention.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
The traditional sound absorption materials (such as sound absorption sponges) have different absorption effects on sound waves incident in different directions, and only have high absorption rate on the sound waves meeting the specific incident direction, so that the sound waves cannot be absorbed in all directions. The omnidirectional absorption herein means that the sound waves incident in different directions have better absorption effect, for example, the sound waves incident in different directions have absorption rate of more than 95%.
Technical personnel also realize coherent perfect absorption of the two sound waves by using the acoustic metamaterial, however, the acoustic wave coherent absorber is only suitable for the condition of two incident sound waves and is not suitable for the condition of more than two incident sound waves; in addition, the shape and size of the coherent acoustic wave absorber also affect the absorption efficiency of the acoustic wave, and the design and manufacturing difficulty is easily increased, so that the preparation cost is increased.
The defects existing in the above schemes are the results obtained after the inventor practices and researches carefully. Therefore, the discovery process of the above-mentioned problems and the solution proposed by the embodiments of the present application in the following description should be the contribution of the inventor to the present application in the course of the present application.
Referring to fig. 1, an omnidirectional sound absorption material 100 suitable for use in a fluid is provided in an embodiment of the present application. The omnidirectional sound absorption material 100 can simultaneously achieve a better absorption effect on a plurality of sound waves incident in different directions. The omnidirectional sound absorbing material 100 includes a substrate 10 and at least one sound absorbing unit 20 embedded within the substrate 10.
The substrate 10 is a dual zero acoustic material. Specifically, a double-zero acoustic material refers to a material in which the mass density and the inverse of the bulk modulus are both close to zero, and generally has the characteristics that the wavelength of sound waves tends to infinity, and the pressure intensity is uniformly distributed in space. In this embodiment, the mass density of the substrate 10 is in a first predetermined range, and the bulk modulus of elasticity is in a second predetermined range, so as to collect the sound waves incident to the substrate 10 from different external directions, and not form reflected sound waves or form very small reflected sound waves. It should be noted that the shape and size of the double-zero acoustic material do not affect the effect of collecting the incident sound wave, whether the collection of the incident sound wave is complete or not is related to the degree that the inverse of the mass density and the bulk modulus of the double-zero acoustic material are close to zero, and the more complete the collection of the incident sound wave is as the inverse of the mass density and the bulk modulus of the double-zero acoustic material are close to zero.
The sound absorption unit 20 serves to absorb sound waves collected by the substrate 10. Specifically, the sound absorption unit 20 may be made of a conventional sound absorption material, such as a sound absorption sponge or a porous medium plate. It should be noted that the embedding position of the sound absorption unit 20 in the substrate 10 does not affect the sound absorption effect of the omnidirectional sound absorption material 100, and whether the absorption of sound waves in the substrate 10 is completely related to the coverage area of the sound absorption unit 20 in the substrate 10 and the sound absorption effect thereof, which is related to the mass density and the bulk modulus thereof. The larger the area covered by the sound absorption unit 20 in the substrate 10, the better the sound absorption effect itself, and the more thoroughly the sound wave in the substrate 10 is absorbed.
Above-mentioned omnidirectional sound absorption material 100, after embedding at least one sound absorption unit 20 in substrate 10, the sound wave of different direction incidences can be absorbed by each sound absorption material in substrate 10 after being gathered by substrate 10, thereby can all realize better absorption effect to the sound wave of different direction incidences simultaneously, and the shape of substrate 10 can be arbitrary, the embedding position of sound absorption unit 20 also can be arbitrary, therefore the application scope of this omnidirectional sound absorption material 100 is wider, technical staff can adjust the shape of this omnidirectional sound absorption material 100 and the embedding position of sound absorption unit 20 according to the structure of the device of practical application, in order to satisfy the adaptation demand of device.
In some embodiments, the mass density of the substrate 10 is less than or equal to one tenth of the mass density of the ambient fluid, and the inverse of the bulk modulus of elasticity of the substrate 10 is less than or equal to one tenth of the inverse of the bulk modulus of elasticity of the ambient fluid. By controlling the mass density and the bulk modulus of the substrate 10 to satisfy the above relationship, the substrate 10 can have better characteristics of a double-zero acoustic material, which is beneficial to more completely collect sound waves incident from different directions in the external fluid.
In some embodiments, the omnidirectional sound absorbing material 100 satisfies the following relationship:
wherein N represents the total number of sound waves incident to the omnidirectional sound absorbing material, ρinDenotes the mass density, κ, of the ambient fluidinRepresenting the bulk modulus of elasticity, omega, of the surrounding fluidnIs the width of the n-th incident sound wave, udIndicating a unit of displacement phi u at the boundary of the sound-absorbing unit 20dDl denotes the displacement unit udLine integrals along the boundary of the sound-absorbing unit 20.
Under the condition of satisfying the above relational expression, the absorption rate of the omnidirectional sound absorption material 100 to sound waves is close to 100%, and at this time, the phases of incident sound waves in different directions are the same or very close to each other, thereby realizing coherent perfect absorption of sound waves. As can be seen from this formula, the above formula can be satisfied by selecting different sound absorbing units 20, knowing the total width of all incident sound waves, so as to achieve perfect absorption of all incident sound waves. In addition, it can be seen from the formula that the formula is independent of the shape and size of the substrate 10 and independent of the position of embedding the sound absorbing unit 20 in the substrate 10.
Further, the mass density ρ of the substrate 10 is not more than 0.1 ρinInverse of bulk modulus of elasticity
Thereby ensuring that the incident acoustic waves are completely picked up by the substrate 10.
In some embodiments, the substrate 10 includes a dielectric phononic crystal. Phononic crystals refer to materials or structures having a periodic distribution of bulk modulus of elasticity and mass density. The dielectric phononic crystal means that it is formed by a periodic arrangement of dielectric materials. According to the equivalent medium theory, the phononic crystal has an equivalent mass density and an equivalent bulk elastic modulus, and the equivalent mass density and the equivalent bulk elastic modulus are related to the size, the mass density and the bulk elastic modulus of each material in the phononic crystal, so that the size, the mass density and the bulk elastic modulus of each material in the phononic crystal can be adjusted according to a related formula of the equivalent medium theory, so that the equivalent mass density and the equivalent bulk elastic modulus of the dielectric phononic crystal are respectively in a first preset range and a second preset range.
In some embodiments, the sound absorbing unit 20 also includes other acoustic materials having sound absorbing properties, such as rock wool, rubber, perforated sound absorbing panels, and the like. The acoustic materials are common materials in daily life, so that the preparation of the omnidirectional sound absorption material is facilitated.
In some embodiments, when the number of incident sound waves is greater than or equal to 2, the omnidirectional sound absorbing material 100 is at a phase differenceTo
The absorption of incident sound waves in the range is greater than 95%. For example, the phase difference may be
Or
In particular, when the phases of the incident sound waves are the same (i.e., the phase difference is 0), the sound wave absorption rate of the omnidirectional sound absorption material 100 is greater than 99% and close to 100%.
Three specific examples are shown below to further illustrate the sound absorption effect of the omnidirectional sound absorption material of the present application. The relevant sound pressure field pattern was simulated by COMSOL multiphysics simulation software.
Detailed description of the preferred embodiment 1
Referring to fig. 2, sound waves are incident to a substrate 10 from two directions, the width of an incident sound wave 1 is 0.8m, the width of an incident sound wave 2 is 0.4m, the phase difference between the incident sound wave 1 and the incident sound wave 2 is 0, a sound absorption unit 20 is arranged in a circular shape (with a radius of 0.4m) and embedded inside the substrate 10, the bulk modulus of elasticity of the sound absorption unit 20 is set to be a complex number in calculation, the magnitude of the imaginary part reflects the intensity of the sound absorption energy, and perfect absorption (i.e. absorption rate close to 100%) can be obtained by adjusting the magnitude of the real part and the imaginary part of the bulk modulus of elasticity. In addition, the external fluid is disposed as air, and the wavelength of the incident sound wave in the air is 1 m.
As can be seen from fig. 2, after incident sound waves 1 and 2 are incident to the omnidirectional sound absorbing material 100, both are collected by the substrate 10 and distributed to the sound absorbing unit 20 for absorption. As can be seen from fig. 2, the sound pressure in the sound absorption unit 20 is very small, which means that both the incident sound wave 1 and the incident sound wave 2 are absorbed by the sound absorption unit 20 after entering the substrate 10, so that a better omnidirectional sound absorption effect is obtained.
Fig. 4 shows the variation of the acoustic absorption rate of the two incident acoustic waves in different directions with the phase difference. Since the absorption rates of the incident acoustic wave 1 and the incident acoustic wave 2 are the same, the absorption rates of the two can be represented by a curve.
As shown in fig. 4, when the phase difference between the two incident sound waves is in
To
When in range, the absorption rate is more than 95%; when the phase difference of the two incident sound waves is an integral multiple of 0 or 2 pi (namely 360 degrees), the two incident sound waves can be perfectly absorbed, and the absorption rate is greater than 99% and is close to 100%.
On the other hand, as can be seen from fig. 4, the sound wave absorption rate of the omnidirectional sound absorption material 100 can be adjusted by changing the phase difference between the incident sound waves in different directions. For example, when the phase difference between two incident acoustic waves is controlled to be pi (i.e., 180 °), the two incident acoustic waves are in anti-phase, and the absorption rate of the acoustic wave is the lowest. Of course, the sound wave absorption rate of the omnidirectional sound absorption material 100 can also be adjusted by embedding a non-sound absorption material (e.g., silica gel) in the substrate 10, which can be specifically selected according to the actual needs and the actual application scenarios, and the present application is not limited thereto.
Specific example 2
The present embodiment will omit a description partly identical to that of embodiment 1. Referring to fig. 3, sound waves are incident to the substrate 10 from three directions, the width of the incident sound wave 1 is 0.8m, the width of the incident sound wave 2 is 0.4m, the width of the incident sound wave 3 is 0.4m, the phases of the incident sound wave 1, the incident sound wave 2 and the incident sound wave 3 are the same, the arrangement of the sound absorbing material and the external fluid is the same as that of embodiment 1, and the wavelength of the incident sound wave in the air is 1 m.
As can be seen from fig. 3, after incident sound waves 1, 2 and 3 are incident to the omnidirectional sound absorption material 100, they are collected by the substrate 10 and distributed to the sound absorption unit 20 for absorption. As can be seen from fig. 2, the sound pressure in the sound absorption unit 20 is very small, which means that the incident sound wave 1, the incident sound wave 2, and the incident sound wave 3 are all absorbed by the sound absorption unit 20 after entering the substrate 10, so that a better omnidirectional sound absorption effect is obtained.
Specific example 3
Referring to fig. 5, after the shape of the substrate 10 is changed, sound waves are incident to the substrate 10 from two directions, the width of the incident sound wave 1 is 0.8m, the width of the incident sound wave 2 is 0.4m, the phase difference between the incident sound wave 1 and the incident sound wave 2 is 0, and the sound absorption unit 20 is configured to be circular (with a radius of 0.4m) and embedded inside the substrate 10. The external fluid is arranged as air, and the wavelength of the incident sound wave in the air is 1 m.
As can be seen from fig. 5, after incident sound waves 1 and 2 are incident to the omnidirectional sound absorbing material 100, they can still be collected by the substrate 10 and distributed to the sound absorbing unit 20 for absorption. As can be seen from fig. 5, the sound pressure in the sound absorption unit 20 is very small, which means that both the incident sound wave 1 and the incident sound wave 2 are absorbed by the sound absorption unit 20 after entering the substrate 10, so that a better omnidirectional sound absorption effect is obtained.
The application also provides a preparation method of the omnidirectional sound absorption material suitable for the fluid, which comprises the following steps:
s100, providing a substrate with mass density within a first preset range and bulk modulus within a second preset range, and collecting external incident sound waves;
specifically, the substrate is preferably a dual-zero acoustic material, namely the mass density of the substrate is less than or equal to one tenth of the mass density of the external fluid, and the reciprocal of the bulk modulus of elasticity of the substrate is less than or equal to one tenth of the reciprocal of the bulk modulus of elasticity of the external fluid;
further, the substrate may be obtained by,
s101, providing a dielectric phononic crystal;
s102, adjusting the size, the mass density and the bulk modulus of each material in the dielectric photonic crystal to enable the equivalent mass density of the dielectric photonic crystal to be within a first preset range and the equivalent bulk modulus to be within a second preset range;
the first preset range refers to that the mass density of the substrate is less than or equal to one tenth of the mass density of the external fluid, and the second preset range refers to that the reciprocal of the bulk elastic modulus of the substrate is less than or equal to one tenth of the reciprocal of the bulk elastic modulus of the external fluid;
s200, embedding at least one sound absorption unit into the substrate;
in particular, the sound absorbing material may be a sound absorbing sponge or an acoustic material having sound absorbing properties.
According to the preparation method, at least one sound absorption unit is embedded into the substrate for collecting external incident sound waves, so that a good absorption effect can be realized on the incident sound waves in different directions, and the sound absorption effect of the omnidirectional sound absorption material can be regulated and controlled by controlling the phase difference between the sound waves in different incident directions.
The present application further provides an omnidirectional sound absorption apparatus comprising a housing made of the omnidirectional sound absorption material as described above. Specifically, the housing has various shapes, and can be in a sheet shape, a cylindrical shape or a semi-closed shape. The object to be sound-insulated is arranged on the inside of the housing, which is directed towards the side on which the sound waves are incident.
Above-mentioned omnidirectional sound absorption device can all realize the absorption of preferred to the incident sound wave of external different directions simultaneously to need not to set up a plurality of sound absorbing material in the equidirectional incident sound wave of absorbing different directions respectively, alright will treat the sound insulation object and isolated with incident sound wave, the preparation cost of omnidirectional sound absorption device that has significantly reduced.
Further, the housing has a cavity for receiving an object to be insulated. After the object to be insulated is placed in the cavity, the sound wave isolation effect can be further ensured, and the complete sound insulation environment is favorably formed.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (12)
1. An omnidirectional sound absorbing material adapted for use with a fluid, comprising:
the acoustic wave sensor comprises a substrate, a sensor and a sensor, wherein the substrate has mass density within a first preset range and bulk elastic modulus within a second preset range and is used for collecting acoustic waves incident from the outside; and the number of the first and second groups,
the sound absorption unit is embedded in the substrate and used for absorbing sound waves collected by the substrate.
2. The omnidirectional sound absorber of claim 1, wherein the substrate has a mass density of less than or equal to one tenth of a mass density of the ambient fluid, and wherein the substrate has an inverse bulk modulus of elasticity of less than or equal to one tenth of an inverse bulk modulus of elasticity of the ambient fluid.
3. The omnidirectional sound absorbing material of claim 1 or 2, wherein the omnidirectional sound absorbing material satisfies the following relationship:
wherein N represents the total number of sound waves incident to the omnidirectional sound absorbing material, ρinDenotes the mass density, κ, of the ambient fluidinRepresenting the bulk modulus of elasticity, omega, of the surrounding fluidnIs the width of the n-th incident sound wave, udA displacement unit representing a boundary of the sound absorption unit,indicating a displacement unit udLine integrals along the boundary of the sound-absorbing unit.
4. An omnidirectional sound absorbing material according to claim 1 or 2, wherein said substrate comprises a dielectric phononic crystal.
5. The omnidirectional sound absorbing material of claim 1, wherein the sound absorbing unit comprises at least one of sound absorbing sponge, rock wool, rubber, or perforated sound absorbing sheet.
6. The omnidirectional sound absorption material according to claim 1 or 2, wherein when the number of incident sound waves is 2 or more, the omnidirectional sound absorption material is at a phase difference
To
The absorption of incident sound waves in the range is greater than 95%.
7. The omnidirectional sound absorption material of claim 6, wherein when the number of incident sound waves is greater than or equal to 2, the absorption rate of the omnidirectional sound absorption material to incident sound waves with the same phase is greater than 99%.
8. An omnidirectional sound absorbing apparatus, comprising a housing made of the omnidirectional sound absorbing material as recited in any one of claims 1 to 7.
9. The omnidirectional sound absorbing apparatus of claim 8, wherein the housing has a cavity for receiving an object to be insulated.
10. A method of making an omnidirectional sound absorbing material suitable for use with a fluid, comprising:
providing a substrate with mass density within a first preset range and bulk modulus within a second preset range for collecting external incident sound waves;
at least one sound absorbing element is embedded within the substrate.
11. The method for preparing a substrate according to claim 10, wherein providing a substrate having a mass density in a first predetermined range and a bulk modulus of elasticity in a second predetermined range comprises:
providing a dielectric phononic crystal;
and adjusting the size, the mass density and the bulk modulus of each material in the dielectric photonic crystal so as to enable the equivalent mass density of the dielectric photonic crystal to be within the first preset range and the equivalent bulk modulus to be within the second preset range.
12. The production method according to claim 10 or 11, wherein the mass density of the substrate is one tenth or less of the mass density of the external fluid, and the inverse number of the bulk modulus of elasticity of the substrate is one tenth or less of the inverse number of the bulk modulus of elasticity of the external fluid.
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