Acoustic metamaterial absorber

Abstract

The present invention discloses an acoustic metamaterial absorber, which comprises an upper layer structure and a lower layer structure. Among them, the upper layer structure includes an upper layer matrix, and a plurality of circular holes distributed in a line array or a surface array are formed on the upper layer matrix. A thin film with a preset tension covering the circular holes is arranged on the upper surface of the upper layer matrix. A first permanent magnet located at the center position of the circular hole is pasted on the thin film. A closed metal ring surrounding the circular hole is arranged on the lower surface of the upper layer matrix; the lower layer structure includes a lower layer matrix supported by a frame, and a second permanent magnet is arranged at a position corresponding to the circular hole on the lower layer matrix. The magnetic pole directions of the first permanent magnet and the second permanent magnet are the same; the upper layer structure and the lower layer structure are bonded to form an integral structure. The present invention can achieve better sound absorption and noise reduction effects.

Description

Technical Field

[0001] The present invention relates to the technical field of sound-absorbing materials, and particularly to an acoustic metamaterial absorber. Background Art

[0002] Most sound-absorbing materials are porous materials, such as slag wool, blankets, etc. The sound-absorbing mechanism is that sound waves penetrate into the pores of the material, and most of the pores are open pores that communicate with each other inside. Due to the friction and viscous resistance of air molecules, and the mechanical vibration of fine fibers, the sound energy is converted into heat energy. However, the sound-absorbing performance of ordinary porous materials is limited and often cannot achieve the desired effect. Summary of the Invention

[0003] The main object of the present invention is to provide an acoustic metamaterial absorber to achieve better sound absorption and noise reduction effects.

[0004] The acoustic metamaterial absorber provided by the present invention includes an upper structure and a lower structure. Among them, the upper structure includes an upper substrate, and a plurality of circular holes are formed in the upper substrate in a linear array or a planar array. A thin film with a preset tension covering the circular holes is arranged on the upper surface of the upper substrate. A first permanent magnet located at the center of the circular hole is pasted on the thin film. A closed metal ring surrounding the circular hole is arranged on the lower surface of the upper substrate; the lower structure includes a lower substrate with a frame support, and a second permanent magnet is arranged at a position corresponding to the circular hole on the lower substrate. The magnetic pole directions of the first permanent magnet and the second permanent magnet are the same; the upper structure and the lower structure are bonded to form an integral structure.

[0005] Optionally, both the upper substrate and the lower substrate are in the form of a film or a thin sheet. The thickness of the upper substrate is greater than the thickness of the lower substrate, and the thickness of the lower substrate is slightly greater than the thickness of the thin film.

[0006] Optionally, the first permanent magnet is a cylindrical permanent magnet magnetized along the axial direction, and its upper surface is pasted on the lower surface of the thin film.

[0007] Optionally, the second permanent magnet is a circular thin film or a thin sheet-shaped permanent magnet magnetized along the axial direction, with a diameter slightly larger than the diameter of the circular hole, and its upper surface is pasted on the lower surface of the lower substrate.

[0008] Optionally, the metal ring is made of copper or soft ferromagnetic material.

[0009] Optionally, the materials of the upper substrate and the lower substrate are selected from polyimide, polyether ether ketone, polyether imide, and polyethylene naphthalate.

[0010] In summary, the present invention provides an acoustic metamaterial absorber. A film with a preset tension (referred to as a circular-hole film) is pasted on each circular hole in the upper-layer structure. A first permanent magnet with a certain mass is pasted at the center of each circular-hole film. A closed metal ring is fixed on the upper-layer matrix around each circular hole. And a corresponding axially magnetized second permanent magnet is installed on the lower-layer matrix at a coaxial position corresponding to each circular hole, jointly constituting a unit. This unit is a resonant unit and has the following functions:

[0011] When the sound pressure of an external sound signal acts on the circular-hole films, the first cylindrical permanent magnet with a certain mass pasted at the center of the circular-hole film and the closed metal ring fixed on the upper-layer matrix will have relative motion, and an induced electromotive force (or current) will be generated in the closed metal ring as the magnitude of the moving speed of the first permanent magnet changes. This current will generate a corresponding magnetic field. The generated magnetic field is opposed to the motion of the first permanent magnet, and this magnetic field also interacts with the corresponding axially magnetized second permanent magnet installed in the lower-layer structure. This interaction is also opposed, so that the second permanent magnet makes a corresponding motion and consumes energy.

[0012] As can be seen from the above, this is a process in which the external sound energy drives the motion of the first permanent magnet. The magnetic field acts on the closed metal ring and is transformed into an induced electromotive force (current) to become electrical energy. Then, the current flowing through the closed metal ring generates a magnetic field to become magnetic energy (part of the energy will be transformed into heat energy). Then, due to the interaction between this magnetic field and the second permanent magnet in the lower-layer structure, the second permanent magnet makes a corresponding motion and consumes energy. Thus, the functions of sound absorption, noise reduction, and shock absorption are achieved. Compared with ordinary sound-absorbing materials, the present invention improves the efficiency of converting sound energy into kinetic energy and heat energy, and can achieve a better sound absorption and noise reduction effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for describing the embodiments and the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0014] Figure 1 is the schematic diagram of the principle without a resonant unit;

[0015] Figure 2 is the schematic diagram of the principle with a resonant unit;

[0016] Figure 3 is the structural schematic diagram of the acoustic metamaterial absorber provided by the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] To enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0018] In the description and claims of the present invention and the above-mentioned accompanying drawings, the terms "first", "second", "third", etc. are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products or devices.

[0019] The solution of the present invention will be described in detail below through specific embodiments.

[0020] In existing acoustic metamaterials, for the structural model of a general spring-mass oscillator, the oscillator is just a simple massless resonant unit, as Figure 1 shown.

[0021] The embodiment of the present invention provides such an acoustic metamaterial absorber, whose structural model includes a resonant unit, and its schematic diagram is as Figure 2 shown.

[0022] Therefore, the acoustic metamaterial absorber of the embodiment of the present invention has a unit structure as Figure 3 shown, including an upper structure and a lower structure. The upper structure includes an upper substrate, a thin film, a first permanent magnet, and a metal ring. The lower structure includes a lower substrate and a second permanent magnet. The upper and lower structures are combined to form the acoustic metamaterial absorber.

[0023] As Figure 3 shown, 1 represents the upper structure, 13 is the upper substrate in the form of a thick film or a thin sheet, 10 are regularly distributed round holes opened on the upper substrate, 11 is a flexible thin film with a preset tension pasted on the round holes of the upper substrate, 12 is a cylindrical first permanent magnet with a certain mass (denoted as mass m), and 14 is a closed metal ring fixed on the upper substrate; 2 represents the lower structure, 21 is the lower substrate in the form of a thick film or a thin sheet, with a frame support and slightly thicker than the thin film of the upper layer, and 22 is a film or thin sheet-shaped second permanent magnet with an axial magnetization slightly larger than the diameter of the round holes on the upper substrate.

[0024] As can be seen from the above, the acoustic metamaterial absorber according to the embodiment of the present invention includes upper and lower layer structures. The upper layer structure mainly includes an upper substrate in the form of a thick film (thin sheet), on which a plurality of circular holes (the diameter of the circular hole is denoted as D, and the center distance of the circular holes is denoted as L) regularly distributed in a line array or a surface array can be provided. A flexible and well-tensioned thin film (or called circular hole thin film) with a preset tension is pasted on the circular holes, and a cylindrical small permanent magnet (denoted as the first permanent magnet) with a certain mass (denoted as m) is pasted at the center of each circular hole thin film. Around the circular holes of the upper substrate, a closed metal ring (the inner diameter of the metal ring is D, and the outer diameter is D + d) is fixed on the upper substrate.

[0025] Optionally, the tension of the thin film pasted on the circular holes of the substrate can be controlled by the following method: First, take a large-sized diaphragm cup used for manufacturing the diaphragm of a condenser microphone, measure the relationship between the resonance frequency and the tension, adjust the required tension to the required x N / m (for example: 7 N / m), and then bond the upper substrate with regularly distributed circular holes in a line array or a surface array on the diaphragm ring. After the adhesive is cured, cut it with a cutter for later use.

[0026] The lower layer structure mainly includes a lower substrate in the form of a thick film or a thin sheet with a frame support, which is slightly thicker than the upper thin film. The thickness of the lower substrate is less than that of the upper substrate. Second permanent magnets are installed at positions corresponding to the circular holes of each upper substrate (coaxial correspondence) on the lower substrate. The second permanent magnets can be permanent magnets in the form of thin films or thin sheets with an axial magnetization and a diameter slightly larger than that of the circular holes of the upper substrate.

[0027] Finally, the upper and lower layer structures are bonded to form an integral structure. This constitutes an acoustic metamaterial absorber in the form of a composite thick film (thin sheet). Among them, the magnetic pole directions of the first permanent magnet and the second permanent magnet are the same, that is, if the magnetic poles on the upper and lower surfaces of the first permanent magnet are NS respectively, then the magnetic poles on the upper and lower surfaces of the second permanent magnet are also NS respectively; conversely, if the magnetic poles on the upper and lower surfaces of the first permanent magnet are SN respectively, then the magnetic poles on the upper and lower surfaces of the second permanent magnet are also SN respectively.

[0028] In the embodiment of the present invention, a thin film with a preset tension is pasted on the circular holes of the upper substrate, and a cylindrical and relatively small first permanent magnet with a certain mass (for example, the mass m is 0.3 g) is pasted at the center of each circular hole thin film. A closed metal ring (the inner diameter of the metal ring is D, and the outer diameter is D + d) fixed on the upper substrate around the circular holes of the upper substrate and the second permanent magnets on the lower substrate with a frame support and slightly thicker than the upper thin film together form a resonant unit. Coupled with the regular distribution of the line array or the surface array, the characteristics of its acoustic metamaterial are formed. It can be seen that the present invention is a derivative structure with a resonant unit structure.

[0029] Around the circular hole of the upper substrate, a closed metal ring is fixed on the upper substrate. There are two considerations for the selection of the material of the metal ring: one is to use copper because the resistivity of copper is small and it has no influence on the external magnetic field; the other is to use soft ferromagnetic materials, which have good effects when under the action of an external magnetic field and have no residual magnetism after the external magnetic field is removed. These two materials can be weighed and selected.

[0030] The material of the substrate (including the upper substrate and the lower substrate) can consider the following materials. For example: Polyimide (the trade name of DuPont is Kapton), an amorphous material, which is difficult to be hot-pressed (it can withstand high temperatures above 400 °C, and the long-term use temperature range is -200 to 300 °C). Another example: Polyetheretherketone (PEEK, poly-ether-ether-ketone, the trade name of Victrex is Aptiv PEEK), a semi-crystalline polymer material, with a melting point of 343 °C, a softening point of 168 °C, and a tensile strength of 132 - 148 MPa. PEEK has a relatively high glass transition temperature (Tg = 143 °C) and melting point (Tm = 343 °C), its heat deflection temperature under load is as high as 316 °C, and the instantaneous use temperature can reach 300 °C. Another example: Polyetherimide (PEI, Polyetherimide) has a heat deflection temperature of 220 °C and can be used for a long time at a working temperature of -160 - 180 °C. And, Polyethylene naphthalate (PEN, Polyethylene naphthalate), with a melting point of 265 degrees, similar to PET, and its glass transition temperature is above 120 degrees, about 50 degrees higher than PET. The above are all basic forms of materials, which can be further made into modified materials by adding minerals, glass fibers, carbon fibers, etc. to meet the needs of different uses. In addition, multiple layers of thin films can be bonded together with a certain glue to form a composite film to improve the acoustic performance.

[0031] As described above, the structure and material of the acoustic metamaterial absorber in the embodiment of the present invention have been described. Next, the technical characteristics of the solution of the present invention will be continued to be introduced.

[0032] (1) A relatively small cylindrical first permanent magnet with a certain mass pasted at the center of each circular hole film and a closed metal ring fixed on the upper substrate must have relative movement. The technologies adopted in the present invention include: one is that the closed metal ring is fixed on the upper substrate; the other is that the film with a cylindrical first permanent magnet with a certain mass pasted at the center of each circular hole is flexible, easy to deform, and the tension can be controllably adjusted. It ensures that when the sound pressure of the incoming sound signal acts on each circular hole film and the cylindrical first permanent magnet with a certain mass pasted at its center, it will not move simultaneously with the closed metal ring fixed on the upper substrate, and ensures that there will be relative movement between the two.

[0033] (2) When the sound pressure of an external sound signal acts on each circular-hole thin film and the cylindrical first permanent magnet with a certain mass pasted on its central part, there will be relative movement between the first permanent magnet and the closed metal ring fixed on the base body. An electromotive force (current) is generated in the closed metal ring as the moving speed of the first permanent magnet changes. This current will generate a corresponding magnetic field, and the generated magnetic field is in opposition to the movement of the first permanent magnet. Moreover, the generation of this magnetic field interacts with the corresponding axially magnetized first permanent magnet installed in the lower layer, and this interaction is also in opposition. Since the closed metal ring in the upper layer is fixed on the upper base body, while the lower base body in the form of a film or sheet with a frame support and slightly thicker than the upper thin film is separated from the upper base body, relative movement can also occur between the closed metal ring in the upper layer and the lower base body with a frame support in the lower layer and the second permanent magnet fixed thereon. Also, because the lower base body and the second permanent magnet thereon have low rigidity and are prone to deformation and movement, the second permanent magnet will thus make corresponding movements and consume energy.

[0034] (3) In the present invention, a thin film with a preset tension is pasted on the circular holes of the upper base body. Cylindrical and relatively small first permanent magnets with a certain mass (mass m) are pasted on the central parts of each circular-hole thin film. Around the circular holes of the upper base body, a closed metal ring (inner diameter of the metal ring is D, outer diameter is D + d) is fixed on the upper base body, and the second permanent magnet thin film (sheet) on the lower base body film with a frame support and slightly thicker than the upper thin film in the lower layer should be a resonant unit. Coupled with the regular distribution of a linear array or a planar array, the characteristics of its acoustic metamaterial are formed.

[0035] As mentioned above, the technical solutions of the present invention have been described in detail through specific embodiments. In the above embodiments, the descriptions of each embodiment have their own focuses. For parts not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0036] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Those of ordinary skill in the art can modify the technical solutions recorded in the above embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and protection scope of the technical solutions of each embodiment of the present invention.

Claims

1. An acoustic metamaterial absorber, characterized in that, it includes an upper structure and a lower structure, wherein, the upper structure includes an upper substrate, and a plurality of circular holes distributed in a line array or a surface array are formed in the upper substrate. A thin film with a preset tension covering the circular holes is arranged on the upper surface of the upper substrate. A first permanent magnet located at the center position of the circular hole is pasted on the thin film. A closed metal ring surrounding the circular hole is arranged on the lower surface of the upper substrate; the lower structure includes a lower substrate with a frame support, and a second permanent magnet is arranged at a position corresponding to the circular hole on the lower substrate. The magnetic pole directions of the first permanent magnet and the second permanent magnet are the same; the upper structure and the lower structure are bonded to form an integral structure; both the upper substrate and the lower substrate are in the form of a film or a thin sheet. The thickness of the upper substrate is greater than the thickness of the lower substrate, and the thickness of the lower substrate is slightly greater than the thickness of the thin film; the first permanent magnet is a cylindrical permanent magnet, magnetized along the axial direction, and pasted on the lower surface of the thin film; the second permanent magnet is a circular thin film or a thin sheet-shaped permanent magnet, magnetized along the axial direction, with a diameter slightly larger than the diameter of the circular hole, and coaxial with the circular hole, and pasted on the lower surface of the lower substrate; the circular hole is closed by the upper substrate and the lower substrate, and the first permanent magnet is located inside the circular hole; when external acoustic energy drives the first permanent magnet to move, the metal ring generates an electric current and generates a corresponding magnetic field. The magnetic field generated by the metal ring opposes the first permanent magnet, and the magnetic field generated by the metal ring also opposes the second permanent magnet, causing the second permanent magnet to make a corresponding movement and consume energy, achieving the functions of sound absorption, noise reduction, and shock absorption.

2. The acoustic metamaterial absorber according to claim 1, characterized in that, the metal ring is made of copper or a soft ferromagnetic material.

3. The acoustic metamaterial absorber according to claim 1, characterized in that, the materials used for the upper substrate and the lower substrate are selected from polyimide, polyether ether ketone, polyether imide, and polyethylene naphthalate.

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