A UNIT CELL FOR CELLULAR LATTICE ACOUSTIC METAMATERIAL FOR SOUND ABSORBING APPLICATIONS

Abstract

The present invention relates to a cellular lattice acoustic metamaterial(100) for sound absorption applications. The unit cell(102) is a smallest unit of the overall structure includes. The unit cell(102) includes a link element(112). The link element(112) includes a resonator chamber(104), a tube(106), a first end(108) and a second end(110). The resonator chamber(104) is wrapped around the tube(106). The second end(110) and the first end(108) are connected with the link element(112) that make a cubical structure for the unit cell(102).

Specification

Description:FIELD OF THE INVENTION
The present invention relates to acoustic metamaterials for sound absorption applications. More specifically, the present invention relates to a cellular lattice acoustic metamaterial designed to effectively absorb low-frequency sound.
BACKGROUND OF THE INVENTION
Acoustic metamaterials are type of materials designed to manipulate sound waves in ways that natural materials cannot. They have gained significant attention in recent years for their potential applications in sound absorption, noise control, and acoustic imaging. Traditional sound-absorbing materials, such as porous foams and fibrous materials, are often effective only at higher frequencies and struggle to provide sufficient attenuation at lower frequencies, that cause problems into environment, from urban settings to industrial spaces. Low-frequency noise, typically below 500 Hz, is challenging to manage due to its long wavelengths and the physical limitations of conventional sound-absorbing materials. Acoustic metamaterials leverage their unique structural properties, often characterized by periodic arrangements or complex geometries, to create effective sound absorption mechanisms that go beyond the capabilities of traditional materials.
Cellular lattice structures, in particular, have emerged as a promising design for acoustic metamaterials. These structures can be engineered to possess specific porosity and connectivity, allowing them to interact with sound waves in a controlled manner. By carefully designing the lattice geometry, it is possible to enhance sound absorption characteristics and optimize performance for low-frequency applications. Furthermore, the lightweight nature of these cellular materials opens new avenues for deployment in various settings, including architectural acoustics, automotive industries, and consumer electronics.

EP2614501B1 discloses a method for fabricating an acoustic metamaterial may include providing a planar pattern of springs arranged in columns and rows and separated from each other by interconnection nodes, providing a planar pattern of mass units separated from each other by a distance corresponding to a distance between the interconnection nodes, providing an array of vertically oriented springs separated from each other by the distance between the interconnection nodes, and aligning and joining the planar pattern of springs, the planar pattern of mass units and the array of vertically oriented springs to form a layer of unit cells.

The present invention addresses the limitations of existing sound absorption technologies by introducing a novel cellular lattice acoustic metamaterial specifically tailored to absorb low-frequency sound. Through the integration of advanced design techniques and material innovations, the invention aims to provide an effective and efficient solution for noise mitigation in a range of environments, contributing to improved acoustic comfort and overall sound quality.

OBJECTIVE OF THE INVENTION
The main objective of the present invention is to provide ultra-low frequency sound absorption, effectively targeting problematic noise ranges between 140 Hz and 500 Hz, which are often challenging to manage with conventional materials.
Another objective of the present invention is to provide a compact design with a metamaterial depth of less than 35 mm, allowing for efficient sound absorption without requiring bulky installations, making it suitable for various applications.
Yet another objective of the present invention is to provide enhanced acoustic energy loss through its unique shape that enables sudden expansion and contraction, promoting effective energy redistribution and improving overall sound absorption performance.
Yet another objective of the present invention is to provide the capability for sub-wavelength local resonances within the resonator chamber, which leads to increased energy losses and significantly enhances low-frequency noise control.
Yet another objective of the present invention is to provide customizable frequency response by allowing for the tuning of geometric parameters, enabling the absorption of specific incident frequencies and tailored solutions for diverse acoustic environments.
Further objectives, advantages, and features of the present invention will become apparent from the detailed description provided herein below, in which various embodiments of the disclosed invention are illustrated by way of example.
SUMMARY OF THE INVENTION
The present invention relates to a cellular lattice acoustic metamaterial for sound absorbing applications. The cellular lattice acoustic metamaterial includes a unit cell, a link element, a resonator chamber, a tube, a first end and a second end. The unit cell is a smallest unit of the overall structure of the cellular lattice acoustic metamaterial. The unit cell has the link element and the link element includes the resonator, the tube, the first end and the second end. The unit cell includes four major geometric features that is resonator chamber length, resonator chamber diameter, tube diameter and tube length. The size of the entire unit cell is in the order of a few millimetres. The unit cell achieves near-complete sound of the frequency absorption, with a thickness of under 35 mm, thus the unit cell can absorb low-frequency with a compact design. The sound waves pass across the unit cell and convert sound energy into heat due to boundary layer formation at the walls, that results in thermal losses and this also occurs as a result of temperature changes brought on by the sound waves alternating compressions and rarefactions. The unit cell is conversely viscous and losses are caused by internal friction in the air and interaction of the walls with the air medium, that sound waves encounter during the passage and the heat is produced when sound waves are facing resistance due to viscosity of the medium. The resonator chamber is wrapped around the tube. The second end and the first end are connected with two more link elements that make a cubical structure for the unit cell. Herein, the unit cell for cellular lattice acoustic metamaterial provides sudden expansion and contraction that causes acoustic energy loss that promotes energy redistribution and the resonator chamber causes sub-wavelength local resonances causing increased energy losses, thus enabling ultra-low frequency sound absorption. Herein, the absorption of sound in the cellular lattice acoustic metamaterial is enhanced by thermal and viscous losses, by dissipating sound waves energy, thermal and viscous losses aid in attenuating sound waves and improve the metamaterial overall capacity to absorb sound. Herein, the unit cell acts a sub wavelength Helmholtz resonator, and hence the length and size of every feature plays a significant role in the sound absorption, the unit cell acts as a neck for the succeeding the unit cell, hence dimensions of the unit cell play a crucial role in determining the frequency response of the metamaterial. Thus, the cellular lattice acoustic metamaterial based acoustic metamaterials is able to be use for multiple frequency absorption by changing the dimensions of the geometric features of the unit cell.
The main advantage of the present invention is that it provides ultra-low frequency sound absorption, effectively targeting problematic noise ranges between 140 Hz and 500 Hz, that are often challenging to manage with conventional materials.
Another advantage of the present invention is that it provides a compact design with a metamaterial depth of less than 35 mm, allows for efficient sound absorption without requiring bulky installations, making it suitable for various applications.
Yet another advantage of the present invention is that it provides enhanced acoustic energy loss through its unique shape that enables sudden expansion and contraction, promoting effective energy redistribution and improving overall sound absorption performance.
Yet another advantage of the present invention is that it provides the capability for sub-wavelength local resonances within the resonator chamber, which leads to increased energy losses and significantly enhances low-frequency noise control.
Yet another advantage of the present invention is that it provides customizable frequency response by allowing for the tuning of geometric parameters, enabling the absorption of specific incident frequencies and tailored solutions for diverse acoustic environments.
Further objectives, advantages, and features of the present invention will become apparent from the detailed description provided herein below, in which various embodiments of the disclosed invention are illustrated by way of example.
BRIEF DESCRIPTION OF DRAWINGS
The accompanying drawings are incorporated in and constitute a part of this specification to provide a further understanding of the invention. The drawings illustrate one embodiment of the invention and together with the description, serve to explain the principles of the invention.
Fig 1. illustrates a unit cell.
Fig 2. illustrates a cellular lattice acoustic metamaterial.
DETAILED DESCRIPTION OF THE INVENTION
Definition
The term "a" or "an", as used herein, is defined as one. The term "plurality", as used herein, is defined as two as or more than one. The term "another", as used herein, is defined as at least a second or more. The terms "including" and/or "having", as used herein, are defined as comprising (i.e., open language).
The term "comprising" is not intended to limit the present invention with such terminology rather is used in a wider sense. Any invention using the term comprising could be separated into one or more claims using "consisting" or "consisting of". The term "comprising" may be used interchangeably with the terms "having" or "containing".
Reference in this document to "one embodiment", "certain embodiments", "an embodiment", "another embodiment", and "yet another embodiment" or similar terms, throughout the document means that a specific feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of such phrases in various places, this specification throughout are not necessarily all referring to the same embodiment. Furthermore, the specific features, structures, or characteristics are combined in any suitable manner in one or more embodiments without limitation.
The term "or" as used herein is to be interpreted as inclusive or meaning any one or more combinations. Therefore, "A, B or C" means any of the following: "A; B; C; A and B; A and C; B and C; A, B and C". An exception to this definition will occur only when a combination of elements, functions, steps, or acts are in mutually exclusive, inherently.
As used herein, the term "one or more" generally refers to, but is not limited to, singular as well as the plural form of the term.
The drawings featured in the figures are to illustrate certain convenient embodiments of the present invention and are not to be considered as a limitation to that. Term "means" preceding a present participle of operation indicates the desired function for which there is one or more embodiments, i.e., one or more methods, devices, or apparatuses for achieving the desired function and that one skilled in the art could select from these or their equivalent in view of the disclosure herein and use of the term "means" is not intended to be limiting disclosure herein and use of the term "means" is not intended to be limiting.
Fig 1. illustrates a unit cell(102). The unit cell(102) is a smallest unit of the overall structure includes. The unit cell(102) includes a link element(112). The link element(112) includes a resonator chamber(104), a tube(106), a first end(108) and a second end(110). The resonator chamber(104) is wrapped around the tube(106). The second end(110) and the first end(108) are connected with the link element(112) that make a cubical structure for the unit cell(102).
Fig 2. illustrates a cellular lattice acoustic metamaterial(100). The cellular lattice acoustic metamaterial(100) for sound absorbing applications. The cellular lattice acoustic metamaterial(100) includes a unit cell (102). The unit cell(102) is a smallest unit of the overall structure of the cellular lattice acoustic metamaterial(100).
The present invention relates to a cellular lattice acoustic metamaterial for sound absorbing applications. The cellular lattice acoustic metamaterial includes a unit cell, a link element, a resonator chamber, a tube, a first end and a second end. The unit cell is a smallest unit of the overall structure of the cellular lattice acoustic metamaterial. The unit cell has the link element and the link element includes the resonator, the tube, the first end and the second end. The unit cell includes four major geometric features that is resonator chamber length, resonator chamber diameter, tube diameter and tube length. The size of the entire unit cell is in the order of a few millimetres. The unit cell achieves near-complete sound of the frequency absorption, with a thickness of under 35 mm, thus the unit cell can absorb low-frequency with a compact design. The sound waves pass across the unit cell and convert sound energy into heat due to boundary layer formation at the walls, that results in thermal losses and this also occurs as a result of temperature changes brought on by the sound waves alternating compressions and rarefactions. The unit cell is conversely viscous and losses are caused by internal friction in the air and interaction of the walls with the air medium, that sound waves encounter during the passage and the heat is produced when sound waves are facing resistance due to viscosity of the medium. The resonator chamber is wrapped around the tube. The second end and the first end are connected with two more link elements that make a cubical structure for the unit cell. Herein, the unit cell for cellular lattice acoustic metamaterial provides sudden expansion and contraction that causes acoustic energy loss that promotes energy redistribution and the resonator chamber causes sub-wavelength local resonances causing increased energy losses, thus enabling ultra-low frequency sound absorption. Herein, the absorption of sound in the cellular lattice acoustic metamaterial is enhanced by thermal and viscous losses, by dissipating sound waves energy, thermal and viscous losses aid in attenuating sound waves and improve the metamaterial overall capacity to absorb sound. Herein, the unit cell acts a sub wavelength Helmholtz resonator, and hence the length and size of every feature plays a significant role in the sound absorption, the unit cell acts as a neck for the succeeding the unit cell, hence dimensions of the unit cell play a crucial role in determining the frequency response of the metamaterial, thus The cellular lattice acoustic metamaterial based acoustic metamaterials is able to be use for multiple frequency absorption by changing the dimensions of the geometric features of the unit cell.
In an embodiment, the method of the cellular lattice acoustic metamaterial for sound absorbing applications includes:
the resonator chamber is wrapped around the tube to form a complete structure of the link element;
the link element includes the first end and the second end, these components are linked together to form a cubical structure;
a method for sound absorption includes:
the sound waves pass across the cellular lattice acoustic metamaterial that converts sound energy into heat due to the formation of boundary layers on the walls;
the sound waves pass across the cellular lattice acoustic metamaterial leads to thermal losses and this process also arises from temperature fluctuations caused by the alternating compressions and rarefactions of the sound waves, that causes heat dissipation;
the passage causes the viscous losses occur due to internal friction in the air;
the sound waves travel through the cellular lattice acoustic metamaterial and when the sound waves are hindered by the viscosity of the medium, the heat is generated.
In an embodiment, the present invention relates to a cellular lattice acoustic metamaterial for sound absorbing applications. The cellular lattice acoustic metamaterial includes a one or more unit cells, a one or more link elements, a resonator chamber, a tube, a first end and a second end. The one or more unit cells are the smallest unit of the overall structure of the cellular lattice acoustic metamaterial. The one or more unit cells have the one or more link elements and the one or more link elements includes the resonator, the tube, the first end and the second end. The one or more unit cells include four major geometric features that is resonator chamber length, resonator chamber diameter, tube diameter and tube length. The size of the entire one or more unit cells are in the order of a few millimetres. The one or more unit cells achieves near-complete sound of the frequency absorption, with a thickness of under 35 mm, thus one or more unit cells can absorb low-frequency with a compact design. The sound waves pass across the one or more unit cells and convert sound energy into heat due to boundary layer formation at the walls, that results in thermal losses and this also occurs as a result of temperature changes brought on by the sound waves alternating compressions and rarefactions. The one or more unit cells are conversely viscous and losses are caused by internal friction in the air and interaction of the walls with the air medium, that sound waves encounters during the passage and the heat is produced when sound waves are facing resistance due to viscosity of the medium. The resonator chamber is wrapped around the tube. The second end and the first end are connected with one or more link elements that makes a cubical structure for the one or more unit cells. Herein, the one or more unit cells for cellular lattice acoustic metamaterial provides sudden expansion and contraction that causes acoustic energy loss that promotes energy redistribution and the resonator chamber causes sub-wavelength local resonances causing increased energy losses, thus enabling ultra-low frequency sound absorption. Herein, the absorption of sound in the cellular lattice acoustic metamaterial is enhanced by thermal and viscous losses, by dissipating sound waves energy, thermal and viscous losses aid in attenuating sound waves and improve the metamaterial overall capacity to absorb sound. Herein, the one or more unit cells acts a sub wavelength Helmholtz resonator, and hence the length and size of every feature plays a significant role in the sound absorption, the one or more unit cells acts as a neck for the succeeding the one or more unit cells, hence dimensions of the one or more unit cells plays a crucial role in determining the frequency response of the metamaterial, thus The cellular lattice acoustic metamaterial based acoustic metamaterials is able to be use for multiple frequency absorption by changing the dimensions of the geometric features of the one or more unit cells.
In an embodiment, the method of the cellular lattice acoustic metamaterial for sound absorbing applications includes:
the resonator chamber is wrapped around the tube to form a complete structure of the link element;
the link element includes the first end and the second end, these components are linked together to form a cubical structure;
a method for sound absorption includes:
the sound waves pass across the cellular lattice acoustic metamaterial that converts sound energy into heat due to the formation of boundary layers on the walls;
the sound waves pass across the cellular lattice acoustic metamaterial leads to thermal losses and this process also arises from temperature fluctuations caused by the alternating compressions and rarefactions of the sound waves, that causes heat dissipation;
the passage causes the viscous losses occur due to internal friction in the air;
the sound waves travel through the cellular lattice acoustic metamaterial and when the sound waves are hindered by the viscosity of the medium, the heat is generated. , Claims:I/ WE CLAIM
1. A cellular lattice acoustic metamaterial(100) for sound absorbing applications, the cellular lattice acoustic metamaterial(100) comprising:
an at least one unit cell(102), the at least one unit cell(102) is a smallest unit of the overall structure of the cellular lattice acoustic metamaterial(100), the at least one unit cell(102) is having:
an at least one link element(112), the at least one link element(112) having
a resonator chamber(104);
a tube(106), the resonator chamber(104) is wrapped around the tube(106);
a first end(108);
a second end(110), the second end(110) and the first end(108) are connected with two more the at least one link element(112) that make a cubical structure for the at least one unit cell(102);
characterized in that, the at least one unit cell(102) for cellular lattice acoustic metamaterial(100), provides sudden expansion and contraction that causes acoustic energy loss that promotes energy redistribution and the resonator chamber(104) causes sub-wavelength local resonances causing increased energy losses, thus enables ultra-low frequency sound absorption;
wherein, the absorption of sound in the cellular lattice acoustic metamaterial(100) is enhanced by thermal and viscous losses, by dissipating sound waves energy, thermal and viscous losses aid in attenuating sound waves and improve the metamaterial overall capacity to absorb sound.
2. The cellular lattice acoustic metamaterial(100) as claimed in claim 1, wherein the at least one unit cell(102) consist of four major geometric features that is resonator chamber length, resonator chamber diameter, tube diameter and tube length.
3. The cellular lattice acoustic metamaterial(100) as claimed in claim 1, wherein the size of the entire at least one unit cell(102) is in the order of a few millimetres.
4. The cellular lattice acoustic metamaterial(100) as claimed in claim 1, wherein the at least one unit cell(102) achieves near-complete sound of the frequency absorption, with a thickness of under 35 mm, thus the at least one unit cell(102) can absorb low-frequency with a compact design.
5. The cellular lattice acoustic metamaterial(100) as claimed in claim 1, wherein the sound waves pass across the at least one unit cell(102) and convert sound energy into heat due to boundary layer formation at the walls, that results in thermal losses and this also occurs as a result of temperature changes brought on by the sound waves alternating compressions and rarefactions.
6. The cellular lattice acoustic metamaterial(100) as claimed in claim 1, wherein, in the at least one unit cell(102) viscous losses are caused by internal friction in the air and interaction of the walls with the air medium that sound waves encounter during the passage and the heat is produced when sound waves are facing resistance due to viscosity of the medium.
7. The cellular lattice acoustic metamaterial(100) as claimed in claim 1, wherein, the cellular lattice acoustic metamaterial(100) enabling ultra-low frequency sound absorption within the range of 140 Hz to 500 Hz.
8. The cellular lattice acoustic metamaterial(100) as claimed in claim 1, wherein, the at least one unit cell(102) acts a sub wavelength Helmholtz resonator, and hence the length and size of every feature plays a significant role in the sound absorption, the at least one unit cell(102) acts as a neck for the succeeding the at least one unit cell(102), hence dimensions of the at least one unit cell(102) play a crucial role in determining the frequency response of the metamaterial, thus The cellular lattice acoustic metamaterial(100) based acoustic metamaterials is able to be use for multiple frequency absorption by changing the dimensions of the geometric features of the at least one unit cell(102).
9. The cellular lattice acoustic metamaterial(100) as claimed in claim 1, wherein the shape of the at least one link element(112) provides for redistribution of acoustic energy which in turn increases the thermal and viscous losses which leads to improved sound absorption coefficient.
10.The method of absorbing applications by the cellular lattice acoustic metamaterial(100) as claimed in claim 1, the method comprising:
the resonator chamber(104) is wrapped around d the tube(106)) to form a complete structure of the at least one link element(112);
the at least one link element(112) having the first end(108) and the second end(110) these components are linked together to form a cubical structure;
a method for sound absorption having:
the sound waves pass across the cellular lattice acoustic metamaterial(100) that converts sound energy into heat due to the formation of boundary layers on the walls;
the sound waves pass across the cellular lattice acoustic metamaterial(100) leads to thermal losses and this process also arises from temperature fluctuations caused by the alternating compressions and rarefactions of the sound waves, that causes heat dissipation;
the passage causes the viscous losses occur due to internal friction in the air;
the sound waves travel through the cellular lattice acoustic metamaterial(100) and when the sound waves are hindered by the viscosity of the medium, the heat is generated.

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