Metacells and Acoustic Metamaterial Panels Comprising at Least One Acoustic Metacell

Abstract

The present invention relates to the development of metacells that can exhibit both passive and meta-properties (i.e., hybrid properties), as well as multifunctional acoustic metamaterial panels comprising at least one hybrid metacell to reduce the transmission of sound waves and / or attenuate sound waves in a desired narrow or broad frequency band.

Description

[Technical field]

[0001] The present invention relates to the development of meta cells that can exhibit both passive and meta (i.e., hybrid) properties, as well as multifunctional acoustic metamaterial panels comprising at least one hybrid metacell to reduce the transmission of sound waves and / or attenuate sound waves in a desired narrow or broad frequency band. [Background technology]

[0002] Sound or noise insulation / reduction / control is basically done using two techniques: active and passive. Furthermore, this reduction or control is generally performed in two different ways: sound absorption loss and sound transmission loss (sound transmission loss iletim kaybi). In terms of sound absorption, active and passive insulation can be described as follows:

[0003] Active isolation is generally performed with a control sound wave that interferes with the source sound wave that it is desired to reduce without applying an insulating material. The control sound wave is adjusted so that it is in antiphase and the frequency of the sound wave that one wants to suppress is the same. This method is very costly. Moreover, this method requires a controlled volume, which limits its application area in practice. In this method, the control sound wave can be generated externally using a sound source or can be generated without a sound source by various elements called resonators. However, this type of control can generally operate in a narrow frequency band (also known as tone) and still requires a controlled volume. To widen the frequency band, more resonators are needed. This means that the area in which the resonators can be placed is increased. To absorb lower frequencies, a larger volume or length of resonators is needed.

[0004] Passive insulation is achieved by placing insulating elements such as sponges, felt, glass wool, rock wool, fiber waste, etc. between the noise source and the receiver. Passive insulating materials provide sound absorption by viscous and thermal effects due to their internal spaces, discontinuities, physical and chemical structure. In addition to that, passive insulating materials can increase the sound propagation path (also known as tortuosity) through the material, thereby reducing the energy of sound waves that follow longer paths. These materials, which can absorb acoustic energy by converting it into thermal energy, are insufficient to absorb low-frequency noise, where sound waves have large wavelengths. This is because, for these types of materials to work efficiently, the material characteristic thickness must be at least 1 / 4 of the wavelength of the sound / noise to be controlled. For example, to absorb a 100Hz sound wave (sound speed: 343m / s), the use of an insulating material with a characteristic thickness of 343 / 100 / 4 ≒ 86cm is required. This makes traditional materials inefficient to use at low frequencies, since this is practically impossible, both physically and economically. Furthermore, the use of these materials in systems such as areas requiring air circulation, food and sanitary equipment, flammable and high temperature environments is very limited.

[0005] With regard to sound transmission reduction / loss, there is essentially no difference between absorption or transmission in active insulation. However, sound transmission loss can be achieved by increasing reflections associated with various acoustic volume-based geometric discontinuities (i.e. expansion chambers). Again, the need for larger volumes continues at low frequencies.

[0006] When sound transmission loss is evaluated in the context of passive control, it is done as a function of the mass of the material and the frequency (known as the mass-frequency law). Thus, as the mass of the material increases, the sound transmission loss increases. Similarly, as the frequency increases, the sound transmission loss increases. Therefore, to achieve higher sound transmission loss at lower frequencies, a greater weight of insulating material must be used. For this purpose, materials such as stone wool or glass wool reinforced concrete, and brick are generally preferred.

[0007] Especially in the last 15 years, there has been intense research into the development of artificial insulating materials, known as acoustic metamaterials, as an alternative to conventional materials for the low-mid frequency range. Acoustic metamaterials have a wide range of applications, mainly in the technical fields of physics and engineering, in many areas such as automobiles, aerospace, industrial machinery, white goods, household appliances, air conditioning and ventilation systems, defense industry, construction and building sectors, etc. In acoustic metamaterials, high sound absorption and / or sound transmission loss can be achieved at a specific single low frequency through negative effective mass, negative effective bulk modulus, or both, by not following the mass-frequency law. The cells are usually formed by arranging them periodically, side by side or in succession. In these materials, the thickness of the material is a key parameter, but the main technique is to design and properly arrange resonant cells, usually of small size (with a characteristic length smaller than the wavelength of sound, i.e., sub-wavelength). However, acoustic metamaterials, also state of the art, absorb in a narrow frequency band and provide transmission loss in a specific region (frequency band) depending on the resonant frequency of the cells. Therefore, acoustic metamaterials need to be developed to provide the desired broad-spectrum absorption and loss. Often, combinations of multiple tailored periodically arranged cells are used to broaden the bandwidth.

[0008] In the state of the art, in patent numbered US Pat. No. 5,399,436, a sound absorbing unit particularly suitable for non-specific low-frequency noise absorption is mentioned, with super-open ventilation and adjustable sound absorption performance. In this cell design, the frequency is adjustable and the aim is sound absorption by allowing air to pass and capturing sound waves at the dead end of the labyrinth. The cell mentioned in the document aims to increase the sound path for low frequencies so that cavity resonances can be absorbed. The cell specified in this context may only feature a local negative bulk module at a singular but adjustable frequency. Also, an internal moving part can perform the frequency adjustment (tuning) process. Thus, the cell has a larger thickness by design. However, the cell does not have the cell function capable of performing sound transmission reduction, i.e. having a negative mass effect.

[0009] In another known state of the art, in the patent numbered US Pat. No. 5,399,466, a three-layer cell is mentioned as follows: 1 - micro-perforated plate, 2 - double helical coil structure, 3 - back plate. In this cell type, the first plate is equipped with two micro-sized holes. Just behind these holes are two channels in the form of a helix to increase the tortuosity. In these two channels, the aim is to absorb at two different frequencies at the same time. With the plate behind, the aim is to cut off the transmission according to the law of mass. These two plates, front and back, do not show any meta-characteristics. Acoustic attenuation is achieved through a micro-perforated front panel and a passively configured dual channel. Again, the acoustic attenuation only acts as a sound absorber at tonal frequencies. The path is designed in a helical manner to increase the tortuosity, but the combination and meta-material technology described in the above document are known techniques.

[0010] Another known state of the art, numbered US Pat. No. 5,999,633, mentions an acoustic metamaterial unit cell, which adds a number of typical Helmholtz resonant cells to provide high sound transmission at Fabry-Perot frequencies. In other words, the cell is not one developed to reduce the transmission of sound waves generated by a noise source and absorb them.

[0011] Another known state of the art, numbered US Pat. No. 5,399,633, maintains another acoustic metamaterial. In this metamaterial, cells with a classical geometric form with a membrane are composed of a rear hard cavity or mass. This is a classical dipole type metamaterial. Classical metamaterials stop sound transmission up to the natural frequency of their membrane. The metamaterial provides a small amount of sound absorption according to the material properties of the membrane. Thus, according to the purpose, some of the cells counted in the state of the art provide sound suppression and some provide sound absorption.

[0012] It is necessary to develop an acoustic metacell that will turn the disadvantages cited in the state of the art into advantages. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Chinese Patent No. 112728275 [Patent Document 2] Chinese Patent No. 111883093 [Patent Document 3] International Publication No. 2017093690 Brochure [Patent Document 4] US Patent Application Publication No. 2021237394(A1) Summary of the Invention

[0014] The objective of the present invention is to realize at least one acoustic hybrid metacell and a multifunctional acoustic metamaterial panel comprising said at least one hybrid metacell, comprising at least one component that is both a passive material and a metafeature (hybrid) developed with a unique geometric form to stop and / or absorb the transmission of sound waves by tuning to a desired narrow or wide frequency band.

[0015] Another object of the present invention is the development of acoustic insulation panels that can be shaped or formed according to the section or location to be applied, panels comprising said hybrid acoustic metacells being able to operate in a desired narrow band and / or in a specific broad frequency band, and being able to provide both high sound absorption losses and high sound transmission losses, and they can be very thin, flexible or rigid (non-flexible, solid).

[0016] The developed cells and panels comprising these cells can exhibit passive insulation material properties as well as acoustic metamaterial properties, hence they are called hybrid acoustic metacells, acoustic hybrid meta-insulation panels / plates.

[0017] Moreover, the cells also have a morphology that allows them to function as resonators at medium and high frequencies. Thus, a composite cell is obtained that can be both a meta, a passive material, and a resonator. In the state of the art, these features do not exist together like this. These panels can be used in a wide range of fields as sound (acoustic, noise) insulation materials.

[0018] Additionally, because the insulation panels can be in a perforated form, the present invention is used to create an innovative insulation system that allows air circulation but not sound / noise transmission.

[0019] The cells of the invention exhibit negative mass properties in the membranes or plates with sub-wavelengths and negative bulk modulus in the cavities and channels (which act like special resonators with sub-wavelengths). These negativities imply a metamaterial effect that creates an exotic behavior that leads to higher sound transmission losses and sound absorption. Furthermore, the geometry, thickness and length of the channels result in high visco-thermal and meandering effects. These effects imply a passive material behavior. This hybrid combination is quite different from the systems mentioned in the state of the art. Thanks to these features, this hybrid combination can take a very thin form compared to the state of the art. The frequency tuning is performed by calculations that include the geometric parameters of both the membranes / plates and the form of the cavities, channels and slits.

[0020] The present invention is an acoustic single cell of any geometrical form, preferably circular, triangular, square, rectangular, polygonal or any hybrid, that can be used in many fields such as automotive, aviation, industrial machinery, white goods, household appliances, air conditioning and ventilation systems, defense industry, construction and building sector. These cells can form multi-cells by connecting single cells with each other through acoustic volume channels. These cells are designed to stop the transmission or provide sound absorption in a very wide frequency range of sound waves generated by a noise source, with at least one first layer (or front or inlet layer) of any geometrical form and physical characteristics, at least one second layer (or middle layer) of any geometrical form and physical characteristics, at least one third layer (or output or back layer) of any geometrical form and physical characteristics. These cells have at least one inner frame of any geometrical form and physical characteristics, and at least one interior acoustic volume that fills the inner frame as much as the interior volume and matches the geometrical form or any geometrical form and physical characteristics of the inner frame. The cell also comprises at least one external acoustic volume channel of any geometric form and physical characteristics, located at a distance relative to the inner frame and in the outer region of the inner frame together with the acoustic volume. Furthermore, at least one external frame of any geometric form and physical characteristics within the cell completely or partially covers the surfaces of the external acoustic volume channel and the second layer of the internal acoustic volume. Due to the geometric form and physical characteristics formed by combining the first layer and the third layer, completely or partially covering the other surfaces, with the second layer, two separate sections are formed within the cell for each of the first and third layers with a predetermined thickness, i.e. a first part and a second part. Each part exhibits different physical properties according to its natural frequency. [Brief description of the drawings]

[0021] [Figure 1]FIG. 2 is a representative side view of a first layer, a second layer, and a third layer included in a metamaterial cell. [Diagram 2] FIG. 1 is a three-dimensional perspective view of an assembled first layer, a second layer, and a third layer comprised in the metamaterial cell that is the subject of the present invention. [Diagram 3] FIG. 2 is a representative diagram of a second layer in one embodiment of the present invention. [Figure 4] In an embodiment of the present invention, FIG. 3 is a representative diagram of a section that is spontaneously formed by combining a first layer and a third layer by placing the first layer before and after the second layer. [Diagram 5] FIG. 13 is an exploded view of (a) a first layer, (b) a second layer, and (c) a third layer of a metamaterial cell in accordance with another embodiment of the present invention. [Figure 6] 1A-1C are representative diagrams of single cell structures of the second layer with different geometric configurations according to an embodiment of the present invention. [Figure 7] FIG. 13 is a representative diagram of a binary cell structure of the second layer that is brought together in two different configurations in one embodiment of the present invention. [Figure 8] 1A-1C are representative diagrams of single cell structures of the first and third layers with different geometric configurations according to an embodiment of the present invention. [Figure 9] In one embodiment of the present invention, an "e" path diagram within the exterior acoustic volume channel of the second layer and an interior acoustic volume diagram, symbolic representation of an "h" section. [Figure 10] FIG. 2 is a symbolic diagram of a panel with a further protective layer (t) forming a gap with the first layer and / or the third layer. [Figure 11] 1 is a graph of the variation of sound transmission loss with frequency in H1 and H4 cell structures. [Explanation of symbols]

[0022] For a better understanding of the invention, corresponding numerals in the figures are given below. 1. Cell 1.1 The first layer 1.10 Entrance Hole 1.2 The second layer 1.20 Outer frame 1.201 External Acoustic Volume Channel 1.21 Inner frame 1.210 Internal acoustic volume 1.3 The third layer 1.30 Exit hole A Mouth (Opening) B1 First part B2 Second part t Protective layer DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The subject of the present invention, a hybrid single acoustic metacell (1), comprises at least one first layer (1.1) (or front or entrance layer) of any geometric form and physical properties, at least one second layer (1.2) (or middle layer) of any geometric form and physical properties, and at least one third layer (1.3) (or output or back layer) of any geometric form and physical properties, in order to become a resonant cell with characteristic dimensions smaller than the wavelength of sound (i.e. subwavelength scale) to stop the transmission and / or absorb sound waves in a wide frequency range (Figures 1 and 2). Said hybridity is provided by technical features resulting from the combination of the three aforementioned layers. In other words, the hybrid structure of the cell (1) of the present invention is obtained by combining both passive material properties and metamaterial properties. In summary, passive material properties; the channels formed inside are much longer than the thickness of the material (i.e., high tortuosity), while narrow channels are formed to provide viscothermal effects, metamaterial characteristics; the acoustic volume is achieved by tuning the volume channels and membranes (or plates) created inside according to the frequency at lower wavelengths to obtain effective negative mass and effective negative bulk modulus. Furthermore, the acoustic volume also has the form of an acoustic cell space that can operate as a resonator at medium and high frequencies, using the A-opening as a neck. Thus, with all of these, a hybrid cell is obtained. All or any part of the hybrid cell (1) can be manufactured from any material. A composite cell (1) structure was formed by combining the above three layers. The single cell (1) can be in any geometric form, a circle, a triangle, a square, a rectangle, a polygon, or any (random, arbitrary) form (shape). The metacells (1) are the first layers that may be added together, the same and / or different, side-by-side and / or back-to-back and / or linearly and / or diagonally and / or arbitrarily and / or periodically and / or randomly.

[0024] To achieve another object of the present invention, an acoustic hybrid metamaterial insulation panel is formed by placing at least one hybrid metamaterial cell (1) on top of and / or back to back and / or side by side and / or in any manner. Thus, the insulation panel comprises at least one hybrid metamaterial cell (1) with different or same geometric forms, positioned as desired. The acoustic channels between the cells can be connected to each other according to the desired frequency settings. Here, the term insulation includes sound transmission stopping function or sound absorption function or both.

[0025] It comprises a second layer (1.2) of a given thickness, an outer frame (1.20) of any geometric form (circle, square, rectangle or any), and at least one inner frame (1.21) of any geometric form, located within the outer frame (1.20) and at a given distance from the outer frame (1.20), which conforms to the geometric form of the outer frame (1.20) (Figure 3). Due to the geometric form of the second layer (1.2), the first layer (1.1) and the third layer (1.3) function as two separate sections (B1 and B2), respectively. A partition is formed spontaneously by combining the first layer (1.1) and the third layer (1.3) by placing the first layer (1.1) and the third layer (1.3) before and after the second layer (1.2). These independent sections are called the first section (or peripheral membrane) (B1) and the second section (or intermediate membrane) (B2) (Figure 4). The formation of the first part (B1) and the second part (B2) is valid in all embodiments of the invention. The sections B1 and B2 can also be subdivided according to the morphology of the inner and outer frames and the way they are connected. Each of these sections is an element of the metacell (1) that functions separately as an absorbing and a conducting section depending on their natural frequencies.

[0026] In an exemplary embodiment of this cell shape (Fig. 5), if the shape of the outer frame (1.20) is square, the shape of the inner frame (1.21) can also be square, but should not be considered as being limited in practice. As mentioned before, both frames are intertwined and positioned at a predetermined distance from each other to form a channel between them. Thus, in all embodiments of the invention, the outer frame (1.20) comprises at least one external acoustic volume channel (1.201) located in the area between itself and the inner frame (1.21) (i.e. the acoustic channel remains between the first section (B1) of the first and third layers). Furthermore, the inner frame (1.21) comprises at least one internal acoustic volume (1.210) filling said inner frame by the same amount as the internal volume (therefore the acoustic volume remains between the second section (B2) of the first and third layers). In this application, the A-slit (opening, opening, neck, neck) is obtained by removing a piece of a predetermined height (length) and width in any desired section on the inner frame (1.21). Due to this slit, the internal acoustic volume (1.210) automatically forms a separate sub-wavelength inner metacell (1) of the type of Helmholtz resonator. Here, the position and neck length of the A-opening can be changed, and both the width and the length of the A-opening can be adjusted at the desired frequency by forming the neck (1.210) of the acoustic volume (acting as a Helmholtz resonator). The internal acoustic volume (1.210) and the external acoustic volume channel (1.201) can be of any geometric form, preferably circular, triangular, square, rectangular, polygonal or any (random, arbitrary) form (shape), but the application is not limited to this. However, the inner frame (1.21) can be provided with structures that form different numbers of channels and / or single or multiple slits (apertures) in the inner frame (1.21) in any form, either integral with itself or associated with the inner frame (1.21) (Figure 6). Due to these structures, the internal acoustic volume (1.210) provided by the inner frame (1.21) can be of various geometric forms.

[0027] In different embodiments of the invention, each same or different metacell (1) can be connected to each other by an acoustic volume channel (1.201) to form a new metacell (1) with two, three or more different acoustic properties. As an example of this application of the invention, two metacells (1) with different mouth openings in shape and position are connected to each other via an acoustic volume channel (Figure 7).

[0028] Each of the first layer (1.1) and the third layer (1.3) for the inlet of sound waves (or air) according to the embodiment of the invention can be equipped with at least one inlet hole (1.10) of a predetermined size, number, various geometric forms (circle, triangle, square, rectangle, polygon or any) and / or at least one outlet hole (1.30) of a predetermined size, number, various geometric forms (circle, triangle, square, rectangle, polygon or any) depending on the cell characteristics (Figure 8). If both holes are present in the cell (1), i.e. if both the first layer (1.1) and the third layer (1.3) are equipped with holes, the cell (1) allows the inlet and outlet of air. Thus, the invention results in a hybrid meta-cell (1) that is able to stop (capture) sound transmission and provide ventilation.

[0029] The first layer (1.1), the second layer (1.2) and the third layer (1.3) have a thickness and can be the same or different thicknesses. The first layer (1.1) and the third layer (1.3) can each be a membrane and / or a plate according to an embodiment of the present invention.

[0030] On the first layer (1.1) and on the third layer (1.3) single, multiple or distributed masses of any shape and weight can be added in any part. By varying the geometrical dimensions, materials, geometrical shapes and values ​​and positions of the masses provided on the first layer (1.1), the second layer (1.2) and the third layer (1.3), the frequency range to be effective can be varied.

[0031] If the general working principle of the cell is technically summarized, the specially designed second layer (1.2) provides high absorption by increasing the tortuosity with the channel type spaces it comprises, allowing the sound to dissipate more energy than it can withstand. This situation is shown in figure 9 as the "e" channel. In addition, as a result of the narrowness of this "e" channel, further sound reduction is provided by friction and heat exchange losses, represented as visco-thermal energy losses. The Helmholtz cell, defined as the "h" section, provides further sound absorption at tonal frequencies according to its volume, by emitting sound waves in anti-phase and resonating with the sound waves that have reduced their energy through "e" by generating a cavity resonance. This second layer (1.2) can be reshaped in different forms as seen in figure 6 in order to provide the aforementioned technical features in the desired frequency band and with the desired amount of insulation.

[0032] A single cell (1); due to its inner (1.21) and outer (1.20) frames and the small internal acoustic volume (1.210) between them and bounded on both sides by a membrane, the single cell exhibits dipole* characteristics and provides more than 50% of the sound at the natural frequency and volume of the cell (1). (*Note: cavities without a small closed volume or without a long volume are monopole and provide up to 50% absorption.)

[0033] By changing the geometry, material, shape and physical properties of the inner frame (1.21), the outer frame (1.20), the internal acoustic volume (1.210), the external acoustic volume channel (1.201), the first part (B1) (peripheral membrane) and the second part (B2) (intermediate membrane), a negative effective mass and a negative effective bulk modulus can be simultaneously provided in the same frequency range. In this way, a double negative metamaterial can be obtained in the desired frequency band. The double negative metamaterial, when vibrated by a sound wave, stops the sound propagation in a certain frequency range depending on the mass, up to their natural frequency if the double negative metamaterial has no mass, and stops the sound propagation (stops the transmission, creates a band gap, performs sound filtering) if the double negative metamaterial has mass. At the same time, passive sound absorption occurs due to the elastic properties of the membrane.

[0034] The inlet holes (1.10) (or wave inlet holes) located in the first layer (1.1) allow the sound waves to enter the cell and travel through the acoustic volume channel (1.210). It is not necessary to have an outlet hole in the third layer (1.3), which is determined by the desired properties of the cell. effective) is longer, the energy of the sound along the path is reduced. Thus, a significant amount of sound absorption is obtained. Thus, the absorption in the cell is increased. For this purpose, it is necessary to have at least one inlet hole (1.10) to perform impedance matching. However, the outlet hole (1.30) does not necessarily have to be. If ventilation is required or a material that does not block the air inlet and outlet is desired, there must be inlet and outlet holes (1.10 and 1.30). For applications where an air inlet and outlet are required, such as compressors or generators, metamaterials with cells having inlet and outlet holes (1.10 and 1.30) can be used to filter sound (stopping sound transmission). The transmission and absorption spectrum of the cell (1) can be modified depending on whether each technological unit (e.g. inlet hole (1.10), neck, internal acoustic volume (1.210)...) equipped in the unit cell (1) that is the subject of the present invention is present in the cell (1) or not. For example, the geometric form of the inlet holes (1.10) (such as circle, square or rectangle...), or even whether said form is present or located on a layer, can completely change the behavior of the cell (1). As mentioned before, the first layer (1.1) and the third layer (1.3) may be at least one and may be a membrane and / or a plate of a given thickness, or made of any material.

[0035] The cell (1), which is the subject of the present invention, acts as both a sound absorber and a sound transmission stopper due to its structure, i.e. the first layer (1.1) or the second layer (1.2) or the third layer (1.3) alone cannot provide these characteristics. However, the aforementioned characteristics (absorbing and transmitting sections) can be realized with the cell (1) according to the present invention only if the first layer (1.1), the second layer (1.2) and the third layer (1.3) together form a combined structure.

[0036] The aim of the present invention is to obtain a cell (1) structure with better sound absorption and sound transmission losses. For better absorption, the surface impedance should be reduced. To reduce the impedance, at least one hole must be drilled in the first layer (1.1). While doing this, the inlet hole (1.10) and / or the outlet hole (1.30) should be drilled in such a way that it does not interfere with the properties of the layer itself. If an inlet hole (1.10) and / or an outlet hole (1.30) of approximately the same size as the volume of the cell is drilled in the center of the cell (1), the membrane will not show the desired vibration characteristics. The dimensions of the inlet hole (1.10) and / or the outlet hole (1.30) are made so as not to interfere with the characteristics of the membrane (plate). Moreover, the aforementioned holes allow sound waves to enter and leave the cell and, with a given geometric form, size and position, the sound path (L effective ) is increased. Furthermore, the holes are positioned so that the sound travels the longest path from the hole where the sound enters to the hole where the sound leaves. Therefore, the large effective length (L effective) is produced. Thus, the center of the cell (1) acts like another membrane, and its periphery acts like another membrane. When sound or air enters through the inlet hole (1.10), the cell (1) exhibits a negative effective mass characteristic. As the sound travels, the metamaterial begins to transform into a negative bulk modulus. In the design of the cell (1) that is the subject of the present invention, the air entering through the hole moves in the external acoustic volume channel (1.201) and the thickness of the material is expanded at least five times in one application by the path that the sound takes. In other words, the present invention provides the necessary conditions to reduce the energy of the sound without the need to make the material very thick. In the case of the mouth opening, the internal acoustic volume (1.210) acts like a Helmholtz resonator. Thus, the geometry of the cell (1) is able to attenuate the sound by exhibiting a wave effect at a specific frequency opposite to the sound, stopping the sound propagation up to this frequency range. Thus, due to the phase difference of the waves at the same frequency (opposite phase (180°)), the waves can be absorbed. If some waves do not pass through, sound transmission losses occur. However, when sound enters the cell and is exposed to the specified geometry of the cell (friction increases when sound passes through a narrow channel), the energy of the sound is also reduced due to friction (heat exchange). Considering that passive materials bring about absorption due to viscothermal effects, the cell (1) that is the subject of the present invention has this geometry, and the cell (1) begins to behave like a passive material. Thus, as mentioned above, hybrid materials are formed by combining passive materials and metamaterials.

[0037] The acoustic volume-based properties of the meta-cells have a multifunctional character, depending on whether there is an inlet hole (1.10) located in the first layer (1.1) and an outlet hole (1.30) located in the third layer (1.30) and whether there is a neck connected to the port (A). Thus, depending on the application area, different meta-cells (1) are obtained whose properties can be easily modified depending on whether only a hole / neck / port is present. Some combinations showing the acoustic volume-based sound transmission loss properties of these meta-cells (1) can be seen in Table 1.

[0038] [Table 1]

[0039] Example of description for Table 1: In the present application, if the cell (1) comprises holes in the first (1.1) and third (1.3) layers, i.e. if the inlet hole (1.10) and the outlet hole (1.30) are located in both layers (H1), the entire acoustic space has the properties of an expansion chamber. As long as only the inlet hole (1.10) is present, the metacell (1) turns into a quarter-wave resonator (H2). As long as the inlet (A) is present, further Helmholtz resonators are formed in the cell (1) (H3 and H4).

[0040] In Fig. 11, the behavior of H1 and H4 cells is given as an example. The frequency at which the minimum transmission loss occurs in H1 is c / (2L eeffective ) can be tuned with frequency of the acoustic volume (6) by changing the width, length, height and size of the interior acoustic volume (1.210) and the entrance opening (A) (as the volume acts like a Helmholtz resonator), so that a high transmission loss is achieved at this frequency. f HR =c / (2L effective ) (c: speed of sound, L effective : Effective path (length)

[0041] In summary, the elongated external acoustic volume channel (1.201) provides higher absorption at lower frequencies by giving it a high tortuosity. However, the sound waves entering through the inlet holes (1.10) travel a distance greater than the channel thickness and are exposed to higher visco-thermal effects as they travel inside the cell (1). This allows the sound waves to dissipate more of their energy and therefore the cell has a higher sound absorption capacity. This feature makes the metacell a hybrid cell. The greater the viscous absorption, the wider the frequency band. With the use of several different cells, the panel comprises a hybrid cell, a feature that allows it to provide absorption in a wider band.

[0042] In addition to those described, the same or different single cells (1) can be connected to each other in double, triple, quadruple and multiple, side-by-side, back-to-back or back-to-back or any other arrangement according to the purpose. Thus, higher absorption is obtained at lower frequencies. The individual cells (1) are all binary (e.g., FIG. 7) and the multiple cells (1) can be circular, triangular, square, rectangular, polygonal or have any shape. With binary and multiple cells (1), further behavior is obtained with respect to the properties and characteristics obtained with the single cell (1). By creating two or more Helmholtz resonators with two or more acoustic volumes and inlets (A), dual or multiple resonant cells (1) are provided. Thus, sound absorption and sound transmission loss are obtained at dual and multiple tonal frequencies. Again, as with the single cell (1), different sound absorption and transmission loss characteristics are obtained according to the combination of opening and closing the inlets (A). With dual and multiple cells (1), the inter-cell paths can be longer effective paths (L effective ), which results in higher acoustic energy absorption at lower frequencies.

[0043] The first layer (1.1), second layer (1.2), and third layer (1.3) are joined together by any available joining method to form single or multiple cells (1). All cell layers, such as single piece or composite structures, can be manufactured by any manufacturing method.

[0044] On the other hand, panels absorbing at various frequencies can be formed by arranging at least one of these same or different cells (1) side by side (or one after the other) or one above the other or in any arrangement according to the purpose. To form a panel, at least one cell (1) mentioned with the same or different geometrical form and physical characteristics can be located on said panel. Thus, a panel consisting of metacells (1), which are the subject of the present invention, can be obtained. Since the panel comprises at least one metacell (1), each cell (1) is arranged on the panel so as to absorb sounds of the same or different frequencies, sound absorption is achieved both in the tonal band and in the broadband.

[0045] The characteristics of the panels obtained from the metacell (1) which is the subject of the present invention are as follows: 1- A panel can be constructed by adding the same and / or different single or multiple hybrid cells (1) to each other side by side and / or back to back and / or linearly and / or diagonally and / or arbitrarily and / or periodically and / or randomly and / or in different orders depending on the desired purpose. 2- The same or different panels formed by having one or more cells (1) can be combined with each other in different arrangements side by side and / or back to back and / or linearly and / or diagonally and / or arbitrarily, periodically and / or randomly and / or according to a desired purpose to create products of any two-dimensional or three-dimensional form. 3- With the panels and / or hybrid meta-cells (1) the insulating products formed by gluing and / or attaching and / or snapping and / or any bonding / adhesive / joining / attaching to each other or to any element can be constructed partially or completely integrally. 4- The panels may be rigid, hard, soft or flexible depending on the material used and may be given any form. The products made from the panels may likewise be rigid, hard, soft or flexible and may be given any form. 5- The main material of these acoustic metamaterial panels can be made from a combination of the most suitable materials (e.g. metal, wood, plastic, foam, plexiglass, PVC, etc.) selected according to the system to be applied and its purpose. That is to say, the layers of cells (1) that the panel has can be made from the same or any different materials by choosing the material that is most suitable for the purpose. The cells (1) that make up the panel can be made alone or in a single part in several ways. In the preferred application of the invention, the panel is made from any additive or pure material suitable for any flammability and / or any safety class. 6- The panels can be of different thickness depending on the thickness of the cell (1). 7- The panels and / or cells (1) can have a circular, triangular, square, rectangular, polygonal or any shape. 8-The panel and / or cell (1) can be provided with at least one further protective layer (t) (plate or layer or cover) forming a gap with the first layer (1.1) and / or the third layer (1.3). (Fig. 10) These layers allow the sections (membrane / plate) to vibrate freely during attachment (gluing, bonding) of the panel to any surface, by blocking the direct contact of the first section (B1) and the second section (B2) with the attachment surface. Furthermore, the first section (B1) and the second section (B2) protect the cell (1) from dust, dirt, piercing and cutting tips, heat, chemical reactions, corrosion, rain, moisture, organisms and all possible internal and external factors, preventing their deterioration. Thus, the panel can be protected with layers not only when it is attached to a surface, but also for the aforementioned factors. 9-Designing the panel as a laminated composite structure makes it easy to manufacture but does not occupy too much space in the application area due to its very thin structure. However, in terms of manufacturing, the panel can be manufactured as a single piece with any manufacturing method. The panel can be specially designed according to the criteria of high performance, ease of manufacturing, and low cost.

[0046] In summary, the insulating panel made of metacells (1), the subject of the present invention, is designed according to the acoustic metamaterial theory. Acoustic metamaterials are a kind of artificial composite structure, single or multi-layer, formed by combining one or more substrates by transforming them into sub-wavelength resonant cells. Spatial and / or vibrating thin plates and / or small weights are placed in a planned manner in the first layer (1.1) and in the third layer (1.3) of this structure, while the geometry, form and dimensions of the second layer (1.2) are specially designed according to the frequency characteristics of the noise to be reduced. When the sound waves of the noise hit this three-layer structure, the noise vibrates and resonates with this specially tuned three-layer structure. The special structures formed by the resonating first layer (1.1), second layer (1.2) and third layer (1.3) and their combination exhibit a negative mass and / or bulk modulus effect up to their resonant frequency, which stops the sound propagation in this area, absorbing the sound energy and thus reducing the sound level to a certain amount. In this way, noise absorption and / or noise transmission stopping is achieved with the cells (1) that are the subject of the present invention. As can be seen, the mechanism of action of such structures is quite different from that of passive insulating materials. While passive insulating materials provide absorption by converting sound energy into thermal energy, these structures reduce sound energy by preventing and manipulating the propagation of sound by the cells at lower wavelengths.

[0047] In addition to exhibiting acoustic metamaterial properties, the resulting panel both transmits and absorbs sound simultaneously over a wider frequency range by utilizing the properties of passive materials, which is why it is called hybrid. Specially designed and optimized through R&D activities, the panel cells (1) operate at maximum efficiency over a wide frequency range from 50 Hz to 20,000 Hz. Application of the invention to industry

[0048] The present invention is a metamaterial panel comprising at least one cell (1) developed for use in many fields such as automotive, aerospace, industrial machinery, white goods, household appliances, air conditioning and ventilation systems, defense industry, construction and building industry, and is industrially applicable.

[0049] The present invention is not limited to the above exemplary embodiments, and those skilled in the art can easily demonstrate different embodiments of the present invention, which should be considered within the scope of protection claimed by the claims of the present invention.

Claims

1. They are suitable for use in many fields such as automotive, aviation, industrial machinery, white goods, domestic appliances, air conditioning and ventilation systems, defense industry, construction and building sectors, and preferably in the form of circles, triangles, squares, rectangles, polygons or any (random, arbitrary) form (shape) of any geometrical form that can be connected to each other via hybrid acoustic single or acoustic volume channels (1.201), - comprising at least one layer for stopping the transmission and / or absorption of sound / noise waves generated by noise sources in a very wide frequency range, A plurality of metacells (11), - at least one first layer (1.1) (or front or inlet layer) of any geometrical form and physical characteristics; - at least one second layer (1.2) (or intermediate layer) of any geometrical form and physical characteristics; - at least one third layer (1.3) (or outlet or back layer) of any geometrical form and physical characteristics; - at least one inner frame (1.21) with any physical feature integral with it or any geometrical form associated with it, and with structures for forming therein different numbers of channels (or slits); - at least one internal acoustic volume (1.210) that fills the inner frame (1.21) to its internal volume and that has any geometrical form and physical properties that are compatible with the geometrical form of the inner frame (1.21); Equipped with - the interior has any geometric shape, located at a predetermined distance from the inner frame (1.21) and in the outer area of ​​the inner frame (1.21) so as to form a channel between the interior and the inner frame (1.21), and comprises at least one external acoustic volume channel (1.201) of any shape and physical characteristics, and at least one outer frame (1.20) of any geometric shape and physical characteristics, the external acoustic volume channel (1.201) and the internal acoustic volume (1.210) being connected to the second layer (1.2) and the third layer (1.2) due to the geometric shape and physical characteristics of all layers; the first layer (1.1) is combined with at least one first section (B1) and at least one section of at least two separate sections of the second layer (1.2), the first layer (1.1) and the third layer (1.3) to a predetermined thickness so as to completely or partially cover one surface of the second layer (1.2), the first layer (1.1) and the third layer (1.3) and to completely or partially cover the other surface according to the purpose, the second layer (1.2) having a predetermined thickness allows it to act as the second part (B2), and the first layer (1.1), the second layer (1.2) and the third layer (1.3) are positioned at a predetermined distance apart. A plurality of metacells (11) characterized in that

2. 2. The meta-cell (1) according to claim 1, characterized in that the first layer (1.1) and the third layer (1.3) are membranes and / or plates.

3. 3. The meta-cell (1) according to claim 2, characterized in that masses can be added to any part of the first layer (1.1) and the third layer (1.3) in any shape, weight and position.

4. 4. The meta-cell (1) according to claim 3, characterized in that the internal acoustic volume (1.210) and the external acoustic volume channel (1.201) are of any geometrical form, preferably circular, triangular, square, rectangular, polygonal or of any (random, arbitrary) form (shape).

5. The first layer (1.1) and the third layer (1.3) comprise at least one inlet hole (1.10) for the waves to enter and at least one outlet hole (1.30) for the waves to exit, the dimensions of the holes being determined so that they do not interfere with the features of the membrane (plate), the holes allowing the sound waves to enter and / or exit the cells, thereby providing an effective length (path) (L) with a given geometry, size and position. ｅｆｆｅｃｔｉｖｅ 5. The meta-cell (1) according to claim 4, characterized in that it increases the

6. 6. The meta-cell (1) according to claim 5, characterized in that the at least one inlet hole (1.10) and / or the at least one outlet hole (1.30) can have various geometric shapes (circular, triangular, square, rectangular, polygonal or any), sizes and can be located anywhere on the layer where they are located, depending on the characteristics of the cell (1).

7. 7. The meta-cell (1) according to claim 6, characterized in that at least one second layer (1.2) comprises at least one port (A) (or opening) connecting the external acoustic volume channel (1.201) with the internal acoustic volume (1.210).

8. 8. The meta-cell (1) according to claim 7, characterized in that it comprises the first layer (1.1), the second layer (1.2) and the third layer (1.3), which may be added to each other side by side and / or back to back and / or linearly and / or diagonally and / or arbitrarily and / or periodically and / or randomly.

9. 10. A panel comprising at least one hybrid metamaterial cell according to claim 1, characterized in that identical and / or different cells can be interconnected side by side and / or back to back and / or linearly and / or diagonally and / or arbitrarily and / or periodically and / or randomly.

10. 10. The product of claim 1, characterized by hybrid meta-cells and / or panels that can be attached to each other or to any element by gluing and / or snapping and / or fitting and / or by any method of fastening / adhering / joining / attaching and / or can be partially or completely integrally formed.

11. 11. Product according to claim 10, characterized in that the cells and / or panels may be circular, triangular, square, rectangular, polygonal or of any shape, which may be formed by combining them side by side and / or behind and / or linearly and / or diagonally and / or arbitrarily, periodically and / or randomly, and may be of different thicknesses depending on the thickness of the same or different cells (1).

12. 12. Product according to claim 10 or 11, characterized in that the cells and / or panels comprise at least one further protective layer (t) (plate or layer or cover) which forms a space together with the first layer (1.1) and / or the third layer (1.3).

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