Acoustic Filter

Abstract

The present invention provides an acoustic filter that is capable of insulating against high-frequency sound without requiring electric power.　Provided is an acoustic filter comprising at least one Helmholtz resonator.

Description

[Technical Field]

[0001] The present disclosure relates to the technical field of acoustics, for example, sound deadening and soundproofing. [Background technology]

[0002] Noise is a serious environmental problem that has various adverse effects on people's health and lifestyles (Non-Patent Document 1). There has been a demand for sound-insulating devices to protect the ears and provide comfort.

[0003] Conventional noise countermeasures include the development and use of passive noise control (PNC), a physical sound-blocking technology using cushions, and active noise control (ANC), an anti-noise technology using electricity. However, due to its nature, PNC technology provides high sound-blocking effectiveness for high-frequency sounds but is insufficient for low-frequency sounds. Furthermore, PNC technology, in principle, is virtually impossible to select and adjust the sound-blocking frequency, making it unsuitable for selectively blocking out noise alone. Blocking out important sounds, such as human voices and hazardous sounds, along with noise can pose a risk to users and reduce work efficiency. While ANC technology is effective against low-frequency sounds through its anti-noise technology, it is virtually ineffective against high-frequency sounds. Furthermore, its power-based design is complex and requires batteries, among other drawbacks.

[0004] Non-Patent Document 3 describes parallel Helmholtz resonators for planar acoustic filters, showing that the notch becomes deeper as the number of Helmholtz resonators increases.

[0005] Helmholtz resonators (HR) are known to have a sound-absorbing effect near their resonant frequencies, and are used to reduce duct noise and in sound-absorbing panels (for example, Non-Patent Documents 4 and 5).

[0006] Patent document 1 (JP 2019-528195 A) describes a sound-absorbing panel including a core made of connected cells, and the drawings show cells with a honeycomb structure.

[0007] New noise control measures are needed. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Special table number 2019-528195 [Non-patent literature]

[0009] [Non-Patent Document 1] DI Nelson et al., Am. J. Ind. Med., vol. 48, pp. 446-458, 2005 [Non-patent document 2] J. Liu et al., Appl. Acoust., vol. 165, p. 107321, 2020 [Non-patent document 3] A. Isozaki et al., Appl. Phys. Lett., vol. 105, p.241907, 2014 [Non-patent document 4] JM de Bedout et al., J. Sound Vib., vol. 202, pp.109-123, 1997 [Non-patent document 5] XD. Zhao et al., Appl. Acoust., vol. 114, pp. 92-98,2016 Summary of the Invention [Problem to be solved by the invention]

[0010] The present disclosure aims to provide an acoustic filter that at least partially solves the above problems. [Means for solving the problem]

[0011] As a result of extensive research into solving the above problems, the present inventors have developed an acoustic filter having a plurality of Helmholtz resonators (HR), and have completed the present invention, which includes this as one embodiment.

[0012] Furthermore, the present inventors have improved this acoustic filter and developed an acoustic notch filter having an acoustic filter, a membrane portion, and a microchannel portion, and capable of tuning the resonance frequency, and have completed the present invention, which includes this as one embodiment.

[0013] The present disclosure encompasses the following embodiments. [1] An acoustic filter having a through portion that penetrates between the front surface and the back surface and a non-through portion, wherein the through portion is hollow, The side surface of the through-hole has one or more connecting holes that connect the air chamber and the through-hole, the connecting hole and the air chamber are hollow and provided in the non-penetrating portion, The air chamber has all walls closed except for the connecting hole, The acoustic filter has two or more of the through portions and the non-through portions. [2] The through-hole has a polygonal shape. The non-penetrating portion is a polygonal pillar. The through portion is polygonal in shape and the non-through portion is a polygonal pillar, or The through-hole has a circular or elliptical shape. 2. An acoustic filter according to embodiment 1. [3] The polygonal shape of the penetrating portion is triangular, and the non-penetrating portion has a triangular prism structure. The polygonal shape of the penetrating portion is quadrangular, and the non-penetrating portion has a quadrangular prism structure. The polygonal shape of the penetrating portion is quadrangular, and the non-penetrating portion has an octagonal prism structure. The polygonal shape of the penetrating portion is hexagonal, and the non-penetrating portion has a triangular prism structure. The polygonal shape of the penetrating portion is hexagonal, and the non-penetrating portion has a hexagonal prism structure. The polygonal shape of the penetrating portion is triangular, and the non-penetrating portion has a hexagonal prism structure. The polygonal shape of the through portion is an octagon, and the non-through portion has a square prism structure; or The polygonal shape of the penetrating portion is octagonal, and the non-penetrating portion has an octagonal prism structure. An acoustic filter according to embodiment 2. [4] An acoustic filter according to embodiment 3, wherein the through-holes have the same number of connecting holes as the number of sides of the through-holes, and the through-holes are connected to the respective air chambers via the respective connecting holes. [5] An acoustic filter according to embodiment 4, wherein each side of the through-hole has one connecting hole, and the through-holes are connected to different air chambers via the respective connecting holes. [6] An acoustic filter according to any one of embodiments 1 to 5, wherein the through portions and the non-through portions have a planar tessellation shape. [7] An acoustic filter according to any one of embodiments 1 to 6, wherein the connecting hole and the air chamber connected thereto are Helmholtz resonators. [8] The Helmholtz resonator has the following formula:

number

[10] The nth Helmholtz resonator has a frequency f n It is designed to resonate with the sound of f n But the lowest frequency f min ~Highest frequency f max 9. The acoustic filter according to embodiment 7 or 8, configured to be within the range of

[11] An acoustic filter comprising two acoustic filters according to any one of embodiments 1 to 10, wherein the input surface of the first acoustic filter is aligned with the output surface of the second acoustic filter.

[12] An acoustic filter having two acoustic filters according to any one of embodiments 1 to 10, wherein the input surface of the first acoustic filter and the input surface of the second acoustic filter are aligned, or the output surface of the first acoustic filter and the output surface of the second acoustic filter are aligned, thereby causing each through-hole to be partially, alternately offset. An acoustic filter.

[13] An acoustic filter according to embodiment 11 or 12, wherein the first acoustic filter and the second acoustic filter have different resonant frequencies.

[14] An acoustic filter according to any one of embodiments 1 to 13, characterized in that a tuning unit is provided that changes the volume of the air chamber to tune the resonance frequency.

[15] An acoustic filter according to embodiment 14, characterized in that the tuning section has a membrane section and a microchannel section, and is configured so that the membrane section is sandwiched between the air chamber and the microchannel section.

[16] An acoustic filter as described in embodiment 15, wherein the tuning section further comprises an air pressure adjusting section that can apply air pressure to the microchannel section or reduce the air pressure in the microchannel section.

[17] A sound-insulating method using the acoustic filter according to any one of embodiments 1 to 16. This specification includes the disclosure of Japanese Patent Application No. 2021-020939, from which this application claims priority. [Effects of the Invention]

[0014] As an effect of the present disclosure, for example, in an environment where noise of a specific frequency is generated, it is possible to selectively block only the noise without impeding conversation sounds, dangerous sounds, etc. Furthermore, for example, by changing the dimensions of the acoustic filter, it is possible to select the frequency to be affected, thereby obtaining a sound blocking effect tailored to the intended use. Furthermore, as an effect of the present disclosure, unlike active noise control that requires power, it is possible to block high-frequency sounds without using power. Furthermore, as an effect of the present disclosure, the acoustic filter allows gas to flow in and out through the through holes, making it breathable.

[0015] Furthermore, as an effect of the present disclosure, an acoustic notch filter capable of tuning the resonant frequency is provided, and the frequency to be blocked can be tuned. [Brief explanation of the drawings]

[0016] [Figure 1] 1 shows a schematic diagram of a device of the present disclosure, in which the device of the present disclosure is attached to headphones. [Figure 2-1] A conceptual diagram of a Helmholtz resonator is shown. The through and non-through parts of the acoustic filter are shown. Each through part is a regular hexagon when viewed from the vertical plane of the acoustic filter, and is connected to six Helmholtz resonators via six connecting holes. Each non-through part is the smallest unit, with three Helmholtz resonators inside. The through part and part of the non-through part form a unit shape. This is a plane tessellation shape. [Figure 2-2] A conceptual diagram of a Helmholtz resonator is shown. Cancellation waves can flow into the penetration through the connecting hole. [Figure 2-3] This is a schematic diagram of one embodiment of a Helmholtz resonator array. The white parts are through-holes, the gray parts are non-through-holes, and the arrows indicate cancellation waves passing through the connecting holes. The schematic diagram omits the thickness of the walls and other details. When viewed from above, the through-holes are triangular, and the unit non-through-hole shapes are also triangular. [Figure 2-4]This is a schematic diagram of one embodiment of a Helmholtz resonator array. The white parts are through-holes, the gray parts are non-through-holes, and the arrows indicate cancellation waves passing through the connecting holes. The schematic diagram omits the thickness of the walls and other details. When viewed from above, the through-holes are rectangular, and the shape of the unit non-through-holes is also rectangular. [Figure 2-5] This is a schematic diagram of one embodiment of a Helmholtz resonator array. The white parts are through-holes, the gray parts are non-through-holes, and the arrows indicate cancellation waves passing through the connecting holes. The schematic diagram omits the thickness of the walls and other details. When viewed from above, the through-holes are hexagonal, and the smallest unit of the non-through-holes is a triangle. [Figure 2-6] This is a schematic diagram of one embodiment of a Helmholtz resonator array. The white parts are through-holes, the gray parts are non-through-holes, and the arrows indicate cancellation waves passing through the connecting holes. The schematic diagram omits the thickness of the walls, etc. When viewed from above, the through-holes are triangular, and the smallest unit of non-through-holes is a hexagon. For example, two through-holes and one non-through-hole can form a unit shape. [Figure 2-7] This is a schematic diagram of one embodiment of a Helmholtz resonator array. The white parts are through-holes, the gray parts are non-through-holes, and the arrows indicate cancellation waves passing through the connecting holes. The schematic diagram omits the thickness of the walls and other details. When viewed from above, the through-holes are octagonal, and the unit non-through-hole shapes are square. [Figure 2-8] This is a schematic diagram of one embodiment of a Helmholtz resonator array. The white parts are through-holes, the gray parts are non-through-holes, and the arrows indicate cancellation waves passing through the connecting holes. The schematic diagram omits the thickness of the walls and other details. When viewed from above, the through-holes are rectangular, and the unit non-through-hole shapes are octagonal. [Figure 2-9] This is a schematic diagram of one embodiment of a Helmholtz resonator array. The white parts are through-holes, the gray parts are non-through-holes, and the arrows indicate the canceling waves passing through the connecting holes. The schematic diagram omits the thickness of the walls, etc. This is an embodiment in which the rectangular through-holes in Figure 2-8 are changed to a circular shape. The non-through-holes are also changed to a corresponding shape. [Figure 2-10] Here are some examples of tessellations: Any unit can be perforated or non-perforated. [Figure 3] This shows a 3D-printed Helmholtz resonator. Dimensions are in millimeters. [Figure 4-1] This is a photograph of a Helmholtz resonator array fabricated using a stereolithography 3D printer. [Figure 4-2] This is a photograph of a Helmholtz resonator array fabricated using a stereolithography 3D printer. [Figure 5] The acoustic simulation results of the HR array are shown below. (A) is a perspective view, and (B) is the sound pressure distribution. [Figure 6] Shown are a single array (Single), two arrays in the same direction (Dual, same direction), and two arrays in opposite directions (Dual, reverse). [Figure 7] 1 shows a frequency response graph of the simulation results. [Figure 8-1] A photograph of the experimental setup for measuring the behavior of sound from a microphone as it passes through the HR array and into the earphones is shown. [Figure 8-2] A schematic diagram of the experimental setup is shown. [Figure 8-3] A schematic diagram of the experimental setup is shown. [Figure 9] The measured frequency response graph is shown. [Figure 10-1] This is a photo of a mannequin with a built-in microphone. [Figure 10-2] Photographs showing the inside of a mannequin. [Figure 11] The results of measuring the microphone sound pressure level when sound was applied from hearing test headphones to a mannequin equipped with a microphone are shown below. [Figure 12] This is a photograph of a comparative example of an active noise canceller (ANC) attached to a mannequin. [Figure 13] The following shows the results of measuring the microphone sound pressure level when ANC is used. For convenience, the case when ANC is off is referred to as PNC (i). The case when ANC is on is (ii). The difference between (i) and (ii) is (iii). [Figure 14] 1 is a photograph of a mannequin fitted with a device of the present disclosure. [Figure 15] The figures show embodiments in which the through-holes are arranged in a staggered pattern. Some of the through-holes overlap. (A) shows an embodiment in which all of the necks have the same shape. (B) shows an embodiment in which two types of necks are alternately connected to one through-hole. (C) shows an embodiment in which six necks of one type are connected to a first array of through-holes, and six necks of a different size are connected to a second array of through-holes. [Figure 16] The simulation results are shown for the case where the inner diameter of the necks in the array is all 2 mm. (i) is a single array, (ii) is two arrays stacked in reverse, and (iii) is a third array (with the same dimensions) stacked on top of it. [Figure 17] Simulation results (i) are shown for the case where all the inner diameters of the necks in the array are 2 mm, and simulation results (ii) and (iii) are shown for the cases where different inner diameters of the necks are used. [Figure 18] This shows a concept sketch of a tunable acoustic notch filter that uses a Helmholtz resonator (HR) array. The tunable acoustic notch filter has a three-layer structure consisting of an air chamber, a membrane, and a microchannel. The chamber volume changes as the membrane deforms. The left side shows the case where pressure is applied to the microchannel, causing the membrane to rise and the chamber volume to decrease. In this case, it is possible to block higher frequency sounds. The right side shows the case where pressure in the microchannel is reduced, causing the chamber volume to increase. In this case, it is possible to block lower frequency sounds. [Figure 19-1] Concept sketch of a tunable acoustic notch filter using a Helmholtz resonator (HR) array. The chamber volume can be changed by applying air pressure to a microchannel with a piston (left) or by reducing air pressure in the microchannel, which deforms the membrane. [Figure 19-2]The piston mechanism shown in Figure 19-1 is provided on the outer ring of the hearing test headphones. [Figure 20] A is a schematic diagram of a tunable acoustic notch filter. B is an enlarged view of the air chamber (left) and the microchannel (right). C shows the entire microchannel layer. The X-X' cross sections of Figures 20A and C are shown in Figure 19-1. Note that the piston is not shown in Figure 20. [Figure 21-1] The acoustic simulation results of the tunable acoustic notch filter are shown. The left shows the sound pressure distribution, and the right shows a perspective view. [Figure 21-2] 1 shows the simulated frequency response of the HR array when subjected to various pressures (including negative pressure). [Figure 22-1] A shows the fabricated HR array holes and membrane. B shows the assembled membrane and microchannel layer. C shows the measurement results of the change in HR chamber volume due to membrane deformation under air pressure. [Figure 22-2] The cross-sectional shape of the membrane deformed by air pressure is shown. [Figure 22-3] The change in HR chamber volume due to membrane deformation under air pressure is shown. [Figure 23-1] We present an experimental setup for measuring the behavior of sound waves from a microphone as they pass through an HR array of tunable acoustic notch filters and enter the microphone. [Figure 23-2] 1 is a photograph of the experimental setup. [Figure 23-3] 1 shows the frequency response of the HR array. [Figure 23-4] The change in notch frequency as a function of pressure is shown. DETAILED DESCRIPTION OF THE INVENTION

[0017] In one embodiment, the present disclosure provides an acoustic filter (also referred to as an acoustic notch filter) having one or more, for example, two or more, through-holes and non-through-holes that penetrate between a sound input surface and an output surface. Each through-hole is hollow. One or more connecting holes are provided on the side of the through-hole. The connecting holes are sometimes referred to as necks or neck portions. The through-holes and the air chambers are connected via the connecting holes. The connecting holes may be hollow cylindrical or polygonal prisms with a substantially circular, circular, perfect circular, or polygonal cross section. The term "substantially circular" refers to shapes that are close to the concept of a circle, such as a circle or ellipse, and shapes that are modified from these. This term encompasses not only perfect circles, but also ellipses that are close to a perfect circle, bean-shaped closed curve figures, and polygons that are close to a perfect circle, such as octagons or higher. A polygonal connecting hole may be a polygon with a number of sides, n, of 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 or more. The connecting holes and the air chambers are hollow and located in the non-through-holes. The air chamber is sometimes called a chamber or a cavity. All of the walls of the air chamber are closed except for the connecting hole. The phrase "having two or more through portions and non-through portions" mentioned above means having two or more unit shapes each consisting of one through portion and an adjacent unit non-through portion shape. The unit non-through portion shape and unit shape will be described later. In this specification, the unit non-through portion shape may be simply called a non-through portion.

[0018] The sound input surface refers to the surface from which sound is expected to mainly enter when viewed from the vertical surface of the acoustic filter. The sound output surface refers to the surface from which sound is expected to mainly exit when viewed from the vertical surface of the acoustic filter. Note that the input surface and output surface are names for convenience, and the acoustic filter according to the present disclosure can also be symmetrical from top to bottom or symmetrical from front to back so that the shape is substantially the same when viewed from the input surface and the output surface. In this case, there is no substantial difference between the input surface and the output surface, and one surface can be called the input surface and the other surface can be called the output surface.

[0019] In one embodiment, the through-hole may have a polygonal shape (when viewed in a direction perpendicular to the acoustic filter, i.e., from the input surface or the output surface). In one embodiment, the non-penetrating portion (or a portion thereof) may be a polygonal prism (polygonal prism). In another embodiment, the through-hole has a polygonal shape, and the non-penetrating portion (or a portion thereof) is a polygonal prism. For example, in one embodiment, the through-hole has a hollow regular polygonal shape, and in one embodiment, it may be a triangle, a square, a regular pentagon, a regular hexagon, an octagon, or the like. For example, in one embodiment, the through-hole has a hollow regular polygonal shape, and in one embodiment, it may be an equilateral triangle, a square, a regular pentagon, a regular hexagon, a regular octagon, or the like.

[0020] The non-penetrating portion refers to a portion of the acoustic filter other than the penetrating portion. The shape of the non-penetrating portion can be designed according to the penetrating portion. In one embodiment, the non-penetrating portion (or a part thereof) has a polygonal prism structure, for example, a triangular prism structure, a square prism structure, a hexagonal prism structure, or an octagonal prism structure. In one embodiment, the non-penetrating portion (or a part thereof) has a regular polygonal prism structure, for example, a regular triangular prism structure, a regular square prism structure, a regular hexagonal prism structure, or a regular octagonal prism structure. The polygonal prism structure referred to here refers to a repetition of polygonal prism structures.

[0021] The present disclosure encompasses any combination of the above-described penetrating portions and non-penetrating portions (or portions thereof). For example, in some embodiments, the penetrating portions may be hexagonal (e.g., regular hexagonal). In this case, the non-penetrating portions (or portions thereof) may have a triangular prism structure (e.g., a regular triangular prism structure) or a hexagonal prism structure (e.g., a regular hexagonal prism structure).

[0022] That is, in one embodiment, The polygonal shape of the through-hole portion is triangular, and the non-through-hole portion (or a part thereof) has a triangular prism structure; or The polygonal shape of the through portion is square, and the non-through portion (or a part thereof) has a square prism structure; or The polygonal shape of the through portion is square, and the non-through portion (or a part thereof) has an octagonal prism structure; or The polygonal shape of the through portion is a hexagon, and the non-through portion (or a part thereof) has a triangular prism structure; or The polygonal shape of the through portion is hexagonal, and the non-through portion (or a part thereof) has a hexagonal prism structure; or The polygonal shape of the through portion is triangular, and the non-through portion (or a part thereof) has a hexagonal prism structure; or The polygonal shape of the through portion is an octagon, and the non-through portion (or a part thereof) has a square prism structure; or There is provided an acoustic filter, wherein the polygonal shape of the through portion is an octagon, and the non-through portion (or a part thereof; the same applies hereinafter) has an octagonal prism structure.

[0023] In another embodiment, the through portion may be circular or elliptical. In this case, the non-penetrating portion may have a shape corresponding to the through portion. The term "corresponding shape" encompasses, for example, an embodiment in which the through portion is polygonal and the non-penetrating portion is a polygonal prism, in which the through portion is changed from a polygonal shape to a circular shape, and the shape of the non-penetrating portion is changed to correspond to the change and has an increased or decreased volume. For example, in an embodiment in which the through portion is a square with sides of 2r and the non-penetrating portion is a rectangular prism with sides of 2r, if the through portion is changed from the square to a circle with a radius r inscribed in the square, the area of ​​the through portion as viewed from above will be (4r 2 -πr 2 ), and the area of ​​the non-penetrating portion seen from above increases accordingly, the volume increases, and the shape changes. Also, for example, in an embodiment in which the non-penetrating portion is a square prism with a side of 2r and the side of the non-penetrating portion is a square prism with a side of 2r, if the penetrating portion is changed from the square to a circle with a radius of (√2)·r circumscribing the square, the area of ​​the penetrating portion seen from above will be (2πr 2 -4r 2 ), and the volume of the non-penetrating portion decreases accordingly, changing its shape. Note that for convenience, the wall thickness has been omitted from the description. The circular shape in this disclosure encompasses not only the case where a square shape is changed to a circular shape as described above, but also the case where any polygonal shape is changed to a circular shape. Furthermore, the corresponding shapes of the non-penetrating portion are disclosed and provided.

[0024] In one embodiment, the through-hole may have the same number of connecting holes as the number of sides of the through-hole. In this case, the through-hole may be connected to each air chamber via each connecting hole. In another embodiment, each side of the through-hole may have one connecting hole. In this case, the through-hole may be connected to each separate air chamber via each connecting hole.

[0025] For example, in some embodiments, a hexagonal through-hole may have six connecting holes. In some embodiments, each side of the hexagonal through-hole may have one connecting hole. In this case, the through-hole may be connected to six air chambers via the respective connecting holes (e.g., Figures 2-5).

[0026] In another embodiment, the rectangular through-hole may have four connecting holes. In one embodiment, each side of the rectangular through-hole may have one connecting hole. In this case, the through-hole may be connected to four air chambers via the respective connecting holes (e.g., Figures 2-4).

[0027] In another embodiment, the triangular through-hole may have three connecting holes. In one embodiment, each side of the triangular through-hole may have one connecting hole. In this case, the through-hole may be connected to three air chambers via the respective connecting holes (e.g., Figures 2-3).

[0028] In another embodiment, the octagonal through-hole may have eight connecting holes. In one embodiment, each side of the octagonal through-hole may have one connecting hole. In this case, the through-hole may be connected to eight air chambers via the respective connecting holes.

[0029] In one embodiment, the through-hole may have connecting holes in half the number of sides of the through-hole. In this case, half of the sides may be connected to the air chambers via the respective connecting holes. In another embodiment, half of the sides of the through-hole may have one connecting hole each. In this case, each half of the sides may be connected to a different air chamber via the respective connecting holes.

[0030] In another embodiment, the octagonal penetration may have four connecting holes. In one embodiment, four of the sides of the octagonal penetration may have one connecting hole each. In this case, the penetration may be connected to four air chambers via the respective connecting holes (e.g., Figures 2-7).

[0031] In other embodiments, configurations are provided in which the polygonal through-holes described above are changed to circular through-holes. In these configurations, the aspects of the sides and connecting holes of the polygonal through-holes described above are applied correspondingly. For example, in a configuration in which a rectangular through-hole has four connecting holes and is connected to four air chambers via the respective connecting holes, even if the rectangular through-hole is changed to a circular through-hole, the changed circular through-hole may also have four connecting holes and be connected to four air chambers via the respective connecting holes (e.g., FIG. 2-9).

[0032] In one embodiment, all of the air chambers can have the same dimensions. In another embodiment, all of the air chambers do not have to have the same dimensions. For example, if the acoustic filter has two air chambers, the first air chamber and the second air chamber can have different dimensions. For convenience, the dimensions referred to here also include the dimensions and shape of the connecting hole, i.e., the radius (inner diameter) r of the connecting hole, the opening area S of the connecting hole, and the length l of the connecting hole. The length l of the connecting hole corresponds to the thickness of the wall of the air chamber that has the connecting hole. In other words, the length l of the connecting hole is the length between the through portion and the air chamber. The dimensions referred to here also include the volume V of the air chamber.

[0033] In some embodiments, a plurality of acoustic filters of the present disclosure can be combined. For example, two acoustic filters having the same or different shapes can be combined. In some embodiments, the present disclosure provides a composite acoustic filter having two acoustic filters, the two acoustic filters being stacked in series so that they are in the same direction, that is, the input surface of the first acoustic filter is aligned with the output surface of the second acoustic filter. The first acoustic filter and the second acoustic filter can be the same or different in shape.

[0034] In another embodiment, the present disclosure provides a composite acoustic filter, which has two acoustic filters, and the two acoustic filters are aligned in opposite directions, that is, the input surface of the first acoustic filter is aligned with the input surface of the second acoustic filter, or the output surface of the first acoustic filter is aligned with the output surface of the second acoustic filter, whereby each through-hole is partially arranged in a staggered manner. The first acoustic filter and the second acoustic filter can be the same or different in shape.

[0035] In one embodiment, the connecting hole and the air chamber connected thereto are Helmholtz resonators. That is, in one embodiment, the connecting hole and the air chamber connected thereto may be configured to function as a Helmholtz resonator.

[0036] The Helmholtz resonator has the following formula:

number

[0037] Helmholtz resonators (HRs) have many variable parameters, allowing for a high degree of freedom in design. For example, even with an HR having the same air chamber volume V, the noise-cutting frequency f0 can be manipulated by changing the numerator S in the square root of the formula, i.e., by widening or narrowing the opening area S of the connecting hole. Similarly, the noise-cutting frequency f0 can be manipulated by changing the denominator l in the square root of the formula, i.e., by lengthening or shortening the length l of the hook portion. Furthermore, by changing the thickness of the walls that make up the air chamber, the cavity volume V inside the air chamber can be increased or decreased, even if the outside dimensions of the air chamber are the same. This high degree of freedom in design is one of the advantages of the Helmholtz resonator.

[0038] In one embodiment, the radius r of the connecting hole can be, but is not limited to, 0.1 mm or more, 0.15 mm or more, 0.2 mm or more, 0.25 mm or more, 0.3 mm or more, 0.35 mm or more, 0.4 mm or more, 0.45 mm or more, 0.5 mm or more, 0.55 mm or more, 0.6 mm or more, 0.65 mm or more, 0.7 mm or more, 0.75 mm or more, 0.8 mm or more, 0.85 mm or more, 0.9 mm or more, 0.95 mm or more, 1 mm or more, 1.1 mm or more, 1.2 mm or more, 1.3 mm or more, 1.4 mm or more, 1.5 mm or more, 2 mm or more, 2.5 mm or more, 3 mm or more, 3.5 mm or more, 4 mm or more, 4.5 mm or more, 5 mm or more, 6 mm or more, 7 mm or more, 8 mm or more, 9 mm or more, for example, 10 mm or more. In some embodiments, the radius r of the connecting hole can be, but is not limited to, 10 mm or less, 9 mm or less, 8 mm or less, 7 mm or less, 6 mm or less, 5 mm or less, 4.5 mm or less, 4 mm or less, 3.5 mm or less, 3 mm or less, 2.5 mm or less, 2 mm or less, 1.5 mm or less, 1.4 mm or less, 1.3 mm or less, 1.2 mm or less, 1.1 mm or less, 1 mm or less, 0.95 mm or less, 0.9 mm or less, 0.85 mm or less, 0.8 mm or less, 0.75 mm or less, 0.7 mm or less, 0.65 mm or less, 0.6 mm or less, 0.55 mm or less, 0.5 mm or less, 0.45 mm or less, 0.4 mm or less, 0.35 mm or less, 0.3 mm or less, 0.25 mm or less, 0.2 mm or less, 0.15 mm or less, for example, 0.1 mm or less. The present disclosure also encompasses ranges incorporating any combination of the above upper and lower limits.

[0039] In one embodiment, the length l of the connecting hole can be, but is not limited to, 0.1 mm or more, 0.2 mm or more, 0.3 mm or more, 0.4 mm or more, 0.5 mm or more, 0.6 mm or more, 0.7 mm or more, 0.8 mm or more, 0.9 mm or more, 1 mm or more, 1.1 mm or more, 1.2 mm or more, 1.3 mm or more, 1.4 mm or more, 1.5 mm or more, 1.75 mm or more, 2 mm or more, 3 mm or more, 4 mm or more, 5 mm or more, 6 mm or more, 7 mm or more, 8 mm or more, 9 mm or more, for example, 10 mm or more. In some embodiments, the length 1 of the connecting hole can be, but is not limited to, 10 mm or less, 9 mm or less, 8 mm or less, 7 mm or less, 6 mm or less, 5 mm or less, 4 mm or less, 3 mm or less, 2 mm or less, 1.75 mm or less, 1.5 mm or less, 1.4 mm or less, 1.3 mm or less, 1.2 mm or less, 1.1 mm or less, 1 mm or less, 0.9 mm or less, 0.8 mm or less, 0.7 mm or less, 0.6 mm or less, 0.5 mm or less, 0.4 mm or less, 0.3 mm or less, 0.2 mm or less, for example, 0.1 mm or less. The present disclosure also encompasses ranges incorporating any combination of the above upper and lower limits.

[0040] In one embodiment, the volume V of the air chamber is 1 mm 3 More than 5mm 3 More than 10mm 3 Above, 15mm 3 Over 20mm 3 Above, 25mm 3 Above, 30mm 3 Above, 35mm 3 Above, 40mm 3 Above, 45mm 3 Above 50mm 3 Above, 55mm 3 Above, 60mm 3 Above, 65mm 3 Above, 70mm 3 Above, 75mm 3 Above, 80mm 3 That's it, 85mm 3 Above, 90mm 3 Above, 95mm 3 Over 100mm 3 Above, 110mm 3 Above, 120mm 3 Above, 130mm3 Above, 140mm 3 More than 150mm 3 More than 160mm 3 Above, 170mm 3 Above, 180mm 3 Over 190mm 3 Over 200mm 3 More than 250mm 3 Over 300mm 3 Above, 350mm 3 Over 400mm 3 Over 450mm 3 Over 500mm 3 Over 600mm 3 Over 700mm 3 Over 800mm 3 Over 900mm 3 or more, for example, 1000 mm 3 In one embodiment, the volume V of the air chamber is 1000 mm 3 Below, 900mm 3 Below, 800mm 3 Below, 700mm 3 Below, 600mm 3 Below, 500mm 3 Below, 450mm 3 Below, 400mm 3 Below, 350mm 3 Below, 300mm 3 Below, 250mm 3 Below, 200mm 3 Below, 190mm 3 Below, 180mm 3 Below, 170mm 3 Below, 160mm 3 Below, 150mm 3 Below, 140mm 3 Below, 130mm 3 Below, 120mm 3 Below, 110mm 3 Below, 100mm 3 Below, 95mm 3 Below, 90mm 3 Below, 85mm 3 Below, 80mm 3 Below, 75mm 3 Below, 70mm3 Below, 65mm 3 Below, 60mm 3 Below, 55mm 3 Below, 50mm 3 Below, 45mm 3 Below, 40mm 3 Below, 35mm 3 Below, 30mm 3 Below, 25mm 3 Below, 20mm 3 Below, 15mm 3 Below, 10mm 3 Below, 5mm 3 Below, 1mm 3 The present disclosure also encompasses ranges combining any of the above upper and lower limits.

[0041] For example, the HR designed with the dimensions shown in Figure 3 has a connecting hole radius r = 1 mm, and the wall thickness is all 1 mm, i.e., the connecting hole length l = 1 mm. Also, the volume of the air chamber is V = 115 mm. 3 The end correction coefficient is expressed as lc = 8r / 3π, where lc = 0.849 mm. The resonance frequency f0 calculated from the formula is f0 = 6.63 kHz. Similarly, for example, if r = 0.25 mm, all wall thicknesses are 2 mm, connecting hole length l = 2 mm, and air chamber volume V = 265 mm 3 By doing so, the end correction coefficient is calculated as lc = 0.212 mm, and the resonance frequency f0 can be set to f0 = 1 kHz. Similarly, for example, r = 1 mm, all wall thicknesses are 1 mm, connecting hole length l = 1 mm, and air chamber volume V = 50.6 mm 3 By doing so, the edge correction coefficient is calculated as lc = 0.849 mm, and the resonance frequency f0 can be set to f0 = 10 kHz.

[0042] In one embodiment, all Helmholtz resonators of the acoustic filter of the present disclosure can be configured to resonate with a sound of a single frequency f0, thereby eliminating or reducing the intended sound of the single frequency f0 (noise, rumble, etc.).

[0043] In another embodiment, all the Helmholtz resonators of the acoustic filter of the present disclosure may not be configured to resonate with a sound of a single frequency f0. For example, the n-th Helmholtz resonator may be configured to resonate with a sound of a frequency f n It can be configured to resonate with the sound of f n , the lowest frequency f min ~Highest frequency f max This allows the intended range f min ~f max It is possible to eliminate or reduce sounds (noise, disturbances, etc.).

[0044] In one embodiment, the lowest frequency f min The maximum frequency f can be, but is not limited to, 1 Hz or more, 10 Hz or more, 20 Hz or more, 50 Hz or more, 100 Hz or more, 200 Hz or more, 300 Hz or more, 400 Hz or more, 500 Hz or more, 600 Hz or more, 700 Hz or more, 800 Hz or more, 900 Hz or more, 1 kHz or more, 1.5 kHz or more, 2 kHz or more, 2.5 kHz or more, 3 kHz or more, 4 kHz or more, 5 kHz or more, 6 kHz or more, 7 kHz or more, 8 kHz or more, 9 kHz or more, 10 kHz or more, 11 kHz or more, 12 kHz or more, 13 kHz or more, 14 kHz or more, 15 kHz or more, 16 kHz or more, 17 kHz or more, 18 kHz or more, 19 kHz or more, for example, 20 kHz or more. maxThe minimum frequency f may be, but is not limited to, 20 kHz or less, 19 kHz or less, 18 kHz or less, 17 kHz or less, 16 kHz or less, 15 kHz or less, 14 kHz or less, 13 kHz or less, 12 kHz or less, 11 kHz or less, 10 kHz or less, 9 kHz or less, 8 kHz or less, 7 kHz or less, 6 kHz or less, 5 kHz or less, 4 kHz or less, 3 kHz or less, 2.5 kHz or less, 2 kHz or less, 1.5 kHz or less, 1 kHz or less, 900 Hz or less, 800 Hz or less, 700 Hz or less, 600 Hz or less, 500 Hz or less, 400 Hz or less, 300 Hz or less, 200 Hz or less, 100 Hz or less, 50 Hz or less, 20 Hz or less, 10 Hz or less, for example, 5 Hz or less. min and the highest frequency f max Any combination of the lowest frequency f min ~Highest frequency f max The frequency can be 1 Hz to 20 kHz, 5 Hz to 19 kHz, 10 Hz to 18 kHz, 20 Hz to 17 kHz, 50 Hz to 16 kHz, 100 Hz to 15 kHz, 1 kHz to 16 kHz, 2 kHz to 15 kHz, 2 kHz to 10 kHz, 2 kHz to 8 kHz, 3 kHz to 14 kHz, 3 kHz to 12 kHz, 3 kHz to 10 kHz, 3 kHz to 8 kHz, 4 kHz to 10 kHz, 4 kHz to 9 kHz, 4 kHz to 8 kHz, for example, 5 Hz to 8 kHz, 3.5 Hz to 8 kHz, 3.6 Hz to 7 kHz, 3.7 Hz to 6 kHz, 3.8 Hz to 6 kHz, 3.9 Hz to 5.9 kHz, for example, 3.9 Hz to 5.8 kHz, but is not limited to this.

[0045] In one embodiment, the through portion and the non-through portion may have the same thickness throughout the acoustic filter of the present disclosure. That is, the acoustic filter of the present disclosure may be flat. In this case, two or more acoustic filters of the present disclosure may be stacked and used.

[0046] In some embodiments, a plurality of acoustic filters of the present disclosure can be combined. For example, two acoustic filters having the same or different shapes can be combined. In some embodiments, the present disclosure provides a composite acoustic filter having two acoustic filters, the two acoustic filters being stacked in series so that they are in the same direction, that is, the input surface of the first acoustic filter is aligned with the output surface of the second acoustic filter. The first acoustic filter and the second acoustic filter can be the same or different in shape (for example, the center of FIG. 6).

[0047] In another embodiment, the present disclosure provides a composite acoustic filter having two acoustic filters, the two acoustic filters being aligned in opposite directions, that is, the input surface of the first acoustic filter and the input surface of the second acoustic filter are aligned, or the output surface of the first acoustic filter and the output surface of the second acoustic filter are aligned, thereby each through-hole is partially arranged to be staggered. The first acoustic filter and the second acoustic filter can be the same or different in shape (for example, FIG. 6 right).

[0048] In an embodiment, the acoustic filter of the present disclosure can have through-holes of the same dimensions in principle. However, this does not apply to through-holes approaching the end of the acoustic filter, and as an exception, a portion of the shape on the end side may be omitted. In another embodiment, the acoustic filter of the present disclosure can have Helmholtz resonators of the same dimensions in principle. However, this does not apply to Helmholtz resonators approaching the end of the acoustic filter, and a portion of the shape on the end side may be omitted. In an embodiment, the acoustic filter of the present disclosure can have a non-through portion at the outer edge of a certain range from the end. This can ensure the strength of the entire acoustic filter (for example, FIG. 4-1).

[0049] In some embodiments, the through and non-through portions may be in the form of a tessellation. For information on tessellations, see general mathematics textbooks, such as Chris Decordova, The Tessellations File (Mathematics Resource Files), March 1, 1997. The contents of these documents regarding tessellations are incorporated herein by reference. Examples of tessellations are shown in Figures 2-10, but the tessellations of this disclosure are not limited to these.

[0050] For example, a plane can be filled with only equilateral triangles, only squares, or only regular hexagons. Such plane filling is sometimes called a regular tessellation. Therefore, in the acoustic filter of the present disclosure, a tessellation shape can be achieved by making the penetrating parts into equilateral triangle shapes and the non-penetrating parts into regular triangular prism structures. Also, in the acoustic filter of the present disclosure, a tessellation shape can be achieved by making the penetrating parts into square shapes and the non-penetrating parts into regular quadrangular prism structures. Also, in the acoustic filter of the present disclosure, a tessellation shape can be achieved by making the penetrating parts into regular hexagonal shapes and the non-penetrating parts into a combination of regular hexagonal prism structures (so-called honeycomb structures).

[0051] The above is merely an example, and any other shape or polygon combination is provided so that the through portion and the non-through portion form a tessellation shape when viewed from the vertical plane of the acoustic filter. For example, there may be eight types of Archimedean tessellation or 15 types of pentagonal tessellation, but this is not limited to these.

[0052] In the acoustic filter of the present disclosure, the through portions and non-through portions can be in the shape of a tessellation. Note that the acoustic filter of the present disclosure having a tessellation shape can be manufactured as an appropriate shape or processed into an appropriate shape. For example, such examples are shown in Figures 4-1 and 4-2. In this case, although the entire acoustic filter is basically configured in a tessellation shape, a portion of the shape approaching the end can be omitted. That is, in the portion of the entire acoustic filter approaching the end, a portion of the through portion may be omitted, and / or a portion of the non-penetrating portion may be omitted. In this specification, even if the shape of the through portion and / or non-penetrating portion at the end of the acoustic filter is partially omitted, as long as the entire acoustic filter is basically configured in a tessellation shape, it is considered to be included in the "tessellation shape" for convenience.

[0053] In this specification, "filling a plane" refers to the operation of tiling a plane with the same shapes (sometimes referred to as unit shapes). Furthermore, in this specification, the entire plane constituted by the tiled unit shapes is referred to as a tessellation shape or a tessellation form. Conversely, a tessellation shape (tessellation form) is a shape in which the same shapes (unit shapes) appear repeatedly and are repeatedly tiled to fill the plane. In one embodiment, the through portions and the non-penetrating portions of the acoustic filter of the present disclosure are tessellation shapes. The phrase "the through portions and the non-penetrating portions are tessellation shapes" means that one through portion and a portion of a non-penetrating portion correspond to the aforementioned unit shape, and therefore correspond to a shape that can fill a plane by repeatedly tiling unit shapes constituted by one through portion and a portion of a non-penetrating portion. The one through portion and the portion of the non-penetrating portion are adjacent to each other. Furthermore, the one through portion and the portion of the non-penetrating portion adjacent thereto may be connected via a connecting hole. Furthermore, a combination of a penetrating portion and a non-penetrating portion (part thereof) that can be formed into a tessellated shape may be referred to as a unit shape (basic structural unit). In some embodiments, the unit shape may be a tessellated shape, i.e., a shape that can be formed into a tessellated shape. In some embodiments, one penetrating portion and a part of a non-penetrating portion connected thereto via a connecting hole may constitute a unit shape.

[0054] In this specification, the portion of a unit shape other than the through-hole portion may be referred to as a unit non-penetrating portion shape. For example, in Figure 2-2, the through-hole portion is a hexagon, and the non-penetrating portion is the portion other than the through-hole portion. As an example, the combination of two hexagonal shapes (each hexagon having three air chambers) located to the right of a certain through-hole among the non-penetrating portions (but excluding the through-hole portion) can be considered a unit non-penetrating portion shape. Furthermore, the unit non-penetrating portion shape and the through-hole portion adjacent to it on the left can form a unit shape. By repeatedly tiling such unit shapes, a plane can be filled. However, in Figure 2-2, the unit shapes and unit non-penetrating portion shapes are not limited to this one type, and any other shape that can fill a plane can be called a unit shape or a unit non-penetrating portion shape.

[0055] In one embodiment, the through portion is a hexagon (for example, a regular hexagon) when viewed from the vertical surface of the acoustic filter, that is, the through portion can be a hollow hexagonal prism (for example, a regular hexagonal prism). Also, in this embodiment, a portion of the non-penetrating portion can be a hexagon (for example, a regular hexagon) when viewed from the vertical surface of the acoustic filter, that is, a portion of the non-penetrating portion can be made into a hexagonal prism (for example, a regular hexagonal prism) honeycomb structure, and two or more hexagonal prisms of the non-penetrating portion can be combined so that the through portion and a portion of the non-penetrating portion have a planar tessellation shape when viewed from the vertical surface of the acoustic filter (for example, FIG. 2-1).

[0056] In another embodiment, the through-hole portion is a triangle (for example, an equilateral triangle) when viewed from the vertical surface of the acoustic filter, that is, the through-hole portion can be a hollow triangular prism (for example, a regular triangular prism). Also, in this embodiment, a part of the non-penetrating portion can be a triangle (for example, an equilateral triangle) when viewed from the vertical surface of the acoustic filter, that is, a part of the non-penetrating portion can be made into a triangular prism (for example, a regular triangular prism) structure, and the through-hole portion and a part of the non-penetrating portion can be configured to have a plane-filling shape when viewed from the vertical surface of the acoustic filter (for example, Figure 2-3).

[0057] In another embodiment, the through-hole portion is a quadrangle (for example, a square) when viewed from the vertical surface of the acoustic filter, that is, the through-hole portion can be a hollow quadrangular prism (for example, a regular quadrangular prism). Also, in this embodiment, a part of the non-penetrating portion can be a quadrangle (for example, a square) when viewed from the vertical surface of the acoustic filter, that is, a part of the non-penetrating portion can be a quadrangular prism (for example, a regular quadrangular prism) structure, and the through-hole portion and a part of the non-penetrating portion can be configured to have a planar filling shape when viewed from the vertical surface of the acoustic filter (for example, Figure 2-4).

[0058] In another embodiment, the through-hole portion is a hexagon (for example, a regular hexagon) when viewed from the vertical surface of the acoustic filter, that is, the through-hole portion can be a hollow hexagonal prism (for example, a regular hexagonal prism). Also, in this embodiment, a part of the non-through-hole portion can be a triangle (for example, a regular triangle) when viewed from the vertical surface of the acoustic filter, that is, a part of the non-through-hole portion can be a triangular prism (for example, a regular triangular prism) structure, and the through-hole portion and a part of the non-through-hole portion can be configured to have a planar filling shape when viewed from the vertical surface of the acoustic filter (for example, Figure 2-5).

[0059] In another embodiment, the through-hole portion is a triangle (for example, an equilateral triangle) when viewed from the vertical surface of the acoustic filter, that is, the through-hole portion can be a hollow triangular prism (for example, a regular triangular prism). Also, in this embodiment, a part of the non-penetrating portion can be a hexagon (for example, a regular hexagon) when viewed from the vertical surface of the acoustic filter, that is, a part of the non-penetrating portion can be a hexagonal prism (for example, a regular hexagonal prism) structure, and the through-hole portion and a part of the non-penetrating portion can be configured to have a planar filling shape when viewed from the vertical surface of the acoustic filter (for example, Figure 2-6).

[0060] In another embodiment, the through-hole portion is an octagon (for example, a regular octagon) when viewed from the vertical surface of the acoustic filter, that is, the through-hole portion can be a hollow octagonal prism (for example, a regular octagonal prism). Also, in this embodiment, a portion of the non-penetrating portion can be a quadrangle (for example, a square) when viewed from the vertical surface of the acoustic filter, that is, a portion of the non-penetrating portion can be a quadrangular prism (for example, a regular quadrangular prism) structure, and the through-hole portion and a portion of the non-penetrating portion can be configured to have a planar filling shape when viewed from the vertical surface of the acoustic filter (for example, Figure 2-7).

[0061] In another embodiment, the through-hole portion is a quadrangle (for example, a square) when viewed from the vertical surface of the acoustic filter, that is, the through-hole portion can be a hollow quadrangular prism (for example, a regular quadrangular prism). Also, in this embodiment, a portion of the non-through-hole portion can be an octagon (for example, a regular octagon) when viewed from the vertical surface of the acoustic filter, that is, a portion of the non-through-hole portion can be an octagonal prism (for example, a regular octagonal prism) structure, and the through-hole portion and a portion of the non-through-hole portion can be configured to have a planar filling shape when viewed from the vertical surface of the acoustic filter (for example, Figure 2-8).

[0062] In another embodiment, the through-holes may be obtained by changing the polygonal shape to a circle. In this embodiment, a part of the non-through-holes may have a corresponding shape. In addition, the circular through-holes and a part of the non-through-holes may be configured to form a plane-filling shape when viewed from the vertical plane of the acoustic filter (for example, FIG. 2-9).

[0063] In one embodiment, a sound insulation method using the acoustic filter of the present disclosure is provided. In a specific embodiment, the acoustic filter of the present disclosure can be used as a noise canceller in headphones or headsets. In another embodiment, the acoustic filter of the present disclosure can be used as a breathable soundproofing sheet, sound-deadening sheet, or sound-blocking sheet. For example, this can be placed as furniture like an object, or can also be used as a partition between desks. In another embodiment, the acoustic filter of the present disclosure can be used for sound-proofing panels along roads or railway tracks, guardrails, overpasses, viaducts, and railway bridges. In another embodiment, the acoustic filter of the present disclosure can be used for automobiles, motorcycles, trains, trams, etc. In another embodiment, the acoustic filter of the present disclosure can be used for balconies, fences, and walls. In another embodiment, the acoustic filter of the present disclosure can be used in a housing that covers a combustion engine, for example, a private generator or engine. Combustion engines require an oxygen supply from the outside and cannot be completely sealed, and a muffler alone may not be able to silence the vibration noise emitted by the entire engine, so the breathable acoustic filter of the present disclosure can be advantageous. In another embodiment, the acoustic filter of the present disclosure may be used in industrial equipment or household equipment that generates noise, such as televisions, computers, air conditioners, outdoor units, refrigerators, washing machines, etc. In another embodiment, the acoustic filter of the present disclosure may be used in buildings, corridors, passageways, rooms, such as exhibition rooms, anechoic chambers, acoustic rooms, recording studios, domes, concert halls, concert venues, etc. In another embodiment, the acoustic filter of the present disclosure may be used in factories, power plants, substations, and transformers. However, the methods and applications of the acoustic filter of the present disclosure are not limited to these.

[0064] The acoustic filter of the present disclosure can be freely designed in terms of dimensions, thickness, number and orientation of layers, and silencing frequency or silencing frequency band for each filter. The Helmholtz resonator portion also has a high degree of freedom in design, allowing the length l of the connecting hole, the radius r of the connecting hole, and the air chamber volume V to be freely designed. This has the advantage of being able to accommodate noise and other sounds over a wide range of frequencies, while still not blocking human voices or dangerous sounds. Another advantage is that it provides sound insulation while also ensuring breathability.

[0065] In one embodiment, the acoustic filter of the present disclosure can be used in headphones. In this case, the headphones may have a frame, one or more acoustic filters of the present disclosure, and ear pads. In this specification, headphones equipped with the acoustic filter of the present disclosure may be referred to as the device of the present disclosure or the present device.

[0066] In this specification, an acoustic filter of the present disclosure having two or more pairs of a through portion and a non-through portion having an air chamber connected thereto via a connecting hole will have two or more Helmholtz resonators when the air chamber and the connecting hole form a Helmholtz resonator. Therefore, in this specification, an acoustic filter according to such an embodiment will be referred to as a Helmholtz resonator array. In this specification, the connecting hole portion will be referred to as a neck, neck portion, or neck portion. Furthermore, the radius of the connecting hole refers to the inner diameter unless otherwise specified.

[0067] In certain embodiments, the acoustic filter of the present disclosure can be provided with a tuning section that tunes the resonant frequency by changing the volume of the air chamber. This allows for tuning the resonant frequency. Therefore, in certain embodiments, the present disclosure provides a tunable acoustic notch filter that utilizes a Helmholtz resonator (HR) array. In certain embodiments, the tuning section (tuning means) can have a membrane section and a microchannel section. In certain embodiments, the membrane section can be configured to be sandwiched between the air chamber and the microchannel section. In certain embodiments, the tunable acoustic notch filter can have three sections: a cavity section, a membrane section, and a microchannel section. In certain embodiments, the tunable acoustic notch filter can have these three sections in a three-layer structure. The cavity section functions as the Helmholtz resonator (HR) chamber and determines the resonant wavelength. The volume of the Helmholtz resonator (HR) chamber can be changed by deforming the membrane with air pressure via the microchannel. This allows for adjustment of the resonant frequency, providing an acoustic notch filter with a tunable cutoff frequency.

[0068] In certain embodiments, the tunable acoustic notch filter can deform the membrane of the membrane portion by applying or reducing air pressure to the microchannel portion, thereby changing the volume of the air chamber. In certain embodiments, the present disclosure provides a tunable acoustic notch filter with a pneumatic pressure adjustment portion. The pneumatic pressure adjustment portion can apply or reduce air pressure to the microchannel portion. In other words, the tuning portion can include a pneumatic pressure adjustment portion that can apply or reduce air pressure to the microchannel portion. Examples of pneumatic pressure adjustment portions include, but are not limited to, a piston. Note that the microchannel can be filled with oil instead of air, and a hydraulic adjustment portion can be used instead of the pneumatic adjustment portion to deform the membrane using hydraulic pressure. Such embodiments are also provided by the present disclosure. Hydraulic pressure adjustment can also be performed by a piston.

[0069] The resonant frequency f0 corresponding to each chamber volume can be calculated using the above formula. Also, the adjustable range of resonant frequency f0 can be calculated from the changing chamber volume. For example, if the chamber volume in the unpressurized state is V, base The resonance frequency at this time is f base Next, let the chamber volume when air pressure (positive pressure) is applied to the microchannel be V. positive The resonance frequency at this time is f positive Applying positive pressure to the microchannel reduces the chamber volume, and the resonant frequency f positive is f base The chamber volume when the air pressure in the microchannel is reduced (negative pressure) is V negative The resonance frequency at this time is f negative When negative pressure is applied to the microchannel, the chamber volume increases, and the resonant frequency f negative is f base The desired tuning range f negative ~f positiveThe tunable acoustic notch filter, including the membrane, can be designed so that the tuning range f negative ~f positive is the lowest frequency f min ~Highest frequency f max The range can be as follows: In certain embodiments, the tunable acoustic notch filter can provide attenuation of 3 dB or more, 4 dB or more, 5 dB or more, 6 dB or more, 7 dB or more, 8 dB or more, 9 dB or more, for example, 10 dB or more. In certain embodiments, the device fabricated according to the present disclosure has an acoustic attenuation effect of 10 dB and achieves frequency tuning at approximately 4 to 5 kHz. This device can accommodate a wide range of high-frequency noises that humans find annoying.

[0070] In some embodiments, the microchannel may be subjected to a pressure of 5 kPa or more, 10 kPa or more, 20 kPa or more, 25 kPa or more, 50 kPa or more, 75 kPa or more, 100 kPa or more, 200 kPa or more, e.g., 300 kPa or more. In other embodiments, the microchannel may be subjected to a negative pressure (vacuum) of -5 kPa or more, -10 kPa or more, -20 kPa or more, -25 kPa or more, -50 kPa or more, -75 kPa or more, -100 kPa or more, -200 kPa or more, e.g., -300 kPa or more. In certain embodiments, applying pressure to the microchannel may adjust the notch frequency by 10 Hz or more, 20 Hz or more, 30 Hz or more, 40 Hz or more, 50 Hz or more, 100 Hz or more, 200 Hz or more, 300 Hz or more, 400 Hz or more, 500 Hz or more, 600 Hz or more, 700 Hz or more, 800 Hz or more, 900 Hz or more, 1 kHz or more, 1.2 kHz or more, e.g., 1.5 kHz or more. In other embodiments, reducing pressure in the microchannel may adjust the notch frequency by -10 Hz or more, -20 Hz or more, -30 Hz or more, -40 Hz or more, -50 Hz or more, -100 Hz or more, -200 Hz or more, -300 Hz or more, -400 Hz or more, -500 Hz or more, -600 Hz or more, -700 Hz or more, -800 Hz or more, -900 Hz or more, -1 kHz or more, -1.2 kHz or more, e.g., -1.5 kHz or more.

[0071] In certain embodiments, the nth Helmholtz resonator has a frequency f n It is designed to resonate with the sound of f n is the lowest frequency f min ~Highest frequency f max f min ~f max A tunable acoustic notch filter is provided by combining the HR array corresponding to the above with the membrane section and microchannel section. In this case, the chamber volume without pressure is V base and the corresponding resonant frequency is f basemin ~f basemax When pressure is applied to the microchannel, f basemin ~f basemax The entire range is f min1 ~f max1 When negative pressure is applied to the microchannel, the entire resonant frequency range shifts to f min2 ~f max2 The applied or reduced pressure may be the same as above. The shifted notch frequency may be the same as above. The entire range after the shift, i.e., f min2 ~f max2 From f min1 ~f max1 The entire range extends up to the lowest frequency f min ~Highest frequency f max A tunable acoustic notch filter can be designed to fall within the range.

[0072] Noise is usually not a single frequency, but rather a range of frequencies. In this case, the lowest frequency of the noise, f min ~Highest frequency f max Furthermore, when a noise source such as an airplane or train moves at high speed, the noise frequency differs depending on whether the object is approaching or receding due to the Doppler effect. In such cases, f min ~f max For an HR array having a noise attenuation range of 100 kHz, further shifting the entire notch frequency range will enable more effective noise attenuation and soundproofing.

[0073] Although embodiments with specific dimensions are described below, these are merely illustrative of the present invention, and the present disclosure is in no way limited to these embodiments.

[0074] [First embodiment] Design and production The conceptual diagram of the Helmholtz resonator array (HR array) is shown in Figures 2-1 and 2-2. When sound passes through a penetration, the air chamber connected to the connecting hole in the penetration functions as a Helmholtz resonator, and when the sound that entered from the input surface is output to the output surface, the sound at the designed frequency f0 is reduced.

[0075] Since the more Helmholtz resonators there are around the through-holes, the greater the noise reduction effect. In the illustrated embodiment, six Helmholtz resonators are provided around each through-hole, and the array structure is designed based on a honeycomb structure to improve strength and area efficiency. In this embodiment, increasing the number of holes and Helmholtz resonators per unit area increases the noise reduction effect while also improving the permeability of sounds other than noise. It also enables the acoustic filter to be made thinner and lighter. Furthermore, the array structure is oval, matching the shape of the ear pads, and designed to be sized to fit over the ear (Figures 1 and 3).

[0076] In this embodiment, to confirm the noise reduction performance of the HR array, the notch frequency was set to approximately 5 to 7 kHz, matching the range of the speakers used in the experiment (2 to 50 kHz) and the audible range. The connecting hole (neck) of each Helmholtz resonator had a radius r = 1 mm, and all wall thicknesses were 1 mm (neck length l = 1 mm). The volume of each air chamber was V = 115 mm. 3 This is what happened.

[0077] The formula for calculating the resonant frequency of HR is c, where c is the speed of sound.

number

[0078] Numerical analysis Analysis conditions To confirm the sound attenuation effect of the Helmholtz resonator array, we performed an acoustic simulation using COMSOL Multiphysics 5.5 (Figure 5A). Because this array has a honeycomb structure, we thought that by overlapping two arrays with an offset, the sound attenuation effect of each hole would be uniform and the overall sound attenuation effect would be improved. The designed array was designed so that the holes were offset alternately by overlapping two arrays in opposite directions, and the analysis compared the results when there was one array and when there were two arrays (same direction and opposite directions) (5-7 in Figure 6).

[0079] Analysis results The sound pressure distribution is shown in Figure 5B. It can be seen that the Helmholtz resonator array provides sufficient sound attenuation. Figure 7 shows a frequency response graph of the simulation results. The notch frequency was 5894 Hz (two Helmholtz resonator arrays facing in opposite directions). When two Helmholtz resonator arrays were placed facing in opposite directions, the dip in the sound pressure level (dB) was the widest and deepest, approximately 50 dB deeper than when there was only one Helmholtz resonator array.

[0080] experiment Experimental configuration A photograph of the experimental setup is shown in Figure 8-1, and schematic diagrams are shown in Figures 8-2 and 8-3. As in the analysis, experiments were conducted with one Helmholtz resonator array and two Helmholtz resonator arrays (in the same direction and in opposite directions). The frequency response (difference) of the Helmholtz resonator array was calculated by comparing it with the measurement results when no Helmholtz resonator array was placed (control).

[0081] result The frequency response graph of the actual measurements is shown in Figure 9. As in the analysis, the greatest noise reduction effect was achieved when two Helmholtz resonator arrays were placed in opposite directions, with a noise reduction effect of about 30 dB obtained near the notch frequency, an improvement of about 10 dB compared to when there was only one array.

[0082] conclusion Both the numerical analysis and the experiment confirmed the noise reduction effect of the Helmholtz resonator array. By placing two Helmholtz resonator arrays in opposite directions, the noise reduction effect was improved, and a noise reduction effect of about 30 dB was obtained near the notch frequency. If more HR arrays are stacked, the dip is thought to become deeper, and the noise reduction effect is thought to be even greater.

[0083] [Second embodiment] An experiment was conducted on a mannequin equipped with a microphone using the following procedure. First, a hole (7 mm in diameter) was drilled in the ear area and a microphone was installed inside (Figures 10-1 and 10-2). The sound pressure level of the microphone was measured when sound (40 dB or 80 dB) was applied from hearing test headphones. The results are shown in Figure 11. This confirmed that there were no problems with the experimental setup.

[0084] (Comparative Example) Next, as a comparative example, we compared the sound insulation effects of a passive noise canceller (PNC) and an active noise canceller (ANC). An active noise canceller is a mechanism that consumes power to dynamically cancel noise. A passive noise canceller is a passive (static) mechanism that does not consume power. Here, we used Sony® catalog number WH-100XM3 headphones as a commercially available active noise canceller (ANC) (comparison example) (Figure 12). Also, here, the case where the active noise canceller (ANC) was turned off was referred to as a passive noise canceller (PNC). The results are shown in Figure 13. In the high-frequency range, there was almost no difference between when the ANC was turned off and when it was turned on. In other words, under these conditions, it was confirmed that the ANC did not provide any sound insulation effect in the frequency range above 0.8 kHz.

[0085] (Device of the present disclosure) Next, a device according to the present disclosure, i.e., headphones equipped with the acoustic filter according to the present disclosure, was used (FIG. 14). As a result, a sound-canceling effect of approximately 40 dB was confirmed near the notch frequency. In other words, it was confirmed that a sufficient sound-blocking effect was obtained as an earmuff device.

[0086] [Third embodiment] It is believed that if the HR arrays are stacked further, the dip will become deeper and the noise reduction effect will be even greater. Therefore, we performed simulations for different headphone frequency characteristics and inner diameters.

[0087] Figure 15 shows three embodiments in which the through-holes are arranged alternately. In Figure 15A, all of the necks have the same shape. In Figure 15B, two types of necks are alternately connected to one through-hole. In Figure 15C, six necks of one type are connected to one through-hole, and six necks of a different size are connected to another through-hole.

[0088] Figure 16 shows the results when all the inner diameters of the necks are 2 mm. Figure 16(i) shows the simulation results for one array. Figure 16(ii) shows the simulation results for two arrays of the same specification stacked in reverse orientation. Figure 16(iii) shows the simulation results for two arrays of the same specification stacked in reverse orientation and a third array of the same specification.

[0089] Figure 17 shows the simulation results for (i) the case where the neck inner diameters are the same, and for (ii) and (iii) the cases where different neck inner diameters are combined. Figure 17(i) shows the analysis results for two HR arrays, all with a 2 mm neck inner diameter, stacked in reverse. The conditions are the same as those for Figure 7(ii). This corresponds to Figure 15A. Figure 17(ii) shows the analysis results for two HR arrays, each with a different neck inner diameter distributed throughout the array, stacked in reverse. The narrow neck is approximately 1.9 mm, and the wide neck is 2.1 mm. This corresponds to Figure 15B. Figure 17(iii) shows the analysis results for two HR arrays, each with a different neck inner diameter distributed throughout the array, stacked in reverse. The first array has a neck inner diameter of approximately 1.9 mm, and the second array has a neck inner diameter of 2.1 mm. This corresponds to Figure 15C.

[0090] [Fourth embodiment] Design and production Next, we fabricated a tunable acoustic notch filter using a Helmholtz resonator (HR) with a membrane that deforms under air pressure. Concept sketches of a tunable acoustic notch filter using a Helmholtz resonator (HR) array are shown in Figures 18 and 19. In the configuration shown, the tunable acoustic notch filter has a three-layer structure consisting of an air chamber, a membrane, and a microchannel. The chamber volume changes as the membrane deforms. For example, the membrane can be deformed by applying or reducing air pressure to the microchannel using an air pressure adjustment unit (such as a piston), thereby changing the chamber volume. This allows the notch frequency to be adjusted.

[0091] In a tunable acoustic notch filter, as shown in Figure 20A, a cavity and a microchannel sandwich a stretchable membrane. Holes are formed on the sides of each cavity, which serve as the necks of Helmholtz resonators (HR). In a specific embodiment, six Helmholtz resonators (HR) are arranged in parallel with one acoustic path hole. To apply uniform air pressure to each membrane, each microchannel can be interconnected. By applying air pressure to the microchannel, the membrane deforms, thereby changing the chamber volume and adjusting the resonant frequency. Examples of the cavity and channel design shown in Figure 20A are shown in Figures 20B and 20C. The exemplified Helmholtz resonator (HR) was designed to have a resonant frequency of approximately 4.5 kHz without any air pressure applied, a frequency that humans find uncomfortable.

[0092] To investigate the acoustic attenuation effect of the Helmholtz resonator (HR), we simulated the acoustic characteristics of the designed structure (Figure 21-1). The simulation model reflected the changes in chamber volume obtained in the experimental results (Figures 22-1 to 22-3). The simulation results also showed that the notch frequency varied in the range of 4.24 to 5.19 kHz (Figure 21-2). The fabricated Helmholtz resonator (HR) array filter is shown in Figures 22-1A and 22-1B. A 1-mm-thick flat silicone membrane was fixed to two steel cavities and a microchannel housing. The deformation of the membrane was observed under a microscope when air pressures ranging from -75 to 100 kPa were applied from a pressure calibrator (Figure 22-1C). Figure 22-2 shows the cross-sectional shape of the deformed membrane. The membrane deformed in the range of 3 mm in height, and the chamber volume varied from 104 to 172 mm. 3The frequency response of the Helmholtz resonator (HR) array filter was experimentally measured using a speaker and microphone (Figs. 23-1 and 23-2). As shown in Fig. 23-3, when the air pressure was changed from -75 to 100 kPa, the notch frequency changed from 4.04 to 4.86 kHz, with an attenuation effect of approximately 10 dB obtained under each condition. The theoretical, simulated, and experimental values ​​for the notch frequency shift were similar to each other (Fig. 23-4). These results confirmed that the notch filter of the present disclosure can be tuned within a 1 kHz range by controlling the air pressure. [Industrial Applicability]

[0093] The acoustic filter of the present disclosure can obtain a high sound-blocking effect only for a specific frequency without using electric power, for example. Also, the acoustic filter of the present disclosure can tune the frequency to be blocked.

[0094] Numerous documents, including patent applications and manufacturer's manuals, are cited herein. The disclosures of these documents, while not considered relevant to the patentability of this disclosure, are hereby incorporated by reference in their entirety. More particularly, all referenced documents are hereby incorporated by reference to the same extent as if each individual document were specifically and individually indicated to be incorporated by reference. [Explanation of symbols]

[0095] 1: Helmholtz resonator (HR) 2::Frame 3:HR array 4:Ear pads 5: Single 6:Dual (same direction) 7:Dual (reverse) 8: Earphones 9: Microphone 10: Output signal 11: Amplifier 12: Input signal 15: Sound pressure evaluation surface 20:Air chamber 21:Membrane 22: Microchannel 23: Chamber volume change 24:Membrane deformation 25:Air pressure 26: Air 30: Pressure calibrator 31: Sound Waves 32: Speaker 40: Air pressure adjustment unit 45: Tunable acoustic notch filter 50: Connection hole All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety.

Claims

1. An acoustic filter having a through portion that penetrates between a front surface and a back surface and a non-through portion, The penetration is hollow, The side surface of the through-hole has one or more connecting holes that connect the air chamber and the through-hole, the connecting hole and the air chamber are hollow and provided in the non-penetrating portion, The air chamber has all walls closed except for the connecting hole, having at least one penetrating portion and at least one non-penetrating portion; The through portion has a polygonal shape, and the non-through portion has a polygonal column shape, The polygonal shape of the penetrating portion is triangular, and the non-penetrating portion has a triangular prism structure. The polygonal shape of the penetrating portion is quadrangular, and the non-penetrating portion has a quadrangular prism structure. The polygonal shape of the penetrating portion is quadrangular, and the non-penetrating portion has an octagonal prism structure. The polygonal shape of the penetrating portion is hexagonal, and the non-penetrating portion has a triangular prism structure. The polygonal shape of the penetrating portion is hexagonal, and the non-penetrating portion has a hexagonal prism structure. The polygonal shape of the penetrating portion is triangular, and the non-penetrating portion has a hexagonal prism structure. The polygonal shape of the through portion is an octagon, and the non-through portion has a square prism structure; or The polygonal shape of the penetrating portion is octagonal, and the non-penetrating portion has an octagonal prism structure. The acoustic filter.

2. 2. The acoustic filter according to claim 1, having two or more of said through portions and said non-through portions.

3. 3. The acoustic filter according to claim 1, wherein the through-holes have the same number of connecting holes as the number of sides of the through-holes, and the through-holes are connected to the respective air chambers via the respective connecting holes.

4. 4. The acoustic filter according to claim 3, wherein each side of said through-hole is provided with one connecting hole, and said through-holes are connected to different air chambers via the respective connecting holes.

5. 5. The acoustic filter according to claim 1, wherein the through portions and the non-through portions have a planar tessellation shape.

6. 6. The acoustic filter according to claim 1, wherein the connecting hole and the air chamber connected thereto are Helmholtz resonators.

7. The Helmholtz resonator has the following formula: [Equation 1] [Wherein, c is the speed of sound, S is the opening area of ​​the connecting hole, l is the length of the connecting hole, i.e., the length between the through-hole and the air chamber, l ｃ is the edge correction factor, and V is the volume of the air chamber] The frequency f calculated from 0 7. The acoustic filter of claim 6, configured to resonate with the sound of

8. All Helmholtz resonators emit light at a single frequency, f 0 8. The acoustic filter according to claim 6 or 7, which is configured to resonate with the sound of

9. The nth Helmholtz resonator operates at frequency f n It is designed to resonate with the sound of f n But the lowest frequency f min ~Maximum frequency f max 8. The acoustic filter according to claim 6 or 7, configured to be included in the range of

10. An acoustic filter comprising two acoustic filters according to any one of claims 1 to 9, wherein the input surface of the first acoustic filter is aligned with the output surface of the second acoustic filter.

11. An acoustic filter comprising two acoustic filters according to any one of claims 1 to 9, wherein the input surface of the first acoustic filter and the input surface of the second acoustic filter are aligned, or the output surface of the first acoustic filter and the output surface of the second acoustic filter are aligned, thereby causing each through-hole to be partially, alternately offset.

12. 12. The acoustic filter according to claim 10, wherein the first acoustic filter and the second acoustic filter have different resonance frequencies.

13. 13. The acoustic filter according to claim 1, further comprising a tuning section for tuning the resonance frequency by changing the volume of the air chamber.

14. 14. The acoustic filter according to claim 13, wherein the tuning section has a membrane section and a microchannel section, and is configured so that the membrane section is sandwiched between the air chamber and the microchannel section.

15. 15. The acoustic filter of claim 14, wherein the tuning section further comprises an air pressure adjusting section that can apply air pressure to the micro-channel section or reduce the air pressure in the micro-channel section.

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