Microphone array

Abstract

A microphone array contains multiple microphone capsules whose outputs are electronically combined for directional recording of sound. The directivity and frequency characteristics of the microphone array depend on the number and position of the microphone capsules. In order to obtain the smallest possible microphone array with only a small number of microphone capsules, with nearly uniform directivity and frequency dependence over the audio frequency range, but which is scalable and robust to small mispositioning of the capsules. Microphone arrays with 15 or 21 microphone capsules (K 15,11 ~K 15,35 ,K 21,11 ~K 21,37 ) are arranged on a carrier (T, T') that are located on three similar branches, each branch being provided with the same number of microphone capsules, which are rotated by 120° with respect to each other. Each of the microphone capsules is located at a triangular corner of the L2 grid in a planar isometric coordinate system (forming an equilateral L2 grid) with three axes (L0, L1, L2) that are rotated by 120° with respect to each other.

Description

[Technical Field]

[0001] The present invention relates to a microphone array, and more particularly to an array of multiple microphone capsules that work together as an array to capture sound. [Background technology]

[0002] Microphone arrays are frequently used for beamforming, noise suppression, or sound source locating. They consist of multiple microphone capsules whose output signals are electronically interconnected and work together for directional recording of speech. The type of interconnection can generate a preferred direction of particular sensitivity for the microphone array in acoustic recording. This preferred direction is electronically adjustable through the electronic combination of individual microphone signals, allowing for changes in preferred direction with extremely short response times. However, microphone arrays do not necessarily have equally good directional effects in all directions, but often have one or more fixed preferred directions depending on the arrangement of the microphone capsules. Furthermore, microphone arrays do not operate equally well across all frequencies, but rather exhibit frequency dependence. This depends, among other things, on the distance between the microphone capsules. Therefore, a crucial aspect of a microphone array is the geometric arrangement of the microphone capsules on the microphone surface. That is, for a given number of microphone capsules, they must cover as many inter-element distances as possible, i.e., the distances between individual microphone capsules in the array, in as many different directions as possible.

[0003] There are various strategies regarding the type, number, and positioning of microphone capsules. Often, for example, in the case of a microphone array that can be mounted on the ceiling of a room, multiple microphone capsules are combined to capture as many different preferred directions and specific frequency ranges as possible. Often, this is the range of speech frequencies, e.g., 100Hz to 10kHz. Typical methods in this field are heuristics, which are very time-consuming searches by "trying" all conceivable analytically descriptive manifolds, such as lines, circles, spirals, etc., and numerical simulations.

[0004] For example, U.S. Patent No. 6205224B1 describes a design in which at least 63 sensor elements, such as antennas or microphone capsules, are arranged concentrically and simultaneously in a spiral, enabling broadband detection with high directivity that is largely independent of direction. The direction and frequency characteristics of the sensor arrangement are shown by a so-called joint array, which indicates the distances between elements and the direction of these distances. U.S. Publication No. 2013 / 0101141A1 also aims at direction-independent broadband detection, with 30 microphone capsules evenly distributed on the surface of a hexagonal circuit board, some of which can be interconnected. In U.S. Publication No. 2016 / 0323668A1, numerous microphone capsules are interconnected to form a microphone array, which is distributed almost evenly across multiple circuit boards. The central board contains 64 microphone capsules, while each of the seven boards arranged in a circular pattern around it contains a further 8 microphone capsules, for a total of 120 microphone capsules. In all of these cases, the large number of microphone signals results in a high computational load, leading to a large overall microphone array.

[0005] Therefore, another strategy besides the documents mentioned is to use as few microphone capsules as possible in the array. In this case, in order to reduce noise or to obtain a high signal-to-noise ratio (SNR), the microphone capsules must have as little noise as possible, i.e., be of high quality. Furthermore, the electroacoustic properties of all microphone capsules in the array must be nearly identical within strict tolerances. German Publication No. 10 2010 012388A1 pursues a mathematical method to minimize the number and positioning of microphone capsules by positioning them at the intersections of Golomb rulers. This reduces the number of microphone capsules, but due to the asymmetric distribution, it results in non-uniform directional characteristics in all directions. Furthermore, the microphone capsules are distributed almost evenly across the entire surface. U.S. Patent No. 9894434B2 describes a microphone array with 17 microphone capsules, arranged on the diagonals of a relatively large square area of ​​approximately 60 × 60 cm. This size is typical for most of the arrays mentioned. Furthermore, most of the arrays mentioned are susceptible to even slight mispositioning of the microphone capsule and have the problem of not being able to scale up or down without causing disruptive nonlinear effects.

[0006] In the field of seismology, research on sensor arrays has been conducted for a long time. An article by R. Haubrich, "Array Design," in the "Bulletin of the Seismological Society of America," Vol. 58, June 1968, describes how arrays for detecting seismic waves, ocean waves, or electromagnetic radio waves can be constructed with as few sensors as possible. The directional and frequency characteristics of various sensor configurations are evaluated using collaborative arrays. Various sensor configurations considered "perfect" or "optimal" are proposed according to this criterion, including isometric arrays where sensors are placed at the intersections of isometric coordinate systems. [Overview of the project] [Means for solving the problem]

[0007] The present invention aims to provide microphone capsules that are as small and few in number as possible, which are more robust to small mispositioning of the capsules, have high direction-independent directivity, have a substantially uniform frequency dependence across the audio frequency range, and can be used as ceiling microphones. This objective is achieved by the microphone array described in claim 1.

[0008] Some of the structures of earthquake sensor arrays proposed by R. Haubrich several years ago have proven suitable for microphone capsule arrays as well. In particular, iso-angle arrays with 15 or 21 microphone capsules have especially good acoustic properties, such as good localization of sound sources and high directivity, as well as other advantages such as low manufacturing costs. This is also true when the size of the array is reduced according to the audio frequency to be recorded, making smaller arrays possible than before.

[0009] According to the present invention, a microphone array has a small number of microphone capsules, particularly 15 or 21 microphone capsules, and a circuit configuration suitable for connecting to the microphone capsules, receiving microphone signals, and processing them together. The microphone capsules are arranged in a plane at specific positions on a carrier, i.e., three similar branches, each having the same number of microphone capsules, and the branches are arranged rotated 120° from each other around a common center. In a plane isoangular coordinate system with three axes rotated 120° from each other, they form a so-called L2 grid of equilateral triangles, and each microphone capsule is located at a corner of the triangle of the L2 grid. The use of electret capsules is particularly advantageous, as they typically have low intrinsic noise and low self-resonance, allowing them to cover a higher sound pressure level range. However, other microphone capsules, such as MEMS, can also be used.

[0010] One advantage of the array according to the present invention is that it has good and uniform directivity in all directions over the entire relevant audio frequency range so that calculations can be performed using a combined array. However, a further advantage of the array according to the present invention includes relatively high robustness against small mispositioning of the microphone capsules, a small array size, a lower cost, and a relatively free possibility of size scalability.

[0011] Further advantageous embodiments are disclosed in claims 2 to 11.

Brief Description of the Drawings

[0012] Further details and advantageous embodiments are shown in the drawings.

[0013] [Figure 1] The arrangement of 15 microphone capsules in the first embodiment of the present invention is shown. [Figure 2] The arrangement of 15 microphone capsules in the second embodiment of the present invention is shown, which is mirror-symmetric to the first embodiment. [Figure 3] The combined array of the arrangement of microphone capsules according to the first or second embodiment is shown. [Figure 4] An example of the arrangement of a circuit board for the arrangement of microphone capsules according to the first embodiment is shown. [Figure 5] The arrangement of 21 microphone capsules in the third embodiment of the present invention is shown. [Figure 6] The arrangement of 6 microphone capsules in the fourth embodiment of the present invention is shown. [Figure 7] A block diagram of the microphone array is shown.

Modes for Carrying Out the Invention

[0014] In the first embodiment of the present invention, FIG. 1 shows the arrangement of 15 microphone capsules on carrier T. The microphone capsules are arranged in three equal groups on a common branch, each rotated 120° from each other. The first branch, for example, includes capsules K 15,11 ,K 15,12 ,K 15,13 ,K 15,14 ,K 15,15 . The second branch includes capsules K 15,21 ~K 15,25 , and the third branch includes capsules K 15,31 ~K 15,35 . For orientation, the Cartesian coordinate system X, Y is shown, but the capsules are located at the intersections of the isometric coordinate system, which is also shown in FIG. 1. The isometric coordinate system has three axes L0, L1, L2 offset by 60° within one plane and is composed of equilateral triangles. Each side of these triangles is parallel to one of the axes L0, L1, or L2. The center of the entire arrangement has three congruent branches rotating around it and is the origin of the Cartesian coordinate system (i.e., X = 0, Y = 0). At the same time, it is also the centroid of the central triangle D M of the isometric coordinate system. The corner of the central triangle D M (on the opposite side of the side parallel to the L0 axis) is arbitrarily selected here as the reference point R of the isometric coordinate system.

[0015] The position of the isometric coordinate system is specified as a multiple of the side length of the equilateral triangle. For example, the upper right corner of the central triangle D M is shifted by one side length in the direction of the L1 axis from the reference point R, which is specified as the position (L0, L1, L2) = (0, 1, 0) in the isometric coordinates. Correspondingly, the upper left corner of the central triangle D M is shifted by one side length in the direction of the L2 axis from the reference point R, that is, it is at the position (L0, L1, L2) = (0, 0, 1) in the isometric coordinates. Starting from the reference point R, the microphone capsules are at the following positions.

[0016] (Table 1) TIFF0007865992000001.tif45155

[0017] In Cartesian coordinates (X,Y), the values ​​are approximately as follows, depending on the scale (for example, as shown in Figure 1, when the side length or equiangled length unit of the triangle is 0.05m each, the unit is meters).

[0018] (Table 2) TIFF0007865992000002.tif28155

[0019] The scale is chosen such that the minimum distance between two microphone capsules corresponds to the side length of a triangle in an isometric coordinate system. Thus, the microphone array shown in Figure 1 has a diameter of approximately 35 cm.

[0020] The position is applied to the coordinate system shown in Figure 1, and naturally, it will deviate numerically if the coordinate system or array is rotated or other reference points are selected. Furthermore, in conformal coordinate systems, the position can be reached in various ways (because the axes are not orthogonal to each other), resulting in different equivalent coordinates. For example, (1,1,0), (0,2,-1), (2,0,1), (3,-1,2) and other further coordinates define the same point. Several equivalent variations can be mapped onto the arrangement shown in Figure 1 by rotating around the center point.

[0021] Figure 2 shows the arrangement of 15 microphone capsules on carrier T' in a second embodiment of the present invention, which is mirror-symmetric to the first embodiment. This has the same acoustic and geometric properties as the arrangement of the first embodiment and is equivalent thereto. Here, mirror symmetry exists along the Y-axis. However, identical and rotated variations can be generated by mirroring the arrangement according to the first embodiment along any axis. Since the sensitivity of the array can be adjusted almost uniformly in all directions, all these variations are equivalent, i.e., the same joint array is obtained and therefore identical to the first or second embodiment. The equiangular coordinate system is, for example, three positions on the outer edge (e.g., K 15,11 ,K 15,12 ,K15,13 or K' 15,21 ,K' 15,22 ,K' 15,23 The location can be determined for a given arrangement or base region by the fact that it lies on a line parallel to one of the axes L0, L1, and L2 of the conformal coordinate system. The distance between two adjacent locations within these three groups corresponds to the side length of a triangle and therefore to the units of the conformal coordinate system.

[0022] Figure 3 shows the joint array arrangements according to the first and second embodiments, which are known in principle from R. Haubrich's theory, but here are adapted to sound waves or speech frequencies, respectively. The points represent the relative positions of the two microphone capsules in the array, i.e., the distance between them and the direction of this distance. In other words, each point in the joint array represents the relative positions of at least one pair of microphone capsules in the array, with respect to each other, relative to the joint array center point C. M This means that the position of this joint array point is the same as that of the point in the isometric coordinate system. Thus, each point represents a possible incident direction and wavelength of sound waves, which can be processed precisely by the microphone array according to their direction, i.e., they can be used to pinpoint the location of the sound source and produce a directional effect. It is important here that no holes occur in the joint array at points in the isometric coordinate system. This is also true here. A hole in the joint array means that the microphone array cannot process sound waves of the corresponding incident direction and wavelength in a directionally accurate manner. However, it is usually not possible to infer a uniquely associated microphone arrangement directly from the joint array.

[0023] The joint array of microphone arrangements according to the present invention has the advantageous characteristic that each joint array point has six neighboring points evenly distributed around it (at least in the inner region of the joint array). This makes it possible to scale the size of the microphone arrangement to match the wavelength of interest. The joint array point with the minimum distance to the origin (minimum inter-element distance) exhibits the highest spatially resolvable frequency before undersampling begins, i.e., below so-called spatial aliasing. The joint array point with the maximum distance to the origin correspondingly determines the performance of the beamformer at low frequencies. As a result, the minimum inter-element spacing of the microphone arrangement can be scaled to match the minimum wavelength or highest frequency of interest, while for all larger inter-element spacings or larger wavelengths, the closest possible coverage of all wavelengths is maintained. For example, scaling the microphone arrangement of the first or second embodiment to a diameter of 35 cm (L=5 cm) yields a highest frequency of approximately 6.9 kHz (below spatial aliasing).

[0024] One advantage of the present invention is that the microphone capsules are not evenly distributed across the entire area of ​​the array, but rather form groups. This results in the elimination of the need to cover relatively large portions of the surface with circuit boards or printed circuit boards in order to make contact with the capsules. In particular, it is not necessary to provide circuit boards or groups of circuit boards across the entire size of the arrangement. This further reduces the manufacturing cost of the array, which is relatively low due to the small number and weight of the microphone capsules. Furthermore, since the microphone capsules are distributed across three congruent branches, the same circuit board can be used for each branch.

[0025] Figure 4 shows an exemplary arrangement of three identical circuit boards P1, P2, and P3 for microphone capsule arrangement according to the first embodiment. Each circuit board P1 to P3 contains five microphone capsules on a branch and is arranged rotated 120° on a carrier. Additional components, such as processing units with one or more processors, AD converters, etc., can also be arranged on these circuit boards. However, it is also possible to house at least some of these additional components on an additional circuit board (not shown) located in the center and connected to the circuit boards P1 to P3 that carry the capsules. Thus, another advantage of this arrangement is that there is ample space on the central circuit board because there is no microphone capsule in the center. As a result, stacking of circuit boards (which makes the array thicker, more complex to manufacture, and more expensive) is not required in this area. Furthermore, the basically symmetrical structure makes assembly easier because the center of gravity of the entire array is in the center. Furthermore, each of the three substrates P1-P3 can be replaced, for example, with two sub-sub

[0026] Figure 5 shows the arrangement of 21 microphone capsules in a third embodiment of the present invention. The same principles apply to this embodiment as to the first and second embodiments described above. In particular, it has similar advantages. However, due to the larger number of microphone capsules, the recording quality may be even better. Starting from the reference point R defined above, and using the coordinate system shown in Figure 5, the microphone capsules are positioned as follows (again, equivalent variations can be generated by mirroring and / or rotating along the axis).

[0027] (Table 3) TIFF0007865992000003.tif57155

[0028] The microphone capsules can be distributed very compactly, for example, on two circuit boards per branch. The five capsules K of the first branch... 21,11 ~K 21,15 Circuit board P 21,1 One of the options is shown in Figure 5. The other two capsules K 21,16 ,K 21,17 Because they are close to each other, they can be mounted very compactly on a second circuit board (not shown). Any additional electronic components required (processors, AD converters, etc.) may be housed on one of the two boards and / or on an additional central board (not shown) in the center of the array. In this case as well, the other two branches are congruent, rotated 120° each, and can use the same type of board as the first branch (i.e., boards with the same layout). An optional central board can also be used. Furthermore, in this embodiment, the total area of ​​at least the capsule-supported circuit boards can be less than half the total area of ​​the array (depending on the space required by other components).

[0029] It should be noted that Figure 5 shows only the relative scale. This is due to the fact that the array according to the present invention (in all embodiments) can be scaled up or down without generating disruptive and computationally difficult nonlinear effects. In the embodiment shown in Figure 5, the radius r of the outermost capsule max The size is approximately L × 6.11 (where L is the side length of an equiangular triangle), and the maximum spacing between elements is approximately d max = L × 11.79. For example, if the array is circular in shape with a scale of L = 5 cm, a diameter D of approximately 61.1 cm is obtained (d max (d = 58.95 cm), and on a scale of L = 4 cm, a diameter D of approximately 48.9 cm is obtained (d max (d = 47.16 cm), and on a scale of L = 3.5 cm, a diameter D of approximately 42.8 cm is obtained (d max(=41.27cm). Conversely, the array diameter or maximum inter-element spacing can be predefined. For example, to obtain an array diameter of approximately 55cm, a scale L=4.5cm would be selected, while at approximately L=3.39cm, for example, d max A maximum element spacing of 40 cm can be obtained. Arrays of different sizes do not fundamentally differ in frequency behavior, but only the frequency range shifts slightly. As is well known, the maximum element spacing is important for the localization and directivity of the sound source at low frequencies, while the minimum element distance (i.e., scale L) is important for the localization and directivity of the sound source at high frequencies. Overall, depending on the embodiment, a scale of L = 3 to 6 cm is useful for speech frequencies, and particularly useful in the range of L = 4 to 5 cm.

[0030] The correspondence regarding scalability also applies to other embodiments. For example, r max =L × 3.512, D = L × 7.024, and d max =L × 6,557 (rounded) applies to the first and second embodiments.

[0031] Figure 6 shows the arrangement of six microphone capsules in the fourth embodiment. This modification is particularly suitable for very small microphone arrays that can be placed, for example, on a conference table, while the embodiments described above are well suited for mounting on ceilings or walls. In this modification, the quality of sound source directivity and localization is not as good as in the modifications described above due to the smaller number of microphone capsules, but it is better than other equivalent arrangements with only six capsules. Starting from the reference point R defined above and using the coordinate system shown in Figure 6, the microphone capsules are in the following positions (again, equivalent modifications can be generated by mirroring and / or rotating along the axis).

[0032] (Table 4) TIFF0007865992000004.tif25153

[0033] In this case, the microphone capsules can be distributed on one circuit board per branch, or, due to their small overall size, all of them can be mounted on a single circuit board P6. The resulting value (rounded) is r max =L × 1.527, D = L × 3.054, and d max = L × 2.646.

[0034] Figure 7 shows an exemplary block diagram of a microphone array that may correspond to, for example, the first or second embodiment. Another embodiment has a different number of microphone capsules per branch and / or further subdivides the circuit board into sub-boards. Three circuit boards P1, P2, and P3 are each identical in structure and are arranged on the carrier T rotated 120° from each other, as shown in Figures 1 and 4. Each of these circuit boards has the same number of microphone capsules K 15,11 ~K 15,15 These signals, including the above, are supplied to individual analog / digital converters AD1-AD5 mounted on the same circuit board. This results in extremely short connections for sensitive analog microphone signals to the AD converters. If necessary, individual digital processing blocks DP1-DP5 and / or a common processing block SP1, such as a processor, can be present on the circuit board. These can, for example, filter the digitized microphone signals. The digital output signals S1-S3 from the circuit board are provided to a central circuit board CP, where processing units perform audio processing AP for the array, particularly beamforming. Furthermore, the audio processing AP for the array can perform acoustic retrieval of the (primary) sound source in real time and align the resulting array beam toward the (primary) sound source. For this purpose, if necessary, signals SD1-SD3 can be reported to circuit boards P1-P3. The resulting digital output signals S A,out This is output. Analog output signals can also be output if needed.

[0035] All microphone capsules in the branch are mounted together on a circuit board or a group of circuit boards, and the positioning of the circuit boards on the carrier T can be done with almost no deviation, so the relative positions of the capsules to each other are extremely precise. The carrier can comprise one or more solid or acoustically reflective plates made of, for example, metal, plastic. In one embodiment, the carrier is a metal or plastic plate with holes through which sound can reach the microphone capsules (from the underside of the ceiling microphones if installed). In this case, since the plate is acoustically reflective, the sound pressure of the microphone capsules is increased by up to 6 dB, and the array operates as a boundary microphone. On the other hand, the arrangement of microphone capsules according to the present invention allows for small deviations from predetermined positions, for example, up to 0.5 mm, which makes assembly easier and therefore less expensive. Conventionally, higher precision is required to achieve a certain level of acoustic quality. The microphone capsules are also three similar (sub)board PCBs. 1,1 ~ PCB 3,2 The substrates can be mounted in at least two groups, with one substrate in each group belonging to each branch. Each (sub)substrate can contain at least two microphone capsules. The central region of the array between the three rotated substrates or substrate groups can contain no substrate or a substrate without a microphone capsule. Alternatively, an additional microphone capsule can be placed in the center, increasing the total number of capsules. Another position remains constant. Thus, the first and second modified embodiments have 16 microphone capsules, the third modified embodiment has 22 capsules, and the fourth modified embodiment has 7 capsules. These central capsules have the advantage of improving the directivity and SNR of the entire array because they acquire the acoustic signal at the position of the highest sound pressure (dynamic pressure). However, because these additional central capsules are not placed at points on the L2 grid, they result in an asymmetrical joint array with holes, so the array has non-uniform directivity and cannot be easily expanded in size.

[0036] Electret capsules are particularly well-suited as microphone capsules. In this case, each microphone signal can be individually corrected or normalized using, for example, filtering in individual digital processing blocks DP1 to DP5. The corresponding filter parameters depend on the characteristics of each microphone capsule, e.g., phase response and frequency response. Therefore, electret capsules having internal memory elements with corresponding correction data that can determine the filter parameters are particularly well-suited. Furthermore, the filter parameters may be affected by the inspection or detected direction of the sound source (i.e., sound source localization or beamforming). Sound source localization and actual acoustic recording from the main sound source can be treated as two separate processes. It is possible to use only a portion of the microphone capsules for localization to reduce processing effort, while using all capsules for actual acoustic recording.

[0037] The advantages of the microphone array according to the present invention are good directivity and high SNR, i.e., good noise suppression. The fewer microphone signals available, the more difficult noise suppression becomes. However, this relationship is nonlinear and difficult to predict, particularly because it depends on the position of the microphone capsules. In particular, the microphone array according to the present invention, having 15 or 21 microphone capsules, exhibits good and uniform directivity across all relevant frequency components and the direction of sound incidence, or, in the case of fewer microphone capsules, exhibits extremely good noise suppression, making it particularly well-suited for ceiling-mounted microphones.

Claims

1. Multiple microphone capsules (K １５，１１ ~K １５，３５ )and, A circuit configuration (AD) that is connected to a microphone capsule to receive microphone signals from the microphone capsule and is suitable for processing the microphone signals together. １ ~AD ５ ,AP) and, The microphone capsule is positioned on a plane on the carrier (T, T'), The microphone capsules are positioned on the carrier on three identical branches, each having the same number of microphone capsules. The branches are rotated 120° from each other around a common center. In a plane isometric coordinate system where the three axes (L0, L1, L2) are rotated 60° relative to each other, forming an equilateral triangular L2 grid, each microphone capsule is located at a corner of the triangle in the L2 grid. The microphone capsules are not uniformly distributed across the entire surface of the array. The geometric center of the array is located at one of the midpoints of the central triangle (D M), The position within the conformal coordinate system is specified in the format (L0, L1, L2) relative to a reference point (R) at the corner of the central triangle (D M) on the opposite side of the triangle parallel to the L0 axis, as a multiple of the triangle's side length. The microphone array comprises exactly 15 microphone capsules (K15,11 to K15,35), which are arranged starting from a reference point (R) at the positions described below or in corresponding mirror-image positions. K 15,11 = (0,4,0), K 15,12 = (1,3,0), K 15,13 = (2,2,0), K 15,14 = (0,2,2), K 15,15 = (0,2,1), K 15,21 = (0,0, -3), K 15,22 = (0, -1, -2), K 15,23 = (0, -2, -1), K 15,24 = (2,0, -1), K 15,25 = (1,0, -1), K 15,31 = (-3,0,1), K 15,32 = (-2,0,2), K 15,33 = (-1,0,3), K 15,34 = (-2,-1,0), K 15,35 = (-2,0,0)

2. Multiple microphone capsules (K ２１，１１ ~K ２１，３７ )and, A circuit configuration (AD) that is connected to a microphone capsule to receive microphone signals from the microphone capsule and is suitable for processing the microphone signals together. １ ~AD ５ ,AP) and, The microphone capsule is positioned on a plane on the carrier (T, T'), The microphone capsules are positioned on the carrier on three identical branches, each having the same number of microphone capsules. The branches are rotated 120° from each other around a common center. In a plane isometric coordinate system where the three axes (L0, L1, L2) are rotated 60° relative to each other, forming an equilateral triangular L2 grid, each microphone capsule is located at a corner of the triangle in the L2 grid. The microphone capsules are not uniformly distributed across the entire surface of the array. The geometric center of the array is located at one of the midpoints of the central triangle (D M), The position within the conformal coordinate system is specified in the format (L0, L1, L2) relative to a reference point (R) at the corner of the central triangle (D M) on the opposite side of the triangle parallel to the L0 axis, as a multiple of the triangle's side length. The microphone array comprises exactly 21 microphone capsules (K21,11 to K21,37), which are arranged starting from a reference point (R) at the positions or corresponding positions in a mirror image arrangement as described below. K 21,11 = (0,5,2), K 21,12 = (0,4,3), K 21,13 = (0,6,0), K 21,14 = (0,0,6), K 21,15 = (-1,0,6), K 21,16 = (0,1,3), K 21,17 =(-1,0,2), K 21,21 = (-5,-1,0), K 21,22 = (-4,-2,0), K 21,23 = (-5,0,1), K 21,24 = (0,-5,0), K 21,25 = (0,-5,-1), K 21,26 = (-1,-2,0), K 21, 27 = (1, -2, 0), K 21,31 = (2,0, -4), K 21,32 = (3,0, -3), K 21,33 = (0,0, -5), K 21,34 = (5,1,0), K 21,35 = (5,2,0), K 21,36 = (3,0,0), K 21,37 =(1,2,0)

3. The microphone array according to claim 1 or 2, wherein the side length of each triangle in the L2 grid corresponds to the minimum distance between two microphone capsules.

4. The geometric center point of the array is provided at one center point of the triangles of the central triangle (D Ｍ ), and is provided at one center point of the triangles of the central triangle (D In an isometric coordinate system, the position is a multiple of the side length of the triangle, and is the central triangle (D) on the opposite side of the side parallel to the L0 axis. Ｍ The microphone array according to claim 1 or 2, which is specified in format (L0, L1, L2) with respect to a reference point (R) located in the corner of the )

5. The microphone capsule consists of three similar circuit boards (PCBs) rotated 120° from each other. １ ~ PCB ３ The microphone array according to claim 1 or 2, mounted on a circuit board group.

6. The microphone capsule consists of three similar circuit boards (PCBs). １，１ ~ PCB ３，２ ) are mounted on at least two groups, Each circuit board includes at least two microphone capsules. The microphone array according to claim 5, wherein one circuit board from each group belongs to each branch.

7. Three rotating circuit boards (PCBs) １ ~ PCB ３ The microphone array according to claim 5, wherein the central region of the array between the or circuit board groups either does not include a circuit board or includes a circuit board without a microphone capsule.

8. The microphone array according to claim 1 or 2, wherein the signal processing involves beamforming.

9. The microphone array is configured to be mounted on the ceiling of the room. The carrier is a metal plate with an acoustic reflective surface. The microphone array according to claim 1 or 2, wherein each microphone capsule is mounted near a hole in a metal plate and receives sound through the hole.

10. The microphone array according to claim 1 or 2, wherein the side lengths of the triangles in the L2 grid are in the range of 3 to 6 cm, particularly in the range of 4 to 5 cm.

11. The microphone array according to claim 1 or 2, wherein the microphone capsules, as a result of their geometric arrangement, cover as many inter-elemental spacings as possible in various directions between individual microphone capsules.

12. The geometric arrangement of the microphone capsules defines a joint array that specifies the relative positions of each pair of microphone capsules in the array relative to each other, according to the distances between them and the direction of these distances. Each point in the shared array has at least one pair of microphone capsules within the array. Their relative positions, with each other as a reference, are the center point of the joint array (C Ｍ This means that the position of this joint array point is the same as that of the ) The microphone array according to claim 1 or 2, wherein no holes appear in the joint array at points in an equiangular coordinate system.

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