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 microphone arrays, and more particularly to an arrangement of multiple microphone capsules operating together as an array to capture sound. [Background technology]

[0002] Microphone arrays are frequently used for beamforming, noise suppression or sound source location. They contain several microphone capsules whose output signals are electronically interconnected and work together for directional recording of sound. The type of interconnection can generate a preferred direction in which the microphone array is particularly sensitive for sound recording. Due to the electronic combination of the individual microphone signals, this preferred direction is electronically adjustable, which allows the preferred direction to be changed with very short response times. However, microphone arrays do not necessarily have an equally good directional effect for all directions, but often have one or more fixed preferred directions depending on the arrangement of the microphone capsules. Furthermore, microphone arrays do not work equally for all frequencies, but rather show a frequency dependency. This depends, among other things, on the distance between the microphone capsules. A very important aspect of microphone arrays is therefore the geometric arrangement of the microphone capsules on the microphone surface. That is, for a given number of microphone capsules, they need to cover as many inter-element distances as possible, i.e. the distances between the individual microphone capsules of the array, in as many different directions as possible.

[0003] There are different strategies regarding the type, number and positioning of microphone capsules. Often, for example in the case of microphone arrays that can be mounted on the ceiling of a room, a number of microphone capsules are interdigitated with each other to capture as many different preferred directions as possible and a certain frequency range. In many cases, this is the range of audio frequencies, for example 100Hz-10kHz. Typical approaches in this field are heuristics, very time-consuming searches by "trying" all possible analytically describable manifolds, for example lines, circles, spirals, etc., and numerical simulations.

[0004] For example, in US6205224B1, at least 63 sensor elements, such as antennas or microphone capsules, are arranged in concentric circles and at the same time in a spiral, allowing for broadband detection with a high degree of directionality without being largely dependent on direction. The direction and frequency characteristics of the sensor arrangement are indicated by a so-called joint array, which indicates the inter-element distances and the direction of these distances. In US2013 / 0101141A1, also aimed at direction-independent broadband detection, 30 microphone capsules are evenly distributed on the surface of a hexagonal circuit board, some of which can be interconnected. In US2016 / 0323668A1, a large number of microphone capsules are also interconnected to form a microphone array, distributed approximately evenly on several circuit boards. The central board contains 64 microphone capsules, while the seven boards arranged in a circle around it each contain a further eight microphone capsules, resulting in a total of 120 microphone capsules. In all these cases, the large number of microphone signals results in high computational complexity and overall large microphone arrays.

[0005] Therefore, another strategy besides the mentioned documents is to use the smallest possible number of microphone capsules in the array. In this case, in order to reduce noise or to obtain a high signal-to-noise ratio (SNR), the microphone capsules need to have as little noise as possible, i.e. be of high quality. Furthermore, the electroacoustic properties of all microphone capsules in the array need to be approximately identical within tight tolerances. In German Publication No. 10 2010 012388 A1, a mathematically theoretical approach is pursued to minimize the number of microphone capsules and their positioning by positioning them at the intersections of a Golomb ruler. This reduces the number of microphone capsules, but due to the asymmetric distribution, it leads to non-uniform directional properties in all directions. Furthermore, the microphone capsules are distributed approximately evenly over the entire surface. In US Pat. No. 9,894,434 B2, a microphone array with 17 microphone capsules is described, arranged on the diagonals of a relatively large square area of ​​about 60 x 60 cm. This size is typical for most of the mentioned arrays. Furthermore, most of the arrays mentioned suffer from being sensitive to even small mispositionings of the microphone capsules and from the fact that they cannot be scaled in size without introducing destructive non-linear effects.

[0006] In the field of seismology, sensor arrays have been studied for a long time. The article "Array Design" by R. Haubrich in the literature ("Bulletin of the Seismological Society of America", Vol. 58, June 1968) describes how arrays for the detection of seismic, ocean or electromagnetic radio waves can be built with as few sensors as possible. The directional and frequency characteristics of various sensor arrangements have been evaluated using a joint array. Various sensor arrangements that are considered "perfect" or "optimal" according to this criterion have been proposed, including conformal arrays, where sensors are placed at the intersections of a conformal coordinate system. Summary of the Invention [Means for solving the problem]

[0007] The present invention aims to provide the smallest possible number of microphone capsules, which are more robust against small mispositioning of the capsules, have a high direction-independent directivity and have an almost uniform frequency dependence over the audio frequency range and can be used as ceiling microphones. This aim is solved by a microphone array as claimed in claim 1.

[0008] Some structures of arrays of seismic sensors proposed by R. Haubrich some years ago have also turned out to be suitable for arrays of microphone capsules. In particular, conformal arrays with 15 or 21 microphone capsules have particularly good acoustic properties, e.g. good localization of the sound source and a high level of directivity, as well as other advantages, e.g. low manufacturing costs. This is also true if the size of the array is reduced according to the audio frequencies to be recorded, allowing smaller arrays than before.

[0009] According to the invention, the microphone array comprises a small number of microphone capsules, in particular 15 or 21 microphone capsules, and a circuit arrangement connected to the microphone capsules and suitable for receiving the 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 with the same number of microphone capsules, the branches being arranged rotated 120° relative to one another around a common center, and in a planar isometric coordinate system with three axes rotated 120° relative to one another, they form a so-called L2 grid of equilateral triangles, each of the microphone capsules being located at a corner of a triangle of the L2 grid. The use of electret capsules is particularly advantageous, as they typically have low inherent noise and low self-resonance, and therefore can cover a higher sound pressure level range. However, other microphone capsules, for example MEMS, can also be used.

[0010] One advantage of the array according to the invention is that it has good uniform directivity in all directions over the entire audio frequency range of interest, as can be calculated with a joint array, but further advantages of the array according to the invention include a relatively high robustness against small mispositioning of the microphone capsules, a small array size, lower cost, and a relatively open possibility of size scalability.

[0011] Further advantageous embodiments are disclosed in claims 2-11. [Brief description of the drawings]

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

[0013] [Figure 1] 1 shows an arrangement of 15 microphone capsules in a first embodiment of the present invention. [Diagram 2] 2 shows an arrangement of 15 microphone capsules in a second embodiment of the present invention, which is a mirror image of the first embodiment. [Diagram 3] 1 shows a collaborative array of microphone capsule arrangements according to the first or second embodiment. [Figure 4] 3 shows an example of a circuit board layout for arranging a microphone capsule according to the first embodiment. [Diagram 5] 13 shows an arrangement of 21 microphone capsules in a third embodiment of the present invention. [Figure 6] 13 shows an arrangement of six microphone capsules in a fourth embodiment of the present invention. [Figure 7] A block diagram of a microphone array is shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] In a first embodiment of the invention, FIG. 1 shows an arrangement of 15 microphone capsules on a carrier T. The microphone capsules are arranged in three equal groups on congruent branches, each rotated 120° relative to the other. The first branch includes, for example, capsules K 15,11 ,K 15,12 ,K 15,13 ,K 15,14 ,K 15,15 The second branch contains capsule K 15,21 ~K 15,25 The third branch includes the capsule K. 15,31 ~K 15,35 The Cartesian coordinate system X,Y is shown for the orientation, but the capsule is located on the intersection of the isometric coordinate system, also shown in Figure 1. The isometric coordinate system has three axes L0, L1, L2 offset by 60° in one plane and consists of equilateral triangles. Each side of these triangles is parallel to one of the axes L0, L1 or L2. The centre of the whole arrangement, around which the three congruent branches rotate relative to one another, is the origin of the Cartesian coordinate system (i.e. X=0, Y=0). At the same time, it is the central triangle D of the isometric coordinate system. M It is also the center of gravity. center triangle D M That corner of (opposite the side parallel to the L0 axis) is arbitrarily chosen here as the reference point R of the conformal coordinate system.

[0015] The positions of the isometric coordinate system are specified as multiples of the side lengths of an equilateral triangle. For example, the central triangle D M The upper right corner of the central triangle D is shifted by one side length in the direction of the L1 axis from the reference point R, which is identified in isometric coordinates as the position (L0, L1, L2) = (0, 1, 0). M is shifted by one side length in the direction of the L2 axis from the reference point R, i.e., is at the position (L0, L1, L2) = (0, 0, 1) in isometric coordinates. Starting from the reference point R, the microphone capsule is located at

[0016] (Table 1) TIFF2024515837000002.tif45155

[0017] In Cartesian coordinates (X,Y), the approximate values ​​are as follows, depending on the scale (for example, as shown in Figure 1, if the side length or isometric length unit of a triangle is 0.05 m, the units are meters):

[0018] (Table 2) TIFF2024515837000003.tif28155

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

[0020] The positions are applied to the coordinate system shown in Figure 1 and will of course deviate numerically if the coordinate system or array is rotated or other reference points are chosen. Furthermore, the positions can be reached in a variety of ways in a conformal coordinate system (because the axes are not mutually orthogonal), 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 a central point.

[0021] FIG. 2 shows an arrangement of 15 microphone capsules on a carrier T' in a second embodiment of the invention, which is a mirror image of the first embodiment. It has the same acoustic and geometric properties as the arrangement of the first embodiment and is equivalent to it. Here there is a mirror symmetry along the Y axis. However, identical and rotated variants can be produced by mirroring the arrangement according to the first embodiment on any axis. These variants are all equivalent, i.e. the same joint array is obtained, identical to the first or second embodiment, since the sensitivity of the array can be adjusted approximately uniformly in all directions. The isometric coordinate system can be, for example, calculated by dividing the 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 ) lie on a line that is parallel to one of the axes L0, L1, L2 of the isometric coordinate system. The distance between two adjacent positions in this group of three corresponds to the side length of the triangle and therefore to a unit of the isometric coordinate system.

[0022] Fig. 3 shows a joint array of arrangements according to the first and second embodiments, which in principle are known from the theory of R. Haubrich, but here adapted to sound waves of speech or audio frequencies, respectively. The points represent the relative positions of two microphone capsules of the array relative to each other, i.e. the distance between them and the direction of these distances. In other words, each point in the joint array is a point corresponding to at least one pair of microphone capsules in the array, the relative positions of which with respect to each other are determined by the joint array centre point C M , which means that the position of this joint array point with respect to the corresponding input direction and wavelength is the same as the position of this joint array point with respect to the corresponding input direction and wavelength. Each point thus represents a possible sound wave incidence direction and wavelength, which can be processed by the microphone array exactly according to its direction, i.e., used to localize the sound source and generate directional effects. It is important here that no holes occur in the joint array at the points of the conformal coordinate system. This is true here as well. Holes in the joint array mean that the microphone array cannot process sound waves of the corresponding input direction and wavelength in a directionally accurate way. However, usually a uniquely associated microphone arrangement cannot be directly inferred from the joint array.

[0023] The joint array of microphone arrangements according to the invention has the advantageous property that each joint array point has six neighboring points evenly arranged around it (at least in the inner region of the joint array). This allows the size of the microphone arrangement to be scaled to the wavelength of interest. The joint array point with the smallest distance to the origin (smallest inter-element distance) represents the highest spatially clearly resolvable frequency before undersampling begins, i.e. below so-called spatial aliasing. The joint array point with the largest distance to the origin accordingly 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 the smallest or highest wavelength 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) results in a highest frequency of about 6.9 kHz (below spatial aliasing).

[0024] One advantage of the present invention is that the microphone capsules are not distributed evenly over the area of ​​the array, but rather form groups. This has the consequence that a relatively large portion of the surface does not need to be covered with a circuit board or printed circuit board in order to contact the capsules. In particular, a circuit board or group of circuit boards does not need to be provided on the size of the entire arrangement. This further reduces the manufacturing costs of the array, which are relatively low due to the small number and weight of the microphone capsules. Furthermore, since the microphone capsules are distributed over three congruent branches, the same circuit board can be used for each branch.

[0025] FIG. 4 shows an exemplary arrangement of three identical circuit boards P1, P2, P3 for the arrangement of microphone capsules according to the first embodiment. The circuit boards P1 to P3 each contain five microphone capsules of a branch and are arranged rotated by 120° on the carrier. Additional components can also be arranged on these circuit boards, such as a processing unit with one or more processors, AD converters, etc. However, it is also possible, in particular, to accommodate at least some of these additional components on an additional circuit board (not shown) located in the middle and connected to the circuit boards P1 to P3 carrying the capsules. Thus, another advantage of this arrangement is that there is enough space on the central circuit board, since there are no microphone capsules in the middle. As a result, no stacking of circuit boards (which would make the array thicker and therefore more complicated and expensive to manufacture) is necessary in this area. Moreover, the basically symmetrical structure makes the assembly easier, since the center of gravity of the entire array is in the middle. Moreover, each of the three boards P1 to P3 can be connected to, for example, two sub-boards P1 1 ,P1 2 ,P2 1 ,P2 2 ,P3 1 ,P3 2 It is also possible to replace the P1 sub-substrate with a P2 sub-substrate, thus reducing the total board area. This is advantageous when the total area of ​​the array and (sub-)substrates is large compared to the area required for the components. Again, at least three sub-substrates, e.g. P1 1 ,P2 1 ,P3 1 is the same. Depending on the space requirements of the additional components, it is possible for all of the circuit boards (or at least the circuit boards carrying the capsules) to be less than half the total area of ​​the array.

[0026] FIG. 5 shows an arrangement of 21 microphone capsules in a third embodiment of the invention. The same applies to this embodiment as to the first and second embodiments described above. In particular, it has similar advantages. However, due to the higher number of microphone capsules, the quality of the recording may be better. Starting from the reference point R defined above and using the coordinate system shown in FIG. 5, the microphone capsules are located at the following positions (again, equivalent variations can be produced by mirroring and / or rotating on an axis):

[0027] (Table 3) TIFF2024515837000004.tif57155

[0028] The microphone capsules can be distributed very compactly, for example on two circuit boards per branch. The five capsules K 21,11 ~K 21,15 A circuit board P 21,1 One of the options is shown in Figure 5. The other two capsules K 21,16 ,K 21,17 are close to each other, allowing for a very compact mounting on a second circuit board (not shown). Any additional electronic components required (processors, A / D converters, etc.) may be accommodated on one of the two boards and / or on an additional central board (not shown) in the middle of the array. Again, the other two branches are congruent, rotated 120° each, and can use the same type of board (i.e. board with the same layout) as the first branch. An optional central board can also be used. Also, in this embodiment, at least the capsule-carrying circuit boards can total 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 a relative scale. This results from the fact that the arrays of the present invention (in all embodiments) are scalable in size without introducing disruptive and difficult to compute non-linear effects. In the embodiment shown in Figure 5, the radius r of the outermost capsule is max is approximately L × 6.11 (L is the side length of an equiangular triangle), and the maximum inter-element spacing is approximately d max = L × 11.79. For example, for a circular array with a scale of L = 5 cm, a diameter D of about 61.1 cm is obtained (d max = 58.95 cm), and on a scale of L = 4 cm, we get a diameter D of about 48.9 cm (d max =47.16 cm), and on a scale of L = 3.5 cm, we obtain a diameter D of about 42.8 cm (d max = 41.27 cm). Conversely, the diameter of the array or the maximum inter-element spacing can be predefined. For example, to obtain an array diameter of about 55 cm, a scale L = 4.5 cm would be chosen, while for about L = 3.39 cm, e.g., d max = 40 cm. Arrays of different sizes do not fundamentally differ in frequency behavior, only the frequency range shifts slightly. As is well known, the maximum inter-element spacing is important for the generation of sound source localization and directivity at low frequencies, while the minimum inter-element distance (i.e. scale L) is important for the generation of localization and directivity at high frequencies. Overall, depending on the embodiment, at audio frequencies a scale of L = 3-6 cm becomes useful, especially in the range of L = 4-5 cm.

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

[0031] FIG. 6 shows an arrangement of six microphone capsules in a fourth embodiment. This variant is particularly suitable for very small microphone arrays that can be placed, for example, on a conference table, whereas the above-mentioned embodiment is well suited for mounting on a ceiling or wall. In this variant, due to the small number of microphone capsules, the quality of the directionality and localization of the sound source is not as good as in the above-mentioned variant, but it is better than other equivalent arrangements with only six capsules. Starting from the reference point R defined as above and using the coordinate system shown in FIG. 6, the microphone capsules are located at the following positions (again, equivalent variations can be generated by mirroring and / or rotating on an axis):

[0032] (Table 4) TIFF2024515837000005.tif25153

[0033] In this case, the microphone capsules can be distributed on one circuit board per branch, or, due to their small overall size, they can all be mounted on a single circuit board P 6 The resulting value (rounded off) is r max = L × 1.527, D = L × 3.054, and d max = L × 2.646.

[0034] FIG. 7 shows an exemplary block diagram of a microphone array, which may correspond, for example, to the first or second embodiment. Alternative embodiments have a different number of microphone capsules per branch and / or further subdivide the circuit board into sub-boards. The three circuit boards P1, P2, P3 are each identical in structure and are arranged on the carrier T rotated 120° relative to each other as shown in FIG. 1 and FIG. 4. Each of these circuit boards has the same number of microphone capsules K 15,11 ~K 15,15 These signals are fed to individual analog-to-digital converters (AD 1 ~AD 5This allows for extremely short connections of the sensitive analog microphone signals to the AD converter. If required, a separate digital processing block DP 1 ~DP 5 and / or common processing block SP 1 , for example, processors can be present on the circuit board. These can, for example, filter the digitized microphone signals. The digital output signal S 1 ~S 3 are provided to a central circuit board CP, where a processing unit performs the audio processing AP of the array, in particular the beamforming. Furthermore, the audio processing AP of the array can perform an acoustic search for the (main) sound source in real time and can align the obtained beam of the array in the direction of the (main) sound source. For this purpose, if necessary, the signal SD 1 ~SD 3 can be reported to the circuit boards P1-P3. The resulting digital output signal S of the array A,out If necessary, an analog output signal can also be provided.

[0035] All microphone capsules of a branch are mounted together on a circuit board or group of circuit boards, and the positioning of the circuit board on the carrier T can also be performed with little deviation, so that the relative position of the capsules to each other is very accurate. The carrier can comprise one or more solid or acoustically reflective plates, for example made of metal, plastic, etc. In one embodiment, the carrier is a metal or plastic plate with holes through which the sound can reach the microphone capsules (from the underside of the ceiling microphone, if installed). In this case, since the plate is acoustically reflective, the sound pressure of the microphone capsules increases by up to 6 dB and the array works as a boundary microphone. On the other hand, the arrangement of the microphone capsules according to the invention allows small deviations from the predefined position, for example up to 0.5 mm, which makes the assembly easier and therefore cheaper. Conventionally, a higher precision is required to achieve a certain acoustic quality. The microphone capsules are also mounted on three similar (sub)boards PCB 1,1 ~PCB 3,2 , with one substrate from each group belonging to each branch. Each (sub) substrate can include at least two microphone capsules. The central region of the array between the three rotated substrates or substrate groups can include 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. The other positions remain unchanged. 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. Such a central capsule has the advantage of acquiring the acoustic signal at the location of the highest sound pressure (dynamic pressure), thus improving the directivity and SNR of the entire array. However, such an additional central capsule is not placed at the point of the L2 lattice, resulting in an asymmetric joint array with holes, which results in an array with non-uniform directivity and cannot be easily scaled in size.

[0036] Electret capsules are particularly suitable as microphone capsules. In this case, each microphone signal is fed to an individual digital processing block DP 1 ~DP 5 The filter parameters can be individually corrected or normalized using a filter process at . The corresponding filter parameters depend on the characteristics of the individual microphone capsules, for example the phase response and the frequency response. Therefore, particularly those electret capsules having an internal memory element with corresponding correction data from which the filter parameters can be determined are well suited. Furthermore, the filter parameters can be influenced by the inspected or detected direction of the sound source (i.e. sound source localization or beamforming). Sound source localization and the actual sound recording from the main sound source can be two separate processes. It is possible to use only a part of the microphone capsules for localization in order to keep the processing effort low while using all capsules for the actual sound recording.

[0037] The advantage of the microphone array according to the present invention is 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 non-linear and difficult to predict, especially since it depends on the position of the microphone capsule. In particular, the microphone array according to the present invention with 15 or 21 microphone capsules shows good and uniform directivity over all relevant frequency components and sound incidence directions, or very good noise suppression when the number of microphone capsules is small, so it is particularly well suited for ceiling-mounted microphones.

Claims

1. A plurality of microphone capsules (K １５，１１ ~K １５，３５ , K ２１，１１ ~K ２１，３７ ) and, Connected to a microphone capsule so as to receive a microphone signal from the microphone capsule, and having a circuit configuration (AD １ ~AD ５ , AP) suitable for jointly signal-processing the microphone signal, and comprising The microphone capsules are arranged on a plane on the carrier (T, T'), The microphone capsules are positioned on the carrier on three identical types of branches, each having the same number of microphone capsules, The branches are rotated 120° from each other around a common center, Three axes (L0, L1, L2) are rotated 60° from each other. In a plane equiangular coordinate system forming an equilateral triangle L2 grid, each of the microphone capsules is located at a corner of the triangle of the L2 grid, The microphone array is characterized in that the microphone capsules are not uniformly distributed over the entire surface of the array.

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

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

4. The microphone array includes exactly 15 microphone capsules (K １５，１１ to K １５，３５ ), which are arranged starting from a reference point (R) at the following positions or corresponding positions in a mirror image arrangement, the microphone array according to claim 3. 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)

5. The microphone array includes exactly 21 microphone capsules (K ２１，１１ ~K ２１，３７ ), which are arranged at the following positions or corresponding positions in a mirror image arrangement starting from a reference point (R), the microphone array according to claim 3. 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)

6. The microphone capsule is mounted on three similar circuit boards (PCB １ ~PCB ３ ) or a group of circuit boards that are rotated 120° from each other, the microphone array according to claim 1.

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

8. Three rotated circuit boards (PCBs １ ~PCBs ３ ) or the central region of the array between circuit board groups contains no circuit boards or circuit boards without microphone capsules, the microphone array according to claim 6.

9. The microphone array according to claim 1, wherein the signal processing performs beamforming.

10. The microphone array is configured to be mounted on the ceiling of a room, The carrier is a metal plate provided with an acoustic reflecting surface, The microphone array according to claim 1, wherein each of the microphone capsules is attached near a hole in the metal plate and receives sound through this hole.

11. The microphone array according to claim 1, wherein the side length of the triangle of the L2 grid is in the range of 3 to 6 cm, particularly in the range of 4 to 5 cm.

12. The microphone array according to claim 1, wherein as a result of the geometric arrangement, the microphone capsules cover as many element spacings as possible between individual microphone capsules in various directions.

13. The geometric arrangement of the microphone capsules defines a common array that specifies the relative position of each two microphone capsules of the array with respect to each other according to the distances between them and the directions of these distances, Each point in the common array has at least one pair of microphone capsules present in the array, meaning that their relative position with respect to each other is the same as the position of this common array point with respect to the common array center point (CM). The microphone array according to claim 1, wherein no holes appear in the common array at the points of the equiangular coordinate system.

Images