Patent Translate Powered by EPO and Google Notice This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate, complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or financial decisions, should not be based on machine-translation output. DESCRIPTION JP2001231089 [0001] FIELD OF THE INVENTION The present invention relates to microphone systems, and more particularly to microphone systems having narrow angle directivity. [0002] 2. Description of the Related Art A navigation system mounted on a motor vehicle often incorporates a so-called voice response function. The core of this voice response function is to recognize the voice emitted by the speaker who is the passenger. It is a speech recognition device. A well-known microphone is applied to convert a speaker's voice into an electrical signal, but in order to improve the recognition rate in the voice recognition apparatus, the speaker's voice is made more sensitive and the speaker emits a voice. It is necessary to make the sensitivity to sounds other than voice (for example, running noise of a car) sufficiently low. [0003] In order to solve the above problems, it is necessary to use a microphone having a sharp directivity (narrow-angle directivity) while having the same gain for wideband speech with a frequency of 300 to 5,000 hertz. . As a method of obtaining narrow angle directivity, although it is possible to obtain directivity mechanically by combining a microphone and a sound collector, an acoustic lens or the like, it is necessary not only to become physically large but also to change 04-05-2019 1 directivity. I can not do it either. [0004] In order to make it possible to change the directivity at the same time as it is compact, it is conceivable to obtain directivity by electrical processing, but the applicant has already applied the narrow-angle directional microphone system to which the three microphone integration method has been applied. It has already been proposed. FIG. 1 is an explanatory view of a threemicrophone integration system, in which the order of three omnidirectional microphones MIC1, MIC0, and MIC2 are arranged in a straight line. [0005] Then, a first directivity function D1 representing the directivity of the difference between the output of the microphone MIC1 and the output of the MIC2 is expressed by [Equation 21]. [0006] Since the value of the directivity function D1 decreases as the frequency of the sound wave decreases, in order to maintain directivity to a low frequency range, the difference between the output of the microphone MIC1 and the output of the MIC2 is integrated by an integrator It is necessary to compensate for gain reduction in the low frequency range. The second directivity function D2 representing the directivity after compensation by the integrator is expressed by [Equation 22]. [0007] From a practical point of view, in order to improve the directivity of the second directivity function D 2 in the high frequency range, the frequency characteristic of the difference between the output of the microphone MIC 1 and the output of the MIC 2 is a low frequency pass filter ( It compensates by LPF). The third directivity function D3 representing the directivity when the difference between the output of the microphone MIC0 and the output of the microphone MIC1 and the output of the MIC2 is added is represented by [Equation 23]. 04-05-2019 2 [0008] FIG. 2 is a graph of the third directivity function D3. The horizontal axis represents the sound wave incident angle θ, and the vertical axis represents the value of D3, ie, the output of the 3microphone integration system. [0009] As can be understood from FIG. 2, the value of D3 (solid line) is maximum at zero at θ = 0 ° and at θ = 180 °. , MIC 0 and MIC 2 need to be located on the MIC 2 side of the straight line connecting the two speakers. [0010] However, FIG. 2 also shows that the three-microphone integration system also has some gain for sound waves that are incident from the direction of θ = 90 °, that is, the perpendicular direction of the straight line connecting the microphones MIC1, MIC0 and MIC2. In order to improve the signal / noise ratio, that is, to reliably detect the sound wave emitted by the speaker and to suppress the detection of noise, it is necessary to make the directivity a narrower angle. [0011] The present invention has been made in view of the above problems, and an object of the present invention is to provide a narrow-angle directional microphone system having extremely sharp directivity using a plurality of nondirectional microphones. [0012] A narrow angle directional microphone system according to a first aspect of the present invention comprises an omnidirectional central microphone (MIC0) and a directional microphone in order to realize directivity shown by a broken line in the graph shown in FIG. Combining the outputs of the central microphone and the surrounding microphones with at least one set of surrounding microphones disposed at symmetrical positions with respect to the central microphone, and the incident direction of the voice to the central microphone being centered on the first microphone with respect to the central microphone And d) directivity providing means for providing directivity for rapidly increasing toward the maximum value in the region near 180 ° when changing in the range of 0 ° to 180 °, and maintaining substantially the minimum value in the other regions. . 04-05-2019 3 [0013] In the present invention, based on the outputs of the central microphone and at least one set of surrounding microphones in the directivity imparting means, directivity is imparted which takes a maximum value in a region close to 180 ° and maintains a substantially minimum value in the other regions. Be done. In the narrow-angle directional microphone system according to the second invention, the surrounding microphones are arranged symmetrically with respect to the center microphone at a first predetermined distance from the center microphone on a first straight line passing through the center microphone. Two non-directional microphones, a front microphone (MIC1) and a rear microphone (MIC2), and a second predetermined from the center microphone on a second straight line intersecting perpendicularly with the first straight line at the center microphone An upper microphone (MICA) and a lower microphone (MICB), which are two omnidirectional microphones arranged symmetrically with respect to MIC 0 with a spacing of. [0014] According to the present invention, the directivity of the combined output of the five nondirectional microphones arranged in a cross shape takes a maximum value for voice incident from a direction of 180 ° with respect to the first straight line. . In a narrow-angle directional microphone system according to a third aspect of the present invention, the directivity imparting means imparts a first directivity characteristic based on the outputs of the front microphone and the rear microphone, and a central microphone A second directivity imparting means for imparting a second directivity characteristic based on the outputs of the upper microphone and the lower microphone, and a first directivity characteristic and a second one imparted by the first directivity imparting means. And D. combining means for combining with the second directivity characteristic given by the directivity giving means. [0015] In the present invention, the first eight-shaped directivity characteristic is based on the outputs of the front microphone and the rear microphone, and the second eight-shaped directivity based on the outputs of the central microphone, the upper microphone and the lower microphone. Characteristics are obtained, and by combining the first and second eight-character directivity 04-05-2019 4 characteristics, the directivity is maximized with respect to voice incident from a direction of 180 ° with respect to the first straight line. can get. [0016] In a narrow-angle directional microphone system according to a fourth aspect of the present invention, two non-directional microphones in which the peripheral microphones are arranged symmetrically with respect to the central microphone at a predetermined distance from the central microphone on a straight line passing through the central microphone Consisting of a front microphone (MIC1) and a rear microphone (MIC2) that are [0017] According to the present invention, the directivity of the combined output of the three nondirectional microphones arranged in a straight line takes a maximum value for voice incident from a direction of 180 ° with respect to the straight line. In a narrow-angle directional microphone system according to a fifth aspect of the present invention, the directivity imparting means applies a third directivity imparting means to impart a third directivity characteristic based on an output difference between the front microphone and the rear microphone; A fourth directivity imparting means for imparting a fourth directivity characteristic based on the outputs of the front microphone and the rear microphone, and a signal and a fourth directivity characteristic imparted by the third directivity imparting means And second combining means for combining with the signal to which the fourth directivity characteristic has been imparted by the directivity imparting means. [0018] In the present invention, in the third directivity imparting means, the first eight-shaped directivity characteristic is based on the outputs of the front microphone and the rear microphone, and in the fourth directivity imparting means, the central microphone, the front microphone The second eight-shaped directivity characteristic is obtained based on the output of the rear microphone and the rear microphone, and the light is incident from the direction of 180 ° with respect to the straight line by combining the first and second eight-shaped directivity characteristics. Directivity which maximizes the sensitivity to the voice. [0019] 04-05-2019 5 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 is a layout view of microphones of a narrow angle directional microphone system according to the first invention, wherein a central microphone MIC0, a front microphone MIC1, and a rear used in the above three microphone integration system. The upper microphone MICA and the lower microphone MICB are added to the microphone MIC2 so as to form a cruciform. [0020] The sound pressure P0 detected by the central microphone MIC0 placed at the center can be expressed by [Equation 24]. [0021] Then, the sound pressures P1 and P2 detected by the front microphone MIC1 and the rear microphone MIC2 can be expressed by [Equation 25]. [0022] Similarly, the sound pressures PA and PB detected by the upper microphone MICA and the lower microphone MICB can be expressed by [Equation 26]. [0023] Therefore, the difference .DELTA.P21 between the sound pressure P2 and P1 detected by the rear microphone MIC2 and the front microphone MIC1, and the sum .SIGMA.PAB of the sound pressure PA and PB detected by the upper microphone MICA and the lower microphone MICB Can be represented by [0024] Therefore, the directivity functions D21 and DAB of the difference sound pressure ΔP21 and the harmonic pressure Σ PAB are respectively expressed by [Equation 28]. [0025] Here, since the directivity function D21 of the difference sound pressure ΔP 21 becomes smaller as the sound becomes lower frequency, it is necessary to compensate the gain in the low frequency range by the integral operation {1 / (jωτ)}. Become. 04-05-2019 6 Here, τ is an integration constant. Then, the directivity function D21 'of the difference sound pressure ΔP21 after integral compensation is expressed by [Equation 29]. [0026] The integration constant τ is determined so that D21 '=-1 at θ = 0 °. That is, when kd << 1 holds, D21 'can be approximated as [Equation 30]. [0027] Therefore, if θ = 0 ° and D21 '=-1 are substituted, the integration constant τ is determined by the following equation (31). [0028] Here, assuming that d = 0.02 m and C = 340 m, the integration constant τ is 120 μsec. FIG. 4 is a graph of directivity functions DAB and D21 ', where (a) shows the directivity function DAB and (b) shows the directivity function D21'. As can be seen from this graph, as the directivity function DAB of the harmonic pressure Σ PAB becomes smaller as the value of (kh) becomes smaller, the directivity function changes from a figure of eight to an ellipse and further to a true circle. Conversely, when the value of (kl) increases, the figure of 8 becomes flat and directivity deteriorates. 04-05-2019 7 [0029] We now find a function f that can obtain a figure of eight characteristic over a wide frequency band of 300 to 5,000 Hertz. FIG. 5 is a graph when cos (khsinθ) is viewed as a function of θ, and its change range is expressed by [Equation 32]. [0030] Therefore, in order to make the minimum value of the function f zero, it is necessary to subtract the minimum value cos (kh) from cos (khsinθ), so the function f is expressed by [Equation 33]. [0031] When the first term and the second term on the right side are respectively Taylor expanded, the function f can be approximated by [Equation 34]. [0032] Here, with regard to the optimum value of the distance l between the central microphone MIC0 and the front microphone MICA or the rear microphone MICB, that is, how the cos (kh) can be approximated in a wide frequency band by Fourier expansion. . An approximate expression by Taylor expansion of cos (kl) is expressed by [Equation 35]. [0033] FIG. 6 is a graph of cos (kh) and an approximation equation, and it can be seen that l = 2 cm can be approximated to a higher frequency (about 5,000 hertz). Therefore, l = 2 cm in the following discussion. 04-05-2019 8 Since the approximate function of the function f is a function of ω 2, the value increases in proportion to the square of the frequency of the sound wave. Then, when it is divided by ω 2 and corrected so as to be a constant value regardless of the frequency, the function f is expressed by [Equation 36]. [0034] The integration constant τ 'is determined using [Equation 37] so that f = 1 at θ = 0 °. [0035] Therefore, if the integration constant τ is 120 μs, then τ 'is 14 μs. From the above, in the narrow-angle directional microphone system according to the present invention, the directivity function Dd represented by [Equation 38] may be realized in the form of an electric circuit. [0036] Alternatively, as described above, an LPF may be inserted in the second term in order to improve the characteristics in the high frequency range. The directivity function Dd in this case is expressed by [Equation 39]. [0037] In order to consider the configuration with specific hardware elements, Eq. 40 can be obtained by decomposing Eq. 39 using Euler's formula. [0038] FIG. 7 is a functional diagram of the narrow angle directional microphone system according to 04-05-2019 9 the present invention, wherein five microphones, ie, the central microphone MIC0, the front microphone MIC1, the rear microphone MIC2, the upper microphone MICA and the lower microphone MICB are directed It is connected to the input terminals 70, 71, 72, 7A and 7B of the property imparting unit 7. [0039] The output of the central microphone MIC0 is led to the first summing element 702 via the computing element 701 which performs the operation represented by [Equation 41] on the output. This part corresponds to the first term in [·] of [Equation 40]. [0040] The outputs of the upper microphone MICA and the lower microphone MICB are summed in the second summing element 703 and subjected to the operation represented by [Equation 42] in the first integrating element 704 to obtain the first summing element 702. Led to This part corresponds to the second term in [·] of [Equation 40]. [0041] The outputs of the front microphone MIC 1 and the rear microphone MIC 2 are led to the first summing element 702 through the LPF 706 after the output of the front microphone MIC 1 is subtracted from the output of the rear microphone MIC 2 in the subtraction element 705. This part corresponds to the third term in [·] of [Equation 40]. Then, the output of the first addition element 702 is output to the output terminal 708 through the second integration element 707. The second integral element 707 corresponds to the first 04-05-2019 10 integral element of [Equation 38]. [0042] The directivity imparting unit 7 can be realized digitally using a DSP (Digital Signal Processor), but can also be realized using an analog circuit. FIG. 8 is an example of the analog circuit according to the first embodiment, and the circuits given the same reference numerals as those in FIG. 7 correspond to the operation elements in FIG. That is, in addition to the fact that the output of the central microphone MIC0 is directly supplied to the inverting input terminal of the first operational amplifier OP1 functioning as an adder, the central operation is performed by a square circuit composed of two NPN transistors 81 and 82. The squared value of the output of the microphone MIC0 is provided. [0043] In the second operational amplifier OP2 functioning as a summing integrator, the output of the first operational amplifier OP1 and the outputs of the upper microphone MICA and the lower microphone MICB are summed and integrated. In the third operational amplifier OP3 functioning as an adder, the outputs of the front microphone MIC1 and the rear microphone MIC2 are added, and the output of the third operational amplifier OP3 is supplied to the input terminal of the fourth operational amplifier OP4 functioning as an LPF. Be done. [0044] In the fifth operational amplifier OP5 functioning as a summing integrator, the output of the second operational amplifier OP2 and the output of the fourth operational amplifier OP4 are integrated and integrated. FIG. 9 is a characteristic graph of the first embodiment, which shows the case where the frequency of the sound wave is 300 Hz, 1000 Hz and 3000 Hz from above. As can be seen from this figure, substantially constant directivity characteristics can be obtained regardless of the frequency in the entire voice frequency band. [0045] 04-05-2019 11 In the first embodiment described above, the distance l between the central microphone MIC0 and the front microphone MICA or the rear microphone MICB is 2 cm, but in order to obtain the desired directivity, the variation of the sensitivity of each microphone is strict Need to manage. In order to reduce the influence of this variation, the distance l between the central microphone MIC0 and the front microphone MICA or the rear microphone MICB may be increased, but the approximation of the approximate expression of cos (kh) is degraded. [0046] The second embodiment solves this problem, and uses up to the third term of Taylor expansion to maintain the approximation of the approximate expression of cos (kh). FIG. 10 is a graph of cos (kh) when l is a parameter, and when l is increased, the change of cos (kh) becomes steep, and the upper limit frequency which can be approximated by [Equation 35] is 4,000 hertz or less Because of the decrease, directivity may be deteriorated in a high frequency range. [0047] Therefore, cos (kh) is approximated by [Equation 43] to improve the degree of approximation. [0048] FIG. 11 is a graph of the best approximation curve, a = 4.8 × 10 −9, b = 2.8 × 10 −18, and a sufficient degree of approximation is maintained up to 5,000 hertz. be able to. Therefore, the directivity function Dd 'of the second embodiment is expressed by [Equation 44]. [0049] By further transforming [Equation 44] and inserting two LPFs in order to compensate for the deterioration of the characteristics in the high frequency range, [Equation 45] is obtained. [0050] FIG. 12 is a functional diagram of the second embodiment based on [Equation 45], and five microphones, ie, the central microphone MIC0, the front microphone MIC1, the rear microphone MIC2, the upper microphone MICA and the lower microphone MICB It is connected to the input 04-05-2019 12 terminals 120, 121, 122, 12A and 12B of the directivity imparting unit 12. [0051] The outputs of the central microphone MIC0, the upper microphone MICA and the lower microphone MICB are summed in a first summing element 1201, integrated in a first integrating element 1202 and directed to a second summing element 1203. This part corresponds to the first term in [·] of [Equation 45]. The output of the central microphone MIC 0 is subjected to an operation corresponding to the second term in [·] of [Equation 45] in the operation element 1204 and is led to the second addition element 1203. [0052] In the second addition element 1203, the output of the first integration element 1202 and the output of the calculation element 1204 are added, and are led to the third addition element 1206 through the first LPF 1205. The outputs of the front microphone MIC1 and the rear microphone MIC2 are led to the third summing element 1206 through the second LPF 1208 after the output of the front microphone MIC1 is subtracted from the output of the rear microphone MIC2 in the subtraction element 1207. This part corresponds to the third term in [·] of [Equation 45]. [0053] Then, the output of the third adding element 1206 is output to the output terminal 1210 via the second integrating element 1209. The second integration element 1209 corresponds to an integration element other than [·] of [Equation 45]. Although the first LPF 1205 is essential, the second LPF 1208 can be omitted. [0054] 04-05-2019 13 FIG. 13 shows an example of the analog circuit according to the second embodiment, in which the outputs of the upper microphone MICA and the lower microphone MICB are added and the output of the central microphone MIC0 is subtracted in the first operational amplifier OP1 functioning as an adder / subtractor. It is then integrated in a second operational amplifier OP2 which functions as an integrator. In addition to the output of the central microphone MIC0 being directly supplied to the inverting input terminal of the third operational amplifier OP3 functioning as an adder, the central microphone calculated by the second-order differential circuit composed of two NPN transistors 131 and 132 The second derivative of the output of MIC0 is provided. The output of the third operational amplifier OP3 is differentiated at the fourth amplifier OP4, which functions as a differentiator. [0055] A fifth operational amplifier OP5 functioning as a subtractor subtracts the output of the second operational amplifier OP2 from the output of the fourth amplifier OP4, and the output of the fourth amplifier OP4 functions as the first LPF 1205. The operational amplifier OP6 of In a seventh operational amplifier OP7 functioning as a subtractor, the outputs of the front microphone MIC1 and the rear microphone MIC2 are subtracted. In the circuit diagram, the second LPF 1208 is omitted. [0056] In the eighth operational amplifier OP8 functioning as a summing integrator, the output of the sixth operational amplifier OP6 and the output of the seventh operational amplifier OP7 are integrated and integrated. FIG. 14 is a characteristic graph of the second embodiment, showing the characteristics of the speech frequencies from 300 Hz, 1000 Hz and 3000 Hz from above. As can be seen from this figure, the directivity is almost the same over a wide frequency range. [0057] In the first invention, two more microphones are added to the three microphones used in the conventional three-microphone integration system, and it is necessary to use a total of five microphones in total. Therefore, the microphone system according to the second invention aims to obtain sharp directivity with the number of microphones remaining three. 04-05-2019 14 [0058] FIG. 15 is a layout view of microphones of a narrow angle directional microphone system according to the second invention, wherein a central microphone MIC0, a front microphone MIC1, and a rear microphone MIC2 are used as in the three microphone integration system. The difference between the outputs of the front microphone MIC1 and the rear microphone MIC2 calculated in the subtraction element 150 is the same as in the 3-microphone integration system, and the low frequency pass filter (LPF) 151, the integrator 152, and the first adder It is led to the second adder 154 via 153. Then, it is added to the output of the central microphone MIC0 in the second adder 154 and becomes an output. [0059] In the narrow-angle directional microphone system according to the second aspect of the invention, the outputs of the central microphone MIC0, the front microphone MIC1 and the rear microphone MIC2 are shown by dashed lines, and the directivity of the three microphone integration system represented by solid lines in FIG. A correction is made to the above addition result via the correction function C defined in [Equation 46] for correcting to the directivity shown. [0060] That is, in the microphone system according to the second invention, the correction function φ (θ) with respect to the output of the central microphone MIC0 is represented by [Equation 47]. [0061] FIG. 16 is a graph showing the ideal characteristic of the correction function φ (θ), and the ideal characteristic is "1" up to a predetermined range (eg -120 ° ≦ θ ≦ 120 °), otherwise It is a square wave that is "-1". The Fourier expansion of the correction function φ (θ) of the rectangular wave results in [Equation 48]. 04-05-2019 15 [0062] Sin (kd · cos θ) can be approximated by [Equation 49] if kd << 1. [0063] Therefore, the directivity function of the output difference between the front microphone MIC1 and the rear microphone MIC2 after integration correction is expressed by [Equation 50]. [0064] Next, the sum cos (kd · cos θ) of the outputs of the front microphone MIC1 and the rear microphone MIC2 is Taylor-expanded, and further, using the double angle formula, the following equation is obtained. [0065] Solving [Equation 51] for cos 2θ yields [Equation 52]. [0066] Substituting the equations 50 and 52 into the equation 48, the correction function φ (θ) is expressed by the equation 53. [0067] Here, when the last term cos (kd) is subjected to Taylor expansion approximation, the correction function φ (θ) is expressed by [Eq. 54]. [0068] However, since θ changes from “1” to “−1” at θ = 120 °, τ, τ ′ and a are as in [Equation 55]. [0069] If d = 2 cm and c = 340 m / s, then τ = 107 (μ sec), τ '= 29 (μ sec), a = 2.02 × 10 -9. Therefore, the directivity function Dd ′ ′ of the narrow-angle directional microphone system 04-05-2019 16 according to the second invention is expressed by [Equation 56]. [0070] FIG. 17 is a functional diagram of the narrow angle directional microphone system according to the second invention, wherein the central microphone MIC0, the front microphone MIC1 and the rear microphone MIC2 are input terminals 170, 171 of the directivity imparting unit 17. And 172 are connected. The outputs of the front microphone MIC1 and the rear microphone MIC2 are connected to a first summing element 1701 which calculates their sum and a subtraction element 1702 which calculates their difference. [0071] The output of the central microphone MIC 0 is added to the output of the first summing element 1701 in the second summing element 1704 via the computing element 1703 which performs the operation {-2 (1-aω 2)}. The output of the second summing element 1704 passes through the first integrating element 1705 to one terminal of the third summing element 1706, and the output of the subtracting element 1702 passes through the low pass filter 1707 for the third summing. It is connected to the other terminal of the element 1706. [0072] The output of the third summing element 1706 is summed with the output of the central microphone MIC0 in the fourth summing element 1709 via the second integrating element 1708 to produce the output of the narrow-angle directional microphone system according to the second invention It becomes. FIG. 18 shows an example of the analog circuit of the narrow-angle directional microphone 04-05-2019 17 system according to the second invention, wherein the first operational amplifier OP1 calculates the sum of the output of the front microphone MIC1 and the output of the rear microphone MIC2, The operational amplifier OP2 calculates the difference between the output of the front microphone MIC1 and the output of the rear microphone MIC2. The third operational amplifier OP3 functions as an LPF, and the fourth operational amplifier OP4 functions as a third summing element. Furthermore, the fifth operational amplifier OP5 functions as a fourth summing element. [0073] FIG. 19 is a characteristic graph of the narrow angle directional microphone system according to the second invention, and although the gain slightly decreases as the frequency increases, it becomes possible to obtain the same directivity regardless of the frequency. [0074] According to the narrow angle directional microphone system according to the present invention, at least one set of surrounding microphones is arranged around the central microphone, and the narrow angle is achieved by performing electrical arithmetic processing by the analog circuit or the digital element. It becomes possible to realize directivity. [0075] Furthermore, when digital elements are used, it is possible to easily change the directivity by exchanging programs. [0076] Brief description of the drawings [0077] 13 is an explanatory view of a microphone integration system. [0078] 2 is a graph of the third directivity function D3. 04-05-2019 18 [0079] 3 is a layout diagram of the microphone of the narrow angle directional microphone system according to the first invention. [0080] 4 is a graph of directivity functions DAB and D21 '. [0081] FIG. 5 is a graph of cos (khsinθ). [0082] 6 is a graph of the approximate expression of cos (kh). [0083] 7 is a functional diagram of the narrow angle directional microphone system according to the first embodiment of the present invention. [0084] 8 is an example of an analog circuit of the first embodiment. [0085] 9 is a characteristic graph of the first embodiment. [0086] It is a graph of cos (kh) when FIG. 10 h is made a parameter. [0087] FIG. 11 is a graph of the best approximation curve. [0088] 04-05-2019 19 12 is a functional diagram of a narrow angle directional microphone system according to a second embodiment of the present invention. [0089] 13 is an example of an analog circuit according to the second embodiment. [0090] 14 is a characteristic graph of the second embodiment. [0091] 15 is a microphone layout diagram of a narrow angle directional microphone system according to the second invention. [0092] 16 is a graph showing an ideal characteristic of the correction function φ (θ). [0093] 17 is a functional diagram of a narrow angle directional microphone system according to the second invention. [0094] 18 is an example of an analog circuit of the narrow angle directional microphone system according to the second invention. [0095] 19 is a characteristic graph of the narrow angle directional microphone system according to the second invention. [0096] Explanation of sign [0097] 04-05-2019 20 MIC0, MIC1, MIC2, MICA, MICB: non-directional microphone 7: directivity imparting unit 701: arithmetic element 702: first sum arithmetic element 703: second sum arithmetic element 704: first integral element 705: difference Arithmetic element 706 ... LPF 707 ... second integral element 04-05-2019 21

1/--страниц