WO2023100262A1

WO2023100262A1 - Sound wave shielding hood and sound source direction detecting device including sound wave shielding hood

Info

Publication number: WO2023100262A1
Application number: PCT/JP2021/043942
Authority: WO
Inventors: 知路岡; 将広小田; 靖夫櫛田
Original assignee: Ｊｆｅアドバンテック株式会社
Priority date: 2021-11-30
Filing date: 2021-11-30
Publication date: 2023-06-08

Abstract

The present invention provides a sound wave shielding hood 8 that can suppress the reception of an external sound arriving from the outside of a direction detection range TA and thereby reduce erroneous detection due to a grating lobe resulting from the external sound and a sound source direction detecting device 1 including the sound wave shielding hood 8. The sound wave shielding hood 8 is configured to prevent an array sensor 3, which includes multiple microphones 9 for receiving sound waves, from receiving an external sound arriving from the outside of a preset direction detection range TA and is configured to shield at least one of the multiple microphones 9 from a sound wave arriving from a periphery OE of the direction detection range TA.

Description

Acoustic shielding hood and sound source azimuth device with acoustic shielding hood

The present invention relates to a sound wave shielding hood that shields sound waves arriving from outside the sound source direction determination range, and a sound source azimuth locating device equipped with the sound wave shielding hood.

A sound source azimuth locating device is known that has an array sensor in which a plurality of microphones that receive sound waves are arranged, and that locates the azimuth where the sound source exists based on the sound pressure signal of the sound waves received by the array sensor. In this type of device, the microphone may also receive sound waves (hereinafter referred to as external sounds) coming from outside a preset azimuth determination range. In that case, depending on the arrangement of the microphones in the array sensor, the regularity of the phase difference obtained with respect to the external sound received by each microphone results in false orientation called grating lobes (when called false signals). ) occurs within the azimuth orientation range, and this may cause misorientation of the sound source azimuth. Therefore, it is desirable to shield the sound source azimuth device from external sounds.

Patent Literature 1 describes an example of a sound collector configured to shield external sounds. The sound collector consists of a sound collecting hood (hereinafter simply referred to as a hood) having a sound reflecting inner wall forming a parabolic curved surface, and a sound receiving surface facing forward, that is, toward the opening of the hood. and a microphone placed in the With the above sound collector, when the opening of the hood is directed toward a predetermined sound source, the microphone receives the sound that enters the hood, and the external sound coming from the outside of the hood toward the microphone is received by the hood. It is designed to be shielded.

Patent No. 5137609

The use of the above-mentioned hood for each microphone of the array sensor is considered to be effective in shielding each microphone from external sounds. However, when the frequency of the sound wave to be measured by the array sensor is high, the spacing between the microphones constituting the array sensor is set narrow in order to prevent grating lobes from occurring near the direction of the sound source. Therefore, there is a possibility that the installation space for attaching the hood becomes narrow, or that adjacent hoods compete for installation space, making it difficult to attach the hood. Also, even if a hood can be attached, the opening of the hood cannot be made sufficiently large due to the narrow spacing between the microphones, making it susceptible to sound wave diffraction. there is a possibility. Specifically, when the opening of the hood is shorter than the wavelength of the external sound, there is a possibility that the external sound cannot be sufficiently shielded due to the diffraction phenomenon of sound waves.

On the other hand, if the distance between the microphones is widened in order to suppress the influence of the external sound due to the diffraction phenomenon, grating lobes due to the external sound are likely to occur within the azimuth determination range, and the direction of the sound source is more likely to be erroneously determined. It may become

Therefore, it is conceivable to cover the entire array sensor with a hood. By doing so, the hood can be attached to the array sensor without being affected by the arrangement of the microphones. In addition, since the opening of the hood can be set large, it is possible to suppress the influence of external noise due to the diffraction phenomenon.

However, if the inner diameter of the hood and the height of the hood are set so that all the microphones in the array sensor can receive the sound waves coming from within the azimuth determination range, when the azimuth determination of the sound source is performed, It may not be possible to obtain a large grating lobe suppression effect. This is because a large number of microphones constituting the array sensor can receive the ambient sound due to the size of the hood, the direction of arrival of the ambient sound with respect to the array sensor, and the arrangement of the microphones.

The present invention has been made in view of the above technical problems, and is capable of suppressing the reception of external sounds coming from outside the azimuth determination range and suppressing misorientation due to grating lobes caused by the external sounds. It is an object of the present invention to provide a sound wave shielding hood and a sound source azimuth device equipped with the sound wave shielding hood.

The features of the present invention for solving such problems are as follows.
[1] A sound wave shielding hood configured to suppress an array sensor having a plurality of microphones for receiving sound waves from receiving external sounds coming from outside a preset azimuth determination range, wherein the plurality of a sound wave shielding hood configured to shield sound waves coming from the perimeter of said azimuth range for at least one of said microphones.
[2] The acoustic wave shielding hood according to [1] above, which is configured to surround at least a portion of the array sensor.
[3] The array sensor has a cylindrical shape, and the height protruding from the array sensor is such that it shields at least one of the plurality of microphones from sound waves arriving from the periphery of the azimuth determination range. The acoustic wave shielding hood according to the above [1] or [2], wherein the hood is set to be at least .
[4] The height protruding from the array sensor is set lower than the height at which the number of microphones that do not block sound waves arriving from the periphery of the azimuth determination range is two among the plurality of microphones. The shielding hood according to any one of [1] to [3] above.
[5] An array sensor having a plurality of microphones for receiving sound waves, and based on the sound pressure information of the sound waves received by the array sensor, calculating the sound pressure in each direction within the azimuth determination range, A sound source direction having a computing means for locating the direction at which the sound pressure is maximum among the directions as the arrival direction of the sound wave from the sound source, and the sound wave shielding hood according to any one of [1] to [4] above. Orientation device.
[6] The sound source azimuth locating device according to [5] above, wherein the average distance d between the plurality of microphones adjacent to each other satisfies the following equation.
d≧90°×λ/(90°+βrange/2) (mm)
λ is the central wavelength (mm) of the sound wave used for calculating the direction of arrival of the sound wave, and βrange is the maximum angle (°) of the azimuth determination range.
[7] The computing means weights the sound pressure information of sound waves received by each of the plurality of microphones according to the height of the sound wave shielding hood, and converts the weighted sound pressure information into The sound source azimuth determination device according to the above [5] or [6], configured to determine the azimuth of the sound source based on the sound source.
[8] The computing means performs delay-and-sum beamforming calculation on a plurality of sound pressure information acquired by each of the plurality of microphones to locate the direction of arrival of the sound wave, above [5] to The sound source azimuth locating device according to any one of [7].

According to the present invention, the sound wave shielding hood is installed so as to surround the array sensor, and shields at least one of the plurality of microphones from sound waves coming from the periphery of the azimuth determination range and external sounds. . Therefore, the reception of external sounds is sufficiently suppressed in the entire device, and the generation of grating lobes due to external sounds can be suppressed. As a result, misorientation of the direction of the sound source due to grating lobes caused by external sounds can be suppressed. As a result, it is possible to improve the accuracy of sound source azimuth determination by the sound source azimuth determination device. In addition, compared to the case where a sound wave shielding hood is provided for each microphone, it is possible to reduce the number of parts and cost of members for the entire device, thereby suppressing an increase in product cost.

1 is a diagram showing an example of a sound source azimuth locating device according to an embodiment of the present invention; FIG. 1 is a perspective view of an example of a sound source azimuth locating device according to an embodiment of the present invention; FIG. FIG. 4 is a diagram showing an example of an arrangement pattern of microphones; 1 is a functional block diagram of a sound source azimuth locating device; FIG. FIG. 2 is a diagram showing an example of a sound source azimuth range by a sound source azimuth determination device; FIG. 4 is a diagram for explaining the direction of arrival of sound waves; FIG. 4 is a schematic diagram showing how sound waves are detected by a plurality of microphones; It is a figure which shows an example of the sound pressure information detected by each microphone. FIG. 10 is a diagram showing another example of the shape of the hood; FIG. 10 is a diagram showing another example of the arrangement pattern of microphones; 11 is a cross-sectional view taken along line BB shown in FIG. 10; FIG. FIG. 10 is a diagram for explaining a range shielded by the hood when the height of the hood is set to a minimum height that satisfies Equation (2); FIG. 5 is a diagram for explaining a range shielded by the hood when the height of the hood is set to the maximum height that satisfies Equation (2); FIG. 10 is a diagram showing a one-dimensional sound wave distribution part of a sound pressure map created by delay-and-sum beamforming calculation when a sound source is in front (0°) of the sound source azimuth locator; 4 is a flowchart for explaining an example of control executed in an embodiment of the present invention; FIG. 5 is a diagram showing an example of received sound pressure distribution for each microphone when the height of the hood is low; FIG. 5 is a diagram showing an example of received sound pressure distribution for each microphone when the height of the hood is high;

Embodiments of the present invention will be described below. 1A and 1B are diagrams showing an example of a sound source azimuth determination apparatus according to an embodiment of the present invention. FIG. 1(a) is a front view of the sound source azimuth determination apparatus, and FIG. FIG. 1(a) is a cross-sectional view taken along line AA shown in FIG. 1(a), and FIG. 1(c) is a rear view of the sound source azimuth locating device. FIG. 2 is a perspective view of a sound source azimuth determination device according to an embodiment of the present invention. The sound source azimuth determination device 1 according to this embodiment shown here includes a camera 2, an array sensor 3, a computing means 4, a display means 5, an input means 6, a housing 7, and a sound wave shielding hood (hereinafter referred to as It is simply described as a hood.) 8 as a main component. In the example shown in FIGS. 1 and 2, the camera 2, the array sensor 3, and the hood 8 are provided on the front side of the housing 7 of the sound source azimuth locating device 1. FIG. Further, a computing means 4 is provided inside the housing 7 . A display means 5 and an input means 6 are provided on the rear side of the housing 7 .

The camera 2 captures an image of the object to be measured, and outputs the captured image obtained to the computing means 4 . The captured image is used for the purpose of superimposing it on a two-dimensional distribution of sound pressure (referred to as a sound pressure map) obtained by the delay-and-sum beamforming calculation. Here, the delay-and-sum method beamforming calculation is a calculation method that uses the phase difference of sound waves measured by a plurality of microphones in the array sensor 3 to obtain the azimuth angle of arrival of sound waves with respect to the front azimuth of the microphones. The magnification and field of view of the camera 2 may be appropriately adjusted according to the search range of the sound source. The camera 2 may be, for example, a digital camera including an image sensor such as a CCD sensor or a CMOS sensor and a lens.

The above camera 2 is provided at the center of the array sensor 3. By providing the camera 2 at the center of the array sensor 3, when the captured image is superimposed on the sound pressure map obtained by the delay sum method beamforming calculation, regardless of the distance to the measurement object, the captured image and the sound pressure You can create an image that overlaps the map without any gap.

The array sensor 3 has multiple microphones 9 . The microphone 9 is configured to receive sound waves emitted from a sound source (not shown) and output sound pressure information of the received sound waves. In the embodiment of the present invention, each microphone 9 is provided on a flat base plate. FIG. 3 is a diagram showing an example of an arrangement pattern of the microphones 9. As shown in FIG. In the example shown in FIG. 3, each microphone 9 as a whole is arranged so as to be non-rotationally symmetrical at each of the vertices of two co-circular polygons (not shown) on the same plane and having the same center. . The microphone 9 is arranged to receive sound waves in the range of audible to 100 kHz frequency. The sound pressure information output from the microphone 9 is input to the computing means 4, band-pass filtered to an arbitrary frequency band by the computing means 4, and delay-and-sum method beamforming calculation is performed. In the embodiment of the present invention, the microphone 9 detects a predetermined broadband sound wave, but it may detect a single-wavelength or narrowband sound wave.

In the example shown in FIG. 3, the array sensor 3 has 13 microphones 9. For example, when a 40 kHz sound wave propagating in the atmosphere (at a temperature of 25° C. and a pressure of 1 atm, a wavelength of about 8.7 mm) is measured, the microphones 9 are used in an outer coherent circle whose circumscribed circle has a diameter of 41 mm. They are provided at the positions of the vertices of the regular heptagon and the positions of the vertices of the inner regular hexagon whose circumscribed circle has a diameter of 15.3 mm. The circumscribed circle of the outer regular heptagon and the circumscribed circle of the inner regular hexagon are provided on concentric circles centered on the camera 2 . It should be noted that the frequency of the sound wave to be measured and the size of the circumscribed circle of the regular n-sided symmetry are not limited to these. For example, the measurement frequency by the microphone 9 may be selected from the range of audible sound (for example, 20 Hz) to 100 kHz, and the size of the circumscribed circle of the regular n-sided symmetry may be appropriately set according to the frequency (wavelength).

In the sound source azimuth locating apparatus 1 according to the embodiment of the present invention, as described above, the 13 microphones 9 are arranged at the apexes of the outer cyclic regular heptagon, which is a symmetrical polygon with the same center, and the inner symmetrical hexagon. It is provided at each vertex of the regular hexagon. The microphones 9 arranged in this manner are rotationally asymmetric as a whole. Here, "non-rotationally symmetrical" means an arrangement in which all the microphones 9 are not simultaneously arranged in the same arrangement as before the rotation while the array sensor 3 is rotated 360° with respect to the center of the circumscribed circle of the symmetrical polygon. In this way, by arranging the plurality of microphones 9 so as to be rotationally asymmetric as a whole, the array sensor 3 can improve directivity while suppressing an increase in the number of installed microphones 9, and can suppress the occurrence of grating lobes. can be

The display means 5 may be, for example, a liquid crystal display (LCD), and is configured to display the superimposed image created by the calculation means 4. The input means 6 may be push switches, for example, and are provided in the vicinity of the display means 5 . When the user presses the input means 6 , a predetermined input signal is input to the computing means 4 . Note that a touch panel type input means 6 may be used in place of the push switch or together with the push switch.

FIG. 4 is a functional block diagram of the sound source azimuth determination device 1. FIG. Display processing of a superimposed image in the sound source azimuth locating apparatus 1 will be described with reference to FIG. The computing means 4 has a processing section 10 and a storage section 11 . The processing unit 10 is, for example, a CPU or the like, and executes predetermined calculations using programs and data stored in the storage unit 11, acquired information, etc., and controls the operation of the sound source azimuth determination device 1. Output command signal. The storage unit 11 is, for example, an information recording medium such as a flash memory capable of updating and recording, a built-in or connected hard disk, a memory card, and a read/write device thereof. The storage unit 11 stores in advance programs for realizing various functions of the sound source azimuth locating apparatus 1, information used during execution of the programs, and the like.

Using the sound pressure information acquired from the array sensor 3, the processing unit 10 divides the azimuth determination range into predetermined azimuth divisions based on, for example, the time difference (phase difference) of the sound pressure information detected by each microphone 9. Perform delay-and-sum beamforming calculations for the partitions. By doing so, a sound pressure map is created in which the sound pressure of each azimuth segment is organized into a two-dimensional distribution. The processing unit 10 creates a superimposed image in which the sound pressure map corresponding to the imaging area of the camera 2 is superimposed on the captured image. Specifically, the processing unit 10 converts the sound pressure map into a transparent image or a translucent image, and superimposes this on the captured image to create a superimposed image. The processing unit 10 also outputs the superimposed image to the display unit 5 for display. In the superimposed image, the subject and the sound pressure distribution are superimposed and displayed. Therefore, by confirming the superimposed image, the user can determine the correspondence relationship between the position of the subject in the captured image and the sound pressure distribution of the sound wave at a glance. Therefore, in addition to locating the azimuth at which the sound pressure is maximum as the arrival azimuth of the sound wave, it is possible to determine which part of the object the sound source is located.

FIG. 5 is a diagram showing an example of a sound source azimuth determination range TA by the sound source azimuth determination device 1. In the example shown in FIG. be done. Therefore, in the embodiment of the present invention, as a result, a sound source (not shown) is searched for within the quadrangular pyramid-shaped region shown in FIG. Further, the four sides of the azimuth determination range TA shown in FIG. 5, that is, the azimuth corresponding to the outer peripheral surface of the bottom of the quadrangular pyramid and the vicinity of the inner side thereof, correspond to the peripheral edge portion OE of the azimuth determination range TA in the embodiment of the present invention. The maximum angle βrange of the azimuth determination range TA in the embodiment of the present invention means the angle between the oblique sides located diagonally on the base of the quadrangular pyramid among the four oblique sides of the quadrangular pyramid shown in FIG. .

FIG. 6 is a diagram for explaining the direction of arrival of sound waves. As shown in FIG. 6, the arrival azimuth of the sound wave is the azimuth in which the sound source exists. ) is expressed as an arrival azimuth angle (θ, ψ) by an azimuth angle φ with respect to an arbitrary azimuth (for example, X azimuth) serving as a reference above. The processing unit 10 uses the sound pressure information detected by the plurality of microphones 9 to determine the arrival azimuth angle (θ, ψ) by delay-and-sum beamforming calculation.

FIG. 7 is a schematic diagram showing how sound waves are detected by a plurality of microphones 9, and FIG. 8 is a diagram showing an example of sound pressure information detected by each microphone 9. As shown in FIG. 7 and 8 illustrate the case where the three

microphones

9a, 9b, and 9c are arranged in a line at equal intervals for the sake of simplicity of explanation. When sound waves arrive from the above arrival azimuth angles (θ, ψ), when the microphone 9a is used as a reference microphone (hereinafter referred to as the first microphone 9a), the second microphone 9b adjacent to the first microphone 9a , the sound waves arrive at the first microphone 9a with a time lag of τ. A time difference τ(s) between arrival of sound waves at the first microphone 9a and the second microphone 9b can be obtained by the following equation (1).
τ=(L×sin θ)/v (1)
In the above formula (1), v is the speed of sound (mm/s), θ is the azimuth angle of the sound wave, and L is the distance between the first microphone 9a and the second microphone 9b (the distance d between the microphones 9 to be described later) ( mm).

Although FIGS. 7 and 8 show that the time difference τ (phase difference) is generated due to the azimuth angle θ, the time difference due to the azimuth angle ψ is also generated. The concept of the azimuth angle ψ is the same as that of the equation (1), and the time difference τ changes according to the arrival azimuth angles (θ, ψ).

Here, consider a case where sound waves arrive from a sound source sufficiently distant from each of the

microphones

9a, 9b, and 9c. The distance 2d between the first microphone 9a and the third microphone 9c, which is the reference, is set to twice the distance d between the first microphone 9a and the second microphone 9b. Therefore, the sound wave reaches the third microphone 9c with a delay of τ with respect to the second microphone 9b. That is, the time difference 2τ between the arrival time of the sound wave at the first microphone 9a and the arrival time of the sound wave at the third microphone 9c is equal to the arrival time of the sound wave at the first microphone 9a and the arrival time of the sound wave at the second microphone 9b. is twice the time difference τ with The sound wave reaches the third microphone 9c with a time delay twice as long as that of the second microphone 9b. Therefore, as shown in FIG. 8, the sound pressure information detected by each of the

microphones

9a, 9b, and 9c is shifted by the time difference τ corresponding to the distance L from the reference first microphone 9a. Using these, the processing unit 10 locates the arrival azimuth angle (θ, ψ) of the sound wave.

Specifically, the processing unit 10 shifts the time of the sound pressure information received by the plurality of microphones 9 by the time difference τ, and calculates an addition value by adding the plurality of time-shifted sound pressure information. A plurality of different time differences τ corresponding to the arrival azimuth angles (θ, ψ) are set in advance in the processing unit 10, and the plurality of different time differences τ are set for each of the plurality of microphones 9 according to the distance L. are set respectively. The processing unit 10 uses a plurality of different set time differences τ to obtain a plurality of addition values by changing the shift time as described above.

The added value added with the time difference τ corresponding to the arrival azimuth angle (θ, ψ) becomes maximum because the phases of the waveforms of each sound pressure information are aligned. On the other hand, among the plurality of added values, the added values added with the time difference τ that do not correspond to the arrival azimuth angles (θ, ψ) are out of phase and cancel each other out and do not increase. Therefore, the processing unit 10 successively changes the assumed arrival azimuth angles (θ', ψ') of the sound waves from the assumed sound source within the azimuth determination range TA of the sound source to obtain a plurality of added values. A sound pressure map, which is a two-dimensional distribution of sound pressure within the azimuth determination range TA, is created using a plurality of added values obtained in this manner. Then, the assumed arrival azimuth angle, which is the maximum added value among the multiple added values, is determined as the azimuth of the sound source.

In addition, in the delay-and-sum method beamforming calculation described above, depending on the relationship between the arrangement of the microphones 9 constituting the array sensor 3 and the sound wave wavelength, grating lobes may occur, which may cause misorientation.

Further, in the embodiment of the present invention, the processing unit 10 exemplifies the delay-and-sum method beamforming calculation in which the arrival azimuth angle (θ, ψ) is determined based on the time difference τ. method can be applied. For example, the sound pressure information observed by the

microphones

9a, 9b, and 9c at the same time is regarded as a two-dimensional spatial sound pressure field. Delay-and-sum method beamforming can also be performed by utilizing the fact that there is a correlation between the spatial wave number obtained by spatially performing a two-dimensional Fourier transform on the sound pressure information and the arrival azimuth angle (θ, ψ). A sound source azimuth determination result that is almost equivalent to the calculation is obtained.

The processing unit 10 is configured to display the superimposed image on the display means 5 as described above. As the sound pressure map used for the superimposed image displayed on the display means 5, a color image in which different colors are continuously assigned according to the sound pressure may be used. The processing unit 10 is configured to store the camera image and the superimposed image in the storage unit 11 when an instruction to save the image displayed on the display unit 5 is input from the input unit 6 .

In the sound source azimuth determination device 1 according to the present embodiment, it is preferable to use the array sensor 3 with high sound source azimuth performance from the viewpoint of increasing the sound source azimuth determination accuracy. The sound source orientation performance of the array sensor 3 is greatly affected by the arrangement of the multiple microphones 9 .

Directivity is one of the sound source azimuth performance indicators. The directivity is an index indicating whether or not the sound source sound pressure (hereinafter referred to as main lobe) observed on the sound pressure map can be displayed sharply. The narrower the full width at half maximum (FWHM) of the main lobe, the higher the directivity, which is advantageous for locating the direction of the sound source. The full width at half maximum (FWHM) of the main lobe is represented by the ratio λ/D (rad) between the wavelength λ of the sound wave detected by the array sensor 3 and the aperture width D of the array sensor 3 . In order to improve the directivity, it is effective to increase the aperture width of the array sensor 3 with respect to the wavelength. The aperture width of the array sensor 3 is the diameter of a virtual circle passing through the plurality of microphones 9 arranged on the outermost side with respect to the center of the array sensor 3. The diameter of the circumscribed circle of the polygon that touches the outer cyclic polygon.

Another sound source azimuth performance index is the sound source strength ratio. The sound source intensity ratio is the ratio of the intensity of the grating lobe to the intensity of the main lobe, and is expressed by dividing the intensity of the main lobe by the intensity of the grating lobe. A high sound source intensity ratio means that the intensity of the grating lobe is sufficiently smaller than the intensity of the main lobe. If the intensity of the grating lobe can be made smaller than the intensity of the main lobe, erroneous determination of the direction of the sound source due to the grating lobe can be suppressed. In order to increase the sound source intensity ratio, it is effective to increase the number of microphones 9 and narrow the arrangement interval of the microphones 9 . However, from the viewpoint of reducing the product cost and reducing the computation load on the computing means 4, it is preferable that the number of microphones 9 is as small as possible. Therefore, the generation of grating lobes may be suppressed by devising the arrangement of the microphones 9 as in the embodiment of the present invention.

Here, the hood 8 in the embodiment of the present invention will be explained. As shown in FIGS. 1 and 2 , the hood 8 is positioned on the plane of arrangement of the array sensor 3 and outside the array sensor 3 to surround the array sensor 3 . In the examples shown in FIGS. 1 and 2, the hood 8 is formed in a square tubular shape. Note that the hood 8 is not limited to a rectangular cylinder. FIG. 9 is a schematic diagram showing another example of the shape of the hood 8. FIG. The hood 8 may have a cylindrical shape as shown in FIG. 9(a), or a truncated conical shell shape as shown in FIG. 9(b). Alternatively, as shown in FIG. 9(c), it may be formed in an elliptical cylindrical shell shape, or as shown in FIG. 9(d), it may be formed in an elliptical trapezoidal shell shape. Alternatively, as shown in (e) of FIG. 9, it may be formed in the shape of a truncated quadrangular pyramid shell.

The shape of the hood 8 does not necessarily have to be a frustum shape in which the observation direction side is wider than the microphone 9 side, that is, a tapered shape. That is, it may have a frustum shape in which the microphone 9 side is wider than the observation direction side. When the shape of the hood 8 is a truncated cone shape in which the observation direction side is wider than the microphone 9 side, the spread angle (taper angle) of the hood 8 is half the maximum angle of the azimuth determination range TA (βrange /2) It is preferable not to spread beyond. This is because if the taper angle of the hood 8 is greater than or equal to the angle described above, the hood 8 cannot shield sound waves coming from the peripheral edge portion OE of the azimuth determination range TA, and as a result, it is possible that sufficient external sound shielding performance cannot be obtained. This is because of the nature of In the example shown in FIGS. 1 and 2, the hood 8 is formed in a square tubular shape, but instead of this, it may be formed in a polygonal tubular shape other than a square tubular shape. Also, instead of the truncated quadrangular pyramid shell shape shown in FIG.

Further, slits extending in the axial direction of the hood 8 may be formed at regular intervals in the circumferential direction of the virtual circle. Alternatively, the hood 8 may be configured by arranging a plurality of plates (not shown) extending in the axial direction at regular intervals in the circumferential direction of the virtual circle as shielding portions. The point is that the hood 8 is positioned outside the array sensor 3 and should be configured to cover at least a portion of the circumference of the array sensor 3 from the outside in the radial direction of the virtual circle.

The hood 8 in the embodiment of the present invention may be composed of a sound insulating material having sound insulating performance, a sound absorbing material having sound absorbing performance, or a combination thereof. The sound insulating material is made of, for example, a synthetic resin material or a metal material, and the sound absorbing material is made of soft urethane, polystyrene foam, melamine foam, rubber sponge, fiber-based glass wool, white wool, or the like. When the hood 8 is composed of a combination of a sound insulating material and a sound absorbing material, it is preferable that the inner portion of the hood 8, that is, the portion on the side of the microphone 9 in the plate thickness direction, is composed of the sound absorbing material. This is to prevent or suppress multiple reflections of sound waves within the hood 8 .

The sizes such as the height of the hood 8 and the inner diameter of the hood 8 described above are determined based on the maximum angle βrange of the azimuth locating range TA of the sound source azimuth locating device 1 and the arrangement pattern of the microphones 9 of the array sensor 3 . Specifically, for example, a case where the microphones 9 are arranged as shown in FIG. 10 will be described as an example. Note that, in the example shown in FIG. 10, the description of sound sources existing outside the azimuth determination range TA is omitted for the sake of simplicity of explanation. Further, the distance d between the microphones 9 in the example shown in FIG. The interval d at which grating lobes due to external sound are generated within β range is set.

In the example shown in FIG. 10, microphones 9 are arranged at regular intervals on each of two virtual circles forming concentric circles centered on the center of the array sensor 3 . Specifically, of the two virtual circles, four microphones 9 are arranged at regular intervals on the outer virtual circle, and four microphones 9 are arranged at regular intervals on the inner virtual circle. Also, in the example shown in FIG. 10, the diameter of the outer virtual circle of the two virtual circles is approximately twice the diameter of the inner virtual circle. In the following explanation, it is assumed that the opening of the hood 8, that is, the inner diameter of the hood 8, is set sufficiently longer than the wavelength of the sound waves measured by the sound source azimuth locating device 1. FIG. It is also assumed that the sound source is sufficiently far away from the microphones 9 and that the plane wave arrives at the array sensor 3 from the sound wave arrival direction indicated by the arrow. Further, the length of the hood 8 and the inner diameter of the hood 8 in the embodiment of the present invention will be explained by applying a ray tracing method that does not particularly consider the diffraction phenomenon of sound waves. In the example shown in FIG. 10, the distance between the microphone 9 and the hood 8 is the narrowest along the sound wave arrival direction. That is, FIG. 10 shows the sound wave arrival direction in which the microphone 9 closest to the hood 8 is most likely to be shielded by the hood 8 .

FIG. 11 is a cross-sectional view along line BB shown in FIG. 10 for explaining the height of the hood 8 and the inner diameter of the hood 8 in the embodiment of the present invention. Here, let θmax be the angle between a line perpendicular to the surface of the array sensor 3 (hereinafter referred to as a normal line) and the peripheral edge OE of the azimuth determination range TA. In the example shown in FIG. 11, the sound source azimuth locating device 1 is configured to measure sound waves arriving from the front side. Further, the hood 8 is configured to shield one microphone 9 among the plurality of microphones 9 installed on the array sensor 3 from sound waves from the peripheral portion OE of the azimuth determination range TA. In FIG. 11, the microphone 9-1 is shielded by the hood 8 against sound waves arriving at the angle θmax. Also, the sound wave that reaches the array sensor 3 from outside the angle θmax is the external sound in the embodiment of the present invention.

A symbol “a” shown in FIG. 11 indicates the distance between the hood 8 and the microphone 9 - 1 that is positioned closest to the sound wave arrival azimuth side among the plurality of microphones 9 . Sound source azimuth using delay-and-sum beamforming calculations requires reception of sound waves by at least two microphones 9 . In the example shown in FIG. 11, when a sound wave arrives at the angle θmax, it is necessary to receive the sound wave at least by the microphones 9-3 and 9-4 on the farthest side from the hood 8 with respect to the arrival direction of the sound wave. . That is, in the examples shown in FIGS. 10 and 11, when a sound wave arrives at the angle θmax, if the sound wave can be received by the microphone 9-3, the sound wave can be received by at least two microphones 9-3 and 9-4. becomes. The symbol "ax" shown in FIG. 11 indicates the distance between the microphone 9-3 and the hood 8 in the sound wave arrival direction. shielding at least one microphone (microphone 9-1 in FIGS. 10 and 11) when a sound wave arrives from the periphery OE of the azimuth determination range TA (from the angle θmax in FIG. 11); Moreover, the height of the hood 8 at which sound waves can be received by two or more microphones 9 (microphones 9-3 and 9-4 in FIGS. 10 and 11) can be expressed by the following equation (2).
a tan (90°-θmax)≦hood height<ax tan (90°-θmax) (2)

FIG. 12 is a diagram for explaining the range shielded by the hood 8 when the height of the hood 8 is set to the minimum height that satisfies Equation (2). On the array sensor 3 shown in FIG. 12, hatched areas are shielded by the hood 8 from sound waves arriving from the peripheral edge OE of the azimuth determination range TA. Note that the arrangement of the microphones 9 in FIG. 12 is the same as the arrangement of the microphones 9 shown in FIG. 3 based on the above-described embodiment. When the height of the hood 8 is set so as to satisfy the lower limit value of the above formula (2), the hood 8 directs at least one microphone 9 to sound waves arriving along the peripheral edge OE of the azimuth determination range TA. shield. Also, the remaining microphones 9 except for at least one microphone 9 are not shielded from incoming sound waves. Therefore, the remaining microphones 9 can receive sound waves arriving along the peripheral portion OE of the azimuth determination range TA.

Therefore, according to the embodiment of the present invention, by using the hood 8 shown in FIG. Although it decreases, reception of external sounds can be suppressed. Therefore, when the delay-and-sum beamforming calculation is performed, it is possible to suppress the occurrence of a Gretsch lobe within the azimuth determination range TA. Further, the sound source azimuth determination apparatus 1 as a whole can acquire sufficient signals required for azimuth determination of the sound source, that is, sound pressure information from each direction within the azimuth determination range TA. Therefore, even if the source of the external sound exists outside the azimuth determination range TA of the sound source azimuth determination device 1, erroneous determination of the sound source can be prevented or suppressed. As a result, the accuracy of azimuth determination of the sound source can be improved.

FIG. 13 is a diagram for explaining the range shielded by the hood 8 when the height of the hood 8 is set to the maximum height that satisfies Equation (2). The area where the hood 8 shields the sound waves arriving from the peripheral edge OE of the azimuth determination range TA is hatched. In the example shown in FIG. 13, among the plurality of microphones 9, two microphones 9, which are the minimum required number when performing the delay-and-sum method beamforming calculation, are used for sound waves arriving along the periphery OE of the sound source azimuth determination range TA. The height of the hood 8 is set so as to receive the

In the configuration shown in FIG. 13, the number of microphones 9 whose hoods 8 shield sound waves coming from the peripheral edge OE of the azimuth determination range TA is increased compared to the configuration shown in FIG. As a result, the effect of shielding external sounds is improved, and the occurrence of grating lobes can be further suppressed. Therefore, even if the source of the external sound exists outside the azimuth determination range TA of the sound source azimuth determination device 1, erroneous determination of the sound source can be prevented or suppressed. As a result, the accuracy of azimuth determination of the sound source can be improved.

Furthermore, the effect of reducing erroneous determination of the sound source within the azimuth determination range TA by the hood 8 differs depending on the arrangement of the microphones 9 of the array sensor 3 . Assume that the microphone 9 is omnidirectional. 3 horizontal direction). In that case, if the microphones 9 are arranged such that the grating lobes are generated within the azimuth locating range TA of the sound source azimuth locating device 1, the hood 8 that shields the sound waves arriving from the azimuth (90°) on the one side is provided. is valid. However, in the case where the microphone 9 is arranged such that no grating lobe occurs within the azimuth determination range TA, the hood 8 shields the sound source outside the azimuth determination range TA, and there is no erroneous determination prevention effect.

When a sound source exists in front of the sound source azimuth locating device 1, the delay and sum method beamforming calculation is performed based on the acquired sound pressure information. A signal with high sound pressure originating from a so-called sound source appears. The angle α (°) of the azimuth at which the grating lobe is generated with respect to the azimuth at which the main lobe appears (sometimes referred to as the reference angle) (hereinafter simply referred to as the generation angle) can be expressed by the following equation (3). .
α=90°/(d/λ) (3)
The above d is the arithmetic mean value of the distance to the closest microphone 9 for each of the plurality of microphones 9, and the above λ is the wavelength of the sound wave emitted from the sound source.

From the above formula (3), it can be understood that as the ratio (d/λ) between the interval d and the wavelength λ of the sound wave increases, the angle α of the grating lobe generation decreases. That is, when the distance d between the microphones 9 is increased, the generation angle α of the signal (not shown) representing the grating lobe appears closer to the main lobe (0°).

Further, when a sound wave arrives at the microphone 9 from a direction (90°) orthogonal to the front, which is the maximum sound wave arrival angle that can be incident on each microphone, The condition for generating grating lobes can be expressed by the following formula (4).
d≧90°×λ/(90°+βrange/2) (4)
That is, when the distance d between the microphones 9 satisfies the formula (4), a signal indicating a grating lobe appears within the maximum angle βrange of the azimuth determination range TA. Also, as noted above, when the spacing d is increased, the signal exhibits a Gretsch lobe closer to the main lobe (0°) than when the spacing d is small.

As described above, in the embodiment of the present invention, even if the distance d between the microphones 9 satisfies the formula (4) and the distance d causes grating lobes due to external sound within the maximum angle βrange of the azimuth determination range TA, , the hood 8 physically shields the array sensor 3 from part or all of external sounds. Therefore, it is possible to suppress the appearance of grating lobes within the azimuth locating range TA when the delay sum method beamforming calculation is performed based on the sound pressure information acquired by the sound source azimuth locating apparatus 1 . As a result, erroneous determination of the sound source can be suppressed.

Further, in the embodiment of the present invention, even if the distance d between the microphones 9 is set large so as to satisfy the expression (4), grating lobes caused by external sounds are generated within the azimuth determination range TA of the sound source. can be suppressed. Therefore, even if the number of microphones 9 is small, the aperture width of the array sensor 3 can be increased to improve directivity. As a result, the accuracy of azimuth determination of the sound source can be improved without increasing the number of parts, computational load, and the like.

On the other hand, when performing delay-and-sum beamforming calculations, side lobes occur around the main lobe in addition to grating lobes. FIG. 14 is a diagram showing a one-dimensional sound wave distribution part of a sound pressure map calculated by the delay-and-sum method beamforming when the sound source is in front of the sound source azimuth locator 1 (0°). The vertical axis in FIG. 14 indicates the sound pressure (dB), and the horizontal axis indicates the angle for searching for the direction of the sound source. According to FIG. 14, it can be seen that a main lobe appears in front (0°) of the sound source azimuth locating apparatus 1, and side lobes are generated around the main lobe. It is generally known that the side lobe is reduced by multiplying the output of each sampling point with a window function. Therefore, by regarding each microphone 9 as each sampling point and combining the shielding effect of the hood 8 and the correction (weighting) of the detection sensitivity of the microphone 9 not shielded by the hood 8, the side lobe by the window function can be obtained. It is possible to obtain the same effect as reduction. The detection sensitivity of the microphone 9 is the sensitivity of the microphone 9 to the received sound pressure.

In another embodiment of the invention, the detection sensitivity of the microphone 9 not shielded by the hood 8 is weighted, i.e. the correction and diffraction of the sound waves coming from the periphery OE of the azimuth range TA by the hood 8. combined with the accompanying damping effect. This is configured to reduce the occurrence of side lobes relative to the main lobe in the vicinity of the peripheral edge OE of the azimuth location range TA when the delay-and-sum beamforming calculation is executed. FIG. 15 is a flowchart for explaining an example of control executed in another embodiment of the invention. The routine shown in FIG. 15 is repeatedly executed at predetermined short time intervals by the computing means 4 described above.

First, a sound wave (n-1) in the first (n-1) measurement is acquired for each microphone 9 of the array sensor 3 (step S1), and a band is obtained for each of the acquired sound waves (n-1). Pass filtering is performed (step S2). Here, n is a natural number of 2 or more. As a result, among the acquired sound waves (n−1), sound waves in a preset frequency band used for searching for the sound source are extracted, and sound waves in unnecessary frequency bands are removed. A delay-and-sum method beamforming calculation is performed on the sound waves extracted in step S2, and a sound pressure map (n−1) corresponding to the sound waves (n−1) acquired in step S1 is created (step S3). .

In (a) of FIG. 16, an example of the received sound pressure distribution for each microphone 9 acquired in step S1 is connected by a smooth line and described by a thick solid line. In the example shown in FIG. 16, there is a sound source (not shown) on the right side of the sound source azimuth determination device 1 (right direction in FIG. 16), and sound waves arrive at the sound source azimuth determination device 1 from the sound source. The hood 8 shields the sound waves incident on the microphone 9 located on the direction of arrival of the sound waves, that is, on the sound source side (right side in FIG. 16). Therefore, as indicated by the thick solid line in FIG. lower than pressure. In addition, as the distance between the hood 8 and the microphone 9 on the direction from which sound waves arrive increases, the sound pressure incident on the microphone 9 gradually increases. This is due to the diffraction phenomenon of sound waves.

The azimuth of the sound source is estimated based on the sound pressure map (n-1) (step S4). Next, a sensitivity correction coefficient (n-1) for each microphone 9 is determined (step S5). That is, there is a correlation between the estimated direction of the sound source and the received sound pressure of each microphone 9 affected by the shielding by the hood 8, and the relative sound pressure distribution of each microphone 9 according to the direction of the sound source is , can be estimated from the dimensions of the hood 8 and the direction of the sound source. Based on the estimated sound pressure distribution, a correction coefficient for each microphone 9 is determined according to the position of the microphone 9 that is not affected by the shielding by the hood 8 .

Following the processing in step S5, the sound wave (n) in the second (n) measurement is obtained (step S6), and bandpass filtering is performed on the sound wave (n) (step S7). The processing in step S7 is the same as the processing in step S2. Subsequently, the sound wave (n) extracted in step S7 is multiplied by the sensitivity correction coefficient (n-1) determined in step S5 for correction (step S8).

Then, delay-and-sum beamforming calculation is performed for each sound wave (n) corrected in step S8, and a sound pressure map (n) corresponding to the sound wave (n) acquired in step S6 is created. (step S9). The sound pressure map (n) is output from the computing means 4 to the display means 5 and displayed. Following this, the position of the sound source is determined based on the sound pressure map (n) created in step S9 (step S10). Note that the position of the sound source may be displayed on the display means 5 .

In FIG. 16(b), an example of the received sound pressure distribution for each microphone 9 after sensitivity correction determined by the position of each microphone 9 and the degree of sound source shielding by the hood 8 is connected by a smooth line and indicated by a dotted line. I have As indicated by the dotted line in FIG. 16B, the correction in step S8 reduces the detection sensitivity of the microphone 9, which is placed far from the sound source and is not affected by the shielding by the hood 8. The received sound pressure distribution of each microphone 9 indicated by the dotted line in FIG. It has a shape similar to the sound pressure distribution after multiplication by the window function of .

Therefore, according to the embodiment of the present invention, by performing sensitivity correction on the detection sensitivity of the microphone 9 not shielded by the hood 8, side lobes are corrected in substantially the same way as when the side lobes are corrected based on the window function. Lobe can be reduced. Therefore, even if there is a sound source in the vicinity of the peripheral edge OE of the azimuth determination range TA, and the use of the hood 8 reduces the strength of the main lobe (sound source signal) at the peripheral edge OE of the azimuth determination range TA, Even if there is, the main lobe can be clearly distinguished. In other words, it is possible to suppress deterioration in accuracy of locating the direction of the sound source by the sound source azimuth determination device 1 .

Also, the above sensitivity correction coefficient is changed to be large or small according to the size of the hood 8 such as its height and inner diameter. This is because the size of the hood 8 changes the range in which the sound waves arriving from the peripheral edge OE of the azimuth determination range TA are shielded and diffracted. FIG. 17 is a diagram showing an example of received sound pressure distribution for each microphone 9 when the height of the hood 8 is higher than that of the hood 8 shown in FIG. In the example shown in FIG. 17, the area covered by the hood 8 is larger than in the example shown in FIG. 17(a), the microphone 9 whose received sound pressure is reduced by the hood 8 reaches near the center of the array sensor 3 compared to FIG. 16(a).

Then, based on the received sound pressure distribution shown in (a) of FIG. 17, the processing of steps S4 to S8 shown in FIG. 15 is executed to determine the sensitivity correction coefficient for each microphone 9, and the sensitivity correction coefficient of the microphone is used to determine the sensitivity correction coefficient. Correct the detection sensitivity every 9. FIG. 17B shows the received sound pressure distribution of each microphone 9 including the shielding effect of the hood 8 after the detection sensitivity of each microphone 9 is corrected. The received sound pressure distribution for each microphone 9 shown in (b) of FIG. 17 has a shape similar to the sound pressure distribution after multiplication by the window function for each microphone 9 when suppressing side lobe generation using a window function. become. Therefore, even if the height of the hood 8 is high, substantially the same functions and effects as those of the embodiment shown in FIG. 16 can be obtained.

(Example)
Next, an example conducted to confirm the effect of the hood 8 in the embodiment of the present invention will be described. An array sensor 3 is configured by arranging microphones 9 at regular intervals on each of two concentric imaginary circles having different outer diameters. Specifically, the outer diameter of the inner virtual circle in the radial direction was set to 15.3 mm, and six microphones 9 were arranged at regular intervals on the circumference of the virtual circle. The outer diameter of the virtual circle on the outer side in the radial direction, that is, the aperture width of the array sensor 3 was set to 41.0 mm, and seven microphones 9 were arranged at regular intervals on the circumference of the virtual circle. The arithmetic mean value of the distance d between the microphones 9 adjacent to each other is 10.8 mm, the wavelength of the sound source, that is, the measured wavelength λ at the array sensor 3 is 8.7 mm, and the ratio of the distance d to the measured wavelength λ (d /λ) was 1.2. Also, the maximum angle βrange of the sound source azimuth determination range TA in the sound source azimuth determination device 1 was set to 62°. Further, a rectangular tube having an inner dimension of 60 mm×60 mm and a height of 43 mm was used as the hood 8 . Since other configurations are the same as those shown in FIGS. 1 to 3, description thereof will be omitted. Note that the height of the hood 8 satisfies the formula (2) described above.

(experimental method)
The sound source azimuth locating device 1 configured as described above was installed on a predetermined mounting surface so as to rotate about a rotation center axis (not shown) extending in a vertical direction and to maintain a substantially horizontal position. A reference position (0°) was set in front of the sound source azimuth locating device 1, and a sound source to be azimuth-located (hereinafter referred to as a first sound source) was placed at the reference position. In addition, when viewed from the sound source azimuth locating device 1, a source of external sound (hereinafter referred to as a second sound source) was installed at a position 50° in one of the left and right directions with respect to the reference position. Then, the sound source azimuth determination device 1 was rotated around the rotation center axis by 50° from the reference position of the sound source azimuth determination device 1 to determine the azimuths of the first sound source and the second sound source. Also, the sound pressure emitted by the first sound source is constant, and the sound pressure of the external sound emitted by the second sound source is increased more than the sound pressure emitted by the first sound source. By doing this, it is evaluated whether or not the azimuth of the first sound source is possible even if the external sound with a higher sound pressure than the sound wave emitted by the first sound source arrives at the sound source azimuth determination device 1. bottom. In addition, when the azimuth determination of the first sound source by such a sound source azimuth determination apparatus 1 is performed a plurality of times, and the ratio of matching between the actual installation position of the first sound source and the azimuth determination result is 50% or more, the first sound source azimuth determination apparatus 1 It was determined that the azimuth determination of the sound source was possible.

(Comparative example 1)
The configuration was the same as that of the example except that the hood 8 was not provided.

(Comparative example 2)
The configuration was the same as that of the embodiment except that the height of the hood 8 was set to be lower than the lower limit height of the hood 8 given by the above formula (2).

(evaluation)
In Comparative Example 1, azimuth determination of the first sound source was possible when the sound pressure of the second sound source (external sound) was up to 2.3 times the sound pressure of the first sound source. In Comparative Example 2, azimuth determination of the first sound source was possible when the sound pressure of the second sound source (external sound) was up to 4.0 times the sound pressure of the first sound source. On the other hand, in the embodiment of the present invention, azimuth determination of the first sound source was possible when the sound pressure of the second sound source (external sound) was up to 8.2 times the sound pressure of the first sound source. . As described above, by using the hood 8 in the embodiment of the present invention, even if a strong external sound source exists outside the azimuth locating range TA of the sound source azimuth device 1, the sound source within the azimuth locating range TA can be detected. It was confirmed that the azimuth determination of

1 Sound source azimuth determination device 2 Camera 3 Array sensor 4 Calculation means 5 Display means 6 Input means 7 Housing 8 Hood 9 Microphone 10 Processing unit 11 Storage unit TA Sound source azimuth determination range in sound source azimuth determination device βrange Sound source in sound source azimuth determination device The maximum angle of the azimuth range of

Claims

A sound wave shielding hood configured to suppress an array sensor having a plurality of microphones for receiving sound waves from receiving external sounds coming from outside a preset azimuth determination range,
A sound wave shielding hood configured to shield sound waves coming from a peripheral portion of the azimuth range for at least one of the plurality of microphones.
The acoustic wave shielding hood according to claim 1, which is configured to enclose at least part of the circumference of the array sensor.
It has a cylindrical shape,
2. The height protruding from the array sensor is set to be equal to or higher than a height at which at least one of the plurality of microphones shields sound waves coming from the periphery of the azimuth determination range. 3. The sound wave shielding hood according to 2.
2. The height protruding from the array sensor is set lower than the height at which the number of microphones from which sound waves arriving from the periphery of the azimuth determination range are not shielded is two among the plurality of microphones. 4. The sound shielding hood according to any one of items 1 to 3.
Based on an array sensor having a plurality of microphones for receiving sound waves and sound pressure information of the sound waves received by the array sensor, the sound pressure in each direction within the azimuth determination range is calculated. 5. A sound source azimuth locating apparatus, comprising computing means for locating the azimuth at which sound pressure is maximized as the arrival azimuth of sound waves from a sound source, and the sound wave shielding hood according to claim 1.
6. The sound source azimuth locating apparatus according to claim 5, wherein an average interval d between the plurality of microphones adjacent to each other satisfies the following equation.
d≧90°×λ/(90°+βrange/2) (mm)
λ is the central wavelength (mm) of the sound wave used for calculating the direction of arrival of the sound wave, and βrange is the maximum angle (°) of the azimuth determination range.
The computing means weights the sound pressure information of the sound waves received by each of the plurality of microphones according to the height of the sound wave shielding hood, and controls the sound source based on the weighted sound pressure information. 7. A sound source azimuth device according to claim 5 or 6, adapted to determine the azimuth of the .
8. The arithmetic unit according to claim 5, wherein said calculating means performs delay-and-sum beamforming calculation on a plurality of sound pressure information acquired by each of said plurality of microphones to locate the direction of arrival of a sound wave. A sound source azimuth locating device according to the above paragraph.