A rotatable spherical microphone array system and a method of measurement

Abstract

A rotatable spherical microphone array system and a measuring method, by rotating the array to change the position of each unit on the spherical microphone array, so as to be equivalent to using a large number of microphone units to measure, to record a higher order accurate HOA signal with fewer microphone units, and to reduce the complexity and cost of system design and assembly.

Description

Technical Field

[0001] This invention belongs to the field of acoustic measurement, specifically relating to a rotatable spherical microphone array system and measurement method. Background Technology

[0002] The recording performance of spatial acoustic signals is closely related to the higher order ambisonics (HOA) order. However, the HOA order N and the required number of microphones M must satisfy the condition M ≥ (N+1). 2 Therefore, manufacturing a spherical microphone array capable of measuring higher-order HOAs requires mounting numerous microphones on the sphere. Due to the high density of microphones, the design and installation are very complex and costly. Currently, commercially available spherical microphone arrays typically have only a few dozen microphone units, which is insufficient for measuring higher-order HOAs. Among existing technologies, the Eigenmike EM32 spherical microphone array has 32 microphone units and only supports 4th-order HOAs.

[0003] Chinese patent CN109974846A, "A Rotating Acoustic Measurement Device with a Variable Array," discloses an acoustic measurement device with a variable array that utilizes a rotating test stage to achieve spatial measurement of the object under test. The objective of this disclosure is only to acquire the sound pressure signal on the radiation envelope of the sound source under test or in certain directions, not to acquire the HOA signal of a specific area under test in space. Furthermore, achieving acoustic measurement by fixing the microphone array and rotating the sound source under test requires placing the sound source on the rotating test stage. However, in practical applications, the sound source under test may not be movable, and because it needs to be placed on the rotating test stage, it is difficult to measure the superimposed sound field of multiple sound sources that are far apart. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a rotatable spherical microphone array system and measurement method. By rotating the array, the position of each unit on the spherical microphone array is changed, which is equivalent to using a large number of microphone units for measurement, thus enabling the recording of signals of higher-order HOA with a smaller number of microphone units.

[0005] The present invention adopts the following technical solution.

[0006] A rotatable spherical microphone array system includes a rotatable spherical microphone array assembly and a spherical microphone array controller assembly. The rotatable spherical microphone array assembly includes a spherical microphone array and a rotary motor; the spherical microphone array controller assembly includes a measurement data buffer, a motor controller, and a microphone unit position calculator; wherein, the spherical microphone array includes a set of microphone units, a rigid spherical baffle, a rotary motor, and a support; the rigid spherical baffle is connected to the rotating shaft of the rotary motor, the shaft passing through the center of the sphere, and the rotary motor is fixed to the support; a set of microphone units are mounted on the rigid spherical baffle, and the mounting method can be equidistant or unequally spaced, mounted along the meridian of the rigid spherical baffle, or tilted.

[0007] The spherical microphone array receives the test sound signal and transmits the measurement results to the measurement data buffer; the motor controller controls one or two orthogonally mounted rotary motors to rotate the spherical microphone array; the microphone unit position calculator calculates and outputs the position coordinates of the microphone unit.

[0008] Preferably, the microphone units are installed at equal intervals along the meridian of the rigid spherical baffle, and the zenith angle θ of the i-th microphone unit is... i and azimuth for

[0009]

[0010]

[0011] In the formula, M represents the number of microphone units.

[0012] Preferably, the microphone units are symmetrically installed, and the zenith angle θ of the i-th microphone unit is... i and azimuth for

[0013]

[0014]

[0015] Preferably, the microphone units are asymmetrically installed, and the zenith angle θ of the i-th microphone unit is... i and azimuth for

[0016]

[0017]

[0018] Preferably, the microphone unit is mounted spirally around a rigid spherical baffle, and the zenith angle θ of the i-th microphone unit is... i and azimuth for

[0019]

[0020]

[0021] Preferably, the microphone units are installed at non-equidistant intervals, and the zenith angle θ of the i-th microphone unit is... i and azimuth for

[0022]

[0023]

[0024] Preferably, the microphone units spirally surround the rigid spherical baffle and are installed at unequal intervals, with the zenith angle θ of the i-th microphone unit being... i and azimuth for

[0025]

[0026]

[0027] A method for measuring a rotatable spherical microphone array includes the following steps:

[0028] Step 1: Place the spherical microphone array at the signal acquisition location;

[0029] Step 2: When playing the signal to be tested, the measurement data buffer records the signals of M microphones on the spherical microphone array. After the signal recording is completed, proceed to step 3.

[0030] Step 3: The motor controller of the spherical microphone array controller controls the rotating motor to rotate the array by 360 / K°, thereby moving the M microphones on the spherical microphone array to a new position. The microphone unit position calculator calculates the new position of each microphone unit. After the motor has finished rotating, proceed to step 4.

[0031] Step 4: Repeat steps 2-3 to measure K times and obtain K sets of measurement signals. Each set of signals contains signals measured by the microphone at M points on the sphere.

[0032] Step 5: After step 4 is completed, the measurement data buffer has recorded the signals measured by the microphones at K*M points, which are the output signals of the ball microphone array. At the same time, the microphone unit position calculator outputs the coordinates of K*M points.

[0033] Step 6: Simulate the external sound field of the rigid sphere using a discretized matrix and the least squares method. Based on the output signal of the sphere microphone array obtained in Step 5, calculate the HOA signal.

[0034] The beneficial effect of this invention is that, compared with the prior art, this invention proposes several microphone unit arrangement schemes, and uses a motor to control the array rotation, and uses a small number of microphone units to measure the sound pressure signal at multiple points on the surface of the sphere.

[0035] 1. Compared with existing microphone arrays, the spherical microphone array of the present invention uses fewer microphone units, reducing the complexity and cost of system design and assembly.

[0036] 2. By repeatedly measuring with array rotation, the method proposed in this invention can support Ambisonics measurements of larger orders, achieving more accurate spatial acoustic signal recording. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of a rotatable spherical microphone array system;

[0038] Figure 2 This is a schematic diagram of a rotatable spherical microphone array;

[0039] Figure 3 These are three views of an installation scheme where microphone units are installed at equal intervals along the meridian.

[0040] Figure 4 These are three views of an installation scheme where microphone units are symmetrically installed along the warp coil.

[0041] Figure 5 This is a three-view diagram of an installation scheme for asymmetrically mounted microphone units along the warp coil;

[0042] Figure 6 These are three views of the installation scheme for the tilted microphone unit;

[0043] Figure 7 These are three views of an installation scheme for mounting a microphone unit on a spirally wound rigid spherical baffle.

[0044] Figure 8 These are three views of an installation scheme where microphone units are installed at unequal intervals along the meridian.

[0045] Figure 9 These are three views of an installation scheme for microphone units mounted at unequal intervals on a spirally wound rigid spherical baffle.

[0046] Figure 10 This is a schematic diagram of a rotating spherical microphone array;

[0047] Figure 11 This is a schematic diagram of a dual-motor rotating ball microphone array. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0049] A rotatable spherical microphone array system, such as Figure 1 As shown, it consists of a rotatable spherical microphone array and a spherical microphone array controller. The rotatable spherical microphone array includes a spherical microphone array and a rotary motor; the spherical microphone array controller includes a measurement data buffer, a motor controller, and a microphone unit position calculator.

[0050] The spherical microphone array receives the test sound signal and transmits the measurement results to the measurement data buffer; the motor controller of the spherical microphone array controller controls the rotating motor to rotate the array; the microphone unit position calculator calculates and outputs the position coordinates of the microphone unit.

[0051] A rotatable spherical microphone array is constructed as follows Figure 2 As shown, it includes a microphone unit 1, a rigid spherical baffle 2, a rotary motor 3, and a bracket 4. The shaft of the rotary motor 3 is connected to the bottom of the rigid spherical baffle 2, and the straight line of the shaft passes through the center of the sphere. The rotary motor 3 is fixed on the bracket 4.

[0052] A set of microphone units 1 is mounted on a rigid spherical baffle 2. Assuming M microphone units are mounted on the rigid spherical baffle 2, the following are some possible microphone unit mounting schemes:

[0053] Example 1:

[0054] like Figure 3 As shown, the microphone units can be installed at equal intervals along the meridian of the rigid spherical baffle 2, and the zenith angle θ of the i-th microphone unit is... i and azimuth for

[0055]

[0056]

[0057] Example 2:

[0058] like Figure 4 As shown, symmetrical installation reduces the number of array rotations during measurement. The zenith angle θ of the i-th microphone unit... i and azimuth for

[0059]

[0060]

[0061] Example 3:

[0062] like Figure 5 As shown, asymmetrical installation allows the spacing between rotating measuring points to exceed the volume limitations of the microphone unit. The zenith angle θ of the i-th microphone unit... i and azimuth for

[0063]

[0064]

[0065] Example 4:

[0066] like Figure 6 As shown, it can be installed at an angle to avoid the connection between the motor and the spherical baffle;

[0067] Example 5:

[0068] like Figure 7 As shown, considering the volume limitation of the microphone unit, it can be installed spirally around the rigid spherical baffle 2. The zenith angle θ of the i-th microphone unit is... i and azimuth for

[0069]

[0070]

[0071] Example 6:

[0072] like Figure 8 As shown, the microphone units can be installed at unequal intervals. Considering that the microphone units located in the lower latitude part of the rigid spherical baffle 2 will have a lower measurement point density during array rotation measurement than the microphone units in the higher latitude part, to make the equivalent measurement points of the rotatable spherical microphone array system more evenly distributed, an optimized microphone installation scheme is: the zenith angle θ of the i-th microphone unit... i and azimuth for

[0073]

[0074]

[0075] Example 7:

[0076] like Figure 9As shown, a preferred embodiment is a spiral surrounding a rigid spherical baffle 2, installed at unequal intervals, with the zenith angle θ of the i-th microphone unit being... i and azimuth for

[0077]

[0078]

[0079] The rotatable spherical microphone array can be controlled by a spherical microphone array controller, which in turn controls a rotating motor 3 to rotate a rigid spherical baffle 2, thereby changing the position of each unit on the spherical microphone array, such as... Figure 10 As shown. Assuming we need to record signals measured by microphones at K*M points, after each measurement, we need to control a rotary motor to rotate the array 360 / K° (for example,...). Figure 4 The installation scheme shown rotates 180 / K°. The final equivalent zenith angle θ and azimuth angle of the measuring point... for

[0080] θ=θ i

[0081]

[0082] Where i = 1, 2, 3, ..., M, k = 1, 2, 3, ..., K.

[0083] Besides using a single motor to drive the spherical baffle's rotation, adding more motors can increase the spherical baffle's rotational degrees of freedom, thereby further reducing the number of microphone units. A dual-motor rotating spherical microphone array is shown below. Figure 11 As shown, two motors control the rotation of a spherical baffle along the horizontal and vertical axes, respectively. Only one microphone unit is mounted on the spherical baffle. Initially, the horizontal axis coincides with the x-axis, and the vertical axis coincides with the z-axis. The microphone unit is installed at the position corresponding to the zenith angle θ0 = 0 on the spherical baffle. The zenith angle θ and azimuth angle need to be measured. When the sound pressure level is reached, the horizontally mounted motor can be rotated by θ, and the vertically mounted motor can be rotated by θ. This is achieved. As can be seen, by controlling the rotation of the spherical baffle with dual motors, the number of microphone units can be reduced to as low as one, and the sound pressure at any position on the surface of the spherical baffle can be measured.

[0084] A method for measuring a rotatable spherical microphone array, specifically including:

[0085] Step 1: Place the spherical microphone array at the signal acquisition location;

[0086] Step 2: When playing the signal to be tested, the measurement data buffer records the signals of M microphones on the spherical microphone array. After the signal recording is completed, proceed to step 3.

[0087] Step 3: The motor controller of the spherical microphone array controller controls the rotating motor to rotate the array by 360 / K°, thereby moving the M microphones on the spherical microphone array to a new position. The microphone unit position calculator calculates the new position of each microphone unit. After the motor has finished rotating, proceed to step 4.

[0088] Step 4: Repeat steps 2-3 to measure K times and obtain K sets of measurement signals. Each set of signals contains signals measured by the microphone at M points on the sphere.

[0089] Step 5: After step 4 is completed, the measurement data buffer has recorded the signals measured by the microphones at K*M points, which are the output signals of the ball microphone array. Simultaneously, the microphone unit position calculator outputs the coordinates of the K*M points.

[0090] Step 6: Simulate the external sound field of the rigid sphere using a discretized matrix and the least squares method. Based on the output signal of the sphere microphone array obtained in Step 5, calculate the HOA signal.

[0091] In step 6,

[0092] For a given position (r, θ, φ) in spherical coordinates, when there exists a rigid sphere of radius r0 at the origin, the sound field at that point with the corresponding angular frequency ω can be approximated as follows:

[0093]

[0094] Where N is the order of the HOA, The HOA coefficients are of order (m,n). Let be a spherical harmonic function of order (m,n).

[0095]

[0096] j n (kr) and Let k be the nth-order spherical Bessel function and the nth-order spherical Hankel function of the second kind, respectively, where k is the wave number. Therefore, by arranging microphones on the surface of a rigid sphere to record the sound pressure signal p h (r,θ,φ,ω) can be derived from the above formula for the HOA coefficient. If M microphones are arranged on the surface of a rigid sphere, the above equation can be discretized into a matrix form.

[0097] p h =Gs

[0098] Where G is M×(N+1)2 Let N be the order of the HOA (House of Applications) and its transfer function matrix. Then, the least squares method can be used to determine the estimated HOA coefficients *s* with the smallest error:

[0099] s=(G H G) -1 G H p h

[0100] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0101] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0102] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0103] Computer program instructions used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing the status information of the computer-readable program instructions to implement various aspects of this disclosure.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A rotatable spherical microphone array system, comprising: a rotatable spherical microphone array assembly and a spherical microphone array controller assembly, wherein the rotatable spherical microphone array assembly comprises a spherical microphone array and a rotating motor, and the spherical microphone array controller assembly comprises a measurement data buffer, a motor controller, and a microphone unit position calculator; wherein the spherical microphone array comprises a set of microphone units, a rigid spherical baffle, a rotating motor, and a support; the rigid spherical baffle is connected to a rotating shaft of the rotating motor, the rotating shaft is located on a straight line passing through the center of the sphere, and the rotating motor is fixed on the support; the set of microphone units are installed on the rigid spherical baffle, and the installation mode comprises equidistant or non-equidistant distribution, installation along the meridian of the rigid spherical baffle, or oblique installation; wherein M is the number of microphone units. The spherical microphone array receives a test sound signal and transmits the measurement results to the measurement data buffer; the motor controller controls a rotating motor or two orthogonally installed rotating motors to rotate the spherical microphone array; and the microphone unit position calculator calculates and outputs the position coordinates of the microphone units. If the microphone units are installed along the meridian of the rigid spherical baffle according to equidistant distribution, the zenith angle θ i and the azimuth angle of the i-th microphone unit are 2.The rotatable spherical microphone array system of claim 1, wherein M is the number of microphone units. 3.The rotatable spherical microphone array system of claim 1, wherein M is the number of microphone units. 4.The rotatable spherical microphone array system of claim 1, wherein M is the number of microphone units. The microphone units are symmetrically installed, the zenith angle θ of the i-th microphone unit i and the azimuth angle is 5.The rotatable spherical microphone array system of claim 1, wherein M is the number of microphone units. 6.The rotatable spherical microphone array system of claim 1, wherein M is the number of microphone units. The microphone units are asymmetrically mounted, the zenith angle θ of the i-th microphone unit i and the azimuth angle is 7.A method for obtaining a HOA signal, comprising the following steps: Step 1, placing a spherical microphone array to a signal acquisition position; The microphone units are mounted in a spiral around a rigid spherical baffle, the zenith angle θ of the i-th microphone unit is i and the azimuth angle is Step 2, when a signal to be measured is played, a measurement data buffer records the signals of M microphones on the spherical microphone array, and after the signal recording is completed, the method proceeds to step 3; Step 3, a motor controller of a spherical microphone array controller controls a rotating motor to rotate the array by 360 / K°, so that the M microphones on the spherical microphone array move to new positions, a microphone unit position calculator calculates the new positions of the microphone units, and after the motor rotation is completed, the method proceeds to step 4; The microphone units are not equidistantly distributed, the zenith angle θ i and the azimuth angle are Step 4, repeating steps 2-3 K times to obtain K sets of measurement signals, each set of signals comprising the signals measured by the microphones at M points on the sphere; Step 5, after step 4 is completed, the measurement data buffer has recorded the signals measured by the microphones at K*M points, which are the output signals of the spherical microphone array, and the microphone unit position calculator outputs the coordinates of the K*M points; The microphone units are helically arranged around a rigid spherical baffle and are mounted with unequal distance, the zenith angle θ i and the azimuth angle are Step 6, based on the output signals of the spherical microphone array obtained in step 5, a HOA signal is calculated by simulating the sound field outside the rigid sphere through a discretization matrix and a least squares method.

7. A rotatable spherical microphone array measurement method, characterized by, 8.A terminal, comprising a processor and a storage medium; characterized in that: the storage medium is used to store instructions; ​ ​ ​ ​ ​ ​ ​ ​ The processor is configured to operate on the instructions to perform the steps of the method of claim 7.

9. A computer readable storage medium having stored thereon a computer program, characterized in that The program, when executed by the processor, implements the steps of the method of claim 7.

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