Sound pressure prediction system, sound pressure prediction device, sound pressure prediction method, and program

Abstract

To provide a sound pressure prediction system with improved suppression performance at control points.SOLUTION: A sound pressure prediction system includes: a reference microphone installed near a noise source; a first control microphone positioned at a predetermined distance D from a desired control point in a predetermined direction θ; a second control microphone positioned at the predetermined distance D from the first control microphone in the predetermined direction θ; and a sound pressure prediction device that acquires a reference microphone observation signal, which is the observation signal from the reference microphone, and a control microphone observation signal, which is the observation signal from the control microphone, and predicts sound pressure at the desired control point.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a sound pressure prediction system, a sound pressure prediction device, a sound pressure prediction method, and a program for predicting sound pressure at a desired control point. [Background technology]

[0002] A conventional technique for active noise control (ANC) is described in Non-Patent Document 1. As shown in FIG. 1, in Non-Patent Document 1, the following process is executed.

[0003] 1) Noise is recorded by the reference microphone 91, and the ANC 94 adjusts the playback sound to generate a cancellation sound that cancels the noise.

[0004] 2) Cancellation sound is played back through the cancellation speaker 92 to cancel out noise.

[0005] 3) The remaining noise is detected by the control microphone 93, and the cancellation sound is actively adjusted by the ANC 94. Return to the procedure of 1). [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Kajikawa, "Recent Topics and Applications of Active Noise Control", Research Report on Music Information Science (MUS), vol. 2015-MUS-107, no. 3, pp. 1-6, May 2015. Summary of the Invention [Problem to be solved by the invention]

[0007] In general active noise control technology such as that described in Non-Patent Document 1, if the position of the control microphone differs from the desired control point, the suppression performance at the control point may decrease if it is outside the sweet spot.

[0008] Therefore, an object of the present disclosure is to provide a sound pressure prediction system with improved suppression performance at control points. [Means for solving the problem]

[0009] The sound pressure prediction system disclosed herein includes a reference microphone installed near a noise source, a first control microphone arranged at a position a predetermined distance D in a predetermined direction θ from a desired control point, a second control microphone arranged at a position a predetermined distance D in the predetermined direction θ from the first control microphone, and a sound pressure prediction device that acquires a reference microphone observation signal, which is an observation signal from the reference microphone, and a control microphone observation signal, which is an observation signal from the control microphone, and predicts the sound pressure at the desired control point. Effect of the Invention

[0010] According to the sound pressure prediction system of the present disclosure, it is possible to improve the suppression performance at the control point. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing an outline of the active noise control technology of Non-Patent Document 1. [Diagram 2] FIG. 13 is a diagram showing an example of a sound pressure prediction system with improved suppression performance at a control point. [Diagram 3] 1A and 1B are diagrams showing problems with a sound pressure prediction system with improved suppression performance at control points. [Figure 4] FIG. 1 is a diagram showing a device configuration and device arrangement of a sound pressure prediction system according to a first embodiment. [Diagram 5] FIG. 13 shows an example of a pure delay-cancelled transfer characteristic of a control microphone. [Figure 6] FIG. 1 is a block diagram showing a functional configuration of a sound pressure prediction device according to a first embodiment. [Figure 7] 4 is a flowchart showing the operation of the sound pressure prediction device according to the first embodiment. [Figure 8] FIG. 13 is a diagram showing conditions for simulation evaluation. [Figure 9] FIG. 13 is a diagram showing simulation results (waveforms). [Figure 10]Graph showing simulation results (sound pressure). [Figure 11] FIG. 13 shows simulation results (frequency characteristics). [Figure 12] FIG. 2 is a diagram showing an example of the functional configuration of a computer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present disclosure will be described in detail. Note that components having the same functions are given the same reference numbers and redundant description will be omitted.

[0013] <Example of a sound pressure prediction system with improved suppression performance at control points> Hereinafter, an example of a sound pressure prediction system for improving suppression performance at a control point will be described with reference to FIG.

[0014] As shown in Figure 1(a), a sound pressure prediction system can be realized that improves the suppression performance at a control point by using a microphone array with a known shape, which includes a first control microphone 81 arranged at a predetermined distance (D) in a predetermined direction (θ) from a desired control point (marked with an x ​​in the figure), and a second control microphone 82 arranged at a predetermined distance D in the predetermined direction θ from the first control microphone 81.

[0015] As shown in Figure 2(b), when the microphone array moves in parallel so that the first control microphone 81 coincides with the desired control point (marked with an x), the second control microphone 82 coincides with the initial position of the first control microphone 81.

[0016] By setting such constraints, the cross-correlation between the first control microphone and the second control microphone is estimated to predict the sound pressure at the desired control point, and then ANC processing is performed, thereby making it possible to estimate the sound pressure at the desired control point with high accuracy, and by constructing a noise control filter using the estimated sound pressure, it is possible to improve suppression performance.

[0017] However, in this sound pressure prediction system, when the noise reaches the control point before the control microphone, as shown in Figure 3, the noise source (dry source) must be known, which poses a practical problem. EXAMPLES

[0018] Hereinafter, with reference to FIG. 4, a device configuration and device arrangement of a sound pressure prediction system according to a first embodiment, which is a further improvement of the above-mentioned sound pressure prediction system, will be described.

[0019] As shown in the figure, the sound pressure prediction system 1 of the first embodiment includes a reference microphone 13 installed near a noise source, a first control microphone 12-1 arranged at a position a predetermined distance D in a predetermined direction θ from a desired control point (marked with an x ​​in the figure), a second control microphone 12-2 arranged at a position a predetermined distance D in the predetermined direction θ from the first control microphone 12-1, and a sound pressure prediction device 11 that acquires a reference microphone observation signal, which is an observation signal from the reference microphone 13, and a control microphone observation signal, which is an observation signal from the control microphones 12-1 and 12-2, and predicts the sound pressure at the desired control point.

[0020] The sound pressure prediction device 11 of this embodiment estimates the transfer function from the reference microphone to each control microphone using an adaptive algorithm. As shown in FIG. 5, the sound pressure prediction device 11 eliminates the pure delay of the transfer function of the second control microphone 12-2. The sound pressure prediction device 11 can estimate the cross-correlation filter from the second control microphone 12-2 to the first control microphone 12-1 by apparently advancing the direct sound arrival time by eliminating the pure delay of the transfer function of the second control microphone 12-2. This allows the sound pressure prediction device 11 to predict the cross-correlation filter from the first control microphone 12-1 to the desired control point.

[0021] 6, the sound pressure prediction device 11 of this embodiment includes a transfer characteristic estimation unit 111, a pure delay elimination unit 112, a prediction filter calculation unit 113, and a prediction unit 114. The operation of each component will be described below with reference to FIG.

[0022] <Transfer characteristic estimation unit 111> The transfer characteristic estimating unit 111 acquires a reference microphone observation signal and a control microphone observation signal, and estimates transfer characteristics from the reference microphone to each control microphone using a normalized least mean square (NLMS) algorithm (S111).

[0023] Transfer function ψ m The estimation formula is shown below.

number

[0024] Below is the pure delay-eliminated transfer characteristic ψ^ when the pure delay parameter is 30. m Here is an example of generating:

number

[0025] <Prediction Filter Calculation Unit 113> The prediction filter calculation unit 113 obtains the pure delay-cancelled transfer characteristic, the reference microphone observation signal, and the control microphone observation signal, and calculates a prediction filter for predicting a signal at a desired control point (S113).

[0026] Specifically, the pure delay-cancelled observation signal d^2 in the second control microphone 12-2 is calculated by the following equation using the pure delay-cancelled transfer characteristic ψ^2 of the second control microphone 12-2.

number

number

[0027] In detail, the prediction unit 114 generates a pure delay-cancelled observed signal d̂1 at the first control microphone 12-1.

number

number

[0028] <Additional Notes> The device of the present disclosure has, as a single hardware entity, an input unit to which a keyboard or the like can be connected, an output unit to which a liquid crystal display or the like can be connected, a communication unit to which a communication device (e.g., a communication cable) capable of communicating with the outside of the hardware entity can be connected, a CPU (which may also have a central processing unit, cache memory, registers, etc.), memories such as RAM and ROM, an external storage device such as a hard disk, and buses connecting the input unit, output unit, communication unit, CPU, RAM, ROM, and external storage device so that data can be exchanged between them. If necessary, the hardware entity may also be provided with a device (drive) capable of reading and writing a recording medium such as a CD-ROM. A physical entity equipped with such hardware resources is, for example, a general-purpose computer.

[0029] The external storage device of the hardware entity stores the programs required to realize the above-mentioned functions and the data required in the processing of these programs (not limited to the external storage device, but for example the programs may be stored in a ROM, which is a read-only storage device). Data obtained by the processing of these programs is stored appropriately in the RAM, the external storage device, etc.

[0030] In the hardware entity, each program stored in an external storage device (or ROM, etc.) and the data required to process each program are loaded into memory as necessary, and interpreted, executed, and processed by the CPU as appropriate, so that the CPU realizes a predetermined function (each of the components represented as the above, "units," "means," etc.).

[0031] The present disclosure is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit of the present disclosure. In addition, the processes described in the above embodiment are not limited to being executed in chronological order according to the order described, but may be executed in parallel or individually depending on the processing capacity of the device that executes the processes or as necessary.

[0032] As described above, when the processing functions of the hardware entities (apparatuses of the present disclosure) described in the above embodiments are realized by a computer, the processing contents of the functions that the hardware entities should have are described by a program. Then, the processing functions of the hardware entities are realized on the computer by executing the program.

[0033] The various processes described above can be implemented by loading a program for executing each step of the above method into the recording unit 10020 of the computer shown in FIG. 12 and operating the control unit 10010, input unit 10030, output unit 10040, etc.

[0034] The program describing the processing contents can be recorded on a computer-readable recording medium. The computer-readable recording medium may be, for example, a magnetic recording device, an optical disk, a magneto-optical recording medium, a semiconductor memory, or any other suitable medium. Specifically, for example, a hard disk drive, a flexible disk, a magnetic tape, or the like can be used as the magnetic recording device, a DVD (Digital Versatile Disc), a DVD-RAM (Random Access Memory), a CD-ROM (Compact Disc Read Only Memory), a CD-R (Recordable) / RW (ReWritable), or the like can be used as the optical disk, an MO (Magneto-Optical disc), or the like can be used as the magneto-optical recording medium, and an EEP-ROM (Electrically Erasable and Programmable-Read Only Memory) or the like can be used as the semiconductor memory.

[0035] The program may be distributed, for example, by selling, transferring, lending, etc. portable recording media such as DVDs and CD-ROMs on which the program is recorded. Furthermore, the program may be distributed by storing the program in a storage device of a server computer and transferring the program from the server computer to other computers via a network.

[0036] A computer that executes such a program, for example, first stores the program recorded on a portable recording medium or the program transferred from a server computer in its own storage device. Then, when executing a process, the computer reads the program stored in its own recording medium and executes a process according to the read program. As another execution form of the program, the computer may directly read the program from the portable recording medium and execute a process according to the program, or may execute a process according to the received program each time a program is transferred from the server computer to the computer. The above-mentioned process may be executed by a so-called ASP (Application Service Provider) type service that realizes a processing function only by issuing an execution instruction and obtaining a result, without transferring a program from the server computer to the computer. Note that the program in this embodiment includes information used for processing by an electronic computer and equivalent to a program (data that is not a direct command to the computer but has a nature that specifies the processing of the computer, etc.).

[0037] In addition, in this embodiment, a hardware entity is configured by executing a specific program on a computer, but at least a part of the processing contents may be realized by hardware.

Claims

1. A reference microphone placed near the noise source; A first control microphone disposed at a predetermined distance D in a predetermined direction θ from a desired control point; A second control microphone is disposed at a predetermined distance D from the first control microphone in a predetermined direction θ; A sound pressure prediction device that predicts sound pressure at the desired control point by acquiring a reference microphone observation signal that is an observation signal from the reference microphone and a control microphone observation signal that is an observation signal from the control microphone. Sound pressure prediction system.

2. The sound pressure prediction system according to claim 1, a transfer characteristic estimating unit that estimates a transfer characteristic from the reference microphone to the control microphone; a pure delay canceller for generating a pure delay cancelled transfer characteristic by obtaining the transfer characteristic and a predetermined pure delay parameter; a prediction filter calculation unit that acquires the pure delay-cancelled transfer characteristic, the reference microphone observation signal, and the control microphone observation signal and calculates a prediction filter for predicting a signal at the desired control point; a prediction unit that obtains the prediction filter, the observation signal of the reference microphone, and the pure delay-cancelled transfer characteristic, predicts the sound pressure at the desired control point, and outputs a prediction signal. Sound pressure prediction device.

3. The sound pressure prediction system according to claim 2, The pure delay elimination unit The distance D, the sound speed c, and the sampling frequency f ｓ , the pure delay parameter is set to Df based on a positive arbitrary constant δ. ｓ / c-δ Sound pressure prediction system.

4. a transfer characteristic estimating unit that acquires a reference microphone observation signal, which is an observation signal from a reference microphone installed near a noise source, a control microphone observation signal, which is an observation signal from a first control microphone arranged at a position away from a desired control point by a predetermined distance D in a predetermined direction θ, and a second control microphone arranged at a position away from the first control microphone by a predetermined distance D in the predetermined direction θ, and estimates a transfer characteristic from the reference microphone to the control microphone; a pure delay canceller for generating a pure delay cancelled transfer characteristic by obtaining the transfer characteristic and a predetermined pure delay parameter; a prediction filter calculation unit that acquires the pure delay-cancelled transfer characteristic, the reference microphone observation signal, and the control microphone observation signal and calculates a prediction filter for predicting a signal at the desired control point; a prediction unit that obtains the prediction filter, the observation signal of the reference microphone, and the pure delay-cancelled transfer characteristic, predicts the sound pressure at the desired control point, and outputs a prediction signal. Sound pressure prediction device.

5. A sound pressure prediction method executed by a sound pressure prediction device, a step of acquiring a reference microphone observation signal, which is an observation signal from a reference microphone installed near a noise source, a first control microphone arranged at a position away from a desired control point by a predetermined distance D in a predetermined direction θ, and a second control microphone arranged at a position away from the first control microphone by a predetermined distance D in the predetermined direction θ, and estimating a transfer characteristic from the reference microphone to the control microphone; obtaining the transfer characteristic and predetermined pure delay parameters to generate a pure delay cancelled transfer characteristic; calculating a prediction filter for predicting a signal at the desired control point by obtaining the pure delay-cancelled transfer characteristic, the reference microphone observation signal, and the control microphone observation signal; The prediction filter, the observation signal of the reference microphone, and the pure delay-cancelled transfer characteristic are obtained to predict the sound pressure at the desired control point, and a prediction signal is output. Sound pressure prediction method.

6. A program for causing a computer to function as the sound pressure prediction device according to claim 4.

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