Cancellation device, method and program

Abstract

A cancellation device according to one aspect of the present invention comprises: a first A / D conversion unit 2 which converts a noise signal that is a signal of noise acquired by a reference microphone for acquiring noise into a digital signal; a second A / D conversion unit 4 which converts an error signal acquired by an error microphone disposed in a region in which noise suppression is desired into a digital signal; a sound signal processing unit 5 which, on the basis of the digital signal of the noise and the digital signal of the error signal, generates a cancellation signal for suppressing the noise; a D / A conversion unit 6 which converts the cancellation signal into an analog signal, and causes a cancellation speaker to emit a sound based on the analog signal of the cancellation signal; and an internal parameter control unit 8 which, according to the statistical feature of the noise, dynamically controls an internal parameter that is used in A / D conversion or D / A conversion in the first A / D conversion unit 2, the second A / D conversion unit 4, and the D / A conversion unit 6.

Description

[Technical Field]

[0001] The present invention relates to a technique for suppressing noise. [Background technology]

[0002] Active noise control is known as a technology for suppressing noise.

[0003] An example of the configuration of a conventional active noise control device is shown in FIG.

[0004] The conventional configuration includes a reference microphone P1 that acquires noise, an ANC processing unit P2 that generates cancellation sound to offset the noise acquired by the reference microphone P1, a cancellation speaker P3 that outputs the cancellation sound, and an error microphone P4 that detects remaining noise and actively adjusts the cancellation sound.

[0005] The error microphone P4 is placed in the region PR where noise is desired to be suppressed. [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] As described above, the ANC processing unit P2 determines the sound to be output from the cancellation speaker P3, which is the secondary sound source, based on the noise signal acquired by the reference microphone P1 and the suppression error input to the error microphone, and the sound is output so that the noise exactly cancels out at the point of the error microphone P4.

[0008] Here, the performance of the ANC changes depending on the delay of the AD converter (ADC) connected to the reference microphone P1 and the error microphone P4, and the delay of the DA converter (DAC) connected to the cancellation speaker P3.

[0009] Therefore, in order to improve noise suppression performance, it is preferable to appropriately change internal parameters, such as delay, used when converting digital or analog signals depending on the usage scene of the active noise control.

[0010] However, until now, there has been no technology that can appropriately change internal parameters depending on the usage scenario of active noise control.

[0011] An object of the present invention is to provide a cancellation device, method, and program that have higher noise suppression performance than conventional devices. [Means for solving the problem]

[0012] A cancellation device according to one embodiment of the present invention includes a first AD conversion unit that converts a noise signal, which is a noise signal acquired by a reference microphone for acquiring noise, into a digital signal; a second AD conversion unit that converts an error signal acquired by an error microphone placed in an area where noise is to be suppressed into a digital signal; a sound signal processing unit that generates a cancellation signal for suppressing noise based on the digital noise signal and the digital error signal; a DA conversion unit that converts the cancellation signal into an analog signal and causes a cancellation speaker to emit sound based on the analog signal of the cancellation signal; and an internal parameter control unit that dynamically controls internal parameters used during AD conversion or DA conversion in the first AD conversion unit, second AD conversion unit, and DA conversion unit according to the statistical characteristics of the noise. The internal parameter is at least one of the delay amount, the time resolution, and the frequency resolution. The internal parameter is the delay amount, and the internal parameter control unit determines a smaller delay amount as the noise level increases or the time change decreases. [Effects of the Invention]

[0013] By dynamically controlling the internal parameters used when converting digital or analog signals in accordance with the statistical characteristics of noise, noise suppression performance can be improved compared to conventional techniques. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram illustrating an example of a functional configuration of a cancellation device. [Figure 2] FIG. 2 is a diagram showing an example of a processing procedure of the cancellation method. [Figure 3] FIG. 3 is a diagram illustrating an example of a functional configuration of a computer. [Figure 4] FIG. 4 is a diagram for explaining the background art. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings, in which like reference numerals are used to designate like components having the same functions, and redundant description will be omitted.

[0016] [Cancellation device and method] 1, the cancellation device includes a first AD conversion unit 2, a second AD conversion unit 4, a sound signal processing unit 5, a DA conversion unit 6, and an internal parameter control unit 8. The cancellation device may further include a reference microphone 1, an error microphone 3, and a cancellation speaker 7.

[0017] The cancellation method is realized, for example, by each component of the cancellation device performing the processes from step S2 to step S8 shown in FIG. 2, as will be described below.

[0018] Each component of the cancellation device will be described below.

[0019] <Reference Mic 1> The reference microphone 1 is a microphone for acquiring noise. The noise signal acquired by the reference microphone 1 is output to the first AD conversion unit 2.

[0020] The reference microphone 1 is placed, for example, near the cancellation speaker 7.

[0021] <First AD conversion unit 2> The first AD conversion unit 2 receives a noise signal acquired by the reference microphone 1 .

[0022] Furthermore, the first AD conversion unit 2 receives the internal parameters determined by the internal parameter control unit 8.

[0023] The first AD conversion unit 2 converts the noise signal, which is a signal of noise acquired by a reference microphone for acquiring noise, into a digital signal (step S2). That is, the first AD conversion unit 2 converts the noise signal, which is an analog signal, into a digital signal.

[0024] The digital signal of the noise converted by the first AD conversion unit 2 is output to the sound signal processing unit 5.

[0025] The first AD conversion unit 2 performs AD conversion based on the internal parameters determined by the internal parameter control unit 8.

[0026] The internal parameters will be explained in the description of the internal parameter control unit 8.

[0027] <Error Mic 3> The error microphone 3 is a microphone placed in an area R where noise is desired to be suppressed. The error signal obtained by the error microphone 3 is output to the second AD conversion unit 4.

[0028] <Second AD conversion unit 4> The second AD conversion unit 4 receives the error signal.

[0029] The second AD conversion unit 4 converts the error signal obtained by the error microphone placed in the area where noise is desired to be suppressed into a digital signal (step S4).

[0030] The digital signal of the error signal converted by the second AD conversion unit 4 is output to the sound signal processing unit 5.

[0031] The second AD conversion unit 4 performs AD conversion based on the internal parameters determined by the internal parameter control unit 8.

[0032] <Audio signal processing unit 5> The audio signal processing unit 5 receives the digital signal of the noise and the digital signal of the error signal.

[0033] The audio signal processing unit 5 generates a cancel signal for suppressing noise based on the digital signal of the noise and the digital signal of the error signal (step S5). The cancel signal is a digital signal. The generated cancel signal is output to the DA conversion unit 6.

[0034] The audio signal processing unit 5 corresponds to the ANC processing unit P2 in the background art.

[0035] For example, the audio signal processing unit 5 generates a cancel signal, which is a drive signal for the cancel speaker 7, based on the digital signal of the noise and the digital signal of the error signal, for example, using an adaptive algorithm.

[0036] The audio signal processing unit 5 may generate a cancel signal by other existing methods other than the adaptive algorithm.

[0037] <DA conversion unit 6> The DA conversion unit 6 receives the cancel signal.

[0038] The DA conversion unit 6 converts the cancel signal into an analog signal. The analog signal of the cancel signal is output to the cancel speaker 7.

[0039] As will be described later, the cancel speaker 7 emits sound based on the analog signal of the cancel signal. Therefore, it can be said that the DA conversion unit 6 converts the cancel signal into an analog signal and causes the cancel speaker 7 to emit sound based on the analog signal of the cancel signal (step S6).

[0040] The DA conversion unit 6 performs DA conversion based on the internal parameters determined by the internal parameter control unit 8.

[0041] <Cancel Speaker 7> An analog signal of the cancellation signal is input to the cancellation speaker 7.

[0042] The cancellation speaker 7 emits a sound based on the cancellation signal.

[0043] This sound is emitted toward an area R where noise is desired to be suppressed.

[0044] <Internal parameter control section 8> The internal parameter control unit 8 receives the digital noise signal converted by the first AD conversion unit 2 .

[0045] The internal parameter control unit 8 dynamically controls the internal parameters used during AD conversion or DA conversion in the first AD conversion unit 2, the second AD conversion unit 4 and the DA conversion unit 6 according to the statistical characteristics of the noise (step S8).

[0046] The internal parameter is at least one of the delay amount, the time resolution, and the frequency resolution. The internal parameter may be another parameter such as an operating clock used in AD conversion or DA conversion.

[0047] The internal parameter control unit 8 extracts statistical characteristics of noise based on the input digital signal of noise converted by the first AD conversion unit 2. The internal parameter control unit 8 determines internal parameters to be used during AD conversion or DA conversion in the first AD conversion unit 2, the second AD conversion unit 4, and the DA conversion unit 6 based on the extracted statistical characteristics of noise. The internal parameter control unit 8 outputs the determined internal parameters to be used during AD conversion in the first AD conversion unit 2 to the first AD conversion unit 2. The internal parameter control unit 8 outputs the determined internal parameters to be used during AD conversion in the second AD conversion unit 4 to the second AD conversion unit 4. The internal parameter control unit 8 outputs the determined internal parameters to be used during DA conversion in the DA conversion unit 6 to the DA conversion unit 6. The first AD conversion unit 2, the second AD conversion unit 4, and the DA conversion unit 6 perform AD conversion or DA conversion based on the input internal parameters. For example, dynamic control by the internal parameter control unit 8 is performed in this manner.

[0048] Examples of the statistical characteristics of noise include the time variation of the noise characteristics and the noise magnitude, although other statistical characteristics may also be used as the statistical characteristics of noise.

[0049] For example, the internal parameter control unit 8 may determine a smaller delay amount as the change in noise characteristics over time becomes smaller.

[0050] The internal parameter control unit 8 may compare the change in the noise characteristics over time with a predetermined threshold, and determine a small delay amount Ds if the change in the noise characteristics over time is small, and determine a large delay amount Dl if the change in the noise characteristics over time is large.

[0051] The delay amounts Ds and Dl are predetermined delay amounts, and Ds <Dlである。

[0052] The internal parameter control unit 8 may determine a smaller delay amount as the noise level increases.

[0053] The internal parameter control unit 8 may compare the noise level with a predetermined threshold and determine a small delay amount Ds if the noise level is large, and a large delay amount Dl if the noise level is small.

[0054] In addition, the internal parameter control unit 8 may control the internal parameters used during AD conversion in the first AD conversion unit 2, the internal parameters used during AD conversion in the second AD conversion unit 4, and the internal parameters used during DA conversion in the DA conversion unit 6 in a linked manner.

[0055] The internal parameter control unit 8 may determine the internal parameters to be the initial values ​​based on advance information input by the user using an input device such as a keyboard or a mouse.

[0056] An example of advance information input by the user is information on a usage scenario in which the cancellation device and method are used.

[0057] For example, if the usage scene input by the user is a scene with a lot of noise, such as a train, car, or airplane, the internal parameter control unit 8 determines a small delay amount Ds.

[0058] On the other hand, if the usage scene input by the user is a scene with a medium level of noise, such as remote work, the internal parameter control unit 8 determines a medium amount of delay Dm.

[0059] Ds and Dm are predetermined delay amounts, and Ds <Dmである。

[0060] As in this example, the internal parameter control unit 8 may determine a smaller delay amount as the expected noise increases.

[0061] The internal parameter control unit 8 may also include a scene determination unit 81. In this case, the internal parameter control unit 8 receives the digital signal of noise converted by the first AD conversion unit 2.

[0062] The scene determination unit 81 of the internal parameter control unit 8 determines the usage scene based on the digital signal of noise. For example, the scene determination unit 81 may determine the usage scene using a learning model that has been learned in advance.

[0063] Generally, when AD conversion and DA conversion are performed with high time resolution and high frequency resolution in order to improve noise suppression performance, the input / output delay increases. If this delay is too large, it becomes difficult for the sound emitted from the cancellation speaker to track the actual noise, and suppression performance may actually decrease.

[0064] On the other hand, if the time resolution and frequency resolution of the AD conversion and DA conversion are made too low in order to reduce delay, it becomes difficult to analyze fine noise, and it becomes impossible to generate a signal that properly cancels out low-volume noise or noise with significant time fluctuations, which can result in reduced suppression performance.

[0065] Therefore, in designing active noise suppression, it is necessary to appropriately handle the above trade-offs in AD conversion and DA conversion.

[0066] As described above, by dynamically controlling the internal parameters used when converting digital or analog signals in accordance with the statistical characteristics of noise, it is possible to appropriately handle, for example, the trade-off described above, and to improve noise suppression performance compared to conventional techniques.

[0067] Furthermore, as mentioned above, it is also possible to reduce the power consumption of the ANC system by dynamically controlling the internal parameters.

[0068] [Variations] The above describes the embodiments of the present invention, but the specific configuration is not limited to these embodiments, and it goes without saying that even if design changes are made as appropriate within the scope of the present invention, they are still included in the present invention.

[0069] The various processes described in the embodiments may not only be executed in chronological order according to the order described, but may also be executed in parallel or individually depending on the processing capabilities of the devices executing the processes or as necessary.

[0070] For example, data may be exchanged directly between the components of the cancellation device, or may be exchanged via a storage unit (not shown).

[0071] [Programs, recording media] The processing of each unit of each of the above-mentioned devices may be realized by a computer, in which case the processing content of the functions to be possessed by each device is described by a program. Then, by loading this program into storage unit 1020 of computer 1000 shown in Fig. 3 and operating arithmetic processing unit 1010, input unit 1030, output unit 1040, etc., various processing functions of each of the above-mentioned devices are realized on the computer. Computer 1000 may also include display unit 1060.

[0072] The program describing the processing contents can be recorded on a computer-readable recording medium, such as a non-transitory recording medium, specifically a magnetic recording device, an optical disk, or the like.

[0073] The program may be distributed, for example, by selling, transferring, lending, etc. a portable recording medium such as a DVD or CD-ROM on which the program is recorded. Furthermore, the program may be stored in a storage device of a server computer, and then transferred from the server computer to another computer via a network, thereby distributing the program.

[0074] A computer that executes such a program, for example, first stores the program recorded on a portable recording medium or transferred from a server computer in its own non-transitory storage device, auxiliary storage unit 1050. Then, when executing a process, the computer loads the program stored in auxiliary storage unit 1050, its own non-transitory storage device, into storage unit 1020 and executes processing in accordance with the loaded program. Alternatively, as another form of execution of this program, the computer may load the program directly from a portable recording medium into storage unit 1020 and execute processing in accordance with the program. Furthermore, each time a program is transferred from a server computer to this computer, the computer may execute processing in accordance with the received program. Alternatively, the server computer may not transfer the program to this computer, but may instead execute the processing function by issuing an execution instruction and obtaining the results, thereby executing the above-described processing through a so-called ASP (Application Service Provider) type service. Note that the program in this embodiment includes information used for processing by a computer that is equivalent to a program (such as data that is not a direct instruction to a computer but has properties that define computer processing).

[0075] In this embodiment, the device is configured by executing a predetermined program on a computer, but at least part of the processing may be realized by hardware. For example, the first AD conversion unit 2, the second AD conversion unit 4, the sound signal processing unit 5, the DA conversion unit 6, and the cancellation speaker 7 may be configured by processing circuits.

[0076] It goes without saying that other modifications are possible without departing from the spirit of the present invention.

Claims

1. a first AD conversion unit that converts a noise signal, which is a noise signal acquired by a reference microphone for acquiring noise, into a digital signal; a second AD conversion unit that converts an error signal obtained by an error microphone placed in an area where noise is to be suppressed into a digital signal; a sound signal processing unit that generates a cancellation signal for suppressing the noise based on the digital signal of the noise and the digital signal of the error signal; a DA conversion unit that converts the cancellation signal into an analog signal and causes a cancellation speaker to emit a sound based on the analog signal of the cancellation signal; an internal parameter control unit that dynamically controls internal parameters used during AD conversion or DA conversion in the first AD conversion unit, the second AD conversion unit, and the DA conversion unit according to statistical characteristics of the noise; Including, the internal parameter is at least one of a delay amount, a time resolution, and a frequency resolution; the internal parameter is a delay amount, the internal parameter control unit determines the delay amount to be smaller as the noise level is larger or as the noise change over time is smaller; Cancellation device.

2. The cancellation device of claim 1, the internal parameter control unit determines the internal parameters in accordance with a usage scene; Cancellation device.

3. a first AD conversion step in which a first AD conversion unit converts a noise signal, which is a signal of noise acquired by a reference microphone for acquiring noise, into a digital signal; a second AD conversion step in which a second AD conversion unit converts an error signal obtained by an error microphone placed in an area where noise is to be suppressed into a digital signal; a sound signal processing step in which a sound signal processing unit generates a cancellation signal for suppressing the noise based on the digital signal of the noise and the digital signal of the error signal; a DA conversion step in which a DA conversion unit converts the cancellation signal into an analog signal and causes a cancellation speaker to emit a sound based on the analog signal of the cancellation signal; an internal parameter control step in which an internal parameter control unit dynamically controls internal parameters used in AD conversion or DA conversion in the first AD conversion unit, the second AD conversion unit, and the DA conversion unit according to the statistical characteristics of the noise; Including, the internal parameter is at least one of a delay amount, a time resolution, and a frequency resolution; the internal parameter is a delay amount, In the internal parameter control step, the delay amount is determined to be smaller as the noise level is larger or the noise change over time is smaller. How to cancel.

4. The cancellation method of claim 3, In the internal parameter control step, the internal parameters are determined in accordance with a usage scene. How to cancel.

5. A program for causing a computer to function as each part of the cancellation device according to claim 1 or 2.

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