Noise suppression device, noise suppression method, and program

Abstract

Provided are a noise suppression device and the like, the noise suppression device being capable of stabilizing operation for noise suppression even if a noise characteristic changes rapidly by controlling the noise suppression device, for example, by correcting the coefficient of an adaptive filter or stopping a cancellation speaker according to the present position of a vehicle such as an electric train. This noise suppression device performs operation corresponding to positional information m of a mobile object in which a cancellation speaker to be used in active noise control is installed, and generates a cancellation signal to be reproduced by the cancellation speaker.

Description

Technical Field

[0001] The present invention relates to a technology of active noise control (ANC) for suppressing external noise at a specific position.

Background Art

[0002] Non-Patent Document 1 is known as a conventional active noise control technology. In active noise suppression, a reference microphone, an error microphone, and a cancellation speaker are generally used. FIG. 1 shows a configuration example of a conventional noise suppression device. The reference microphone 91 picks up the noise emitted from the noise source. The cancellation speaker 92 reproduces the cancellation signal generated by the suppression signal generation device 90 and emits a cancellation sound that cancels out the noise. Further, the error microphone 93 picks up and feeds back the remaining noise. The suppression signal generation device 90 actively controls and generates a cancellation signal using the sound pickup signal of the reference microphone 91 and the sound pickup signal of the error microphone 93 so that the remaining noise is reduced. In order to emit an appropriate noise-suppressing sound from the cancellation speaker 92, the suppression signal generation device 90 applies an adaptive filter to the sound picked up by the reference microphone 91 to generate a cancellation signal.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the statistical properties such as the bias of volume or frequency components change significantly over time, the adaptive filter cannot keep up with the changes, and appropriate filter coefficients cannot be calculated, resulting in unstable suppression performance. In particular, in a situation where noise suppression is performed while moving inside a train, the above problem becomes prominent at the timing when the noise-generating environment changes significantly, such as when entering or exiting a tunnel.

[0005] An object of the present invention is to provide a noise suppression device, a noise suppression method, and a program that can stabilize the noise suppression operation even when the characteristics of the noise change rapidly by controlling the noise suppression device by correcting the coefficients of the adaptive filter or stopping the cancellation speaker according to the current position of a vehicle such as a train.

Means for Solving the Problems

[0006] In order to solve the above problems, according to one aspect of the present invention, a noise suppression device performs an operation corresponding to the position information m of a moving body provided with a cancellation speaker used in active noise control, and generates a cancellation signal to be reproduced by the cancellation speaker.

Effects of the Invention

[0007] According to the present invention, there is an effect that the noise suppression operation can be stabilized even when the characteristics of the noise change rapidly.

Brief Description of the Drawings

[0008]

Figure 1

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Modes for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described. In the drawings used in the following description, components having the same function and steps performing the same process are denoted by the same reference numerals, and redundant descriptions are omitted.

[0010] <Points of the First Embodiment> · In order to utilize the relationship that a specific noise environment is likely to occur at a specific position, position information and noise information are used in association with each other.

[0011] · In a train or the like, since the travel route is fixed, the characteristic that the reproducibility of the noise environment based on the position information is high is utilized.

[0012] <First Embodiment> FIG. 2 shows a functional block diagram of the noise suppression system according to the first embodiment, and FIG. 3 shows its processing flow.

[0013] The noise suppression system includes a reference microphone 91, a cancellation speaker 92, an error microphone 93, a suppression signal generation unit 110, a determination unit 120, a position information acquisition unit 130, and a noise map information storage unit 140. An apparatus including the suppression signal generation unit 110, the determination unit 120, and the noise map information storage unit 140 is also referred to as a noise suppression apparatus.

[0014] The noise suppression apparatus takes as inputs the sound collection signal x(r) of the reference microphone 91, the sound collection signal x(e) of the error microphone 93, and the position information acquired by the position information acquisition unit 130, performs operations corresponding to the position information of the moving body where the reference microphone 91, the cancellation speaker 92, and the error microphone 93 are installed, generates a cancellation signal (hereinafter, also referred to as a "suppression signal") y, and outputs it to the cancellation speaker 92.

[0015] The noise suppression device is a special device configured by loading a special program into a known or dedicated computer having, for example, a central processing unit (CPU) and a main memory device (RAM: Random Access Memory). The noise suppression device executes each process under the control of, for example, the central processing unit. Data input to the noise suppression device and data obtained in each process are stored, for example, in the main memory device, and the data stored in the main memory device is read out to the central processing unit as needed and used for other processes. At least a part of each processing unit of the noise suppression device may be configured by hardware such as an integrated circuit. Each storage unit included in the noise suppression device can be configured by, for example, a main memory device such as a RAM (Random Access Memory), or middleware such as a relational database or a key-value store. However, each storage unit does not necessarily have to be provided inside the noise suppression device, and may be configured by an auxiliary storage device configured by a semiconductor memory element such as a hard disk, an optical disk, or a flash memory (Flash Memory), and may be provided outside the noise suppression device.

[0016] The following describes each part.

[0017] <Reference microphone 91> The reference microphone 91 picks up the sound to be suppressed (S91) and outputs a picked-up sound signal x(r). The sound to be suppressed picked up by the reference microphone 91 is hereinafter referred to as "noise".

[0018] <Error microphone 93> The error microphone 93 picks up the sound not suppressed by the playback sound reproduced from the cancellation speaker 92, including the remaining noise (S93) and outputs a picked-up sound signal x(e).

[0019] <Position information acquisition unit 130> The position information acquisition unit 130 acquires (S130) and outputs the position information m of the moving body on which the reference microphone 91, the cancellation speaker 92, and the error microphone 93 included in the noise suppression system are installed. For example, the position information acquisition unit 130 consists of a GPS (Global Positioning System) or the like and is installed inside the moving body on which the reference microphone 91, the cancellation speaker 92, and the error microphone 93 are installed.

[0020] <The determination unit 120 and the noise map information storage unit 140> The noise map information storage unit 140 stores the noise map information corresponding to the position information. The noise map information is information on the noise associated with the position information and is information indicating whether the position is a position where the noise characteristics change significantly. Note that the noise characteristics are characteristics indicating the bias and magnitude of the frequency band of the sound included in the noise, and may be rephrased as the statistical characteristics of the noise. For example, the noise map information storage unit 140 may store, as the noise map information, the position (for example, coordinates) and its range where the noise characteristics change significantly, or the position (for example, coordinates) and its range where the noise characteristics do not change significantly, or information indicating whether the position (for example, each coordinate) is a position where the noise characteristics change significantly. For example, when the reference microphone 91, the cancellation speaker 92, and the error microphone 93 are installed inside a vehicle such as a railway or an automobile, the noise characteristics change significantly at the entrance and exit of a tunnel, etc. Therefore, the noise map information corresponding to the position information of the entrance and exit of the tunnel indicates that it is a position where the noise characteristics change significantly.

[0021] The determination unit 120 takes the position information m as an input and determines (S120) whether the position of the position information m is a position where the noise characteristics change significantly with reference to the noise map information storage unit 140.

[0022] When it is a position where the noise characteristics change significantly (YES in S120), the determination unit 120 outputs a control signal indicating that the ANC operation is not to be performed. Since it is only necessary to be able to control so as not to perform the ANC operation, as the output destination of the control signal, the suppression signal generation unit 110, the cancellation speaker 92, etc. described later can be considered. (i) The determination unit 120 may control so as not to perform the ANC operation by stopping the reproduction of the cancellation signal y in the cancellation speaker 92. In this case, a control signal may be output to the cancellation speaker 92 to stop the reproduction of the cancellation signal y, or a control signal may be output to the suppression signal generation unit 110 to stop the generation or output of the cancellation signal y in the suppression signal generation unit 110. Also, (ii) the determination unit 120 may control so as not to perform the ANC operation by outputting a control signal to the suppression signal generation unit 110 and stopping the update of the adaptive filter. Depending on the situation, (i) to (ii) may be switched for control. However, by adopting (i) and maintaining the update of the adaptive filter, it is possible to prevent the operation at the time of restarting the ANC operation from becoming unstable. The time during which the ANC operation is not performed may be set to the time required until the ANC operation becomes stable.

[0023] When it is not a position where the noise characteristics change significantly (NO in S120), the determination unit 120 outputs a control signal indicating that the ANC operation is to be performed. However, when a control signal indicating that the ANC operation is not to be performed is not received in each unit, it may be configured to basically perform the ANC operation, and the determination unit 120 may be configured not to output a control signal indicating that the ANC operation is to be performed. In this case, when it is not a position where the noise characteristics change significantly (NO in S120), the determination unit 120 does not perform any processing and transfers the processing to the suppression signal generation unit 110.

[0024] <Suppression signal generation unit 110> The suppression signal generation unit 110 takes the collected sound signals x(r) and x(e) as inputs, generates (S110), and outputs a cancellation signal y for suppressing noise by using the collected sound signal x(r) and the model. Further, the suppression signal generation unit 110 updates the model by using the collected sound signals x(r) and x(e). For example, the model is an adaptive filter, and its filter coefficients are updated.

[0025] As a method for generating the cancellation signal, a conventional technique can be used. For example, the method of Non-Patent Document 1 can be used. In the present embodiment, a feedforward type ANC is realized by the collected sound signal x(r), the collected sound signal x(e), and the cancellation signal y. The interference sound between the noise from the noise source and the reproduced sound of the cancellation signal y is detected by the error microphone 93, the noise from the noise source is detected by the reference microphone 91, and the collected sound signal x(r) of the reference microphone 91 is input to an adaptive filter realized by a digital filter to generate the cancellation signal y, which is reproduced by the cancellation speaker 92. The reproduced sound of the cancellation signal y propagates through the secondary path, which is a series of transmission systems from the cancellation speaker 92 to the error microphone 93. Then, by using the collected sound signal x(r) of the reference microphone 91 and the collected sound signal x(e) of the error microphone 93, the filter coefficients of the adaptive filter are updated by an adaptive algorithm so that the input to the error microphone 93 is minimized. Since a conventional update method can be used as the method for updating the filter coefficients of the adaptive filter, the description thereof is omitted. In the feedforward type ANC, a secondary path model obtained by estimating the secondary path is used to compensate for the influence of the secondary path in the adaptive algorithm.

[0026] <cancellation speaker 92> The cancellation speaker 92 takes the cancellation signal y as an input and reproduces the cancellation signal y (S92). When the reproduced sound from the cancellation speaker 92 and the noise to be suppressed are in a completely opposite phase, the reproduced sound and the noise to be suppressed overlap, that is, the waves cancel each other out because the sound waves overlap, so the noise is suppressed. As described above, the sound not suppressed by the reproduced sound from the cancellation speaker 92 is collected by the error microphone 93.

[0027] <Effect> With the above configuration, even if the characteristics of the noise change abruptly, the operation of noise suppression can be stabilized.

[0028] In the conventional feedforward type ANC, the coefficients of the adaptive filter are updated using the sound collection signal x(r) of the reference microphone 91 and the sound collection signal x(e) of the error microphone 93. Therefore, the change in the noise characteristics can only be detected from the sound collection signal x(r) and the sound collection signal x(e) actually collected by the reference microphone 91 and the error microphone 93. The calculation of the appropriate filter coefficients cannot keep up with the change in the noise characteristics, and the noise suppression performance may temporarily decrease, or the ANC may not operate stably. For example, there is a possibility of howling, the ANC may not catch up and output a large noise, or an excessive sound may be output depending on the adaptive algorithm.

[0029] In this embodiment, the change in the future noise characteristics is predicted using the position information, and at the position where the noise characteristics change greatly, the ANC operation is controlled not to be performed, thereby preventing unstable operations such as howling of the ANC. This embodiment is particularly effective when the reference microphone 91, the cancellation speaker 92, and the error microphone 93 are installed inside a vehicle whose driving route, such as a train, is determined, because the determination accuracy in the determination unit 120 is improved.

[0030] <Second Embodiment> The description will focus on the parts different from the first embodiment.

[0031] FIG. 4 shows a functional block diagram of the noise suppression system according to the second embodiment, and FIG. 5 shows its processing flow.

[0032] The noise suppression system includes a reference microphone 91, a cancellation speaker 92, an error microphone 93, a suppression signal generation unit 210, a determination unit 220, a position information acquisition unit 130, and a noise map information storage unit 240. The device composed of the suppression signal generation unit 210, the determination unit 220, and the noise map information storage unit 240 is also referred to as a noise suppression device.

[0033] <Determination unit 220 and noise map information storage unit 240> The noise map information storage unit 240 stores noise map information corresponding to the position information. The noise map information of the present embodiment is information on noise associated with the position information, and is a model adapted to the information indicating whether the position is a position where the noise characteristics change significantly and the changed noise characteristics at the position where the noise characteristics change significantly. The information indicating whether the position is a position where the noise characteristics change significantly is as described in the first embodiment. The model adapted to the changed noise characteristics is, for example, an adaptive filter, and the filter coefficients thereof are stored in the noise map information storage unit 240. Hereinafter, the model will be described as an adaptive filter and its filter coefficients, but other models may be used. The filter coefficients may be obtained by calculation as the filter coefficients of an adaptive filter adapted to the changed noise characteristics (for example, the noise characteristics when driving in a tunnel), or may be the filter coefficients of an adaptive filter obtained by the suppression signal generation unit 210 at the same position (for example, inside the tunnel) in the past. For example, when a reference microphone 91, a cancellation speaker 92, and an error microphone 93 are installed in a vehicle such as a railway vehicle or an automobile, the noise characteristics change significantly at the entrance of the tunnel, etc. Therefore, the noise map information corresponding to the position information of the entrance of the tunnel is information indicating that the position is a position where the noise characteristics change significantly and the filter coefficients of an adaptive filter adapted to the noise characteristics when driving in the tunnel.

[0034] The determination unit 220 takes the position information m as an input, and refers to the noise map information storage unit 140 to determine whether the position of the position information m is a position where the noise characteristics change significantly (S220).

[0035] If it is a position where the noise characteristics change significantly (YES in S220), the determination unit 220 reads out the filter coefficients of the adaptive filter adapted in advance to the changed noise characteristics corresponding to the position information m from the noise map information storage unit 240, and changes the filter coefficients of the adaptive filter of the suppression signal generation unit 210 to the read filter coefficients (S220-2).

[0036] When it is not the position where the noise characteristics change significantly (NO in S220), the determination unit 220 does not perform any processing and transfers the processing to the suppression signal generation unit 210.

[0037] <Suppression signal generation unit 210> The suppression signal generation unit 210 takes the received sound signal x(r) and the received sound signal x(e) as inputs, and uses the received sound signal x(r) and the model to generate (S210) and output a cancellation signal y for suppressing noise. Also, the suppression signal generation unit 110 updates the model using the received sound signal x(e). For example, the model is an adaptive filter, and its filter coefficients are updated.

[0038] The method of generating the cancellation signal itself is the same as that of the first embodiment. However, when it is the position where the noise characteristics change significantly, the filter coefficients of the adaptive filter are changed by the determination unit 220, which is different. Note that after the change, the suppression signal generation unit 210 updates the sequential filter coefficients by an adaptive algorithm using the received sound signal x(e) in the same manner as the conventional feed-forward type ANC.

[0039] <Effect> With such a configuration, the same effects as those of the first embodiment can be obtained. Furthermore, an improvement in the accuracy and speed of the cancellation signal in the suppression signal generation unit can be expected. This embodiment and the first embodiment may be combined. For example, at a position where a model adapted to the changed noise characteristics has not been prepared, control is performed so that the ANC operation is not performed by the method of the first embodiment, and at a position where a model adapted to the changed noise characteristics has been prepared, it is changed to a model adapted to the changed noise characteristics by the method of this embodiment.

[0040] <Modification example> In this embodiment, the case of entering the tunnel from outside the tunnel has been described. However, the noise characteristics also change significantly when exiting the tunnel from inside the tunnel. That is, at the position where the noise characteristics change significantly, the case of changing from noise characteristic A to noise characteristic B and the case of changing from noise characteristic B to noise characteristic A are considered. When the reference microphone 91, the cancellation speaker 92, and the error microphone 93 are installed in a moving body whose traveling route such as a railway is predetermined, since how the noise characteristics change is predetermined, this embodiment can be applied. When the reference microphone 91, the cancellation speaker 92, and the error microphone 93 are installed in a moving body whose traveling route is not predetermined, for one piece of information indicating whether or not it is a position where the noise characteristics change significantly, as a model adapted to the changed noise characteristics, a model for the case of changing from noise characteristic A to noise characteristic B and a model for the case of changing from noise characteristic B to noise characteristic A may be prepared and stored in the noise map information storage unit 240. Here, although two models are used, when changing to three or more noise characteristics, three or more models may be prepared. The main point is that for one piece of information indicating whether or not it is a position where the noise characteristics change significantly, one or more changed noise characteristics may be associated according to the type of change.

[0041] The determination unit 220 takes the position information m as an input and refers to the noise map information storage unit 140 to determine whether the position of the position information m is a position where the noise characteristics change significantly (S220).

[0042] If it is a position where the noise characteristics change significantly (YES in S220), the determination unit 220 determines the changed noise characteristics from the time series of the position information m. For example, the determination unit 220 determines whether to enter the tunnel or exit the tunnel from the time series of the position information m. When entering the tunnel, the changed noise characteristics are determined as the noise characteristics inside the tunnel, and when exiting the tunnel, the changed noise characteristics are determined as the noise characteristics outside the tunnel.

[0043] The determination unit 220 extracts a filter coefficient corresponding to the changed noise characteristics from among the filter coefficients corresponding to the position information m from the noise map information storage unit 240, and changes the filter coefficient of the adaptive filter of the suppression signal generation unit 210 to the filter coefficient corresponding to the changed noise characteristics (S220-2).

[0044] With such a configuration, for one position where the noise characteristics change significantly, one or more changed noise characteristics can be associated according to the type of change, and ANC can be applied more flexibly.

[0045] <Other Modification Examples> The present invention is not limited to the above-described embodiments and modification examples. For example, the various processes described above may be executed not only in time series according to the description, but also in parallel or individually according to the processing ability of the device that executes the processes, or as necessary. In addition, appropriate changes can be made without departing from the spirit of the present invention.

[0046] <Program and Recording Medium> The various processes described above can be implemented by causing the storage unit 2020 of the computer shown in FIG. 6 to read a program that causes each step of the above method to be executed, and causing operations on the control unit 2010, the input unit 2030, the output unit 2040, and the like.

[0047] The program describing this processing content can be recorded on a computer-readable recording medium. As the computer-readable recording medium, for example, any of a magnetic recording device, an optical disk, a magneto-optical recording medium, a semiconductor memory, etc. may be used.

[0048] In addition, the distribution of this program is performed, for example, by selling, transferring, lending, etc. a portable recording medium such as a DVD or a CD-ROM on which the program is recorded. Furthermore, the program may be stored in the storage device of a server computer, and the program may be distributed by transferring the program from the server computer to other computers via a network.

[0049] A computer that executes such a program first stores, for example, a program recorded on a portable recording medium or a program transferred from a server computer in its own storage device. Then, at the time of executing the process, the computer reads the program stored in its own recording medium and executes the process according to the read program. As another execution form of this program, the computer may directly read the program from the portable recording medium and execute the process according to the program. Furthermore, each time a program is transferred from the server computer to this computer, the computer may sequentially execute the process according to the received program. Also, the above-described process may be executed in a so-called ASP (Application Service Provider) type service in which the transfer of the program from the server computer to this computer is not performed, and the processing function is realized only by the execution instruction and result acquisition. Note that the program in this embodiment includes information used for processing by an electronic computer and equivalent to the program (data having a property of defining the processing of the computer but not being a direct instruction to the computer).

[0050] Also, in this embodiment, the present apparatus is configured by causing a computer to execute a predetermined program, but at least a part of these processing contents may be realized hardware-wise.

Claims

Performs an operation corresponding to the position information m of a moving body provided with a cancellation speaker used in active noise control, generates a cancellation signal to be reproduced by the cancellation speaker, A noise map information storage unit that stores information indicating whether the position is a position where the noise characteristics change significantly, A determination unit that refers to the noise map information storage unit and determines whether the position of the position information m is a position where the noise characteristics change significantly, A suppression signal generation unit that generates the cancellation signal for suppressing noise using the sound collection signal of the reference microphone and the model Ma, and updates the model Ma using the sound collection signal of the error microphone, Performs different processes depending on whether the position of the position information m is a position where the noise characteristics change significantly, When the position of the position information m is a position where the noise characteristics change significantly, controls so as not to perform active noise control, A noise suppression device.

2. The noise suppression device according to claim 1, In the noise map information storage unit, information indicating whether the position is a position where the noise characteristics change significantly and a model adapted to the changed noise characteristics at the position where the noise characteristics change significantly are stored, When the position of the position information m is a position where noise characteristics change significantly, the determination unit selects from the noise map information storage unit a model M adapted to the changed noise characteristics corresponding to the position of the position information m. b is extracted, and the model M ａ The model M b Change to, A noise suppression device.

3. Performs an operation corresponding to the position information m of a moving body provided with a cancellation speaker used in active noise control, generates a cancellation signal to be reproduced by the cancellation speaker, Assume that the noise map information storage unit stores information indicating whether the position is a position where the noise characteristics change significantly, A determination step of referring to the noise map information storage unit and determining whether the position of the position information m is a position where the noise characteristics change significantly, The reference microphone's sound pickup signal and the model M ａ are used to generate the cancellation signal for suppressing noise, and the sound pickup signal of the error microphone is used to update the model M ａ including a suppression signal generation step of updating, Performs different processes depending on whether the position of the position information m is a position where the noise characteristics change significantly, When the position of the position information m is a position where the noise characteristics change significantly, controls so as not to perform active noise control, A noise suppression method.

4. A program for causing a computer to function as the noise suppression device according to any one of claims 1 to 2.

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