Active noise reduction device, active noise reduction system, and active noise reduction method

Abstract

To provide an active noise reduction device capable of adjusting a parameter used for generating a cancel signal.SOLUTION: An active noise reduction device 40 includes: a signal processing part 41 which generates a cancel signal for outputting cancel sound for reducing noise in a space in a vehicle 50; and a communication part 42 for receiving a change request requesting that a parameter related to generation of the cancel signal be changed to a user-specified parameter which a user specifies. The signal processing part 41 generates the cancel signal by using the user-specified parameter based on the received change request.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an active noise reduction system and an active noise reduction method for actively reducing noise by interfering a cancellation sound with the noise.

Background Art

[0002] Conventionally, an active noise reduction device that actively reduces noise by outputting a cancellation sound for canceling the noise from a cancellation sound source using a reference signal correlated with the noise and an error signal based on a residual sound obtained by interfering the noise and the cancellation sound in a predetermined space is known. As an example of an active noise reduction device, Patent Document 1 discloses a vehicle noise control device that can quickly respond to changes in the situation inside the vehicle that occur during travel and maintain the effect of noise control.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides an active noise reduction device capable of adjusting parameters used for generating a cancellation signal (cancellation sound).

Means for Solving the Problems

[0005] An active noise reduction device according to one aspect of the present disclosure is a signal processing unit that generates a cancellation signal for outputting a cancellation sound to reduce noise in the space within a mobile device, the signal processing unit that generates the cancellation signal by applying an adaptive filter, whose coefficients are updated based on an error signal indicating the state of the noise when the cancellation sound is output, to a reference signal correlated with the noise, and a communication unit that receives a change request requesting to change the parameters relating to the generation of the cancellation signal to user-specified parameters specified by the user, wherein the signal processing unit generates the cancellation signal using the user-specified parameters based on the received change request. [Effects of the Invention]

[0006] An active noise reduction device according to one aspect of the present disclosure can adjust the parameters used to generate a cancellation signal. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a diagram showing the functional configuration of an active noise reduction system according to an embodiment. [Figure 2] Figure 2 is a flowchart showing the basic operation of the active noise reduction device according to the embodiment. [Figure 3] Figure 3 is a sequence diagram of the parameter change operation. [Figure 4] Figure 4 is a sequence diagram of the anomaly notification process. [Figure 5] Figure 5 shows an example of a notification screen indicating an abnormality. [Figure 6] Figure 6 is a flowchart of the process for changing the judgment criteria. [Figure 7] Figure 7 is a flowchart of the fail-safe operation. [Figure 8] Figure 8 is a flowchart illustrating the change in the timing of the fail-safe process. [Figure 9] Figure 9 is a sequence diagram of the notification process for noise reduction effectiveness. [Figure 10] FIG. 10 is a diagram showing an example of a notification screen for a noise reduction effect. [Figure 11] FIG. 11 is a sequence diagram of an upload operation of user-specified parameters. [Figure 12] FIG. 12 is a sequence diagram of a download operation of user-specified parameters. [Figure 13] FIG. 13 is a diagram showing an example of a download screen of user-specified parameters. [Figure 14] FIG. 14 is a diagram showing a functional configuration of an active noise reduction system according to Modification 1. [Figure 15] FIG. 15 is a diagram showing a functional configuration of an active noise reduction system according to Modification 2. [Figure 16] FIG. 16 is a diagram showing a functional configuration of a signal processing unit according to the modification. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments will be specifically described with reference to the drawings. Note that each of the embodiments described below shows a comprehensive or specific example. Numerical values, shapes, materials, components, arrangement positions and connection forms of the components, steps, order of steps, etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure. In addition, among the components in the following embodiments, components not described in the independent claims are described as optional components.

[0009] Each drawing is a schematic diagram and is not necessarily drawn precisely. In each drawing, substantially the same configuration is denoted by the same reference numeral, and redundant descriptions may be omitted or simplified.

[0010] (Embodiment) [Configuration] Hereinafter, the configuration of the active noise reduction system according to the embodiment will be described. FIG. 1 is a diagram showing a functional configuration of the active noise reduction system according to the embodiment.

[0011] The active noise reduction system 10 is a system for reducing noise in the space (the interior space of the vehicle) inside the vehicle 50. The active noise reduction system 10 includes a user interface device 20, a server device 30, an active noise reduction device 40, a reference signal source 51, a cancellation sound source 52, and a plurality of error signal sources 53.

[0012] The user interface device 20 is a device that the user operates to perform various settings of the active noise reduction device 40. The user interface device 20 is realized by, for example, an information terminal such as a car navigation device, a personal computer, a smartphone, or a tablet terminal. The user interface device 20 is realized by, for example, installing a predetermined application program in a general-purpose information terminal. The user interface device 20 includes an operation reception unit 21, a display unit 22, a communication unit 23, an information processing unit 24, and a storage unit 25.

[0013] The operation reception unit 21 receives the user's operation. Specifically, the operation reception unit 21 is realized by, for example, a touch panel.

[0014] The display unit 22 displays an image. The display unit 22 is realized by, for example, a display panel such as a liquid crystal panel or an organic EL panel.

[0015] The communication unit 23 is a communication circuit (communication module) for the user interface device 20 to communicate with the server device 30 and the active noise reduction device 40. The communication unit 23 communicates with the server device 30 via a wide area communication network such as the Internet, and communicates with the active noise reduction device 40 via a local communication network or a wide area communication network. The communication performed by the communication unit 23 may be wireless communication or wired communication.

[0016] The information processing unit 24 performs information processing related to various settings of the active noise reduction device 40 in response to user operations received by the operation reception unit 21. The information processing unit 24 is implemented, for example, by a microcomputer, but may also be implemented by a processor or dedicated circuit. The functions of the information processing unit 24 are realized by the execution of a computer program (software) stored in the storage unit 25 by the hardware, such as the microcomputer or processor that constitutes the information processing unit 24. This computer program includes the predetermined application program described above.

[0017] The memory unit 25 is a storage device that stores computer programs and the like executed by the information processing unit 24. The memory unit 25 is implemented, for example, by semiconductor memory.

[0018] The server device 30 manages parameters related to noise reduction (generation of cancellation sound, described later) used in the active noise reduction device 40. The server device 30 is a cloud server installed outside the vehicle 50. The server device 30 comprises a communication unit 31, an information processing unit 32, and a storage unit 33.

[0019] The communication unit 31 is a communication circuit (communication module) for the server device 30 to communicate with the user interface device 20 and the active noise reduction device 40. The communication unit 31 communicates with the user interface device 20 and the active noise reduction device 40, for example, via a wide-area communication network. The communication performed by the communication unit 31 may be wireless communication or wired communication.

[0020] Furthermore, the active noise reduction system 10 can also be implemented as a system in which the server device 30 and the active noise reduction device 40 do not communicate directly with each other. In this case, it is not essential that the communication unit 31 has the function to communicate with the active noise reduction device 40.

[0021] The information processing unit 32 manages parameters related to noise reduction. The information processing unit 32 is implemented, for example, by a microcomputer, but may also be implemented by a processor or dedicated circuit. The functions of the information processing unit 32 are realized by the execution of a computer program (software) stored in the storage unit 33 by the hardware, such as the microcomputer or processor that constitutes the information processing unit 32.

[0022] The information processing unit 32 includes a parameter providing unit 34 as a functional component. The specific processing performed by the parameter providing unit 34 will be described later.

[0023] The memory unit 33 is a storage device that stores computer programs and the like executed by the information processing unit 32. The memory unit 33 is implemented by, for example, an HDD (Hard Disk Drive), but it may also be implemented by semiconductor memory.

[0024] The active noise reduction device 40 performs signal processing to reduce noise in the space inside the vehicle 50. The active noise reduction device 40 comprises a signal processing unit 41, a communication unit 42, an information processing unit 43, and a storage unit 44.

[0025] The signal processing unit 41 generates a cancellation signal for outputting a cancellation sound from the cancellation sound source 52 by performing signal processing on a reference signal acquired from the reference signal source 51. The cancellation sound is a sound used to reduce noise in the space inside the vehicle 50. The signal processing unit 41 is realized, for example, by a processor such as a DSP (Digital Signal Processor) or a microcomputer executing a computer program (software) stored in the memory unit 44.

[0026] The signal processing unit 41 specifically includes an adaptive filter unit 41a, a simulated acoustic transmission characteristic filter unit 41b, a filter coefficient update unit 41c, gain adjustment units 41d1 to 41d3, BPF (Band Pass Filter) units 41e1 to 41e3, an anomaly detection unit 46, and an effect calculation unit 47. The specific signal processing performed by the signal processing unit 41 will be described later. Note that the anomaly detection unit 46 and the effect calculation unit 47 may be provided by the information processing unit 43, and the effect calculation unit 47 may be provided by the user interface device 20 or the server device 30.

[0027] The communication unit 42 is a communication circuit (communication module) for the active noise reduction device 40 to communicate with the user interface device 20 and the server device 30. The communication unit 42 communicates with the user interface device 20, for example, via a local communication network or a wide-area communication network, and communicates with the server device 30 via a wide-area communication network. The communication performed by the communication unit 42 is, for example, wireless communication.

[0028] Furthermore, the active noise reduction system 10 can also be implemented as a system in which the server device 30 and the active noise reduction device 40 do not communicate directly with each other. In this case, it is not essential that the communication unit 42 has the function to communicate with the server device 30.

[0029] The information processing unit 43 performs information processing such as reflecting various settings instructed by the user to the user interface device 20 to the signal processing unit 41. The information processing unit 43 is implemented by, for example, a microcomputer, but may also be implemented by a processor or dedicated circuit. The functions of the information processing unit 43 are realized by the execution of a computer program (software) stored in the storage unit 44 by the hardware, such as the microcomputer or processor that constitutes the information processing unit 43. This computer program includes the predetermined application program described above.

[0030] The information processing unit 43 includes an acquisition unit 45 as a functional component. The specific processing performed by the acquisition unit 45 will be described later.

[0031] The memory unit 44 is a storage device that stores computer programs and the like executed by the information processing unit 43. The memory unit 44 is implemented by, for example, an HDD (Hard Disk Drive), but may also be implemented by semiconductor memory.

[0032] The reference signal source 51 is a transducer that outputs a reference signal correlated with the noise in the space inside the vehicle 50. The reference signal source 51 is, for example, an acceleration sensor and is located outside the space inside the vehicle 50. Specifically, the reference signal source 51 is mounted on a subframe or a wheel well, etc. The mounting position of the reference signal source 51 is not particularly limited. When the reference signal source 51 is an acceleration sensor, the active noise reduction device 40 can reduce the road noise component included in the noise in the space inside the vehicle 50. Since road noise has a complex propagation path, a configuration in which acceleration sensors are placed in multiple locations is useful. The reference signal source 51 may also be a microphone.

[0033] The cancellation sound source 52 outputs a cancellation sound into the space inside the vehicle 50 using a cancellation signal. In this embodiment, the cancellation sound source 52 is a speaker, but the cancellation sound may also be output when a part of the structure of the vehicle 50 (for example, a sunroof) is vibrated by a drive mechanism such as an actuator. In addition, multiple cancellation sound sources 52 may be installed inside the vehicle 50. The mounting position of the cancellation sound source 52 is not particularly limited.

[0034] The error signal source 53 detects residual sound resulting from the interference of noise and cancellation sound within the space inside the vehicle 50 and outputs an error signal based on the residual sound. The error signal source 53 is a transducer such as a microphone and is preferably installed in the space inside the vehicle 50, such as in the headliner. In the example in Figure 1, two error signal sources 53 are installed inside the vehicle 50, but it is sufficient to have at least one error signal source 53 installed inside the vehicle 50.

[0035] The error signal source 53 is installed, for example, in a seat inside the vehicle 50. If one of the two error signal sources 53 is installed in the driver's seat and the other in the rear seat, the amount of noise reduction for the user sitting in the driver's seat and the amount of noise reduction for the user sitting in the rear seat can be adjusted individually.

[0036] [Basic operation] As described above, the active noise reduction device 40 performs noise reduction operations. First, the basic operation of the active noise reduction device 40 will be explained with reference to Figure 2. Figure 2 is a flowchart of the basic operation of the active noise reduction device 40. In the following explanation, the case where there is one error signal source 53 will be mainly described, with the case where there are multiple error signal sources 53 being explained supplementarily.

[0037] First, a reference signal correlated with noise is input from the reference signal source 51 to the signal processing unit 41 of the active noise reduction device 40 (S11).

[0038] The reference signal input to the signal processing unit 41 is gain-adjusted by the gain adjustment unit 41d1 and output to the adaptive filter unit 41a. The reference signal input to the signal processing unit 41 is also gain-adjusted by the gain adjustment unit 41d1, and after the BPF 41e1 is applied, it is output to the simulated acoustic transmission characteristic filter unit 41b.

[0039] The adaptive filter unit 41a generates a cancellation signal by applying (convolving) an adaptive filter to a reference signal whose gain has been adjusted by the gain adjustment unit 41d1 (S12). The adaptive filter unit 41a is implemented by a so-called FIR filter or IIR filter. The adaptive filter unit 41a outputs the generated cancellation signal to the cancellation sound source 52 (S13). The cancellation sound source 52 outputs a cancellation sound based on the cancellation signal.

[0040] The error signal source 53 detects residual noise resulting from the interference between the cancellation sound output from the cancellation sound source 52 and the noise, and outputs an error signal corresponding to the residual noise. In other words, the error signal is a signal that indicates the noise level in the space inside the vehicle 50 when the cancellation sound is being output. As a result, the error signal is input to the signal processing unit 41 (S14).

[0041] The error signal input to the signal processing unit 41 is gain-adjusted by the gain adjustment unit 41d2 (or gain adjustment unit 41d3), and after the BPF 41e2 (or BPF 41e3) is applied, it is output to the filter coefficient update unit 41c.

[0042] The simulated acoustic transmission characteristic filter unit 41b generates a filtered reference signal by correcting the reference signal with a simulated transmission characteristic that simulates the acoustic transmission characteristics from the position of the cancellation sound source 52 to the position of the error signal source 53 (i.e., the acoustic transmission characteristics in space) (S15). The simulated transmission characteristic is measured in advance in the space inside the vehicle 50 and stored in the memory unit 44. The simulated transmission characteristic may be determined by an algorithm that does not use predetermined values.

[0043] The filter coefficient update unit 41c sequentially updates the coefficients W of the adaptive filter based on the gain-adjusted and BPF-applied error signal and the generated filtered reference signal (S16).

[0044] Specifically, the filter coefficient update unit 41c uses the LMS (Least Mean Square) method to calculate the coefficients of the adaptive filter so that the sum of squares of the error signals is minimized, and outputs the calculated adaptive filter coefficients to the adaptive filter unit 41a. The filter coefficient update unit 41c also sequentially updates the coefficients of the adaptive filter. If the error signal vector is represented as e and the filtered reference signal vector as R, the coefficients W of the adaptive filter are expressed by the following equation (Equation 1). Here, n is a natural number and represents the nth sample with a sampling period Ts. μ is a scalar quantity and is a step size parameter that determines the amount of update of the adaptive filter coefficients W per sample.

[0045]

number

[0046] Furthermore, if two error signal sources 53 are provided within the vehicle 50, two filtered reference signals corresponding to the two error signal sources 53 are R 000 , R 001 The vectors of the two error signals are e'0 and e'1, and the step size parameter is μ. 000 , μ 001 The coefficients W of the adaptive filter 00 This is expressed by (Equation 2) below. Note that the coefficient W of the adaptive filter when considering the leakage coefficient α is also shown. 00 This is expressed by (Equation 3) below.

[0047]

number

[0048] As described above, the signal processing unit 41 of the active noise reduction device 40 can generate a cancellation signal by applying an adaptive filter, whose coefficients are updated based on the error signal, to the reference signal.

[0049] [Parameter change behavior] The signal processing unit 41 generates a cancellation signal based on default parameters set in advance by the designer or the like. These parameters are used to adjust the cancellation sound when the cancellation sound is being output into the space inside the vehicle 50 (the cancellation sound is on).

[0050] The parameters include a gain coefficient multiplied by the reference signal by the gain adjustment unit 41d1, a gain coefficient multiplied by the error signal by the gain adjustment unit 41d2, a gain coefficient multiplied by the error signal by the gain adjustment unit 41d3, and a step size parameter μ. As described above, the two error signal sources 53 are installed, for example, at different seats in the vehicle 50, and by adjusting the gain coefficient multiplied by the error signal by the gain adjustment unit 41d2 and the gain coefficient multiplied by the error signal by the gain adjustment unit 41d3, the balance of noise reduction can be set for each seat.

[0051] Furthermore, the parameters include the characteristics of BPF41e1~41e3 (e.g., passband). The passband of BPF41e1~41e3 corresponds to the frequency band targeted for noise reduction (also referred to as the control frequency band). While the characteristics of BPF41e1~41e3 are basically set to the same value, they may be set to different values.

[0052] Incidentally, it is likely that many ordinary users would like to tune the performance of vehicle 50 to their liking, but the aspects related to the driving safety of vehicle 50 cannot be easily tuned. However, the above parameters for reducing noise in the space inside vehicle 50 do not directly affect driving safety, so it is thought that there is room for users to tune them.

[0053] Therefore, in the active noise reduction system 10, the default parameters can be changed by a general user (the end user who actually uses the vehicle 50), not the designer. In other words, the active noise reduction device 40 (signal processing unit 41) can change the default parameters to user-specified parameters and generate a cancellation signal. The operation of changing such parameters will be explained below. Figure 3 is a sequence diagram of the parameter change operation.

[0054] First, the user performs a parameter change operation on the operation reception unit 21 of the user interface device 20, and the operation reception unit 21 accepts this operation (S21). When the information processing unit 24 receives the change operation from the operation reception unit 21, it sends a change request to the active noise reduction device 40 using the communication unit 23, requesting that the above parameter be changed to a user-specified parameter (S22).

[0055] The communication unit 42 of the active noise reduction device 40 receives a change request. The acquisition unit 45 acquires the change request (S23) and reflects the user-specified parameters included in the acquired change request to the signal processing unit 41. Based on the acquired change request, the signal processing unit 41 generates a cancellation signal using the user-specified parameters (S24).

[0056] In this way, the active noise reduction device 40 can generate a cancellation signal by changing the default parameters described above to user-specified parameters. It is not necessary for the user to be able to change all of the above parameters; it is sufficient for the user to be able to change at least one of them.

[0057] [Notification of abnormality] Incidentally, the active noise reduction device 40 can determine that there is an abnormality in noise control when there is a possibility that the noise cannot be properly reduced by the cancellation sound (for example, when the cancellation sound itself becomes an abnormal noise), and can notify the user that an abnormality has been determined. Figure 4 is a sequence diagram of such an abnormality notification operation.

[0058] When the signal processing unit 41 of the active noise reduction device 40 generates a cancellation signal according to the basic operation described above, that is, when the filter coefficient update unit 41c updates the coefficient W of the adaptive filter (S31), the abnormality determination unit 46 acquires abnormality determination parameters related to the adaptive filter unit 41a (S32). Based on the acquired abnormality determination parameters, the abnormality determination unit 46 determines whether or not there is an abnormality (S33).

[0059] The abnormality detection parameter is, for example, the coefficient W of the adaptive filter, but it may also be the absolute value |ΔW| of the update amount of the adaptive filter coefficient W. More specifically, |ΔW| is calculated from the second term onwards on the right-hand side. Alternatively, the abnormality detection parameter may also be the amplitude (signal level) of the cancellation signal output by the adaptive filter unit 41a. Furthermore, the abnormality detection unit 46 may use two or more of the adaptive filter coefficient W, the update amount ΔW of the adaptive filter coefficient, and the amplitude of the cancellation signal as abnormality detection parameters. In other words, the abnormality detection parameter only needs to include at least one of the adaptive filter coefficient W, the update amount ΔW of the adaptive filter coefficient W, and the amplitude of the cancellation signal.

[0060] The abnormality detection parameter is expected to increase in value when noise control becomes unstable. Therefore, the abnormality detection unit 46 determines, for example, that there is an abnormality in noise control if the abnormality detection parameter remains above a threshold for a certain period of time or longer, and determines that there is no abnormality in noise control otherwise. In this case, the certain period and the threshold are determined appropriately based on experience or experimentation. Alternatively, the abnormality detection unit 46 may determine that there is an abnormality in noise control if the abnormality detection parameter exceeds a threshold a predetermined number of times within a certain period, and determine that there is no abnormality in noise control otherwise. In this case, the certain period, the threshold, and the predetermined number of times are determined appropriately based on experience or experimentation.

[0061] Another method for determining whether or not there is an abnormality may be adopted, which uses the number of taps of the adaptive filter. If x[n] is the nth sample of the reference signal and W[n] is the nth coefficient of the adaptive filter, the convolution operation can be expressed as x[0]·W[i]+x[1]·W[i-1]+x[2]·W[i-2]+···+x[L-1]·W[i-(L-1)], where L is the number of taps. The abnormality determination unit 46 may determine that there is an abnormality if the sum of n terms in descending order of value out of the L terms of the convolution operation is greater than or equal to a threshold, and that there is no abnormality if the sum of n terms is less than the threshold. Alternatively, the abnormality determination unit 46 may determine that there is an abnormality if the number of terms whose value is outside a predetermined range out of the L terms of the convolution operation is greater than or equal to a predetermined number, and that there is no abnormality if the number of terms whose value is within the predetermined range is less than a predetermined number.

[0062] If the abnormality detection unit 46 determines that there is an abnormality in the noise control, it outputs (transmits) information indicating the determination result to the user interface device 20 via the information processing unit 43 and the communication unit 42 (S34).

[0063] The communication unit 23 of the user interface device 20 receives information indicating the determination result. Based on the information indicating the determination result received by the communication unit 23, the information processing unit 24 displays a notification screen as shown in Figure 5 on the display unit 22 (S35). Figure 5 is a diagram showing an example of the notification screen.

[0064] Although not shown in Figure 4, the abnormality detection unit 46 does not output information indicating the detection result if it determines that there is no abnormality in the noise control. However, the abnormality detection unit 46 may output (transmit) information indicating the detection result to the user interface device 20 even if it determines that there is no abnormality in the noise control.

[0065] As described above, the active noise reduction system 10 includes an abnormality determination unit 46 that determines whether or not there is an abnormality based on at least one of the coefficient W of the adaptive filter, the update amount of the coefficient W of the adaptive filter, and the signal level of the cancellation signal. If the abnormality determination unit 46 determines that there is an abnormality, it outputs information indicating the determination result to the user interface device 20.

[0066] This allows the active noise reduction system 10 to notify the user if an abnormality occurs in noise control. When the active noise reduction device 40 generates a cancellation sound using user-specified parameters, abnormalities in noise control may be more likely to occur, but the function of the abnormality detection unit 46 makes it easier for the user to recognize when an abnormality occurs in noise control.

[0067] In step S33, the criteria for determining whether or not there is an abnormality in noise control (such as the aforementioned period, threshold, and predetermined number of times) may be changed based on whether the noise control is performed based on default parameters or user-specified parameters. Figure 6 is a flowchart of the operation for changing the determination criteria.

[0068] The abnormality determination unit 46 determines whether or not noise control is being performed based on default parameters (S36). Whether or not noise control is being performed based on default parameters can be determined, for example, by referring to information (such as flags) indicating the setting status of the parameters stored in the storage unit 44. If the abnormality determination unit 46 determines that noise control is being performed based on default parameters (Yes in S36), it adopts the first determination criterion (S37). On the other hand, if the abnormality determination unit 46 determines that noise control is being performed based on user-specified parameters rather than default parameters (No in S36), it adopts a second determination criterion that is more likely to indicate an abnormality than the first determination criterion (S38).

[0069] For example, if the first criterion is that the abnormality detection parameter remains above a threshold for a certain period of time, then in the second criterion, the threshold will be set to a smaller value than the first criterion, or the period will be set to be shorter than the first criterion. Also, if the first criterion is that the abnormality detection parameter exceeds a threshold a predetermined number of times within a certain period, then in the second criterion, the threshold will be set to a smaller value than the first criterion, the predetermined number of times will be set to be fewer than the first criterion, or the period will be set to be longer than the first criterion.

[0070] In this way, while a cancellation signal is being generated using user-specified parameters, the abnormality detection unit 46 changes the criteria for determining whether or not there is an abnormality to a more likely value than when a cancellation signal is being generated using default parameters. As a result, the active noise reduction system 10 can suppress the generation of abnormal noise early (with sufficient time) even if the user-specified parameters are not appropriate.

[0071] Conversely, the anomaly detection unit 46 may change the criteria for determining whether an anomaly exists while a cancellation signal is being generated using user-specified parameters, so that it becomes less likely to determine that an anomaly exists. This makes it less likely for notifications of an anomaly to occur, and makes it easier for the user to perceive (not by notification) that an anomaly has occurred based on user-specified parameters.

[0072] Furthermore, at least one of the first and second criteria (i.e., the criterion for determining whether or not there is an abnormality) may be set based on the user's operation of the user interface device 20.

[0073] [Failsafe operation] Furthermore, the active noise reduction device 40 may perform fail-safe processing in lieu of, or in addition to, notifying the system of an abnormality in noise control. Figure 7 is a flowchart of the fail-safe operation (an operation that performs fail-safe processing when it is determined that there is an abnormality in noise control).

[0074] When the signal processing unit 41 of the active noise reduction device 40 generates a cancellation signal according to the basic operation described above, that is, when the filter coefficient update unit 41c updates the coefficient W of the adaptive filter (S41), the abnormality determination unit 46 acquires abnormality determination parameters related to the adaptive filter unit 41a (S42). Based on the acquired abnormality determination parameters, the abnormality determination unit 46 determines whether or not there is an abnormality (S43). The processing in steps S41 to S43 is the same as the processing in steps S31 to S33 in the abnormality notification operation (Figure 4), so a detailed explanation is omitted.

[0075] If the abnormality detection unit 46 determines that there is an abnormality in the noise control (Yes in S43), it performs fail-safe processing (S44). As fail-safe processing, the abnormality detection unit 46 performs processing to stop the output of the cancellation sound. For example, the abnormality detection unit 46 stops the output of the cancellation sound by fixing the coefficient W of the adaptive filter to 0 (i.e., setting the amplitude of the cancellation signal to 0).

[0076] Furthermore, the abnormality detection unit 46 may perform a fail-safe process to reset the coefficient W of the adaptive filter to its initial value (0 or a predetermined value). The abnormality detection unit 46 may also perform a fail-safe process to reduce the leak coefficient or to reduce the step size parameter.

[0077] On the other hand, if the abnormality detection unit 46 determines that there is no abnormality in the noise control (No in S43), it does not perform fail-safe processing. In this case, normal noise control (updating the filter coefficient W) continues.

[0078] Thus, when the abnormality detection unit 46 determines that there is an abnormality in the noise control, it performs a fail-safe process, which includes at least one of the following: stopping the output of the cancellation sound and resetting the coefficient W of the adaptive filter.

[0079] This allows the active noise reduction system 10 to suppress the cancellation sound from becoming an abnormal noise when noise control is being performed.

[0080] Furthermore, the time from the moment in step S43 when an abnormality is determined in the noise control to the moment in step S44 when the fail-safe process is performed may be changed depending on whether the noise control is performed based on default parameters or user-specified parameters. Figure 8 is a flowchart of the operation for changing the timing of the fail-safe process.

[0081] The abnormality determination unit 46 determines whether noise control is performed based on default parameters (S46). Whether noise control is performed based on default parameters can be determined, for example, by referring to information (such as flags) indicating the parameter setting status stored in the memory unit 44. If the abnormality determination unit 46 determines that noise control is performed based on default parameters (Yes in S46), it executes failsafe processing after a first time has elapsed since the abnormality was determined (S47). On the other hand, if the abnormality determination unit 46 determines that noise control is performed based on user-specified parameters rather than default parameters (No in S46), it executes failsafe processing after a second time has elapsed since the abnormality was determined (S48). The second time is, for example, a longer time than the first time.

[0082] In this way, the abnormality detection unit 46 extends the time from when an abnormality is detected until the failsafe process is performed, while a cancellation signal is being generated using user-specified parameters, compared to when a cancellation signal is being generated using default parameters. By deliberately making the noise control slightly unstable, the effect is obtained that makes it easier for the user to perceive that an abnormality has occurred due to the user-specified parameters.

[0083] Furthermore, at least one of the first time and the second time (i.e., the time from when an abnormality is detected until fail-safe processing is performed) may be set based on the user's operation of the user interface device 20.

[0084] [Noise reduction effect calculation process] Furthermore, the active noise reduction device 40 can calculate the extent to which noise is reduced by the cancellation sound (hereinafter also referred to as the noise reduction effect) and notify the user of the calculation result. Figure 9 is a sequence diagram of this noise reduction effect notification operation.

[0085] When the signal processing unit 41 of the active noise reduction device 40 generates a cancellation signal according to the basic operation described above, that is, when the filter coefficient update unit 41c updates the coefficient W of the adaptive filter (S51), the effect calculation unit 47 generates a corrected cancellation signal by multiplying the cancellation signal by a simulated transfer function (S52). The corrected cancellation signal can be said to be a signal that indicates the state of the cancellation sound at the position of the error signal source 53.

[0086] Next, the effect calculation unit 47 acquires the error signal output by the error signal source 53 (S53). The error signal can be said to be a signal that indicates the combined state of noise and cancellation sound at the location of the error signal source 53.

[0087] Next, the effect calculation unit 47 generates a noise signal by subtracting the corrected cancellation signal from the error signal (S54). The noise signal can be said to be a signal that indicates the noise state at the location of the error signal source 53 (assuming that the cancellation sound was not output).

[0088] Next, the effect calculation unit 47 calculates the noise reduction effect based on the difference between the noise signal generated in step S54 and the error signal acquired in step S53 (S55). Since a larger difference between the noise signal and the error signal indicates a higher noise reduction effect, the effect calculation unit 47 can score the noise reduction effect according to the magnitude of the difference.

[0089] Next, the effect calculation unit 47 outputs (transmits) information indicating the calculated noise reduction effect (score) to the user interface device 20 via the information processing unit 43 and the communication unit 42 (S56).

[0090] The communication unit 23 of the user interface device 20 receives information indicating the noise reduction effect. Based on the information indicating the noise reduction effect received by the communication unit 23, the information processing unit 24 displays a notification screen as shown in Figure 10 on the display unit 22 (S57). Figure 10 is a diagram showing an example of the notification screen. Note that on the notification screen, the specific amount of noise reduction may be displayed in dB (decibels).

[0091] As described above, the active noise reduction system 10 includes an effect calculation unit 47 that calculates the noise reduction effect due to the cancellation sound, and the effect calculation unit 47 outputs information indicating the calculated noise reduction effect to the user interface device 20.

[0092] This allows the active noise reduction system 10 to notify the user of the extent of the noise reduction effect. When the active noise reduction device 40 generates a cancellation sound using user-specified parameters, it may be difficult to determine whether or not a noise reduction effect has been achieved. However, the function of the effect calculation unit 47 helps the user understand the noise reduction effect.

[0093] [Uploading user-specified parameters] The user can upload user-specified parameters to the server device 30. Figure 11 is a sequence diagram of the user-specified parameter upload operation.

[0094] First, the user performs an operation to upload user-specified parameters to the operation reception unit 21 of the user interface device 20 (hereinafter also referred to as the upload operation), and the operation reception unit 21 accepts the upload operation (S61). When the information processing unit 24 receives the upload operation from the operation reception unit 21, it sends an upload request to the active noise reduction device 40 using the communication unit 23, requesting that the user-specified parameters be uploaded (S62).

[0095] The communication unit 42 of the active noise reduction device 40 receives an upload request. The acquisition unit 45 acquires the upload request (S63), and the information processing unit 43 transmits upload information, including user-specified parameters, to the server device 30 using the communication unit 42 based on the acquired upload request (S64). At this time, the information processing unit 43 may include, in addition to user-specified parameters, user identification information (user name), the noise reduction effect obtained by the user-specified parameters, and the stability of noise control by the user-specified parameters in the upload information. The noise reduction effect is calculated by the effect calculation unit 47. The stability of noise control is determined, for example, by the frequency with which the abnormality determination unit 46 determines an abnormality.

[0096] The communication unit 31 of the server device 30 receives the upload information. The information processing unit 32 stores the upload information received by the communication unit 31 in the storage unit 33 (S65).

[0097] In this way, users can upload user-specified parameters to the server device 30. Although not shown in the diagram, other users can also upload user-specified parameters they have created to the server device 30.

[0098] For example, manufacturers and distributors of the active noise reduction device 40, and manufacturers and distributors of the vehicles 50 on which the active noise reduction device 40 is installed, can collect user-specified parameters from a large number of users by managing the server device 30 (or entrusting the management of the server device 30 to a server management company), and accumulate know-how by analyzing the collected user-specified parameters. This enables manufacturers and distributors of the active noise reduction device 40, and manufacturers and distributors of the vehicles 50, to develop active noise reduction devices 40 that can control noise with even greater precision.

[0099] In the example shown in Figure 11, the upload information was transmitted from the active noise reduction device 40 to the server device 30, but the communication path for transmitting the upload information is not particularly limited. For example, the user interface device 20 may receive user-specified parameters from the active noise reduction device 40 and transmit the received user-specified parameters to the server device 30. If the upload information (user-specified parameters) is already stored in the user interface device 20, communication between the user interface device 20 and the active noise reduction device 40 can be omitted, and the upload information can be transmitted from the user interface device 20 to the server device 30.

[0100] [Download operation of user-specified parameters] According to the user-specified parameter upload operation described above, the user and several other users can upload user-specified parameters to the server device 30. Then, the user can download and use user-specified parameters created by other users from the server device 30. Figure 12 is a sequence diagram of the user-specified parameter download operation.

[0101] The display unit 22 of the user interface device 20 displays a download screen for user-specified parameters (S71). Figure 13 shows an example of the download screen for user-specified parameters. In the download screen of Figure 13, user-specified parameters stored in the storage unit 33 of the server device 30 are displayed in a list. More specifically, in the download screen of Figure 13, multiple user-specified parameters stored in the storage unit 33 of the server device 30 are displayed in a ranking format in descending order of the number of downloads. Note that the multiple user-specified parameters here are parameters that apply to the same type of vehicle 50 (same vehicle model).

[0102] The user performs an operation to download user-specified parameters (hereinafter also referred to as the download operation) to the operation reception unit 21 of the user interface device 20, and the operation reception unit 21 accepts the download operation (S72). The download operation includes a selection operation to select one of several user-specified parameters.

[0103] When the information processing unit 24 receives a download operation from the operation reception unit 21, it sends a download request to the server device 30 using the communication unit 23, requesting that the selected user-specified parameters be downloaded (S73).

[0104] The communication unit 31 of the server device 30 receives a download request. Based on the received download request, the parameter provision unit 34 transmits download information, including the user-specified parameters selected by the selection operation described above, to the active noise reduction device 40 using the communication unit 31 (S74). In other words, the parameter provision unit 34 provides the selected user-specified parameters to the active noise reduction device 40.

[0105] The communication unit 42 of the active noise reduction device 40 receives download information. The acquisition unit 45 acquires the download information (S75) and reflects the user-specified parameters included in the acquired download information to the signal processing unit 41. The signal processing unit 41 generates a cancellation signal using the downloaded user-specified parameters (S76).

[0106] Thus, the active noise reduction system 10 includes a storage unit 33 that stores multiple user-specified parameters of multiple users other than the user, and a parameter provision unit 34 that provides one of the multiple user-specified parameters to the signal processing unit 41 based on the user's selection operation to the user interface device 20. When a selection operation is performed, the multiple user-specified parameters are displayed in a ranking format on the display unit 22. This allows the user to apply user-specified parameters created by other users to the active noise reduction device 40.

[0107] In the example shown in Figure 12, the download information was transmitted from the server device 30 to the active noise reduction device 40, but the communication path for transmitting the download information is not particularly limited. For example, the user interface device 20 may receive the download information from the server device 30 and transmit the received download information to the active noise reduction device 40. When transmitting the download information from the user interface device 20 to the active noise reduction device 40, for example, the procedure shown in the sequence diagram of Figure 3 may be used.

[0108] [Modified example 1 of the functional configuration of an active noise reduction system] In the above embodiment, the substantial information processing related to the generation of cancellation sounds was performed by the active noise reduction device 40. In other words, the active noise reduction system 10 was realized by the active noise reduction device 40, which includes a signal processing unit 41. The substantial information processing related to the generation of cancellation sounds may also be performed by the user interface device 20. Figure 14 is a diagram showing the functional configuration of the active noise reduction system according to Modification 1.

[0109] As shown in Figure 14, the active noise reduction system 10a comprises a user interface device 20a, a server device 30a, an active noise reduction device 40a, a reference signal source 51, a cancellation sound source 52, and a plurality of error signal sources 53. In the active noise reduction system 10a, the user interface device 20a includes a signal processing unit 26, and the information processing unit 24 includes an acquisition unit 27. In other words, in the active noise reduction system 10a, the processing described as being performed by the active noise reduction device 40 in the active noise reduction system 10 is performed by the user interface device 20a. Specifically, in the above embodiment, the signal processing unit 41 and the acquisition unit 45 may be read as the signal processing unit 26 and the acquisition unit 27.

[0110] In this case, the active noise reduction device 40a functions as a communication interface device for the reference signal source 51, the cancellation sound source 52, and the multiple error signal sources 53.

[0111] Thus, the active noise reduction system 10a can be realized by a user interface device 20a that includes a signal processing unit 26 and a signal acquisition unit 27.

[0112] [Modified configuration of the active noise reduction system, part 2] Furthermore, the substantial information processing related to the generation of cancellation sounds may be performed by the server device 30. Figure 15 is a diagram showing the functional configuration of the active noise reduction system according to the modified example 2.

[0113] As shown in Figure 15, the active noise reduction system 10b comprises a user interface device 20b, a server device 30b, an active noise reduction device 40b, a reference signal source 51, a cancellation sound source 52, and a plurality of error signal sources 53. In the active noise reduction system 10b, the server device 30b includes a signal processing unit 35, and the information processing unit 32 includes an acquisition unit 36. In other words, in the active noise reduction system 10b, the processing described as being performed by the active noise reduction device 40 in the active noise reduction system 10 is performed by the server device 30b. Specifically, in the above embodiment, the signal processing unit 41 and the acquisition unit 45 may be read as the signal processing unit 35 and the acquisition unit 36.

[0114] In this case, the active noise reduction device 40b functions as a communication interface device for the reference signal source 51, the cancellation sound source 52, and the multiple error signal sources 53.

[0115] Thus, the active noise reduction system 10b can be realized by a server device 30b that includes a signal processing unit 35 and a signal acquisition unit 36.

[0116] [Differential examples of signal processing] Furthermore, the signal processing unit 41 may be configured as shown in Figure 16. Figure 16 is a diagram showing the functional configuration of the signal processing unit 41 according to a modified example.

[0117] As shown in Figure 16, the signal processing unit 41f specifically comprises an adaptive filter unit 41a, a simulated acoustic transmission characteristic filter unit 41b, a filter coefficient update unit 41c, gain adjustment units 41d1 to 41d3, Fourier transform units 41g1 to 41g3, and an inverse Fourier transform unit 41h.

[0118] The Fourier transform unit 41g1 performs an FFT (Fast Fourier Transform) on the reference signal input to the signal processing unit 41, which has been gain-adjusted by the gain adjustment unit 41d1.

[0119] The Fourier transform unit 41g2 (or Fourier transform unit 41g3) performs an FFT on the error signal output by the error signal source 53, which has been gain-adjusted by the gain adjustment unit 41d2 (or gain adjustment unit 41d3).

[0120] The filter coefficient update unit 41c calculates the coefficients of the adaptive filter for each frequency component using (Equation 1), (Equation 2), or (Equation 3).

[0121] The adaptive filter section 41a multiplies each frequency component of the reference signal by the filter coefficients, and the inverse Fourier transform section 41h performs an IFFT (Inverse Fast Fourier Transform) on the filter coefficients to output the coefficients of the FIR filter. The adaptive filter section 41a outputs a cancellation signal by convolving the time-domain reference signal onto the coefficients of the FIR filter.

[0122] In the signal processing unit 41f described above, the step size parameter can be considered as a vector composed of multiple elements corresponding to multiple frequency components. Although the signal processing unit 41f does not have BPFs 41e1 to 41e3, adjustment equivalent to that of BPFs 41e1 to 41e3 can be achieved by adjusting the step size parameter.

[0123] Furthermore, the signal processing unit 26 and signal processing unit 35 may also be configured in the same way as the signal processing unit 41f.

[0124] [Effects, etc.] The following describes examples of technologies that can be obtained from the disclosures in this specification, and explains the effects and other benefits that can be obtained from such technologies.

[0125] Technology 1 is an active noise reduction device 40 comprising a signal processing unit 41 that generates a cancellation signal for outputting a cancellation sound to reduce noise in the space inside a vehicle 50, the signal processing unit 41 that generates a cancellation signal by applying an adaptive filter, whose coefficients are updated based on an error signal indicating the state of the noise when the cancellation sound is being output, to a reference signal correlated with the noise, and a communication unit 42 that receives a change request requesting to change the parameters related to the generation of the cancellation signal to user-specified parameters specified by the user, the signal processing unit 41 generating a cancellation signal using the user-specified parameters based on the received change request. The vehicle 50 is an example of a mobile device.

[0126] Such an active noise reduction device 40 can reduce noise in the space inside the vehicle 50 using user-specified parameters. In other words, the active noise reduction device 40 can adjust the parameters used to generate the cancellation signal.

[0127] Technology 2 is an active noise reduction device 40 according to Technology 1, wherein the parameters include at least one of a gain coefficient multiplied by a reference signal, a gain coefficient multiplied by an error signal, and a step size parameter for determining the amount of update of the coefficients of the adaptive filter.

[0128] Such an active noise reduction device 40 can reduce noise in the space inside the vehicle 50 using at least one of a gain coefficient multiplied by a reference signal, a gain coefficient multiplied by an error signal, and a step size parameter for determining the update amount of the coefficients of the adaptive filter, as specified by the user.

[0129] Technology 3 is an active noise reduction device 40 of Technology 1 or 2, in which the parameters include the characteristics of the BPF applied to the reference signal and the error signal, respectively.

[0130] Such an active noise reduction device 40 can reduce noise in the space inside the vehicle 50 by using the characteristics of the BPF applied to a reference signal and an error signal specified by the user.

[0131] Technology 4 is an active noise reduction device 40 according to any of Technologies 1 to 3, wherein the signal processing unit 41 further includes an abnormality determination unit 46 that determines whether or not there is an abnormality based on at least one of the coefficient of the adaptive filter, the update amount of the coefficient of the adaptive filter, and the signal level of the cancellation signal, and the abnormality determination unit 46 outputs information indicating the determination result when it determines that there is an abnormality.

[0132] Such an active noise reduction device 40 can notify the user of whether or not there is an abnormality in noise control.

[0133] Technology 5 is an active noise reduction device 40 of Technology 4, wherein the abnormality detection unit 46 performs fail-safe processing when it determines that there is an abnormality, and the fail-safe processing includes at least one of the following: stopping the output of the cancellation sound and resetting the coefficient of the adaptive filter.

[0134] Such an active noise reduction device 40 can prevent the cancellation sound from becoming an abnormal noise through fail-safe processing.

[0135] Technology 6 is an active noise reduction device 40 of Technology 4 or 5, wherein the abnormality determination unit 46 changes the criteria for determining whether an abnormality is present to make it easier to determine that an abnormality is present while a cancellation signal is being generated using user-specified parameters.

[0136] Such an active noise reduction device 40 can suppress the generation of abnormal noise early (with sufficient time) even if the user-specified parameters are not appropriate.

[0137] Technology 7 is an active noise reduction device 40 of Technology 4 or 5, wherein the abnormality determination unit 46 changes the criteria for determining whether an abnormality is present while a cancellation signal is being generated using user-specified parameters, so as to make it less likely to determine that an abnormality exists.

[0138] Such an active noise reduction device 40 makes it easier for the user to perceive when an abnormality occurs based on user-specified parameters.

[0139] Technology 8 is an active noise reduction device 40 of Technology 5, in which the abnormality determination unit 46 extends the time from when an abnormality is determined to occur until fail-safe processing is performed, while a cancellation signal is being generated using user-specified parameters.

[0140] With this type of active noise reduction device 40, by deliberately making the noise control slightly unstable, it is possible to obtain an effect that makes it easier for the user to perceive that an abnormality is occurring due to user-specified parameters.

[0141] Technology 9 is an active noise reduction device 40 according to any of Technologies 1 to 8, wherein the signal processing unit 41 further includes an effect calculation unit 47 that calculates the noise reduction effect by the cancellation sound, and the effect calculation unit 47 outputs information indicating the calculated noise reduction effect.

[0142] Such an active noise reduction device 40 can notify the user of the noise reduction effect.

[0143] Technology 10 is an active noise reduction device 40 according to any of technologies 1 to 9, in which the communication unit 42 receives a change request output by the user interface device 20 based on user operations on the user interface device 20.

[0144] With such an active noise reduction device 40, the user can change the parameters related to the generation of the cancellation signal to user-specified parameters based on the user's operation on the user interface device 20.

[0145] Technology 11 is an active noise reduction system 10 comprising an active noise reduction device 40 of any of Technologies 1 to 10, a server device 30, and a user interface device 29, wherein the server device 30 comprises a storage unit 33 that stores multiple user-specified parameters of multiple users other than the user, and a parameter provision unit 34 that provides one of the multiple user-specified parameters to a signal processing unit 41 based on a user's selection operation to the user interface device 20.

[0146] Such an active noise reduction system 10 can reduce noise in the space inside the vehicle 50 using user-specified parameters generated by other users.

[0147] Technology 12 is an active noise reduction system 10 of Technology 11, in which multiple user-specified parameters are displayed in a ranking format on a user interface device 20.

[0148] Such an active noise reduction system 10 can assist a user in selecting one of the user-specified parameters generated by other users.

[0149] Technology 13 is a computer-based active noise reduction method. The active noise reduction method includes a first signal processing step for generating a cancellation signal to output a cancellation sound to reduce noise in the space inside a vehicle 50, which includes a first signal processing step for generating a cancellation signal by applying an adaptive filter, whose coefficients are updated based on an error signal indicating the state of the noise when the cancellation sound is being output, to a reference signal correlated with the noise; a receiving step for receiving a change request that requests to change the parameters relating to the generation of the cancellation signal to user-specified parameters specified by the user; and a second signal processing step for generating a cancellation signal using the user-specified parameters based on the received change request.

[0150] Such an active noise reduction method can reduce noise in the space inside the vehicle 50 using user-specified parameters. In other words, the active noise reduction method can adjust the parameters used to generate the cancellation signal.

[0151] (Other embodiments) Although embodiments have been described above, this disclosure is not limited to the embodiments described above.

[0152] For example, an active noise reduction system may be implemented by multiple devices (e.g., a user interface device, a server device, and an active noise reduction device), or by a single device (e.g., a single device of the user interface device, a server device, and an active noise reduction device). When an active noise reduction system is implemented by multiple devices, the components of the active noise reduction system (in particular, the functional components) may be distributed among the multiple devices in any way.

[0153] Furthermore, in the above embodiment, the active noise reduction system was a system that performed noise control based on the Filtered-X LMS algorithm, but it may also be implemented as a system that performs noise control using the SAN (Single-frequency Adaptive Notch filter) algorithm or the SAN Filtered-x LMS algorithm.

[0154] Furthermore, the active noise reduction device according to the above embodiment may be mounted on a mobile device other than a vehicle. The mobile device may be, for example, an aircraft or a ship. Moreover, this disclosure may be implemented as such a mobile device other than a vehicle.

[0155] Furthermore, the configuration of the active noise reduction device according to the above embodiment is merely an example. For instance, the active noise reduction device may include components such as a D / A converter, a filter, a power amplifier, or an A / D converter.

[0156] Furthermore, the processing performed by the active noise reduction device according to the above embodiment is merely an example. For instance, some of the digital signal processing described in the above embodiment may be implemented by analog signal processing.

[0157] Furthermore, for example, in the above embodiment, a process executed by a specific processing unit may be executed by another processing unit. Also, the order of multiple processes may be changed, or multiple processes may be executed in parallel.

[0158] Furthermore, in the above embodiment, each component may be realized by executing a software program suitable for each component. Each component may also be realized by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0159] Furthermore, in the above embodiment, each component may be implemented by hardware. For example, each component may be a circuit (or integrated circuit). These circuits may form a single circuit as a whole, or they may be separate circuits. Also, each of these circuits may be a general-purpose circuit or a dedicated circuit.

[0160] Furthermore, each component may be a circuit (or integrated circuit). These circuits may form a single circuit as a whole, or they may be separate circuits. Also, each of these circuits may be a general-purpose circuit or a dedicated circuit.

[0161] Furthermore, the general or specific embodiments of this disclosure may be implemented in systems, apparatus, methods, integrated circuits, computer programs, or non-temporary recording media such as computer-readable CD-ROMs. They may also be implemented in any combination of systems, apparatus, methods, integrated circuits, computer programs, and computer-readable non-temporary recording media.

[0162] For example, this disclosure may be implemented as an active noise reduction method performed by an active noise reduction device (computer or DSP), or as a program to cause a computer or DSP to perform the above active noise reduction method. Furthermore, this disclosure may be implemented as an application program installed on a user interface device. Also, this disclosure may be implemented as a computer-readable non-temporary recording medium on which these programs are recorded.

[0163] Furthermore, this disclosure also includes forms obtained by applying various modifications to each embodiment that a person skilled in the art could conceive, or forms realized by arbitrarily combining the components and functions of each embodiment without departing from the spirit of this disclosure. [Industrial applicability]

[0164] The active noise reduction device of this disclosure is useful, for example, as a device that can reduce noise inside a vehicle cabin. [Explanation of symbols]

[0165] 10, 10a, 10b Active noise reduction system 20, 20a, 20b User Interface Devices 21 Operation Reception Section 22 Display section 23, 31, 42 Communications Department 24, 32, 43 Information Processing Unit 25, 33, 44 Storage section 26, 35, 41, 41f Signal Processing Unit 27, 36, 45 Acquisition section 28 Abnormality determination section 29 Effect Calculation Unit 30, 30a, 30b Server devices 34 Parameter Provisioning Section 36 Acquisition Department 40, 40a, 40b Active noise reduction device 41a Adaptive filter section 41b Simulated Acoustic Transmission Characteristics Filter Section 41c Filter coefficient update section 41d1, 41d2, 41d3 Gain adjustment section 41e1, 41e2, 41e3 BPF 41g1, 41g2, 41g3 Fourier transform section 41h Inverse Fourier Transform section 50 vehicles 51 Reference signal source 52 Cancellation sound source 53 Error signal source

Claims

1. A signal processing unit that generates a cancellation signal for outputting a cancellation sound to reduce noise in the space within a mobile device, the signal processing unit that generates the cancellation signal by applying an adaptive filter, whose coefficients are updated based on an error signal indicating the state of the noise when the cancellation sound is output, to a reference signal correlated with the noise, The system includes a communication unit that receives one of several user-specified parameters from a server device that stores multiple user-specified parameters of multiple users other than the user, based on a user selection operation on the user interface device, The signal processing unit generates the cancellation signal by changing the parameters related to the generation of the cancellation signal to the received user-specified parameter. Active noise reduction device.

2. The parameters include at least one of a gain coefficient multiplied by the reference signal, a gain coefficient multiplied by the error signal, and a step size parameter for determining the update amount of the coefficients of the adaptive filter. The active noise reduction device according to claim 1.

3. The aforementioned parameters include the characteristics of the Band Pass Filter (BPF) applied to the reference signal and the error signal, respectively. The active noise reduction device according to claim 1.

4. The signal processing unit further includes an abnormality determination unit that determines whether or not there is an abnormality based on at least one of the coefficient of the adaptive filter, the update amount of the coefficient of the adaptive filter, and the signal level of the cancellation signal. The abnormality detection unit outputs information indicating the detection result when it determines that an abnormality exists. The active noise reduction device according to claim 1.

5. If the abnormality detection unit determines that an abnormality exists, it performs fail-safe processing. The fail-safe process includes at least one of the following: stopping the output of the cancellation sound and resetting the coefficients of the adaptive filter. The active noise reduction device according to claim 4.

6. The abnormality determination unit modifies the criteria for determining whether an abnormality exists while the cancellation signal is being generated using the user-specified parameters, so that it is more likely to determine that an abnormality exists. The active noise reduction device according to claim 4.

7. The abnormality determination unit modifies the criteria for determining whether an abnormality exists while the cancellation signal is being generated using the user-specified parameters, so as to make it less likely to determine that an abnormality exists. The active noise reduction device according to claim 4.

8. The abnormality detection unit extends the time from when an abnormality is detected until the failsafe process is performed, while the cancellation signal is being generated using the user-specified parameters. The active noise reduction device according to claim 5.

9. The signal processing unit further includes an effect calculation unit that calculates the noise reduction effect due to the cancellation sound, The effect calculation unit outputs information indicating the calculated noise reduction effect. The active noise reduction device according to claim 1.

10. An active noise reduction device according to any one of claims 1 to 9, The server device and, The user interface device is provided, The server device is A storage unit that stores the aforementioned multiple user-specified parameters, The system comprises a parameter providing unit that provides one of the user-specified parameters from among the plurality of user-specified parameters to the signal processing unit based on the user's selection operation to the user interface device. Active noise reduction system.

11. The user-specified parameters are displayed in a ranking format on the user interface device. The active noise reduction system according to claim 10.

12. A computer-based active noise reduction method, A first signal processing step for generating a cancellation signal for outputting a cancellation sound to reduce noise in the space within a mobile device, the first signal processing step for generating the cancellation signal by applying an adaptive filter, whose coefficients are updated based on an error signal indicating the state of the noise when the cancellation sound is being output, to a reference signal correlated with the noise, The steps include receiving one user-specified parameter from a server device that stores multiple user-specified parameters of multiple users other than the user, based on a user selection operation on the user interface device, The process includes a second signal processing step of generating the cancellation signal by changing the parameters related to the generation of the cancellation signal to the received user-specified parameter. Active noise reduction method.

Images