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

Abstract

The active noise reduction device (10) comprises: a reference signal input terminal (11) to which a reference signal is input from a reference signal source (51) installed in a vehicle (50); a simulated vibration transfer characteristic filter unit (15) which generates a second signal obtained by correcting a first signal using a simulated vibration transfer characteristic, the first signal being used to output a sound different from a cancelling sound from a speaker (52) installed in the vehicle (50), the simulated vibration transfer characteristic being obtained by simulating a vibration transfer characteristic from the speaker (52) to the reference signal source (51); a first subtraction unit (16) which outputs a corrected reference signal obtained by subtracting the generated second signal from the reference signal input to the reference signal input terminal (11); and an adaptive filter unit (17) which generates a cancelling signal used to output the cancelling sound by applying an adaptive filter to the corrected reference signal output from the first subtraction unit (16).

Description

Technical Field

[0001] The present disclosure relates to an active noise reduction device that actively reduces noise by interfering with canceling sound, a mobile device including the active noise reduction device, and an active noise reduction method. Background Art

[0002] Conventionally, active noise reduction devices are known (for example, see Patent Document 1). These devices actively reduce noise by using a reference signal correlated with the noise and an error signal based on the residual sound resulting from interference between the noise and the canceling sound within a predetermined space. This outputs a canceling sound from a canceling sound source to cancel the noise. The active noise reduction device updates an adaptive filter based on a coefficient update algorithm and convolves the reference signal with the adaptive filter to generate a canceling signal for outputting the canceling sound.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 10-207470 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] In an active noise reduction device, when a reference signal includes a signal component of a sound other than noise, such as music, the sound other than noise may also be reduced.

[0008] The present disclosure provides an active noise reduction device capable of suppressing sounds other than noise from being reduced.

[0009] Solutions for solving problems

[0010] An active noise reduction device according to one embodiment of the present disclosure includes: a reference signal input unit to which is input a reference signal correlated with noise in a space within a mobile device and output by a reference signal source installed in the mobile device; a simulated vibration transfer characteristic filter unit to generate a second signal obtained by correcting a first signal using a simulated vibration transfer characteristic, the first signal being used to output a sound different from a canceling sound for reducing the noise from a speaker installed in the mobile device, the simulated vibration transfer characteristic being obtained by simulating a vibration transfer characteristic from the speaker to the reference signal source; a first subtraction unit to output a corrected reference signal obtained by subtracting the generated second signal from the reference signal input to the reference signal input unit; and an adaptive filter unit to generate a canceling signal used to output the canceling sound by applying an adaptive filter to the corrected reference signal output from the first subtraction unit.

[0011] Effects of the Invention

[0012] The active noise reduction device of the present disclosure can suppress sounds other than noise from being reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic diagram showing a vehicle equipped with the active noise reduction device according to the first embodiment as viewed from above.

[0014] Figure 2 This is a block diagram showing the functional configuration of the active noise reduction device according to the first embodiment.

[0015] Figure 3 This is a flowchart of the operation of the active noise reduction device according to the first embodiment.

[0016] Figure 4A This is a first block diagram showing the functional configuration of the active noise reduction device according to the second embodiment.

[0017] Figure 4B This is a second block diagram showing the functional configuration of the active noise reduction device according to the second embodiment.

[0018] Figure 5 This is a flowchart of the operation of the abnormality determination unit included in the active noise reduction device according to the second embodiment. DETAILED DESCRIPTION

[0019] Below, the embodiment is described in detail with reference to the accompanying drawings. In addition, the embodiment described below shows general or specific examples. The numerical values, shapes, materials, components, configuration positions of components, connection methods, steps, order of steps, etc. shown in the following embodiment are examples and are not intended to limit the present disclosure. In addition, for the components in the following embodiment that are not recorded in the independent claims, they are described as arbitrary components.

[0020] In addition, each figure is a schematic diagram and does not necessarily illustrate the true image. In addition, in each figure, substantially the same structure is marked with the same reference numeral, and the repeated description is sometimes omitted or simplified.

[0021] (Implementation 1)

[0022] [Structure of a vehicle equipped with active noise cancellation]

[0023] In the first embodiment, an active noise reduction device mounted on a vehicle will be described. Figure 1 This is a schematic diagram showing a vehicle equipped with the active noise reduction device according to the first embodiment as viewed from above.

[0024] Vehicle 50 is an example of a mobile device and includes active noise reduction device 10 according to Embodiment 1, a reference signal source 51, a speaker 52, an error signal source 53, an external sound source 54, a vehicle body 55, and four wheels 57. Specifically, vehicle 50 is an automobile, but the present invention is not particularly limited thereto.

[0025] The reference signal source 51 is a transducer that outputs a reference signal that is correlated with the noise in the space 56 inside the vehicle 50. The noise here also includes vibration. In the first embodiment, the reference signal source 51 is an acceleration sensor and is arranged outside the space 56. Figure 1 In the example, reference signal source 51 is mounted on the subframe near the left front wheel, but it can also be mounted on a tire cover or steering knuckle, etc. The mounting location of reference signal source 51 is not particularly limited. Alternatively, reference signal source 51 can be a microphone. Furthermore, the active noise reduction device 10 primarily targets road noise, for example. Because the propagation path of road noise is complex, using an acceleration sensor as reference signal source 51 is useful.

[0026] Speaker 52 uses the canceling signal to output canceling sound to space 56. Speaker 52 also uses the first signal output from external sound source 54 to output music or the like to space 56. ANC device 10 may use multiple speakers 52, and the installation locations of speakers 52 are not particularly limited.

[0027] Error signal source 53 detects residual sound resulting from interference between noise and canceling sound in space 56 and outputs an error signal based on the residual sound. Error signal source 53 is a transducer such as a microphone and is preferably installed in space 56, such as on a ceiling. Vehicle 50 may also include multiple error signal sources 53.

[0028] The external sound source 54 is, for example, an audio reproduction device that outputs an audio signal for allowing the listener to enjoy music in the space 56. The external sound source 54 is an active noise reduction device other than the active noise reduction device 10, and may be a cancellation signal output by the other active noise reduction device. Other active noise reduction devices, for example, refer to devices that reduce the roar of the engine based on a signal that is correlated with the engine speed. In addition, the external sound source 54 is a device that generates a sound source for ASC (Active Sound Control) and can output a signal used for ASC. The external sound source 54 can output a warning sound (buzzer sound, etc.) signal related to the usage status of the vehicle 50. The signal output from the external sound source 54 is also recorded as the first signal.

[0029] The vehicle body 55 is a structure composed of the chassis and body of the vehicle 50. The vehicle body 55 forms a space 56 (vehicle interior space) in which the speaker 52, the error signal source 53, and the external sound source 54 are arranged.

[0030] [Structure of active noise reduction device]

[0031] Next, the structure of the active noise reduction device 10 will be described. Figure 2 is a block diagram showing the functional structure of the active noise reduction device 10 .

[0032] like Figure 2 As shown, the active noise reduction device 10 includes: a reference signal input terminal 11, a cancellation signal output terminal 12, an error signal input terminal 13, an external signal input terminal 14, a simulated vibration transfer characteristic filter unit 15, a first subtraction unit 16, an adaptive filter unit 17, a signal adjustment unit 18, an addition unit 19, a first simulated sound transfer characteristic filter unit 20, a second subtraction unit 21, a second simulated sound transfer characteristic filter unit 22, a filter coefficient update unit 23 and a storage unit 24.

[0033] The reference signal input terminal 11 , the cancel signal output terminal 12 , the error signal input terminal 13 , and the external signal input terminal 14 are each a terminal formed of metal or the like, for example.

[0034] The analog vibration transfer characteristic filter unit 15, the first subtraction unit 16, the adaptive filter unit 17, the signal adjustment unit 18, the addition unit 19, the first analog sound transfer characteristic filter unit 20, the second subtraction unit 21, the second analog sound transfer characteristic filter unit 22 and the filter coefficient update unit 23 (hereinafter also referred to as the analog vibration transfer characteristic filter unit 15, etc.) are implemented by executing software through a processor such as a DSP (Digital Signal Processor) or a microcomputer.

[0035] The simulated vibration transfer characteristic filter unit 15 and the like can also be implemented using hardware such as circuits. Alternatively, a portion of the simulated vibration transfer characteristic filter unit 15 and the like can be implemented using software, while another portion can be implemented using hardware. For example, the first subtraction unit 16 and the second subtraction unit 21 can be implemented using a subtraction circuit using an operational amplifier or the like. Furthermore, the addition unit 19 can be implemented using an addition circuit using an operational amplifier or the like.

[0036] The storage unit 24 is a storage device that stores the simulated vibration transfer characteristics, simulated sound transfer characteristics, and other parameters described later. Specifically, the storage unit 24 is implemented using a semiconductor memory or the like. Furthermore, if the simulated vibration transfer characteristic filter unit 15 and the like are implemented using a processor such as a DSP, the storage unit 24 also stores a control program executed by the processor. The storage unit 24 may also store other parameters used in signal processing performed by the simulated vibration transfer characteristic filter unit 15 and the like.

[0037] Furthermore, the active noise reduction device 10 and the external sound source 54 can also be implemented as an active noise reduction system 30. Specifically, the active noise reduction system 30 is an in-vehicle infotainment (IVI) device or an audio amplifier. The active noise reduction device 10 and the IVI device or audio amplifier can be configured as separate units and connected using vehicle wiring, or they can be integrated into a single system.

[0038] [action]

[0039] In space 56 within vehicle 50, speaker 52 outputs a composite sound N1, which is a combination of a cancelling sound and a sound from an external sound source 54, such as music, which is different from the cancelling sound. Since the cancelling sound is used to reduce noise N0, the sound from external sound source 54 is preferably not reduced. However, when the vibration of speaker 52 when outputting composite sound N1 is transmitted to reference signal source 51 (acceleration sensor) via a structure such as vehicle body 55, the reference signal contains a signal component correlated with the sound from external sound source 54. As a result, the cancelling sound may be reduced, and even the sound from external sound source 54 may be reduced.

[0040] To address this problem, the active noise reduction device 10 is configured so that the canceling sound does not reduce the sound from the external sound source 54. Figure 2 In addition, refer to Figure 3 The operation of the active noise reduction device 10 will be described. Figure 3 1 is a flowchart of the operation of the active noise reduction device 10 .

[0041] The simulated vibration transfer characteristic filter unit 15 generates a second signal (S11) by correcting the first signal input from the external sound source 54 to the external signal input terminal 14 using the simulated vibration transfer characteristic. The simulated vibration transfer characteristic is a transfer characteristic obtained by simulating the vibration transfer characteristic from the position of the speaker 52 to the position of the reference signal source 51. The simulated vibration transfer characteristic is actually measured after the reference signal source 51 and the speaker 52 are installed in the vehicle 50 and stored in the storage unit 24. The simulated vibration transfer characteristic filter unit 15 reads the simulated vibration transfer characteristic stored in the storage unit 24 and uses it.

[0042] The first subtraction unit 16 subtracts the generated second signal from the reference signal input to the reference signal input terminal 11 and outputs a corrected reference signal obtained by the subtraction ( S12 ).

[0043] The adaptive filter unit 17 generates a cancellation signal by convolving the corrected reference signal output from the first subtraction unit 16 with an adaptive filter ( S13 ). The adaptive filter unit 17 is implemented by a so-called FIR filter or IIR filter. The generated cancellation signal is output to the signal adjustment unit 18 .

[0044] The signal adjustment unit 18 adjusts the cancellation signal generated by the adaptive filter unit 17 through signal processing (S14). For example, the signal adjustment unit 18 performs signal processing such as multiplying the cancellation signal by a gain. The adjusted cancellation signal is output to the adder 19. Alternatively, the signal adjustment unit 18 may be omitted. In this case, the cancellation signal generated by the adaptive filter unit 17 is output to the adder 19.

[0045] The adding unit 19 adds the adjusted canceling signal to the first signal input from the external sound source 54 to the external signal input terminal 14 (S15). The canceling signal to which the first signal is added is output to the speaker 52 via the canceling signal output terminal 12. As a result, the speaker 52 outputs a synthesized sound N1, which is a combination of the canceling sound for reducing the noise N0 and the sound from the external sound source 54.

[0046] The first simulated sound transfer characteristic filter unit 20 generates a third signal (S16) by correcting the first signal input from the external sound source 54 to the external signal input terminal 14 using the first simulated sound transfer characteristic. The first simulated sound transfer characteristic is a transfer characteristic that simulates the sound transfer characteristic in the space 56. More specifically, the first simulated sound transfer characteristic is a transfer characteristic that simulates the sound transfer characteristic from the position of the speaker 52 to the position of the error signal source 53. The first simulated sound transfer characteristic is, for example, actually measured in advance in the space 56 and stored in the storage unit 24. The first simulated sound transfer characteristic filter unit 20 reads out the first simulated sound transfer characteristic stored in the storage unit 24 and uses it.

[0047] Second subtraction unit 21 subtracts the generated third signal from the error signal input to error signal input terminal 13 and outputs the corrected error signal obtained by this subtraction (S17). The error signal input to error signal input terminal 13 corresponds to the residual sound generated by the interference between synthesized sound N1 (including the canceling sound) and noise N0, and is output by error signal source 53.

[0048] The second simulated sound transfer characteristic filter unit 22 generates a filtered reference signal (S18) obtained by correcting the corrected reference signal output from the first subtraction unit 16 using the second simulated sound transfer characteristic. The second simulated sound transfer characteristic is a transfer characteristic obtained by simulating the sound transfer characteristic in the space 56. More specifically, the second simulated sound transfer characteristic is a characteristic from immediately after the output of the adaptive filter unit 17 to the input of the filter coefficient update unit, and is a transfer characteristic obtained by simulating the sound transfer characteristic from the position of the speaker 52 to the position of the error signal source 53, including the characteristics of the signal adjustment unit. The second simulated sound transfer characteristic is actually measured in advance in the space 56 and stored in the storage unit 24. The second simulated sound transfer characteristic filter unit 22 reads the second simulated sound transfer characteristic stored in the storage unit 24 and uses it.

[0049] The second analog sound transfer characteristic may be the same as the first analog sound transfer characteristic, or it may be different from the first analog sound transfer characteristic. In the absence of signal adjustment unit 18, the second analog sound transfer characteristic is made the same as the first analog sound transfer characteristic, and the analog sound transfer characteristic stored in storage unit 24 is shared by both the first and second analog sound transfer characteristics.

[0050] The filter coefficient updating unit 23 sequentially updates the coefficient W of the adaptive filter using the corrected error signal output from the second subtracting unit 21 and the filter reference signal generated by the second pseudo-sound transfer characteristic filter unit 22 ( S19 ).

[0051] Specifically, the filter coefficient update unit 23 uses the LMS (Least Mean Square) method to calculate the adaptive filter coefficients W so as to minimize the sum of squares of the corrected error signal, and outputs the calculated adaptive filter coefficients to the adaptive filter unit 17. Furthermore, the filter coefficient update unit 23 sequentially updates the adaptive filter coefficients. When the vector of the corrected error signal is represented by e and the vector of the filtered reference signal is represented by R, the adaptive filter coefficients W are expressed by the following (Equation 1). Furthermore, n is a natural number representing the nth sample in terms of the sampling period Ts. μ is a scalar parameter that determines the step size parameter for determining the update amount of the adaptive filter coefficients W for each sampling.

[0052] [Formula 1]

[0053] W(n+1)=W(n)-μ·e(n)·R(n)··(Formula 1)

[0054] Furthermore, the filter coefficient updating unit 23 may update the coefficient W of the adaptive filter using a method other than the LMS method.

[0055] As described above, the active noise reduction device 10 includes the simulated vibration transfer characteristic filter unit 15 and the first subtraction unit 16 as components for reducing signal components contained in the reference signal that are correlated with the sound from the external sound source 54. Furthermore, the active noise reduction device 10 includes the first simulated sound transfer characteristic filter unit 20 and the second subtraction unit 21 as components for reducing signal components contained in the error signal that are correlated with the sound from the external sound source 54. This active noise reduction device 10 can suppress the cancellation sound from reducing the sound from the external sound source 54, thereby effectively reducing the noise N0.

[0056] In addition, in embodiment 1, the canceling sound and the sound based on the external sound source 54 are output from the same speaker 52, but they can also be output from different speakers. For example, the sound based on the external sound source 54 can be output from the first speaker, and the canceling sound can be output from the second speaker different from the first speaker. In this case, the active noise reduction device 10 does not include the adding unit 19. In addition, in this case, the simulated vibration transfer characteristic is a transfer characteristic obtained by simulating the vibration transfer characteristic from the position of the first speaker to the position of the reference signal source 51 including the signal adjustment unit 18. The first simulated sound transfer characteristic is a transfer characteristic obtained by simulating the sound transfer characteristic from the position of the first speaker to the position of the error signal source 53, and the second simulated sound transfer characteristic is a transfer characteristic obtained by simulating the sound transfer characteristic from the position of the second speaker to the position of the error signal source 53.

[0057] (Implementation Method 2)

[0058] [Structure of the Active Noise Cancellation Device According to Embodiment 2]

[0059] In the first embodiment, a simplest active noise reduction device 10 is described, in which the (number of reference signal sources - number of loudspeakers - number of error signal sources) is (1-1-1). However, in practice, in many cases, the number of reference signal sources, the number of loudspeakers, and the number of error signal sources are each multiple. Therefore, in the second embodiment, the structure of such an active noise reduction device is described. Figure 4A and Figure 4B This is a block diagram showing the functional configuration of the active noise reduction device according to the second embodiment. Figure 4A and Figure 4B It was originally one picture, but was split into two pictures due to size limitations. Figure 4A (a)~(d) and Figure 4B In the following second embodiment, detailed descriptions of matters that have already occurred will be omitted.

[0060] like Figure 4A and Figure 4B As shown, in the active noise reduction device 40 according to Embodiment 2, (the number of reference signal sources - the number of speakers - the number of error signal sources) is (2-2-2). In addition, the number of external sound sources is also 2. Therefore, the active noise reduction device 40 includes 2 reference signal input terminals, 2 cancellation signal output terminals, 2 error signal input terminals, and 2 external signal input terminals. Figure 4A and Figure 4B In the diagram, terminals are indicated by white circles.

[0061] In addition, the active noise reduction device 40 includes four pseudo-vibration transfer characteristic filter units. The number of pseudo-vibration transfer characteristic filter units is determined by, for example, the number of external sound sources × the number of speakers. Figure 4A and Figure 4B In the example, the mark at the end of the simulated vibration transfer characteristic filter section indicates that the simulated vibration transfer characteristic used by the simulated vibration transfer characteristic filter section simulates the vibration transfer characteristic from which speaker to which reference signal source. For example, the simulated vibration transfer characteristic used by the simulated vibration transfer characteristic filter section L0 simulates the vibration transfer characteristic from the position of the speaker L to the position of the reference signal source 0.

[0062] Furthermore, the active noise reduction device 40 includes four first simulated sound transfer characteristic filter sections. The number of first simulated sound transfer characteristic filter sections is determined, for example, by multiplying the number of speakers by the number of error signal sources. The symbol at the end of a first simulated sound transfer characteristic filter section indicates that the first simulated sound transfer characteristic used by that first simulated sound transfer characteristic filter section simulates the sound transfer characteristic from which speaker to which error signal source. For example, the simulated sound transfer characteristic used by the first simulated sound transfer characteristic filter section La simulates the sound transfer characteristic from the position of speaker L to the position of error signal source a.

[0063] Furthermore, the active noise reduction device 40 includes four sets of adaptive filter units (ADFs in the figure), filter coefficient update units, and signal adjustment units (ADJs in the figure). The number of sets of adaptive filter units, filter coefficient update units, and signal adjustment units is determined, for example, by multiplying the number of reference signal sources by the number of speakers. The active noise reduction device 40 includes two second-simulated sound transfer characteristic filter units for each filter coefficient update unit. In other words, the active noise reduction device 40 includes eight second-simulated sound transfer characteristic filter units.

[0064] The symbol at the end of the second pseudo-acoustic transfer characteristic filter section indicates that the second pseudo-acoustic transfer characteristic used by the second pseudo-acoustic transfer characteristic filter section simulates the acoustic transfer characteristic from which speaker to which error signal source. For example, the pseudo-acoustic transfer characteristic used by the second pseudo-acoustic transfer characteristic filter section La simulates the acoustic transfer characteristic from the position of the speaker L to the position of the error signal source a.

[0065] Furthermore, when this active noise reduction device 40 is actually installed in a vehicle 50 and the sound based on the external sound source is evaluated, the following results are obtained: even if only a portion of the multiple first analog sound transfer characteristic filter portions are set to be valid and the other portion of the first analog sound transfer characteristic filter portions are set to be invalid, the quality of the sound based on the external sound source can be maintained. In this case, a portion of the multiple first analog sound transfer characteristic filter portions can also be set to be invalid. In other words, a portion of the multiple first analog sound transfer characteristic filter portions can also be set to be invalid in advance through tuning by the installer or developer of the active noise reduction device 40. In this way, it is possible to achieve a reduction in processing load (amount of calculation) and a reduction in storage resources.

[0066] Similarly, there is the following situation: even if the simulated vibration transfer characteristic filter portion of only a part of the multiple simulated vibration transfer characteristic filter portions is set to valid and the simulated vibration transfer characteristic filter portion of another part is set to invalid, the quality of the sound based on the external sound source can be maintained. In this case, the simulated vibration transfer characteristic filter portion of a part in the multiple simulated vibration transfer characteristic filter portions can also be set to invalid. In other words, the simulated vibration transfer characteristic filter portion of a part in the multiple simulated vibration transfer characteristic filter portions can also be set to invalid in advance by the tuning of the setter or the developer etc. Thus, it is possible to achieve a reduction in processing load (amount of computation) and a reduction in storage resources etc.

[0067] [Operation of the Abnormality Determination Unit Using the Active Noise Cancellation Device According to Embodiment 2]

[0068] The active noise reduction device 40 also includes an abnormality determination unit 41. This unit detects the DC offset of each of the input reference signals and, based on the detection result, stops the operation of at least some of the components included in the active noise reduction device 40. Specifically, the abnormality determination unit 41 is implemented by a microcomputer, but may also be implemented by a processor or dedicated circuit.

[0069] Next, the operation of the abnormality determination unit 41 will be described. Figure 5 This is a flowchart of the operation of the abnormality determination unit 41. Figure 5 The operation is performed during the period when the active noise reduction device 40 is actually operating (that is, during the output of the synthesized sound N1).

[0070] First, the abnormality determination unit 41 detects the DC offset of each of the multiple reference signals obtained from the multiple reference signal input terminals (S21). Specifically, the abnormality determination unit 41 can detect the DC offset by digitizing and averaging each of the multiple reference signals. The DC offset detection method is not limited to this method; other methods may also be used.

[0071] Next, the abnormality determination unit 41 determines whether at least one of the multiple reference signal sources has an abnormality based on the detected DC offset (S22). For example, if a reference signal source fails, the DC offset may remain at a positive power supply voltage. Therefore, the abnormality determination unit 41 can determine that a reference signal source whose detected DC offset exceeds a predetermined value for a predetermined period of time is an abnormal reference signal source.

[0072] If all of the multiple reference signal sources are determined to be normal ("No" in S22), the abnormality determination operation is terminated. On the other hand, if at least one reference signal source is determined to be abnormal ("Yes" in S22), the abnormality determination unit 41 stops the operation of the component using the reference signal output from the reference signal source determined to be abnormal (S23).

[0073] For example, if reference signal source 1 is determined to be normal and reference signal source 0 is abnormal, the operation of the simulated vibration transfer characteristic filter section L0 and the simulated vibration transfer characteristic filter section R0 used to correct the reference signal output by reference signal source 0 is stopped. In addition, the operation of the two sets of adaptive filter sections, filter coefficient update sections, and signal adjustment sections that use the reference signal output by reference signal source 0 is stopped, and the operation of the four second simulated sound transfer characteristic filter sections associated with the two filter coefficient update sections whose operations have been stopped is also stopped.

[0074] Thus, if the operation of the component using the reference signal output from the reference signal source determined to be abnormal is stopped, the cancellation sound is suppressed from becoming noise. In addition, the processing load (computational load) and storage resources can be reduced.

[0075] (Effects, etc.)

[0076] As described above, the active noise reduction device 10 includes: a reference signal input terminal 11 to which is input a reference signal correlated with noise N0 in a space 56 within the vehicle 50 and output from a reference signal source 51 installed in the vehicle 50; a simulated vibration transfer characteristic filter unit 15 that generates a second signal by correcting a first signal using a simulated vibration transfer characteristic that simulates the vibration transfer characteristic from the speaker 52 to the reference signal source 51, so that the speaker 52 installed in the vehicle 50 can output a sound different from the canceling sound used to reduce noise N0; a first subtraction unit 16 that outputs a corrected reference signal obtained by subtracting the generated second signal from the reference signal input to the reference signal input terminal 11; and an adaptive filter unit 17 that generates a canceling signal used to output the canceling sound by applying an adaptive filter to the corrected reference signal output from the first subtraction unit 16. The vehicle 50 is an example of a mobile device, and the reference signal input terminal 11 is an example of a reference signal input unit.

[0077] This active noise reduction device 10 includes a simulated vibration transfer characteristic filter unit 15 and a first subtraction unit 16. This reduces signal components contained in the reference signal that are correlated with sounds other than the canceling sound. Consequently, the active noise reduction device 10 can suppress the reduction of sounds other than the noise N0 (that is, sounds other than the canceling sound).

[0078] In addition, for example, the active noise reduction device 10 further includes: a cancellation signal output terminal 12 for outputting the generated cancellation signal to the outside; an error signal input terminal 13 to which an error signal corresponding to residual sound generated by interference between the cancellation sound and the noise N0 is input; a first simulated sound transfer characteristic filter unit 20 for generating a third signal obtained by correcting the first signal using a first simulated sound transfer characteristic, wherein the first simulated sound transfer characteristic is obtained by simulating the sound transfer characteristics in the space 56; a second subtraction unit 21 for outputting a corrected error signal obtained by subtracting the generated third signal from the error signal input to the error signal input terminal 13; a second simulated sound transfer characteristic filter unit 22 for generating a filtered reference signal obtained by correcting the corrected reference signal using the second simulated sound transfer characteristic, wherein the second simulated sound transfer characteristic is obtained by simulating the sound transfer characteristics in the space 56; and a filter coefficient updating unit 23 for updating the coefficients of the adaptive filter using the output corrected error signal and the generated filtered reference signal. The cancellation signal output terminal 12 is an example of a cancellation signal output unit, and the error signal input terminal 13 is an example of an error signal input unit.

[0079] This active noise reduction device 10 uses the first pseudo-sound transfer characteristic filter unit 20 and the second subtraction unit 21 to reduce signal components contained in the error signal that are correlated with sounds other than the canceling sound. Consequently, the active noise reduction device 10 can suppress the reduction of sounds other than the noise N0 (that is, sounds other than the canceling sound).

[0080] For example, the active noise reduction device 10 further includes an adding unit 19 that adds the first signal to the canceling signal. The canceling signal to which the first signal is added is output to the speaker 52 via the canceling signal output terminal 12 .

[0081] Such an active noise reduction device 10 can output, from the speaker 52 , a synthesized sound of the canceling sound and a sound different from the canceling sound.

[0082] In addition, for example, the active noise reduction device 10 further includes a signal adjustment unit 18 that adjusts the generated cancellation signal through signal processing.

[0083] Such an active noise reduction device 10 can adjust the signal level (amplitude) of the canceling sound and the like.

[0084] Furthermore, for example, the active noise reduction device 40 includes a plurality of first pseudo-sound transfer characteristic filter sections, and disables some of the plurality of first pseudo-sound transfer characteristic filter sections.

[0085] Such an active noise reduction device 40 can achieve a reduction in processing load (amount of calculation) and storage resources by disabling the first pseudo-acoustic transfer characteristic filter section that has a low influence on the quality of sounds other than the canceling sound.

[0086] Furthermore, for example, the active noise reduction device 40 includes a plurality of pseudo-vibration transfer characteristic filter sections, and some of the plurality of pseudo-vibration transfer characteristic filter sections are disabled.

[0087] Such an active noise reduction device 40 can achieve a reduction in processing load (amount of calculation) and storage resources by disabling a pseudo-vibration transfer characteristic filter portion that has a low influence on the quality of sounds other than the canceling sound.

[0088] Furthermore, for example, the active noise reduction device 40 includes a plurality of reference signal input terminals corresponding to a plurality of reference signal sources, and an abnormality determination unit 41 for determining abnormalities in the plurality of reference signal sources. The abnormality determination unit 41 stops the operation of the simulated vibration transfer characteristic filter unit used to correct the reference signal from the reference signal source determined to have an abnormality, and stops the convolution operation of the adaptive filter unit to which the reference signal from the reference signal source determined to have an abnormality is input.

[0089] This active noise reduction device 40 can reduce processing load (amount of calculation) and storage resources by stopping the operation of the simulated vibration transfer characteristic filter unit used to correct the reference signal output from the reference signal source determined to have an abnormality.

[0090] In addition, in the active noise reduction method executed by a computer such as the active noise reduction device 10, a second signal is generated by correcting a first signal using a simulated vibration transfer characteristic. The first signal is used to output a sound different from the canceling sound used to reduce the noise N0 in the space 56 within the vehicle 50 from the speaker 52 installed in the vehicle 50. The simulated vibration transfer characteristic is obtained by simulating the vibration transfer characteristic from the speaker 52 to the reference signal source 51 installed in the vehicle 50. A corrected reference signal is output by subtracting the generated second signal from the reference signal output by the reference signal source 51. An adaptive filter is applied to the output corrected reference signal to generate a canceling signal used to output the canceling sound.

[0091] This active noise reduction method can suppress sounds other than the noise N0 (sounds different from the canceling sound) from being reduced.

[0092] (Other Embodiments)

[0093] As mentioned above, although embodiment was described, this disclosure is not limited to the said embodiment.

[0094] For example, the active noise reduction device in the above embodiment mainly targets road noise, but it may also target other noises such as structure-borne noise or airborne noise. There is no particular limitation on the type and frequency band of noise that the active noise reduction device mainly targets.

[0095] Furthermore, the active noise reduction device described in the above embodiments may also be mounted on a mobile device other than a vehicle. For example, the mobile device may be an aircraft or a ship. Furthermore, the present disclosure may be implemented as such a mobile device other than a vehicle.

[0096] The configuration of the active noise reduction device according to the above embodiment is merely an example. For example, the active noise reduction device may include components such as a D / A converter, a filter, a power amplifier, or an A / D converter.

[0097] Furthermore, the processing performed by the active noise reduction device according to the above embodiment is merely an example. For example, part of the digital signal processing described in the above embodiment may also be implemented by analog signal processing.

[0098] Furthermore, for example, in the above-described embodiment, a process executed by a specific processing unit may be executed by another processing unit. Furthermore, the order of multiple processes may be changed, and multiple processes may be executed in parallel.

[0099] In the above embodiments, each component can be implemented by executing a software program suitable for each component. Each component can also be implemented by a program execution unit such as a CPU or a processor reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory.

[0100] In addition, in the above-mentioned embodiments, each component can also be implemented by hardware. For example, each component can also be a circuit (or integrated circuit). These circuits can constitute a single circuit as a whole, or they can be independent circuits. In addition, these circuits can be general circuits or dedicated circuits.

[0101] In addition, each component may be a circuit (or integrated circuit). These circuits may constitute a single circuit as a whole, or they may be independent circuits. In addition, these circuits may be general circuits or dedicated circuits.

[0102] Furthermore, the overall or specific aspects of the present disclosure may also be implemented by a system, apparatus, method, integrated circuit, computer program, or non-transitory recording medium such as a computer-readable CD-ROM. Furthermore, the present disclosure may also be implemented by any combination of a system, apparatus, method, integrated circuit, computer program, and computer-readable non-transitory recording medium.

[0103] For example, the present disclosure may be implemented as an active noise reduction method executed by an active noise reduction device (a computer or DSP), or as a program for causing a computer or DSP to execute the active noise reduction method. Furthermore, the present disclosure may be implemented as a mobile device (e.g., a vehicle) equipped with the active noise reduction device and a reference signal source according to the above embodiments. Furthermore, the present disclosure may be implemented as a noise reduction system according to the above embodiments.

[0104] Furthermore, the present disclosure also includes forms obtained by applying various modifications to the embodiments that may be conceived by those skilled in the art, or forms achieved by arbitrarily combining the components and functions in the embodiments without departing from the spirit of the present disclosure.

[0105] Industrial applicability

[0106] The active noise reduction device of the present disclosure is useful as a device capable of reducing noise in a vehicle cabin, for example.

Claims

1. An active noise reduction device comprising: a reference signal input unit to which a reference signal outputted from a reference signal source installed in the mobile device and having a correlation with noise in a space within the mobile device is input; a simulated vibration transfer characteristic filter unit configured to generate a second signal by correcting a first signal using a simulated vibration transfer characteristic for outputting a sound different from a canceling sound for reducing the noise from a speaker mounted on the mobile device, the simulated vibration transfer characteristic being a simulation of a vibration transfer characteristic from the speaker to the reference signal source; a first subtraction unit that outputs a corrected reference signal obtained by subtracting the generated second signal from the reference signal input to the reference signal input unit; an adaptive filter unit that generates a cancellation signal used to output the cancellation sound by applying an adaptive filter to the corrected reference signal output from the first subtraction unit; a cancellation signal output unit, configured to output the generated cancellation signal to the outside; an error signal input unit to which an error signal corresponding to a residual sound generated by interference between the canceling sound and the noise is input; a first simulated sound transfer characteristic filter unit configured to generate a third signal by correcting the first signal using a first simulated sound transfer characteristic, the first simulated sound transfer characteristic being obtained by simulating a sound transfer characteristic in the space; a second subtraction section that outputs a corrected error signal obtained by subtracting the generated third signal from the error signal input to the error signal input section; a second simulated sound transfer characteristic filter unit configured to generate a filtered reference signal obtained by correcting the corrected reference signal using a second simulated sound transfer characteristic obtained by simulating a sound transfer characteristic in the space; and A filter coefficient updating unit updates coefficients of the adaptive filter using the output corrected error signal and the generated filter reference signal.

2. The active noise reduction device according to claim 1, wherein: further comprising an adding unit configured to add the first signal and the cancellation signal, The canceling signal to which the first signal is added is output to the speaker via the canceling signal output unit.

3. The active noise reduction device according to claim 1, wherein: The active noise reduction device includes a plurality of the first pseudo-sound transfer characteristic filter units. Some of the first pseudo-acoustic transfer characteristic filter sections are disabled.

4. The active noise reduction device according to claim 1, wherein: The active noise reduction device includes a plurality of the simulated vibration transfer characteristic filter units. Some of the plurality of pseudo-vibration transfer characteristic filter sections are disabled.

5. The active noise reduction device according to claim 1, wherein: The device further includes a signal adjustment unit configured to adjust the generated cancellation signal through signal processing.

6. An active noise reduction device comprising: a reference signal input unit to which a reference signal outputted from a reference signal source installed in the mobile device and having a correlation with noise in a space within the mobile device is input; a simulated vibration transfer characteristic filter unit configured to generate a second signal by correcting a first signal using a simulated vibration transfer characteristic for outputting a sound different from a canceling sound for reducing the noise from a speaker mounted on the mobile device, the simulated vibration transfer characteristic being a simulation of a vibration transfer characteristic from the speaker to the reference signal source; a first subtraction unit that outputs a corrected reference signal obtained by subtracting the generated second signal from the reference signal input to the reference signal input unit; an adaptive filter unit that generates a cancellation signal used to output the cancellation sound by applying an adaptive filter to the corrected reference signal output from the first subtraction unit; a plurality of reference signal input sections corresponding to the plurality of reference signal sources; and an abnormality determination unit that determines abnormalities in the plurality of reference signal sources; in, The abnormality determination unit stops the operation of the simulated vibration transfer characteristic filter unit used to correct the reference signal from the reference signal source determined to have an abnormality, and the convolution operation of the adaptive filter unit to which the reference signal from the reference signal source determined to have an abnormality is input.

7. A mobile device comprising: The active noise reduction device according to any one of claims 1 to 6; and The reference signal source.

8. An active noise reduction method, executed by a computer, in which: generating a second signal by correcting a first signal using a simulated vibration transfer characteristic that simulates a vibration transfer characteristic from the speaker to a reference signal source installed in the mobile device, the first signal being used to output, from a speaker installed in the mobile device, a sound different from a canceling sound for reducing noise in a space within the mobile device; outputting a corrected reference signal obtained by subtracting the generated second signal from a reference signal output by the reference signal source, generating a cancellation signal used to output the cancellation sound by applying an adaptive filter to the output corrected reference signal, outputting the generated cancellation signal to the outside, inputting an error signal corresponding to a residual sound generated by interference between the canceling sound and the noise, generating a third signal obtained by correcting the first signal using a first simulated sound transfer characteristic, wherein the first simulated sound transfer characteristic is obtained by simulating a sound transfer characteristic in the space; outputting a corrected error signal obtained by subtracting the generated third signal from the error signal, generating a filtered reference signal obtained by correcting the corrected reference signal using a second simulated sound transfer characteristic, wherein the second simulated sound transfer characteristic is obtained by simulating a sound transfer characteristic in the space; The coefficients of the adaptive filter are updated using the output corrected error signal and the generated filter reference signal.

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