Active noise reduction device

Abstract

To reduce noise stably and effectively. [Solution] The active noise reduction device 1 used in a moving object comprises a noise cancellation output device 12 that outputs a noise cancellation sound y to cancel out noise d, and a control device 15 that controls the noise cancellation output device 12. The control device 15 includes at least one adaptively updatable filter W2, C^2, H^2, and changes the processing amount in the adaptive updating process of the filter W2, C^2, H^2 according to the speed V of the moving object.

Description

[Technical Field]

[0001] This invention relates to an active noise reduction device. [Background technology]

[0002] Conventionally, active noise reduction devices are known that reduce noise by interfering with noise using a cancellation sound that is in the opposite phase to the noise. For example, Patent Document 1 discloses an active noise reduction device configured to stop the generation of cancellation sound by controlling the signal level of a cancellation signal (a signal for generating cancellation sound) when the speed of a moving object is lower than a threshold. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-81396 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, as mentioned above, if the generation of sound cancellation is stopped when the speed of the moving object is below the threshold, the noise reduction performance of the active noise reduction device will not be realized, and there is a risk that noise reduction will not be stable and effective.

[0005] In view of the above background, one aspect of the present invention aims to provide an active noise reduction device that can stably and effectively reduce noise. [Means for solving the problem]

[0006] To solve the above problems, one aspect of the present invention provides an active noise reduction device for use in a moving object, comprising: a noise cancellation output device that outputs noise cancellation sound to cancel out noise; and a control device that controls the noise cancellation output device, wherein the control device includes at least one adaptively updatable filter, and changes the processing amount in the adaptive updating process of the filter according to the speed of the moving object. [Effects of the Invention]

[0007] According to the above embodiments, an active noise reduction device capable of stably and effectively reducing noise can be provided. [Brief explanation of the drawing]

[0008] [Figure 1] A schematic diagram showing a vehicle to which an active noise reduction device according to this embodiment is applied. [Figure 2] Block diagram showing an active noise reduction device according to an embodiment. [Figure 3] A flowchart showing an example of executing the processing volume change control according to the embodiment. [Figure 4] Graph showing the setting lines of the μ table according to the embodiment. [Figure 5] A graph showing the setting lines for table η according to the embodiment. [Modes for carrying out the invention]

[0009] The active noise reduction device 1 (hereinafter abbreviated as "noise reduction device 1") according to the embodiment will be described below with reference to Figures 1 to 5. In this specification, the symbol "^" (hat) accompanying various symbols indicates an identified value or an estimated value. In figures and mathematical formulas, "^" is placed above the symbols, but in the text, it is placed after the symbols.

[0010] <Vehicle 3> FIG. 1 is a schematic diagram showing a vehicle 3 (an example of a moving object) to which a noise reduction device 1 is applied. The vehicle 3 includes a vehicle body 5, a plurality of wheels (not shown) arranged below the vehicle body 5, a plurality of suspensions 6 arranged between the vehicle body 5 and the plurality of wheels, and a vehicle speed sensor 7 that detects the speed of the vehicle 3 (hereinafter referred to as "vehicle speed V"). A vehicle compartment 8 is formed inside the vehicle body 5. A plurality of occupant seats 9 are installed in the vehicle compartment 8. Each occupant seat 9 includes a seat cushion 9A, a seat back 9B arranged rearward and above the seat cushion 9A, and a headrest 9C fixed to the upper end of the seat back 9B.

[0011] <Noise reduction device 1> Referring to FIG. 1, the noise reduction device 1 is an ANC device (Active Noise Control Device) for reducing noise d generated in the vehicle compartment 8 of the vehicle 3. More specifically, the noise reduction device 1 reduces the noise d by generating a canceling sound y having a phase opposite to that of the noise d and causing the generated canceling sound y to interfere with the noise d.

[0012] The noise reduction device 1 includes a plurality of acceleration sensors 11 that generate an acceleration signal x based on the noise d, a plurality of speakers 12 (an example of a canceling sound output device) that output a canceling sound y for canceling the noise d, a plurality of microphones 13 that generate a microphone signal m based on the noise d, and a control device 15 that controls the plurality of speakers 12 based on the acceleration signal x and the microphone signal m.

[0013] <Acceleration sensor 11> Referring to FIG. 1, each acceleration sensor 11 is installed on a corresponding suspension 6. The acceleration sensor 11 detects the acceleration of the suspension 6 in accordance with the noise d, and generates the acceleration signal x in accordance with the acceleration of the suspension 6. The acceleration signal x is used as a reference signal corresponding to the noise d.

[0014] <Speaker 12> Referring to FIG. 1, each speaker 12 is installed at a position of the vehicle 3 other than the occupant seat 9 (for example, a door lateral to the occupant seat 9 or a space behind the occupant seat 9). In other embodiments, the speaker 12 may be installed on the occupant seat 9 (for example, the headrest 9C of the occupant seat 9).

[0015] <Microphone 13> Referring to FIG. 1, each microphone 13 is installed near the headrest 9C of the occupant seat 9 or near a noise source. In other embodiments, the microphone 13 may be installed at a position of the vehicle 3 other than the vicinity of the occupant seat 9 or the noise source (for example, a ceiling above the occupant seat 9).

[0016] The microphone 13 is used simultaneously as a microphone that generates an error signal e corresponding to an error between noise d and canceling sound y, and a microphone that generates a reference signal r corresponding to the noise d. In other words, the microphone signal m is used simultaneously as the error signal e and the reference signal r. For example, in a control channel that targets the speaker 12 adjacent to the driver's seat, the microphone 13 installed at the driver's seat generates the error signal e, and the microphones 13 installed at seats other than the driver's seat or in the vicinity of the noise source generate the reference signal r. On the other hand, in a control channel that targets the speaker 12 adjacent to the front passenger seat, the microphone 13 installed at the front passenger seat generates the error signal e, and the microphones 13 installed at seats other than the front passenger seat or in the vicinity of the noise source generate the reference signal r. Hereinafter, the microphone 13 that generates the error signal e is referred to as "error microphone 13e", and the microphone 13 that generates the reference signal r is referred to as "reference microphone 13r".

[0017] <Control device 15> Referring to FIG. 2, the control device 15 is constituted by a computer including an arithmetic processing unit (processors such as CPU and MPU) and a storage device (memories such as ROM and RAM). The control device 15 may be configured as a single piece of hardware, or may be configured as a unit composed of a plurality of pieces of hardware.

[0018] The control device 15 has, as functional components, a plurality of first control signal generation units 16 (an example of a first control unit), a plurality of first sound field learning units 17 (an example of a first control unit), a plurality of second control signal generation units 18 (an example of a second control unit), a plurality of second sound field learning units 19 (an example of a second control unit), a control signal addition unit 20, and a processing control unit 22. The number of first control signal generation units 16 and first sound field learning units 17 corresponds to the number of acceleration sensors 11. The number of second control signal generation units 18 and second sound field learning units 19 corresponds to the number of reference microphones 13r. Note that in Figure 2, only one of each of the first control signal generation unit 16, first sound field learning unit 17, second control signal generation unit 18, and second sound field learning unit 19 is shown.

[0019] <First control signal generation unit 16> Each first control signal generation unit 16 of the control device 15 receives an acceleration signal x (reference signal) from the acceleration sensor 11. Each first control signal generation unit 16 includes a control filter unit 24, a reference signal correction unit 25, and a control update unit 26.

[0020] The control filter unit 24 is composed of a control filter W1. The control filter W1 is composed of an FIR filter (finite impulse response filter). In other embodiments, the control filter W1 may be composed of a SAN filter (single frequency adaptive notch filter) or the like. The control filter unit 24 generates a first control signal u1 by filtering the acceleration signal x (reference signal) with the control filter W1. The control filter unit 24 outputs the generated first control signal u1 to the first sound field learning unit 17 and the control signal summing unit 20.

[0021] The reference signal correction unit 25 is composed of a secondary path filter C^1. The secondary path filter C^1 is a filter that shows an estimated value of the transfer function C of the secondary path from the speaker 12 to the error microphone 13e. The secondary path filter C^1 is composed of an FIR filter. In other embodiments, the secondary path filter C^1 may be composed of a SAN filter or the like. The reference signal correction unit 25 corrects the acceleration signal x (reference signal) by applying filtering to the acceleration signal x using the secondary path filter C^1. The reference signal correction unit 25 outputs the corrected acceleration signal x to the control update unit 26.

[0022] The control update unit 26 adaptively updates the control filter W1 using an adaptive algorithm such as the LMS algorithm (Least Mean Square Algorithm). More specifically, the control update unit 26 adaptively updates the control filter W1 according to equation (1) below so that the error signal e output from the error microphone 13e is minimized.

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[0023] <First Sound Field Learning Section 17> Each first sound field learning unit 17 of the control device 15 receives an acceleration signal x (reference signal) from the acceleration sensor 11. Each first sound field learning unit 17 includes a cancellation sound estimation signal generation unit 31, a secondary path update unit 32, a noise estimation signal generation unit 33, a primary path update unit 34, a cancellation sound estimation signal inversion unit 35, a noise estimation signal inversion unit 36, and a virtual error signal generation unit 37.

[0024] The negation sound estimation signal generation unit 31, like the reference signal correction unit 25, is configured with a second-order path filter C^1. The negation sound estimation signal generation unit 31 applies filtering to the first control signal u1 using the second-order path filter C^1 to generate a first negation sound estimation signal y^1, which indicates the estimated value of the negation sound y. The negation sound estimation signal generation unit 31 outputs the generated first negation sound estimation signal y^1 to the negation sound estimation signal inversion unit 35.

[0025] The secondary path update unit 32 adaptively updates the secondary path filter C^1 of the cancellation sound estimation signal generation unit 31 using an adaptive algorithm such as the LMS algorithm. More specifically, the secondary path update unit 32 updates the first virtual error signal e output from the virtual error signal generation unit 37. v The quadratic path filter C^1 is adaptively updated by equation (2) below so that 1 (details below) is minimized.

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[0026] Furthermore, when the secondary path update unit 32 updates the secondary path filter C^1 of the sound cancellation estimation signal generation unit 31 as described above, the updated secondary path filter C^1 is output to the reference signal correction unit 25, and the secondary path filter C^1 of the reference signal correction unit 25 is updated.

[0027] The noise estimation signal generation unit 33 is composed of a primary path filter H^1. The primary path filter H^1 is a filter that shows an estimated value of the transfer function H of the primary path from the noise source to the error microphone 13e. The primary path filter H^1 is composed of, for example, an FIR filter. In other embodiments, the primary path filter H^1 may be composed of a SAN filter or the like. The noise estimation signal generation unit 33 generates a first noise estimation signal d^1 that shows an estimated value of noise d by filtering the acceleration signal x (reference signal) with the primary path filter H^1. The noise estimation signal generation unit 33 outputs the generated first noise estimation signal d^1 to the noise estimation signal inversion unit 36.

[0028] The primary path update unit 34 adaptively updates the primary path filter H^1 using an adaptive algorithm such as the LMS algorithm. More specifically, the primary path update unit 34 uses the first virtual error signal e output from the virtual error signal generation unit 37. v The first-order path filter H^1 is adaptively updated by equation (3) below so that 1 (details below) is minimized.

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[0029] The negation estimation signal inversion unit 35 inverts the polarity of the first negation estimation signal y^1 output from the negation estimation signal generation unit 31. The negation estimation signal inversion unit 35 outputs the first negation estimation signal y^1 with inverted polarity to the virtual error signal generation unit 37.

[0030] The noise estimation signal inversion unit 36 ​​inverts the polarity of the first noise estimation signal d^1 output from the noise estimation signal generation unit 33. The noise estimation signal inversion unit 36 ​​outputs the first noise estimation signal d^1 with inverted polarity to the virtual error signal generation unit 37.

[0031] The virtual error signal generation unit 37 generates the first virtual error signal e by adding the error signal e output from the error microphone 13e, the first sound cancellation estimation signal y^1 that has passed through the sound cancellation estimation signal inversion unit 35, and the first noise estimation signal d^1 that has passed through the noise estimation signal inversion unit 36. v The virtual error signal generation unit 37 generates the first virtual error signal e vThe value 1 is output to the secondary route update unit 32 and the primary route update unit 34.

[0032] <Second control signal generation unit 18> Each second control signal generation unit 18 of the control device 15 receives a reference signal r from the reference microphone 13r. Each second control signal generation unit 18 includes a control filter unit 44, a reference signal correction unit 45, and a control update unit 46. The components of the second control signal generation unit 18 are the same as those of the first control signal generation unit 16. Below, only the differences between the second control signal generation unit 18 and the first control signal generation unit 16 will be described.

[0033] The control filter unit 44 generates a second control signal u2 by applying a filter to the reference signal r (the reference signal output from the reference microphone 13r) using the control filter W2. The control filter unit 44 outputs the generated second control signal u2 to the second sound field learning unit 19 and the control signal summing unit 20.

[0034] The reference signal correction unit 45 corrects the reference signal r (the reference signal output from the reference microphone 13r) by applying a filter process to it using a second-order path filter C^2. The reference signal correction unit 45 outputs the corrected reference signal r to the control update unit 46.

[0035] The control update unit 46 adaptively updates the control filter W2 according to equation (4) below so that the error signal e output from the error microphone 13e is minimized.

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[0036] <Second Sound Field Learning Section 19> A reference signal r from a reference microphone 13r is input to each second sound field learning unit 19 of the control device 15. Each second sound field learning unit 19 includes a canceling sound estimated signal generating unit 51, a secondary path updating unit 52, a noise estimated signal generating unit 53, a primary path updating unit 54, a canceling sound estimated signal inverting unit 55, a noise estimated signal inverting unit 56, and a virtual error signal generating unit 57. The constituent elements of the second sound field learning unit 19 are the same as the constituent elements of the first sound field learning unit 17. Only differences between the second sound field learning unit 19 and the first sound field learning unit 17 will be described below.

[0037] The canceling sound estimated signal generating unit 51 performs filtering processing on a second control signal u2 using a secondary path filter C^2 to generate a second canceling sound estimated signal y^2 indicating an estimated value of canceling sound y. The canceling sound estimated signal generating unit 51 outputs the generated second canceling sound estimated signal y^2 to the canceling sound estimated signal inverting unit 55.

[0038] The secondary path updating unit 52 outputs a second virtual error signal e output from the virtual error signal generating unit 57 v 2 (details will be described later) adaptively updates the secondary path filter C^2 by the following equation (5) so that

Formula

[0039] The noise estimated signal generating unit 53 performs filtering processing on the reference signal r (the reference signal output from the reference microphone 13r) using a primary path filter H^2 to generate a second noise estimated signal d^2 indicating an estimated value of noise d. The noise estimated signal generating unit 53 outputs the generated second noise estimated signal d^2 to the noise estimated signal inverting unit 56.

[0040] The primary path updating unit 54 outputs a second virtual error signal e output from the virtual error signal generating unit 57 v 2 (details will be described later) adaptively updates the primary path filter H^2 by the following equation (6) so that

Formula

[0041] The sound cancellation estimation signal inversion unit 55 inverts the polarity of the second sound cancellation estimation signal y^2 output from the sound cancellation estimation signal generation unit 51. The sound cancellation estimation signal inversion unit 55 outputs the second sound cancellation estimation signal y^2 with inverted polarity to the virtual error signal generation unit 57.

[0042] The noise estimation signal inversion unit 56 inverts the polarity of the second noise estimation signal d^2 output from the noise estimation signal generation unit 53. The noise estimation signal inversion unit 56 outputs the second noise estimation signal d^2 with inverted polarity to the virtual error signal generation unit 57.

[0043] The virtual error signal generation unit 57 generates a second virtual error signal e by adding the error signal e output from the error microphone 13e, the second sound cancellation estimation signal y^2 that has passed through the sound cancellation estimation signal inversion unit 55, and the second noise estimation signal d^2 that has passed through the noise estimation signal inversion unit 56. v The virtual error signal generation unit 57 generates the second virtual error signal e v Output 2 to the secondary route update unit 52 and the primary route update unit 54.

[0044] <Control signal addition unit 20> The control signal summer 20 of the control device 15 generates a control signal u for controlling the speaker 12 by adding together the first control signals u1 output from each of the multiple first control signal generation units 16 and the second control signals u2 output from each of the multiple second control signal generation units 18. The control signal summer 20 outputs the generated control signal u to the speaker 12. When the control signal u is input to the speaker 12, the speaker 12 generates a cancellation sound y corresponding to the magnitude of the control signal u.

[0045] <Processing Control Unit 22> Referring to Figure 2, the processing control unit 22 of the control device 15 controls the adaptive update process of the second control signal generation unit 18 and the second sound field learning unit 19 by transmitting predetermined signals (for example, signals related to the step size parameter μ and the forgetting coefficient η) to the control update unit 46, the secondary path update unit 52, and the primary path update unit 54. The adaptive update process is a process of adaptively updating the control filter W2, the secondary path filter C^2, and the primary path filter H^2 (hereinafter referred to as "adaptive update filters W2, C^2, and H^2").

[0046] The processing control unit 22 acquires the vehicle speed V from the vehicle speed sensor 7 via CAN (Controller Area Network). The processing control unit 22 changes the processing amount in the adaptive update process according to the vehicle speed V. Hereinafter, the control that changes the processing amount in the adaptive update process according to the vehicle speed V will be referred to as "processing amount change control".

[0047] <Example of execution of processing volume change control> Referring to Figure 3, when the processing amount change control is started, the processing control unit 22 obtains the current vehicle speed V from the vehicle speed sensor 7 via CAN (step ST1).

[0048] Next, the processing control unit 22 determines the step size parameter μ based on the vehicle speed V obtained from the vehicle speed sensor 7 and the μ table which shows the relationship between the vehicle speed V and the step size parameter μ (step ST2). Details of the μ table will be described later.

[0049] Furthermore, the processing control unit 22 determines the forgetting coefficient η based on the vehicle speed V obtained from the vehicle speed sensor 7 and the η table, which shows the relationship between the vehicle speed V and the forgetting coefficient η (step ST3). Details of the η table will be described later.

[0050] Next, the processing control unit 22 performs an adaptive update process using the step size parameter μ and the forgetting coefficient η determined in steps ST2 and ST3 to adaptively update the adaptive update filters W2, C^2, and H^2 (see equations (4) to (6) above). Furthermore, the processing control unit 22 uses the control filter W2 that has been adaptively updated by the adaptive update process to output the cancellation sound y to the speaker 12 (step ST4).

[0051] <μ Table> Referring to Figure 4, in the μ table, the step size parameter μ is kept at 0 when the vehicle speed V is less than the speed V1. Therefore, the adaptive update process is stopped when the vehicle speed V is less than the speed V1.

[0052] In the μ table, when the vehicle speed V is greater than or equal to speed V1 and less than speed V2 (an example of a first speed) which is higher than speed V1, the step size parameter μ increases continuously as the vehicle speed V increases. Therefore, when the vehicle speed V increases from a value less than speed V1 to a value greater than or equal to speed V1, the adaptive update process is started.

[0053] In the μ table, when the vehicle speed V is greater than or equal to speed V1 and less than speed V2, the step size parameter μ becomes continuously smaller as the vehicle speed V decreases. Therefore, as the vehicle speed V decreases, the update amount of the adaptive update filters W2, C^2, and H^2 in the adaptive update process (the second term on the right-hand side of equations (4) to (6) above: an example of the processing amount in the adaptive update process) becomes continuously smaller.

[0054] In the μ table, the step size parameter μ is kept at its maximum value when the vehicle speed V is greater than or equal to speed V2, and less than speed V3 (an example of a second speed) which is higher than speed V2. Therefore, the amount of updates for the adaptive update filters W2, C^2, and H^2 in the adaptive update process is greatest.

[0055] In the μ table, when the vehicle speed V is greater than or equal to speed V3 and less than speed V4 (which is higher than speed V3), the step size parameter μ becomes continuously smaller as the vehicle speed V increases. Therefore, as the vehicle speed V increases, the amount of updates to the adaptive update filters W2, C^2, and H^2 in the adaptive update process becomes continuously smaller.

[0056] In the μ table, when the vehicle speed V is V4 or greater, the step size parameter μ is kept at a constant value greater than 0 and less than the maximum value. As a result, in the μ table, when the vehicle speed V is V3 or greater, the step size parameter μ is smaller than when the vehicle speed V is V2 or greater but less than V3. Therefore, when the vehicle speed V is V3 or greater, the amount of updates to the adaptive update filters W2, C^2, and H^2 in the adaptive update process is less than when the vehicle speed V is V2 or greater but less than V3.

[0057] <η Table> Referring to Figure 5, in the η table, the forgetting coefficient η is kept at its minimum value when the vehicle speed V is less than the speed V5. Therefore, the amount by which the current values ​​of the adaptive update filters W2, C^2, and H^2 are reflected in the updated values ​​of the adaptive update filters W2, C^2, and H^2 in the adaptive update process (the first term on the right-hand side of equations (4) to (6) above: an example of the amount of processing in the adaptive update process) is minimized. As a result, the decay of the adaptive update filters W2, C^2, and H^2 is maximized.

[0058] In the η table, when the vehicle speed V is greater than or equal to speed V5 and less than speed V6 (an example of a reference speed), the forgetting coefficient η decreases continuously as the vehicle speed V decreases. Therefore, as the vehicle speed V decreases, the amount by which the current values ​​of the adaptive update filters W2, C^2, and H^2 are reflected in the updated values ​​of the adaptive update filters W2, C^2, and H^2 in the adaptive update process decreases continuously.

[0059] In the η table, the forgetting coefficient η is kept at 1 when the vehicle speed V is greater than or equal to speed V6. Therefore, the current values ​​of the adaptive update filters W2, C^2, and H^2 are reflected most heavily in the updated values ​​of the adaptive update filters W2, C^2, and H^2 during the adaptive update process. This results in the smallest attenuation of the adaptive update filters W2, C^2, and H^2. The speed V6 in the η table is set lower than the speed V2 in the μ table.

[0060] <Effects> The noise d generated inside the passenger compartment 8 of vehicle 3 includes road vibration noise and aerodynamic noise. The control device 15 controls the speaker 12 based on the acceleration signal x. This effectively reduces road vibration noise. However, controlling the speaker 12 based solely on the acceleration signal x may not sufficiently reduce aerodynamic noise. Therefore, the control device 15 controls the speaker 12 based on both the acceleration signal x and the microphone signal m (more specifically, the reference signal r). This allows for sufficient reduction of not only road vibration noise but also aerodynamic noise.

[0061] The noise reduction device 1 is designed to have a higher control effect in the vicinity of the microphone 13. Therefore, in this embodiment, the microphone 13 is installed on the headrest 9C of the occupant seat 9. This allows the occupant's head to be brought closer to the microphone 13, thereby increasing the control effect that the occupant can perceive.

[0062] On the other hand, if the microphone 13 is installed on the headrest 9C of the passenger seat 9, the position of the microphone 13 changes significantly when the fore-aft position of the passenger seat 9 is adjusted or when the seat back 9B of the passenger seat 9 is reclined, causing a large change in the transfer function C of the secondary path from speaker 12 to microphone 13. Consequently, if the difference between the transfer function C of the secondary path and the secondary path filters C^1 and C^2 becomes large, there is a risk that the noise reduction device 1 may not be able to sufficiently reduce noise d, or that noise d may be amplified. Therefore, the control device 15 adaptively updates the secondary path filters C^1 and C^2. This allows the secondary path filters C^1 and C^2 to change in response to changes in the transfer function C of the secondary path. As a result, the noise reduction device 1 can sufficiently reduce noise d and suppress the amplification of noise d.

[0063] By the way, if microphone 13 is installed on the headrest 9C of the passenger seat 9, microphone 13 will be closer to the passenger's mouth, making it easier for microphone 13 to pick up the passenger's conversation sounds. In other words, speech components are more likely to be mixed into the microphone signal m. If the microphone signal m mixed with speech components is used as a reference signal r, a control signal u will be generated based on the reference signal r mixed with speech components, and therefore, speech components will also be mixed into the cancellation sound y output based on the control signal u. As a result, there is a risk that an audio echo will occur in the passenger compartment 8, causing discomfort to the passenger.

[0064] In this regard, when the vehicle speed V is high, aerodynamic noise increases. In such conditions, even if the occupants converse, the aerodynamic noise drowns out the sound of their conversation, making voice echo less likely to occur. Conversely, when the vehicle speed V decreases, the aerodynamic noise decreases. In such conditions, if the occupants converse, the sound of their conversation becomes louder relative to the aerodynamic noise, making voice echo more likely to occur. Furthermore, when the vehicle speed V is low, aerodynamic noise is less likely to occur in the first place, so there is less need to control the speaker 12 based on the reference signal r to reduce aerodynamic noise.

[0065] Therefore, the control device 15 changes the update amount of the adaptive update filters W2, C^2, and H^2 (filters for controlling the speaker 12 based on the reference signal r) and the amount by which the current values ​​of the adaptive update filters W2, C^2, and H^2 are reflected in the update values ​​of the adaptive update filters W2, C^2, and H^2, according to the vehicle speed V. More specifically, when the vehicle speed V is greater than or equal to speed V1 and less than speed V2, the control device 15 reduces the update amount of the adaptive update filters W2, C^2, and H^2 as the vehicle speed V decreases. Also, when the vehicle speed V is greater than or equal to speed V5 and less than speed V6, the control device 15 reduces the amount by which the current values ​​of the adaptive update filters W2, C^2, and H^2 are reflected in the update values ​​of the adaptive update filters W2, C^2, and H^2 as the vehicle speed V decreases. As a result, when the vehicle speed V is low (when the conversation sound is louder than the aerodynamic noise), the occurrence of voice echo can be suppressed by reducing the update amount and reflection amount of the adaptive update filters W2, C^2, and H^2. On the other hand, when the vehicle speed V is high (when aerodynamic noise is louder than conversational noise), aerodynamic noise can be suppressed by increasing the update and reflection amounts of the adaptive update filters W2, C^2, and H^2. In other words, it is possible to ensure the reduction of aerodynamic noise when the vehicle speed V is high while suppressing the generation of voice echo when the vehicle speed V is low.

[0066] <Variation> In the above embodiment, the control device 15 changes the processing amount in the adaptive update process of the second control signal generation unit 18 and the second sound field learning unit 19 (an example of the second control unit). In other embodiments, the control device 15 may change the processing amount in the adaptive update process of the first control signal generation unit 16 and the first sound field learning unit 17 (an example of the first control unit), or it may change both the processing amount in the adaptive update process of the second control signal generation unit 18 and the second sound field learning unit 19 and the processing amount in the adaptive update process of the first control signal generation unit 16 and the first sound field learning unit 17.

[0067] In the above embodiment, the control device 15 adaptively updates the adaptive update filters W2, C^2, and H^2 using equations (4) to (6) above. However, equations (4) to (6) above are merely examples of equations used for the adaptive update of the adaptive update filters W2, C^2, and H^2. Therefore, in other embodiments, the control device 15 may adaptively update the adaptive update filters W2, C^2, and H^2 using equations other than those (4) to (6) above. For example, the control device 15 may use equations (7) to (9) below instead of equations (4) to (6) above (details are omitted, but similar substitutions are possible for equations (1) to (3) above).

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[0068] In the above embodiment, the control device 15 uses the current values ​​(W2(t), C^2(t), H^2(t)) of the adaptive update filters W2, C^2, and H^2 as the values ​​before adaptive update of the adaptive update filters W2, C^2, and H^2. In other embodiments, the control device 15 may use the past values ​​(for example, W2(t-1), C^2(t-1), H^2(t-1)) of the adaptive update filters W2, C^2, and H^2 as the values ​​before adaptive update of the adaptive update filters W2, C^2, and H^2, or it may use both the current and past values ​​of the adaptive update filters W2, C^2, and H^2 (the same applies to the control filter W1, the secondary path filter C^1, and the primary path filter H^1).

[0069] In the above embodiment, the control device 15 includes multiple adaptive update filters W2, C^2, and H^2. In other embodiments, the control device 15 may include only one adaptive update filter.

[0070] In the above embodiment, both the acceleration signal x and the microphone signal m are used as reference signals. In other embodiments, only one of the acceleration signal x or the microphone signal m may be used as a reference signal.

[0071] In the above embodiment, the noise reduction device 1 is applied to the passenger compartment 8 of the vehicle 3. In other embodiments, the noise reduction device 1 may be applied to the interior space of a moving object other than the vehicle 3 (for example, a ship or an aircraft).

[0072] This concludes the description of specific embodiments, but the present invention is not limited to the above embodiments or modifications and can be broadly modified and implemented.

[0073] <Summary of Embodiments> The active noise reduction device 1 used in the mobile body 3 comprises a noise cancellation output device 12 that outputs a noise cancellation sound y to cancel out noise d, and a control device 15 that controls the noise cancellation output device 12. The control device 15 includes at least one adaptively updatable filter W2, C^2, H^2, and changes the processing amount in the adaptive updating process of the filter W2, C^2, H^2 according to the speed V of the mobile body 3.

[0074] According to this embodiment, noise d can be reduced stably and effectively by changing the processing amount in the adaptive update process according to the speed V of the moving body 3.

[0075] The active noise reduction device 1 further comprises an acceleration sensor 11 that generates an acceleration signal x based on the noise d, and a microphone 13 that generates a microphone signal m based on the noise d. The control device 15 includes first control units 16 and 17 to which the acceleration signal x is input as a reference signal corresponding to the noise d, and second control units 18 and 19 to which the microphone signal m is input as a reference signal. The control device 15 changes the processing amount in the adaptive update process of the second control units 18 and 19 according to the speed V of the moving body 3.

[0076] According to this embodiment, not only can noise associated with road surface vibration be reduced based on the acceleration signal x, but aerodynamic noise can also be reduced based on the microphone signal m. In other words, both noise associated with road surface vibration and aerodynamic noise can be reduced. Furthermore, by changing the processing amount in the adaptive update process of the second control units 18 and 19 (control units to which the microphone signal m is input) according to the speed V of the moving body 3, the occurrence of voice echo can be suppressed.

[0077] When the speed V of the moving body 3 is less than the first speed V2, the control device 15 reduces the amount of updates of the filters W2, C^2, and H^2 in the adaptive update process of the second control units 18 and 19 as the speed V of the moving body 3 decreases.

[0078] According to this embodiment, when the speed V of the mobile body 3 is low (when the conversation sound is louder than the aerodynamic noise), the occurrence of voice echo can be suppressed by reducing the update amount of filters W2, C^2, and H^2 in the adaptive update processing of the second control units 18 and 19 (control units to which the microphone signal m is input). On the other hand, when the speed V of the mobile body 3 is high (when the aerodynamic noise is louder than the conversation sound), the aerodynamic noise can be suppressed by increasing the update amount of filters W2, C^2, and H^2 in the adaptive update processing of the second control units 18 and 19. In other words, it is possible to ensure the reduction effect of aerodynamic noise when the speed V of the mobile body 3 is high, while suppressing the occurrence of voice echo when the speed V of the mobile body 3 is low.

[0079] When the speed V of the moving body 3 is less than the reference speed V6, the control device 15 reduces the amount by which the values ​​of the filters W2, C^2, and H^2 before adaptive update are reflected in the adaptively updated values ​​of the filters W2, C^2, and H^2 in the adaptive update process of the second control units 18 and 19, as the speed V of the moving body 3 decreases.

[0080] According to this embodiment, when the speed V of the mobile body 3 is low (when the conversation sound is louder than the aerodynamic noise), the amount of reflection in the adaptive update processing of the second control units 18 and 19 (control units to which the microphone signal m is input) can be reduced to suppress the occurrence of voice echo. On the other hand, when the speed V of the mobile body 3 is high (when the aerodynamic noise is louder than the conversation sound), the amount of reflection in the adaptive update processing of the second control units 18 and 19 can be increased to suppress the aerodynamic noise. In other words, it is possible to ensure the effect of reducing aerodynamic noise when the speed V of the mobile body 3 is high, while suppressing the occurrence of voice echo when the speed V of the mobile body 3 is low.

[0081] The control device 15 changes the update amounts of the filters W2, C^2, and H^2 in the adaptive update process according to the speed V of the moving body 3.

[0082] According to this embodiment, noise d can be reduced more stably and effectively by changing the update amounts of filters W2, C^2, and H^2 in the adaptive update process according to the speed V of the moving body 3.

[0083] When the speed V of the moving body 3 is less than the first speed V2, the control device 15 reduces the update amount as the speed V of the moving body 3 decreases.

[0084] According to this embodiment, when the speed V of the moving body 3 is low (when the conversation sound is louder than the aerodynamic noise), the update amount of filters W2, C^2, and H^2 is suppressed to be excessive, thereby improving the stability of the control.

[0085] The control device 15 reduces the update amount when the speed V of the moving body 3 is higher than the first speed V2, i.e., when the speed V of the moving body 3 is higher than the second speed V3, compared to when the speed V of the moving body 3 is greater than or equal to the first speed V2 and less than the second speed V3.

[0086] According to this embodiment, when the speed V of the moving body 3 is high (when aerodynamic noise is louder than conversational noise), the update amount of filters W2, C^2, and H^2 becomes excessive, thereby improving the stability of the control.

[0087] The control device 15 changes the amount by which the values ​​of the filters W2, C^2, and H^2 before adaptive update are reflected in the adaptively updated values ​​of the filters W2, C^2, and H^2 in the adaptive update process, according to the speed V of the moving body 3.

[0088] According to this embodiment, noise d can be reduced more stably and effectively by changing the amount of reflection in the adaptive update process according to the speed V of the moving body 3.

[0089] When the speed V of the moving body 3 is less than the reference speed V6, the control device 15 reduces the reflection amount as the speed V of the moving body 3 decreases.

[0090] According to this embodiment, when the speed V of the moving body 3 is low (when the conversation sound is louder than the aerodynamic noise), it is possible to suppress the cancellation sound y (control output) from becoming excessive.

[0091] When the speed V of the moving body 3 is less than the first speed V2, the control device 15 reduces the amount of updates of the filters W2, C^2, and H^2 in the adaptive update process as the speed V of the moving body 3 decreases, and sets the reference speed V6 lower than the first speed V2.

[0092] In this embodiment, as the velocity V of the moving body 3 increases, the velocity V of the moving body 3 reaches the reference velocity V6 before reaching the first velocity V2. This allows the amount of reflection in the adaptive update process to reach its maximum value before the amount of update in the adaptive update process to reach its maximum value. Therefore, the update speed (update efficiency) of the adaptive update process can be improved. [Explanation of Symbols]

[0093] 1: Active noise reduction device 3: Vehicles (an example of a mobile device) 11: Accelerometer 12: Speaker (an example of a sound-canceling output device) 13: Mike 15: Control device 16: First control signal generation unit (an example of the first control unit) 17: First sound field learning unit (an example of the first control unit) 18: Second control signal generation unit (an example of a second control unit) 19: Second sound field learning unit (an example of a second control unit) W2: Control filter (an example of a filter) C^2: Quadratic path filter (an example of a filter) H^2: First-order path filter (an example of a filter)

Claims

1. An active noise reduction device that uses a mobile body, A noise cancellation output device that outputs noise cancellation sound to cancel out noise, The system includes a control device for controlling the sound-canceling output device, The control device is Includes at least one adaptively updatable filter, An active noise reduction device that changes the processing amount in the adaptive update process of the filter according to the speed of the moving body.

2. An acceleration sensor that generates an acceleration signal based on the aforementioned noise, The system further comprises a microphone that generates a microphone signal based on the aforementioned noise, The control device is The system includes a first control unit to which the acceleration signal is input as a reference signal corresponding to the noise, and a second control unit to which the microphone signal is input as a reference signal, The active noise reduction device according to claim 1, wherein the processing amount in the adaptive update process of the second control unit is changed according to the speed of the moving body.

3. The active noise reduction device according to claim 2, wherein the control device, when the speed of the moving body is less than the first speed, reduces the amount of filter update in the adaptive update process of the second control unit as the speed of the moving body decreases.

4. The control device, when the speed of the moving body is less than the reference speed, reduces the amount by which the value of the filter before adaptive update is reflected in the value of the filter after adaptive update in the adaptive update process of the second control unit as the speed of the moving body decreases.

5. The active noise reduction device according to claim 1 or 2, wherein the control device changes the amount of filter update in the adaptive update process according to the speed of the moving body.

6. The control device, when the speed of the moving body is less than a first speed, reduces the amount of update as the speed of the moving body decreases, according to claim 5.

7. The control device, when the speed of the moving body is a second speed or higher which is higher than the first speed, reduces the amount of update compared to when the speed of the moving body is greater than or equal to the first speed but less than the second speed.

8. The control device changes the amount by which the value of the filter before adaptive update is reflected in the value of the filter after adaptive update in the adaptive update process, according to the speed of the moving body.

9. The control device, when the speed of the moving body is less than the reference speed, reduces the amount of reflection as the speed of the moving body decreases, according to claim 8.

10. The control device is When the speed of the moving body is less than the first speed, the amount of filter update in the adaptive update process is reduced as the speed of the moving body decreases. The active noise reduction device according to claim 9, wherein the reference speed is set lower than the first speed.

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