Active noise control system

Abstract

An active noise control system capable of canceling noise independently of displacement of a user's head is provided. In a first system signal processing section (111), adaptive filters (1111-1114) generate noise canceling sounds, a first system selector (1117) selects an output of a first system auxiliary filter corresponding to a noise canceling position matching a detected position of the user's right ear, out of outputs of a plurality of first system auxiliary filters (1116) corresponding to different noise canceling positions, respectively, a first system subtracter (1115) subtracts the selected output from an output of a first microphone (13), and outputs the result as an error signal to the first system adaptive filters and second system adaptive filters of a second system signal processing section (112). The noise canceling positions corresponding to the plurality of first system auxiliary filters are arranged at prescribed intervals only within a space in which the user seated on a seat can move the right ear by turning, laterally bending the head within a prescribed range in the up-down and front-back directions.

Description

Technical Field

[0001] This invention relates to an active noise control (ANC) technique that reduces noise by emitting noise-canceling sounds to eliminate noise. Background Technology

[0002] As an active noise control technique that reduces noise by emitting noise-canceling tones to eliminate noise, there is a known technique that includes a microphone and a speaker positioned near the noise cancellation location, and an adaptive filter that adaptively sets a transfer function for the output signal of the noise source or a signal that is suspected to be the output signal, thereby generating a noise-canceling tones to be output from the speaker. In the adaptive filter, the transfer function is adaptively set as an error signal by using an auxiliary filter to correct the output of the microphone (e.g., Patent Document 1).

[0003] In this technique, an auxiliary filter is provided with a pre-learned transfer function, which is a transfer function that is modified by the difference between the transfer function from the noise source to the noise cancellation location and the transfer function from the noise source to the microphone, and the difference between the transfer function from the speaker to the noise cancellation location and the transfer function from the speaker to the microphone. By using such an auxiliary filter, noise can be cancelled at a noise cancellation location that is different from the location of the microphone.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2018-72770 Summary of the Invention

[0007] When using the aforementioned technique of using an auxiliary filter to cancel noise at a noise cancellation position different from the microphone position to eliminate noise audible to the user, if the user's head moves away from the noise cancellation position along with the user's displacement, there is a possibility that the noise audible to the user cannot be effectively eliminated.

[0008] Therefore, consider the following approach: Set up multiple auxiliary filters that have been learned for different noise cancellation positions. As the user's head moves, switch the auxiliary filter to be used for the head position to the auxiliary filter that has been learned for the corresponding noise cancellation position, thereby canceling the noise that the user can hear regardless of the user's head movement.

[0009] However, if noise can be effectively eliminated at all locations within a three-dimensional area surrounding the standard position of the user's head, multiple noise cancellation locations need to be set, resulting in an excessive number of auxiliary filters.

[0010] Therefore, the objective of this invention is to provide an active noise control system that can eliminate noise independently of the user's head displacement in a relatively simple structure.

[0011] To achieve the aforementioned objectives, the present invention provides an active noise control system for reducing noise, comprising: a head detection unit for detecting the position of a user's head while seated; a switching control unit; a speaker for outputting noise-canceling sounds; a microphone for detecting error signals; multiple auxiliary filters corresponding to multiple different noise cancellation positions, generating and outputting correction signals based on a noise signal representing noise, wherein the correction signals correct the error signals detected by the microphone by compensating for the difference between the noise cancellation position corresponding to the auxiliary filter and the microphone position; an error correction unit that corrects the error signal output by the microphone using the correction signals output by any one of the auxiliary filters, and outputs the corrected error signal; and an adaptive filter that performs adaptive operation using the corrected error signal output by the error correction unit, generating noise-canceling sounds to be output from the speaker from the noise signal. Here, the switching control unit, based on the head position detected by the head detection unit, causes the error correction unit to correct the error signal using the correction signals output by the auxiliary filters, which are auxiliary filters whose corresponding noise cancellation positions match the head position detected by the head detection unit. In addition, the multiple noise cancellation positions corresponding to the multiple auxiliary filters are multiple positions configured at predetermined intervals only within a space that allows a user to move their head by rotating or laterally bending their head when seated, with their head upright and facing forward, positioned at the center of the seat in the left-right direction and at any position within a predetermined range in the up-down and front-back directions.

[0012] Furthermore, to achieve the aforementioned objectives, the active noise control system for noise reduction of the present invention includes: a head detection unit for detecting the positions of the left and right ears of a user seated in a seat; a switching control unit; and two noise control systems: a noise control system for the right ear and a noise control system for the left ear. Each noise control system includes: a loudspeaker for outputting a noise-canceling tone; a microphone for detecting error signals; multiple auxiliary filters corresponding to multiple different noise cancellation positions, generating and outputting a correction signal based on a noise signal representing noise, the correction signal being a correction signal that corrects the error signal detected by the microphone by compensating for the difference between the noise cancellation position corresponding to the auxiliary filter and the position of the microphone; an error correction unit that corrects the error signal output by the microphone using the correction signal output by any one of the auxiliary filters, and outputs the corrected error signal; and an adaptive filter that performs an adaptive operation using the corrected error signal output by the error correction unit of the right ear noise control system and the corrected error signal output by the error correction unit of the left ear noise control system, generating a noise-canceling tone to be output from the loudspeaker from the noise signal. Furthermore, the switching control unit, for the position of the right ear detected by the head detection unit, causes the error correction unit of the right ear noise control system to correct the error signal using a correction signal output by an auxiliary filter. This auxiliary filter is an auxiliary filter whose corresponding noise cancellation position matches the position of the right ear detected by the head detection unit. Similarly, for the position of the left ear detected by the head detection unit, the switching control unit causes the error correction unit of the left ear noise control system to correct the error signal using a correction signal output by an auxiliary filter. This auxiliary filter is an auxiliary filter whose corresponding noise cancellation position matches the position of the left ear detected by the head detection unit. Furthermore, the multiple noise cancellation positions corresponding to the multiple auxiliary filters of the right ear noise control system are multiple positions arranged at predetermined intervals only within the right ear target space. The right ear target space is the space in which a user, when seated upright and facing forward, is positioned at the center of the seat in the left-right direction and at any position within a predetermined range in the up-down and front-back directions, allowing the right ear to move by rotating or tilting the head. Similarly, the multiple noise cancellation positions corresponding to the multiple auxiliary filters of the left ear noise control system are multiple positions arranged at predetermined intervals only within the left ear target space. The left ear target space is the space in which a user, when seated upright and facing forward, is positioned at the center of the seat in the left-right direction and at any position within a predetermined range in the up-down and front-back directions, allowing the left ear to move by rotating or tilting the head.

[0013] Alternatively, in such an active noise control system, the right ear target space can be defined as a three-dimensional space such that, when the head is positioned at the center of the seat in the left-right direction and at any position within the specified range in the up-down and front-back directions, a point at the position of the right ear on the head rotates around the rotation axis of the head at that position by a specified angle within a range of rotatable angles, forming a line as the trajectory of this rotation. This line is then rotated around the lateral flexion axis of the head at that position by a specified angle within a range of lateral flexion angles, forming a surface as the trajectory of this rotation. This surface is then moved within the specified range within which the right ear moves in the up-down and front-back directions in tandem with the head moving upright and facing forward, forming a trajectory of this movement. The three-dimensional space is obtained by tracing the trajectory of the left ear object. The three-dimensional space is defined as follows: when the head is in a position in the center of the seat in the left-right direction and in any position in the up-down and front-back direction within the specified range, a point existing at the position of the left ear of the head is rotated around the rotation axis of the head in that position by a specified angle within the range of rotatable angles. A line is obtained as the trajectory of this rotation. The line is rotated around the lateral flexion axis of the head in that position by a specified angle within the range of lateral flexion angles. A surface is obtained as the trajectory of this rotation. The surface is moved within the specified range along the up-down and front-back direction of the head as it moves upright and facing forward, and the left ear moves in the up-down and front-back direction. The three-dimensional space is obtained as the trajectory of this movement.

[0014] According to the active noise control system described above, the noise cancellation position of the auxiliary filter can be limited to the range where the user's head and ears can be located. Therefore, by setting only a small number of auxiliary filters, noise can be eliminated regardless of the displacement of the user's head.

[0015] In the above-described active noise control system, it is preferable that the specified interval is a distance of 1 / 10 of the wavelength of the upper limit frequency of the noise that the active noise control system is targeting to eliminate.

[0016] Therefore, the noise cancellation location and the number of auxiliary filters can be minimized to a range that can effectively cancel noise regardless of the user's head displacement.

[0017] In addition, in such an active noise control system, the seat can be a car seat.

[0018] Invention Effects

[0019] As described above, according to the present invention, it is possible to provide an active noise control system that can eliminate noise independently of the user's head displacement in a relatively simple structure. Attached Figure Description

[0020] Figure 1 This is a block diagram illustrating the structure of an active noise control system according to an embodiment of the present invention.

[0021] Figure 2 This is a diagram showing the configuration of the loudspeaker and microphone in an active noise control system according to an embodiment of the present invention.

[0022] Figure 3 This is a block diagram illustrating the structure of the signal processing module according to an embodiment of the present invention.

[0023] Figure 4 This is a diagram illustrating a method for setting a point set according to an embodiment of the present invention.

[0024] Figure 5 This is a diagram illustrating a method for setting a point set according to an embodiment of the present invention.

[0025] Figure 6 This is a block diagram illustrating the structure for learning the transfer function of the auxiliary filter according to an embodiment of the present invention.

[0026] Figure 7 This is a block diagram illustrating the structure for learning the transfer function of the auxiliary filter according to an embodiment of the present invention. Detailed Implementation

[0027] The embodiments of the present invention will be described below.

[0028] Figure 1 This illustrates the structure of the active noise control system of this embodiment.

[0029] As shown in the figure, the active noise control system 1 includes a signal processing module 11, a first speaker 12, a first microphone 13, a second speaker 14, a second microphone 15, a controller 16, and a DMS17 (Driver Monitoring System 17) that detects the position, posture, and other states of the user's head through a near-infrared camera.

[0030] Furthermore, the active noise control system 1 of this embodiment is a system installed in a car. It is a system that eliminates noise generated by a noise source at each of the two elimination points, using the position of the user's standard right ear as the first elimination point and the position of the user's standard left ear as the second elimination point.

[0031] Here, as Figure 2 As shown in a1 and a2, the first speaker 12 and the first microphone 13 are positioned near the headrest of the noise-cancellation target seat (driver's seat in the figure), which is the standard position for the right ear of the user sitting in the seat. The second speaker 14 and the second microphone 15 are positioned near the headrest of the user's seat, which is the target of noise cancellation, which is the standard position for the left ear of the user sitting in the seat.

[0032] Or, it can be like Figure 2 As shown in b1 and b2, the first speaker 12 is positioned above and in front of the standard position of the right ear of the user seated in the noise-cancellation target seat on the ceiling of the vehicle cabin. The second speaker 14 is positioned above and in front of the standard position of the left ear of the user seated in the noise-cancellation target seat on the ceiling of the vehicle cabin. The first microphone 13 is positioned to the right of the first speaker 12 and closer to the noise-cancellation target seat than the first speaker 12 on the ceiling in front of the user. The second microphone 15 is positioned to the left of the second speaker 14 and closer to the noise-cancellation target seat than the second speaker 14 on the ceiling in front of the user. Furthermore, with the first speaker 12 and the second speaker 14 positioned on the ceiling in this way, super-directional parametric speakers can also be used as the first speaker 12 and the second speaker 14.

[0033] return Figure 1 The signal processing module 11 uses the noise signal x(n) representing the noise generated by the noise source, the sound signal picked up by the first microphone 13 (i.e., the first microphone error signal err1(n), and the sound signal picked up by the second microphone 15 (i.e., the second microphone error signal err2(n)) to generate a first cancellation signal CA1(n) and output it from the first speaker 12, and generates a second cancellation signal CA2(n) and output it from the second speaker 14.

[0034] Furthermore, noise generated by the noise source is eliminated at the first elimination point and the second elimination point by the first elimination signal CA1(n) output from the first speaker 12 and the second elimination signal CA2(n) output from the second speaker 14.

[0035] Next, as Figure 3 As shown, the signal processing module 11 mainly includes a first system signal processing unit 111 that performs processing related to the generation of the first cancellation signal CA1(n), and a second system signal processing unit 112 that mainly performs processing related to the generation of the second cancellation signal CA2(n).

[0036] Furthermore, the first system signal processing unit 111 includes: a first system variable filter 1111, a first system adaptive algorithm execution unit 1112, a first system first estimation filter 1113 with a pre-set transfer function S11^(z), a first system second estimation filter 1114 with a pre-set transfer function S21^(z), a first system subtractor 1115, n first system auxiliary filters 1116 with pre-set transfer functions H1_i(z), and a first system selector that selects and outputs any one of the outputs of the n first system auxiliary filters 1116. Here, i is an integer from 1 to n, and the transfer function H1_i(z) represents the transfer function of the i-th first system auxiliary filter 1116.

[0037] In the structure of the first system signal processing unit 111, the input noise signal x(n) is output to the first speaker 12 as a first cancellation signal CA1(n) after passing through the first system variable filter 1111.

[0038] Furthermore, the input noise signal x(n) is sent to the first system selector 1117 after passing through each of the first system auxiliary filters 1116. The first system selector 1117 selects the output of any of the first system auxiliary filters 1116 and outputs it to the first system subtractor 1115. The first system subtractor 1115 subtracts the output of the first system selector 1117 from the first microphone error signal err1(n) picked up by the first microphone 13, and outputs it as error e1 to the first system adaptive algorithm execution unit 1112 and the second system signal processing unit 112.

[0039] Next, the first system variable filter 1111, the first system adaptive algorithm execution unit 1112, the first system first estimated filter 1113, and the first system second estimated filter 1114 constitute a Multiple Error Filtered-X adaptive filter. In the first system first estimated filter 1113, an estimated transfer characteristic S11^(z) of the transfer function S11(z) from the first system signal processing unit 111 to the first microphone 13, which is calculated through actual measurement, is preset. The first system first estimated filter 1113 convolves the transfer characteristic S11^(z) with the input noise signal x(n) and then inputs it to the first system adaptive algorithm execution unit 1112. In addition, in the second estimation filter 1114 of the first system, there is a preset estimated transfer characteristic S21^(z) that represents the transfer characteristic S21(z) from the signal processing unit 111 of the first system to the second microphone 15 calculated by actual measurement, etc. The second estimation filter 1114 of the first system convolves the transfer characteristic S21^(z) with the input noise signal x(n) and inputs it to the adaptive algorithm execution unit 1112 of the first system.

[0040] Furthermore, the first system adaptive algorithm execution unit 1112 takes the noise signal x(n) after convolving the transfer function S11^(z) in the first system first estimation filter 1113, the noise signal x(n) after convolving the transfer function S21^(z) in the first system second estimation filter 1114, the error e1 output from the first system subtractor 1115, and the error e2 output from the second system signal processing unit 112 as inputs, executes adaptive algorithms such as NLMS, updates the coefficients of the first system variable filter 1111 so that the errors e1 and e2 become 0, and makes the transfer function W1(z) adaptive.

[0041] The second system signal processing unit 112 also has the same structure as the first system signal processing unit 111. The second system signal processing unit 112 includes: a second system variable filter 1121, a second system adaptive algorithm execution unit 1122, a second system first estimation filter 1123 with a pre-set transfer function S22^(z), a second system second estimation filter 1124 with a pre-set transfer function S12^(z), a second system subtractor 1125, n second system auxiliary filters 1126 with a pre-set transfer function H2_i(z), and a second system selector 1127 that selects and outputs any one of the outputs of the n second system auxiliary filters 1126. Here, i is an integer from 1 to n, and the transfer function H2_i(z) represents the transfer function of the i-th second system auxiliary filter 1126.

[0042] In the structure of the second system signal processing unit 112, the input noise signal x(n) is output to the second speaker 14 as the second cancellation signal CA2(n) after passing through the second system variable filter 1121.

[0043] Furthermore, the input noise signal x(n) is sent to the second system selector 1127 after passing through each of the second system auxiliary filters 1126. The second system selector 1127 selects the output of any of the second system auxiliary filters 1126 and outputs it to the second system subtractor 1125. The second system subtractor 1125 subtracts the output of the second system selector 1127 from the second microphone error signal err2(n) picked up by the second microphone 15, and outputs it as error e2 to the second system adaptive algorithm execution unit 1122 and the first system signal processing unit 111.

[0044] Next, the second system variable filter 1121, the second system adaptive algorithm execution unit 1122, the second system first estimated filter 1123, and the second system second estimated filter 1124 constitute a Multiple Error Filtered-X adaptive filter. In the second system first estimated filter 1123, an estimated transfer characteristic S22^(z) of the transfer function S22(z) from the second system signal processing unit 112 to the second microphone 15, calculated through actual measurements, is preset. The second system first estimated filter 1123 convolves the transfer characteristic S22^(z) with the input noise signal x(n) and inputs it to the second system adaptive algorithm execution unit 1122. Furthermore, in the second estimation filter 1124 of the second system, there is a pre-set estimated transfer characteristic S12^(z) that represents the transfer characteristic S12(z) from the second system signal processing unit 112 to the first microphone 13, which is calculated by means of actual measurement, etc. The second estimation filter 1124 of the second system convolves the transfer characteristic S12^(z) with the input noise signal x(n) and inputs it to the second system adaptive algorithm execution unit 1122.

[0045] Then, the second system adaptive algorithm execution unit 1122 takes the noise signal x(n) after convolving the transfer function S22^(z) in the first estimation filter 1123 of the second system, the noise signal x(n) after convolving the transfer function S12^(z) in the second estimation filter 1124 of the second system, the error e2 output from the second system subtractor 1125, and the error e1 output from the first system signal processing unit 111 as inputs, executes the NLMS and other adaptive algorithms, updates the coefficients of the second system variable filter 1121 to make the errors e1 and e2 become 0, and makes the transfer function W2(z) adaptive.

[0046] In addition, n point sets are pre-defined for the active noise control system 1. Each point set is a pair of a first cancellation point and a second cancellation point. The i-th first system auxiliary filter 1116 of the first system signal processing unit 111 corresponds to the first cancellation point of the i-th point set, and the i-th second system auxiliary filter 1126 of the second system signal processing unit 112 corresponds to the second cancellation point of the i-th point set.

[0047] In addition, the combination of the user's head position and posture is used as the head state. Each set of points is set to correspond to different head states. The first elimination point is equivalent to the position of the right ear in the head state corresponding to the set of points to which the first elimination point belongs, and the second elimination point is equivalent to the position of the left ear in the head state corresponding to the set of points to which the second elimination point belongs.

[0048] In addition, the head state corresponding to the point set is determined as follows.

[0049] First, considering the differences in seating position and posture for each user, calculate the approximate front-to-back range of a user's head when sitting upright and facing forward in the noise cancellation target seat, and use this range as... Figure 4 The range Y of the user's head in the forward-backward direction, as shown in figure a, is set. Furthermore, considering the differences in seating height and posture for each user, the approximate vertical range of the user's head when sitting upright and facing forward in the noise cancellation target seat is determined, and this range is used as... Figure 4 The range Z of the user's head in the vertical direction is defined as shown in b. The position of the head in the front-back direction is represented by the position of the ears in the front-back direction, and the position of the head in the vertical direction is represented by the position of the ears in the vertical direction.

[0050] In addition, considering the range of natural head movement for a forward-facing human body, the angle range of head movement that a user sitting in the noise-cancellation seat can approximately rotate around the vertical axis is set as follows: Figure 4 The vertical angle range θ of the car around its axis is shown in Figure c. Additionally, considering the range within which a forward-facing human head can naturally tilt, the range within which a user seated in the noise-cancellation target seat can approximately tilt their head around its axis in the fore-and-aft direction is set as follows: Figure 4 The angle range φ of the head around the axis in the front-rear direction of the car is shown by d.

[0051] Furthermore, starting from any position in the left-right direction at the center of the seat, and in the front-back and up-down directions within both the range Y and the range Z, if the head, which is upright and facing forward, is rotated around the rotation center axis by any angle within the range θ, and the head is laterally flexed around the lateral flexion center axis by any angle within the range φ, the range of possible combinations of positions and postures that the head can take is set as the head state range. From the head state range, as many points as possible are selected to set the head state of the point set in such a way that the interval between each first elimination point and the interval between each second elimination point of each point set is a predetermined distance L.

[0052] Here, the specified distance L, which is the interval between the first elimination points and the interval between the second elimination points, is set to 1 / 10 of the wavelength of the upper limit frequency of the noise to be eliminated, since the spatial range that can effectively eliminate noise, i.e., the zone of Quiet, is a spherical space centered on the first elimination point / second elimination point with a diameter of 1 / 10 of the wavelength of the frequency relative to each frequency.

[0053] In this way, the number of the first elimination point, the second elimination point, the first system auxiliary filter 1116, and the second system auxiliary filter 1116 can be minimized to a minimum within the range that can effectively eliminate noise regardless of the displacement of the user's head.

[0054] However, the specified distance L, which serves as the interval between the first elimination points and the interval between the second elimination points, can also be set to an interval shorter than 1 / 10 of the wavelength of the upper limit frequency of the noise to be eliminated.

[0055] In addition, the point set setting described above can also be done more specifically as follows.

[0056] That is, firstly, such as Figure 4 As shown in c, find the trajectory 41 of the right ear when the head, positioned upright and facing forward, is rotated within the angle range θ at the center of the seat in the left-right direction and within the ranges Y and Z in the front-back and up-down directions, and as shown in c. Figure 4 As shown in d, the trajectory of the right ear when the head is laterally flexed within the angle range φ is determined.

[0057] Then, as Figure 5 Find b in that way as to make Figure 5 The plane obtained by moving along trajectory 42 from trajectory 41 (as shown in figure a) is used as the reference point 43, where the right ear is positioned on the plane without rotation or lateral flexion of the head. Then, as... Figure 5 The solid is obtained by moving the plane back and forth within the range Y and up and down within the range Z, as shown in c. The solid is then set as the range of the first elimination point.

[0058] In addition, for the left ear, the 3D shape is also calculated and used as the range of the second elimination point.

[0059] Then, multiple first elimination points are set at intervals of a predetermined distance L, covering the entire range of the first elimination points. Here, each of these first elimination points represents the position of the right ear in different head states within the range of head states, and the corresponding head state can be calculated based on the position of the first elimination point.

[0060] Therefore, for each first elimination point, the points within the range of the second elimination point corresponding to the same head state as the first elimination point are set as the second elimination point of the same set of points as the first elimination point.

[0061] Furthermore, the transfer function H1_i(z) set in the n first system auxiliary filters 1116 of the first system signal processing unit 111 and the transfer function H2_i(z) set in the n second system auxiliary filters 1126 of the second system signal processing unit 112 are transfer functions that have been learned in advance.

[0062] The following explains the learning of the transfer functions H1_i(z) of the n first system auxiliary filters 1116 and the transfer functions H2_i(z) of the n second system auxiliary filters 1126.

[0063] First, the learning of the transfer function H1_i(z) of the first system auxiliary filter 1116 and the transfer function H2_i(z) of the second system auxiliary filter 1126 is carried out for integers from 1 to n, with the number set as i, and the following first-stage learning process and second-stage learning process are performed.

[0064] The first stage of learning is handled as follows: Figure 6 As shown, this is done in a structure where the signal processing module 11 is replaced with the first-stage learning processing module 4.

[0065] In addition, the first stage of learning processing is performed by connecting the first learning microphone 51 configured at the first elimination point of the i-th point set and the second learning microphone 52 configured at the second elimination point of the i-th point set to the first learning processing module.

[0066] The configuration of the first learning microphone 51 and the second learning microphone 52 is performed, for example, by the following process: placing the virtual mascot in the noise cancellation target seat, adjusting the position and posture of the virtual mascot so that the right ear is located at the first cancellation point of the i-th point set and the left ear is located at the second cancellation point of the i-th point set, setting the first learning microphone 51 at the position of the right ear of the virtual mascot, and setting the second learning microphone 52 at the position of the left ear of the virtual mascot.

[0067] The first-stage learning processing module 4 includes a first-stage learning processing unit 41 of the first system and a second-stage learning processing unit 42 of the second system.

[0068] Furthermore, the first-stage learning processing unit 41 of the first system has the following structure: From Figure 3The first system signal processing unit 111 of the signal processing module 11 shown removes the first system subtractor 1115, the first system auxiliary filter 1116, and the first system selector 1117, and replaces the first system first learning estimation filter 1113 with a first system first learning estimation filter 411. This first system first learning estimation filter 411 is a learning estimation of the estimated transfer function Sv11^(z) of the transfer function Sv11(z) from the first system first stage learning processing unit 41 to the first learning microphone 51. The filter is a first system second learning estimation filter 412, which replaces the first system second estimation filter 1114. The first system second learning estimation filter 412 is a learning estimation filter that sets the estimated transfer function Sv21^(z) of the transfer function Sv21(z) from the first stage learning processing unit 41 of the first system to the second learning microphone 52. The output of the first learning microphone 51 and the output of the second learning microphone 52 are both input as errors to the first system adaptive algorithm execution unit 1112.

[0069] In addition, the first-stage learning processing unit 42 of the second system has the following structure: From Figure 3 The second system signal processing unit 112 of the signal processing module 11 shown removes the second system subtractor 1125, the second system auxiliary filter 1126, and the second system selector 1127, and replaces the second system first learning estimation filter 1123 with a second system first learning estimation filter 421. This second system first learning estimation filter 421 is a learning estimation filter that sets the estimated transfer function Sv22^(z) of the transfer function Sv22(z) from the second system first stage learning processing unit 42 to the second learning microphone 52. A second learning estimation filter 422 is set to replace the second learning estimation filter 1124 of the second system. The second learning estimation filter 422 is a learning estimation filter that sets the estimated transfer function Sv12^(z) of the transfer function Sv12(z) from the first stage learning processing unit 42 of the second system to the first learning microphone 51. The output of the first learning microphone 51 and the output of the second learning microphone 52 are both input as errors to the second system adaptive algorithm execution unit 1122.

[0070] Furthermore, in this structure, the transfer function W1(z) of the first system variable filter 1111 is made to converge and stabilize through the adaptive action of the first system adaptive algorithm execution unit 1112, and the transfer function W2(z) of the second system variable filter 1121 is made to converge and stabilize through the adaptive action of the second system adaptive algorithm execution unit 1122. The converged and stabilized transfer functions W1(z) and W2(z) are obtained as the result of the first stage of learning processing.

[0071] Next, in the second phase of learning processing, such as Figure 7 As shown, this is carried out in a structure in which the signal processing module 11 is replaced by the second-stage learning processing module 6.

[0072] The second-stage learning processing module 6 includes a first-system second-stage learning processing unit 61 and a second-system second-stage learning processing unit 62.

[0073] Furthermore, the first system second-stage learning processing unit 61 includes a first system fixed filter 611 that sets the transfer function W1(z) obtained as the result of the first-stage learning processing as the transfer function, a first system second-stage learning variable filter 612, a first system second-stage learning adaptive algorithm execution unit 613, and a first system second-stage learning subtractor 614.

[0074] In addition, the second system second stage learning processing unit 62 includes a second system fixed filter 621 that sets the transfer function W2(z) obtained as the result of the first stage learning processing as the transfer function, a second system second stage learning variable filter 622, a second system second stage learning adaptive algorithm execution unit 623, and a second system second stage learning subtractor 624.

[0075] The noise signal x(n) input to the second stage learning processing unit 61 of the first system is output to the first speaker 12 after passing through the fixed filter 611 of the first system. The noise signal x(n) input to the second stage learning processing unit 62 of the second system is output to the second speaker 14 after passing through the fixed filter 612 of the second system.

[0076] Additionally, the noise signal x(n) input to the first system second stage learning processing unit 61 is sent to the first system second stage learning subtractor 614 after passing through the first system second stage learning variable filter 612. The first system second stage learning subtractor 614 subtracts the output of the first system second stage learning variable filter 612 from the signal picked up by the first microphone 13, and outputs it as an error to the first system second stage learning adaptive algorithm execution unit 613 and the second system second stage learning adaptive algorithm execution unit 623 of the second system second stage learning processing unit 62.

[0077] Additionally, the noise signal x(n) input to the second system second stage learning processing unit 62 is sent to the second system second stage learning subtractor 624 after passing through the second system second stage learning variable filter 622. The second system second stage learning subtractor 624 subtracts the output of the second system second stage learning variable filter 622 from the signal picked up by the second microphone 15, and outputs it as an error to the second system second stage learning adaptive algorithm execution unit 623 and the first system second stage learning adaptive algorithm execution unit 613 of the first system second stage learning processing unit 61.

[0078] Furthermore, the first system second stage learning adaptive algorithm execution unit 613 of the first system second stage learning processing unit 61 updates the transfer function H1_i(z) of the first system second stage learning variable filter 612 in such a way that the errors input from the first system second stage learning subtractor 614 and the second system second stage learning subtractor 624 are 0, and the second system second stage learning adaptive algorithm execution unit 623 of the second system second stage learning processing unit 62 updates the transfer function H2_i(z) of the second system second stage learning variable filter 622 in such a way that the errors input from the first system second stage learning subtractor 614 and the second system second stage learning subtractor 624 are 0.

[0079] Furthermore, in this structure, through the adaptive action of the first system second stage learning adaptive algorithm execution unit 613, the transfer function H1(z) of the first system second stage learning variable filter 612 is made to converge and stabilize, and the converged and stabilized transfer function H1(z) is set as the transfer function H1_i(z) of the i-th first system auxiliary filter 1116 of the first system signal processing unit 111 of the signal processing module 11. And through the adaptive action of the second system second stage learning adaptive algorithm execution unit 623, the transfer function H2(z) of the second system second stage learning variable filter 622 is made to converge and stabilize, and the converged and stabilized transfer function H2(z) is set as the transfer function H2_i(z) of the i-th second system auxiliary filter 1126 of the second system signal processing unit 112 of the signal processing module 11.

[0080] Next, the control performed by the controller 16 during the actual operation of the active noise control system 1 will be explained.

[0081] The controller 16 repeatedly performs the following processing: based on the head position and posture of the user sitting in the noise cancellation target seat detected by the DMS 17, it calculates the positions of the user's right and left ears; within a set of n points, it identifies the set of points where the first and second cancellation points best match the positions of the user's right and left ears; it controls the first system selector 1117 of the first signal processing unit by selecting and outputting the output of the first system auxiliary filter 1116 corresponding to the identified set of points; and it controls the second system selector 1127 of the second signal processing unit by selecting and outputting the output of the second system auxiliary filter 1126 corresponding to the identified set of points. Furthermore, the set of points where the first and second cancellation points best match the positions of the user's right and left ears is, for example, the set of points where the maximum value of the distance between the first and second cancellation points and the user's right and left ear positions is minimized.

[0082] The embodiments of the present invention have been described above.

[0083] Here, the above implementation shows the case where there is only one noise source. However, by extending the structure of the signal processing module 11 to consider the propagation of each noise source to each cancellation point, the above implementation can also be applied to the case where there are multiple noise sources.

[0084] Furthermore, in the above embodiments, a microphone, speaker, and signal processing unit were provided for the right ear and left ear respectively. However, this embodiment can also be applied to a situation where a microphone, speaker, and signal processing unit are provided for the head, and the noise that can be heard by the right ear and left ear is concentrated and eliminated by using a microphone, speaker, and signal processing unit shared by the right ear and left ear.

[0085] Explanation of reference numerals in the attached figures

[0086] 1…Active noise control system, 4…First-stage learning processing module, 6…Second-stage learning processing module, 11…Signal processing module, 12…First speaker, 13…First microphone, 14…Second speaker, 15…Second microphone, 16…Controller, 17…DMS, 41…First system first-stage learning processing unit, 42…Second system first-stage learning processing unit, 51…First learning microphone, 52…Second learning microphone, 61…First system second-stage learning processing unit, 62…Second system second-stage learning processing unit, 111…First system signal processing unit, 112…Second system signal processing unit, 411…First system first learning estimated filter, 412…First system second learning estimated filter, 421…Second system first learning estimated filter, 422…Second system second learning estimated filter, 611…First system fixed filter, 612…First system second-stage learning variable filter, 613… The system consists of: 614… First system second-stage learning adaptive algorithm execution unit, 621… Second system fixed filter, 622… Second system second-stage learning variable filter, 623… Second system second-stage learning adaptive algorithm execution unit, 624… Second system second-stage learning subtractor, 1111… First system variable filter, 1112… First system adaptive algorithm execution unit, 1113… First system first estimated filter, 1114… First system second estimated filter, 1115… First system subtractor, 1116… First system auxiliary filter, 1117… First system selector, 1121… Second system variable filter, 1122… Second system adaptive algorithm execution unit, 1123… Second system first estimated filter, 1124… Second system second estimated filter, 1125… Second system subtractor, 1126… Second system auxiliary filter, 1127… Second system selector.

Claims

1. An active noise control system, which is an active noise reduction control system, has the following characteristics: The head detection unit detects the position of the user's head while seated. Switching control unit; Speaker, outputs noise-canceling sound; Microphone, detecting error signals; Multiple auxiliary filters, corresponding to multiple different noise cancellation positions, generate and output a correction signal based on the noise signal representing the noise. This correction signal is a correction signal that corrects the erroneous signal detected by the microphone in a way that compensates for the difference between the noise cancellation position corresponding to the auxiliary filter and the position of the microphone. The error correction unit corrects the error signal output by the microphone using a correction signal output by any one of the auxiliary filters, and outputs the corrected error signal. as well as The adaptive filter performs adaptive operation using the corrected error signal output by the error correction unit, and generates a noise-cancelled tone to be output from the speaker from the noise signal. The switching control unit switches the auxiliary filter according to the head position detected by the head detection unit, so that the error correction unit corrects the error signal using the correction signal output by the auxiliary filter. This auxiliary filter is an auxiliary filter whose corresponding noise cancellation position matches the head position detected by the head detection unit. The multiple noise cancellation positions corresponding to the multiple auxiliary filters are multiple positions configured at specified intervals only within a space that allows a user, when seated upright and facing forward, to move their head by rotating or laterally bending their head, with the head positioned at the center of the seat in the left-right direction and within any position within a specified range in the up-down and front-back directions.

2. An active noise control system, which is an active noise reduction control system, comprising: The head detection unit detects the position of the left and right ears of the user sitting in the seat; Switching control unit; and The two noise control systems are a noise control system for the right ear and a noise control system for the left ear. Each noise control system is equipped with: Speaker, outputs noise-canceling sound; Microphone, detecting error signals; Multiple auxiliary filters, corresponding to multiple different noise cancellation positions, generate and output a correction signal based on a noise signal representing noise. This correction signal corrects the erroneous signal detected by the microphone by compensating for the difference between the noise cancellation position corresponding to the auxiliary filter and the position of the microphone. The error correction unit corrects the error signal output by the microphone using a correction signal output by any one of the auxiliary filters, and outputs the corrected error signal. as well as An adaptive filter performs adaptive operation using the corrected error signal output by the error correction unit of the right ear noise control system and the corrected error signal output by the error correction unit of the left ear noise control system, generating a noise-cancelling tone to be output from the speaker from the noise signal. The switching control unit switches the auxiliary filter according to the position of the right ear detected by the head detection unit, so that the error correction unit of the right ear noise control system corrects the error signal using the correction signal output by the auxiliary filter. This auxiliary filter is an auxiliary filter whose corresponding noise cancellation position matches the position of the right ear detected by the head detection unit. The switching control unit switches the auxiliary filter according to the position of the left ear detected by the head detection unit, so that the error correction unit of the left ear noise control system corrects the error signal using the correction signal output by the auxiliary filter. This auxiliary filter is an auxiliary filter whose corresponding noise cancellation position matches the position of the left ear detected by the head detection unit. The multiple noise cancellation positions corresponding to the multiple auxiliary filters of the right ear noise control system are multiple positions configured at predetermined intervals only within the right ear target space. This right ear target space is the space within which a user, when seated upright and facing forward, can move their right ear by rotating or laterally tilting their head, with their head positioned at the center of the seat in the left-right direction and within any predetermined range in the up-down and front-back directions. The multiple noise cancellation positions corresponding to the multiple auxiliary filters of the left ear noise control system are multiple positions configured at predetermined intervals only within the left ear target space. The left ear target space is the space in which a user, when seated, with their head upright and facing forward, is located at the center of the seat in the left-right direction and at any position within a predetermined range in the up-down and front-back directions, and can move their left ear by rotating or laterally bending their head.

3. The active noise control system according to claim 2, The right ear object space is a three-dimensional space defined as follows: when the head is positioned at the center of the seat in the left-right direction and at any position within the specified range in the up-down and front-back directions, a point at the position of the right ear on the head is rotated around the rotation axis of the head at that position by a specified angle within a range of rotatable angles, forming a line as the trajectory of this rotation. This line is then rotated around the lateral flexion axis of the head at that position by a specified angle within a range of lateral flexion angles, forming a surface as the trajectory of this rotation. This surface is then moved within the specified range along the up-down and front-back directions of the head as it moves upright and facing forward, with the right ear moving in the up-down and front-back directions, forming the trajectory of this movement, thus creating the three-dimensional space. The left ear object space is a three-dimensional space in which, when the head is in a position centered on the seat in the left-right direction and in any position within the specified range in the up-down and front-back directions, a point at the position of the left ear on the head is rotated around the rotation axis of the head in that position by a specified angle within the range of rotatable angles, and a line is obtained as the trajectory of this rotation. This line is then rotated around the lateral flexion axis of the head in that position by a specified angle within the range of lateral flexion angles, and a surface is obtained as the trajectory of this rotation. This surface is then moved within the specified range along the up-down and front-back directions of the head as it moves upright and facing forward, and the left ear moves along the up-down and front-back directions, and this movement is obtained as the trajectory of the movement, thus forming the three-dimensional space.

4. The active noise control system according to any one of claims 1 to 3, The specified interval is a distance of 1 / 10 of the wavelength of the upper limit frequency of the noise, and the noise is the target of this active noise control system.

5. The active noise control system according to claim 4, The seat in question is a car seat.

6. The active noise control system according to any one of claims 1 to 3, The seat in question is a car seat.

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