Signal processing device, signal processing method, and program
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2026-01-20
- Publication Date
- 2026-08-13
Smart Images
Figure JP2026001601_13082026_PF_FP_ABST
Abstract
Description
Signal processing device, signal processing method, and program
[0001] The present disclosure relates to a signal processing device, a signal processing method, and a program, and more particularly to a signal processing device, a signal processing method, and a program that can achieve more suitable noise cancellation.
[0002] In load noise cancellation using an acceleration sensor, when designing a noise cancellation filter (NC filter), it is necessary to cope with various environmental changes in the vehicle interior. The noise path from the tire (referred to as the primary path) may change, or the transmission path from the speaker that outputs the cancellation signal to the ear position serving as the control point (listening point) (referred to as the secondary path) may change.
[0003] As a method for coping with environmental changes, there is a method of preparing in advance filters suitable for each environment (condition) and switching to the optimal filter for each condition or updating the filter coefficients according to environmental changes.
[0004] Patent Document 1 discloses an active noise control system that performs adaptive processing using an auxiliary filter and a microphone for coping with fluctuations in the detected listening position.
[0005] Japanese Unexamined Patent Application Publication No. 2022-13141
[0006] On the other hand, in the method of preparing and switching fixed filters for each condition for all speakers, it is necessary to prepare a huge number of filters according to the conditions.
[0007] The present disclosure has been made in view of such a situation and is intended to achieve more suitable noise cancellation.
[0008] The signal processing device of the present disclosure includes a noise canceling processing unit that outputs a cancellation signal from a plurality of speakers to cancel noise at each of a plurality of control points in the space of the moving body, based on sensor values obtained from an acceleration sensor mounted on the moving body, wherein the noise canceling processing unit generates the cancellation signal using a first filter that is switched on a condition basis for a first speaker where the sound interference to all the control points is greater, and generates the cancellation signal using a second filter that is not switched on a condition basis at least for a second speaker where the interference is smaller.
[0009] The signal processing method of the present disclosure is a signal processing device that outputs cancellation signals from a plurality of speakers to cancel noise at each of a plurality of control points in the space of a mobile body based on sensor values obtained from an acceleration sensor mounted on the mobile body, and includes a process of generating the cancellation signal using a first filter that is switched on a condition basis for a first speaker where the sound interference to all of the control points is greater, and generating the cancellation signal using a second filter that is not switched on a condition basis at least for a second speaker where the interference is smaller.
[0010] The program of this disclosure is a program that causes a computer to output cancellation signals from multiple speakers to cancel noise at each of multiple control points in the space of a mobile body, based on sensor values obtained from an acceleration sensor mounted on the mobile body, to generate the cancellation signal using a first filter that is switched on a condition basis for the first speaker where the sound interference to all the control points is greater, and to generate the cancellation signal using a second filter that is not switched on a condition basis for the second speaker where the interference is smaller.
[0011] In this disclosure, based on sensor values obtained from an acceleration sensor mounted on a moving body, cancellation signals for canceling noise at each of a plurality of control points in the space of the moving body are output from a plurality of speakers. For a first speaker where the sound interference to all of the control points is greater, the cancellation signal is generated using a first filter that is switched on a condition-by-condition basis, and for a second speaker where the interference is smaller, the cancellation signal is generated using a second filter that is not switched on a condition-by-condition basis at least.
[0012] This is a diagram showing an example of a noise-canceling system configuration. This is a flowchart explaining the flow of noise-canceling operation. This is a diagram explaining the design of a filter. This is a diagram explaining the measurement of the transmission characteristics from the speaker to the microphone. This is a diagram showing examples of the transmission characteristics measured for each microphone. This is a diagram explaining the sum of acoustic power. This is a diagram explaining the noise reduction effect in normal conditions. This is a diagram explaining the noise reduction effect in a reclined state. This is a diagram showing other examples of noise-canceling system configurations. This is a diagram showing an example of noise-canceling processing according to the seat arrangement. This is a diagram showing an example of noise-canceling processing according to the seat arrangement. This is a block diagram showing an example of computer hardware configuration.
[0013] The following describes the forms for implementing this disclosure (hereinafter referred to as embodiments). The explanation will be given in the following order.
[0014] 1. Challenges of the Conventional Technology and an Overview of the Technology Disclosed 2. Configuration and Operation of the Noise Cancelling System 3. Example of Filter Design 4. Noise Reduction Effect 5. Use of Adaptive Filters 6. Example of Noise Cancelling Processing According to Sheet Arrangement 7. Application Examples 8. Example of Computer Hardware Configuration
[0015] <1. Issues with the Conventional Technology and an Overview of the Technology in This Disclosure> (Issues with the Conventional Technology) When designing an NC filter for road noise cancellation using an acceleration sensor, it is necessary to accommodate various environmental changes inside the vehicle's cabin. The noise path from the tires (primary path) may change, or the transmission path (secondary path) from the speaker that outputs the cancellation signal to the control point (listening point), which is the ear position, may change.
[0016] One way to adapt to environmental changes is to prepare filters suitable for each environment (condition) in advance, and then switch to the optimal filter for each condition or update the filter coefficients in response to environmental changes.
[0017] For example, Patent Document 1 (Japanese Patent Application Publication No. 2022-13141) discloses an active noise control system that performs adaptive processing using an auxiliary filter and microphone to respond to changes in the detected listening position. However, in the active noise control system disclosed in Patent Document 1, there are concerns about the divergence of cancellation signals and the increase in computational load during adaptive processing.
[0018] On the other hand, one can consider responding to environmental changes using only fixed NC filters, without using microphones or adaptive filters. In this case, to detect changes in the environment (conditions), vehicle information related to the vehicle can be acquired, for example, from the in-vehicle ECU (Electronic Control Unit), and the NC filters can be switched based on the acquired vehicle information. However, this would require preparing a huge number of NC filters according to the conditions, and considering the memory capacity of the in-vehicle DSP (Digital Signal Processor), it is desirable to have a small number of NC filters.
[0019] Now, let's consider how many filters will actually be needed.
[0020] For example, let's say we prepare NC filters for the two front seats of a vehicle, according to the seat recline angle and the variable seat position (forward and backward). Specifically, let's assume that the recline angle has three patterns each for the front left and front right seats (forward tilt, middle, and backward tilt), and the seat position has three patterns each for the front left and front right seats (forward, middle, and backward). In this case, a filter corresponding to (3 x 3) x (3 x 3) = 81 conditions is required per seat.
[0021] Typically, a vehicle has two or more seats, and if each seat has a seat speaker, then for four seats, 81 x 4 = 324 filter sets would be needed. Furthermore, if there are six different seat positions, and the number of corresponding patterns is increased by considering factors such as the passenger's height and the seat height, the number of filters required increases exponentially.
[0022] (Summary of the technology related to this disclosure) In contrast, if the number of necessary filters can be halved, it will be advantageous in terms of reducing memory capacity in automotive DSPs and other devices where hardware constraints are severe.
[0023] Therefore, in the technology disclosed herein, the filter is switched for speakers that are greatly affected by environmental changes, while a fixed filter is used for speakers that are less affected by environmental changes. This reduces the risk of cancellation signal divergence and the computational load, while aiming to achieve more suitable noise cancellation.
[0024] <2. Configuration and Operation of the Noise Cancelling System> The configuration and operation of a noise cancelling system to which the technology related to this disclosure is applied will be described below.
[0025] (System Configuration) Figure 1 shows an example of the configuration of a noise-canceling system to which the technology described herein is applied.
[0026] The noise-canceling system 1 shown in Figure 1 is configured to include sensors 10-1 to 10-N and a noise-canceling processing unit 20. The noise-canceling processing unit 20 is implemented in a signal processing device that constitutes an in-vehicle electronic device mounted on a vehicle as a mobile object.
[0027] Sensors 10-1 to 10-N are each configured as acceleration sensors mounted on a vehicle. Sensors 10-1 to 10-N are configured as acceleration sensors used for road noise cancellation inside the vehicle's cabin. In this case, sensors 10-1 to 10-N are installed near the vehicle's tires, which are the source of the noise. Hereafter, unless distinguished, sensors 10-1 to 10-N will simply be referred to as sensor 10.
[0028] Furthermore, the sensor 10 may be used to cancel noise such as wind noise generated as the vehicle is in motion. In this case, the sensor 10 can be placed on the side panel or ceiling inside the vehicle.
[0029] The noise cancellation processing unit 20 generates a noise cancellation signal based on the sensor values obtained from each sensor 10 and the built-in noise cancellation filter while the vehicle is in motion, with the left and right ear positions of the occupants P1 and P2 as cancellation points (multiple control points). The noise cancellation processing unit 20 then outputs the generated noise cancellation signal through speakers SP_f1, SP_f2 and speakers SP_r1, SP_r2 installed in the vehicle's cabin, thereby performing road noise cancellation.
[0030] Here, passenger P1 is seated in the front seat of the two rows, and speakers SP_f1 and SP_f2 are installed, for example, near the headrest of the front seat. On the other hand, passenger P2 is seated in the rear seat of the two rows, and speakers SP_r1 and SP_r2 are installed, for example, near the headrest of the rear seat.
[0031] The noise cancellation processing unit 20 includes a first filter 31, a second filter 32, a filter selection unit 33, and a filter holding unit 34.
[0032] The noise-canceling processing unit 20 generates a cancellation signal for the speakers SP_f1 and SP_f2 installed in the front seats using the first filter 31. The noise-canceling processing unit 20 also generates a cancellation signal for the speakers SP_r1 and SP_r2 installed in the rear seats using the second filter 32.
[0033] The filter selection unit 33 switches the first filter 31 using NC filters stored (stored) in the filter holding unit 34, based on vehicle information acquired from the in-vehicle ECU or the like. The filter holding unit 34 stores NC filters designed for each condition. Vehicle information includes the seat position in the cabin, the positions of speakers SP_f1 and SP_f2 installed on the front seats, physical information such as the passenger's sitting height, and vehicle position information such as GPS (Global Positioning System) information. The filter selection unit 33 may also switch the first filter 31 based on the relative position (positional relationship) between the speakers SP_f1 and SP_f2 installed on the front seats and the passenger. In this case, the relative position can be calculated based on the vehicle information described above. Alternatively, the relative position can be calculated based on sensing information obtained by sensing the cabin. For example, the relative position may be calculated based on the distance to the passenger measured by a distance measuring sensor such as LiDAR (Light Detection and Ranging) installed at the positions of speakers SP_f1 and SP_f2. Alternatively, the relative position may be calculated by outputting inaudible human sounds from speakers SP_f1 and SP_f2 and capturing the reflected sound with a microphone built into the front seat.
[0034] Thus, the first filter 31 is an NC filter that can be switched on a condition-by-condition basis, while the second filter 32 is an NC filter that cannot be switched on a condition-by-condition basis at least. Hereafter, the second filter 32 will be assumed to be a fixed NC filter, but it may be an NC filter that is switched less frequently than the first filter 31.
[0035] (Noise Cancelling Operation) The flow of noise cancellation operation by the noise cancellation processing unit 20 will be explained with reference to the flowchart in Figure 2. The process in Figure 2 is executed when the vehicle is in motion.
[0036] In step S11, the noise cancellation processing unit 20 acquires sensor values from each sensor 10 (accelerometer).
[0037] In step S12, the noise cancellation processing unit 20 generates a cancellation signal using the first filter 31, which is switched according to the conditions, for speakers SP_f1 and SP_f2, which have greater sound interference to all control points.
[0038] On the other hand, in step S13, the noise cancellation processing unit 20 generates a cancellation signal using the second filter 32 for speakers SP_r1 and SP_r2, which have less sound interference to all control points compared to speakers SP_f1 and SP_f2.
[0039] Then, in step S14, the noise cancellation processing unit 20 outputs cancellation signals from speakers SP_f1, SP_f2 and speakers SP_r1, SP_r2, respectively.
[0040] Thus, the speakers that output the cancellation signal using the second filter 32, which is a fixed NC filter, are speakers with a fixed position and orientation, that is, speakers SP_r1 and SP_r2 installed in the rear seats where the seat position is fixed. When the seats are fixed, such as in the rear seats, environmental changes are unlikely to occur, so even with a fixed NC filter, a relatively good sound-dampening effect can be obtained.
[0041] On the other hand, the speakers that output the cancellation signal using the first filter 31, which is a switchable variable NC filter, are speakers with variable position and orientation, that is, the front seat speakers SP_f1 and SP_f2 whose position and orientation change. Since the optimal NC filter is switched based on the seat position acquired as vehicle information, the body information of the passenger, and the relative position between the speakers SP_f1 and SP_f2 and the passenger, a noise reduction effect corresponding to environmental changes can be obtained.
[0042] According to the above processing, for the speakers greatly affected by environmental changes, the filter is switched to generate a cancellation signal, and for the speakers less affected by environmental changes, a cancellation signal using a fixed filter is generated. As a result, compared with the configuration of preparing and switching filters for each condition for all speakers, it is possible to reduce the memory capacity while maintaining the noise reduction effect corresponding to environmental changes, and to realize more suitable noise cancellation.
[0043] <3. Example of Filter Design> Referring to FIG. 3, the design of the NC filter that is switched for each condition such as the first filter 31 will be described.
[0044] In FIG. 3, an example of designing a filter for reducing noise at all control points (here, four points) for the front and rear two seats of the vehicle is shown.
[0045] First, under condition A where the seat position and speaker position are in the default state, as Step 1, a filter for noise reduction control by all speakers for all control points is designed. Here, a filter A1 for the front speakers installed on the front seat and a filter A2 for the rear speakers installed on the rear seat (hereinafter, referred to as the front SP filter A1, the rear SP filter A2, etc.) are designed.
[0046] Next, as condition B, assume a case where the seat position is changed from condition A, for example, by changing the reclining of the front seat.
[0047] Here, if new filters for the front SP and the rear SP are designed for the noise at each control point when the seat position is changed, the number of necessary filters will increase accordingly. Therefore, in the technology according to the present disclosure, even under condition B, the rear SP filter A2 will be used as it is.
[0048] That is, as Step 2, with the rear SP filter A2, obtain the residual signal between the cancellation signal and the noise at all control points in the state where the cancellation signal is reproduced only from the rear speaker (rear SP). And as Step 3, design the front SP filter B1 so as to cancel the residual signal at all control points only with the front speaker (front SP). During the noise cancellation operation, as Step 4, perform the noise cancellation operation using the front SP filter B1 for the front SP and the rear SP filter A2 for the rear SP.
[0049] Thus, in the technology according to the present disclosure, by only designing the front SP filter B1, it is not necessary to design the rear SP filter corresponding to condition B, and the same noise reduction effect as when using the rear SP filter corresponding to condition B can be maintained.
[0050] For other conditions C and D where the state of the front seat is changed, it is only necessary to design the front SP filter C1 and the front SP filter D1, and there is no need to design the rear SP filter corresponding to conditions C and D. Therefore, the necessary filters for various conditions are only the front SP filters, and the number of necessary filters can be halved compared to the case where the front SP filter and the rear SP filter are designed for each condition.
[0051] Here, the reason for switching the filter for the front SP will be explained.
[0052] Figure 4 illustrates the measurement of transmission characteristics from a speaker to a microphone. In Figure 4, an example is shown in which the transmission characteristics are measured with the front seat reclined, using microphone MIC_f located at the ear position of a passenger seated in the front seat and microphone MIC_r located at the ear position of a passenger seated in the rear seat.
[0053] Specifically, Figure 4A shows an example of measuring the transmission characteristics from speaker SP_f installed on the front seat to microphone MIC_f on the front seat and microphone MIC_r on the rear seat. Figure 4B shows an example of measuring the transmission characteristics from speaker SP_r installed on the rear seat to microphone MIC_f on the front seat and microphone MIC_r on the rear seat.
[0054] Figure 5 shows examples of transfer characteristics measured in microphone MIC_f and microphone MIC_r under the conditions shown in Figure 4.
[0055] Figure 5A shows the acoustic power (sound pressure level) at microphone MIC_f measured with speaker SP_f as the sound source as a solid line, and the acoustic power (sound pressure level) at microphone MIC_f measured with speaker SP_r as the sound source as a dashed line. As shown in the figure, the acoustic power from speaker SP_f, which is closer to microphone MIC_f, is higher than the acoustic power from speaker SP_r.
[0056] In Figure 5B, the acoustic power (sound pressure level) measured at microphone MIC_r with speaker SP_f as the sound source is shown by a solid line, and the acoustic power (sound pressure level) measured at microphone MIC_r with speaker SP_r as the sound source is shown by a dashed line. As shown in the figure, the acoustic power from speaker SP_r, which is closer than microphone MIC_r, is higher than the acoustic power from speaker SP_f. However, the acoustic power from speaker SP_f shown in Figure B (solid line) is at a slightly higher level compared to the acoustic power from speaker SP_r shown in Figure A (dashed line).
[0057] Figure 6 illustrates the sum of acoustic power measured at microphones MIC_f and MIC_r, respectively, using speakers SP_f and SP_r as sound sources.
[0058] Specifically, in Figure 6, the sum of the acoustic power measured at microphones MIC_f and MIC_r using speaker SP_f as the sound source is shown by a solid line, and the sum of the acoustic power measured at microphones MIC_f and MIC_r using speaker SP_r as the sound source is shown by a dashed line. As shown in the figure, when the front seat is reclined, the acoustic power from speaker SP_f to each microphone is greater than the acoustic power from speaker SP_r to each microphone.
[0059] In other words, when the front seats are reclined, the speaker SP_f installed in the front seats interferes more with each control point than the speaker SP_r installed in the rear seats. Therefore, by making speaker SP_f a speaker that outputs a cancellation signal generated using filters switched according to the conditions, the sound dampening effect can be maintained more effectively than switching filters for speaker SP_r, which has lower sound power.
[0060] Therefore, in the noise-canceling system 1 shown in Figure 1, speakers SP_f1 and SP_f2 are defined as speakers that, depending on the conditions, increase the sum of acoustic power across all control points, while speakers SP_r1 and SP_r2 are defined as speakers that, regardless of the conditions, have a smaller sum of acoustic power than speakers SP_f1 and SP_f2.
[0061] In addition to determining the speaker that causes the greatest sound interference to each control point based on acoustic power and sound pressure level, if the effects of reflected waves and standing waves in space are small, the speaker that causes the greatest sound interference to each control point may also be determined based on the distance from the speaker. Since the sound interference from the speaker increases as the distance between the speaker and the control point decreases, it is desirable to use the speaker that outputs the cancellation signal generated using filters switched according to the conditions as the speaker with the smallest sum of distances to each control point.
[0062] In other words, in the noise-canceling system 1 shown in Figure 1, speakers SP_f1 and SP_f2 may be speakers whose sum of distances to all control points is smaller, and speakers SP_r1 and SP_r2 may be speakers whose sum of distances to all control points is larger than that of speakers SP_f1 and SP_f2.
[0063] However, in enclosed spaces such as the interior of a car, the relationship between distance and acoustic power (sound pressure level) is not inversely proportional due to the effects of reflection and other factors. Therefore, it is desirable to pre-measure the transmission characteristics from the speaker to the control point and use the speaker with the largest total acoustic power as the speaker that outputs the cancellation signal generated using filters switched according to the conditions.
[0064] <4. Noise Reduction Effect> The noise reduction effect of the technology related to this disclosure will be explained.
[0065] Figure 7 illustrates the noise reduction effect when the front right seat and rear right seat of the vehicle are in their normal state (not reclined).
[0066] Figure 7A shows the noise reduction obtained at one of the control point ear positions (the right ear position on the window side) based on actual measurements, after designing the NC filter for the front right seat under normal conditions. Figure 7B shows the noise reduction obtained at one of the control point ear positions (the right ear position on the window side) based on actual measurements, after designing the NC filter for the rear right seat under normal conditions. In both Figures A and B, the measurement results for 1 / 3 octave band analysis in the 160-250 Hz range are shown.
[0067] As shown in the diagram, a noise reduction of up to approximately 10 dB is achieved in both the front right seat and the rear right seat.
[0068] Figure 8 illustrates the noise reduction effect when the rear right seat of the vehicle is in its normal position and the front right seat is reclined (tilted approximately 15° from the normal position).
[0069] Figure 8A shows the amount of noise reduction obtained at one of the control point ear positions (the right ear position on the window side) after designing the NC filter for the front right seat using each method and conducting actual measurements. Figure 8B shows the amount of noise reduction obtained at one of the control point ear positions (the right ear position on the window side) after designing the NC filter for the rear right seat using each method and conducting actual measurements.
[0070] Specifically, in Figures A and B of Figure 8, the graph for CASE 1, shown by a solid line, represents the amount of noise reduction when using the NC filter designed under normal conditions as explained with reference to Figure 7.
[0071] The graph for CASE 2, shown by the dotted line, illustrates the noise reduction achieved when newly designed and used NC filters for the front right seat and the rear right seat in a reclined position. In other words, this is the conventional method of preparing all the necessary filters for each condition.
[0072] The graph for CASE 3, shown by the long dashed line, shows the amount of noise reduction when the NC filter for the rear right seat, designed under normal conditions, is used as is, while a new NC filter for the front right seat is designed and used in the reclined position using the method disclosed herein.
[0073] The graph for CASE 4, shown by the short dashed line, illustrates the noise reduction when the NC filter for the rear right seat, designed under normal conditions, is used as is, while a new NC filter is designed to apply noise reduction control only to the control point of the front right seat when the seat is reclined. In other words, the NC filter for the front right seat is designed while ignoring the noise reduction effect at the control point of the rear right seat.
[0074] As shown in the graph for CASE 1, when the NC filter designed under normal conditions is used as is, a deterioration in noise reduction effect is particularly observed in the reclined front right seat (Figure A).
[0075] As shown in the graph for CASE 2, a good noise reduction effect can be obtained by newly designing and using NC filters for the front right seat and the rear right seat. However, the method in CASE 2 has the disadvantage that the number of filters required for each condition becomes enormous.
[0076] As shown in the graph of CASE 3, when a new NC filter for the front right seat is designed and used using the method of this disclosure, a noise reduction effect close to that of the CASE 2 method (deterioration limited to about 2 dB) can be obtained for both the front right seat and the rear right seat. Furthermore, compared to the CASE 2 method, the method of this disclosure reuses the NC filter for the rear right seat, thus suppressing the increase in the number of filters required.
[0077] As shown in the graph in CASE 4, when a new NC filter is designed and used to apply noise reduction control only to the control point of the front right seat, a slight noise reduction effect is obtained in the front right seat (Figure A), but the noise reduction effect deteriorates in the rear right seat (Figure B). From the graph in CASE 4, it can be seen that when designing NC filters for each condition, it is necessary to consider the interference of each speaker to each control point.
[0078] The above demonstrates the superiority of filter design using the CASE3 method with the technology described herein.
[0079] <5. Use of Adaptive Filters> Figure 9 shows another example of a noise-canceling system to which the technology described herein is applied.
[0080] The noise-canceling system 201 shown in Figure 9 differs from the noise-canceling system 1 in Figure 1 in that, in the noise-canceling processing unit 20, an adaptive filter 231 is provided in place of the first filter 31, and the filter coefficient can be adjusted based on the error signal.
[0081] In the noise-canceling system 201 shown in Figure 9, the filter coefficients of the adaptive filter 231 are determined by LMS (Least Mean Squares) based on the error signal obtained by the error microphone MIC_e installed inside the vehicle cabin.
[0082] In the adaptive filter 231, the sensor value from the sensor 10 is filtered using filter coefficients obtained by the LMS, thereby generating cancellation signals output from speakers SP_f1 and SP_f2. The cancellation signals output from speakers SP_f1 and SP_f2 are picked up along with noise by the error microphone MIC_e. The signal consisting of the cancellation signal and noise picked up by the error microphone MIC_e in this way is supplied to the LMS as a new error signal.
[0083] In the above configuration, for speakers that are greatly affected by environmental changes, a cancellation signal is generated using an adaptive filter with adjustable filter coefficients, while for speakers that are less affected by environmental changes, a cancellation signal is generated using a fixed filter. This reduces the amount of computation required for adaptive processing compared to a configuration that generates a cancellation signal using an adaptive filter for all speakers, while suppressing the complexity of processing to control divergence, thereby enabling more suitable noise cancellation.
[0084] <6. Example of noise cancellation processing according to seat arrangement> In the technology relating to this disclosure, since the sound interference to each control point of the seat speaker is determined according to the seat arrangement, noise cancellation processing is performed according to the seat arrangement.
[0085] (Example of front seat rotation) As vehicle driving becomes more automated in the future, it is expected that the degree of freedom in the orientation and position of seats in the vehicle interior will increase. For example, as shown in Figure 10, it is conceivable that in the interior of vehicle 300, the front seat on which speaker group G310 is installed may rotate to face the rear seat on which speaker group G320 is installed.
[0086] In this case, the positions of the control points and speakers change significantly, making it essential to update or switch the NC filters to avoid degrading the sound-dampening effect. On the other hand, the high degree of flexibility in sheet placement could result in a large number of NC filters being required to maintain the sound-dampening effect.
[0087] In contrast, by applying the technology described herein, only the NC filters used for speakers whose position and orientation change significantly, such as the speaker group G310 installed in the front seats, are switched. This makes it possible to reduce the number of filters required while maintaining the sound-dampening effect at each control point.
[0088] (Example of a 3-row seating arrangement) Figure 11 shows a vehicle 400 having three rows of seats. It is assumed that noise cancellation processing is performed using 12 speakers, speaker groups G410, G420, and G430, which are installed in the first row, second row, and third row of seats, respectively, within the interior of the vehicle 400.
[0089] First, in the normal state shown on the left side of the diagram, the NC filters for each speaker are designed to target the first to third rows of seats for sound reduction. This ensures that the sound reduction effect is evenly distributed across all seats.
[0090] Next, as shown on the right side of the figure, consider a situation where the in-vehicle environment changes, such as when the passengers in the third row seats are removed, and it is desired that the sound-canceling effect be obtained only for the first and second row seats. In this case, using the technology disclosed herein, the residual signal between the cancellation signal and noise is obtained at the control points of the first and second row seats while the cancellation signal is being reproduced only from the speaker group G410 of the first row seats and the speaker group G430 of the third row seats. Then, a new NC filter is designed so that the residual signal at the control points of the first and second row seats is canceled using only the speaker group G420 of the second row seats. During noise cancellation operation, the sound-canceling effect of the first and second row seats can be enhanced by switching the NC filter for speaker group G420.
[0091] (Examples of other seat arrangements) Figure 12 shows a vehicle 500 with one seat in the front row and three seats in the rear row (left, center, and right). We will assume a case where noise cancellation processing is performed using eight speakers in the interior of vehicle 500: speaker group G510 installed on the front seat and speaker groups G520, G530, and G540 installed on the rear left, center, and right seats, respectively.
[0092] In conventional methods, as mentioned above, if a seat speaker is installed for each seat, then for four seats, 81 x 4 = 324 filter sets would be required.
[0093] In contrast, in the technology disclosed herein, the speaker group G530, which is installed on the center back seat, is the speaker that causes the greatest sound interference for each seat, that is, the speaker that generates the largest total sound power (smallest total distance) for all control points. Specifically, a NC filter that is switched according to the conditions is used for speaker group G530, while a fixed NC filter is used for the other speaker groups G510, G520, and G540. As a result, only 81 filters for speaker group G530 and 3 filters each for speaker groups G510, G520, and G540, totaling 84 filters, is required, which reduces the number of filters needed to about one-quarter compared to conventional methods.
[0094] <7. Examples of Application> In the above, an embodiment of the technology relating to this disclosure has been described in which it is applied to a vehicle (automobile) equipped with an acceleration sensor. However, it can also be applied to other vehicles such as railway cars, ships, aircraft, and even other mobile devices including drones.
[0095] In this case, a noise-canceling system applying the technology described herein can output cancellation signals from multiple speakers to cancel noise at each of multiple control points in the space of the moving object, based on sensor values obtained from an acceleration sensor mounted on the moving object. At this time, for the first speaker where the sound interference to all control points is greater, a cancellation signal is generated using a first filter that is switched on a condition-by-condition basis, and for the second speaker where the interference is less than that of the first speaker, a cancellation signal is generated using a second filter that is not switched on a condition-by-condition basis at least.
[0096] This allows for a more optimal noise cancellation solution compared to a configuration that requires setting and switching between conditional filters for all speakers, even in any moving object, while reducing memory capacity and maintaining noise reduction effectiveness in response to environmental changes.
[0097] <8. Examples of Computer Hardware Configurations> The series of processes described above can be executed by hardware or by software. When the series of processes are executed by software, the programs that make up the software are installed from a program storage medium onto a computer that is built into dedicated hardware, or a general-purpose personal computer.
[0098] Figure 13 is a block diagram showing an example of the hardware configuration of a computer that executes the series of processes described above by a program. At least a part of the in-vehicle electronic equipment (signal processing device) that constitutes the noise canceling system 1,201 is composed of, for example, a computer 800 having a configuration similar to that shown in Figure 13.
[0099] The CPU (Central Processing Unit) 801, ROM (Read Only Memory) 802, and RAM (Random Access Memory) 803 are interconnected by a bus 804.
[0100] An input / output interface 805 is further connected to the bus 804. An input unit 806 consisting of a keyboard, mouse, etc., and an output unit 807 consisting of a display, speakers, etc. are connected to the input / output interface 805. In addition, a storage unit 808 consisting of a hard disk, non-volatile memory, etc., a communication unit 809 consisting of a network interface, etc., and a drive 810 that drives removable media 811 are connected to the input / output interface 805.
[0101] In the computer 800 configured as described above, the CPU 801 loads, for example, a program stored in the memory unit 808 into the RAM 803 via the input / output interface 805 and the bus 804, and executes it, thereby performing the series of processes described above.
[0102] The program executed by the CPU 801 is recorded on removable media 811, for example, or provided via a wired or wireless transmission medium such as a local area network, the internet, or digital broadcasting, and installed in the storage unit 808.
[0103] The program executed by the computer 800 may be a program that is processed chronologically in the order described herein, or it may be a program that is processed in parallel or at necessary times, such as when a call is made.
[0104] In this specification, a system refers to a collection of multiple components (devices, modules (parts), etc.), regardless of whether all components are located in the same enclosure. Therefore, multiple devices housed in separate enclosures and connected via a network, and a single device containing multiple modules within a single enclosure, are both considered systems.
[0105] The effects described herein are illustrative and not limited to those described herein, and other effects may also occur.
[0106] The embodiments of this disclosure are not limited to those described above, and various modifications are possible without departing from the spirit of this disclosure.
[0107] For example, an embodiment of the present disclosure can take the form of cloud computing, in which a single function is shared and processed collaboratively by multiple devices via a network.
[0108] Furthermore, each step described in the flowchart above can be performed by a single device, or it can be divided and performed by multiple devices.
[0109] Furthermore, if a single step includes multiple processes, those processes can be executed by a single device or shared among multiple devices.
[0110] The technology relating to this disclosure can have the following configuration: (1) A signal processing device comprising a noise canceling processing unit that outputs a cancellation signal from a plurality of speakers to cancel noise at each of a plurality of control points in the space of the moving body based on sensor values obtained from an acceleration sensor mounted on the moving body, wherein the noise canceling processing unit generates the cancellation signal using a first filter that is switched on a condition basis for a first speaker in which the sound interference to all the control points is greater, and generates the cancellation signal using a second filter that is not switched on a condition basis for a second speaker in which the interference is smaller. (2) The signal processing device according to (1), wherein the first speaker is a speaker in which the sum of the acoustic power to all the control points is greater depending on the condition, and the second speaker is a speaker in which the sum of the acoustic power is smaller than that of the first speaker, regardless of the condition. (3) The signal processing device according to (1), wherein the first speaker is a speaker whose total distance to all the control points is smaller, and the second speaker is a speaker whose total distance is larger than that of at least the first speaker. (4) The signal processing device according to (1), wherein the first speaker has a variable position and orientation, and the second speaker has a fixed position and orientation. (5) The signal processing device according to any one of (1) to (4), wherein the second filter is a fixed noise-canceling filter. (6) The signal processing device according to any one of (1) to (4), wherein the second filter is a noise-canceling filter that is switched less frequently than the first filter. (7) The signal processing device according to any one of (1) to (6), wherein the moving body is a vehicle, and the plurality of speakers are provided inside the vehicle's cabin. (8) The signal processing device according to (7), wherein the noise-canceling processing unit switches the first filter using vehicle information relating to the vehicle as the condition. (9) The signal processing device according to (8), wherein the vehicle information includes at least one of the seat position in the vehicle interior, the passenger's physical information, and the vehicle's location information.(10) The signal processing device according to (7), wherein the noise canceling processing unit switches the first filter based on the relative position between the first speaker and the passenger as the condition. (11) The signal processing device according to (10), wherein the relative position is calculated based on vehicle information relating to the vehicle or sensing information obtained by sensing the interior of the vehicle. (12) The signal processing device according to any one of (1) to (11), wherein the first filter is a noise canceling filter designed to cancel the residual signal at all of the control points when the cancellation signal generated using the second filter is output from the second speaker for each of the conditions. (13) The signal processing device according to (1), wherein the first filter includes an adaptive filter whose filter coefficients can be adjusted based on an error signal. (14) A signal processing device that outputs cancellation signals from a plurality of speakers to cancel noise at each of a plurality of control points in the space of a mobile body based on sensor values obtained from an acceleration sensor mounted on the mobile body, the device includes a process to generate the cancellation signal using a first filter that is switched on a condition basis for a first speaker where the sound interference to all the control points is greater, and a process to generate the cancellation signal using a second filter that is not switched on a condition basis for a second speaker where the interference is smaller. (15) A program that causes a computer that outputs cancellation signals from a plurality of speakers to cancel noise at each of a plurality of control points in the space of a mobile body based on sensor values obtained from an acceleration sensor mounted on the mobile body, to execute a process to generate the cancellation signal using a first filter that is switched on a condition basis for a first speaker where the sound interference to all the control points is greater, and a process to generate the cancellation signal using a second filter that is not switched on a condition basis for a second speaker where the interference is smaller.(16) A noise-canceling system comprising: a plurality of speakers; an acceleration sensor mounted on a moving body; and a noise-canceling processing unit that outputs a cancellation signal from the plurality of speakers to cancel noise at each of a plurality of control points in the space of the moving body based on sensor values obtained from the acceleration sensor, wherein the noise-canceling processing unit generates the cancellation signal for a first speaker where the sound interference to all of the control points is greater, using a first filter that is switched on a condition-by-condition basis, and generates the cancellation signal for a second speaker where the interference is smaller, using a second filter that is not switched on a condition-by-condition basis at least.
[0111] 1 Noise-canceling system, 10, 10-1 to 10-N sensors, 20 Noise-canceling unit, 31 First filter, 32 Second filter, 33 Filter selection unit, 34 Filter holding unit, 231 Adaptive filter
Claims
1. A noise-canceling processing unit that outputs cancellation signals from multiple speakers to cancel noise at each of multiple control points in the space of a moving object, based on sensor values obtained from an acceleration sensor mounted on the moving object, wherein the noise-canceling processing unit generates the cancellation signal using a first filter that is switched on a condition basis for a first speaker where the sound interference to all of the control points is greater, and generates the cancellation signal using a second filter that is not switched on a condition basis for a second speaker where the interference is smaller.
2. The signal processing apparatus according to claim 1, wherein the first speaker is a speaker that increases the sum of acoustic power to all the control points under the above conditions, and the second speaker is a speaker that, regardless of the above conditions, has a sum of acoustic power that is at least smaller than that of the first speaker.
3. The signal processing apparatus according to claim 1, wherein the first speaker is a speaker whose sum of distances to all the control points is smaller, and the second speaker is a speaker whose sum of distances is larger than that of at least the first speaker.
4. The signal processing apparatus according to claim 1, wherein the first speaker has a variable position and orientation, and the second speaker has a fixed position and orientation.
5. The signal processing apparatus according to claim 1, wherein the second filter is a fixed noise-canceling filter.
6. The signal processing apparatus according to claim 1, wherein the second filter is a noise-canceling filter with a lower switching frequency than the first filter.
7. The signal processing device according to claim 1, wherein the moving body is a vehicle, and the plurality of speakers are provided inside the vehicle's cabin.
8. The signal processing device according to claim 7, wherein the noise canceling processing unit switches the first filter using vehicle information relating to the vehicle as the condition.
9. The signal processing device according to claim 8, wherein the vehicle information includes at least one of the seat position in the vehicle interior, the position of the first speaker, the physical information of the passenger, and the position information of the vehicle.
10. The signal processing device according to claim 7, wherein the noise cancellation processing unit switches the first filter based on the relative position between the first speaker and the passenger.
11. The signal processing device according to claim 10, wherein the relative position is calculated based on vehicle information relating to the vehicle or sensing information obtained by sensing the interior of the vehicle.
12. The signal processing apparatus according to claim 1, wherein the first filter is a noise-canceling filter designed to cancel the residual signals at all control points when the cancellation signal generated using the second filter is output from the second speaker for each of the conditions.
13. The signal processing apparatus according to claim 1, wherein the first filter includes an adaptive filter whose filter coefficients can be adjusted based on an error signal.
14. A signal processing device that outputs cancellation signals from multiple speakers to cancel noise at each of multiple control points in the space of a moving object based on sensor values obtained from an acceleration sensor mounted on the moving object, the device includes a process to generate the cancellation signal using a first filter that is switched on a condition basis for a first speaker where the sound interference to all of the control points is greater, and a process to generate the cancellation signal using a second filter that is not switched on a condition basis for a second speaker where the interference is smaller.
15. A program to cause a computer that outputs cancellation signals from multiple speakers to cancel noise at each of multiple control points in the space of a mobile body based on sensor values obtained from an acceleration sensor mounted on the mobile body, to generate the cancellation signal for a first speaker where the sound interference to all the control points is greater, using a first filter that is switched on a condition-by-condition basis, and to generate the cancellation signal for a second speaker where the interference is smaller, using a second filter that is not switched on a condition-by-condition basis at least.