Signal processing device, signal processing method, and signal processing system

Abstract

The present disclosure pertains to a signal processing device, a signal processing method, and a signal processing system that make it possible to achieve more suitable noise cancellation. A signal processing device according to the present disclosure comprises a noise cancellation processing unit that outputs, from a speaker and on the basis of a sensor value obtained from a sensor mounted on a mobile body, a cancellation signal for cancelling noise by using, as a control point, a user's ear position within a space of the mobile body. The noise cancellation processing unit changes an output mode of the cancellation signal according to the position of the speaker and the user's ear position acquired in the space. The technology according to the present disclosure can be applied to, for example, a road noise cancellation system.

Description

Signal processing apparatus, signal processing method, and signal processing system

[0001] The present disclosure relates to a signal processing apparatus, a signal processing method, and a signal processing system, and particularly relates to a signal processing apparatus, a signal processing method, and a signal processing system that enable more suitable noise canceling to be achieved.

[0002] When designing a noise canceling filter (NC filter) for road noise canceling using an acceleration sensor, it is necessary to accommodate various environmental changes in the vehicle cabin of a vehicle. The noise path from the tire (referred to as a primary path) may change, and the transmission path from the speaker that outputs a canceling signal to the ear position serving as a control point (listening point) (referred to as a secondary path) may also change.

[0003] When each path changes, a suitable noise reduction effect can be obtained by using an optimal filter according to the change. On the other hand, if the filter before the path change continues to be applied even though the path has changed, there is a risk that noise will be increased.

[0004] Patent Document 1 discloses an active noise reduction device that detects a reference distance, which is the distance from a speaker to the head position of an occupant, and controls the speaker based on the reference distance.

[0005] Japanese Unexamined Patent Publication No. 2023-148050

[0006] Only detecting the distance from the speaker to the head position cannot provide a sufficient noise reduction effect, because when the occupant turns their head or the like, the distance from the speaker to the ear position changes. Furthermore, when using a speaker configured to be displaceable in a space, the position of the speaker changes, so a suitable noise reduction effect cannot be obtained only by acquiring the ear position.

[0007] The present disclosure has been made in view of such circumstances, and achieves more suitable noise canceling.

[0008] The signal processing device of this disclosure includes a noise canceling processing unit that outputs a cancellation signal from a speaker to cancel noise, using the position of the user's ear in the space of the moving object as a control point, based on sensor values ​​obtained from a sensor mounted on the moving object, and the noise canceling processing unit is a signal processing device that changes the output mode of the cancellation signal according to the position of the user's ear and the position of the speaker acquired in the space.

[0009] The signal processing method of this disclosure is a signal processing device that outputs a cancellation signal from a speaker to cancel noise using the position of the user's ear in the space of the moving object as a control point, based on sensor values ​​obtained from a sensor mounted on the moving object, and the output mode of the cancellation signal is changed according to the position of the user's ear and the position of the speaker acquired in the space.

[0010] The signal processing system of this disclosure includes a signal processing device that outputs a cancellation signal from a speaker to cancel noise using the position of the user's ear in the space of the moving object as a control point, based on sensor values ​​obtained from a sensor mounted on the moving object; an ear position acquisition device that acquires the position of the user's ear in the space; and a speaker position acquisition device that acquires the position of the speaker in the space, wherein the signal processing device changes the output mode of the cancellation signal according to the position of the user's ear and the position of the speaker acquired in the space.

[0011] In this disclosure, a cancellation signal for canceling noise is output from a speaker based on sensor values ​​obtained from a sensor mounted on the mobile body, with the user's ear position in the space of the mobile body as the control point, and the output mode of the cancellation signal is changed according to the user's ear position and the position of the speaker acquired in the space.

[0012] This is a diagram illustrating an example of a noise-canceling system configuration. This is a flowchart illustrating an example of a filter design. This is a flowchart illustrating an example of noise-canceling operation. This is a diagram illustrating an example of the filter's application range. This is a diagram illustrating changes in speaker position. This is a diagram illustrating the noise reduction effect according to speaker position. This is a diagram illustrating the noise reduction effect according to ear position and speaker position. This is a diagram illustrating the noise reduction effect according to ear position and speaker position. This is a diagram illustrating differences in the breadth of the filter's application range. This is a diagram illustrating the noise reduction effect according to the breadth of the filter's application range. This is a diagram illustrating the noise reduction effect according to the breadth of the filter's application range. This is a diagram illustrating the effect of reducing the number of filters. This is a diagram illustrating noise cancellation using adaptive filters. This is a flowchart illustrating another example of noise-canceling operation. This is a flowchart illustrating yet another example of noise-canceling operation. This is a diagram illustrating control when ear position changes significantly. This is a diagram illustrating control when ear position changes significantly. This is a block diagram illustrating an example of a 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. Noise Reduction Effect 4. Noise Cancelling Using Adaptive Filters 5. Other Examples of Noise Cancelling Operation 6. Control in Cases of Significant Changes in Ear Position 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, and the transmission path (secondary path) from the speaker that outputs the cancellation signal to the ear position, which is the control point (listening point), may also change.

[0016] When each path changes, using the optimal filter according to the change can achieve a suitable sound reduction effect. On the other hand, if the filter used before the path changed continues to be applied even though the path has changed, there is a risk of increased noise.

[0017] 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.

[0018] For example, Patent Document 1 (Japanese Patent Application Publication No. 2023-148050) discloses an active noise reduction device that detects a reference distance, which is the distance from the speaker to the position of the occupant's head, and controls the speaker based on the reference distance.

[0019] Furthermore, Japanese Patent Publication No. 2022-13141 discloses an active noise control system that detects the user's ear position and generates a cancellation sound by switching an adaptive filter according to that ear position.

[0020] However, simply detecting the distance from the speaker to the head position is insufficient because the distance from the speaker to the ear position changes when, for example, the head is turned to look in the side mirror, and therefore sufficient sound cancellation cannot be obtained. Furthermore, when using a speaker that is configured to be displaceable in space, for example, when using a seat speaker installed in a vehicle seat, the position of the speaker changes when the seat is reclined, so simply obtaining the ear position is not sufficient to obtain a suitable sound cancellation effect.

[0021] (Overview of the technology disclosed) In contrast, the technology disclosed makes it possible to achieve more suitable noise cancellation by using the detection results of the user's ear position, posture, and speaker position, even when these change.

[0022] Specifically, we propose a noise-canceling system that includes an ear position acquisition device that senses two points on the ear rather than the head position to acquire the ear position, and a speaker position acquisition device that senses the speaker position to acquire the speaker position, so that it can respond even when the head is turned.

[0023] Furthermore, switching filters based on such diverse conditions (ear position and speaker position) would require a vast number of filters. Considering the memory capacity of the in-vehicle DSP (Digital Signal Processor), it is desirable to have a small number of NC filters. Therefore, in order to reduce the number of filters required while maintaining the noise reduction effect, the system will match the detected position with the filters and switch filters accordingly, so that the closer the user's ear position is to the speaker position, the narrower the application range of each filter, and the farther the user's ear position is from the speaker position, the wider the application range of each filter.

[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] Furthermore, if it is possible to remove sounds that do not originate from the noise source, a microphone may be used as the sensor 10.

[0030] When sensor 10 is configured as an accelerometer, an acceleration value is obtained as the sensor value. When sensor 10 is configured as a microphone, an audio signal is obtained as the sensor value.

[0031] 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 positions of the passenger P1's left and right ears as cancellation points (control points). The noise cancellation processing unit 20 then outputs the generated noise cancellation signal through speakers SP_1 and SP_2 installed in the vehicle's cabin, thereby performing road noise cancellation.

[0032] Here, passenger P1 is seated in a vehicle seat, and speakers SP_1 and SP_2 are configured as seat speakers, for example, near the headrest of the seat, or as headrest speakers, or as speakers mounted on the headrest. Speakers SP_1 and SP_2 may also be configured as neck speakers that can be worn around the neck or shoulders of passenger P1. In other words, speakers SP_1 and SP_2 are speakers configured to be displaceable within the space (inside the vehicle).

[0033] Furthermore, the noise-canceling system 1 is equipped with an ear position acquisition device 30 and a speaker position acquisition device 40. The ear position acquisition device 30 acquires ear position information representing the ear position of the user (passenger P1) inside the vehicle and supplies it to the noise-canceling processing unit 20. The speaker position acquisition device 40 acquires speaker position information representing the positions of speakers SP_1 and SP_2 inside the vehicle and supplies it to the noise-canceling processing unit 20. The noise-canceling processing unit 20 changes the output mode of the cancellation signal according to the ear position of passenger P1 represented by the ear position information from the ear position acquisition device 30 and the positions of speakers SP_1 and SP_2 represented by the speaker position information from the speaker position acquisition device 40.

[0034] The noise cancellation processing unit 20 includes a cancellation signal generation unit 51, a filter switching unit 52, and a filter holding unit 53.

[0035] The cancellation signal generation unit 51 generates a cancellation signal for speakers SP_1 and SP_2 based on the sensor values ​​obtained from each sensor 10, using the filter switched (selected) by the filter switching unit 52.

[0036] The filter switching unit 52 switches the filter used by the cancellation signal generation unit 51 to generate a cancellation signal, according to the position of the passenger P1's ears and the positions of speakers SP_1 and SP_2. The filter holding unit 53 holds NC filters designed for each position of the passenger P1's ears and the positions of speakers SP_1 and SP_2.

[0037] At this time, the filter switching unit 52 changes the frequency of filter switching according to the distance between the position of the passenger P1's ears and the positions of speakers SP_1 and SP_2. Specifically, the further the passenger P1's ears are from the positions of speakers SP_1 and SP_2, the lower the frequency of filter switching, and the closer the passenger P1's ears are to the positions of speakers SP_1 and SP_2, the higher the frequency of filter switching.

[0038] (Method for acquiring ear position) The method for acquiring the ear position of passenger P1 using the ear position acquisition device 30 will be explained below.

[0039] As a method for acquiring two ear positions, ear tracking using a binocular camera can be mentioned, for example. Alternatively, two ear positions can also be obtained by measuring the relative position between the eyes and ears in advance using a three-dimensional position measurement technique for the three-dimensional positions of both eyes of an occupant P1 from the camera position. Although it is possible to acquire the three-dimensional coordinates of ear positions directly from an image, since the ears may be covered by hair or the like in some cases, the latter method may be appropriately employed.

[0040] Any sensing device can be employed as the ear position acquisition device 30 as long as it can acquire the three-dimensional coordinates of ear positions. For example, as the ear position acquisition device 30, a magnetic sensor provided in a headset worn on the head, a distance sensor provided in a speaker, or the like may be employed.

[0041] Two ear positions can also be estimated by detecting the position and inclination of the head. For example, the ear position can be estimated by acquiring the position of the center of the head or the forehead and the angle of the head by combining a camera, a laser rangefinder, a gyro sensor, and the like. Alternatively, the position of the other ear may be estimated by estimating the position of one ear and the inclination of the head.

[0042] Of course, as the ear position acquisition device 30, an RGB camera, an IR (infrared) sensor, a ToF (Time of Flight) sensor, or the like may also be employed. In this case, the ear position acquisition device 30 may be arranged on the ceiling or a seat in addition to being arranged in front of the occupant P1.

[0043] (Method for acquiring speaker position) A method for acquiring the positions (speaker positions) of speakers SP_1 and SP_2 by a speaker position acquisition device 40 will be described.

[0044] As speaker position information representing the positions of the speakers SP_1 and SP_2, for example, once the position of the seat is determined, the positions of the speakers SP_1 and SP_2 are also determined, so that seat position information representing the position of the seat is acquired.

[0045] Not only ear positions but also speaker positions can be acquired by a camera using machine learning. Alternatively, the speaker positions may be acquired by a magnetic sensor.

[0046] The speaker position can also be estimated by outputting an ultrasonic signal or the like outside the audible band from a speaker and recording the signal with a ceiling microphone or the like installed in the vehicle cabin. Furthermore, the speaker position may be obtained by installing an IMU (Inertial Measurement Unit) on the seat to estimate the inclination and movement amount of the seat.

[0047] (Reference Sensor) In the noise canceling system 1 of the present embodiment, the sensor 10 serving as a reference sensor used for noise canceling is configured as an acceleration sensor. However, the sensor is not limited to an acceleration sensor as long as it can measure noise caused by vibration of a structure. For example, as described above, a microphone may be employed as the sensor 10. In addition, for vibration caused by rotation of an engine or the like, a pulse sensor that detects a pulse signal corresponding to rotation or a gyro sensor may be employed as the sensor 10. Furthermore, noise may be measured by measuring displacement from an image using a camera, a laser sensor, or the like.

[0048] (Example of Filter Design) Here, an example of filter design in the noise canceling system 1 will be described with reference to the flowchart of FIG. 2. The process in FIG. 2 is executed when the vehicle is traveling, in a state where a passenger P1 is seated on the seat, or in a state where a doll imitating the passenger P1 is placed on the seat.

[0049] In step S11, the ear position acquisition device 30 acquires ear position information representing the ear position of the passenger P1.

[0050] In step S12, the speaker position acquisition device 40 acquires speaker position information representing the positions of speakers SP_1 and SP_2.

[0051] In step S13, the noise canceling processing unit 20 acquires sensor values from each sensor 10.

[0052] In step S14, the noise cancellation processing unit 20 generates a filter that reduces noise based on the sensor value and the noise recorded by the microphone placed at the ear position.

[0053] In step S15, the noise cancellation processing unit 20 associates the generated filters with the respective position information (ear position information, speaker position information) and stores them in the filter holding unit 53.

[0054] (Example of noise cancellation operation) Next, an example of noise cancellation operation in the noise cancellation system 1 will be explained with reference to the flowchart in Figure 3. The process in Figure 3 is executed when the vehicle is in motion and the passenger P1 is seated in the seat.

[0055] In step S31, the noise cancellation processing unit 20 sets an initial filter corresponding to the reference ear position and speaker position.

[0056] In step S32, the ear position acquisition device 30 acquires ear position information representing the ear position of the passenger P1.

[0057] In step S33, the speaker position acquisition device 40 acquires speaker position information representing the positions of speakers SP_1 and SP_2.

[0058] The processes in steps S32 and S33 (acquisition of ear position information and speaker position information) are performed immediately after the initial filter is set.

[0059] In step S34, the noise cancellation processing unit 20 (filter switching unit 52) ​​determines whether or not a filter switch is necessary based on the acquired ear position information and speaker position information. Specifically, it determines whether the current ear position and speaker position have deviated from the reference ear position and speaker position. If it is determined that a filter switch is not necessary, the process returns to step S32, and the subsequent processing (acquisition of ear position information and speaker position information) is repeated.

[0060] On the other hand, if it is determined in step S34 that a filter switch is necessary, the process proceeds to step S35, where the noise cancellation processing unit 20 (filter switching unit 52) ​​switches the set filter to the filter corresponding to the acquired ear position information and speaker position information.

[0061] Then, in step S35, the noise cancellation processing unit 20 (cancellation signal generation unit 51) uses the switched filters to generate a cancellation signal based on the sensor values ​​acquired from each sensor 10, and outputs it from speakers SP_1 and SP_2.

[0062] Through the above process, filters corresponding to the detected ear and speaker positions are selected and applied, making it possible to achieve more optimal noise cancellation not only when the user's ear position changes, but also when the speaker position changes. Furthermore, if there are multiple users or multiple speakers, it would suffice to generate or switch to the optimal filter based on each user's position.

[0063] (Reduction in the number of filters) In the noise-canceling system 1 of this embodiment, if a filter is prepared for each user's ear position and each speaker position, an enormous number of filters would be required. In contrast, the number of filters can be reduced based on the distance between the user's ear position and the speaker position. In other words, the application range of filter 1 can be set based on the distance between the user's ear position and the speaker position. Specifically, as shown in Figure 4, the application range Fs of filter 1 is set to be wider the further the passenger P1's ear position is from the speaker SP position, and narrower the closer the passenger P1's ear position is from the speaker SP position. Note that in the example in Figure 4, the application range Fs is divided linearly for simplicity, but in reality, since sound waves are spherical waves, it is desirable to divide them according to their wavefronts.

[0064] This reduces the number of filters selected when the passenger P1's ear is far from the speaker SP.

[0065] Normally, the sound pressure of sound output from a speaker is inversely proportional to the distance. For example, if the distance doubles, the sound pressure decreases by 6 dB. In other words, when the ear is close to the speaker, even a slight change in position will cause a large fluctuation in the sound pressure level of the cancellation signal reaching the ear from the speaker. The sound pressure level of noise reaching the cabin from the noise source does not fluctuate as much with ear position as the sound pressure level of the cancellation signal output from the speaker. On the other hand, the closer the ear is to the speaker, the greater the sound pressure level of the cancellation signal becomes, so it is necessary to optimize the cancellation signal.

[0066] For example, if the distance between the user's ear and the speaker changes from 8 cm to 16 cm, the sound pressure of the cancellation signal decreases by 6 dB. On the other hand, if the distance between the user's ear and the speaker changes from 8 cm to 4 cm, the sound pressure of the cancellation signal increases by 6 dB.

[0067] Thus, the closer the ear is to the speaker, the greater the sound pressure level of the cancellation signal becomes. Therefore, to achieve optimal noise reduction, if the ear is close to the speaker, the filter needs to be switched even for slight changes in ear position. Conversely, if the ear is far from the speaker, there is no need to switch the filter for slight changes in ear position.

[0068] Therefore, when using speakers that are far from the user's ears, such as door woofers, for noise cancellation, it is not necessary to switch filters frequently. On the other hand, when using speakers that are placed in seats or headrests and are close to the user's ears for noise cancellation, frequently switching filters can suppress the deterioration of the noise cancellation effect.

[0069] <3. Noise Reduction Effect> The noise reduction effect of the noise canceling system 1 of this embodiment will be described below.

[0070] (Noise reduction effect according to speaker position) The noise reduction effect according to speaker position will be explained with reference to Figures 5 and 6.

[0071] Figure 5 illustrates the change in speaker position.

[0072] Figure 5A shows the seat with the speaker SP installed in the reclined position, with the headrest 26 cm away from the user's ears. Figure 5B shows the seat with the speaker SP installed in the back up position, with the user's ear position unchanged, with the headrest 6 cm away from the user's ears. An ear position acquisition device 30 is positioned in front of the user.

[0073] Figure 6 shows the noise reduction effect according to the speaker position.

[0074] Specifically, Figure 6 shows the analysis results of a 1 / 3 octave frequency analysis from 90 to 170 Hz, illustrating the noise reduction ([dB]) when noise cancellation processing is performed compared to the noise without noise cancellation processing. In the figure, the solid line shows the noise reduction when noise cancellation processing is performed using the filter generated in the state shown in Figure 5A, in the state shown in Figure 5A (reclining enabled). The dashed line shows the noise reduction when noise cancellation processing is performed using the filter generated in the state shown in Figure 5A, in the state shown in Figure 5B (not reclining enabled).

[0075] In both Figure 5A and Figure 5B, the user's ear position is the same, and therefore the noise reaching from the noise source is also the same. However, as shown by the dashed line in Figure 6, when the speaker position changes, the noise is amplified instead of being properly silenced. In other words, it is shown that proper noise reduction cannot be achieved unless both the ear position and the speaker position are acquired and the filter is switched accordingly.

[0076] (Noise reduction effect according to ear position and speaker position) The noise reduction effect according to ear position and speaker position will be explained with reference to Figures 7 to 9.

[0077] Figure 7A shows the user seated in the standard (default) position of the seat where the speaker is installed.

[0078] Figure B shows the results of a 1 / 3 octave frequency analysis at the right ear position, from 90 to 170 Hz, when noise cancellation processing is performed in the state shown in Figure A. In the figure, the solid line shows the amount of noise reduction when noise cancellation processing is performed using a fixed filter corresponding to the standard position, the dashed line shows the amount of noise reduction when noise cancellation processing is performed using a filter that is switched based on the detection of only the ear position, and the dotted line shows the amount of noise reduction when noise cancellation processing is performed using a filter that is switched based on the detection of both the ear position and the speaker position.

[0079] In the case shown in Figure 7, an appropriate sound-dampening effect is obtained under all processing conditions.

[0080] Figure 8A shows the user seated in the standard position (default position) of the seat where the speaker is installed, with their head turned approximately 40° to the left, such as when looking out the window.

[0081] Figure B shows the results of a 1 / 3 octave frequency analysis at the right ear position, with noise cancellation processing performed in the state shown in Figure A. In the figure, the solid, dashed, and dotted lines are the same as those in Figure 7B.

[0082] In the case shown in Figure 8, processing using a fixed filter drastically worsens the sound reduction effect.

[0083] Figure 9A shows the user with their head turned approximately 40° to the left while the seat with the speaker installed is reclined.

[0084] Figure B shows the results of a 1 / 3 octave frequency analysis at the right ear position, with noise cancellation processing performed in the state shown in Figure A. In the figure, the solid, dashed, and dotted lines are the same as those in Figure 7B.

[0085] In the case shown in Figure 9, the noise cancellation effect deteriorates not only with processing using a fixed filter, but also with processing using a filter that is switched based only on the detection of the ear position. A good noise cancellation effect can be obtained by detecting the ear position and the speaker position and switching the filter, as in the noise cancellation processing to which the technology described herein is applied.

[0086] Furthermore, the reason why the sound reduction effect is better in the case of Figure 9 than in the case of Figure 8 when processing with a fixed filter is that the head leans against the headrest when reclining, bringing the distance between the speaker and the right ear closer to that of the default position.

[0087] (Noise reduction effect according to the width of the filter's application range) The noise reduction effect according to the width of the filter's application range will be explained with reference to Figures 10 to 13.

[0088] Figure 10 illustrates the differences in the scope of application of filters.

[0089] Figure 10A shows how, in noise cancellation processing using the technology of this disclosure, the filter application range Fs is switched in 5 cm increments according to the distance between the position of speaker SP and the ear position of passenger P1. Figure 10B shows how, in noise cancellation processing using the technology of this disclosure, the filter application range Fs is switched in 1 cm increments according to the distance between the position of speaker SP and the ear position of passenger P1.

[0090] Figure 11A shows the user sitting in a seat with a speaker installed, turning their head to the left, and applying noise cancellation processing to the right ear, which is furthest from the speaker.

[0091] Figure B shows the results of a 1 / 3 octave frequency analysis at the right ear position, with noise cancellation processing performed in the state shown in Figure A. In the figure, the dashed line shows the amount of noise reduction when noise cancellation processing is performed with the filter application range Fs set to 5 cm units, as in Figure 10A, and the dotted line shows the amount of noise reduction when noise cancellation processing is performed with the filter application range Fs set to 1 cm units, as in Figure 10B.

[0092] As shown in Figure 11B, when the ear is far from the speaker, a noise reduction effect can be obtained by setting the filter's application range Fs to 1 cm increments and increasing the switching frequency. On the other hand, a certain degree of noise reduction can also be obtained by setting the filter's application range Fs to 5 cm increments and decreasing the switching frequency.

[0093] Figure 12A shows the user sitting in a seat with a speaker installed, turning their head to the left, and applying noise cancellation processing to the left ear, which is closest to the speaker.

[0094] Figure B shows the results of a 1 / 3 octave frequency analysis at the left ear position, when noise cancellation processing is performed in the state shown in Figure A. In the figure, the dashed and dotted lines are the same as those in Figure 11B.

[0095] As shown in Figure 12B, when the ear is close to the speaker, a noise reduction effect can be obtained by setting the filter application range Fs to 1 cm increments and increasing the switching frequency. However, if the filter application range Fs is set to 5 cm increments and the switching frequency is decreased, the noise reduction effect deteriorates significantly.

[0096] From the above, it can be said that when the distance between the user's ear and the speaker is short, it is necessary to divide the application range of a single filter into small sections, while when the distance is far, a certain degree of noise reduction can be maintained even if the application range of a single filter is coarse. If the application range of a single filter is set finely, a good noise reduction effect can be obtained regardless of the distance between the user's ear and the speaker, but in that case, a huge number of filters would need to be prepared.

[0097] Therefore, in the technology disclosed herein, the frequency of filter switching is changed (the width of the application range of a single filter is varied) according to the distance between the user's ear position and the speaker position.

[0098] When the ear is close to the speaker, i.e., the distance is short, the noise reduction effect will deteriorate significantly unless the filter is switched with a finer application range in response to even slight changes in ear position. Therefore, the noise reduction effect is maintained by switching the filter frequently. On the other hand, when the ear is far from the speaker, i.e., the distance is long, even if the same filter is applied to slight changes in ear position, a certain degree of noise reduction effect can be obtained, as explained with reference to Figure 11.

[0099] Regarding how to set the width of the filter's application range, based on the aforementioned phenomenon that "if the distance doubles, the sound pressure decreases by 6 dB," one possible approach is to double the width of the filter's application range (for example, the length of one side of a square) if the distance between the ear and the speaker doubles.

[0100] For example, as shown in Figure 13A, if the filter application range Fs is set to the same width regardless of the distance between the passenger P1's ear position and the speaker SP, then seven filters would be required. Note that in Figure 13, for simplicity, only the application range Fs along one direction from the speaker SP is shown.

[0101] On the other hand, according to the technology disclosed herein, as shown in Figure 13B, the width of the filter's application range Fs can be set according to the distance between the passenger P1's ear position and the speaker SP's position, so that almost the same noise reduction effect can be obtained by preparing only three filters. In the example in Figure 13, the number of filters can be reduced to less than half when setting the application range Fs along one direction, so the number of filters can be greatly reduced when setting the filter's application range on a two-dimensional or three-dimensional coordinate system.

[0102] (Practical considerations) When switching filters, considering practical use, if there are two or more control points such as ear position, it is desirable to designate the control point closer to the speaker as the control target and prepare filters according to the distance.

[0103] (Speaker transmission characteristics) Because speakers are directional, it is desirable to finely adjust the filter's application range, especially in the direction of sound radiation from the speaker. In areas outside the direction of radiation, the sound pressure level of the cancellation signal from the speaker tends to attenuate. Therefore, in environments with many reflections, the filter's application range may be set according to the difference in sound pressure level at different distances, taking into account the transmission characteristics of each speaker.

[0104] <4. Noise Cancellation Using Adaptive Filters> The filter in the technology relating to this disclosure may also be an adaptive filter whose filter coefficients can be adjusted based on an error signal.

[0105] Figure 14 illustrates noise cancellation using an adaptive filter.

[0106] Figure 14 shows an active noise control system using the Filtered-X LMS algorithm. The system in Figure 14 is configured to include a speaker 111 that outputs pseudo-noise to cancel out noise, an error sensor 112 that observes the noise reduction effect, and a reference sensor 113 that detects a reference signal.

[0107] In the system shown in Figure 14, the filter coefficients of the noise canceling filter are sequentially updated using the error sensor 112 in response to changes in the transfer function from the noise to the ear position EP (first-order path) and the transfer function from the speaker 111 to the ear position EP (second-order path) so that the noise at the ear position EP becomes zero. That is, the signal detected by the reference sensor 113, which is located upstream of the noise, is processed by the control filter 131 to become pseudo-noise output from the speaker 111. Then, at the location of the error sensor 112, the coefficient update unit 132 adjusts the filter coefficients of the control filter 131 so that the error signal e(n) from the error sensor 112 is minimized, so that the noise and pseudo-noise cancel each other out.

[0108] Here, we will explain the noise cancellation operation when using ear position EP tracking in the system shown in Figure 14.

[0109] First, the ear position EP is detected by tracking. Next, the secondary path model modification unit 133 modifies the secondary path model by determining the secondary path according to the ear position EP. The coefficient update unit 132 uses the modified secondary path model and the error signal e(n) from the error sensor 112 to adaptively determine the filter coefficients of the control filter 131 so that the error signal e(n) becomes smaller.

[0110] In the technology disclosed herein, only the secondary path model is stored in memory, and the filter is updated by changing the secondary path model based on the detection results of the ear position and speaker position. However, in the system shown in Figure 14, the user is always required to wear the error sensor 112, i.e., the microphone, at the ear position, which makes it impractical to use. Therefore, a noise cancellation control method using a virtual microphone may be applied. Specifically, during the first stage of adjustment, the microphone is worn at the ear position and the filter is designed, and during the second stage of control, a virtual microphone is used without wearing the microphone at the ear position, and control is performed to minimize the error signal from the virtual microphone.

[0111] <5. Other Examples of Noise Canceling Operation> In the embodiment described above, since multiple filters are required to switch filters according to the user's ear position and the speaker position, it is unavoidable that memory capacity will be strained. Therefore, it is also possible to use only one NC filter and change the level (gain) and delay of the cancellation signal output from the speaker.

[0112] First, referring to the flowchart in Figure 15, we will explain an example of noise cancellation operation when the level of the cancellation signal is changed.

[0113] Note that the processes in steps S51 to S53 of the flowchart in Figure 15 are basically the same as the processes in steps S31 to S33 of the flowchart in Figure 3, so their explanation will be omitted.

[0114] In other words, in step S54, the noise cancellation processing unit 20 determines whether or not to change the level of the cancellation signal based on the ear position information and speaker position information acquired in steps S52 and S53. If it is determined that the level of the cancellation signal should not be changed, the process returns to step S52, and the subsequent processing (acquisition of ear position information and speaker position information) is repeated.

[0115] On the other hand, if it is determined in step S54 to change the level of the cancellation signal, the process proceeds to step S55, where the noise cancellation processing unit 20 sets the level of the cancellation signal according to the acquired ear position information and speaker position information. Specifically, the noise cancellation processing unit 20 increases the level of the cancellation signal the further the user's ear position is from the speaker position, and decreases the level of the cancellation signal the closer the user's ear position is from the speaker position.

[0116] Then, in step S55, the noise cancellation processing unit 20 (cancellation signal generation unit 51) uses an initial filter to generate a cancellation signal based on the sensor values ​​obtained from each sensor 10, and outputs it from speakers SP_1 and SP_2 at a set level.

[0117] Next, referring to the flowchart in Figure 16, we will explain an example of noise cancellation operation when the delay of the cancellation signal is changed.

[0118] Note that the processes in steps S71 to S73 of the flowchart in Figure 16 are basically the same as the processes in steps S31 to S33 of the flowchart in Figure 3, so their explanation will be omitted.

[0119] In other words, in step S74, the noise cancellation processing unit 20 determines whether or not to change the delay of the cancellation signal based on the ear position information and speaker position information acquired in steps S72 and S73. If it is determined that the delay of the cancellation signal should not be changed, the process returns to step S72, and the subsequent processing (acquisition of ear position information and speaker position information) is repeated.

[0120] On the other hand, if it is determined in step S74 to change the delay of the cancellation signal, the process proceeds to step S75, where the noise cancellation processing unit 20 sets the delay of the cancellation signal according to the acquired ear position information and speaker position information. Specifically, the noise cancellation processing unit 20 reduces the delay of the cancellation signal the further the user's ear position is from the speaker position, and increases the delay of the cancellation signal the closer the user's ear position is from the speaker position.

[0121] Then, in step S75, the noise cancellation processing unit 20 (cancellation signal generation unit 51) uses an initial filter to generate a cancellation signal based on the sensor values ​​obtained from each sensor 10, and outputs it from speakers SP_1 and SP_2 with a set delay.

[0122] The above processing makes it possible to achieve more optimal noise cancellation even when the user's ear position changes, as well as when the speaker position changes, while avoiding strain on memory capacity. In the above processing, the level and delay of the cancellation signal are changed uniformly regardless of the bandwidth, but the level and delay of the cancellation signal may also be changed by performing optimal parameter control for each bandwidth using an equalizer or the like.

[0123] <6. Control when ear position changes significantly> In light of the future automation of vehicles, it is conceivable that users will frequently move seats within the vehicle.

[0124] For example, the left diagram of Figure 17 shows how the ear position of passenger P1, who is closer to speakers SP_1 and SP_2, is being tracked by the ear position acquisition device 30. In this case, noise cancellation processing is performed with passenger P1 as the control target.

[0125] On the other hand, suppose that, starting from the state shown in the left diagram of Figure 17, passengers P1 and P2 move within the vehicle, as shown in the right diagram, and passenger P2's ear position approaches speakers SP_1 and SP_2. In this case, if the noise cancellation processing that controls passenger P1 continues to be performed, it will adversely affect passenger P2. Therefore, the control target may be changed to the user whose ear position is closest to the position of speakers SP_1 and SP_2, based on the distance between the ear position and the speaker position. Note that since two ear positions are used as control points, at least two speakers are required per person.

[0126] Furthermore, as shown in Figure 18, if the distance between the passenger P1's ear position and the positions of speakers SP_1 and SP_2 exceeds a certain distance, the output of speakers SP_1 and SP_2 may become extremely high. In such cases, control may be performed to turn off the noise cancellation process based on the distance between the ear position and the speaker position.

[0127] <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.

[0128] In this case, a noise-canceling system applying the technology described herein can output a cancellation signal from a speaker to cancel noise, using the user's ear position within the space of the moving object as a control point, based on sensor values ​​obtained from an acceleration sensor mounted on the moving object. At this time, the output form of the cancellation signal should change according to the user's ear position and the speaker position acquired within the space of the moving object.

[0129] As a result, even with any moving object, a filter corresponding to the detected ear position and speaker position is selected and applied, making it possible to achieve more optimal noise cancellation not only when the user's ear position changes, but also when the speaker position changes.

[0130] <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.

[0131] Figure 19 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 is composed of, for example, a computer 500 having a configuration similar to that shown in Figure 19.

[0132] The CPU (Central Processing Unit) 501, ROM (Read Only Memory) 502, and RAM (Random Access Memory) 503 are interconnected by a bus 504.

[0133] An input / output interface 505 is further connected to the bus 504. An input unit 506 consisting of a keyboard, mouse, etc., and an output unit 507 consisting of a display, speakers, etc. are connected to the input / output interface 505. In addition, a storage unit 508 consisting of a hard disk, non-volatile memory, etc., a communication unit 509 consisting of a network interface, etc., and a drive 510 that drives removable media 511 are connected to the input / output interface 505.

[0134] In the computer 500 configured as described above, the CPU 501 loads, for example, a program stored in the memory unit 508 into the RAM 503 via the input / output interface 505 and the bus 504, and executes it, thereby performing the series of processes described above.

[0135] The program executed by the CPU 501 is recorded on removable media 511, 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 508.

[0136] The program executed by the computer 500 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.

[0137] 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.

[0138] The effects described herein are illustrative and not limited to those described herein, and other effects may also occur.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] Furthermore, if a single step includes multiple processes, those processes can be executed by a single device or shared among multiple devices.

[0143] The technology relating to this disclosure can have the following configurations: (1) A signal processing device comprising a noise-canceling processing unit that outputs a cancellation signal from a speaker to cancel noise, using the position of the user's ear in the space of the moving body as a control point, based on sensor values ​​obtained from a sensor mounted on the moving body, wherein the noise-canceling processing unit changes the output mode of the cancellation signal according to the position of the user's ear and the position of the speaker acquired in the space. (2) The signal processing device according to (1), wherein the speaker is configured to be displaceable in the space. (3) The signal processing device according to (2), wherein the moving body is a vehicle, and the speaker includes at least one of a seat speaker provided on a seat of the vehicle, a headrest speaker provided on the headrest of the seat, and a neck speaker that can be worn on the neck or shoulder of a passenger. (4) The signal processing device according to any one of (1) to (3), wherein the noise-canceling processing unit switches a filter for generating the cancellation signal according to the position of the user's ear and the position of the speaker. (5) The signal processing device according to (4), wherein the noise canceling processing unit changes the frequency of switching the filter according to the distance between the user's ear position and the speaker position. (6) The signal processing device according to (5), wherein the noise canceling processing unit lowers the frequency of switching the filter as the user's ear position is farther from the speaker position, and increases the frequency of switching the filter as the user's ear position is closer to the speaker position. (7) The signal processing device according to (6), wherein the application range of the filter is set to be wider as the user's ear position is farther from the speaker position, and narrower as the user's ear position is closer to the speaker position. (8) The signal processing device according to (4), wherein the filter includes an adaptive filter whose filter coefficients can be adjusted based on an error signal. (9) The signal processing device according to any one of (1) to (3), wherein the noise canceling processing unit changes the level of the cancellation signal according to the user's ear position and the speaker position.(10) The signal processing device according to (9), wherein the noise canceling processing unit increases the level of the cancellation signal as the user's ear position is farther from the speaker position, and decreases the level of the cancellation signal as the user's ear position is closer to the speaker position. (11) The signal processing device according to any one of (1) to (3), wherein the noise canceling processing unit changes the delay of the cancellation signal according to the user's ear position and the speaker position. (12) The signal processing device according to (11), wherein the noise canceling processing unit decreases the delay of the cancellation signal as the user's ear position is farther from the speaker position, and increases the delay of the cancellation signal as the user's ear position is closer to the speaker position. (13) The signal processing device according to any one of (1) to (12), wherein the noise canceling processing unit generates the cancellation signal based on acceleration values ​​obtained from an acceleration sensor mounted on the moving body. (14) The noise-canceling processing unit generates the cancellation signal based on an audio signal obtained from a microphone mounted on the mobile body, as described in any of (1) to (12). (15) A signal processing method in which a signal processing device outputs a cancellation signal from a speaker to cancel noise using the position of the user's ear in the space of the mobile body as a control point, based on sensor values ​​obtained from a sensor mounted on the mobile body, and changes the output mode of the cancellation signal according to the position of the user's ear and the position of the speaker acquired in the space. (16) A signal processing system comprising: a signal processing device that outputs a cancellation signal from a speaker to cancel noise using the position of the user's ear in the space of the mobile body as a control point, based on sensor values ​​obtained from a sensor mounted on the mobile body; an ear position acquisition device that acquires the position of the user's ear in the space; and a speaker position acquisition device that acquires the position of the speaker in the space, wherein the signal processing device changes the output mode of the cancellation signal according to the position of the user's ear and the position of the speaker acquired in the space.

[0144] 1 Noise-canceling system, 10, 10-1 to 10-N sensors, 20 Noise-canceling unit, 30 Ear position acquisition device, 40 Speaker position acquisition device, 51 Cancellation signal generation unit, 52 Filter switching unit, 53 Filter holding unit

Claims

1. A noise-canceling processing unit that outputs a cancellation signal from a speaker to cancel noise, using the position of the user's ear in the space of the mobile body as a control point, based on sensor values ​​obtained from a sensor mounted on the mobile body, wherein the noise-canceling processing unit changes the output mode of the cancellation signal according to the position of the user's ear and the position of the speaker acquired in the space.

2. The signal processing apparatus according to claim 1, wherein the speaker is configured to be displaceable within the space.

3. The signal processing device according to claim 2, wherein the moving body is a vehicle, and the speaker includes at least one of a seat speaker provided on a seat of the vehicle, a headrest speaker provided on the headrest of the seat, and a neck speaker that can be worn on the neck or shoulder of a passenger.

4. The signal processing device according to claim 1, wherein the noise cancellation processing unit switches a filter for generating the cancellation signal according to the position of the user's ear and the position of the speaker.

5. The signal processing device according to claim 4, wherein the noise cancellation processing unit changes the frequency of switching the filter according to the distance between the user's ear position and the speaker position.

6. The signal processing device according to claim 5, wherein the noise cancellation processing unit reduces the frequency of switching the filter as the user's ear position is farther from the speaker position, and increases the frequency of switching the filter as the user's ear position is closer to the speaker position.

7. The signal processing device according to claim 6, wherein the application range of the filter in 1 is set to be wider the further the user's ear position is from the speaker position, and narrower the closer the user's ear position is from the speaker position.

8. The signal processing apparatus according to claim 4, wherein the filter includes an adaptive filter whose filter coefficients can be adjusted based on an error signal.

9. The signal processing device according to claim 1, wherein the noise cancellation processing unit changes the level of the cancellation signal according to the position of the user's ear and the position of the speaker.

10. The signal processing device according to claim 9, wherein the noise canceling processing unit increases the level of the cancellation signal as the user's ear position is farther from the speaker position, and decreases the level of the cancellation signal as the user's ear position is closer to the speaker position.

11. The signal processing device according to claim 1, wherein the noise canceling processing unit changes the delay of the cancellation signal according to the position of the user's ear and the position of the speaker.

12. The signal processing device according to claim 11, wherein the noise canceling processing unit reduces the delay of the cancellation signal as the user's ear position is farther from the speaker position, and increases the delay of the cancellation signal as the user's ear position is closer to the speaker position.

13. The signal processing device according to claim 1, wherein the noise cancellation processing unit generates the cancellation signal based on acceleration values ​​obtained from an acceleration sensor mounted on the moving body.

14. The signal processing device according to claim 1, wherein the noise cancellation processing unit generates the cancellation signal based on an audio signal obtained from a microphone mounted on the mobile body.

15. A signal processing device that outputs a cancellation signal from a speaker to cancel noise using the position of the user's ear in the space of the mobile body as a control point, based on sensor values ​​obtained from a sensor mounted on the mobile body, and a signal processing method that changes the output mode of the cancellation signal according to the position of the user's ear and the position of the speaker acquired in the space.

16. A signal processing system comprising: a signal processing device that outputs a cancellation signal from a speaker to cancel noise using the position of the user's ear in the space of the mobile body as a control point, based on sensor values ​​obtained from a sensor mounted on the mobile body; an ear position acquisition device that acquires the position of the user's ear in the space; and a speaker position acquisition device that acquires the position of the speaker in the space, wherein the signal processing device changes the output mode of the cancellation signal according to the user's ear position and the position of the speaker acquired in the space.

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