Active noise control device for a vehicle and control method thereof

Abstract

The present invention relates to an active noise control apparatus for a vehicle and a control method thereof, which can make it difficult for a passenger in the vehicle to hear the voice of another passenger, thereby implementing privacy protection. The active noise control method includes: first determining a noise level based on a first microphone signal input through a microphone corresponding to a first seat; second determining whether to output an anti-noise signal generated based on the first microphone signal and determining an amplitude of the anti-noise signal based on the noise level and a level of the first microphone signal; and outputting the anti-noise signal through a headrest speaker of a second seat in response to the second determination.

Description

Technical Field

[0001] This invention relates to an active noise control device and method for a vehicle, which makes it difficult for passengers in the vehicle to hear the voices of other passengers, thereby achieving privacy protection. Background Technology

[0002] To date, vehicle manufacturers have made significant efforts to reduce in-vehicle noise. As part of these efforts, in addition to passive noise control systems (such as adding or improving sound insulators or vibration dampers), active noise control systems have been introduced, which generate sound that has the opposite phase to the noise, overlapping with it to reduce noise.

[0003] In recent years, a method has been provided that utilizes this active noise control system to not only control noise introduced from outside the vehicle (e.g., road noise) but also to shield noise between passengers. This will refer to... Figure 1 To describe.

[0004] Figure 1 An example of an active noise control configuration for a vehicle that utilizes anti-noise is shown.

[0005] exist Figure 1 In this scenario, suppose a driver is driving a vehicle with a driver and a passenger in the back seat. The passenger in the back seat is making a phone call. In this situation, the passenger in the back seat typically does not want the driver to hear their phone conversation in order to protect their privacy.

[0006] To this end, the passenger's voice can be input into microphones located in the rear seats. The amplitude of the voice signal can be analyzed for each frequency band to generate a sound with the opposite phase required to cancel out the voice (i.e., anti-noise). This anti-noise can be output through a speaker mounted in the driver's seat headrest. Thus, the passenger's voice and the anti-noise can overlap, thereby canceling each other out and making it difficult for the driver to recognize the passenger's telephone conversation.

[0007] However, in the above method, when the rear seat passengers are not speaking, but air conditioning noise, road noise, or nearby noise caused by the open windows are input to the microphone, noise immunity can be output, which may lead to driver auditory fatigue.

[0008] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art. Summary of the Invention

[0009] Various aspects of the present invention are intended to provide an active noise control device and method for a vehicle that substantially avoids one or more problems arising from the limitations and disadvantages of the prior art.

[0010] Various aspects of the present invention aim to provide an active noise control device and method for a vehicle, configured to more effectively make it difficult for the driver to hear the voices of passengers.

[0011] Various aspects of the present invention aim to provide an active noise control device and method for a vehicle configured to control noise immunity by taking into account the amplitude of nearby noise.

[0012] The purpose of this invention, designed to solve the problem, is not limited to the above-described purposes, and other unmentioned purposes will be clearly understood by those skilled in the art based on the following detailed description of the invention.

[0013] To achieve these and other advantages, and in accordance with the purposes of the invention as embodied and broadly described herein, an active noise control method for a vehicle may include: first determining a noise level based on a first microphone signal input via a microphone corresponding to a first seat; second determining whether to output an anti-noise signal generated based on the first microphone signal and determining the amplitude of the anti-noise signal based on the noise level and the level of the first microphone signal; and outputting the anti-noise signal via a headrest speaker of a second seat in response to the second determination.

[0014] In another aspect of the invention, the active noise control device for a vehicle may include: a microphone corresponding to a first seat; an active noise control unit configured to generate an anti-noise signal based on a first microphone signal input through the microphone; and a headrest speaker disposed in a second seat, the headrest speaker being configured to output noise corresponding to the anti-noise signal; wherein the active noise control unit may determine a noise level based on the first microphone signal, and determine whether to output the generated anti-noise signal and determine the amplitude of the anti-noise signal based on the noise level and the level of the first microphone signal.

[0015] It should be understood that the foregoing general description of the invention and the following detailed description are exemplary and explanatory, and are intended to provide further explanation of the claimed invention.

[0016] The methods and apparatus of the present invention have other features and advantages that will be apparent from the accompanying drawings incorporated herein and the detailed description which follow, or will be set forth in detail in the accompanying drawings incorporated herein and the detailed description which together serve to explain the particular principles of the invention. Attached Figure Description

[0017] The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings:

[0018] Figure 1 An example of an active noise control configuration for a vehicle that utilizes noise immunity is shown.

[0019] Figure 2 This is an exemplary schematic diagram illustrating a concept of an active noise control device according to various exemplary embodiments of the present invention;

[0020] Figure 3 An example of a configuration that outputs noise immunity due to nearby noise rather than speech is shown;

[0021] Figure 4 An example of a noise-resistant configuration that takes into account nearby noise is shown, according to an exemplary embodiment of the present invention;

[0022] Figure 5 This shows an example of a noise level change configuration;

[0023] Figure 6 Examples illustrating the construction of an active noise control device according to various exemplary embodiments of the present invention;

[0024] Figure 7 Examples illustrating the construction of a noise level determination unit according to various exemplary embodiments of the present invention;

[0025] Figure 8 An example illustrating the construction of an active noise control device according to another exemplary embodiment of the present invention; and

[0026] Figure 9 This is an example flowchart illustrating the control process of an active noise control device according to each implementation scheme.

[0027] It will be understood that the accompanying drawings are not drawn to scale, but rather present appropriately simplified depictions of various features illustrating the basic principles of the invention. Specific design features of the invention as described herein (including, for example, specific dimensions, orientations, positions, and shapes) will be determined in part by the specific environment in which they will be applied and used.

[0028] In the accompanying drawings, throughout the multiple figures, the same or equivalent parts of the invention are indexed by the same reference numerals. Detailed Implementation

[0029] Reference will now be made in detail to exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. The following embodiments are given by way of example to enable those skilled in the art to fully understand the spirit of the invention. Therefore, the invention is not limited to the following embodiments and can be implemented in various other forms. For clarity of description, components unrelated to the description of the invention have been omitted from the drawings. Where possible, the same reference numerals will be used throughout the specification to denote the same or similar components.

[0030] Unless otherwise stated, the terms “comprising” or “including” as used herein should not be construed as excluding other elements, but rather as further including such other elements. Furthermore, throughout this specification, the same reference numerals denote the same constituent elements.

[0031] In the following description, it is assumed that the passenger speaking is a passenger in the rear seat, and the passenger hearing the noise-canceling audio configured to interfere with voice recognition is the driver in the driver's seat.

[0032] Figure 2 This is an exemplary schematic diagram illustrating a concept of an active noise control device according to various exemplary embodiments of the present invention.

[0033] refer to Figure 2 When the passenger 10 in the rear seat speaks, the speech r(n) is input to the reference microphone 110 as it propagates into the vehicle interior. The reference microphone 110 may be positioned where the speech from the rear seat speaker is appropriately input to the reference microphone, for example, on the roof of the rear seat; however, the invention is not limited thereto.

[0034] Speech input to reference microphone 110 is converted into a microphone signal s(n) input to active noise control unit 140. Control unit 140 uses the microphone signal s(n) to generate an anti-noise signal y(n) and sends it to speaker 130. Preferably, speaker 130 is a speaker 130 arranged in the headrest of the driver's seat. An audio amplifier may be arranged between control unit 140 and speaker 130. The anti-noise signal y(n) reflects the characteristics of the acoustic path (i.e., the second path S(z)) between speaker 130 and a specific position of the driver's seat (i.e., the position corresponding to the driver's ear), thereby providing anti-noise signal y(n). s (n) is transmitted to the driver's ears via speaker 130.

[0035] In noise immunity s During the transmission of (n), the speech r(n) propagating into the vehicle reflects the characteristics of the acoustic path from the rear seat to the driver's seat (i.e., the first path P(z)), thereby transmitting the noise d(n) to the driver.

[0036] As a result, the driver heard noise d(n) and anti-noise y. s The combination of (n) is overlapping noise, making it difficult to identify noise d(n).

[0037] In noise d(n) and noise immunity y s The residual noise (i.e., error) left after the overlap and cancellation is input to the error microphone 120, thereby feeding the error microphone signal e(n) back to the control unit 140. The control unit 140 can detect the control error from the microphone signal and can adaptively select a filter configured to output an anti-noise signal in the direction that minimizes the control error. Here, the control error can be detected by determining the transfer function. The transfer function This includes the characteristics of all transmission paths from the output of the noise immunity signal by the control unit 140 until the noise immunity signal is input to the error microphone 120 via the speaker 130; applying the transfer function to the microphone signal s(n) and comparing it with the error microphone signal e(n) (e.g., the minimum mean square error (LMS) algorithm).

[0038] Elements considering the characteristics of the transfer path may include at least one of a DAC, a reconstruction filter, an audio amplifier, a speaker 130, an acoustic path from the speaker 130 to the error microphone 120, a microphone preamplifier, an anti-aliasing filter, and an ADC; however, the invention is not limited thereto. Furthermore, preferably, a pre-set transfer function is calculated, experimentally verified, and adjusted.

[0039] The active noise control device can utilize a separate switch to allow the passenger to determine whether to output noise immunity; however, the invention is not limited thereto. Furthermore, when the active noise control device is activated, it is preferable to disable the hands-free function of the passenger's mobile terminal.

[0040] However, in reference Figure 2 The described active noise control device may output noise immunity even during periods when passengers are not speaking, due to nearby noise. (See reference...) Figure 3 Describe the situation.

[0041] Figure 3 An example of a configuration that outputs noise immunity due to nearby noise rather than speech is shown.

[0042] refer to Figure 3When the active noise control unit is activated, a predetermined background sound (e.g., natural sounds such as flowing water or birdsong) is continuously played, and noise immunity can be output in response to a microphone signal. However, noise immunity may be continuously output during periods other than when passengers are speaking, due to the introduction of external noise such as road noise, air conditioning noise, or due to open windows.

[0043] To address this problem, embodiments of the present invention aim to provide a method that determines a noise level based on nearby noise in active noise control for protecting the privacy of passengers speaking in a vehicle; outputs anti-noise when the microphone signal exceeds the noise level; and prevents the output of anti-noise during non-speaking periods. Furthermore, various aspects of the present invention aim to provide a method that reduces the magnitude of anti-noise based on the noise level to reduce the auditory burden on another passenger due to the anti-noise.

[0044] Reference Figure 4 Describe the control concept according to an exemplary implementation.

[0045] Figure 4 An example of a noise-resistant configuration that takes into account nearby noise is shown, according to an exemplary embodiment of the present invention.

[0046] refer to Figure 4 , in order to Figure 3 Background sound is output in the same way, and noise immunity can be output only during speaking periods (when the microphone signal level is higher than the noise level considering nearby noise). Figure 3 In this method, the amplitude of noise immunity is determined based on microphone signals that include nearby noise. However, in an exemplary embodiment of the invention, the amplitude of noise immunity is reduced by taking into account the noise level of nearby noise, thereby reducing auditory discomfort for the driver.

[0047] Figure 5 This shows an example of a noise level change configuration.

[0048] exist Figure 5 In the graph, the horizontal axis represents time, and the vertical axis represents the level (amplitude) of the microphone signal.

[0049] refer to Figure 5 In the first half, excluding the speaking period, the noise level NL n Maintain uniformity, but the noise level (NL) n+1The increase begins from the point in time when the noise environment changes. For example, this could be a situation where, while driving with the windows closed, nearby external noise is introduced into the vehicle when the windows are opened at a point in time when the noise environment changes. Even with a reduction in the noise immunity output level due to the increased noise level, privacy protection can still be adequately achieved under these conditions of increased noise levels.

[0050] As mentioned above, since noise levels vary depending on the circumstances, an appropriate method for determining noise levels is needed, which will be referenced. Figures 6 to 8 Describe the construction of such an active noise control device.

[0051] Figure 6 Examples illustrating the construction of an active noise control device according to various exemplary embodiments of the present invention are shown.

[0052] refer to Figure 6 The active noise control device may include a reference microphone 110, an error microphone 120, a speaker 130, an active noise control unit 140, and an audio amplifier 150.

[0053] The microphone signal input to the reference microphone 110 can be converted into a digital signal by preprocessing (i.e. by ADC 142) after passing through the anti-aliasing filter 141 of the active noise control unit 140.

[0054] The preprocessed microphone signal is passed through a digital high-pass filter (HPF) 144-1 and a digital low-pass filter (LPF) 144-2, thereby allowing only the human speech audio band to be extracted.

[0055] Furthermore, the preprocessed microphone signal can be input to the noise level determination unit 143, and the noise level determination unit 143 can determine the noise level based on nearby noise. (See reference...) Figure 7 The operation of the noise level determination unit 143 is described in more detail.

[0056] The active noise control (ANC) algorithm 145 can generate an anti-noise signal y(n) based on the signal corresponding to the speech band, and can determine whether to output the anti-noise signal y(n) and determine the amplitude of the anti-noise signal y(n) based on the noise level determined by the noise level determination unit 143.

[0057] The noise-resistant signal y(n) can be output through speaker 130 via digital LPF 146 and audio amplifier 150. The error signal e(n), acquired by error microphone 120, can be converted into a digital signal via microphone preprocessing (i.e., by ADC 148) after passing through anti-aliasing filter 147 for adaptive selection by digital LPF 146. Here, audio amplifier 150 can be a multimedia sound output amplifier for an audio / video / navigation (AVN) system or a separate amplifier for active noise control.

[0058] Figure 7 Examples of the construction of a noise level determination unit according to various exemplary embodiments of the present invention are shown.

[0059] refer to Figure 7 The noise level determination unit 143 may include an average sound pressure determination unit, an average sound pressure non-volatile storage unit, and a reference level determination unit.

[0060] The average sound pressure determination unit determines the average sound pressure based on the preprocessed microphone signal every first cycle (e.g., every 1 second).

[0061] The average sound pressure level (SPL) storage unit stores a predetermined integer N average sound pressure levels determined by the average sound pressure level determination unit. Once the predetermined number of N average sound pressure levels has been stored, the previously stored average sound pressure level can be discarded. Therefore, the average sound pressure level non-volatile storage unit can manage the average sound pressure levels in a first-in, first-out (FIFO) manner; however, the invention is not limited to this. For example, assuming the first period is 1 second and N is 20, the average sound pressure level storage unit can continuously store average sound pressure level information for 20 consecutive seconds, with each second representing a unit of average sound pressure level.

[0062] The reference level determination unit can arrange a predetermined number of average sound pressures stored in the average sound pressure storage unit in the order of amplitude for each second cycle, and can determine the average value of a predetermined bottom range (e.g., the bottom 20%) as the reference level. Preferably, the second cycle is longer than the first cycle and shorter than N × the first cycle. The reason is that if the second cycle is too long, it is difficult to respond quickly to environmental changes; if the second cycle is too short, all speaking periods correspond to the second cycle, and the noise level may be set too high.

[0063] For example, assuming the first cycle is 1 second, N is 20, and the second cycle is 5 seconds, the baseline level determination unit can determine the baseline level based on the average sound pressure level determined every second over the most recent 20 seconds. In this case, the non-speaking period can be fully included within the relatively long time of 20 seconds, and the baseline level can be determined every 5 seconds (shorter than the above time), thus faithfully following environmental changes.

[0064] The reference level determination unit can use a predetermined initial value before determining the reference level based on the data first stored in the average sound pressure storage unit. The initial value can be a value pre-adjusted while the vehicle is stationary, and the noise level determination unit 143 can add the predetermined value (margin) to the reference level to finally determine the noise level.

[0065] Meanwhile, in another exemplary embodiment of the invention, the predicted noise level can be utilized. (Refer to...) Figure 8 Describe the construction of such a device.

[0066] Figure 8 An example of the construction of an active noise control device according to another exemplary embodiment of the present invention is shown.

[0067] In addition to further including an AVN system 160, an air conditioning control unit 170, and an ADAS control unit 180, and changing the noise level determination unit 143 of the active noise control unit 140 into a noise level prediction / determination unit 143' of the active noise control unit 140', Figure 8 The structure and Figure 6 The construction is the same. Therefore, it will be based on Figure 8 and Figure 6 The structural differences between them are described.

[0068] refer to Figure 8 The noise level prediction / determination unit 143' can receive information required for noise level prediction from the AVN system 160, the air conditioning control unit 170, and the ADAS control unit 180. For example, the active noise control unit 140' may be equipped with a modem supporting vehicle communication protocols (e.g., Controller Area Network (CAN), CAN-FD (Flexible Data Rate), Local Interconnect Network (LIN), or Ethernet) and can receive data from other control units 160, 170, and 180. Therefore, the noise level prediction / determination unit 143' can receive information about the road ahead or traffic conditions from the AVN system, information related to changes in air conditioning status from the air conditioning control unit 170, and information related to changes in vehicle behavior from the ADAS control unit 180. Of course, this information is shown, but the invention is not limited thereto. For example, although not shown, the noise level prediction / determination unit can receive information related to the status of the windows from the body control unit.

[0069] The noise level prediction / determination unit 143' can predict changes in nearby noise in advance based on the aforementioned information, and can variably set the noise level using the prediction information and the cumulative average sound pressure level information of the microphone signal. For example, when determining the noise level, if the changes in the information received from the external control units 160, 170, and 180 are within a predetermined range, the noise level prediction / determination unit can set the second period to be longer than the default period; conversely, if the changes in the received information deviate from the predetermined range, the noise level prediction / determination unit can set the second period to be shorter than the default period. Furthermore, the noise level prediction / determination unit 143' can learn the relationship between the information received from the external control units 160, 170, and 180 and the noise level to determine the noise level.

[0070] Reference Figure 9 The flowcharts describe the operation of the active noise control device according to each of the above exemplary embodiments.

[0071] Figure 9 This is an example flowchart illustrating the control process of an active noise control device according to each implementation scheme.

[0072] refer to Figure 9 The active noise control unit 140 or 140' can determine the noise level based on the microphone signal, or can predict the noise level based on information obtained from other control units (S910).

[0073] The active noise control unit 140 or 140' can determine whether the level of the microphone signal is greater than a predicted or determined noise level (S920). When the level of the microphone signal is greater than the predicted or determined noise level (Yes in S920), the active noise control unit is configured to determine the change in the current noise level relative to the previous noise level (S930). When the change in the noise level is greater than a predetermined threshold (Yes in S930), the active noise control unit 140 or 140' can perform control such that the noise immunity is output proportionally to the value obtained by subtracting the current noise level from the level of the microphone signal (S940A). On the other hand, when the change in the noise level is equal to or less than the threshold (No in S930), the active noise control unit 140 or 140' can perform control such that the noise immunity is output proportionally to the value obtained by subtracting the previous noise level from the level of the microphone signal (S940B). These operations are performed to prevent changes in the noise immunity amplitude when the noise level changes.

[0074] If the microphone signal level is equal to or less than the noise level (No in S920), noise immunity can be omitted (S950).

[0075] The present invention described above can be implemented as a computer-readable program stored in a computer-readable recording medium. The computer-readable medium can be any type of recording device that stores data in a computer-readable manner. Computer-readable media can include, for example, hard disk drives (HDDs), solid-state drives (SSDs), silicon disk drives (SDDs), read-only memory (ROM), random access memory (RAM), optical disc read-only memory (CD-ROM), magnetic tape, floppy disks, and optical data storage devices.

[0076] As is apparent from the above description, the active noise control device for vehicles associated with at least various exemplary embodiments of the present invention is configured to achieve privacy protection in the vehicle through more effective voice shielding.

[0077] In various exemplary embodiments of the invention, noise immunity is output only when the passenger is speaking, taking into account the amplitude of nearby noise, and the amplitude of noise immunity is controlled in response to the noise level, thereby protecting the hearing of the driver who hears the noise immunity.

[0078] Those skilled in the art will understand that the effects achievable by the present invention are not limited to those specifically described above, and that other effects of the present invention will be more clearly understood from the above detailed description.

[0079] Furthermore, terms related to control devices such as "controller," "control unit," "control device," or "control module" refer to hardware devices including a memory and a processor, the processor being configured to execute one or more steps interpreted as an algorithmic structure. The memory stores the algorithmic steps, and the processor executes the algorithmic steps to perform one or more processes according to various exemplary embodiments of the invention. A control device according to exemplary embodiments of the invention can be implemented using non-volatile memory and a processor, the non-volatile memory being configured to store algorithms for controlling the operation of various components of a vehicle or data regarding software commands for executing the algorithms, and the processor being configured to perform the aforementioned operations using the data stored in the memory. The memory and processor can be separate chips. Alternatively, the memory and processor can be integrated into a single chip. The processor can be implemented as one or more processors. The processor can include various logic circuits and arithmetic circuits, capable of processing data according to a program provided from the memory, and generating control signals based on the processing results.

[0080] The control device may be at least one microprocessor operated by a predetermined program, which may include a series of commands for performing methods included in the foregoing various exemplary embodiments of the present invention.

[0081] The invention described above can also be implemented as computer-readable code on a computer-readable recording medium. A computer-readable recording medium is a storage device capable of storing data and storing and executing program instructions, the data and the program instructions being subsequently readable by a computer system. Examples of computer-readable recording media include hard disk drives (HDDs), solid-state drives (SSDs), silicon disk drives (SDDs), read-only memory (ROM), random access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, and implementations as carrier waves (e.g., transmission over the Internet). Examples of program instructions include machine language code generated by a compiler, and high-level language code executable by a computer using an interpreter. In various exemplary embodiments of the invention, each of the above operations can be performed by a control device, and the control device can be configured by multiple control devices or an integrated single control device.

[0082] In various exemplary embodiments of the present invention, the control device may be implemented in hardware or software, or in a combination of hardware and software.

[0083] For ease of interpretation and precise definition in the appended claims, the terms “upper,” “lower,” “inner,” “outer,” “up,” “lower,” “upward,” “downward,” “front,” “back,” “rear,” “internal,” “external,” “inward,” “outward,” “inside,” “outside,” “inner,” “outer,” “forward,” and “backward” are used with reference to the positions of these features shown in the figures to describe features of the exemplary embodiments. It will be further understood that the term “connection” or its derivatives refer to both direct and indirect connections between the two.

[0084] The foregoing description of specific exemplary embodiments of the present invention is for illustrative and descriptive purposes. These descriptions are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling others skilled in the art to implement and utilize various exemplary embodiments of the invention, as well as various alternatives and modifications. The scope of the invention is intended to be defined by the appended claims and their equivalents.

Claims

1. An active noise control method for a vehicle, the active noise control method comprising: The control unit first determines the noise level based on a first microphone signal input through a microphone corresponding to the first seat; The control unit determines whether to output an anti-noise signal generated based on the first microphone signal based on the determined noise level and the level of the first microphone signal, and determines the amplitude of the anti-noise signal. In response to the second determination, the control unit outputs an anti-noise signal through the headrest speaker of the second seat; The first determination includes: The average sound pressure level of the first microphone signal is determined in each first cycle; The noise level is determined every second cycle based on N recently stored sequentially determined average sound pressure levels, where N is an integer; The noise level determination for each second cycle includes: A reference sound pressure corresponding to a predetermined bottom ratio is determined based on N defined average sound pressures; A predetermined margin is applied to a given reference sound pressure level to determine the noise level; The second determination includes: when it is determined that the level of the first microphone signal is greater than the noise level, controlling the anti-noise signal to be proportional to the value obtained by subtracting the noise level from the level of the first microphone signal; The second determination further includes determining the change in the noise level relative to the previously determined noise level; Controlling the noise immunity signal includes: when it is determined that the change is equal to or less than a predetermined threshold, controlling the noise immunity signal to be proportional to a value obtained by subtracting a previously determined noise level from the level of the first microphone signal.

2. The method according to claim 1, wherein, The first cycle is shorter than the second cycle; The second period is shorter than the product of the first period and N.

3. The method according to claim 1, wherein, The first determination includes: Receive vehicle operating status information from at least one vehicle control unit; The noise level is predicted based on the received vehicle operating status information.

4. The method according to claim 1, wherein, The second determination includes: When it is determined that the level of the first microphone signal is greater than a determined noise level, an anti-noise signal is output. If the level of the first microphone signal is determined to be equal to or less than a determined noise level, it is determined that no noise immunity signal will be output.

5. The method of claim 1, further comprising: The control unit receives the second microphone signal via the microphone corresponding to the second seat; The control unit applies a transfer function to the first microphone signal, the transfer function corresponding to the acoustic transmission path between the headrest speaker and a predetermined position, the predetermined position corresponding to the second seat; The control unit generates error information based on the first microphone signal and the second microphone signal, which have been processed by a transfer function. The control unit adaptively selects the filter to be applied to the noise-resistant signal based on the error information.

6. A non-volatile computer-readable recording medium comprising a program for performing the active noise control method for a vehicle according to claim 1.

7. An active noise control device for a vehicle, the active noise control device comprising: The microphone corresponding to the first seat; An active noise control unit configured to generate an anti-noise signal based on a first microphone signal input through the microphone; as well as A headrest speaker, disposed in the second seat, is configured to output noise corresponding to an anti-noise signal; The active noise control unit is configured to: determine the noise level based on the first microphone signal, and determine whether to output the generated anti-noise signal and determine the amplitude of the anti-noise signal based on the determined noise level and the level of the first microphone signal; The active noise control unit is configured to: determine the average sound pressure level of the first microphone signal every first cycle, and determine the noise level every second cycle based on the N most recently stored determined average sound pressure levels, where N is an integer; The active noise control unit is configured to: determine a reference sound pressure corresponding to a predetermined bottom ratio based on N determined average sound pressures, and apply a predetermined margin to the reference sound pressure to determine the noise level; The active noise control unit is configured to: when it is determined that the level of the first microphone signal is greater than the noise level, control the anti-noise signal to be proportional to the value obtained by subtracting the noise level from the level of the first microphone signal; The active noise control unit is configured to: determine the change in noise level relative to a previously determined noise level, and when it is determined that the change is equal to or less than a predetermined threshold, control the anti-noise signal to be proportional to the value obtained by subtracting the previously determined noise level from the level of the first microphone signal.

8. The active noise control device for a vehicle according to claim 7, wherein, The first cycle is shorter than the second cycle; The second period is shorter than the product of the first period and N.

9. The active noise control device for a vehicle according to claim 7, wherein, The active noise control unit is configured to receive vehicle operating status information from at least one vehicle control unit and predict the noise level based on the received vehicle operating status information.

10. The active noise control device for a vehicle according to claim 7, wherein, The active noise control unit is configured to: output an anti-noise signal when the level of the first microphone signal is greater than the noise level, and not output an anti-noise signal when the level of the first microphone signal is equal to or less than the determined noise level.

11. The active noise control device for a vehicle according to claim 7, further comprising: The microphone corresponding to the second seat; The active noise control unit is configured to: apply a transfer function to a first microphone signal, generate error information based on the first microphone signal to which the transfer function has been applied and a second microphone signal input via a microphone corresponding to the second seat, and adaptively select a filter to be applied to the noise suppression signal based on the error information, wherein the transfer function corresponds to the acoustic transmission path between the headrest speaker and a predetermined position, wherein the predetermined position corresponds to the second seat.

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