Active oscillation noise controller

Abstract

To stably and effectively reduce noise by removing voice components without significantly increasing a computational load.SOLUTION: A noise controller (100) includes speakers (12a-12d) for outputting a canceling sound (y) to cancel noise, error microphones (13a-13d) for generating an error signal (e) from the noise (d) and the canceling sound (y), and a reference microphone (13e) for detecting a reference signal (r). The noise controller (100) further includes a removal filter (21) which is adaptively updated on the basis of a current reference signal r(t) and a past reference signal r(t-T), and a filter processing unit (10) for generating the canceling sound.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an active vibration noise control device. [Background technology]

[0002] Conventionally, an active noise control device includes a noise canceling output device that outputs a canceling sound to cancel out noise, a plurality of noise microphones that generate a plurality of noise signals based on the noise, and a control device that controls the noise canceling output device based on the plurality of noise signals. The control device acquires a plurality of noise signals output from a plurality of noise microphones, and selects from the plurality of noise signals a reference signal corresponding to the noise and an error signal corresponding to the error between the noise and the cancellation sound. Then, a corrected reference signal is generated by removing the canceling component from the reference signal, and a control signal for controlling a canceling output device is generated based on the corrected reference signal (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-144581 Summary of the Invention [Problem to be solved by the invention]

[0004] However, placing a microphone on the headrest puts it close to the occupant's mouth. This makes it easier to detect the occupant's conversation. In particular, when using a microphone signal as a reference signal, the control output generated from the microphone signal contains a voice component. Therefore, if the signal is output from a speaker, it may cause an echo in the vehicle cabin, which may cause discomfort to the occupant. Furthermore, when calculating the audio components to be removed from the reference signal actually picked up by a microphone, it is necessary to extract them by frequency band and perform complex convolution calculations, which increases the amount of calculation required. For this reason, further improvements are needed in active noise and vibration control systems, which must generate cancellation sounds in a short amount of time. The object of the present invention is to provide an active vibration noise control device that can stably and effectively reduce noise by removing audio components without significantly increasing the amount of calculation. [Means for solving the problem]

[0005] To achieve the above object, an active vibration noise control system of the present invention includes a speaker that outputs a cancellation sound to cancel out the noise, an error microphone that generates an error signal from the noise and the cancellation sound, and a reference microphone that detects a reference signal. The active vibration noise control system also includes a cancellation filter that is adaptively updated based on a current reference signal and a past reference signal. The cancellation filter generates a cancellation signal from the past reference signal, and generates the cancellation sound using a modified reference signal obtained by subtracting the cancellation signal from the current reference signal. [Effects of the Invention]

[0006] According to the present invention, an active vibration noise control system is provided that can stably and effectively reduce noise by removing audio components without significantly increasing the amount of calculation. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic plan view of a vehicle to which an active vibration noise control device according to a first embodiment is applied. [Figure 2] 1 is a block diagram showing the functions of an active vibration noise control device according to a first embodiment; [Figure 3] FIG. 2 is a functional block diagram illustrating a removal filter according to the first embodiment. [Figure 4] FIG. 10 is a diagram showing a state in which a voice component is included in a microphone signal. [Figure 5]FIG. 10 is a diagram showing a state in which a voice component has been removed from a microphone signal. [Figure 6] FIG. 10 is a block diagram showing the configuration of a main part of an active vibration noise control device according to a second embodiment. [Figure 7] 10 is a graph showing an example of a frequency band removed by a band-stop filter in the second embodiment. [Figure 8] FIG. 10 is a block diagram showing the overall configuration of an active vibration noise control device according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] The following describes embodiments of the present invention with reference to the drawings as appropriate. Identical components are given the same reference numerals, and duplicate explanations will be omitted. In this specification, the "^" (hat) next to various reference numerals indicates an identified value or an estimated value. In the drawings, the "^" is placed above the various reference numerals, but in the main text, it is placed after the various reference numerals. [First embodiment] FIG. 1 shows a vehicle 1 to which an active vibration noise control device 100 (hereinafter also abbreviated as "noise control device 100") according to a first embodiment is applied. In the description of vehicle 1, identical elements are given the same numbers, and duplicate descriptions will be omitted. Furthermore, when describing directions, the descriptions will be based on front, back, left, right, up and down as seen from the driver of vehicle 1. Note that the vehicle width direction and left and right direction are synonymous.

[0009] The noise control device 100 is an ANC (Active Noise Control Device) for reducing noise d generated in the passenger compartment 2 of the vehicle 1. More specifically, the noise control device 100 generates a canceling sound y that is in the opposite phase to the noise d, and causes the generated canceling sound y to interfere with the noise d. In this way, the noise control device 100 can reduce the noise d that is the target for reduction.

[0010] For example, the noise d to be reduced by the noise control device 100 is road noise caused by wheel vibration due to force from the road surface. Note that the noise d to be reduced by the noise control device 100 may be noise other than road noise (for example, drivetrain noise or wind noise caused by vibration of a drive source such as an internal combustion engine or an electric motor).

[0011] 1 includes a plurality of speakers 12a-12d that output a cancellation sound y to cancel out a noise d. The noise control device 100 also includes a plurality of error microphones 13a-13d that generate an error signal e from the noise d and the cancellation sound y. The noise control device 100 also includes a reference microphone 13e that detects a reference signal r.

[0012] Furthermore, the noise control device 100 includes a filter processing unit 10 and a voice elimination unit 20. The filter processing unit 10 and the voice elimination unit 20 may be provided for each of the speakers 12a-12d or each of the error microphones 13a-13d. 2, the filter processing unit 10 has a noise control unit 110 and a sound field learning unit 120. The noise control unit 110 and the sound field learning unit 120 are configured by, for example, a computer having an arithmetic processing unit (a processor such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit)) and a storage device (memory such as a ROM (Read Only Memory) or RAM (Random Access Memory)). In addition, the noise control device 100 may be configured such that the components other than the speakers 12a-12d, the error microphones 13a-13d, and the reference microphone 13e, the voice removal unit 20, the noise control unit 110, and the sound field learning unit 120, are configured as a single piece of hardware, or may be configured as a unit consisting of multiple pieces of hardware.

[0013] Of these, the noise control unit 110 is mainly configured to include a noise control filter 111 , a secondary path filter unit 112 , and a control update unit 113 .

[0014] The noise control unit 110 receives the modified reference signal rp sent from the speech removal unit 20 in place of the reference signal r corresponding to the noise d. The noise control filter 111 generates a control signal u from the modified reference signal rp. When the control signal u is input to each of the speakers 12a-12d, it controls each of the speakers 12a-12d to output the canceling sound y.

[0015] The noise control filter 111 of the first embodiment corresponds to, for example, an FIR (Finite Impulse Response) filter. The FIR filter is a type of digital filter, and is a filter whose impulse response has a finite duration. In other words, the FIR filter is a filter whose output signal (impulse response) converges within a finite time when an impulse signal is input.

[0016] The secondary path filter unit 112 is configured by a secondary path filter having a filter characteristic C^. The secondary path filter is a filter having a filter characteristic C corresponding to an estimated value of the transfer characteristic of the cancellation sound y from the speakers 12a-12d to the error microphones 13a-13d. The secondary path filter may be an FIR filter or a SAN (Single Frequency Adaptive Notch) filter, which is a single-tap adaptive filter specialized for periodic noise.

[0017] Furthermore, the control update unit 113 adaptively updates the filter characteristic W of the noise control filter 111 using an adaptive algorithm such as the LMS algorithm (Least Mean Square Algorithm). The control update unit 113 receives the modified reference signal rp generated by the speech canceller 20 and the error signal e generated by the error microphones 13a-13d. Then, control update unit 113 adaptively updates filter characteristic W of noise control filter 111 using modified reference signal rp so that error signal e is minimized.

[0018] This allows the noise control filter 111 to filter the modified reference signal rp using the adaptively updated filter characteristic W, and generate the control signal u that controls the output of the speakers 12a-12d. The noise control filter 111 then outputs the generated control signal u to the speakers 12a-12d. The speakers 12a-12d generate a canceling sound y in accordance with the control signal u, thereby effectively reducing the noise d in the vehicle interior 2.

[0019] Furthermore, the sound field learning unit 120 of the noise control device 100 receives the modified reference signal rp sent from the speech removal unit 20 as input. The sound field learning unit 120 includes a primary path filter unit 121 and a primary path update unit 122. The primary path filter unit 121 and the primary path update unit 122 are configured to receive the modified reference signal rp.

[0020] Furthermore, the control signal u generated by the noise control filter 111 is input to the sound field learning unit 120 . The sound field learning unit 120 includes a secondary path filter unit 123 and a secondary path update unit 124. The secondary path filter unit 123 and the secondary path update unit 124 are configured to receive a control signal u.

[0021] The sound field learning unit 120 is also provided with a first polarity inversion unit 125, a second polarity inversion unit 126, and an adder 127. The first polarity inversion unit 125 inverts the polarity of the noise signal d̂ input from the primary path filter unit 121 and sends it to the adder 127.

[0022] Furthermore, the second polarity inversion unit 126 inverts the polarity of the cancellation signal ŷ of the cancellation signal y input from the secondary path filter unit 123 and sends it to the adder 127 . The adder 127 adds the noise signal d^ with the polarity inverted, the cancellation signal y^ with the polarity inverted, and the error signal e generated by the error microphones 13a-13d to obtain the error signal e^. The error signal e^ is sent to the primary path update unit 122 and the secondary path update unit 124 and is used for adaptive updating of the primary path filter unit 121 and the secondary path filter unit 123.

[0023] The speech removal unit 20 of the first embodiment is provided on the input side of the filter processing unit 10. The speech removal unit 20 receives the current reference signal r(t) from the reference microphone 13e. Then, the speech canceller 20 uses the cancel filter 21 to remove the cancellation signal p from the current reference signal r(t) to generate a modified reference signal rp. This allows the speech removal unit 20 to send the modified reference signal rp, which is composed of a noise component signal from which the speech component signal has been removed, to the noise control unit 110 and sound field learning unit 120 of the filter processing unit 10.

[0024] In detail, as shown in FIG. 3, the speech removal unit 20 of the first embodiment includes a removal filter 21 and a delay process (Z -T ) and a delay processing unit 22 that performs the delay processing. Furthermore, the speech removal unit 20 includes an adaptive update unit 23. The adaptive update unit 23 adaptively updates the removal filter 21 based on the current reference signal r(t) input from the reference microphone 13e and the past reference signal r(tT) delayed by the delay processing unit 22.

[0025] In the first embodiment, the adaptive update unit 23 refers to a past reference signal r(tT) and a modified reference signal (rp) obtained by removing the speech component from the current reference signal r. For this reason, the speech removal unit 20 is provided with a polarity inversion unit 24 and an adder 25. The polarity inversion unit 24 inverts the polarity of the periodic removal signal p (speech signal) sent from the removal filter 21. The polarity inversion unit 24 outputs the removal signal p with the inverted polarity to the adder 25. As a result, the speech removal unit 20 of the first embodiment can output the modified reference signal rp from which the speech component has been removed, using the removal filter 21 that has been adaptively updated by the adaptive update unit 23.

[0026] The elimination filter 21 of the first embodiment is an FIR (Finite Impulse Response) filter to predict audio having multiple frequency components. Alternatively, an IIR (Infinite Impulse Response) filter P1 may be used as the elimination filter 21. An FIR filter is a type of digital filter, and is a filter whose impulse response has a finite duration. In other words, an FIR filter is a filter whose output signal (impulse response) converges within a finite time when an impulse signal is input.

[0027] The elimination filter 21 extracts a periodic signal contained in the past reference signal r(tT) and generates an elimination signal p. Furthermore, the elimination filter 21 generates a modified reference signal rp by removing the elimination signal p from the current reference signal r(t).

[0028] Generally, the output p(t) of a prediction filter, which serves as a removal filter, is calculated from a reference signal r delayed by time T as shown in Equation (1).

[0029] TIFF2025154966000002.tif11144Here, T: delay time, t: discrete time, *: convolution operation. The error signal ep for adaptively updating the prediction filter is the difference between the current reference signal r(t) and the output p(t) from the prediction filter, and is expressed by the following equation (2):

[0030] TIFF2025154966000003.tif10144When the error signal ep converges to 0, the output p(t) becomes the current reference signal r. In other words, the adaptively updated linear prediction filter is a filter for predicting the current reference signal r(t) from the past reference signal r(tT).

[0031] A typical algorithm for separating speech from environmental noise requires the use of multiple microphones, making the system expensive. Furthermore, signal processing requires a large amount of computation because it involves multiple convolution operations and frequency-domain calculations using DFT (Discrete Fourier Transform) and FFT (Fast Fourier Transform). Such computationally intensive algorithms have the problem of taking a long time to separate speech from environmental noise. Furthermore, high-performance processors capable of executing algorithms in a short time are expensive and are not suitable for noise removal in vehicles 1, where increases in manufacturing costs must be kept in check.

[0032] Therefore, as a measure with a small amount of calculation and little processing delay, the present invention focuses on the fact that speech characteristics can be used to effectively separate speech from environmental noise such as indoor noise. FIG. 4 shows a microphone signal with a voice component superimposed on the environmental noise component. In Figure 4, the vertical axis represents frequency (kHz) and the horizontal axis represents time (s), and the difference in shading visualizes that the darker (black) areas have a louder volume (dB) than the lighter (white) areas. Here, for example, as shown in part A, the voice components are a combination of multiple periodic sounds. It is known that this periodicity is due to the resonant frequencies (formant frequencies) caused by the structure of the human vocal cords and mouth, and their harmonics. Formant frequencies differ depending on the individual speaker and the syllable, but the fact remains that any voice has periodicity due to the combination of formant frequencies and their harmonics.

[0033] In contrast, the interior noise of the vehicle 1 has characteristics that differ from the voice component. For example, in the electric driving mode of an electric vehicle or hybrid vehicle, there are no noise sources with strong periodicity, such as engine noise. The noise inside the passenger compartment 2 is dominated by road noise and aerodynamic noise, and is highly random. Figure 5 shows that the microphone signal does not contain any audio components, but mainly contains indoor noise components. Comparing Figure 5 with Figure 4, we can see that part B of Figure 5, which corresponds to part A of Figure 4, does not contain any audio components, which are a combination of multiple periodic sounds. That is, the noise control device 100 needs to separate periodic sounds from random, noisy noises in order to obtain a control signal u suitable for canceling sounds.

[0034] Speech is periodic and therefore predictable. On the other hand, indoor noise is highly random and therefore unpredictable. This proposal focuses on this difference in periodicity to realize a noise reduction method. That is, it is considered that the noise control device 100 of the first embodiment can extract and separate predictable audio components from indoor noise by using an adaptive linear prediction filter.

[0035] Specifically, the removal filter 21 provided in the speech removal unit 20 of the first embodiment extracts a periodic signal contained in a past reference signal r(tr) and sets it as a removal signal p. The removal signal p is a predictable speech component of the reference signal r. Therefore, by removing the removal signal p from the current reference signal r(t), unpredictable noise components remain, and a modified reference signal rp is generated.

[0036] Furthermore, the elimination filter 21 of the first embodiment has a very short delay due to the filtering process, can cancel out noise in real time, and is suitable for removing signals containing voice components. In this way, the noise control device 100 of the first embodiment uses the modified reference signal rp generated by the speech removal unit 20, instead of the reference signal r that is directly input from the reference microphone 13e. The modified reference signal rp is generated mainly from only the noise components from which the speech components have been removed. This allows the noise control section 110 of the filter processing section 10 to easily generate the control signal u that is effective only against noise with a small amount of calculation, without increasing the amount of calculation.

[0037] The noise control unit 110 of the filter processing unit 10 generates the control signal u using the modified reference signal rp that does not include a signal of a voice component generated by the voice removal unit 20. Therefore, in the vehicle 1 of the first embodiment, noise control by the noise control device 100 causes the cancellation sound y that is effective only against noise to be output in a timely manner from each of the speakers 12a-12d. Therefore, it is possible to stably and effectively reduce noise while suppressing voice echoes, and therefore the vehicle 1 of the first embodiment can create a quiet, comfortable, and high-quality space inside the vehicle cabin 2.

[0038] [Second embodiment] 6 is a block diagram illustrating the configuration of the main parts of an active vibration noise control device 200 (hereinafter also abbreviated as "noise control device 200") according to a second embodiment. Note that parts that are the same as or equivalent to those in the active vibration noise control device 100 according to the first embodiment are given the same reference numerals and their description will be omitted.

[0039] The noise control device 200 of the second embodiment includes a band elimination unit 30 that is provided with a band stop filter 32 and that eliminates a specific frequency band. The band elimination unit 30 includes a random noise generator 31 that generates random noise x that is uncorrelated with other signals, and a band-stop filter 32 that blocks a desired frequency band from passing through the random noise x. The band elimination unit 30 also has a gain amplifier unit 33 that adjusts the gain of the band elimination signal xw sent to the adaptive update unit 23 of the speech elimination unit 20, and a sub-elimination filter 34 that generates an error signal ew from the band elimination signal xw corresponding to the output outside the elimination band and sends the error signal ew to the adaptive update unit 23.

[0040] In the noise control device 200 of the second embodiment, the band elimination signal xw containing random noise that has been passed through the band-stop filter 32 and the error signal ew are further added, and the adaptive update unit 23 of the speech elimination unit 20 is configured to adaptively update the elimination filter 21.

[0041] More specifically, the band-stop filter 32 of the noise control device 200 blocks random noise only in the frequency band where voice echo becomes a problem, thereby limiting the influence of the voice removal process. That is, the evaluation function for adaptively updating the elimination filter 21 is expanded by the following equation (3).

[0042] TIFF2025154966000004.tif11144Here, in equation (3), ew = x * BS * p. Also, BS (bandstop filter 32) passes signals in bands other than the band from which speech is to be removed. Therefore, the error signal ew corresponds to the output of the removal filter 21 outside the removal band. The noise control device 200 of the second embodiment performs adaptive updating so that the evaluation function is minimized (0), and therefore attempts to simultaneously set ep and ew to 0. By reducing ew, the noise control device 200 can suppress the output of the elimination filter 21 outside the elimination band. Furthermore, the noise control device 200 can extract periodic audio components contained in the reference signal by reducing ep. The update formula for the removal filter 21 based on this evaluation function is the following formula (4). Formula 4

[0043] TIFF2025154966000005.tif11144As a result, in the frequency band removed by the band-stop filter 32, audio components can be extracted and output by adaptively updating the elimination filter 21. In the frequency band not removed by the band-stop filter 32, the updating of the elimination filter 21 is suppressed, and the output is small. Therefore, the elimination filter 21 is adaptively updated using the error signal ew to which random noise has been added after passing through the band-stop filter 32, together with the past reference signal r(tT) sent from the delay processing unit 22. By using the adaptively updated elimination filter 21, it is possible to generate a modified reference signal rp in which periodic audio components have been removed from the reference signal r in the frequency band removed by the band-stop filter 32. Furthermore, in the frequency band not removed by the band-stop filter 32, the output of the elimination filter 21 is suppressed, and therefore the effect on the reference signal r is small. In this way, in the noise control device 200 of the second embodiment, only the frequency band in which the voice echo occurs can be effectively removed by the band removal unit 30 having the band-stop filter 32. Therefore, the noise control device 200 can further limit the influence of the voice removal process.

[0044] Fig. 7 is a graph showing an example of a frequency band removed by the band-stop filter 32 in the second embodiment. In Fig. 7, part C, which is the removal area, is set to a frequency band from which speech is to be removed. In this way, by setting the removal area to the frequency band with the most speech components, the noise control device 200 can more reliably remove speech components with the removal filter 21.

[0045] Therefore, sound removal is performed only on frequency components that cause discomfort to passengers due to the influence of sound (echo), and the influence of sound removal processing on other frequency bands can be minimized. The other configurations and effects are the same as those of the first embodiment, so the description will be omitted.

[0046] [Third embodiment] 8 is a block diagram illustrating the overall configuration of an active vibration noise control device 300 (hereinafter also abbreviated as "noise control device 300") according to a third embodiment. Note that parts that are the same as or equivalent to those in the active vibration noise control device 100 according to the first embodiment are given the same reference numerals and their description will be omitted.

[0047] The noise control device 300 of the third embodiment includes a second speech elimination unit 40. The second speech elimination unit 40 has a second elimination filter 41 that is adaptively updated based on the current error signal e'(t) and the past error signal e'(tT). In detail, the second speech removal unit 40 has a second removal filter 41 , a second delay processing unit 42 , a second adaptive update unit 43 , a polarity inversion unit 44 , and an error adder 45 .

[0048] The second audio canceller 40 is connected to the error microphones 13a-13d and receives the error signals e' sent from the error microphones 13a-13d. The second speech removal unit 40 is provided with a second adaptive update unit 43 that adaptively updates the second removal filter 41 using the past error signal e'(tT) sent from the second delay processing unit 42. In addition, a polarity inversion unit 44 inverts the polarity of the second removal signal p2 output from the second adaptive update unit 43 and sends it to an error adder 45. The error adder 45 adds the current error signal e'(t) and the second cancellation signal p2 with the polarity reversed to generate a modified error signal e(p2). The modified error signal e(p2) is sent to the noise control unit 110 and the sound field learning unit 120, which are configured in the same way as in the first embodiment, and is used for adaptively updating the respective filters.

[0049] In the noise control device 300 of the third embodiment configured as described above, the second elimination filter 41 extracts a periodic signal contained in the past error signal e'(tT) and generates a second elimination signal p2. The second elimination filter 41 also generates a modified error signal e(p2) by removing the second elimination signal p2 from the current error signal e'. The filter processing unit 10 is then adaptively updated based on the modified error signal e(p2). Therefore, the noise control device 300 of the third embodiment can effectively remove periodic audio signals from the error signal e' as well, thereby providing a practically beneficial effect of being able to adaptively update the filter processing unit 10 with higher accuracy and reduce noise stably and effectively. The other configurations and effects are the same as those of the first embodiment, so the description will be omitted.

[0050] As described above, this proposal, like the active vibration noise control device (noise control device) 100 of the first embodiment shown in FIG. 1, includes speakers 12a-12d that output canceling sounds to cancel out noise, error microphones 13a-13d that generate error signals from the noise d and the canceling sounds y, and reference microphone 13e that detects a reference signal. The noise control device 100 also includes a elimination filter 21 that is adaptively updated based on a current reference signal and a past reference signal, as shown in Fig. 2. The elimination filter 21 generates a elimination signal from the past reference signal, and generates a cancellation sound using a modified reference signal obtained by subtracting the elimination signal from the current reference signal. As a result, the noise control device 100 can stably and effectively reduce noise by removing the voice component without significantly increasing the amount of calculation.

[0051] In more detail, for example, the elimination filter 21 may extract a periodic signal contained in a past reference signal to generate an elimination signal p, and may also generate a modified reference signal rp by removing the elimination signal P from the current reference signal. Then, the noise control filter 111 generates a cancellation sound y using the modified reference signal rp. 3, the elimination filter 21 used in the speech elimination unit 20 of the present invention extracts a periodic speech signal contained in a past reference signal r(tT) to obtain an elimination signal p. The elimination filter 21 is then adaptively updated by an adaptive update unit 23 based on the current reference signal r(t) and the past reference signal r(tT). By adaptively updating the elimination filter 21, the speech elimination unit 20 can extract a predictable periodic speech component. This makes it possible to obtain the cancellation signal p to be subtracted from the current reference signal r(t) with a small amount of calculation, and to generate the modified reference signal rp by removing the cancellation signal p from the current reference signal r(t) in a short time.

[0052] Then, the noise control filter 111 uses the modified reference signal rp to output the cancellation sound y from the speakers 12a-12d, with the sound components removed. This reduces the noise d, which is random noise. Furthermore, the cancellation sound y does not contain any sound components. Therefore, it is not affected by interference from the sound components. This reduces the sound echo in the vehicle interior 2, eliminating any discomfort felt by the occupants. Therefore, the noise control device 100 of the present invention can stably and effectively reduce noise by removing the voice component without significantly increasing the amount of calculation.

[0053] 6, the present invention includes a band-stop filter 32 that removes a specific frequency band. The removal filter 21 is adaptively updated by further adding random noise that has passed through the band-stop filter 32. Therefore, in the frequency band removed by the band-stop filter 32, the voice component can be extracted and output by adaptively updating the elimination filter 21. In the frequency band not removed by the band-stop filter 32, the updating of the elimination filter 21 is suppressed, and the output is small. Therefore, the removal filter can extract the audio component by limiting the frequency band that becomes an echo due to the influence of the audio, and generate a modified reference signal. Therefore, only the frequency band in which the voice echo occurs can be effectively removed by the band-stop filter 32, thereby limiting the influence of the voice removal process.

[0054] The present invention also includes a second removal filter 41 that is adaptively updated based on the current error signal e'(t) and the past error signal e'(tT), as in the noise control device 300 shown in FIG. The second elimination filter 41 generates a second elimination signal p2 from the past error signal e'(tT). The second elimination filter 41 also generates a modified error signal e(p2) by subtracting the second elimination signal p2 from the current error signal e'(tT). The filter processing unit 10 is then adaptively updated based on the modified error signal e(p2). Therefore, the noise control device 300 can effectively remove the periodic audio signal from the error signal e' as well. Therefore, the filter processing unit 10 can be adaptively updated with higher accuracy, which is a practically beneficial effect.

[0055] The present invention is not limited to the above-described embodiments, and various modifications are possible. The above-described embodiments are provided as examples to facilitate understanding of the present invention, and are not necessarily limited to those including all of the configurations described. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to delete part of the configuration of each embodiment, or to add or replace other configurations. Possible modifications of the above-described embodiments include, for example, the following.

[0056] That is, the noise control device 200 of the second embodiment includes a band elimination unit 30, and the noise control device 300 of the third embodiment includes a second audio elimination unit 40. However, the present invention is not particularly limited to this. For example, a single active vibration noise control device may include both the band elimination unit 30 and the second audio elimination unit 40. In this way, as long as the active vibration noise control device of the present invention is equipped with the filter processing unit 10 and the removal filter 21 as in the first embodiment, the other configurations that perform the respective functions and the combinations of these other configurations are not limited to the configurations of the first to third embodiments. [Explanation of symbols]

[0057] 10 Filter processing section 12a~12d Speakers 13a~13d Error microphone 13e Reference Microphone 21 Removal Filter r reference signal rp modified reference signal y cancellation sound

Claims

1. a speaker that outputs a canceling sound to cancel out noise; an error microphone for generating an error signal from the noise and the cancellation sound; a reference microphone for detecting a reference signal; a rejection filter that is adaptively updated based on the current reference signal and the past reference signal; The active vibration noise control device is characterized in that the elimination filter generates an elimination signal from the past reference signal and generates the cancellation sound using a modified reference signal obtained by subtracting the elimination signal from the current reference signal.

2. Equipped with a band-stop filter that removes a specific frequency band, 2. An active vibration noise control device according to claim 1, wherein the elimination filter is adaptively updated by further adding random noise passed through the band-stop filter.

3. a second elimination filter that is adaptively updated based on the current error signal and the past error signal; 2. The active vibration noise control device according to claim 1, wherein the second elimination filter generates a second elimination signal from the past error signal and generates a modified error signal by subtracting the second elimination signal from the current error signal, and the filter processing unit is adaptively updated based on the modified error signal.

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