JPH0732947A - Active type noise control device - Google Patents

Abstract

PURPOSE:To carry out a good noise reduction control without giving an unpleasant feeling to occupants, by filter-processing a residual noise signal by a transfer function reverse filter, so as to make into a constitution to produce an identification signal. CONSTITUTION:A residual noise signal e1 to indicate the residual noise in a car room 3 detected by microphones 8a to 8c is delayed a specific time in a delay processor 13. The result is filter-processed by a transfer function reverse filter C<-1>1m having a frequency characteristics reverse with a transfer function C1m in the car room 3, so as to produce an identification signal ID. After the level of the produced identification signal ID is attenuated a specific level by a damper processor 15, it is added to a driving signal Ym produced by a driving signal producer 11 at an adding processor 16, and the adding result is fed to a loud speaker 9 as a new driving signal Ym. And the filter function of the first adaptation filter for identifation C1m is renewed according to an LMS algorithm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active noise control device for reducing noise by causing a control sound generated from a control sound source to interfere with noise transmitted from a noise source,
Particularly, even in a space where the acoustic transfer characteristics change relatively frequently, such as a vehicle interior of a vehicle, good noise reduction control can be performed without causing discomfort to an occupant or the like.

[0002]

2. Description of the Related Art Conventional active noise control devices include those described in British Patent No. 2149614 and Japanese Patent Publication No. 1-501344. These conventional devices are noise reduction devices applied to, for example, a closed space such as a cabin of an aircraft, and microphones installed at a plurality of positions in such a closed space to detect sound pressure, and the closed space. A plurality of loudspeakers that generate control sounds are provided, and based on the noise generation state of the noise source, a control sound having a phase opposite to the noise transmitted to the closed space is generated from the loudspeakers to cancel the noise.

As a method of generating a control sound emitted from a loudspeaker, PROCEEDINGS OF THE IEEE, VOL.
63 PAGE 1692-1975, “ADAPTIVE NOISE CANSELLATION
: "PRINCIPLES AND APPLICATIONS" described in "LMS Algorithm" is applied to multiple channels. The contents of the algorithm are "A MULTIPLE ERROR LMS ALGORITHM AND
ITS APPLICATION TO THE ACTIVE CONTROL OF SOUND AN
D VIBRATION ”, IEEE TRANS.ACOUST., SPEECH, SIGNAL PR
It is also described in OCESSING, VOL.ASSP −35, PP.1423−1434,1987.

That is, the LMS algorithm is one of the algorithms suitable for updating the filter coefficient of the adaptive digital filter, and is, for example, the so-called Filt.
In the ered-X LMS algorithm, a filter representing the transfer function from the loudspeaker to the microphone is set for all combinations of the loudspeaker and the microphone, and a reference signal representing the noise generation state of the noise source is set by the filter. The filter coefficient of the adaptive digital filter provided for each loudspeaker is updated based on the processed value and the residual noise detected by each microphone.

Here, in such an active noise control device, it is premised that the filter representing the transfer function from the loudspeaker to the microphone accurately represents the transfer function, and the transfer represented by the filter is assumed. Functions,
If the deviation from the actual transfer function of the physical space is large, not only noise cannot be reduced but also 90 in the frequency domain.
On the other hand, if a close phase difference occurs, it may diverge.

Then, as a conventional technique capable of solving such a problem, the applicant of the present invention has previously proposed Japanese Patent Laid-Open No. 3-20.
There is a technique described in Japanese Patent No. 3492, and in such a conventional solution, a test signal including white noise is supplied to a loudspeaker when a sound level in a space is high, and the test signal and the test signal are supplied. The transfer function between the loudspeaker and the microphone is calculated based on the detection result of the microphone when it is supplied to the loudspeaker, and the calculated transfer function is incorporated into the noise reduction control. I tried to eliminate the gap between the transfer function and the physical space of.

As a result, even when the transfer function varies relatively quickly in a short time due to various factors such as temperature, humidity, opening and closing of windows, the number of passengers, etc.
It is possible to reduce noise.

[0008]

Certainly, according to the above-mentioned conventional solution, the signal supplied to the loudspeaker for the identification calculation of the transfer function is white noise having the same power over the entire frequency band. Therefore, an identification sound having the same power is generated from the loudspeaker over the entire frequency band, so that an effective transfer function is identified for the entire frequency band and noise can be reduced.

However, as shown in FIG. 16, the fact that the identification sound has a constant level over the entire frequency band means that the noise remaining in the actual space has some frequency characteristic, so that it is more than the noise. There is a frequency band where the level of the identification sound is higher, or conversely, there is a frequency band where the level of the identification sound is lower than that of noise. However, there is a problem that the identification sound takes a long time because it has many noise components for the identification calculation in a frequency band where the level of the identification sound is extremely low compared to the noise. . Therefore, if the level of the identification sound is set to be lower than the noise level in the entire frequency band, the problem that the identification sound is heard by the occupants is mitigated, but the identification of the transfer function becomes extremely slow and the In a space where the transfer function fluctuates significantly, the identification of the transfer function will not be in time, and conversely, if the level of the identification sound is raised, the identification of the transfer function will be quick and accurate, but the occupant will feel uncomfortable. Will increase.

Further, when the noise source emits periodic noise, the noise has power at the fundamental frequency and its harmonics (that is, exhibits a line spectrum) as shown in FIG. The problem caused by emitting the identification sound having a constant power over the entire frequency band is particularly remarkable. And, while it is important that the transfer function has an accurate value at a frequency at which the noise has power, in such a case, since the frequency band where the noise has no power is very wide, it is often used for identification. It means that the useless calculation of was performed.

The present invention has been made by paying attention to the unsolved problems of the prior art as described above. It is possible to solve the problem that an occupant or the like hears an identification sound, and the transfer function is identified. It is an object of the present invention to provide an active noise control device that can be performed with high accuracy in a short time.

[0012]

In order to achieve the above object, the invention according to claim 1 is a control sound source capable of generating a control sound in a space where noise is transmitted from the noise source, and noise of the noise source. A noise occurrence state detecting means for detecting an occurrence state and outputting it as a reference signal; a residual noise detecting means for detecting residual noise at a predetermined position in the space and outputting it as a residual noise signal; and an adaptive digital filter having a variable filter coefficient,
Driving signal generating means for generating a signal for driving the control sound source by filtering the reference signal with the adaptive digital filter, and a transfer function filter modeling acoustic transfer characteristics between the control sound source and the residual noise detecting means. When,
Filter coefficient updating means for updating the filter coefficient of the adaptive digital filter so as to reduce noise in the space based on a value obtained by filtering the reference signal with the transfer function filter and the residual noise signal, and the transfer function. A transfer function inverse filter having a frequency characteristic opposite to that of the filter; an identification signal generating means for generating an identification signal by filtering the residual noise signal with the transfer function inverse filter and supplying the identification signal to the control sound source; A signal level attenuating means arranged in series with the signal generating means and the control sound source and attenuating an input signal by a predetermined level, and arranged in series relationship with the identification signal generating means and the control sound source; A signal delay means for delaying an input signal by a predetermined time and outputting the signal, and based on the identification signal and the residual noise signal, A transfer function filter setting means for setting the transfer function filter to identify the transfer function between the control sound and the residual noise detecting means, with a.

In order to achieve the above object, the invention according to claim 2 detects a control sound source capable of generating a control sound in a space where noise is transmitted from the noise source and a noise generation state of the noise source. Noise generating state detecting means for outputting as a reference signal, residual noise detecting means for detecting residual noise at a predetermined position in the space and outputting as a residual noise signal, an adaptive digital filter with a variable filter coefficient, and the reference signal Drive signal generating means for generating a signal for driving the control sound source by filtering with the adaptive digital filter, transfer function filter modeling acoustic transfer characteristics between the control sound source and the residual noise detecting means, and the reference Based on the value obtained by filtering the signal with the transfer function filter and the residual noise signal, the adaptive disc is reduced so as to reduce noise in the space. Filter coefficient updating means for updating the filter coefficient of the digital filter, identification signal generating means for delaying the residual noise signal for a predetermined time to generate an identification signal and supplying it to the control sound source, the identification signal generating means and the control sound source. A signal level attenuating means arranged in series with and attenuating an input signal by a predetermined level and outputting the signal, and a transfer function between the control sound source and the residual noise detecting means based on the identification signal and the residual noise signal. And a transfer function filter setting means for identifying and setting the transfer function filter.

In order to achieve the above object, the invention according to claim 3 detects a control sound source capable of generating a control sound in a space where noise is transmitted from the noise source and a noise generation state of the noise source. Noise generating state detecting means for outputting as a reference signal, residual noise detecting means for detecting residual noise at a predetermined position in the space and outputting as a residual noise signal, an adaptive digital filter with a variable filter coefficient, and the reference signal Drive signal generating means for generating a signal for driving the control sound source by filtering with the adaptive digital filter, transfer function filter modeling acoustic transfer characteristics between the control sound source and the residual noise detecting means, and the reference Based on the value obtained by filtering the signal with the transfer function filter and the residual noise signal, the adaptive de-multiplexer is configured to reduce noise in the space. Filter coefficient updating means for updating the filter coefficient of the digital filter, white noise signal generating means for generating a white noise signal, variable pass characteristic for generating an identification signal by filtering the white noise signal and supplying it to the control sound source , A residual noise frequency characteristic detecting means for detecting the frequency characteristic of the residual noise signal, and both the frequency characteristic detected by the residual noise frequency characteristic detecting means and the frequency characteristic opposite to the transfer function filter. A filter characteristic setting means for setting the pass characteristic of the pass characteristic variable filter so as to match the multiplied frequency characteristic, and a signal which is arranged and input in series with the pass characteristic variable filter and the control sound source is predetermined. Signal level attenuating means for level-attenuating and outputting, the identification signal and the residual noise signal Equipped with a transfer function filter setting means for setting the identified said transfer function filter transfer function between the control sound source and the residual noise detecting means based on and.

Further, in order to achieve the above object, the invention according to claim 4 detects a control sound source capable of generating a control sound in a space where noise is transmitted from the noise source, and a noise generation state of the noise source. Noise generating state detecting means for outputting as a reference signal, residual noise detecting means for detecting residual noise at a predetermined position in the space and outputting as a residual noise signal, an adaptive digital filter with a variable filter coefficient, and the reference signal Drive signal generating means for generating a signal for driving the control sound source by filtering with the adaptive digital filter, transfer function filter modeling acoustic transfer characteristics between the control sound source and the residual noise detecting means, and the reference Based on the value obtained by filtering the signal with the transfer function filter and the residual noise signal, the adaptive de-multiplexer is configured to reduce noise in the space. Filter coefficient updating means for updating the filter coefficient of the digital filter, white noise signal generating means for generating a white noise signal, variable pass characteristic for generating an identification signal by filtering the white noise signal and supplying it to the control sound source Variable pass characteristic filter, residual noise frequency characteristic detecting means for detecting the frequency characteristic of the residual noise signal, and pass characteristic of the variable pass characteristic filter so as to match the frequency characteristic detected by the residual noise frequency characteristic detecting means. Filter characteristic setting means for setting, a signal level attenuating means arranged in series with the variable pass characteristic filter and the control sound source, for attenuating an input signal by a predetermined level and outputting the signal, the identification signal and the residual signal Before identifying the transfer function between the control sound source and the residual noise detecting means based on the noise signal A transfer function filter setting means for setting a transfer function filter, comprising a.

In order to achieve the above object, the invention according to claim 5 is a control sound source capable of generating a control sound in a space where the noise is transmitted from a noise source which emits periodic noise,
A noise generation state detecting means for detecting a noise generation state of the noise source and outputting it as a reference signal, a residual noise detection means for detecting residual noise at a predetermined position in the space and outputting it as a residual noise signal, and a variable filter coefficient An adaptive digital filter, drive signal generating means for generating a signal for driving the control sound source by filtering the reference signal with the adaptive digital filter, and a model of acoustic transfer characteristics between the control sound source and the residual noise detecting means. And a filter coefficient for updating the filter coefficient of the adaptive digital filter so that the noise in the space is reduced based on the residual noise signal and the value obtained by filtering the reference signal with the transfer function filter. Update means,
White noise signal generation means for generating a white noise signal, a pass characteristic variable filter for varying the pass characteristic which filters the white noise signal to generate an identification signal and supplies the identification signal to the control sound source, and the basic of the periodic noise A fundamental frequency detecting means for detecting a frequency, a filter characteristic setting means for setting the pass characteristic of the pass characteristic variable filter so that the fundamental frequency detected by the fundamental frequency detecting means and its harmonics become a pass band, and the pass characteristic A signal level adjusting means arranged in series with the variable characteristic filter and the control sound source and adjusting the level of an input signal, and the control sound source and the residual noise detecting means based on the identification signal and the residual noise signal. And a transfer function filter setting means for identifying the transfer function between and setting the transfer function filter.

[0017]

According to the first aspect of the present invention, the identification signal generating means generates the identification signal by filtering the residual noise signal with the transfer function inverse filter. Therefore, the frequency characteristic of the identification signal is the residual noise. It has the same shape as the frequency characteristic of the generated sound when it is considered that the noise at the position where the detecting means is arranged is emitted from the control sound source.

Further, since the signal level attenuating means is in series with the identification signal generating means and the control sound source, the level of the identification signal at the time of being supplied to the control sound source is lower than the level of the residual noise signal by a predetermined level. Has become. further,
Since the signal delay means also has a serial relationship with the identification signal generation means and the control sound source, the identification signal at the time of being supplied to the control sound source is a signal delayed by a predetermined time from the residual noise signal.

From the above, when the identification signal is supplied to the control sound source and the identification sound is emitted from the control sound source, at the position where the residual noise detecting means is arranged, the frequency characteristic having the same shape as the residual noise is obtained, and An identification sound that is lower by a predetermined level and is uncorrelated with the residual noise arrives, and a person in the space cannot distinguish the noise and the identification sound. That is,
In the first place, the level of the identification sound becomes high in the frequency band where the noise level is high and it is difficult for human beings in the space to hear the identification sound.Therefore, if the transfer function filter setting means performs the transfer function filter setting process, The identification of the transfer function is performed with high accuracy in a short time, but high accuracy is required for the transfer function only in the frequency band where the noise level is high (that is, in the frequency band where noise does not have power). Does not generate control sound), avoiding an increase in discomfort for humans in the space,
The most efficient noise reduction control will be executed.

On the other hand, the invention of claim 2 is substantially equivalent to the invention of claim 1 in which the transfer function inverse filter is omitted. Therefore, since the identification signal at the time of being supplied to the control sound source is a signal lower than the level of the residual noise signal by a predetermined level and delayed from the residual noise signal by a predetermined time, it is the same as the residual noise from the control sound source. With the frequency characteristics of the shape, an identification sound lower than the residual noise by a predetermined level and uncorrelated with the residual noise is emitted.

The identification sound propagates in the space while reaching the residual noise detecting means while being influenced by the acoustic transfer characteristics between the control sound source and the residual noise detecting means. The identification sound at the position where the residual noise detecting means is installed does not become louder than the residual noise unless the characteristic is such that the band component is amplified. Not stick.

Therefore, even in the invention described in claim 2, the accuracy is slightly lower than that of the invention described in claim 1, but the frequency is high in the first place and a person in the space cannot hear the identification sound. Since the level of the identification sound becomes high in the band, if the transfer function filter setting means performs the transfer function filter setting process, the transfer function can be identified in such a frequency band in a short time and with high accuracy. .

Next, in the invention according to claim 3, the white noise signal generated by the white noise signal generating means is filtered by the variable pass characteristic filter to generate the identification signal. The frequency characteristic of is determined by the pass characteristic of the variable pass characteristic filter. The pass characteristic of the pass characteristic variable filter is the frequency characteristic of the residual noise signal detected by the residual noise frequency characteristic detecting means by the filter characteristic setting means,
Since the frequency characteristic of the identification signal is set to match the frequency characteristic obtained by multiplying both the inverse frequency characteristic of the transfer function filter and the inverse frequency characteristic of the transfer function filter, the frequency characteristic of the identification signal is the inverse of the frequency characteristic of the residual noise signal. The frequency characteristic will be the same as the frequency characteristic obtained by multiplying both of them. That is,
The frequency characteristic of the identification signal is the frequency characteristic of the generated sound when it is considered that the noise at the position where the residual noise detecting means is arranged is emitted from the control sound source.

Also, the identification signal at the time of being supplied to the control sound source is lower than the level of the residual noise signal by a predetermined level by the signal level attenuation means provided in series with the variable pass characteristic filter and the control sound source. . Furthermore, the white noise signal is a signal that is uncorrelated with the noise in the space. From the above, even with the invention according to claim 3,
When the identification signal is supplied to the control sound source and the identification sound is emitted from the control sound source, the level of the residual noise detection means is adjusted appropriately with the same frequency characteristics as the residual noise at the position where the residual noise detecting means is provided.
Moreover, since the identification sound uncorrelated with the noise in the space arrives, it is impossible for a person in the space to distinguish between the noise and the identification sound.

Therefore, since the level of the identification sound becomes high in the frequency band where the noise level is high and the identification sound is hard for human beings to hear in the space, when the transfer function filter setting means performs the transfer function filter setting process, The transfer function can be identified in such a frequency band in a short time with high accuracy. And even in the invention according to claim 4,
Similarly to the invention described in claim 3, since the white noise signal generated by the white noise signal generating means is filtered by the variable passage characteristic filter to generate the identification signal, the frequency characteristic of the identification signal is It depends on the pass characteristic of the variable characteristic filter.

The pass characteristic of the variable pass characteristic filter is set by the filter characteristic setting means so as to match the frequency characteristic of the residual noise signal detected by the residual noise frequency characteristic detecting means. The frequency characteristic of is in agreement with the frequency characteristic of the residual noise signal. Further, the identification signal at the time of being supplied to the control sound source is lower than the level of the residual noise signal by a predetermined level by the signal level attenuation means provided in series with the variable pass characteristic filter and the control sound source.

Furthermore, the white noise signal is a signal that is uncorrelated with the noise in the space. From the above, this claim 4
In the invention described, when the identification signal is supplied to the control sound source and the identification sound is emitted from the control sound source, the level characteristic is appropriately adjusted with the frequency characteristic of the same shape as the residual noise, and the noise in the space is An uncorrelated identification sound will be emitted.

The identified sound propagates in the space while reaching the residual noise detecting means while being influenced by the acoustic transfer characteristics between the control sound source and the residual noise detecting means. The identification sound at the position where the residual noise detecting means is installed does not become louder than the residual noise unless it has a characteristic of amplifying the band component. It does not stick.

Therefore, even in the invention described in claim 4, the accuracy is slightly lower than that of the invention described in claim 3, but in the first place, the frequency of the noise level is high and it is difficult for human beings in the space to hear the identification sound. Since the level of the identification sound becomes high in the band, if the transfer function filter setting means performs the transfer function filter setting process, the transfer function can be identified in such a frequency band in a short time and with high accuracy. .

Here, the noise targeted by the active noise control device according to the inventions of claims 1 to 4 may be periodic noise or random noise.
Alternatively, the noise may be a mixture thereof. On the other hand, the invention according to claim 5 is an active noise control device which particularly targets periodic noise, and even in the invention according to claim 5, the white noise signal generating means generates the white noise. Since the noise signal is filtered by the variable pass characteristic filter to generate the identification signal, the frequency characteristic of the identification signal is determined by the pass characteristic of the variable pass characteristic filter.

The pass characteristic of the variable pass characteristic filter is set by the filter characteristic setting means such that the fundamental frequency of the noise detected by the fundamental frequency detecting means and its harmonics are in the pass band. Therefore, the identification signal becomes a signal having power at the fundamental frequency of noise and its harmonics.

Further, since the signal level adjusting means provided in series with the variable pass characteristic filter and the control sound source appropriately adjusts the level of the identification signal, for example, the level of the residual noise signal or the size of the filter coefficient of the adaptive digital filter. If the level adjustment is performed so that the identification sound is slightly lower than the noise in the space, the level of the identification sound becomes a level masked by the noise in the space.

Further, the white noise signal is a signal that is uncorrelated with the noise in the space. From the above, when the identification signal is supplied to the control sound source and the identification sound is emitted from the control sound source, with the frequency characteristic of the same shape as the noise transmitted in the space,
The level is adjusted appropriately, and an identification sound that is uncorrelated with the noise in the space is emitted. Then, the identification sound propagates in the space while reaching the residual noise detecting means while being influenced by the acoustic transfer characteristic between the control sound source and the residual noise detecting means, and the acoustic transfer characteristic is, for example, a component of a specific frequency band. Since the identification sound at the position where the residual noise detecting means is provided does not become louder than the residual noise unless it has a characteristic that amplifies the noise, the human in the space cannot distinguish between the noise and the identification sound. .

That is, since the identified sound has power at the fundamental frequency of the noise and its harmonics, if the transfer function filter setting means performs the transfer function filter setting process, the identification of the transfer function in such a frequency band is short. Although it is performed in time and with high accuracy, high accuracy of the transfer function is required only at the fundamental frequency of noise and its harmonics, so avoiding an increase in discomfort to humans in space. Meanwhile, the most efficient noise reduction control is executed.

[0035]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are diagrams showing a configuration of a first embodiment of the present invention, in which the active noise control device according to the present invention is applied to a vehicle active noise control device 1. is there. Here, the first embodiment corresponds to the invention described in claim 1.

First, the structure will be described. As shown in FIG. 1, the vehicle active noise control system 1 is transmitted from a noise source between a wheel 2a and a road surface 4 into a vehicle interior 3 as a space. In a device for reducing road noise as noise, an acceleration sensor 5 as noise generation state detecting means is arranged at a predetermined position near the wheel 2a. The reference signal x, which is the vibration acceleration generated at 1, is supplied to the controller 10 composed of a microcomputer or the like. It should be noted that FIG. 1 shows only the acceleration sensor 5 provided on one of the four wheels 2a, but in reality, the acceleration sensor is provided corresponding to each wheel, A plurality of reference signals x _k (k
= 1 to K: K is the number of acceleration sensors, and if there is one for each wheel, K = 4) is supplied to the controller 10.

On the other hand, in the passenger compartment 3, microphones 8a, 8b and 8c as residual noise detecting means for measuring the sound pressure of the noise remaining in the passenger compartment 3, and a control for issuing a control sound in the passenger compartment 3 A loudspeaker 9 as a sound source is provided, and the microphones 8a to 8c use the measured residual noise in the vehicle interior 3 as a residual noise signal e _l in the controller 1
It is designed to supply 0. In addition, although only three microphones 8a to 8c are shown in FIG. 1, the microphones 8a to 8c are actually disposed at a large number of positions such as the vicinity of the occupant's ears, and the residual noise signals e _l detected by these microphones are detected. (L = 1 to L: L is the number of microphones) is supplied to the controller 10.

The controller 10 executes a predetermined calculation process based on the supplied reference signal x _k and residual noise signal e _l so that the road noise transmitted between the wheels 2 a and the road surface 4 into the vehicle interior 3 is reduced. A drive signal y _m is supplied to the loudspeaker 9 so that a control sound that can be canceled is emitted from the loudspeaker 9. Although only one loudspeaker 9 is shown in FIG. 1, a plurality of loudspeakers 9 are actually arranged at predetermined positions, and the controller 10 allows each of the loudspeakers 9 to be provided in each loudspeaker 9. Correspondingly, a drive signal y _m (m = 1 to M: M is the number of loudspeakers 9) is supplied.

As shown in FIG. 2, which is a block diagram showing the functional configuration of the controller 10, the controller 10 has K × M signals corresponding to K reference signals x _k and M loudspeakers 9.
Adaptive filter with variable filter coefficients W
_km , this adaptive digital filter W _km and the reference signal x
and a drive signal generation unit 11 that calculates a drive signal y _m by convolving _k and adding the results for each subscript m.

Further, the controller 10 is an adaptive digitizer.
Le Filter W_kmFilter coefficient to update the filter coefficient of
The filter coefficient updating unit 12 has an updating unit 12.
Is an adaptive digital filter based on the LMS algorithm.
Ruta W_kmEach filter coefficient W of _kmi(I = 0, 1, ..., I
-1: I is the adaptive digital filter W_kmWith the number of taps
It will be updated accordingly.

Further, the controller 10 includes a loudspeaker 9 and microphones 8a to 8c in the passenger compartment 3.
It has a transfer function filter C ^ _lm that models the transfer function _Clm between the two in the form of a finite impulse response function. Specifically, since there are M × L combinations between the M loudspeakers 9 and the L microphones 8a to 8c, M
There are provided × L transfer function filters C _lm . Here, each filter coefficient of the transfer function filter C ^ _lm is C ^
_lmj (j = 0, 1, ..., J-1: J is the number of taps of the transfer function filter C ^ _lm ).

[0042] have been inputted reference signal x _k is the transfer function filter C ^ _lm, the reference signal x _k the result of filtering by a transfer function filter C ^ _lm, specifically, the reference signal x _k Reference processing signal r _klm which is the result of _convolving each filter coefficient C ^ _{lmj of the} transfer function filter C ^ _lm
Are supplied to the filter coefficient updating unit 12. The residual noise signal e _l is also supplied to the filter coefficient updating unit 12.

Here, since the filter coefficient updating process in the filter coefficient updating unit 12 follows the LMS algorithm, the filter coefficient W of the adaptive digital filter W _km.
If the convergence coefficient is α, the update formula for _kmi is
It becomes like a formula. On the other hand, the controller 10, the transfer function filter C ^ have a transfer function inverse filter C ^ _lm ^-1 indicating the _lm opposite frequency characteristics, delay processing unit in the transfer function inverse filter C ^ _lm ^-1 13 The residual noise signal e _l delayed by C is input, and the residual noise signal e _l is transferred to the transfer function inverse filter C.
The identification signal I _D is generated by filtering with ^ _lm ^-1 . Here, the identification signal generation unit 14 is configured.

The identification signal I _D generated by the identification signal generation unit 14 is supplied to the addition processing unit 16 via the attenuation processing unit 15 which attenuates the level of the input signal by a predetermined level and outputs the attenuated signal. The drive signal y _m is supplied to the unit 16 in addition to the identification signal I _D. Then, the output of the addition processing unit 16 is supplied to the loudspeaker 9 as the drive signal y _m .

The identification signal I _D is also supplied to the first identification adaptive filter _Ĉlm ^* provided for identifying the transfer function filter _Ĉlm . That is, the first identification adaptive filter C ^ _lm ^* eliminates the difference between the transfer function filter C ^ _lm required for the generation processing of the drive signal y _m and the actual transfer function C _lm in the passenger compartment 3. The filter coefficient updating unit 20 provided corresponding to the adaptive filter updates the filter coefficient as appropriate. Then, the filter coefficient updating unit 20 is also adapted to update the filter coefficient based on the LMS algorithm.

Therefore, the filter coefficient updating unit 20 is supplied with the identification signal _ID as the reference signal and the subtraction result of the subtraction processing unit 21 as the error signal. Is the residual noise signal e _l
From the residual noise signal e _l 'after being amplified to a predetermined level by the amplification processing unit 17, the result of filtering the identification signal I _D with the first identification adaptive filter C ^ _lm ^* is subtracted and output. . Therefore, the filter coefficient updating unit 20
LMS so that the output of the subtraction processing unit 21 approaches zero.
First identification adaptive filter C _lm ^* according to the algorithm
Update the filter coefficient of.

Then, the first identification adaptive filter C ^ _lm ^* after appropriately converging is used as the transfer function filter C ^ _lm . Furthermore, the controller 10
To identify the transfer function inverse filter C ^ _lm ⁻¹ ,
It has a second identification adaptive filter C ^ _lm ^{-1 *} and a filter coefficient updating unit 25 that updates the filter coefficient of the second identification adaptive filter C ^ _lm ^{-1 *} according to the LMS algorithm.

That is, this second identification adaptive filter C ^ _lm
^The residual noise signal e _l 'which has been amplified to a predetermined level by the amplification processing unit 17 is input to ^{-1 *.}
_The result obtained by filtering _l ′ with the second identification adaptive filter C ^ _lm ^{-1 *} is input to the subtraction processing unit 26. The subtraction processing unit 26 is also supplied with the result of the delay processing of the identification signal I _D by the delay processing unit 27.
A value obtained by subtracting the output of the second identification adaptive filter C ^ _lm ^{-1 *} from the output of the delay processing unit 27 is supplied to the filter coefficient updating unit 25 as an error signal.

Further, the filter coefficient updating section 25 has a residual noise signal e _l 'which is amplified by the amplification processing section 17 by a predetermined level.
Is input as the reference signal. Therefore, the filter coefficient update unit 25 updates the filter coefficient of the second identification adaptive filter C ^ _lm ^{-1 *} according to the LMS algorithm so that the output of the subtraction processing unit 26 becomes zero. Then, the second adaptive filter for identification C ^ _lm ^{-1 *} after appropriately converging is used as the transfer function inverse filter C ^ _lm ^-1 .

Here, the purpose of the delay processing in the delay processing unit 13 is to delay the residual noise signal e _l for a predetermined time so that the correlation between the residual noise signal e _l and the identification signal I _D generated based on the residual noise signal e _l is obtained. I will lose it. This is because the road noise transmitted to the passenger compartment 3 is random noise having almost no periodicity, and therefore noises at two different points on the time axis have no correlation with each other. Therefore, the delay time in the delay processing unit 13 is not particularly limited and may be any value.

[0051] The object of the attenuation process in the attenuation processor 15, by the lowering predetermined level the level of the identification signal I _D, the level of the identification tone emitted from the loudspeaker 9 in response to the identification signal I _D, cabin The noise level is set to be lower than the noise level in 3 so that the identification sound cannot be heard by an occupant. Therefore, it is desirable that the attenuation level in the attenuation processing unit 15 is obtained by an experiment using an actual vehicle, but according to the findings of the present inventors, an attenuation level of 5 to 30 dB can achieve the above object. .

The purpose of the amplification processing in the amplification processing unit 17 is to amplify the level of the identification signal I _D in the attenuation processing unit 15 by the amount attenuated, whereby the filter coefficient updating unit 20 and the filter coefficient updating unit 25 are amplified. It is to be able to accurately perform the update calculation in. Therefore, the amplification level in the amplification processing unit 17 may be the same as the attenuation level in the attenuation processing unit 15.

Further, the purpose of the delay processing in the delay processing unit 27 is the time difference between the residual noise signal e _l input as a reference signal to the filter coefficient updating unit 25 and the output of the subtraction processing unit 26 input as an error signal. To adjust. Therefore, the delay time in the delay processing unit 27 is such that the identification signal _ID is the attenuation processing unit 15 and the addition processing unit 1.
6, loudspeaker 9, passenger compartment 3, microphone 8a-
8c and the time required to pass through each part of the amplification processing unit 17 are taken into consideration.

FIG. 3 is a flow chart showing the outline of the processing executed in the controller 10. The operation of this embodiment will be described below with reference to FIG. That is, the process shown in FIG. 3 is executed as an interrupt process at every predetermined sampling cycle.
At, the reference signal x _k and the residual noise signal e _l are read.

[0055] Then, the process proceeds to step 102, calculates a residual noise signal e _l 'the residual noise signal e _l was predetermined level amplification. The calculation in step 102 corresponds to the processing in the amplification calculation section 17 shown in FIG. Then, the process proceeds to step 103, and the identification signal I _D is calculated based on the residual noise signal e ₁ read in step 101. Specifically, the identification signal I _D is calculated by delaying the residual noise signal e _l for a predetermined time and then filtering the delayed result with the transfer function inverse filter C ^ _lm ⁻¹ . The process in step 103 is as shown in FIG.
It corresponds to the processing in the delay processing unit 13 and the identification signal generation unit 14 shown in FIG.

Next, in step 104, the identification signal I _D and the residual noise signal e amplified in step 102 are processed.
The filter coefficient of the first identification adaptive filter C ^ _lm ^* is updated based on _l ′ and. Specifically, the residual noise signal e
_{From l} ', the identification signal I _D is converted into the first identification adaptive filter C ^.
The filter coefficient of the first identification adaptive filter C ^ _lm ^* is updated according to the LMS algorithm so that the result of subtracting the value filtered by _lm ^* becomes zero.

Then, the _{routine proceeds} to step 105, where the transfer function filter C ^ _lm used in the calculation of the reference processed signal r _klm described later is replaced with the first identification adaptive filter C ^ _lm ^* updated at step 104. To do. The process of step 105 does not necessarily have to be executed for each sampling process, and may be executed intermittently, for example, for every several sampling processes.

Next, the routine proceeds to step 106, where the second adaptive filter for identification C ^ _lm ^-1 is based on the value obtained by delaying the identification signal I _D for a predetermined time and the residual noise signal e _l 'obtained at step 102. ^* Update filter coefficient. Specifically, the residual noise signal e _l 'is converted into the second identification adaptive filter C ^.
The second identification adaptive filter C ^ _lm according to the LMS algorithm so that the result obtained by subtracting the value obtained by delaying the identification signal I _D from the value filtered by _lm ^{-1 *} becomes zero.
^-Update the filter coefficient of ^{-1 *} .

Then, the process proceeds to step 107, and the transfer function inverse filter C ^ _lm ^-1 used when the identification signal I _D is generated in step 103 is set to step 106.
It is replaced with the second identification adaptive filter C ^ _lm ^{-1 *} that has been updated. Note that the process of step 107 does not necessarily have to be executed for each sampling process as in the process of step 105, and may be executed intermittently, for example, for every several sampling processes.

Next, in step 108, the reference signal x _k is filtered by the transfer function filter C ^ _lm to generate the reference processed signal r _klm . Then, the process _proceeds to step 109, and the above equation (1) is used. According to the above, each filter coefficient W _kmi of the adaptive digital filter W _km is updated.
After updating all filter coefficients W _kmi of all adaptive digital filters W _km in this step 109, step 11
0, and the reference signal x _{k is changed} to the adaptive digital filter W
Filter by _km and the result of the filtering is the subscript m
The drive signal y _m is calculated by adding up each time.

Then, the process proceeds to step 111 and the step
Drive signal y calculated in step 110_mTo the identification signal I_DWhere
A new drive signal y_mTo
Calculate However, all drive signals y_mIdentification message
Issue I_DIf you add
The identification sound is emitted from all of _lm
Sampling once because accurate identification of
In processing, one drive signal y_mIdentification signal I only
_DIs added. Therefore, steps 104 and 106 above
Is performed by the first identification adaptive filter C ^._lm ^*as well as
Second identification adaptive filter C ^_lm ^{-1 *}To target
Without identification signal I_DDrive signal y to which is added_mAgainst
Only those that respond are subject.

Then, in step 112, the drive signal y _m calculated in step 110 or 111 is output to each loudspeaker 9. Then, from the loudspeaker 9 into the passenger compartment 3, the drive signal y _m, which is the result of filtering the reference signal x _k with the adaptive digital filter W _km.
A control sound is generated according to the control sound. However, immediately after the control is started, each filter coefficient W _kmi of the adaptive digital filter W _km does not always converge to the optimum value, and therefore the control sound is transmitted to the vehicle interior 3. It cannot be said that the road noise generated is not necessarily reduced.

However, when the processing shown in FIG. 3 is repeatedly executed, the filter coefficient updating unit 12 determines the filter coefficient W _kmi of the adaptive digital filter W _km based on the LMS algorithm so as to reduce the noise in the passenger compartment 3. Since the value is updated, after the filter coefficient W _kmi has properly converged, the road noise is canceled by the control sound emitted from the loudspeaker 9, and the noise in the vehicle interior 3 is reduced.

On the other hand, the loudspeaker 9 to which the drive signal y _m to which the identification signal I _D has been added is supplied with the control sound and the identification sound corresponding to the identification signal I _D. The frequency characteristic of this identification sound is such that the identification signal I _D transfers the residual noise signal e _l to the transfer function inverse filter C ^ _lm.
^Since it is a signal filtered by ^-1 , the residual noise at the positions where the microphones 8a to 8c are arranged has the same shape as the frequency characteristic of the generated sound when it is considered that the sound is emitted from the loudspeaker 9. Therefore, the frequency characteristic of the identification sound at the time of reaching the microphones 8a to 8c has the same shape as the frequency characteristic of noise remaining at the positions where the microphones 8a to 8c are arranged.

Since the identification signal I _D is attenuated by a predetermined level and then supplied to the loudspeaker 9, the level of the identification sound is lower than the level of the residual noise by the amount of the attenuation, so that the microphone 8a. The level of the identification sound at the time of reaching ~ 8c is the microphone 8a.
It becomes lower than the level of the noise remaining at the position of 8c.

Therefore, the frequency characteristic of the identification sound at the time of reaching the microphones 8a to 8c is as shown in FIG.
The characteristics are such that the noise remaining at the positions where the microphones 8a to 8c are arranged is reduced by a predetermined level for each frequency component. Therefore, the identification sound is masked by noise, and the occupant cannot distinguish the identification sound from the noise. For example, when the sound pressure level of the identification sound is 10 dB lower than the sound pressure level of the noise, the increase in the overall sound pressure level is about 0.4 dB, and it is actually masked that the identification sound is emitted. Phenomena ("Hearing Handbook" page 126
Details on Nakanishiya Publishing (1984). ) Cannot be recognized by the crew.

Therefore, there is no problem that the occupant's discomfort is increased by issuing the identification sound. Then, the identification sound emitted from the loudspeaker 9 propagates through the vehicle interior 3 and reaches each of the microphones 8a to 8c,
The residual noise signal e is measured here as a part of the residual noise.
It is supplied to the controller 10 in the form included in _l .

In the controller 10, the residual noise signal e
_Based on the residual noise signal e _l ′ obtained by amplifying _l by a predetermined level and the identification signal I _D , the first identification adaptive filter C ^ _lm ^*
And the identification process of the second adaptive filter C ^ _lm ^{-1 *} is executed, and the identification signal I that is the basis of the identification sound is
_{Since D} is generated through the process of delaying the residual noise signal for a predetermined time, the identification sound actually existing in the vehicle interior 3 and the noise are uncorrelated.

Therefore, if the processing according to the LMS algorithm is executed in the controller 10 based on the residual noise signal e ₁ and the identification signal _ID , the first identification adaptive filter C ^
Identification of _lm ^* and the second identification adaptive filter C ^ _lm ^{-1 *} is possible without any problem. For the same reason, the update calculation of the filter coefficient W _kmi of the adaptive digital filter W _km by the filter coefficient updating unit 12 can be performed without any problem, and therefore noise reduction control and the transfer function filter C ^ _lm are performed as in the present embodiment.
There is no particular problem even if the identification process is performed in parallel.

As shown in FIG. 4, the sound pressure level of the identification sound is high in the frequency band where the noise sound pressure level is high, and is low in the frequency band where the noise sound pressure level is low.
The identification process of the first identification adaptive filter C ^ _lm ^* and the second identification adaptive filter C ^ _lm- ^{1 *} can be performed in the shortest possible time and with high accuracy within a possible range. Moreover, the frequency band in which the sound pressure level of such noise is high is the frequency band in which the noise reduction effect is desired to be exhibited, and the transfer function filter C ^ _lm is required to have high accuracy, so that the occupant's discomfort is given. It is possible to perform the most efficient identification process while suppressing the number to a minimum.

Then, the first identification adaptive filter C ^ _lm ^*
Is identifiable means that the transfer function filter C ^
_{Since lm} does not significantly deviate from the actual transfer function C _{lm in} the passenger compartment 3, the acoustic transfer characteristics in the passenger compartment 3 change depending on factors such as temperature, humidity, opening and closing of windows, and the number of passengers. However, the accuracy of the transfer function filter C ^ _lm does not drop extremely, and therefore, it is a controlled object whose acoustic transfer characteristics change frequently within a relatively short time due to various factors such as a vehicle. However, good noise reduction control can be performed.

Further, in the present embodiment, the second identification adaptive filter C ^ _lm ^{-1 *} is provided, and the second identification adaptive filter C is provided.
Since the identification process is performed so that ^ _lm ^{-1 *} matches the inverse frequency characteristic of the transfer function C _lm , the accuracy of the transfer function inverse filter C ^ _lm ^-1 is prevented from being extremely reduced. . Therefore, even after the transfer function C _lm changes, the relationship between the noise and the identification sound as shown in FIG. 4 can be maintained, and the occupant does not have to hear the identification sound.

Here, in the present embodiment, the drive signal generating means is constituted by the drive signal generating portion 11 and the processing of step 110, and the filter coefficient updating means is constituted by the filter coefficient updating portion 12 and the processing of step 109. The identification signal generation unit 14, the addition processing unit 16 and the processing of Step 103 and Step 111 constitute identification signal generation means, the attenuation processing unit 15 and the processing of Step 102 constitute signal level attenuation means, and the delay processing unit. 13 and a part of the processing of step 103 constitutes the signal delay means, and the first identification adaptive filter C ^ _lm ^* , the filter coefficient updating unit 20, the subtraction processing unit 21, the amplification processing unit 1
The transfer function filter setting means is constituted by the processing of 7 and steps 104 and 105.

FIG. 5 is a diagram showing the configuration of the second embodiment of the present invention, and is a block diagram showing the functional configuration of the controller 10 as in FIG. 2 of the first embodiment. The same components as those in the first embodiment are designated by the same reference numerals, and their duplicate description will be omitted. The other configurations are the same as those in the first
Since it is similar to the embodiment, its illustration and description are omitted. Here, the second embodiment corresponds to the invention described in claim 2.

That is, in the second embodiment, of the functions of the controller 10 of the first embodiment, the transfer function inverse filter C ^ _lm ^-1 and the function necessary for its identification processing are omitted. And the output of the delay processing unit 13 is the identification signal I
_D is supplied to each part. FIG. 6 is a flow chart showing the outline of the processing executed in the controller 10 of the present embodiment, but it is substantially the same as the outline of the processing in the first embodiment described above, except that step 103 in FIG. 3 is different. Instead, it is to execute the process of step 201. That is, in step 201, the residual noise signal e _l
Is delayed for a predetermined time to generate the identification signal I _D.

Therefore, the identification signal I _D at the time of being supplied to the loudspeaker 9 is a signal obtained by subjecting the residual noise signal e _l to delay processing and level attenuation processing, and therefore the identification signal _ID
From the loudspeaker 9 to which the drive signal y _m to which is added is added, the frequency characteristics of the same shape as the frequency characteristics of the noise at the positions where the microphones 8a to 8c are arranged are lower than the residual noise by a predetermined level, and An identification sound that is uncorrelated with noise is emitted.

Then, the identified sound propagates in the passenger compartment 3 while being influenced by its acoustic transfer characteristics, and propagates through the microphone 8
a-8c to reach that microphone 8a-8
The frequency characteristic of the identified sound at the time point when it reaches c is deformed according to the characteristic of the transfer function C _lm in the vehicle interior 3. Therefore, according to the configuration of the first embodiment, as shown in FIG. 4, the frequency characteristics of the noise and the frequency characteristics of the identification sound at the positions where the microphones 8a to 8c are arranged are similar to each other. The frequency characteristic of the identification sound is not completely similar to the frequency characteristic of noise, but in a space that is not intended to exert a special acoustic effect like the ordinary passenger compartment 3, a specific frequency is not used. It does not exhibit acoustic transfer characteristics such that the band component is extremely increased.

Therefore, even with the configuration of this embodiment, the frequency characteristics of the identification sound at the positions where the microphones 8a to 8c are arranged are slightly lower than those of the first embodiment, but the frequency characteristics of the identification sounds are It has almost the same shape as the frequency characteristic. Therefore, as in the case of the first embodiment, there is no inconvenience that the occupant's discomfort is increased by issuing the identification sound. Other functions and effects are similar to those of the first embodiment.

Here, in the present embodiment, the delay signal processing section 13 and the processing of step 103 constitute the identification signal generating means. FIG. 7 is a diagram showing the configuration of the third embodiment of the present invention, and is a block diagram showing the functional configuration of the controller 10 as in FIG. 2 of the first embodiment. The same components as those in the first embodiment are designated by the same reference numerals, and their duplicate description will be omitted. Further, the other structure is similar to that of the first embodiment, and therefore its illustration and description are omitted.
Here, the third embodiment corresponds to the invention described in claim 3.

That is, the controller 10 according to the present embodiment has the M-sequence signal generator 31 for generating the white noise signal N _W.
And a digital filter 32 having a variable pass characteristic for filtering the white noise signal N _W generated by the M-sequence signal generation unit 31 to generate an identification signal I _D, which is generated by the digital filter 32. Identified signal I
_D is supplied to each part.

Further, the controller 10 is suitable for the first identification.
Response filter C ^_lm ^*Fourier transform of
And a Fourier transform unit 33 for generating the data
Transmission based on the frequency domain data generated by the conversion unit 33
Function C_lmIn the frequency domain with the inverse frequency characteristics of
Function inverse filter C ^_lm ^-1C ^ to calculate (ω)_lm ^-1Calculation
And the residual noise signal e_lFourier transform of
Area residual noise signal e _lFourier transform to generate (ω)
Part 35 and C ^_lm ^-1In the frequency domain calculated by the calculation unit 34
Transfer function inverse filter C ^_lm ^-1(Ω) and Fourier transform
Residual noise signal e in the frequency domain calculated by the unit 35
_lFilter of digital filter 32 based on (ω)
Pass the digital filter 32 after setting the coefficient appropriately.
And a filter coefficient setting unit 36 for setting the characteristic.
There is.

Here, the filter coefficient setting unit 36 determines that the pass characteristics of the digital filter 32 are the transfer function inverse filter C ^ _lm ^-1 (ω) and the residual noise signal e in the frequency domain.
_l (ω) is multiplied by each frequency component so that the digital filter 32 is matched with the frequency characteristic obtained.
The filter coefficient of is set. Figure 8
4 is a flowchart showing an outline of processing executed in the controller 10 of the present embodiment. It should be noted that the same step numbers are assigned to the steps that perform the same processing as the processing contents of FIG. 3 described in the first embodiment.

That is, after executing the processes of steps 101 and 102, the process proceeds to step 301, the first identification adaptive filter C ^ _lm ^* is Fourier-transformed, and the magnitude of each frequency component obtained as a result is set to a predetermined reference. The transfer function inverse filter C ^ _lm ^-1 (ω) in the frequency domain is generated by reversing the value. Next, in step 302, the residual noise signal e _l is Fourier transformed this time to generate a residual noise signal e _l (ω) in the frequency domain.

These transfer function inverse filters C ^ _lm ^-1 (ω)
When the residual noise signal e _l (ω) is generated, the process proceeds to step 303, and the transfer function inverse filter C ^ _lm ^-1 (ω) and the residual noise signal e _l (ω) are multiplied for each frequency component. Based on the result, the filter coefficient of the digital filter 32 is set. Note that these steps 301 to 303
In particular, since the FFT requires the number of points to the power of 2 for the FFT, for example, it is possible to store the required number of data (for example, 256 (= 2 ⁸ ) data). Data is updated every sampling process, and the oldest data is discarded every sampling process, and the FFT using the updated data is performed.

Therefore, the pass characteristic of the digital filter 32 matches the frequency characteristic obtained by multiplying the frequency characteristic of the residual noise signal e _{l and} the frequency characteristic of the transfer function inverse filter C ^ _lm ^-1 . Therefore, step 304
To generate a white noise signal N _W , and then to step 305 to generate the white noise signal N _W.
When the identification signal I _D is generated by filtering the signal with the digital filter 32, the white noise signal N _W has the same power in the entire frequency band. Therefore, the frequency characteristic of the identification signal I _D is the residual noise signal e. It becomes the same as the frequency characteristic of the signal obtained as a result of filtering _l by the transfer function inverse filter C ^ _lm ^-1 .

That is, the identification signal I _D obtained in this embodiment is
Is apparently the same as the identification signal _ID obtained in the process of the first embodiment. Therefore, after executing step 305, the same step 10 as in the first embodiment is performed.
If the processings 4, 105, 108 to 112 are executed, the same operational effect as that of the first embodiment can be obtained. Further, in this embodiment, the residual noise signal e _l is not used as it is, but its frequency characteristic is determined by the digital filter 3
Since the white noise signal N _W is represented by 2, and the identification signal I _D is generated by filtering the white noise signal N _W with the digital filter 32, it is not necessary to perform delay processing. This is because the white noise signal N _W has no correlation with the residual noise in the vehicle compartment 3 in the first place.

Therefore, since the delay processing is unnecessary, the identification sound similar to the frequency characteristic of the noise in the passenger compartment 3 can be generated without a time delay, so that the occupant can hear more than the first embodiment. It is possible to generate a difficult identification sound. Here, in the present embodiment, the M-sequence signal generation unit 31
And the processing of step 304 constitute white noise signal generating means, the digital filter 32 and the processing of step 305 constitute a variable passage characteristic filter, and the Fourier transform unit 35 and the processing of step 302 constitute residual noise frequency characteristic detecting means. The filter coefficient setting unit 36 and the process of step 303 constitute a filter characteristic setting unit.

FIG. 9 is a diagram showing the configuration of the fourth embodiment of the present invention, and shows the functional configuration of the controller 10 as in FIG. 2 of the first embodiment and FIG. 7 of the third embodiment. It is a block diagram. The same components as those in the first and third embodiments are designated by the same reference numerals, and their duplicated description will be omitted. Further, the other structure is similar to that of the first embodiment, and therefore its illustration and description are omitted. The fourth embodiment corresponds to the invention described in claim 4.

That is, the configuration of the present embodiment is substantially the same as that of the third embodiment, except that the Fourier transform unit 33 and the C ^ _lm ^-1 operation unit 34 are omitted and the filter coefficient setting unit 36 is omitted. Is that the filter coefficient of the digital filter 32 is set so that the pass characteristic of the digital filter 32 matches each frequency component of the residual noise signal e _l (ω).

FIG. 10 is a flow chart showing the outline of the processing executed in the controller 10 of this embodiment, but it is substantially the same as the outline of the processing in the third embodiment, except that step 102 is different. After execution, the process proceeds to step 302 without executing step 301 to generate the residual noise signal e _l (ω) in the frequency domain, and then the process proceeds to step 401 where the residual noise signal e _l
The filter coefficient of the digital filter 32 is set so that each frequency component of (ω) has the frequency characteristic as it is.

Therefore, the pass characteristic of the digital filter 32 matches the frequency characteristic of the residual noise signal e _l . Therefore, when the processing from step 304 onward is executed, the frequency characteristic of the identification signal _ID becomes the residual noise signal e _l.
Since it has the same shape as the frequency characteristic of, the identification signal I
_D is apparently the same as the identification signal I _D obtained in the process of the process of the second embodiment. Therefore, step 305
After executing step 10, the same step 10 as in the first embodiment is performed.
If the processings 4, 105, 108 to 112 are executed, the same operational effect as the second embodiment can be obtained.

Further, in the present embodiment, similarly to the third embodiment, since it is not necessary to perform the delay processing to generate the identification signal I _D , the identification close to the frequency characteristic of the noise in the passenger compartment 3 is performed. The sound can be generated without a time delay, and the second
It is possible to generate an identification sound that is more difficult for the occupant to hear than in the embodiment. Here, in this embodiment, the filter characteristic setting means is configured by the filter coefficient setting unit 36 and the processing of step 401.

FIGS. 11 and 12 are diagrams showing the configuration of the fifth embodiment of the present invention. In this embodiment, the active noise control device according to the present invention is used from the engine 40 as the noise source to the passenger compartment. The present invention is applied to an active noise control device 1 for a vehicle for reducing muffled noise as periodic noise transmitted to the inside of the vehicle. Here, the fifth embodiment corresponds to the invention described in claim 5. The same components as those in the above-described embodiments are designated by the same reference numerals, and the duplicated description will be omitted.

That is, as shown in FIG.
Is provided with a crank angle sensor 41 that generates a reference signal x composed of a crank angle signal synchronized with the rotation of the crank shaft and supplies the reference signal x to the controller 10. The reference signal x generated by the crank angle sensor 41 needs to be a signal synchronized with the noise that is a problem generated in the engine 40. Therefore, for example, if the engine 40 is a reciprocating 4-cylinder engine, the reference signal x is 1/2 of the crankshaft.
It becomes a pulse signal or sine wave synchronized with the rotation.

Controller 10 to which the reference signal x is supplied
12 has a functional configuration as shown in FIG. 12, and basically has the same functional configuration as each of the above-described embodiments, but the controller 10 of the present embodiment is configured so that the residual noise signal e _l or its residual noise signal e _l It does not have a function of generating the identification signal I _D in consideration of frequency characteristics and the like. The controller 10 has a cycle detection unit 42 that detects the cycle (fundamental frequency) of the reference signal x, and the cycle N _x of the reference signal x detected by the cycle detection unit 42 is the filter coefficient setting unit 36. To be supplied to.

The filter coefficient setting unit 36 of the digital filter 32 sets the fundamental frequency of the muffled sound and its harmonics to the pass band of the digital filter 32 based on the cycle N _x of the reference signal x. It is designed to set the filter coefficient. FIG. 12 is a flowchart showing an outline of processing executed in the controller 10 of this embodiment. The same step numbers are assigned to the steps that perform the same processing as the processing content described in each of the above embodiments.

That is, after the processes of steps 101 and 102 are executed, the process proceeds to step 501 and the period N _x of the reference signal x is obtained. The period N _x is obtained by measuring the interval of the reference signal x if the reference signal x is a pulse signal and the interval at the time of passing the zero point if the reference signal x is a sine wave. Next, in step 502, the filter coefficient of the digital filter 32 is set based on the cycle N _{x so} that the fundamental frequency of the muffled sound and its harmonics are in the pass band. The pass band of the digital filter 32 and the fundamental frequency of muffled sound and their harmonics do not have to be exactly the same, and the fundamental frequency of muffled sound and its harmonics and their vicinity become the pass band. , The filter coefficient of the digital filter 32 may be set.

Next, after the processes of steps 304 and 305 are executed, the process proceeds to step 306, and the level of the identification signal I _D is adjusted. In the present embodiment, the level adjustment is a level attenuation process for attenuating the signal level by a certain level, and the level attenuation is performed so that the identification sound becomes slightly lower than the noise level in the vehicle compartment 3. ing. After the processing of step 503 is executed, steps 104 and 10
5, 108 to 112 are executed.

As a result of the above processing, the identification signal I _D
Since the signal has power at the fundamental frequency of the muffled sound, its harmonics, and the vicinity thereof, the relationship between the problem noise in the vehicle interior 3 and the identification sound is as shown in FIG. Therefore, even in the present embodiment, the identification sound is masked by the noise in the passenger compartment 3 as in the above-described embodiments, so that the passenger in the passenger compartment 3 can distinguish the noise from the identification sound. It does not stick. Therefore, the transfer function filter C ^ _lm can be identified without giving an occupant an uncomfortable feeling, and good noise reduction control can be realized.

Moreover, in this embodiment, as shown in FIG. 14, the identification sound has power only in the vicinity of the fundamental frequency of the noise in the passenger compartment 3 and its harmonics. Since high precision is required for the transfer function filter C _lm in such a frequency band, the most efficient transfer function filter C _lm identification process can be performed while minimizing discomfort to the occupant. It can be done.

Here, in the present embodiment, the crank angle sensor 41 corresponds to the noise generation state detecting means, and the damping processing unit 15
And the signal level adjusting means is constituted by the processing of step 503. In each of the above embodiments, the attenuation processing unit 1
Although the attenuation level in 5 is constant, this does not have to be constant. For example, in the first to fourth embodiments, the noise level in the vehicle compartment 3 changes particularly under the influence of the vehicle speed, and the higher the noise level, the harder it is to hear the identification sound. Therefore, for example, as shown in FIG. 15, the damping level may be reduced as the vehicle speed increases. Further, in the fifth embodiment, the filter coefficient W _mi of the adaptive digital filter W _m tends to increase as the noise level in the passenger compartment 3 increases, so that as the filter coefficient W _mi increases. The attenuation level may be reduced, or in addition, the attenuation level may be reduced as the level of the residual noise signal e _l increases.

In each of the above embodiments, the addition processing unit 16
Although the subtraction processing unit 15 is provided immediately before, the subtraction processing unit 15 includes the identification signal generation unit 14 and the addition processing unit 16.
The arrangement position is not particularly limited as long as it has a serial relationship with. Therefore, for example, the subtraction processing unit 15 may be provided at a stage before the signal on the downstream side of the identification signal generation unit 14 branches, and in that case, the amplification processing unit 17 becomes unnecessary. However, considering the calculation accuracy, it is desirable to provide the subtraction processing unit 15 immediately before the addition processing unit 16 as in the above-described embodiments. Further, the delay processing unit 13 is not particularly limited in its arrangement position as long as it is in serial relation with the identification signal generating unit 14 and the addition processing unit 16.

Further, in each of the above embodiments, the active noise control system according to the present invention is applied to the vehicle active noise control system 1 for reducing road noise and muffled noise transmitted to the vehicle interior 3 of the vehicle. However, the present invention is not limited to this, and may be, for example, a device for reducing noise in the cabin of an aircraft or a device for reducing noise in the interior of a building.

[0104]

As described above, according to the present invention,
Since the frequency characteristic has the same shape as the frequency characteristic of noise in the space and is lower than the noise by a predetermined level, and the identification sound of the transfer function filter is generated by generating the identification sound uncorrelated with the noise, It is possible to perform the identification process while minimizing the discomfort given to existing humans, and thus it is possible to perform good noise reduction control even in a space where the acoustic transfer characteristics frequently change within a relatively short time. effective.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an overall configuration of a first embodiment.

FIG. 2 is a block diagram showing a functional configuration of a controller according to the first embodiment.

FIG. 3 is a flowchart showing an outline of processing executed in the controller of the first embodiment.

FIG. 4 is a frequency characteristic diagram showing a relationship between noise and identification sound.

FIG. 5 is a block diagram showing a functional configuration of a controller according to a second embodiment.

FIG. 6 is a flowchart showing an outline of processing executed in the controller of the second embodiment.

FIG. 7 is a block diagram showing a functional configuration of a controller according to a third embodiment.

FIG. 8 is a flowchart showing an outline of processing executed in the controller of the third embodiment.

FIG. 9 is a block diagram showing a functional configuration of a controller according to a fourth embodiment.

FIG. 10 is a flowchart showing an outline of processing executed in the controller of the fourth embodiment.

FIG. 11 is a conceptual diagram showing the overall configuration of the fifth embodiment.

FIG. 12 is a block diagram showing a functional configuration of a controller according to a fifth embodiment.

FIG. 13 is a flowchart showing an outline of processing executed in the controller of the fifth embodiment.

FIG. 14 is a frequency characteristic diagram showing a relationship between noise and identification sound in the fifth embodiment.

FIG. 15 is a graph illustrating an example of a method of setting an attenuation level.

FIG. 16 is a frequency characteristic diagram illustrating a conventional problem.

FIG. 17 is a frequency characteristic diagram illustrating a conventional problem.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Active noise control device for vehicle 2a Wheel 3 Vehicle compartment (space) 4 Road surface 5 Acceleration sensor (noise generation state detection means) 8a-8c Microphone (residual noise detection means) 9 Loudspeaker (control sound source) 10 Controller 11 Drive signal Generation unit 12 Filter coefficient update unit 13 Delay processing unit 14 Identification signal generation unit 15 Attenuation processing unit 16 Addition processing unit 20 Filter coefficient update unit 21 Subtraction processing unit 31 M sequence signal generation unit 32 Digital filter 33, 35 Fourier transform unit 34 C ^ _Lm ^-1 calculation unit 36 filter coefficient setting unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H03H 21/00 8842-5J

Claims (5)

[Claims] 1. A control sound source capable of generating a control sound in a space in which noise is transmitted from a noise source, a noise generation state detecting means for detecting a noise generation state of the noise source and outputting it as a reference signal, and in the space. Residual noise detecting means for detecting residual noise at a predetermined position and outputting it as a residual noise signal, an adaptive digital filter having a variable filter coefficient, and a signal for driving the control sound source by filtering the reference signal with the adaptive digital filter. Drive signal generating means, a transfer function filter modeling the acoustic transfer characteristics between the control sound source and the residual noise detecting means, a value obtained by filtering the reference signal with the transfer function filter, and the residual noise signal. Filter coefficient update for updating the filter coefficient of the adaptive digital filter so as to reduce noise in the space based on Means, a transfer function inverse filter having a frequency characteristic opposite to that of the transfer function filter, and an identification signal which is generated by filtering the residual noise signal with the transfer function inverse filter and is supplied to the control sound source. Generating means, signal level attenuating means arranged in series relationship with the identification signal generating means and the control sound source, and for attenuating a signal input thereto by a predetermined level, and outputting the same, the identification signal generating means and the control sound source in series A signal delay means arranged in a relation and outputting a signal delayed by a predetermined time, and a transfer function between the control sound source and the residual noise detecting means is identified based on the identification signal and the residual noise signal. A transfer function filter setting means for setting the transfer function filter, the active noise control device. 2. A control sound source capable of generating a control sound in a space where noise is transmitted from a noise source, a noise generation state detecting means for detecting a noise generation state of the noise source and outputting it as a reference signal, and the inside of the space. Residual noise detecting means for detecting residual noise at a predetermined position and outputting it as a residual noise signal, an adaptive digital filter having a variable filter coefficient, and a signal for driving the control sound source by filtering the reference signal with the adaptive digital filter. Drive signal generating means, a transfer function filter modeling the acoustic transfer characteristics between the control sound source and the residual noise detecting means, a value obtained by filtering the reference signal with the transfer function filter, and the residual noise signal. Filter coefficient update for updating the filter coefficient of the adaptive digital filter so as to reduce noise in the space based on Means, an identification signal generation means for delaying the residual noise signal for a predetermined time to generate an identification signal and supplying the identification sound source to the control sound source, and the identification signal generation means and the control sound source are arranged in series and input. A signal level attenuating means for attenuating a signal by a predetermined level and a transfer for identifying a transfer function between the control sound source and the residual noise detecting means based on the identification signal and the residual noise signal and setting the transfer function filter. An active noise control device comprising: a function filter setting means. 3. A control sound source capable of generating a control sound in a space where the noise is transmitted from the noise source, a noise generation state detecting means for detecting a noise generation state of the noise source and outputting it as a reference signal, and the inside of the space. Residual noise detecting means for detecting residual noise at a predetermined position and outputting it as a residual noise signal, an adaptive digital filter having a variable filter coefficient, and a signal for driving the control sound source by filtering the reference signal with the adaptive digital filter. Drive signal generating means, a transfer function filter modeling the acoustic transfer characteristics between the control sound source and the residual noise detecting means, a value obtained by filtering the reference signal with the transfer function filter, and the residual noise signal. Filter coefficient update for updating the filter coefficient of the adaptive digital filter so as to reduce noise in the space based on Means, a white noise signal generating means for generating a white noise signal, a pass characteristic variable filter for varying the pass characteristic for generating an identification signal by filtering the white noise signal and supplying it to the control sound source, and the residual noise signal Of the residual noise frequency characteristic detecting means for detecting the frequency characteristic of, and the frequency characteristic detected by the residual noise frequency characteristic detecting means and the frequency characteristic obtained by multiplying the frequency characteristic opposite to the transfer function filter so as to match the frequency characteristic. Filter characteristic setting means for setting the pass characteristic of the variable pass characteristic filter, and signal level attenuating means arranged in series with the pass characteristic variable filter and the control sound source for attenuating an input signal by a predetermined level and outputting the attenuated signal. Transmission between the control sound source and the residual noise detecting means based on the identification signal and the residual noise signal Active noise control apparatus characterized by comprising: a transfer function filter setting means for setting the transfer function filter to identify the number, the. 4. A control sound source capable of generating a control sound in a space where noise is transmitted from a noise source, a noise generation state detecting means for detecting a noise generation state of the noise source and outputting it as a reference signal, and in the space. Residual noise detecting means for detecting residual noise at a predetermined position and outputting it as a residual noise signal, an adaptive digital filter having a variable filter coefficient, and a signal for driving the control sound source by filtering the reference signal with the adaptive digital filter. Drive signal generating means, a transfer function filter modeling the acoustic transfer characteristics between the control sound source and the residual noise detecting means, a value obtained by filtering the reference signal with the transfer function filter, and the residual noise signal. Filter coefficient update for updating the filter coefficient of the adaptive digital filter so as to reduce noise in the space based on Means, a white noise signal generating means for generating a white noise signal, a pass characteristic variable filter for varying the pass characteristic for generating an identification signal by filtering the white noise signal and supplying it to the control sound source, and the residual noise signal Residual noise frequency characteristic detecting means for detecting the frequency characteristic of, and filter characteristic setting means for setting the pass characteristic of the pass characteristic variable filter so as to match the frequency characteristic detected by the residual noise frequency characteristic detecting means; A signal level attenuating unit that is arranged in series relation with the variable characteristic filter and the control sound source and attenuates a signal input by a predetermined level and outputs the signal, and the control sound source and the residual sound source based on the identification signal and the residual noise signal Transfer function filter setting means for identifying the transfer function between the noise detecting means and setting the transfer function filter; Active noise control apparatus characterized by comprising. 5. A control sound source capable of generating a control sound in a space in which noise is transmitted from a noise source that emits periodic noise, and a noise generation state detection that detects the noise generation state of the noise source and outputs it as a reference signal. Means, residual noise detection means for detecting residual noise at a predetermined position in the space and outputting it as a residual noise signal, adaptive digital filter with variable filter coefficient, and filtering the reference signal with the adaptive digital filter. Driving signal generating means for generating a signal for driving a control sound source, a transfer function filter modeling the acoustic transfer characteristic between the control sound source and the residual noise detecting means, and the reference signal filtered by the transfer function filter. Updating the filter coefficient of the adaptive digital filter so as to reduce noise in the space based on the value and the residual noise signal A filter coefficient updating means for generating a white noise signal, a white noise signal generating means for generating a white noise signal, a variable passage characteristic filter for generating an identification signal by filtering the white noise signal and supplying the identification signal to the control sound source, A fundamental frequency detecting means for detecting the fundamental frequency of the periodic noise, and a filter for setting the pass characteristic of the pass characteristic variable filter so that the fundamental frequency detected by the fundamental frequency detecting means and its harmonics become a pass band. Characteristic setting means, signal level adjusting means for adjusting the level of a signal that is arranged in series with the variable pass characteristic filter and the control sound source, and the control based on the identification signal and the residual noise signal Transfer function filter for identifying the transfer function between the sound source and the residual noise detecting means and setting the transfer function filter Active noise control apparatus characterized by comprising: a setting means.