JP2894035B2 - Active noise control device - Google Patents

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 from a noise source. The present invention relates to an active noise control device that reduces a noise suppression effect on noise in a frequency range or a sound pressure range required by a device.

[0002]

2. Description of the Related Art As a conventional active noise control device, for example, a device described in Japanese Patent Application Laid-Open Publication No. 1-501344 or British Patent Publication No. 2149614 is known. These devices are applied to a cabin of an aircraft or a similar closed space, and include a plurality of loudspeakers (control sound sources) and microphones (residual noise detecting means) disposed in the closed space.
Frequency detection means for detecting the frequency of a single noise source such as an engine located outside the closed space; detection signals from the plurality of microphones; and the plurality of detection signals based on the detection signals from the frequency detection means. And a signal output device for controlling the driving of the loudspeaker. The signal output device minimizes the evaluation function by using, for example, a sum of squares of detection signals (sound pressures) of a plurality of microphones as an evaluation function. Adaptive control is performed. As a result, the control sound emitted from the loudspeaker controlled by the signal output device and the noise transmitted from the noise source interfere with each other to attenuate the vibration energy of the noise, thereby reducing the residual noise at the observation position. doing.

[0003]

However, in the conventional active noise control apparatus, adaptive control is performed so that the sum of squares of the residual noise detection signal of the microphone is used as an evaluation function to minimize the evaluation function. As a result, the noise suppression effect is exhibited for all noises.For example, occupants such as metal noise due to mechanical system failure and road noise etc. for recognizing the traveling road surface condition in the case of vehicles. There is an unsolved problem that the determination of a failure or a road surface condition is delayed because the specific sound that needs to be recognized is attenuated.

Accordingly, the present invention has been made in view of the above-mentioned unresolved problems of the prior art, and reduces the noise suppression effect for a specific sound that needs to be recognized by an occupant, thereby recognizing the specific sound. It is an object of the present invention to provide an active noise control device that can be easily provided.

[0005]

To achieve the above object, according to the solution to ## active noise control apparatus according to claim 1, as shown in FIG. 1, generating interfering control sound noise transmitted from the noise source A control sound source to be controlled, residual noise detecting means for detecting residual noise between the noise and the control sound, and reducing the residual noise signal based on the residual noise detection signal of the residual noise detecting means .
And a control means for driving and controlling the control sound source in such a manner that the residual noise detection signal of the residual noise detection means has a noise signal of a frequency range set in advance.
And a noise state detecting means for detecting that the state is a predetermined noise state including a signal, and when the noise state detecting means detects the predetermined noise state, the control means controls the noise suppression effect on the noise in the noise state. And a noise suppression effect reducing means for reducing the noise.

An active noise control device according to a second aspect of the present invention.
Generates control sounds that interfere with the noise transmitted from the noise source
The control sound source to be controlled and the residual noise between the noise and the control sound are detected.
And a residual noise detecting unit that emits the residual noise.
Reducing the residual noise signal based on the noise detection signal.
And control means for driving and controlling the control sound source.
In the type noise control device, the loudness of the control sound is a predetermined value.
Detects the specified noise condition when
Noise state detecting means, and a predetermined noise generated by the noise state detecting means.
When a state is detected, the noise suppression effect by the control means
Noise reduction effect reducing means for reducing
Features. Furthermore, the active noise control according to claim 3
The control device is a control sound that interferes with the noise transmitted from the noise source.
Control sound source that generates noise, and the residual noise between the noise and the control sound.
Residual noise detecting means for detecting sound, and the residual noise detecting means
Reducing the residual noise signal based on the residual noise detection signal of
Control means for driving and controlling the control sound source so that
In the active noise control device, the control means includes
Controls the output of signals in a preset frequency range to the sound source.
Characteristic frequency limiting means.
ing.

[0007]

In the active noise control device according to the first aspect , the noise state is detected by the residual noise detecting means.
Included in the residual noise detection signal is a signal in the frequency range required by the occupant, such as a preset mechanical failure or road noise.
The specified noise state is detected, and the specified noise state is detected.
By reducing the noise suppression effect for the specific sound by the control means by the noise suppression effect reduction means when issued ,
It makes it easy for the occupant to recognize the specific sound. Active type according to claim 2
In a noise control device, the control means controls the residual noise from the control sound source.
While controlling to suppress the sound, output with the control sound source.
Noise when the volume of the control sound to be applied exceeds a predetermined value
The state detection means detects that the vehicle is in the predetermined noise state, and
Low noise reduction effect by control means
Reducing occupants, regardless of frequency range,
It makes it easy to recognize a specific sound. The active noise control according to claim 3.
In the control device, specific frequency limiting means
The output of a signal in a preset frequency range
Therefore, noise suppression is required for signals in this restricted frequency range.
Crew members can recognize specific sounds without exerting any control effect
Make it easier.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a schematic configuration diagram showing one embodiment when the present invention is applied to a vehicle equipped with a four-cylinder engine. In FIG. 2, reference numeral 1 denotes a vehicle body, and a four-cylinder engine 3 as a first vibration source is disposed in front of a cabin 2. In the passenger compartment 2, a front seat 4F and a rear seat 4R are provided, and loudspeakers 5a and 5b also serving as control sound sources for outputting audio signals to a lower portion of the dashboard and a rear side of the rear seat 4R, for example. And microphones 6a, 6b and 6c as residual noise detecting means are provided at the front, center and rear of the ceiling, respectively. As shown in FIG. 5, the microphones 6a to 6c are provided with a dead zone in advance, and the input sound pressure is set to a relatively small upper limit value of a relatively small sound pressure which needs to be recognized by an occupant such as a road noise. during the residual noise detecting signals e ₁ to e ₃ up exceeds S ₁ is maintained zero, the sound pressure S ₁ or more when it comes to increase in direct proportion to the increase in sound pressure residual noise detecting signals e ₁ to e ₃ output Is done.

A crank angle sensor 7 is attached to the engine 3. The crank angle sensor 7 outputs a crank angle detection signal as a reference signal consisting of one cycle of a sinusoidal signal every time the crankshaft rotates 180 degrees, for example. X is output. Then, the residual noise detection signals e _{1 to} e ₃ output from the microphones 6a to 6c are
5, and a crank angle detection signal X of the crank angle sensor 7 is also input to the controller 15.

[0010] As shown in FIG.
A / D that A / D converts and outputs crank angle detection signal X
A conversion circuit 21, an amplifier 22a~22c for amplifying the residual noise detecting signals e ₁ to e ₃ microphones 6a~6c
A / D conversion circuits 23a to 23c for A / D converting and outputting the amplified outputs of the amplifiers 22a to 22c,
/ A microcomputer 26 D conversion output of the conversion circuit 21,23a~23c is input, loudspeaker 5a outputted from the microcomputer 26, outputs a drive signal y _1, y ₂ and 5b by D / A conversion D / A conversion circuits 27a and 27b, and these D / A conversion circuits 27a and 27b
The analog signal output from the loudspeaker 5a is amplified through the analog switches 28a and 28b.
5b are supplied to the amplifiers 5a and 5b.

Here, the microcomputer 26 always performs a convolution operation of the crank angle detection signal X as a reference signal based on the filter coefficient W _mi which is sequentially updated, and thereby drives the loudspeakers 5a and 5b with the driving signal y _{1. ,} y
₍₂₎ an adaptive digital filter process for calculating ₂ and a reference filtered by a filter coefficient corresponding to a modeled model space transfer function according to the number of combinations of the space transfer function between the microphone and the speaker based on the crank angle detection signal X A digital filter process for generating a signal r _km (see equation (5) to be described later), and a filter in the adaptive digital filter process based on the filtered reference signal r _km and the selected residual noise detection signals e _{1 to} e _3. Coefficient W
A filter coefficient update process for updating _mi using an LMS (Least Mean Square) algorithm and a noise suppression effect reduction process for reducing the noise suppression effect in the sound pressure range required by the occupant are executed.

Here, the silencing control principle of the microcomputer 26 will be described using a general formula. Now, the residual noise detecting signals the k-th microphone 6a~6h detects e _k (n), the k-th microphone 6a when the control sound from the loudspeakers 5a and 5b (secondary sound) is not
The residual noise detection signal ~6h detects e _pt (n), the transfer function H _miles FIR (finite impulse response) function between the m-th loudspeaker 5a and 5b and the k-th microphone 6a~6h J-th (j =
0, 1, 2, {I _c -1), the filter coefficient corresponding to the term C _kmj ′, the crank angle detection signal X (n), and the crank angle detection signal X (n). I-th adaptive digital filter for driving loudspeakers 5a and 5b
Th _{(i = 0,1,2, ─I F -1} ) When the coefficients of the W _mi, the following equation (2) is satisfied.

[0013] Here, each term with (n) is a sample value at sampling time n, and K is the microphone 6a
6c (three in this embodiment), M is the number of loudspeakers 5a and 5b (two in this embodiment), and I _C is FIR
The number of taps of the filter coefficients C _miles' expressed by the digital filter (filter order), a I _F is the number of taps of the filter coefficient W _mi represented in the adaptive digital filter (filter order).

In the expression (2), “2W _mi · X (nj
-i) The term “｝” (= y _m ) represents the output when the crank angle detection signal X is subjected to the adaptive digital filter processing.
Section _{C km j · {ΣW mi ·} X (nji)} "is the signal energy input to the m-th speaker 5a and 5b is output as the acoustic energy from these speakers 5a and 5b, spatial transfer function of the vehicle interior The signal at the time of arriving at the k-th microphone 6a to 6c via C _km is shown. Further, the second signal on the right side of “{C _kmj ｛ΣW _mi ＸX (nji)｝”
The whole term represents the sum of the secondary sounds reaching the k-th microphones 6a to 6c because the signals reaching the k-th microphones 6a to 6c are added up for all the speakers.

Next, an evaluation function J is placed as shown in the following equation (3). In this embodiment, the LMS algorithm is adopted,
A filter coefficient W _mi that minimizes the evaluation function J is obtained, and each filter coefficient W _mi of the adaptive digital filter processing is calculated as follows.
Update according to equation (4). That, LMS algorithm is the steepest descent method, n th value W _mi (n) is used as the filter coefficient of the adaptive digital filter processing to calculate the gradient ∂J / ∂W _mi of mean square error, alpha multiplied this Then, the (n + 1) -th value W _mi (n + 1) is obtained, and an operation is performed to reduce the value of the evaluation function J.

[0016] However, Is a convergence coefficient, which is related to the speed at which the adaptive digital filter processing converges optimally and the stability at that time.

As described above, the filter coefficient W _mi (n + 1) in the adaptive digital filter processing is determined by the microphone 6
Residual noise detection signals e ₁ (n) to e output from a to 6c
₃ (n) and the crank angle detection signal X from the crank angle sensor 7
(n) in accordance with the LMS algorithm, so that the input residual noise detection signals e ₁ (n) to
Drive signals y ₁ (n) and y ₂ (n) that minimize e ₃ (n) are formed, are supplied to the loudspeakers 5a and 5b, and are controlled by the control sounds output from the loudspeakers 5a and 5b. Noise is offset.

Next, the operation of the above embodiment will be described with reference to the flowchart of FIG. When the key switch is turned on, the entire system is turned on, and the microcomputer 26 executes a timer interrupt process shown in FIG. 4 every predetermined time (for example, 1 msec). The control signal CA is set to the logical value "1" in the initialization processing by the main program when the power is turned on, and the analog switches 28a, 28
b is controlled to the on state.

First, in step S1, the microphone 6
After reading the residual noise detection signals e _{1 to} e ₃ and the crank angle detection signal X (n) from a to 6c, the process proceeds to step S2, where digital filter processing corresponding to the equation (11) is performed to perform filter processing. The calculated reference signal r _km is then calculated, and then the process proceeds to step S3, and in accordance with equation (13) based on the calculated filtered reference signal r _km and the residual noise detection signals e _{1 to} e ₃ . A filter coefficient update process is performed to calculate a filter coefficient W _mi (n + 1).
4 to perform adaptive digital filter processing based on the calculated filter coefficient W _mi (n + 1) to calculate drive signals y _{1 and} y ₂ for the loudspeakers 5a and 5b, and then to step S5. the transition drive signal y _1, y ₂ which is calculated to shift the D / a conversion circuit 27a, since the output 27b to step S6.

In step S6, the loudspeakers 5a,
Drive signal y _m value of for example mechanical systems required by the occupant failure against 5b (when defective meshing gear mission, etc.)
Relatively large sound pressure (for example, 90
It is determined whether or not the threshold value is equal to or higher than a threshold value y _S corresponding to a sound pressure threshold value S ₂ set in advance corresponding to dB). If y _m <y _S, it is determined that no abnormal sound is generated. Terminates the timer interrupt processing and returns to the specified main program.
When y _m ≧ y _S, it is determined that an abnormal sound is occurring, and the process proceeds to step S7.

In this step S7, it is determined whether or not the abnormal sound generation state is continued. This determination is made based on whether the occurrence of the abnormal sound has continued for a predetermined time or whether the number of occurrences of the abnormal sound within the predetermined time is equal to or more than a set value,
When the abnormal sound generation state is not continued, the timer interrupt processing is terminated as it is, and when the abnormal sound generation state is continued, the process proceeds to step S8 to output the control signal CA of the logical value "0". And the analog switches 28a and 28
After b is turned off, the output of the control sound is stopped, and then the noise suppression control process ends.

In the process shown in FIG.
The processing of S5 corresponds to the control means, and steps S6 and S7
And the dead zone set in the microphones 6a to 6c correspond to the noise state detecting means, and the processing in step S8 corresponds to the noise suppression effect reducing means. Therefore, now
Assuming that the key switch and the ignition switch are both ON and the vehicle is running, the processing of FIG. 4 is executed by the microcomputer 26, and the residual noise detection signals e _{1 to} e output from the microphones 6a to 6c.
₃ ) Read the crank angle detection signal X (step S1),
Based on these, the filter coefficients in the adaptive digital filter processing are sequentially updated according to the LMS algorithm, and the loudspeaker 5 is adjusted so that the evaluation function J is minimized.
Drive signals y _{1 and} y ₂ for a and 5b are calculated and supplied to the loudspeakers 5a and 5b via D / A conversion circuits 27a and 27b. Therefore, the loudspeaker 5
a, the control sound corresponding to the drive signal y _1, y ₂ is emitted from 5b, by which interfere with the noise, the noise suppression as the residual noise detecting signals e ₁ to e ₃ microphones 6a~6c is minimized Control is performed.

For this reason, a large noise suppression effect is exerted on noise from the engine 3 and noise that is higher than the set sound pressure S ₁ such as muffled sound. However, since the dead zones are set in the microphones 6a to 6c as described above, noise having relatively small sound pressure such as road noise does not have a noise suppressing effect and is transmitted to the occupant as it is. And the occupant can grasp the road surface condition by the road noise.

On the other hand, if an abnormal sound that is louder than a noise such as a muffled sound due to normal engine noise is generated due to a mechanical failure or the like, this is detected by the microphones 6a to 6c, and the abnormal sound is attenuated. loudspeaker 5a, the drive signals y _1, y ₂ and 5b becomes a large value. For this reason, the process shifts from step S6 to step S7 to determine whether or not the large drive signal state due to the abnormal sound continues. If the abnormal sound continues, the process shifts to step S8 to control the control signal CA. Is a logical value “0”. Thus, the analog switches 28a, 28b are turned off, the drive signal y _1, y ₂ loudspeakers 5a, will be supplied to 5b is cut off, and the noise suppressing effect is no longer exerted, abnormal sound occupant occurrence of an abnormal state is listened to can recognize.

However, transient loud noises such as when closing the door with a loud noise or when passing through a railway guard are not determined to be abnormal noises in step S7. The suppression processing is continued, and a comfortable acoustic space can be maintained. As described above, according to the above-described embodiment, as shown in FIG. 6, the noise that needs to be recognized by the occupants of the set sound pressure S ₁ or less and S ₂ or more is transmitted to the occupant as it is, and the set sound pressure S ₁ and engine noise between S _2, for muffled sound or the like can exhibit an excellent noise suppression effect. Moreover, since the noise state is detected in the sound pressure range, it can be applied to a wide range of abnormal sounds of various different frequencies.

In the above embodiment, the set sound pressure S
_The case where the noise suppression processing is stopped when the number becomes ₂ or more has been described, but is not limited thereto.
As shown by the chain line in FIG. 6, it may be gradually so as to reduce noise suppressing effect when a set sound pressure S ₂ or more. Next, a second embodiment of the present invention will be described with reference to FIG.

In the second embodiment, a specific sound
Instead of reducing in the pressure range, reduce in the specific frequency range.
That's what I did. That is, as shown in FIG.
In the controller 15, any one of the microphones
6c residual noise detection signal e_ThreePart of the preset
Bandpass fill to pass through the frequency range that includes ordinary sound
And the filter output of the band-pass filter 30
Shaping circuit 31 for shaping the waveform and its waveform shaping output
V_FIs a preset value V_SCompared to V_F<V_S
, The logical value “1”, V_F≧ V _SArgument when
The control signal CA having the logical value “0” is supplied to the analog switch 28a,
28b, and a microphone 32
In the computer 26, the steps S1 to S1 in FIG.
Except that only the noise suppression processing of S5 is performed.
3 has the same configuration as the first embodiment described above, and FIG.
Corresponding parts are denoted by the same reference numerals, and the detailed description
Omitted.

[0028] According to the second embodiment, in the normal state where the abnormal sound does not occur, since the abnormal sound frequency components contained in the residual noise detecting signal e ₃ microphones 6c is small, passed through band-pass filter 30, Waveform shaping circuit 3
1 and the output whose waveform is shaped by a small value, the control signal CA having the logic value "1" from the comparator 32 is output analog switches 28a, to 28b, they are controlled to the ON state, the microcomputer 26 drive signal y _1, y ₂ which is output by being supplied loudspeaker 5a, in 5b, the noise suppression effect is exhibited from.

From this state, for example, an abnormal sound in a specific frequency range set in the band-pass filter 30 such as a metallic sound due to a mechanical system failure (for example, a sound near a frequency of 400 Hz at the time of poor meshing of the transmission gear). When There occurs, the output V _F that waveform shaping filters the output of the band-pass filter 30 by the waveform shaping circuit 31 becomes a set value V _S or higher, the control signal CA outputted from the comparator 32 is inverted to logic value "0" . Therefore, the analog switch 28
a, 28b is in the OFF state, the drive signal y _1, y ₂ loudspeakers 5a outputted from the microcomputer 26, by supply to 5b is cut off, the loudspeaker 5a, the control sound from 5b The output is stopped, and the noise suppression processing is stopped. As a result, the occupant hears the abnormal sound and can recognize the occurrence of the abnormal state. In addition, since the noise suppression control is stopped only for the abnormal sound in the specific frequency range, the noise suppression effect can be surely exerted in other frequency ranges.

In the second embodiment, the case where the band-pass filter 30 extracts a specific frequency range including an abnormal sound has been described. However, the present invention is not limited to this, and the output sides of the microphones 6a to 6c are not limited to this. It is also possible to interpose a band rejection filter for blocking the passage of a specific frequency band, so that the noise suppression processing by the microcomputer 26 is not performed in the specific frequency band.

In each of the above embodiments, the loudspeakers 5a, 5b are applied by applying the analog switches 28a, 28b.
The case where the output of the control sound from the loudspeaker is stopped has been described, but the present invention is not limited to this.
a, may be to greatly attenuated driving signals y _1, y ₂ to reduce the control sound for 5b.

Further, in each of the above embodiments, the case where the loudspeaker is applied as the control sound source has been described.
The present invention is not limited to this, and a vibrator can be applied, and an acceleration vibration sensor can be applied instead of the microphone that detects the residual noise. Furthermore, the number of loudspeakers and microphones to be installed is not limited to each of the above embodiments, but may be an arbitrary number of two or more.

Further, in each of the above embodiments, the case where the engine noise is suppressed has been described. However, the present invention is not limited to this. The wind noise can be suppressed by detecting the vibration of the window glass. Can be suppressed. Further, in each of the above embodiments, the case where the microcomputer 26 performs the adaptive digital filter processing and the digital filter processing of the filter coefficient corresponding to the spatial transfer function between the loudspeaker and the microphone has been described. Adaptive digital filters and digital filters can also be applied,
Further, the filter coefficients of the adaptive filter may be updated by applying an algorithm other than the LMS algorithm.

Furthermore, in the above embodiment, the case where the present invention is applied to a vehicle has been described. However, the present invention is not limited to this, and can be applied to a case where noise in a closed space such as an aircraft is attenuated.

[0035]

As described above, according to the active noise control device of the first aspect, the state of generation of a specific sound required by the occupant such as an abnormal sound such as a mechanical system failure is determined by the residual noise. Since the noise state detection means detects the noise based on the residual noise detection signal detected by the detection means, and the noise suppression effect reduction means accordingly reduces the noise suppression effect of the specific sound by the control means. The sound can be heard by the occupant, and the effect that the abnormality occurrence state and the road surface condition can be accurately grasped can be obtained.

Further, according to the active noise control device of the second aspect, the control for generating a predetermined noise state by the control sound source.
Since the detection is based on the loudness of the sound,
It emits control sounds corresponding to loud abnormal sounds, regardless of the number.
When a certain noise condition is detected.
Can be applied to a wide range of abnormal sounds of different frequencies
The effect that it can be obtained is obtained. Further, claim 3
According to the active noise control device according to the
Because it limits the output of the signal in the preset frequency range,
Noise suppression effect for signals in this limited frequency range
No noise, and noise suppression in other frequency ranges
The effect can be exerted, and the crew can recognize the specific sound more
The effect that it can be made easy is obtained.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram showing an outline of the present invention.

FIG. 2 is a schematic configuration diagram of a first embodiment of the present invention.

FIG. 3 is a block diagram illustrating an example of a controller.

FIG. 4 is a flowchart illustrating an example of a processing procedure of a microcomputer.

FIG. 5 is a characteristic diagram showing a relationship between an input sound and an output of a microphone.

FIG. 6 is a characteristic diagram illustrating a relationship between a noise sound pressure and a sound pressure heard by an occupant.

FIG. 7 is a block diagram showing a second embodiment of the present invention.

[Explanation of symbols]

 2 Cab 3 Engine 5a, 5b Loudspeaker 6a-6c Microphone 7 Crank angle sensor 15 Controller 26 Microcomputer 30 Bandpass filter 31 Waveform shaping circuit 32 Comparator

Claims (3)

(57) [Claims] 1. A control sound source that generates a control sound that interferes with noise transmitted from a noise source, a residual noise detection unit that detects residual noise between the noise and the control sound, and a residual noise of the residual noise detection unit. The residual noise signal is calculated based on the detection signal.
Control means for controlling the drive of the control sound source so as to reduce the noise level, wherein the residual noise detection signal of the residual noise detection means has a frequency range set in advance.
A noise state detecting means for detecting a predetermined noise state including a noise signal; and a noise suppressing effect on the noise in the noise state by the control means when the noise state detecting means detects the predetermined noise state. An active noise control device comprising: a noise suppression effect reducing unit that reduces noise. 2. A system for interfering with noise transmitted from a noise source.
A control sound source for generating a control sound, and a residual of the noise and the control sound.
Residual noise detecting means for detecting the residual noise, and the residual noise detection
Reducing the residual noise signal based on the residual noise detection signal of the means.
Control means for driving and controlling the control sound source so as to reduce
An active noise control device provided with:
Is in the specified noise state when the
Noise state detecting means for detecting noise, and the noise state detecting means
When a predetermined noise state is detected by the control means,
Noise suppression effect reducing means for reducing the noise suppression effect.
An active noise control device characterized by the following . 3. A system for interfering with noise transmitted from a noise source.
A control sound source for generating a control sound, and a residual of the noise and the control sound.
Residual noise detecting means for detecting the residual noise, and the residual noise detection
Reducing the residual noise signal based on the residual noise detection signal of the means.
Control means for driving and controlling the control sound source so as to reduce
In the active noise control device provided, the control means includes:
Output of a signal in a preset frequency range to the control sound source
Characteristic frequency limiting means for limiting frequency
Active noise control system according to.