JPH0527775A - Active type noise controller - Google Patents

Abstract

PURPOSE:To accurately perform noise control by restricting a rise in sound pressure when it is judged that a 1st specific value which is higher than the sound pressure level of a noise to be controlled by a sound pressure rise detecting means at an evaluation point is exceeded and canceling the operation of a restricting means when it is judged that the rise in sound pressure exceeds a 2nd specific value higher than a 1st specific value. CONSTITUTION:Filling sound detection parts 3a and 3b detect a filling sound, which has its phase and amplitude adjusted by a secondary sound generation part and is outputted to secondary sound output parts 1a and 1b. The secondary sound output parts 1a and 1b output an opposite-phase secondary sound corresponding to the sound pressure level to reduce the filling sound in a car room. In this case, a secondary sound level decision part 9 monitors the secondary sound level and sends a signal for stopping the output of the secondary sound output part 1a and 1b when the 1st specific value is exceeded. When an in-room noise level decision part 11 judges that the 2nd specific value higher than the 1st specific value is exceeded, a cancellation signal is outputted to the secondary sound level decision part 9 to continue the output of the secondary sound.

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 actively reducing noise in a passenger compartment of an automobile or a passenger compartment of an aircraft.

[0002]

2. Description of the Related Art As a conventional active noise control device of this type, there is, for example, a device shown in FIG. 7 of JP-A-60-151150. This conventional device is used, for example, as a device for reducing noise in the passenger compartment of an automobile, in particular, "muffled noise".
And the microphone 103, and the loudspeaker 10
1 generates a secondary sound (control sound) that interferes with "muffled sound (noise)", and the microphone 103 detects an evaluation point for noise reduction, for example, a residual signal (residual noise) at the occupant's ear position. It is supposed to do.

That is, the signal from the microphone 103 passes through a preamplifier 105 and a bandpass filter 107,
It is converted into a rectangular wave by the saturation amplifier 109, and further the phase shifter 11
At 1, the phase is delayed.

Further, the duty ratio is set to 5 by the PLL circuit 113.
After being adjusted to a rectangular wave of 0%, it is converted into a sine wave by the converter 115, amplified by the amplifiers 117 and 119, and output as a secondary sound from the loudspeaker 101. The control of the phase of the secondary sound received by the phase shifter 111 is performed by the control circuit 125 including the frequency-voltage converter 121 and the weighting circuit 123.

A voltage level detection circuit 131 consisting of a detection circuit 127 and a smoothing circuit 129 applies a voltage according to the level of "crowded sound", thereby controlling the voltage control amplifier 117 to generate a secondary sound. The amplitude is to be determined. Therefore, such feedback control can reduce the muffled sound in the vehicle interior.

[0006]

However, in a control circuit having a feedback system such as the conventional active noise control device as described above, the secondary sound output by itself when the wrong control is once entered is "muffled". Even if the sound quality is deteriorated, it is judged that a larger secondary sound is necessary and the secondary sound is kept increasing, and there is a possibility that the sound will eventually become unbearable. This phenomenon is called divergence below.

Since the magnitude of the "muffled sound" to be controlled is generally known in an automobile or the like, the level of the secondary sound is detected before and after the power amplifier 119, or the secondary sound level is input to the voltage controlled amplifier 117. Or if the level of the secondary sound becomes higher than a predetermined value exceeding the "muffled sound", or the number of times the level of the secondary sound exceeds the predetermined value is a predetermined number of times. A method of terminating the control of the device when it exceeds the limit (hereinafter referred to as “divergence stop”) is conceivable. This can prevent the device from diverging (Japanese Patent Application No. 3-171054).

However, this method is not perfect in some cases. That is, it may not be possible to distinguish between the case where the sound pressure level of the frequency of the "muffled sound" to be controlled due to the influence of the car stereo or the noise outside the vehicle becomes high and the case where the noise control device malfunctions. Is.
In the conventional noise control device, the DC voltage proportional to the sound pressure level of the "muffled sound" detected by the microphone 103 is output by the smoothing circuit 129, amplified appropriately, and output from the loudspeaker 101 as a secondary sound. For example, even if an appropriate secondary sound is output from the loudspeaker 101 according to the "muffled sound" in the vehicle interior detected by the microphone 103, the microphone may be erroneously operated by the car stereo or the noise outside the vehicle may temporarily increase. When the sound pressure level of the noise detected by 103 temporarily increases, the loudspeaker 101 outputs a secondary sound with a large level corresponding to this, and the device diverges from this state and the secondary sound is emitted. Can not be distinguished from the case where
There was a risk that the device would stop diverging despite proper noise control.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an active noise control device capable of performing noise control more accurately.

[0010]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a control sound source for reducing a noise at an evaluation point by generating a control sound that interferes with noise, and a residual of a predetermined position after the interference. Means for detecting noise, means for detecting a signal relating to the noise generation state of the noise source, and a signal for driving the control sound source based on the output signal of the residual noise detection means and the output signal of the noise generation state detection means. An active noise control device comprising a control means for outputting, a means for detecting an increase in sound pressure at the evaluation point, and a sound pressure rise detected by the sound pressure rise detecting means is a sound pressure level of noise to be controlled. Means for activating the sound pressure increase when a first predetermined value higher than the level is exceeded, and determining that the sound pressure increase exceeds a second predetermined value higher than the first predetermined value. When the operation of the regulation means is canceled And a configuration and means for Le.

[0011]

The control means outputs a signal for driving the control sound source based on the output signal of the residual noise detecting means and the output signal of the noise generation state detecting means. As a result, the control sound source
Control noise that interferes with noise is generated to reduce noise at the evaluation point.

When the sound pressure rise detection means at the evaluation point determines that the sound pressure level exceeds the first predetermined value which is higher than the sound pressure level of the noise to be controlled, the restricting means operates and the sound pressure at the evaluation point due to divergence or the like. Rise is regulated. When it is determined that the sound pressure increase at the evaluation point exceeds the second predetermined value which is higher than the first predetermined value due to an erroneous operation of the car stereo, the canceling means cancels the operation of the restricting means.

[0013]

Embodiments of the present invention will be described below. In addition,
The description will be given taking the vehicle interior space of the vehicle as an example.

FIG. 1 is a block diagram of an active noise control system according to an embodiment of the present invention, in which loudspeakers 1a and 1b as control sound sources in a closed space and a microphone as residual noise detecting means are shown. 3a and 3b, the loudspeakers 1a and 1b generate a control sound that interferes with the noise, and the microphones 3a and 3b attempt to reduce the noise, for example, a residual signal (residual noise at the occupant's ear position). ) Is to be measured. The loudspeakers 1a and 1b are the power amplifier 5
It is connected to the signal processor 7 via a and 5b, and the microphones 3a and 3b are also connected to the signal processor 7.

The noise in the passenger compartment is caused by, for example, a power plant. The power plant has a transmission as an engine and a power transmission device.
The differential gear is housed integrally. A crank angle signal sensor 8 is used as the noise generation state detecting means, and the detected crank angle signal is output to a digital filter in the signal processor 7. It should be noted that the noise generation state detection means is only required to be able to detect the reference signal relating to the noise generation state of the noise source, and as the signal, for example, the output signal of the vibration sensor provided on the outer surface of the engine, the ignition pulse signal of the engine,
It is also possible to use a rotation speed signal or the like obtained by detecting the rotation speed of the crankshaft with a rotation speed sensor.

On the other hand, the embodiment of the present invention includes a divergence limiting circuit 9 and a canceling circuit 11.

The divergence regulating circuit 9 detects the sound pressure rise at the evaluation point, and when it judges that the detected sound pressure rise exceeds a first predetermined value higher than the sound pressure level of the noise to be controlled. And means for operating so as to regulate the increase in sound pressure.

When functioning as a sound pressure rise detecting means,
The configuration is such that it is constantly determined whether the movement of the signal voltage to the power amplifiers 5a and 5b exceeds a first predetermined value. That is, as the noise to be controlled, for example, the “muffled sound” in the vehicle interior is targeted, and the sound pressure level of this “muffled sound” is known in advance. Therefore, the first predetermined value higher than this sound pressure level is set. Incidentally, when the value exceeds the first predetermined value, it is determined that the device is in the diverging state. In this determination, it is also possible to determine that the device is in the divergent state when the movement of the signal voltage exceeds the first predetermined value a plurality of times, for example, three times.

When the divergence restricting circuit 9 functions as sound pressure increase restricting means, a signal is sent to the switch 13 when the divergent condition is judged. This switch 13 is an ON-OFF switch of the device, and when the signal is sent from the divergence regulation circuit 9, the signal is turned off and the device is stopped, and the outputs from the loudspeakers 1a and 1b are set to zero, and at the evaluation point. Controls sound pressure rise. The canceling circuit 11 constitutes the canceling means in this embodiment, and is composed of a bandpass filter, an adder, etc. When it is determined that the value exceeds the above, the operation of the divergence restricting circuit 9 as the restricting means is canceled. That is, the cancel circuit 11 constantly determines whether or not the movement of the signal voltage from the microphones 3a and 3b exceeds the second predetermined value. This second predetermined value is set to be higher than the first predetermined value of the divergence level, and when it is determined that the movement of the signal voltage exceeds the second predetermined value, a signal is output to the divergence regulation circuit 9. Then, the divergence regulation circuit 9 cancels the output to the switch 13.

FIG. 2 is a functional block diagram of the apparatus of FIG. That is, the muffled sound detection unit corresponds to the microphones 3a and 3b, the secondary sound generation unit 7 corresponds to the signal processor 7, and the secondary sound output unit corresponds to the loudspeakers 1a and 1b. The in-vehicle noise level determination unit corresponds to the cancel circuit 11, and the secondary sound level determination unit corresponds to the divergence regulation circuit 9. Therefore, each reference numeral in FIG. 1 is attached to the corresponding block in FIG.

The muffled sound detectors 3a and 3b detect the "muffled sound" in the passenger compartment, and the muffled sound detector 3 is detected.
The phase and amplitude are adjusted in the secondary sound generation unit 7 by the signal input from the a3b, and output to the secondary sound output unit 1a1b. The secondary sound output units 1a and 1b output the secondary sound of the opposite phase corresponding to the sound pressure level of the "muffled sound", so that the muffled sound in the vehicle interior can be reduced.

The secondary sound level judging section 9 constantly monitors the secondary sound level. When the secondary sound level exceeds the first predetermined value, the secondary sound output section 1a, 1
A signal is issued to stop the output from b (divergence stop signal). That is, the output of the secondary sound is lost.

When the in-vehicle noise level judging section 11 judges that the value exceeds the second predetermined value which is higher than the first predetermined value, a cancel signal (divergence stop cancel signal) is outputted to the secondary sound level judging section 9. Then, the secondary sound level determination unit 9 outputs a signal for canceling the output stop from the secondary sound output units 1a and 1b (divergence stop cancellation signal). That is, the output of the secondary sound is continued.

FIG. 3 shows a control flow chart.

First, in step S ₁ , the microphone 3
The microphone noise (residual noise “muffled sound”) detected in a and 3b is taken in, and the secondary sound is generated by the secondary sound generation unit 7 in step S ₂ . Subsequently, in step S ₃ , it is determined by the secondary sound level determination unit 9 whether the secondary sound level exceeds the threshold value as the first predetermined value, and if it does not exceed the threshold value, the secondary sound output unit is executed in step S ₄ . Secondary sound output by 1a and 1b is performed.

If the secondary sound level exceeds the threshold value in step S _3, it is determined in step S ₅ whether or not the in-vehicle noise level exceeds the threshold value as the second predetermined value, as determined by the in-vehicle noise level determination section 11. If it is not exceeded, it is determined that the rise of the secondary sound determined in step S ₃ is due to the divergence of the device, the secondary sound = 0 is set in step S ₆ , and the secondary sound is output in step S ₄ . Will not be done.

If the in-vehicle noise level exceeds the threshold value in step S ₅ , it is determined that a large volume such as an erroneous operation of the car stereo has an effect, although the secondary sound control is normally performed. In step S ₄ , the secondary sound output is continued.

Therefore, when the secondary sound generator 7 attempts to generate an excessively large secondary sound due to, for example, erroneously increasing the volume of the car stereo by such control, the secondary sound that receives the signal is generated. The sound level determination unit 9 tries to send a divergence stop signal to the secondary sound output units 1a and 1b in order to stop the output of the secondary sound of the first predetermined value or more. On the other hand, the in-vehicle noise level determination unit 11 detects that the in-vehicle noise is already higher than the first predetermined value and sends a divergence stop cancel signal to the secondary sound level determination unit 9, so that the divergence stop is released and the normal state is released. The muffled sound control is continued.

Now, let us consider a case where the control is actually erroneously made into a divergent state, not the influence of the car stereo or noise outside the vehicle.

Since the noise level inside the vehicle producing the "muffled noise" is not originally high, the in-vehicle noise level determination section 11 does not output the divergence stop cancel signal. On the other hand, the secondary sound generation unit 7 outputs a signal corresponding to the secondary sound larger than the first predetermined value, and at the same time, sends the signal of that level to the secondary sound level determination unit 9. The secondary sound level determination unit 9 outputs a divergence stop signal in response to this signal to stop the secondary sound output at the secondary sound output units 1a and 1b (steps S ₁ → S ₂ → S ₃ → S ₅ → S ₆ → S ₄ ). Therefore, it is possible to prevent the sound pressure from increasing due to divergence at the occupant's ear position. At this time, the in-vehicle noise level determination unit 11 issues a determination level (second
If the determination level (first predetermined value) at which the divergence stop signal is output by the secondary sound level determination unit 9 is set lower than the divergence stop cancel function, If you set so that it is easy to operate, the divergence stop function that worked once will not be accidentally released by an erroneous secondary sound generated by itself. Also, in the situation where the divergence stop is operating due to a malfunction of the control, even if the divergence stop cancellation signal is issued due to noise outside the vehicle and the divergence stop is released, it will be incorrect while the outside noise continues. The large secondary sound is masked by the noise outside the vehicle and cannot be heard by the occupant. If the noise outside the vehicle disappears, the divergence stop cancel signal cannot be issued, and divergence stops and there is no problem.

FIG. 4 shows the relationship between the change in the sound pressure level at the occupant's ear position and the first predetermined value and the second predetermined value. The curve in the figure shows a process in which the sound pressure level temporarily decreases due to the secondary sound, but the secondary sound diverges due to incorrect control, and the sound pressure level gradually increases. When the sound pressure level reaches the first predetermined value due to this divergence, the control is stopped, and the interior of the vehicle becomes the muffled sound level at the time of non-control. Further, the second predetermined value is set to a value higher than the first predetermined value, and diverges when the sound pressure level exceeds the second predetermined value due to an erroneous operation of the car stereo or noise outside the vehicle. It is determined that the sound pressure is not increased due to, and the stop of the device is canceled, and the noise control is continued.

Next, the control method will be described.

Now, the noise signal detected by the 1st microphones 3 and 3b is represented by e _l (n), and the loudspeakers 1 and 1
1st microphone 3 when there is no control sound from b
The noise signals detected by a and 3b are e _pl (n), and the jth (j) of the transfer function FIR (finite impulse response) function between the mth loudspeakers 1a and 1b and the lth evaluation point.
= 0, 1, 2, ..., I _c −1) is represented by a digital filter, the filter coefficient is C _lmj , the reference signal, that is, the sound source information signal is x _p (n), and the reference signal x _p (n). Of the adaptive filter for driving the m-th loudspeakers 1a and 1b by inputting (i = 0, 1, 2, ..., I _k -1)
Let W _mi be the coefficient of

[0034]

[Equation 1]

Is satisfied. Here, the term with (n) is
Both are sample values at the sampling time n, and L is the number of microphones 3 and 3b (2 in this embodiment).
, M is the number of loudspeakers 1 and 1b (two in this embodiment), IC is the number of taps (filter order) of the transfer function Clm represented by the FIR digital filter, and IK is the number of taps of the adaptive filter (filter). Order).

In the above equation (1), "Σ W _mi · x on the right side
_p (n-j-i) "(= y _m) of the section signal to the filter (coefficients W _m) for each output channel in the adaptive filter x
_It represents the output when _p is input, and is expressed as “Σ C _lmj · {Σ
W _mi · (n−j−i)} ”is the mth speaker 1
The signal energy input to a and 1b is the speaker 1a,
1b represents a signal when it is output as acoustic energy and reaches the 1st microphones 3a and 3b via the transfer function Clm in the vehicle interior, and further represents "Σ Σ C _lmj · {ΣW
_The entire right side of “ _mi · w _p (n−j−i)” adds the arrival signals to the l-th microphones 3a and 3b for all speakers, so that the secondary sound reaching the l-th evaluation point. Represents the sum of

Next, the evaluation function (variable to be minimized) J
e

[0038]

[Equation 2]

Let us say that.

Then, in order to obtain the filter coefficient W _m that minimizes the evaluation function Je, the LMS algorithm is adopted in this embodiment. That is, the filter coefficient W _{mi is} a value obtained by partially differentiating the evaluation function Je with respect to each filter coefficient W _mi.
To update.

[0041]

[Equation 3]

From equation (1),

[0043]

[Equation 4]

Therefore, the right side of the equation (4) is r
_{If lm} (n−i) is written, the rewriting formula of the filter coefficient is obtained by the following formula (5).

[0045]

[Equation 5]

Here, α is a convergence coefficient and is involved in the speed at which the filter converges optimally and the stability at that time.

By performing such control, when the "muffled sound" is generated, it is possible to minimize the muffled sound and effectively eliminate the "muffled sound". ..

FIG. 5 shows another embodiment.

In this embodiment, a vehicle condition determining unit 15 is used instead of the in-vehicle noise level determining unit 11 shown in FIG.

That is, in this embodiment, the vehicle condition judging section 15 constitutes canceling means. The vehicle condition determination unit 15 does not directly determine whether or not the increase in sound pressure at the occupant's ear position exceeds the second predetermined value, but indirectly determines it based on vehicle conditions. The vehicle condition determination unit 15 determines whether or not the current vehicle state matches the condition for outputting the divergence stop cancel signal, based on various information regarding the vehicle state. The state of the vehicle to be considered may be, for example, the open / closed state of windows and the vehicle speed. That is, when the window is opened during high-speed traveling, the sound pressure level in the passenger compartment rises due to the wind noise, and the rise of this sound pressure level cancels the output of the divergence stop signal to the secondary sound output units 1a and 1b. .. As another example of the vehicle state, the volume of car tele, the horn switch, the suspension vibration level, the engine vibration level, and the like can be considered.

Specifically, a logical product of "one of the windows is open" and "the vehicle speed is equal to or higher than a predetermined value",
If the logical sum of "the horn switch is pressed" and "the suspension vibration level is equal to or higher than a predetermined value" is true, a divergence stop cancel signal is output.

Here, the suspension vibration level is taken into consideration so as to avoid outputting the divergence stop signal to the secondary sound output units 1a and 1b because the road noise which is not considered as a control target in this embodiment is too large. This is because. In the case of muffled sound control, it is also effective to confirm that the engine vibration that is the noise source does not exceed the assumed vibration level. That is, when the engine vibration level is equal to or higher than the predetermined value, the "muffled noise" in the vehicle may exceed the predetermined value. In that case, therefore, the divergence stop cancel signal is not output.

In this embodiment, in addition to the same effects as the above-mentioned embodiment, the erroneous operation of divergence stop for noises such as wind noise during high-speed running that keeps coming out as long as a constant vehicle condition continues is prevented. Is effective for.

FIG. 6 shows still another embodiment.

In this embodiment, a vehicle outside noise level determining section 17 of the embodiment shown in FIG. 2 is replaced with an outside vehicle noise level determining section 17 and an outside vehicle noise detecting section 19. The exterior noise detector 19 is composed of a microphone, a preamplifier, etc.,
The output is input to the exterior noise level determination unit 17. The vehicle exterior noise level determination unit 17 constitutes a canceling means, and indirectly determines that the sound pressure increase at the occupant's ear position exceeds the second predetermined value by determining the detected vehicle exterior noise. There is something.

Therefore, the vehicle exterior noise level determination unit 17 outputs a divergence stop cancel signal to the secondary sound level determination unit 9 when the vehicle exterior noise exceeds a predetermined value corresponding to the second predetermined value, and the vehicle exterior excessive noise level is detected. It is possible to prevent malfunction of the divergence stop function due to noise.

This embodiment has the same effects as the above embodiment, and is also effective when used in an environment where it is often exposed to a high level exterior noise.

In each of the above embodiments, the in-vehicle noise level determining section 11, the vehicle condition determining section 15 and the outside vehicle noise level determining section 17 are separately provided, but they may be used in any combination. Further, in each of the above-described embodiments, the "muffled noise" of the automobile has been described as a control target, but road noise and wind noise may be controlled, and the invention is not limited to noise and may be applied to vibration control. Furthermore, the invention can be applied to aircrafts, ships, etc. instead of automobiles.
When the device diverges, it is possible to modify the LMS algorithm accordingly without stopping the device, as if it were actuated to regulate the increase in sound pressure. The residual noise detection means is not limited to one that detects residual noise at an evaluation point such as the occupant's ear position, but detects residual noise at spatially distant positions,
It is also possible to measure the transfer function ratio between the noise source and the evaluation point and the control sound source and the evaluation point in advance.

[0059]

As is apparent from the above, according to the configuration of the present invention, whether the device causes an increase in sound pressure due to erroneous control, or even if the control is normal, noise is generated by other noise factors. It is possible to distinguish whether the pressure increase is being caused, and when the device is causing the sound pressure increase due to erroneous control, the sound pressure increase can be regulated by stopping the control, etc. When the sound pressure is increased due to the factor, the control stop can be canceled to continue the proper control of the device, and the accurate active noise control can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram according to an embodiment of the present invention.

FIG. 2 is a functional block diagram according to an embodiment.

FIG. 3 is a flowchart according to one embodiment.

FIG. 4 is a graph showing changes in sound pressure level.

FIG. 5 is a functional block diagram according to another embodiment.

FIG. 6 is a functional block diagram according to still another embodiment.

FIG. 7 is a block diagram according to a conventional example.

[Explanation of symbols]

1a, 1b loudspeaker (control sound source) 3a, 3b microphone (residual noise detection means) 7 signal processor (control means) 9 divergence regulation circuit (sound pressure rise detection means and sound pressure rise regulation means) 11 cancellation circuit (cancellation means) ) 15 Vehicle condition determination unit (cancellation means) 17 Vehicle exterior noise level determination unit (cancellation means)

Claims (1)

Claim: What is claimed is: 1. A control sound source for generating a control sound that interferes with noise to reduce noise at an evaluation point, a means for detecting residual noise at a predetermined position after the interference, and a noise source. And a control means for outputting a signal for driving the control sound source based on the output signal of the residual noise detection means and the output signal of the noise generation state detection means. Type noise control device, a first predetermined value for detecting a sound pressure increase at the evaluation point, and a sound pressure increase detected by the sound pressure increase detecting means being higher than a sound pressure level of noise to be controlled. Means for activating the sound pressure increase when it is determined that the sound pressure rise exceeds a second predetermined value that is higher than the first predetermined value. And means for canceling Active noise control apparatus according to claim and.