JP2005257720A - Active noise control device - Google Patents

Abstract

The present invention relates to a feedback active noise control apparatus that cancels noise with a control sound having a phase opposite to that of noise, and obtains a noise reduction effect without being affected by fluctuations in noise characteristics and speaker transfer functions.
An active noise control device comprises a noise detection microphone, a speaker reverse characteristic correction means, a high frequency component attenuation means, an inverting amplifier, and a control sound speaker. The cut-off frequency of the high-frequency component attenuation means is automatically adjusted according to the noise characteristic fluctuation to be detected, and the speaker inverse characteristic correction characteristic is automatically adjusted so that the difference in open-loop transfer function characteristic from the design time is eliminated for fluctuations in the speaker transfer function. Since the operation is changed, the noise reduction effect can be continuously obtained.
[Selection] Figure 2

Description

  The present invention relates to an active noise control device.

  In addition to passive noise control technology that fills the noise propagation path with a sound absorbing material, etc., there are active noise control technologies that reduce noise by interfering noise with the same amplitude and opposite phase control sound. Proposed. The active noise control technology includes a feedback type in which the noise detection means and the control error detection means (control point) are the same and an acoustic closed loop is formed between the control sound generation means, the noise detection means, and the control sound generation means. The feed forward type in which each means is installed so that an acoustic loop is not formed between them can be roughly classified. When the feedforward type active noise control technology is used, the control target noise is limited because it is necessary to detect the control target noise in advance at the control point. On the other hand, when using feedback-type active noise control technology, it is not necessary to detect the control target noise before it arrives at the control point, but the closed loop becomes unstable because the control sound has a time delay with respect to the control target noise. There is a problem that it is easy. In view of this, there has been proposed an apparatus that achieves both system stability and noise control effect in a continuous frequency band when using the feedback type active noise control technology (see, for example, Patent Document 1).

  Hereinafter, a feedback type active noise control apparatus will be described with reference to the drawings. FIG. 1 shows a feedback type active noise control apparatus. In FIG. 1, 30 is a duct, 31 is a noise source, 32 is an error detector, 33 is a secondary sound generation filter, and 34 is a secondary sound radiation speaker. The secondary sound generation filter 33 includes a fixed multiple signal processing unit 35, an inversion unit 36, an inverse characteristic signal processing unit 37, and a low frequency pass signal processing unit 38. The operation of the feedback active noise control apparatus shown in FIG.

  The length of the cross section of the duct 30 is sufficiently shorter than the wavelength of noise. In this case, the sound wave inside the duct 30 can be handled as a plane wave, and is realized in the vicinity of the error detection unit 32 that detects the interference signal between the noise from the noise source 31 and the secondary sound from the secondary sound radiation speaker 34. The controlled effect is realized uniformly in the cross section of the duct 30. The output signal of the error detector 32 is input to the fixed signal processor 35 and amplified. The output signal of the fixed signal processing unit 35 is input to the inverting unit 36 and inverted. The inverse characteristic signal processing unit 37 responds to the frequency amplitude characteristics of the elements excluding the dead time element in the transfer function (hereinafter referred to as speaker transfer function) from the input signal of the secondary sound emitting speaker 34 to the output signal of the error detection unit 32. The output signal of the inverting unit 36 is processed with an amplitude characteristic that is an inverse characteristic relationship. The output signal of the inverse characteristic signal processing unit 37 is input to the low frequency band signal processing unit 38, and the high frequency band component is reduced. The secondary sound radiation speaker 34 is driven by the output signal of the low frequency band signal processing unit 38 to radiate the secondary sound into the duct 30. The transfer function (open loop transfer function) from the input signal of the secondary sound radiation speaker 34 to the output signal of the low-frequency-pass signal processing unit 38 has a flat amplitude characteristic in the low frequency band where the influence of the phase delay due to the dead time is small. In the high frequency band where the influence of the phase delay due to the dead time is large, the amplitude level is small.

With the above operation, the error detection unit 32 can obtain a uniform noise reduction effect in the frequency band excluding the high frequency band where the influence of the phase delay is large, and the stability can be maintained even in the high frequency band. However, if the phase difference between the secondary sound radiation speaker 34 and the error detection unit 32 is increased due to the necessity to install the speaker 34 and the speaker transfer function includes a lot of time elements, the low frequency band is passed. Since the cut-off frequency of the signal processing unit 38 must be reduced and a predetermined control frequency band is narrowed, the secondary sound generation filter 33 once designed cannot control noises of various frequencies. Therefore, when the active noise control apparatus shown in FIG. 1 is used, noise that fluctuates in frequency characteristics depending on the running state or the like is controlled even if it is stationary noise such as cabin noise of a high-speed moving body. For this purpose, the secondary sound generation filter 33 is redesigned each time, or a plurality of secondary sound generation filters 33 for each control frequency band are designed in advance and stored in the memory to generate the secondary sound according to the noise characteristics. There exists a subject that the effort which replaces the processing coefficient of the filter 33 is required. In addition, since the processing characteristics of the secondary sound generation filter 33 are fixed, there is a problem that the control performance deteriorates when the speaker transfer function fluctuates due to aging of the device characteristics. In particular, when a plurality of active noise control devices are used, enormous effort is required to replace or redesign the secondary sound generation filter 33 described above. Although the secondary sound generation filter 33 is composed of an adaptive filter, it is possible to continuously obtain a noise reduction effect by updating the filter coefficient in accordance with the fluctuations. However, in order to realize the adaptive filter, active noise control is performed. There exists a subject that the circuit scale of an apparatus becomes large.
JP 2002-55684 A

  In view of the above problems, the present invention automatically changes the processing characteristics of the active noise control device by following the fluctuations in the frequency characteristics of the noise and the speaker transfer function, so that control can be performed even in an environment with a large dead time element. It is an object of the present invention to provide a feedback type active noise control device that continuously obtains an effect of reducing noise of various frequencies without significantly increasing the circuit scale of the device.

  In order to solve the above problems, an active noise control apparatus according to the present invention includes a noise detection unit, a control characteristic adjustment unit that inputs an output signal of the noise detection unit, an output signal of the noise detection unit, and the control characteristic adjustment unit. Active noise control apparatus comprising a control means for inputting the output signal of the control circuit and a speaker for inputting the output signal of the control means, wherein the control characteristic adjusting means is based on the output signal of the noise detection means. A processing coefficient signal is output, and the control means outputs a signal that attenuates the output signal of the noise detection means based on the processing coefficient signal output from the control characteristic adjustment means.

  The active noise control device according to the present invention includes a noise detection unit, a noise generation device operation state detection unit, a control characteristic adjustment unit that inputs an output signal of the noise generation device operation state detection unit, and an output signal of the noise detection unit. And an active noise control device comprising: a control means for inputting an output signal of the control characteristic adjusting means; and a speaker for inputting the output signal of the control means, wherein the control characteristic adjusting means comprises the noise generating device operating state detection means. The control means outputs a processing coefficient signal of the control means based on the output signal, and the control means outputs a signal that attenuates the output signal of the noise detection means based on the processing coefficient signal output from the control characteristic adjustment means. It is the composition to output.

  In the active noise control apparatus according to the present invention, the control means corrects an input signal with a gain reverse characteristic of the speaker and outputs the same, a high-frequency component attenuation means for attenuating and outputting a high-frequency component of the input signal, and a signal It has a configuration characterized by comprising inverting amplification means.

  The active noise control apparatus according to the present invention is characterized in that the inverse characteristic correcting means comprises at least one band component correcting means capable of adjusting a passing amount of a predetermined frequency band component of the input signal. Yes.

  The active noise control apparatus of the present invention is characterized in that the control means has a variable cutoff frequency of the high frequency component attenuation means determined based on a processing coefficient signal output from the control characteristic adjustment means. .

  In the active noise control apparatus according to the present invention, the control means outputs a signal that attenuates a signal having a high frequency component among the output signals of the noise detection means.

  The active noise control apparatus according to the present invention is characterized in that the control means has a variable gain of the signal inversion amplification means determined based on a processing coefficient signal output from the control characteristic adjustment means. Yes.

  In the active noise control apparatus according to the present invention, the control characteristic adjustment unit determines whether the output signal of the noise detection unit is stable or unstable, and determines whether to input the output signal of the determination unit A result display unit is further provided, and the determination result display unit displays the determination result of the determination unit by a predetermined method.

  The active noise control device according to the present invention is characterized in that the control means stops the control operation when the determination unit determines that the output signal of the noise detection means is oscillating unstablely. Yes.

  In the active noise control apparatus of the present invention, the control means stops the control operation when the determination unit determines that the output signal of the noise detection means is oscillating unstablely, and then the signal inversion amplification means The control means is changed to an amplification factor that does not cause unstable oscillation, and the control means restarts the control operation.

  The active noise control device of the present invention includes a noise detection means, a signal generation means, a control means input switching means for inputting an output signal of the noise detection means and an output signal of the signal generation means, and an output of the noise detection means. A control characteristic adjusting means for inputting a signal and an output signal of the signal generating means, a control means for inputting an output signal of the control means input switching means and an output signal of the control characteristic adjusting means, and an output signal of the control means. An active noise control device having an input speaker, wherein when the control means input switching means outputs an output signal of the signal generation means, the control characteristic adjustment means outputs the output of the noise detection means from the input of the control means. When the control means input switching means outputs the output signal of the noise detecting means, the control characteristic adjusting means outputs the output signal of the noise detecting means. The control means outputs a processing coefficient signal from the control means, and the control means outputs a signal that attenuates the output signal from the control means input switching means based on the processing coefficient signal output from the control characteristic adjustment means. It is the composition to do.

  In the active noise control device according to the present invention, when the control means input switching means outputs the output signal of the signal generating means, the control characteristic adjusting means is configured to detect the noise detection means from the input of the control means in a predetermined frequency band. A processing coefficient signal is output so that the transfer function gain characteristic up to the output becomes flat.

  The active noise control device of the present invention is configured to include M (M is an integer of 2 or more) active noise control devices.

  The active noise control apparatus of the present invention is characterized in that a processing coefficient signal output from at least one of the control characteristic adjusting means is different from a processing coefficient signal output from the other control characteristic adjusting means. .

  In the active noise control device of the present invention, the control characteristic adjusting means constituting the M-1 active noise control devices excluding the first of the M active noise control devices is omitted, and the first active active control device is omitted. The processing coefficient signal output from the control characteristic adjusting means constituting the noise control device is inputted to the control means constituting the first active noise control device, and M-1 except for the first. Input to the control means constituting the active noise control device, and the control means constituting the M active noise control devices are outputted from the control characteristic adjusting means constituting the first active noise control device. Based on the processing coefficient signals to be output, a signal is output so that the output signals of the noise detection means constituting the M active noise control devices are attenuated.

  In the active noise control device of the present invention, the control characteristic adjusting means constituting the M-1 active noise control devices excluding the first of the M active noise control devices is omitted, and the first active active control device is omitted. In addition to the output signal of the noise detecting means constituting the first active noise control device, the control characteristic adjusting means constituting the noise control device further includes M-1 active noise controls other than the first. An output signal of the noise detection means constituting the apparatus is input, and the control characteristic adjusting means determines whether the output signal of the noise detection means is stable or unstable oscillation, and A determination result display unit for inputting an output signal is further provided, and the determination result display unit displays the determination result of the determination unit by a predetermined method.

  The active noise control device according to the present invention is configured such that the control unit that the determination unit determines that the output signal of the noise detection unit oscillates unstablely stops the control operation.

  In the active noise control apparatus according to the present invention, the control unit that the determination unit determines that the output signal of the noise detection unit is oscillating unstablely, the signal inversion constituting the control unit after the control operation is stopped. The amplification means is configured to change the amplification factor such that the control means does not oscillate in an unstable manner, and the control means restarts the control operation.

  The active noise control device of the present invention includes at least two or more noise detection means, signal generation means, at least two or more input signals from the signal generation means and the noise detection means. The control means input switching means, at least two or more control characteristic adjustment means input switching means for inputting the respective output signals of the noise detection means, and the output signals of the control characteristic adjustment means input switching means are inputted. An adder, the signal generating means, a control characteristic adjusting means for inputting an output signal of the adder, an output signal of the control characteristic adjusting means and an output signal of each of the control means input switching means; An active noise control device comprising one or more control means and at least two or more speakers each receiving an output signal of each of the control means, the control means When the force switching means outputs the output signal of the signal generating means, the control characteristic adjusting means input switching means connected to the control means input switching means outputs the output signal of the noise detecting means, and the control means input Calculating a transfer function from the input of the control means connected to the switching means to the output of the noise detecting means connected to the control means input switching means, and the control characteristic adjusting means not connected to the control means input switching means The input switching means does not output the output signal of the noise detection means, and when all the control means input switching means output the output signal of the noise detection means, the control characteristic adjustment means input switching means is the noise detection means. The control characteristic adjusting means outputs a processing coefficient signal of the control means based on the output signal of the adder, and the control means The output signal of the connected the control unit input switching means based on the processing coefficient signals outputted from sexual adjusting means has a configuration for outputting a signal for attenuation.

  In the active noise control device of the present invention, when the control means input switching means outputs the output signal of the signal generating means, the control characteristic adjusting means is connected to the control means input switching means in a predetermined frequency band. A processing coefficient signal is output so that the transfer function gain characteristic from the input of the control means to the output of the noise detection means connected to the control means input switching means becomes flat.

  The active noise control device according to the present invention is characterized in that the control means and the control characteristic adjusting means are composed of analog circuits.

  As described above, according to the present invention, the inverse characteristic correcting means constituting the control device according to the noise frequency characteristic detected by the noise detecting means or the noise generating device operating state detecting means or the fluctuation of the open loop transfer function, or The processing characteristics of the high frequency component attenuation means or the inverting amplification means are automatically changed. As described above, according to the active noise control device according to the present invention, even in an environment with a large dead time element, the effect of continuously reducing noises of various frequencies can be obtained without significantly increasing the circuit scale of the control device. be able to.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

(Embodiment 1)
FIG. 2 is a diagram illustrating the active noise control apparatus according to the first embodiment. In FIG. 2, 1 is a noise detection microphone, 2 is a control sound speaker, 3 is a control device, 4 is an inverse characteristic correction means, 5 is a high frequency component attenuation means, 6 is an inverting amplification means, and 7 is a cutoff frequency changing means. It is. FIG. 2 shows a case where the frequency characteristic of noise is changed because the cutoff frequency of the high frequency component attenuation means is changed and the frequency for controlling noise is shifted in accordance with the output signal of the noise detection microphone as compared with the configuration of FIG. However, it is an active noise control device that does not have a duct, and obtains a uniform control effect in a predetermined frequency band following the change.

  The operation of the configuration shown in FIG. 2 and the design method of the control device 3 will be described below. The noise signal detected by the noise detection microphone 1 is input to the control device 3 and the cutoff frequency changing means 7. The signal input to the control device 3 is processed by the inverse characteristic correcting means 4, the high frequency component attenuating means 5, and the inverting amplifying means 6 to be corrected to a control signal that attenuates noise. The control signal is input to the control sound speaker 2 and is emitted as a control sound to interfere with noise. The design of the control device 3 for reducing noise as a result of interference between noise and control sound will be described. The transfer function (speaker transfer function) from the input to the control sound speaker 2 to the output of the noise detection microphone 1 is P (s), and the input / output transfer function (control device transfer function) of the control device 3 is N. When C (s) and the control error signal (the output signal of the noise detection microphone 1) are e, the ratio of the control error signal and the noise is expressed by (Equation 1).

  If C (s) is designed so that the open-loop transfer function P (s) · C (s) is in the opposite phase and the gain is increased from (Equation 1), a noise reduction effect can be obtained. That is, in order to obtain a uniform noise reduction effect in a wide frequency range, the control device 3 may be designed so that the gain of the open-loop transfer function is constant and the phase is opposite in that frequency range. . Based on the design policy, the control device 3 may be designed to have the inverse characteristic correcting means 4 for performing the inverse characteristic processing of the speaker transfer function on the input signal and the inverting amplification means 6 for performing the phase inversion processing. .

3 shows the speaker transfer function gain characteristic, the gain characteristic of the inverse characteristic correcting means, the speaker transfer function, and the open loop transfer function when the control device 3 is composed only of the inverse characteristic correcting means 4 in the configuration shown in FIG. It is the figure which showed the gain characteristic. In the figure, f ₀ is the primary resonance frequency of the control sound speaker 2, and the control sound speaker 2 is proportional to the input signal in order to exhibit nonlinear behavior when the input signal is large at a frequency of f ₀ or less. There is no sound. Therefore, it is difficult to flatten the gain characteristic of the open loop transfer function by the inverse characteristic correction means 4 at a frequency of f ₀ or less.

FIG. 4 is a diagram showing the phase characteristics of the open-loop transfer function when the control device 3 is composed only of the reverse characteristic correction means 4, and FIG. 5 is a diagram showing the reverse characteristic correction means 4 and the inverting amplification means 6. It is the figure which showed the phase characteristic of the open loop transfer function in the case comprised by. When the control device 3 is composed of the reverse characteristic correcting means 4, the phase does not become flat. This is because the reverse characteristic of the primary resonance of the speaker cannot be corrected, and the time required for the sound to reach from the control sound speaker 2 to the noise detection microphone 1 or the group of the control sound speakers 2 themselves. This is because there is a dead time element due to the delay. That is, if the distance between the control sound speaker 2 and the noise detection microphone 1 approaches zero as much as possible and a speaker without group delay is used as the control sound speaker 2, the phase characteristic becomes zero in the entire frequency band. In reality, there is no such speaker. On the other hand, since the phase characteristic of the open-loop transfer function by adding an inverted amplifying means 6 to the control device 3 [pi [rad] shifts, noise is reduced in f ₁ to be the opposite phase when closing the feedback loop. In general, in active noise control technology that reduces noise by interfering with noise and anti-phase control sound, the noise is not a complete anti-phase control sound but a phase shift within the opposite phase ± π / 4 [rad]. Is reduced. Therefore, noise is reduced at a frequency satisfying f ₂ <f <f ₃ in FIG. However, the signal in the feedback loop since the f ₄ phase becomes positive phase from falling out of control oscillates. Therefore, the control device 3 to the high frequency component attenuation means 5 can prevent oscillations if attenuates f ₄ or more signals in addition. However, the high frequency component attenuating means 5 has a characteristic of attenuating the high frequency component and delaying the phase of the control device 3.

FIG. 6 shows the gain phase characteristics of the open loop transfer function in a configuration in which the high frequency component attenuation means 5 is added to the control device 3. By adding the high frequency component attenuating means 5, the frequency range in which noise is reduced is shifted to f ₆ <f <f ₇ . FIG. 7 shows the relationship between the cutoff frequency of the secondary low-pass filter and the gain phase characteristic as an example of the high-frequency component attenuation means 5. The low-pass filter has a characteristic that the lower the cutoff frequency, the lower the frequency at which the phase starts to lag. Therefore, the open-loop transfer function phase characteristic of the active noise control device is changed by changing the cutoff frequency of the high-frequency component attenuation means 5 by some method, that is, the control frequency range (f ₆ <f <f _{7 in} FIG. 6). Can be changed.

Next, a procedure for changing the cutoff frequency of the high-frequency component attenuation means 5 will be described. In FIG. 2, the output signal of the noise detecting microphone 1 is input to the cutoff frequency changing means 7. The cutoff frequency changing means 7 analyzes the frequency of the input signal and inputs the cutoff frequency of the high frequency component attenuating means 5 based on the peak frequency of the noise. FIG. 8 shows the frequency analysis result of the noise detection microphone signal when the center frequency of the control frequency band when the control device 3 is designed is f ₀ and the peak frequency of the signal input from the noise detection microphone 1 is f ₀ + Δf. Shown in Assuming that the speaker transfer function is P, the transfer function of the inverse characteristic correction means 4 is C ₁ , the transfer function of the high frequency component attenuation means 5 is C ₂ , the cutoff frequency is f _C , and the transfer function of the inverting amplification means 6 is C ₃ ,

The cutoff frequency changing means 7 inputs a predetermined signal for changing the cutoff frequency f _C of C ₂ to the high frequency component attenuating means 5 so as to satisfy the above. When the high frequency component attenuation means 5 is a digital filter, the cutoff frequency changing means 7 inputs a predetermined filter coefficient to the high frequency component attenuation means 5. When the high-frequency component attenuating means 5 is an analog filter, the cut-off frequency changing means 7 is input to the signal high-frequency component attenuating means 5 for changing the resistance value of the semi-fixed resistor constituting the filter, or mechanically a semi-fixed resistor. Change the value. FIG. 9 shows a signal of the noise detection microphone 1 at the time of control and non-control, that is, a noise reduction effect, when the center frequency of the control frequency band is f ₀ and f ₀ + Δf.

The control device 3 and the cut-off frequency changing means 7 may be realized by an analog circuit or a digital circuit. When the control device 3 is realized by an analog circuit, for example, the high-frequency component attenuation means 5 can be realized by a circuit as shown in FIG. In the high frequency component attenuating means 5 shown in FIG. 10, the cut-off frequency f _C is determined by the following equation.

By mechanically changing the cut-off frequency changing means 7 the resistance value of the semi-fixed resistor R ₂ from equation (3) can change the cutoff frequency of the high frequency component attenuation means 5 to a predetermined frequency. When the cutoff frequency changing means 7 is realized by an analog circuit, the frequency analysis of the input signal can be realized by performing octave analysis using a plurality of band pass filters. FIG. 11 shows a configuration when the cutoff frequency changing means 7 is realized by an analog circuit. The input noise signal is output to the band-pass filter A86, the band-pass filter B87, and the band-pass filter C88 and is divided into bands. The signal level comparison unit 84 compares the levels of the output signals of the band pass filters 86 to 88 and inputs the pass frequency information of the filter that has output the highest level signal to the cutoff frequency coefficient calculation unit 85. The cut-off frequency coefficient calculation unit 85 outputs the processing coefficient signal of the high-frequency component attenuating means 5 using (Equation 2) and (Equation 3) from the pass frequency signal. In FIG. 11, three band pass filters are prepared, but may be increased according to the resolution of frequency analysis.

Note that the cut-off frequency changing means 7 does not always determine the noise characteristics based only on the noise signal input from the noise detecting microphone 1. FIG. 12 shows that when a device that generates noise is known, the cut-off frequency changing means discriminates the noise characteristic based on the information on the operating state of the noise generating device, and the cut-off frequency change signal is used as the high-frequency component attenuating means. It is an active noise control device to be input to. Compared with the configuration shown in FIG. 2, FIG. 12 includes a noise generating device 8 and a noise generating device operating state detecting unit 9, and a cutoff frequency changing unit 7 receives a signal from the noise generating device operating state detecting unit 9. This is a configuration. Since the noise control operation is the same as that shown in FIG. 2, the noise discrimination method of the cutoff frequency changing means 7 will be described. For example, when noise is generated by the rotation of a motor included in the noise generating device 8, the generated noise fluctuates at a frequency indicating a peak level in proportion to the motor rotation number as shown in FIG. Therefore, the noise generating device operating state detecting means 9 detects the motor rotational speed N inside the noise generating equipment 8 and inputs the motor rotational speed information to the cutoff frequency changing means 7. On the other hand, the cut-off frequency changing means 7 stores a relationship H between the motor rotation speed N and the generated noise peak frequency f _max as shown in (Expression 4) in advance.

The cut-off frequency changing means 7 inputs a predetermined signal for changing the cut-off frequency f _C of C ₂ to the high-frequency component attenuating means 5 by using (Equation 2) and (Equation 4). For example, the noise can be reduced at a frequency at which the noise shows a peak level.

In the case where the noise generating device 8 is a device such as a vacuum cleaner or an air conditioner in which the user can arbitrarily select an operation mode from several prepared operation modes, or a device in which the operation mode is automatically switched. Knows the peak frequency of the noise characteristics generated according to the operation mode. FIG. 14 shows the noise characteristics generated from the noise generating device 8 in which three operation modes of a strong mode, a medium mode, and a weak mode are prepared. For the three operation modes, the peak frequency of the generated noise varies as f ₁ , f ₂ , and f ₃ . The noise generating device operating state detecting means 9 sends the type of the operating mode to the cut-off frequency changing means 7. The cut-off frequency changing means 7 stores Δf ₁ , Δf ₂ , Δf ₃ satisfying (Equation 2) for f ₁ , f ₂ , f ₃ , and Δf according to the input operation mode information _{It is} only necessary to input ₁ , Δf ₂ , Δf ₃ to the high-frequency component attenuation means 5.

  In addition, as shown in FIG. 15, the structure which does not input the output signal of the microphone 1 for noise detection or the noise generation apparatus driving | running state detection means 9 to the cutoff frequency change means 7 may be sufficient. In the configuration shown in FIG. 15, the user who installs the active noise control device in the noise environment can arbitrarily control the noise by changing the cutoff frequency of the high frequency component attenuation means 5 using the cutoff frequency changing means 7 as an input interface. The frequency can be changed.

  As shown in FIG. 16, when a plurality of active noise control devices are used in combination, the cut-off frequency changing means 7 may be shared. In the configuration shown in FIG. 16, the cut-off frequency changing means 7 uses the output signal of the noise detecting microphone 1a to calculate the cut-off frequency of the high-frequency component attenuating means constituting the control device 3a calculated based on the method described above. Is output. The control characteristics of the high-frequency component attenuating means constituting the control device 3a are updated so that the noise can be continuously reduced based on the input cutoff frequency signal. This cut-off frequency signal is also input to the control devices 3b to 3n, and the high-frequency component attenuation means is updated to an appropriate cut-off frequency as in the case of the control device 3a. If such a configuration is used, only one cut-off frequency changing means 7 needs to be prepared in spite of using a plurality of active noise control devices, and the circuit scale can be reduced.

  With the above operation, it is possible to automatically change the processing characteristics of the active noise control device following changes in the frequency characteristics of noise, and to obtain a reduction effect for noises of various frequencies.

(Embodiment 2)
FIG. 17 shows an active noise control apparatus according to the second embodiment. FIG. 17 shows an active noise control device that can always keep the amplification factor of the inverting amplification means at an appropriate value so that the active noise control device can operate stably and obtain a noise reduction effect. In FIG. 17, there is no cutoff frequency changing means compared to the configuration shown in FIG. 2, a feedback gain changing means 10 is added, and the feedback gain changing means 10 receives a signal from the noise detecting microphone 1 and inverts amplifying means. 6 is a configuration for outputting a gain setting signal. Since the basic operation of the noise control is the same as that shown in FIG. 2, the operation of the feedback gain changing means 10 will be described. FIG. 18 shows a calculation algorithm of the gain setting signal that is input to the inverting amplification unit 6 by the feedback gain changing unit 10.

First, the active noise control device does not supply power to the control device 3, that is, power is supplied only to the noise detection microphone 1 and the feedback gain changing means 10 without performing a control operation (start). The noise signal detected by the noise detecting microphone 1 is input to the feedback gain changing means 10 and the power spectrum S _off is calculated. S _off is stored in a memory in the feedback gain changing means 10. Next, power is supplied to the control device 3 to start the control operation. Maximum of feedback gain changing means 10 the power spectrum _{S on} the noise signal inputted from the noise detecting microphone 1, the difference spectrum between the _{S off} stored in the memory _S off _{-S on} the difference spectrum _S off _{-S on} Values and minimum values are calculated. S _on , S _off , and S _off -S _on are shown in FIG. At this time, if | maximum value | ≦ | minimum value |, it is considered that the active noise control device oscillates unstablely, and power supply to the control device 3 is stopped. When the amplification factor of the inverting amplification means 6 at that time is _Gn , the feedback gain changing means 10

After the gain setting signal is input to the inverting amplification means 6 with the new gain as the new gain, the power supply to the control device 3 starts again. Δg ₁ (> 0) can be arbitrarily designed, but if it is too small, unstable oscillation is not improved. On the other hand, in the case of | maximum value |> | minimum value |, the magnitudes of the maximum value and the desired noise reduction amount a are compared. At this time, when the maximum value ≧ a, it is considered that the noise reduction effect satisfies the control specification, and the feedback gain changing means 10 does not input the gain setting signal to the inverting amplification means 6 and the control operation is continued as it is. . On the other hand, if the maximum value <a,

Is a new gain, and the feedback gain changing means 10 inputs the gain setting signal to the signal inversion amplifying means 6. Δg ₂ (> 0) can be arbitrarily designed, but if it is too large, unstable oscillation occurs. Thereafter, the maximum value and the minimum value of the frequency characteristics S _on , S _off -S _on , and S _off -S _on of the noise signal are calculated again. In the case of | maximum value | ≦ | minimum value |, after power supply to the control device 3 is stopped,

Is a new gain, and the feedback gain changing means 10 inputs the gain setting signal to the inverting amplification means 6. Δg ₃ (> 0) can be arbitrarily designed, but if it is too small, unstable oscillation is not improved. Here, G _n-1 indicates the amplification factor set in the inverting amplification means 6 before the gain G _n is changed to the current amplification factor G _n . Thereafter, power supply to the control device 3 is started again, and _Son is calculated. On the other hand, in the case of | maximum value |> | minimum value |, the process proceeds again to the step of determining whether the noise reduction effect satisfies the control specification.

  With the above calculation algorithm, the active noise control apparatus shown in FIG. 17 can always keep the amplification factor of the inverting amplification means at an appropriate value so as to perform a stable and noise-reducing operation.

In the active noise control apparatus shown in FIG. 17, the inverting amplification means can be realized with a circuit configuration as shown in FIG. In the analog amplifier of FIG. 20, the amplification factor of the output signal V ₂ with respect to the input signal V ₁ is expressed by the following equation.

The amplification factor can be continuously adjusted by adjusting the semi-fixed resistor R ₂ from the equation (8).

  It should be noted that the active noise control device stability determination unit of the gain setting signal calculation algorithm shown in FIG. 18 is used as the stability determination means, and the configuration shown in FIG. 21 allows the user to visually observe the stability of the active noise control device. At the same time, the control operation can be automatically stopped when an unstable oscillation state occurs. FIG. 21 shows a configuration in which the feedback gain changing means 10 is deleted from the active noise control apparatus shown in FIG. 17 and a stability determining means 75 and a determination result displaying means 76 are added. The basic operation of the noise control is the same as the configuration shown in FIG. 2, and the stability determination means 75 determines the stability of the active noise control device according to the algorithm shown in FIG. And control OFF. The discrimination result is input to the discrimination result display means 76, and can be confirmed by the user by display means such as an LED.

  In the active noise control apparatus shown in FIG. 17, it has been described that the gain of the inverting amplifier 6 is continuously variable by the feedback gain changing unit 10, but a plurality of amplifier circuits for realizing a predetermined gain are prepared. In addition, the gain can be automatically selected by the feedback gain changing means 10 or can be arbitrarily selected by the user.

  As shown in FIG. 23, the feedback gain changing means 10 may be shared when a plurality of active noise control devices are used in combination. In the configuration of FIG. 23, the output signals of the noise detection microphones 1 a to 1 n constituting each active noise control device are input to the feedback gain changing means 10. The feedback gain changing means 10 maintains a proper feedback gain so as to continuously obtain a noise reduction effect by performing stability determination on the signal indicating the maximum level among the input signals based on the algorithm described above. By this operation, the stability of the active noise control device having a large noise signal level is always maintained, so that the interference of the oscillating sound with other active noise control devices is suppressed, and the entire system using a plurality of active noise control devices is suppressed. Stability is improved.

(Embodiment 3)
FIG. 24 shows an active noise control apparatus according to the third embodiment. FIG. 24 shows the gain flattening of the open-loop transfer function in a predetermined frequency range by changing the transfer function of the control device according to the fluctuation of the speaker transfer function in order to make the active noise control device operate stably and to obtain a noise reduction effect. This is an active noise control device that retains the characteristics. 24 does not have a reverse characteristic correction unit as compared with the configuration shown in FIG. 2, and includes a first reverse characteristic correction unit 41 and a first reverse characteristic correction unit 41 that are units for changing a reverse characteristic correction unit and a correction coefficient for each predetermined frequency range. Correction coefficient changing means 71, second reverse characteristic correcting means 42, second correction coefficient changing means 72, third reverse characteristic correcting means 43, third correction coefficient changing means 73, control device input switching device 11, and signal generating device 12 The transfer function calculation device 13 is added. The operation of the configuration shown in FIG. 24 will be described below.

  The active noise control device has two operation modes depending on the signal input / output setting of the control device input switching device 11. First, a case where 1 and 3 are connected among the three terminals (1, 2, 3) inside the control device input switching device 11 and a signal input from the noise detection microphone 1 is input to the control device 3 will be described. A noise signal detected by the noise detection microphone 1 is input to the control device 3 and the transfer function calculation device 13 via the control device input switching device 11. A signal input to the control device 3 is processed by the first reverse characteristic correction means 41, the second reverse characteristic correction means 42, the third reverse characteristic correction means 43, the high frequency component attenuation means 5, and the reverse amplification means 6 to attenuate the noise. Such a control signal is corrected. The control signal is input to the control sound speaker 2 and radiated as a control sound to interfere with noise.

FIG. 25 shows speaker transfer function gain characteristics of the active noise control device, and transfer function gain characteristics of the first reverse characteristic correction unit 41, the second reverse characteristic correction unit 42, and the third reverse characteristic correction unit 43. The first inverse characteristic correcting means 41 is designed to realize the inverse characteristic of the peak characteristic of the frequency f ₀ out of the peak dip of the speaker transfer function gain characteristic. Similarly, the second reverse characteristic correction unit 42 and the third reverse characteristic correction unit 43 are designed to realize the reverse characteristics of the peak dip characteristics of the frequencies f ₁ and f ₂ among the peak dip of the speaker transfer function gain characteristics. Yes. That is, similarly to the inverse characteristic correction unit 4 in the active noise control apparatus shown in FIG. 2, the gain characteristic of the open loop transfer function is corrected flatly in a predetermined frequency range by these inverse characteristic correction units 41 to 43. The high frequency component attenuating means 5 is designed to have a cut-off frequency so as to attenuate a frequency component in which the phase of the open loop transfer function is positive at high frequencies. The inverting amplification means 6 is appropriately designed so that the active noise control device does not oscillate in an unstable manner. On the other hand, a noise signal is also input from the noise detection microphone 1 to the transfer function calculation device 13. The transfer function calculation device 13 performs frequency analysis of the noise signal and inputs the analysis result to the cutoff frequency changing means 7. The cut-off frequency changing means 7 cuts the high-frequency component attenuating means 5 based on the frequency characteristics of the input noise signal so as to reduce the noise at the frequency at which the noise shows a peak, as described in the first embodiment. Change the off frequency.

  Next, the case where 1 and 2 are connected among the three terminals (1, 2, 3) inside the control device input switching device 11 and a signal input from the signal generator 12 is input to the control device 3 will be described. The signal generator 12 outputs a broadband signal such as white noise and is input to the control device input switching device 11 and the transfer function calculation device 13. The broadband signal input to the control device input switching device 11 is processed by the inverse characteristic correction means 41 to 43, the high frequency component attenuation means 5 and the inverting amplification means 6 in the control device 3 and input to the control sound speaker 2. The noise detection microphone 1 detects a wideband processing signal radiated from the control sound speaker 2 and inputs it to the transfer function calculation device 13. The transfer function calculation device 13 is a transfer function from the input of the control device 3 to the output of the noise detection microphone 1 based on the signal input from the signal generation device 12 and the signal input from the noise detection microphone 1, that is, Calculate the open loop transfer function of the active noise controller. FIG. 26 shows the difference between the speaker transfer function gain characteristic of the active noise control apparatus and the transfer function gain characteristic of the control apparatus 3, the measurement open loop characteristic and the design open loop characteristic, and the measurement open loop characteristic and the design open loop characteristic. Here, the design open-loop characteristic indicates the open-loop transfer function gain characteristic at the time of controller design obtained from the speaker transfer function and the control-device transfer function, and the measured open-loop characteristic indicates the measured open-loop transfer function gain characteristic. . The transfer function calculation device 13 calculates the difference between the design open loop characteristic stored in advance and the measurement open loop characteristic. The measurement open loop characteristic varies to a characteristic different from the design open loop characteristic due to the influence of the device characteristics over time, the sound transmission characteristics from the control sound speaker 2 to the noise detection microphone 1 over time, and the like. Alternatively, when a plurality of active noise control devices of the same design are used, there is a difference in the open loop characteristics of each device due to variations in component characteristics. The transfer function calculation device 13 inputs information regarding the calculated open loop characteristic difference to each correction coefficient changing means 71 to 73. Each of the correction coefficient changing units 71 to 73 inputs a coefficient change signal to each of the inverse characteristic correcting units 41 to 43 so that the open loop characteristic difference is eliminated based on the input open loop characteristic difference. Hereinafter, the operations of the correction coefficient changing units 71 to 73 and the inverse characteristic correcting units 41 to 43 for eliminating the open loop characteristic difference shown in FIG. 26 will be described.

FIG. 26 shows that since there is a slight error in the peak dip reverse characteristic correction at the frequency f ₀ , there is an open loop characteristic difference between the gain difference α dB and the frequency β Hz. At this time, each correction coefficient changing means 71 to 73 has an open loop characteristic difference information matrix.

Is entered. Similarly, for example, when there is an error in the peak-dip inverse characteristic correction of the frequency f ₁ is error information enters the second column of the [Delta] H. The first correction coefficient changing means 71 sets the coefficient change vector ΔC according to the following (Expression 10), the second correction coefficient changing means 72 according to the following (Expression 11), and the third correction coefficient changing means 73 according to the following (Expression 12). decide.

  The correction coefficient changing units 71 to 73 change the processing coefficients of the inverse characteristic correction units 41 to 43 in accordance with the coefficient change vector ΔC input from the transfer function calculation device. FIG. 27 shows the signal input / output relationship between the first correction coefficient changing means 71 and the first reverse characteristic correcting means 41. In the first inverse characteristic correcting means 41, the signal input from the control device input switching device 11 is input to the adder 16 and the band pass filter 14. The signal processed by the band pass filter 14 is processed by the amplifier 15 and then input to the adder 16 where it is added to the output signal of the control device input switching device 11. In addition, a signal for changing the processing coefficient is input from the first correction coefficient changing means 71 to the band pass filter 14 and the amplifier 15.

  Next, the processing coefficient changing method of the first inverse characteristic correcting means 41 will be described. From (Equation 9) and (Equation 10), the first correction coefficient changing unit 71 changes the characteristic of the first inverse characteristic correcting unit 41 by −ΔC = [− αdB−βHz]. The band pass filter 14 constituting the first inverse characteristic correcting means 41 can be realized by the circuit configuration shown in FIG. 28, for example. The amplifier 15 can be realized by a circuit similar to the analog amplifier of FIG. 20 described in the second embodiment, for example. In the analog band pass filter 14 shown in FIG. 28, the center frequency of the pass band is expressed by the following equation.

The variation ΔR ₂ of the semi-fixed resistor R ₂ in FIG. 20 when the characteristic of the amplifier 15 is changed by −α dB satisfies the following expression from (Equation 8).

  (Equation 14) is modified to obtain the following equation.

The fluctuation amount ΔR ₅ of the semi-fixed resistor R ₅ when the center frequency of the band pass filter 14 is changed by −β Hz satisfies the following expression from (Equation 13).

(Number 15), it is given to the semi-fixed resistor _{R 5} of the semi-fixed resistor _{R 2} and the band-pass filter 14 of the semi-fixed resistance value variation [Delta] R _2, the [Delta] R _5, each amplifier 15 to satisfy the equation (16), The difference between the current open loop characteristics and the design open loop characteristics can be eliminated. As a method of changing the resistance value of the semi-fixed resistor, for example, there is a method of mechanically rotating the semi-fixed knob based on the changed value. FIG. 29 shows the result of changing the transfer function gain characteristic of the first inverse characteristic correcting means 41 in this way.

  By the operation described above, the active noise control device shown in FIG. 24 has a function of correcting the open loop transfer function to the transfer function at the time of design, so that the control performance at the time of design is maintained.

Note that the terminals of the control device input switching device 11 may be switched arbitrarily or automatically by the user. However, when 1 and 2 of 3 terminals (1, 2 and 3) are connected to perform an open loop characteristic difference correction operation, the noise detecting microphone 1 is radiated from the control sound speaker 2 when there is noise. Since noise is detected in addition to sound, the SN of the signal input to the transfer function calculation device 13 is deteriorated and an accurate open loop transfer function cannot be calculated. Therefore, as shown in the flow of FIG. 30, if the terminal connection of the control device input switching device 11 is automatically switched according to the magnitude of the output signal level of the noise detecting microphone 1 and the predetermined signal level N ₀ , Since the open loop characteristic difference can be reliably reduced based on an accurate open loop transfer function during the open loop characteristic difference correction operation, a noise reduction effect can be continuously obtained.

  In addition, as shown in FIG. 31, the structure which does not input the output signal of each correction coefficient change means 71-73 to each reverse characteristic correction means 41-43 may be sufficient. In the configuration shown in FIG. 31, a display 74 for inputting open-loop characteristic difference information calculated by the transfer function calculation device 13 is added. The display 74 displays an open loop characteristic difference based on the input information. The user continuously changes the characteristics of the inverse characteristic correction means 41 to 43 using the correction coefficient changing means 71 to 73 as input interfaces so that the open loop characteristic difference displayed on the display 74 becomes zero. Noise reduction effect can be obtained.

  Further, as shown in FIG. 32, the cut-off frequency changing means 7 is deleted and the feedback gain changing means 10 is added, and the output signal of the transfer function calculating device 13 is sent to the correction coefficient changing means 71 to 73 and the feedback gain changing means 10. If the configuration is such that the input and the output signal of the feedback gain changing means 10 is inputted to the inverting amplification means 6, it is possible to suppress the difference in the open loop characteristics of the active noise control device and to continuously and stably operate so as not to cause unstable oscillation. Is possible. Of course, the cut-off frequency changing means is not deleted, and the output signal of the transfer function calculating device 13 is inputted to the correction coefficient changing means 71 to 73, the cut-off frequency changing means 7 and the feedback gain changing means 10, and the cut-off frequency is changed. If the configuration is such that the output signal of the changing means 7 is input to the high frequency component attenuating means 5 and the output signal of the feedback gain changing means 10 is input to the inverting amplifying means 6, the active noise control device is continuously prevented from unstable oscillation. In addition to stable operation, it is possible to reduce noise at a frequency where the noise level shows a peak.

  In the configuration of FIG. 24, there are three inverse characteristic correction means and three correction coefficient changing means, but it is not always necessary to have three.

  33, when a plurality of active noise control devices are used in combination, the cutoff frequency changing means 7, the signal generating device 12, the transfer function calculating device 13, and the first to third correction coefficient changing means 71 to 73 are used. It is also possible to adopt a configuration in which The configuration shown in FIG. 33 is a configuration in which two active noise control devices shown in FIG. 24 are used in combination, and the cutoff frequency changing means 7, the signal generating device 12, and the transfer function calculating device 13 of one active noise control device. Except for the first to third correction coefficient changing means 71 to 73, a transfer function calculation device input switching device 77 for inputting the output signal of each noise detection microphone and an output signal of each transfer function calculation device input switching device are input. The first correction coefficient changing means output switching devices 81a and 81b, the second correction coefficient changing means output switching devices 82a and 82b, which receive the output signals of the adder 78 and the first to third correction coefficient changing means 71 to 73, and the third The correction coefficient changing means output switching devices 83a and 83b are added.

  First, the input / output relationship in the transfer function measurement mode will be described. When measuring a transfer function of a noise control device (hereinafter referred to as an active noise control device B) comprising a noise detection microphone 1b, a control sound speaker 2b, and a control device 3b, the transfer function calculation device input switching device 77b is a noise detection microphone. The output signal 1b is input to the adder 78. The control device input switching device 11b inputs the output signal of the signal generator 12 to the control device 3b. The first to third correction coefficient changing means output switching devices 81b to 83b input the output signals of the first correction coefficient changing means 71 to 73 to the first to third reverse characteristic correcting means 41b to 43b. On the other hand, the noise control device (hereinafter referred to as active noise control device A) comprising the noise detection microphone 1a, the control sound speaker 2a, and the control device 3a does not operate. At this time, the signal generation device 12 inputs a broadband signal such as white noise to the transfer function calculation device 13 and the control device input switching devices 11a and 11b. The transfer function calculating device 13 calculates the transfer function of the active noise control device B from the signal input from the signal generating device 12 and the signal input from the adder 78, and sends it to the first to third correction coefficient changing means 71 to 73. An open loop characteristic difference information matrix expressed by (Equation 8) is input. The first to third correction coefficient changing means output switching devices 81b to 83b use the open loop characteristic difference information matrix to eliminate the difference between the active noise control device B and the open loop characteristic at the time of design based on the method described above. In the same manner, the processing coefficients of the first to third inverse characteristic correcting means 41b to 43b are changed.

  Next, the input / output relationship during the control operation will be described. The control device input switching devices 11a and 11b input the output signals of the noise detection microphones 1a and 1b to the control devices 3a and 3b. The transfer function calculation device input switching devices 77a and 77b input the output signals of the noise detection microphones 1a and 1b to the adder 78. The adder 78 inputs the output signals of the transfer function calculation device input switching devices 77 a and 77 b to the transfer function calculation device 13. The transfer function calculation device 13 simply operates as a frequency analyzer of the input signal, analyzes the frequency of the output signal of the adder, and reduces the noise at the frequency at which the noise shows a peak, as described in the first embodiment. The cutoff frequency of the high frequency component attenuation means 5a, 5b is changed. At this time, the first to third correction coefficient changing means output switching devices 81a to 83a and 81b to 83b are connected to 1 and 3 among the three internal terminals (1, 2, 3) so that the first to third reverse characteristic corrections are performed. No signal is input to the means 41a to 43a and 41b to 43b.

  As described above, the active noise control device according to the present invention is used for the purpose of automatically changing the control processing characteristics following the fluctuation of the noise characteristics and the speaker transfer function, and continuously obtaining noise reduction, etc. can do.

The figure which shows the conventional feedback type active noise control device The figure which shows the active noise control apparatus in Embodiment 1 of this invention The figure which shows the open loop transfer function gain characteristic after correction | amendment by a speaker transfer function gain characteristic and a reverse characteristic correction means gain characteristic The figure which shows the open loop transfer function phase characteristic in case a control apparatus is comprised only with a reverse characteristic correction means. The figure which shows an open-loop transfer function phase characteristic in case a control apparatus is comprised with a reverse characteristic correction means and an inversion amplification means. The figure which shows the open loop transfer function characteristic in case a control apparatus is comprised with a reverse characteristic correction means, an inversion amplification means, and a high frequency component attenuation means. The figure which shows the characteristic of the high frequency component attenuation means The figure which shows the frequency analysis result of the microphone signal for noise detection Diagram showing noise reduction effect The figure which shows the analog circuit which actualizes the high frequency component attenuation means The figure which shows the structure in the case of implement | achieving a cutoff frequency change means in an analog circuit in Embodiment 1 of this invention. In Embodiment 1 of this invention, the figure which shows an active noise control apparatus in the case of changing a high frequency component attenuation | damping means cutoff frequency with reference to a noise generation apparatus driving | running state A diagram showing the relationship between the noise-generating motor speed and noise characteristics A diagram showing the relationship between noise generator operation mode and noise characteristics The figure which shows the active noise control apparatus in Embodiment 1 of this invention when a user changes the high frequency component attenuation means cutoff frequency arbitrarily In Embodiment 1 of this invention, it is a figure which shows the structure in the case of using a cut-off frequency change means in common, when using a plurality of active noise control apparatuses. The figure which shows the active noise control apparatus in Embodiment 2 of this invention. Diagram showing calculation algorithm of feedback gain setting signal Figure showing the power spectrum of a noise signal The figure which shows the analog circuit which actualizes the inverting amplification means The figure which shows an active noise control apparatus in the case of providing the stability determination means and the determination result display means in Embodiment 2 of this invention. Diagram showing stability discrimination algorithm The figure which shows the structure in the case of using a common feedback gain change means when using in combination with two or more active noise control apparatuses in Embodiment 2 of this invention. The figure which shows the active noise control apparatus in Embodiment 3 of this invention. The figure which shows the gain characteristic of the 1st-3rd reverse characteristic correction means Diagram showing the difference between the measured open loop gain characteristics and the open loop gain characteristics when designing the controller The figure which shows the signal input / output relationship of a 1st correction coefficient change means and a 1st reverse characteristic correction means. Diagram showing an analog circuit that implements a bandpass filter The figure which shows the characteristic of the 1st reverse characteristic correction means changed by the 1st correction coefficient change means The figure which shows the terminal connection switching algorithm of a control apparatus input switching device The figure which shows the active noise control apparatus in Embodiment 3 of this invention when a user changes a reverse characteristic correction means characteristic arbitrarily. The figure which shows an active noise control apparatus in Embodiment 3 of this invention in the case of maintaining a feedback gain appropriately so that a control apparatus may operate | move stably. In Embodiment 3 of this invention, when using combining multiple active noise control apparatuses, the figure which shows the structure in the case of sharing a signal generator, a transfer function calculation apparatus, and the 1st-3rd correction coefficient change means.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1a-1n Noise detection microphone 2,2a-2n Control sound speaker 3,3a-3n Control device 4 Inverse characteristic correction means 5,5a, 5b High frequency component attenuation means 6,6a, 6b Inversion amplification means 7 Cut-off Frequency changing means 8 Noise generating equipment 9 Noise generating equipment operating state detecting means 10 Feedback gain changing means 11, 11a, 11b Control device input switching device 12 Signal generating device 13 Transfer function calculating device 14 Band pass filter 15 Amplifier 16 Adder 30 Duct 31 Noise Source 32 Error Detection Unit 33 Secondary Sound Generation Filter 34 Secondary Sound Radiation Speaker 35 Fixed-Signal Signal Processing Unit 36 Inverting Unit 37 Inverse Characteristic Signal Processing Unit 38 Low Frequency Passing Signal Processing Unit 41, 41a, 41b First Inverse Characteristic correction means 42, 42a, 42b Second reverse characteristic correction means 43, 43a, 43b Third Inverse characteristic correction means 71 First correction coefficient changing means 72 Second correction coefficient changing means 73 Third correction coefficient changing means 74 Display 75 Stability determining means 76 Determination result displaying means 77a, 77b Transfer function calculating device input switching device 78 Adder 81a , 81b First correction coefficient changing means output switching device 82a, 82b Second correction coefficient changing means output switching device 83a, 83b Third correction coefficient changing means output switching device 84 Signal level comparison section 85 Cut-off frequency coefficient calculation section 86 Band pass Filter A
87 Band pass filter B
88 Band pass filter C

Claims (21)

Noise detection means;
Control characteristic adjusting means for inputting an output signal of the noise detecting means;
Control means for inputting the output signal of the noise detecting means and the output signal of the control characteristic adjusting means;
An active noise control device including a speaker for inputting an output signal of the control means;
The control characteristic adjusting means outputs a processing coefficient signal of the control means based on the output signal of the noise detecting means,
The active noise control apparatus characterized in that the control means outputs a signal that attenuates the output signal of the noise detection means based on the processing coefficient signal output from the control characteristic adjustment means. Noise detection means;
A noise generating device operating state detecting means;
Control characteristic adjusting means for inputting an output signal of the noise generating equipment operating state detecting means;
Control means for inputting the output signal of the noise detecting means and the output signal of the control characteristic adjusting means;
An active noise control device including a speaker for inputting an output signal of the control means;
The control characteristic adjustment means outputs a processing coefficient signal of the control means based on the output signal of the noise generating equipment operating state detection means,
The active noise control apparatus characterized in that the control means outputs a signal that attenuates the output signal of the noise detection means based on the processing coefficient signal output from the control characteristic adjustment means. The control means comprises reverse characteristic correction means for correcting and outputting an input signal with the gain reverse characteristic of the speaker, high frequency component attenuation means for attenuating and outputting a high frequency component of the input signal, and signal inversion amplification means. The active noise control device according to claim 1 or 2. 4. The active noise control device according to claim 3, wherein the inverse characteristic correcting means comprises at least one band component correcting means capable of adjusting a passing amount of a predetermined frequency band component of the input signal. 5. The active noise control according to claim 3, wherein the control means has a variable cut-off frequency of the high-frequency component attenuation means determined based on a processing coefficient signal output from the control characteristic adjustment means. apparatus. 6. The active noise control apparatus according to claim 5, wherein said control means outputs a signal that attenuates a signal having a high frequency component among the output signals of said noise detection means. 5. The active noise control apparatus according to claim 3, wherein the control means has a variable gain of the signal inversion amplification means determined based on a processing coefficient signal output from the control characteristic adjustment means. . The control characteristic adjusting means determines whether the output signal of the noise detecting means is stable or unstable, and
A determination result display unit for inputting an output signal of the determination unit;
The active noise control apparatus according to claim 7, wherein the determination result display unit displays the determination result of the determination unit by a predetermined method. 9. The active noise control apparatus according to claim 8, wherein the control unit stops the control operation when the determination unit determines that the output signal of the noise detection unit oscillates unstablely. When the control unit determines that the output signal of the noise detection unit oscillates unstablely, the control unit stops the control operation,
9. The active noise control apparatus according to claim 8, wherein the signal inversion amplification means is changed to an amplification factor so that the control means does not oscillate in an unstable manner, and the control means restarts the control operation. Noise detection means;
Signal generating means;
Control means input switching means for inputting the output signal of the noise detection means and the output signal of the signal generation means;
Control characteristic adjusting means for inputting the output signal of the noise detecting means and the output signal of the signal generating means;
Control means for inputting the output signal of the control means input switching means and the output signal of the control characteristic adjusting means;
An active noise control device including a speaker for inputting an output signal of the control means;
When the control means input switching means outputs the output signal of the signal generation means, the control characteristic adjustment means calculates a transfer function from the input of the control means to the output of the noise detection means,
When the control means input switching means outputs the output signal of the noise detection means, the control characteristic adjustment means outputs the processing coefficient signal of the control means based on the output signal of the noise detection means,
The active noise control apparatus characterized in that the control means outputs a signal that attenuates the output signal of the control means input switching means based on the processing coefficient signal output from the control characteristic adjusting means. When the control means input switching means outputs the output signal of the signal generating means, the control characteristic adjusting means has a flat transfer function gain characteristic from the input of the control means to the output of the noise detecting means in a predetermined frequency band. 12. The active noise control apparatus according to claim 11, wherein a processing coefficient signal is output as follows. An active noise control apparatus comprising M (M is an integer of 2 or more) active noise control apparatuses according to any one of claims 1 to 10. 14. The active noise control apparatus according to claim 13, wherein a processing coefficient signal output from at least one of the control characteristic adjusting means is different from a processing coefficient signal output from the other control characteristic adjusting means. The control characteristic adjusting means constituting the M-1 active noise control devices excluding the first of the M active noise control devices is omitted,
In addition to the processing coefficient signal output from the control characteristic adjusting means constituting the first active noise control device being input to the control means constituting the first active noise control device,
Furthermore, it is input to the control means constituting the M-1 active noise control devices except the first,
The control means configuring the M active noise control devices is configured to control the M active noise control devices based on a processing coefficient signal output from the control characteristic adjusting unit configuring the first active noise control device. 14. The active noise control apparatus according to claim 13, wherein a signal that attenuates an output signal of the noise detecting means is provided. The control characteristic adjusting means constituting the M-1 active noise control devices excluding the first of the M active noise control devices is omitted,
In the control characteristic adjusting means constituting the first active noise control device,
In addition to the output signals of the noise detection means constituting the first active noise control device, the output signals of the noise detection means constituting the M-1 active noise control devices except for the first are further inputted. ,
The control characteristic adjusting means determines whether the output signal of the noise detecting means is stable or unstable, and
A determination result display unit for inputting an output signal of the determination unit;
The active noise control apparatus according to claim 13, wherein the determination result display unit displays a determination result of the determination unit by a predetermined method. 17. The active noise control apparatus according to claim 16, wherein the control unit that the determination unit determines that the output signal of the noise detection unit oscillates unstablely stops the control operation. The control means that the determination unit determines that the output signal of the noise detection means oscillates unstablely, after the control operation is stopped,
17. The active noise control according to claim 16, wherein the signal inverting amplification means constituting the control means is changed to an amplification factor such that the control means does not oscillate in an unstable manner, and the control means restarts the control operation. apparatus. At least two noise detection means;
Signal generating means;
At least two or more control means input switching means for inputting the output signals of the signal generating means and the output signals of the noise detecting means;
At least two or more control characteristic adjusting means input switching means for inputting each output signal of the noise detecting means;
An adder for inputting each output signal of the control characteristic adjusting means input switching means;
Control characteristic adjusting means for inputting the output signal of the signal generating means and the adder;
At least two or more control means for inputting an output signal of the control characteristic adjusting means and an output signal of each of the control means input switching means;
An active noise control device comprising at least two or more speakers each receiving an output signal of each of the control means;
When the control means input switching means outputs the output signal of the signal generating means, the control characteristic adjusting means input switching means connected to the control means input switching means outputs the output signal of the noise detection means,
Calculate a transfer function from the input of the control means connected to the control means input switching means to the output of the noise detection means connected to the control means input switching means,
The control characteristic adjustment means input switching means not connected to the control means input switching means does not output the output signal of the noise detection means,
When all the control means input switching means output the output signal of the noise detection means, the control characteristic adjustment means input switching means outputs the output signal of the noise detection means,
The control characteristic adjusting means outputs a processing coefficient signal of the control means based on the output signal of the adder,
The active noise control apparatus characterized in that the control means outputs a signal that attenuates the output signal of the control means input switching means connected based on the processing coefficient signal output from the control characteristic adjusting means. When the control means input switching means outputs the output signal of the signal generating means, the control characteristic adjusting means is configured to input the control means from an input of the control means connected to the control means input switching means in a predetermined frequency band. 20. The active noise control apparatus according to claim 19, wherein a processing coefficient signal is output so that a transfer function gain characteristic up to an output of the noise detecting means connected to the switching means becomes flat. 21. The active noise control apparatus according to claim 1, wherein the control unit and the control characteristic adjusting unit are formed of an analog circuit.

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