JPH0659689A - Noise control device - Google Patents

Abstract

PURPOSE:To easily set the amplification of amplifiers for plural speekers and plural of microphones in pairs therewith and achieve a short converging time of noise frequency, if it is wide. CONSTITUTION:A noise control device is provided with plural speekers 1-1, 1-2,..., 1-n set up in a space where noise elimination is required to form compensation sound, plural microphones 2-1, 2-2,..., 2-n set up corresponding to them to detect an error signal as a result of sound residing in noise and the compensation sound, an applicable filter 5 to form a compensation signal which forms the compensation sound, speeker amplifiers 3-1, 3-2,..., 3-n to amplify the compensation signal, microphone amplifiers 4-l, 4-2,..., 4-n to amplify the error signal from the respective microphones and a gain adjusting means 12 to adjust the amplification of the respective amplifiers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention eliminates noise by outputting a compensating signal for noise and anti-phase equal sound pressure from a speaker.
Particularly, in the present invention, it is easy to set the amplification degree of the amplifier of the plurality of speakers and the plurality of microphones paired therewith,
The present invention also relates to a noise control device that shortens the convergence time when the noise frequency is wide.

[0002]

2. Description of the Related Art Conventionally, a passive muffler such as a muffler has been used to reduce noise generated from an internal combustion engine, etc., but improvements have been made in terms of size, muffling characteristics and the like. On the other hand, the noise generated from the sound source and the opposite phase
An active noise control device has been proposed which outputs a compensation sound of equal sound pressure from a speaker to cancel noise. By the way, the frequency characteristic or stability of the active noise control device itself is not sufficient, and its practical application has been delayed. However, as a result of the recent development of signal processing technology for processing digital signals and expansion of the frequency range to be handled, many practical noise control devices have been proposed (for example, Japanese Patent Laid-Open No. 63-311396).

By the way, in a conventional digital signal processing device of a noise control device, FIR (Finite Impulse Response) is used.
Although the e) type adaptive filter is used, the filter coefficient Ck (n + 1) of this time in this adaptive filter satisfies the convergence condition by the least squares with respect to the previous filter coefficient Ck (n). Updated to, for example,
It is formed.

Ck (n + 1) = Ck (n) + α × Se (n) / Sr (n) (1) where k is the filter coefficient number, α is the convergence coefficient, and Se is
(n) is an error signal, and Sr (n) is a reference signal, that is, a noise signal. Here, the convergence coefficient α has a characteristic that when the value is large, the convergence is fast but the optimum value is difficult to find, and when the convergence coefficient is small, the convergence is accurate at the optimum point but it takes time to converge.
In this case, the error signal Se (n) is detected by the microphone and amplified by the amplifier with a predetermined amplification degree, and the predetermined amplification degree and the convergence coefficient are closely related. That is, when the amplification degree is large, the convergence coefficient is apparently large, and when the amplification degree is small, the convergence coefficient is apparently small.

The compensating signal for canceling noise is formed by an adaptive filter, and the amplification degree of the speaker amplifier used for converting the compensating signal into the compensating sound has an appropriate value corresponding to the noise level. Is set to. If the compensation sound is distorted with respect to a noise signal of a large level where the amplification level is too large, or if the amplification level is too small to secure a compensation sound of an appropriate level for a noise signal of a small level, This is to prevent appropriate convergence from becoming difficult due to the relationship with the convergence coefficient α.

[0006]

By the way, in the conventional digital signal processing device of the noise control device, the adaptive filter becomes large in size and converges as a multi-channel for controlling a plurality of pairs of speakers and microphones by one adaptive filter. It is prevented that the time becomes large (because the number k of the filter coefficient becomes large in the above equation). However, in this multi-channel, it is necessary to adjust the amplification degree of the amplifier for each speaker and microphone, and the level of the error signal depends on this adjustment, and as a result, it is closely related to the convergence condition of the filter coefficient. Therefore, there is a problem that the adjustment is complicated. In addition, when the frequency of noise changes widely, it is difficult to obtain appropriate accuracy if the processing scale of the adaptive filter is increased. Therefore, the convergence time of the filter coefficient becomes long, but the convergence time of the filter coefficient is further increased. There is a problem that it should be small.

Therefore, the present invention facilitates the adjustment of the amplification factor of the multi-channel speaker and the microphone by one adaptive filter, and can appropriately control the convergence time of the filter coefficient even when the noise changes in a wide band frequency. The purpose is to provide a noise control device.

[0008]

In order to solve the above problems, the present invention provides a noise control device for forming a compensating sound of noise and anti-phase equal sound pressure, a plurality of speakers, a plurality of microphones and an adaptive filter. ,, speaker amplifier, microphone amplifier, and gain adjusting means. The plurality of speakers are installed in a space to be muted to form the compensation sound.

The plurality of microphones are installed corresponding to the plurality of speakers and detect an error signal which is a residual sound of the noise and the compensation sound. The adaptive filter forms a compensation signal for forming a compensation sound. The speaker amplifier switches and inputs the compensation signal from the adaptive filter, amplifies the compensation signal, and drives each of the speakers.

The microphone amplifier amplifies the error signal from the microphone, and the amplified error signal is switched to be returned to the adaptive filter. The gain adjusting means detects a level of a compensation signal which is an input signal of the speaker amplifier and corresponds to a noise level, and adjusts each amplification degree according to the level of the compensation signal. The amplification degree of the microphone amplifier is adjusted according to the level.

The gain adjusting means may set the amplification factor of the microphone amplifier in proportion to the level of the compensation signal, and the amplification factor of the microphone amplifier in inverse proportion to the level of the compensation signal. It may be set, or may be changed to another amplification degree when the difference signal detected by the microphone amplifier is larger than a predetermined value. Further, the gain adjusting means, by an instruction from the outside,
The amplification degree of the microphone amplifier may be set.

Further, the noise control device includes a first band filter for limiting a frequency band of the compensation signal when the compensation signal from the adaptive filter is switched and output to each of the speakers, and a plurality of front filters. A second band-pass filter for limiting the frequency band of the error signal when the error signal from the microphone is switched back to the adaptive filter.

Further, the noise control device detects the frequency of noise, analyzes the frequency, and changes the first band-pass filter based on the result of the analysis of the frequency, and the second band filter. A frequency adjusting unit for adjusting the frequency band of the variable band filter may be provided. The frequency adjusting means may set a frequency characteristic similar to that of noise in the first and second variable band filters.

The frequency adjusting means may set a frequency characteristic opposite to the frequency characteristic of noise in the first and second variable band filters.

[0015]

According to the noise control device of the present invention, the compensation sound is formed by the plurality of speakers installed in the space to be silenced. An error signal, which is a residual sound of the noise and the compensation sound, is detected by the plurality of microphones installed corresponding to the plurality of speakers. The adaptive filter forms a compensation signal for forming the compensation sound. The compensating signal from the adaptive filter is switched by the speaker amplifier and then input, and the compensating signal is amplified to drive the speakers. The error signals from the microphones are amplified by the microphone amplifiers, and the amplified error signals are switched to return to the adaptive filter. The gain adjusting means detects the level of a compensating signal which is the input signal of the speaker amplifier and corresponds to the level of the noise signal, and adjusts the amplification degree of each in accordance with the level of the compensating signal. The amplification factor of the microphone amplifier is adjusted in consideration of the convergence coefficient of the filter coefficient. Therefore, the amplification degree is easily set.
The gain adjusting means sets the amplification factor of the microphone amplifier in proportion to the level of the compensation signal, and sets the amplification factor of the microphone amplifier in inverse proportion to the level of the compensation signal. Accordingly, it becomes possible to freely change, and when the difference signal detected by the microphone amplifier is larger than a predetermined value, it is changed to another amplification degree and the adjustment can be automatically changed. According to this configuration, the desired noise control effect can be obtained by the gain adjusting means setting the amplification degree of the microphone amplifier according to an instruction from the outside.

Further, the noise control device includes a first band-pass filter for limiting a frequency band of the compensation signal when the compensation signal from the adaptive filter is switched and output to each of the speakers, and each of the plurality of filters. By providing a second band-pass filter that limits the frequency band of the error signal when the error signal from the microphone is switched back to the adaptive filter, the adaptive filter performs signal processing on all frequency bands for noise. Therefore, the filter scale of signal processing can be reduced and the convergence time can be shortened. The frequency adjusting means detects the frequency of noise, analyzes the frequency, and adjusts the frequency bands of the first variable band filter and the second variable band filter based on the result of the analysis of the frequency. By doing so, it becomes possible to cope with changes in the frequency of noise. By the frequency adjusting means, for example, a frequency characteristic similar to the frequency characteristic of noise is set in the first and second variable band filters, or a frequency characteristic opposite to the frequency characteristic of noise is set in the first and second variable bands. By being set in the filter, it becomes possible to respond freely to changes in the frequency of noise.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a noise control device according to a first embodiment of the present invention. The noise control device shown in the figure has a plurality of speakers 1-1 installed in a space where noise should be eliminated,
1-2, ..., 1-n and the noise from the speakers 1-1, 1-
Microphones 2-1, 2-2, ... Detecting the residual sound erased by the compensation sound from 2, ..., 1-n as an error signal
2-n and speaker amplifier 3 for adjusting the amplification degree of signals for driving the speakers 1-1, 1-2, ..., 1-n.
-1, 3-2, ..., 3-n and the microphone 2-1,
In order to form microphone amplifiers 4-1, 4-2, ..., 4-n for amplifying the signals from 2-2 ,. Adaptive filter 5 composed of FIR (Finite Impulse Response), coefficient updating means 6 for updating the filter coefficient of the adaptive filter 5, and the compensation signal from the adaptive filter 5 is converted from a digital signal to an analog signal. Then, the compensation signal via the interface 7 for converting the analog signal to the coefficient updating means 6 into a digital signal and the interface from the adaptive filter 5 are supplied to the speaker amplifiers 3-1 and 3-2. , ..., 3-n for time-divisional output, and microphone amplifiers 4-1, 4-2 interlocking with the switch means 8
..., switch means 9 for time-dividing each error signal from 4-n and outputting to the coefficient updating means 6 via the interface 7.
And a level detecting means 10 provided on the input side of the switch means 8 for detecting the level of each signal to the speaker amplifiers 3-1, 3-2, ..., 3-n, and installed on the output side of the switch means 9. Microphone amplifiers 4-1, 4-2,
,, Level detecting means 11 for detecting the level of each error signal from 4-n, and the speaker amplifiers 3-1, 3-2, ... based on the signals from the level detecting means 10 and 11.
3-n and microphone amplifiers 4-1, 4-2,
..., and a gain adjusting means 12 for adjusting the amplification degree of 4-n. The coefficient updating means 6 may form the filter coefficient by the above-mentioned equation (1).

Next, details of the gain adjusting means 12 will be described. FIG. 2 is a diagram showing the configuration of the gain adjusting means of FIG. The gain adjusting means 12 shown in the figure is composed of a microcomputer or the like, and based on the level of the compensation signal of the adaptive filter 5 from the level detecting means 10, speaker amplifiers 3-1, 3-2, ..., 3-n. Gain (amplification degree)
The following is provided with the gain forming means 121 of the speaker amplifier for forming.

FIG. 3 is a diagram showing the relationship between the compensation signal level and the amplification degree of the speaker amplifier. As shown in this figure,
The gain forming means 121 of the speaker amplifier forms an amplification degree that is inversely proportional to the level of the compensation signal. Therefore, when the level of the compensation signal is small, the amplification degree is large, and conversely, when the level of the compensation signal is small, the amplification degree is set small.

The gain adjusting means 12 is the level detecting means 1
For a microphone for forming a gain (amplification degree) to the microphone amplifiers 4-1, 4-2, ..., 4-n based on the level of the compensation signal of the adaptive filter 5 from 0 as follows. The gain forming means 122 of the amplifier is provided. FIG. 4 is a diagram showing the relationship between the compensation signal level and the amplification degree of the microphone amplifier. As shown in FIG. 7A, the gain forming means 122 of the microphone amplifier is used.
Have a plurality of amplification degree relationships proportional to the compensation signal level. The level detecting means 11 is used by switching based on the level of the error signal detected by the level detecting means 11. Therefore, the microphone amplifiers 4-1 and 4- are proportional to the noise level.
By setting gains of 2, ..., 4-n, the effect of accelerating the convergence time occurs at a place where the noise level is high.

As shown in FIG. 3B, the gain forming means 122 of the microphone amplifier has a plurality of amplification degree relationships inversely proportional to the compensation signal level. It is the same as described above that it is switched and used based on the level of the error signal detected by the level detection means 11. Therefore, the microphone amplifier 4 is inversely proportional to the noise level.
Since the gains of 1, 4-2, ..., 4-n are set, the effect that the noise effect is uniform not only at the high noise level but also at the low noise level is produced.

Further, the gain adjusting means 12 sets the amplification degree of the gain forming means 121 of each speaker amplifier and the gain forming means 122 of the microphone amplifier to each speaker amplifier 3-1, 3-2, ..., 3-n, and the microphone. .., 4-n for setting the amplification degree and the like 123 and 124. The operation of these amplification degree setting means 123 and 124 will be described.

FIG. 5 is a flow chart for explaining the first example of setting the amplification degree of the speaker amplifier and the microphone amplifier. As shown in the figure, in the setting means 123 and 124 such as the amplification degree, in step 1, first the ordinal number j
Set = 1. In steps 2, 3, 4, and 5, the level detection means 1 is synchronized with the switching of the switch means 8 and 9.
Based on the compensation level of 0 (substantially noise level), the amplification degrees of the speaker amplifiers 3-1, 3-2, ..., 3-n and the microphone amplifiers 4-1, 4-2 ,. It is stored using the relationship shown in FIG. 3 and the relationship shown in FIG.

In steps 6 and 7, the stored amplification factors are set in the speaker amplifiers 3-1, 3-2, ..., 3-n and the microphone amplifiers 4-1, 4-2 ,. To be done. In step 8, the error signal is detected by the post-setting level detection means 11 in steps 6 and 7, and it is determined whether it is less than or equal to the predetermined value δo. If the error signal is smaller than this predetermined value, it can be determined that the above setting is good. However, when the error signal is larger than the predetermined value δo, the process returns to step 1 and is reset again by using another relationship of different gradient of FIG.

FIG. 6 is a flow chart for explaining a second example of setting the amplification degree of the speaker amplifier and the microphone amplifier. As shown in the figure, in step 11, it is judged whether or not the switching means 8 and 9 are switched. In steps 12 and 13, if there is switching in step 11, the corresponding speaker amplifiers 3-1, 3-2,
The gain forming means 121 of the speaker amplifier is shown at 3-n.
3, the amplification factor of the speaker amplifier shown in FIG. 3 is extracted and set by the amplification factor setting means 123, and the corresponding microphone amplifiers 4-1, 4-2 ,.
Then, the amplification degree of the microphone as shown in FIG. 4B is taken out from the gain forming means 122 of the microphone amplifier and set by the setting means 123 of the amplification degree or the like.

At step 14, it is judged whether the error signal level of the level detecting means 11 is smaller than a predetermined value δo. If the error signal is smaller than this predetermined value, it can be determined that the above setting is good. However, the error signal is
If it is greater than o, return to step 13
The setting is performed again by using the different relationship of the different gradient of (b). FIG. 7 is a flow chart showing a third example of setting the amplification degree of the speaker amplifier and the microphone amplifier. As shown in the figure, in step 21, it is judged whether or not there is an external instruction, for example, an instruction by key input.

In steps 22 and 23, speaker amplifiers 3-1, 3-2, whose amplification degree is to be changed by key input,
..., 3-n, microphone amplifiers 4-1, 4-2,
, 4-n are designated, and the amplification degree of the designated amplifier is given to each, and the designated amplifier is set through the amplification degree setting means 123 and 124. In step 24, it is judged whether the error signal level of the level detecting means 11 is smaller than the predetermined value δo. If the error signal is smaller than this predetermined value, it can be determined that the above setting is good. However, when the error signal is larger than the predetermined value δo, the process returns to step 21 and a new instruction is obtained.

Therefore, according to this embodiment, it is possible to freely perform different optimizations for each channel in the multi-channel. FIG. 8 shows the second aspect of the present invention.
It is a figure which shows the principal part of the noise control apparatus which concerns on the Example of this.
The noise control device shown in this figure is composed of the switch means 8 and the speaker amplifiers 3-1, 3-2, ..., 3 in the first embodiment.
Variable band filters 2 provided respectively between -n and
0-, 20-2, ..., 20-n, and variable band filters 21-1, respectively provided between the switch means 9 and the microphone amplifiers 4-1, 4-2 ,.
21-2, ..., 21-n, a microphone 23 installed in a place where the influence of the compensation sound is small, an amplifier 24 for amplifying a signal of the microphone 23, and the amplifier 24.
Frequency analyzing means 25 for frequency-analyzing the signal of FIG. 1, and variable band filters 20-1, 20-2, ..., 20-n, variable band filters 21-1, 21-, based on the frequency analysis result from the frequency analyzing means 25 .., 21-n, and filter adjusting means 26 for changing the cut frequency.

The frequency analyzer 25 may be a fast Fourier transform (FFT) means, and a plurality of band-pass filters are provided to extract frequency information from the levels of the plurality of band-pass filters. May be. In the noise control device having the above configuration, the variable band filters 20-1, 20-2, ..., 20-n and the variable band filters 21-1, 21-2 ,. If so, the frequency band may be fixed around the target band irrespective of the frequency analysis device 25.

The frequency analysis device 25 analyzes the frequency of noise from the microphone 23 and obtains the same frequency characteristic as the frequency characteristic thereof through the filter adjusting means 26.
Variable band filters 20-1, 20-2, ..., 20-
n, variable band filters 21-1, 21-2, ..., 21-
It may be set to n. As a result, it is possible to exert the effect of noise control centering on a high noise band.

Further, the frequency analysis means 25 analyzes the frequency of the noise from the microphone 23, and the frequency characteristics of the characteristics opposite to the frequency characteristics thereof are passed through the filter adjustment means 26 to the variable band filters 20-1, 20-. 2, ..., 20
-N, variable band filters 21-1, 21-2, ..., 21
It may be set to -n. This makes it possible to exert a flat noise control effect over the entire selected band regardless of the noise level.

The case of multi-channel has been described above, but the same effect can be obtained even in the case of one channel. Therefore, since the frequency components to be reduced are limited to the entire frequency band of noise, the adaptive filter 5
Can be reduced, which reduces the convergence time and improves responsiveness.

[0033]

As described above, according to the present invention, each speaker and each microphone in a multi-channel noise control device including a plurality of speakers and the plurality of microphones installed corresponding to these speakers. Since the amplification degree of the amplifier and is automatically adjusted, the adjustment is easy, and further, only the necessary part of the total frequency of noise is automatically extracted for signal processing. Becomes smaller and the convergence time is shortened.

[Brief description of drawings]

FIG. 1 is a diagram showing a noise control device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a gain adjusting means of FIG.

FIG. 3 is a diagram showing a relationship between a compensation signal level and an amplification degree of a speaker amplifier.

FIG. 4 is a diagram showing a relationship between a compensation signal level and an amplification degree of a microphone amplifier.

FIG. 5 is a flowchart illustrating a first example of setting the amplification degree of a speaker amplifier and a microphone amplifier.

FIG. 6 is a flowchart illustrating a second example of setting the amplification degree of a speaker amplifier and a microphone amplifier.

FIG. 7 is a flowchart showing a third example of setting the amplification degree of a speaker amplifier and a microphone amplifier.

FIG. 8 is a diagram showing a main part of a noise control device according to a second embodiment of the present invention.

[Explanation of symbols]

 1-1, 1-2, ..., 1-n ... Speakers 2-1, 2-2, ..., 2-n ... Microphones 3-1, 3-2, ..., 3-n ... Speaker amplifier 4-1 , 4-2, ..., 4-n ... Amplifier for microphone 5 ... Adaptive filter 6 ... Coefficient updating means 7 ... Interface 8, 9 ... Switch means 10, 11 ... Level detecting means 12 ... Gain adjusting means 20-1, 20 -, ..., 20-n ... Variable band filter 21-1, 21-2, ..., 21-n ... Variable band filter 23 ... Microphone 24 ... Amplifier 25 ... Frequency analysis means 26 ... Filter adjustment means 121 ... Speaker amplifier Gain forming means 122 ... Gain forming means of microphone amplifier

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiro Sakiyama 1-2-2 Goshodori, Hyogo-ku, Kobe, Hyogo Prefecture Inside Fujitsu Ten Limited

Claims (10)

[Claims] 1. A noise control device for forming a compensating sound having an anti-phase equal sound pressure with respect to noise, comprising: a plurality of speakers (1-1, 1-2, ...) Installed in a space to be silenced to form the compensating sound. 1-n) and a plurality of speakers installed corresponding to the plurality of speakers (1-1, 1-2, ..., 1-n) and detecting an error signal which is a residual sound of the noise and the compensation sound. Microphone (2-
1, 2-2, ..., 2-n), an adaptive filter (5) that forms a compensation signal for forming the compensation sound, and the compensation signal from the adaptive filter (5) is switched and input. Then, the compensation signal is amplified to amplify the speaker (1-1, 1).
-2, ..., 1-n) and speaker amplifiers (3-1, 3-2, ..., 3-n) respectively driving the microphones (2-1, 2-2, ..., 2-n). The amplifiers (4-1, 4-2, ..., 4) for amplifying the error signals from the respective amplifiers and switching the amplified error signals to be returned to the adaptive filter (5).
-N) and the speaker amplifier (3-1, 3-2, ..., 3-n)
Of the compensation signal corresponding to the noise level, the amplification degree of each is adjusted in accordance with the level of the compensation signal, and the microphone amplifier (4) is adjusted in accordance with the level of the compensation signal. -1, 4-2, ..., 4
-N) gain adjusting means (1) for adjusting the amplification degree respectively.
2) A noise control device comprising: 2. The gain adjusting means (12) sets the amplification degree of the microphone amplifiers (4-1, 4-2, ..., 4-n) in proportion to the level of the compensation signal. 1. The noise control device according to 1. 3. The gain adjusting means (12) sets the amplification degree of the microphone amplifiers (4-1, 4-2, ..., 4-n) in inverse proportion to the level of the compensation signal. Item 1. The noise control device according to item 1. 4. The gain adjusting means (12) comprises the microphone amplifiers (4-1, 4-2, ..., 4-n).
The noise control device according to claim 2 or 3, wherein when the difference signal detected by is larger than a predetermined value, the difference is changed to another amplification degree. 5. The gain adjusting means (12) receives the instruction from the outside, and the microphone amplifier (4-).
The amplification degree of 1, 4-2, ..., 4-n) is set.
The described noise control device. 6. A noise control device for forming a compensating sound having an anti-phase equal sound pressure to a noise, comprising: a plurality of speakers (1-1, 1-2, ...) Installed in a space to be silenced and forming the compensating sound. 1-n) and a plurality of speakers installed corresponding to the plurality of speakers (1-1, 1-2, ..., 1-n) and detecting an error signal which is a residual sound of the noise and the compensation sound. Microphone (2-
1, 2-2, ..., 2-n), an adaptive filter (5) that forms a compensation signal for forming the compensation sound, and a compensation signal from the adaptive filter (5) is switched to each A band filter (20-1, 20-2, ..., 20-n) that limits the frequency band of the compensation signal when outputting to the speakers (1-1, 1-2, ..., 1-n). , Each front plural microphones (2-1, 2-2, ..., 2-
n), the adaptive filter by switching the error signal (5)
And a bandpass filter (21-1, 21-2, ..., 21-n) that limits the frequency band of the error signal when returning to the noise control device. 7. A noise control device for forming a compensating sound having an anti-phase equal sound pressure with respect to noise, comprising: a plurality of speakers (1-1, 1-2, ...) Installed in a space to be silenced to form the compensating sound. 1-n) and a plurality of speakers installed corresponding to the plurality of speakers (1-1, 1-2, ..., 1-n) and detecting an error signal which is a residual sound of the noise and the compensation sound. Microphone (2-
1, 2-2, ..., 2-n), an adaptive filter (5) that forms a compensation signal for forming the compensation sound, and a compensation signal from the adaptive filter (5) is switched to each Variable band filter (20-1, 20-2, ..., 20-) that limits the frequency band of the compensation signal when outputting to the plurality of speakers (1-1, 1-2, ..., 1-n).
n) and each of the plurality of microphones (2-1, 2-2, ..., 2)
Variable band filters (21-1, 21-2, ..., 21) that limit the frequency band of the error signal when the error signal from (-n) is switched back to the adaptive filter (5).
-N), the frequency of noise is detected, this frequency is analyzed, and based on the result of the analysis of this frequency, the variable band filter (2
Frequency adjusting means (24, 25, 26) for adjusting the frequency band of the variable band filters (21-1, 21-2, ..., 21-n). A noise control device comprising: 8. The frequency adjusting means (24, 25, 2)
6) is a variable-band filter (20-1, 20-2, ..., 20-) having frequency characteristics similar to those of noise.
n), variable band filters (21-1, 21-2, ..., 2)
The noise control device according to claim 7, wherein the noise control device is set to 1-n). 9. The frequency adjusting means (24, 25, 2)
6) is a variable band filter (20-1, 20-2, ...
n), variable band filters (21-1, 21-2, ..., 2)
The noise control device according to claim 7, wherein the noise control device is set to 1-n). 10. A noise control device for forming a compensating sound having an anti-phase equal sound pressure with respect to noise, comprising: a plurality of speakers (1-1, 1-2, ...) Installed in a space to be silenced to form the compensating sound. 1-n) and a plurality of speakers installed corresponding to the plurality of speakers (1-1, 1-2, ..., 1-n) and detecting an error signal which is a residual sound of the noise and the compensation sound. Microphone (2-
1, 2-2, ..., 2-n), an adaptive filter (5) that forms a compensation signal for forming the compensation sound, and the compensation signal from the adaptive filter (5) is switched and input. Then, the compensation signal is amplified and the plurality of speakers (1-
, 1-2, ..., 1-n), speaker amplifiers (3-1, 3-2, ..., 3-n) for driving them, and the plurality of microphones (2-1, 2-2, …, 2-
n) amplifying the error signals respectively, and the amplified error signals are switched so that the adaptive filter (5)
Amplifier for microphone (4-1, 4-2,
..., 4-n) and the speaker amplifier (3-1, 3-2, ..., 3-n).
Of the input signal of the compensation signal corresponding to the level of the noise signal, the amplification degree of each is adjusted according to the level of the compensation signal, and the microphone amplifier ( 4-1, 4-2, ...
Gain adjusting means (12) for adjusting the amplification degree of 4-n) respectively, and the speaker amplifiers (3-1, 3-2, ..., 3-n).
Variable band filter (20) that limits the band of the input signal to
, 20-2, ..., 20-n) and the microphone amplifiers (4-1, 4-2, ..., 4)
-N) variable band filter (21-1, 21-2, ..., 21-n) that limits the band of the output signal, and detects the frequency of noise, analyzes this frequency, and The variable band filter (2
Frequency adjusting means (24, 25, 26) for adjusting the frequency band of the variable band filters (21-1, 21-2, ..., 21-n). A noise control device comprising: