JP2001092469A - Noise control device - Google Patents

Abstract

(57) [Summary] PROBLEM TO BE SOLVED: To surely reduce noise at a plurality of points away from a speaker with a simple configuration. SOLUTION: A noise signal detected by a microphone 1 arranged at a first control point which is a position where noise should be controlled has a same amplitude as the noise signal in a first control signal generation circuit 3a. An out-of-phase control signal is generated. And
A noise control sound based on the noise control signal is output to the first control point by the first speaker 2a. Also,
The noise signal is supplied to a second control signal generation circuit,
The control signal is processed into a control signal having the same amplitude and opposite phase as the noise at the second control point different from the control point. The noise control sound based on this control signal is output to the second control point by the second speaker 2b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise control device for actively reducing noise emitted from a noise source.

[0002]

2. Description of the Related Art In recent years, air conditioners, refrigerators, and the like using active noise control technology for reducing noise by interfering a noise control sound of a phase opposite to the noise generated from a motor or the like have been put into practical use. Is being transformed.

FIG. 22 shows an example of such a noise control device. This noise control device is configured to control noise emitted from a noise source 41 such as a motor at two different positions, and a first control point and a second control point which are respective noise control positions include: A first microphone 31a as a noise detector for detecting noise at each control point
And a second microphone 31b. The noise control device also includes a first speaker 32a that outputs a noise control sound to each of the first and second control points in order to reduce noise at the first control point and the second control point. Two speakers 32b are provided.

The noise signal detected by the first microphone 31a is supplied to a feedback-type first control signal generation circuit 3.
3a, the first control signal generation circuit 33
In a, a noise control signal having the same amplitude as the noise signal detected by the first microphone 31a and having the opposite phase is generated and output to the first speaker 32a.
The first speaker 32a includes a first control signal generation circuit 33a.
And outputs a noise control sound based on the noise control signal generated at the first control point.

The noise control signal output from the first speaker 32a interferes with the noise at the first control point, so that the noise at the first control point is reduced.

The noise signal detected by the second microphone 31b is supplied to a feedback-type second control signal generation circuit 33b, and in the second control signal generation circuit 33b, the noise signal is detected by the second microphone 31b. The detected noise signal generates a noise control signal having the same amplitude and opposite phase, and outputs the generated noise control signal to the second speaker 32b. The second speaker 32b outputs a noise control sound based on the noise control signal generated by the second control signal generation circuit 33b to the second control point.

The noise control signal output from the second speaker 32b interferes with the noise at the second control point, so that the noise at the second control point is reduced.

[0008]

In such a noise control device, the first speaker 32a is moved from the second control point so that the noise control sound output from the first speaker 32a does not affect the second control point. It is necessary to arrange them apart from each other, and similarly, the second control sound is output from the second speaker 32b so that the noise control sound is not affected at the first control point.
It is necessary to arrange the speaker 32b away from the first control point. For this purpose, the first control point and the second control point
It is necessary to install them at appropriate intervals. The first and second speakers 32a and 32b are configured to control only the vicinity of the first and second control points, respectively, so that the first and second speakers 32a and 32b are controlled.
It may not be possible to control the noise at positions away from a and 32b.

If the characteristics of the feedback control signal generating circuits 33a and 33b are independently set to control the noise at positions distant from the speakers 32a and 32b, the noise control output from the first speaker 32a is controlled. The out-of-band sound of the target interferes with the noise at the second control point, and the out-of-band sound of the noise control target output from the second speaker 32b interferes with the noise at the first control point, resulting in noise. Level may increase or new noise may occur.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a noise control device having a relatively simple configuration and capable of stably controlling noise at a plurality of positions. Is to do.

[0011]

According to the noise control apparatus of the present invention, at a first control point which is a position where noise is to be controlled,
A first noise detector arranged to detect noise at the first control point, and control of a noise signal detected by the first noise detector from the noise signal detected by the first noise detector to have the same amplitude and opposite phase as the noise signal. A first control signal generation circuit for generating a signal, a first speaker for outputting a noise control sound based on the noise control signal generated by the first control signal generation circuit to a first control point, and controlling the noise A second control signal generation unit that generates a control signal having the same amplitude and opposite phase as noise at a second control point different from the first control point from a noise signal detected by the noise detector. A second speaker that outputs a noise control sound based on a noise control signal generated by the second control signal generation circuit to a second control point;
It is characterized by having.

The noise to be controlled is periodic noise or pseudo-periodic noise.

[0013] The output of the noise detector is limited to a predetermined frequency band.

[0014] The first control point is located near the maximum amplitude of the standing wave in the space where the standing wave exists.

At the second control point, a second noise detector for detecting noise at the control point is arranged, and the second control signal generation circuit generates an error detected by the second noise detector. The output control signal is adjusted based on the signal.

The second control signal generation circuit has a digital filter configuration having an adaptive filter.

The second control signal generation circuit adjusts a control signal to be output using a noise signal detected by a first noise detector arranged at a first control point as an error signal.

The first control signal generation circuit adjusts a control signal to be output using a noise signal detected by a first noise detector arranged at a first control point as an error signal.

The first control signal generation circuit has a digital filter configuration having an adaptive filter.

Further, the noise control device of the present invention is arranged so as to detect the noise at a position where the noise characteristic of the noise at the first control point which is the position where the noise is to be controlled can be obtained. A first noise detector, a first control signal generation circuit that generates a control signal having the same amplitude as the noise signal and an opposite phase from the noise signal detected by the first noise detector, A first speaker that outputs a noise control sound based on a noise control signal generated by a first control signal generation circuit to a first control point, and a position where noise is to be controlled, wherein the first control point is A second control signal generating circuit that generates a control signal having the same amplitude and opposite phase as noise at a different second control point from the noise signal detected by the noise detector; and a second control signal generating circuit. Noise based on the generated noise control signal A second speaker to output a control tone to the second control point, characterized by including the.

The controlled noise is periodic noise or pseudo-periodic noise.

The output of the noise detector is limited to a predetermined frequency band.

The first control point is located near the maximum amplitude of the standing wave in the space where the standing wave exists.

At the second control point, a second noise detector for detecting noise at the control point is arranged, and the second control signal generation circuit generates an error detected by the second noise detector. The output control signal is adjusted based on the signal.

The second control signal generation circuit has a digital filter configuration having an adaptive filter.

A third noise detector for detecting noise at the control point is disposed at the first control point, and the second control signal generation circuit includes a third noise detector disposed at the first control point. The output control signal is adjusted using the noise signal detected by the detector as an error signal.

The first control signal generation circuit adjusts a control signal to be output using a noise signal detected by a third noise detector disposed at a first control point as an error signal.

The first control signal generation circuit has a digital filter configuration having an adaptive filter.

[0029]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing an example of an embodiment of a noise control device according to the present invention. This noise control device controls noise emitted from a noise source 41 such as a motor at two different positions, and a first control point which is one of the noise control positions has a noise at the control point. Is detected, a microphone 1 as a noise detector is arranged. The noise control device also includes a first speaker 2a that outputs a noise control sound to each of the first and second control points in order to reduce noise at the first control point and the second control point A. 2nd speaker 2
b are provided respectively.

The noise signal detected by the microphone 1 is supplied to a feedback-type first control signal generation circuit 3a and a feed-forward-type second control signal generation circuit 3b. The feedback-type first control signal generation circuit 3a generates a noise control signal having the same amplitude as the noise signal detected by the microphone 1 and having the opposite phase, and outputs the generated noise control signal to the first speaker 2a. It has become. The first speaker 2a outputs a noise control sound based on the noise control signal generated by the first control signal generation circuit 3a to the first control point.

The feedforward type second control signal generation circuit 3b converts the noise signal detected by the microphone 1 into a noise control signal having the same amplitude as the noise at the second control point and having the opposite phase. And outputs it to the second speaker 2b. The second speaker 2b outputs a noise control sound based on the noise control signal generated by the second control signal generation circuit 3b to the second control point.

In the noise control device having such a configuration, the noise signal detected by the microphone 1 is divided into the first and second noise signals.
Are provided to the respective control signal generation circuits 3a and 3b. Feedback-type first control signal generation circuit 3
In a, a microphone 1 as a noise detector is installed at a first control point, and a noise control signal is generated so as to reduce noise detected by the microphone 1, and a noise based on the noise control signal is generated. The control sound is the first speaker 2a
Is output to the first control point where the microphone 1 is arranged.

As described above, the feedback control is performed at the first control point. Therefore, within the frequency band where the signal is processed by the feedback control signal generating circuit 3a, the noise at the first control point is reduced. All will be reduced. Therefore, the noise control signal output from the second speaker 2b arranged to control the second control point A different from the first control point is detected by the microphone 1 arranged at the first control point. However, the noise control signal is also reduced. Thereby, the microphone 1
Is provided, the noise can be reduced in a state where the influence of the noise control sound from the speaker 2b that outputs the noise control signal to the second control point A is eliminated.

On the other hand, in the feedforward type second control signal generation circuit 3b, the control point different from the control point where the microphone 1 is arranged is based on the noise signal detected by the microphone 1 which is a noise detector. A noise control signal of the control point A is generated, and thus feedforward control is performed. The feedforward type control signal generating circuit 3b includes a feedback type second control signal generating circuit 3b.
According to the noise control signal generated by the control signal generation circuit 3a, the noise control sound output from the first speaker 2a is also detected by the microphone 1; The characteristic is set so that the noise from the noise source 41 is simultaneously reduced at the control point A. Thus, at the second control point A, the first speaker 2
The noise control sound from a can also be reduced at the same time.

The characteristics of the feedforward type second control signal generation circuit 3b will be described more specifically. In the state where the noise control sound based on the noise control signal generated by the feedback-type first control signal generation circuit 3a is output from the first speaker 2a, as shown in FIG.
The noise 100 detected by the microphone 1 arranged at the first control point is reduced as indicated by a broken line 101.

On the other hand, at the second control point A, as shown in FIG. 3, the noise 200 increases as indicated by a broken line 202 due to the noise control sound 103 output from the speaker 2a. However, depending on the conditions, the noise level may not increase. When the noise level at the second control point A increases, the noise control sound based on the noise control signal output from the feedforward type control signal generation circuit 3b is output from the second speaker 2b,
As shown in FIG. 4, at the second control point A, the noise 202 increased by the synthesis of the noise control sound output from the first speaker 2a and the noise from the noise source 41 is changed to a dashed line 2
01, it can be reduced.

In this case, as shown in FIG. 5, when compared with the noise 200 of only the noise source 41 at the second control point A,
When the noise level is reduced as shown by the broken line 201, the difference between the two becomes the noise control effect at the second control point A.

At the first control point where the microphone 1 is provided, as shown in FIG. 6, due to the noise control sound 203 output from the second speaker 2b, the noise 100
May increase as shown by the dashed line 102. However, depending on the conditions, such an increase in the noise level may not occur. Even if the noise level increases at the first control point, the feedback-type control signal generation circuit 3a
However, since a noise control signal for controlling all the noise signals detected by the microphone 1 is generated, the noise control signal is reduced as shown by a broken line 104 in FIG. Dashed line 104 is the first
The noise control effect at the control point is shown, and the difference between the increased noise level 102 and the reduced noise level 104 is equal to the difference between the noise level 100 and the reduced noise level 101 shown in FIG. I have. In practice, the noise level 100 shown in FIG.
The difference from 4 is a noise control effect due to detection of a noise signal by the microphone 1.

As described above, the first control point at which the microphone 1 is provided and the second control point A different from the first control point
In the above, the noise from the noise source 41 is reduced while eliminating the influence of each noise control sound by the noise control sounds output from the first and second speakers 2a and 2b for each control point. As a result, the noise at each of the plurality of control points can be reliably reduced.

In the present embodiment, the noise emitted from the noise source 41 is the noise emitted from the noise source 41 such as a motor, but the characteristics are not described in detail. The noise emitted from the noise source 41 is
In the case of periodic noise or pseudo-periodic noise such as mechanical rotation noise of a motor or the like or siren noise, the causality (time order) of the feedforward type second control signal generation circuit 3b does not matter. Microphone 1 for noise and second speaker 2b for second control point A
There is no time constraint on the arrangement relationship between the microphone 1 and the second speaker 2b. Therefore, the microphone 1 and the second speaker 2b can be arranged more freely than in the case of controlling random noise.

Further, when the noise emitted from the noise source 41 is random noise, as shown in FIG. 8, the detection signal of the microphone 1 is changed by a band limiting filter (band pass filter, hereinafter referred to as BPF) 4. In a state limited to the frequency to be controlled, a configuration may be adopted in which the frequency is given to each of the first and second control signal generation circuits 3a and 3b. This reduces random noise as well as periodic noise.

As shown in FIG. 9, when a standing wave 11 is generated in the space 10, the microphone 1 is moved to the maximum amplitude of the standing wave 11 in order to control the standing wave 11. It may be installed near the part. This makes it possible to control the standing wave as in the case of the periodic noise.

FIG. 10 is a block diagram showing another embodiment of the noise control device according to the present invention. In this noise control device, a first microphone 1a that is a noise detector is disposed at a first control point, and a second microphone that is an error detector is disposed at a second control point different from the first control point. The microphone 1b is arranged. The noise signal detected by the first microphone 1a is supplied to a feedback-type first control signal generation circuit 3a and a feedforward-type second control signal generation circuit 3b. Then, the noise control signal generated by the first control signal generation circuit 3a is given to a first speaker 2a that outputs a noise control sound to a first microphone 1a arranged at a first control point.

A noise signal detected by the second microphone 1b is given as an error detection signal to the feedforward type second control signal generation circuit 3b, and the noise signal detected by the first microphone 1a A noise control signal is generated based on the error signal detected by the second microphone 1b. Then, the generated noise control signal is output to a speaker 2b that outputs a noise control sound to a second control point provided with the second microphone 1b.

In the noise control device having such a configuration, the first
The noise signal detected by the microphone 1a is provided to the first control signal generation circuit 3a and the second control signal generation circuit 3b, respectively. In the feedback-type first control signal generation circuit 3a, the noise control sound output from the first speaker 2a provided for the first control point has the same amplitude as the noise signal detected by the first microphone 1a. The noise control signal is generated so that the noise control signals are in opposite phases. The generated noise control signal is output to the first speaker 2a, and the first microphone 2a is output from the first speaker 2a.
A noise control sound that interferes with the noise detected at is output. Thereby, noise at the first control point is reduced.

In the feedforward type second control signal generating circuit 3b, the noise signal detected by the first microphone 1a located at the first control point is replaced by the noise signal detected by the second microphone 1b. Are processed to have the same amplitude and opposite phase to generate a noise control signal. Then, the generated noise control signal is output to the second speaker 2b provided for the second control point.

As described above, the feedforward type second
In the control signal generation circuit 3b, while monitoring the error signal detected by the second microphone 1b, the control characteristics are determined so that the error signal is reduced, and the noise signal detected by the first microphone 1a is determined. It is processed. Then, a noise control sound based on the noise control signal output from the second control signal generation circuit 3b is output from the second speaker 2b. Thereby, the noise detected by the second microphone 1b is reduced by the noise control sound at the second control point.

The noise control signal generated from the feedback type first control signal generation circuit 3a is, like the noise control device shown in FIG. 1, a frequency band for signal processing in the feedback type first control signal generation circuit 3a. Within the first
All noise signals detected by the microphone 1a are reduced. Therefore, the noise control sound output from the second speaker 2b and detected by the first microphone 1a is also reduced. As a result, noise detected by the first microphone 1a is transmitted to the second speaker 2
The influence of the noise control sound output from b is reduced.

The feedforward-type second control signal generating circuit 3b arranges a first microphone 1a as a noise detector and a second microphone 1b as an error detector at different control points, respectively. On the basis of the noise signal detected at 1a, a noise control signal for controlling the noise at the second control point where the second microphone 1b is arranged is generated, and the feedforward control is performed. The feedforward-type second control signal generation circuit 3b also controls the first microphone 2 for the noise control sound output from the first speaker 2a by the noise control signal generated by the feedback-type first control signal generation circuit 3a. 1a, the first speaker 2
The characteristic may be such that the noise control sound output from a and the noise from the noise source 41 are simultaneously reduced. With such characteristics, at the control point where the second microphone 1b is arranged, the noise control sound output from the first speaker 2a can be reduced together with the noise from the noise source 41.

In the present embodiment as well, the characteristics of the noise emitted from the noise source are not particularly limited, but include mechanical rotation noise such as motor noise, periodic noise such as siren noise, or pseudo-periodic noise. There is no problem with noise. Further, in the case of periodic noise or pseudo-periodic noise, the causality of the second control signal generation circuit 3b of the feedforward type (time order) does not matter, so the first control point disposed at the first control point. A microphone 1a,
The position of the second speaker 2b and the second microphone 1b with respect to the second control point is not limited in terms of time, and can be installed more freely than random noise.

Further, when the noise is random noise,
As in the device shown in FIG. 8, the detection signals of the first microphone 1a and the second microphone 1b are
If it is configured to output to each of the control signal generation circuits 3a and 3b only at the frequency to be controlled, respectively, the noise can be handled in the same manner as periodic noise.

When a standing wave is generated in the space, the first microphone 1a is operated similarly to the apparatus shown in FIG.
By placing the second microphone 1b near the maximum amplitude of the sound pressure of the standing wave, the standing wave can be controlled.

FIG. 11 is a block diagram showing still another embodiment of the noise control device according to the present invention. In this noise control device, a noise signal detected by a first microphone 1a disposed at a first control point is supplied to a feedback-type first control signal generation circuit 3a, and a feedforward-type second control signal is provided. The noise signal detected by the second microphone 1b disposed at the second control point is also supplied to the feed-forward second control signal generation circuit 3b.
The feedforward type second control signal generation circuit 3 b has a digital filter configuration including the adaptive filter 5.

The second control signal generating circuit 3b having the digital filter configuration outputs the output of the first microphone 1a located at the first control point via the subtractor 9 to the adaptive filter (AF).
IR) 5. The coefficients of the adaptive filter 5 are
Updated by the LMS calculator 7. The detection signal of the second microphone 1b located at the second control point is given to the LMS calculator 7. The noise signal output from the first microphone 1a is also supplied to the LMS calculator 7 via the subtractor 9 and the Fx filter 6. The output of the adaptive filter 5 is provided to a subtractor 9 via a feedback canceller (FC) 8 and also to a second speaker 2b.

In the noise control device having such a configuration, the first
The noise signal detected by the microphone 1a is supplied to a feedback-type first control signal generation circuit 3a and a feed-forward-type second control signal generation circuit 3b. In the feedback type control signal generation circuit 3a,
The noise signal detected by the first microphone 1a is
Signal processing is performed so that the noise and the noise detected by the microphone 1a have the same amplitude and opposite phases. Thereby, the noise detected by the first microphone 1a arranged at the first control point interferes with the noise control sound output from the first speaker 2a and is reduced.

In the feedforward type second control signal generating circuit 3b, the noise signal output from the first microphone 1a is subjected to signal processing in the adaptive filter 5. In the adaptive filter 5, the first microphone 1a
From the noise detected by the second microphone 1b is processed so as to have the same amplitude and opposite phase.
This is a noise control signal. The generated noise control signal is output to the second speaker 2b, and a noise control sound based on the noise control signal is output from the second speaker 2b.

The noise control sound output from the second speaker 2b interferes with the noise detected by the second microphone 1b, and the residual component thereof is detected as an error signal by the second microphone 1b and subjected to the LMS calculation. Input to the device 7. On the other hand, the first microphone 1a can also use the second speaker 2
b, the noise control sound output from
The signal detected by the microphone 1a includes a noise source 41
And the noise control signal output from the second speaker 2b.

In order to remove a noise control signal included in the signal detected by the first microphone 1a, the output of the adaptive filter 5 is input to the feedback canceller 8,
The output of the feedback canceller 8 is subtracted from the output of the first microphone 1a by a subtracter 9. In the feedback canceller 8, an approximate value of the transfer characteristic C3 from the second speaker 2b to the first microphone 1a is set as a coefficient. Thereby, the first microphone 1a
From the noise signal detected by the above, a signal from which the component of the noise control sound by the second speaker 2b has been removed is obtained.

The output of the subtractor 9 is input to the Fx filter 6. The Fx filter 6 includes a second speaker 2b
The approximate value of the transfer characteristic C4 from the second microphone 1b to the second microphone 1b is set as a coefficient, and the noise signal and this coefficient are convolution-operated, and the operation result is output to the LMS calculator 7. In the LMS calculator 7, based on the output signal from the Fx filter 6 and the error signal from the second microphone 1 b, the adaptive filter 5 is controlled to minimize the error signal detected by the second microphone 1 b. The coefficient is updated. Thereby, the noise signal detected by the second microphone 1b is reduced.

Such an algorithm is called Filtered-x L
The MS algorithm (for example, see B. Widrow an
d S. Stearns, `` Adaptive Signal Processing '' (Prentice
-Hall, Englewood Cliffs, NJ, 1985)).

As described above, the feedforward type second
By using the adaptive filter 5 in the control signal generation circuit 3b, the characteristics of the second control signal generation circuit 3b are
Since it can be changed one by one based on the error signal detected by the second microphone 1b, it is possible to easily cope with fluctuations in the noise level and the like.

The use of the adaptive filter 5 in the feedforward type second control signal generation circuit 3b allows the second control signal generation circuit 3b to reduce noise detected by the second microphone 1b. The characteristics can be easily obtained, but after the coefficients of the adaptive filter 5 converge, the feedforward type second control signal generation circuit 3b
The characteristic between the input (in) and the output (out) of the (input / output characteristics = transfer characteristics) is measured, and an analog filter having the characteristics is measured.
When used as the second control signal generation circuit 3b, the second control signal generation circuit 3b can be realized in a small size and at low cost. When using such an analog filter,
The second microphone 1b for detecting the error signal becomes unnecessary, and therefore has the same configuration as the noise control device shown in FIG.

In the apparatus of the present embodiment, the signals detected by the first microphone 1a are all reduced in the frequency band processed by the first control signal generation circuit 3a, so that the second speaker The noise control sound output from the second microphone 2b and detected by the first microphone 1a is also reduced. Therefore, the first microphone 1a provided with the first microphone 1a
Noise at the control point can be reliably reduced, including the influence of the noise control sound from the second speaker 2b.

The feedforward type second control signal generating circuit 3b is configured to control the second microphone 1 based on the noise signal detected by the first microphone 1a which is a noise detector.
b generates a control signal for controlling the noise at the second control point where the noise is output, and the noise output from the first speaker 2a by the noise control signal from the feedback-type first control signal generation circuit 3a. Since the control sound is also detected by the first microphone 1a, the adaptive filter 5 has the characteristic that the noise control sound output from the first speaker 2a and the noise from the noise source can be reduced at the same time. Therefore, also at the second control point where the second microphone 1b is provided, the noise control sound output from the speaker 2a can be reduced together with the noise from the noise source.

In the present embodiment as well, the characteristics of the noise emitted from the noise source are not particularly limited, and the periodic noise such as a mechanical rotation sound such as a motor sound, the siren sound or the pseudo-periodic noise. There is no problem with noise. Further, in the case of periodic noise or pseudo-periodic noise, the causality of the second control signal generation circuit 3b of the feedforward type (time order) does not matter, so the first control point disposed at the first control point. A microphone 1a,
The position of the second speaker 2b and the second microphone 1b with respect to the second control point is not limited in terms of time, and can be installed more freely than random noise.

Further, even if the noise is random noise, the first microphone 1a is similar to the device shown in FIG.
By limiting the detection signal of the second microphone 1b to the frequency to be controlled by the BPF and outputting it to each of the control signal generation circuits 3a and 3b, it is possible to treat the detection signal in the same manner as periodic noise.

When a standing wave is generated in the space, the first microphone 1a is operated similarly to the apparatus shown in FIG.
By installing the second microphone 1b near the maximum amplitude of the standing wave, the standing wave can be controlled.

FIG. 12 is a block diagram showing still another embodiment of the noise control device according to the present invention. In this noise control device, a noise signal detected by a first microphone 1a disposed at a first control point is output to a feedback-type first control signal generation circuit 3a, and a feedforward-type second control signal is generated. The noise signal and the error signal are also output to the signal generation circuit 3b. And
The feedforward-type second control signal generation circuit 3b includes:
A control signal for reducing a noise signal detected by each of the microphones 1a and 1b is generated. Other configurations are the same as those of the noise control device shown in FIG.

In the noise control device having such a configuration, FIG.
0, a noise signal detected by the first microphone 1a is input to the first control signal generation circuit 3a and the second control signal generation circuit 3b, respectively, and a feedback-type first control signal generation circuit In the circuit 3a, the first
The noise signal from the first microphone 1a is processed so that the noise control sound output from the speaker 2a has the same amplitude and opposite phase as the noise detected by the microphone 1a.
Thereby, the first microphone 1a which is the first control point
Is reduced by interfering with the noise control sound from the speaker 2a.

The feedforward type control signal generating circuit 3b monitors noise signals detected by the first microphone 1a and the second microphone 1b, respectively, and controls the feedforward type control signal generation circuit 3b so that each noise signal becomes small. Of the second control signal generation circuit 3b. In the feedforward type second control signal generation circuit 3b, the noise control sound output from the second speaker 2b is divided into a first microphone 1a disposed at the first control point and a second microphone 1b corresponding to the second control point. The noise signal from the microphone 1a is processed so as to have the same amplitude and the opposite phase to the noise detected by.

As a result, noise detected by the first microphone 1a and the second microphone 1b interferes with the noise control sound output from the second speaker 2b and is reduced. As described above, in the apparatus according to the present embodiment, the feedforward type second control signal generation circuit 3b can further reduce the noise detected by the first microphone 1a and the second microphone 1b, thereby reducing the noise. The effect is further improved.

In the present embodiment as well, the characteristics of the noise emitted from the noise source are not particularly limited, but include mechanical rotation noise such as motor noise, periodic noise such as siren noise, or pseudo-periodic noise. There is no problem with noise. Further, in the case of periodic noise or pseudo-periodic noise, the causality of the second control signal generation circuit 3b of the feedforward type (time order) does not matter, so the first control point disposed at the first control point. A microphone 1a,
The position of the second speaker 2b and the second microphone 1b with respect to the second control point is not limited in terms of time, and can be installed more freely than random noise.

Further, even if the noise is random noise, the first microphone 1a is similar to the device shown in FIG.
And the detection signal of the second microphone 1b is limited to the frequency to be controlled by the BPF and is output to each of the control signal generation circuits 3a and 3b. Can handle.

When a standing wave is generated in the space, the first microphone 1a is used as in the case of the apparatus shown in FIG.
By installing the second microphone 1b near the maximum amplitude of the standing wave, the standing wave can be controlled.

FIG. 13 is a block diagram showing still another embodiment of the noise control device according to the present invention. In this noise control device, the feedforward control signal generation circuit 3b has a digital filter configuration having an adaptive filter.

The second control signal generating circuit 3b having the digital filter configuration outputs the output of the first microphone 1a located at the first control point via the subtractor 9 to the adaptive filter (AF).
IR) 5. The coefficients of the adaptive filter 5 are
It is updated by the first and second LMS operators 7a and 7b, respectively. The detection signal of the first microphone 1a located at the first control point is given to the first LMS calculator 7a, and the detection signal of the second microphone 1b located at the second control point is given to the second LMS calculator 7b. ing. Further, the noise signal output from the first microphone 1a is supplied to the first LMS computing unit 7a via the subtractor 9 and the first Fx filter 6a, and the second LM
The noise signal output from the first microphone 1a is given to the S calculator 7b via the subtractor 9 and the second Fx filter 6b. The output of the adaptive filter 5 is provided to a subtractor 9 via a feedback canceller (FC) 8 and also to a second speaker 2b.

In the noise control device having such a configuration, the first
The noise signal detected by the microphone 1a is input to the first control signal generation circuit 3a and the second control signal generation circuit 3b, respectively. In the feedback-type first control signal generation circuit 3a, the noise control sound output from the first speaker 2a is output from the microphone 1a such that the noise control sound has the same amplitude and opposite phase as the noise detected by the first microphone 1a. Signal processing of the noise signal. Accordingly, noise detected by the first microphone 1a, which is the first control point, is reduced by interfering with the noise control sound output from the first speaker 2a.

In the feedforward type second control signal generation circuit 3b, the noise signal detected by the first microphone 1a is converted into the first and second noise control sounds by the adaptive filter 5 from the second speaker 2b. Signal processing is performed so that the noises detected by the second microphones 1a and 1b have the same amplitude and opposite phases. The generated control signal is given to the second speaker 2b,
A noise control sound is output from the speaker 2b.

The noise control sound output from the second speaker 2b interferes with the noise detected by the first microphone 1a and the second microphone 1b to reduce the noise. Then, the reduced noise is transmitted to the first microphone 1a.
And the second microphone 1b respectively detect
The signals are input to the first and second LMS operators 7a and 7b, respectively. On the other hand, since the control sound output from the second speaker 2b is also detected by the first microphone 1a, the noise signal detected by the second microphone 1a includes not only the noise emitted from the noise source 41, The control sound output from the second speaker 2b is also included.

In order to remove a noise control signal included in the signal detected by the first microphone 1a, the output of the adaptive filter 5 is input to the feedback canceller 8,
The output of the feedback canceller 8 is subtracted from the output of the first microphone 1a by the subtracter 9. In the feedback canceller 8, an approximate value of the transfer characteristic C3 from the second speaker 2b to the first microphone 1a is set as a coefficient. As a result, a signal obtained by removing the component of the noise control sound from the second speaker 2b from the noise signal detected by the first microphone 1a is obtained.

The output of the subtractor 9 is the first Fx filter 6a
And the second Fx filter 6b. In the first Fx filter 6a, an approximate value of the transfer characteristic C3 from the second speaker 2b to the first microphone 1a is set as a coefficient, and in the second Fx filter 6b, the approximate value of the transfer characteristic C3 from the second speaker 2b to the second microphone 1b is set. The approximate value of the transfer characteristic C4 is set as a coefficient.
Each of the first and second Fx filters 6a and 6b performs a convolution operation on each coefficient with respect to the noise signal,
The respective calculation results are output to the first and second LMS calculators 7a and 7b, respectively. In each of the LMS operators 7a and 7b, the output signals from the first and second Fx filters 6a and 6b and the first microphone 1
a, based on the detection signals at the second and first microphones 1b, so that the signals respectively detected at the first and second microphones 1a and 1b are minimized.
The coefficient of the adaptive filter 5 is updated. Thereby, noise signals detected by the first and second microphones 1a and 1b are reduced.

Such an algorithm is described in Multiple Err
or Filtered-x LMS algorithm (for example, refer to SJ Elliott, IM Stothers and PA Nelso
n, ("Amultiple error LMS algorithm and its applicat
ion to the active controlof sound and vibration. "I
EEE Trans. Acoust. Speech Signal Process. ASSP-35,
pp1423-1434 (1987))).

As described above, the feedforward type second
By applying a digital filter configuration having the adaptive filter 5 to the control signal generation circuit 3b, its characteristics can be changed one by one, so that it is possible to easily cope with a noise level fluctuation or the like.

As described above, the feedforward type second control signal generating circuit 3b can be configured as an analog filter. In this case, the configuration is the same as that of the device shown in FIG.

In the apparatus of the present embodiment, the detection signal of the first microphone 1a is also an error signal of the feed-forward type second control signal generating circuit 3b, and therefore the feed-forward type The second control signal generation circuit 3b operates to reduce the detection signals of the first and second microphones 1a and 1b.
As a result, in the device of the present embodiment, the noise control signal generated by the feedforward type second control signal generation circuit 3b can reduce the noise at each of the first and second control points. In addition to the effect of the device shown in FIG. 11, the effect of noise reduction is further improved.

FIG. 14 is a block diagram showing still another embodiment of the noise control device according to the present invention. In this noise control device, the output characteristics of the feedback-type first control signal generation circuit 3a are determined based on a noise signal detected by the first microphone 1a. It is the same as the device shown in FIG.

In such a noise control device, in the feedback-type first control signal generation circuit 3a, the noise control sound output from the first speaker 2a is transmitted to the first microphone 1a.
In this case, the noise signal from the microphone 1a is signal-processed so as to have the same amplitude as that of the noise and the opposite phase. In this case, the feedback-type first control signal generation circuit 3a uses the first microphone 1a While monitoring the noise signal detected by the control unit, the control characteristic is determined so that the detection signal becomes small. Thus, noise detected by the first microphone 1a disposed at the first control point is reliably reduced by being interfered by the noise control sound output from the first speaker 2a.

FIG. 15 is a block diagram showing still another embodiment of the noise control device according to the present invention. This noise control device is different from the noise control device shown in FIG. 11 in that the feedback-type first control signal generation circuit 3a also includes:
This is a digital filter configuration having an applicable filter.

The first control signal generating circuit 3a having the digital filter configuration outputs the output of the first microphone 1a located at the first control point to the adaptive filter (A
FIR) 15. The coefficients of the adaptive filter 15 are updated by the LMS calculator 17. The detection signal of the first microphone 1a located at the first control point is L
It is provided to the MS calculator 17. The noise signal output from the first microphone 1a is given to the LMS calculator 17 via the subtractor 19 and the Fx filter 16. The output of the adaptive filter 15 is supplied to a subtracter 19 via a feedback canceller (FC) 18 and also to a first speaker 2a.

In the feedback-type first control signal generating circuit 3a, the noise signal from the first microphone 1a is detected by the adaptive filter 15, and the noise control sound output from the first speaker 2a is detected by the first microphone 1a. The signal is processed so as to have the same amplitude and opposite phase as the noise generated to generate a control signal. Then, a noise control sound is output from the first speaker 2a according to the control signal.

The noise control sound output from the first speaker 2a interferes with the noise detected by the first microphone 1a, and the remaining noise component is detected by the first microphone 1a as an error signal and subjected to the LMS calculation. Input to the device 17. Since the noise control sound output from the second speaker 2b is also detected by the first microphone 1a, the signal detected by the first microphone 1a includes not only the noise from the noise source but also the noise from the second speaker 2b. The output noise control signal is also included.

In order to remove the noise control signal included in the signal detected by the first microphone 1a, the output of the adaptive filter 15 is input to the feedback canceller 18, and the output of the first microphone 1a is subtracted by the subtractor 19 from the output. The output of the feedback canceller 18 is subtracted. In the feedback canceller 18, an approximate value of the transfer characteristic C1 from the first speaker 2a to the first microphone 1a is set as a coefficient. Thereby, the first speaker 2 is obtained from the noise signal detected by the first microphone 1a.
The signal from which the component of the noise control sound due to a is removed is obtained.

The output of the subtractor 19 is input to the Fx filter 16. In the Fx filter 16, an approximate value of the transfer characteristic C1 from the first speaker 2a to the first microphone 1a is set as a coefficient, and the noise signal and this coefficient are convolution-operated.
Output to 17. In the LMS operation unit 17, the Fx filter
Based on the output signal from 16 and the error signal from the first microphone 1a, the coefficient of the adaptive filter 15 is updated so that the error signal detected by the first microphone 1a is minimized. Thereby, the noise signal detected by the first microphone 1a is more reliably reduced.

As described above, by adopting the digital filter configuration having the adaptive filter 15 in the feedback control signal generating circuit 3a, its characteristics can be changed one by one, so that it is possible to easily cope with fluctuations in noise level. be able to.

The structure of the feedforward type second control signal generation circuit 3b is the same as that of the second control signal generation circuit of the device shown in FIG. 11, and functions similarly.

Also in this case, the first and second control signal generation circuits 3a and 3b may be respectively configured as analog filters as described above.

FIG. 16 is a block diagram showing still another embodiment of the noise control device according to the present invention. In this noise control device, in the device shown in FIG. 14, the feedforward type second control signal generation circuit 3b monitors noise signals detected by the first and second microphones 1a and 1b, respectively. The characteristics are determined so that each noise signal becomes small. Other configurations are the same as those of the device shown in FIG.

In the apparatus of the present embodiment, the noise at the control points where the microphones 1a and 1b are arranged can be reduced more reliably than the apparatus shown in FIG.

FIG. 17 is a block diagram showing still another embodiment of the noise control device according to the present invention. In this noise control device, in the device shown in FIG. 15, the noise signal detected by the first microphone 1a is also used as an error signal of the feedforward type second control signal generation circuit 3b. 15 is the same as the device shown in FIG.

In the noise control device of this embodiment, the feedforward type second control signal generation circuit 3b reduces the noise signals detected by the first and second microphones 1a and 1b, respectively. To work,
The noise at each control point can be reduced more reliably than the device shown in FIG.

FIG. 18 is a block diagram showing still another embodiment of the noise control device according to the present invention. In this noise control device, the microphone 1 serving as a noise detector detects noise at the first control point A, not at the two first control points A and the second control points B, which are two positions at which noise is to be controlled. It is arranged at a position where a noise signal having substantially the same noise characteristics as that of the signal is detected. Therefore, in the microphone 1, almost the same sound pressure and phase as the noise signal detected at the first control point A can be obtained. Other configurations are the same as those of the apparatus shown in FIG.

In such a noise control device as well, the noise signal detected by the microphone 1 is converted into a noise control sound output from the speaker 2a in the first control signal generation circuit 3a and a noise signal at the first control point A. Signal processing is performed so that they have the same amplitude and opposite phases. Thus, the noise at the first control point A interferes with the noise control sound output from the first speaker 2a and is reduced.

In the second control signal generation circuit 3b, the noise signal from the microphone 1 is set so that the noise control sound output from the second speaker 2b has the same amplitude and opposite phase as the noise at the second control point B. Is processed. Then, a noise control signal based on the generated noise control signal is output from the second speaker 2b. Thereby, the noise at the second control point B interferes with the noise control sound output from the second speaker 2b and is reduced.

As described above, even when microphones cannot be installed at each of the control points A and B, the microphones
By arranging 1 at a position having substantially the same noise characteristics as the noise characteristics of the control point A, the noise at each of the control points A and B can be reduced.

In this embodiment, the characteristics of the noise emitted from the noise source 41 will not be described in detail.
Although an unspecified noise is assumed, there is no problem even if the noise emitted from the noise source 41 is a periodic noise such as a mechanical rotation sound such as a motor sound, a siren sound, or a pseudo-periodic noise. In the case of periodic noise or pseudo-periodic noise, the causality (time order) of the second control signal generation circuit 3b does not matter, so the noise control signal is applied to the microphone 1 and the second control point B. There is no time restriction on the installation position of the second speaker 2b that outputs the microphone 1, and therefore, the microphone 1 and the second speaker 2b
Can be installed more freely than in the case of controlling random noise.

Further, when the noise emitted from the noise source 41 is random noise, as shown in FIG. 8, the detection signal of the microphone 1 is changed by a band limiting filter (band pass filter, hereinafter referred to as BPF) 4. The configuration may be such that the signal is output to the first and second control signal generation circuits 3a and 3b in a state limited to the frequency to be controlled.
This reduces random noise as well as periodic noise.

As shown in FIG. 19, when the standing wave 11 is generated in the space 10, the microphone 1 is moved to the maximum amplitude of the standing wave 11 in order to control the standing wave 11. It may be installed near the part. Thus, the standing wave can be reliably controlled as in the case of the periodic noise. FIG.
In the example, the standing wave 11 has two maximum amplitude parts in the space 10, one of the maximum amplitude parts is the first control point A, and the microphone 1 is installed at the other maximum amplitude part. ing. Note that the microphone 1 may be arranged near the first control point A.

As shown in FIG. 20, the first control point A
The first microphone 1a is arranged at a position where noise having substantially the same noise characteristics as the noise characteristics of the noise signal detected at the position can be detected, and the second microphone 1b is arranged at the second control point. The control characteristic of the second control signal generation circuit 3b may be determined based on the noise signal detected by the second microphone 1b.

Further, as shown in FIG. 21, the first microphone 1a is arranged at a position where noise having substantially the same noise characteristics as that of the noise signal detected at the first control point can be detected. At the same time, the second microphone 1b is arranged at the second control point, and the third microphone 1c is arranged also at the first control point, and the noise signal detected by the second microphone 1b and the third microphone are arranged.
The control characteristic of the second control signal generation circuit 3b may be determined based on the noise signal detected at 1c.

When the microphone is arranged at a position different from the control point, the second control signal generation circuit 3b is
A digital filter having an applicable filter may be used, or an analog filter having input / output characteristics determined by the digital filter may be used.

[0112]

As described above, the noise control apparatus of the present invention
Despite the simple configuration, noise at different control points can be reliably reduced. In addition, the noise at the control point can be reduced without disposing the noise detector at the control point by detecting the noise having the same noise characteristic as the noise characteristic of the noise to be controlled. be able to.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of an embodiment of a noise control device according to the present invention.

FIG. 2 is a graph showing a noise control effect when only a feedback-type second control signal generation circuit in the noise control device is operated.

FIG. 3 is a graph showing the effect of noise control sound on noise at a second control point A when only a feedback type second control signal generation circuit in the noise control device is operated.

FIG. 4 is a graph showing a noise control effect at a second control point A by the noise control device.

FIG. 5 is a graph showing a control effect on noise at a second control point A by a feedforward type control signal generation circuit in the noise control device.

FIG. 6 is a graph showing an influence of a noise control sound from a second speaker at a first control point in the noise control device.

FIG. 7 is a graph showing a noise control effect at a first control point in the noise control device.

FIG. 8 is a block diagram showing another example of the embodiment of the noise control device of the present invention.

FIG. 9 is a block diagram showing still another example of the embodiment of the noise control device of the present invention.

FIG. 10 is a block diagram showing still another example of the embodiment of the noise control device of the present invention.

FIG. 11 is a block diagram showing still another example of the embodiment of the noise control device of the present invention.

FIG. 12 is a block diagram showing still another example of the embodiment of the noise control device of the present invention.

FIG. 13 is a block diagram showing still another example of the embodiment of the noise control device of the present invention.

FIG. 14 is a block diagram showing still another example of the embodiment of the noise control device of the present invention.

FIG. 15 is a block diagram showing still another example of the embodiment of the noise control device of the present invention.

FIG. 16 is a block diagram showing still another example of the embodiment of the noise control device of the present invention.

FIG. 17 is a block diagram showing still another example of the embodiment of the noise control device of the present invention.

FIG. 18 is a block diagram showing still another example of the embodiment of the noise control device of the present invention.

FIG. 19 is a block diagram showing still another example of the embodiment of the noise control device of the present invention.

FIG. 20 is a block diagram showing still another example of the embodiment of the noise control device of the present invention.

FIG. 21 is a block diagram showing still another example of the embodiment of the noise control device of the present invention.

FIG. 22 is a block diagram illustrating an example of a conventional noise control device.

[Explanation of symbols]

 1, 1a, 1b, 1c Microphone 2a, 2b Speaker 3a First control signal generation circuit 3b Second control signal generation circuit 4 Bandpass filter 5, 15 Adaptive filter 6, 6a, 6b, 16 Fx filter 7, 7a, 7b, 17 LMS calculator 8, 18 Feedback canceller 9, 19 Subtractor 10 Space 11 Standing wave

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Isao Kakuhari 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Toshihiko Ohashi 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F-term (reference) 5D020 AC05 5D061 FF02

Claims (18)

[Claims] 1. A first noise detector arranged to detect noise at a first control point, which is a position where noise is to be controlled, at the first control point; A first control signal generation circuit for generating a control signal having the same amplitude and the opposite phase from the detected noise signal from the detected noise signal; and a noise based on the noise control signal generated by the first control signal generation circuit. A first control sound is output to a first control point.
A speaker, and a control signal having the same amplitude and opposite phase as noise at a second control point different from the first control point at a position where noise is to be controlled, is generated from the noise signal detected by the noise detector. And a second speaker that outputs a noise control sound based on the noise control signal generated by the second control signal generation circuit to a second control point. Characteristic noise control device. 2. The noise control device according to claim 1, wherein the controlled noise is periodic noise or pseudo-periodic noise. 3. The noise control device according to claim 1, wherein an output of said noise detector is limited to a predetermined frequency band. 4. The noise control device according to claim 1, wherein the first control point is located near a maximum portion of a standing wave in a space where the standing wave exists. 5. A second noise detector for detecting noise at the control point is arranged at the second control point, and the second control signal generation circuit detects the noise at the second control point. 2. The noise control device according to claim 1, wherein an output control signal is adjusted based on the error signal. 6. The noise control device according to claim 1, wherein the second control signal generation circuit has a digital filter configuration having an adaptive filter. 7. The control signal output from the second control signal generation circuit is adjusted using a noise signal detected by a first noise detector disposed at a first control point as an error signal. 2. The noise control device according to 1. 8. The control signal output from the first control signal generation circuit is adjusted using a noise signal detected by a first noise detector disposed at a first control point as an error signal. 2. The noise control device according to 1. 9. The noise control device according to claim 1, wherein the first control signal generation circuit has a digital filter configuration including an adaptive filter. 10. A first arrangement for detecting a noise at a position where a noise at which a noise characteristic of the noise substantially coincides at a first control point which is a position where the noise is to be controlled is obtained.
A noise detector; a first control signal generation circuit for generating, from a noise signal detected by the first noise detector, a control signal having the same amplitude and an opposite phase as the noise signal; and the first control signal. A first output of a noise control sound based on the noise control signal generated by the generation circuit to the first control point;
A speaker, and a control signal having the same amplitude and opposite phase as noise at a second control point different from the first control point at a position where noise is to be controlled, is generated from the noise signal detected by the noise detector. And a second speaker that outputs a noise control sound based on the noise control signal generated by the second control signal generation circuit to a second control point. Characteristic noise control device. 11. The noise control device according to claim 10, wherein the controlled noise is periodic noise or pseudo-periodic noise. 12. The noise control device according to claim 10, wherein an output of said noise detector is limited to a predetermined frequency band. 13. The noise control device according to claim 10, wherein the first control point is arranged near a maximum amplitude of the standing wave in a space where the standing wave exists. 14. A second noise detector for detecting noise at the control point is provided at the second control point, and the second control signal generation circuit detects the noise at the second control point. The noise control device according to claim 10, wherein the output control signal is adjusted based on the error signal. 15. The noise control device according to claim 10, wherein the second control signal generation circuit has a digital filter configuration having an adaptive filter. 16. A third noise detector for detecting noise at the first control point, wherein the third noise detector detects noise at the first control point.
The noise control device according to claim 10, wherein the control signal generation circuit adjusts the output control signal using the noise signal detected by the third noise detector disposed at the first control point as an error signal. 17. The control signal output from the first control signal generation circuit is adjusted using a noise signal detected by a third noise detector disposed at a first control point as an error signal. The noise control device according to claim 10. 18. The noise control device according to claim 10, wherein the first control signal generation circuit has a digital filter configuration having an adaptive filter.