JPH07219559A - Adaptive active noise elimination device - Google Patents

Abstract

PURPOSE:To enable an acoustic transfer characteristic in between a speaker and an evaluating microphone to be identified by performing an adaptive active control and making the acoustic transfer characteristic in between the speaker and the evaluating microphone required at the time of eliminating a noise in a duct become the same condition as the transfer characteristic of noise eliminating operation executing state. CONSTITUTION:A random noise from a noise generator 33 is supplied to a speaker 25 and adaptive filters 34, 42. A microphone for a sound source 24 and an evaluating microphone 26 detect the random noise outputted from the speaker 25. Extraction circuits 37, 45 extract direct sound components among detection signals of the microphones 24, 26 to supply them to adaptive filters 34, 42 and acoustic transfer characteristics between A to 0 and between A to S are identified. At this time, since acoustic transfer characteristic is identified based on only the direct sound component, the acoustic transfer characteristic can be identified as the transfer characteristic of the noise eliminating operation state where a component reflected at the opening part 21a of a duct 21 is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adaptive active noise canceling apparatus which cancels noise in a propagation path by generating sounds having the same amplitude and opposite phases to cause sound wave interference.

[0002]

2. Description of the Related Art In recent years, for example, with respect to noise in a ventilation duct for air conditioning, a sound having the same amplitude and opposite phase to the noise is generated to cause sound wave interference to positively mute the noise.
Attention has been paid to an active silencer that reduces noise leaking outside the air duct as much as possible.

The active noise reduction technique applied to such an active noise reduction device is a technique for reducing noise by utilizing an electronics applied technique, in particular, an acoustic data processing circuit and acoustic interference. The sound from the source is converted into an electric signal by a sound receiver (for example, a microphone) provided in the air duct, and the control sounder (for example, a speaker) is operated based on the signal processed by the arithmetic unit. By doing so, the control sound generator generates an artificial sound having the same amplitude as the original sound (sound from the noise source) at the control target point, but the original sound is attenuated by causing the artificial sound to interfere with the original sound. It is to let it.

As a result, a muffling effect of 10 dB or more can be expected in the low-frequency muffling frequency band, and there is almost no pressure loss unlike conventional mufflers. By introducing such a device, the noise generated from the air-conditioning air duct can be reduced as much as possible and a quiet viewing space can be formed.

Further, in order to realize such active control, it is necessary to make adjustments in response to characteristic fluctuations due to aging of components constituting a signal system for silencing and characteristic fluctuations due to ambient temperature. Therefore, in practical use, the calculation coefficient (acoustic transfer function) of the calculator is adjusted to follow the fluctuation of the silencing ability. That is, an evaluation sound receiver (for example, a microphone) for monitoring the muffling effect of the control sounder is provided, and when the result of monitoring by the evaluation sound receiver is out of a predetermined allowable range, the calculation of the arithmetic unit is performed. Application control means for changing the coefficient to control the monitor result to fall within the allowable range is provided, thereby performing so-called adaptive control in which the muffling ability during active control is always kept optimal in accordance with fluctuations in characteristics. I am trying.

An example of such an active silencer is shown in FIGS. 7 to 9. In FIG. 7, a noise source 2 such as an air conditioner is provided inside the duct 1 whose one end is open (left end in the figure), and noise generated from the noise source 2 is emitted from the opening 1 a of the duct 1 to the outside. An active silencer 3 is arranged so as to prevent it from coming out. In the duct 1, a sound source microphone 4 for detecting noise is located at a point S along a noise propagation path (a direction from left to right in the duct 1 in the figure), and a speaker 5 for outputting an interfering sound is A. The evaluation microphone 6 is sequentially provided at a point and at an O point near the opening 1a.

The control unit 7 controls the sound source microphone 4 at point S.
The detection signal of the noise source detected by the above is signal-processed so that the sound pressure becomes zero by sound wave interference at the point O corresponding to the position of the evaluation microphone 6 on the side of the opening 1a, and is output from the speaker 5 as a control sound. . When the control sound is output from the speaker 5 toward the opening 1a of the duct 1, a sound wall is formed at the point O to prevent noise from being emitted outside by trapping the noise in the duct 1. Is muted. Further, when the control unit 7 receives a detection signal of the sound volume at the sound deadening point O of the opening 1a from the evaluation microphone 6, the control unit 7 performs adaptive control based on the detection signal.

In this case, in the adaptive control, in order to produce the control sound in order to always exert the silencing effect sufficiently,
This is provided as a function capable of automatically adjusting in consideration of a change in the acoustic transfer characteristic in the duct 1 due to a change over time of the sound source microphone 4 or the speaker 5 or a change in temperature or the like. Then, in this adaptive active muffling control system, the evaluation microphone 6 arranged at the point O, which is the muffling point, detects the remaining sound that is not muted by the control sound, and controls so that the detected amount is minimized. The part 7 is fed back to maintain a high silencing effect.

FIG. 8 is an example showing an internal configuration of the control unit 7 in such an adaptive active noise reduction system. The detection signal of the sound source microphone 4 is passed through the calculator 8 to the FI.
The R filter 9 and the filter 10 to which the transfer characteristic G AO is set are input. The transfer characteristic G AO of the filter 10 is determined by the evaluation microphone 6 from the speaker 5 through the duct 1.
The transmission characteristic is the same as the acoustic transmission characteristic G AO of the transmission path leading to.

The FIR filter 9 gives the generated control signal to the speaker 5 and gives it to the subtraction input terminal of the computing unit 8 via the cancel filter 11 in which the transfer characteristic G AS is set. The transfer characteristic GAS of the cancel filter 11 is
It has the same transfer characteristic as the acoustic transfer characteristic GAS of the transfer path from the speaker 5 to the sound source microphone 4 through the duct 1. The adaptive filter 12 is adapted to receive a signal from the filter 10 and a detection signal at the muffling point O from the evaluation microphone 6, and the known F
Based on the filtered-X LMS algorithm, the calculation coefficient of the FIR filter 9 is adjusted so that the detection signal given from the evaluation microphone 6 becomes zero.

According to the above construction, when the noise emitted from the noise source 2 propagates in the duct 1 toward the opening 1a, the control unit 7 detects the noise at the point S by the sound source microphone 4. Then, based on this detection signal, a control signal for causing noise by interfering with noise at the muffling point O is calculated by the FIR filter 9 and given to the speaker 5. At this time, the control signal is also given to the calculator 8 via the cancel filter 11. This is because when the control sound output from the speaker 5 propagates upstream in the duct 1 and is detected by the sound source microphone 4 at the point S, howling may occur, so that the sound source microphone 4 is detected. This is for canceling the detection component due to the control sound from the signal.

Then, the control sound output from the speaker 5 has the same amplitude as the amplitude of the noise propagating from the noise source 2 at the muffing point O, but has an opposite phase, causing interference with the noise and canceling it. It will be muted. Therefore, at the mute point O, the evaluation microphone 6
The signal of the sound detected by should ideally be zero, but in reality, the change of the acoustic transfer characteristics in the duct 1 due to the change over time of the sound source microphone 4 and the speaker 5 and the change of the temperature and the like. Therefore, it may not be zero.

Therefore, F is set by the application filter 12 so that the detection signal from the evaluation microphone 6 becomes zero.
The calculation coefficient of the IR filter 9 is adjusted. Applied filter 1
The same signal as the detection signal input to the FIR filter 9 is input to the signal 2 via the filter 10, and the detection signal from the evaluation microphone 6 is applied to the signal 2. In this case, the filter 10 is interposed because the signal detected by the evaluation microphone 6 propagates in the duct 1 from the speaker 5 and reaches the sound deadening point O at the acoustic transfer characteristic G.
AO is taken into consideration.

Therefore, with such a structure, the muffling point O is always muted in response to a change in the acoustic transfer characteristic in the duct 1 due to a change with time of the sound source microphone 4 or the speaker 5 or a change in temperature or the like. The muffling operation can be performed while maintaining the maximum effect.

By the way, in the case of performing the adaptive active noise reduction control as described above, prior to the control operation, the acoustic transfer characteristic GAO of the filter 10 and the canceling filter 1 are performed.
In order to set the acoustic transfer characteristic GAS of No. 1, it is necessary to measure the actual acoustic transfer characteristics GAO and GAS in the duct 1 in advance. That is, the fact that these acoustic transfer characteristics are set accurately is a prerequisite for performing the above-mentioned adaptive active control, and is a condition for obtaining a sufficient silencing effect. . A configuration for identifying these acoustic transfer characteristics is shown in FIG.
Is shown in.

The noise generator 13 outputs a random noise signal such as white noise, and its output terminal is connected to the speaker 5 to output white noise in the duct 1. Adaptive filter 1 for identifying acoustic transfer characteristics G AO
Reference numeral 4 is composed of an identification circuit 15 and an arithmetic unit 16. The identification circuit 15 is supplied with a random noise signal from the noise generator 13 and an output signal of the arithmetic unit 16, and the output of the identification circuit 15 is The subtraction is input to the calculator 16. The identification circuit 15 performs digital processing on the sampling signal to perform identification processing of GAO, and further performs identification based on a signal given from the calculator 16 as a signal of a difference between the output signal and the detection signal from the evaluation microphone 6. The acoustic transfer characteristic GAO is identified by advancing the processing.

Adaptive filter 1 for identifying acoustic transfer characteristics GAS
Reference numeral 7 is composed of an identification circuit 18 and an arithmetic unit 19, and identifies the acoustic transfer characteristic GAS by performing signal processing similarly to the above-mentioned adaptive filter 14.

With the above configuration, a white noise signal is output from the noise generator 13, white noise is output to the inside of the duct 1 by the speaker 5, propagates in the duct 1, and is detected by the sound source microphone 4 and the evaluation microphone 6. The adaptive filter 14 based on
And 17 identify the acoustic transfer characteristics G AO and G SA. The acoustic transfer characteristics G AO and G SA obtained as a result may be set as the transfer characteristics of the filter 10 and the cancel filter 11, respectively.

[0019]

By the way, in the case of performing the silencing operation as described above, the acoustic transfer characteristics GSO and GAO between the speaker 5 and the sound source microphone 4 and the evaluation microphone 6 are measured and identified. If the products are applied as they are, the following problems occur.

That is, when white noise or the like is output from the speaker 5 at the time of identification, the noise sound propagates in the duct 1 and reaches the evaluation microphone 6 directly, and the direct wave component and the opening 1a portion of the duct 1 (right end). Both the reflected wave component (shown by the broken line arrow in FIG. 9) that is reflected by and reaches the evaluation microphone 6 are detected by the evaluation microphone 6.

Then, the acoustic transfer characteristics are identified based on these detected noise sounds. In the actual muffling operation, when the muffling operation is started and becomes stable, the speaker is turned on. The control sound output from 5 propagates through the duct 1 and is muted at the position O of the evaluation microphone 6 by interfering with the noise of the noise source, and a sound wall is generated at that position, so the silencing operation is performed. By doing so, the acoustic characteristics on the side of the opening 1a with respect to the sound deadening point O change, and the component of the sound reaching the opening 1a of the duct 1 disappears and the component of the reflected sound returning to the evaluation microphone 6 also disappears. Will be lost.

Therefore, the acoustic transfer characteristic G AO or G SA obtained at the time of identification deviates from the actual acoustic transfer characteristic at the time of the silencing operation, which causes a faithful control sound to be output from the speaker 5 to perform the silencing operation. There is a possibility that it becomes impossible to obtain a sufficient silencing effect, and in some cases, control error diverges due to accumulation of calculation errors.

The state of the trouble caused by such a reflected wave component changes depending on the amount of the reflected sound and the time until it is reflected, and therefore exhibits different properties depending on the acoustic environment before and after the silencer. For example, when installed in an air-conditioning duct, etc., since the acoustic characteristics before and after the duct differ depending on the installation location, the muffling effect also changes depending on the installation location. It is not possible, and it will hinder the silent design. In addition, even when installing to prevent noise generation of a compressor such as a refrigerator, if the installation location cannot be specified at the design stage, the silencing effect cannot be estimated in advance in the same manner as above. , Similar problems will occur.

The present invention has been made in view of the above circumstances, and an object thereof is to identify acoustic characteristics in a noise propagation path without being influenced by the surrounding acoustic environment and perform acoustic transmission corresponding to a silencing operation. It is an object of the present invention to provide an adaptive active silencer capable of accurately identifying the characteristics and further improving the silencing effect.

[0025]

In order to solve the above-mentioned problems, the adaptive active noise canceling apparatus of the present invention includes a first sound receiving means provided in a noise propagation path and the noise propagation path having the above-mentioned first sound receiving means. A control sounding device which is provided at a position downstream of the first sound receiving means and outputs an interference sound with respect to the noise, and a second sounding device which is provided at a position downstream of the control sounding device in a propagation path of the noise. Sound receiving means, control means for generating a control signal by performing arithmetic processing based on the detection signal of the first sound receiving means, and outputting the interference sound to the control sounder, and the arithmetic means. Of the first sound receiving means, and a canceling means for inputting the control signal generated by the above, filtering by the acoustic transfer characteristic between the control sounding device and the first sound receiving means, and outputting as a cancel signal. Cancel from the detection signal Arithmetic means for subtracting the cancellation signal of the stage and giving it to the control means, and an output signal of the arithmetic means is filtered by a sound transmission characteristic between the control sounding device and the second sound receiving means to serve as a reference signal. Based on the output signal converting means, the detection signal of the second sound receiving means, and the reference signal from the signal converting means, the calculation coefficient of the control means is set so that the volume of sound muted by the control sounder becomes maximum. Adaptive control means for adjusting, noise generation means for outputting random noise from the control sounder,
Random noise output from the control sound generator reaches the second sound reception means in the shortest time based on the detection signal of the second sound reception means with respect to the random noise output from the control sound generator. Extraction means for extracting a component, the control sounding device to be set in the signal conversion means based on the extraction signal from the extraction means and the random noise signal from the noise generation means, and the second sound receiving means. It is characterized in that it is provided with an identification means for identifying the acoustic transfer characteristics between and.

In the above structure, the extraction means delays the detection signal of the second sound receiving means by a predetermined time, the detection signal of the second sound receiving means and the delay means. Random output from the control sounder by identifying a reflected component of the random noise from the control sounder that does not reach the second sound receiving means in the shortest time based on the detected signal. An extraction adaptive filter that outputs a component in which noise reaches the second sound receiving unit in the shortest time can be provided.

Further, in the above arrangement, the delay means for delaying the random noise signal from the noise generating means for a predetermined time, the random noise signal output from the noise generating means and the random noise signal delayed by the delay means. It is also possible to provide a signal adjusting means for removing a component having a periodicity from the random noise signal based on the above and outputting it as a random noise signal to the control sounding device.

In the above structure, the periodic component extracting means for extracting a periodic component from the random noise signal output from the noise generating means, and the random noise by the second sound receiving means by the extracting means. The periodic component contained in the random noise signal is removed based on the periodic component extracted by the periodic component extracting unit when the component reaching the second sound receiving unit in the shortest time is extracted from the detection signal It may be configured by providing a correction means for performing such correction.

[0029]

According to the adaptive type active muffler of claim 1,
The acoustic transfer characteristics to be set in the signal converting means necessary for the silencing control operation by the control means and the adaptive filter, that is, the acoustic transfer characteristics between the control sounding device and the second sound receiving means are identified as follows. It

First, when a random noise signal such as white noise is output from the noise generator to the control sounder, the random noise is output to the noise propagation path. The random noise output in the propagation path is detected by the second sound receiving means by propagating in the space,
The detected sound component is a sound component that propagates through the space of the propagation path from the control sounding device and arrives directly, that is, a direct sound component, and in addition to this, passes through the side portion of the second sound receiving means. Then, the signal is a signal including a sound component that is reflected on the exit side of the propagation path and then returns to the upstream side of the propagation path, that is, a reflected sound component. In this case, the time until the reflected sound component reaches the second sound receiver is longer than that of the direct wave component by the time it is reflected.

Then, the extracting means, based on the detection signal from the second sound receiving means, selects the random noise detected by the second sound receiving means that reaches the sound from the control sounder in the shortest time. The component, that is, the direct sound component is extracted and given to the identification means. The identifying means identifies the acoustic transfer characteristic between the control sounder and the second sound receiving means based on the direct sound component of the random noise given from the extracting means. Therefore, the acoustic transfer characteristic identified in this case corresponds to the acoustic transfer characteristic of random noise propagating in the shortest space of the propagation path between the control sounder and the second sound receiving means, and In order to be able to identify an acoustic transmission characteristic of a reflected sound component that has propagated to the downstream side of the second sound receiving means from the sound generator and is reflected and then reaches the second sound receiving means. Become.

When the acoustic transfer characteristic thus identified is set in the signal converting means, the control means detects the noise propagating in the propagation path by the first sound receiving means and detects the detected signal. A control signal is generated based on the above, and the interference sound is output from the control sounding device. As a result, the noise and the interference sound having the same amplitude but the opposite phase cancel each other out and are silenced.

In this case, when the silencing operation progresses to a steady state, an interference sound output from the control sounding device creates an acoustic wall at the position of the second sound receiving means and propagates downstream thereof. Noise will not propagate to the route. Therefore, in the second sound receiving means, there is no component of noise reflected from the downstream side as in the case of identifying the acoustic transfer characteristic. With the state in which the acoustic transfer characteristics identified in correspondence with the direct wave component between the second sound receiving unit and the second sound receiving unit are met, an accurate silencing operation can be performed.

In the above-mentioned noise detection by the first sound receiving means, the canceling means is provided because the interference sound from the control sounding device is detected by the first sound receiving means. In order to prevent the signal from being mixed with the signal, the acoustic transfer characteristic of the path from the control sounder to the first sound receiving means via the propagation path is set in the canceling means, and the control signal from the control means is set. By canceling,
This is because only the noise is detected and the control signal is generated.

According to the adaptive active noise canceling apparatus of the second aspect, in the process of extracting the direct sound component by the above-mentioned extracting means, the extracting adaptive filter has the detection signal output from the second sound receiving means. The reflected sound component of the random noise signal detected by the second sound receiving device is identified based on the signal delayed by the signal delay device for a predetermined time, and the direct sound component not identified at this time is output. Become.

In this case, the reflected sound component arriving later than the direct sound component contained in the random noise signal detected by the second sound receiving means is the direct sound component delayed by the signal delay means for a predetermined time. It is possible to set the filter characteristic by sequentially identifying by the extraction adaptive filter, but it is output from the second sound receiving means without passing through the signal delay means. Since there is no signal to refer to the direct sound component, the direct sound component cannot be identified and is output as it is.

That is, the sound component that cannot be identified by the extraction adaptive filter becomes a signal corresponding to the direct sound component of the random noise detection signal detected by the second sound receiving means. Therefore, by performing identification by the identification means based on the output signal of the extraction adaptive filter, the acoustic transfer characteristic of the propagation path through which the direct sound from the control sounder to the second sound receiving means propagates as described above. Can be identified.

According to the adaptive active noise suppressor of the third aspect, when the identifying means performs the identification, the signal adjusting means removes the periodic component of the random noise signal output from the noise generator. When a noise signal is artificially generated by the generator, even if a sound component with a short cycle is included, it can be given to the control sounder as a random noise signal with that cycle component removed. As a result, it becomes possible to more accurately identify the acoustic transfer characteristics by the identifying means, and as a result, the silencing operation by the control means can be performed accurately and the silencing effect can be improved.

According to the adaptive active noise suppressor of the fourth aspect, when identification is performed by the identification means, the random noise signal from the noise generation means is given to the control sounder to output the random noise to the propagation path. At the same time, the random noise signal is given to the periodic component extracting means to extract the component having the periodicity. Then, when the direct sound component is extracted from the detection signal of the random noise detected by the second sound receiving means by the extraction means, the periodic component of the random noise signal included in the detection signal is corrected by the correction means and removed. Then, it will be given to the identification means.

As a result, when the noise signal output from the noise generating means has periodicity or autocorrelation as described above, if the periodic component is removed and is given to the control sounder, the output is generated. In the case where the level of is decreased, it is possible to output random noise from the control sounding device so as not to decrease the level of the output and to detect it by the second sound receiving means. Even in this case, it becomes possible to accurately identify the acoustic transfer characteristic by eliminating the detection error due to the component having the periodicity included in the random noise signal.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment in which the present invention is applied to an air conditioning duct will be described below with reference to FIGS. That is, FIG. 2 showing a block configuration of the active silencer.
A noise source 22 such as an air conditioner is provided in the interior of the duct 21 (left end in the figure) as a noise propagation path whose one end is open, and the conditioned air due to the air conditioning operation is leftward in the figure (upstream side). The air is blown toward the right side (downstream side), and the noise generated by the air conditioning operation is similarly propagated.

The muffler 23 is arranged so as to prevent noise generated from the noise source 22 from going out through the opening 21 a of the duct 21. In the duct 21,
A sound source microphone 24 as a first sound receiving means for detecting noise is provided at point S on the upstream side along the noise propagation path (along the direction from left to right in the duct 21 in the figure). A speaker 25 as a control sounding device that outputs an interference sound is provided at a point A on the downstream side, and an evaluation microphone 26 as a second sound receiving means is provided at a point O on the further downstream side.
Is provided.

The control unit 27 detects the noise source detection signal detected by the sound source microphone 24 at the point S by sound pressure by sound wave interference at the point O corresponding to the position of the evaluation microphone 26 on the side of the opening 21a of the duct 21. Signal is processed so as to be zero and is output from the speaker 25 as a control sound. When the control sound is output from the speaker 25 toward the opening 21a of the duct 21, a sound wall is formed at the point O to prevent noise from being trapped in the duct 21 and to be emitted to the outside. Is muted. Further, the control unit 27 is adapted to perform adaptive control based on the detection signal of the sound deadening volume at the sound deadening point O of the opening 21a from the evaluation microphone 26.

In this case, in the adaptive control, in order to always produce the silencing effect sufficiently, in order to produce the control sound,
This is provided as a function capable of automatically adjusting in consideration of a change in the acoustic transfer characteristic in the duct 21 due to a change with time of the sound source microphone 24 or the speaker 25 or a change in temperature and the like. In this adaptive active muffling control system, the evaluation microphone 26 arranged at the point O, which is a muffling point, detects the sound left unmuted by the control sound, and controls so as to minimize the detected amount. It is intended to provide feedback to the section 27 to maintain a high silencing effect.

The detection signal of the sound source microphone 24 is passed through an arithmetic unit 28 as an arithmetic unit to a FI as a control unit.
The R filter 29 and the signal conversion filter 30 as the signal conversion means in which the transfer characteristic G AO is set are input. The transfer characteristic GAO of the signal conversion filter 30 is set to the same transfer characteristic as the acoustic transfer characteristic GAO of the transfer path from the speaker 25 to the evaluation microphone 26 via the duct 21, and the identification processing is performed as described later. Is performed to identify and obtain the actual acoustic transfer characteristics, and then set.

The FIR filter 29 gives the generated control signal to the speaker 25, and also gives it to the subtraction input terminal of the arithmetic unit 28 via the cancel filter 31 as the canceling means in which the transfer characteristic G AS is set. The transfer characteristic GAS of the cancel filter 31 is the same transfer characteristic as the acoustic transfer characteristic GAS of the transfer path from the speaker 25 to the sound source microphone 24 via the duct 21. Then, with respect to this acoustic transfer characteristic GAS as well, after performing the identification processing as described later to identify and obtain the actual acoustic transfer characteristic,
It is supposed to be set.

Adaptive filter 32 as adaptive control means
Is provided with a signal from the signal conversion filter 30 and a detection signal at the muffling point O from the evaluation microphone 26. The evaluation microphone 26 outputs a digital operation based on a known LMS algorithm. The calculation coefficient of the FIR filter 29 is adjusted so that the detection signal given becomes zero.

Next, FIG. 1 shows a configuration for identifying the acoustic transfer characteristics G AO and G AS set in the signal conversion filter 30 and the cancellation filter 31 described above. A circuit for identification is provided. Noise generator 33 as noise generating means
Is a device that artificially generates and outputs a random noise signal such as white noise, and its output terminal is the speaker 2
5 and outputs white noise into the duct 21.

The adaptive filter 34 as the identification means for identifying the acoustic transfer characteristic G AO includes an identification circuit 35 and an arithmetic unit 36.
The identification circuit 35 receives the random noise signal as a reference signal from the noise generator 33 and the output signal of the calculator 36.
The output of 5 is subtracted and input to the calculator 36. Identification circuit 35
Performs the identification processing of GAO by digitally processing the sampling signal, and further advances the identification processing based on the signal given from the calculator 36 as the signal of the difference between the output signal and the detection signal from the evaluation microphone 26. The acoustic transfer characteristic G AO is identified by proceeding.

The extraction circuit 37 as the extraction means is for extracting and outputting the direct sound component by identifying the autocorrelation function from the detection signal of the white noise detected by the evaluation microphone 26, and as the signal delay means. The delay circuit 38 and the extraction adaptive filter 39 are included. The extraction adaptive filter 39 is composed of an identification circuit 40 for identifying a reflected sound and a calculator 41.

The output terminal of the evaluation microphone 26 is connected to the input terminal of the delay circuit 38 and the addition input terminal of the arithmetic unit 41. Delay circuit 38
Outputs an input signal with a predetermined time delay, and its output terminal is connected to the input terminal of the identification circuit 40. The identification circuit 40 identifies the reflected sound component from the detection signal of the evaluation microphone 26 based on the detection signal of the evaluation microphone 26 and the calculation output signal from the calculation unit 41, and its output terminal is the output terminal of the calculation unit 41. It is connected to the subtraction input terminal, and the output terminal of the arithmetic unit 41 is connected to the addition input terminal of the arithmetic unit 36 of the adaptive filter 34 described above.

Adaptive filter 4 for identifying acoustic transfer characteristics GAS
2 includes an identification circuit 43 and an arithmetic unit 44. The identification circuit 43 receives a random noise signal from the noise generator 33 as a reference signal and the arithmetic unit 4
4 is given, and the output of the identification circuit 43 is subtracted and input to the calculator 44. The identification circuit 43 digitally processes the sampling signal to execute the identification process of GAO, and further identifies the signal based on the signal given from the calculator 36 as a signal of the difference between the output signal and the detection signal from the sound source microphone 24. The acoustic transfer characteristic G AO is identified by advancing the processing.

The extraction circuit 45 includes a sound source microphone 24.
Is to directly extract a sound component from the detection signal of the white noise detected by and output it, and is composed of a delay circuit 46 and an extraction adaptive filter 47. The extraction adaptive filter 47 includes an identification circuit 48 for identifying a reflected sound and a computing unit 49.

The output terminal of the sound source microphone 24 is connected to the input terminal of the delay circuit 46 and also to the addition input terminal of the arithmetic unit 49. Delay circuit 46
Outputs an input signal after delaying it for a predetermined time, and its output terminal is connected to the input terminal of the identification circuit 48. The identification circuit 48 identifies the reflected sound component from the detection signal of the sound source microphone 24 based on the detection signal of the sound source microphone 24 and the calculation output signal from the calculation unit 49, and its output terminal is of the calculation unit 49. It is connected to the subtraction input terminal, and the output terminal of the arithmetic unit 49 is connected to the addition input terminal of the arithmetic unit 44 of the adaptive filter 42 described above.

Next, the operation of the present embodiment will be described with reference to FIGS. 3 and 4 as well. First, the principle and operation of (1) active mute control and adaptive control will be described, followed by ( 2) An identification process for identifying the acoustic transfer characteristic will be described.

(1) Explanation of operation principle of active noise reduction and noise reduction operation Now, as shown in FIG. 2, a position S point of the sound source microphone 24 which is a noise detection point in the duct 1 and an evaluation point of noise reduction are evaluated. The acoustic transfer characteristics between the point O of the microphone 26 and the point A of the speaker 25, which is the output point of the interference sound, are defined as follows. That is, the acoustic transfer characteristic of the propagation path from point A to point S is G
AS, the acoustic transfer characteristics of the propagation path from point A to point O
The acoustic transfer characteristics of the propagation path from the O and S points to the O point
And

Then, the relationship between these three acoustic transfer characteristics can be expressed as the following equation. GSO = GSA.GAO (1) Therefore, the filter characteristic G required for the FIR filter 29 may be a transfer characteristic having a phase opposite to the acoustic transfer characteristic GSA between the points S and A described above. From the above formula (1), G = -GSA = -GSO / GAO (2) That is, the filter characteristic G of the FIR filter 29
Is set as in equation (2), the evaluation microphone 2
It can be seen that the noise can be silenced by the control sound output from the speaker 25 at the position of 6.

Next, the adaptive control will be described. Now, letting x be the detection signal of the noise reaching the sound source microphone 24 and y be the detection signal of the sound received at the opening 21a (point O), the relationship of y = GSO · x (3) holds. Then, the opening 21a (O
In order to make the detection signal y at the point) zero, the signal −y having the opposite phase to the detection signal y may be superposed on the opening 21a. Therefore, assuming that the control sound signal output from the speaker 25 is a, then-y = GAO.a (4), so if the filter characteristic of the FIR filter 29 is G, then a = G.x = -GSO / GAO · x (5) y = (− G) · GAO · x (6) Since the detection signal y of the evaluation microphone 26 and the detection signal x of the sound source microphone 24 are acoustic transfer characteristics GAO.
From the signal G AO · x processed by the signal conversion filter 30 of No. 2, -G is identified and obtained by the adaptive filter 32, and the sign is inverted to obtain the filter characteristic of the FIR filter 29.
When this processing is performed using a digital filter, the characteristic is obtained as a filter coefficient, and therefore the sign inversion is obtained by subtracting each tap coefficient value from zero.

Further, the acoustic transfer characteristic GSO of the space shifts to GSO 'due to a change in the environment, etc., and the optimum value Gnew of the filter characteristic of the FIR filter 29 is changed to the current silence filter characteristic Gol.
When Gnew = Gold−ΔG (7) due to the deviation from d by d, assuming that the detection signal at the opening 21a that has been silenced is y ′, y ′ = x · G · GAO + x · Since GSO '... (8), the relationship at the time of optimum silencing is x (G-.DELTA.G) .GAO + x.GSO' = 0 (9). Therefore, if GSO 'is eliminated from the equations (8) and (9), the relation of y' = xG * GAO-x * (G-ΔG) * GAO = (x * GAO) * ΔG (10) can get.

As a result, similarly to the case of the equation (6), from the detection signal y'of the evaluation microphone 26 and the signal GAO.x obtained by processing the sound source signal x with the filter characteristic GAO by the signal conversion filter 30, The adaptive filter 32 can identify and obtain ΔG, which is a deviation component of G. Thereby, a new optimum silencing filter characteristic of the FIR filter 29 can be obtained by the equation (7).

By comparing the equations (6) with the equations (7) and (10), the acoustic transfer characteristic G of the FIR filter 29 to be obtained first is the equation (7), and the value of the equation when Gold = 0 is set. It is found that the initial value of the characteristic of the FIR filter 29 is set to “0”, and the adaptation process represented by the formula (10) and the coefficient updating process represented by the formula (7) are repeated.
You can bring the muffling to the optimum state.

In this case, the coefficient update is actually performed by the equation (7).
Rather than multiplying ΔG by the feedback gain parameter μ and expressing it as Gnew = Gold −μΔG, it is often convenient because the feedback gain parameter μ can improve or adjust the convergence speed and stability. .

On the basis of such a silencing principle, the silencing operation is performed as follows. When the noise emitted from the noise source 22 propagates in the duct 21 toward the opening 21a, the control unit 23 detects the noise at the point S by the sound source microphone 24, and the noise reduction is performed based on this detection signal. At a point O, a control signal for causing noise by interfering with noise is calculated by the FIR filter 29 and given to the speaker 25. At this time, the control signal is also given to the arithmetic unit 28 via the cancel filter 31. This is because when the control sound output from the speaker 25 propagates upstream in the duct 21 and is detected by the sound source microphone 24 at the point S, howling may occur, so that the sound source microphone 24 is detected. This is for canceling the detection component due to the control sound from the signal.

The control sound output from the speaker 25 has the same amplitude as the amplitude of the noise propagating from the noise source 22 at the muffling point O and has a phase opposite to that of the noise. It will be muted. Therefore, at the muffling point O, the sound signal detected by the evaluation microphone 26 should ideally be zero, but in reality, the sound source microphone 24.
In some cases, the sound transmission characteristics in the duct 21 may change due to changes in the speaker 25 over time, changes in the temperature, and the like, and thus may not be zero.

Therefore, the application filter 32 adjusts the operation coefficient of the FIR filter 29 so that the detection signal from the evaluation microphone 26 becomes zero. To the applied filter 32, the same signal as the detection signal input to the FIR filter 29 is input via the signal conversion filter 30, and the detection signal from the evaluation microphone 26 is applied. In this case, the signal conversion filter 30 is interposed because the signal detected by the evaluation microphone 26 propagates from the speaker 25 in the duct 21 and the sound deadening point O.
The acoustic transfer characteristic G AO of the route to the point is taken into consideration.

Therefore, with such a configuration, the muffling point O is always muted in response to the change in the acoustic transfer characteristic in the duct 21 due to the change over time of the sound source microphone 24 or the speaker 25 or the change in the temperature. The muffling operation can be performed while maintaining the maximum effect.

When performing the silencing operation by the adaptive active control as described above, the transfer characteristics to be set in each of the FIR filter 29, the signal conversion filter 30, and the cancel filter 31 are set according to the acoustic transfer characteristics of the duct 21. Therefore, it is essential to identify them accurately. In particular, in the configuration in which adaptive control is performed as in this case, it is necessary to identify the acoustic transfer characteristic GAO set in the signal conversion filter 30 as the signal conversion means as the transfer characteristic corresponding to the muffling operation for the reason described above. It will be.

(2) Identification processing of acoustic transfer characteristics G AO and G AS Therefore, the content of the identification processing of the acoustic transfer characteristics will be described with reference to FIG. First, the noise generator 33 outputs a white noise signal as a random noise signal, and the speaker 25 outputs the white noise into the duct 21. This white noise propagates through the duct 21 and is detected by the sound source microphone 24 and the evaluation microphone 26. In the extraction circuit 45 based on the detection signal of the sound source microphone 24, by identifying the autocorrelation function, the sound component that reaches the sound source microphone 24 from the speaker 25 through the duct 21 in the shortest time, that is, directly. A sound component is extracted and output, and based on the detection signal of the evaluation microphone 26, in the extraction circuit 37, a sound component that reaches the evaluation microphone 26 from the speaker 25 through the duct 21 in the shortest time, that is, a direct sound component. Is extracted and output.

The operation of the extraction process of the direct sound in the extraction circuits 37 and 45 will be described by taking the operation of the extraction circuit 37 as a representative. That is, in the detection signal from the evaluation microphone 26, the direct sound component directly detected from the speaker 25 via the duct 21 and the evaluation microphone 2 are included.
A reflected sound component (a portion indicated by a dashed arrow in FIG. 1) that passes through the vicinity of 6 and is partially reflected by the opening portion 21a of the duct 21 and returns to the evaluation microphone 26 is included. .

The delay circuit 38 includes the evaluation microphone 26.
The detection signal given by the signal is delayed by a predetermined delay time and output to the identification circuit 40. The identification circuit 40 executes the identification process so that the error signal output from the calculator 41 becomes zero. At this time, from the evaluation microphone 26 to the calculator 4
As described above, the detection signal given to 1 is a signal in which the direct sound component and the reflected sound component detected with a delay of a certain time from the direct sound component are overlapped with each other.
Since the detection signal corresponding to the direct sound component has not yet been input from the delay circuit 38 to the identification circuit 40 side at the time of being input to, the direct sound component cannot be identified and the direct sound component is always As it is, the computing unit 3 of the adaptive filter 34
Will be given to 6. On the other hand, at the time when the signal corresponding to the direct sound component is input from the delay circuit 38 to the identification circuit 40, the detection signal of the reflected sound component is given from the evaluation microphone 26 to the calculator 41. The calculator 41 calculates and outputs the difference between these detection signals, and therefore the identification circuit 40 advances the identification process for the reflected sound component. As a result, by passing through the extraction circuit 37, only the signal of the direct sound component of the detection signal from the evaluation microphone 26 can be extracted and given to the adaptive filter 34.

The delay time set in the delay circuit 38 is determined by the sampling period and the positions of the microphones 24 and 26 and the speaker 25 provided in the duct 21 when the silencing system is designed. It is set to be less than the time difference between the direct sound and the reflected sound.

Then, in the adaptive filter 34, based on the direct sound component of the detection signal of the evaluation microphone 26 given from the extraction circuit 37 and the white noise signal given from the noise generator 33 as a reference signal, both The filter coefficient of the identification circuit 35 is set so that the signal of is zero. In this case, the identification circuit 3
The filter coefficient set in 5 is the noise generator 3
The white noise signal output from 3 is a value that identifies the difference between the white noise signal output from the speaker 25 as a sound and the detection signal obtained via the propagation path reaching the evaluation microphone 26 through the duct 21. That is, the acoustic transfer characteristic GAO of the propagation path from the speaker 25 to the evaluation microphone 26 is the acoustic transfer characteristic to be obtained and the transfer characteristic GAO to be set in the signal conversion filter 30.

Further, the extraction circuit 45 and the adaptive filter 4
In 2, the acoustic transfer characteristic GAS between the speaker 25 and the sound source microphone 24 can be identified by performing the same identification process as described above, and this becomes the transfer characteristic to be set in the cancel filter 31. is there.

The inventors of the present invention also detect the detection signal obtained by extracting only the direct sound from the detection signal of the evaluation microphone 26 as in the above embodiment and the detection signal itself of the evaluation microphone 26 corresponding to the conventional one, that is, the reflected sound. When the identification process was performed for each of the included detection signals, the results shown in FIGS. 3A and 3B were obtained, respectively. That is, in FIG. 6A, which is the result of the case where only the direct sound is extracted and the identification is performed, the adverse effect of the reflected sound does not occur (the area indicated by A in the figure), but the reflected sound is also included In the same figure (b) which is the result of the case identified by (1), there is an adverse effect due to the reflected sound (area indicated by a in the figure).

When the sound transfer characteristics G AO and G AS identified in this way are set in the signal conversion filter 30 and the cancel filter 31 respectively to perform the muffling operation (when the control is on), the muffling operation is not performed. It was found that the sound deadening effect as shown in FIG. 4A was obtained compared to (when the control was off). As a result, even if compared with the result of the conventional control (see FIG. 7B),
It was found that the sound deadening effect was greatly improved in the frequency region of 50 Hz or higher (regions indicated by B and b in the figure).

According to the present embodiment as described above, when the acoustic transfer characteristics G AO and G AS to be set in the signal conversion filter 30 and the cancel filter 31 are identified prior to the muffling control, the extraction circuit 37, 45 are provided respectively so that the reflected sound component is removed from the detection signal of the random noise detected by each of the sound source microphone 24 and the evaluation microphone 26, and only the direct sound component is extracted and given to the adaptive filter 34 or 42. Therefore, the respective acoustic transfer characteristics can be identified based on only the direct sound component, and the duct 21 in the silencing operation state can be identified.
It becomes possible to accurately identify and set the sound transmission characteristics in the inside, and it is possible to output the accurate interference sound according to the sound transmission characteristics at the time of the silencing operation from the speaker 25, and improve the silencing effect. Therefore, it is possible to always obtain a certain silencing effect without being influenced by the acoustic environment of the place where the device is installed.

Further, according to the present embodiment, the extraction circuit 37
Is composed of the delay circuit 38 and the adaptive filter 39, and the direct sound component is extracted by identifying the autocorrelation function of the detection signal from the evaluation microphone 26. Therefore, the signal conversion is performed with a simple configuration. Filter 3
The acoustic transfer characteristic G AO to be set to 0 can be identified as described above.

FIG. 5 shows the second embodiment of the present invention. The difference from the first embodiment is that the noise generator 33 is used.
The random noise signal output from the speaker is provided to the speaker 25 and the identification circuits 35 and 43 via the periodic component removing circuit 50.

That is, in this embodiment, when the random noise signal generated by the noise generator 33 contains a periodic component or the noise signal itself has an autocorrelation characteristic, the periodicity obtained by removing the periodic component is used. It is intended to be used as a random noise signal without noise. As the random noise signal used for the identification processing, it is preferable to use a random noise signal having no periodicity or having periodicity such as M-sequence noise, the period of which is sufficiently longer than the response length when the signal processing is handled. Although ideal, the characteristics of the noise generator actually used may not always satisfy this condition.

In this case, if the random noise signal contains a short periodic component, there is an adverse effect due to autocorrelation when the direct sound component is extracted by the extraction circuits 37 and 45 in the first embodiment. However, there is a problem in that the sound component cannot be accurately extracted directly.

Further, in order to identify the acoustic transfer characteristics by using the random noise signal of only the frequency band to be silenced in the identification processing, when the random noise signal is band-limited and output through a bandpass filter or the like, Even if the random noise signal is completely random, the convolved signal with the impulse response of the filter makes the correlated signals overlap with each other with a time difference, which may adversely affect the extraction of the direct sound.

This embodiment is for coping with such a problem, and the periodic component removing circuit 50 comprises a delay circuit 51 as a delay means and a periodic component identifying adaptive filter 52 as a signal adjusting means. The periodic component identification adaptive filter 52 is composed of an identification circuit 53 and a calculator 54. In this configuration, a periodic component is identified from the random noise signal output from the noise generator 33 by performing a process substantially similar to that of the extraction circuit 37 or 45 described in the first embodiment, and the identification is performed. The random noise signal is randomized and used by outputting the component that cannot be obtained.

Therefore, according to the second embodiment, even if the random degree of the random noise signal generated by the noise generator 33 is incomplete, it is used as a random noise signal having sufficient randomness. Therefore, the direct sound can be surely extracted.

FIG. 6 shows a third embodiment of the present invention, which is similar to the second embodiment, except that the random noise signal output from the noise generator 33 by the periodic component removing circuit 50 is used. It is configured to deal with a case where the power of the output signal is significantly reduced when the periodic component is removed.

That is, the output terminal of the noise generator 33 is connected to the speaker 25 and the identification circuits 35 and 43 through the band pass filter (BPF) 55 having a pass band in the frequency band in which the random noise signal is silenced. At the same time, the periodic component extracting circuit 56 as the periodic component extracting means.
It is connected to the. The periodic component extraction circuit 56 is composed of a delay circuit 57 and an adaptive filter 58, and the adaptive filter 58 is composed of an identification circuit 59 as a correction means and a calculator 60.

In the above structure, the adaptive filter 58 is
By performing the same processing steps as the extraction circuit 37,
The periodic component is identified from the random noise signal given from the noise generator 33 through the BPF 55, and the autocorrelation data of the periodic component identified by the identification circuit 59 is extracted by the identification circuit 40 of the extraction circuits 37 and 45. , 48, and when the extraction circuits 37, 45 extract the direct sound component, the coefficient updating operation is stopped to correct the filter coefficient.

As a result, the adaptive filters 34 and 42 can perform the acoustic transfer characteristic identification processing based on the detection signal of the direct sound component. Further, in the case where the band limitation is performed via the BPF 55 in this way, by performing the correction in this way, it is possible to prevent a problem in which the amplitude of the impulse response of the identified acoustic transfer characteristic is emphasized near the cutoff frequency. it can.

The present invention is not limited to the above embodiment, but can be modified or expanded as follows. The noise source 22 and the noise propagation path 21 may be a combination of a compressor of a refrigerator and its exhaust duct. A plurality of speakers 25 can be provided.

The random noise signal is not limited to white noise, but may be M-series random noise or the like. Identification means 4
2 functions as an identification unit that identifies the acoustic transfer characteristic of the propagation path from the speaker 25 to the sound source microphone 24 through the duct 21, and the extraction circuit 45 extracts the direct sound component from the detection signal of the sound source microphone 24. It functions as an extracting means for extracting.

[0090]

According to the adaptive active noise canceling apparatus of the first aspect, the control sound generator and the control sounding device set in the signal converting means necessary for performing the adaptive active noise canceling operation by the adaptive control means, and the second aspect. In identifying the acoustic transfer characteristic with the sound receiving means, the extraction means is provided, and the component that arrives in the shortest time from the random noise detection signals from the noise generating means by the second sound receiving means, that is, the direct sound. Since only the component is extracted and identified by the identifying means, the identifying means determines between the control sounder and the second sound receiving means based on the direct sound component of the random noise given from the extracting means. Acoustic transfer characteristics can be identified.

As a result, at the time of execution of the adaptive active noise reduction control, in the sound wall formed at the position of the second sound receiving means by the interference sound output from the control sounder in the steady state of the noise reduction operation, Also, since the same acoustic transfer characteristics as when the noise does not propagate to the downstream propagation path are set in the signal conversion means,
This has an excellent effect of enabling accurate muffling operation in a steady state.

According to another aspect of the adaptive active silencer of the present invention, the extracting means is composed of the signal delay means and the extracting adaptive filter, and the detection signal from the second sound receiving means is
Of the random noise signals detected by the second sound receiving means, based on the detection signal output from the second sound receiving means by the extraction adaptive filter and the signal delayed by the signal delay means for a predetermined time. The reflected sound component of is identified, and the direct sound component is extracted by outputting the unidentified direct sound component at this time.Therefore, it is possible to identify the acoustic transfer characteristics to be set in the signal conversion means while having a simple configuration. There is an excellent effect that it is possible to carry out an accurate identification process as the one suited to the state during the muffling operation.

According to the adaptive active noise suppressor of the third aspect, the signal adjusting means is provided, and the periodic component of the random noise signal output from the noise generator is output by the signal adjusting means when the identification is performed by the identifying means. Since a noise component is artificially generated by the noise generator, even if a short cycle sound component is included, it is given to the control sounder as a random noise signal with the cyclic component removed. As a result, it becomes possible to more accurately identify the acoustic transfer characteristic by the identifying means, and as a result, the silencing operation by the controlling means can be performed accurately and the silencing effect is improved. It has an excellent effect that

According to the adaptive active noise suppressor of the fourth aspect, when identification is performed by the identification means, the random noise signal from the noise generation means is given to the control sounder to output the random noise to the propagation path. At the same time, when this random noise signal is given to the periodic component extraction means to extract the component having the periodicity, and the direct sound component is extracted from the random noise detection signal detected by the second sound receiving means by the extraction means. Since the periodic component of the random noise signal contained in the detection signal is removed by being corrected by the correcting means and given to the identifying means, the periodic component is extracted from the noise signal output from the noise generating means as described above. If the output level drops if you try to remove it and give it to the control sound generator, do not lower the output level. Random noise can be output from the voice generator to be detected by the second sound receiving means. Even in this case, a detection error due to a periodic component included in the random noise signal can be eliminated. It has an excellent effect that the acoustic transfer characteristics can be accurately identified.

[Brief description of drawings]

FIG. 1 is a block configuration diagram at the time of identification showing a first embodiment of the present invention.

FIG. 2 is a block configuration diagram when performing adaptive active muffling.

FIG. 3 is an impulse response measurement result diagram of acoustic transfer characteristics G AO in the case of identifying by extracting only direct sound (a) and the case of including reflected sound (b).

FIG. 4 is a frequency characteristic diagram of a result of measuring a sound deadening effect using acoustic transfer characteristics G AO in the case of identifying only a direct sound (a) and the case of including a reflected sound (b).

FIG. 5 is a view corresponding to FIG. 1 showing a second embodiment of the present invention.

FIG. 6 is a view corresponding to FIG. 1 showing a third embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of active silencing showing a conventional example.

FIG. 8 is a view corresponding to FIG.

FIG. 9 is a view equivalent to FIG.

[Explanation of symbols]

21 is a duct (noise propagation path), 22 is a noise source, and 23
Is a muffler, 24 is a sound source microphone (first sound receiving means), 25 is a speaker (control sound generator), 26 is an evaluation microphone (second sound receiving means), 27 is a control unit, 28
Is an arithmetic unit (arithmetic means), 29 is an FIR filter (control means), 30 is a signal conversion filter (signal conversion means), 31
Is a cancellation filter (cancellation means), 32 is an adaptive filter (adaptive control means), 33 is a noise generator (noise generation means), 34 is an adaptive filter (identification means), 35
Is an identification circuit, 36 is an arithmetic unit, 37 is an extraction circuit (extraction means), 38 is a delay circuit (signal delay means), 39 is an adaptive filter for extraction, 40 is an identification circuit, 41 is an arithmetic unit, 42 is an adaptive filter, 43 is an identification circuit, 44 is an arithmetic unit, 45 is an extraction circuit, 46 is a delay circuit, 47 is an adaptive filter for extraction, 48 is an identification circuit, 49 is an arithmetic unit, 50 is a periodic component removal circuit, and 51 is a delay circuit (delay circuit). Means), 52 is an adaptive filter (signal adjusting means) for periodic component identification, 53 is an identification circuit, 54 is a computing unit, 55 is a bandpass filter, 56 is a periodic component extraction circuit (periodic component extraction means), and 57 is a delay circuit. , 58 are adaptive filters, 59 is an identification circuit (correction means), and 60 is an arithmetic unit.

Claims (4)

[Claims] 1. A first sound receiving means provided in a noise propagation path, and a noise interference sound for the noise provided in a position downstream of the first sound receiving means in the noise propagation path. A control sounder, a second sound receiving unit provided at a position downstream of the control sounder in the noise propagation path, and arithmetic processing based on a detection signal of the first sound receiving unit. Control means for generating a control signal to output the interference sound to the control sounder by performing, and the control sounder and the first sound receiving means to which the control signal generated by the calculation means is input. Canceling means for filtering as a canceling signal by filtering the acoustic transfer characteristic between the canceling means and the calculating means for subtracting the canceling signal of the canceling means from the detection signal of the first sound receiving means and applying the canceling signal to the control means. Calculation The output signal of the means is transmitted to the control sound generator and the second sound generator.
Signal converting means for filtering with the acoustic transfer characteristic between the sound receiving means and the reference signal from the second sound receiving means and the reference signal from the signal converting means. Adaptive control means for adjusting the calculation coefficient of the control means so that the volume of sound produced by the sounding device is maximized, noise generating means for outputting random noise from the control sounding device, and output from the control sounding device Extraction means for extracting a component in which the random noise output from the control sound generator reaches the second sound receiving means in the shortest time based on the detection signal of the second sound receiving means for the random noise. The control sound generator and the second sound receiver to be set in the signal converting means based on the extracted signal from the extracting means and the random noise signal from the noise generating means. An adaptive active muffling apparatus comprising: an identification unit that identifies a sound transfer characteristic between the stage and the stage. 2. The extracting means includes a signal delay means for delaying a detection signal of the second sound receiving means by a predetermined time, a detection signal of the second sound receiving means and a detection signal delayed by the delay means. The random noise output from the control speaker is identified by identifying the reflection component that does not reach the second sound receiving means in the shortest time among the random noise from the control speaker. 2. The adaptive active silencer according to claim 1, further comprising: an extraction adaptive filter that outputs a component that reaches the second sound receiving means in the shortest time. 3. A delay unit for delaying a random noise signal from the noise generating unit for a predetermined time, based on the random noise signal output from the noise generating unit and a random noise signal delayed by the delay unit. 3. The adaptive active silencer according to claim 1, further comprising signal adjusting means for removing a component having periodicity from the random noise signal and outputting the random noise signal to the control sounding device. . 4. A periodic component extracting means for extracting a component having a periodicity from a random noise signal output from the noise generating means, and the random noise detection signal by the second sound receiving means by the extracting means. When the component that reaches the second sound receiving means in the shortest time is extracted, correction is performed based on the periodic component extracted by the periodic component extracting means so as to remove the periodic component included in the random noise signal. A correction means is provided, The said 1 or 2 characterized by the above-mentioned.
The adaptive active silencer described.