JP2955855B1 - Active noise canceller - Google Patents

Abstract

An identification sound used for identifying a secondary sound path (transfer function) C is made inconspicuous in audibility. SOLUTION: When identifying a secondary sound path C, a pseudo signal m (k) generated by a pseudo signal generator 15 is supplied to a level adjusting unit 18.
After adjusting the level by the secondary sound source speaker 7
From the second sound path C as an identification sound. At this time, the error microphone 1 when this identification sound is not emitted
The level of the output signal e (k) of the exhaust duct 1 is detected by the level detector 19, thereby detecting the noise level remaining in the exhaust duct 1 without being completely removed. Then, by controlling the level adjusting unit 18 based on the detection level, the emission level of the identification sound is set to a level necessary and sufficient for identifying the secondary sound path C, that is, approximately equal to the noise level. This prevents the identified sound from being more noticeable than noise.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active noise eliminator for canceling noise existing in a transmission line by causing a signal having substantially the same phase as that of the noise to interfere with the noise.

[0002]

2. Description of the Related Art As an active noise eliminator as described above, for example, an active silencer as shown in FIG. 7 is conventionally known. This silencer cancels the exhaust sound by causing a sound wave, for example, an exhaust sound of an engine (not shown) to interfere with a sound wave having substantially the same phase as that of the exhaust sound. It is assumed that the exhaust sound to be silenced by the silencer propagates in the exhaust duct 1 from left to right in FIG.

As shown in FIG. 1, the silencer includes a reference microphone 2 on the inlet side (left side in FIG. 1) of an exhaust duct 1 for collecting the exhaust noise.
The output signal of the microphone 2 is amplified by the amplifier 3 and further digitized by the A / D converter 4 to obtain a noise signal x (k) (where k is an index representing time). An input FIR adaptive digital filter (hereinafter simply referred to as an adaptive filter) 5 is provided. The adaptive filter 5 performs a predetermined filtering process on the noise signal x (k) input thereto by using a filter coefficient set by an LMS calculation unit 6 described later, for example, is represented by the following equation 1. Such a convolution sum operation is performed, and the operation result y (k) is output.

[0004]

(Equation 1)

In the equation 1, N is the number of taps of the adaptive filter 5, and i is an index representing the tap number (order). W _k (i) represents a filter coefficient of the adaptive filter 5.
Represents the filter coefficient of the i-th tap in.

On the other hand, a secondary sound source speaker (hereinafter simply referred to as a speaker) 7 is provided downstream of the reference microphone 2 in the exhaust duct 1 with respect to the exhaust sound so as to emit sound into the exhaust duct 1. Is provided. The output signal y (k) of the adaptive filter 5 is supplied to the loudspeaker 7 by an adder 8, a D / A converter 9 and an amplifier 10.
Is entered via The speaker 7 emits a sound wave corresponding to the signal y (k) into the exhaust duct 1 and
This exhaust noise is canceled by interfering with the exhaust noise propagating inside.

Further, an error microphone 11 is disposed at the outlet side of the exhaust duct 1, and the error microphone 11 cancels the exhaust sound with the sound emitted from the speaker 7, that is, the sound of the exhaust sound. Speaker 7
The so-called residual components which are not completely canceled by the emission sound of are detected. The output of the error microphone 11 is amplified by the amplifier 12, digitized by the A / D converter 13, and the digitized signal is used as the error signal e (k) as the LMS signal described above.
It is supplied to the arithmetic unit 6. The LMS operation unit 6 includes:
In addition to the error signal e (k), a signal obtained by processing a noise signal x (k) by an FIR filter 14 described below (hereinafter, this signal is referred to as a filtered reference) r (k).
Is also supplied.

[0008] The LMS calculation unit 6 is adapted to provide the error signal e (k) supplied thereto and the filtered reference r (k).
Accordingly, a transfer function _obtained by combining the transfer function W _k of the adaptive filter 5 and a transfer function C of a secondary sound path (error path) described below (hereinafter, simply referred to as a secondary sound path) (ie, A transfer function [W _k × C] obtained by multiplying them by the primary sound path (primary) existing between the reference microphone 2 and the error microphone 11 in the exhaust duct 1 is obtained.
path) transfer function (hereinafter simply referred to as a primary sound path) P
LMS represented by the following equation 2 so as to be complementary to
According to the algorithm, the filter coefficient W _k (i) of the adaptive filter 5 is updated, that is, W _{k + 1} (i) is obtained.

[0009]

(Equation 2)

[0010] In the equation (2), μ _w is a step size parameter of the adaptive filter 5.

As described above, in this silencer, the transfer function [W _k × C] _obtained by combining the transfer function W _k of the adaptive filter 5 and the secondary sound path C is made complementary to the primary sound path P. For the first time, the exhaust sound in the exhaust duct 1 can be canceled by the radiation sound of the speaker 7. Moreover, resulting acoustic properties, for example, changes over time in the exhaust duct 1, this also changes the primary sound path P, transmission of the adaptive filter 5 according to the change function W _k be the filter coefficient W _k Since it changes with the updating of (i), a stable noise reduction effect can always be obtained.

However, in order to obtain such a silencing effect,
It is known that the control system of this silencer needs to be configured with the Filtered-xLMS algorithm. That is, FIG.
In the configuration shown in (1), the error is output from the output terminal of the adaptive filter 5 through the adder 8, the D / A converter 9, the amplifier 10, the speaker 7, and a part of the exhaust duct 1 (downstream of the noise from the speaker 7). The secondary sound path C described above exists up to the microphone 11. Therefore, the above-mentioned muffling effect is obtained by the adaptive operation of the adaptive filter 5 by the LMS operation unit 6 (that is, the combined transfer function [W _k × C] of the transfer function W _k of the adaptive filter 5 and the secondary sound path C is Primary sound path P
In order to make the secondary sound path C complementary, it is necessary to compensate the secondary sound path C. Therefore, in the configuration of FIG. 7, the FIR filter 14 described above has the secondary sound path C equivalent transfer function Se _k, between the reference microphone 2 and the LMS computation unit 6 (strictly speaking, A / D (Between the converter 4 and the LMS operation unit 6). The FIR filter 14 supplies the signal obtained by processing the noise signal x (k), that is, the filtered reference r (k) to the LMS calculation unit 6, thereby forming the secondary sound path C. Compensated. The filtered reference r (k) is expressed by the following equation (3).

[0013]

(Equation 3)

However, in Equation 3, N is the FIR
The number of taps of the filter 14, here, the number of taps N
Is the same as the number of taps N of the adaptive filter 5. Se _k (i) represents a filter coefficient of the FIR filter 14 at time k.

When the engine operates and its rotation speed changes, the temperature and the flow velocity in the exhaust duct 1 change in accordance with the change in the rotation speed. The change in the temperature and flow velocity in the exhaust duct 1 and the change in the output characteristics of the loudspeaker 7 caused by the change and the like cause the secondary sound path C
Is known to change over time. Therefore, in order to always obtain a stable noise reduction effect during the operation of the engine, the FIR is changed in accordance with the change of the secondary sound path C.
As also alter the transfer function Se _k of the filter 14,
For example, it is necessary to periodically re-identify the secondary sound path C. Therefore, in this silencer, the secondary sound path C
For example, a pseudo signal (pseudo random noise) m (k) of a generally known M-sequence signal (MLS)
Is provided, and the pseudo signal m
By processing (k) on the path indicated by the dotted line in FIG. 7, the secondary sound path C is identified. This will be described with reference to FIG.

FIG. 8 is an excerpt of the control system for identifying the path indicated by the dotted line in FIG. 7, that is, the secondary sound path C, in order to make the description easy to understand. In FIG. 8, the adder 8, the D / A converter 9, and the amplifier 1 in FIG.
0, 12, and the A / D converter 13 are also omitted.

As shown in FIG. 8, in this control system, an FIR filter 14 for identifying a secondary sound path C is provided.
Is, for example, an operation unit 1 different from the above-described LMS operation unit 6.
6, an adaptive filter configuration that is adaptively controlled according to, for example, an LMS algorithm. The pseudo signal m (k) generated by the pseudo signal generator 15 is transmitted to the speaker 7, F
The output signal of the error microphone 11 and the signal obtained by processing the pseudo signal m (k) by the FIR filter 14 are compared by an arithmetic unit 17 while being supplied to the IR filter 14 and the LMS operation unit 16. Ε (k)
This is supplied to the LMS operation unit 16. The LMS operation unit 16 reduces the error signal ε (k) according to the pseudo signal m (k) and the error signal ε (k) supplied thereto, that is, the pseudo signal m (k) Is passed through the secondary sound path C, and the signal after the pseudo signal m (k) is processed by the FIR filter 14 is equal to each other, for example, an LMS algorithm represented by the following equation (4). According to the FIR
Update the filter coefficients of the filter 14 Se _k (i), namely finding a _{Se k + 1} (i).

[0018]

(Equation 4)

Here, μ _S is a step size parameter of the FIR filter 14.

Based on the equation (4), the FIR filter 14
By updating the filter coefficient Se k _(i),
And transfer of the FIR filter 14 functions Se _k and secondary sound path C becomes substantially equivalent secondary sound by FIR filter 14 path C
Can be realized, and a high noise reduction effect can be obtained.

However, the FIR filter 14 processes the pseudo signal m (k) at the time of the operation of identifying the secondary sound path C, but at the time of the adaptive operation (LM) for silencing the exhaust sound described above.
At the time of adaptive control of the adaptive filter 5 by the S operation unit 6),
Process the noise signal x (k). Therefore, in the configuration of FIG.
The operation of identifying the secondary sound path C and the operation of adapting for silencing cannot be performed simultaneously. Therefore, in this silencer, the operation of identifying the secondary sound path C and the adaptive operation for silencing are alternately performed.

That is, the adaptive filter 5 has a transfer function W _k (strictly speaking, which can obtain a certain noise reduction effect).
The filter coefficient W _k (i)) is set in advance. Also, the FIR filter 14, the secondary sound path C transmission are be identified with a certain degree of precision function Se k _(strictly speaking, the filter coefficient Se k _(i)) is set in advance.

In this state, for example, first, the adaptive operation of the adaptive filter 5 by the LMS calculation unit 6 is stopped, and the adaptive filter 5 is made to function as a simple FIR filter whose transfer function _Wk is fixed. Then, the pseudo signal m (k) is generated from the pseudo signal generator 15, and the adaptive operation of the FIR filter 14 by the LMS operation unit 16 is performed, thereby accurately identifying the secondary sound path C.

Next, the adaptive operation of the FIR filter 14 is stopped, and the FIR filter 14 is changed to its transfer function Se.
_k serves as a fixed simple FIR filter.
Note that the transfer function Se of the FIR filter 14 at this time is
_k is the transfer function Se at the time of stopping the adaptive operation.
_k . At the same time, the generation of the pseudo signal m (k) is stopped, and this time, the adaptive operation of the adaptive filter 5 by the LMS calculation unit 6 is executed, thereby further increasing the noise reduction effect of the noise reduction device.

Thereafter, as described above, the LMS
If the operation of identifying the secondary sound path C in which the FIR filter 14 is adaptively controlled by the arithmetic unit 16 and the adaptive operation for silencing in which the adaptive filter 5 is adaptively controlled by the LMS arithmetic unit 6 are alternately executed, Even if the secondary sound path C changes,
A stable noise reduction effect is always obtained.

The adaptive filter 5, the LMS operation unit 6, the adder 8, the FIR filter 14, the LMS operation unit 1
6. The arithmetic unit 17 is constituted by, for example, a DSP (Digital Signal Processing Unit) or a CPU (Central Processing Unit). The DSP, CPU, and the like execute the adaptive operation for silencing, the operation of identifying the secondary sound path C, and the like in accordance with a program stored in a storage unit such as a memory (not shown).

Further, as described above, the secondary sound path C is identified using the pseudo signal m (k) in a state where the engine is operating, that is, in an environment where the exhaust sound of the engine exists. In this case, if the sound emitted from the speaker 7 based on the pseudo signal m (k) (hereinafter, this sound is called the identification sound) is smaller than the exhaust sound, the identification sound is buried in the exhaust sound. In this case, the secondary sound path C cannot be accurately identified. Therefore, in order to accurately identify the secondary sound path C using the identification sound, the level of the identification sound needs to be at least substantially equal to or higher than the level of the exhaust sound. Therefore, conventionally, the level of the identification sound has been set slightly higher than the expected maximum level of the exhaust sound.

[0028]

As described above, according to the above-mentioned prior art, the level of the identification sound is set slightly lower than the expected maximum level of the exhaust sound so that the identification sound is not buried in the exhaust sound. Since it is set to be relatively large, the secondary sound path C can be accurately identified, and a stable noise reduction effect can be obtained. However, as the noise reduction effect is improved, the exhaust sound output from the exhaust duct 1 is reduced, but the level of the identification sound is always constant, so that the identification sound is relatively compared with the exhaust sound. This causes a problem that the identification sound becomes conspicuous in terms of hearing. The problem that the identification sound, that is, the pseudo signal m (k) is conspicuous is that if the configuration is the same as that in FIG. 7 (and FIG. 8), for example, in other active noise removing devices such as an echo canceller, Occurs similarly.

In order to accurately identify the transfer function similar to that of the secondary sound path C using the pseudo signal m (k) of the identification sound or the like, the signal level of the pseudo signal m (k) must be It is not necessary to keep it constant as in the prior art. The signal level of the pseudo signal m (k) is at least substantially equal to the level of the noise after removal by the active noise removal device (in other words, the residual component of the so-called noise remaining without being completely removed). If so, the above identification can be accurately realized, that is, it is necessary and sufficient to accurately realize the identification. Therefore, the present invention focuses on this point, and changes the level of the pseudo signal m (k) to a level necessary and sufficient to accurately realize the above identification according to the noise level after removal. , While accurately realizing the above identification and at the same time, the pseudo signal m (k)
It is an object of the present invention to provide an active noise elimination device that can make the noise less noticeable.

[0030]

In order to achieve the above object, the invention according to claim 1 comprises a first detecting means for detecting a signal input to a transmission line having a first transfer function;
Second detection means for detecting a signal output from the transmission path; adaptive filter means for processing an output signal of the first detection means and emitting the signal to the transmission path;
And the respective output signals of the second detecting means are input, and in response thereto, the transfer function of the adaptive filter means and the second side of the adaptive filter means from the output side through a part of the transmission path. An adaptive control for controlling the transfer function of the adaptive filter means so that a first combined transfer function obtained by combining the second transfer function existing up to the detection means and the first transfer function is complementary. Filter control means, pseudo signal generation means for generating a pseudo signal, level adjustment means for adjusting the signal level of the pseudo signal according to a level adjustment command, and then inputting the signal to the second transfer function; Detects the signal level of the output signal of the second detection means when the second transfer function is in a non-input state with respect to the second transfer function, and detects the second detection means corresponding to the detected signal level. Detection by And the level of the signal in the transmission path at the device and the pseudo signal at the position detected by the second detection means when the pseudo signal is input to the second transfer function via the level adjustment means. And the second transfer function interposed between the first detection means and the adaptive filter control means so that the signal level of the second transfer function is substantially equal to the signal level of the second transfer function. Digital filter means for identifying the
In the non-input state for the transfer function of
And fixing the transfer function of the digital filter means.
An output of the first detecting means by a digital filter means
The signal after processing the signal is sent to the adaptive filter control means.
Input to the adaptive filter control means.
Control of the transfer function of the
Input to the second transfer function via the level adjusting means.
The adaptive filter control means
Control of the transfer function of the adaptive filter means by
To fix the transfer function of the adaptive filter means,
The pseudo signal or the pseudo signal is supplied to the level adjusting means.
The signal after level adjustment by the digital filter
Input to the digital filter means.
The processed signal and the output signal of the second detection means are substantially the same.
And an identification filter control means for controlling a transfer function of the digital filter means.

According to the first aspect of the present invention, the first detecting means detects a signal input to the transmission line, for example, noise to be removed, and the second detecting means detects the signal to be removed. A signal output via a transmission path having a transfer function of 1 is detected. Then, the signal after the output signal of the first detecting means is processed by the adaptive filter means is emitted to the transmission path. Note that a second transfer function exists between the output side of the adaptive filter unit and the second detection unit via a part of the transmission path. Then, the adaptive filter control means responds to each output signal of the first and second detection means,
The transfer function of the adaptive filter means is, for example, an LMS algorithm so that a first combined transfer function obtained by combining the transfer function of the adaptive filter means and the second transfer function is complementary to the first transfer function. The control is performed based on an arithmetic expression such as By complementing the first combined transfer function and the first transfer function in this way, the noise can be canceled by a signal emitted from the adaptive filter means into the transmission path. Further, digital filter means for identifying the second transfer function is provided between the first detection means and the adaptive filter control means, whereby a control system of the entire active noise elimination apparatus is provided. Filtered-x
LMS algorithm configuration.

In the first aspect of the present invention, a pseudo signal is used to identify the second transfer function by the digital filter means. That is, a pseudo signal generating means for generating a pseudo signal is provided, the level of the pseudo signal is adjusted by a level adjusting means, and the pseudo signal is input to a second transfer function, which is detected by a second detecting means. I have. Therefore, at the time of identification of the second transfer function, the second detection means emits the pseudo signal whose level has been adjusted by the level adjustment means and the noise from the adaptive filter means into the transmission path. The so-called residual components remaining without being completely canceled by the signal are simultaneously detected. Then, the identification filter control means inputs the pseudo signal or the signal after level adjustment of the pseudo signal by the level adjustment means to the digital filter means.
And the signal processed by this digital filter means
And the pseudo signal is transmitted through the level adjusting means in the second transmission.
Output signal of the second detection means when input to the function
And digital filter means so that
Control the transfer function. This realizes accurate identification of the second transfer function by the digital filter means.
According to this configuration, the digital filter means includes:
Interposed between the detection means and the adaptive filter control means
When the control system of Filtered-x LMS algorithm configuration is formed
In addition to its original function, the second transfer function
Function to derive a transfer function for identification
Will do. And the digital filter means
The control system of the above Filtered-x LMS algorithm configuration is formed.
The first detection
Processing the output signal of the means to accurately determine the second transfer function
Demonstrates the function of deriving a transfer function for identification
In some cases, the pseudo signal or this pseudo signal is
The signal after the level adjustment by the adjusting means is processed.

In order to accurately identify the second transfer function using the pseudo signal, as described above, the signal level of the pseudo signal input to the second transfer function to be identified is as described above. Must be at least approximately equal to the level of noise remaining uncancelled in the second transfer function. And if these levels are almost equal,
The second transfer function can be identified sufficiently accurately.

Therefore, according to the first aspect of the present invention, the signal level of the output signal of the second detection means when the pseudo signal is not input to the second transfer function is detected by the level control means. By doing so, noise remaining without being canceled in the second transfer function is detected. Then, the level control means determines the residual noise level obtained by the detection,
The signal level of the pseudo signal at the position detected by the second detection means when the pseudo signal is input to the second transfer function via the level adjusting means (in other words, the pseudo signal is converted to the second transfer function) (A signal level of the pseudo signal detected by the second detection means when the signal is input), and a level adjustment command for controlling the level adjustment means is generated. As a result, the signal level of the pseudo signal input to the second transfer function is automatically adjusted to a level necessary and sufficient to identify the second transfer function.

According to experiments, even if the signal level of the pseudo signal at the position detected by the second detecting means is slightly lower than the signal level of the residual noise at the position detected by the second detecting means, A result was obtained in which the second transfer function could be accurately identified. Therefore, the above-mentioned “substantially equivalent” means that the signal level of the pseudo signal at the position detected by the second detecting means is slightly smaller than the signal level of the residual noise at the position detected by the second detecting means. And equivalent cases, and even slightly larger cases.

According to a second aspect of the present invention, the first transfer function
Detection for detecting a signal input to a transmission line having
Means for detecting a signal output from the transmission path;
And the output signal of the first detecting means is processed.
Adaptive filter means for emitting this to the transmission path,
Each output signal of the first and second detection means is input,
According to these, the transfer function of the adaptive filter means
From the output side of the adaptive filter means
A second part existing between a part and the second detecting means.
And the first combined transfer function resulting from the combination of
The adaptive filter is set in a state complementary to the first transfer function.
Adaptive filter control means for controlling a transfer function of the filter means;
A pseudo signal generator for generating a pseudo signal composed of an M-sequence signal
And the signal level of the pseudo signal according to the level adjustment command.
And then input this to the second transfer function.
Level adjusting means, wherein the pseudo signal is the second transfer function
Of the second detection means when in the non-input state with respect to
The signal level of the output signal is detected, and the signal obtained by this detection
At the position detected by the second detecting means corresponding to the level
The level of the signal in the transmission path and the pseudo signal
Input to the second transfer function via the level adjusting means.
At the position detected by the second detecting means when
When the signal level of the signal is
Level control means for generating an adjustment command, and the first detection
Between the output means and the adaptive filter control means.
Digital filter means for identifying the second transfer function;
Including the pseudo signal or the pseudo signal
The signal after level adjustment by the
Signal to the second transfer function via the level adjusting means.
When the second detecting means is in the input state,
An output signal is input, and the second
Of the transfer function of
Set as the transfer function of the digital filter means,
The second transmission is performed by a correlation method using a so-called M-sequence signal.
Identification filter control means for identifying the arrival function .

[0037]

The digital filter means is an example
For example, only the output signal of the first detecting means is input to this.
Then, only the output signal of the first detecting means is processed,
The processed signal is input to the adaptive filter control means.
It is good also as a structure which makes it. And the above-mentioned identification filter control
The configuration of the means is different from that of the above digital filter means.
The pseudo signal or the pseudo signal is connected to the level adjusting means.
The signal whose level has been adjusted by
Input to the second transfer function via the bell adjusting means
And the output signal of the second detecting means in the state.
And estimate a second transfer function by their correlation.
And the transfer function obtained by this estimation
Means for setting as a transfer function of the filter means.
You. With this configuration, the adaptive operation for adaptively controlling the adaptive filter means by the adaptive filter control means and the identification operation for accurately identifying the second transfer function are simultaneously executed. The so-called online identification (or real-time identification or background identification) can be realized.

According to a third aspect of the present invention, a first detecting means for detecting a signal input to a transmission line having a first transfer function, and a second detecting means for detecting a signal output from the transmission line.
Detecting means, an adaptive filter means for processing and outputting the output signal of the first detecting means, and adjusting the level of the output of the adaptive filter means in accordance with a level adjustment command, and releasing the output to the transmission line. Level adjusting means, and the output signals of the first and second detecting means are input, and the transfer function of the adaptive filter means
A second transfer function obtained by synthesizing a transfer function of the level adjusting means and a second transfer function existing between the output side of the level adjusting means and the second detecting means via a part of the transmission path. An adaptive filter control means for controlling the transfer function of the adaptive filter means and a pseudo signal are generated so that the combined transfer function is complementary to the first transfer function, and the level of the pseudo signal is adjusted by the level adjusting means. A pseudo signal generating means for inputting the signal to the second transfer function, and detecting a signal level of an output signal of the second detecting means when the pseudo signal is in a non-input state with respect to the second transfer function. And
The level of the signal in the transmission line at the position detected by the second detecting means corresponding to the signal level obtained by the detection and the pseudo signal are converted to the second transfer function via the level adjusting means. Level control means for generating the level adjustment command so that the signal level of the pseudo signal at the detection position by the second detection means when the signal is input is substantially equal to the first detection means; Digital filter means for identifying a third combined transfer function obtained by combining the transfer function of the level adjusting means and the second transfer function interposed between the pseudo-signal and the adaptive filter control means.
Signal is in a non-input state with respect to the second transfer function.
Fix the transfer function of the digital filter means
At the same time, the first detection is performed by the digital filter means.
After processing the output signal of the
Input to the filter control means, and
Control of the transfer function of the adaptive filter means;
The pseudo signal is transmitted to the second transmission via the level adjusting means.
When in the state of being entered into the function, the adaptive fill
Of the transfer function of the adaptive filter means by the
Stop the control and fix the transfer function of the adaptive filter means
The pseudo signal and the digital filter
Input to the stage and processed by this digital filter
Is substantially equal to the output signal of the second detecting means.
In that state, it is to anda identification filter control means for controlling the transfer function of the digital filter means.

That is, the active noise eliminator according to the third aspect of the present invention also employs a Filtered-x control system similar to the active noise eliminator according to the first aspect of the present invention.
LMS algorithm configuration. However, the present claim 3
In the invention described in (1), the output of the adaptive filter means is emitted to the transmission path via the level adjustment means.This point is that the output of the adaptive filter means is directly transmitted to the transmission path without passing through the level adjustment means. This is a point different from the invention described in claim 1 described above. According to this aspect, according to the first aspect of the invention, only the second transfer function is to be identified by the digital filter means, whereas in the third aspect of the invention, the level adjustment means is provided. The third combined transfer function obtained by combining the transfer function of the second transfer function and the second transfer function is to be identified by the digital filter means.

When the third combined transfer function including the second transfer function is identified, the level control means controls the signal level of the pseudo signal input to the second transfer function via the level adjusting means (specifically, , The signal level of the pseudo signal at the position detected by the second detection means) is automatically adjusted to a level necessary and sufficient for identifying the third combined transfer function, in particular, the second transfer function. Is the same as in the first aspect of the present invention.

According to a fourth aspect of the present invention, the first transfer function
Detection for detecting a signal input to a transmission line having
Means for detecting a signal output from the transmission path;
And the output signal of the first detecting means is processed.
And adaptive filter means for outputting the adaptive filter
The output of the means was adjusted according to the level adjustment command.
After a level adjustment means for releasing it to the transmission line, the upper
Each output signal of the first and second detection means is input, and
Accordingly, the transfer function of the adaptive filter means,
Transfer function of the level adjusting means, and the level adjusting means
From the output side of the second detection means through a part of the transmission path.
And the second transfer function existing between the stages
The second combined transfer function is complementary to the first transfer function
Control the transfer function of the adaptive filter means to a state
Adaptive filter control means, and a pseudo signal comprising an M-sequence signal
And adjust the level by the level adjusting means.
The pseudo signal generating means for inputting to the second transfer function
A step, wherein the pseudo signal is non-input to the second transfer function.
Signal of the second detection means in the power state.
Signal level, and corresponds to the detected signal level
The transmission line at a position detected by the second detecting means.
The level of the signal in
The above when input to the second transfer function via a stage
The signal level of the pseudo signal at the position detected by the second detecting means.
The above level adjustment command is issued so that the
Generating level control means, the first detection means, and the
The above level adjustment is interposed between the adaptive filter control means
The second transfer function is obtained by combining the transfer function of the means and the second transfer function.
Digital filter means for identifying the composite transfer function of
Including the pseudo signal and the pseudo signal
State being input to the second transfer function via the means
And the output signal of the second detection means when the
From these correlations, the third combined transfer function is estimated.
Transfer function obtained by this estimation
Identification filter control method set as transfer function of filter means
And a step .

That is, the active noise elimination apparatus according to the fourth aspect of the present invention also provides the active noise elimination apparatus according to the third aspect of the present invention.
As with the removal device, the output of the adaptive filter means
Release to the transmission line via the adjustment means and level adjustment
A third combination of the transfer function of the means and the second transfer function.
The composite transfer function is identified by a digital filter
An elephant. And this third combined transfer function
When identifying the active type, the active type of the invention according to claim 2 described above is used.
Similar to the noise removing device, the pseudo signal and the second detecting means
The third combined transfer function is calculated by the correlation with the output signal of
Utilize correlation method using so-called M-sequence signal to identify
I do.

The invention according to claim 5 is the invention according to claims 1, 2,
5. The active noise elimination device according to the invention described in 3 or 4, wherein the signal input to the transmission path is a sound wave, and the active noise elimination device is an active noise reduction device for removing the sound wave. It is characterized by the following.

[0045]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the case where an active noise elimination device according to the present invention is applied to, for example, an active silencer,
The first embodiment will be described with reference to FIGS.

FIG. 1 is a schematic configuration diagram of the first embodiment. As shown in the figure, the first embodiment is different from the conventional muffler shown in FIG. 7 in that the pseudo signal m generated by the pseudo signal generator 15 is provided on the output side of the pseudo signal generator 15. Level adjusting section 18 for adjusting the level of (k)
Is provided. That is, the level adjustment unit 18
The level of the pseudo signal m (k) generated by the pseudo signal generator 15 is adjusted in accordance with a level adjustment signal supplied from a level detector 19 described later, and the adjusted signal is added to the adder 8.
(Eventually, speaker 7), FIR filter 14 and L
Each is supplied to the MS operation unit 16.

On the other hand, the level detector 19 takes in the error signal e (k) output from the error microphone 11 via the amplifier 12 and the A / D converter 13, detects the signal level, and detects the signal level. The level adjustment signal is generated according to the detected signal level. However, when the pseudo signal generator 15 does not generate the pseudo signal m (k), that is, when the pseudo signal generator 15 does not generate the pseudo signal m (k), the sound wave (that is, the identification sound) based on the pseudo signal m (k) is emitted from the speaker 7. Error signal e (k) only when
Is detected. Therefore, the level detection unit 19 removes the so-called noise remaining without being completely canceled by the sound wave emitted from the speaker 7 based on the output y (k) of the adaptive filter 5 among the noise propagating in the exhaust duct 1. Residual components will be detected. Then, based on the detected signal level,
The level of the residual component of the noise at the installation position of the error microphone 11 and the level of the identification sound at the installation position of the error microphone 11 when the identification sound is emitted from the speaker 7 are substantially equal to each other. A level adjustment signal for controlling the adjustment unit 18 is generated. In addition,
When the identification sound is emitted from the speaker 7, that is, when the secondary sound path C is identified by performing the adaptive operation of the FIR filter 14 by the LMS calculation unit 16, the level detection unit 19 outputs the error signal. Does not detect the signal level of e (k).

The remaining structure of the first embodiment is the same as that of the conventional silencer shown in FIG. 7, and therefore, these same parts are designated by the same reference numerals as in FIG.
A detailed description thereof will be omitted.

In the silencer configured as described above,
For example, the exhaust sound of an engine (not shown) is shown in FIG.
Propagation from left to right
You. The adaptive filter 5 has a certain amount of silencing effect.
Transfer function W that can obtain _k(Strictly speaking, Phil
Coefficient W_k(i)) is set in advance and the FIR
The filter 14 identifies the secondary sound path C with a certain degree of accuracy.
Transfer function Se_k(Strictly speaking, the filter
Coefficient Se_k(i)) shall be set in advance.
You. Also, the level adjustment unit 18 controls the transfer function (amplification).
Rate) L is in a so-called through state where L = 1.

In this state, for example, first, the pseudo signal m (k) is prevented from being generated from the pseudo signal generator 15 and the FIR filter 14 is connected to its transfer function Se _k.
Function as a simple FIR filter fixed to the preset value. Then, the adaptive operation of the adaptive filter 5 by the LMS operation unit 6 is executed. by this,
The noise reduction effect of the noise reduction device itself is improved, and the noise in the exhaust duct 1 is gradually reduced. Further, the level of the error signal e (k) at this time is detected by the level detecting section 19 to detect the noise level after the sound is muted. The level detector 19 detects the detected noise level and the level of the identification sound to be emitted from the speaker 7 (specifically, the level at the installation position of the error microphone 11 when the identification sound is emitted from the speaker 7). A level adjustment signal for controlling the level adjustment unit 18 is generated such that the level of the identification sound is substantially equal to the level of the identification sound.

Next, the adaptive operation of the adaptive filter 5 by the LMS operation unit 6 is stopped, and the adaptive filter 5 is
Its transfer function W _k is to function as a mere FIR filter fixed. Incidentally, the transfer function W _k of the adaptive filter 5 at this time, the transfer function W _k at the stop time of itself adaptive operation. At the same time, a pseudo signal m (k) is generated from the pseudo signal generator 15, and this time, the LMS
By executing the adaptive operation of the FIR filter 14 by the calculation unit 16, the secondary sound path C is accurately identified.

However, at this time, the pseudo signal m (k) is the level of the identification sound emitted from the speaker 7 based on the pseudo signal m (k) (specifically, the installation position of the error microphone 11 when the identification sound is emitted from the speaker 7). The signal level is adjusted by the level adjusting unit 18 controlled in accordance with the level adjustment signal so that the level of the identification sound in (1) is substantially equal to the noise level remaining in the exhaust duct 1. Note that the level of the identification sound at the installation position of the error microphone 11 is at least substantially equal to or higher than the level of the residual noise at the installation position of the error microphone 11, and strictly speaking, the level of the identification sound is at least slightly lower than the residual noise level. As described above, the secondary sound path C can be identified sufficiently accurately if it is small. Therefore, as the noise level in the exhaust duct 1 decreases, the identification sound emitted from the speaker 7 when the secondary sound path C is identified automatically decreases.

Thereafter, as described above, the LMS
The operation of detecting the noise level remaining in the exhaust duct 1 by the level detecting unit 19 while adaptively controlling the adaptive filter 5 by the calculating unit 6, and the level detecting unit 19
Signal m according to the noise level detected by
The operation of adaptively controlling the FIR filter 14 by the LMS calculation unit 16 while adjusting the signal level of (k) is performed alternately. As a result, even if the secondary sound path C changes, not only can a stable muffling effect be obtained at all times, but also
According to the noise level in the exhaust duct 1, the identification time is automatically adjusted to a level necessary and sufficient to accurately identify the secondary sound path C. Therefore, unlike the above-described related art, when the secondary sound path C is identified, the identified sound can be prevented from being conspicuous.

Further, since the level of the identification sound is suppressed to the minimum level required for identifying the secondary sound path C, the identification sound having a relatively large level is always output. Compared to the prior art, the amplifier 10 and the speaker 7
Can be reduced.

The level adjusting unit 18 and the level detecting unit 19 newly provided in the first embodiment are:
For example, it is configured by a DSP, a CPU, and the like. Since they only perform a very simple process of detecting the noise level remaining in the exhaust duct 1 and adjusting the signal level of the pseudo signal m (k) according to the detected level, for example, Even if an inexpensive DSP, CPU, or the like is used, the processing speed can be increased. Since the level adjusting section 18 and the level detecting section 19 can be constituted by such inexpensive DSPs and CPUs, the first embodiment can be realized at low cost. It should be noted that the above-mentioned DSP or C
The operation of the PU and the like is controlled according to a program stored in a storage unit (not shown).

By the way, in FIG.
(Adder 8), FIR filter 14, and LMS operation unit 1
Although the pseudo signal m (k) whose level has been adjusted by the level adjusting unit 18 is supplied to each of the devices 6, the present invention is not limited to this. That is, in view of the gist of the present invention that the level of the identification sound emitted from the speaker 7 is substantially equivalent to the noise level remaining in the exhaust duct 1, the pseudo signal m
Strictly, the level of (k) needs to be adjusted only for the speaker 7. Therefore, as shown in FIG. 2, the pseudo signal m (k) whose level has been adjusted by the level adjustment unit 18 is supplied only to the speaker 7, and the pseudo signal m (k) is supplied to the FIR filter 14 and the LMS calculation unit 16. The pseudo signal m (k) may be directly supplied from the signal generator 15.

However, in the configuration of FIG. 2, when the secondary sound path C is identified by the path indicated by the dotted line in FIG. 2, the transfer function Se of the FIR filter 14 for identifying the secondary sound path C is used.
_The LMS calculation unit 16 that obtains _k is a transfer function including not only the secondary sound path C but also the transfer function L of the level adjustment unit 18, that is, the transfer function L of the level adjustment unit 18 and the secondary sound path C. Will be obtained as a transfer function [L × C]. Therefore, in this case, only the secondary sound path C is obtained from the composite transfer function [L × C], and the obtained secondary sound path C is used as the FI.
It must be set as a transfer function Se _k of R filter 14. Therefore, in the configuration of FIG. 2, information on the transfer function L of the level adjustment unit 18 included in the level detection unit 19 (the transfer function L of the level adjustment unit 18 is
, The level detection unit 19 recognizes the transfer function L of the level adjustment unit 18) as shown by the dashed line in FIG.
It is supplied to the calculation unit 16. Then, the LMS calculation unit 16 calculates the combined transfer function [L × C] obtained by itself.
The, as shown in the following equation 5, by dividing by the transfer functions L, we obtain the secondary sound path C, and set it as a transfer function Se _k of the FIR filter 14.

[0058]

## EQU5 ## Se = (L × C) '/ L ≒ C

Here, the symbol '(dash) indicates that it is an estimated value of the combined transfer function [L × C].

The configuration of the first embodiment shown in FIGS. 1 and 2 corresponds to the invention described in claims 1 (and 5). Then, the primary sound path P and the secondary sound path C in the first embodiment are respectively
The transfer function [W _k × C] _obtained by combining the transfer function W _k of the adaptive filter 5 and the secondary sound path C corresponds to the first and second transfer functions of the first aspect of the present invention. Corresponding to the composite transfer function.

The reference microphone 2 and the error microphone 11 correspond to the first and second detecting means, respectively, according to the first aspect of the present invention, and the adaptive filter 5 and the LMS operation section 6 for controlling the adaptive filter 5 are respectively provided. It corresponds to an adaptive filter means and an adaptive filter control means.
The FIR filter 14 corresponds to the digital filter means according to the first aspect of the present invention, and the combination of the FIR filter 14 and the LMS operation unit 16 for controlling the FIR filter 14 and the operation unit 17 constitutes an identification filter control. Corresponding to the means.

Further, the pseudo signal generator 15 corresponds to the pseudo signal generating means according to the first aspect of the present invention, and the level adjusting section 18 corresponds to the level adjusting means. The level detector 19 corresponds to the level controller according to the first aspect of the present invention.
The level adjustment signal given to 8 corresponds to the level adjustment command.

In the first embodiment, the case where the present invention is applied to a muffler has been described. However, this technique can be applied to other uses such as an echo canceller.

Although the LMS algorithm is used to identify the secondary sound path C by the FIR filter 14, any other algorithm may be used, or the above-mentioned second method may be performed by another method not using these algorithms. Next sound path C
May be identified. For example, the secondary sound path C is identified by a correlation method using a so-called M-sequence signal by identifying (estimating) the secondary sound path C based on the correlation between the pseudo signal m (k) and the error signal ε (k). You may. Thus, the phase using the M-sequence signal
An embodiment in which the secondary sound path C is identified by the related method
Corresponds to the invention described in claim 2. The output of the secondary sound path C (the pseudo signal m after passing through the secondary sound path C)
(k)) is converted to the input signal of the secondary sound path C (that is, the pseudo signal m
(k)) (specifically, by converting each of these input / output signals into the frequency domain and then performing the division), the secondary sound path C can also be obtained. Further, the secondary sound path C may be obtained using a generally known cross spectrum method.

Further, an error signal e (k) (a noise component remaining in the exhaust duct 1) is detected by the level detector 19.
When the level is detected, the level detection may be performed based on a temporally averaged value such as integrating the error signal e (k). That is, since the error signal e (k) is a signal that fluctuates greatly in time, the fluctuation can be suppressed to some extent by averaging it in time, and this makes it possible to detect the noise level. May be convenient.

Then, in the first embodiment,
Although the M-sequence signal (MLS) is used as the pseudo signal m (k), the period of the M-sequence signal is set to be shorter than the operation time of the identification of the secondary sound path C by the FIR filter 14 (LMS operation unit 16). It is desirable to make it longer. That is, it is generally known that the pseudo signal m (k) must be a completely random signal in order to perform accurate identification, whereas the M-sequence signal is strictly a pseudo signal. Is a random signal. However, since it is known that this M-sequence signal is almost completely random within one cycle, the cycle of this M-sequence signal is set to be sufficiently longer than the above-described identification operation. By terminating the identification operation within one cycle of the M-sequence signal, the identification accuracy of the secondary sound path C can be improved.

For the pseudo signal m (k), other signals such as white noise may be used as long as they are random signals.

Next, a second embodiment of the present invention will be described with reference to FIGS.

As shown in FIGS. 3 and 4, the second embodiment is different from the first embodiment shown in FIGS. 1 and 2 in that the FIR filter 14 is replaced with another FI.
The R filter 20 is provided between the reference microphone 2 (strictly, the output side of the A / D converter 4) and the input side of the LMS operation unit 6. Then, the FIR filter 14 is made to function purely for identification (estimation) of the secondary sound path C, and the transfer function Se obtained by identifying the secondary sound path C by the FIR filter 14 is obtained by the above-described method. FIR
The filter 20 is set so that the FIR filter 20 functions only for compensating the secondary sound path C. Note that this F
The IR filter 20, like the adaptive filter 5 and the like, is constituted by, for example, a DSP or a CPU, and a program for controlling the operation is stored in a storage unit (not shown). For other configurations, see FIGS.
Therefore, the same reference numerals are given to the same parts, and the detailed description thereof will be omitted.

As described above, according to the second embodiment, the FIR filter 14 for identifying (estimating) the secondary sound path C is used to compensate the secondary sound path C for obtaining the sound deadening effect. Filter 20 is provided separately from the FIR filter 20. Accordingly, an adaptive operation for silencing by adaptively controlling the adaptive filter 5 by the LMS operation unit 6 and the LMS operation unit 16
Thus, the identification operation of accurately identifying the secondary sound path C by adaptively controlling the FIR filter 14 can be simultaneously executed, that is, the above-described online identification can be realized. Therefore, unlike the first embodiment described above, the identification operation of the secondary sound path C can be performed without stopping the adaptive operation for silencing, and therefore, compared to the first embodiment, A more stable silencing effect can be obtained.

However, in the second embodiment,
In order to detect the noise level remaining in the exhaust duct 1, the operation of identifying the secondary sound path C, that is, the generation of the pseudo signal m (k) (the emission of the identification sound) is stopped, for example, periodically. The level of the noise signal remaining in the exhaust duct 1 is detected by detecting the signal level of the error signal e (k) at this time by the level detecting section 19, and the level adjusting section is controlled in accordance with the detected level. 18 to generate a level adjustment signal.

In the second embodiment as well,
The above-described correlation method is used to identify (estimate) the secondary sound path C.
May be used. Thus, in the second embodiment,
Therefore, a mode in which the secondary sound path C is identified by the above-described correlation method is also provided.
The invention according to claim 2 (and 5) of the claims.
Corresponding to

Next, a third embodiment of the present invention will be described with reference to FIG.

As shown in the figure, in the third embodiment, the level adjusting section 18 in FIG. 1 is provided between the output side of the adder 8 and the input side of the D / A converter 9. It is provided. In addition, regarding other configurations, FIG.
Therefore, the same parts are denoted by the same reference numerals as in FIG. 1 and detailed description thereof is omitted.

However, in the configuration of FIG.
When the secondary sound path C is identified by the path indicated by the dotted line in FIG.
Transfer function S of FIR filter 14 for identifying secondary sound path C
e_k The LMS calculation unit 16 for obtaining the above is shown in FIG.
Similar to the configuration, not only the secondary sound path C but also the level adjustment unit
Transfer function including 18 transfer functions L, that is, level
The transfer function of the synthesis of the transfer function L of the adjustment unit 18 and the secondary sound path C
The number [L × C] will be obtained. However, this FIG.
According to the configuration described above, the level adjusting unit 18 outputs the pseudo signal m (k)
Not only the level of the output y (k) of the adaptive filter 5
This is adjusted and supplied to the speaker 7. Obedience
Therefore, the FIR filter 14 is identified during the mute operation.
The target of (compensation) is the transmission function of the level adjustment unit 18.
A composite transfer function [L ×
C]. Therefore, in the configuration of FIG.
Unlike the configuration shown in FIG. 2, the composite transfer function [L × C]
It is not necessary to determine only the secondary sound path C from the above.

According to the configuration shown in FIG. 5, the level adjusting unit 18 is also one component of the control system of the above-described Filtered-x LMS algorithm. Therefore, this Fi
The LMS calculation unit 6 that adaptively controls the adaptive filter 5 based on the ltered-x LMS algorithm includes a transfer function _obtained by combining the transfer function W _k of the adaptive filter 5, the transfer function L of the level adjustment unit 18, and the secondary sound path C. The transfer function W _k is controlled so that [W _k × L × C] is complementary to the primary sound path P.

The configuration of the third embodiment corresponds to the invention described in claims 3 (and 5). Then, the combined transfer function [W _k × L × C] in the third embodiment is the second transfer function according to the third aspect of the present invention.
And the combined transfer function [L × C] to be identified (compensated) by the FIR filter 14 is
Corresponding to the composite transfer function. In addition, the third embodiment
In the above, the composite transfer function [L × C] is identified (inferred).
For example, the above-described correlation method may be used. This
Thus, in the third embodiment, the correlation method
An embodiment for identifying the composite transfer function [L × C] is described in the claims.
This corresponds to the invention described in claim 4 (and 5) of the scope.

Next, a fourth embodiment of the present invention will be described with reference to FIG.

As shown in the drawing, the fourth embodiment differs from the third embodiment shown in FIG.
Instead of the filter 14, another FIR filter 2
0 is provided between the reference microphone 2 (strictly, the output side of the A / D converter 4) and the input side of the LMS operation unit 6. That is, similarly to the second embodiment shown in FIGS. 3 and 4 described above, the FIR filter 14 for identifying (estimating) the secondary sound path C is provided with the secondary sound path C Is provided separately from the FIR filter 20 for compensating the above, thereby enabling the above-described online identification. Therefore, since the operation of identifying the secondary sound path C can be performed without stopping the adaptive operation for silencing, a more stable silencing effect can be obtained. In the fourth embodiment, as in the second embodiment, when detecting the noise level remaining in the exhaust duct 1, the generation (identification) of the pseudo signal m (k) is performed. Needless to say, the sound emission) needs to be stopped, for example, periodically.

Note that also in the fourth embodiment,
The above-described correlation method is used to identify (estimate) the secondary sound path C.
May be used. Thus, in the fourth embodiment,
Therefore, a mode in which the secondary sound path C is identified by the above-described correlation method is also provided.
The invention according to claim 4 (and 5) of the claims.
Corresponding to

[0081]

As described above, according to the active noise elimination device of the present invention, the signal level of the pseudo signal is changed according to the level of the noise remaining without being completely eliminated by the active noise elimination device. Is also automatically adjusted to a level necessary and sufficient to identify the second transfer function. Therefore, when the noise reduction effect of the active noise reduction device is improved and the noise is reduced, the pseudo signal (identification sound) becomes conspicuous because the pseudo signal also decreases in accordance with the change in the noise level. The above-mentioned problems of the conventional technology can be solved.

[0082] In addition, in the present onset Akira of the active noise cancellation device,
The problem of the prior art is solved by a very simple process of detecting the level of the residual component of the noise and adjusting the signal level of the pseudo signal according to the level. Therefore, the level control means and the level adjustment means for executing these processes can be configured simply and inexpensively.
There is an effect that the present onset Ming active noise cancellation device can be realized at low cost. In addition, even if the level control means and the level adjustment means have a simple and inexpensive configuration, their processing contents are extremely simple, so that high-speed processing can be ensured. These effects are based on active silencers
Can also be obtained in devices intended to remove
It is.

[0083]

[0084]

[0085]

[0086]

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment in which an active noise elimination device according to the present invention is applied to an active silencer.

FIG. 2 is a diagram showing another example different from FIG.

FIG. 3 is a schematic configuration diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing another example different from FIG. 3;

FIG. 5 is a schematic configuration diagram showing a third embodiment of the present invention.

FIG. 6 is a schematic configuration diagram showing a fourth embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of a conventional active silencer.

FIG. 8 is a diagram in which a part of FIG. 7 is extracted.

[Explanation of symbols]

 Reference Signs List 1 exhaust duct 2 reference microphone 5 adaptive filter 6 LMS calculation unit 7 secondary sound source speaker 11 error microphone 14 FIR digital filter 15 pseudo signal generator 16 LMS calculation unit 18 level adjustment unit 19 level detection unit

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-8-123444 (JP, A) JP-A-7-32947 (JP, A) JP-A-5-265468 (JP, A) JP-A-10-1998 11076 (JP, A) JP-A-9-171389 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G10K 11/178 F01N 1/00 H03H 17/00

Claims (5)

(57) [Claims] A first detection unit for detecting a signal input to a transmission line having a first transfer function; a second detection unit for detecting a signal output from the transmission line; An adaptive filter means for processing an output signal of the detection means and emitting the output signal to the transmission line; and output signals of the first and second detection means,
Accordingly, the transfer function of the adaptive filter means is combined with the second transfer function existing between the output side of the adaptive filter means and the second detection means via the transmission path. Is the first combined transfer function
An adaptive filter control means for controlling a transfer function of the adaptive filter means, a pseudo signal generation means for generating a pseudo signal, and a signal level of the pseudo signal adjusted in accordance with a level adjustment command. And a level adjusting means for inputting the signal to the second transfer function, and a signal level of an output signal of the second detecting means when the pseudo signal is in a non-input state with respect to the second transfer function. And the level of the signal in the transmission line at the position detected by the second detecting means corresponding to the signal level obtained by the detection and the pseudo signal are transmitted through the level adjusting means to the second level. Level control means for generating the level adjustment command so that the signal level of the pseudo signal at the detection position by the second detection means when input to the transfer function of Digital filter means for identifying the second transfer function interposed between the first detection means and the adaptive filter control means, wherein the pseudo signal is the second transfer function
When there is no input to
Not only the transfer function of the
The output signal of the first detecting means is processed by the filtering means.
The input signal is input to the adaptive filter control means and
Transmission of the adaptive filter means by the adaptive filter control means.
Function control and the pseudo signal adjusts the level
State being input to the second transfer function via the means
The adaptive filter control means
Control of the transfer function of the
Fixes the transfer function of the filter means, the pseudo signal
Alternatively, this pseudo signal is leveled by the level adjusting means.
Input the adjusted signal to the digital filter
Signal after processing by this digital filter means
And a state in which the output signal of the second detection means is substantially equivalent
And an identification filter control means for controlling a transfer function of the digital filter means. 2. A signal input to a transmission path having a first transfer function.
First detection means for detecting a signal output from the transmission line , and a second detection means for detecting a signal output from the transmission path.
And processing the output signal of the first detection means and transmitting it to the
Adaptive filter means for emitting to the transmission path, and output signals of the first and second detection means are input,
According to these, the transfer function of the adaptive filter means
And the above transmission path from the output side of the adaptive filter means.
A second transmission existing through the second detection means
A first combined transfer function by combining the
Adaptive filter means in a state complementary to the transfer function of
Adaptive filter control means for controlling a transfer function of a pseudo-signal, and a pseudo-signal generating means for generating a pseudo signal comprising an M-sequence signal.
And the signal level of the pseudo signal according to the level adjustment command.
After the adjustment, the level is input to the second transfer function.
Adjusting means, wherein the pseudo signal is in a non-input state with respect to the second transfer function;
The signal level of the output signal of the second detection means when
Signal and detect the signal level corresponding to the detected signal level.
The signal in the transmission path at the position detected by the second detecting means
Signal level and the pseudo signal through the level adjusting means.
And the second transfer function is input to the second transfer function.
The signal level of the pseudo signal at the position detected by the detecting means;
Generates the above level adjustment command so that they are almost equivalent.
Between the first detection means and the adaptive filter control means.
A digital file for identifying the second transfer function
Filter means for transmitting the pseudo signal or this pseudo signal.
Signal after level adjustment by the above level adjustment means
And the pseudo signal is transmitted through the level
2 when the state is input to the transfer function 2
2 and the output signal of the detection means are input, and the correlation
Therefore, the second transfer function was estimated and obtained by this estimation.
Let the transfer function be the transfer function of the digital filter
Active noise cancellation apparatus comprising: a identification filter control means for setting Te. 3. A first detection means for detecting a signal input to a transmission path having a first transfer function; a second detection means for detecting a signal output from the transmission path; An adaptive filter means for processing and outputting an output signal of the detecting means, and a level adjusting means for adjusting the level of the output of the adaptive filter means in accordance with a level adjustment command and then discharging the output to the transmission line; Each output signal of the first and second detection means is input,
Accordingly, the transfer function of the adaptive filter means, the transfer function of the level adjustment means, and the transfer function existing between the output side of the level adjustment means and the second detection means via the transmission path. An adaptive filter control means for controlling a transfer function of the adaptive filter means so that a second combined transfer function obtained by combining the transfer function of the first and second transfer functions is complementary to the first transfer function; And a pseudo signal generating means for inputting the pseudo signal to the second transfer function after level-adjusting the pseudo signal by the level adjusting means; The signal level of the signal in the transmission line at the position detected by the second detection means corresponding to the signal level obtained by detecting the signal level of the output signal of the second detection means, and the pseudo signal are Up When the signal level of the pseudo signal at the position detected by the second detection unit when the signal is input to the second transfer function via the level adjustment unit is substantially equal to the level adjustment command, the level adjustment command is issued. A level control means for generating, a third combined transfer function interposed between the first detection means and the adaptive filter control means, and a combination of the transfer function of the level adjustment means and the second transfer function Digital filter means for identifying the
In the non-input state for the transfer function of
And fixing the transfer function of the digital filter means.
An output of the first detecting means by a digital filter means
The signal after processing the signal is sent to the adaptive filter control means.
It said adaptive by said adaptive filter control means enter Fi
Control of the transfer function of the
Input to the second transfer function via the level adjusting means.
The adaptive filter control means
Control of the transfer function of the adaptive filter means by
To fix the transfer function of the adaptive filter means,
Inputting the pseudo signal to the digital filter means,
The signal processed by this digital filter means
An active noise eliminator comprising: an identification filter controller for controlling a transfer function of the digital filter so that an output signal of the second detector is substantially equivalent to the output signal of the second detector . 4. A signal input to a transmission path having a first transfer function.
First detection means for detecting a signal output from the transmission line , and a second detection means for detecting a signal output from the transmission path.
Stage and an adaptive processing and output signal of the first detection means
Type filter means and the output of the adaptive filter means in accordance with a level adjustment command.
After adjusting the level by
And output signals of the first and second detection means are input,
According to these, the transfer function of the adaptive filter means
And the transfer function of the level adjustment means, and the level adjustment
From the output side of the means via the transmission path to the second detecting means
And a second transfer function existing between
2 that the combined transfer function is complementary to the first transfer function.
In another embodiment, the adaptive filter means controls the transfer function.
A pseudo-signal consisting of an M-sequence signal and generating the pseudo-signal
After adjusting the level by the
A pseudo signal generating means for inputting a number, wherein the pseudo signal is in a non-input state relative to the second transfer function
The signal level of the output signal of the second detection means when
Signal and detect the signal level corresponding to the detected signal level.
The signal in the transmission path at the position detected by the second detecting means
Signal level and the pseudo signal through the level adjusting means.
And the second transfer function is input to the second transfer function.
The signal level of the pseudo signal at the position detected by the detecting means;
Generates the above level adjustment command so that they are almost equivalent.
Between the first detection means and the adaptive filter control means.
And the transfer function of the level adjusting means and the second
Identify a third combined transfer function by combining with the transfer function
Including digital filter means, the pseudo signal,
The pseudo signal is transmitted to the second transmission via the level adjusting means.
The second detection when the function is being input
The output signal of the means is input and the correlation
The third combined transfer function is estimated, and the transfer obtained by the estimation is estimated.
Function as the transfer function of the above digital filter means.
Active noise cancellation apparatus comprising a identified filter control means for constant for, a. 5. The signal input to the transmission line is a sound wave, and the active noise elimination device is an active noise reduction device for removing the sound wave.
5. The active noise elimination device according to 2, 3, or 4.