JP3383325B2 - Noise cancellation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise canceling system.
In particular, the engine at a predetermined position (observation point) in a car
Cancel the gin sound to provide a comfortable car interior environment
The present invention relates to a noise canceling device that can be provided. [0002] 2. Description of the Related Art As a countermeasure against noise, a sound absorbing material is conventionally used.
(Passive control) is known. But sucking
In the method using sound material, a quiet area with low noise is formed.
Is difficult to perform and bass cannot be effectively eliminated.
There is a title. In particular, to prevent noise in the cabin of a car
Increases the weight of the car and effectively reduces noise.
There is a problem that can not be done. As a result, the noise capa
Method to reduce noise by emitting cancel sound from speaker
(Active control) is in the limelight, such as factories and offices
Is being put to practical use in some indoor spaces. In addition,
Active control reduces noise even in the passenger compartment
A scheme has been proposed. FIG. 3 shows a conventional noise canceling apparatus.
FIG. 11 is a configuration diagram of an installation, where 11 is an engine that is a noise source,
Is a rotation speed sensor for detecting the engine rotation speed R, and 13 is an air speed sensor.
Constant amplitude sine having a frequency corresponding to the engine speed R
Wave signal to reference signal S_NGenerated by the reference signal generator
is there. If the noise source is an engine, the noise
The generated noise has periodicity (periodic noise),
The wave number depends on the engine speed. For example, 4-cylinder engine
In the case of gin, the rotation speed is 600 rpm (10 rpm).
Frequency of the second-order high frequency periodic noise generated in the vehicle interior
Is 20Hz and the rotation speed is 6000rpm (100rpm)
, The frequency of the periodic noise generated in the cabin is 200
Hz, and the second harmonic of the engine speed is dominant.
You. Therefore, the reference signal generator 13 converts the sine wave data into R
Store it in the OM and read the data as needed
Then, a reference signal is generated by output. In addition, this
The data read / output timing is the engine speed R
Is controlled according to the engine speed R
A reference signal with the frequency of the generated periodic noise is output
It is supposed to be. [0004] 14 is a noise canceling controller.
The reference signal S generated from the reference signal generator 13_NEnter
The noise canceling position (observation point)
And the noise Sn near the driver's ear, for example).
A synthesized sound signal of the cancel sound Sc is input as an error signal Er.
Adaptive signal processing so that the error signal is minimized.
Go to noise cancellation signal Nc_DIs output. Noise can
The cell controller 14 includes an adaptive signal processing unit 14a,
An adaptive filter 14b having a digital filter configuration and a speaker
Sound propagation system (secondary
(Sound Propagation System)
_NIs input to the filter 14c. 15 is suitable
Filter output (noise cancellation signal Nc_DAnalog)
Noise cancellation signal Nc_ADA converter to convert to
16 is a noise cancel signal Nc_AAmplifies the power
And 17 are cancellations that emit a noise cancellation sound Sc.
The speaker 18 is located at the noise canceling point, and the noise S
n and the cancel sound Sc are detected, and the synthesized sound signal is
An error microphone that outputs the error signal Er, and 19 is an error microphone
-An AD converter that converts the signal Er to digital
You. [0005] The adaptive signal processing section 14a has a noise canceling point.
And the error signal Er through the filter 14c.
Signal S_N′, And use these signals to generate noise
Adapted to cancel noise at the cancellation point
Performs signal processing to determine coefficients of adaptive filter 14b
You. For example, the adaptive signal processing unit 14a uses a well-known LMS (Least
Mean Square)
18 so that the error signal Er input from 18 is minimized.
The coefficients of the adaptive filter 14b are determined. Adaptive filter 1
4b is in accordance with the coefficient determined by the adaptive signal processing unit 14a.
The reference signal S _NDigitally filtered to DA
Noise cancel signal N from converter 15_CAOutput
You. Note that the reference signal S_NHas a high correlation with the noise Sn to be eliminated.
Signals that are not correlated with the reference signal.
Will not be left. When the engine 11 rotates, its rotation speed R
Is detected by the rotation speed sensor 12, and the reference signal generation unit 1
3 is a reference signal S having a frequency corresponding to the engine speed R
_N(See Fig. 4 (a))
Input to the server 14. At this time, the engine 11
The periodic engine sound (periodic noise)
Sky with noise propagation system (primary sound propagation system) with transfer function
Propagating inside and reaching the noise cancellation point. Therefore, the noise
The noise (engine sound) Sn at the cancellation point is a level
Is slightly weakened and slightly delayed as shown in FIG.
Become. First, the noise cancellation controller 14
For example, the reference signal S_NNoise canceling signal Nc whose phase is opposite to
_AIs output from the cancel speaker 16 as shown in FIG.
A cancel sound Sc is output. However, the level of noise Sn
And the phase is shifted, the noise is caused by the cancel sound Sc.
Is not canceled, and an error signal Er is generated. noise
The cancel controller 14 determines that the error signal Er is minimum.
Adaptive signal processing is performed so that
4 (d)
The phase of the cancel sound Sc is opposite to the phase of the noise Sn.
And match the levels to cancel the noise. For the sake of simplicity, the noise source is described above.
One cancel sound source (speaker)
This is an example in which one cancel point (observation point) is set. Only
However, there are actually multiple noise sources, and
There are several points (observation points) that we want to
The speaker cannot cancel the noise at each observation point,
There are multiple manufacturers. Figure 5 shows K noise sources and speakers
Conventional noise canceling with M observation points and L observation points
It is a block diagram of a cell apparatus. 21 is the noise at each observation point
Noise canceling controller that operates to cancel
Roller, 22 from each noise source (not shown) to each observation point
A primary sound virtual propagation system that expresses the system in which noise propagates (noise propagation
, 23 each include the characteristics of a speaker (not shown)
A system in which the cancellation sound propagates from the speaker to each observation point
Secondary sound propagation system (cancellation sound propagation system) expressing
Is a signal synthesizer that expresses the microphone function at each observation point
And the adder 24₁~ 24₁'Is the microphone at the first observation point
And the adder 24_Two~ 24_Two'At the second observation point
Equivalent to a microphone,..._L~ 24_L'Is the L view
Equivalent to a microphone at a measurement point. d_d1n~ D_dLnIs each observation
External noise that is not a cancellation target at the point. still,
A DA converter, an AD converter, and the like are omitted. [0008] In the noise cancellation controller 21
21a is a reference signal corresponding to the noise generated from each noise source.
No. x_a1n~ X_aKn(Output from a reference signal generator (not shown)
Is input and the noise cancel signal y_a1n~ Y_aMnTo
A multi-input / multi-output adaptive filter input to each speaker
(Hereinafter simply referred to as an adaptive filter), 21b is a secondary sound propagation system 2
Using each element (propagation element) of the transfer function matrix of No.3
Filter for creating a filtered X signal
The reference signal x corresponding to the noise generated from the noise source_{a1 n}~
x_aKnIs input at 21c.
Signal e_1n~ E_LnAnd the filter output from the filter 21b.
Filtered X signal r_111n~ R_LMKnIs entered and these
To cancel noise at each observation point
The adaptive signal processing to determine the coefficient of the adaptive filter 21a.
It is an adaptive signal processing unit to determine. FIG. 6 is an explanatory diagram of the primary sound virtual propagation system 22.
As shown in FIG. 6A, the K noise sources NG₁~ NG_K
The noise generated from the noise has a certain frequency / phase characteristic.
Microphones (M
IC₁~ MIC_L). Therefore, the ith noise
The noise from the source NGi is the jth microphone MIC_jThe story that reaches
Set the transfer characteristics of the transport system to H_jiThen, the primary sound virtual propagation system 22
Is represented as shown in FIG. 6 (b), and its transfer function matrix
(H) is as follows. [0010] (Equation 1) Each element H of the transfer function matrix (H)_ijIs
Modeled by the FIR digital filter shown in FIG.
It is. That is, the input signal is sequentially delayed by one sampling time.
Delay element DL to be extended and a coefficient h₀,
h₁, H_Two, Multiplying unit ML, and multiplying unit output
Digital filter consisting of an adder AD that adds
Is converted to FIG. 8 is an explanatory diagram of the secondary sound propagation system 23,
As shown in FIG.₁~ SP_MOriginated from
Noise canceling sound has predetermined frequency and phase characteristics
Microphones provided at each observation point by propagating through the secondary sound propagation system 23
MIC₁~ MIC_LTo reach. Therefore, the ith noise
Cancel signal y_ainJ-th cancellation sound based on
Microphone MIC_jThe transfer characteristic of the secondary sound propagation system up to_ji
In this case, the secondary sound propagation system 23 has a mode as shown in FIG.
And its transfer function matrix (C) is
Swell. [0012] (Equation 2) Each element of the transfer function matrix (C) is linear
As in the case of the sound virtual propagation system 22, the FIR type shown in FIG.
Modeled by a digital filter. That is,
A delay element DL for sequentially delaying a force signal by one sampling time
And a coefficient c for each delay element output ₀, C₁, C_Two, ...
Multiplying unit ML for performing the calculation and an adding unit A for adding the outputs of the respective multiplying units
It is modeled by a digital filter consisting of D. Figure 9
Each element of the transfer function matrix (C) of the secondary sound propagation system 23
C_ijFilter for creating a filtered X signal
It is a block diagram of the router 21b. The adaptive signal processing unit 21c
Illumination signal x_a1n~ X_aKnAnd noise at each station
Synthesized signal (error signal) with cell sound e_1n~ E_LnBased on
Update adaptive filter coefficients by executing adaptive signal processing
The adaptive filter 21a outputs the reference signal x_a1n~ X_aKnEnter
Noise cancel signal y_a1n~ Y_aMnSpies
Input to the vehicle and cancel the noise at each observation point. The output from the adaptive filter 21a is
Noise cancel signal y_a1n~ Y_{a Mn}Is the observation point
Frequency and phase of the secondary sound propagation system 23
Reached under the influence of characteristics. For this reason, adaptive signal processing
The unit 21c outputs the reference signal x_a1n~ X_aKnJust use
And a signal obtained by adding the characteristics of the secondary sound propagation system 23 to the reference signal.
X LMS (MEFX LMS)
Adopting algorithm, more advanced noise cancellation control
Is going. That is, the filtered X LMS algorithm
In the rhythm, the reference signal x_a1n~ X_aKnTo the filter 21b
More filtered signal (filtered X signal)
Adaptive filter 2 using error signal at each observation point
1a is updated. In FIG. 9, C_ijIs the secondary sound propagation system 23
Element C of transfer function matrix (C) in_ij(FIG. 8
FIR type digital filter that realizes the above-mentioned function. H
The filter 21b receives each reference signal x_a1n~ X_aKnTo all propagation
And apply filters (filters corresponding to all propagation elements)
Let through) filtered X signal r_111n~ R_LMKnOutput
It is supposed to. That is, the reference signal x_a1nSecond
Propagation element C from the first speaker to all observation points₁₁~ C
_L1To make the filtered X signal r_111n~ R _L11nOut
Force the reference signal x_a1nAll observations from the second speaker
Propagation element C to point₁₂~ C_L2Act to filter
X signal r_121n~ R_L21nIs output, and the reference signal x is output._a1n
The propagation element C from the Mth loudspeaker to all observation points_1M
~ C_LMTo make the filtered X signal r_1M1n~ R_LM1n
, And similarly, the reference signal x_a2n~ X_aKnTo all
Activate the propagation element. still, R₁₁= (R_111n, R_211n, ... r_L11n) R_{twenty one}= (R_121n, R_221n, ... r_L21n) ... R_M1= (R_1M1n, R_2M1n, ... r_LM1n) ... R_MK= (R_1MKn, R_2MKn, ... r_LMKn) Is expressed as FIG. 10 shows a multi-input / multi-output adaptive filter 2.
1a is a configuration diagram of a primary sound virtual propagation system 22 and a secondary sound transmission system.
It has the same structure as the transport system 23. A_11n~ A_MKnIs F
It is composed of an IR digital filter, for example, an input signal
Are sequentially delayed by one sampling time.
l2... and a coefficient a for each delay element output₀, A₁, A_Two・ ・
Multiplying units ML1, ML2, ML3...
Implemented by adders AD1, AD2,.
It is. The number of delay stages is not limited to two. Each reference signal x
_a1n~ X_aKnTo digital filter A_11n~ A_1KnEnter
Noise input to the first speaker by adding
Cancel signal y_a1nAnd each reference signal x_a1n~ X
_aKnTo digital filter A_21n~ A_2KnAnd add
Noise cancel input to the second speaker.
Cell signal y_a2n... Each reference signal x_a1n~ X
_aKnTo digital filter A_M1n~ A_MKnAnd add
Noise canceling input to the Mth speaker
Cell signal y_aMnIs obtained. Each FIR type data in the adaptive filter 21a
Digital filter A_11n~ A_MKnBy three coefficients (two-stage delay)
, The adaptive signal processing unit 21 c
Tal filter A_11n~ A_MKnAdaptive signal processing for each of the three coefficients
To determine the coefficient value. That is, one FIR
Type digital filter A_ijCoefficient a of₀, A₁, A_Twoabout
The coefficient a is calculated using the coefficient update equation₀, A₁, A
_TwoTo determine. [0018] (Equation 3) In equation (1), (n) is the current sampling time
(N-1) is the value one sampling time before, and (n-2) is two samples
The value before the sampling time, (n + 1) is the next sample from the current time.
It means the value up to the switching time. Therefore, R_ij(n-2) is
Filter 21 corresponding to reference signal two sampling times before
b means output, R_ij(n-1) is one sampling time before
Filter output according to the reference signal, R_ij(n) is the current time
Is a filter output corresponding to the reference signal. Also, μ is adaptive
A value less than or equal to 1 that determines the step for updating the filter coefficients
Number (step size parameter)
It is set to an appropriate value according to the system. In addition,
The larger the value of the size parameter μ, the greater the
The number approaches the optimal value, the speed increases, and the followability improves.
However, when approaching, overshoot occurs and stability is low.
Down. Also, the value of the step size parameter μ is small
The speed of approaching the optimum coefficient value becomes slower, and the followability becomes worse.
However, the overshoot after approaching the optimum value is small and cheap.
The qualification becomes good. e_nIs the noise at each of the L observation points
And cancel sound, and R_ij, E_nEach
It is expressed as follows. [0020] (Equation 4)According to such a noise canceling device,
The signal processing unit 21c is a filter which is an output of the filter 21b.
Tard X signal r_111n~ R_LMKnAnd the noise at each observation point
Sound signal (error signal) e of the sound and the cancel sound_1n~ E
_LnAdaptive signal processing is performed based on
Fa Digital Filter A Constituting 1a_11n~ A
_MKnAnd the adaptive filter 21a determines the coefficient of the reference signal x
_a1n~ X_aKnAnd the noise cancel signal y_a1n~ Y
_aMnGenerating speaker SP₁~ SP_MFill in (Fig. 8)
Each speaker generates a cancellation sound and the noise at each observation point
Acts to cancel the sound. FIG. 11 shows the number of noise sources K = 2 and the number of speakers M =
2. Specific conventional cases when the number of observation points (number of microphones) L = 2
FIG. 21A is a configuration diagram of the noise canceling device of FIG.
FIR digital filter A₁₁, A_{twenty one}, A₁₂, A_{twenty two}In
The formed adaptive filter 21b is a transmission function of the secondary sound propagation system.
Each propagation element C of the number matrix (C)₁₁, C_{twenty one}, C₁₂,
C_{twenty two}X signal composed of digital filters
Creation filters, 21c-1 to 21c-4 are adaptive signal processing units (ME
FX LMS algorithm), SP₁, SP_TwoIs speedy
Mosquito, MC₁, MC_TwoIs a microphone installed at the observation point. Incidentally, the engine speed includes the engine speed.
High-order harmonic component of the four-cylinder engine
In the case of, the noise level of the second harmonic is dominant the most
It is a target. FIG. 12 shows higher harmonic components included in the engine sound.
It is an explanatory diagram of the second harmonic component is the largest, fourth order,
The noise level decreases as the order increases to sixth order.
It becomes. Odd-order harmonic components also occur depending on the vehicle model.
You. Only the most dominant higher harmonic components of the engine sound
When canceling (for example, only the second harmonic component)
Is the higher harmonic component by the configuration shown in FIG. 2 or FIG.
Can be canceled. However, other higher harmonic components are also
If you want to cancel the noise,
It is necessary to provide a controller. FIG. 13 shows the second order and the fourth order included in the engine sound.
Conventional noise canceling cancels the next and sixth harmonic components
FIG. 2 is a configuration diagram of a cell device, and the same parts as those in FIG.
Is attached. The difference from FIG. For each higher harmonic component you want to cancel,
Noise cancellation controller 14, noise for fourth harmonic
Cancel controller 24, noise control for 6th higher harmonic
A point that a cancel controller 34 is provided; The reference signal generation unit 13 outputs the second and fourth engine speeds.
Next and sixth harmonic reference signal S_N2, S_N4, S_N6Occurs
The corresponding higher harmonic noise cancellation control
Points input to the rollers 14, 24, 34, Adders 41 and 42 are provided to control noise cancellation
Roller output N_CD2, N_CD4, N_CD6Add noise cancellation
Signal N_CDOutput as The synthesized sound signal detected by the error microphone 18 (error
-Signal) Er to each noise canceling controller 14, 2
That is, feedback is provided to 4,34. Noise canceling controller for each higher harmonic
14, 24, and 34 are reference signals S_N2, S_N4, S
_N6Using the synthesized sound signal Er and the step size parameter μ
Then, the adaptive signal processing described above is performed by the coefficient update equation of equation (1).
Determine the coefficients of each adaptive filter (not shown)
And the reference signal S_N2, S_N4, S_N6Input to the adaptive filter
And the noise cancellation signal N_CD2, N_CD4, N_CD6Output
You. Adders 41 and 42 are noise cancellation controllers.
Output N_CD2, N_CD4, N_CD6Add noise cancellation signal
No.N_CDAs input to the DA converter 15 and the DA converter
The data 15 is converted into an analog noise canceling signal and
Input to a speaker to output noise cancellation sound. [0026] [Problems to be Solved by the Invention] In the coefficient updating equation of the equation (1),
The value of the step size parameter μ in
Engine sound can be canceled while satisfying both qualities
Has been determined to be. For this reason, it is included in the engine sound.
Dominant, that is, the secondary height with the highest noise level
Harmonic component cancels after satisfying both tracking and stability.
Will be However, other higher-order harmonic components with lower levels are
When using the coefficient update equation of equation (1) to cancel, noise
Noise output from the sound cancel controllers 24 and 34
Sound cancel signal N_CD4, N_CD6Is too large
There is. In such a case, these signals are second harmonic components
Other high-order harmonic components cannot be canceled.
It becomes new noise, and other higher harmonic components increase (negative
Problem). For this reason, other than the second harmonic component
It is conceivable to reduce μ in the coefficient update equation.
If this is not done, the tracking performance will be reduced, and the noise that changes every moment (high
Problem that quickly follows the second harmonic component and cannot be canceled
There is a title. Also, noise cancellation control of all higher harmonics
Adaptive filter output increased in coefficient update formula
Output limiting term that limits the output
However, in such a method, the dominant
The problem that the second harmonic component cannot be canceled with good tracking
is there. From the above, the object of the present invention is included in the engine sound.
Cancel each high-order harmonic component with good tracking
It is an object of the present invention to provide a noise canceling method capable of reducing noise. Book
Another object of the invention is to provide an example other than the highest harmonic component at the maximum level.
For example, 4th, 6th,... Harmonic sound cancellation signal
Noise that can solve the negative problem without being too loud
The purpose is to provide a cancellation method. [0028] The above object is achieved by the present invention.
The higher harmonics of the engine speed contained in the engine sound
Minutes and output limit terms
Specified height for adaptive signal processing using
Noise cancellation controller and output limit for subharmonic components
Perform adaptive signal processing using a coefficient update formula incorporating a term
With noise cancellation controller for other higher harmonic components
More achieved. [0029] [Function] Higher order of engine speed included in engine sound
Of the higher harmonic components with relatively large levels in the wave components
A noise canceling controller is provided for each
The noise cancellation controller for constant higher harmonic components
That does not incorporate an output limiting term that limits the output signal amplitude of
Performs adaptive signal processing using the number update formula, and
The noise canceling controller controls the output signal amplitude.
Adaptation using coefficient updating formula incorporating output limiting term
Performs signal processing and outputs each noise cancellation controller
Add the signal to the speaker as a noise cancellation signal.
Power. As described above, a predetermined higher harmonic (for example, second harmonic)
Noise canceling controller for the
The adaptive filter coefficient is determined by the following coefficient update formula,
The reference signal is input to the adaptive filter and the noise cancel signal
Output, so both tracking and stability are not satisfied.
Meanwhile, a predetermined higher harmonic component can be canceled. Also other
Noise for higher order harmonics (eg higher order harmonics of 4th, 6th, etc.)
Sound cancel controller updates coefficient including output limit term
The coefficient of the adaptive filter is determined by the equation, and the reference signal is
Whether to output the noise cancellation signal by inputting
Make the cancellation sound signal of other higher harmonic components too large.
Can solve the negative problem. [0030] FIG. 1 is a block diagram showing an embodiment of the present invention.
Cancels the second, fourth and sixth harmonic components contained in the sound
This is an embodiment in the case where the application is executed. The second harmonic component is dominant
Target (highest level).Overall configuration In the figure, 11 is an engine which is a noise source, and 12 is an engine
A rotational speed sensor for detecting the rotational speed R, 13 is the engine rotational speed
Three sine with second, fourth and sixth harmonic frequencies of R
Wave signal S_N2, S_N4, S_N6Reference generated as a reference signal
It is a signal generator. 14-1 is a noise cap for the second harmonic
Cancel controller, 14-2 is the noise control for the fourth harmonic
Canceller controller, 14-3 is noise for 6th harmonic
Cancel controller, 14-4, 14-5 are each noise
Cancel controller output N_{CD Two}, N_CD4, N_CD6Add
The noise cancellation signal Nc_DIs an adder that outputs
You. 15 is a noise cancel signal Nc_DAnalog noise key
Cancel signal Nc_ADA converter to convert to 16
Sound cancel signal Nc_AA power amplifier that amplifies
A cancel speaker that emits a noise cancel sound Sc;
Reference numeral 18 is located at the noise cancellation point,
The synthesized sound of the cell sound Sc is detected, and the synthesized sound signal is output as an error signal.
An error microphone which outputs as Er, 19 is an error signal Er
Is an A / D converter that converts to digital. Each noise canceling controller 14-1
14-3 are the second-order and fourth-order signals from the reference signal generator 13, respectively.
Reference signal S of next and sixth harmonic components_N2, S_N4, S_N6Enter
Noise at the noise cancellation position in the passenger compartment
Synthesized sound signal (error signal) E of sound Sn and cancel sound Sc
r is input and the corresponding
Adaptive signal processing to minimize the higher harmonic components
Noise cancel signal N_CD2, N_CD4, N_CD6Output
You. [0032]Noise cancellation controller for second harmonic Second harmonic noise cancellation controller 14-1
Is connected to the adaptive signal processing unit 14a as shown in FIG.
An adaptive filter 14b having a digital filter configuration and a speaker
Sound propagation system (secondary
(Sound Propagation System)
_N2X-signal creation filter 14 to which is input
c. Adaptive filter 14b and filtered X
The signal generation filter 14c is shown in FIGS. 10 and 9, respectively.
Configuration. The adaptive signal processing unit 14a
Error signal Er and filtered X signal at the cancel point
Output signal S of creation filter 14c_N'Is input.
Using these signals and the step size parameter μ, (1)
Performs adaptive signal processing according to the coefficient update
The coefficient of the filter 14b is determined. In addition, the coefficient update equation of equation (1)
Output signal N_CD2An output limiting term that limits the amplitude of
Not caught. The adaptive filter 14b is an adaptive signal processing unit
14a according to the coefficient determined by the reference signal S_N2To
Digital filter processing and signal N_CD2Is output. [0033]Noise cancellation controller for other higher harmonics Noise canceling capacitors for higher harmonics other than the second harmonic
The rollers 14-2 and 14-3 are as shown in FIG.
And an adaptive signal processing unit 14a 'and a digital filter
Adaptive filter 14b 'and noise canceller
Transmission of the cancellation sound propagation system (secondary sound propagation system) up to the point
The reference signal S created based on the function_N4Or S_N6Is input
Filtered X signal creation filter 14c '
are doing. Adaptive filter 14b ', filtered X signal
The creation filter 14c 'is the adaptive filter shown in FIG.
Filter 14b, a filter 14c for creating a filtered X signal,
It has the same configuration. The adaptive signal processing unit 14a '
The error signal Er and the output signal N at the cancel point_CD4Ma
Or N_CD6And Filter 14 for creating filtered X signal
c 'output signal S _N″, And these signals and step
Using the size parameter μ
Adaptive signal processing is performed according to the update formula, and the adaptive filter 14
Determine the coefficient of b '. The adaptive filter 14b '
Signal according to the coefficient determined by the signal processing unit 14a '.
No. S_N4Or S_N6To the digital filter
N_CD4Or N_CD6Is output. The adaptive signal processing unit 14a '
The coefficients of the adaptive filter 14b 'are determined as follows.
You. That is, each FIR in the adaptive filter 14b '
Type digital filter A_11n~ A_MKn(See Figure 10)
3 coefficients a each₀, A₁, A_Two(Two-stage delay)
At this time, the adaptive signal processing unit 14a '
Ruta A_ijn(A_11n~ A_MKnThe coefficient update formula shown below for each
To calculate the coefficient a₀, A₁, A _TwoDetermine the value of
You. [0034] (Equation 5) In equation (2), (n) is the current sampling time
(N-1) is the value one sampling time before, and (n-2) is two samples
The value before the sampling time, (n + 1) is the next sample from the current time.
It means the value up to the switching time. Therefore, x_ajn(n-2)
Is the reference signal two sampling times earlier, x_ajn(n-1) is 1
Reference signal before sampling time, x_ajn(n) refers to the current time
Signal. Also, R_ij(n-2) is the reference two sampling times earlier.
Illumination signal x_ajn(n-2)
Means the output of the filter 14c ', R_ij(n-1) is 1 sample
Signal x before the ringing time_ajnFilter 14 according to (n-1)
the output of c ', R_ij(n) is the current reference signal x_ajn(n)
Is the output of the filter 14c 'corresponding to e_nIs L
This is a synthesized sound signal of noise and cancellation sound at each observation point.
And expressed as follows. [0036] (Equation 6) In the coefficient updating equation of equation (2), the right side [0038] (Equation 7)Is the output y of the adaptive filter 14b '_ain(Figure
1. N in FIG._CD4, N_CD6Is equivalent to)
Output limit term to be limited, output y_ainGrows bigger
Limit its size so that it does not break. Where β is
This is an output limit parameter of 1 or less, which is set to an appropriate value in advance.
Is determined. In the coefficient update equation of equation (2), [0040] (Equation 8) Is a synthesized sound signal (error signal) similar to the equation (1).
Update direction of the adaptive filter based on the magnitude and sign of
And the steps of update, follow-up, stability
Is a term that contributes toOverall behavior When the engine rotates, its rotational speed R is measured by a rotational speed sensor 12.
And is input to the reference signal generator 13. reference
The signal generator 13 is configured to output the second, fourth, and sixth order of the engine speed R.
Three harmonic reference signals S_N2, S_N4, S_N6And that
Noise cancellation controllers 14-1 and 14-, respectively
2, 14-3. At this time, the engine 11
Generated periodic engine sound (2nd, 4th, 6th order
Harmonic component) is a noise having a predetermined transfer function
Propagation in the air with a propagation system (primary sound propagation system)
To the point of cancellation. Error microphone 18 is noise cancellation point
Detects the synthesized sound of the noise and cancellation sound in the
The signal (error signal) Er is passed through the AD converter 19.
Each noise cancellation controller 14-1, 14-2, 1
4-3 adaptive signal processing units 14a, 14a ', 14a'
(Fig. 2). Each noise canceling controller 14-
1, 14-2, 14-3
The filters 14c, 14c ', 14c'_N2, S
_N4, S_N6And the filter used for adaptive signal processing
DO signal S_N', S_N″, S_N"To the adaptive signal processing unit 14
a, 14a 'and 14a' (FIG. 2). 2nd harmonic
The noise cancellation controller 14-1
The response signal processing unit 14a outputs the error signal Er and the filtered X
Filtered output from signal creation filter 14c
X signal S_N′ And the step size parameter μ
Adaptive signal processing is performed according to the equation (1), and the adaptive filter 14
Determine the coefficient of b. The adaptive filter 14b performs adaptive signal processing.
The reference signal S according to the coefficient determined by the_N2
To the digital signal N_CD2Output
You. Noise cancellation for fourth and sixth harmonics
Adaptive signal processing in controllers 14-2 and 14-3
The sections 14a 'and 14a' respectively provide an error signal Er and a signal.
Filter 14c ', 14c'
Filtered X signal S output from_N″, S_N″
Adaptive signal according to equation (2) using the size parameter μ.
Signal processing and the coefficients of the adaptive filters 14b 'and 14b'
To determine. Each noise cancellation controller 14-2,
14-3 adaptive filters 14b 'and 14b'
According to the coefficients determined by the processing units 14a ', 14a'.
Reference signal S_N4, S_N6Digital filtering
And the signal N_CD4, N_CD6Is output. Each of the adders 14-4 and 14-5 is a
Cancel controller output N_CD2, N_{C D4}, N_CD6And add
Noise cancel signal Nc_DTo generate the DA converter 1
5 and the D / A converter 15
Cancel signal Nc_DIs the analog noise cancellation signal N_CATo
After conversion and input to the speaker 17 via the power amplifier 16.
You. As a result, a noise canceling sound is generated from the speaker 17.
The noise is canceled and output via the secondary sound propagation system 20.
And the second, fourth and sixth harmonics contained in the engine sound
Acts to cancel wave components. After that,
The work is repeated, and the noise is quickly canceled. Less than
Although the present invention has been described with reference to the embodiments, the present invention is not limited to the claims.
Various modifications are possible in accordance with the gist of the present invention described in the scope.
Yes, the present invention does not exclude these. [0045] As described above, according to the present invention, a predetermined higher order harmonic
Noise cancellation controller for (eg, second harmonic)
Is an adaptive filter by a coefficient update formula that does not include an output restriction term.
And the adaptive filter determines the coefficients based on the determined coefficients.
Digital filter processing for the second harmonic reference signal
Configured to output noise cancellation signal
Therefore, while satisfying both the tracking performance and the stability,
Higher harmonic components can be canceled. Also other higher
Noise carriers for harmonics (eg, fourth, sixth, etc. harmonics)
Canceling the coefficients, each including an output limiting term
The coefficients of the adaptive filter are determined by the new formula, and each adaptive filter is determined.
Is a reference to the 4th and 6th harmonics based on the determined coefficient
Apply digital filter processing to the signal for noise cancellation
Output signals, each adaptive filter
If the filter output increases, the output decreases accordingly.
The coefficients of the adaptive filter can be determined as
Cancellation sound signal of other higher harmonic components other than the second harmonic
Can not be too big and can solve the negative problem
it can.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of an embodiment of a noise canceling system according to the present invention. FIG. 2 is a configuration diagram of each noise cancellation controller. FIG. 3 is a configuration diagram of a conventional noise canceling device. FIG. 4 is a waveform diagram for explaining a noise canceling operation. FIG. 5 is a configuration diagram of a conventional noise canceling device when there are a plurality of noise sources, speakers, and observation points. FIG. 6 is an explanatory diagram of a primary sound virtual propagation system. FIG. 7 is a configuration diagram of a digital filter that realizes each element of a transfer function matrix. FIG. 8 is an explanatory diagram of a secondary sound propagation system. FIG. 9 is a configuration diagram of a filter for creating a filtered X signal. FIG. 10 is a configuration diagram of an adaptive filter. FIG. 11 is a configuration diagram of a conventional noise canceling device when there are two noise sources, a speaker, and two microphones. FIG. 12 is an explanatory diagram of higher-order harmonic components included in the engine sound. FIG. 13 is a configuration diagram of a conventional noise canceling device that cancels each higher-order harmonic component included in an engine sound. [Description of Signs] 12 ··· Rotation speed sensor 13 ··· Reference signal generator 14-1 ··· Noise cancel controller 14-2 for second harmonic ··· Noise cancel controller 14-3 for fourth harmonic ·・ Sound cancellation controller for 6th harmonic 17 ・ Speaker 18 ・ Error microphone

Continued on the front page (51) Int.Cl. ⁷ Identification code FI H03H 21/00 G10K 11/16 H (72) Inventor Go Yamashita 1-4-1, Chuo, Wako-shi, Saitama Pref. ) Inventor Kunio Miyauchi 1-4-1 Chuo, Wako-shi, Saitama Pref. Honda Technology Laboratory Co., Ltd. (56) References JP-A-5-61483 (JP, A) JP-A-5-73075 (JP, A) JP-A-6-28011 (JP, A) JP-A-6-110470 (JP, A) JP-A-5-11783 (JP, A) JP-A-2-306684 (JP, A) JP-A-3-275917 ( JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G10K 11/178 B60R 11/02 F01N 1/00 F01N 1/06 H03H 17/02 601 H03H 21/00 G01P 1/08

Claims (1)

(57) [Claims] [Claim 1] A cancel sound source that outputs a cancel sound to cancel an engine sound at a noise cancel point, and a combined sound of the noise and the cancel sound at the noise cancel point are detected. And a reference signal corresponding to the engine sound generated from the engine which is the noise source at the noise canceling point. A noise cancellation controller that determines a coefficient of the adaptive filter so as to cancel the engine sound at the cancellation point, inputs a reference signal to the adaptive filter, generates a noise cancellation signal, and inputs the noise cancellation signal to a cancellation sound generation source. In the noise cancellation method of the noise cancellation device equipped with A noise canceling controller is provided for each of the higher harmonic components having a relatively high level among the higher harmonic components of the engine speed included in the engine sound, and the noise canceling controller for the predetermined higher harmonic component is Adaptive signal processing is performed using a coefficient update formula that does not incorporate an output restriction term that limits the output signal amplitude.The noise cancellation controller for other higher harmonic components incorporates an output restriction term that limits the output signal amplitude. A noise canceling method characterized by performing adaptive signal processing using a coefficient updating formula and adding output signals of respective noise canceling controllers to obtain a noise canceling signal.