JPH0635480A - Noise canceling device - Google Patents

Abstract

PURPOSE:To prevent a noise due to deterioration of frequency characteristics of a speaker in the low frequency range from being generated. CONSTITUTION:A canceling sound is outputted by the speaker 17 so as to cancel a noise at a noise cancellation point and a microphone 18 detects the composite sound of the noise at the noise cancellation point and the canceling sound. A noise cancellation controller 14 performs an adaptive signal process by using the composite sound signal and noise at the noise cancellation point so as to cancel the noise at the noise cancellation point and determines the coefficient of an adaptive filter 14b, which filters a reference signal corresponding to the coefficient to generate a noise canceling signal and inputs the noise canceling signal to the speaker 17 through a speaker characteristic simulating filter 14d. The speaker characteristic simulating filter 14d has nearly the same frequency characteristics with the speaker 17, so low-frequency components outputted from the adaptive filter 14d are cut off according to the characteristics and no noise is generated by the speaker 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise canceling device, and more particularly to a noise canceling device capable of canceling noise at a predetermined position (observation point) in a vehicle to provide a comfortable vehicle interior environment.

[0002]

2. Description of the Related Art As a noise countermeasure, a method using a sound absorbing material (passive control) has been conventionally known. However, in the method using the sound absorbing material, it is troublesome to form a quiet area where noise is small, and there is a problem that the bass cannot be effectively eliminated. In particular, in order to prevent noise in the passenger compartment of an automobile, there is a problem that the weight of the automobile increases and the noise cannot be effectively eliminated. For this reason, a method (active control) of radiating a noise canceling sound having a phase opposite to that of the noise from the speaker to reduce the noise has been in the spotlight and is being put to practical use in a part of indoor space such as a factory or an office. Also, a method has been proposed in which noise is reduced by active control even in the passenger compartment of an automobile.

FIG. 4 is a block diagram of a conventional device for realizing noise cancellation, 11 is an engine which is a noise source, and 12 is a noise source.
Is a rotation speed sensor for detecting the engine rotation speed R, and 13 is a reference signal generator for generating a sine wave signal having a constant amplitude and having a frequency according to the engine rotation speed R as a reference signal S _N. When the noise source is an engine, noise generated by engine rotation has a periodicity (periodic noise), and its frequency depends on the engine speed. For example, in the case of a 4-cylinder engine, the frequency of the secondary high frequency periodic noise generated in the vehicle compartment is 20 Hz when the rotation speed is 600 rpm, and the frequency of the periodic noise generated in the vehicle compartment is 200 Hz when the rotation speed is 6000 rpm. And the second harmonic of the engine speed is dominant. Therefore, the reference signal generator 13
Stores the sine wave data in the ROM, reads the data as needed, and outputs the data to generate the reference signal. The data read / output timing is controlled according to the engine speed R,
A reference signal having a frequency of periodic noise generated according to the engine speed R is generated.

Reference numeral 14 is a noise canceling controller, which receives the reference signal S _N generated from the reference signal generating unit 13 and also causes noise Sn at a noise canceling position (observation point, for example, near the driver's ear) in the vehicle interior. The synthesized sound signal of the cancel sound Sc and the cancel sound Sc is input as an error signal Er, and adaptive signal processing is performed so as to minimize the error signal and a noise cancel signal Nc _D is output. The noise cancellation controller 14 is created based on the adaptive signal processing unit 14a, the adaptive filter 14b having a digital filter configuration, and the transfer function of the cancel sound propagation system (secondary sound propagation system) from the speaker to the noise cancellation point. Signal S
_It has a filter 14c to which _N is input. Reference numeral 15 denotes a DA converter for converting the adaptive filter output (noise canceling signal Nc _D ) into an analog noise canceling signal Nc _A ,
Reference numeral 16 is a power amplifier for amplifying the noise canceling signal Nc _A , 17 is a canceling speaker for radiating the noise canceling sound Sc, and 18 is a noise canceling point.
An error microphone for detecting a synthesized sound of n and the cancel sound Sc and outputting the synthesized sound signal as an error signal Er, and an AD converter 19 for converting the error signal Er into a digital signal.

The adaptive signal processing unit 14a has a noise canceling point.
Input via the error signal Er and the filter 14c at
Signal S_N'Is input and noise is generated using these signals.
Adapted to cancel the noise at the cancellation point
Signal processing is performed to determine the coefficient of the adaptive filter 14b.
It For example, the adaptive signal processing unit 14a is a well-known LMS (Least
Mean Square) According to the adaptive algorithm, the error microphone
The error signal Er input from 18 should be minimized.
The coefficient of the adaptive filter 14b is determined. Adaptive filter 1
4b is in accordance with the coefficient determined by the adaptive signal processing unit 14a.
Reference signal S _NDigital filter is applied to the DA
Noise cancellation signal N from converter 15_CAOutput
It The reference signal S_NHas a high correlation with the noise Sn to be deleted.
Sound that is uncorrelated with the reference signal
I won't leave. When the engine 11 rotates, its rotation speed R
Is detected by the rotation speed sensor 12, and the reference signal generator 1
3 is a reference signal S having a frequency corresponding to the engine speed R
_N(See Fig. 5 (a))
Enter in LA14. At this time, generated from the engine 11
Engine sound with periodicity (periodic noise)
Sky with noise propagation system (first-order sound propagation system) having transfer function
It propagates through and reaches the noise cancellation point. Therefore, the noise
The noise (engine sound) Sn at the cancellation point is the level
Is slightly weakened and slightly delayed, as shown in Fig. 5 (b).
Become.

First, the noise canceling controller 14 detects the noise canceling signal Nc whose phase is opposite to that of the reference signal S _N , for example.
_A is output, and the cancel speaker 16 outputs the cancel sound Sc shown in FIG. 5 (c). However, since the noise Sn is out of phase with the noise Sn, the noise is not canceled by the cancel sound Sc, and the error signal Er is generated. The noise canceling controller 14 performs adaptive signal processing so that the error signal Er is minimized, and the adaptive filter 14b.
In the ideal case, the phase of the cancel sound Sc is made opposite to the phase of the noise Sn, and the levels are matched to cancel the noise in the ideal case.

In order to simplify the explanation, the above is an example in which there is one noise source, one cancellation sound generation source (speaker), and one noise cancellation point (observation point). However, in reality, there are a plurality of noise sources and a plurality of points (observation points) where noise is desired to be canceled. Therefore, one speaker cannot cancel noise at each observation point, and a plurality of speakers exist. FIG. 6 is a configuration diagram of a conventional noise canceling device when there are K noise sources, M speakers, and L observation points. Reference numeral 21 is a noise canceling controller that operates to cancel noise at each observation point, and 22 is a primary sound virtual propagation system (noise propagation system) that represents a system in which noise propagates from each noise source (not shown) to each observation point. ), 23 is a secondary sound propagation system (cancellation sound propagation system) expressing a system in which a cancellation sound propagates from each speaker to each observation point, including characteristics of a speaker (not shown), 24
Is a signal combining unit expressing the function of the microphone at each observation point, the addition units 24 _{1 to} 24 ₁ ′ correspond to the microphones at the first observation point, and the addition units 24 _{2 to} 24 ₂ ′ are the microphones at the second observation point. The addition units 24 _{L to} 24 _L ′ correspond to the microphone at the Lth observation point. _{d d1n} ~d dLn is an external noise is not a cancellation target in each observation point. still,
A DA converter, an AD converter, etc. are omitted.

[0008] In the noise cancellation controller 21, 21a is the reference signal x _a1n ~x _AKN corresponding to noise generated from the noise source (output from the reference signal generating section, not shown) is input, the noise cancellation signal y _a1n ~ A multi-input-multi-output adaptive filter (hereinafter simply referred to as an adaptive filter) for inputting _yaMn into each speaker, 21b is a secondary sound propagation system 2
3 is a filter for creating a filtered X signal created by using each element (propagation element) of the transfer function matrix of 3 and a reference signal x _{a1 n}
those enter x _AKN, 21c are input to filtered-X signal r _111n ~r _LMKn output from the error signal e _1n to e _Ln and the filter 21b at each observation point, at each observation point by using these signals This is an adaptive signal processing unit that performs adaptive signal processing so as to cancel noise and determines the coefficient of the adaptive filter 21a.

FIG. 7 is an explanatory diagram of the primary sound virtual propagation system 22. As shown in FIG. 7A, K noise sources NG _{1 to} NG _{K are provided.}
The noise generated from the microphone propagates through the primary sound propagation system 22 having a predetermined frequency / phase characteristic, and the microphone (M
IC _{1 to} MIC _L ). Therefore, assuming that the transfer characteristic of the propagation system in which the noise from the i-th noise source NGi reaches the j-th microphone MIC _j is H _ji , the primary sound virtual propagation system 22
Is expressed as shown in FIG. 7 (b), and its transfer function matrix (H) is as follows.

[0010]

[Equation 1]

Each element H _ij of the transfer function matrix (H) is modeled by the FIR type digital filter shown in FIG. That is, the delay element DL that sequentially delays the input signal by one sampling time and the coefficient h ₀ ,
It is modeled by a digital filter including a multiplication unit ML that multiplies h ₁ , h ₂ , ... And an addition unit AD that adds the outputs of the multiplication units. FIG. 9 is an explanatory diagram of the secondary sound propagation system 23,
As shown in FIG. 9A, the noise canceling sound generated from each of the speakers SP _{1 to} SP _M propagates through the secondary sound propagation system 23 having a predetermined frequency / phase characteristic and the microphone MIC ₁ provided at each observation point. ~ Reach MIC _L. Therefore, the transfer characteristic of the secondary sound propagation system in which the cancel sound based on the i-th noise cancel signal y _ain reaches the j-th microphone MIC _j is C _ji.
Then, the secondary sound propagation system 23 is modeled as shown in FIG. 9B, and its transfer function matrix (C) is as follows.

[0012]

[Equation 2]

Each element of the transfer function matrix (C) is a primary
Similar to the case of the virtual sound propagation system 22, the FIR type shown in FIG.
It is modeled by a digital filter. That is, enter
Delay element DL for sequentially delaying the force signal by one sampling time
And the coefficient c for each delay element output ₀, C₁, C₂, ...
Multiplier ML for adding and adder A for adding the outputs of the respective multipliers
Modeled with a digital filter consisting of D. Figure 10
Is each element of the transfer function matrix (C) of the secondary sound propagation system 23.
Element C_ijA filter for creating a filtered X signal created using
It is a block diagram of the filter 21b. The adaptive signal processing unit 21c
Reference signal x_a1n~ X_aKnAnd noise and noise at each observation point.
Synthetic signal with error sound (error signal) e_1n~ E_LnBased on
Then, adaptive signal processing is performed to update the adaptive filter coefficients.
Newly, the adaptive filter 21a has a reference signal x_a1n~ X_aKnEnter
Forced noise canceling signal y_a1n~ Y_aMnOccurs and
Input to the peaker and cancel the noise at each observation point.

By the way, the noise cancellation signal y _a1n ~y _{a Mn} output from the adaptive filter 21a is as not to reach the observation point, and reaches under the influence of the frequency and phase characteristics of the secondary sound propagation system 23. Therefore, the adaptive signal processing unit 21c does not use the reference signals x _{a1n to} x _{aKn as} they _are , but uses a filtered X LMS (MEFX LMS) algorithm that uses a signal obtained by adding the characteristics of the secondary sound propagation system 23 to the reference signal. Adopted for more advanced noise cancellation control. That, filtered-X In LMS algorithm, the reference signal x _a1n ~x _AKN a signal filtered by the filter 21b (filtered-X signal) indicated by using the error signal at each observation point filter 2
The coefficient of 1a is updated.

In FIG. 10, C _ij is the secondary sound propagation system 23.
10 is an FIR digital filter that realizes each element C _ij (see FIG. 9) of the transfer function matrix (C) in FIG.
Filter 21b is adapted to output the reference signal x _a1n ~x _AKN in by the action of all the propagation element (passed through a filter corresponding to all the propagation element) filtered-X signal r _111n ~r _LMKn There is. That is, in the reference signal x _a1n , the propagation element C ₁₁ from the first speaker to all the observation points
By the action of C _L1 outputs the filtered-X signal r _111n ~r _L11n, the reference signal x _a1n reacted propagation elements C ₁₂ -C _L2 from the second speaker to the total observation point filtered-X signal r _121n ~r _L21n outputs a, ... reference signal x
Propagation elements C _{1M to} C _LM from the M-th speaker to all the observation points are _applied to _a1n , and filtered X signals r _{1M1n to} r 1 are _transmitted.
Outputs _LM1n, likewise exerts all propagation elements in the reference signal x _a2n ~x _AKN below. _{Incidentally, R 11 = (r 111n,} r 211n, ··· r L11n) R 21 = (r 121n, r 221n, ··· r L21n) ··· R M1 = (r 1M1n, r 2M1n, ··· r _LM1n ) ... R _MK = (r _1MKn , r _2MKn , ... R _LMKn )

FIG. 11 shows a multi-input-multi-output adaptive filter 2.
It is a block diagram of 1a, and has the same structure as the primary sound virtual propagation system 22 and the secondary sound propagation system 23. A _11n- A _MKn is F
For example, delay elements DL1 and D configured by an IR type digital filter for sequentially delaying an input signal by one sampling time
l2 ... And the coefficients a ₀ , a ₁ , a ₂ ...
Are implemented by multiplying units ML1, ML2, ML3 ..., And addition units AD1, AD2. The number of delay stages is not limited to two. Each reference signal x
_{By inputting and} adding _a1n to x _aKn to the digital filters A _{11n to} A _1Kn , the noise cancellation signal y _a1n to be input to the first speaker is obtained, and each reference signal x _{a1n to} x.
noise cancellation signal y _a2n to be input to the second speaker is obtained by adding to input _aKn to the digital filter A _21n ~A _2Kn, ···· each reference signal x _a1n ~x
_By inputting and adding _aKn to the digital filters A _{M1n to} A _MKn , the noise cancellation signal y _aMn input to the M-th speaker is obtained.

Each FIR type digital filter A _{11n to} A _MKn in the adaptive filter 21a has three coefficients (two-stage delay).
In the above configuration, the adaptive signal processing unit 21c performs adaptive signal processing for each of the three coefficients of the FIR digital filters A _{11n to} A _MKn to determine the coefficient value. Ie one FIR
The coefficients a ₀ , a ₁ and a ₂ of the type digital filter A _ij are calculated according to the following equation to determine the coefficients a ₀ , a ₁ and a ₂ .

[0018]

[Equation 3]

In equation (1), (n) is the value at the current sampling time, (n-1) is the value one sampling time before, (n-2) is the value two sampling times before, and (n + 1). Means the value from the current time to the next sampling time. Therefore, R _ij (n-2) is the filter 21 corresponding to the reference signal two sampling times before.
This means the output of b, R _ij (n-1) is the filter output according to the reference signal one sampling time before, and R _ij (n) is the filter output according to the reference signal at the current time. Further, mu is a constant of 1 or less (step size parameter), e _n is the composite signal of the noise and canceling sound in the L each observation point.

[0020] according According to the noise cancellation device, adaptive signal processing unit 21c filtered-X signal r _111n ~r _LMKn and synthesized sound signal (error signal between the noise and the canceling sound at each observation point, which is the output of the filter 21b ) E _1n ~ e
Adaptive filter 2 by executing adaptive signal processing based on _Ln
FIR type digital filters A _{11n to} A constituting 1a
The coefficient of _MKn is determined, and the adaptive filter 21a determines the reference signal x
_{a1n ~} x _aKn is input and the noise cancellation signal y _a1n ~ y
_aMn is generated and input to the speakers SP _{1 to} SP _M (FIG. 9), and each speaker acts to cancel the noise at each observation point by generating a cancel sound.

In FIG. 12, the number of noise sources K = 2 and the number of speakers M =
2 is a configuration diagram of a specific conventional noise canceling device when the number of observation points (the number of microphones) L = 2, and 21a is configured by four FIR type digital filters A ₁₁ , A ₂₁ , A ₁₂ and A _22. And an adaptive filter 21b, each propagation element C ₁₁ , C ₂₁ , C ₁₂ , of the transfer function matrix (C) of the secondary sound propagation system.
C ₂₂ is a filter for creating a filtered X signal configured by a digital filter, 21c-1 to 21c-4 are adaptive signal processing units (ME
FX LMS algorithm), SP ₁ and SP ₂ are speakers, and MC ₁ and MC ₂ are microphones installed at observation points.

[0022]

The frequency characteristics of the speaker are not flat but change according to the frequency. FIG. 13 is a frequency characteristic diagram of the speaker, which changes in a substantially linear manner in accordance with the frequency up to a certain low frequency.
Subsequent frequencies are almost flat. By the way, the noise cancellation controller performs adaptive signal processing on the assumption that the frequency characteristics of the speaker are flat over the entire area, and outputs a noise cancellation signal. However, the speaker actually has the frequency characteristic shown in FIG. For this reason, the speaker does not emit a canceling sound as instructed by the noise canceling controller in the low frequency range, and outputs a signal (noise) having a frequency component completely different from the signal output by the adaptive filter. Therefore, the error signal detected by the error microphone does not become small, and the noise cancellation controller outputs a larger signal in order to cancel it. After that, these operations are repeated and the noise output from the speaker becomes very large. FIG. 14 is an explanatory diagram of a conventional noise canceling effect. The horizontal axis is the engine speed rpm (noise frequency Hz), the vertical axis is the sound pressure level (dB), 51 is the noise sound pressure level curve at the observation point when noise is not canceled, 52 is the observation point when noise is canceled Noise sound pressure level curve at, NC is a noise reduction area where noise is canceled and reduced,
NG is a sound increase area where noise increases. In the noise reduction region NC equal to or higher than the rotation speed r _L (noise frequency f _L ), the noise canceling effect indicated by diagonal lines is obtained. However, the rotation speed r
Noise is not canceled in the low-frequency sound increase region that is equal to or lower than _L (noise frequency f _L ), and the cancel sound output by the noise cancel control becomes new noise, and the noise is increasing. From the above, the purpose of the present invention is
(EN) Provided is a noise canceling device capable of preventing the generation of noise due to the deterioration of the frequency characteristic of a power source in a low range.

[0023]

According to the present invention, the above problem is solved by a cancel sound generation source (speaker), a sensor (microphone) for detecting a synthesized sound of noise and a cancel sound at a noise cancel point, and noise cancel. A noise cancellation controller that performs adaptive signal processing so as to cancel noise at a noise canceling point using a synthetic sound signal at a point and a reference signal, and outputs a noise cancellation signal,
This is achieved by a speaker characteristic simulating filter provided in the preceding stage of the canceling sound generating source or in the subsequent stage of the reference signal generating section and having a frequency characteristic substantially equal to that of the canceling sound generating source.

[0024]

In the first aspect of the present invention, the cancel sound is output from the speaker to cancel the noise at the noise cancel point, and the synthesized sound of the noise and the cancel sound at the noise cancel point is detected by the microphone. The noise cancellation controller performs adaptive signal processing so as to cancel the noise at the noise cancellation point by using a synthesized sound signal (error signal) at the noise cancellation point and a signal corresponding to the noise, and determines the coefficient of the adaptive filter. Applies a filtering process according to the coefficient to the reference signal to generate a noise cancellation signal, and inputs the noise cancellation signal to the speaker via the speaker characteristic simulation filter. Since the speaker characteristic simulation filter has almost the same frequency characteristic as the speaker, even if the low-frequency component output from the adaptive filter becomes large, the passage of the low-frequency component is blocked according to the characteristic, and noise is emitted from the speaker. It never happens. That is, when the speaker characteristic simulating filter is included in the noise canceling controller, the noise canceling controller generates the noise canceling signal in consideration of the frequency characteristic of the speaker, so that the low-frequency component becomes large and noise does not occur.

In the second aspect of the present invention, in order to cancel the noise at the noise canceling point, a canceling sound is output from the speaker, and a synthesized sound of the noise at the noise canceling point and the canceling sound is detected by the microphone to detect the noise canceling controller. And the reference signal is input to the noise canceling controller via the speaker characteristic simulation filter (adding the frequency characteristic of the speaker to the reference signal). The noise cancellation controller performs adaptive signal processing to cancel the noise at the noise cancellation point by using the synthesized sound signal at the noise cancellation point and the reference signal that has passed through the speaker characteristic simulation filter, determines the coefficient of the adaptive filter, and Applies a filtering process according to the coefficient to the output signal of the speaker characteristic simulating filter to generate a noise cancellation signal and input it to the speaker. The reference signal input to the adaptive filter of the noise canceling controller has its low frequency range suppressed by the speaker characteristic simulating filter, so the low frequency component of the noise canceling signal does not increase, and noise is generated from the speaker. There is no.

[0026]

【Example】

(a) Overall configuration of the first embodiment of the present invention FIG. 1 shows the first embodiment of the noise canceling device of the present invention.
4 is a block diagram of the embodiment of the present invention, in which the same functional parts as those of the conventional device of FIG. In the figure, 11 is an engine as a noise source, 12 is a rotation speed sensor for detecting the engine rotation speed R, and 13 is a sine wave signal of a constant amplitude having a frequency corresponding to the engine rotation speed R as a reference signal S _N. It is a reference signal generator. When the noise source is an engine, noise generated by engine rotation has a periodicity (periodic noise), and the noise frequency depends on the engine speed. Therefore, the reference signal generation unit 13 stores the sine wave data in the ROM, reads the data as needed, and outputs the data to generate the reference signal. The timing for reading / outputting this data is controlled according to the engine speed R, and a reference signal having the frequency of periodic noise generated according to the engine speed R is generated.

Reference numeral 14 denotes a noise canceling controller, which receives the reference signal S _N generated from the reference signal generating unit 13 and also causes a noise Sn at a noise canceling position in the passenger compartment (observation point, for example, near the driver's ear). The synthesized sound signal of the cancel sound Sc and the cancel sound Sc is input as an error signal Er, and adaptive signal processing is performed so that the error signal is minimized to output a noise cancel signal Nc _D ′. 15 is a noise canceling signal, which is an analog noise canceling signal Nc _A
A DA converter for converting into noise, a power amplifier 16 for amplifying the noise canceling signal Nc _A , a canceling speaker 17 for radiating the noise canceling sound Sc, and 18 arranged at the noise canceling point, for the noise Sn and the canceling sound Sc. An error microphone that detects a synthesized sound and outputs the synthesized sound signal as an error signal Er, 19 is an AD converter that converts the error signal Er into a digital signal, and 20 is a cancel sound propagation in which a cancel sound propagates from a speaker to a noise cancel point It is a system (secondary sound propagation system). Note that FIG. 1 shows a case where there is only one noise source, speaker, and error microphone for simplification of description, but the present invention is not limited to such a case, and a plurality of noise sources, a plurality of speakers, and a plurality of speakers are provided. It is also applicable when an error microphone is provided.

Noise Canceling Controller The noise canceling controller 14 is a DSP (digital
Signal processor), an adaptive signal processing unit 14a, an adaptive filter 14b having a digital filter configuration, a filtered X signal generation filter (filtered X signal generation filter) 14c used for adaptive signal processing, and A speaker characteristic simulating filter 14d simulating the frequency characteristic of the speaker is provided. The speaker characteristic simulating filter 14d digitally has the same characteristic as the frequency characteristic of the speaker 17 (FIG. 13).
b output.

The adaptive signal processing unit 14a receives the error signal Er at the noise canceling point and the filtered X signal S input through the filtered X signal generating filter 14c.
_N ′ is input, adaptive signal processing is performed using these signals according to the equation (1) so as to cancel the noise at the noise canceling point, and the coefficient of the adaptive filter 14b is determined. That is, the adaptive signal processing unit 14a uses the well-known LMS (L
east Mean Square)
The coefficient of the adaptive filter 14b is determined so that the error signal Er input from the microphone 18 is minimized. The adaptive filter 14b digitally filters the reference signal S _N according to the coefficient determined by the adaptive signal processing unit 14a, and outputs the noise cancel signal N _CD .

When the entire operating engine 11 rotates, its rotational speed R is detected by the rotational speed sensor 12, and the reference signal generator 13 generates a reference signal S _N having a frequency corresponding to the engine rotational speed R to cancel noise. Input to the controller 14. At this time, a periodic engine sound (periodic noise) generated from the engine 11 propagates through the air having a noise propagation system (primary sound propagation system) having a predetermined transfer function and reaches a noise cancellation point. The error microphone 17 detects the synthesized sound of the noise and the cancel sound at the noise cancel point, and inputs the synthesized sound signal (error signal) Er to the adaptive signal processing unit 14a. In parallel with the above, the filtered X signal generation filter 14c
Receives the reference signal S _N and inputs the filtered X signal S _N ′ used for LMS adaptive signal processing to the adaptive signal processing unit 14a. The adaptive signal processing unit 14a receives the error signal Er and the filtered X signal S _N ′ output from the filter 14c.
Is used to perform LMS adaptive signal processing according to equation (1), and the coefficient of the adaptive filter 14b is determined.

The adaptive filter 14b is an adaptive signal processing unit 14
The reference signal S _N is digitally filtered according to the coefficient determined by a to output the noise cancel signal Nc _D , and the speaker characteristic simulation filter 14d adds the frequency characteristic of the speaker to the noise cancel signal Nc _D. The DA converter 15 DA-converts the output signal N _CD ′ of the speaker characteristic simulation filter 14 d and inputs it to the speaker 17 via the power amplifier 16. Thereby, the noise canceling sound is output from the speaker 17, reaches the noise canceling point through the secondary sound propagation system 20, and acts to cancel the noise. Thereafter, the above operation is repeated and the noise is promptly canceled. In the above description, the speaker characteristic simulating filter 14d has substantially the same frequency characteristic as the speaker 17, so that the noise canceling signal N _CD output from the adaptive filter 14b is given the speaker characteristic and the low frequency component is attenuated. Therefore, the low-frequency component of the noise cancellation signal N _CD does not become large and noise is not generated from the speaker. That is, the noise cancellation controller 1
No. 4 generates the noise cancellation signal Nc _D ′ in consideration of the frequency characteristic of the speaker 17, so that the low frequency component of the adaptive filter 14b does not become large and noise does not occur.

(B) Second Embodiment of the Present Invention FIG. 2 is a block diagram of another embodiment of the present invention, in which the same parts as those in the first embodiment are designated by the same reference numerals. The second embodiment differs from the first embodiment in that a speaker characteristic simulating filter simulating the frequency characteristic of the speaker 17 is placed outside the noise canceling controller 14 and has an analog configuration. That is, the speaker characteristic simulating filter 21 having an analog structure for simulating the frequency characteristic of the speaker is provided in the subsequent stage of the DA converter 15, and the other points are the same as those in the first embodiment. In such a configuration, when the speaker characteristic simulating filter 21 is included in the noise canceling controller, the noise canceling controller generates a noise canceling signal in consideration of the frequency characteristic of the speaker as in the first embodiment, so that the low-frequency component is reduced. It does not grow and no noise occurs.

(C) Third Embodiment of the Present Invention FIG. 3 is a block diagram of a third embodiment of the present invention, in which the same parts as those in the first embodiment are designated by the same reference numerals. The third embodiment is different from the first embodiment in that a speaker characteristic simulation filter 14d 'for simulating the frequency characteristic of the speaker 17 is provided at a stage subsequent to the reference signal generator 13 and the adaptive filter 14b and the filtered X signal are generated. This is the point provided before the filter 14c.

In the third embodiment, a cancel sound is output from the speaker 17 in order to cancel the noise at the noise cancel point, and the synthesized sound of the noise and the cancel sound at the noise cancel point is detected by the microphone 18 to generate the noise. Input to the cancel controller 14. Further, the reference signal S _N is input to the adaptive filter 14b and the filtered X signal generating filter 14c via the speaker characteristic simulation filter 14d '(adding the frequency characteristic of the speaker to the reference signal S _N ). The adaptive signal processing unit 14a
Adaptive signal processing is performed so as to cancel noise using the synthesized sound signal Er at the noise canceling point and the output signal S _N ′ of the filtered X signal generating filter 14c to determine the coefficient of the adaptive filter 14b. Adaptive filter 14
Reference numeral b denotes a filter processing in accordance with the coefficient, which is applied to the output signal of the speaker characteristic simulation filter 14d 'to generate a noise canceling signal N _CD and the speaker 1 via the DA converter 15.
Type in 7. Thereby, the noise canceling sound is output from the speaker 17, reaches the noise canceling point through the secondary sound propagation system 20, and acts to cancel the noise. Thereafter, the above operation is repeated and the noise is promptly canceled. Since the reference signal S _N ″ input to the adaptive filter 14b and the filtered X signal generation filter 14c is provided with the frequency characteristic of the speaker 17 in the speaker characteristic simulation filter 14d ′, the low frequency band is suppressed, and therefore the reference signal S _N ″ is suppressed. The low-frequency component of the noise cancellation signal N _CD does not increase, and noise does not occur from the speaker.

When the reference signal generating section 13 outputs an analog reference signal S _N , an analog speaker characteristic simulating filter is provided at the subsequent stage of the reference signal generating section 13 and the speaker characteristic simulating filter output is used as an AD converter. The noise canceling controller 14 may be input as a reference signal via the. When there are a plurality of noise sources, speakers, and observation points, the same number of speaker characteristic simulation filters as the speakers are provided, and the noise cancellation signal output from the adaptive filter is input to each and input to the corresponding speaker. To configure. Although the present invention has been described above with reference to the embodiments, the present invention can be variously modified according to the gist of the present invention described in the claims, and the present invention does not exclude these.

[0036]

As described above, according to the present invention, the speaker characteristic simulation filter for simulating the frequency characteristic of the speaker is arranged between the adaptive filter for outputting the cancel sound signal and the speaker as the source of the cancel sound. Even if the low-frequency component output from the speaker becomes large, the passage of the low-frequency component is blocked according to its characteristics, and noise is not generated from the speaker. That is, when the speaker characteristic simulating filter is included in the noise canceling controller, the noise canceling controller generates the noise canceling signal in consideration of the frequency characteristic of the speaker, so that the low-frequency component becomes large and noise does not occur. Further, according to the present invention,
Since a speaker characteristic simulating filter for simulating the frequency characteristic of the speaker is arranged after the reference signal generation source and the reference signal is input to the noise canceling controller via the speaker characteristic simulating filter, the noise canceling controller is adapted. Since the low frequency range of the reference signal input to the filter can be suppressed, the low frequency range component of the noise canceling signal does not increase, and therefore noise does not occur from the speaker.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a third embodiment of the present invention.

FIG. 4 is a configuration diagram of a conventional noise canceling device.

FIG. 5 is a waveform diagram for explaining a noise canceling operation.

FIG. 6 is a configuration diagram of a conventional noise canceling device when there are a plurality of noise sources, speakers, and observation points.

FIG. 7 is an explanatory diagram of a primary sound virtual propagation system.

FIG. 8 is a configuration diagram of a digital filter that realizes each element of a transfer function matrix.

FIG. 9 is an explanatory diagram of a secondary sound propagation system.

FIG. 10 is a configuration diagram of a filter for generating a filtered X signal.

FIG. 11 is a configuration diagram of an adaptive filter.

FIG. 12 is a configuration diagram of a conventional noise canceling device when there are two noise sources, speakers, and observation points.

FIG. 13 is a frequency characteristic diagram of a speaker.

FIG. 14 is an explanatory diagram of a conventional noise canceling effect.

[Explanation of symbols]

 Reference signal generator 13 Noise cancel controller 14a Adaptive signal processor 14b Adaptive filter 14c Filtered X signal creation filter 14d, 14d 'Speaker speaker simulation filter 14e Frequency characteristic Correction unit 17 ... Speaker 18 ... Error microphone

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kunio Miyauchi 1-4-1 Chuo, Wako City, Saitama Prefecture Honda R & D Co., Ltd. (72) Inventor Akira Sudo 1-4-1 Chuo, Wako City, Saitama Prefecture Stock Company Honda Technical Research Institute

Claims (2)

[Claims] 1. A cancel sound generation source for outputting a cancel sound to cancel noise at a noise cancel point, a sensor for detecting a synthesized sound of noise at the noise cancel point and the cancel sound, and a synthesized sound at the noise cancel point. A signal and a reference signal corresponding to the noise generated from the noise source are input, adaptive signal processing is performed using these signals to cancel the noise at the noise cancellation point, and a noise cancellation signal is generated to generate a cancellation sound generation source. In a noise canceling device equipped with a noise canceling controller for inputting to a noise canceller, a filter having substantially the same frequency characteristics as the canceling sound source is provided between the adaptive filter of the noise canceling controller and the canceling sound source. And a noise canceling device. 2. A cancel sound generation source for outputting a cancel sound for canceling noise at a noise cancel point, a sensor for detecting a synthesized sound of noise at the noise cancel point and the cancel sound, and a synthesized sound at the noise cancel point. A signal and a reference signal corresponding to the noise generated from the noise source are input, adaptive signal processing is performed using these signals to cancel the noise at the noise cancellation point, and a noise cancellation signal is generated to generate a cancellation sound generation source. A noise canceling device having a noise canceling controller for inputting to a noise canceling device, characterized in that a filter having substantially the same frequency characteristics as that of a canceling sound generating source is provided at a stage subsequent to the reference signal generating section.