JP2604516B2 - Noise control device - 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 control apparatus for canceling noise by outputting a signal having the same phase opposite sound pressure to the noise of an engine or a motor from a speaker. An object of the present invention is to prevent an abnormal operation from occurring when the transfer characteristic to be formed deviates from the condition of the initial equalization simulating the transfer characteristic.

[0002]

2. Description of the Related Art Conventionally, a passive muffler such as a muffler has been used to reduce noise generated from an internal combustion engine or the like, but improvements have been made in view of size, muffling characteristics, and the like. On the other hand, the noise generated from the sound source
There has been proposed an active noise control device that outputs a compensation sound of equal sound pressure from a speaker and cancels noise. By the way, the frequency characteristics or the stability of the active noise control device itself are not sufficient, and its practical use has been delayed. However, in recent years, as a signal processing technique for processing digital signals has been developed and a frequency range to be handled has been expanded, a large number of practical noise control devices have been proposed (for example, JP-A-63-31396).

[0003]

By the way, in the conventional digital signal processing device of the noise control device, the FIR (Fini
te Impulse Response) type adaptive filter is used. The current filter coefficient Ck (n + 1) of this adaptive filter is based on the convergence condition by the least square with respect to the previous filter coefficient Ck (n). It is updated to satisfy and is formed, for example, as shown in the following equation.

Ck (n + 1) = Ck (n) + α × Sm (n) Te (n) (1) where k is the number of filter coefficients, α is a convergence coefficient, and Sm
(N) is an error signal, Te is a reference signal, that is, a noise signal Se.
Is corrected by the transfer characteristic . In this case, since the error signal Sm (n) is a result of receiving the transfer characteristics of a speaker, a microphone, or the like, the noise signal Se (n) differs from the error signal Sm (n) in the transfer characteristics. is there. This difference is unique because it is determined by the operating conditions of the noise control device. In order for the adaptive filter to process this, it is necessary to simulate and correct only the transfer characteristics. Simulating such transfer characteristics is called initial equalization.

[0005] However, if the use conditions of the noise control device are different, the noise control device deviates from the set initial equalization, and if it is used in this state, the noise control device may cause an abnormal operation. In addition, there is a case where it is desired to perform initial equalization only to a specific use condition. Therefore, if the use condition is not satisfied, an abnormality occurs. Therefore, an object of the present invention is to provide a noise control device that can prevent occurrence of an abnormality due to deviation from initial equalization when use conditions are different in view of the above problems.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a noise control device for forming a compensation signal having the same phase and the same sound pressure as noise, a speaker, a microphone, an adaptive filter, and coefficient updating means. , A simulated transfer characteristic correcting means and an operation unnecessary request detecting means. The speaker is installed in a closed space to be silenced, and converts the compensation signal into a silence sound.

The microphone is installed in the closed space, and detects the residual sound of the cancellation sound and the noise as an error signal. The adaptive filter inputs a noise reference signal and automatically varies a filter coefficient to cancel the noise to form the compensation signal. The coefficient updating means updates a filter coefficient of an adaptive filter based on the error signal and the noise correction signal.

In order to form the correction signal, the simulated transfer characteristic correcting means simulates a transfer characteristic from the output of the adaptive filter to the input of the coefficient updating means under a certain condition. Correction by initial equalization. The operation-unnecessary detecting unit detects the operation-unnecessary state to exclude an operation different from the initial equalized condition, and stops the generation of the correction signal.

A window opening / closing detector for detecting the opening / closing of the window in the closed space and not operating when the window is opened may be provided as the operation unnecessary state detecting means. A noise level detector may be provided for detecting and not operating when the noise level is lower than a predetermined value, and detecting a noise level of only a desired frequency band in the closed space, and determining a noise level of the desired frequency band. A band noise level detector may be provided to prevent operation when the vibration level is less than the predetermined value, and a vibration that causes noise in the closed space is detected, and the operation is performed when a vibration level at a desired vibration frequency is lower than a predetermined value. A vibration level detector for preventing the movement may be provided, and a speed detector for detecting a speed when the closed space moves and for not operating the speed when the speed is equal to or more than a predetermined value may be provided.

[0010]

According to the noise control device of the present invention, the compensation signal is converted into an erasing sound by the loudspeaker installed in the closed space to be silenced. The microphone and the residual sound of the noise are detected as error signals by the microphone installed in the closed space. The adaptive filter to which the noise reference signal is input automatically changes the filter coefficient to eliminate the noise, thereby forming the compensation signal.
The filter coefficient of the adaptive filter is updated by the coefficient updating means based on the error signal and the noise correction. In order to form the correction signal by the simulated transfer characteristic correcting means, the reference signal of the noise simulates the transfer characteristic from the output of the adaptive filter to the input of the coefficient updating means under a certain condition, and is initially simulated. It is corrected by equalization. The operation-unnecessary state is detected by the operation-unnecessity detecting means to exclude an operation different from the initial equalized condition, and the generation of the compensation signal is stopped.
Therefore, even if the use condition is different from the initial equalization, the noise control device detects the deviation from the initial equalization and stops the noise control device. In particular,
By providing a window opening / closing detector for detecting the opening / closing of the window in the closed space and not operating when the window is opened as the operation-unnecessary state detecting means, a state in which the transmission characteristics are different is detected. By providing a noise level detector for detecting the noise level in the closed space and not operating when the noise level is less than the predetermined value, the noise level is low and the operation unnecessary state of the noise control device is detected. In this manner, a state in which the target noise is not detected is detected, and malfunction can be prevented. Detecting the noise level of only the desired frequency band in the closed space,
By providing a band noise level detector to prevent operation when the noise level of the desired frequency band is less than the predetermined value, the cause of malfunction in the low frequency region where the output of the speaker is not efficient and in the high frequency region where sound silencing is difficult Can be detected. By detecting a vibration that causes noise in the closed space and providing a vibration level detector for preventing operation when the vibration level of a desired vibration frequency is less than a predetermined value, the vibration of the engine, motor, etc. can be directly detected. Since the measurement can be performed, the frequency can be detected without being affected by the speaker. Further, by detecting a speed when the closed space moves, and providing a speed detector for not operating when the speed is equal to or higher than a predetermined value, wind noise other than the target noise is detected.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a noise control device according to an embodiment of the present invention. The noise control device shown in FIG. 1 includes a speaker 2 installed in a closed space 1 to be silenced, a power amplifier 3 for driving the speaker 2, and a low-pass filter 4 for removing high-frequency components to the power amplifier 3. And a D / A converter 5 (Digital to Analog Converter) for converting a digital signal into an analog signal and outputting the analog signal to the low-pass filter 4. A microphone 6 for detecting an error signal which is a residual sound as a result of silencing intruding noise by the speaker 2, an amplifier 7 for amplifying a signal from the microphone 6, and a high frequency component included in an analog signal from the amplifier 7 A low-pass filter 8 for removing the signal and avoiding aliasing, and an A / D converter 9 (Analog to Digital Convert) for converting an analog signal from the low-pass filter 8 into a digital signal. e
r), a compensating signal is output to the D / A converter 5 to cause the speaker 2 to form an erasing sound, and a FIR (Finite Impulse Res
and a coefficient updating means for updating a filter coefficient of the adaptive filter 10 from an error signal from the A / D converter 9 and a noise correction signal to be described later according to equation (1). 11 and a reference signal of the same noise as that of the adaptive filter 10 are inputted, a unique transfer characteristic from the output of the adaptive filter 10 to the coefficient updating means 11 is simulated, and a correction signal is outputted to the coefficient updating means 11. A first transfer characteristic simulating means 12, a second transfer characteristic simulating means 13 connected to the output side of the adaptive filter 10 and simulating the same transfer characteristic as the first transfer characteristic simulating means 12,
The noise signal is reproduced by calculating the difference between the output signal of the transfer characteristic simulating means 13 and the output signal of the A / D converter 9, and the reproduced noise signal is used as the adaptive filter 10 and the first transfer characteristic simulating means. 12 includes a difference signal calculation means 14 for outputting the difference signal. The power amplifier 3 has a structure capable of muting by an external signal.

Further, the noise control device includes an operation unnecessary state detecting means 20 for detecting a state in which the operation of the noise control device itself is not required. If the closed space 1 is, for example, a passenger compartment, the operation unnecessary state detecting means 20 detects a window opening / closing detector 21 for detecting opening / closing of a window, a microphone 22 for detecting a sound pressure level of the closed space 1, and the microphone 22. Noise level detector 23 for detecting a noise level below a certain value
A band-pass filter 24 for extracting a signal only in a desired frequency band (for example, 100 Hz to 500 Hz) from an output signal of the microphone 22;
, A vibration level detector 25 installed in a closed space, and a desired frequency band (for example, from 100 Hz to 1K) based on an output signal of the vibration detector 26.
Hz), and a band-pass filter 27 for extracting a signal of only
A vibration level detector 28 for detecting an output level of the band-pass filter 27 and a speed detector 30 for detecting a vehicle speed used in the engine control means 29 for moving the closed space 1 are provided. .

The noise control device receives signals from the window opening / closing detector 21, noise level detector 23, band level detector 25, vibration level 28, and vehicle speed detector 30 in the operation unnecessary state detecting means 20. In a predetermined case, for example, an OFF control means 31 for muting the power amplifier 3 is included. Here, the noise reproduction signal Se which is the output of the difference signal calculating means 14 will be described. The noise signal is Sn,
The error signal output from the microphone 6 is Smo, the input signal Sm to the coefficient updating means 11 is a compensation signal Sc output from the adaptive filter 10, and the adaptive filter 1
Assuming that a transfer characteristic Hd from the output of 0 to the microphone 6 and a transfer characteristic Hm from the microphone 6 to the filter coefficient updating means 11, the input signal Sm of the coefficient updating means 11
Is Sm = Smo · Hm (2), and the other input signal Te is the noise reproduction signal Se.
Then, the transfer characteristic Hd1 is calculated by the first transfer characteristic simulating means 9.
Required. The transfer characteristic Hd1 simulated by the first transfer characteristic simulation means 12 and the second transfer characteristic simulation means 13 is Hd1 = Hd · Hm (3), and the signal Smo detected by the microphone 6 is as follows. Become.

Smo = Sn + Sc · Hd (4) The difference signal Se, which is a noise reproduction signal which is an input signal of the adaptive filter 10 and the like, and which is a calculation result of the difference signal calculation means 14, has the above configuration. Equations (2), (3),
It is obtained from (4) as follows. Se = Sm-Sc.Hd1 = Smo.Hm-Sc.Hd1 = (Sn + Sc.Hd) .Hm-Sc.Hd.Hm = (Sn + Sc.Hd-Sc.Hd) .Hm = Sn.Hm ... (5 ) Is formed. The difference signal Se is later used as the noise reproduction signal.
Used as Since the filter coefficient is changed by the adaptive filter 10 so that the input signal Sm of the coefficient updating means 11 becomes zero, the compensation signal Sc which is the output signal of the adaptive filter 10 is Sm = 0, that is, Smo = It is determined as follows from the above equation (4) as 0.

Sc ≒ −Sn / Hd (6) Next, the formation of initial equalization of the simulated transfer characteristic by the first simulated transfer characteristic correction means 12 and the like will be described. FIG. 2 is a diagram showing initial equalization of the transfer characteristics in FIG. As shown in the figure, the white noise generating means 40 for generating white noise
The input of the adaptive filter 10 and the D / A converter 5 of FIG. 1 are connected, and the white noise signal SWC is converted into an error signal Swm via the speaker 2, the microphone 6, the A / D converter 9, and the like as the difference signal calculating means 14. And a difference from the output signal of the adaptive filter 10 is obtained to form a difference signal Swe. Further, the coefficient of the adaptive filter 10 is updated by the coefficient updating means 11 to which the input signal of the adaptive filter 10 and the difference signal Swe are input. In this case, there is no noise. Assuming that the transfer characteristic of the adaptive filter 10 is H _ADF , Swe = Swm−Swc · H _ADF (7) The adaptive filter 10 is adjusted so that Swe = 0, and the transfer characteristic H _ADF is obtained as follows. .

[0016] _{H ADF = Swm / Swc ... (} 8) Therefore H _ADF becomes transfer characteristic Swm from Swc, used as Hdl. In this way, the first and second transfer characteristic simulation means 12 and 13 in FIG. 1 are initialized. Next, OF
The F control means 31 will be described.

FIG. 3 is a flowchart for explaining the operation of the OFF control means of FIG. As shown in this figure, in step 1, it is determined whether a window is open or closed based on a signal from the window open / close detector 21. Normally, initial equalization is performed with the window closed, so that when it is opened, the transfer characteristics in the vehicle interior change.
For this reason, if it is determined by the signal from the window opening / closing detector 21 that the window is opened, the process proceeds to step 8, for example, the power amplifier 3 is muted to stop the output from the speaker 2, that is, the noise control device is turned off.

In step 2, if the window is closed in step 1, if the closed space 1 is lower than the predetermined sound pressure by the noise level detector 23, there is no need to operate the noise control device. Similarly, the noise control device is turned off. In step 3, if the sound pressure is equal to or higher than the predetermined sound pressure in step 2, the band level detector 25 determines whether the noise level in the band of the predetermined frequency is equal to or higher than the predetermined value. If the noise level of the specified frequency band is less than the specified value
In this case, the noise control device is turned off in the same manner as described above. to this
More particularly in the low frequency range where noise control devices are more effective
The noise control device can be activated according to the noise level.
Wear.

In step 4, the vibration level detector 2
8 by the vibration level of the band of the predetermined frequency to determine Ah <br/> Luke than a predetermined value. This is advantageous when the detection by the band level detector 25 is difficult. Vibration of engine, motor, etc. can be measured directly, so noise is not affected by speaker 2.
This is because the state of can be detected. If there is no vibration exceeding a certain level in the predetermined frequency band, the noise control device is turned on as described above.
Set to FF.

In step 5, the speed detector 30 determines whether the speed of the vehicle is high. In the case of high speed (for example, 80 km / h or more), since the wind noise increases and differs from the original target noise, the noise control device is turned off as described above. In step 6, normal noise control is performed except when operation is unnecessary or when malfunction is likely to occur as described above.

In step 7, the above operation is repeated until the noise control device is turned off for another reason. Although the above steps are configured in a series, they may be provided alone or separately in any combination.

[0022]

As described above, according to the present invention, the operation unnecessary state is detected in order to exclude an operation different from the initial equalized condition, and the generation of the compensation signal is stopped by this detection. If the use conditions are different and the initial equalization comes off, this is detected and the noise control device is stopped, so that the occurrence of abnormalities can be prevented.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing initial equalization of transfer characteristics in FIG. 1;

FIG. 3 is a flowchart illustrating an operation of an OFF control unit in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Closed space 2 ... Speaker 3 ... Power amplifier 6 ... Microphone 10 ... Adaptive filter 11 ... Coefficient updating means 12, 13 ... Transfer characteristic simulation means 14 ... Difference signal calculating means 20 ... Operation unnecessary state detecting means 21 ... Window opening and closing Detectors 22 and 23 Noise level detectors 24 and 25 Band level detectors 26, 27 and 28 Vibration level detectors 30 Speed detectors 31 OFF control means

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kazuhiro Sakiyama 1-2-28 Goshodori, Hyogo-ku, Kobe-shi, Hyogo Prefecture Inside Fujitsu Ten Co., Ltd. (56) References JP-A-4-11291 (JP, A) Kaihei 5-216484 (JP, A)

Claims (5)

(57) [Claims] 1. A noise control device for forming a compensation signal having an equal sound pressure in opposite phase to noise, comprising: a loudspeaker (2) installed in a closed space (1) to be silenced and converting the compensation signal into a silence sound; A microphone (6) installed in a closed space (1) for detecting the cancellation sound and the residual sound of the noise as an error signal; and automatically inputting a reference signal of the noise and automatically changing a filter coefficient for eliminating the noise. An adaptive filter (10) for forming the compensation signal; and a coefficient updating unit (1) for updating a filter coefficient of the adaptive filter (10) with the error signal and the noise correction signal.
1) the reference signal of the noise to form the correction signal;
Wherein the simulated transfer characteristics compensation means for initializing equalization Gishi simulating a transfer characteristic to the input of said coefficient updating means from the output of the adaptive filter (10) (11) (12), different from said initial equalization criteria A window opening / closing detector (2) for detecting opening / closing of a window in the closed space (1) to exclude operation
1) The noise control device, wherein the generation of the compensation signal is stopped by the window opening / closing detector (21) based on opening / closing of the window. 2. A noise control device for forming a compensation signal having the same sound pressure in opposite phase to noise, comprising: a speaker (2) installed in a closed space (1) to be silenced and converting the compensation signal into a silence sound; A microphone (6) installed in a closed space (1) for detecting the cancellation sound and the residual sound of the noise as an error signal; and automatically inputting a reference signal of the noise and automatically changing a filter coefficient for eliminating the noise. An adaptive filter (10) for forming the compensation signal; and a coefficient updating unit (1) for updating a filter coefficient of the adaptive filter (10) with the error signal and the noise correction signal.
1) the reference signal of the noise to form the correction signal;
Simulated transfer characteristic correction means (12) for simulating the transfer characteristic from the output of the adaptive filter (10) to the input of the coefficient update means (11) for initial equalization; and noise in the closed space (1). A noise control device comprising: a noise level detector (22, 23) for detecting a level and stopping generation of the compensation signal when the noise level is less than a predetermined value. 3. A noise control device for forming a compensation signal having an equal sound pressure in opposite phase to noise, comprising: a speaker (2) installed in a closed space (1) to be silenced and converting the compensation signal into a silence sound; A microphone (6) installed in a closed space (1) for detecting the cancellation sound and the residual sound of the noise as an error signal; and automatically inputting a reference signal of the noise and automatically changing a filter coefficient for eliminating the noise. An adaptive filter (10) for forming the compensation signal; and a coefficient updating unit (1) for updating a filter coefficient of the adaptive filter (10) with the error signal and the noise correction signal.
1) the reference signal of the noise to form the correction signal;
Simulated transfer characteristic correction means (12) for simulating transfer characteristics from the output of the adaptive filter (10) to the input of the coefficient updating means (11) for initial equalization; A noise detection unit configured to detect a noise level in a frequency band and to stop the generation of the compensation signal when the noise level in the desired frequency band is less than a predetermined value; Control device. 4. A noise control device for forming a compensation signal having the same phase and the same sound pressure as noise, comprising: a speaker (2) installed in a closed space (1) to be silenced and converting the compensation signal into a silence sound; A microphone (6) installed in a closed space (1) for detecting the cancellation sound and the residual sound of the noise as an error signal; and automatically inputting a reference signal of the noise and automatically changing a filter coefficient for eliminating the noise. An adaptive filter (10) for forming the compensation signal; and a coefficient updating unit (1) for updating a filter coefficient of the adaptive filter (10) with the error signal and the noise correction signal.
1) the reference signal of the noise to form the correction signal;
Simulated transfer characteristic correction means (12) for simulating the transfer characteristic from the output of the adaptive filter (10) to the input of the coefficient update means (11) for initial equalization; and noise in the closed space (1). To detect the vibration that causes
From the detected vibrations, the vibration level of the desired frequency band is
A vibration level detector (26, 2) for stopping the generation of the compensation signal when the vibration level is less than a predetermined value.
7, 28) A noise control device characterized by comprising: 5. A noise control device for forming a compensation signal having the same sound pressure in opposite phase to noise, comprising: a speaker (2) installed in a closed space (1) to be silenced and converting the compensation signal into a silence sound; A microphone (6) installed in a closed space (1) for detecting the cancellation sound and the residual sound of the noise as an error signal; and automatically inputting a reference signal of the noise and automatically changing a filter coefficient for eliminating the noise. An adaptive filter (10) for forming the compensation signal; and a coefficient updating unit (1) for updating a filter coefficient of the adaptive filter (10) with the error signal and the noise correction signal.
1) the reference signal of the noise to form the correction signal;
Simulated transfer characteristic correction means (12) for simulating transfer characteristics from the output of the adaptive filter (10) to the input of the coefficient update means (11) for initial equalization; and the closed space (1) moves. A noise control device comprising: a speed detector (30) for detecting a speed in a case and stopping the generation of the compensation signal when the speed is equal to or more than a predetermined value.