JPH08328568A - Active muffler - Google Patents

Abstract

PURPOSE: To prevent movement to unstableness of control when a disturbance occurs by comparing with a value of an initial state, judging the occurrence of the disturbance and stopping the control of active muffling. CONSTITUTION: Noise information of a rotary body 2 being a noise source is detected by a first sensor 7, and is amplified by an amplifier 8, and is converted to a digital signal X by an A/D converter 9 to be inputted to an adaptive digital filter 14 and a digital signal Y for an input of a speaker 5 is generated. The digital signal Y is converted to an analog signal by a D/A converter 13, and is power amplified by the amplifier 12, and an additional sound for reducing a noise is generated from the speaker 5. Further, the noise information before the active muffling is operated or immediately after operation is detected by a second sensor 6, and the initial value of the digital signal E is stored in a storage part 18. The initial value is compared with the digital signal E successively detected from the second sensor 6 by a comparison part 17 while operating, and when the detected value becomes larger than the initial value, a switch SW is switched, and the digital signal Y is made zero.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an active silencer.

[0002]

2. Description of the Related Art The sound deadening effect of an active sound deadening device increases in proportion to the degree of correlation between signals of a first sensor and a second sensor for detecting noise of interest, that is, the magnitude of coherence. However, when there are multiple external noise sources, external noise is input to the second sensor (microphone),
As these levels increase, the volume of the sound is reduced or the control becomes unstable. Therefore, it is required to solve the problem.

Conventionally, a control method for disturbance noise of an active silencer is disclosed in, for example, Japanese Patent Laid-Open No. 6-230789. The structure of the active silencer is such that the first microphone and the second microphone are arranged in the propagation path with the speaker interposed therebetween, and the signals of the first and second microphones are the microphone amplifier, the A / D converter and the system bus. It is input to the digital signal processor via. Further, the processing result for muffling is input to the speaker via the system bus, the D / A converter, and the power amplifier. The control method for disturbance noise is to compare the output signals of the first microphone and the second microphone with a digital signal processor, and as a result, determine that the output signal of the first microphone is smaller than the output signal of the second microphone. If so, a method of reducing the output of the speaker is used.

[0004]

The above invention requires that the first microphone and the second microphone are of the same type, and that the gains of the first and second microphone amplifiers are known. So instead of the first microphone,
For example, when an acceleration sensor is used, it is not possible to make a simple comparison.

It is an object of the present invention to provide an active muffler for reducing noise leaking from a semi-enclosed space having a through-hole, when an external disturbance is generated, a signal obtained from a second sensor is used as an initial state. Provide an active muffling device that can determine the occurrence of disturbance by comparing with the value and stop the control of active muffling or set the speaker input level to zero to prevent the transition to unstable control. To do.

[0006]

In order to achieve the above object, the present invention provides a rotating body that emits noise, a shield wall provided so as to shield the rotating body, and at least one of the shield walls. A through-hole provided, a first sensor for detecting the noise information, a speaker provided in the through-hole for silencing noise propagating through the through-hole, and a vicinity of the speaker And a second sensor for detecting the sound pressure level near the speaker,
In an active muffler having a controller for generating an input signal of the speaker based on signals from the first sensor and the second sensor, active muffling with respect to a signal output from the second sensor. A storage unit that stores the magnitude of the control before or immediately after the control of the device, and a comparison unit for comparing the magnitude of the signal of the storage unit and the magnitude of the signal output from the second sensor under control. And a means for setting the input signal level of the speaker to zero when the output signal under control becomes larger.

Regarding the signal output from the second sensor, a signal averaging unit for averaging the magnitude of the signal and an average value of the signal before or after the control of the active silencer is stored. A storage unit, a comparison unit for comparing the average value of the signal of the storage unit with the average value of the signal output from the second sensor in control, and the average value of the output signal in control is larger. And a means for setting the input signal level of the speaker to zero when the level becomes low.

Further, the controller is composed of an adaptive filter and a coefficient updating unit for updating the coefficient of the adaptive filter. Before the control of the active silencer is started with respect to the signal output from the second sensor. Alternatively, a storage unit that stores the magnitude immediately after the start of control, a comparison unit that compares the magnitude of the signal of the storage unit with the magnitude of the signal output from the second sensor that is being controlled, and A means is provided for stopping the updating process in the coefficient updating unit when the output signal becomes larger.

Further, the controller comprises an adaptive filter and a coefficient updating unit for updating the coefficient of the adaptive filter, and averages the magnitudes of the signals output from the second sensor. A signal averaging section for
A storage unit that stores the average value of the signal before or immediately after the control of the active silencer is compared with the average value of the signal of the storage unit and the average value of the signal output from the second sensor that is in control. And a means for stopping the updating process in the coefficient updating unit when the average value of the output signals under control becomes larger.

With respect to the second sensor, the number of times that the output signal under control becomes larger is determined, and when the number of times exceeds the number of times, the input signal of the speaker becomes zero or the update processing by the coefficient updating unit. A means for stopping is provided.

Further, there is provided means for defining a threshold value for the output signal from the comparing section and for stopping the update processing of the input signal of the speaker to zero or the coefficient updating section when the threshold value is exceeded.

[0012]

[Operation] The signal data detected by the second sensor is stored in the storage unit before or immediately after the control of the active silencer, and the comparison unit sequentially detects the signal data of the storage unit and the signal data of the storage unit by the second sensor during control. The signal input is compared with the signal data, and the input signal level of the speaker is set to zero when the signal data being controlled becomes larger.

Further, an average value is obtained by the signal averaging unit from a plurality of signal data detected by the second sensor before or immediately after the control of the active silencer, and the result is stored in the storage unit. During control, the average value is obtained by the signal averaging unit from the multiple signal data detected by the second sensor, and the comparison unit compares the average value in the storage unit with the average value detected during control, When the average value of the output signal of is larger, the input signal level of the speaker is set to zero.

Further, the signal data detected by the second sensor is stored in the storage unit before or immediately after the control of the active silencer, and the comparison unit sequentially stores the signal data of the storage unit and the signal data of the storage unit during the second control. The signal data detected by the sensor is compared, and when the signal data under control becomes larger, the updating process in the coefficient updating unit is stopped.

Further, an average value is obtained by the signal averaging unit from a plurality of signal data detected by the second sensor before or immediately after the control of the active silencer is started, and the result is stored in the storage unit. During control, the average value is obtained by the signal averaging unit from the multiple signal data detected by the second sensor, and the comparison unit compares the average value in the storage unit with the average value detected during control, When the average value of the output signal of 1 becomes larger, the updating process in the coefficient updating unit is stopped.

Further, the number of times that the signal data detected by the second sensor becomes larger during the control is determined, and when the number of times exceeds the number, the input signal of the speaker is made zero or the updating process in the coefficient updating unit is stopped. .

Further, a threshold value is set for the output signal from the comparison unit, and when the threshold value is exceeded, the input signal of the speaker is made zero or the updating process in the coefficient updating unit is stopped.

[0018]

【Example】

(First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, 1 is a shielding wall, 2 is a rotating body, 3 is a rotating body supporting portion, 4 is a sound propagation path, 5 is a speaker, 6 is a second sensor (for example, a microphone), and 7 is a first sensor ( Acceleration sensor), 8 is a first sensor amplifier, 10 is a second sensor amplifier, and 9 and 11 are A
/ D converter, 12 is a speaker amplifier, 13 is a D / A converter, 14 is an adaptive digital filter, 15 is a digital filter, 16 is an LMS algorithm, 17 is a comparison section, 18 is a storage section, and 30 is a through hole. is there.

When the rotating body 2 operates, noises such as aerodynamic noise for a fan, electromagnetic noise for a motor, and meshing noise for a gear are generated, and propagate through the through hole 30 of the shield wall 1. And leaks to the outside of the shield wall 1. Noise of 1 kHz or higher can be reduced by a silencer such as a sound absorbing material, but for noise of 1 kHz or lower, an active silencer is used to reduce leakage noise. Although the subscripts a and b are used in the drawing, the subscripts are omitted in the following description because they have the same configuration. The signal flow in the active muffler is as follows. First, the noise information of the rotating body 2 which is the noise source is detected by the first sensor 7, amplified by the amplifier 8, and then the digital signal X by the A / D converter 9.
Convert to. The digital signal X is input to the adaptive digital filter 14 to generate a digital signal Y for input to the speaker 5. The digital signal Y is converted into an analog signal by the D / A converter 13, the power is amplified by the amplifier 12, and the speaker 5 generates an additional sound for noise reduction. On the other hand, the mute state in the sound propagation path 4 is detected by the second sensor 6, amplified by the amplifier 10, and converted into the digital signal E by the A / D converter 11. The digital signal X is passed through a digital filter 15 simulating an impulse response from the speaker 5 to the second sensor 6 to generate a digital signal R. The digital signal E and the digital signal R are adjusted by the adaptive digital filter 1 so that the digital signal E is minimized by the LMS algorithm 16.
The coefficient 4 is updated. By the above operation, the leakage sound from the through hole 30 can be reduced.

However, during operation, when a noise different from the noise of the rotating body 2 is detected from the outside of the shield wall 1 by the second sensor 6, the coefficient of the adaptive digital filter 14 is erroneously updated. Therefore, the additional sound generated from the speaker 5 becomes loud. Therefore, the input signal Y of the speaker 5 is made zero by the following method.

First, the noise information before or immediately after the active noise reduction operation is detected by the second sensor 6, and the initial value of the digital signal E is stored in the storage section 18. Comparison unit 17 during operation
The initial value and the value of the digital signal E sequentially detected by the second sensor 6 are compared with each other, and when the detected value becomes larger than the initial value, the switch SW is switched to change the digital signal Y.
To zero.

As shown in FIG. 2, the signal averaging unit 19
Is provided, the average value of the digital signal E detected by the second sensor 6 in an arbitrary period is calculated, and the same processing is performed thereafter. Digital signal E before or immediately after active silence operation
The initial average value of is stored in the storage unit 18, the initial average value is compared with the average value of the digital signal E sequentially detected by the comparison unit 17 during operation, and when the detected average value becomes larger than the initial average value. , The switch SW is switched to set the digital signal Y to zero.

The above description is an example of the case where there are two through holes 30 or two sound propagation paths 4.
It can be applied even when there are a plurality of penetrating pieces 30 or a plurality of sound propagation paths 4.

It is also possible to arbitrarily set the number of times the detected (average) value becomes larger than the initial (average) value, and switch the switch SW to make the digital signal Y zero when the detected (average) value exceeds the number.

Further, an arbitrary threshold value is set for the value when the detected (average) value becomes larger than the initial (average) value, and when the value exceeds the set value, the switch SW is switched, and the digital signal Y can also be zero.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to FIGS. In FIG. 3, 1
Is a shield wall, 2 is a rotating body, 3 is a rotating body supporting portion, 4 is a sound propagation path, 5 is a speaker, 6 is a second sensor (for example, a microphone), 7 is a first sensor (for example, an acceleration sensor),
8 is the first sensor amplifier, 10 is the second sensor amplifier,
9 and 11 are A / D converters, 12 is a speaker amplifier, 1
3 is a D / A converter, 14 is an adaptive digital filter,
Reference numeral 15 is a digital filter, 16 is an LMS algorithm, 20 is a comparison unit, 18 is a storage unit, and 30 is a through hole.

Although the subscripts a and b are used in the drawing, the subscripts are omitted in the following description because they have the same structure. The signal flow in the active silencer is the same as in the first embodiment.

When a noise different from the noise of the rotating body 2 is detected from the outside of the shield wall 1 by the second sensor 6 during the operation of the active silencer, the adaptive digital filter 14 adjusts the adaptive digital filter 14 against the coefficient of the adaptive digital filter 14. When the coefficient of the filter 14 is W, the coefficient update is calculated with Wnew = Wold−μRE μ: step size parameter, so that an incorrect coefficient update process is performed. Therefore, the LM
The step size parameter at the time of updating the coefficient in the S algorithm 16 is set to zero.

First, the noise information before or immediately after the active noise reduction operation is detected by the second sensor 6, and the initial value of the digital signal E is stored in the storage section 18. Comparison unit 20 during operation
The initial value and the value of the digital signal E sequentially detected by the second sensor 6 are compared with each other, and the step size parameter is set to zero when the detected value becomes larger than the initial value.

Further, as shown in FIG. 4, a signal averaging unit 21 is provided, the average value of the digital signal E detected by the second sensor 6 is obtained in an arbitrary period, and the same processing is performed thereafter. Digital signal E before or immediately after active silence operation
Of the digital signal E sequentially detected by the comparison unit 20 during operation, and the detected average value becomes larger than the initial average value. , Set the step size parameter to zero.

The above description is an example of the case where there are two through holes 30 or two sound propagation paths 4.
It can be applied even when there are a plurality of penetrating pieces 30 or a plurality of sound propagation paths 4.

Further, the number of times that the detected (average) value becomes larger than the initial (average) value can be arbitrarily set, and the step size parameter can be set to zero when the detected (average) value becomes equal to or larger than the number of times.

Further, an arbitrary threshold value is set for the value when the detected (average) value is larger than the initial (average) value, and the step size parameter is set to zero when the detected (average) value exceeds the set value. You can also

[0034]

According to the present invention, in the active silencer for reducing the noise leaking from the semi-enclosed space having the through-hole, it is possible to prevent the control from becoming unstable when the disturbance occurs. It will be possible.

[Brief description of drawings]

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

FIG. 2 is a block diagram in which averaging processing is added to the first embodiment.

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

FIG. 4 is an overall configuration diagram in which averaging processing is added to the second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Shielding wall, 2 ... Rotating body, 14 ... Adaptive digital filter, 15 ... Digital filter, 16 ... LMS algorithm, 17, 20 ... Comparison part, 18 ... Storage part, 19, 2
1 ... Signal averaging section.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yasushi Takano Yasushi Takano 502 Jinritsucho, Tsuchiura-shi, Ibaraki Hiritsu Manufacturing Co., Ltd. Mechanical Research Laboratory (72) Shigeru Koizumi 1st Horiyamashita, Hadano-shi, Kanagawa Hiritsu Manufacturing Co., Ltd. General-purpose computer division

Claims (6)

[Claims] 1. A rotating body that emits noise, a shielding wall provided so as to shield the rotating body, a through hole provided in at least one of the shielding walls, and for detecting the noise information. No. 1 sensor, a speaker provided in the through-hole for canceling noise propagating through the through-hole, and a speaker provided near the speaker to detect a sound pressure level near the speaker. A second sensor for
In an active muffler having a controller for generating an input signal of the speaker based on signals from the first sensor and the second sensor, active muffling with respect to a signal output from the second sensor. A storage unit that stores the magnitude of the control before or immediately after the control of the device, and a comparison unit for comparing the magnitude of the signal of the storage unit and the magnitude of the signal output from the second sensor under control. And a means for setting the input signal level of the speaker to zero when the output signal under control becomes larger. 2. A rotating body which emits noise, a shielding wall which is provided so as to shield the rotating body, a through hole which is provided in at least one of the shielding walls, and which detects the noise information. No. 1 sensor, a speaker provided in the through-hole for canceling noise propagating through the through-hole, and a speaker provided near the speaker to detect a sound pressure level near the speaker. A second sensor for
In an active silencer having a controller for generating an input signal of the speaker based on signals from the first sensor and the second sensor, regarding a signal output from the second sensor, A signal averaging unit for averaging the magnitudes, a storage unit for storing an average value of signals before or immediately after the control of the active silencer, and an average value of the signals in the storage unit and the second during control. A means for comparing the average value of the signal output from the sensor, and means for setting the input signal level of the speaker to zero when the average value of the output signal under control becomes larger. An active silencer characterized by being provided. 3. A rotating body which emits noise, a shielding wall which is provided to shield the rotating body, a through hole which is provided in at least one of the shielding walls, and which detects the noise information. No. 1 sensor, a speaker provided in the through-hole for canceling noise propagating through the through-hole, and a speaker provided near the speaker to detect a sound pressure level near the speaker. A second sensor for
In an active silencer having a controller for generating an input signal of the speaker based on signals from the first sensor and the second sensor, the controller includes an adaptive filter, and a coefficient of the adaptive filter. A signal output from the second sensor, the storage unit storing a magnitude of the signal output from the second sensor before or immediately after the control of the active silencer. Is provided with a comparison unit for comparing the magnitude of the signal output from the second sensor being controlled, and when the output signal being controlled becomes larger, the updating by the coefficient updating unit is performed. An active silencer, which is provided with means for stopping processing. 4. A rotating body which emits noise, a shielding wall which is provided so as to shield the rotating body, a through hole which is provided in at least one of the shielding walls, and which detects the noise information. No. 1 sensor, a speaker provided in the through-hole for canceling noise propagating through the through-hole, and a speaker provided near the speaker to detect a sound pressure level near the speaker. A second sensor for
In an active silencer having a controller for generating an input signal of the speaker based on signals from the first sensor and the second sensor, the controller includes an adaptive filter, and a coefficient of the adaptive filter. Composed of a coefficient updating unit for updating, the signal output from the second sensor, a signal averaging unit for averaging the magnitude of the signal, and before or immediately after the start of control of the active silencer A storage unit that stores the average value of the signal, and a comparison unit that compares the average value of the signal of the storage unit with the average value of the signal output from the second sensor that is being controlled, and the output that is being controlled An active muffling apparatus comprising means for stopping the updating process in the coefficient updating unit when the average value of the signal becomes larger. 5. The loudspeaker input signal according to claim 1, 2, 3 or 4, wherein the number of times that an output signal during control is greater with respect to the second sensor is determined. Or an active muffling device provided with means for stopping the updating process in the coefficient updating unit. 6. A threshold value is set for an output signal from said comparing section, and when the threshold value is exceeded, the input signal of said speaker becomes zero or said coefficient updating section. An active muffling device that is provided with means for stopping the updating process in step 1.