JP3522018B2 - 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 device for forming a canceling sound having a phase opposite to that of noise, and more particularly to a device capable of detecting abnormal operation.

[0002]

2. Description of the Related Art In the above noise control device, a speaker is used to output a cancel sound, and a microphone is used to detect a residual sound for feeding back the interference result of the cancel sound and noise as an error signal. Has been done.

[0003]

However, dynamic devices such as speakers and microphones used in the above noise control device have aged deterioration, and this aged deterioration of the cancel sound transmission system causes noise. There is a problem that the control system as a whole of the control device collapses, abnormal noise is generated, and the effect amount of noise control is reduced.

Therefore, in view of the above problems, the present invention enables maintenance of speakers, microphones and the like.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention proposes a speaker which outputs a cancel sound having an opposite phase with respect to engine noise, and a residual sound which is a result of interference between the noise and the cancel sound. To a noise control device having a microphone that detects as an error signal, the engine pulse as a reference signal and the error signal is input as feedback, an adaptive filter that forms a cancellation signal, and noise control of the adaptive filter. An effect reduction determination unit for determining the effect reduction and warning the deterioration of the speaker and the microphone is provided. By this means, noise control effect amount fluctuations outside a certain reference value and range are detected,
It is possible to judge that the noise control device is abnormal and issue a warning, and it becomes easy to judge the maintenance time with respect to deterioration of the speaker, the microphone, and the like.

The effect reduction judging section may judge the noise control effect reduction by comparing the filter coefficient of the adaptive filter with a previously prepared engine speed vs. assumed filter coefficient. By this means, it is possible to determine that the noise control device is abnormal and issue a warning. The effect reduction determination unit may determine the effect reduction of noise control by comparing the error signal level with a previously prepared engine speed vs. assumed error signal level. By this means, it is possible to determine that the noise control device is abnormal and issue a warning.

The effect reduction judging section may judge the effect reduction of noise control by comparing the cancel signal level with a previously prepared engine speed vs. assumed cancel signal level. By this means, it is possible to determine that the noise control device is abnormal and issue a warning. The effect reduction determination unit, before the engine rotational speed
The determination may be made based on the engine pulse . By this means, it is possible to determine that the noise control device is abnormal and issue a warning.

The effect reduction determination unit may stop the operation of the adaptive filter when it is determined that the effect of noise control is reduced. By this means, the operation of the noise control device can be stopped.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an overall outline of a noise control device according to the present invention. As shown in the figure, exhaust gas from an engine 1 of a vehicle or the like is exhausted to the atmosphere via an exhaust pipe 2, a muffler 3, and a tail pipe 4. The exhaust noise of the exhaust gas is reduced by the muffler 3 and is emitted to the atmosphere via the tail pipe 4. The noise control device includes a speaker 5 that outputs a cancel sound having a phase opposite to that of noise that is exhaust sound emitted to the atmosphere, and a microphone 6 that detects a residual sound that is a result of interference between the noise and the cancel sound as an error signal.
And an engine pulse (E / P) signal from the engine 1 as a reference signal and an error signal of the microphone 6 as a feedback signal, and a cancel sound mainly occurs due to transmission of space, and a sound pressure is attenuated. And a noise control unit 7 that controls a noise by forming a cancellation signal in which the above are corrected.

FIG. 2 is a diagram for explaining the noise control unit 7 of FIG. 1 according to the embodiment of the present invention, which detects the reduction of the effect amount by the change of the filter coefficient. As shown in the figure, the noise control unit 7 receives an engine pulse from the engine 1 as a reference signal and an error signal from the microphone 6 as a feedback signal, and outputs an adaptive filter (a cancel signal to the speaker 5). ADF) 7
1 and the effect reduction determination unit 72 for determining the effect reduction of the noise control of the adaptive filter 71 to warn the deterioration of the speaker and the microphone, and the result of the effect reduction determination unit 72 are input. If the effect amount is reduced, the system controller 73 is provided which outputs a warning signal of deterioration of the speaker 5 and the microphone 6 and stops the operation of the adaptive filter 71. The effect reduction determination unit 72 receives an engine pulse and a filter coefficient from the adaptive filter 71, and detects an effect amount reduction detection unit 74 for detecting an effect amount reduction of noise control caused by deterioration of the speaker 5, the microphone 6, and the like, The effect amount reduction detection unit 74 is provided with a detection data storage unit 75 which provides detection data for detecting the effect amount reduction of noise control. Here, the adaptive filter 71 is a FIR (Finite Impulse R)
esponse) filter.

FIG. 3 is a diagram showing the structure of the FIR filter in the adaptive filter 71 of FIG. As shown in the figure, in the FIR filter, the filter coefficients F1, F2, ..., Fn are sequentially updated so that the error signal is minimized. The detection data storage unit 75 has filter coefficients F10 and F2 of the adaptive filter 7 which are assumed to be optimal when the engine has a certain rotation speed R0.
0, ..., Fn0 are stored.

The effect amount reduction detector 74 obtains the engine speed R from the engine pulse, and when the detected engine speed R is R0, the adaptive filter 71,
Each filter coefficient is read from the detection data 73 and the following calculation is performed. ΔFav = {(ΔF1) ² + (ΔF2) ² + ... + (ΔFn) ² } ^1/2 (1) where ΔFk = Fk−Fk0 k = 1 to n. Then, the effect amount reduction detection unit 74 has a predetermined reference value ΔFav0 for determining that the effect amount is reduced, and determines whether ΔFav ≧ ΔFav0 (2) holds. When this judgment is established, the effect amount reduction is detected.

Further, ΔFk ≧ ΔFk0 (3) k = 1 to n where ΔFk0 is a predetermined reference value for determining that the effect amount is reduced, and is set in the effect amount reduction detector 74.

As described above, the system control section 73 receives the effect amount reduction information from the effect reduction detection section 74, and
The operation of the adaptive filter 71 is stopped, but in this case,
All the filter coefficients of the FIR filter of the adaptive filter 71 may be set to "0". In this way, when the noise control effect amount deviates from a certain reference value, it is possible to detect the effect amount variation, that is, determine that the noise control device is abnormal and issue a warning. Therefore, it becomes easy to determine the maintenance time of the speaker 5, the microphone 6, and the like. Further, the operation can be stopped according to the content of the abnormality of the noise control device.

FIG. 4 shows another embodiment of the present invention, which is shown in FIG.
FIG. 7 is a diagram for explaining the noise control unit 7 of FIG. 1 that detects reduction of the effect amount by changing the level of the error signal. As shown in this figure, the configuration different from that of FIG.
4A and the detection data storage unit 75A. Figure 5
It is a figure explaining the detection data storage part 75A of FIG.
As shown in the figure, the detection data storage unit 75A stores, as data, the relationship between the engine pulse input ratio corresponding to a certain engine speed and the error signal level.
This relationship utilizes the phenomenon that the error signal level increases as the engine pulse input ratio increases when the noise control effect amount is normal. That is,
Assuming that the error signal level increases with an increase in the engine pulse input ratio, and the reference value is within a certain range (margin width z) as the reference value, the noise control effect amount is within the normal range. It is a judgment. Specifically, when the engine pulse input ratio in this figure is dx ₀ / dt, assuming that the lower limit error signal level is A and the upper limit error signal level is B, the error signal level y is A <y <B When (4), the effect amount is normal, but when A> y, B <y (5), the effect amount is reduced.

Further, the effect amount detecting section 74A inputs the engine pulse x and the error signal y, and detects the data storage section 7 for detection.
The upper and lower error signal levels of the reference value corresponding to the engine pulse input ratio are read out from 5A, and these are compared with the level of the input error signal y. And equation (4),
It is determined whether any of (5) holds. FIG. 6 is a diagram illustrating a noise control unit 7 of FIG. 1 according to another embodiment of the present invention, which detects a reduction in the effect amount by changing the level of a cancel signal. As shown in this figure, the configuration different from that of FIG. 2 is an effect amount detection section 74B and a detection data storage section 75B. The detection data storage unit 75B stores, as data, the relationship between the engine pulse input ratio corresponding to a certain rotation speed of the engine and the cancel signal level. This relationship uses the phenomenon that the cancel signal level increases as the engine pulse input ratio increases when the noise control effect amount is normal. That is, as in the case of FIG. 5, assuming that the cancel signal level increases with an increase in the engine pulse input ratio, the reference value is set as a reference value, and when the reference value is within a certain range (margin width z), the noise control It is determined that the effect size is within the normal range.

Further, the effect amount detecting section 74B inputs the engine pulse x and the cancel signal y, and reads the upper and lower error signal levels of the reference value corresponding to the engine pulse input ratio from the detection data storing section 75B. Then, these are compared with the level of the input cancel signal y. And
Similarly, it is determined whether any one of the equations (4) and (5) holds.

FIG. 7 shows a noise control unit 7 of FIG. 4 according to still another embodiment of the present invention, which detects a reduction of the effect amount by the level change of the error signal and converts the engine pulse signal into the engine speed. It is a figure explaining what is done. As shown in this figure, the configuration different from that of FIG. 4 is an engine speed detection unit 77, an effect amount detection unit 74C, and a detection data storage unit 75C. The engine speed detector 77 detects an engine pulse as an engine speed.
In the adaptive filter 71, if the engine pulse is directly used as the reference signal, harmonics are mixed in, so a sine wave generated based on this engine speed or its harmonic may be used as a reference signal to form a cancellation signal. is there. In such a case, the effect amount detection unit 74C and the detection data storage unit 7
Although 5C is based on the engine pulse in the example of FIG. 4, instead of this, the effect amount may be detected based on the engine speed and the detection data may be stored.

Similar to the above, as still another embodiment of the present invention, the noise control unit 7 in FIG. 6 detects the reduction of the effect amount by the level change of the cancel signal, and outputs the engine pulse signal as the engine speed. You may make it convert into.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall outline of a noise control device according to the present invention.

FIG. 2 is a noise control section 7 of FIG. 1 according to an embodiment of the present invention.
FIG. 6 is a diagram for explaining what detects a reduction in the effect amount due to a change in the filter coefficient.

3 is a diagram showing a configuration of an FIR filter in the adaptive filter 71 of FIG.

FIG. 4 is a diagram illustrating a noise control unit 7 of FIG. 1 according to another embodiment of the present invention, which detects reduction of an effect amount by changing a level of an error signal.

5 is a diagram illustrating a detection data storage unit 75A of FIG.

FIG. 6 is a diagram illustrating a noise control unit 7 of FIG. 1 according to another embodiment of the present invention, which detects a reduction in the effect amount based on a level change of a cancel signal.

FIG. 7 is a noise control unit 7 of FIG. 4 according to still another embodiment of the present invention, which detects reduction of the effect amount by changing the level of the error signal and converts the engine pulse signal into the engine speed. It is a figure explaining.

[Explanation of symbols]

71 ... Adaptive filter 72 ... Effect reduction determination unit

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-24483 (JP, A) JP-A-6-250671 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F01N 1/00 G08B 23/00 530 G10K 11/178 H03H 17/02 601 H03H 21/00

Claims (6)

(57) [Claims] 1. A noise control device comprising: a speaker that outputs a canceling sound having an opposite phase to engine noise; and a microphone that detects a residual sound that is a result of interference between the noise and the canceling sound as an error signal. Is input as a reference signal and the error signal is fed back as feedback, and an adaptive filter (71) that forms a cancellation signal and a noise control effect amount at the detected engine speed are adjusted.
The location corresponding to the engine speed prepared in advance.
Based on the constant reference value, the adaptive filter determines the effect reduction of noise control, the speaker, the noise control device, characterized in that it comprises effect reduction determination unit that warning degradation of the microphone and (72). 2. The effect reduction determination unit determines the effect reduction of noise control by comparing the filter coefficient of the adaptive filter with a previously prepared engine speed versus assumed filter coefficient. The noise control device according to claim 1. 3. The effect reduction determination unit determines the effect reduction of noise control by comparing the error signal level with a preliminarily prepared engine speed vs. assumed error signal level. Item 1. The noise control device according to item 1. 4. The effect reduction determination unit determines the effect reduction of noise control by comparing the cancel signal level with a previously prepared engine speed vs. assumed cancel signal level. Item 1. The noise control device according to item 1. Wherein said effective reduction determination unit, the noise control device according to any one of claims 1 to 4, characterized in that to determine the engine speed from the engine pulses. 6. The effect reduction determination section stops the operation of the adaptive filter when determining the effect reduction of noise control, according to any one of claims 1 to 5. Noise control device described in>.