JPH06250671A - Device for detecting abnormality in noise control - Google Patents

Abstract

PURPOSE:To prevent a user from feeling displeasure by providing an abnormality detection part detecting the abnormality in a noise controller and interrupting the formation of a cancel sound according to the detection of the abnormality in the abnormality detection part. CONSTITUTION:A switch being turned on by the pressure of a diaphragm due to abnormal large vibration is provided on the rear side of the diaphragm of a speaker 1 as a detector detecting the state where the output of the speaker 1 being an actuator becomes large abnormally, and an electrical circuit is formed by connecting a resistor and a battery to the switch. When the voltage of one end of the resistor is increased/decreased by the on/off of the switch, the voltage is compared with a reference voltage fVr1, and the abnormality is decided when the reference voltage is exceeded by the voltage to output an abnormality detection signal S1. That is, an excess level is outputted from the speaker 1 being the actuator, and the amplitude of the vibration in the diaphragm becomes large, and the abnormality is detected. Then, the formation of the cancel sound is interrupted according to the detection of the abnormality.

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 detecting noise and forming a canceling sound having a phase opposite to that of the noise.
In particular, the present invention relates to a device for detecting an abnormality in order to prevent an unpleasant sound from being generated due to an abnormality of the noise control device itself.

[0002]

2. Description of the Related Art Conventionally, as a technique in such a field, a passive canceling sound device such as a muffler has been used to reduce noise generated from an internal combustion engine or the like.
Improvements have been made from the viewpoint of cancellation sound characteristics. On the other hand, there has been proposed an active noise control device that cancels noise by outputting a canceling sound of opposite phase and equal sound pressure to noise generated from a sound source from a speaker. By the way, the frequency characteristic or stability of the active noise control device itself is not sufficient, and its practical application has been delayed. However, as a result of the recent development of signal processing technology using digital circuits and expansion of the frequency range to be handled, many practical noise control devices have been proposed. As a technique in such a field, there is one described in Japanese Patent Laid-Open No. 63-311396. What is described in this is that noise is detected by a noise source microphone installed upstream of the duct, and a signal processing circuit outputs a signal of opposite phase and equal sound pressure from the speaker installed downstream of the duct and is canceled. A combination of a feedback system that detects and feeds back the result with a canceling microphone and a feedforward system,
This is a so-called 2-microphone / 1-speaker type active noise control device.

[0003]

However, in the conventional noise control device, when an abnormality occurs in the device for some reason, the actuator, which is a speaker, outputs a sound having a phase opposite to that of the noise source and cancels the noise. However, there is a problem that an abnormal sound is generated and the user feels uncomfortable.

Therefore, in view of the above problems, it is an object of the present invention to provide a noise control abnormality detecting device having a fail-safe function against abnormalities in order to prevent abnormal noises due to abnormalities of the device itself.

[0005]

In order to solve the above problems, the present invention detects an abnormality in a noise control device in a noise control device having a speaker that outputs a cancel sound of equal sound pressure in a phase opposite to that of the noise. The abnormality detection unit is provided, and the formation of the cancel sound is stopped by the abnormality detection by the abnormality detection unit. Specifically, the abnormality is detected by the large amplitude of the diaphragm of the speaker, the temperature change of the voice coil of the speaker is detected, and the abnormality is detected by the rise of the detected temperature, and the output from the power amplifier of the speaker to the speaker is detected. The change in the magnetic flux density of the current is detected, an abnormality is detected by the increase in the detected magnetic flux density change, the signal is branched from the signal before input to the power amplifier of the speaker, the branch signal level change is detected, and the detected branch signal level is abnormal. To remove the cancellation signal from the branched signal from the signal before input to the power amplifier of the speaker, detect a change in the removal signal level, detect an abnormality due to increase in the removal signal level, and detect the power of the speaker. The signal before input to the amplifier is branched, the phase of this branched signal is compared with that of the noise signal, and the compared signal level changes. Detecting the detecting the abnormality due to a decrease in the detection signal level. Further, the noise control device may be provided with an abnormality detection unit that detects an abnormality at a plurality of points, and the abnormality detection unit may stop the formation of the cancel sound at a plurality of points in the noise control device.

[0006]

According to the noise control abnormality detecting device of the present invention, the noise controlling device is provided with an abnormality detecting portion for detecting an abnormality of the noise controlling device, and the formation of the cancel sound is stopped by the abnormality detecting portion detecting the abnormality. It is possible to stop the output of the cancel sound from the device, improve the reliability of the noise control device, and prevent the user from feeling uncomfortable. Specifically, the reason why abnormality can be detected by the large amplitude of the diaphragm of the speaker is that when the speaker outputs an excessive level, the vibration amplitude of the diaphragm also increases and the abnormality can be detected due to the diaphragm vibration width. This is because Further, the temperature change of the voice coil of the speaker can be detected and the abnormality can be detected by the increase of the detected temperature, because an excessive abnormal output signal current flows through the boil coil of the speaker and the abnormality occurs due to the temperature rise of the voice coil. This is because it can be detected. The change in the magnetic flux density of the output current from the power amplifier of the speaker to the speaker is detected, and the abnormality can be detected by the increase in the detected change in the magnetic flux density. This is because an abnormality can be detected due to a large change in The reason why the branch of the signal before the power amplifier of the speaker is branched, the branch signal level change is detected, and the abnormality can be detected by the increase of the detected branch signal level is that the maximum level of the cancel signal can be predicted in advance. This is because it is possible to determine that there is an abnormality due to some cause when the reference voltage corresponding to is exceeded. Similar to the above, it is assumed that an abnormality can be detected by detecting a change in the level of the removal signal by detecting a cancellation signal from the signal branched from the signal before input to the power amplifier of the speaker and by removing the cancellation signal from the branch signal. This is because the abnormality can be detected and only the level of the noise signal is detected. Therefore, the S / N is improved as compared with the above. It is said that the signal before input to the power amplifier of the speaker is branched, the branched signal and the noise signal are phase-compared, the compared signal level change is detected, and the abnormality can be detected by the decrease of the detected signal level. When there is no abnormality, the cancellation signal and the noise signal have the same frequency and only differ in phase by π, so the output level of the phase comparison is maximum, but these frequencies are abnormal and do not match. This is because the output level of the phase comparison becomes smaller and the frequency mismatch is considered to have caused an abnormality for some reason. Further, the noise control device is provided with an anomaly detection unit for detecting anomalies at a plurality of locations, and the abnormality detection unit stops the formation of the cancel sound at a plurality of locations of the noise control device, thereby providing a plurality of locations of the noise control device. By stopping the formation of the canceling sound at, even if one of the plurality of abnormality detecting functions does not operate, it is possible to detect the abnormality by a different operation principle instead of it, and further, by a plurality of means, the canceling sound from the noise control device can be detected. Output can be stopped.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the overall configuration of a noise control abnormality detection device according to an embodiment of the present invention. The noise control device shown in the figure comprises a speaker 1 that outputs a cancel sound of equal sound pressure in a phase opposite to that of noise emitted from an engine that is a noise source through a muffler, and a power amplifier 2 that drives the speaker 1.
A low-pass filter 3 connected to the power amplifier 2 for removing unnecessary high-frequency components, and a D / A connected to the low-pass filter 3 for converting a digital signal into an analog signal
A converter 4 (Digital to Analog Converter), a microphone 5 for detecting a residual sound as a result of canceling noise by the speaker 1, an amplifier 6 for amplifying an electric signal detected and converted by the microphone 5, and the amplifier. 6, a low-pass filter 7 for removing unnecessary high-frequency components, and an A / D converter 8 (Anal for converting an analog signal to a digital signal connected to the low-pass filter 7).
og to Digital Converter) and a controller section 9 for forming a cancel signal to output a cancel sound to the speaker 1 as an error signal using the residual sound detected by the microphone 5 and outputting the cancel signal to the D / A converter 4. To do. The controller section 9 itself is not directly related to the present invention, so a detailed description thereof will be omitted. An outline thereof is a DSP (Digi) as a signal processing technique using a digital circuit for processing a digital signal using a predetermined sampling frequency.
tal Signal Processor) is used, and the DSP has an adaptive filter (Adaptive Signal Processor) that performs main processing.
Is provided, a signal for canceling noise is formed by this adaptive filter, and the DSP is controlled by the microcomputer. And for example,
When controlling the noise of a vehicle, a simulated signal generated as noise from an engine rotation pulse is formed and used as a reference signal to the adaptive filter. Thus, according to this noise control device, steady low-frequency noise generated from the noise source can be reduced.

As a noise control abnormality detecting device, a microphone 10 for detecting noise, and the microphone 1
An amplifier 11 that amplifies the electric signal detected and converted by 0, a low-pass filter 12 that is connected to the amplifier 11 and removes unnecessary high-frequency components, and an abnormality detection unit 13 are further provided. To the low-pass filter 12 as an abnormality detection signal. Further, as described in detail below, from each part of the noise control device, the abnormality detection signal is input to process these abnormality detection signals. A reset signal for the microcomputer in the controller unit 9, a level-down signal for the cancel sound, and a stop signal for stopping the function of forming the cancel signal by turning off the power switch 14 of the controller unit 9 are formed. The power amplifier 2 may be put in the standby state or the mute state by the abnormality detection unit 13.
Next, the details of the abnormality detection unit 13 will be divided into the case where the state where the output level of the speaker 1 which is an actuator is abnormally high and the case where the state where the output signal frequency of the speaker 1 fluctuates are detected. The former will be explained first.

FIG. 2 is a diagram showing an example of processing the abnormality detection signal in the abnormality detection unit 13 of FIG. 1, that is, processing the abnormal vibration signal of the diaphragm of the speaker 1. As a case of detecting a state where the output level of the speaker 1, which is an actuator, becomes abnormally high, as shown in this figure, the diaphragm is pressed by the abnormal large vibration to the back side of the diaphragm of the speaker 1 at the position shown by in FIG. A switch that is turned on is provided, and a resistor and a battery are connected to this to form an electric circuit. Since the voltage at one end of the resistor increases or decreases depending on whether the switch is turned on or off, this voltage is compared with the reference voltage Vr1 and when the voltage exceeds the reference voltage, it is determined as an abnormality and the abnormality detection signal S1 is output. That is, an excessive level is output from the speaker 1, which is an actuator, because the vibration amplitude of the diaphragm is large, so that an abnormality can be detected due to the diaphragm vibration width.

FIG. 3 is a diagram showing an example of processing the abnormality detection signal in the abnormality detection unit 13 of FIG. 1, that is, processing the abnormal temperature rise signal of the voice coil of the speaker 1. As shown in this figure, a thermocouple is provided near the boil coil of the speaker 1 at the position shown in FIG. 1, the thermoelectromotive force is converted into a voltage signal, and this voltage signal is compared with the reference voltage Vr2. If it exceeds the value, it is determined as an abnormality and an abnormality detection signal S2 is output. That is, since an excessive abnormal output signal current flows through the boil coil of the speaker 1 which is the actuator, the abnormality can be detected due to the temperature rise of the voice coil.

FIG. 4 is a diagram showing an example of processing an abnormality detection signal in the abnormality detection unit 13 of FIG. 1, which is an example of processing an abnormal current signal detected from a change in magnetic flux density due to an output current from the power amplifier 2 to the speaker 1. Is. As shown in FIG.
The output signal from the magnetic flux density detector installed in the cable through which the output current to the speaker 1 at the position indicated by is rectified and smoothed, and the output signal is compared with the reference voltage Vr3, and this reference voltage is exceeded. In this case, an abnormality is detected and an abnormality detection signal S3 is output. That is, when an abnormal output signal having a large output current and a small cycle flows to the speaker 1, which is an actuator, the abnormality can be detected due to the change in the magnetic flux density.

FIG. 5 is a diagram showing an example of processing the abnormality detection signal in the abnormality detection unit 13 of FIG. 1 and processing the abnormal current signal from the level change of the cancel signal before being input to the power amplifier 2. . As shown in the figure, the signal between the power amplifier 2 and the low-pass filter 3 at the position shown in FIG. 1 is branched, rectified, smoothed, and the output signal is compared with the reference voltage Vr4. If this reference voltage is exceeded, it is determined that there is an abnormality and an abnormality detection signal S4 is output. That is, the level of the cancel signal can be predicted to be the maximum value in advance, and when the reference voltage corresponding to this level is exceeded, it can be determined that the abnormality is due to some cause.

Next, the latter case of detecting the fluctuation of the output signal frequency of the speaker 1 will be described. FIG. 6 is a diagram showing an example of processing the abnormality detection signal in the abnormality detection unit 13 of FIG. 1 and processing the abnormal current signal from the level change of the removal signal obtained by removing the cancellation signal before being input to the power amplifier 2. Is. As shown in the figure, the signal between the power amplifier 2 and the low-pass filter 3 is branched at the position shown by in FIG. 1, and the branched signal is passed through a band elimination filter to remove the cancel signal, thereby removing the signal. The generated signal is rectified and smoothed, and the output signal is compared with the reference voltage Vr5. When the output voltage exceeds the reference voltage, it is determined as an abnormality and the abnormality detection signal S5 is output. FIG. 7 is a diagram for explaining the characteristics of the band elimination filter (BEF) shown in FIG. The frequency f1 shown in the figure is the center frequency (frequency of the cancellation signal) of the noise source (dotted line), and the frequency f2 is the frequency of the abnormal actuator output signal (solid line). Will only be detected. Thus, the S / N is improved, although the signal level is similar to the example of FIG.

FIG. 8 shows the processing of the abnormality detection signal in the abnormality detection unit 13 of FIG. 1. The abnormal current signal is obtained by comparing the frequencies of the cancel signal before input to the power amplifier 2 and the noise signal of which noise is detected. It is a figure which shows the example which processes. As shown in the figure, the signal between the power amplifier 2 and the low-pass filter 3 is branched at the position indicated by in FIG. 1, and the branched signal and the noise signal which is the output signal of the low-pass filter 12 are separated. The high-frequency components are multiplied to remove the high-frequency components, and the phases of the two signals are compared with each other.
If this reference voltage cannot be exceeded in comparison with r6, it is determined as an abnormality and an abnormality detection signal S6 is output. That is, when there is no abnormality, the cancellation signal and noise signal have the same frequency and only differ in phase by π, so the absolute level of the phase comparison output is maximum, but these frequencies are abnormal and match. This is because the level of the output of the phase comparison becomes small when it disappears, and it is considered that the frequency mismatch is caused by an abnormality for some reason.

FIG. 9 is a diagram for explaining the fail-safe function realized by the abnormality detector 13 of FIG. As shown in this figure, the logical sum of the abnormality detection signals shown in FIGS. 2, 3, 4, 5, 6 and 8 is taken, the microcomputer is reset by the result, the level of the cancel signal is lowered, or the controller unit 9 Turn off the power of. Therefore, even if one of the plurality of abnormality detection functions does not operate, an abnormality can be detected by a different operation principle instead of it, and the output of the cancellation sound from the noise control device can be stopped by a plurality of means, and the reliability of the noise control device can be improved. The property is improved and the user does not feel uncomfortable.

[0016]

As described above, according to the present invention, since the abnormality detecting section for detecting the abnormality of the noise control apparatus is provided and the cancel sound is stopped by the abnormality detecting section, the noise control apparatus is stopped. The reliability of is improved and the user does not feel uncomfortable.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of a noise control abnormality detection device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of processing an abnormality detection signal in an abnormality detection unit 13 of FIG. 1, which is an abnormal vibration signal of a diaphragm of a speaker 1;

3 is a diagram showing an example of processing an abnormality detection signal in an abnormality detection unit 13 in FIG. 1, which is an abnormal temperature rise signal of a voice coil of a speaker 1. FIG.

4 is a diagram showing an example of processing an abnormality detection signal in an abnormality detection unit 13 of FIG. 1, which is an abnormal current detected from a change in magnetic flux density due to an output current from a power amplifier 2 to a speaker 1. FIG.

5 is a diagram showing an example of processing an abnormality detection signal in an abnormality detection unit 13 of FIG. 1, in which an abnormal current signal is processed based on a level change of a cancel signal before being input to a power amplifier 2. FIG.

FIG. 6 is a diagram showing an example of processing an abnormality detection signal in an abnormality detection unit 13 of FIG. 1 in which an abnormal current signal is processed from a level change of a removal signal obtained by removing a cancellation signal before being input to a power amplifier 2. Is.

FIG. 7 is a diagram illustrating characteristics of the band elimination filter (BEP) in FIG.

8 is a process of an abnormality detection signal in an abnormality detection unit 13 of FIG. 1, in which an abnormal current signal is processed by comparing frequencies of a cancel signal before input to the power amplifier 2 and a noise signal in which noise is detected. It is a figure which shows an example.

9 is a diagram illustrating a fail-safe function realized by the abnormality detection unit 13 in FIG.

[Explanation of symbols]

 1 ... Speaker 2 ... Power amplifier 5, 10 ... Microphone 9 ... Controller section 13 ... Abnormality detection section 1

Claims (8)

[Claims] 1. A noise control device having a speaker (1) for outputting a cancel sound of equal sound pressure in a phase opposite to that of noise, comprising: an abnormality detection part (13) for detecting an abnormality of the noise control device, A noise control abnormality detection device characterized in that the formation of a cancellation sound is stopped by the abnormality detection by an abnormality detection section (13). 2. The noise control abnormality detecting device according to claim 1, wherein the abnormality is detected by a large amplitude of the diaphragm of the speaker (1). 3. The noise control abnormality detecting device according to claim 1, wherein a change in temperature of the voice coil of the speaker (1) is detected and an abnormality is detected by an increase in the detected temperature. 4. The noise according to claim 1, wherein a change in the magnetic flux density of the output current from the power amplifier (2) of the speaker (1) to the speaker (1) is detected, and an abnormality is detected by the increase in the detected magnetic flux density change. Control abnormality detection device. 5. The noise control according to claim 1, wherein the speaker is branched from a signal before being input to the power amplifier (2) of the speaker (1), a change in the branch signal level is detected, and an abnormality is detected by an increase in the detected branch signal level. Anomaly detection device. 6. The power amplifier (2) of the speaker (1) is branched from a signal before input, a cancel signal is removed from this branched signal, a change in the level of the removed signal is detected, and an abnormality is caused by an increase in the level of the detected removal signal. The noise control abnormality detection device according to claim 1, which detects a noise. 7. A signal before input to a power amplifier (2) of the speaker (1) is branched, the phase of the branched signal is compared with that of a noise signal, and the detected signal level change is detected. The noise control abnormality detection device according to claim 1, wherein the abnormality is detected by a decrease in level. 8. A noise control device having a speaker (1) for outputting a canceling sound of equal sound pressure in a phase opposite to that of noise, comprising an abnormality detecting section (13) for detecting an abnormality at a plurality of points of the noise control device. The noise control abnormality detection device according to claim 1, further comprising: stopping the formation of the cancel sound at a plurality of points of the noise control device by detecting an abnormality in the abnormality detection unit (13).