JPH06118971A - Electronic silencer - Google Patents

Abstract

PURPOSE:To prevent the electronic silencer used for an air-conditioning duct etc., from causing an abnormal phenomenon such as divergence. CONSTITUTION:When the output signal from an adaptive filter is outputted by a speaker 4 corresponding to the signal from a noise source 1 which is detected by a detection microphone 3 for noise detection installed in the noise passage 2 of the duct, etc., to cancel a noise, a comparator 22 compares the input and output signal levels of the adaptive filter and a controller 22 is controlled with the output of the comparator 21 when the output signal level of the adaptive filter is larger to stop updating the coefficient of the adaptive filter or stop operating the system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic muffler, and more particularly to an electronic muffler that prevents abnormal noises from occurring in an abnormal state.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram schematically showing a conventional silencer of this type. In FIG. 2, reference numeral 1 is a noise source such as an air conditioning fan, 2 is a passageway for noise such as an air conditioning duct, and 3 Is a detection microphone, 4 is a speaker that generates secondary noise, 5 is a monitor microphone that monitors the muffling effect, 6 is an adaptive filter, and 7 is a CPU including an algorithm for operating the adaptive filter, and the filter coefficient of the adaptive filter 6 is calculated. Then, the filter coefficient is updated, and the signal supplied to the adaptive filter 6 is processed and output. 8 is an A / D converter,
Reference numeral 9 is a D / A converter, 10 is an A / D converter, 11 is a flow direction of air, and 12 is an outlet of air.

Next, the operation of this conventional silencer will be described. Noise from the noise source 1 flows in the air flow direction 11
The noise detected by the detection microphone 3 is converted into a digital signal by the A / D converter 8 and supplied to the adaptive filter 6 and the CPU 7. Here, the adaptive filter 6 updates the coefficient of the filter to the coefficient calculated by the CPU 7 to form a new filter, and processes the signal sent from the A / D converter 8 into a signal suitable for canceling noise. Output.

The signal output from the adaptive filter 6 is converted into an analog signal by the D / A converter 9 and is output as a sound from the speaker 4 to cancel out the noise from the noise source 1 to cancel the noise. This muffling effect is monitored by the monitor microphone 5, converted into a digital signal by the A / D converter 10 and supplied to the CPU 7. In the CPU 7, the filter coefficient of the adaptive filter 6 is calculated and updated as described above. , The signal supplied to the adaptive filter 6 is processed and output, and the signal is output from the speaker 4 to cancel the noise, thereby performing a cycle operation.

[0005]

Since the conventional electronic silencer is constructed as described above, an erroneous signal such as extraneous noise is input in addition to the monitor microphone, and the filter coefficient is calculated under an erroneous condition. In this case, there is a problem that the silencer becomes a noise source.

An object of the present invention is to solve the above-mentioned conventional problems, and it is an object of the present invention to provide an electronic muffling apparatus which prevents occurrence of abnormal sound due to phenomena such as divergence.

[0007]

According to the present invention, there is provided an electronic silencer comprising a noise detecting microphone, a speaker for generating secondary noise for canceling the detected noise, and a monitor microphone for monitoring the canceled noise. A signal from the microphone, an adaptive filter that processes into a signal suitable for canceling noise and outputs the signal to the speaker, and a comparator that compares the signal level from the noise detection microphone and the level output from the adaptive filter, Control means for updating the coefficient of the adaptive filter based on the signal from the monitor microphone and stopping the update of the coefficient of the adaptive filter or stopping the operation of the system by the output of the comparator. ing.

[0008]

According to the electronic silencer of the present invention, the comparator compares the signal processed by the adaptive filter with the signal detected by the detection microphone, and when the level of the processed signal is higher than the signal from the detection microphone. Since a phenomenon such as divergence may occur and noise may be increased, the control means is controlled to stop updating the coefficient of the adaptive filter or stop the operation of the system.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The electronic muffler according to the present invention will be described below in more detail with reference to the embodiments shown in the drawings. In the drawings showing the embodiment of the present invention, the same or corresponding components as those of the conventional silencer shown in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted.

FIG. 1 is a block diagram schematically showing an electronic silencer according to an embodiment of the present invention. The electronic muffler 20 of this embodiment includes a comparator 21 that constantly compares the level of the noise source 1 and the output level of the adaptive filter 6, and the comparator 2
1 supplies the output to the CPU 22 which is a control device.

The CPU 22 corresponds to the CPU 7 in the conventional electronic silencer shown in FIG. 2,
The CPU 22 here also performs control such that the coefficient update of the adaptive filter 6 is stopped or the operation of the system, that is, the electronic silencer 20 is stopped according to a condition described later.

According to the electronic muffler 20 of the embodiment having such a configuration, the noise generated from the noise source 1 is detected by the detection microphone 3, converted into a digital signal by the A / D converter 8 and then the adaptive filter 6 is supplied. , CPU 22 and comparator 21.

The signal supplied to the adaptive filter 6 is the CPU
22 is processed by the algorithm according to 22 and enters the D / A converter 9, is converted back into an analog signal by the D / A converter 9 and is output as voice by the speaker 4, and cancels out the noise from the noise source 1. The noise is silenced.

The muffling effect is monitored by the monitor microphone 5, and the monitor signal is converted into a digital signal by the A / D converter 10 and supplied to the CPU 22. The CPU 22 calculates the monitor signal in the direction of decreasing the adaptive filter 6
Update the filter coefficient of.

At this time, a signal processed by the updated coefficient is output, and the signal and the level of the signal from the A / D converter 8 are compared by the comparator 21, and the signal from the A / D converter 8 is compared. When the level of the processed signal is high, noise may be increased by causing a phenomenon such as divergence. Therefore, the CPU 22 should stop the coefficient update of the adaptive filter 6 or stop the operation of the system. To control.

[0016]

As described above, according to the electronic silencer of the present invention, the input and output levels of the adaptive filter are compared,
When the output level is higher, the transfer coefficient of the adaptive filter is stopped from updating or the operation of the device itself is stopped, so that the divergence phenomenon of the device can be prevented.
It is possible to prevent noise from occurring.

[Brief description of drawings]

FIG. 1 is a block diagram schematically showing an electronic silencer according to an embodiment of the present invention.

FIG. 2 is a block diagram schematically showing a conventional silencer.

[Explanation of symbols]

 1 noise source 2 noise path 3 noise detection microphone 4 speaker 5 monitor microphone 6 adaptive filter 8 A / D converter 9 D / A converter 10 A / D converter 11 air flow direction 12 air outlet 20 electronic silencer 21 Comparator 22 CPU

Claims (1)

[Claims] 1. An electronic muffler comprising a noise detection microphone, a speaker that generates secondary noise that cancels the detected noise, and a monitor microphone that monitors the canceled noise, and a signal from the noise detection microphone An adaptive filter that processes the signal into a signal suitable for canceling and outputs the signal to the speaker, a comparator that compares the signal level from the noise detection microphone with the level output from the adaptive filter, and a signal from the monitor microphone. An electronic muffling apparatus comprising: a control means for updating the coefficient of the adaptive filter based on the output and stopping the update of the coefficient of the adaptive filter or stopping the operation of the system according to the output of the comparator.