JPH1020865A - Active noise control method and device - Google Patents

Abstract

(57) [Summary] [Problem] To improve the noise reduction effect over the entire time range by controlling the optimum noise reduction operation in each time interval when the characteristics of noise sources are different when divided in time. It is intended to be. An active noise control method for reducing noise by emitting a degaussing sound obtained by converting a noise or an input signal having a signal correlated with the noise into an input signal and converting the output signal into a sound. In the case where there are a plurality of signal processing contents for creating the output signal from the input signal, while switching to a predetermined signal processing content by temporally or physically detecting the timing of noise generation having a plurality of different properties. ,
An active noise control method and device for performing a silencing operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for actively canceling a noise wave by canceling the noise wave with a sound wave.
More particularly, the present invention relates to an active noise control method and an apparatus for a case where a noise generating object generates a plurality of types of noises shifted in time.

[0002]

2. Description of the Related Art For example, an active noise control device is used to reduce noise generated from a duct of an air conditioner, to reduce noise emitted from a window opened in a closed space, or to mute noise in a three-dimensional space. May be used. The active noise reduction control device is a device that reduces noise by generating a noise reduction sound that cancels a noise wave generated from a noise source.
FIG. 4 shows the configuration of a conventional active noise control device. Noise source 1
Generates a noise wave when the vibration surface 2 vibrates. A detection sensor 3 for detecting a noise wave is attached to the vibration surface 2.

The output signal of the detection sensor 3 is
To an appropriate voltage level and input to the anti-aliasing filter 5. The anti-aliasing filter 5 limits the frequency band of the signal to a range that can be handled in digital signal processing performed later.
The analog signal that has passed through the anti-aliasing filter is A
The signal is converted into a digital signal by the D converter 6 and input to the muffling signal creation filter 7.

[0004] The muffling signal creation filter 7 is a FIR filter (Finite Impulse Response).
Filter) and has a function of creating a sound-absorbing sound.

[0005] The output of the muffling signal creation filter 7 is converted into an analog signal by a DA converter 8, smoothed by a smoothing filter 9 to remove harmonic components, and then amplified by a power amplifier 10. The amplified signal drives an electroacoustic transducer (for example, a speaker) 11 installed at a predetermined position downstream of the noise source 1 with respect to the propagation direction of the noise wave, and generates a sound-absorbing sound.

On the other hand, an error microphone 12 for detecting a noise wave after being silenced by the active noise control device.
Is provided at a predetermined position on the downstream side of the electro-acoustic transducer 11 that generates the sound cancellation in the propagation direction of the noise wave. The error microphone 12 detects the noise wave after silencing and converts it into an electric signal. The output of the error microphone 12 is
Preamplifier 13, anti-aliasing filter 14,
The signal is converted into a digital signal through the AD converter 15 and input to the signal processing controller 16.

The signal processing control section 16 sets the filter coefficient of the muffling signal generation filter 7 based on the signals supplied from the AD converters 6 and 15 so that the output of the error microphone 12 becomes as small as possible. Thus, the optimum filter coefficient is determined, so that noise can be reduced efficiently.

The algorithm used in the signal processing control unit 16 is, for example, LMS (Least M
Ean Square) algorithm and Filter
The ed-X LMS algorithm is used. These algorithms are described in, for example, Shigeo Tsujii, Kazuto Kubota, Toshihiro Furukawa, Shinki Zhao, Adaptive Signal Processing, Shokodo, pp. 20-2
8 and pp. 56-59 (1995).

[0009]

The active noise control device according to the prior art is based on the premise that the nature of the noise source 1 is substantially stationary over time. Therefore, when the noise emitted from the noise source 1 is divided into a plurality of properties when divided temporally, it has not been possible to sufficiently cope with the case.

[0010] For example, FIG. 3 shows the noise generated from a stamping press. The noise caused by a single punching operation of the workpiece is the sound when the die starts moving and the die starts falling.The sound when the die hits the workpiece. It consists of three types of sound, "can", which gives the impact of dropping the workpiece from the mold.

[0011] These types of sounds are different from each other in terms of the cause and location of the sound, so that the manner in which noise waves are transmitted to the detection microphone and the error microphone is different. On the other hand, the conventional active noise control device ignores these differences and tries to mute all sounds uniformly. Therefore, it was not possible to perform a silencing operation suitable for each sound.

The present invention has been made in view of this limitation of the active noise control apparatus of the prior art, and has an optimum noise reduction in each time section when noise sources have different characteristics when divided in time. By controlling the operation, the purpose is to achieve a better silencing effect over the entire time range.

[0013]

SUMMARY OF THE INVENTION According to the present invention, a noise or a noise-reducing sound obtained by converting an output signal generated by subjecting an input signal to which a noise or a signal correlated with the noise is inputted into a sound into a sound is emitted. In the active noise control method for reducing noise, when there are a plurality of signal processing contents for creating the output signal from the input signal, a predetermined time lapse is measured from a time when a noise generation timing is detected, and the predetermined A noise active control method characterized by performing a silencing operation while switching to a predetermined signal processing content after a lapse of time.In addition, instead of measuring the lapse of time, the timing of noise generation is stepwisely changed. It is to detect.

Further, the present invention provides an input means for inputting noise or a signal correlated with the noise, a signal processing means for performing signal processing on an input signal from the input means to generate an output signal, An output unit that converts an output signal into sound and emits degaussing sound into the air, and in an active noise control apparatus that emits degaussing sound into the air to reduce noise, a signal for generating the output signal from the input signal. There are a plurality of processing contents, a trigger means for detecting the timing of noise generation, a timer for outputting a signal obtained by measuring the passage of a predetermined time from the time obtained by the trigger means to the switching means, and a predetermined signal by the timer. An active noise control device for performing a muffling operation while switching signal processing contents at predetermined times by a switching means for switching processing contents. , And the addition, in which stepwise detects the timing of the noise generated in place to measure the time elapsed.

Still further, the present invention provides an input means for inputting noise or a signal correlated with the noise, a signal processing means for performing signal processing on an input signal from the input means to generate an output signal, Output means for converting the output signal into sound to emit a sound-absorbing sound into the air, noise-canceling-result detecting means for detecting a noise wave after sound-canceling downstream of the noise from the output means, and detecting the sound-ceasing result. A signal processing control unit that controls the content of signal processing so as to reduce the noise wave after the noise has been detected by the means. There is a plurality of contents of signal processing for creating the output signal from there, and a plurality of contents of control information in a signal processing control unit. A timer for outputting a signal obtained by measuring the passage of a predetermined time from the set time to the switching unit, and a switching unit for switching the content of the predetermined signal processing by the timer. An active noise control device for performing a silencing operation while switching between the control information of the signal processing control unit and the content of the control information. Also, instead of measuring the passage of time, the timing of noise generation is detected stepwise.

When the noise from the object to be silenced is divided into a plurality of properties when divided in time, optimal silence control is performed individually for each noise portion.

Specifically, for example, three times of different sounds having different characteristics (eg, when the mold starts descending, when the mold collides with the workpiece, (When the impact is applied to drop the workpiece after punching). Since the causes and characteristics of each sound are different from each other, it is necessary to perform an optimal silencing operation for each sound.

In view of this, a plurality of filter coefficients for signal processing for generating a muffling signal are prepared, and the operation is switched for each sound. The timing of switching is determined based on the passage of time (claims 1, 3, and 5) or the detection of an intermediate stage of noise generation (claims 2, 4, and 6).

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A case in which a signal processing in an active noise control device is performed by a noise reduction signal generation filter will be described below.

FIG. 1 is a block diagram showing the configuration of the active noise control device according to the first embodiment of the present invention. This active noise control device is a device that cancels noise by generating a sound wave from the speaker 111 that cancels a noise wave generated from the press machine 101.

The press machine 101 generates a plurality of noise waves in one press operation, for example, three parts (T1, T2, T3 in FIG. 3) of "dung", "don", and "can". I do. This noise wave is received by the detection microphone 103, and is sent to the muffling signal generation filter 107 via the preamplifier 104, the anti-aliasing filter 105, and the AD converter 106. Muffling signal generation filter 107
The muffled sound generated by the speaker 1 passes through a DA converter 108, a smoothing filter 109, and a power amplifier 110,
Released from 11. On the other hand, the noise wave after silencing is detected by the error microphone 112 which is the silencing result detecting means, and the preamplifier 113 and the anti-aliasing filter 11
4. The signal is supplied to the signal processing control unit 116 via the AD converter 115.

The signal processing control unit 116 controls the AD converter 106
The filter coefficient of the noise reduction signal creation filter 107 is
12 is set to be as small as possible. The above configuration is almost the same as the configuration described in the related art.
The signal processing described in the configuration of the present invention is performed in steps 104 to 110. When the detection microphone 103 detects not only the noise wave but also the degaussing sound propagating from the speaker 111 to the detection microphone 103, the noise elimination component is subtracted to extract only the noise wave and then generate the degaussing sound. It is appropriate to do. This subtraction processing is described in, for example, Toshiro Oga, Yoshio Yamazaki, Yutaka Kaneda, Acoustic System and Digital Processing, IEICE, pp. 226-227
(1995).

The press machine has a press operation start switch 121.
Performs one press operation. In this embodiment, the timer 122 is started by obtaining a trigger signal from the press operation start switch. That is, the trigger means described in the configuration of the invention is implemented by the press operation start switch. “Zun”, “Don”, “Kang” based on the time when the press operation start switch 121 is pressed down
The time when the sound is generated is measured in advance and set in the timer 122. This allows the timer 12
Reference numeral 2 indicates to the switching means 123 at the beginning of the period of each of the sounds "Zun", "Don", and "Kang". For example, in FIG. 3, the timer 122 is switched at times t1 (= 0), t2, and t3, which are slightly before the time when each of the sounds "Zun", "Don", and "Kang" starts, with some allowance. The means 123 is notified.

When the muffling signal generation filter 107 is implemented by an FIR filter, it is not always necessary to prepare a plurality of FIR filters to switch the content of the signal processing, but only by changing the coefficients of the FIR filter. The content of the signal processing can be switched. In such a case, it is not necessary to prepare extra multipliers and adders for implementing the FIR filter, and a RAM memory for storing coefficients to be replaced may be prepared.

The switching means 123 exchanges the coefficient of the muffling signal generation filter 107 with that of the RAM memory 124 in accordance with the signal from the timer 122.

When the silencing signal generation filter 107 is constituted by an FIR filter, the FIR filter
The relationship between input xn and output yn is (Xn-i represents an input signal before i samples).
Regarding the coefficients ai (i = 0,..., N−1), the optimum coefficients ai (i = 0,.
1) are different from each other. The RAM memory 124 is
It has a capacity to store a plurality of coefficients ai, and stores coefficients ai for each of the sounds "Zun", "Don" and "Kang".

In accordance with the appearance timings of the sounds "Zun", "Don" and "Kang", the switching means 123 saves the coefficient ai for the previous sound from the silencing signal generation filter 107 to the RAM memory 124, and then sets the coefficient ai for the next sound. ai is returned from the RAM memory 124 to the muffling signal generation filter 107. Note that the past input value xn-i stored in the muffling signal generation filter 107 does not necessarily need to be initialized, but in order to prevent the occurrence of undesired noise beforehand, it is necessary to reset the coefficient ai to 0 when switching the coefficient ai. It is safe to initialize to

When the signal processing control section 116 has control information relating to the muffling signal generation filter 107 (for example, a new coefficient value ai when updating the coefficient ai to maintain it in an optimum state) As the coefficient of the muffling signal generation filter 107 switches, the control information of the signal processing control unit 116 also needs to be switched. Reference numeral 125 denotes a RAM for storing the control information. In such a case, the switching unit 123 switches both the muffling signal generation filter 107 and the signal processing control unit 116 according to the signal from the timer 122.

It is to be noted that a configuration in which the signal processing unit 116 is not used when performing the silencing operation according to the present invention is also possible. Specifically, the coefficient ai is not always maintained and updated to the optimum state during the silencing operation, but the coefficient ai is set in advance before the silencing operation.
i may be calculated, and an active noise control device that does not update the coefficient ai during the silencing operation may be implemented. Such devices are:
For example, a sound other than the press sounds of “Zun”, “Don” and “Kang” suddenly comes from another, and the signal processing control unit 1
This is useful when updating of the filter coefficient ai in 16 can lead to deficiencies.

In the above description, the trigger signal is obtained from the press start switch. However, the trigger signal may be generated by processing the sound emitted from the press 101. For example, a microphone (detection microphone 1)
03 may be used) and a comparator for comparing the output of the microphone with a threshold value is provided, and when the output exceeds a preset threshold value, it is determined that the press operation has started. , The timer 122 may be activated.

FIG. 2 is a block diagram showing a configuration of an active noise control device according to a second embodiment of the present invention. In the figure, portions denoted by reference numerals 101 to 125 have the same functions and configurations as the portions denoted by the same reference numerals in FIG. The trigger means for detecting an intermediate stage of the noise generation described in the configuration of the present invention includes:
31 to 136. 131, 132, 13
Reference numeral 3 denotes a photoelectric switch for detecting the position and the moving direction of the press die. 134, 135, and 136 are light sources for projecting light to 131, 132, and 133 photoelectric switches, respectively. When the press die moves up and down, the light from the light source to the photoelectric switch is blocked or passed. Each photoelectric switch generates a trigger signal by detecting the transition of the light from the blocking state to the passing state or the transition from the passing state to the transmission state.

More specifically, the photoelectric switch 131 detects that light has been transmitted, that is, that the press die has almost risen up, and then a “dummy” sound comes. This is notified to the switching means 123. The photoelectric switch 132 detects that the light has been cut off, that is, that the press die has reached the position immediately before the impact, and then notifies the switching means 123 that a “don” sound comes. I do. The photoelectric switch 133 detects that light has been transmitted, that is, that the press die has been hit and is rising, and then the switching means 123 notifies the switching means 123 that a “can” sound comes. Notice.

The switching means 123 switches both the muffling signal generation filter 107 and the signal processing control section 116 in accordance with the temporal trigger signal from each photoelectric switch. The contents of the switching are exactly the same as those described in FIG.

In the above description of the embodiment, the case where the press machine generates three sounds of "Zun", "Don" and "Kang" has been described as an example. Even if it is a case of a plurality of sounds other than one, or a case of a noise source other than the press machine, the content of the signal processing is FIR
Needless to say, the present invention can be applied to a case using a muffling signal generating unit other than a filter.

[0035]

According to the present invention, a noise canceling process which is optimal for a noise wave whose noise property changes with time and at each stage of noise generation at each stage of noise generation. Can be switched, thereby making it possible to create an optimal sound deadening for the noise wave in each time segment, and to achieve effective sound deadening over the entire time range.

Also, the present invention creates an optimum filter coefficient in advance for a noise wave whose noise characteristics are expected to change at each stage of noise generation. This is a device that can perform optimal noise cancellation processing for noise waves that can always create optimal noise cancellation for noise waves composed of a combination of noises with different properties, Therefore, it is possible to manufacture a device that can prevent confusion in control.

Further, according to the present invention, an apparatus for switching the optimal sound-reducing process for each noise generation stage for a noise wave whose noise characteristic changes at each stage of noise generation. Thereby, it is possible to always produce an optimal sound deadening for a noise wave composed of a combination of noises having different properties, and to manufacture a device capable of realizing an effective sound deadening over the entire noise wave. it can.

[Brief description of the drawings]

FIG. 1 is a block diagram according to an embodiment of the present invention.

FIG. 2 is a block diagram according to another embodiment of the present invention.

FIG. 3 is a waveform diagram of noise in the embodiment of the present invention.

FIG. 4 is a block diagram in the related art.

[Explanation of symbols]

 1: Noise source 2: Vibration surface 3: Detection sensor 7, 107: Silencing signal generation filter 11: Electroacoustic transducer 12, 112: Error microphone 16, 116: Signal processing control unit 101: Press machine 111: Speaker 123: Switching Means 124, 125: RAM memory

Claims (6)

[Claims] 1. An active noise control method for reducing noise by emitting noise-reducing sound obtained by subjecting noise or an input signal having a signal correlated with the noise to an input signal and converting the output signal into a sound. In the case where there are a plurality of contents of signal processing for creating the output signal from the input signal, the time lapse is measured from the time when the noise generation timing is detected, and the predetermined signal processing is performed at a predetermined time in the time lapse. An active noise control method characterized by performing a silencing operation while switching to the content of (1). 2. An active noise control method for reducing noise by emitting noise-reducing sound obtained by subjecting noise or an input signal having a signal correlated with the noise to an input signal and converting the output signal into sound. In the case where there are a plurality of contents of the signal processing for creating the output signal from the input signal, detecting the noise generation timing stepwise, and performing the silencing operation while switching to the predetermined signal processing contents. Characteristic active noise control method. 3. Input means for inputting noise or a signal correlated with the noise, signal processing means for performing signal processing on an input signal from the input means to generate an output signal, and converting the output signal into sound. The output means for converting the input signal into the air and emitting the degaussing sound into the air reduces the noise by emitting the degaussing sound into the air.In the active noise control device, the content of the signal processing for creating the output signal from the input signal is There are a plurality of, a trigger means for detecting the timing of noise generation, a timer for outputting to the switching means a signal obtained by measuring the passage of a predetermined time from the time obtained by the trigger means, the contents of the predetermined signal processing by the timer An active noise control apparatus characterized in that a sound-muffling operation is performed while switching the content of signal processing at predetermined time intervals by a switching means. 4. Input means for inputting noise or a signal correlated with the noise, signal processing means for performing signal processing on an input signal from the input means to generate an output signal, and converting the output signal into sound. The output means for converting the input signal into the air and emitting the degaussing sound into the air reduces the noise by emitting the degaussing sound into the air.In the active noise control device, the content of the signal processing for creating the output signal from the input signal is A plurality of triggering means for detecting a stage in the middle of noise generation, and a switching means for switching the content of predetermined signal processing based on a signal obtained by the triggering means perform a silencing operation while switching the content of signal processing. An active noise control device, characterized in that: 5. Input means for inputting noise or a signal correlated with the noise, signal processing means for performing signal processing on an input signal from the input means to generate an output signal, and converting the output signal into sound. Output means for converting the noise into noise and emitting the sound to the air, a noise suppression result detection means for detecting a noise wave after the noise is provided on the downstream side of the noise from the output means, and a noise reduction detected by the noise reduction result detection means. By a signal processing control unit that controls the content of the signal processing so as to reduce the subsequent noise wave, in an active noise control device that reduces noise by emitting noise cancellation into the air, the output signal from the input signal There are a plurality of contents of the signal processing to be created and the contents of the control information in the signal processing control unit, a trigger means for detecting a timing of noise generation, and a predetermined time from a time obtained by the trigger means. A timer that outputs a signal whose progress has been measured to the switching unit, and a switching unit that switches the content of predetermined signal processing by the timer, and the content of the signal processing of the signal processing unit and the content of the signal processing control unit at predetermined time intervals by the switching unit. An active noise control device that performs a silencing operation while switching between contents of control information. 6. Input means for inputting noise or a signal correlated with the noise, signal processing means for performing signal processing on an input signal from the input means to generate an output signal, and converting the output signal into sound. Output means for converting the noise into noise and emitting the sound to the air, a noise suppression result detection means for detecting a noise wave after the noise is provided on the downstream side of the noise from the output means, and a noise reduction detected by the noise reduction result detection means. By a signal processing control unit that controls the content of the signal processing so as to reduce the subsequent noise wave, in an active noise control device that reduces noise by emitting noise cancellation into the air, the output signal from the input signal There are a plurality of contents of the signal processing to be created and a plurality of contents of the control information in the signal processing control unit, and a trigger means for detecting a stage in the middle of the noise generation, and a location based on the signal obtained by the trigger means. Active noise control system by a switching means for switching the contents of the signal processing and performs mute operation while switching the contents of the control information of the content and the signal processing control unit of the signal processing of the signal processing means.