JPH0728478A - Active muffling device - Google Patents

Abstract

PURPOSE:To provide a high performance active muffling device employing an inexpensive computation device by controlling the noise and interference waves which cancel the noise so that they synchronize with inverse amplitudes at a sound interference position. CONSTITUTION:First, a press is stopped, multiplying coefficient data H set in a coefficient control section 14 is multiplied with the noise data stored in a noise data memory 13 by using a multiplyer 15, interference wave data equivalent to a single operation are supplied to a D/A converter 16, converted into analog signals and interference sound waves are generated through a filter, an amplifier and an interference sound output speaker. Next, the press is started, noise is generated and a control section 3 multiplies the noise data of the memory 13 with multiplying coefficients H in the multiplier 16 by using the synchronization pulse input from a noise synchronization means and interference sound waves are outputted from the speaker. A delay control section 18 controls the start of the noise data of the memory 13 and adjusts the timing of interference sound wave generation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active muffling apparatus which muffles the noise of a device such as a press or a forging machine used for metal working, which generates noise with a constant cycle.

[0002]

2. Description of the Related Art There are two methods for silencing noise propagating in three dimensions. The first method is a method of muting only a range that causes a trouble due to noise, and the second method is a method of shutting off the noise source itself. The second method is ideal, but in reality, it is difficult to completely block the entrance and exit of the workpiece.

Therefore, an active muffling system, which muffles the range of a person and the entrance / exit of a device by sound wave interference by the first method, is attracting attention. 3 such as conventional press
There is a system disclosed in Japanese Patent Laid-Open No. 3-36897, Japanese Patent Laid-Open No. 3-79500, or the like, when the three-dimensional radiated noise is reduced by an active noise reduction system.

[0004]

However, the above disclosed technique requires a vibration pickup for detecting the vibration or rotation of a noise source, and a high-speed calculation using an FIR digital filter or an adaptive FIR digital filter. Therefore, there is a problem that the system becomes expensive.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an inexpensive active muffler capable of stable control with a simple structure and suitable for a press machine or the like. To do.

The noise of a general press machine or forging machine produces an impact sound having a peak at a low frequency. In most cases, the same processing is repeated on the equipment, and the impact noise is
Repeatedly producing almost the same noise. The present invention focuses on the above points and provides a practical system.

[0007]

SUMMARY OF THE INVENTION Therefore, according to the present invention, a sound wave of opposite phase and the same sound pressure is generated with respect to a sound wave propagating from a noise source, and the sound wave is silenced at a predetermined position by the sound wave interference. Noise synchronization detection means for detecting noise that is repeatedly generated from the source, interference sound wave output means for emitting sound waves for canceling the noise, and sound wave detection means for detecting the noise and sound waves after sound wave interference. A noise data memory for storing noise data of a noise waveform input from the sound wave detecting means, the noise data memory executing a noise data storing operation in accordance with the noise detection by the noise synchronization detecting means; A delay means for delaying the noise data according to the delay data and sending it to the interfering sound wave output means, and the noise data for interfering sound wave data in order to minimize the sound wave after the sound wave interference. To output by multiplying the multiplier coefficient is to provide an active noise reduction apparatus comprising a coefficient control unit and supplied to the silencing acoustic output means.

Further, the present invention provides an active muffler comprising a delay time correcting means for correcting the delay time and a coefficient correcting means for correcting the coefficient.

The present invention also provides an active silencer in which the sound wave detecting means is formed by one microphone.

Further, the present invention also provides an active silencer for storing the delay data of the delay means, the multiplication coefficient data of the coefficient control section and the noise data of the noise data memory in a non-volatile memory.

[0011]

The present invention focuses on the fact that a machine tool such as a press machine generally produces repetitive noise with the same sound pressure amplitude. If controlled, muffling is guaranteed. This is solved only by having a coefficient controller for amplitude adjustment and a delay controller for time adjustment. Further, since the coefficient control unit and the delay control unit change and monitor the coefficient and the delay time toward the direction in which the sound wave interference result decreases, adaptability can be provided.

Therefore, it is sufficiently adaptable to variations in sound velocity due to the influence of temperature and secular changes in delay characteristics of the interference speaker.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of an active silencer according to the present invention. In FIG. 1, 1 is a press machine which is a noise source, and 2 is noise synchronization provided near the side of the press machine. Detecting means 3, a control unit composed of a microcomputer having a configuration described later, 4 a filter circuit connected to the interference sound wave output unit 3a of the control unit 3, 5 an amplifier for amplifying the output of the filter circuit 4, 6 Is a speaker for outputting an interference sound wave which is driven by the output of the amplifier 5 and emits an interference sound wave.

Reference numeral 7 is a microphone as a sound wave detecting means,
Reference numeral 8 is an amplifier for amplifying the output of the microphone 7, and 9 is a filter circuit for supplying only the specific component of the output of the amplifier 8 to the noise / interference sound wave input section 3b of the control section.

The basic structure of the active noise canceling device according to the present invention is the above-mentioned structure, and examples of arrangement of the interfering sound wave output speaker 6 and the microphone of such a noise canceling device are shown in FIGS.

In FIG. 3, the speaker 6 is provided at the upper edge of the opening 10a provided in the side wall of the soundproof room 10 surrounding the press machine 1, and the speaker 6 projects laterally from the soundproof room 10 through the opening 10a. The microphone 7 is installed on the workbench 10b. Therefore, in this example, the worker can work in a quiet space.

In the arrangement example of FIG. 4, the speaker 6 is provided at the upper edge of the opening (monitoring window) 10a of the soundproof room 10 as in FIG. The microphone 7 faces the entire surface of the opening 10a. Therefore, in this example, even when it is necessary to monitor from a glass window such as an automated work, the work can be performed in a quiet space.

FIG. 2 is a diagram showing the basic concept of the present invention. As shown in this figure, in the present invention, the noise A generated from the noise source 1 passes through the propagation path in the middle and the target acoustic wave interference occurs. Reach position P.

Generally, the noise waveform A changes under the influence of reverberation characteristics such as reflection and sound absorption in this propagation path, but in the present invention, even if the waveform changes, the waveform at the sound wave interference position is controlled. Therefore, it is not affected.

Therefore, the noise waveforms are the same.
At this sound wave interference position, an interference waveform having the same phase and amplitude as the noise waveform is generated at the same time, and the noise is silenced.

This anti-phase and same-amplitude waveform is generated by the silencer of the present invention. In order to generate the interfering sound wave at the same time every time, the synchronizing signal of the noise is repeatedly used.

Therefore, according to the present invention, there is no need for a vibration sensor for inputting a noise waveform as in the technique disclosed in the conventional example, and an inexpensive sensor such as one using light or a mechanical switch can be used. Good.

Next, the operation of the silencer according to the present invention having the above mechanism will be described. (1) Storage of Noise Data Each time a noise is generated from the press machine 1 which is a noise source, a synchronization pulse is input from the noise synchronization detection means 2 to the control unit 3 (one synchronization pulse for each noise).

When a sync pulse is input to the sync pulse input section 3c, the sync pulse detection circuit 11 shown in FIG. 5 detects the sync pulse in the control section 3 including a memory such as a microcomputer and an arithmetic section, and responds to the detection. Then, the noise signal input to the noise / interference sound wave input unit 3b through the microphone 7-amplifier 8-filter 9 is quantized by the A / D converter 12 at a predetermined sampling time.

The quantized noise data is sequentially retained in the noise data memory 13. The noise data may be stored multiple times and the data may be averaged.

(2) Setting of Same Amplitude (Determination of Multiplication Coefficient H) Next, the press machine 1 is stopped and the noise data stored in the noise data memory 13 is multiplied by the multiplication coefficient data H set in the coefficient control unit 14. (The initial value is tentatively determined to be about −0.5) is multiplied by the multiplier 15, and the data of one interference sound wave is D / A.
The signal is supplied to the converter 16 and converted into an analog signal, and an interference sound wave is generated through the filter 4, the amplifier 5, and the interference sound wave output speaker 6.

This interfering sound wave is received by the microphone 7, enters the control section 3 through the amplifier 8 and the filter 9, and
The A / D converter 12 converts the digital data, the noise data stored in the noise data memory 13 is compared and calculated by the comparator 17, and the multiplication coefficient H in the coefficient control unit 14 is corrected by the calculation result. And decide.

For example, when the multiplication coefficient H is output as -0.5 and the input amplitude is half, the coefficient H is doubled to -1 to obtain the same amplitude as the noise waveform. By making the multiplication coefficient H negative, the output has an inverse amplitude. This coefficient may be determined by calculating all data and then averaging or calculating data of maximum amplitude.

If the multiplication coefficient H overflows, it is possible to change the gain of the speaker amplifier of the control unit by a warning lamp (not shown).

(3) Time delay and sound wave interference Next, when the press machine 1 is operated to generate noise, the control unit 3 multiplies the noise data in the noise data memory 13 by the input of the synchronization pulse from the noise synchronization detection means 2. In step 16, the multiplication coefficient H is calculated, and the interference sound wave is output from the interference sound wave output speaker 6.

The leading data of the noise data in the noise data memory 13 is managed by the delay control section 18 which adjusts the generation time of the sound wave for interference.

The relationship between the delay and the sound wave for interference will be described with reference to FIGS. In FIG. 6, S indicates a sampling cycle.
As shown in FIG. 6, the noise data string is stored in the _n (U _{1 to} Un) noise data memory 13 for each synchronization pulse. For example, if the first data is the first, U ₁ → U ₂ ·
When output is →→ U _n , the output waveform is as shown in (a) of FIG. 7, and when the first data is the sixth, U ₆ → U ₇ ...
・ ・ → U _n → U ₁ → U ₂ → U ₃ → U ₄ → U ₅ is output.
As shown in FIG. 7B, an output waveform having the same waveform but delayed in time can be generated.

Therefore, by controlling this delay time, it is possible to output the sound wave for interference which is arbitrarily shifted with respect to the noise waveform. The delay time here will be described as T in the following.

Since the amplitudes are set to the same reverse amplitude by the same amplitude control, if the delay time T is controlled, there is always a delay time closest to the antiphase with the noise, and as a result, the sound can be canceled by the sound wave interference.

(4) Control Method of Delay Time / Coefficient The control method of the delay control section 7 is not always constant due to the fluctuation of the delay time of the speaker / amplifier / filter and the fluctuation of the environmental temperature and the fluctuation of the amplifier gain, and is adapted to the fluctuation. There is a need to.

In the present invention, the delay time T and the multiplication coefficient data H
In order to have the adaptability of 1), it also has a function of constantly monitoring the interference result by the microphone and correcting the delay time T and the multiplication coefficient data H. The method will be described with reference to FIG. Delay time T
Considering the matrices of the multiplication coefficient data H, the delay time T at the point X and the coefficient H are temporarily determined at the start. In this state, an interference sound wave is added to obtain a result of interference with the microphone. (The interference result may be averaged over a plurality of synchronization pulses).

Next, the delay time T is changed (the width of change may be increased or decreased according to the interference result, or may be decreased to reach the optimum condition quickly), and the delay time T with the minimum interference result is obtained.
Next, the multiplication coefficient data H is similarly changed and the interference result is evaluated to determine the optimum condition Y point.

By alternately and always determining the optimum conditions such as the delay time T and the multiplication coefficient data H, adaptability to the fluctuation can be obtained. Even if the determined delay time T, the multiplication coefficient data H, and the memory 2 (noise waveform data) are stored in the non-volatile memory and the power of the system is turned off, the optimum condition can be approached sooner next time.

[0039]

As described above, according to the present invention, F
It is possible to realize an active muffling apparatus that is sufficiently possible with an inexpensive arithmetic device (for example, a microcomputer) as compared with the conventional technology that requires high-speed arithmetic with an IR digital filter or an adaptive FIR digital filter. Further, since the feedback control is not performed, the howling phenomenon does not occur.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an active silencer according to the present invention.

FIG. 2 is a diagram showing a basic concept of the present invention.

FIG. 3 is a diagram showing an application example of the active silencer according to the present invention.

FIG. 4 is a diagram showing another application example of the active silencer according to the present invention.

FIG. 5 is a block-like circuit diagram showing a specific circuit example of the control unit of the active silencer according to the present invention.

FIG. 6 is a conceptual diagram of noise data in a noise data memory used for explaining the operation of the present invention.

FIG. 7 is a diagram showing different output states of noise data used for explaining the operation of the present invention.

FIG. 8 is a diagram provided for explaining the operation of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Press machine 2 Noise synchronization detection means 3 Control part 6 Interference sound wave output speaker 7 Microphone 13 Noise data memory 14 Coefficient control part 17 Comparator 18 Delay control part

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H04R 3/00 310

Claims (4)

[Claims] Claim: What is claimed is: 1. A sound wave of opposite phase and the same sound pressure is generated with respect to a sound wave propagating from a noise source, and the sound wave is silenced at a predetermined position by sound wave interference. A noise synchronization detection means for detecting noise, an interference sound wave output means for radiating a sound wave for canceling the noise, a sound wave detection means for detecting the sound wave after the noise and sound wave interference, and an input from the sound wave detection means. A noise data memory for storing noise data of a noise waveform, the noise data memory executing a noise data storage operation in accordance with the noise detection by the noise synchronization detecting means, and the noise data in the noise storage memory being delayed according to the delay data to cause interference. Delay means for sending to the sound wave output means, and output the above noise data by multiplying the interference sound wave data by a multiplication coefficient in order to minimize the sound wave after sound wave interference. Serial muffling sound waves active silencer comprising a coefficient control unit and to the output means. 2. The active silencer according to claim 1, further comprising delay time correction means for correcting the delay time and coefficient correction means for correcting the coefficient. 3. The active silencer according to claim 1, wherein the sound wave detecting means is formed by one microphone. 4. The delay data of the delay means, the multiplication coefficient data of the coefficient controller and the noise data of the noise data memory are stored in a non-volatile memory.
The active silencer described in.