JP2002147830A - Active silencing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an active silencing system wherein noise emitted from a soundproofing chamber opening section in a production factory, etc., is reduced effectively. SOLUTION: An active silencing system is provided, in which a duct 11 is provided across an opening section 5 of a soundproofing chamber 1, and there are mounted on the duct 11 from a noise source side a noise detection microphone 12 for detecting noise, a loudspeaker 13 for radiating additional sound, and appraisal microphone 14 for detecting remaining sound, after the interference with the additional noise and the noise in this order. Further, the microphone 14 is connected with a controller 15, and the loudspeaker 13 is mounted in the duct 11 directed, in the direction where the additional sound is radiated so as to oppose the advance direction of the noise.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active noise reduction system for reducing noise in a sound-absorbing space by means of acoustic interference between noise and additional sound, and more particularly to a noise reduction system in a duct provided at an opening of a soundproof room. It relates to the intended active silence system.

[0002]

2. Description of the Related Art In a production factory or the like, as shown in FIG. 5, for example, a noise generated by a production machine 100 such as a press machine is loud. . However, in an automated production plant, a belt conveyor 103 for transporting the product 102 to the outside is provided, and an opening 104 is required to pass the belt conveyor 103. Therefore, the sound not absorbed by the sound absorbing material in the soundproof room 101 is
Since the noise leaks out of the opening 104 and becomes noise, noise countermeasures at the opening 104 are conventionally taken. Therefore, conventionally, a soundproof curtain 105 made of a flexible nylon soundproofing material is used, and the opening 104 is closed so as to make a gap as little as possible while preventing the conveyance of the product 102 from being hindered. Was.

[0003]

However, since the opening 104 cannot be sealed with such a soundproof curtain 105, the leakage of noise is large and the soundproof measure cannot be taken sufficiently. Further, if the opening 104 is closed by the soundproof curtain 105, the product 102 flowing on the belt conveyor 103 has poor visibility, and there is a problem that the work is difficult. Accordingly, an object of the present invention is to provide an active noise reduction system that effectively reduces noise emitted from a soundproof room opening of a production factory or the like.

[0004]

SUMMARY OF THE INVENTION An active noise reduction system according to the present invention provides active noise control that reduces noise by actively adding an additional sound having the same amplitude and opposite phase as noise to interfere with the additional sound. Utilizing, a duct is provided in the opening of the soundproof room having an opening, a noise detection microphone that detects noise sequentially from the noise source side with respect to the duct, a speaker that emits additional sound, and additional sound and noise. An evaluation microphone for detecting residual noise after interference is attached and connected to a controller, wherein the speaker faces the direction in which additional sound is emitted so as to face the traveling direction of the noise. It is characterized by being attached to.

Therefore, according to the active type noise reduction system of the present invention, the active noise control is enabled by providing the duct in the soundproof room opening, and the additional sound is radiated in the direction opposite to the noise traveling direction. By installing the speaker, the noise emitted from the opening of the soundproof room in a production factory or the like can be effectively reduced.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an active silence system according to the present invention will be described below with reference to the drawings. 2. Description of the Related Art In recent years, active noise control for reducing noise by actively adding and adding an additional sound having the same amplitude as noise and opposite phase has been put to practical use and is being used in various fields. In view of this, the present embodiment also focuses on such active noise control, and has provided an active noise reduction system that reduces noise emitted from a soundproof room opening, such as a production factory having an opening.

In the active noise control, in a three-dimensional space, a sound wave is radiated three-dimensionally and a complex sound field is formed by reflection, diffraction, and interference. Therefore, it is difficult to obtain a sufficient noise-reducing effect in a large space. It is. Therefore, a sufficient noise reduction effect cannot be obtained simply by providing an active noise reduction system in a soundproof room such as a production factory. Therefore, in the present embodiment, a duct is provided at the opening of the production factory, and an active silence system is configured there. FIG. 1 is a diagram illustrating an active noise reduction system according to the present embodiment provided in a production factory.

The production plant has a soundproof room 1 in which a sound absorbing material for absorbing high frequency noise is attached to an inner wall, and a product 2
A belt conveyor 3 for transporting the outside to the outside extends from a production machine (for example, a press machine) 4 through an opening 5. In the active silencer system of the present embodiment (hereinafter simply referred to as “silencer system”), the duct 11 is provided in the opening 5 so as to surround the belt conveyor 3. This is because the noise
1 to propagate to the outside. In other words, by setting the space in which the noise going to the outside travels in only one direction, it can be treated as a low-frequency one-dimensional sound field, and an environment suitable for active noise control can be provided. is there.

Next, in the noise reduction system, a noise detection microphone 12, a speaker 13 and an evaluation microphone 14 are sequentially attached to the duct 11 from inside the production factory to outside, and these are connected to the controller 15. The noise detection microphone 12 is a microphone for detecting noise entering the duct 11, the evaluation microphone 14 is a microphone for detecting residual noise after interference between the additional sound and the noise, and the speaker 13 is It is for radiating additional sound that interferes with noise inside. Further, the controller 15 generates a control signal for generating an additional sound from the speaker 13 based on the noise signal and the residual noise signal output from the noise detection microphone 12 and the evaluation microphone 14.

In the present embodiment, the speaker 13 is used.
Is arranged near the outlet of the duct 11 and is mounted toward the soundproof room 1 on the noise source side so that the additional sound radiated therefrom is opposed to the traveling direction of the noise. Active noise control is conventionally used in air conditioning and ventilation equipment, in which a speaker 23 is generally provided on the wall of the duct 21 so as to radiate an additional sound perpendicular to the traveling direction of the noise as shown in FIG. Installed. This is because, in the case of an air-conditioning duct, it is necessary to reduce the pressure loss in blowing air, and a speaker cannot be arranged inside.

However, in the present embodiment, such a limitation is not imposed because the silencing system is provided in the duct 11 at the opening where it is not necessary to consider the flow of air. Therefore, in addition to such a conventional mounting method, a method for further improving the noise reduction effect was examined. In the study, in addition to the cases shown in FIGS. 1 and 2, a comparison was also made for the case shown in FIG. FIG. 3 shows the speaker 3
3 is disposed in the duct 31 and attached so that the radiated additional sound is in the same direction as the traveling direction of the noise. As a result of conducting a verification test of the silencing volume by using these three patterns, the embodiment of the present invention (FIG. 1), 63 to 25
About 6 to 15dB at 0Hz band (1/3 octave band)
It turned out that there was a degree of silencing, and that the silencing effect was the highest.

FIG. 4 conceptually shows the sound pressure wavefronts of the noise and the additional sound. FIG. 4A shows the pattern of the present embodiment shown in FIG. 1, and FIG. FIG. 2 shows a conventional pattern, and FIG. 2C shows another pattern shown in FIG. The noise generated in the soundproof room
As shown in each figure, the air enters from one of the ducts 11, 21, 31 and propagates out from the other. Therefore, when the additional sound is radiated from the speakers 13, 23, and 33 in each direction with respect to the noise, sound interference occurs between the noise and the additional sound, and a silencing region is formed on the downstream side. in this case,
For sound wave interference that reduces noise, the sound pressure wavefront created by the noise and the sound pressure wavefront created by the additional sound match as much as possible (coincidence of phase)
It is important that you do.

Looking at the sound pressure wavefronts of the respective embodiments shown in FIGS. 1 to 3 from such a viewpoint, as shown in FIG. 4, in the case of this embodiment, the region P1 where the sound pressure wavefront coincides most is wide, and The area P3 of the pattern of FIG. 3, which emits sound in the same direction as the noise, is large and is used in ventilation ducts as shown in FIG.
In the case of the conventional pattern, the region P2 where the sound pressure wavefront coincides most becomes narrow. Therefore, from the results of these studies, it can be said that the region where the sound pressure wavefronts coincide with the silencing result of the above-described verification test overlaps, and that the embodiment of FIG.

Therefore, as described above, in the sound deadening system of the present embodiment, as shown in FIG. 1, the speaker 13 is mounted so that the additional sound is radiated in the direction opposite to the traveling direction of the noise. Then, next, the silencing control of the silencing system of the present embodiment shown in FIG. 1 will be briefly described. For example, the products processed in the production factory by the operation of the press machine are sequentially sent out on the belt conveyor 3, and the noise generated at that time enters the duct 11 as shown by the arrow. In this case, since high-frequency noise is absorbed by the sound absorbing material in the soundproof room 1, the noise in the duct 6 is mainly low frequency (500 Hz or less).

When the noise is detected by the noise detection microphone 12, the controller 15 analyzes a waveform from the noise signal, and calculates an additional sound from the analysis result. The additional sound is emitted from the speaker 13 according to the additional sound signal of the controller 15, and the noise is reduced by sound wave interference with the additional sound. Then, the residual noise that cannot be completely eliminated is detected by the evaluation microphone 14, and the residual noise signal is transmitted to the controller 15.
And is reflected in the subsequent control in order to improve the silencing effect. The control of the active noise reduction by the controller 15 may be performed by successively updating the filter coefficients according to the adaptive algorithm so as to minimize the control error so that the residual noise signal is minimized. As the adaptive control algorithm, for example, The widely used Filtered-X
The LMS algorithm is used.

As described above, in this embodiment, active noise control is enabled by providing the duct 11 in the soundproof room opening, and the speaker 13 is attached so that the additional sound is radiated in the direction opposite to the noise traveling direction. Therefore, it is possible to provide a silencing system having a high silencing effect. Further, conventionally, in a production factory, the opening was blocked by a soundproof curtain and visibility of workers was poor, but by providing this silencing system, the visibility of the product 2 flowing through the belt conveyor 3 is improved, and work is performed. It became easier.

The present invention is not limited to the above embodiment, and various changes can be made without departing from the gist of the present invention. For example, in the above-described embodiment, an application example of the active noise reduction system according to the present invention is described by taking a production factory as an example, but the measures against noise coming out of the soundproof room opening are not limited to any examples.

[0018]

According to the present invention, a duct is provided in an opening of a soundproof room having an opening, and a speaker mounted in the duct is directed in a direction of radiating additional sound so as to face a traveling direction of noise. As a result, it has become possible to provide an active noise reduction system that effectively reduces noise emitted from the soundproof room opening of a production factory or the like.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment in which an active silencing system according to the present invention is provided in a production factory.

FIG. 2 is a diagram illustrating an example of an active silencer that radiates an additional sound perpendicularly to a traveling direction of noise.

FIG. 3 is a diagram illustrating an example of an active silencer that emits an additional sound in a traveling direction of noise.

FIG. 4 is a diagram schematically showing a sound pressure wavefront of noise and an additional sound in the active silencer of FIGS. 1 to 3;

FIG. 5 is a diagram showing a conventional production factory.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Soundproof room 2 Product 3 Belt conveyor 4 Production machine 5 Opening 11 Duct 12 Noise detection microphone 13 Speaker 14 Evaluation microphone 15 Controller

Claims (1)

[Claims] 1. An active type noise reduction system using active noise control for reducing noise by actively adding an additional sound having the same amplitude and opposite phase as noise to interfere with the additional sound. A duct is provided in the opening of the chamber,
A noise detection microphone that detects noise sequentially from the noise source side, a speaker that emits additional sound, and an evaluation microphone that detects residual noise after interference between the additional sound and the noise are attached to the duct and connected to the controller. An active type noise reduction system, wherein the speaker is mounted in the duct so as to face a direction in which the additional sound is emitted so as to face a traveling direction of the noise.