JPH0527774A - Electronic noise elimination device for opening part radiation noise - Google Patents

Abstract

PURPOSE:To provide the electronic noise elimination device for the opening part radiation noise which can improve the noise elimination effect at an opening part such as a ventilation opening formed in the sound insulation cover in a sound insulation room and an operator's entrance and exit, etc. CONSTITUTION:It is confirmed that sufficient noise elimination effect is not obtained at the opening part because of the influence of reflected sounds at the peripheries of the corner parts of a tetragonal opening part. For a countermeasure, the opening part 16 is made circular so as to no corner part and active noise control 26 is installed in the circular opening part 16. Consequently, reflected sounds of noises generated at the opening part 16 are greatly reducible, so the noise elimination effect at the opening part 16 is sufficiently obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic noise muffling apparatus for radiated noise in openings, and in particular, muffles noise radiated from openings such as ventilation openings formed in a soundproof cover in a construction building and entrances and exits for workers The present invention relates to an electronic silencer for radiated noise in openings.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, an electronic muffler of this type has ventilation ports 2 formed on both sides of a soundproof cover 1,
The sound absorbing tubes 3 and 3 are attached to the sound absorbing cover 1 toward the outside of the soundproof cover 1, respectively. The sound-absorbing tubes 3 and 3 are provided with sound-absorbing materials 4 and 4 made of a porous material on their inner peripheral surfaces, and are curved so that their outlet openings are directed downward.

As a result, of the noise radiated from the noise source 7 in the room 6, the noise radiated to the ventilation ports 2 and 2 is absorbed by the sound absorbing members 4 and 4 and is silenced. Further, the sound deadening effect can be further improved by lengthening the sound absorbing tubes 3 and 3 or devising the shape thereof. However, the silencer having the above-mentioned pipe structure has a drawback that it cannot be applied to mechanical equipment that emits low-frequency noise, because the sound-absorbing material 4 itself is inferior in low-frequency silencer ability.
Further, if the sound absorbing tube 3 is lengthened, the device becomes large, and if the shape of the sound absorbing tube 3 is complicated, pressure loss increases and the ventilation effect deteriorates.

On the other hand, as another noise device for silencing the noise radiated from the opening 2, an additional sound having a phase opposite to that of the noise of the noise source 7 and having the same sound pressure is radiated, and its sound wave is emitted. There is an electronic muffling device that forcibly produces a muffling effect by interference. With respect to this type of silencer, research results from various viewpoints have been announced one after another along with the rapid development of electronic devices, signal processing technology and the like.

Regarding this muffling device, the applicant of the present application has already disclosed a system configuration for practical use in Japanese Patent Application No. 61-7115. When such a siltem configuration is applied to the silencer of the present case, a sensor microphone for detecting noise from a noise source and an error microphone are added as sound sources (hereinafter referred to as speakers).
Based on the above, the square ventilation ports will be installed at the upstream and downstream positions in the noise emission direction. The sensor microphone is installed indoors in order to prevent it from being affected by noise outside the soundproof cover, and the error microphone is installed near the ventilation port. Then, the sensor microphone, the error microphone, and the speaker are connected to the control device. This control device creates a drive signal for causing the speaker to generate an additional sound having an opposite phase and the same sound pressure with respect to the noise radiated to the outside from the ventilation port, based on the signals from the sensor microphone and the error microphone. ..

Since the system configuration of the present invention is premised on the control of the one-dimensional sound field, it is possible to muffle the sound deadenable band up to the plane wave propagation frequency determined by the diameter of the ventilation opening. This has already been disclosed by the applicant of the present application in the specification of JP-A-62-164400.

[0007]

However, the conventional electronic muffler for radiated noise in the opening has a drawback that it cannot sufficiently obtain the muffling effect at the ventilation port. The present invention has been made in view of the above circumstances, and an object thereof is to provide an electronic silencer for radiated noise in an opening, which can improve the silencing effect in the opening.

[0008]

In order to achieve the above object, the present invention radiates noise from a noise source installed in a room surrounded by a soundproof cover from an opening formed in the soundproof cover. An electronic noise muffling apparatus for radiating noise in an opening for silencing the generated noise, wherein a propagating sound wave radiated from the noise source is detected by noise information detecting means, and the same sound is in antiphase with the detected propagating sound wave. In the electronic silencer for the radiated noise of the opening, in which the additional sound of pressure is generated from the speaker, and the sound is muted by the sound wave interference at the position of the error microphone installed near the opening, the opening is circularly opened, The error microphone is installed in the circular opening.

[0009]

According to the present invention, it has been confirmed that the sound absorbing effect at the opening cannot be sufficiently obtained due to the influence of the reflected sound around the corner of the square opening. Open in a circular shape and install an error microphone in this circular opening. As a result, the reflected sound generated at the opening can be significantly reduced, so that the silencing effect at the opening can be sufficiently obtained.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An electronic silencer for radiated noise in an opening according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows an embodiment to which an electronic muffler for opening radiated noise according to the present invention is applied, and a machine tool 14 as a noise source is installed in a soundproof room 12 surrounded by a soundproof cover 10. Further, the soundproof cover 10 is formed with openings 16 on both sides thereof for ventilation in the soundproof room 12 and for carrying luggage.

As shown in FIG. 2, each of the openings 16 has a circular shape, and an electronic silencer 18 is installed in the vicinity thereof. The electronic muffler 18 includes a pair of speakers 2
0, 22, a sensor microphone 24, an error microphone (hereinafter referred to as active noise control) 26, and a controller 28. The pair of speakers 20,
22 are arranged above and below the opening 16 and inside the soundproof chamber 12, and are attached so that the additional sound generation surfaces face each other toward the center of the opening 16.

The sensor microphone 24 detects the noise propagated from the machine tool 14, converts the noise into an electric signal, and outputs the converted electric signal to the controller 28. The active noise control 26 is arranged on the plane of the opening 16. In addition, the active noise control 26 is applied to the machine tool 14
The interference sound in which the noise propagated from the speaker and the additional sound generated from the speakers 20 and 22 interfere is detected, the interference sound is converted into an electric signal, and the converted electric signal is output to the controller 28.

The controller 28 includes the sensor microphone 2
4. Driving for causing the speakers 20, 22 to generate an additional sound having a phase opposite to that of the noise radiated to the outside from the opening 16 and having the same sound pressure based on the electric signal input from the active noise control 26. Create a signal. As a result, according to the electronic silencer 18 of the present case, the machine tool 1
The additional sound having the same sound pressure and the opposite phase with respect to the noise of No. 4 is emitted from the speakers 20 and 22. Then, the noise is silenced at the position of the active noise control 26, that is, the position of the opening 16 by the sound wave interference with the additional sound of the speakers 20 and 22.

Further, in the present embodiment, since the shape of the opening 16 is a circle without corners, the conventional opening in which the silencing effect is not sufficiently obtained due to the reflected sound around the corners of the rectangular opening. The sound deadening effect can be significantly improved as compared with the electronic noise muffling apparatus for partially radiated noise.

[0015]

As described above, according to the electronic noise muffling apparatus for radiated noise in the opening of the present invention, the opening is opened in a circle without corners, and the error microphone is installed in the circular opening. Since the reflected sound generated at the opening is greatly reduced, it is possible to sufficiently obtain the sound deadening effect at the opening.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of an electronic silencer for radiated opening noise according to the present invention.

FIG. 2 is a side view showing an embodiment of an electronic silencer for radiated noise in an opening according to the present invention.

FIG. 3 is an explanatory view of a conventional silencer for radiation noise from an opening.

[Explanation of symbols]

 10 ... Soundproof cover 12 ... Soundproof room 16 ... Circular opening 18 ... Electronic silencer 20, 22 ... Speaker 24 ... Sensor microphone 26 ... Active noise control 28 ... Controller

Claims (1)

Claim: What is claimed is: 1. An opening radiated noise that silences noise radiated from an opening formed in the soundproof cover among noises from a noise source installed in a room surrounded by the soundproof cover. An electronic silencer for use, wherein a propagating sound wave radiated from the noise source is detected by a noise information detecting means, and an additional sound having an opposite phase and the same sound pressure to the detected propagating sound wave is generated from a speaker, In an electronic noise suppressor for radiated noise in an opening, which muffles sound waves at the position of the error microphone installed near the opening, the opening is circularly opened, and the error microphone is installed in the circular opening. An electronic muffler for radiated noise in openings.