JP2006053503A - Active noise elimination controller of directly emitted noise - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To actively perform noise elimination control of noise in space where a noise source can be seen without being obstructed. <P>SOLUTION: An active noise elimination controller is constituted of; wall surfaces which suppress the diffusing of noise; a sound wave reflecting board 2 which collects signal samples of noise to a focus; a noise detecting microphone 3 which is arranged at the focus of the sound wave reflecting board 2; a reverse phase speaker 4 which emits a sound wave whose phase is opposite to that of the noise, and whose sound pressure is the same as that of the noise outputted by the noise detecting microphone 3; and a sound emitting unit 5 which shapes the emission state of the sound wave which is emitted from the reverse phase speaker 4, and is characterized in that timing in which the sound wave emitted from a noise source 21 is made to coincide with timing in which the sound wave emitted from the reverse phase speaker 4, and whose phase is opposite to that of the noise, and whose sound pressure is the same as that of the noise join at the surface 22 and also an interference limit angle is given to angles of incidence to the surface 22 of wave bundles of both sound waves and also the size of the surface 22 is set to a size which does not exceeds a half of an interference limit wavelength. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus for actively silencing a certain space where a noise source can be seen.

  It has been a long time since traffic noise problems such as railways and motorways were taken up as environmental problems. In order to deal with these noise problems, measures have been taken so far, such as railways and motorways that have been elevated with safety in mind, or surrounded by tall sound barriers, but they are still improving. There are many challenges that must be addressed. A tall sound barrier not only damages the landscape but also has a negative effect on the human mind. Therefore, the appearance of a wall that is short and excellent in soundproofing is expected, and a technology to reduce diffraction noise by installing an active noise reduction control device (active noise control) at the tip of the soundproofing wall will be developed. Became.

The soundproof wall to which the active sound deadening control device is attached is intended to reduce the noise that passes over the front end of the soundproof wall and goes around to the back side of the wall. For the diffracted sound that turns the soundproof wall edge back like a new sound source, radiates the sound of the opposite phase from the sound diffracted from the speaker installed at the soundproof wall edge in the same direction as the direction of the noise. Thus, the wave energy is canceled by causing both sound waves to interfere with each other.
Japanese Patent Laid-Open No. 7-234689 JP-A-9-54593

  However, although the noise reduction by the above-mentioned method is related to the technology for reducing the noise diffusing into the three-dimensional space, it is intended for the sound that diffracts the noise barrier edge, that is, the sound that cannot be seen through the sound source. It was.

  A wall surface that suppresses diffusion of noise emitted from a noise source, a first sound wave reflection plate that collects a noise signal sample traveling in a certain direction in the vicinity of the wall surface at a focal point, and a focus point of the first sound wave reflection plate The first noise detecting microphone, the first antiphase speaker that emits the sound wave having the opposite phase and the same sound pressure as the noise by the output of the first noise detecting microphone, and the first antiphase speaker In the active silencing control device comprising the first sound emitter for adjusting the radiation state of the sound wave to be generated, the sound wave emitted from the noise source, the noise emitted from the first anti-phase speaker, and the anti-phase / sound pressure When the position where the sound waves merge with each other is the interference surface of both sound waves, the sound source, the interference surface, and the sound waves emitted from the noise source enter the first sound collecting microphone, and the first sound collecting microphone From negative phase speaker The optical distance relationship between the propagation path of the sound wave that travels along the two routes to the interference surface is made equal, and the incident angle of both sound waves and the wave packet to the interference surface is within the interference limit angle. In addition, the maximum length that can be connected in a straight line in the interference plane does not exceed 1/2 of the maximum interference wavelength, and is radiated to a certain space where the noise source can be seen by configuring a series of systems. This is a direct noise active silencing control device that reduces noise.

  A second sound wave reflecting plate for collecting a signal sample of noise diffracting the wave guide plate end edge of the first sound wave emitter at a focal point; and a second sound wave reflecting plate disposed at the focal point of the second sound wave reflecting plate. A noise detecting microphone, a second anti-phase speaker that emits a sound wave having a phase opposite to that of the diffracted sound by the output of the second noise detecting microphone, and a second sound emitter having a slit-like opening And a sound wave diffracted by using the waveguide plate end of the first sound wave radiator as a diffraction edge, and a sound wave having an opposite phase and the same sound pressure as the diffraction sound emitted from the slit-shaped opening of the second sound wave radiator Is a large area in a three-dimensional space that combines a certain area where the wave is absorbed by the interference and the noise source can be seen directly, and the back area that is hidden behind the noise control device and cannot be seen directly. noise The energy efficiently to reduce.

  When a plurality of sets of the direct noise active silencing control device are arranged at arbitrary positions and used, the directivity strong against the wave packet of the sound wave emitted by each of the first reverse phase speaker and the first sound wave emitter is used. Noise radiated to a certain large space that gives a characteristic and provides a large interference surface that covers a certain range as a whole by connecting individual interference surfaces corresponding to multiple sets of devices. Reduce.

  The direct noise active silencing control device according to the present invention creates an area where the sound radiated from the sound source is not reduced without reaching even if it is a position where the noise source radiated from the noise radiator can be directly seen. Noise that diffracts around the back of the wall where the noise source cannot be directly seen can be reduced, so that a quiet area where the influence of noise is weakened can be created in a large three-dimensional space. .

The best mode for carrying out the present invention will be described below in detail with reference to the drawings.
In addition, in each figure, the same part attaches | subjects the same code | symbol and the overlapping description is abbreviate | omitted.

1, FIG. 2 and FIG. 3 are diagrams showing the configuration and operation principle of the first embodiment. In Example 1, the present invention is used for a soundproof wall of a highway and a short soundproof wall of a general motorway. 1, 2, and 3, 21 is a noise source, 22 is an interference surface, and 23 is a diffraction edge.
1 and 2 show a large number of direct noise active silencing control devices according to the present invention arranged in a row in the front end portion of the soundproof wall 1. The first sound wave reflecting plate 2 is a parabolic reflecting plate having a focal point for collecting noise components radiated from a traveling vehicle with high accuracy, and the rotation axis of the paraboloid of revolution is directed toward the noise source 21. Installed. The first noise detection microphone 3 is an omnidirectional microphone arranged at the focal point of the first sound wave reflector 2, and the first reverse-phase speaker 4 is detected by the first noise detection microphone 3. Based on the information thus obtained, the speaker emits a sound wave having an opposite phase and the same sound pressure at the interference surface 22 from the propagation characteristics of the noise emitted from the noise source 21. The first acoustic wave emitter 5 is an irregular cylindrical shape in which a part of the upper surface is cut out, and gives directivity to the traveling direction of the wave packet of the acoustic wave radiated from the first antiphase speaker 4. The diffusion of the first reversed-phase speaker 4 outside the defense range is prevented.

  The second sound wave reflector 12 has a focal point for obtaining a sound reference signal diffracting the diffraction edge 23 at the end of the wave guide plate 24 of the first sound wave emitter 5 of the direct noise active sound deadening control device. Therefore, it is installed in the immediate vicinity of the diffraction edge 23. The second noise detection microphone 13 is a microphone arranged at the focal point of the second sound wave reflection plate 12, and the second reverse-phase speaker 14 is based on information detected by the second noise detection microphone 13. The sound diffracting at the diffraction edge 23 is radiated to the sound having the opposite phase and the same sound pressure. The second sound wave emitter 15 has a tip so that the sound wave outputted from the second anti-phase speaker 14 can radiate a sound having a property capable of interfering with the diffracted wave diffracting the diffraction edge 23 through the slit-shaped opening. Has been narrowed down into a slit shape.

The operation will be described below with reference to FIGS.
Noise generated when driving a car diffuses radially in a semi-free space. This spreading noise is indicated by a noise source 21.
Here, a surface having a certain size perpendicular to the direction of noise propagation is assumed in the space near the upper edge of the soundproof wall 1, and the properties of sound waves of noise passing through the open surface are considered.
The sound wave radiating surface of the noise source 21 is not a point sound source but has a planar size, and wave surfaces formed by envelopes of sound waves radiated radially from the respective points constituting the planar spread portions are successively formed. When propagating and passing through the open surface, it is possible to set a surface that is average and approximately perpendicular to the traveling direction of the sound wave incident from each direction on the open surface. When it is within ½ of the wavelength of the passing sound wave, the amplitude and phase of the passing sound wave have relatively stable characteristics with little characteristic difference and disturbance over the entire area of each part in the open surface. Therefore, if this opening surface is the interference surface 22 by the direct noise active silencing control device, the noise passing through the vicinity of the upper edge of the soundproof wall can be efficiently absorbed by the sound wave interference. The wavelength or frequency of the sound wave at this time is hereinafter referred to as an interference limit wavelength or interference limit frequency.

  Noise reference signals radiated from the noise source 21 and passing through the interference surface 22 are collected at the focal point of the first acoustic wave reflector 2 and input to the first noise detection microphone 3 installed at the focal point. It is extracted by the signal. From the first anti-phase speaker 4, a wave front that has an opposite phase and the same sound pressure as that of the sound wave when the noise radiated from the noise source 21 reaches the interference surface 22 is electrically processed and output. The At this time, the propagation path of the sound wave radiated from the noise source 21 to the interference surface 22, the first sound wave reflection plate 2, the first noise detection microphone 3, the first antiphase speaker 4, In addition, by making the propagation path of the sound wave that travels along the two routes to the interference surface 22 optically equidistant, the sound wave propagation timings of both are made coincident and howling due to the acoustic bridge is suppressed.

  The traveling direction of the noise radiated from the noise source 21 travels in an approximately one-dimensional wavefront in the direction of the interference surface 22, whereas the first antiphase speaker 4 has a wave absorption efficiency. A certain angle at which the deterioration does not increase, hereinafter referred to as an interference limit angle. For example, a radiation angle within 20 ° is given, and the noise and anti-phase / sound pressure are one-dimensionally directed toward the interference surface 22. A sound wave having a wave front is emitted. As described above, when sound waves having the same traveling pressure and having the same sound pressure with the opposite phase are merged at the interference surface 22, the energy of both sound waves is efficiently absorbed and the energy as a wave is consumed instantaneously and dramatically. Is done. The energy of the once lost noise does not appear again in the entire downstream side beyond the interference surface 22, and the noise radiated to the space where the noise source 21 can be seen is reduced uniformly.

FIG. 1 is an example in which the present invention is applied to a soundproof wall 1 of a highway, and the interference surface 22 of each device is a sound wave radiated from the noise source 21 to the interference surface 22 and the first antiphase speaker. The angle formed by the traveling direction of the sound wave radiated from 4 to the interference surface 22 is a surface to which an interference limit angle is given, and the size of the interference surface 22 serving as the defense range of each device is the interference limit wavelength. The size is set not to exceed 1/2. The noise source 21 is noise from a traveling vehicle, and the straight-ahead sound traveling to the interference surface 22 is silenced by the first reverse-phase speaker 4.
FIG. 2 shows an example in which the present invention is applied to a short soundproof wall 1 of a general automobile road, and the noise source 21 can be directly seen at the back of the soundproof wall 1 while maintaining the interference limit angle at the position of the interference surface 22. The area is greatly expanded, and the interference surface 22 is set outside the diffraction edge 23. Since the diffraction edge 23 is in front of and inside the position of the interference surface 22, noise diffracts the diffraction edge 23 and leaks to the outside of the sound barrier 1. Therefore, a second sound wave emitter 15 having a slit width opened to about 1/20 of the interference limit wavelength emits a sound wave having a phase opposite to the diffraction noise and the same sound pressure, and diffracts the diffraction edge 23 by diffracting it. Noise is absorbed by the interference effect.
FIG. 3 shows a part of the parabolic surface in which the shape of the first sound wave radiator 5 has a focal point, and the speaker sound of the first antiphase speaker 4 is radiated from the focal part. Since the sound wave radiated from the first reverse-phase speaker 4 becomes a one-dimensional plane wave having strong directivity, the interference surface 22 is placed at a position where an arbitrary distance is provided outside the tip of the soundproof wall 1. Can be set. Although it is limited to a specific range in a certain direction with respect to the noise source 21, even in a space where the noise source 21 can be completely seen on the downstream side beyond the interference surface 22, a silent region guarded from noise is raised. .

A second embodiment will be described with reference to FIG.
FIG. 4 is a perspective view illustrating the configuration and operation of the second embodiment. Example 2 uses this invention for a ventilation duct. Portions common to FIGS. 1, 2, and 3 are denoted by common reference numerals.
28 is a duct.
FIG. 4 shows a configuration in which a plurality of direct noise active silencing control devices according to the present invention are attached to the outer peripheral portion of the opening end of the air duct 28 having a large opening surface. The position of the corresponding interference surface 22 of each device of the plurality of sets is a surface immediately outside the diffraction edge 23 and perpendicular to the central axis direction of the duct 28, and is an interference that is a defense range of each device. The size of the surface 22 is set to a size that does not exceed 1/2 of the interference limit wavelength. The noise source 21 is inside the duct 28, and the straight sound traveling to the interference surface 22 is silenced by the first antiphase speaker 4, and the diffracted sound diffracting the diffraction edge 23 is silenced by the second antiphase speaker 14. Even if a large aperture surface is used, the interference limit frequency is substantially exceeded by connecting the individual interference surfaces corresponding to each set of devices to create a large interference surface that covers a certain range as a whole. Therefore, it is possible to configure a system that can control sound of a short frequency with a short wavelength, so that noise radiated to the outside from the opening of the duct 28 is effectively and uniformly reduced over the entire area.
The operation of each part is the same as in the first embodiment.

  In the above embodiment, the case where the present invention is applied to a soundproof wall of an automobile road or a blower duct is described. However, the present invention performs active silencing control on a space where a noise source can be seen, that is, direct noise, and also diffraction noise. In addition, active silencing control is performed to create a quiet area in a large three-dimensional area, and there are a wide range of industrial applications. For example, the opening of the soundproof chamber surrounding the machinery and equipment that generates noise, ventilation, etc. can not vent of that absolutely sealed because such waste heat, the contactless moving or breathable applications such like to desired but sound blocking The present invention can be applied to the same as the above embodiment. Even when the present invention is applied as described above, the same effects as those of the above-described embodiment can be obtained.

It is explanatory drawing which shows the 1st Embodiment and operating principle of this invention. It is explanatory drawing which shows the 2nd Embodiment and operating principle of this invention. It is explanatory drawing which shows the 3rd Embodiment and operating principle of this invention. It is a perspective view which shows the 4th Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Soundproof wall 2 1st sound wave reflection board 3 1st noise detection microphone 4 1st reverse phase speaker 5 1st sound wave radiator 12 2nd sound wave reflection board 13 2nd noise detection microphone 14 2nd Negative phase speaker 15 second sound radiator 21 noise source 22 interference surface 23 diffraction edge 24 waveguide plate 28 duct

Claims (3)

  A wall surface that suppresses diffusion of noise emitted from a noise source, a first sound wave reflection plate that collects a noise signal sample traveling in a certain direction in the vicinity of the wall surface at a focal point, and a focus point of the first sound wave reflection plate The first noise detecting microphone, the first antiphase speaker that emits the sound wave having the opposite phase and the same sound pressure as the noise by the output of the first noise detecting microphone, and the first antiphase speaker In the active silencing control device comprising the first sound emitter for adjusting the radiation state of the sound wave to be generated, the sound wave emitted from the noise source, the noise emitted from the first anti-phase speaker, and the anti-phase / sound pressure When the position where the sound waves merge with each other is the interference surface of both sound waves, the sound source, the interference surface, and the sound waves emitted from the noise source enter the first sound collecting microphone, and the first sound collecting microphone From negative phase speaker The optical distance relationship between the propagation path of the sound wave that travels along the two routes to the interference surface is made equal, and the incident angle of both sound waves and the wave packet to the interference surface is within the interference limit angle. A direct noise active silencing control device characterized in that the maximum length that can be connected in a straight line within the interference plane is not larger than half of the maximum interference wavelength.   2. The direct noise active silencing control device according to claim 1, wherein a second sound wave reflector for collecting a signal sample of noise diffracting a waveguide plate end edge of the first sound wave emitter at a focal point; A second noise detecting microphone disposed at the focal point of the sound wave reflecting plate, a second antiphase speaker that emits a sound wave having a phase opposite to that of the diffracted sound by the output of the second noise detecting microphone, and a slit; A second sound wave radiator having a ring-shaped opening, and radiating from a sound wave diffracting with the waveguide plate end of the first sound wave radiator as a diffraction edge and a slit-shaped opening of the second sound wave radiator 2. The direct noise active silencing control device according to claim 1, wherein the diffracted sound and the sound wave having the opposite phase and the same sound pressure are wave-absorbed by interference.   When a plurality of sets of the direct noise active silencing control device described above are arranged and used at an arbitrary position, they are resistant to a wave packet of sound waves radiated by each of the first reverse phase speaker and the first sound wave emitter. 3. A large interference surface that provides a directivity characteristic and that covers a certain range as a whole by connecting individual interference surfaces corresponding to each of a plurality of sets of devices, respectively. Direct noise active silencing control device.

Images