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JP2005241706

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DESCRIPTION JP2005241706
PROBLEM TO BE SOLVED: In a conventional muffling apparatus, a space area having a muffling
effect and a space area in which the muffling effect does not work are generated. SOLUTION: The
noise S1 from the noise source 16 is first-order diffracted at the upper end edge 13a of the
enclosure 13 and turns to the side opposite to the noise source 16 of the sound barrier 12 and
interferes with the control sound C from the speaker 14 to reduce It is done. The reduced sound
is further second-order diffracted at the side 17 a of the diffraction plate 17 and propagates to
the opposite side to the noise source 16 of the sound barrier 12. For this reason, the noise S2
interferes with the control sound C at the position 19 to be reduced, and secondarily diffracts at
the side 17a of the diffraction plate 17 and propagates to the opposite side of the noise source
16 of the sound barrier 12. Therefore, on the opposite side of the noise source 16 of the sound
barrier 12, the reduced sound interferes with the control sound C and propagates uniformly.
[Selected figure] Figure 2
Silencer
[0001]
The present invention relates to a silencer installed at the upper end of a soundproof wall that
isolates noise from a noise source and causes control noise with the same amplitude and the
same amplitude as the noise to interfere with the noise to silence the noise.
[0002]
As a conventional muffling apparatus of this type, for example, there is a muffling apparatus 1
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shown in FIG.
The noise reduction device 1 is configured by housing a speaker in an enclosure 2 and is
installed at the upper end of a soundproof wall 5 that isolates the noise 4 from the noise source
3. The control sound 6 or the control sound 7 having the same amplitude and the same phase as
the noise 4 ′ picked up by the microphone is output from the speaker housed in the enclosure
2. The control sound 6 or 7 interferes with the noise 4a or 4 'to mute the noise 4a or 4'.
[0003]
As a control sound 6 is output toward the direction A away from the noise source 3 on the side
opposite to the noise source 3 of the enclosure 2, there is a silencer disclosed in Patent
Document 1 conventionally. Further, as the control sound 7 is outputted toward the upper
direction B of the soundproof wall 5, there is a noise reduction device disclosed in Non-Patent
Document 1 conventionally.
[0004]
When the control sound 6 is output in the direction A away from the noise source 3, the control
sound 6 interferes with the noise 4 a diffracted at the upper edge 2 a of the enclosure 2 as
shown in the drawing and mutes the noise 4 a Let When the control sound 7 is output in the
upward direction B of the soundproof wall 5, the control sound 7 interferes with the noise 4
'reaching the upper side of the enclosure 2 and mutes the noise 4'. JP, 9-54593, A Mitsubishi
Heavy Industries Technical Review Vol. 39 No. 2 (March 2002) "Active soft edge sound
insulation wall which makes sound disappear with sound"
[0005]
However, in the silencer device 1 in which the conventional control sound 6 is output in the
direction A, the direction A in which the control sound 6 is emitted with the upper end edge 2a of
the enclosure 2 as the element wave generation source of the diffraction noise 4a. Is adjusted.
For this reason, in the space area 8 surrounded by the dotted line in the figure adjusted so that
the diffraction noise 4a and the control sound 6 overlap, the control sound 6 and the noise 4a
interfere with each other and there is a muffling effect. There is no muting effect in the area.
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[0006]
The same applies to the silencer 1 in which the conventional control sound 7 is output in the
direction B. That is, the direction B in which the control sound 7 is emitted is adjusted so that the
position of the noise source 3 is set to an arbitrary position and the noise 4 'from the noise
source 3 placed at the set position is silenced. Be done. Therefore, also in this case, the control
sound 7 and the noise 4 'interfere with each other to generate a space area having the muffling
effect and a space area in which the muffling effect is not effective.
[0007]
That is, in the conventional noise reduction device 1, the sound emission directions A and B of
the control sounds 6 and 7 output from the speaker in a state where the two sound sources of
the noise source 3 and the control sound source are respectively set at arbitrary positions. Has
been adjusted. For this reason, since the spread of the sound of the two sound sources is based
on different places, a space area in the adjustment range and having the silencing effect and a
space area out of the adjustment range and in which the silencing effect does not work are
generated.
[0008]
The present invention has been made to solve these problems, and it is an enclosure installed at
the upper end of a soundproof wall, and a diffraction plate having a side projecting from the side
opposite to the noise source of the enclosure and having a projecting tip. A sensor microphone
provided at the head of the enclosure for detecting noise from a noise source, and a muffling
control device for generating a muffle signal having the same amplitude as the noise detected by
the sensor mike and having a reverse phase. The speaker is housed in an enclosure and emits
control sound in accordance with a muffling signal generated by the muffling control device, and
the speaker emits sound in response to noise from a noise source diffracted at the upper edge of
the enclosure A noise suppressor is provided, which is characterized in that the sound produced
by causing the control sound to interfere is diffracted at the side of the diffraction plate as a new
sound source.
[0009]
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According to this configuration, the noise from the noise source is diffracted at the upper end
edge of the enclosure to go to the side opposite to the noise source of the soundproof wall, and is
reduced by interfering with the control sound from the speaker.
The reduced sound is further diffracted at the side of the diffraction plate, and this side is
transmitted as a new sound source to the side opposite to the noise source of the soundproof
wall.
[0010]
For this reason, the output direction of the control sound of the speaker may be set to a direction
that interferes with the noise diffracted at the upper edge of the enclosure, and can be adjusted
regardless of the generation position of the noise source. Moreover, the noise interferes with the
control sound to be reduced, and then is diffracted at the side of the diffraction plate and
propagates to the opposite side of the noise source of the noise barrier. Therefore, on the side
opposite to the noise source of the soundproof wall, the reduced sound interfering with the
control sound propagates uniformly as a new sound source on the side of the diffraction plate. As
a result, unlike the prior art, there is no space area with a muffling effect and a space area
without a muffling effect, and the muffling effect is uniformly applied on the opposite side to the
noise source of the soundproof wall.
[0011]
Also, the present invention is characterized in that the speaker emits control sound from a sound
emission port opened immediately below the sensor microphone on the side opposite to the
noise source of the enclosure.
[0012]
According to this configuration, since the distance between the sensor microphone and the
speaker is short, the noise detected by the sensor microphone reduces a waveform error between
the noise and the noise at the interference position of the control sound.
Therefore, the muffling signal generated by the muffling control device based on the noise
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detected by the sensor microphone becomes a waveform that exactly cancels out the noise at the
interference position by the waveform of the control sound outputted from the speaker, and the
muffling effect is enhanced .
[0013]
Further, the present invention is characterized in that the noise cancellation control device
performs analog processing to generate a noise cancellation signal.
[0014]
According to this configuration, the time during which the silencing control device generates the
silencing signal is shorter than when the digital processing is performed to generate the silencing
signal.
For this reason, the difference between the time when the detected noise reaches the interference
position and the time when the control sound generated from the detected noise reaches the
interference position is reduced. As a result, even with this configuration, the muffling signal
generated by the muffling control device based on the noise detected by the sensor microphone
becomes a waveform that exactly cancels out the noise at the interference position by the
waveform of the control sound output from the speaker The muffling effect is enhanced.
[0015]
Furthermore, the present invention is characterized in that the side of the diffraction plate is in
the immediate vicinity of the sound emission port of the speaker.
[0016]
According to this configuration, the control sound output from the sound emission port of the
speaker immediately interferes with the noise from the noise source diffracted at the upper edge
of the enclosure after being emitted, and this interference sound interferes with the side of the
diffraction plate As a new sound source.
For this reason, before the control sound and the noise interfere with each other, there is less
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room for the noise other than the control sound and the noise to enter the interference between
the control sound and the noise. Therefore, the interference sound diffracted at the side of the
diffraction plate is sufficiently reduced without being affected by noise.
[0017]
According to the present invention, as described above, a noise eliminator is provided in which
the sound dissipating effect is uniformly effective on the opposite side to the noise source of the
noise barrier.
[0018]
Next, the best mode for carrying out the present invention will be described.
[0019]
FIG. 2 (a) is a schematic system configuration diagram of an active noise suppressor 11
according to an embodiment in which the present invention is applied to a sound barrier on a
road, and FIG. 2 (b) is a single perspective view of the noise suppressor 11. The same figure (c) is
a block diagram which shows the electric circuit structure of this muffling apparatus 11. As
shown in FIG.
[0020]
The noise reduction device 11 is configured such that an enclosure 13 is installed at the upper
end of the soundproof wall 12.
The enclosures 13 have a box shape, and the required number of the enclosures 13 are
continuously installed adjacent to the upper end of the soundproof wall 12 along the extension
direction of the soundproof wall 12.
Each enclosure 13 houses a speaker 14 and a sensor microphone 15 is installed on the head.
The speaker 14 emits a control sound C from a sound emission port 14 a which is opened in a
rectangular shape along the extending direction of the soundproof wall 12 directly below the
sensor microphone 15 on the side opposite to the noise source 16 of the enclosure 13.
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[0021]
In addition, a diffraction plate 17 is provided on the side surface of the enclosure 13 opposite to
the noise source 16, that is, the side surface on which the noise S1 is to be muffled. The
diffraction plate 17 projects in a direction away from the noise source 16 on the side surface of
the enclosure 13 directly below the sound emission port 14a, and lays its plate surface below the
sound emission port 14a, and the projecting end has a side 17a. Have. In the present
embodiment, the side 17 a is in the immediate vicinity of the sound emission port 14 a of the
speaker 14.
[0022]
The sensor microphone 15 detects the noise S 1 ′ from the noise source 16. The noise
reduction control device 18 includes a filter circuit 18a electrically connected to the sensor
microphone 15, and noise in a predetermined frequency band (for example, 100 [Hz] to 1.6
[KHz]) input through the filter circuit 18a. A control circuit 18b that generates a mute signal
having the same amplitude as S1 'and having the opposite phase and a power amplifier 18c that
amplifies the mute signal generated by the control circuit 18b are configured to perform analog
processing. Generate a mute signal. The speaker 14 emits the control sound C in accordance with
the mute signal output from the power amplifier 18 c.
[0023]
The sound emission direction of the control sound C output from the speaker 14 is directed to a
position 19 near the side 17 a of the diffraction plate 17. Accordingly, the noise S2 from the
noise source 16 diffracted first-order at the upper edge 13a of the enclosure 13 interferes with
the control sound C output from the speaker 14 at the position 19 and then second-order
diffraction at the side 17a of the diffraction plate 17 Do. Then, the side 17a is propagated to the
opposite side of the noise source 16 of the enclosure 13 as a new sound source.
[0024]
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As described above, in the noise reduction device 11 of the present embodiment, the noise S1
from the noise source 16 undergoes first-order diffraction at the upper end edge 13a of the
enclosure 13 and wraps around to the opposite side of the noise source 16 of the noise barrier
12 It interferes with the control sound C and is reduced. The reduced sound is further secondorder diffracted at the side 17 a of the diffraction plate 17 and propagates to the opposite side to
the noise source 16 of the sound barrier 12.
[0025]
For this reason, the output direction of the control sound C of the speaker 14 may be set to a
direction that interferes with the noise S2 that is first-order diffracted by the upper end edge 13a
of the enclosure 13. Is possible. Moreover, the noise S2 interferes with the control sound C at the
position 19 to be reduced, and then secondarily diffracts at the side 17a of the diffraction plate
17 and propagates to the opposite side to the noise source 16 of the sound barrier 12. Therefore,
on the opposite side of the noise source 16 of the soundproof wall 12, the sound reduced by
interference with the control sound C uniformly propagates as the new sound source on the side
17a of the diffraction plate 17. As a result, unlike the prior art, there is no space area with a
muffling effect and a space area without a muffling effect, so that the muffling effect works
equally well on the opposite side of the noise source 16 of the soundproof wall 12 Become.
[0026]
Further, in the present embodiment, since the distance between the sensor microphone 15 and
the speaker 14 is short, the noise S1 ′ detected by the sensor microphone 15 is the noise S2 at
the interference position 19 between the noise S2 and the control sound C. The waveform error
is reduced. For this reason, the muffling signal generated by the muffling control device 18 based
on the noise S1 'detected by the sensor microphone 15 accurately uses the waveform of the
control sound C output from the speaker 14 to accurately generate the noise S2 at the
interference position 19. It becomes a waveform that cancels out, and the muffling effect is
enhanced.
[0027]
Furthermore, in the present embodiment, since the silencing control device 18 performs analog
processing to generate a silencing signal, the time during which the silencing control device 18
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generates a silencing signal performs digital processing to generate a silencing signal. It will be
shorter than the case. Therefore, the difference between the time when the detected noise S1
'reaches the interference position 19 and the time when the control sound C generated from the
detected noise S1' reaches the interference position 19 decreases. As a result, also by this, the
muffling signal generated by the muffling control device 18 approaches the waveform that
exactly cancels the noise S2 at the interference position 19 by the waveform of the control sound
C outputted from the speaker 14, and the muffling effect is It will increase further.
[0028]
Further, in the present embodiment, since the side 17 a of the diffraction plate 17 is in the
immediate vicinity of the sound outlet 14 a of the speaker 14, the control sound C output from
the sound outlet 14 a of the speaker 14 is at the upper edge 13 a of the enclosure 13. The noise
S 1 ′ from the diffracted noise source 16 is emitted immediately and then interferes
immediately, and this interference sound propagates along the side 17 a of the diffraction plate
17 as a new sound source. For this reason, until the control sound C and the noise S1 'interfere
with each other, there is less room for the noise other than the control sound C and the noise S1'
to enter the interference between the control sound C and the noise S1 '. Therefore, the
interference sound diffracted at the side 17 a of the diffraction plate 17 is sufficiently reduced
without being affected by noise.
[0029]
As a result of measuring the noise muffled by the above-mentioned muffling apparatus 11 at the
evaluation position 20 directly below the tip of the diffraction plate 17, the noise S1 of the noise
source 16 is in the band of 100 [Hz] to 1.6 [KHz] It was confirmed that the reduction was 8.2 dB.
[0030]
In the above-mentioned embodiment, the case where one enclosure 14 was provided with one
speaker 14 was explained.
However, as shown in FIG. 3 (a), one enclosure 13 is provided with a plurality of speakers 14,
and the width of the diffraction plate 17 is such that the plate surface lies below the sound
emission opening 14a of each speaker 14. It may be In addition, as shown in FIG. 6B, one
diffraction plate 17 may be provided in a plurality of enclosures 13.
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[0031]
Further, the material of the diffraction plate 17 is not limited to a specific one. For example, the
diffraction plate 17 can be made of any material such as wood, resin, metal or the like.
[0032]
In addition, the angle θ, width W, length L and thickness t of the diffraction plate 17 shown in
FIG. 4A should be set to any value as long as the noise S2 and the control sound C can interfere
with each other. Can do.
For example, in the above embodiment, the case where the installation angle θ of the diffraction
plate 17 with respect to the side surface of the enclosure 13 is vertical has been described.
However, as shown in FIG. 6B, the installation angle θ can be made to the side surface of the
enclosure 13. Further, although depending on the use of the noise reduction device 11, as shown
in FIG. 6C, in the case where several enclosures 13 are arranged on the soundproof wall 12, the
width W of each diffraction plate 17 is at least the width of the speaker 14. It may be equal to or
less than the width of the enclosure 13.
[0033]
Further, the shape of the diffraction plate 17 can also be set to an arbitrary shape as long as the
noise S2 and the control sound C can interfere with each other. For example, as shown in FIG. 5
(a), even if the tip of the diffraction plate 17 is curved and has a curved shape, the tip of the
diffraction plate 17 is bent as shown in FIG. 5 (b). It may have a bent shape. Further, as shown in
FIG. 7C, the shape of the slit formed at the tip of the diffraction plate 17 and the shape of the tip
of the diffraction plate 17 as shown in FIG. It is also good.
[0034]
Further, as shown in FIG. 6A, the diffraction plate 17 may be formed by the shape of the
soundproof wall 12 itself. Moreover, as shown to the same figure (b), you may form as another
components pinched between the enclosure 13 and the soundproof wall 12. As shown in FIG.
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Moreover, as shown to the same figure (c), it may be inserted and formed in the front surface of
the enclosure 13 as another part.
[0035]
Further, the installation angle of the speaker 14 can also be set to any angle as long as the noise
S2 and the control sound C can interfere with each other. For example, as shown in FIG. 7 (a), the
installation angle in the direction away from the noise source 16 as shown in FIG. 7 (b) or the
installation angle facing obliquely upward as shown in FIG. 7 (c). The installation angle may be
diagonally downward.
[0036]
Further, as shown in FIG. 8A, the shape of the enclosure 13 is the same as in FIG. 8A even if the
location where the noise S1 from the noise source 16 undergoes first-order diffraction is two
edges 13a and 13b. As shown in b), three edges 13a, 13b and 13c may be provided. Further, the
places where the noise S2 which is reduced due to interference with the control sound C is
second-order diffracted are, as shown in FIG. 6C, like the sides 17a and 17a 'of the two
diffraction plates 17 and 17'. There may be more than one.
[0037]
Moreover, in the said embodiment, the case where the enclosure 13 was installed in the upper
end of the sound barrier 12 was demonstrated. The soundproof wall 12 is not limited to a normal
wall, but may be mechanical equipment, building equipment or the like that can isolate the noise
S1 from the noise source 16 to some extent.
[0038]
In the said embodiment, although the case where this invention was applied to the sound barrier
of a road was demonstrated, this invention is not limited to this. For example, the present
invention can be applied to the soundproof wall beside the railway track where noise complaints
are a problem, the soundproof wall surrounding a building or facility having a noise source, etc.,
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as in the above embodiment. is there. And, even when the present invention is applied as
described above, the same function and effect as the above embodiment can be obtained.
[0039]
It is a figure which shows schematic structure of the conventional muffling apparatus. (A) is a
schematic system configuration diagram of a silencer according to an embodiment of the present
invention, (b) is a perspective view of a single silencer according to an embodiment, (c) is an
electric circuit configuration of a silencer according to an embodiment Is a block diagram
showing FIG. It is a figure which shows the modification of the arrangement structure of the
enclosure which comprises the silencer by one Embodiment of this invention, a diffraction plate,
and a speaker. It is a figure which shows the modification of the installation dimension of a
diffraction plate which comprises the silencer according to one Embodiment of this invention,
and an installation angle. It is a figure which shows the modification of the shape of the
diffraction plate which comprises the silencer by one Embodiment of this invention. It is a figure
which shows the modification of the structure of the diffraction plate which comprises the
silencer by one Embodiment of this invention. It is a figure which shows the modification of the
installation angle of the speaker which comprises the silencer by one Embodiment of this
invention. It is a figure which shows the modification of the number of the primary diffraction
points of the silencer according to one embodiment of the present invention, and the number of
secondary diffraction points.
Explanation of sign
[0040]
11: sound deadening device 12: soundproof wall 13: enclosure 14: speaker 14a: sound outlet of
speaker 14 15: sensor microphone 16: noise source 17: diffraction plate 17a: side of diffraction
plate 17: sound deadening control device 19: interference position 20 ... Evaluation position
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