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JP2017102229

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JP2017102229
Abstract: [PROBLEMS] To make it possible to mute very low frequency sound without using a
large speaker. A low frequency sound reduction system 1 according to the present invention is
provided with a first unit installation zone 9a and a second unit installation zone 9b in a side
plate 8b of an enclosure 8 constituting a control speaker 2, and The speaker units 7a and 7b are
distributed to the unit installation zones 9a and 9b, and the control unit 3 determines that the
control sound output from the speaker unit 7a and the control sound output from the speaker
unit 7b have opposite phases to each other. It is configured to be When the low frequency sound
of the vibrating screen 5 is to be silenced, the first unit installation zone 9a is located above the
height of the screen 6 constituting the vibrating screen 5, and the second unit installation zone
9b is high in the screen 6 The control speaker 2 is erected close to the vibrating screen 5 so as to
be at a lower position than the height. [Selected figure] Figure 2
Low frequency sound reduction system
[0001]
The present invention relates to a low frequency sound reduction system used to mute low
frequency sound generated by a low frequency sound source, in particular ultra low frequency
sound of a vibrating screen.
[0002]
When drilling is performed using a muddy water circulation type drilling machine such as a
horizontal multi-axis rotary drilling machine or a mud water shield machine, the sludge
generated by the drilling is subjected to predetermined treatment after the soil is separated by
the earth and sand separator It is reused as muddy water again.
03-05-2019
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[0003]
The soil separator is attached to a frame called a screen and a blind plate called an eliminator,
and installed on the frame via a spring, and the exciter attached to the upper side of the frame By
vibrating the frame at this time, it is possible to sort the soil on the screen attached to the frame
according to the particle size.
[0004]
Such a sediment separator is a kind of vibrating sieve, and vibrating sieves are widely used for
sorting of various particles such as crushed stone, gravel, and glass besides soil sorting. In
addition to various operation noises being generated from each part, the screen becomes a sound
wave generation surface, and an ultra low frequency noise of about 17 Hz or about 20 Hz is
generated.
[0005]
Among these, the operating noise propagates as noise and the infrasound is near the lower limit
of the audible range that can be heard by the human ear, so even if it is not a direct noise, It
causes discomfort, and it vibrates fittings such as shoji, windows and doors to generate rattling
noise.
[0006]
Therefore, when installing a sediment separator, which is a vibrating screen, in a city area to
perform sediment separation work, the whole sediment separator is covered with a soundproof
box, and the noise generated by the operation noise from each part of the device or the screen
vibrates. It is necessary to take sufficient measures to prevent low frequency sound from leaking
to the outside as much as possible, but for ultra low frequency sound, the sound pressure level
outside the soundproof box due to the sound insulation performance and sound absorption
performance in that frequency range. It is difficult to drop enough.
[0007]
On the other hand, active noise control (ANC) is used as a noise countermeasure, and it has been
examined whether it can be used also for ultra low frequency sound (Patent Document 1).
[0008]
JP, 2014-153653, A
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[0009]
In ANC, a control sound is generated separately as a control sound that is opposite in phase to
the target sound coming from the sound source to be reduced in sound pressure, and the
principle of wave superposition is used to achieve super It is said that it is also effective in the
reduction of low frequency sound.
[0010]
Here, it is desirable that the control sound be output by the speaker so that the control sound can
immediately follow the phase change and the amplitude change of the target sound, but with the
speaker unit alone, the sound wave from the back of the cone wraps forward and In order to
cancel out the sound wave which came out, in order to intercept the sound wave from the back, it
usually uses by attaching to a baffle board or an enclosure.
[0011]
In particular, when the frequency is low, the sound waves emitted from the rear of the cone are
diffracted and easily move forward, so the speaker unit must be attached to a closed enclosure
and configured for use as a measure against ultra low frequency sound.
[0012]
However, in the case of a closed type speaker, air in the enclosure acts as a spring and interferes
with the vibration of the cone. Therefore, in order to reduce the influence thereof, it is necessary
to increase the volume and depth of the enclosure. When trying to mute such low frequency
sound with large sound pressure energy with a large amplitude, it is essential to increase the
capacity of the enclosure.
[0013]
Therefore, it is costly to produce a speaker capable of muting very low frequency sound, and a
large space is required for installing a speaker in the field, and also a problem that it takes time
and money for transportation and installation work. It had arose.
[0014]
The present invention has been made in consideration of the above-described circumstances, and
an object thereof is to provide a low frequency sound reduction system capable of muting very
low frequency sound without using a large speaker.
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[0015]
In order to achieve the above object, a low frequency sound reduction system according to the
present invention comprises a plurality of speaker units for outputting an input control sound
signal as a control sound and the plurality of speaker units as described in claim 1 Control
speaker configured by an enclosure to which the plurality of speaker units are attached so as to
surround the space behind each cone, and control means connected to the control speaker to
create the control sound signal In the low frequency noise reduction system, the enclosure is
provided with a first unit installation zone and a second unit installation zone such that the entire
zones are adjacent to each other, and the first unit installation zone and the second unit
installation The plurality of speaker units are distributed to zones and installed, and each speaker
unit is configured The enclosure is configured such that each space behind the frame is
integrated in the first unit installation zone and the second unit installation zone, respectively,
and mutually communicate between the zones, and the plurality of speaker units Among them,
the control sound output from the speaker unit installed in the first unit installation zone and the
control sound output from the speaker unit installed in the second unit installation zone have
mutually opposite phases. The control means is configured.
[0016]
In the low frequency sound reduction system according to the present invention, a plurality of
speaker units distributed to the first unit installation zone and a plurality of speaker units
distributed to the second unit installation zone are provided.
[0017]
In the low frequency noise reduction system according to the present invention, the first unit
installation zone is located above the height of the screen forming the vibrating screen, and the
second unit installation zone is below the height of the screen. The control speaker is erected at a
position close to the vibrating screen so as to be positioned.
[0018]
In the low frequency noise reduction system according to the present invention, the control
speaker is disposed on both sides of the vibrating screen so as to sandwich the vibrating screen.
[0019]
Further, in the low frequency noise reduction system according to the present invention, the
enclosure is constituted by a single box body, and the side plate of the box body is provided with
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the first unit installation zone and the second unit installation zone. It is a thing.
[0020]
In the low frequency noise reduction system according to the present invention, the first box
body, the second box body, and the inner plate of the first box body and the bottom plate of the
first box body communicate with each other. The first unit installation zone is provided on the
side plate of the first box body, and the second unit installation zone is formed with the side
plate. It is provided in the side plate of the said 2nd box of the same side.
[0021]
In the low frequency noise reduction system according to the present invention, when installing
the plurality of speaker units in the enclosure, the first unit installation zone and the second unit
installation zone are placed in the enclosure so that the entire zones are adjacent to each other.
The above-mentioned plurality of speaker units are distributed and installed in these unit
installation zones, and the spaces behind the cones constituting each speaker unit are integrated
in each of the above-mentioned unit installation zones and mutually between the zones. The
control unit is configured such that the control sounds output from the speaker units installed in
each unit installation zone out of the plurality of speaker units are in opposite phase to each
other after the enclosure is configured to communicate.
[0022]
Thus, when control sound is output from the speaker unit attached to each unit installation zone,
the speaker unit attached to the first unit installation zone and the speaker unit attached to the
second unit installation zone The cones of one unit installation zone are displaced to the front
side when the cones of one unit installation zone are displaced to the rear side, and the cones of
one unit installation zone are displaced. Is displaced to the front side, the cone of the other unit
installation zone is displaced to the rear side.
[0023]
That is, when the cone is displaced to the rear side in one unit installation zone and air in the
vicinity of the cone rear side is pushed in, the cone is displaced to the front side in the other unit
installation zone and the air in the vicinity of the cone rear surface is pushed out. Therefore, even
if the cone vibrates, the air in the enclosure as a whole hardly increases in pressure, so that the
air in the enclosure does not act on the back of the cone as a spring.
[0024]
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Therefore, it becomes difficult to cause the air spring to act on the back of the cone to inhibit the
vibration of the cone as in the conventional case, and thus the low frequency of sufficient
amplitude from the speaker unit without increasing the volume and depth of the enclosure. Wave
sound can be output.
[0025]
The low frequency sound reduction system according to the present invention is a sound source
that generates a low frequency sound, that is, a sound of about 100 Hz or less, and two
representative sounds in opposite phase relationship are opposite as represented by plate
vibration. While any sound source can be targeted as long as it propagates in the direction, an
ultra low frequency sound as a frequency range, that is, a sound of about 20 Hz or less, and a
vibration sieve as a sound source are typically applied. It becomes an object.
Hereinafter, the above-described sound source is referred to as a target sound source.
[0026]
When applying the low frequency sound reduction system of the present invention to a
predetermined target sound source, the first unit installation zone and the first unit installation
zone in which the respective propagation sides of the two target sounds in the target sound
source are provided in the enclosure of the control speaker The control speakers are arranged in
the target sound source so as to be close to the unit installation zone 2 respectively.
[0027]
In this case, one of the two target sounds is a control sound from the speaker unit disposed in the
first unit installation zone, and the other is a control sound from the speaker unit disposed in the
second unit installation zone. In addition to being muffled respectively, the air spring does not act
on the back of the cone as described above in the inner space of the enclosure, so the control
sound of sufficient amplitude is output from the control speaker to muffle the target sound
reliably It becomes possible.
[0028]
The control means is optional as long as the control sound mutes the target sound generated by
the target sound source by phase interference when the created control sound signal is output
from the control speaker as the control sound. Although processing by analog electronic circuits
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is also possible, digital processing by an adaptive filter using a DSP is a typical example.
[0029]
Although there may be only one speaker unit distributed to the first unit installation zone and
one speaker unit distributed to the second unit installation zone, a plurality of speaker units
distributed to each unit installation zone may be used instead. If it is configured as a single
speaker unit, the reduction in the cone diameter of each speaker unit reduces the amplitude
(output of low frequency sound) by the number of speaker units, in other words, the radiation
area. Overall production costs can be kept low.
[0030]
As a specific configuration in the case of applying to the vibrating screen, the first unit
installation zone is located above the height of the screen that constitutes the vibrating screen,
and the second unit installation zone is located below the screen height. The control speaker may
be set up in the vicinity of the vibrating screen so that
[0031]
Here, only one control speaker may be disposed on the side of the vibrating screen, but if the
configuration is disposed on both sides of the vibrating screen so as to sandwich the vibrating
screen, the muffling effect is sufficient. It is possible to
[0032]
As long as the enclosure is configured such that the spaces behind the cones constituting the
speaker units are integrated in the first unit installation zone and the second unit installation
zone, respectively, and that the respective zones communicate with each other, It is optional how
to configure, for example, a configuration in which the enclosure is configured in a single box,
and one side plate of the box is provided with the first unit installation zone and the second unit
installation zone. It can be done.
[0033]
Such a configuration makes it easy to unite the spaces behind the cone in the first unit
installation zone and the second unit installation zone, and to facilitate mutual communication
between the zones, because the enclosure has a simple structure. .
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In addition, a single box is not necessarily limited to being integral structure, and the form which
comprises a single box by assembling several parts may be used.
[0034]
On the other hand, each end of the enclosure is connected to the bottom plate of the first box and
the top plate of the second box so that the first box, the second box and their internal spaces are
communicated with each other. The first unit installation zone is provided on the side plate of the
first box and the second unit installation zone is provided on the side plate of the second box on
the same side as the side plate. Configuration is also possible.
[0035]
In such a configuration, it is possible to flexibly cope with the difference in the specifications of
the vibrating screen by preparing the communicating pipe in various sizes in advance.
[0036]
BRIEF DESCRIPTION OF THE DRAWINGS Schematic of the low frequency sound reduction system
1 which concerns on this embodiment.
It is a figure of the speaker 2 for control, (a) is a whole perspective view, (b) is a perpendicular
sectional view.
Explanatory drawing which showed the effect | action of the low frequency sound reduction
system 1. FIG.
It is a figure of the low frequency sound reduction system which concerns on a modification, (a)
is schematic, (b) is a plane arrangement | positioning figure.
The schematic of the low frequency sound reduction system which concerns on another
modification.
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[0037]
Hereinafter, an embodiment of a low frequency sound reduction system according to the present
invention will be described with reference to the attached drawings.
[0038]
FIG. 1 is a schematic view showing a low frequency sound reduction system according to the
present embodiment.
As shown in the figure, the low frequency sound reduction system 1 according to the present
embodiment is an object sound source for the earth and sand separator 5 as a vibrating screen,
and an ultra low frequency sound generated by the vibration of the screen 6 constituting the
earth and sand separator. This is an example in which the present invention is applied to a target
sound, and includes a control speaker 2, a control unit 3 connected to the control speaker, and
an error microphone 4 connected to the control unit.
[0039]
The error microphone 4 is installed at a predetermined position separated from the earth and
sand separator 5 so that the sound pressure at this position can be measured.
[0040]
The control unit 3 performs feedback using the sound pressure data obtained by the error
microphone 4 as an error signal so that the super low frequency sound generated by the earth
and sand separator 5 is silenced by the control sound output from the control speaker 2 The
control sound signal is generated by control, and the control unit constitutes the control means
of the present invention together with the error microphone 4.
[0041]
The control unit 3 can be configured by providing an adaptive filter in the DSP, but a known
technique can be appropriately adopted as an algorithm to be used, and the description is
omitted here.
[0042]
The control speaker 2 is composed of a speaker unit 7a and a speaker unit 7b as a plurality of
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speaker units and an enclosure 8 as an enclosure to which they are attached. The enclosure is a
speaker as shown in FIG. By surrounding the space behind each cone 21 which comprises unit
7a, 7b, it is comprised so that the sound wave from this cone back may not leak outside.
[0043]
The enclosure 8 is constituted by a single box body composed of a rectangular bottom plate 8a,
four side plates 8b, 8c, 8d, 8e erected from their respective peripheral edges, and a rectangular
top plate 8f joined to their upper edges. In addition, among the side plates, the side plate 8b is
provided with the first unit installation zone 9a and the second unit installation zone 9b such that
the entire zones are adjacent to each other, and the above-described speaker units 7a and 7b are
It distributes to these unit installation zones 9a and 9b, that is, a total of eight speaker units 7a
are installed in the first unit installation zone 9a, and a total of eight speaker units 7b are
installed in the second unit installation zone 9b. Yes.
[0044]
Here, the enclosure 8 is configured as a single box as described above, so that the space behind
the cone 21 constituting the speaker unit 7a is integrated over the range of the first unit
installation zone 9a, and The space behind the cone 21 constituting the unit 7b is integrated over
the range of the second unit installation zone 9b, and the space behind these cones is the first
unit installation zone 9a and the second unit installation zone They are mutually connected with
9b.
[0045]
On the other hand, in the control unit 3, the control sound output from the speaker unit 7a
installed in the first unit installation zone 9a and the control sound output from the speaker unit
7b installed in the second unit installation zone 9b It is configured to be in opposite phase to
each other.
[0046]
In order to use the low frequency sound reduction system 1 according to the present
embodiment to silence the ultra low frequency sound generated by the earth and sand separator
5, first, the control speaker 2 and the first unit installation zone 9a are the vibrating screen 5 The
sediment separator is erected in the vicinity of the vibrating screen 5 so that the second unit
installation zone 9b is positioned lower than the height of the screen 6 constituting the Each
propagation side of the two target sounds in 5, that is, the immediate upper side of the screen 6
is brought close to the first unit installation zone 9a, and the lower side of the screen 6 is brought
close to the second unit installation zone 9b (FIG. )reference).
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[0047]
Next, the control sound signal created by the control unit 3 is output from the control speaker 2
while operating the sediment separator 5.
[0048]
When creating a control sound signal by the control unit 3, an object that is an ultra-low
frequency sound generated by the screen 6 of the earth and sand separator 5 while performing
feedback control using sound pressure data obtained by the error microphone 4 as an error
signal. Although the control sound of the opposite phase to the sound is output from the control
speaker 2, particularly in the present embodiment, it is propagated upward among two target
sounds generated on the screen 6 of the earth and sand separator 5 and propagating in the
vertical direction. A control sound in reverse phase to the target sound is output from the
speaker unit 7a attached to the first unit installation zone 9a, and a control sound in reverse
phase to the target sound propagating downward is transmitted to the second unit installation
zone 9b. The output is made from the attached speaker unit 7b.
[0049]
In this way, the two target sounds propagating in the vertical direction of the screen 6 propagate
downward as the control sound from the speaker unit 7a disposed in the first unit installation
zone 9a propagates upward. The target sound is muffled by the control sound from the speaker
unit 7b disposed in the second unit installation zone 9b.
[0050]
In addition, in the low frequency sound reduction system 1 according to the present
embodiment, when the control sound is output from the speaker units 7a and 7b attached to the
unit installation zones 9a and 9b, respectively, the first unit installation zone 9a The speaker unit
7a attached to the speaker unit 7a and the speaker unit 7b attached to the second unit
installation zone 9b vibrate in the opposite phase of their cones 21 and the cone 21 of the
speaker unit 7a is displaced to the back side Sometimes, as shown in FIG. 3 (a), when the cone 21
of the speaker unit 7b is displaced to the front side and the cone 21 of the speaker unit 7a is
displaced to the front side, as shown in FIG. 3 (b) The cone 21 of the unit 7b is displaced to the
back side.
[0051]
Note that, as described above, the speaker unit 7a outputs, from the speaker unit 7a, a control
03-05-2019
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sound of a phase opposite to the target sound propagating to the upper side of the screen 6, and
a control sound of the phase opposite to the object sound propagating downward. Therefore, the
displacement of the cone 21 described above is interlocked with the displacement of the screen
6, and when the cone 21 of the speaker unit 7a is displaced to the back side and the cone 21 of
the speaker unit 7b is displaced to the front side, the screen 6 is displaced upward When the
cone 21 of the speaker unit 7a is displaced to the front side and the cone 21 of the speaker unit
7b is displaced to the rear side, the screen 6 is displaced downward (FIG. 6B).
[0052]
Thus, when the cone 21 of the speaker unit 7a is displaced to the back side and the air in the
vicinity of the back surface of the cone is pushed in because the speaker unit 7a and the speaker
unit 7b vibrate in the opposite phase. The cone 21 of the speaker unit 7b is displaced to the front
side, and the air in the vicinity of the rear face of the cone is pushed out (the same is true in the
opposite case).
[0053]
Therefore, even if the cone 21 vibrates, the air in the enclosure 8 does not generally increase in
pressure as a whole, so the air in the enclosure 8 does not act on the back of the cone 21 as a
spring.
[0054]
As described above, according to the low frequency noise reduction system 1 according to the
present embodiment, the air spring acts on the back of the cone as in the conventional case, and
the situation of inhibiting the vibration of the cone hardly occurs. The speaker units 7a and 7b
can output low frequency sound with sufficient amplitude without increasing the volume and
depth of the volume, and at the site, the measures against the extremely low frequency sound of
the earth and sand separator 5 can be taken with a small installation space. It becomes possible
to take it and the workability in transportation and installation work is also improved.
[0055]
Further, according to the low-frequency sound reduction system 1 according to the present
embodiment, a plurality of the speaker units 7a and 7b distributed to each unit installation zone
9a and 9b, respectively, eight in the present embodiment, Since the reduction in amplitude due to
the reduction in the cone diameter of the speaker units 7a and 7b can be compensated by the
number of the speaker units 7a and 7b, that is, the radiation area, the overall manufacturing cost
of the speaker units can be reduced.
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[0056]
Moreover, according to the low frequency sound reduction system 1 according to the present
embodiment, since the enclosure 8 is configured as a single box, the space behind each cone 21
is set to the first unit installation zone 9a and the second unit installation It becomes easy to
integrate over the range of zone 9b, respectively, and it becomes easy to make it mutually
connect between each unit installation zones 9a and 9b.
[0057]
Although not particularly mentioned in this embodiment, as long as it is disposed in the vicinity
of the earth and sand separator 5, it is optional at which location the control speaker 2 is
installed, and the transport upstream of the screen 6 as in this embodiment. Instead of the side,
the downstream side of conveyance or the side may be used.
[0058]
Further, in the present embodiment, the control speaker 2 is disposed only on one side of the
sediment separator 5, that is, on the conveyance upstream side of the screen 6. Instead of this,
the sediment separator 5 is sandwiched. For example, as shown in FIG. 4, the control speakers 2
are separated from each other on the sides of the control speaker 2 so that the unit installation
zones 9a and 9b are parallel to the transport direction of the screen 6 (arrows in FIG. 4). It may
be arranged close to 5.
It is desirable that the error microphone 4 be placed on an axis of symmetry of the control
speakers 2 and 2, for example, on an extension of the transport direction of the screen 6 as
shown in the plan layout view of FIG.
[0059]
According to this configuration, it is possible to more reliably silence the super low frequency
sound generated by the earth and sand separator 5, and the earth and sand separator 5 is
sandwiched between the control speakers 2 and 2, The operation noise is less likely to be
transmitted to the surroundings, and the possibility that the feedback control using the error
microphone 4 is disturbed is also reduced.
[0060]
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In addition, if the facing arrangement of the control speakers 2 described above is performed in
two orthogonal directions, the earth and sand separator 5 is surrounded by the four control
speakers 2, and the above-described effects are further improved.
[0061]
Further, in the present embodiment, the control speaker 2 is erected vertically, but in the case of
being installed on the transport upstream side or transport downstream side of the screen 6,
instead of the vertical posture, the arrangement plane of the screen 6 It may be arranged in an
inclined posture so as to be orthogonal to
[0062]
According to such a configuration, it is possible to mute the target sound propagating to the
upper and lower sides of the screen 6 evenly.
[0063]
Further, in the present embodiment, a plurality of speaker units 7a and 7b distributed to each
unit installation zone 9a and 9b are respectively configured, but instead, a single speaker unit is
respectively added to each unit installation zone 9a and 9b It may be distributed.
[0064]
Moreover, in this embodiment, although the control part 3 was comprised so that the target
sound which generate | occur | produces in the earth and sand separator 5 may be muffled by
feedback control, it replaces with this and the reference microphone (not shown) The control unit
3 may be configured such that the above-described target sound is silenced by feedforward
control using the reference microphone and the error microphone 4 in addition to the abovedescribed configuration.
[0065]
Further, in the present embodiment, the enclosure 8 is constituted by a single box, but instead, as
shown in FIG. 5, the first box 51, the second box 52, and their internal spaces And an enclosure
54 consisting of a communication tube 53 whose ends are respectively connected to the bottom
plate of the first box body and the top plate of the second box body so as to communicate with
each other; The zone 9a can be provided on the side plate of the first box 51, and the second unit
installation zone 9b can be provided on the side plate of the second box 52 on the same side as
the side plate.
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[0066]
With this configuration as well, the same effects as those of the above-described embodiment can
be obtained. In addition, by preparing the communication tube 53 in various sizes in advance, it
is possible to flexibly cope with the difference in the specifications of the vibrating screen 5.
Become.
[0067]
Moreover, although the case where a vibrating screen is the earth-and-sand separator 5 was
made into the example in this embodiment, it can not be overemphasized that this invention is
applicable also to the vibrating screen which makes uses other than earth-and-sand sorting.
[0068]
Reference Signs List 1 low-frequency sound reduction system 2 control speaker 3 control unit
(control means) 4 error microphone (control means) 5 sediment separator (vibration screen,
target sound source) 6 screen 8 enclosure (enclosure, single box) 7a , 7 b Speaker unit 9 a First
unit installation zone 9 b Second unit installation zone 21 cone 51 first box 52 second box 53
communication tube 54 enclosure (enclosure)
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