JP6675581B2 - Low frequency sound reduction system - Google Patents

Description

  The present invention relates to a low-frequency sound reduction system used for silencing low-frequency sound generated by a low-frequency sound generation source, particularly, a very low-frequency sound of a vibration sieve.

  When excavating using a mud circulation type excavator such as a horizontal multi-axis rotary excavator, mud shield machine, etc., after the excavated sediment is separated by a sediment separator, After that, it is reused as mud again.

  The sediment separator is provided with a screen functioning as a sieve (screen) and an iron plate called a blind plate mounted on a frame, the frame mounted on a gantry via a spring, and a shaker mounted above the frame. By vibrating the frame, the sediment on the screen attached to the frame can be sorted according to the particle size.

  Such a sediment separator is a type of vibrating sieve. In addition to sediment sorting, vibrating sieves used for sorting various granular materials such as crushed stone, gravel, and glass are widely used. When the is driven, various operation sounds are generated from each part, and the screen serves as a sound wave generating surface to generate an ultra-low frequency sound of about 17 Hz or about 20 Hz.

  Of these, the operating sound becomes noise and propagates to the surroundings, and the very low frequency sound is near the lower limit of the audible range that can be heard by the human ear, so even if it does not become direct noise, It causes discomfort, and vibrates fittings such as shoji, windows, and doors to produce rattling noises.

  Therefore, when installing a sediment separator, which is a vibrating sieve, in an urban area to perform sediment separation work, cover the entire sediment separator with a soundproof box, and use supersonic noise generated by the operation noise from each part of the device and the vibration of the screen. Sufficient measures must be taken to prevent low-frequency sound from leaking to the outside as much as possible.For ultra-low-frequency sound, the sound pressure level is outside the soundproof box due to the sound insulation performance and sound absorption performance in that frequency range. It is difficult to drop enough.

  On the other hand, active noise control (ANC) has been used as a noise countermeasure, and it has been studied whether it can be used for very low frequency sound (Patent Document 1).

JP 2014-153653 A

  In the ANC, a sound having a phase opposite to that of a target sound emitted from a sound source to be reduced in sound pressure is separately generated as a control sound so as to mute the sound. It is said to be effective in reducing low-frequency sound.

  Here, it is desirable that the control sound be output by a speaker so that it can instantaneously follow the phase change and amplitude change of the target sound.However, with the speaker unit alone, the sound wave emitted from the back of the cone goes around forward and It is usually used by attaching it to a baffle plate or enclosure in order to cancel out the emitted sound waves and to cut off sound waves from behind.

  In particular, when the frequency is low, the sound wave emitted from the back of the cone is easily diffracted and sneak forward. Therefore, as a countermeasure application for the extremely low frequency sound, the speaker unit must be attached to a closed enclosure.

  However, in a closed speaker, the air inside the enclosure acts as a spring and hinders the vibration of the cone.To reduce the effect, it is necessary to increase the volume and depth of the enclosure. In order to muffle such an ultra-low frequency sound having a large sound pressure energy with a large amplitude, it is essential to increase the capacity of the enclosure.

  For this reason, it is costly to manufacture a speaker that can mute very low frequency sounds, and it requires a large space for installing the speaker at the site, and it takes time and money for transportation and installation work. Was occurring.

  The present invention has been made in consideration of the above-described circumstances, and has as its object to provide a low-frequency sound reduction system that can mute an extremely low-frequency sound without using a large speaker.

In order to achieve the above object, a low frequency sound reduction system according to the present invention includes a plurality of speaker units that output an input control sound signal as a control sound, and the plurality of speaker units. A control speaker configured by an enclosure to which the plurality of speaker units are attached so as to surround a space behind each cone, and a control unit connected to the control speaker to generate the control sound signal. Low frequency sound reduction system
A first unit installation zone and a second unit installation zone are provided in the enclosure so that the entire zone is adjacent to each other, and the plurality of speaker units are provided in the first unit installation zone and the second unit installation zone. In addition to distributing and installing, the respective spaces behind the cones constituting the respective speaker units are integrated with each other in the first unit installation zone and the second unit installation zone and communicate with each other between the zones. An enclosure is formed, and among the plurality of speaker units, a control sound output from a speaker unit installed in the first unit installation zone and a control sound output from a speaker unit installed in the second unit installation zone. The control means is configured such that the control sounds are in opposite phases to each other ,
A sound source in which two target sounds having opposite phases propagate in opposite directions is set as a target sound source. By arranging the control speaker in the target sound source so as to be close to each zone, one of the two target sounds is a control sound from a speaker unit arranged in the first unit installation zone, The other is muted by a control sound from a speaker unit arranged in the second unit installation zone .

  Further, the low-frequency sound reduction system according to the present invention includes a plurality of speaker units that are assigned to the first unit installation zone and a plurality of speaker units that are assigned to the second unit installation zone.

The low-frequency sound reduction system according to the present invention, the Shun the target sound vibration sieve, the first unit installation zone becomes an upper position than the height of the screen constituting the vibrating screen, the second unit installed The control speaker is erected at a position close to the vibrating sieve so that a zone is located below a height of the screen.

  In the low frequency sound reduction system according to the present invention, the control speaker is disposed on both sides of the vibration sieve so as to sandwich the vibration sieve.

  Further, in the low-frequency sound reduction system according to the present invention, the surrounding body is formed of a single box, and the first unit installation zone and the second unit installation zone are provided on a side plate of the box. Things.

  The low-frequency sound reduction system according to the present invention may further include a first box, a second box, and a bottom plate of the first box so that the inner space thereof can communicate with the enclosure. The first unit installation zone is provided on a side plate of the first box body, and the second unit installation zone is provided on the side plate of the first box body. It is provided on the side plate of the second box on the same side.

  In the low-frequency sound reduction system according to the present invention, when installing a plurality of speaker units in the enclosure, the first unit installation zone and the second unit installation zone are connected to the enclosure so that the entire zone is adjacent to each other. In addition to disposing and installing the above-mentioned plurality of speaker units in these unit installation zones, each space behind the cone that constitutes each speaker unit is integrated in each unit installation zone described above and mutually between each zone The enclosure is configured so as to communicate with each other, and the control means is configured so that control sounds output from the speaker units installed in each unit installation zone of the plurality of speaker units have phases opposite to each other.

  With this configuration, when the 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 Means that when the cones vibrate in opposite phases and the cone in one unit installation zone is displaced to the rear, the cone in the other unit installation zone is displaced to the front and the cone in one unit installation zone Is displaced to the front side, the cone of the other unit installation zone is displaced to the rear side.

  That is, when the cone is displaced rearward in one unit installation zone and the air near the back of the cone is pushed in, the cone is displaced frontward in the other unit installation zone and the air near the back of the cone is pushed out. Therefore, even if the cone vibrates, the air in the enclosure does not substantially increase in pressure as a whole, and therefore the air in the enclosure does not act as a spring on the rear surface of the cone.

  Therefore, unlike the conventional case, it is difficult for the air spring to act on the back of the cone to hinder the vibration of the cone.Thus, even if the volume and depth of the enclosure are not increased, a sufficient amplitude low frequency Wave sound can be output.

  The low-frequency sound reduction system according to the present invention is a sound source that generates low-frequency sound, that is, a sound of about 100 Hz or less, and two target sounds having opposite phases, as represented by plate vibration, are inverted. Any sound source can be targeted as long as it propagates in the direction, but a very low frequency sound, that is, a sound of about 20 Hz or less is used as a frequency range, and a vibration sieve is used as a sound source. Be eligible. Hereinafter, the above sound source is referred to as a target sound source.

  In applying the low-frequency sound reduction system of the present invention to a predetermined target sound source, the respective propagation sides of the two target sounds in the target sound source are connected to the first unit installation zone 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 two unit installation zones.

  In this case, one of the two target sounds is a control sound from the speaker unit arranged in the first unit installation zone, and the other is a control sound from the speaker unit arranged in the second unit installation zone. As described above, in the inner space of the enclosure, the air spring does not act on the back of the cone, and the control sound of sufficient amplitude is output from the control speaker, so that the target sound is reliably muted. It becomes possible.

  The control means may have any configuration as long as the generated control sound signal is output from the control speaker as the control sound, as long as the control sound can mute the target sound generated by the target sound source by phase interference. Although processing by an analog electronic circuit is also possible, digital processing by an adaptive filter using a DSP is a typical example.

  The number of the speaker units allocated to the first unit installation zone and the number of the speaker units allocated to the second unit installation zone may be one. Alternatively, a plurality of speaker units may be allocated to each unit installation zone. If the number of speaker units reduces the amplitude (output of low-frequency sound) due to the smaller cone diameter of each speaker unit, the number of speaker units, in other words, the radiation area, can be compensated for. Production costs can be kept low as a whole.

  As a specific configuration when applied to a vibrating sieve, the first unit installation zone is located above the height of the screen constituting the vibrating sieve, and the second unit installation zone is located below the height of the screen. In this case, the control speaker may be provided upright at a position close to the vibrating sieve.

  Here, the control speaker may be arranged only on one side of the vibrating sieve, but if it is arranged on both sides of the vibrating sieve so as to sandwich the vibrating sieve, a sufficient silencing effect can be obtained. Can be increased.

  As long as the surrounding body is configured such that each space behind the cone that constitutes each speaker unit is united in the first unit installation zone and the second unit installation zone, and that the zones communicate with each other, How to configure is arbitrary, for example, a configuration in which the enclosure is configured as a single box, and a first unit installation zone and a second unit installation zone are provided on one side plate of the box. It can be.

  In such a configuration, since the enclosure has a simple structure, the respective spaces behind the cone can be easily integrated into the first unit installation zone and the second unit installation zone, and can be easily communicated with each other. . Note that a single box is not necessarily limited to an integral configuration, and may be configured to form a single box by assembling a plurality of parts.

  On the other hand, each end is respectively attached 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. A configuration is also possible.

  In such a configuration, by preparing the communication pipe in various sizes in advance, it is possible to flexibly cope with a difference in the specification of the vibration sieve.

FIG. 1 is a schematic diagram of a low-frequency sound reduction system 1 according to the embodiment. It is a figure of the control speaker 2, (a) is a whole perspective view, (b) is a vertical 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 concerning a modification, (a) is a schematic diagram, (b) is a plane arrangement figure. The schematic diagram of the low frequency sound reduction system concerning another modification.

  Hereinafter, embodiments of a low-frequency sound reduction system according to the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram 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 includes a sediment separator 5 as a vibration sieve, a target sound source, and an ultra-low frequency sound generated by vibration of a screen 6 constituting the sediment separator. This is an example in which the present invention is applied to the control 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.

  The error microphone 4 is installed at a predetermined position separated from the sediment separator 5, so that the sound pressure at the position can be measured.

  The control unit 3 uses the sound pressure data obtained by the error microphone 4 as an error signal so that the very low frequency sound generated by the sediment separator 5 is silenced by the control sound output from the control speaker 2. The control sound signal is created by the control, and the control unit constitutes a control means of the present invention together with the error microphone 4.

  The control unit 3 can be configured by providing an adaptive filter in the DSP. However, a known technique can be appropriately used for an algorithm and the like to be used, and the description is omitted here.

  The control speaker 2 includes a speaker unit 7a and a speaker unit 7b as a plurality of speaker units, and an enclosure 8 as an enclosure to which the speaker units 7a and 7b are attached. As shown in FIG. By surrounding the space behind each of the cones 21 constituting the units 7a and 7b, the sound waves from the back of the cones are prevented from leaking to the outside.

  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 respective peripheral edges thereof, and a rectangular top plate 8f joined to their upper edges. In addition, among the side plates, a first unit installation zone 9a and a second unit installation zone 9b are provided on the side plate 8b such that the entire zones are adjacent to each other. The above-described speaker units 7a and 7b Allocated 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 similarly installed in the second unit installation zone 9b. I have.

  Here, since the enclosure 8 is constituted by a single box as described above, 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 formed by the first unit installation zone 9a and the second unit installation zone 9b. 9b.

  On the other hand, the control unit 3 controls 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 so that the phases are opposite to each other.

  In order to mitigate the extremely low frequency sound generated in the sediment separator 5 using the low frequency sound reduction system 1 according to the present embodiment, first, the control speaker 2 is set to the first unit installation zone 9a and the vibration sieve 5 is used. And the second unit installation zone 9b is located below the height of the screen 6 so that the second unit installation zone 9b is located below the height of the screen 6. 5, the two target sound propagation sides, that is, the area directly above the screen 6 is brought close to the first unit installation zone 9a, and the area immediately below the screen 6 is brought close to the second unit installation zone 9b (FIG. 2 (b )reference).

  Next, the control sound signal generated by the control unit 3 is output from the control speaker 2 while operating the sediment separator 5.

  When the control sound signal is generated by the control unit 3, the sound pressure data obtained by the error microphone 4 is subjected to feedback control as an error signal, and the target is an ultra-low frequency sound generated on the screen 6 of the sediment separator 5. A control sound having a phase opposite to that of the sound is output from the control speaker 2. In the present embodiment, among the two target sounds that are generated on the screen 6 of the sediment separator 5 and propagated in the vertical direction, the sound propagates upward. A control sound having a phase opposite to the target sound is output from the speaker unit 7a attached to the first unit installation zone 9a, and a control sound having a phase opposite to the target sound propagating downward is sent to the second unit installation zone 9b. Output is made from the attached speaker unit 7b.

  With this configuration, the two target sounds that propagate in the vertical direction of the screen 6 are the control sounds from the speaker unit 7a disposed in the first unit installation zone 9a, and the target sound that propagates upward propagates downward. The target sound is silenced by the control sound from the speaker unit 7b arranged in the second unit installation zone 9b.

  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 are such that their cones 21 vibrate in opposite phases, and the cones 21 of the speaker unit 7a are displaced rearward. Sometimes, as shown in FIG. 3A, the cone 21 of the speaker unit 7b is displaced to the front side, and when the cone 21 of the speaker unit 7a is displaced to the front side, as shown in FIG. The cone 21 of the unit 7b is displaced rearward.

  As described above, the control sound having the opposite phase to the target sound propagating above the screen 6 is output from the speaker unit 7a, and the control sound having the opposite phase to the target sound propagating below the screen 6 is output from the speaker unit 7b. Therefore, when the cone 21 of the speaker unit 7a is displaced to the rear side and the cone 21 of the speaker unit 7b is displaced to the front side, the screen 6 is displaced upward. Then, when the cone 21 of the speaker unit 7a is displaced toward the front and the cone 21 of the speaker unit 7b is displaced toward the back, the screen 6 is displaced downward (see FIG. 2B).

  As described above, since the cones 21 of the speaker unit 7a and the speaker unit 7b vibrate in opposite phases, when the cone 21 of the speaker unit 7a is displaced to the rear side and the air near the rear surface of the cone is pushed in. Then, the cone 21 of the speaker unit 7b is displaced to the front side, and the air near the back of the cone is pushed out (the same applies to the opposite case).

  Therefore, even if the cone 21 vibrates, the air in the enclosure 8 hardly increases in pressure as a whole, so that the air in the enclosure 8 does not act as a spring on the rear surface of the cone 21.

  As described above, according to the low-frequency sound reduction system 1 according to the present embodiment, a situation in which an air spring acts on the back surface of the cone and hinders the vibration of the cone unlike the related art is less likely to occur, and thus the enclosure 8 The speaker units 7a and 7b can output low-frequency sound of sufficient amplitude without increasing the volume and depth of the loudspeaker, and at the site, the countermeasures against ultra-low-frequency sound of the sediment separator 5 can be achieved with a small installation space. This makes it possible to improve the operability of transport and installation work.

  Further, according to the low-frequency sound reduction system 1 according to the present embodiment, since the speaker units 7a and 7b allocated to the unit installation zones 9a and 9b are respectively plural, and in the present embodiment, eight speaker units 7a and 7b are used. Since the decrease in the amplitude due to the decrease in the cone diameter of the speaker units 7a and 7b can be compensated for 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.

  Further, according to the low-frequency sound reduction system 1 according to the present embodiment, since the enclosure 8 is formed of a single box, the space behind each cone 21 is divided into the first unit installation zone 9a and the second unit installation zone. It is easy to integrate each over the range of the zone 9b, and it is easy to mutually communicate between the unit installation zones 9a and 9b.

  Although not specifically mentioned in the present embodiment, as long as the control speaker 2 is installed in the vicinity of the sediment separator 5, it is optional to install the control speaker 2 at any position. Instead of the side, it may be on the downstream side of the conveyance or on the side.

  Further, in the present embodiment, the control speaker 2 is arranged only on one side of the sediment separator 5, that is, on the upstream side of the screen 6 in the conveyance, but instead, the sediment separator 5 is sandwiched. On each side, for example, as shown in FIG. 4, the control speakers 2 are respectively separated from the earth and sand separator so that the unit installation zones 9a and 9b are parallel to the transport direction of the screen 6 (open arrows in FIG. 4). 5 may be arranged in the vicinity. The error microphone 4 is desirably installed on the axis of symmetry of the control speakers 2 and 2, for example, as shown in the plan layout of FIG.

  According to such a configuration, the extremely low frequency sound generated in the sediment separator 5 can be more reliably silenced, and the sediment separator 5 is sandwiched between the control speakers 2 so that the sediment separator 5 The operation sound is less likely to propagate to the surroundings, and the possibility that the feedback control using the error microphone 4 is hindered is reduced.

  If the above-described opposing arrangement of the control speakers 2 is performed in two orthogonal directions, the sediment separator 5 will be surrounded by the four control speakers 2, and the above-described operation and effect will be further improved.

  Further, in the present embodiment, the control speaker 2 is set up vertically. However, when the control speaker 2 is installed on the upstream side or the downstream side of the transport of the screen 6, instead of the vertical posture, the arrangement plane of the screen 6 is used. It may be arranged in an inclined posture so as to be orthogonal to.

  According to such a configuration, the target sound propagating above and below the screen 6 can be evenly silenced.

  In the present embodiment, a plurality of speaker units 7a and 7b are allocated to each of the unit installation zones 9a and 9b. Instead, a single speaker unit is provided for each of the unit installation zones 9a and 9b. You can sort them.

  Further, in the present embodiment, the control unit 3 is configured so that the target sound generated in the sediment separator 5 is silenced by the feedback control. Instead, a reference microphone (not shown) is connected to the sediment separator 5. , And the control unit 3 may be configured so that the above-mentioned target sound is muted by feedforward control using the reference microphone and the error microphone 4.

  Further, in the present embodiment, the enclosure 8 is constituted by a single box, but instead, as shown in FIG. 5, a first box 51, a second box 52, and their internal spaces are provided. Is connected to the bottom plate of the first box body and the top plate of the second box body, and an enclosure 54 composed of a communication pipe 53 connected at each end to the first box body. The zone 9a may be provided on the side plate of the first box 51, and the second unit installation zone 9b may be provided on the side plate of the second box 52 on the same side as the side plate.

  With such a configuration, the same operation and effect as those of the above-described embodiment can be obtained. In addition, by preparing the communication pipe 53 in various sizes in advance, it is possible to flexibly cope with the difference in the specification of the vibration sieve 5. Become.

  Further, in this embodiment, the case where the vibrating sieve is the sediment separator 5 is described as an example, but it goes without saying that the present invention can be applied to a vibrating sieve used for purposes other than sediment sorting.

DESCRIPTION OF SYMBOLS 1 Low frequency sound reduction system 2 Control speaker 3 Control part (control means)
4 Error microphone (control means)
5 Sediment separator (vibrating sieve, target sound source)
6 screen 8 enclosure (enclosure, single box)
7a, 7b Speaker unit 9a First unit installation zone 9b Second unit installation zone 21 Cone 51 First box 52 Second box 53 Communication tube 54 Enclosure (enclosure)

Claims (6)

A plurality of speaker units that output the input control sound signal as control sound, and an enclosure to which the plurality of speaker units are attached so as to surround the space behind each cone that forms the plurality of speaker units. A low-frequency sound reduction system including a control speaker and control means connected to the control speaker to generate the control sound signal,
A first unit installation zone and a second unit installation zone are provided in the enclosure so that the entire zone is adjacent to each other, and the plurality of speaker units are provided in the first unit installation zone and the second unit installation zone. In addition to distributing and installing, the respective spaces behind the cones constituting the respective speaker units are integrated with each other in the first unit installation zone and the second unit installation zone and communicate with each other between the zones. An enclosure is formed, and among the plurality of speaker units, a control sound output from a speaker unit installed in the first unit installation zone and a control sound output from a speaker unit installed in the second unit installation zone. The control means is configured such that the control sounds are in opposite phases to each other ,
A sound source in which two target sounds having opposite phases are propagated in opposite directions is set as a target sound source, and the respective propagation sides of the two target sounds emitted from the target sound source are the first unit setting zone and the second unit setting. By arranging the control speaker in the target sound source so as to be close to each zone, one of the two target sounds is a control sound from a speaker unit arranged in the first unit installation zone, A low-frequency sound reduction system, wherein the other is silenced by a control sound from a speaker unit arranged in the second unit installation zone . 2. The low-frequency sound reduction system according to claim 1, wherein a plurality of speaker units are assigned to the first unit installation zone and a plurality of speaker units are assigned to the second unit installation zone. Wherein the target sound source Shun vibrating screen, the first unit installation zone becomes an upper position than the height of the screen constituting the vibrating sieve, so that the second unit installation zone becomes lower position than the height of the screen 3. The low-frequency sound reduction system according to claim 1, wherein the control speaker is erected at a position close to the vibration sieve. 4. The low-frequency sound reduction system according to claim 3, wherein the control speaker is disposed on both sides of the vibration sieve so as to sandwich the vibration sieve. The low-frequency sound reduction according to claim 3 or 4, wherein the enclosure is formed of a single box, and the first unit installation zone and the second unit installation zone are provided on a side plate of the box. system. Each end of the enclosure is connected to a bottom plate of the first box and a top plate of the second box so that the first box, the second box, and their internal spaces communicate with each other. The first unit installation zone is provided on a side plate of the first box, and the second unit installation zone is provided on a side plate of the second box on the same side as the side plate. The low-frequency sound reduction system according to claim 3 or 4.

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