JP2008009420A - Ultra low frequency sound reducing device and soundproof house with the ultra low frequency sound reducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultra low frequency sound reducing device configured to easily suppress the leakage of the ultra low frequency sound from an opening which is disposed at a soundproof house and cannot be closed, and the soundproof house with the ultra low frequency sound reducing device. <P>SOLUTION: In the soundproof house H with the ultra low frequency sound reducing device in the opening through which the ultra low frequency sound emitted from the internally arranged device passes, the ultra low frequency sound reducing device includes a communicative connection tube 21 which has slits on its peripheral surface and is communicatively connected at its base end with the opening, and a resonance tube 22 which is mounted on the peripheral surface of the communicative connection tube 21 communicatively connected with the communicative connection tube via the slits, and the communicative connection tube is formed to have a spread-opening state from the base end toward the front end. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ultra-low frequency sound reduction device and a soundproof house equipped with the ultra-low frequency sound reduction device, and in particular, to reduce the ultra-low frequency sound generated during work at a construction site or the like. The present invention relates to a very low frequency sound reducing device and a soundproof house equipped with this very low frequency sound reducing device.

  Conventionally, in construction sites and the like, extremely annoying noise has been generated with work, and in order to make it difficult to make complaints due to leakage of these noises to the outside, various noise suppression measures have been taken in recent years. Yes.

  In particular, in underground excavation work such as subway construction, since water is used for excavation during the excavation, it is necessary to separate water from the sediment that contains water generated during excavation. Therefore, a vibration sieving machine that easily generates relatively large noise, vibration, and extremely low frequency sound is used for the separation work, and sufficient noise countermeasures are required.

  Therefore, a vibration sieve machine is usually installed inside a soundproof house on the ground, and earth and sand containing water generated during excavation is transported to the ground by a conveyor, etc., and the vibration sieve machine is used inside the soundproof house. By separating the earth and sand, noise including ultra-low frequency sound is prevented from leaking outside.

  In particular, a vibrating screen for separating earth and sand often uses a cylindrical screen with a rotational speed of about 1000 rpm, and therefore, very low frequency sound is likely to be generated. This ultra-low frequency sound cannot be silenced by a sound-proof wall of a general sound-proof house, and it has been proposed to use a sound-absorbing wall using a Helmholtz resonator to mute the ultra-low frequency sound (for example, , See Patent Document 1).

  Alternatively, it has also been proposed to install a plurality of vibrating screens in the soundproof house and attenuate each other with the respective ultra-low frequency sounds generated by the vibrating screens (see, for example, Patent Document 2).

Here, the ultra-low frequency sound is a sound of 20 Hz or less, which is a lower limit of a human audible sound range of 20 to 20 kHz, and is a low frequency sound that cannot be heard by human ears. However, although it cannot be heard directly by humans, it is known that when it propagates to a house, it may cause secondary noise due to vibration of window glass and fittings. Therefore, it is very important to prevent leakage of ultra-low frequency sound.
JP 2003-253627 A JP-A-10-57725

  In this way, for ultra-low frequency sound that needs to be suppressed, a sound barrier and a silencing mechanism have been proposed to quickly attenuate the generated ultra-low frequency sound, but a vibration sieve was installed. The soundproof house requires a discharge opening for discharging the earth and sand separated by the vibration sieve because of its structure, and it is difficult to prevent leakage of ultra-low frequency sound from this opening. It was.

  In view of such a current situation, the present inventors have conducted research and development to suppress leakage of ultra-low frequency sound from an opening that is provided in a soundproof house and cannot be closed, and have achieved the present invention. It is.

  The ultra-low frequency sound reducing device of the present invention is an ultra-low frequency sound reducing device provided in an opening through which an ultra-low frequency sound passes, and has a communication pipe having a slit on the peripheral surface and a base end connected to the opening. And a resonance pipe attached to the peripheral surface of the communication pipe while communicating with the communication pipe through the slit, and the communication pipe is expanded from the proximal end to the distal end.

Furthermore, the ultra-low frequency sound reducing device of the present invention is also characterized by the following points. That is,
(1) The resonance pipe is attached to the communication pipe with its longitudinal direction facing in a direction orthogonal to the longitudinal direction of the communication pipe.
(2) A blocking plate having an opening having the same shape as the opening is attached to the tip of the communication pipe.
(3) The longitudinal direction of the communication pipe is the horizontal direction, and the resonance pipe is provided along the vertical direction.
(4) A plurality of resonant tubes having different lengths are attached to the communication tube.
(5) The resonance tube has an adjusting means for adjusting the length.
(6) Ultra low frequency sound detecting means for detecting the sound pressure level for each frequency of the ultra low frequency sound is provided, and the length of the resonance tube is adjusted by the adjusting means based on the detection result of the ultra low frequency sound detecting means. A control unit is provided.

  The soundproof house of the present invention is a soundproof house in which a rectangular internal space is formed by a front side wall, a rear side wall, a left side wall, a right side wall, and a ceiling plate, and an opening is provided in the front side wall. At the same time, the opening portion is provided with an ultra-low frequency sound reducing device that suppresses leakage of ultra-low frequency sound emitted from the device arranged in the internal space.

Furthermore, the soundproof house of the present invention is also characterized by the following points. That is,
(1) A standing wave suppressing means for suppressing the generation of standing waves generated in the internal space is provided.
(2) The standing wave suppressing means is a flat plate arranged to be inclined at a predetermined angle with respect to at least any one inner surface of the rear side wall, the left side wall, the right side wall, and the ceiling plate.
(3) The inclination angle of the flat plate should be adjustable.

  According to the first aspect of the present invention, there is provided an ultra-low frequency sound reducing device provided in an opening through which ultra-low frequency sound passes, the communication pipe having a slit on the peripheral surface and having a proximal end connected to the opening. Resonance tube functioning as a Helmholtz resonator by connecting the communication tube with the communication tube through the slit and mounting the resonance tube on the peripheral surface of the communication tube, and expanding the communication tube from the base end to the tip It is possible to make the sound easy to mute by affecting the directivity characteristics of the ultra-low frequency sound passing through the opening by a synergistic effect of the muffling effect by the tube and the muffling effect of the expanded communicating pipe.

  According to a second aspect of the present invention, in the ultra-low frequency sound reducing device according to the first aspect, the resonance pipe is attached to the communication pipe in a direction perpendicular to the longitudinal direction of the communication pipe so as to resonate. The pipe can be easily attached to the communication pipe, and an ultra-low frequency sound reducing device with low manufacturing cost can be obtained. In addition, the arrangement can be such that the resonance tube having a relatively long dimension does not get in the way.

  According to the invention described in claim 3, in the ultra-low frequency sound reduction device according to claim 1 or 2, by attaching a closing plate having an opening having the same shape as the opening to the tip of the communication pipe, The silencing effect can be improved.

  According to a fourth aspect of the present invention, in the ultralow frequency sound reducing device according to any one of the first to third aspects, the longitudinal direction of the communication pipe is a horizontal direction, and the resonance pipe is provided along the vertical direction. Therefore, it is possible to prevent the resonance tube having a relatively long dimension from interfering.

  According to the fifth aspect of the present invention, in the ultra-low frequency sound reduction device according to any one of the first to fourth aspects, the plurality of resonance pipes having different lengths are attached to the communication pipe, thereby silencing the sound. The effect can be improved.

  According to the invention described in claim 6, in the ultra-low frequency sound reduction device according to any one of claims 1 to 4, by providing the adjustment means for adjusting the length of the resonance tube in the resonance tube. The length of the resonance tube can be adjusted according to the ultra-low frequency sound of the frequency to be silenced, and the silencing effect of the ultra-low frequency sound of the desired frequency can be improved.

  According to the seventh aspect of the present invention, in the ultra-low frequency sound reducing device according to the sixth aspect, the ultra-low frequency sound detecting means for detecting the sound pressure level for each frequency of the ultra-low frequency sound is provided, By providing a control unit that adjusts the length of the resonant tube by the adjusting means based on the detection result of the wave sound detecting means, this change occurs when the spectrum of the generated very low frequency sound changes with time. It is possible to follow, and the muffling effect can be improved.

  According to invention of Claim 8, it is a soundproof house which formed the rectangular-shaped internal space with the front side wall, the rear side wall, the left side wall, the right side wall, and the ceiling board, and the opening is formed in the front side wall. The ultra-low frequency sound reduction device according to any one of claims 1 to 7 is mounted on the opening portion to suppress leakage of ultra-low frequency sound emitted from the device arranged in the internal space. Affects the directional characteristics of ultra-low frequency sound passing through the opening by a synergistic effect of the silence effect of the resonance tube functioning as a Helmholtz resonator in the ultra-low frequency sound reduction device and the silence effect of the expanded communication tube It is possible to provide a soundproof house that can effectively silence the sound.

  According to the ninth aspect of the present invention, in the soundproof house according to the eighth aspect, the standing wave suppression means for suppressing the generation of the standing wave generated in the internal space of the soundproof house is provided, so that the It is possible to suppress the increase of the sound pressure of the low frequency sound and improve the silencing effect of the ultra low frequency sound.

  According to the invention described in claim 10, in the soundproof house according to claim 9, the standing wave suppressing means is provided on at least one inner surface of the rear side wall, the left side wall, the right side wall, and the ceiling plate. By using a flat plate inclined at a predetermined angle, it is possible to suppress the occurrence of standing waves without causing a significant increase in cost, and to improve the silencing effect of ultra-low frequency sound.

  According to the invention described in claim 11, in the soundproof house according to claim 10, when the spectrum of the generated ultra-low frequency sound changes with time by adjusting the angle of inclination of the flat plate, By adjusting the inclination angle of the flat plate following the change, it is possible to improve the silencing effect of the ultra-low frequency sound.

  In the soundproof house equipped with the ultralow frequency sound reducing device and the ultralow frequency sound reducing device of the present invention, the ultralow frequency sound reducing device is installed in the opening provided in the soundproof house, and is generated in the soundproof house. Thus, the very low frequency sound passing through the opening is muted.

  In particular, the soundproof house is provided with a standing wave suppression means that suppresses the generation of standing waves generated in the soundproof house itself, thereby suppressing the generation of standing waves. Since it can suppress that a sound pressure becomes high, the silencing effect of the very low frequency sound by a very low frequency sound reduction apparatus can be improved further.

  Specifically, as shown in FIG. 1, a soundproof house H having a rectangular internal space having a predetermined internal volume is provided with an opening 10 at a predetermined position. The low frequency sound reduction device 20 is installed.

  As shown in FIGS. 2 to 6, the ultra-low frequency sound reduction device 20 has a slit 23 at a predetermined position on the peripheral surface and communicates via the slit 23 with a communication pipe 21 having a base end connected to the opening 10. The resonance pipe 22 is mounted on the peripheral surface of the communication pipe 21 while communicating with the pipe 21. 2 is a front view of the ultra-low frequency sound reducing device 20, FIG. 3 is a rear view of the ultra-low frequency sound reducing device 20, FIG. 4 is an enlarged view of the main part of the XX section of FIG. 2, and FIG. FIG. 6 is an enlarged perspective view of the main part of the ultra-low frequency sound reducing device 20.

  In particular, the communication pipe 21 is expanded from the base end connected to the opening 10 toward the distal end. Normally, the opening 10 has a rectangular shape. As the pyramidal surface shape, a trapezoidal first surface 21-1 positioned vertically downward, a trapezoidal second surface 21-2 positioned vertically upward facing the first surface 21-1, A trapezoid-shaped third surface 21-3 located on the left side of the first surface 21-1, and the second surface 21-2, and a trapezoid-shaped third surface positioned on the right side of the first surface 21-1, and the second surface 21-2. It consists of four sides 21-4.

  The resonance tube 22 is a cylindrical body whose bottom is closed, and is attached to the outer surface of the first to fourth surfaces 21-1 to 4-4 with the longitudinal direction facing in a direction perpendicular to the longitudinal direction of the communication tube 21. 2 to 6, the resonance tube 22 has a rectangular tube shape, but is not limited to a rectangular tube shape, and may be, for example, a cylindrical shape.

  The resonance tube 22 communicates with the communication tube 21 through slits 23 provided at predetermined positions on the first to fourth surfaces 21-1 to 21-4 to form a Helmholtz resonator.

  2-6, two resonant tubes 22 are mounted on the first surface 21-1 and the second surface 21-2, respectively, and one resonance is performed on each of the third surface 21-3 and the fourth surface 21-4. Although the tubes 22 are attached, the number of the resonance tubes 22 is not limited to this, and a larger number of resonance tubes 22 may be attached as necessary.

  In particular, as shown in FIGS. 2 and 3, the resonance tubes 22 attached to the communication tube 21 do not necessarily have the same length, and the length of the resonance tube 22 is set to the frequency of the very low frequency sound to be silenced. A plurality of resonance tubes 22 having different lengths may be attached to the communication tube 21.

  Alternatively, as shown in FIG. 7, the resonance tube 22 ′ includes an inner tube 22′a having an end attached to the communication tube 21, and an outer tube 22′b slidably fitted to the inner tube 22′a. The length of the resonance tube 22 'can be adjusted by moving the outer tube 22'b forward and backward with respect to the inner tube 22'a, and the frequency of the very low frequency sound to be silenced can be adjusted. It may be variable.

  In particular, when the outer tube 22′b is moved forward and backward with respect to the inner tube 22′a, the spiral shaft 25 is rotatably mounted on the inner tube 22′a via the spiral shaft support 24, and the spiral shaft A movable body 26 screwed to 25 is attached to the outer tube 22'b, and the helical shaft 25 is rotated by a drive motor 27 attached to the helical shaft support 24 so that one of the movable bodies 26 with respect to the helical shaft 25 is The outer tube 22'b can be moved forward and backward by moving forward and backward.

  Furthermore, a microphone 31 is mounted at a predetermined position such as in the communication pipe 21, and the ultralow frequency sound passing through the opening 10 is sampled by the microphone 31 so that the sound pressure level for each frequency of the ultra low frequency sound is super low frequency. The length of the resonant tube 22 ′ passes through the opening 10 by detecting the wave sound detection means in the analysis unit 32 and controlling the drive motor 27 in the control unit 33 based on the detection result in the analysis unit 32. It may be adjustable according to the state of the very low frequency sound.

  As described above, the ultra-low frequency sound reduction device 20 is connected to the communication pipe 21 whose base end is connected to the opening 10 and the resonance mounted on the peripheral surface of the communication pipe 21 while communicating with the communication pipe 21 via the slit 23. By configuring with the tube 22, not only the silencing effect by the resonance tube 22 functioning as a Helmholtz resonator, but also the synergistic effect with the silencing effect of the expanded communication tube 21, as described later, the opening The directivity characteristics of the ultra-low frequency sound that passes through the sound can be influenced, and the silencing process can be facilitated.

  In particular, the resonance tube 22 is attached to the peripheral surface of the communication tube 21 with its longitudinal direction facing the direction orthogonal to the longitudinal direction of the communication tube 21, thereby facilitating the mounting structure of the resonance tube 22 to the communication tube 21. Therefore, the ultra-low frequency sound reducing device 20 with low manufacturing cost can be obtained.

  At this time, it is desirable to provide the resonance tube 22 along the vertical direction as much as possible. By providing the resonant tube 22 along the vertical direction, when the ultra-low frequency sound reduction device 20 is attached to the opening 10 of the soundproof house H, the resonant tube 22 is unlikely to become an obstacle, and the presence of the resonant tube 22 is a concern. Can be prevented, and the appearance can be improved.

  Moreover, when the ultra-low frequency sound reduction device 20 is actually installed in the soundproof house H, the resonance tube 22 mounted on the vertically lower side of the communication tube 21 is embedded in the ground as shown in FIG. Can be made inconspicuous. Further, since the resonance pipe 22 mounted on the vertical upper side of the communication pipe 21 is also arranged in the vertical direction along the wall surface of the soundproof house H, it can be made inconspicuous because it looks like a simple duct at first glance.

  On the other hand, as shown in FIG. 1, when the resonance tube 22 is attached to the communication tube 21 in the horizontal direction, the resonance tube 22 becomes very conspicuous. It is desirable to make the resonance tube 22 as short as possible.

  Alternatively, instead of being mounted on the communication pipe 21 in the horizontal direction, for example, the opening 10 formed in the soundproof house H has a regular hexagonal shape, and the communication pipe 21 has a hexagonal pyramid shape. The resonance tube 22 may be provided toward the bottom, and the resonance tube 22 may be disposed in two directions that form an angle of about 120 ° with the resonance tube 22 directed vertically downward.

  In addition, when mounting a plurality of resonance tubes 22 to the communication tube 21, by mounting a plurality of resonance tubes 22 with different lengths, the frequency range of the ultra-low frequency sound to be silenced can be expanded, The silencing effect can be improved.

  Alternatively, when the resonance tube 22 'is inserted into the outer tube 22'b, for example, so that the inner tube 22'a can be moved forward and backward, the resonance tube 22' can be moved forward and backward, and an ultra-low frequency sound can be generated. It is also possible to adjust the frequency of the ultra-low frequency sound to be silenced by adjusting the length of the resonance tube 22 ′ according to the state of occurrence.

  In particular, when separating earth and sand with a vibrating sieve, the peak of the frequency of the very low frequency sound generated may vary depending on the state of the earth and sand put into the vibrating sieve and the amount of earth and sand. By adjusting the length of the resonance tube 22 ′ in accordance with the peak, it is possible to improve the silencing efficiency of the ultra-low frequency sound.

  In addition, as shown in FIG. 8, when a closing plate 29 having an opening 28 having the same shape as the opening 10 in the soundproof house H is attached to the tip of the communication pipe 21, the low frequency sound on the low frequency side is reduced. The efficiency can be improved, and the ultra-low frequency sound reduction device 20 with higher noise reduction performance can be obtained.

  On the other hand, the standing wave suppression means provided in the soundproof house may be a structure that can suppress the generation of standing waves. Specifically, the standing wave suppression means is provided by reducing the symmetry of the internal space of the soundproof house. Wave generation can be suppressed.

  That is, since the soundproof house has a generally assembled structure, the front side wall, the rear side wall, the left side wall, the right side wall, and the ceiling plate form a rectangular internal space, In order to reduce the symmetry of the internal space, for example, as shown in FIG. 9, the rear flat plate L1 disposed at a predetermined angle with respect to the inner side surface of the rear side wall h1 of the soundproof house H, or FIG. As shown in FIG. 11, the side plate L2 is disposed at a predetermined angle with respect to the inner surface of the left side wall h2 of the soundproof house H, or the inner surface of the ceiling plate h3 of the soundproof house H as shown in FIG. On the other hand, the upper flat plate L3 arranged to be inclined at a predetermined angle can be used as the standing wave suppressing means. Here, the opening 10 is provided in the front side wall h4 of the soundproof house H.

  FIG. 9 is a schematic plan view of the soundproof house H formed in a rectangular shape. The soundproof house H has a predetermined shape with respect to the inner side surface on the inner side surface of the rear side wall h1 facing the front side wall h4 provided with the opening 10. A rear flat plate L1 inclined by an angle is provided.

  The rear flat plate L1 is desirably formed of a material having a strength that does not cause vibration in the rear flat plate L1 itself and a large internal loss, and is preferably a plate having a thickness of about several centimeters.

  In the present embodiment, the rear flat plate L1 has one end pivotably pivoted in the vicinity of a corner formed by the right side wall h5 and the rear side wall h1 facing the left side wall h2 of the soundproof house H. The rear flat plate L1 is inclined at a predetermined angle with respect to the inner side surface of the rear side wall h1.

  By providing the rear flat plate L1 in this way, the symmetry of the internal space of the soundproof house H can be reduced, and standing waves can be suppressed from being generated in the soundproof house H. It is possible to suppress the increase of the sound pressure of the wave sound and improve the silencing effect of the ultra-low frequency sound.

  As shown in FIG. 9, the rear flat plate L1 is not only formed in one large size so as to have substantially the same area as the inner surface of the rear side wall h1, but for example, as shown in FIG. The first rear flat plate L1 and the second rear flat plate L2 that are approximately half the size of the above may be provided side by side, or as shown in FIG. A plurality of convex walls 41 may be disposed on the inner side surface of the rear side wall h1. However, for ultra-low frequency sound, it is more effective to provide a large area flat plate than to provide a large number of small area flat plates. The rear flat plate L1 may be appropriately provided with an opening for ventilation or an opening for daylighting.

  In the present embodiment, the edge on the right side wall h5 side of the rear flat plate L1 is brought close to the rear side wall h1, while the end edge on the left side wall h2 side of the rear flat plate L1 is separated from the rear side wall h1 to be inclined. Conversely, the end edge on the left side wall h2 side of the rear flat plate L1 may be brought close to the rear side wall h1, while the end edge on the right side wall h5 side of the rear flat plate L1 may be separated from the rear side wall h1 to be inclined. However, in the direction perpendicular to the opening surface formed by the opening 10 provided in the front side wall h4 of the soundproof house H, especially the internal space of the soundproof house H is as large as possible, and the air movement in that space is not obstructed Therefore, in the present embodiment, the edge on the right side wall h5 side of the rear flat plate L1 is brought close to the rear side wall h1, while the end edge on the left side wall h2 side of the rear flat plate L1 is separated from the rear side wall h1 and inclined. It is in the shape.

  The rear plate L1 is equipped with an actuator equipped with a rod that can be appropriately expanded and contracted, and the rear plate L1 can be rotated by expanding and contracting the rod of this actuator, and the inclination to the inner surface of the rear side wall h1 The angle may be adjustable. In particular, the ultra-low frequency sound passing through the opening 10 is sampled by the microphone 31 mounted in a predetermined position such as the inside of the communication pipe 21 described above, and the sound pressure level for each frequency of the ultra-low frequency sound is detected by the analysis unit 32, The angle of the rear flat plate L1 may be adjusted in accordance with the state of the ultra-low frequency sound passing through the opening 10 by controlling the actuator by the control unit 33 based on the detection result. Note that the rotation operation means of the rear flat plate L1 is not limited to an actuator, and an appropriate drive mechanism can be used.

  FIG. 10 is a schematic plan view of the soundproof house H formed in a rectangular shape, and the left side wall h2 provided between the front side wall h4 provided with the opening 10 and the rear side wall h1 facing the front side wall h4. Of the right side wall h5, a side flat plate L2 is provided on the left side wall h2 side.

  In particular, in this embodiment, since the opening 10 is provided near the right side wall h5 of the front side wall h4, it is in the direction perpendicular to the opening surface formed by the opening 10 as described above, and in particular, the internal space of the soundproof house H. Since it is desirable that the space be as large as possible so that the movement of air in the space is not hindered, the side plate L2 is provided on the left side wall h2 side that can be provided as far as possible from the opening 10.

  For the same reason, in the present embodiment, the side flat plate L2 is pivotally attached to one side edge in the vicinity of the corner formed by the rear side wall h1 and the left side wall h2, and the side flat plate L2. Is inclined at a predetermined angle with respect to the inner surface of the left side wall h2.

  The side flat plate L2 is also preferably made of a material having a strength that does not cause vibration in the side flat plate L2 itself and a large internal loss, and is preferably a plate having a thickness of about several centimeters.

  Even when the side flat plate L2 is provided in this way, the symmetry of the internal space of the soundproof house H can be reduced and the occurrence of standing waves in the soundproof house H can be suppressed. It is possible to suppress the increase of the sound pressure of the low frequency sound and improve the silencing effect of the ultra low frequency sound.

  The side flat plate L2 is not only formed in a single large size, but may be provided with a plurality of flat plates having a small area, or a convex shape with a cross-sectional mountain shape that is convex toward the inside of the soundproof house H. A plurality of walls may be arranged on the inner side surface of the left side wall h2, and the side flat plate L2 may be rotated by using an appropriate drive mechanism.

  FIG. 11 is a schematic front view of the soundproof house H formed in a rectangular shape, and is provided with an upper flat plate L3 that is disposed at a predetermined angle with respect to the inner surface of the ceiling plate h3 of the soundproof house H. Is.

  In particular, since it is desirable that the interior space of the soundproof house H be as large as possible in the direction perpendicular to the opening surface formed by the opening 10 as described above, the movement of air in the space should not be hindered. L3 is pivotally pivoted at one end in the vicinity of the corner formed by the rear side wall h1 and the ceiling plate h3, so that the upper flat plate L3 is at a predetermined angle with respect to the inner surface of the ceiling plate h3. Inclined state.

  The upper flat plate L3 is also preferably formed of a material having a strength that does not cause vibration in the upper flat plate L3 itself and a large internal loss, and preferably a plate having a thickness of about several centimeters.

  Even when the upper flat plate L3 is provided in this way, the symmetry of the internal space of the soundproof house H can be reduced and the occurrence of standing waves in the soundproof house H can be suppressed. It is possible to suppress the increase in the sound pressure of the frequency sound and improve the silencing effect of the ultra-low frequency sound.

  The upper flat plate L3 is not only formed into a single large sheet, but may be provided with a plurality of flat plates with a small area, or a convex wall with a mountain-shaped cross section that is convex toward the interior of the soundproof house H. May be arranged on the inner side surface of the ceiling plate h3, and the upper flat plate L3 may be rotated by using an appropriate drive mechanism.

  In the interior space of the soundproof house H, any one of the rear flat plate L1, the side flat plate L2, and the upper flat plate L3 may be provided, or these may be provided in appropriate combination.

  In the following, as an embodiment of the present invention, an embodiment using a model having a scale of 1/12 of the actual product will be described in detail.

  In this embodiment, as shown in FIG. 14, the soundproof house H is a rectangular body having a width of 650 mm, a height of 810 mm, and a depth of 1000 mm, and is constituted by an acrylic plate having a thickness of 10 mm. The acrylic plate was adopted because the sound equivalent loss TL is close to the equivalent loss of the actual outer plate. In addition, since the strength at the time of assembly is not enough with the acrylic plate alone, an L-angle frame is assembled into a rectangular parallelepiped, the acrylic plate is screwed to this frame, and the gap is filled with an acoustic putty to prevent sound leakage. ing.

  An opening 10 is provided on one side of the soundproofing house H in the same manner as the opening through which the earth and sand are actually carried out. The opening 10 has a rectangular shape with a length of 82 mm and a width of 163 mm. The distance from the adjacent side wall in the soundproof house H in the central portion in the lateral direction was 107.7 mm. The position and size of the opening 10 was determined from a general soundproof house currently used.

  Inside the soundproof house H, a structure (not shown) imitating a vibration sieving machine was installed, and a small speaker with a diameter of 80 mm serving as a source of ultra-low frequency sound was installed in this structure. In this embodiment, two structures equipped with small speakers are arranged inside the soundproof house H.

  The ultra-low frequency sound reduction device 20 to be installed in the opening 10 of the soundproof house H is the ultra-low frequency sound reduction device 20 shown in FIGS. 2 to 6, and has a slit 23 at a predetermined position on the peripheral surface. Resonance attached to the peripheral surface of the communication tube 21 in communication with the communication tube 21 communicating with the opening 10 and the communication tube 21 through the slit 23, with the longitudinal direction facing the direction perpendicular to the longitudinal direction of the communication tube 21 It consists of a tube 22.

  The resonance tube 22 constitutes a Helmholtz resonator. In the Helmholtz resonator, as shown in FIG. 15, a cavity 13 having a predetermined volume V connected to a wall surface 11 through a hole 12 having a diameter d and a length h is provided. Sound is absorbed by using the air in the hole 12 part as a `` weight '' and the air confined in the cavity 13 in a space smaller than the wavelength as a `` spring ''. When the air mass is incident from the front of the cavity 13, the air mass in the hole 12 is vibrated vigorously, and the air mass vibrates with the inside of the pore 12 to convert the vibration energy into heat energy and absorb the sound. It is.

  This resonance frequency fr is expressed by the following equation.

  Here, S is the cross-sectional area of the hole 12 (S = πd2 / 4). “0.8d” is called pipe end correction, and takes into account correction of the additional mass of external air at the inlet / outlet of the hole 12.

  The resonance frequency in the case of a finite-length slit differs from the tube end correction of equation (1) and is expressed by the following equation.

  Here, a is the length dimension of the slit 23 and b is the width dimension of the slit 23.

  Considering the cavity 13 as an elongated shape, rewriting equation (2) with the aperture ratio P of the cavity 13 and the volume V of the cavity 13, the aperture ratio P = the sectional area of the slit 23 / the bottom sectional area of the cavity 13 = S / D, the volume of the cavity 13 V = the length of the cavity 13 × the bottom cross-sectional area of the cavity 13 = L × D.

  In this embodiment, the resonance frequency is set to 192 Hz in consideration of the scale ratio, the thickness of the communication tube 21 to which the resonance tube 22 is attached is 5 mm (h = 5 mm), and the length of the slit 23 is 55.5 mm (a = 55.5 mm), and the cross-sectional area of the resonance tube 22 is constant 55.5 mm × 97.5 mm, and the length L of the resonance tube 22, the aperture ratio P of the slit 23, and the slit 23 The width dimension b was calculated. The calculation results are shown in FIG. Based on FIG. 16, the aperture ratio of the slit 23 was 0.16, and the width of the slit 23 was 16 mm. The length of the resonance tube 22 was 475.53 mm. In this embodiment, the lengths of the resonance tubes 22 attached to the communication tube 21 are all the same. The length of the resonance tube 22 is the length from the position of the slit 23 provided in the communication tube 21.

  In this embodiment, the communication pipe 21 includes a trapezoidal first surface 21-1 positioned vertically downward, and a trapezoidal second surface positioned vertically upward facing the first surface 21-1. 21-2, a trapezoidal third surface 21-3 located on the left side of the first surface 21-1 and the second surface 21-2, and on the right side of the first surface 21-1 and the second surface 21-2 It is an expanded tube whose tip is expanded into a quadrangular pyramid shape with the trapezoidal shaped fourth surface 21-4, and the base end side is a 163 mm × 82 mm rectangular shape having the same dimensions as the opening of the soundproof house H The tip side is opened in a rectangular shape of 385 mm × 300 mm, and the length is 113 mm.

  Two slits 23 are arranged in parallel on the first surface 21-1 and the second surface 21-2, respectively, and the outer surfaces of the first surface 21-1 and the second surface 21-2 are respectively inserted through the slits 23. Two communication pipes 22 communicating with the communication pipe 21 are mounted, and one slit is disposed on each of the third surface 21-3 and the fourth surface 21-4, and the third surface 21-3 and the fourth surface 21-4 are arranged. A single communicating tube 22 communicating with the communicating tube 21 through a slit 23 is attached to the outer surface of the surface 21-4.

  The low-frequency noise output from a small speaker is 1/3 octave band center frequency 12.5Hz, 16.0Hz, 20.0Hz, 25.0Hz in the actual soundproof house. As the measurement frequency in the experiment, a 1/3 octave band center frequency of 160 Hz, 200 Hz, 250 Hz, or 315 Hz was used.

  Pink noise was generated from a small speaker to simulate low frequency noise, and an audio test CD (AUDIO TEST CD-1) was used as a source of pink noise. The signal is pink noise with a level of -20 dB, 20-20 kHz. The signal generated from the CD player was amplified by a 100 W × 2 amplifier to drive a small speaker.

  The total sound pressure level generated in the soundproof house H was approximately 90 dB (A), and all sound pressure levels were the same in the measurement. The background noise level in the measurement chamber was 20 dB (A) or less. Note that the noise level in the absence of a measurement signal was approximately 42 dB (A) in the soundproof house H due to residual noise in an amplifier for driving a small speaker. This value was judged to be sufficiently measurable because the level difference from the signal was approximately 50 dB.

  The sound pressure measurement inside and outside the soundproof house H was performed using four 1/2 inch measurement microphones (Ono Sokki, MI-1233) and an FFT measurement device (Ono Sokki, DS-2100). The measured signal was subjected to 1/3 octave band analysis, and the sound pressure level for each frequency was measured.

  The sound pressure measurement is performed at the position shown in FIG. 17 which is a plan view of the soundproof house H when FIG. 14 is a front view, and the reference length is 82 mm of the height dimension of the opening 10, and is doubled. Measurements were taken at 5x and 10x distances. In all cases, the height of the microphone used for measurement was 134 mm, and the distance from the bottom of the soundproof house H to the center of the opening 10 was used.

  The sound pressure attenuation inside and outside the soundproof house H when the ultra-low frequency sound reduction device 20 is not installed in the opening 10, and the characteristics in the P2 direction with reference to the attenuation amount in the P3 direction in FIG. FIG. 19 shows the characteristics in the P5 direction.

  The sound pressure attenuation inside and outside the soundproof house H when the ultra-low frequency sound reduction device 20 is installed in the opening 10 as shown in FIG. 14, and in the P2 direction based on the attenuation amount in the P3 direction in FIG. FIG. 20 shows the characteristics and FIG. 21 shows the characteristics in the P5 direction.

  A very low frequency sound reducing device 20 is attached to the opening 10 as shown in FIG. 14, and the opening of the soundproof house H is provided at the tip of the communication pipe 21 in the very low frequency sound reducing device 20 as shown in FIG. FIG. 17 is a diagram illustrating the sound pressure attenuation inside and outside the soundproof house H when the closing plate 29 having the opening 28 having the same shape as that of FIG. 10 is mounted, and the characteristic in the P2 direction with reference to the attenuation amount in the P3 direction in FIG. FIG. 23 shows the characteristics in the P5 direction. 18 to 23 also show straight lines of −6 dB / dd and −3 dB / dd for reference.

  18 to 23, it can be seen that there is no difference in the tendency of attenuation depending on the presence or absence of the ultra-low frequency sound reducing device 20.

  On the other hand, the attenuation in the P5 direction is 5 times the basic length and the center frequency is 315 Hz, and when the ultra-low frequency sound reduction device 20 is attached to the opening 10 than when the ultra-low frequency sound reduction device 20 is not installed. Similarly, it can be seen that the ultra low frequency sound reduction device 20 having the closing plate 29 attached thereto at -1 dB is -5 dB, and the noise tends to increase at -5 dB. The same tendency is shown for other places and frequencies.

  The attenuation in the P2 direction is when the very low frequency sound reduction device 20 equipped with the closing plate 29 is installed in the opening 10, and the basic length is 2 dB at the center frequency 160 Hz and twice the basic length, and the basic length at the center frequency 160 Hz. It can be seen that an attenuation effect of 3 dB can be obtained at 5 times as high as.

  From this, it is possible to influence the directivity characteristics of the ultra-low frequency sound by installing the ultra-low frequency sound reduction device 20 in the opening 10, and to mute the sound by arranging a further silencing structure based on this directivity characteristic In particular, the ultra-low frequency sound reduction device 20 equipped with the closing plate 29 can improve the silencing effect of the ultra-low frequency sound on the low frequency side with the ultra-low frequency sound reduction device 20. it can.

  Below, the Example at the time of providing a standing wave suppression means in the soundproof house H is described. In addition, in order to make it easy to confirm the effect of the standing wave suppressing means, the present embodiment was carried out without providing an ultra-low frequency sound reduction device.

  The soundproof house H of this example was a rectangular body having a width of 670 mm, a height of 810 mm, and a depth of 1000 mm, and was composed of an acrylic plate having a thickness of 10 mm. This acrylic plate was mounted on an L-angle frame assembled in a rectangular parallelepiped and arranged in a rectangular shape. In this case, the standing wave generated in the depth direction is 173 Hz, the standing wave generated in the width direction is 262 Hz, and the standing wave generated in the height direction is 210 Hz.

  The front side wall h4 of the soundproof house H is provided with a rectangular opening 10 having a width of 166 mm and a length of 83 mm centering on a position of 124.5 mm in height, 118 mm from the inner surface of the right side wall h5.

  Inside the soundproof house H, a structure (not shown) imitating a vibration sieving machine was installed, and a small speaker with a diameter of 80 mm serving as a source of ultra-low frequency sound was installed in this structure. In this embodiment, two structures equipped with small speakers are arranged inside the soundproof house H.

  As in the case of Example 1, the low-frequency noise output from the small speaker was measured using the 1/3 octave band center frequencies of 160 Hz, 200 Hz, 250 Hz, and 315 Hz.

  Pink noise was generated from a small speaker to simulate low frequency noise, and an audio test CD (AUDIO TEST CD-1) was used as a source of pink noise. The signal is pink noise with a level of -20 dB, 20-20 kHz. The signal generated from the CD player was amplified by a 100 W × 2 amplifier to drive a small speaker.

  The sound pressure in the soundproof house H is measured at the center of the right side wall h5 in the width direction, at a height of 124.5 mm and at a position 50 mm from the inner side of the right side wall h5, and a microphone preamplifier (microphone preamplifier ( Sound pressure spectrum data was generated by performing FFT analysis using MI-3110) manufactured by Ono Sokki.

  FIG. 24 shows the case where the rear flat plate L1 is disposed at a predetermined angle with respect to the inner surface of the rear side wall h1 of the soundproof house H as shown in FIG. 9, and the inclination angle θ = 6.15 °. , 7.45 ° and 8.75 ° are graphs showing the sound pressure reduction amount by the rear flat plate L1 in each case. For the rear flat plate L1, a vinyl chloride flat plate having a thickness of 5 mm was used.

  In this case, a reduction effect of about 7 to 15 dB was obtained at a center frequency of 160 Hz, and a reduction effect of about 2 to 3 dB was obtained at a center frequency of 200 Hz. In particular, a reduction effect of 3 dB was obtained when θ = 6.15 °.

  FIG. 25 shows the case where the side flat plate L2 is disposed at a predetermined angle with respect to the inner side surface of the left side wall h2 of the soundproof house H as shown in FIG. 10, and the inclination angle Φ = 1.91. It is the graph which showed the amount of sound pressure reduction by the side flat plate L2 in each case as °, 3.81 °, and 5.73 °. The side flat plate L2 was a vinyl chloride flat plate having a thickness of 5 mm.

  In this case, if the angle is increased, the reduction effect is high at a center frequency of 160 Hz, a reduction effect of about 8 dB is obtained at Φ = 5.73 °, and is highest at Φ = 3.81 ° at a center frequency of 200 Hz. A reduction effect of about 5 dB was obtained.

  FIG. 26 shows the case where the upper flat plate L3 is disposed at a predetermined angle with respect to the inner surface of the ceiling plate h3 of the soundproof house H as shown in FIG. 11, and the inclination angle γ = 1.91 °. It is the graph which showed the amount of sound pressure reduction by the upper flat plate L3 in each case as 3.81 degrees and 5.73 degrees. As the upper flat plate L3, a flat plate made of vinyl chloride having a thickness of 5 mm was used.

  In this case, a reduction effect of about 2 to 4 dB was obtained at the center frequencies of 160 Hz and 250 Hz. However, no reduction effect was obtained at a center frequency of 200 Hz.

  As described above, it is possible to reduce the sound pressure of the standing wave in the soundproof house H by providing a flat plate in the interior space of the soundproof house H. It is possible to improve the silencing effect of the low frequency sound.

It is a side view of the soundproof house equipped with the ultra-low frequency sound reduction device according to the embodiment of the present invention. It is a front view of the very low frequency sound reduction device concerning the embodiment of the present invention. It is a rear view of the very low frequency sound reduction device concerning the embodiment of the present invention. It is a principal part enlarged view of the XX cross section of FIG. FIG. 3 is an enlarged view of a main part of the YY cross section of FIG. 2. It is a principal part expansion perspective view of the ultra-low frequency sound reduction device which concerns on embodiment of this invention. It is explanatory drawing of the resonance pipe which expands / contracts. It is a principal part expansion perspective view of an ultra-low frequency sound reduction device which attaches a closure board to the tip of a communicating pipe. It is explanatory drawing of the arrangement | positioning state of the rear flat plate by the plane schematic diagram of a soundproof house. It is explanatory drawing of the arrangement | positioning state of the side part flat plate by the plane schematic diagram of a soundproof house. It is explanatory drawing of the arrangement | positioning state of the upper flat plate by the plane schematic diagram of a soundproof house. It is explanatory drawing of the modification of a rear part flat plate. It is explanatory drawing of the modification of a rear part flat plate. It is a front view of the soundproof house equipped with the ultra low frequency sound reduction device. It is explanatory drawing of a Helmholtz resonator. It is a graph which shows the calculation result of the length of a resonant tube, the aperture ratio of a slit, and the width dimension of a slit. It is explanatory drawing of a sound pressure measurement position. It is a graph which shows the characteristic of the P2 direction on the basis of the attenuation amount of a P3 direction, which is the sound pressure attenuation inside and outside the soundproof house when the ultra low frequency sound reduction device is not attached to the opening. It is a graph which shows the characteristic of the P5 direction on the basis of the attenuation amount of the P3 direction, which is the sound pressure attenuation inside and outside the soundproof house when the ultra low frequency sound reduction device is not attached to the opening. It is a graph which shows the characteristic of the P2 direction on the basis of the attenuation amount of the P3 direction, which is the sound pressure attenuation inside and outside the soundproof house when the ultra low frequency sound reduction device is attached to the opening. It is a graph which shows the characteristic of the P5 direction on the basis of the attenuation amount of the P3 direction, which is the sound pressure attenuation inside and outside the soundproof house when the ultra low frequency sound reduction device is attached to the opening. A graph showing sound pressure attenuation inside and outside the soundproof house when a blocking plate is attached to the end of the communication pipe and an ultra-low frequency sound reduction device is attached to the opening, and shows characteristics in the P2 direction with reference to the attenuation amount in the P3 direction It is. A graph showing sound pressure attenuation inside and outside the soundproof house when a blocking plate is attached to the end of the communication pipe and an ultra-low frequency sound reduction device is attached to the opening, and shows characteristics in the P5 direction with reference to the attenuation amount in the P3 direction It is. It is a graph which shows the sound pressure reduction effect by a rear flat plate. It is a graph which shows the sound pressure reduction effect by a side part flat plate. It is a graph which shows the sound pressure reduction effect by an upper flat plate.

Explanation of symbols

H Soundproof House
10 opening
21 Communication pipe
22 Resonant tube
23 Slit
21-1 1st page
21-2 Second side
21-3 Third side
21-4 4th page

Claims (11)

An ultra-low frequency sound reduction device provided in an opening through which ultra-low frequency sound passes,
A communication pipe having a slit on the peripheral surface and having a base end connected to the opening;
A resonance pipe mounted on the peripheral surface of the communication pipe while communicating with the communication pipe through the slit;
The communication pipe is an ultra-low frequency sound reduction device in which the communication pipe is expanded from the base end to the tip.   2. The ultra-low frequency sound reduction device according to claim 1, wherein the resonance tube is attached to the communication tube with its longitudinal direction oriented in a direction orthogonal to the longitudinal direction of the communication tube.   The ultra-low frequency sound reduction device according to claim 1 or 2, wherein a blocking plate having an opening having the same shape as the opening is attached to a tip of the communication pipe.   The ultra-low frequency sound reduction device according to any one of claims 1 to 3, wherein a longitudinal direction of the communication pipe is a horizontal direction, and the resonance pipe is provided along a vertical direction.   The ultra-low frequency sound reduction device according to any one of claims 1 to 4, wherein a plurality of resonance tubes having different lengths are attached to the communication tube.   The ultra-low frequency sound reducing device according to any one of claims 1 to 4, wherein the resonance tube includes an adjusting unit that adjusts a length.   An ultra-low frequency sound detecting means for detecting a sound pressure level for each frequency of the ultra-low frequency sound is provided, and the length of the resonance tube is adjusted by the adjusting means based on a detection result of the ultra-low frequency sound detecting means. The ultra-low frequency sound reduction device according to claim 6, further comprising a control unit that performs the control. A soundproof house in which a rectangular internal space is formed by a front side wall, a rear side wall, a left side wall, a right side wall, and a ceiling board,
Providing an opening in the front side wall;
The soundproof house in which the ultra-low frequency sound reducing device according to any one of claims 1 to 7 is mounted in the opening portion to suppress leakage of ultra-low frequency sound emitted from a device arranged in the internal space.   The soundproof house according to claim 8, further comprising a standing wave suppressing unit that suppresses generation of a standing wave generated in the internal space.   The standing wave suppressing means is a flat plate disposed at a predetermined angle with respect to at least one inner surface of the rear side wall, the left side wall, the right side wall, and the ceiling plate. The soundproof house according to claim 9. The soundproof house according to claim 10, wherein an angle of inclination of the flat plate is adjustable.

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