JP3658644B2 - Reduction structure of traffic noise radiated upward - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a structure for reducing traffic noise on a road or railway having walls on both sides and an opening at the top.
[0002]
[Prior art]
  In order to prevent noise on expressways and railways, either a straight type soundproof wall or a soundproof wall with a reversing structure at the top end is installed on both sides of the road or railroad. A method of installing a sound absorbing plate or a method of covering with a wall and a ceiling on both sides has been adopted.
[0003]
  Tunnel-type roads with a ceiling or covering at the top are highly soundproof,(1)Exhaust equipment is required to fill the exhaust gas.(2)There was a problem of requiring lighting equipment. As a method for solving these problems, for example, in Japanese Patent Publication No. 54-18492, a tunnel-like soundproof wall is provided so as to surround the roadway, and a gap structure (opening portion) is formed so that the outside can be seen on the soundproof wall. ) Is described. According to this method, the problem of exhaust and lighting can be almost solved, but sound is emitted as it is from the opening provided in the soundproof wall and radiated to the surroundings including the side of the road. It is.
[0004]
  On the other hand, Japanese Patent Application Laid-Open No. 49-17026 describes that one or a plurality of strip-shaped sound absorbing plates are vertically installed in an upper opening portion of a road having a moat split structure along the extending direction of the road. According to the publication, since the sound colliding with the sound absorbing plate disappears or attenuates, the horizontal component of the sound generated on the road is reduced, and noise transmitted to houses along the road can be reduced.
  Japanese Patent Application Laid-Open No. 55-11705 discloses an assembly of a large number of cylindrical cells made of a sound absorbing material or the like that are opened in the vertical direction at the upper opening of a road having soundproof walls on either side or a moat structure. It is described to install. According to the publication, sound having a directivity at an angle close to or perpendicular to it exits the cylindrical cell as it is, but other sounds collide with the inner wall of the cylindrical cell, or repeatedly collide and attenuate. The sound radiated from the opening has less directivity to the side of the road, and the noise on the side of the road can be reduced.
[0005]
[Problems to be solved by the invention]
  By the way, in recent years, a high-rise building has been constructed in the vicinity of the moat split road, and traffic noise may be a problem on the upper floor. In this case, the sound pressure distribution around the Horiwara road was simulated by numerical analysis using the well-known boundary element method (Reference: Proceedings of the Japan Society of Mechanical Engineers (C) Vol.60, No.453 (May 1984) ) P.848-856). FIG. 26 (b) shows the simulation result of the sound field observed on the Horiwara road shown in FIG. 26 (a), within the Horiwari road when the sound source is arranged in S, and in the range of 80m in width and 40m in the ground surface. . The analysis target moat split road has an overall width W1: 20.5 m, a height to the ceiling H1: 7.0 m, an opening width W2: 9.5 m, an existing sound absorbing plate height h1: 4 m, from the ceiling The height H2 to the ground surface was 2.5 m, the height of the block wall H3 was 1.8 m, and the frequency of the sound source was 1000 Hz. From this simulation result, it was found that the sound field has a wide spread angle such that the sound wave is emitted to the side of the road as it goes upward.
[0006]
  As a method of suppressing the spread of this sound wave, as shown in FIG. 27, a plurality of rows of sound absorbing plates (height h2: 2.7 m, width t2: 0, 2 m, both sides at the opening of a moat split road) When the sound absorbing surface total length: 43.2 m) is installed vertically along the extending direction of the road (a), the horizontal direction is the same as described in JP-A-49-17026 or JP-A-55-11705. Since sound with components collides with the sound-absorbing plate or attenuates by repeated collisions, the directivity to the side of the sound radiated from the opening through the sound-absorbing plate is weakened, and the spread to the side of the road is suppressed. (B). However, in order to realize a sufficient damping effect, it is necessary to arrange a large number of sound absorbing plates having a considerable vertical length as described above, which causes a problem in economy.
[0007]
  The present invention has been made in view of the above-described problems of the prior art, and is economical in reducing traffic noise radiated upward from an opening in a road or a railway having walls on both sides and having openings in the upper part. The object is to obtain a structure for reducing traffic noise that does not significantly impede natural ventilation and lighting.
[0008]
[Means for Solving the Problems]
  In the present invention, in order to efficiently reduce traffic noise radiated upward in a road or railway having both sides walls and openings in the upper part, instead of installing the sound absorbing surface of the sound absorbing plate in the vertical direction, Multiple sound absorbersSound absorption surface is horizontalIt installs so that it may become, and it may install so that adjacent sound absorption boards may mutually space.
  Thereby, the area where the direct sound radiated upward from the traffic noise source collides with the sound absorbing surface, that is, the effective sound absorbing area can be widened, and the sound is efficiently absorbed. Moreover, since there is a gap between adjacent sound absorbing plates, natural ventilation and lighting are ensured.
[0009]
  Specifically, the reduction structure of the present invention is:(1)When the cross section perpendicular to the extension direction of the road or railway is viewed, a plurality of sound-absorbing plates having a downward sound-absorbing surface that is horizontal in the opening are installed at intervals.One of the wide surfaces of the sound absorbing plate is the sound absorbing surface, and both side surfaces are also sound absorbing surfaces. The sound absorbing plate is composed of a sound absorbing material and a frame surrounding the sound absorbing material, and the back of the frame without holes. Face plate Shields the back side of the sound absorbing materialThat's it. Or(2)A plurality of sound-absorbing plates having a downward sound-absorbing surface that is horizontal in the opening are spaced apart from each other and installed in multiple stages above and belowThe vertical projection of the sound absorbing plate is substantially in contact with or partially overlapping, and one of the wide surfaces of the sound absorbing plate is the sound absorbing surface, and the sound absorbing plate is composed of a sound absorbing material and a frame surrounding the sound absorbing material. The back plate having no holes in the frame shields the back side of the sound absorbing material.That's it.
[0010]
  In this reduction structure, the wide surface of the sound absorbing plate is used as a sound absorbing surface, and the sound absorbing surface is disposed so as to be horizontal downward. For this reason, the sound absorption area with respect to a direct wave is large. When both side surfaces are sound absorbing surfaces, the sound absorbing area is further increased.
In this reduction structure, the plurality of sound absorbing plates are installed at intervals. For this reason, natural ventilation and lighting can be secured, but on the other hand, direct sound and reflected sound are radiated upward from the gap. However, by installing a plurality of sound absorbing plates in multiple stages above and below and making the vertical projections almost touch each other or partially overlap, the upper sound absorbing plate absorbs it and attenuates the sound efficiently. be able to.
Further, in this reduction structure, the sound absorbing plate can be installed along the extending direction of the road or railway. In this case, the noise reduction effect to the side is large, and a uniform noise reduction effect can be obtained over the entire area along the extending direction.
[0011]
  In the reduction structure, when the horizontal interval of the sound absorbing plates covering the openings is reduced, or when the sound absorbing plates are installed in multiple stages, the light to the road space below is correspondingly blocked. To compensate for this decrease in daylighting, the back surface of the sound absorbing plate is made of a material that reflects sunlight as necessary (for example, the back plate covering the back surface of the sound absorbing material is made of aluminum). Can do. The same applies to the sound-absorbing surface (for example, a porous plate disposed on the front surface of the sound-absorbing material is made of aluminum), and both sides of the sound-absorbing plate can be appropriately made of a material that reflects sunlight.HorizontalA plurality of sound absorbing plates having sound absorbing surfacesMultiple steps up and downWhen installed, sunlight is scattered between the lower back surface and the upper sound absorbing surface, and the light is easily guided to the road space below. As the shape of the back side surface that reflects and scatters sunlight, for example, a flat surface or a convex shape can be considered.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, with reference to FIGS. 1-25, the specific example of the reduction structure of the traffic noise which concerns on this inventionAnd reference examplesSome are explained.
  The structure shown in FIG. 1 is a structure in which a plurality of sound absorbing plates having inclined sound absorbing surfaces are installed at the opening of a moat split road along the road extension direction and at the same interval a in the horizontal direction. In particular, the reduction of noise on the left side of the road is emphasized, and the sound absorption area for the sound toward the left side of the road is widened. In this case, it is sufficient that at least the downward wide surface 1 is a sound absorbing surface. However, if higher noise reduction performance is required, the upward wide surface 2 and the downward narrow surface 3 of some or all of the sound absorbing plates are also sound absorbing. It should be the surface.
  In this example, when the vertical projection of each sound absorbing plate is viewed, the interval b is open, but if importance is placed on noise reduction performance, a larger number of sound absorbing plates may be installed densely, or each sound absorbing plate may be The width b may be increased to reduce the interval b, or the projections in the vertical direction may be substantially in contact (b = 0) or partially overlap. Even in that case, since the sound absorbing plates are installed at intervals in the horizontal direction, natural ventilation and lighting are ensured.
[0013]
  The structure shown in FIG. 2 is not arranged with the sound absorbing plate inclined in the same direction as in the structure of FIG. 1, but is inclined with respect to the left and right objects. There is an effect of reducing.
  In the structure shown in FIG. 3, the sound absorbing plates whose directions of inclination are reversed are installed in two upper and lower stages, and the sound absorbing plates in each stage are spaced apart from each other in the horizontal direction. Thus, the vertical projections are partially overlapped. This structure blocks direct sound from the noise source from exiting the opening.
  The structure shown in FIG. 4 is a structure in which a plurality of sound absorbing plates having a cross-sectional shape are horizontally spaced from each other, and the structure shown in FIG. 5 is the same shape of sound absorbing plates spaced from each other in the horizontal direction. In addition, the structure shown in FIG. 6 is installed so that the projections in the vertical direction of the respective sound absorbing plates are almost in contact with each other, and the sound absorbing plates having a shape in which two “U” characters are connected in the vertical direction are spaced apart from each other in the horizontal direction. It is a thing. In any case, the sound absorption area can be widened, and the effect of attenuating external noise is high.
[0014]
  In the structure shown in FIG. 7, a plurality of sound-absorbing plates having a horizontal sound-absorbing surface 4 are provided in the horizontal direction along the road extension direction at the opening of the moat split road, and the upper and lower tiers are arranged at the same interval c. It is installed. The upper and lower sound absorbing plates are arranged in a staggered manner so that the projections in the vertical direction just touch each other. Since the sound absorbing surface 4 is horizontal, the sound absorbing area for direct sound is wide. In this case, it is sufficient that at least the lower wide surface 4 of the upper and lower sound absorbing plates is a sound absorbing surface. However, if higher noise reduction performance is required, the lower sound absorbing plate is partially or entirely upward wide surface 5. In addition, the left and right narrow surfaces 6 and 7 may be sound absorbing surfaces, and the upper and lower sound absorbing plates may be part or all of the left and right narrow surfaces 6 and 7 as sound absorbing surfaces.
  The structure shown in FIG. 8 is such that the horizontal intervals of the sound absorbing plates at each stage are narrowed so that the projections in the vertical direction are overlapped to prevent direct sound from the noise source from exiting the opening. High noise reduction performance.
[0015]
  In the structure shown in FIG. 9, a sound absorbing plate having an inclined downward sound absorbing surface and a sound absorbing plate having a horizontal downward sound absorbing surface are installed in two stages, and in each stage, the sound absorbing plates are spaced horizontally. is set up. Although it can be said that it is substantially equivalent to the structure shown in FIG. 3, the installation area can be saved somewhat.
  The structure shown in FIG. 10 is a structure in which a sound absorbing plate having both surfaces as sound absorbing surfaces and a sound absorbing plate facing in the vertical direction and a sound absorbing plate having a horizontal downward sound absorbing surface are installed in two stages. The lower sound absorbing plate absorbs the oblique component of the sound, and the remaining vertical component is effectively absorbed and blocked by the upper sound absorbing plate.
  The structure shown in FIG. 11 is a combination of a general soundproof wall having a sound absorbing surface on the inside and a sound absorbing plate having an inclined downward sound absorbing surface.
  In the structure shown in FIG. 12, the sound absorbing surfaces on both sides are vertically arranged, and the sound absorbing plates are vertically arranged in two steps, and the sound absorbing plates in each step are spaced apart from each other in the horizontal direction. The board is staggered. In this case, it is more advantageous in terms of natural ventilation and lighting than if the same number of sound absorbing plates are densely arranged in one stage, and the tendency is further increased if the lower end of the upper sound absorbing plate is spaced from the upper end of the lower sound absorbing plate. Strengthen.
[0016]
  The sound absorbing plate shown in FIG. 13 is an example of a sound absorbing plate used in the above-described traffic noise reduction structure. For example, the frame member 11 made of an extruded aluminum material, and the sound absorbing material 12 whose surface is covered with a protective film, for example, aluminum. It consists of a perforated plate 13 made of a perforated metal made of metal and covering the front surface and both side surfaces of the sound absorbing material, and a vibration damping material 14 affixed inside the upper surface (back surface plate) of the frame member 11. In this sound absorbing plate, the frame member 11 and the perforated plate 13 constitute a hollow frame surrounding the sound absorbing material 12. A locking portion 11a is formed on the back plate of the frame member 11, and a bolt head or the like can be inserted into the locking portion 11a and can be suspended from an opening of a moat split road or the like. Further, the sound absorbing plate shown in FIG. 14 has a similar structure, and has a frame member 21, a sound absorbing material 22, and a perforated plate 23 whose upper surface (back plate) has an upwardly convex curved surface (arc shape). The vibration damping material 24 is used. In this sound absorbing plate, the frame member 21 and the perforated plate 23 constitute a hollow frame surrounding the sound absorbing material 22. Each of the sound absorbing plates has a lower surface and part of both side surfaces as a sound absorbing surface, and is installed horizontally or inclined at an opening of a moat split road or the like.
[0017]
  In these sound absorbing plates, the upper surface (back plate) of the frame member has a horizontal or convex curved surface, and if this is a metal such as aluminum, it reflects sunlight well, and the porous plate is also made of aluminum. Such a metal reflects sunlight well. Therefore, as shown in FIG. 15, for example, when these sound absorbing plates are installed in the upper and lower two stages, the sunlight reflected by the upper surface of the lower sound absorbing plate is the sound absorbing surface (perforated plate) of the upper sound absorbing plate. ), The sunlight is scattered between the two, and the light is easily guided to the road space below, so that it is possible to compensate for a decrease in daylighting performance. Alternatively, even when the sound absorbing plates are not installed in multiple stages, sunlight is reflected on the inclined upper surface (see, for example, FIG. 1) or curved, and the light is guided to the road space below. Note that the color of the back plate may be a color that reflects sunlight well by painting or the like.
  In addition, if the upper surface (back plate) of the frame member is inclined or curved upward with respect to a horizontal plane, water easily flows on the surface, which is advantageous for drainage during rainfall, and the attached dirt is There is also an effect that it is easily removed by rainwater. In this case, it is more effective if the surface of the back plate (or the entire frame member) is covered with a hydrophilic coating film such as a fluororesin. Note that if the upper surface has a convex shape, for example, a triangular shape, trapezoidal shape, or the like, as shown in FIGS. This has the same effect as that of the curved shape of FIG.
  Furthermore, when a damping material is attached to the inner side of the back plate like the sound absorbing plate illustrated in FIGS. 13 and 14, the vibration of the plate is suppressed, and for example, the sound reduction of rain sound generated due to rain fall is suppressed. The effect is obtained. This action is achieved by the plate on the back side (or the entire frame member) itself having damping properties, for example, a sandwich damping plate in which a damping resin exhibiting viscoelasticity is sandwiched between elastic plates (eg, steel plate or aluminum plate). It is also possible to obtain the same by using a damping steel plate or a damping aluminum plate sandwiching a sheet-like damping resin.
[0021]
  FIG. 17 shows another example of the sound absorbing plate in which one wide surface and the other surface of a hollow frame surrounding the sound absorbing material are sound absorbing surfaces, and a sound absorbing material having a wide surface facing downward and narrow surfaces (side surfaces) on both sides as sound absorbing surfaces. The board is shown. FIG. 17A shows an example of the basic structure, which includes a sound absorbing material 32 and a hollow rectangular frame surrounding the sound absorbing material 32, and this frame includes a plate member 31 disposed on the back surface side of the sound absorbing material 32. The perforated plate 33 is disposed on the front side and both sides of the sound absorbing material 32 and fixed to the plate member 31.
  In the sound absorbing plate of FIG. 17A, the narrow surfaces on both sides are the sound absorbing surfaces. However, when a plurality of sound absorbing plates are connected horizontally as shown in FIG. Since the surface is required only for the sound absorbing plates at both ends, in such a case, if the sound absorbing plates at both ends have only a wide surface and only one side that becomes the outside when in use, the inner sound absorbing plate only has the wide surface as the sound absorbing surface. Good.
[0018]
  Although it is the same as the sound absorbing plate previously shown in FIGS. 13 to 14, the perforated plate 33 is made of a punching metal, an expanded metal or the like, and may be formed of a steel plate, a stainless steel plate or the like in addition to aluminum. The plate member 31 can also be formed of the same material as the porous plate 33, and for example, a plate material, an aluminum extruded material, or the like can be used. The sound absorbing material 32 may be a fibrous sound absorbing material such as glass wool, rock wool, or non-woven fabric, and may be covered with a film such as polyvinyl fluoride for waterproofing from rainwater or the like. In addition, a sound absorbing material other than the fibrous material can also be used. When using fiber sound absorbers such as glass wool, noise reduction performance is achieved by placing a sound absorber with a low bulk density on the sound source side and a sound absorber with a high bulk density on the back side to form a density gradient type laminated structure. The bulk density is 32kg / m.³~ 48kg / m³It is desirable to use a sound absorbing material. Moreover, noise reduction performance can be improved also by providing the air layer 34 in the front surface and back surface of the sound-absorbing material 32, and it is desirable that the layer thickness shall be 10-30 mm.
[0019]
  As will be described in detail later with reference to FIGS. 18 to 19, the sound absorbing plate comprises at least a sound absorbing material and a frame surrounding the sound absorbing material, and has one wide surface and two narrow surfaces of the frame. In the sound absorbing plate in which at least one surface is a sound absorbing surface,(1)The sound absorbing material is composed of a separate wide-surface sound-absorbing material (sound-absorbing material facing only the wide surface) and a narrow-surface sound-absorbing material (mainly the sound-absorbing material facing the narrow surface and also facing the wide surface), each held inside the frame An air layer is provided on the sound-absorbing surface side (the side facing the perforated plate constituting the sound-absorbing surface) and the back side of each sound-absorbing material, if necessary, or(2)The sound absorbing material is made of an integral sound absorbing material, and is held inside the frame. Similarly, an air layer is provided on the sound absorbing surface side (the side facing the perforated plate constituting the sound absorbing surface) and the back side of the sound absorbing material as necessary. It can also be said that.
  In the above sound absorbing plate, the sound absorbing material has sufficient thickness on any sound absorbing surface, is a density gradient type laminated structure, or is effectively combined with an air layer. It is desirable to achieve noise reduction performance. In addition, in order not to impair the noise reduction performance, the area that covers the surface of the sound absorbing material by the sound absorbing material mounting member or holding part is made as small as possible. When the sound absorbing material is covered with a film, the vibration of the film is not restrained. For this reason, it is desired to devise such as making the contact area between the sound absorbing material mounting member or the holding portion and the sound absorbing material as small as possible. Each example of FIGS. 18 and 19 described below is devised to satisfy this requirement.
[0020]
  The sound absorbing plate shown in FIG. 18A is composed of a frame made up of a plate member 41 and a perforated plate 43, and sound absorbing materials 42a and 42b surrounded by the frame, and the plate member 41 has a sectional rigidity of the sound absorbing plate. And a holding portion 41a for holding the sound absorbing material 42a is integrally provided. The holding portion 41a (and the connecting portion 41b) may be integrally formed with the plate member 41 by using, for example, an aluminum extruded shape, or may be integrally assembled by molding separately. The sound absorbing material 42a for absorbing the wide surface is arranged with the plate member 41 and the porous plate 43 and the air layer 44a separated, and the sound absorbing material 42b for absorbing the narrow surface also has the plate member 41, the porous plate 43 and the air layer 44b. Spaced apart. At this time, the sound absorbing material 42b is held at intervals by a plurality of band-shaped or wire-shaped mounting members 45 so as not to impair the noise reduction performance, and is fixed to the holding portion 41a with rivets or tapping screws.
[0021]
  The sound absorbing plate shown in FIG. 18B is composed of a frame made up of a plate member 51 and a perforated plate 53, and sound absorbing materials 52a and 52b surrounded by the frame, and the plate member 51 has a sectional rigidity of the sound absorbing plate. The holding portion 51a for holding the sound absorbing material 52a and the holding portion 51c for holding the sound absorbing material 52b are integrally provided. Also in this plate member 51, the holding portion 51a (and the connecting portion 51b) and the holding portion 51c can be integrally formed with an aluminum extruded profile or the like. The sound absorbing material 52a is disposed with the plate member 51 and the perforated plate 53 and the air layer 54a therebetween, and the sound absorbing material 52b is disposed with the air layer 54b between the perforated plate 53 and its back surface (the side of the holding portion 51a). ) Is also provided with an air layer 54b.
[0022]
  The sound absorbing plate shown in FIG. 19 (a) is composed of a frame made up of a plate member 61 and a porous plate 63, and sound absorbing materials 62a and 62b surrounded by the frame, and the plate member 61 is basically the same as FIG. 18 (a). The holding part 61a is integrally provided. Since the sound absorbing material 62b has a semi-cylindrical cross section, the arc portion faces the narrow surface and is supported by the porous plate 63, and the flat surface portion is supported by the holding portion 61a (and the connecting portion 61b). Therefore, the air layer 64b can be secured and held in the frame body.
  The sound absorbing plate shown in FIG. 19 (b) has only a single sound absorbing material 72 without providing a new sound absorbing material for narrow surface sound absorption. The plate member 71 and the perforated plate 73 constitute a frame, and the plate member 71 is integrally provided with a holding portion 71a, while the holding portion 71b is a separate body, for example, both ends of the sound absorbing plate (perpendicular to the paper surface). The sound absorbing material 72 is arranged in the frame body with the holding portions 71a and 71b separating the air layer 74a. Note that the holding portions 71a and 71b may be installed at the end of the sound absorbing material 72 (the left end of the sound absorbing material in the drawing).
[0023]
  Subsequently, in FIGS. 20 to 22, a numerical simulation was performed to compare the noise attenuation effect when the sound absorbing surface of the sound absorbing plate was installed so as to face the vertical direction and when the sound absorbing surface was placed so as to face the horizontal direction. Results are shown. Here, in FIG. 20, it is assumed that sound absorbing plates having a height h3: 0.3 m, a width t3: 0.2 m, and sound absorbing surfaces on both sides and the bottom surface are installed at equal intervals, and in FIG. 9 m, width t4: 0.2 m, sound absorbing surfaces on both sides, and in FIG. 22, a sound absorbing plate having a width h5: 1.5 m, thickness t5: 0.1 m, and only the bottom surface is a sound absorbing surface is 1 m in the horizontal direction. It was assumed that there was a staggered arrangement in two upper and lower stages at intervals, and the other conditions were the same as in FIGS.
[0024]
  In the examples of FIGS. 20 to 22, the length of the sound absorbing surface in the cross section is approximately the same as 12.8 m, 14.4 m, and 14.5 m, respectively. Looking at the pressure distribution state, the example of FIG. 22 according to the present invention is overwhelmingly superior. Moreover, the average sound reduction (average sound reduction at 41 points between heights 0.2 m and 40.2 m) at the 25 m point on both sides of the road according to the simulation results is 9.0 dB, 8.4 dB, and 14.5 at the left 25 m point, respectively. It is 8.4 dB, 6.5 dB, and 14.8 dB at 7 dB and the right 25 m point, respectively, and the effect amount of FIG. 22 according to the present invention exceeds the others.
  According to this simulation result, it can be seen that the structure of the present invention has an excellent effect even if the sound absorbing plate has the same sound absorbing surface area or the same volume.
[0025]
  Next, in the case where the sound absorbing plates are installed at intervals in the horizontal direction, the noise when only the wide surface facing the sound absorbing plate horizontally and downward is used as the sound absorbing surface, and when the other surface is used as the sound absorbing surface. The reduction effect was investigated by numerical simulations using the known boundary element method.
  The structure of the analytically slicing road is the same as that of FIG. 26 as shown in FIG.₃: 1 m). Further, the cross-sectional size of the sound absorbing plate arranged in the opening is the same as that in FIG. 22, the horizontal distance d is 0.5 m, and the sound absorbing performance of the sound absorbing surface is the oblique incident sound absorption rate specified by the Ministry of Construction. In FIG. 23 (b), one-surface sound absorption having a performance of 0.88 (only the horizontally-facing wide surface is the sound-absorbing surface) or three-surface sound absorption (the horizontally-facing wide surface and both vertical narrow surfaces are sound-absorbing surfaces). As shown in FIG. And when the distance between the upper ends of the sound absorbing plates arranged in the upper and lower two stages (interval between upper and lower stages) c is 0.3 m and 1.0 m, the case where the sound absorbing plate with one surface absorbing sound is arranged and the three surfaces The difference in noise reduction effect between the two types of cases where a sound absorbing sound absorbing plate is arranged was examined.
[0026]
  As shown in FIGS. 23 (a) and 23 (b), the loudness of the surrounding sound when the sound sources S1 and S2 in the excavated road are used as a sound source is obtained, and the fact that the excavated road cross-sectional shape is almost bilaterally symmetrical is used. Then, when a car travels in the four lanes inside the digging, the noise level in the range of 0.2m to 40.2m above the ground at the 25m point from the road center inside the digging is calculated for each case, and the measures for the opening are The noise reduction effect when compared with the case without it was calculated. The result is shown in FIG.
  FIG. 23 (c) shows that when the three-surface sound absorbing plate is used regardless of whether the upper and lower step distance c is 1.0 m or 0.3 m, it is 3 dB compared to the case of the one-surface sound absorbing plate. It has been shown that the noise reduction effect increases. In the case of three-surface sound absorption, the sound absorption surface area is 1.13 times {(1.5 × 10 + 0.1 × 20) / (1.5 × 10)} compared to the case of single-surface sound absorption. As an increase, + 0.5dB (10log₁₀Although it should be expected only 1.13), it has been shown that a large noise reduction effect of about +3 dB can be realized in practice. In this way, the effect more than the increase in the sound absorbing surface area is obtained. In this sound absorbing plate arrangement, a plurality of sound absorbing plates are arranged at intervals, and the sound wave passing through the gap faces the gap even if the area is small. This is because sound is efficiently absorbed by making the portion a sound absorbing surface.
[0027]
  As described above, in this sound absorbing plate arrangement, it has been clarified that the noise reduction effect is increased by about 3 dB in the case of the three-surface sound absorption as compared with the single-surface sound absorption. However, it is conceivable that this noise reduction effect varies depending on the distance d between the sound absorbing plates. Therefore, in order to examine the difference in noise reduction effect when the distance d is changed, the energy of noise radiated to the outside from the moat split road will be evaluated. Study was carried out. The structure of the analytically symmetric cutting road is the same as in FIG. 23 (a), and the cross-sectional size of the sound absorbing plate arranged in the opening is the same as in FIG. 23 (b). The sound absorption performance of the sound absorbing surface is a single-surface sound absorption with a grazing incidence absorption coefficient specified by the Ministry of Construction of 0.88 (only horizontally wide wide surfaces only). Sound absorption surface) or three-surface sound absorption (horizontal downward wide and vertical narrow surfaces are sound absorption surfaces). And in the case where the horizontal interval between the sound absorbing plates is 0.5 m and 1.0 m, there are two types of cases where a sound absorbing plate with one surface absorbing sound is arranged and a sound absorbing plate with three surfaces absorbing sound are arranged The difference of noise reduction effect was investigated.
[0028]
  A cross section in parallel in the traveling direction of the moat split road is as shown in FIG. 24 (a), and horizontal beams 81 are installed at almost constant intervals. Therefore, considering a model as shown in (b) where one pitch from one cross beam to the next cross beam is taken out, the total noise power radiated from one pitch to the outside is the power passing through the horizontal plane above the model. Can be evaluated by integrating. Based on this idea, numerical simulations using the known boundary element method were performed as before, and the difference in noise reduction effect in each case was examined.
  Table 1 shows numerical values obtained from the simulation results (relative noise reduction effect with reference to 0 dB when the horizontal spacing is 0.5 m and a single-surface sound absorbing plate is arranged).
[0029]
[Table 1]
[0030]
  From Table 1, the noise reduction effect in the case of three-surface sound absorption is +3.1 dB when the horizontal distance between the sound-absorbing plates is 0.5 m, and +0.6 dB when 1.0 m. Yes, it varies greatly depending on the horizontal interval. Note that the numerical value of +3.1 dB when the horizontal interval is 0.5 m substantially coincides with the numerical value of about +3 dB seen in FIG.
  About the data obtained here, FIG. 25 is a graph in which the vertical axis represents the noise reduction effect and the horizontal axis represents the relative interval (ratio between the horizontal interval of the sound absorbing plate and the width of the sound absorbing plate). It can be seen that the noise reduction effect is so large that the relative interval should be 0.6 or less in order to obtain a significant noise reduction effect of at least 1 dB or more by three-surface sound absorption. Similar results are obtained with respect to the relative spacing, at least when the sound-absorbing plate cross-sectional size (thickness: 80 to 200 mm) considered to be standard and the arrangement form (upper and lower step spacing: 50 to 200 cm).
[0031]
【The invention's effect】
  According to the present invention, in roads or railways having walls on both sides and having openings in the upper part, traffic noise radiated upward from the openings is reduced, which is economical and does not significantly hinder natural ventilation and lighting. A noise reduction structure can be obtained.
[Brief description of the drawings]
FIG. 1 shows an example of a structure for reducing traffic noise in a section perpendicular to the longitudinal direction of a moat split road.
[Figure 2] Traffic noise reduction structureExampleIt is.
[Figure 3] Traffic noise reduction structureExampleIt is.
[Figure 4] Traffic noise reduction structureExampleIt is.
[Fig.5] Traffic noise reduction structureExampleIt is.
[Figure 6] Traffic noise reduction structureExampleIt is.
[Fig. 7] Traffic noise reduction structureExampleIt is.
[Figure 8] Traffic noise reduction structureExampleIt is.
[Fig. 9] Traffic noise reduction structureExampleIt is.
[Fig. 10] Traffic noise reduction structureExampleIt is.
[Fig. 11] Traffic noise reduction structureExampleIt is.
[Fig. 12] Traffic noise reduction structureExampleIt is.
FIG. 13 is a cross-sectional view of a sound absorbing plate according to the present invention.
FIG. 14 is a cross-sectional view of a sound absorbing plate according to the present invention.
FIG. 15 is a diagram illustrating reflection of sunlight by a sound absorbing plate.
FIG. 16 is a view schematically showing a cross section of a sound absorbing plate according to the present invention.
FIG. 17 is a view schematically showing a cross section of a sound absorbing plate according to the present invention.
FIG. 18 is a diagram showing a specific structure thereof.
FIG. 19 is a diagram similarly showing a specific structure thereof.
FIG. 20 is a diagram showing a simulation result of a sound pressure distribution state in the structure of the comparative example.
FIG. 21 is a diagram showing a simulation result of a sound pressure distribution state in the structure of the comparative example.
FIG. 22 is a diagram showing a simulation result of a sound pressure distribution state in the structure of the present invention.
FIG. 23 is a diagram showing simulation results of noise reduction effects in the case of three-surface sound absorption and single-surface sound absorption when the sound absorbing plates are arranged in two horizontal stages.
FIG. 24 is a diagram for explaining preconditions for evaluating the noise reduction effect by numerical simulation in the case of three-surface sound absorption and single-surface sound absorption when the sound absorbing plates are arranged in two horizontal stages.
FIG. 25 is a diagram showing the result of the numerical simulation.
FIG. 26 is a diagram showing a simulation result of a sound pressure distribution state in a conventional structure.
FIG. 27 is a diagram illustrating a simulation result of a sound pressure distribution state in the structure of the comparative example.

Claims (8)

A structure for reducing traffic noise in a road or railway having walls on both sides and an opening in the upper part, and having a downward sound-absorbing surface that is horizontal in the opening when viewed in a cross section perpendicular to the extending direction of the road or railway Plates are installed at a distance from each other , one of the wide surfaces of the sound absorbing plate is the sound absorbing surface, and both side surfaces are also sound absorbing surfaces, and the sound absorbing plate comprises a sound absorbing material and a frame surrounding the sound absorbing material. A structure for reducing traffic noise radiated upward, wherein a back plate having no holes in the frame body shields the back side of the sound absorbing material . The upwardly radiated traffic according to claim 6, wherein the sound absorbing plates are installed in a plurality of stages above and below, and the projections in the vertical direction of the sound absorbing plates are substantially in contact with each other or partly overlapped with each other. Noise reduction structure. A structure for reducing traffic noise on roads or railways with walls on both sides and openings in the upper part, and a plurality of sound-absorbing plates with downward sound-absorbing surfaces that are horizontal in the openings are spaced apart from each other and installed in multiple stages above and below The vertical projection of the sound absorbing plate is substantially in contact with or partially overlapping, and one of the wide surfaces of the sound absorbing plate is the sound absorbing surface, and the sound absorbing plate is composed of a sound absorbing material and a frame surrounding the sound absorbing material. A structure for reducing traffic noise radiated upward, wherein a back plate having no holes in the frame body shields the back side of the sound absorbing material . The structure for reducing traffic noise emitted upward according to claim 3, wherein both side surfaces of the sound absorbing plate are also sound absorbing surfaces. The structure for reducing traffic noise radiated upward according to any one of claims 1 to 4 , wherein the sound absorbing plate is installed along an extending direction of a road or a railway. The traffic noise reduction structure according to claim 1 , wherein the surface of the back plate of the frame body is made of a material or color that reflects sunlight. The traffic noise reduction structure according to any one of claims 1 to 5 , wherein the back plate of the frame has a flat surface or a convex shape upward. Paste or damping material on the inside of the back surface plate of the frame body, the traffic noise as set forth in claim 1, characterized by being configured of a plate material having vibration-damping properties of the back surface plate itself Reduction structure .

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