JP2019044573A - Sound barrier - Google Patents

Abstract

To provide a sound barrier capable of sufficiently reducing noise from a sound source located above a vehicle.SOLUTION: It is provided with an upright wall 2 provided in a standing manner and facing a side surface of a vehicle 11, and an overhang member 3 overhanging from an upper end part of the upright wall 2 toward the vehicle 11. A top surface of the overhang member 3 is a sound absorption surface which absorbs noise and is tilted upward obliquely from the upright wall 2 toward the sound source S.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a soundproof wall that reduces noise from a sound source located at the top of a vehicle.

  As a countermeasure against railway noise, a noise barrier is provided along the track. In order to enhance the noise reduction effect, it is effective to increase the height of the soundproof wall. However, when the height of the soundproof wall is increased, the sunlight, the landscape, and the view are deteriorated, a feeling of pressure is generated, and problems such as radio wave interference and an increase in wind pressure load occur.

  Therefore, Patent Document 1 discloses a soundproof wall in which a sound-absorbing cylinder body is projected obliquely upward in the direction opposite to the sound source at the top end. Significantly reduces the noise that goes over the soundproof wall from behind by the diffraction sound reduction effect by the overhanging sound absorption cylinder, the sound absorption effect by the sound absorption convex part of the sound absorption cylinder and the sound insulation effect of the base part Effect is obtained.

  However, the soundproof wall of Patent Document 1 has a sound absorptive cylinder projecting outward (on the side opposite to the sound source) from the soundproof wall, so that when it is projecting on private land, the problem of belonging to aerial rights arises. In order to install a soundproof wall so that the sound-absorbing cylinder does not protrude onto private land, it is necessary to bring the soundproof wall to the track side, and the scenery and view deteriorate, causing a feeling of pressure. In addition, the sound reduction effect is reduced.

  On the other hand, in Patent Document 2, a flange is horizontally projected from the upper end of a vertically arranged vertical wall toward the sound source, and a sound absorbing material is provided in the rectangular parallelepiped hollow body of the flange. A soundproof wall in which a large number of holes are opened on the lower surface and the front end surface is disclosed. It is possible to absorb the noise incident from the hole opened in the sound source side lower surface of the collar part facing the roadway or the track side, and to absorb the diffracted sound of the noise incident from the hole opened in the tip surface of the collar part. .

JP 2001-32219 A JP 2008-111307 A

  The soundproof wall of Patent Document 2 has no problem due to projecting outward (anti-sound source side) because the flange portion projects horizontally toward the vehicle side (sound source side). However, the present inventors have limited the effect of reducing the noise from the sound source located in the upper part of the vehicle, depending on the positional relationship between the sound source and the sound receiving point, in the shape in which the collar portion projects in the horizontal direction. I found out.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a soundproof wall that can sufficiently reduce noise from a sound source located at the top of a vehicle.

  The present invention is a soundproof wall for reducing noise from a sound source located at an upper part of a vehicle, and is provided upright, an upright wall facing a side surface of the vehicle, and an upper end of the upright wall toward the vehicle. And an upper surface of the protruding member is a sound absorbing surface that absorbs the noise, and is inclined obliquely upward from the upright wall toward the sound source. It is characterized by.

  According to the present invention, the sound absorbing surface which is the upper surface of the projecting member projecting toward the vehicle is inclined obliquely upward from the upright wall toward the sound source. Thereby, the noise from the sound source located in the upper part of the vehicle can be advanced along the sound absorbing surface. Therefore, compared to a configuration in which noise is vertically incident on the sound absorbing surface facing the sound source and a configuration in which the upper surface of the projecting member projecting horizontally on the vehicle side is the sound absorbing surface, the sound absorbing surface has a noise absorbing surface. It is easy to increase the distance of the part that travels along. Thereby, the noise from the sound source located in the upper part of the vehicle can be sufficiently reduced.

It is a side view of the soundproof wall of 1st Embodiment. It is a side view of the soundproof wall of the structure which the overhang | projection member protruded to the vehicle side in the horizontal direction. It is a side view of the soundproof wall of a modification. It is a figure which shows the result of having evaluated the noise reduction effect by varying the inclination-angle of a protrusion member. It is a side view of the soundproof wall of 2nd Embodiment. It is a figure which shows the result of having evaluated the noise reduction amount with the case where there is a sound absorption surface on the upper surface of an upright wall, and the case where it does not exist. It is a side view of the soundproof wall of 3rd Embodiment. It is a side view of the soundproof wall of 4th Embodiment. It is a side view of the soundproof wall of 4th Embodiment. It is a side view of the soundproof wall of 5th Embodiment. It is a side view of the soundproof wall used when evaluating the amount of noise reduction with and without the upright member. It is a figure which shows the result of having evaluated the noise reduction amount with the case where an upright member is provided and the case where it does not provide. It is a side view of a soundproof wall when the upper end of an upright member is higher than a sound absorption surface.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
(Configuration of sound barrier)
The soundproof wall according to the first embodiment of the present invention reduces noise generated from a vehicle. In railways such as the Shinkansen, the main noises are vehicle lower sound, current collecting sound, upper aerodynamic sound, and structure sound. Here, the vehicle lower part sound is rolling sound, aerodynamic sound around the carriage, and the current collecting system sound is sound generated from the overhead line / pantograph system such as pantograph aerodynamic sound. Further, the upper aerodynamic sound is an aerodynamic sound of a vehicle connecting portion or the like, and the structure sound is a vibration radiation sound from an elevated structure. Of these, the source (sound source) of the current collecting sound and the upper aerodynamic sound is usually located at a higher position than the sound barrier. The soundproof wall of the present embodiment mainly reduces noise (collection system sound, upper aerodynamic sound) from a sound source located in the upper part of the vehicle.

  As shown in FIG. 1, which is a side view of the soundproof wall 1, the soundproof wall 1 has an upright wall 2 and an overhang member 3. The upright wall 2 is provided upright on the ground and faces the side surface of the vehicle 11. The overhang member 3 projects from the upper end of the upright wall 2 toward the vehicle 11.

  In the present embodiment, the upright wall 2 is a rigid wall that does not have sound absorption performance, but may have sound absorption performance.

  The upper surface of the overhang member 3 is a sound absorbing surface that absorbs noise. In the present embodiment, the sound absorbing material 4 is attached to the upper surface of the overhang member 3. As the sound absorbing material 4, fiber systems such as glass wool and polyester, and foam systems such as urethane foam can be used. The sound absorbing material 4 is covered with a punching metal or the like. The sound absorbing material 4 covered with a punching metal or the like forms a sound absorbing portion 12. The sound absorbing surface is the upper surface of the sound absorbing portion 12.

  The upper surface (sound absorbing surface) of the overhang member 3 is inclined obliquely upward from the upright wall 2 toward the sound source S located at the upper part of the vehicle 11. The lower surface of the overhang member 3 is parallel to the upper surface. Here, the upper end of the sound absorbing surface (the upper surface of the sound absorbing portion 12) is positioned below the sound source S. The sound receiving point R is located on the opposite side of the upright wall 2 from the vehicle 11 and below the upper end of the upright wall 2. The sound receiving point R is provided, for example, at a position 25 m away from the track and at a height of 1.2 m from the ground.

  Here, the obtuse angle θ1 formed by the overhanging member 3 and the upright wall 2 is larger than the obtuse angle θ2 formed by the upright wall 2 and the straight line passing from the sound source S to the upper end of the sound absorbing surface (the upper surface of the sound absorbing unit 12). The obtuse angle θ3 formed by a straight line passing from the point R through the lower end of the sound absorbing surface (the upper surface of the sound absorbing portion 12) and the upright wall 2 is made smaller.

  Sound waves usually travel straight through the shortest path to the destination. Therefore, the main propagation path of the noise from the sound source S to the sound receiving point R is after the noise emitted from the sound source S is diffracted at the upper end of the sound absorbing portion 12 and travels along the sound absorbing surface (the upper surface of the sound absorbing portion 12). This is a path that diffracts at the lower end of the sound absorbing portion 12 and reaches the sound receiving point R. In this case, since the noise travels along the sound absorption surface, the distance of the portion of the noise propagation path that travels along the sound absorption surface becomes long.

  On the other hand, as shown in FIG. 2 which is a side view, when the projecting member 3 projects horizontally to the vehicle side, the main noise propagation path from the sound source S to the sound receiving point R is from the sound source S. This is a path through which the emitted noise is diffracted at the upper end of the sound absorbing unit 12 on the side opposite to the sound source and reaches the sound receiving point R. In this case, since the noise is diffracted at the end of the sound absorbing portion 12, the distance of the portion of the noise propagation path that travels along the sound absorbing surface is shortened.

  In the soundproof wall 1 of the present embodiment, the sound absorbing surface that is the upper surface of the overhanging member 3 is inclined obliquely upward from the upright wall 2 toward the sound source S. Thereby, the noise from the sound source S located in the upper part of the vehicle 11 can be advanced along the sound absorption surface. Therefore, compared to the configuration in which noise is vertically incident on the sound absorbing surface facing the sound source S and the configuration in which the upper surface of the projecting member 3 projecting horizontally on the vehicle 11 side is the sound absorbing surface (configuration in FIG. 2), It is easy to increase the distance of the portion that travels along the sound absorbing surface in the noise propagation path. Thereby, the noise from the sound source S located in the upper part of the vehicle 11 can be reduced sufficiently.

  Of course, in the configuration of Patent Document 2, since the upper surface of the collar portion is not a sound absorbing surface, it goes without saying that the soundproof wall 1 of the present embodiment can sufficiently reduce noise.

  In addition, by positioning the upper end of the sound absorbing surface below the sound source S, the noise from the sound source S located at the top of the vehicle 11 is reduced, and the height of the soundproof wall 1 is higher than the configuration of the upright wall 2 alone. This can be suppressed. Thereby, sunlight, a landscape, a view can be prevented from deteriorating, or a feeling of pressure can be prevented.

  The obtuse angle θ1 formed by the overhanging member 3 and the upright wall 2 is larger than the obtuse angle θ2 formed by the straight wall passing from the sound source S to the upper end of the sound absorbing surface (the upper surface of the sound absorbing unit 12) and the upright wall 2, and the sound receiving point By making the angle smaller than the obtuse angle θ3 formed by the straight wall 2 and the straight line passing through the lower end of the sound absorbing surface (the upper surface of the sound absorbing portion 12) from R, the main propagation path of noise is diffracted at the upper end of the sound absorbing portion 12, The path can be diffracted once again at the lower end of the portion 12. Thereby, since the distance of the part which advances along a sound absorption surface among the propagation paths of noise can be lengthened, noise can be reduced further.

  In the present embodiment, the inclination angle of the overhang member 3 can be adjusted. Specifically, the upper end side surface of the upright wall 2 and the lower surface of the overhanging member 3 are connected by a connecting member such as a hinge. The overhang member 3 can be fixed at a desired inclination angle by a fixing means (not shown).

  The positional relationship between the sound source S and the sound receiving point R differs depending on the height of the overhead and the place where noise is desired to be reduced. Therefore, the inclination angle of the overhang member 3 that is optimal for the location also varies depending on the location. By making the inclination angle of the overhanging member 3 adjustable, it is possible to select an optimum inclination angle for each of various places even for the same soundproof wall 1. Thereby, noise can be reduced in various places.

(Modification)
As shown in FIG. 3 which is a side view, the protruding member 3 may have a configuration in which the upper surface (sound absorbing surface) is a perforated plate 5 and the inside is a cavity. With such a configuration, sound absorption can be performed by the porous plate 5 and the air layer 6 inside the projecting member 3 instead of the sound absorbing material 4. Here, the overhang member 3 provided with the porous plate 5 forms a sound absorbing portion 12. The sound absorbing surface is the upper surface of the sound absorbing portion 12. In addition, since the sound absorption principle by the perforated plate 5 and the air layer 6 is known, the description thereof is omitted.

  The perforated plate 5 is often made of metal such as iron or aluminum, but may be made of plastic or the like. The sound absorption coefficient and frequency characteristics of the porous plate 5 are determined by the plate thickness, hole diameter, aperture ratio, and volume of the air layer 6. Since the frequency characteristics can be changed by controlling the volume of the air layer 6, the overhang member 3 can be used by utilizing the volume of the internal space of the upright wall 2 for low-frequency noise that requires a large volume. It is possible to reduce low-frequency noise without increasing the thickness.

  Further, if the sound absorbing material 4 is wet with rain, it may absorb moisture and the desired sound absorbing effect may not be obtained, and aged deterioration due to moisture may occur, but sound is absorbed by the porous plate 5 and the air layer 6. If the drainage hole is provided in the overhanging member 3, the original performance is exhibited after the rain.

(Evaluation)
Next, the inclination angle of the overhang member 3 was varied, and the noise reduction effect was evaluated by simulation. The evaluation is based on the configuration of only the upright wall 2 having a height of 2 m, the height from the ground to the upper end of the overhang member 3 (sound absorbing portion 12) is fixed at 3.5 m, and the upper surface of the overhang member 3 is This was done by calculating the amount of noise reduction relative to the reference while varying the angle with the upright wall 2. The result is shown in FIG.

  It can be seen that the noise reduction effect is greater when the overhanging member 3 is tilted than when the angle between the upper surface of the overhanging member 3 and the upright wall 2 is 90 degrees (configuration in FIG. 2). It can also be seen that the noise reduction effect is greater when the angle between the upper surface of the overhanging member 3 and the upright wall 2 is 130 degrees or 150 degrees.

(effect)
As described above, according to the soundproof wall 1 according to the present embodiment, the sound absorbing surface (the upper surface of the sound absorbing portion 12) that is the upper surface of the overhanging member 3 that protrudes toward the vehicle 11 is connected to the sound source S from the upright wall 2. Inclined obliquely upward toward Thereby, the noise from the sound source S located in the upper part of the vehicle 11 can be advanced along the sound absorption surface. Therefore, compared to the configuration in which noise is vertically incident on the sound absorbing surface facing the sound source S and the configuration in which the upper surface of the projecting member 3 projecting horizontally on the vehicle 11 side is the sound absorbing surface (configuration in FIG. 2), It is easy to increase the distance of the portion that travels along the sound absorbing surface in the noise propagation path. Thereby, the noise from the sound source S located in the upper part of the vehicle 11 can be reduced sufficiently.

  Further, by positioning the upper end of the sound absorbing surface (the upper surface of the sound absorbing portion 12) below the sound source S, the noise from the sound source S located at the upper part of the vehicle 11 is sufficiently reduced, and only the upright wall 2 is provided. Compared with the configuration, the height of the soundproof wall 1 can be suppressed. Thereby, sunlight, a landscape, a view can be prevented from deteriorating, or a feeling of pressure can be prevented.

  Further, the obtuse angle θ1 formed by the overhanging member 3 and the upright wall 2 is larger than the obtuse angle θ2 formed by the straight wall passing from the sound source S through the upper end of the sound absorbing surface and the upright wall 2, and the lower end of the sound absorbing surface is formed from the sound receiving point R. The obtuse angle θ3 formed by the straight line passing through and the upright wall 2 is made smaller. As a result, the main propagation path of noise can be diffracted at the upper end of the sound absorbing unit 12 and once again diffracted at the lower end of the sound absorbing unit 12. Therefore, since the distance of the part which advances along a sound absorption surface among the propagation paths of noise can be lengthened, noise can be reduced further.

  In addition, by making the inclination angle of the overhanging member 3 adjustable, it is possible to select an optimum inclination angle for each of various places even for the same soundproof wall 1. Thereby, noise can be reduced in various places.

[Second Embodiment]
Next, the soundproof wall according to the second embodiment will be described with reference to the drawings. In addition, description is abbreviate | omitted about the structure which is common in 1st Embodiment, and the effect show | played by it, and a different point from 1st Embodiment is mainly demonstrated. In addition, about the same member as 1st Embodiment, the same code | symbol as 1st Embodiment is attached | subjected.

(Configuration of sound barrier)
As shown in FIG. 5, which is a side view of the soundproof wall 101, the soundproof wall 101 of the present embodiment is a sound absorbing surface that absorbs noise. Specifically, the sound absorbing material 7 is also provided on the upper surface of the upright wall 2. The sound absorbing material 7 is covered with a punching metal or the like. The sound absorbing material 7 covered with a punching metal or the like forms a sound absorbing portion 12. The sound absorbing surface is the upper surface of the sound absorbing portion 12. Thereby, since the sound absorption area increases, noise can be further reduced. The upper surface of the upright wall 2 may be configured to absorb sound with a perforated plate and an air layer.

(Evaluation)
Next, the amount of noise reduction was evaluated by simulation with and without a sound absorbing surface on the upper surface of the upright wall 2. The result is shown in FIG. It can be seen that the noise reduction amount increases in the frequency band of 400 Hz or more when the sound absorbing surface is on the upper surface of the upright wall 2.

(effect)
As described above, according to the soundproof wall 101 according to the present embodiment, the sound absorption area is increased by making the upper surface of the upright wall 2 a sound absorbing surface that absorbs noise, so that noise can be further reduced. .

[Third Embodiment]
Next, a soundproof wall according to a third embodiment will be described with reference to the drawings. In addition, description is abbreviate | omitted about the structure which is common in 1st Embodiment, and the effect show | played by it, and a different point from 1st Embodiment is mainly demonstrated. In addition, about the same member as 1st Embodiment, the same code | symbol as 1st Embodiment is attached | subjected.

(Configuration of sound barrier)
As shown in FIG. 7, which is a side view of the soundproof wall 201, the soundproof wall 201 of the present embodiment has a protruding member 203 attached to the upper end of the upright wall 2, and the lower surface of the protruding member 203 is in the left-right direction. Parallel to Here, the left-right direction includes a horizontal direction and a direction slightly inclined from the horizontal direction. In the present embodiment, the overhang member 203 has a perforated plate 205 on the top surface and a hollow inside. That is, the inside of the overhang member 203 is an air layer 206. The overhang member 203 provided with the perforated plate 205 forms the sound absorbing portion 12. The sound absorbing surface is the upper surface of the sound absorbing portion 12.

  The lower surface of the overhanging member 203 hardly affects the noise (current collection system sound, upper aerodynamic sound) from the sound source S located at the upper part of the vehicle 11. On the other hand, the lower surface of the overhang member 203 affects the noise from the sound source located in the lower part of the vehicle 11 (vehicle lower part sound, structure sound). This is because a sound field is formed in the space formed by the vehicle 11, the upright wall 2, and the lower surface of the overhang member 203, and the noise at the sound receiving point R is determined by the internal sound pressure.

  By making the lower surface of the overhanging member 203 parallel to the left-right direction, it is possible to prevent noise from the sound source located at the lower part of the vehicle 11 from going out of the upright wall 2. Further, if the lower surface of the overhanging member 203 is parallel to the left and right direction, it is easy to attach the overhanging member 203 to the upper end portion of the upright wall 2, so that the attachment cost can be reduced.

(effect)
As described above, according to the soundproof wall 201 according to the present embodiment, the noise from the sound source located at the lower part of the vehicle 11 is generated from the upright wall 2 by making the lower surface of the overhanging member 203 parallel to the left-right direction. You can prevent going out. Further, if the lower surface of the overhanging member 203 is parallel to the left-right direction, when the overhanging member 203 is attached to the upper end portion of the upright wall 2, the attachment is facilitated, so that the attachment cost can be reduced.

[Fourth Embodiment]
Next, a soundproof wall according to a fourth embodiment will be described with reference to the drawings. In addition, description is abbreviate | omitted about the structure which is common in 1st Embodiment, and the effect show | played by it, and a different point from 1st Embodiment is mainly demonstrated. In addition, about the same member as 1st Embodiment, the same code | symbol as 1st Embodiment is attached | subjected.

(Configuration of sound barrier)
As shown in FIG. 8 which is a side view of the soundproof wall 301, the soundproof wall 301 of the present embodiment absorbs noise having a higher frequency as the sound absorption characteristic of the sound absorbing surface of the projecting member 3 is farther from the sound source S. Is set to Specifically, the sound absorbing material 8 is attached from the end of the overhanging member 3 on the sound source S side to the end of the upright wall 2 on the opposite sound source side, and the portion of the upright wall 2 that is farther from the sound source S is closer to the sound absorbing material. The thickness of 8 is reduced. Here, the sound absorbing material 8 is covered with a punching metal or the like. The sound absorbing material 8 covered with a punching metal or the like forms a sound absorbing portion 12. The sound absorbing surface is the upper surface of the sound absorbing portion 12.

  The sound absorption characteristics of sound waves are related to the wavelength and the thickness of the sound absorbing material 8. The part located on the upper surface of the upright wall 2 in the sound absorbing material 8, that is, the part far from the sound source S exhibits a noise reduction effect particularly for noise in a high frequency region, as shown in FIG. And even if the thickness of this part is gradually reduced, since the high-frequency sound wave has a short wavelength, it is possible to obtain a sufficient noise reduction effect for noise in the high-frequency region. Further, the cost can be reduced by gradually reducing the thickness of the sound absorbing material 8.

  By setting the sound absorption characteristics of the sound absorbing surface of the overhanging member 3 so as to absorb higher frequency noise as the part is further away from the sound source S, low frequency noise is absorbed at the part closer to the sound source S of the sound absorbing material 8. In a portion far from the sound source S of the sound absorbing material 8, high frequency noise is absorbed. Thereby, noise can be reduced in a wide frequency range.

  In addition, as shown in FIG. 9 which is a side view of the soundproof wall 301, in the configuration in which sound absorption is performed by the perforated plate 305 and the air layer 306, the thickness of the air layer 306 is increased even if the perforated plate 305 has the same specifications. The part farther away from the sound source S is made thinner. As described above, the portion located on the upper surface of the upright wall 2 exhibits a noise reduction effect particularly for noise in a high frequency region as shown in FIG. Here, the overhang member 303 provided with the porous plate 305 forms the sound absorbing portion 12. The sound absorbing surface is the upper surface of the sound absorbing portion 12. In the present embodiment, the lower surface of the overhang member 303 is parallel to the left-right direction. As a result, it is possible to configure such that a part closer to the sound source S absorbs noise having a lower frequency and a part farther from the sound source S absorbs noise having a higher frequency.

  Further, by partitioning the air layer 306 with the partition plate 9, the frequency characteristics can be made different between the adjacent air layers 306. And by making it the frequency characteristic matched with the frequency range of the noise from the sound source S, noise can be reduced suitably.

(effect)
As described above, according to the soundproof wall 301 according to the present embodiment, the sound absorption characteristics of the sound absorption surface are set so as to absorb noise having a higher frequency as the part is further away from the sound source S. Thus, low frequency noise can be absorbed at a site close to the sound source S, and high frequency noise can be absorbed at a site far from the sound source S, so that noise can be reduced in a wide frequency range.

[Fifth Embodiment]
Next, a soundproof wall according to a fifth embodiment will be described with reference to the drawings. In addition, description is abbreviate | omitted about the structure which is common in 1st Embodiment, and the effect show | played by it, and a different point from 1st Embodiment is mainly demonstrated. In addition, about the same member as 1st Embodiment, the same code | symbol as 1st Embodiment is attached | subjected.

(Configuration of sound barrier)
As shown in FIG. 10 which is a side view of the soundproof wall 401, the soundproof wall 401 of this embodiment further includes an upright member 10. The upright member 10 extends upward from the upper end of the upright wall 2 and is separate from the upright wall 2. The upper end of the upright member 10 is located at a height equal to or lower than the upper end of the sound absorbing surface (the upper surface of the sound absorbing portion 12).

  In the present embodiment, the upright member 10 and the overhanging member 3 are integrated, but may not be integrated. In the case of being integrated, the upright member 10 and the overhanging member 3 can be easily attached to the upright wall 2 already installed by retrofitting.

  Further, the upper surface of the upright member 10 may be a sound absorbing surface that absorbs noise. In this case, when the sound absorbing material is provided on the upper surface of the upright member 10, the upper end of the sound absorbing material is positioned below the upper end of the upper surface of the sound absorbing portion 12.

  When it is difficult to make the sound absorption coefficient of the sound absorption surface close to 1, the sound absorption effect is lowered, and the contribution of diffraction attenuation is relatively increased. Therefore, by providing the upright member 10 on the upright wall 2, this diffraction attenuation can be positively obtained.

  In the soundproof wall 401 of this embodiment, the lower surface of the overhang member 3 may be parallel to the left-right direction. Further, the sound absorption characteristics of the sound absorbing surface may be set so as to absorb noise having a higher frequency as the part is further away from the sound source S.

(Evaluation)
Next, the amount of noise reduction was evaluated by simulation when the upright member 10 was provided and when it was not provided. As shown in FIG. 11 which is a side view of the soundproof wall, the evaluation is made only with the configuration (A) of the upright wall 2 having a height of 2 m, and the angle between the upper surface of the overhanging member 3 and the upright wall 2 is 90 degrees. A configuration without the upright member 10 (B) (configuration of FIG. 2), an angle between the upper surface of the overhanging member 3 and the upright wall 2 larger than 90 degrees, and a configuration without the upright member 10 (C) (configuration of FIG. 1) ) And (C), the configuration (D) in which the upright member 10 is provided, and the configuration (E) in which the upright member 10 is provided in (C).

  Here, in (B) to (E), the lengths of the sound absorbing surfaces are equal. In (C) to (E), the angle of the overhanging member 3 with respect to the upright wall 2 is the same. In (D), the upper end of the upright member 10 is positioned at the same height as the upper end of the sound absorbing surface. In (E), the upper end of the upright member 10 is the intermediate height between the upper end and the lower end of the sound absorbing surface. Is located.

  The evaluation was performed by calculating the amount of noise reduction with respect to the standard based on the configuration of (A). The result is shown in FIG. Here, the sound absorption coefficient of the sound absorbing surface in this simulation uses the sound absorption coefficient equivalent to the actual machine, and the sound absorption coefficient equivalent to the actual machine is a value estimated by the measured value of the normal incident sound absorption coefficient using an acoustic tube and its extrapolation. It is calculated using and.

  As the sound source at the upper part of the vehicle, there are current collecting sound and upper aerodynamic sound, but it is generally the current collecting sound that is considered to contribute greatly, and its main frequency is around 250 Hz. It is known. Therefore, attention was paid to the amount of noise reduction in the vicinity of the 250 Hz band.

  From FIG. 12, it can be confirmed that (B) to (E) are more effective in the 250 Hz band than (A). (D) is the most effective and is in the order of (E), (B), (C).

  The main sound reduction mechanisms in the sound barrier of this embodiment are sound absorption and diffraction. The reason why the order of the effects is as described above is that, in this simulation, when considering the sound ray from the sound source to the sound receiving point (representing the sound propagation path as a straight line), in each configuration of FIG. This is probably because the upper right corner is the diffraction point. In (C), the diffraction point is the lower end of the sound absorbing surface, and in (D) and (E), the diffraction point is the upper end of the upright member 10. The higher the diffraction point, the greater the difference in the path of the diffracted sound, making it easier to obtain the effect of diffraction attenuation.

  On the other hand, when (B) and (D) having the same diffraction point are compared, since (D) is more effective, it is effective to arrange the sound absorbing surface along the sound ray for sound absorption. It can be said that it is appropriate. From the above, it can be seen that when the sound absorption coefficient of the sound absorbing surface is less than 1, the shape as shown in (D) is effective.

  Further, when (D) and (E) are compared, it can be seen that the upper end of the upright member 10 should be as high as possible because the (D) direction is more effective. However, when the upper end of the upright member 10 becomes higher than the sound absorbing surface, the distance L between the sound absorbing surface and the sound ray becomes longer as shown in FIG. It becomes difficult to be. Therefore, it is better to position the upper end of the upright member 10 at a height equal to or lower than the upper end of the sound absorbing surface.

  From the above, when it is difficult to bring the sound absorption coefficient of the sound absorbing surface close to 1, the upright member 10 is provided on the upright wall 2 so that diffraction attenuation contributes positively, and the upper end of the upright member 10 is the upper end of the sound absorbing surface. It can be seen that it is preferable that the position is as high as possible.

  Note that the upright member 10 is unnecessary if the sound absorption rate of the sound absorbing surface can be made close to 1.

(effect)
As described above, the soundproof wall 401 according to the present embodiment further includes the upright member 10 extending upward from the upper end of the upright wall 2. When it is difficult to make the sound absorption coefficient of the sound absorption surface close to 1, the sound absorption effect is lowered, and the contribution of diffraction attenuation is relatively increased. Therefore, by providing the upright member 10 on the upright wall 2, this diffraction attenuation can be positively obtained. However, if the upper end of the upright member 10 is higher than the sound absorbing surface, it is difficult to obtain a sound absorbing effect, so the upper end of the upright member 10 is positioned at a height equal to or lower than the upper end of the sound absorbing surface. Thereby, diffraction attenuation can be obtained effectively.

  Moreover, since the upright member 10 and the overhang member 3 are integral, the upright member 10 and the overhang member 3 can be easily attached to the upright wall 2 that has already been installed.

  The embodiment of the present invention has been described above, but only specific examples are illustrated, and the present invention is not particularly limited, and the specific configuration and the like can be appropriately changed in design. Further, the actions and effects described in the embodiments of the invention only list the most preferable actions and effects resulting from the present invention, and the actions and effects according to the present invention are described in the embodiments of the present invention. It is not limited to what was done.

1,101,201,301,401 Soundproof wall 2 Upright wall 3,203,303 Overhang member 4 Sound absorbing material 5,205,305 Perforated plate 6,206,306 Air layer 7,8 Sound absorbing material 9 Partition plate 10 Upright member 11 Vehicle 12 Sound absorption part

Claims (10)

A soundproof wall that reduces noise from a sound source located at the top of the vehicle,
An upright wall provided upright and facing the side of the vehicle;
A projecting member projecting from the upper end of the upright wall toward the vehicle;
Have
The soundproof wall, wherein an upper surface of the projecting member is a sound-absorbing surface that absorbs the noise, and is inclined obliquely upward from the upright wall toward the sound source.   The soundproof wall according to claim 1, wherein an upper end of the sound absorbing surface is located below the sound source. The sound receiving point is opposite to the vehicle with respect to the upright wall, and is located below the upper end of the upright wall,
The obtuse angle formed by the overhanging member and the upright wall is larger than the obtuse angle formed by the sound source from the sound source and the upper end of the sound absorbing surface and the upright wall, and the straight line passing from the sound receiving point through the lower end of the sound absorbing surface. The soundproof wall according to claim 1, wherein the soundproof wall is smaller than an obtuse angle formed by the upright wall.   The soundproof wall according to any one of claims 1 to 3, wherein an upper surface of the upright wall is a sound absorbing surface that absorbs the noise. An upright member extending upward from the upper end of the upright wall;
The soundproof wall according to any one of claims 1 to 3, wherein an upper end of the upright member is positioned at a height equal to or lower than an upper end of the sound absorbing surface.   The soundproof wall according to claim 5, wherein the upright member and the overhang member are integrated.   The soundproof wall according to claim 5 or 6, wherein an upper surface of the upright member is a sound absorbing surface that absorbs the noise.   The soundproof wall according to claim 1, wherein a lower surface of the overhang member is parallel to the left-right direction.   The soundproof wall according to any one of claims 1 to 8, wherein a sound absorbing characteristic of the sound absorbing surface is set so as to absorb the noise having a higher frequency as the part moves away from the sound source.   The soundproof wall according to any one of claims 1 to 9, wherein an inclination angle of the overhang member is adjustable.

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