JPH03199515A - Soundproof wall for traffic noise reduction - Google Patents

Abstract

PURPOSE:To achieve good soundproof effect by providing a hood wall toward the inside on the upper end of a straight wall set perpendicular to a trajectory floor surface, providing an upward indicating wall on the front end thereof, and by providing a buckling wall on the upper end of the straight wall. CONSTITUTION:A hood wall 2 is projected toward a trajectory side, on the upper end of a straight wall 1 set perpendicular to a trajectory floor surface R, and an upward indicating wall 3 is provided on the point thereof. Sound absorbing materials 32, 33 are mounted on the surface on the trajectory side of the upward indicating wall 3, or on the reverse surface side thereof, as required. A buckling wall 4 is provided on the upper end of the straight wall 1, if required, so as to shade downward sound from the upper part as well as upward sound from the lower part. Various kinds of noise can be effectively reduced thereby, including the noise generated at a lower part, diffraction sound wave, collector noise, and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a soundproof wall for reducing traffic noise for reducing noise generated by running vehicles on railways, expressways, etc.

[Conventional technology]

Conventionally, the soundproofing effect of this type of soundproof wall depends on its height, but the height is limited by the visibility from the train window and the wind load resistance especially in the case of elevated tracks, so it is not enough. The reality is that the effects have not been achieved.

On the other hand, conventionally, as shown in FIG. 14, a horizontal eave wall W2 is provided at the upper end of the upright wall W1 toward the track side, and this eave wall W1 reflects the transfer noise of the vehicle T downward, thereby reducing the noise from the track floor R. An inverted-shaped soundproof wall that absorbs noise has been proposed (for example, see Japanese Patent Laid-Open No. 12502/1983). Note that No. 4 Recapture is an example of a soundproof wall used in elevated railways such as the Shinkansen.

[Problem to be solved by the invention]

However, even with this inverted-shaped soundproof wall, many sounds still escape through the gap between the eaves wall W1 and the vehicle T (the effect of this point will be explained later as a comparison with the present invention).
However, the soundproofing effect was not satisfactory, and this was a factor that prevented high-speed railways from running at higher speeds than current trains.

In addition, in the case of railway vehicles, there is noise from the current collection system due to the pantograph T1 and overhead wire T2, but conventional soundproof walls, including the above-mentioned inverted type, are almost defenseless against such noise from above. It became.

Therefore, the present invention provides a soundproof wall for reducing traffic noise that can exhibit a high soundproofing effect against vehicle running noise on railways, expressways, etc.

[Means to solve the problem]

The invention of claim 1 is characterized in that an eave wall is provided at the upper end of an upright wall provided perpendicularly to the track floor surface to protrude toward the track side, and an upwardly directed wall projects upward at the tip of the eave wall. The upwardly oriented wall is provided with a sound absorbing structure on the track side surface.

Further, the invention according to claim 2 is based on the configuration according to claim 1, and a sound absorbing structure is provided on the surface of the upwardly oriented wall opposite to the track side.

Furthermore, the invention of claim 3 is such that, in addition to the structure of claim 1 or 2, an overhanging wall is provided at the upper end of the upright wall to block downward sound from above and upward sound from below. .

[Effect]

According to the configuration of claim 1, noise generated at a low position (transfer noise) can be effectively attenuated by the upwardly directed wall at the exit portion (the effect in this respect will be described in detail later). For this reason, a higher soundproofing effect can be obtained compared to conventional soundproofing walls, including inverted-shaped ones that do not have this effect.

Further, according to the second aspect of the present invention, among the sound waves that turn diagonally downward from the upper end of the upwardly oriented wall due to a diffraction phenomenon, the sound waves that wrap around the outer surface of the same directional wall can be absorbed by the sound absorbing structure.

Furthermore, according to the third aspect of the present invention, the diffracted sound wave can be second-order diffracted at the tip of the overhanging wall to weaken the sound wave energy. Therefore, the sound emitted from the outlet is further attenuated by the overhanging wall, further enhancing the soundproofing effect.

Furthermore, since this overhanging wall acts as a soundproof wall against general noise directed from above to below, it is also effective against current collection system noise.

〔Example〕

Embodiments of the present invention will be described with reference to FIGS. 1 to 13.

First Embodiment (See FIGS. 1 to 6) In this embodiment, a soundproof wall used in an elevated railway is taken as an example.

In Fig. 1, reference numeral 1 denotes an upright wall provided perpendicularly to the track floor surface R, and a horizontal eaves wall 2 is provided at the upper end of this upright wall 1 to protrude toward the track (vehicle T) side. An upwardly oriented wall 3 is vertically projected upward from the tip of the eaves wall 2 to constitute a soundproof wall.

These upright walls 1, eaves walls 2, and upwardly directed walls 3 are made of materials with sound insulation performance such as concrete, slate, plastic, steel plates, aluminum plates, etc.
1 is formed on the upright wall 1 on the track side surface of the main body wall work 1, and on both the inner and outer surfaces of the main body wall 21 on the eaves wall 2 and the upwardly directed wall 3, rock wool, glass wool, foam metal, ceramic, etc. are formed. , sound absorbing materials such as foam concrete 12
゜22.23.32.33 are provided.

In addition, these sound absorbing materials 12.22, 23.32°33 are
Bolts, pins, adhesives (not shown), depending on the material etc.
It is attached to the main body wall using a perforated plate or wire mesh.

In addition, the total height of this soundproof wall, like conventional soundproof walls, is limited in terms of visibility from the car window, wind load resistance, etc.

The function of this soundproof wall will be explained by comparing it with a conventional inverted-shaped soundproof wall.

As is well known from Huygens' principle, sound waves generated from a single sound source have the property of spreading and progressing while creating new sound sources and wavefronts one after another.

FIG. 2 shows how sound waves move forward in a conventional inverted-shaped soundproof wall, and FIG. 3 shows how sound waves move forward in a soundproof wall according to the present embodiment.

In both figures, the arc a-a represents the wave front position from the sound source P located at an arbitrary position, and the arc b-b' represents the wave front position a-
The wave front positions at the time point when Δ has elapsed from a' are shown. Also, the black spot on the wave front bb' is
The position of a minute sound source through which a sound wave propagates starting from the wave front surface is exemplarily shown. Furthermore, the wave front position after a certain period of time has passed when the sound wave spreads from each of these minute sound sources as a starting point is shown by a broken line arc.

Comparing the two, the amount of minute sound sources that are the source of sound waves radiated to the outside from the opening surface o-o' is found in the soundproofing wall of this embodiment shown in Figure 3 compared to the inverted-shaped soundproofing wall shown in Figure 2. This is less than in the case of a wall (for example, there is no influence from the sound waves emitted from the minute sound source in the left side area of the figure than on the line segment o-a such as Q construction, Q2゜Q3), and the external radiated sound is correspondingly smaller. Become.

In addition, the soundproof wall of this example is superior to the inverted-shaped soundproof wall in the following points in terms of soundproofing effect.

(I) In Fig. 2, the sound wave that spread from the sound source P to the arc a-a spreads at the exit O-0' to the arc d-0', which is wider than the exit, as shown by the two-dot chain line in the figure, so the eaves If the inner surface of wall W2 is completely sound absorbing (o-o' distance/
d − o 'distance) times and is emitted.

On the other hand, in the case of the soundproof wall of this embodiment shown in FIG.
The sound waves that have spread to ' are absorbed by the inner sound absorbing material 32 of the upwardly oriented wall 3 before reaching the exits 0-0 (a-o), and the rest is radiated.

Assuming that the distance to the vehicle side wall is constant, the sound energy ♂ absorbed here is approximately lCcα・(o−
a distance) (α is the sound absorption coefficient), so it is possible to reduce the sound by more than (o-o'distance/d-o' distance) in the case of an inverted-shaped soundproof wall.

(II) Comparing the intensity of the sound wave propagating along the path A near the directional wall 3 shown by the dashed line in FIG. 3 with the intensity of the sound wave propagating along the same path B as the path A shown in FIG. A
Since the sound waves that propagate are attenuated to a greater extent by the sound absorbing material 32, considering the directionality of the sound that is extracted upward from the exit 0-o', the sound waves that propagate upward are more directivity in the case of the soundproof wall of this embodiment. Sexuality is strengthened. Accordingly, the force of the sound waves that circulate downward from the exit can be reduced.

In order to demonstrate the difference in soundproofing effect between the conventional soundproofing wall and the soundproofing wall of this example, and also to understand how the soundproofing effect changes depending on the height of the upwardly directed wall 3, the present inventor conducted a computer sound field study. Figure 4 shows the calculation results of the simulation. Here, 500 is a typical noise frequency.
Calculations were performed in Hz. The vertical axis in Figure 4 shows the amount of soundproofing improvement (dB) for an inverted-shaped soundproofing wall of the same height.
) is taken.

As a result of this calculation, as shown in the figure, the height of the upwardly directed wall 3 is 200. , it was confirmed that a sufficient soundproofing effect can be obtained.

On the other hand, computer simulation results of the sound pressure distribution around the soundproof wall are shown in FIG. 5 (in the case of the inverted-shaped soundproof wall) and FIG. 6 (in the case of the soundproof wall of this embodiment).

From both figures, it can be seen that in the soundproof wall of this example, the directivity of sound waves is stronger in the upward direction and weaker in the lateral direction, and the magnitude of the externally radiated sound is smaller.

Second embodiment (see Figures 7 to 11) Only the differences from the first embodiment will be explained.

In the soundproof wall of the second embodiment, in addition to the soundproof wall of the first embodiment, an overhanging wall 4 is provided at the upper end of the upright wall 1 and projects obliquely upward on the side opposite to the track side. Like the other walls 1, 2.degree. 3, this overhanging wall 4 is made up of a sound absorbing material 42 provided on the upper surface of a main body wall 41 having sound insulating properties.

The function of this soundproof wall will be explained with reference to FIG.

In the case of the soundproof wall of the first embodiment without the overhanging wall 4, if we consider a sound wave that passes diagonally upward and passes over the upper end of the upwardly directed wall 3, as shown by x-x' in FIG. The part moves straight in the direction of
Sound waves passing further outside travel straight downward diagonally without regulation, as shown by the two-dot chain line.

Furthermore, in addition to such diffracted sound waves, most of the obliquely downward sound waves of current collection system noise are emitted unregulated around the orbit.

On the other hand, according to the soundproof wall of the second embodiment, Fig. 8 (b)
As shown by the broken line I, a large portion of the diffracted sound waves at point D enters the overhanging wall 4, a portion is absorbed by the sound absorbing material 42, and the rest is emitted obliquely upward.

In addition, the sound wave that passes from point D to the outside by passing over the tip F of the overhanging wall 4 as shown by the two-dot chain line is also diffracted once more (secondary diffraction) at point F, as shown by the one-dot chain line, and its energy is weakened. Turn diagonally downward.

This results in the overhanging wall 4 having the same effect as providing an upright wall 1' high enough to block the view from the train window, as shown by the thick two-dot chain line in Figure 8(0). .

In addition, for the -order diffraction sound wave, the broken line ■ in Figure 8 (b)
As shown in , some sound waves are reflected from the upper surface of the eaves wall 2 and reach point F, but since most of the sound waves incident on this eave wall 2 are absorbed by the sound absorbing material 23, the sound waves reaching point F are The absolute amount of can be kept small.

Furthermore, the first-order diffracted sound wave that wraps around from point D to the outer surface of the directing wall 3 as shown by the broken line ■ is absorbed by the sound absorbing material 33 . This point also applies to the first embodiment. Also,
Although not shown, this sound absorbing material 33 also exhibits a sound absorbing effect on sound waves that are reflected by the overhanging wall 4 and incident on the directional wall 3.

On the other hand, the overhanging wall 4 exhibits an unprecedented soundproofing effect against the diagonally downward component of current collection noise through the effects of reflection, sound absorption, and diffraction.

FIG. 9 shows the calculation results of a sound field simulation conducted by the present inventor in order to verify the soundproofing effect of the overhanging wall 4 and to understand how the soundproofing effect changes depending on the length of the overhanging wall 4. Here, in the case of a 500 Hz downward sound source [Fig. 9 (a)] and in the case of a 500 Hz upward sound source [Fig. 9 (b)], the amount of soundproofing improvement over the soundproof wall of the example without the overhanging wall 4 is shown. (dB) was calculated.

As is clear from both figures, in both the case of the downward sound source and the upward sound source, substantially sufficient soundproofing improvement results were obtained if the overhanging wall 4 had a diameter of 400 or more.

On the other hand, computer simulation results of the sound pressure distribution around the soundproof wall are shown in FIG. In the soundproof wall of this example, the angle θ between the overhanging wall 4 and the upright wall 1 was 45°, and the length was 900#ll11.

As a result, the sound pressure in the lower region was reduced by about 4 dB as a soundproofing effect of the soundproof wall of this example.

By the way, the angle θ of the overhanging wall 4 with respect to the upright wall I is not particularly limited, and experiments have shown that if it is in the range of 90° to 180°, a remarkable effect on transfer noise and current collection system noise is exhibited. confirmed. In addition, the longer the length of the overhanging wall 4 is, the more effective it will be within the permissible range in terms of strength such as wind load resistance and ensuring visibility from the car window, but normally, a length of 300 #11 or more is sufficient. This was confirmed through experiments.

Other Embodiments FIG. 12 is based on the configuration of the first embodiment, and
FIG. 3 shows a case where the upwardly oriented wall 3 is extended toward the track floor R side, based on the configuration of the second embodiment. In this way, the sound absorption effect of the above-mentioned upwardly oriented wall 3 will be even higher.

Further, in the above embodiment, all of the walls constituting the soundproof wall are provided with a sound absorbing structure. In the invention, a sound absorbing structure may be provided at least on the track side surface of the directional wall 3 (in particular, the sound absorbing material 23 on the upper surface side of the eave wall 2 may be omitted).

Furthermore, this sound absorbing structure is not limited to the structure in which a sound absorbing material is provided on the main body wall as in the above embodiment, but it is also possible to use a structure such as foamed concrete that serves as both a wall material and a sound absorbing material.

[Effects of the Invention] As described above, according to the invention of claim 1, an eave wall is provided at the upper end of the upright wall protruding toward the track side, and a sound absorbing structure is provided on the side surface of the track at the tip of the eave wall. Since the upwardly directed wall is provided to protrude upward, noise generated at a low position can be effectively attenuated by the upwardly directed wall at the exit portion. For this reason, a higher soundproofing effect can be obtained compared to conventional soundproofing walls, including inverted-shaped ones that do not have this effect.

Furthermore, in addition to the configuration of claim 1, the invention of claim 2 provides a sound absorbing structure on the outside surface (opposite to the track side) of the upwardly oriented wall, so that the outer surface of the directional wall is This sound absorbing structure can absorb diffracted sound waves that go around to the side.

Furthermore, according to the invention of claim 3, based on the configuration of claim 1 or 2, an overhanging wall is provided at the upper end of the upright wall to block downward sound from above and upward sound from below, so that the diffracted sound waves are The sound wave energy can be weakened by secondary diffraction at the tip of the overhanging wall. Therefore, the sound emitted from the outlet is further attenuated by the overhanging wall, further enhancing the soundproofing effect.

Furthermore, since this overhanging wall acts as a soundproof wall against general noise directed from above to below, it is also effective against current collection system noise.

As described above, compared to conventional soundproof walls, various traffic noises can be reduced and noise pollution can be suppressed.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing the first embodiment of the present invention, Fig. 2 shows the soundproofing effect of the conventional inverted-shaped soundproof wall and its problems, and Fig. 3
The figures are diagrams for explaining the soundproofing effect and the advantages of the soundproofing wall of the first embodiment, FIG. 4 is a graph for explaining the improved soundproofing effect of the soundproofing wall of the first embodiment, and FIG.
The figure shows the sound pressure distribution in the case of the conventional inverted-shaped soundproof wall, FIG. 6 shows the sound pressure distribution according to each computer sound field simulation in the case of the first embodiment soundproof wall, and FIG. 7 shows the sound pressure distribution in the case of the second embodiment of the present invention. 8(a) and 8(b) are graphs for explaining the soundproofing effect of the soundproofing wall of the same example and the soundproofing wall of the first example and the soundproofing improved state of the soundproofing wall of the second example. Fig. 10 shows the sound pressure distribution in the case of the conventional inverted-shaped soundproof wall, Fig. Example, FIG. 13 is a sectional view showing yet another example,
FIG. 14 is a sectional view of a conventional inverted-shaped soundproof wall. 1... Vertical wall, 2... Eaves wall, 3... Upward oriented wall, 32.33... Solid wall sound absorbing material, 4... Overhanging wall. Figure 1

Claims (1)

[Claims] 1. An eaves wall is provided at the upper end of an upright wall provided perpendicularly to the track floor surface to protrude toward the track side, and an upwardly oriented wall is provided at the tip of this eave wall to face upward. A soundproof wall for reducing traffic noise, characterized in that the upwardly oriented wall is provided with a sound absorbing structure on its track side surface. 2. The soundproof wall for reducing traffic noise according to claim 1, wherein a sound absorbing structure is provided on the surface of the upwardly oriented wall opposite to the track side. 3. The soundproof wall for reducing traffic noise according to claim 1 or 2, wherein an overhanging wall is provided at the upper end of the upright wall to block downward sound from above and upward sound from below.