WO2002099200A1

WO2002099200A1 - Noise barrier wall

Info

Publication number: WO2002099200A1
Application number: PCT/NL2002/000362
Authority: WO
Inventors: Henricus Johannes Raymundus Antonius Pessers
Original assignee: Pessers Henricus Johannes Raym
Priority date: 2001-06-06
Filing date: 2002-06-04
Publication date: 2002-12-12
Also published as: EP1397558A1; NL1018220C2

Abstract

A noise screen for a traffic route, said screen being composed of a substantially vertically extending wall, which extends alongside the traffic route. In order to limit the inflence of wind on the effectiveness of the noise screen a construction of (2) of mesh material is provided on the top edge of the wall of the noise screen for breaking the wind, said construction of mesh material extending over some distance above the wall of the screen, en projects over some distance beyond the side of the wall of the screen facing the traffic route (A). Preferably the construction of mesh material is composed of two concentric in cross section circular mesh walls (3,4), a strip of sound-absorbing material being situated in the center point. The outer mesh wall (3) has a greater air permeability than the inner mesh wall (4).

Description

NOISE BARRIER WALL

The present invention relates to a noise screen for a noise source, such as a traffic route, which screen is composed of a substantially vertically extending wall, which extends alongside the traffic route.

The currently known noise screens generally work according to the principle that said screens form an obstacle for the sound waves coming from the traffic towards the buildings situated near the traffic route. The sound waves in this case are reflected and/or deadened by the screen. In other words, the noise screen creates a so-called "acoustic shadow" behind the screen, the noise level being clearly lower within this acoustic shadow. However, in the case of the current noise screens little or no account is taken of the influence of wind, although it is known that the wind has a great influence on the propagation of the noise. In the most unfavorable situation, in which the wind flows from the noise source (the traffic) to the recipient (the buildings) behind the noise screen, i.e. virtually perpendicularly to the noise screen, a considerable reduction of the acoustic shadow is caused. The wind, as it were, bends the noise down over the screen. The effectiveness of the noise screen can thus be reduced considerably by the wind.

EP-A-0 315 710 discloses a sound-absorbing pipe, which serves, inter alia, to be fixed on a wall surrounding a noise source. In this patent specification no mention whatsoever is made of the influence of the wind, and the pipe serves only to absorb the sound.

DE 195 09 678 discloses a similar sound-absorbing pipe, which is fitted on the top edge of a noise screen. Here again, it is purely a matter of absorbing the sound on the spot, and the influence of the wind is disregarded. The object of the present invention is then to design a noise screen in such a way that the negative influence of the wind on its functioning is counteracted, or in any case is considerably reduced, and the noise level in the region behind the screen is considerably reduced.

This object is achieved according to the invention by the fact that a construction of mesh material is provided on the top edge of the noise screen, in order to break the wind, which construction of mesh material extends over some distance above the wall of the screen, and projects over some distance beyond the side of the wall of the screen facing the traffic route.

The invention is based on the idea that breaking the wind along the top edge of the noise screen produces a considerable increase in the "acoustic shadow" behind the noise screen. By means of this construction of mesh material, it is ensured that both the wind flowing upward along the wall of the screen and the wind flowing directly above the top edge of the wall is curbed by the construction, and therefore cannot now have any reinforcing effect on the deflection of the noise over the wall.

According to the invention, the construction of mesh material preferably comprises two walls of mesh material situated at a distance from each other, in the case of which, viewed from the traffic route, the first mesh wall has a greater air permeability than the second mesh wall situated behind it. The construction of mesh material preferably comprises a strip of sound- absorbing material which, viewed from the traffic route, is situated behind the mesh wall or mesh walls. The sound energy present directly above the wall of the screen is the first to reach the ground behind the screen, so that the influence of that sound energy is the greatest. This sound energy is now absorbed in the region in which the wind speed has been reduced virtually to zero.

According to a very expedient embodiment of the invention, the construction of mesh material has a tubular configuration with two concentric mesh walls, the strip of sound-absorbing material being situated inside the inner mesh wall with the lower air permeability. The two mesh walls are preferably circular, with the top edge of the wall of the screen forming the center point of the circle, in which center point of the circle the strip of sound-absorbing material is situated.

The invention is explained in greater detail with reference to the appended drawing, in which: Figure 1 shows diagrammatically a cross section of a noise screen according to the invention, and

Figure 2 shows on a smaller scale the noise screen according to the invention with the airflow caused by it.

In Figure 1 a wall of a noise screen is shown by the reference numeral 1, which wall may be of any suitable type and/or construction. A traffic route extends on the side A of the noise screen, the noise source being formed by the traffic traveling along that route. The buildings are situated on the other side B of the noise screen. The object of the noise screen is to arrest or deaden the sound energy of the traffic, in order to limit the noise nuisance to the buildings as much as possible.

A construction of mesh material is situated along the top edge of the wall 1 the noise screen, which construction is indicated in its entirety by the reference numeral 2. This construction of mesh material, which projects over some distance above the top edge of the wall 1, and projects over some distance beyond the side of the wall 1 facing the traffic route, is composed of two concentric, circular mesh walls 3 and 4, the outer mesh wall 3 of which has an air permeability of 60%, and the inner mesh wall of which has an air permeability of 32%. The mesh used for these mesh walls is a stainless steel mesh, of the type that is used in screens for combating wind and draft nuisance, such as described, for example, in Dutch Patent 1008597 of the Applicant. It will be clear that other types of mesh that meet the specifications can also be used. The center point of the circle of the mesh walls is situated directly above or on the top edge of the wall 1 of the screen, and a strip 5 of sound-absorbing material is provided in this center point, which strip is fitted concentrically with the abovementioned mesh walls and in fact rests upon the top edge of the wall 1. Any suitable sound-absorbing material that is weatherproof can be used for this purpose.

The functioning of the noise screen is substantially based upon the damping of the wind speed directly above top edge of the noise screen and also absorption of the sound on the spot in the region within the construction of mesh material, where the wind speed is virtually zero. Owing to the fact that the construction of mesh material also projects beyond the side of the wall of the screen facing the traffic route, the wind that flows upward along the wall 1 is also damped.

Figure 2 shows the effect of the noise screen according to the invention on the airflow. Owing to the construction of mesh material, a zone 6 with turbulent airflow is created behind and above the noise screen. Said turbulence is caused by the flow on the top side of the construction of mesh material. It was found from earlier research that when sound is propagated through a turbulent zone, a deadening effect is obtained. In other words, the sound will therefore find it more difficult to penetrate through this turbulent zone. Furthermore, the laminar airflow will be deflected upward by the turbulent layer, as is demonstrated by the arrows 7 and 8. The result of this is that a considerably better sound deadening is obtained.

The construction of mesh material can also be provided in the case of already existing noise screens, so that the effectiveness of these existing screens can be increased in a simple, rapid and economic manner, without the height of the screens being essentially increased.

It will be clear that the invention is not restricted to the embodiment illustrated and described here, but that a large number of variants are possible within the scope of the appended claims. For instance, the design of the construction of mesh material can be varied, so long as said construction of mesh material projects above the wall of the noise screen and also beyond the side of the wall facing the traffic route. The construction of mesh material can be fixed on the wall of the noise screen with fixing means that are known per se. Although the invention has been described here as a noise screen for a traffic route, the principle can, of course, also be used in the case of noise screens around noise sources other than those of a traffic route, such as, for example, industrial sites.

Claims

A noise screen for a noise source, such as a traffic route, which screen is composed of a substantially vertically extending wall, which extends alongside the traffic route, characterized in that a construction (2) of mesh material is provided on the top edge of the noise screen, in order to break the wind, which construction of mesh material extends over some distance above the wall of the screen, and projects over some distance beyond the side of the wall of the screen facing the traffic route (A).

10

2. The noise screen according to Claim 1, characterized in that the construction of mesh material comprises two mesh walls (3, 4) situated at a distance from each other, in the case of which, viewed from the traffic route, the first mesh wall has a greater air permeability than the second mesh wall situated

15 behind it.

3. The noise screen according to Claim 1 or 2, characterized in that the construction of mesh material comprises a strip (5) of sound-absorbing material, which, viewed from the traffic route, is situated behind the mesh wall or mesh

20 walls.

4. The noise screen according to the preceding Claims 2 or 3, characterized in that the construction of mesh material has a tubular configuration with two concentric mesh walls, the strip of sound-absorbing material being situated

25 inside the inner mesh wall with the lower air permeability.

5. The noise screen according to Claim 4, characterized in that the two mesh walls, viewed perpendicularly to the wall of the screen, are formed substantially as two concentric circles, with the sound-absorbing strip situated in

30 the center point of the circle.

6. The noise screen according to Claims 5, characterized in that the strip of sound-absorbing material is situated on the top edge of the wall of the screen.

357. The noise screen according to one or more of the preceding Claims 2 - 6, characterized in that the air permeability of the first, outer mesh wall is approximately 60%, and that of the second, inner mesh wall is approximately 30%. The noise screen according to one or more of the preceding Claims 5 - 7, characterized in that the radius of the outer mesh wall lies in the region of 150 - 200 mm.