WO2005116341A1

WO2005116341A1 - Noise barrier wall

Info

Publication number: WO2005116341A1
Application number: PCT/FI2005/000218
Authority: WO
Inventors: Erkki NÄRHI
Original assignee: Rautaruukki Oyj
Priority date: 2004-05-31
Filing date: 2005-05-12
Publication date: 2005-12-08
Also published as: FI117209B; FI20040738A0; FI20040738A

Abstract

The invention relates to a noise barrier wall (10), comprising at least two metal plates parallel to the noise barrier wall, the first and the possible third metal plate (1; 3) being provided with sound permeating perforations (11) and the second metal plate (2) not containing perforations. The first and the possible third plate are at least partly located at a distance from the second plate, forming between them an interior space or interior spaces (V1; V2), and in it/them porous sound damping material. The porous sound damping material (4a; 4b) is polyester fibre wool, the fibres of which have additionally been treated with a finishing agent of finishing agent or finishing agents, increasing the hydrophobicity of the polyester surface.

Description

Noise barrier wall

The present invention relates to a noise barrier wall, which comprises: at least two metal plates parallel to the noise barrier wall, of which at least the first metal plate is provided with sound penetrating perforations and at least the second metal plate does not contain perforations, the plates being located at least partly at a first distance from each other forming the first interior space between them; porous noise damping material in the said first interior space between the said metal plates; and the said first interior space containing lowermost the bottom wall and the opposite top edge.

Noise barrier walls are commonly used in the margins of roads to prevent the traffic noise from transferring, e.g. to settled areas. Noise barrier walls can be very heavy, such as concrete walls, their mass preventing the noise from travelling. Alternatively, noise barrier walls can be of a lighter structure, in which case they contain porous sound absorbing wool, typically mineral wool between two metal plates, of which the one facing toward the road is perforated and the one facing away from the road is solid. The sounds of traffic can then penetrate through the perforations in the metal plate facing toward the road to the mineral wool and be dampened so that they will not reflect back when the opposite solid metal plate prevents the sound from passing through the noise barrier wall. Because rain and condensing water will in any case penetrate between the metal plates, wetting the sound absorbing mineral wool, the removal of water and moisture has to be seen to in some way in these kinds of noise barrier walls. Otherwise, the mineral wool will freeze in winter, and its sound insulating ability may then disappear altogether and its structure may break. In addition, while staying moist, mineral wool can start to grow lichen, moss, etc., which will impair its sound insulating ability and finally destroy the whole noise barrier wall by the action of corrosion. One way to remove water from between the metal plates of the noise barrier wall is to arrange a perforated pipe to the lower part of the wall, which will operate as a discharge route for water, preventing simultaneously the mineral wool from moving to the bottom. Mineral wool extending or moving to the bottom would namely block the discharge route.

Another respective way to keep the lower part of the noise barrier wall be- tween the metal plates free of mineral wool is described in the publication

EP-1 148 175, according to which a mineral wool board or fibreglass board lower than the height of the noise barrier wall element has been glued to a solid metal plate at a distance from the bottom of the element. In this publication, also the thickness of the mineral wool or fibreglass board is smaller than the distance of the metal plates of the wall element, which makes it possible to ventilate the intermediate space by means of an air slot on the side facing toward the perforated metal plate. However, such an air slot will increase the thickness of the wall element. In the publication EP-0 368 135 it has again been tried to solve the problems by making the back plate of a noise wall panel of a wood cement plate, the porous sound absorbing sec- tion of two layers of fibreglass repelling water in an undefined way, the density of the layer farther back being bigger than of the one facing toward the noise source. Instead of a uniform plate, the front side of this wall panel consists of a number of inclined lamellas. In all these noise wall solutions, water is very problematic in spite of its various prevention methods because, simi- lar to mineral wool, also fibreglass will always become wet irrespective of any known pretreatment. There will then occur the said molding and, consequently, corrosion of metal plates, i.e. fast loss of sound prevention properties and structural damage in the entire noise barrier wall. Especially the thickness of the noise barrier wall according to EP-0 368 135 is even bigger than that of the wall element of EP-1 148 175, due to the lamellas, naturally when structures with the same sound insulating ability are compared, the big thickness clearly not being considered a detrimental feature in any way.

The publication JP-11081515 discloses a sound damping element, in which polyvinylidene chloride fiber is used as sound absorbing material; it is slightly harder than ordinary PVC, but its other properties are similar to PVC. These sound insulating fibers are glued to each other by melting bridging polyester fibers so that this portion of fibers is a melt glue. The publication JP-2004197404 describes an acoustic panel, in which the cover plates of all side surfaces are perforated, and untreated polyester fibre is used as the sound insulating material. A piece made of sound insulating polyester fibre material is as a whole wrapped inside a cladding material, which consists of non-woven polyester fibre fabric. It can be understood from the publication that the non-woven fabric is so tight that it does not substantially permeate water, i.e it repels water. The publication KR-9607197 discloses a sound in- sulation structure, in which, first of all, the surface plates are made of ABS plastic and the structure further contains an extra air layer beween the second surface plate and the sound insulating material, and a grid-type guide plate achieving a respective air layer between the perforated surface plate and the sound insulating material, the purpose of the slots being to prevent water from contacting the sound insulating material, as has been explained above. The sound damping material is a uniform piece of polyester fibre wrapped in a silk net; i.e. the solution is equivalent to the one disclosed in JP-2004197404. As is well known, silk is extremely hydrophilic, which is one reason for it being so pleasant e.g. in clothes.

The object of the invention is to produce a noise barrier wall, in which the detrimental effects of moisture would be eliminated as efficiently as possible. The second object of the invention is to produce such a noise barrier wall, the total thickness of which would be as small as possible while simultaneously keeping the sound insulating ability sufficient or excellent. The third object of the invention is to produce such a noise barrier wall, which could damp sound coming from both directions.

The problems disclosed above can be eliminated and the objects defined above can be achieved by a noise barrier wall according to the invention, which is characterised in what is defined in the characterising part of claim 1.

The most essential advantage of the invention is that, when using the sound absorbing wool according to it, the detrimental effects of moisture can be prevented as efficiently as possible. By means of a special embodiment of the invention it is surprisingly also possible to achieve a very thin noise wall structure, which would not be possible by using the known solution methods. As the second advantage, this very thin structure again makes possible the implementation of a two-sided noise wall, i.e. a noise wall damping noise coming from both opposite directions, which can be used, for example, in railways between the rail pairs. The rail pairs or tracks have very little room especially in settled areas, due to the dimensioning of tracks and the kinematic gauges of trains but, nevertheless, it must be possible to reduce noise on both sides of the tracks in order to achieve an efficient effect. The third advantage of the invention is that this kind of a thin two-sided noise wall can be made so rigid and strong that it will endure the air pressure shocks caused by trains passing with great speed without being damaged. A further advantage of the invention is the fast, simple and thus cost-effective manufacture of the noise barrier wall according to it, which is caused e.g. by the sound damping wool used in the invention being flexible and compressible. The invention will next be explained in more detail, referring to the enclosed drawings, in which

Figure 1 discloses a two-sided noise barrier wall according to the most advantageous embodiment of the invention, in which the sound damping mate- rial according to the invention is used, in an axonometric view, partly cut open. In this embodiment, metal plates provided with apertures are connected to an unperforated metal plate in the middle by mechanical fasteners.

Figure 2A shows a phase in the assembling of the two-sided noise barrier wall according to Figure 1 before the compression of the perforated surface plates to the unperforated metal plate in the middle, in section III - III of Figure 3, corresponding to the direction I in Fig. 1.

Figure 2B shows a phase in the assembling of the two-sided noise barrier wall according to Figure 1 , in which the perforated surface plates are compressed to the unperforated metal plate in the middle, i.e. a finished noise barrier wall according to Figure 1 , in a section IV - IV of Figure 2, corresponding to the direction II of Figure 1. The one surface plate is connected to the centrere plate by mechanical fasteners, and the other surface plate is connected to the centre plate in another way.

Figure 3 shows a one-sided noise barrier wall according to a second em- bodiment of the invention, in which sound damping material of the invention is used, in an axonometric view, partly cut open. In this embodiment, the metal plates provided with apertures are connected to a second unperforated metal surface plate by a suitable design.

The noise barrier walls and also panels or elements, of which the noise bar- rier walls can be assembled, typically comprise two metal plates parallel to the noise barrier wall, i.e the surface plates of the wall or wall panel. Of these surface plates, which most often have been made of plastic-coated steel plates, the first metal plate 1 is provided with sound permeating perforations 11 , the plate being arranged to point towards the noise source when assembled. Of these surface plates, the second metal plate 2 does not contain perforations, i.e. it is a solid or unperforated plate, and it will be placed on the side of the noise barrier wall, which points away from the noise source. These metal surface plates 1 and 2 are located at least partly at the first distance S1 from each other, forming the first interior space V1 between them. This first interior space V1 between the metal plates contains porous sound damping material 4a, which absorbs sound coming to the interior space through the perforations 11 or similar apertures in the first metal plate 1. The solid second metal plate 2 again prevents the passing through of sound that has entered the interior space. Because the noise barrier wall 10, as the panels operating as structural elements of the wall, necessarily has a certain height - this substantially in the direction of gravity - the first interior space V1 has lowermost the bottom surface 6 and the opposite upper edge 7. Generally described, the noise barrier wall or wall panel or wall element is a box, which contains a certain amount of sound-absorbing material, and of the opposite plate surfaces of which the one is sound permeating and the second sound non-permeating. The opposite surface plates are connected to each other either from the area of the edges or from the middle sections.

According to the invention, the porous sound damping material 4a i.e. sound absorbing material is polyester fibre wool, the fibres of which have additionally been treated with a finishing agent or agents, increasing the hydropho- bicity of the polyester surface. More exactly, essentially the surfaces of all the fibres of the polyester fibre wool comprise a hydrophobic surface treatment, i.e the surface treatment according to the invention extends to the fi- bres in the interior of the sound insulating piece in the same way as to the fibres near the outer surface of the piece. Tolerances and variations related to different matters must naturally be taken into account, i.e. nothing is perfect in real pieces. Polyester has inherently a considerably higher or stronger hy- drophobicity than the basic material for fibreglass or mineral wool. In other words, the contact angle of a drop of water on a pure polyester surface is relatively big so that water stays as a drop and will thus not wet the polyester surface. Such material can also be called water repellent. The higher the value of the contact angle, the stronger or higher the hydrophobicity. As the opposite, for example, the contact angle of a drop of water on a pure glass surface is relatively small so that water will spread widely and wet the glass surface. Thus, a glass surface can be considered mainly a hydrophilic surface. The effect, which notoriously is a situation of three conditions or phases, is also called wetting. Thus, the invention uses a sound damping material made of polyester fibre so that the contact angle of water is big - i.e. water wets poorly - and this contact angle is still increased by a suitable finishing agent or suitable finishing agents - i.e. one tries to minimise the wetting by water. Such a sound damping material of the invention consisting of a highly hydrophobic polyester fibre, more exactly polyester fibre wool, allows practically all the water landing on or in it for any reason to flow through fast and efficiently, by the action of its own weight. The flow-through of water can be made so efficient that such a porous sound damping material 4a in the first interior space V1 can be in contact both with the first metal plate and the second metal plate and to extend to the said bottom surface 6 in the interior space, i.e. fill the volume defined by the first metal plate 1 and the second metal plate 2 and the bottom surface 6 and, naturally, also the upper edge 7. It can especially be stated that no air slot or air slots are needed in the noise barrier wall 10, which has a sound damping layer consisting of hydrophobic polyester fibre wool according to the invention. When the intermediate space V1 between the metal surface plates 1 and 2 can be totally filled with sound damping material, the sound insulating ability can be made better with the same thickness of the wall or, alternatively, the same sound insulating ability can be achieved with a thinner wall. No horizontal discharge channel is needed in the bottom section i.e. on the bottom surface 6 of a noise barrier wall with a sound damping layer consisting of hydrophobic polyester wool according to the invention. Thus, it is not necessary to glue the sound damping material to the surface plates to leave a channel to the lower edge of the wall, or to install a perforated water discharge pipe to the lower edge of the wall to prevent the wool from flowing down. The structure will be simple and efficient. For the part of the upper edge 7 of the noise barrier wall, one can proceed as desired for other reasons. Such a basic form of the noise barrier wall of the invention, which is intended for damping the noise M coming from one side, is shown in Figure 3.

A special embodiment of the invention further comprises a third metal plate 3, which is provided with sound permeating perforations 11. The said third metal plat 3 is at least partly located at the second distance S2 from the unperforated second metal plate 2, forming the second interior space V2 be- tween. The second interior space V2 has lowermost the bottom surface 6 and the opposite upper edge 7, in the same way as the first interior space V1. Further, according to the invention, the second interior space V2 has sound damping material 4b, i.e. sound absorbing material, the material used being polyester fibre wool, the fibres of which have additionally been treated with a finishing agent or finishing agents, increasing the hydrophobicity of the polyester surface, as has been explained above. In other words, the third metal plate 3, the second metal plate 2 and the sound damping material 4b in the second interior space V2 form a sound damping and insulating structure of the same type as, but not necessarily identical with the one consisting of the first metal plate, the second metal plate 2 and the sound damping material 4a in the first interior space V1. The third metal plate 3 and the sound damping material 4b in the second interior space V2 are located generally as a mirrored image in relation to the second metal plate 2, compared with the location of the first metal plate 1 and the sound damping material 4a in the first interior space V2. The unperforated second metal plate 2 is thus possibly located in the middle sections of the noise barrier wall, but at least between the sound damping materials 4a and 4b, the perforated first and third metal plates 1 and 3 being again located on their outer surfaces. As has been explained relating to the first interior space V1 , such a porous sound damping material 4b in the second interior space V2 can be in contact with both the third metal plate and the second metal plate and extend until the said bottom surface 6 in the interior space, i.e. fill entirely the volume defined by the third metal plate 2 and the second metal plate 2 and the bottom surface and, naturally, also the upper edge 7. Such a further developed form of the noise barrier wall of the invention intended to damp the noise M coming from both sides has been shown in Figures 1 and 2B.

The two-sided noise barrier wall 10 described above can be made both thin and enduring external loadings, such as pressure waves, by using corrugated plates as the first metal plate 1 , the second metal plate 2, and the third metal plate 3, as is shown in Figure 1 - 2B. The corrugations of corrugated plates can be trapezoidal, as the middlemost metal plate 2 shown in the Fig- ures, or sine wave, as the first metal surface plate 1 in the Figures, or a combination of opposite hemi-circle corrugations, as the third metal surface plate 3 in the Figures, or some other respective form. The corrugated plates are preferably steel plates, which have, for example, been zinc-coated and/or plastic-coated and/or finished in some other desired way. The corru- gated plates are known as such, so they will not be explained in more detail here. The corrugated plates, more exactly their corrugated forms have the corrugation width W_A, W_B, W_c, which is perpendicular to both the generally known corrugation length and the corrugation height. The corrugation length W_B of the unperforated second metal plate 2, located between the first and second perforated metal plates, is transverse in relation to the corrugation width W_A of the first metal plate 1 and the corrugation width W_c of the third metal plate 2, as is shown in the Figures. It has to be understood that the corrugations of the unperforated second corrugated metal plate 2 form alternating corrugation cavities Q2a and Q2b on the opposite sides of the plate, which are thus defined by the metal plate surfaces or the plane or envelope travelling through the ridges of the corru- gation form. Because in this case there is a two-sided noise barrier wall and the plate in its middle, there are effective corrugation cavities on both sides of the plate. Respectively, the corrugations of the first corrugated metal plate 1 form corrugation cavities Q1 and the corrugations of the second corrugation metal plate 2 form the corrugation cavities Q2, which are thus defined by the metal plate surfaces and the planes or envelopes travelling through the ridges of the corrugation forms. However, these corrugation cavities Q1 , Q2 are only found on one side, i.e. the interior side of the plates, because these metal plates are surface plates, the opposite other side or outer side is open to the environment. Thus, here the word "corrugation" refers exactly to the corrugation plate. The porous sound damping materials 4a and 4b in the first interior space V1 and second interior space V2 fill as a uniform piece the crossed corrugation cavities Q1 and Q2a; Q3 and Q2b between the first and second metal plate and the third and second metal plate, respectively. In other words, the spaces between the surfaces of the first, second and third metal plate are substantially entirely filled by the sound damping material. In this case all the sound damping material layers of different densities attached or supported to the sound damping material 4a and/or 4b and all possible other support layers or protective layers or fabrics or films, etc. are considered to be part of the sound damping material 4a and 4b. Especially all layers of polyester are part of the sound damping material 4a and 4b.

The first metal plate 1 is attached to the second metal plate 2 from the first areas A1 of the corrugation form ridges 8a, 8b pointing toward each other. Respectively, the third metal plate 3 is attached to the second metal plate 2 from the second areas A1 of the corrugation form ridges 9a, 9b pointing to- ward each other. The metal plates 1 and 2 and the metal plates 3 and 2, respectively, are attached to each other by screws 12, rivets 13, such as pop rivets, or glue 14. The first metal plate 1 and the second metal plate 2 are on the first areas A1 at least at the spacing S from each other, and the third metal plate 3 and the second metal plate, respectively, are on the second areas A1 at least at the spacing S from each other. This spacing S, which is as small as possible, is caused by the preferable manufacturing method of the noise barrier wall of the invention, due to which the spacing S has com- pressed sound damping material 4a and/or 4b. The noise barrier wall can be manufactured by superimposing or assembling side by side all the laminar components of the wall, e.g. sound damping materials 4a and 4b as flat plates, as is shown in Figure 2. When the first and third metal plates are then pressed towards each other with force F, sound damping material of the invention based on polyester wool is transferred to the corrugation cavities Q1 and Q2a; Q3 and Q2b in the direction of the dashed lines N at the same time as it is compressed on the areas A1 , A2 of the corrugation form ridges 8a, 8b and/or 9a, 9b. This technique is based on the resilience of the polyester fibre wool. After this, the fastening between the metal plates is made with glue, rivets or screws. It is clear that also one-sided noise barrier walls can be made in a respective way and that even two-sided noise barrier walls can be asymmetrical.

The finishing agent of the sound damping polyester fibre wool used in the invention contains at least polyvinyl alcohol and secondary alkyl sulphonate, the mixture ratio of polyvinyl alcohol (PVA) and secondary alkyl sulphonate (SAS) being between 30% PVA + 70% SAS - 50% PVA + 50% SAS. Preferably, the share of polyvinyl alcohol is approx. 40% and that of secondary alkyl sulphonate is approx. 60%. In the finishing agent, secondary alkyl sul- phonate is preferably triethanol amine C 6-20. Further, the finishing agent can include an intermediary substance, which can, for example, be poly- fluorophosphate.

Claims

1. Noise barrier wall, comprising:

- at least two metal plates parallel to the noise barrier wall (10), of which at least the first metal plate (1 ) is provided with sound permeating perforations (11 ) and at least the second metal plate (2) does not contain perforations, the plates being located at least partly at a first distance (S1) from each other, forming between them a first interior space (V1 );

- porous sound damping material (4a) in said first interior space between said metal plates; - said first interior space has lowermost a bottom surface (6) and an opposite upper edge (7), characterised in that said porous sound damping material (4a) is polyester fibre wool, the fibres of which being additionally treated with such a finishing agent or finishing agents, which increase the hydrophobicity of the polyester surfaces.

2. Noise barrier wall according to claim 1 , characterised in that it further comprises:

- a third metal plate (3) provided with sound permeating perforations (11 ) and located at least partly at a second distance (S2) from the unperforated second metal plate (2), forming therebetween a second interior space (V2) that has lowermost a bottom surface (6) and an opposite upper edge (7);

- porous sound damping material (4b) in said second interior space (V2), said material being polyester fibre wool, the fibres of which being additionally treated with a finishing agent or finishing agents increasing the hydrophobic- ity of the polyester surfaces.

3. Noise barrier wall according to claim 1 or 2, characterised in that

- said porous sound damping material (4a) in the first interior space (V1 ) is in contact both with the first metal plate and the second metal plate, and extends until said bottom surface (6) in the interior space; and/or - said porous sound damping material (4b) in the second interior space (V2) is in contact both with the second metal plate and the third metal plate, and extends until said bottom surface (6) in the interior space.

4. Noise barrier wall according to claim 1 or 2, characterised in that said first metal plate (1 ), said second metal plate (2), and said third metal plate (3) are corrugated plates.

5. Noise barrier wall according to claim 4, characterised in that the corrugation width (W_B) of said unperforated second metal plate (2) located between the first and second metal plate is transverse in relation to the corrugation width (W_A) of said first metal plate (1 ) and the corrugation width (W_c) of said third metal plate (2).

6. Noise barrier wall according to claim 5, characterised in that the porous sound damping materials (4a and 4b) in the first and second interior space (V1 and V2) fill as a uniform piece the crossing corrugation cavities (Q1 and Q2a; Q3 and Q2b) between the first and second metal plate, and between the third and second metal plate, respectively.

7. Noise barrier wall according to claim 5 or 6, characterised in that the first metal plate (1 ) is attached to the second metal plate (2) from first areas (A1 ) of corrugation form ridges (8a, 8b) pointing toward each other, and the third metal plate (3) is attached to the second metal plate (2) from second areas (A2) of corrugation form ridges (9a, 9b) pointing toward each other.

8. Noise barrier wall according to claim 7, characterised in that the first metal plate (1 ) and the second metal plate (2) are from the first areas (A1 ) at maximum at a spacing (S) from each other, and respectively, the third metal plate (3) and the second metal plate (2) are from the second areas (A2) at maximum at a spacing (S) from each other; and that there is compressed sound damping material (4a;4b) in said spacing (S).

9. Noise barrier wall according to claim 7 or 8, characterised in that the first metal plate (1 ) and the second metal plate (2), and the third metal plate (3) and the second metal plate (2), respectively, are attached to each other by screws (12), rivets (13) or glue (14).

10. Noise barrier wall according to one of the preceding claims, characterised in that said finishing agent of the sound damping polyester fibre wool contains at least polyvinyl alcohol and secondary alkyl sulphonate.

11. Noise barrier wall according to claim 10, characterised in that the mix- ture ratio of polyvinyl alcohol and secondary alkyl sulphonate is between

30%+70% - 50%+50%.

12. Noise barrier wall according to claim 10 or 11 , characterised in that said secondary alkyl sulphonate in the finishing agent is triethanolamine C 6-20.

13. Noise barrier wall according to claim 10 or 11 or 12, characterised in that said finishing agent of the polyester fibre wool further comprises an intermediary substance; and that the intermediary substance is polyfluoro- phosphate.