The present invention relates to a sound absorbing and/or noise reducing wall or baffle primarily for outdoor use. Such wall or baffle may, for example, be used in order to screen off residential areas and for isolating estates from sources of noise, such as airports, road traffic, waste product granulators, shooting ranges, etc.

Walls of this type are well known and disclosed for example in WO 94/03679, EP-A-0393735, EP-A-0576875, DE-A-3027542, AT 336069, and US-A-4143495. All of these sound absorbing walls comprise posts or frame parts which must be safely anchored in the ground, for example by means of blocks of concrete.

The present invention provides a sound absorbing and/or reducing wall or baffle which may be mounted in a much more simple manner without using such posts.

Thus, the present invention provides a sound absorbing and/or reducing wall or baffle primarily for outdoor use, said wall comprising a core of a sound absorbing and/or reducing material, a perforated outer cover covering the major part of the outer surface of the sound absorbing core material and having lower edge portions extending longitudinally along opposite sides of the wall or baffle, and anchoring means for anchoring the opposite lower edge portions of the perforated cover to the ground or to another supporting surface.

When the lower edge portions of the perforated outer cover, which is preferably sufficiently stiff to function as a frame, are fastened to the ground or supporting surface, the vertically extending supports or posts used in connecting with the known walls or baffles may be dispensed with. A wall or baffle according to the invention may be made relatively short so that it may easily be carried or transported to the place of use where the lower edge portion of the perforated

cover may be fastened to the ground or supporting surf ce. Such relatively short wall sections may be mounted in end to end relationship so that a wall of any desired length may be obtained. As the wall or baffle according to the invention may be made in longitudinal sections which may be transported and installed at the position of use relatively easily, the wall of baffle according to the invention is also suitable for use in private gardens or other private properties.

The lower edge portions of the cover may comprise cover parts extending outwardly transversely to the plane of the wall or baffle. Thereby, the lower wall surface being in contact with the ground surface may be substantially increased so as to further stabilize the wall or baffle. Such transversely extending cover parts may be formed as continuous flanges or as lugs or ears extending substantially parallel to the ground or supporting surface. These flanges, lugs or ears may then be anchored to the ground by suitable anchoring means .

In order to increase the stability of the sound absorbing wall, the transversely extending cover parts should preferab- ly be rigidly connected to the remaining part of the cover.

Therefore, reinforcing means, such as ribs for strengthening the connection between the transversely extending cover parts and the adjacent parts of the cover may be provided.

The anchoring means for anchoring the lower edge portions of the perforated cover to the ground may be of any suitable type. As an example, the edge portions of the perforated cover may be connected to heavy iron rails or concrete blocks, which are placed on the ground surface, for example by means of releasable connecting means, such as bolts, hooks, or the like. Alternatively, heavy objects, such as concrete blocks or iron rails may be placed on the upper side of the transversely extending cover parts or flanges. How¬ ever, the anchoring means preferably comprise anchoring members to be driven into the ground, such as rods, pegs or the like.

The core material of the wall or baffle according to the invention may comprise any suitable non-degradable, fibrous, sound absorbing and/or reducing material, such as a fibrous inorganic material. Thus, the core material may comprise inner blocks of mineral wool of relatively low density and outer panels of mineral wool of higher density. Granulated material, such as foamed plastic granules and granules of mineral wool, may also be used as core material. The granu¬ lated material may, for example, be a recycled product.

The core may consist of one or more vertical layers, and each layer may have a varying density along its width. The density of the layer or layers preferably increases with the distance away from the centre of the core. However, the use of a core having inner blocks of uniform density is one of the pre- ferred alternatives. In case the core material is made of fibres, the fineness of the fibres may vary across the width of the core.

The average density of the core material may be 40-450 kg/m ³ , preferably 80-200 kg/m ³ , such as about 100 kg/m ³ . Average densities of the utilised core materials are between 40 and 150 kg/m ³ , preferably 100 kg/m ³ , for the central layer(s) , and between 150 and 450 kg/m ³ , commonly 200 kg/m ³ , for the outer layers.

Since both the granulated materials and the mineral wool are very often used as layers having one dimension negligible in comparison with the other two, such as sheets or the like, the density of the layers expressed in terms of weight per surface unit may be in the range of 15 to 40 kg/m ² , preferab¬ ly in the range of 20 to 25 kg/m ² .

The core material is preferably surrounded by or sandwiched between a netting, which is preferably made from plastic material . A woven or non-woven textile material such as a fibrous web, a fabric or the like may also be used as a covering for the core material, the non-woven structure of

the textile material providing good containment of the fibres or granules in the core. A combination of netting and non- woven textile material may also be used. The core material and the surrounding netting may then form a unit, if desired. The core material may comprise at least one capillary brake extending transversely through the core material.

The perforated outer cover may be of any suitable type capable of imparting sufficient stability and stiffness to the wall or baffle. Alternatively or additionally, a stiffen- ing frame may be fastened to the outer cover. The lower edge portions may also extend from the frame. As an example, the perforated outer cover may define a net or grid structure made for example from wires or rods of steel. These wires or rods may for example be made from stainless steel or be provided with a corrosion preventing coating, such as galvan¬ ization. As an example, the net or grid structure may com¬ prise a plurality of substantially vertically extending spaced wires or rods and a plurality of substantially hori¬ zontally extending spaced wires or rods. The wires or rods may also be made wholly from a relatively stiff plastic material. In case the net or grid structure is not self- supporting, a frame extending along the contour of the wall or baffle may be fastened to the net or grid so as to impart the necessary stiffness thereto.

Alternatively, the cover may be made from perforated plates or panels which may, for example, be made from plastics or wooden material. The cover may instead be made from perfo¬ rated sheet metal. The outer surface of the sheet metal may, for example, be galvanized or provided with another anticorrosive coating.

The perforated cover may have a cross-sectional shape like an inverted U. However, in order to facilitate the manufacture, the cover is preferably made from a pair of halves, which are interconnected along the edges of the wall .

In order to increase the stability of the wall or baffle, the cover parts covering opposite side surfaces of the core material may be interconnected by connecting members, such as rod or wire members, extending through the core material.

The invention will now be further described with reference to the drawings, wherein:

Figs. 1-3 are diagrammatical cross-sectional views of three different embodiments of the sound absorbing or noise redu¬ cing wall according to the invention, and Fig. 4 is a diagrammatical side view of the embodiment of Fig. 1,

Figs. 5 and 6 are exploded views of two different embodiments of the wall according to the invention. Fig. 7 and 8 are diagrammatical cross-sectional views of a further embodiment of the wall according to the invention anchored in different ways,

Fig. 9a and 9b are a front view and a side view, respective¬ ly, of a frame to be used for a wall according to the inven¬ tion, Fig. 10a is a diagrammatical top view of a baseplate to be used for anchoring a wall according to the invention, Fig. 10b is a diagrammatical cross-sectional view of the baseplate of Fig. 10a, Fig. 11 is a diagrammatical cross-sectional view of the anchoring of the frame of Figs. 9a and 9b to the baseplate of Figs. 10a and 10b,

Fig. 12 is a diagrammatical top view of a wall anchored by means of the method of Fig. 11, and Fig. 13 is a diagrammatical side view of a wall made of a combination of rectangular and trapezoidal elements.

The sound absorbing and/or noise reducing wall shown in the drawings comprises a core, which is made from inner blocks 10 of mineral wool having a relatively low density and outer plates or panels 11, which are also made from mineral wool having a density being substantially higher than that of the blocks 10. The blocks 10 are stacked on top of each other,

and the plates 11 cover the opposite outer side surfaces of the stacked blocks. The blocks 10 are arranged between the plates 11 which are backed up by a protective net 25 made, for example, of high density polyethylene. The wall further comprises an outer perforated cover 12 which may, for example, be made from perforated sheet metal or from inter¬ connected wires or rods forming a net or grid structure. The outer cover 12 is preferably made from two almost identical halves 13, which are interconnected along its edges, for example by releasable clamping devices, by welding or by other fastening means.

Oppositely transversely directed flanges or lugs 15 are formed at the lower edge portions of the cover 12. These flanges or lugs 15, which are in contact with a ground sur- face 16, may be formed by bending the lower edge portions of the cover halves 13 or may be integrally connected with these halves in any other manner. As shown in Fig. 2, stiffening fins or webs 17 may interconnect the flanges or lugs 15 and the adjacent outer side surface of the cover 12. The stabil- ity of the wall may be further increased by means of wires or rods 18 extending transversely through the core material of the wall and interconnecting the opposite sides of the cover 12.

The wall or baffle may be fastened to the ground by suitable fastening means, which are able to maintain the flanges or lugs 15 in close contact with the ground surface 16. These fastening means may, for example, be heavy objects, such as concrete blocks, which are placed on the upper surface of the flanges or lugs 15. Preferably, however, the flanges or lugs 15 are kept in close contact with the ground surface 16 by means of rods or pegs 19, which extend through the flanges or lugs 15 and which are driven into the ground.

In Figs. 1 and 2 the sound absorbing wall has a substantially uniform thickness. In the embodiment shown in Fig. 3, how- ever, the wall is tapered upwardly whereby the ground con-

tacting surface of the wall and consequently the stability of the wall is increased.

As illustrated in Fig. 4, the wall may be composed by two or more wall sections or elements which are arranged in end to end relationship, and the wall sections or elements may be interconnected at the joints 20 by means of suitable fasten¬ ing means, such as rivets. The wall may be anchored to the ground by means of spaced apart iron rods 26, the iron rods 26 being buried in the ground or embedded in concrete at a spacing corresponding to the spacing of the joints 20. As indicated in Fig. 4, the wall may be completely or partly covered by bushes or other plants 21.

In the embodiment shown in Fig. 5 the sound absorbing core of the wall is formed by superposed layers 22 of blocks 10. Each layer comprises two rows of blocks arranged in side by side relationship and the joints 23 between end surfaces of adja¬ cent blocks are offset in the side by side rows. Capillary blocking plates 24, which may, for example, be made from expanded polystyrene, are sandwiched between the layers 22 of the blocks 10. A protective net 25 which may be made from plastic, such as high density polyethylene, is sandwiched between the outer grid-like cover 12 and the core of the wall in a manner similar to the one shown in Figs. 1 and 2. The size of the meshes of the net 25 is preferably substantially smaller than that of the grid-like cover 12. As an example, the mesh size of the net 25 may be about 7 mm.

In the embodiment shown in Fig. 6 the core of the wall com¬ prises a single vertical layer of blocks 10 sandwiched between the panels 11. Furthermore, a net 25 is sandwiched between the cover 12 and the panels 11.

Figs. 7 and 8 show different methods of anchoring the wall according to the invention. In Fig. 7, the flanges 15 are bolted to an elongated metal plate or strip 27 which is

welded to a number of mutually spaced, upright anchoring members 28, such as metal profiles.

In Fig. 8, lugs 30 connected to the lower edge portion of the cover plates 14 are fastened to a cement slab 32. The lugs 30 may be made from an angle iron 30.

Fig. 9a is a front view of a frame which may be used for a wall according to the invention, the frame comprising side angle bars 34 and 38 and a bottom angle bar 36. The angle bars are connected to each other by means of releasable clamping devices or by welding and also connected to the outer perforated cover 12. The reference numerals 15 and 17 in Fig. 9b are flanges or lugs and stiffening fins or webs similar to the ones described with reference to Figs. 1 and 2.

Fig. 10a is a diagrammatical top view of a baseplate 40 which may be used for anchoring a wall according to the invention, The baseplate 40 is of rectangular shape, being provided at each of its ends, on the longer side of the rectangle, with an elongated hole 42 for anchoring a wall frame having flanges 15 or lugs 30. At the central area of the baseplate 40 an H-profile has been welded thereto, the two parallel webs of the H-profile being parallel to the elongated holes 42 and the shorter sides of the rectangular baseplate 40. Fig. 10b is a cross-sectional view of the baseplate 40 of Fig. 10a, and Fig. 11 shows in a cross-sectional view the attachment between the wall frame 34 and the baseplate 40. As can be seen from Fig. 11, the wall frame 34 is provided with flanges or lugs 15 and stiffening fins or webs 17, the flanges 15 having holes 50 positioned such as to correspond with the spacing between the two elongated holes 42 of the baseplate 40. Bolts 46 extend through the flange holes 50 and the elongated baseplate holes 42, ensuring a fixed and safe attachment of the wall 34. The same attachment can be seen in Fig. 12, which is a diagrammatical top view of a wall anchored by means of the baseplate shown in Fig. 11.

Fig. 13 shows a wall or baffle made by combining a number of substantially identical rectangular wall elements 50 with a number of substantially identical trapezoidal elements 52. Each of the trapezoidal elements 52 has a bottom side 53 extending at right angles to the mutually parallel opposite sides 54 and 55, and the length of the side 55 is the same as the length of the opposite sides 56 of the rectangular elements 50.

The wall shown in Fig. 13 has been installed on a sloping or curved ground which has been prepared such as to form steps 57 each having a horizontal extension coresponding to the bottom side length of the respective wall element arranged thereon. Because of the trapezoidal shape of the wall elements 52, the wall may follow the contour of the curved or sloping ground such that the upper edge 58 of the wall forms a continuous, possibly angular line. This results in an improved aesthetic quality of the wall. A set of wall elements for making a wall on a sloping or curved ground may comprise a number of identical rectangular elements 50 and a number of identical trapezoidal elements 52. Such a prefabri¬ cated set of elements may be used on grounds having a slope or curvature within a certain range. The set of wall elements may, however, further comprise trapezoidal wall elements having an upper side or edge with a different slope. As can be seen from Fig. 13, the adjacent, parallel edges of the wall elements are perpendicular to the horizontal line of the ground below each element. Parallelogram-shaped elements may also be used instead of the trapezoidal elements 52, and in this case the lower edge of the parallelogram-shaped elements will not be perpendicular to the parallel sides of said elements, but closer to the initial slope. This may save an important amount of ground preparing work, as it may not be necessary to dig and level the ground in order to achieve a perfectly horizontal supporting surface for each wall element. The anchoring in Fig. 13 is achieved by mutually spaced iron rods 26 embedded in concrete.

EXAMPLE

A rectangular wall section of the type illustrated in Fig. l has a length of about 3 m and a height of about 2 m. The stacked blocks 10 have a width of 180 mm and are made from water absorbing stone wool with a density of 80 kg/m ³ . The plates or panels 11 have a thickness of 30 mm and are made from water absorbing stone wool with a density of 200 kg/m ³ . The cover 12 is made from a plurality of mutually spaced, vertically and horizontally extending wires or bars of steel, which are interconnected so as to form a net or grid struc¬ ture. The cross-sectional diameter of the wires or bars is 8 mm and the mutual spacing of the vertical as well as of the horizontal wires or bars is 200 mm. The blocks 10 and plates 11 are tightly surrounded by a netting of high density polyethylene with the mesh dimensions 7 x 7 mm. The total thickness or width of the wall is 260 mm.

One or more of such plate sections or elements may be used when building a noise protecting wall. As each element has a relatively low weight, it may be carried by hand, and as it is relatively simple to fasten when it has been arranged in position, it may be installed by persons without special expertise.