Noise-protection screen

Abstract: A noise-protection screen (1) provided with a number of sound-damping elements (2) and over the length of the noise-protection screen, spaced at a distance from each other with girders for the support of the elements, and a sound-damping element for a noise-protection screen. The noise-protection screen comprises an air cavity (8) delimited at one side by the sound-damping elements (2) and at the other side by panel-like elements (9). At the side of the sound-damping elements the air cavity is preferably in contact with the surroundings by means of air openings, preferably in the form of air gaps running longitudinally along the noise-protection screen.

Description: The invention relates to a noise-protection screen having a vertical height provided with a number of sound-damping elements and over the length of the noise-protection screen, spaced at a distance from each other with girders for the support of the elements, wherein said noise-protection screen comprises an air cavity delimited at one side by the sound-damping elements and at the other side by panel-like elements, and wherein at the side of said sound-damping elements said air cavity is in contact with the surroundings by means of air openings, preferably in the form of air gaps running longitudinally along said noise-protection screen. Various embodiments of noise-protection screens or noise-protection walls are known. CH-A-675738 discloses a noise-protection screen provided with a number of sound-damping elements and over the length of the noise-protection screen, spaced at a distance from each other with girders for the support of the elements, the noise-protection screen comprising an air cavity, delimited at one side by the sound-damping elements and at the other side by panel-like elements. US-A-4,095,669 discloses a noise-protection screen with sound damping elements, wherein at the side of the sound-damping elements the air cavity is in contact with the surroundings by means of air openings. EP-A-0 417 049 discloses a sound-damping element whose whole thickness is built up cf wood fibre concrete. Finally applicants bring a noise-protection wall on the market under the name of Dumex, of which the sound-damping elements consist of a layer of reinforced concrete provided on one or both sides with a layer of wood fibre concrete. The objective of the invention is in the first place to provide a noise-protection screen having a vertical height with improved sound-damping properties. To this end the noise-protection screen having a vertical height according to the invention is characterized in that the vertical height of said screen is provided with two or more sound-damping elements placed on top of each other, whereby between two adjacent elements an air gap is provided. In this way a noise-protection screen is obtained having excellent sound-damping properties, especially in the low frequency range. The air cavity is at the side of the sound-damping elements in contact with the surroundings by means of air holes, preferably in the form of air gaps running longitudinally along the noise-protection screen. In this way the air cavity acts as a resonator whereby excellent sound absorption is achieved. By choosing the appropriate dimensions for the air cavity and the air holes the sound absorption effect of the air cavity can be adjusted to the desired frequency range. The sound absorbing properties of the noise-protection screen according to the invention are thus obtained by the sound-damping elements and the air cavity acting as resonator. In this manner a sound-damping element is obtained having a weight considerably lower than that of the conventional sound-damping elements. This greatly simplifies the handling of the elements, such as during transport and assembly. Further, the important advantage is gained that it suffices to apply less extensive foundations. Both sides of the sound-damping element according to the invention are absorbent. As the total thickness of the sound-damping element consists of absorbent material a high degree of sound absorption is achieved. Moreover, the fabrication of such a sound-damping element made from one type of material is relatively simple, keeping fabrication costs lower. According to the invention it is therefore preferred to apply these sound-damping elements. The invention will be further elucidated with the aid of the drawing, showing an embodiment of the noise-protection screen with sound-damping elements according to the invention. Fig. 1 is a vertical section of an embodiment of the noise-protection screen according to the invention. Fig. 2 is a horizontal section of part of the noise-protection screen as in Fig. 1. Fig. 3 shows the detail III of Fig. 2 on a larger scale. In Figures 1 and 2 a noise-protection screen 1 is shown in vertical and horizontal section respectively. The noise-protection screen 1 is provided with sound-damping elements 2, their whole thickness being built up of wood fibre concrete. By using suitable wood fibre a sound-damping element of the required strength is obtained and it is possible to fabricate elements that can span up to about 3 m. The sound-damping elements 2 of the embodiment shown in the drawing have a length of 2 m and a hight of 60 cm. Naturally other dimensions are also possible. The sound-damping element is comprised of a basic part 3 onto which profile ribs 4 are mounted. The thickness of the basic part 3 is 15 cm, the thickness of the profile ribs 4 is 5 cm. Again, other dimensions and also other profile forms are possible, depending on the requirements. The noise-protection screen 1 further comprises girders 5 which are placed at a distance from each other over the length of the noise-protection screen 1. The short sides of the sound-damping elements 2 are slid into slots 6 of the girders 5, so that the girders 5 provide a support for the sound-damping elements 2. Between the slot walls and the sound-damping elements 2 rubber strips 7 are provided. The noise-protection screen 1 further comprises an air cavity 8 which is delimited at one side by the sound-damping elements 2 and at the other side by the panel-like elements 9. The dimensions of these panel-like elements 9 are in the present embodiment 400x50x20 cm. Naturally, here as well other dimensions are possible. In the present embodiment example elements are applied which are composed of mineralized wood fibre concrete and a compression layer of reinforced concrete. Alternatively the panels 9 may be executed as single or double sided sound-damping elements. Another alternative is that also the whole thickness of the panels 9 is built up of wood fibre concrete. The panels 9 are fastened to the girders 5 as shown in the drawing. Depending on the requirements to be met it is possible to provide the sound-damping elements with an internal reinforcement. In the embodiment example shown, the air cavity 8 is 15 cm deep. Depending on the circumstances the air cavity may also have a different depth. The present noise-protection screen 1 shows a vertical height of three sound-damping elements 2 placed on top of each other. Between two successive sound-damping elements 2 distance pieces 10 are provided leaving an air gap between the elements 2. These air gaps can, for instance, be 15-60 mm. At the top the noise-protection screen is closed by a cover 11 which is also separated by an air gap from the top sound-damping element 2 with the aid of distance pieces 10. Further, between the lowest elements 2, and a not represented foundation, distance pieces 10 are provided, so that here again an air gap is provided. At the side of the sound source the air cavity 8 is in contact with the surroundings by means of air gaps, so that the air cavity acts as a resonator. By the appropriate choice of the dimensions of the air cavity 8 and the air gaps 10 the sound absorption can be adjusted to the desired frequency range. During tests with the noise-protection screen 1 as described, excellent sound-damping properties have been measured, especially in the low frequency range, as a result of the air cavity acting as resonator. Depending on the requirements to be met by the sound-damping properties, the noise-protection screen may be fabricated exclusively from sound-damping elements 2. Although the sound-damping material used in the above described embodiment example is wood fibre concrete, it is naturally possible to use other sound-damping materials.

Claims: A noise-protection screen (1) having a vertical height provided with a number of sound-damping elements (2) and over the length of the noise-protection screen, spaced at a distance from each other with girders (5) for the support of the elements, wherein said noise-protection screen (1) comprises an air cavity (8) delimited at one side by the sound-damping elements (2) and at the other side by panel-like elements (9), and wherein at the side of said sound-damping elements (2) said air cavity is in contact with the surroundings by means of air openings, preferably in the form of air gaps running longitudinally along said noise-protection screen (1), characterized in that the vertical height of said screen (1) is provided with two or more sound-damping elements (2) placed on top of each other, whereby between two adjacent elements an air gap is provided. The screen (1) according to claim 1, characterized in that said noise-protection screen (1) is closed off at the top side by a cover (11). The screen (1) according to claim 1 or 2, characterized in that between said cover (11) and the adjacent sound-damping panel (2) an air gap is provided. The screen (1) according to claims 1-3, characterized in that beneath the lowest sound-damping element (2) an air gap is provided. The screen (1) according to claims 1-4, characterized in that the whole thickness of each sound-damping element (2) is built up of wood fibre concrete. The screen (1) according to claims 1-5, characterized in that said panel-like elements (9) are executed in the form of single or double sided sound-damping elements (2). The screen (1) according to claims 1-6, characterized in that said panel-like elements (9) are executed as sound-damping elements (2) of which the whole thickness is built up of wood fibre concrete. The screen (1) according to claims 1-7, characterized in that said girders (5) at the same time support the panel-like elements (9).

Inventors: VAN TOL GERT JAN, VELDHOEN AREND JAN, VAN TOL, GERT JAN, VELDHOEN, AREND JAN
Applicants: DURISOL RAALTE B V, DURISOL RAALTE B.V.
Application year: 1995
Main classification: E01F8
IPC codes: E01F8, E04B1