权利要求：
1. A system for noise reduction of moving fluids, including waves, comprising at least one open cell absorption layer (A) and at least one layer (B), wherein layer (B) is an absorption and a drainage layer, and wherein both layers, the open cell absorption layer (A) and layer (B) are obtained from expanded polymer based material showing a total average density of less than 1000 kg/m3, and wherein layer (B) contains at least 50% closed cells.
2. The system according to claim 1 wherein layer (B) contains at least 70% closed cells and shows a density of less than 700 kg/m3, preferably of less than 300 kg/m3.
3. The system according to one of claims 1-2 wherein the open cell layer (A) shows a density of less than 500 kg/m3, preferably less than 200 kg/m3.
4. The system according to one of claims 1-3 wherein the open cell layer (A) consists of reticulated foam.
5. The system according to claim 4 wherein the reticulated foam shows a cell structure of 10 to 300 pores per inch, preferably 20 to 120 pores per inch and wherein the polymer based material cell wall columns show a diameter thinner than the average cell diameter.
6. The system according to one of claims 1-4 wherein the layer (B) comprises polyolefin and/or polyalkylidene terephthalate.
7. The system according to one of claims 1-6 where drainage holes and/or ridge structures are applied in layer (B) and/or open cell layer (A).
8. A process for manufacturing the material according to one of claims 1-7 in a moulding and adhesion or continuous extrusion process and/or co-lamination, followed by applying the desired structures, respectively.
9. The use of a system according to one of claims 1-7 for applications requiring noise reduction of moving fluids, preferably for flowing and/or falling fluids or fluids creating waves, such as on channels and ponds, in cooling towers and at shores.