Abstract: A silencer comprising one or more sound-absorbing parts of ceramic material. The ceramic material is porous and the sound-absorbing parts are self-supporting and have a specific resistance to air flow of 10.sup.3 -10.sup.7 Pas/m.sup.2 and a compression strength of at least 40 kN/m.sup.2, preferably at least 400 kN/m.sup.2.

Abstract: A method of eliminating creep in screw joints or riveted joints in a vibration damping so-called laminated sheet, consisting of at least one vibration damping layer of plastic or rubber applied between two metal sheets to a unit, whereupon holes for screws or rivets have been made in the sheet for instance by punching or drilling. The method comprises embossing the laminated sheet from one or both sides around the holes or the prospective holes after or before the formation of the holes, so that the embossing penetrates the damping layer and the sheets are getting a metallic contact with each other, and so that the distance between the sheets is maintained even if the intermediate layer would lose its carrying capacity.

Abstract: Device for absorption of airborne sound, comprising a rigid, air permeable and self-supporting carrying layer having a flexible, air impermeable membrane applied thereto. The device is characterized in that the carrying layer has an air flow resistance of less than 10,000 Pas/m, that the layer has a thickness of 1-60 mm, preferably 5-20 mm, and that at least one surface of the layer is provided with a relief pattern. The device is further characterized in that a flexible membrane having a surface weight of less than 2 kg/m.sup.2 is firmly attached to the carrying layer by gluing or the like. The membrane is resting on the upper parts of the relief pattern, whereby an air gap is obtained between the membrane and the lower parts of the relief pattern.