SOUND ABSORPTION ELEMENT OF ANNULAR TYPE Russian patent published in 2017 - IPC E04B1/84 

FIELD: machine engineering.

SUBSTANCE: sound-absorbing element contains smooth and perforated surfaces, between which a multi-layered sound-absorbing structure is placed. The sound absorber is made in the form of a ring which walls are made in the form of the rigid and the perforated walls with two layers therebetween: a sound-reflecting layer adjacent to the rigid wall and a sound-absorbing layer adjacent to the perforated wall. The sound reflecting material layer is made of the complex profile, consisting of the uniformly distributed hollow tetrahedras, that allow to reflect the sound waves falling in all directions, and the perforated wall has the following perforation parameters: the diameter of the holes is 3÷7 mm, the perforation percent is 10%÷15%. According to the shape the holes can be made as the holes, having round, triangular, square, rectangular or diamond profile. In case of non-circular holes, the maximum diameter of the circle inscribed in the polygon should be considered as the nominal diameter, and the mineral wool on the basalt basis of the Rockwool type, or the mineral wool of the URSA type, or basalt wool of the P-75 type, or the glass wool with the glass fiber lining, or the foamed polymer, for example, polyethylene or polypropylene is used as the sound-absorbing material. The surface of the fiber absorbers is treated with porous air-permeable paints (for example, "Acutex T") or covered with air-permeable fabrics or non-woven materials, for example "Lutrasil". A porous sound-absorbing ceramic material with a bulk density of 500÷1000 kg/m³, and consisting of 100 wt % parts of pearlite with a particle diameter of 0.5÷2.0 mm, 100÷200 wt % parts of one or more sintering materials and 10÷20 wt % parts of binding materials, is used as the sound-adsorbing material.

EFFECT: improved sound absorption efficiency and structure reliability.

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