SOUND ABSORBING STRUCTURE Russian patent published in 2016 - IPC E04B1/84 

FIELD: acoustics.

SUBSTANCE: invention relates to industrial acoustics. Sound absorbing structure is composed of two perforated walls, between which there is a multilayer sound absorbing element which is double-layered. Layer adjacent to one of walls is sound-absorbing, and layer adjacent to other perforated wall is made of sound reflecting material with a complex profile, consisting of evenly distributed hollow tetrahedrons, which enable to reflect sound waves incident in all directions. Each of perforated walls has following perforation parameters: hole diameter - 3÷7 mm, perforation percentage 10÷15 %. Apertures can be made as holes of circular, triangular, square, rectangular or rhomboid profile. In case of non-circular holes, it is necessary to consider as nominal diameter maximum diameter of circle inscribed in polygon. Sound-absorbing material used is plates made from mineral wool on basalt base of “Rockwool” type, or "URSA" mineral wool, basalt wool P-75, or glass wool with glass felt. Sound absorbing element over its entire surface is lined with an acoustically transparent material, for example, EZ-100 glass fabric or "poviden" type polymer. Between sound-absorbing layer and layer of sound reflecting material of complex profile adjacent thereto, there is an element of resonance type, made in form of a rigid resonance plate with resonance holes serving as necks of Helmholtz resonators. Function of volumes of Helmholtz resonator is performed by layer of sound reflecting material of complex profile, consisting of evenly distributed hollow tetrahedrons, which enable to reflect sound waves incident in all directions.

EFFECT: technical result consists in improvement of efficiency and reliability.

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