NOISE-ABSORPTION DEVICE Russian patent published in 1999 - IPC

FIELD: protection of metro passengers and inhabitants of adjacent buildings against noise of heavy tunnel ventilation. SUBSTANCE: air flow in ventilation column encounters panel which is made from sound-absorbing assemblies which carry members with convex perforated envelope which has sound-absorbing materials, for example, glass fibers and fine basalt fiber. Envelopes of members of each assembly provide channels for passing air. Said channels provide converging tube-diffuser pairs in orthogonal cross sections. Thickness of layer of fine basalt fiber is at least 20 mm and is snug against perforated envelope, rest of which is filled with glass fiber. Cavities of members also carries Helmholtz resonators which holes are directed towards holes in perforated envelope. EFFECT: increased efficiency of noise absorption. 9 dwg