Abstract: Disclosed is a noise barrier which comprises a hollow-cell type block having as its principal components a perforated sound-absorbing plate opposed to the noise source and a sound-insulating plate disposed opposite said sound-absorbing plate and incorporating therebetween a sound-absorbing material, a free spacing plate disposed behind said block across an intervening free air layer and means for absorbing and damping sound energy (a vibration-repressing coupling). There is also disclosed a noise barrier having a plurality of adjacent hollow-cell type blocks provided jointly with a free spacing plate by the medium of a support column so as to cover the supporting face.

Abstract: A noise barrier having a large magnitude of transmission loss is disclosed which is formed of a cell-box-type noise barrier comprising (A) a hollow cell-type block having a perforated sound-absorbing plate disposed on the side confronting the source of noise and a sound-insulating plate disposed on the opposite side relative to said perforated sound-absorbing plate and incorporating therein a sound-absorbing material and (B) a free-spacing plate disposed opposite said sound-insulating plate across a space and held in position by the medium of an elastic member, with a free air layer intervening between said free-spacing plate and said sound-insulating plate. Also disclosed is a method for insulating noise by providing a free-spacing plate at a distance from a noise source in such a way as to create a free air layer.