Abstract: A sound absorber comprises an acoustical horn whose mouth is turned towards a source of sound the radiation of which is to be deadened or absorbed and at its narrow throat is provided with a small plug sound-absorbing material of selected acoustical impedance. Such a unit can be made of hard construction material such as plaster or concrete, wood or metal and fiberglass or rock wool of predetermined density may be employed as the sound absorber at the narrow throat of the horn. The horn is preferably of exponential shape. Two absorbers of this kind facing each other can be used as building block of a double shell sound attenuating wall, with high sound transmission loss (STL).