Definicija: Pregrade za zmanjševanje širjenja zvoka: splošno uporabne so v industriji in vzdolž cest ter železnic, saj prejemnike ščitijo pred viri zvoka. Pregrade ne zmanjšujejo hrupa na prejemnikovi strani, ampak ga povečujejo, razen kadar niso pokrite z absorpcijskimi materiali.

Definicija: Barriers for reducing the propagation of sound: they are widely used in industry and alongside roads and railways to shield receivers from noise sources. Barriers will not reduce the noise on the receivers side, but will increase it, unless the barrier is also covered in absorbing material.