Studies have shown that the leaves of plants attenuate sound by reflecting, refracting and absorbing acoustic energy in small amounts. The amount of noise reduction is proportional to the number of plants that are present in a room. Green walls contain such a large number of plants that the acoustics of a room can be substantially improved.
Plants and trees have been used for years as barriers against traffic and other urban noise pollution. Green walls built on the exteriors of buildings will do the same. They insulate against noise, vibrations and reduce sound penetration. In addition they help to absorb the echo bouncing off buildings and dampen the noise pollution of modern cities.