Acoustic absorption, scattering, and diffusion provided by green roof systems
A. Tadeu, João Dias Carrilho, Andreia Cortês, F. Ferreira, João Almeida
Abstract
Green roof systems can contribute to sustainable urban planning in terms of acoustics by absorbing sound energy and thereby reducing sound levels. However, these positive contributions may vary depending on the substrate's nature, the characteristics of the plants, and the extent of vegetation coverage. In this work, experimental measurements were carried out in both a reverberation chamber and in an anechoic chamber to assess the effect of two different substrates (an engineered substrate specifically prepared for green roof systems and an ordinary soil), three plant species (Thymus pulegioides, Festuca glauca, and Sedum sediforme), and three levels of vegetation coverage (0 %, 50 %, and 100 %) on the acoustic behaviour of a typical green roof system. Initially, the experimental setups and the characteristics of plants and substrates used are fully described. Subsequently, the results are analysed to inspect the individual and collective influence of the different variables on the sound absorption, scattering, and diffusion properties. The results confirmed the expected good sound absorption behaviour and the relatively lesser important scattering properties of the combined effect of substrate and plants. The substrate was found to have a significant impact on the acoustic absorption. Additionally, the scattering results suggest that plant morphology can also influence such systems’ acoustic behaviour.