Webinar: Reflection and Transmission of Sound by Vegetation – a review

Prof. Keith Attenborough

Emeritus Professor of Acoustics at the Open University

Reflection and Transmission of Sound by Vegetation – a review

Abstract:

The many forms of vegetation, including low growing plants, crops, hedges, bushes, trees and forests influence on sound propagation near and through them. The physical phenomena involved are visco-thermal losses, scattering and ‘soft’ ground effect. The presence of plant root systems increases the porosity and reduces the flow resistivity of the soils in which they are planted which leads to a lower surface impedance than typical of uncultivated bare soil or compacted grassland. The visco-thermal losses in foliage can be modelled in a similar way to that used to describe the acoustical properties of porous materials. A successful empirical model uses factors of leaf area per unit volume and mean leaf size. In crops, scattering by stems and to a lesser extent by foliage reduces the destructive interference due to ground effect, whereas ground effect due to leaf litter is important in forests. Also there is evidence of a non-reciprocal forest edge effect. The low flow resistivity of the substrate used on green roofs means that it is externally reacting. However, a model of a locally reacting slit-pore double layer has proved useful.

Affiliation:

Emeritus Professor of Acoustics at the Open University

Biography:

Keith Attenborough graduated in Physics at University College London in 1965 and was awarded a PhD in the department of Civil Engineering at Leeds University in 1969. Since 2021 he has been Emeritus Professor of Acoustics at the Open University, having been a part time research Professor from 2008 to 2021. He worked at the Open University also from 1970 to 1999 and was awarded a Personal Chair in Acoustics in 1992. At the University of Hull, he was Head of Engineering between July 1999 and April 2002 and Research Professor in Engineering between 2002 and 2007. He has carried out theoretical and experimental studies on linear and nonlinear acoustical characteristics of porous surfaces, acoustical methods for surveying soils, sound propagation through suspensions, emulsions and bones, outdoor sound propagation and acoustic metamaterials and surfaces. His research has resulted in textbooks on predicting outdoor sound and on aircraft noise. He has supervised 25 Ph.D. theses, had 151 papers published in refereed journals and given more than 180 international conference presentations (including 12 invited). Much of his work on vegetation acoustics was carried out through an EC FP7 project ‘Holistic and Sustainable Actions against Noise by combinations of Natural and Artificial means’ (HOSANNA) which involved thirteen organisations.