Then it got possible to develop studies on new solutions in order to optimise the behaviour of buildings in accord to the climatic changes; most of all it was possible to advance connections between different fields of study: practices that appeared suitable from a thermal perspective also resulted as convenient from the technological approach for constructive simplicity.

Recent studies have shown that vegetation has potential benefits in increasing the health and well-being of citizens improving the air quality, increasing the insulation of building components, reducing the urban heat-islands effect and limiting the storm water runoff. The objective of this thesis is to investigate the effectiveness of vegetated surfaces applied in urban spaces, analysing green from the acoustical viewpoint. Noise pollution, in fact, is a major environmental problem within the EU and during the last few years vegetation was tested as noise abatement mean; several projects aiming to investigate strategies to reduce traffic noise in urban and rural areas have been initiated considering green as effective element of noise abatement.

One of these projects, in which I have personally been enrolled, is named HOSANNA (Holistic and sustainable abatement of noise by optimized combinations of natural and artificial means), is funded under the 7th FWP (Seventh Framework Programme) and is carried on by researchers from several European Countries including Universities and research centres.

This work of research contributes entirely to the improvement that HOSANNA is proposed to carry out in the dose future, and most of all this study intends to agree with the main objectives of the project like making applicable some prediction methods to abate urban noise (which can also be used in noise mapping softwares), delivering a good practice guide for the end-users, delivering assessment methods for the perceived noise environment, and exploiting that designing green areas and surfaces can minimise the noise impact on citizens and lead to a better use of resources.

This work is an investigation on the effectiveness of three types of green walls in terms of reduction of SPL in two theoretical urban case studies, namely an idealised rectangular square and an idealised octagonal square. Four main aspects of the usage of vegetation in the outdoor spaces were evaluated, so that its influence on the reduction of perception of noise from traffic could be studied: effect of the amount of vegetation, effect of changing in the scattering coefficient of vegetation, effect of vegetation in different receiver positions and effect if vegetation on groups of receivers.

The aim of the investigation was to consider different kinds of theoretical urban open spaces with all their features such as the height of buildings, the width of streets and squares, the length of the streets and type of facade. The entire work of analysis and simulation of the acoustic parameters was carried out with the use of three different software, namely CATT-Acoustic, CRR (Combined Ray-tracing and Radiosity) and Odeon 11, so that the use of vegetation as surface coverage could be evaluated in order to find out some improved layouts that reduce the perception of noise from traffic all over the urban space under exam.

The thesis is divided in four chapters. The first one is the background chapter which contains a series of starting concepts that stand on the base of the practical research. It is about definitions, standardisation and introduction on the uses of vegetation in modem architecture. The second chapter is about theoretical and experimental assumptions, so it describes some laboratory experiments and the studies done to define traffic noise in all its features. A dissertation on the definition of the scattering coefficients used to run simulation and on the theoretical models selected is here provided. Chapter three is about parametric studies: it contains an introduction to the acoustical software used and to the uncertainties referred to the simulation process that must be taken into account, and then the results over the proposed layouts that include vegetation as noise abatement mean to reduce the sound pressure level due to the presence of traffic. The last chapter, number four, is referred to some practical guidelines and on the investigation of technological solutions that enrich the possibility of integrating green coverages with architecture: schematic representations are explored and some examples of existent architectures that use those types of technology are provided. The conclusions and an overview on further works complete the dissertation.