Figure shows the increase in relative attenuation

Figure 15 shows the increase in relative attenuation with increasing greenery c-Myc tag at various distances from the source for buildings that were 4 and 12m high. The plots clearly show that building height has no significant effect on the resultant relative attenuation. This fact attributes the propagation characteristics to the lower parts of the building façade. The height of receiver points was set to be at the human ear level 1.8m from the ground. The results demonstrate a linear relationship between relative attenuation and the absorption coefficient of the vertical greenery system, with relative attenuation increasing with the absorption coefficient. This phenomenon is enhanced by increasing distance from the source location, which indicates that the effect of the installation of a vertical greenery system on street façades will be more efficient at remote locations. This phenomenon can be observed in actual urban environments where the resultant background noise originates from various remotely located sources.
Conclusion A computer model based on the energy exchange theory was developed. Energy exchange was calculated using solid angle fraction measurements to account for the diffuse sound field present in the urban texture, given that all street façades are assumed to exhibit Lambertian diffuse reflections at higher orders of reflections. The urban texture was modeled as a simple rectangular building with lateral and longitudinal streets that intersect at right angles. Energy was distributed from a simple point source located somewhere in the urban setting for all visible façades. Furthermore, energy was exchanged through a network of nodes located at the center of each building façade, considering visibility and occlusion. Contour plots and results for an urban area with visual and geometrical characteristics similar to those of an Islamic pattern, such as a 410m×410m site with six lateral and six longitudinal streets with a building density of 73%, showed that the relative attenuation added after installing vertical greenery increased effectively near the source. However, the relative attenuation of remote locations from the source tended to have constant rates. The parametric investigation outlined the effect of applying vertical greenery to street façades. The effect of increasing building height was proven to add marginally to the relative attenuation rate, thus designating the propagation characteristics of sound to the lower parts of the street façades that are near the source and receiver levels. Further investigation also proved that the relative attenuation of vertical greenery is more effective at long distances from the source location, which is another benefit of installing vertical greenery on street façades in terms of dealing with remotely located sources in urban settings. Given that the simulations in this study are based on the outlined Islamic urban pattern characteristics, the attenuation rates related to installed greenery on street façades should not be cross-referenced to other urban pattern characteristics. In addition, less attenuation rates could be expected for urban patterns of wider streets because of the reduced surface area of relative façades in the urban scene and the wider street channel open to the sky. However, this assumption requires further investigation.
Introduction The primary purpose of buildings is to provide occupants with conducive, safe, comfortable, healthy and secured indoor environment to carry out different kinds of activities ranging from work, study, leisure and family life to social interactions. In order to achieve this purpose, buildings are designed, planned, constructed and managed based on standards and specifications established by governments, professionals and experts who are supposed to have adequate knowledge of users\' needs and expectations. Studies (Kaitilla, 1993; Ukoha and Beamish, 1997; Zeiler and Boxem, 2008; Meir et al., 2009) have however shown that sometimes these standards and specifications do not conform to the changing needs and expectations of users; and thus users are not always satisfied with the performance of their buildings. The consequences of this are manifested in building related illness and ‘sick building syndrome\' (Kian et al., 2001), increase in the desire for remodelling or modifications or abandonment of completed buildings (Kim et al., 2005) which may cause waste of energy and sometimes even damage to the building envelope components and the surrounding environment (Mitterer et al., 2012).